US 5515480

I'll research this patent across multiple sources.

Let me check the claims in full and look specifically for any 2026 CAFC activity.

Let me pull the full claim set directly.

US Patent 5,515,480 — Research Summary

Sources consulted: Google Patents (https://patents.google.com/patent/[US5515480A](/patent/US5515480A)/en), Unified Patents portal (https://portal.unifiedpatents.com/patents/patent/US-5515480-A), EveryPatent (http://www.everypatent.com/comp/pat5515480.html), PlainSite (https://www.plainsite.org/profiles/dp-tek-inc/). All of these returned data for the literal number 5,515,480 and no other number was substituted.

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Bibliographic data

Assignment chain (per Google Patents assignment records): DP-TEK, INC. → DP TEK DEVELOPMENT COMPANY, LLC (1996-06-03) → HEWLETT-PACKARD COMPANY (1997-08-01) → Hewlett-Packard Development Company, L.P. (2011-09-22).

Foreign family: EP 0765508 B1, DE 69532445 T2, KR 100340366 B1, JP H10-503896 A, AU 28239/95 A, PCT/US1995/007402 (WO 1995/034873 A1).

Classification: H04N 1/4055, H04N 1/4058 (digital halftoning); G06K 15/1209 (intensity control of the optical beam); G06K 15/1223 (resolution control / edge or detail enhancement).

⚠️ Discrepancies noted: Google Patents and Unified Patents disagree by one day on both the priority/filing date and the grant date, and therefore on the expiration date. I have not reconciled this against the face of the printed patent, so treat the exact date as ±1 day. PlainSite also lists a 1996-06-03 record and a 1994-06-15 record for application 08260085.

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Abstract (verbatim)

"Gray scale input data, derived from continuous tone data, is transformed into pulse patterns for driving a marking engine so that a variety of marks of different sizes and shapes are formed in any given pixel region. Gray scale input data is arranged (received) as an array of pixels, in the native engine resolution, including multi-bit per pixel gray level values. A pixel in the array is analyzed in a transformation (window) to determine the pulse pattern output based on the gray level value of the current pixel and on the gray level values of adjacent vertical and horizontal pixels. The pulse pattern output for driving the marking engine in the current pixel location is adjusted by the transformation to produce sub-pixel sized marks of various shapes, sizes, positions, and orientations that, in combination with neighboring marks so produced, provides for the flexible production of marking patterns that contain a number of gray scale levels substantially exceeding the number of gray scale levels contained in the input data, and that enhance the simulation of graphic features produced. The transformation flexibly selects from an optimized subset of pulse patterns available to produce the most accurately calibrated tones and features based on the input data."

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Plain-language overview of the independent claims

⚠️ Confidence caveat: I was able to retrieve the full text of claims 5 and 9 and partial text of other claims through third-party claim reproductions, but not a complete verbatim claim set from an authoritative USPTO source. Claims 1–4 and anything above claim 12 are only partially recoverable from my searches. The overviews below are therefore reconstructions, not certified verbatim quotations. The claim count is unknown to me.

Claim 1 — Method (pulse-position method). A method claim directed at energizing a marking engine's energizing element during a pixel period using pulses placed at different positions within that pixel period. The recovered text recites the pulse being disposed at one of "(2) the end of said pixel period; (3) the center of said pixel period" and elsewhere in the specification the four positions are enumerated as (1) beginning, (2) end, (3) center, and (4) both beginning and end of the pixel period. The preamble and full step language were not recoverable, so treat this description as incomplete.

Claim 5 — System (pulse generator + table + feature detection circuit). A system for enhancing graphic features produced by a marking engine, where graphic data comes from a multi-bit-per-pixel raster source at a resolution equivalent to the marking engine's native resolution. The system comprises:

• a pulse generator providing an energization pulse to the engine's energizing element for a current pixel in a current pixel period, responsive to a pulse code indication;
• a table containing a plurality of pulse code values optimized to enhance graphic features produced by the marking engine; and
• a feature detection circuit that decodes multi-bit value patterns for each of a plurality of pixels in the raster source and responsively indexes a pulse code value from the table to supply to the pulse generator.
• Each pulse code value encodes both a predetermined duration for the energization pulse and at least one predetermined position of the pulse within the current pixel period.

Claim 6 (dependent on 5) — The feature detection circuit detects highlight and shadow features by detecting one of first and second threshold values in pixels adjacent the current pixel, and indexes correspondingly optimized highlight or shadow sub-tables.

Claim 7 (dependent on 5) — The feature detection circuit detects right and left edge features by comparing multi-bit values of adjacent pixels, and indexes correspondingly optimized right-edge or left-edge sub-tables.

Claim 8 (dependent on 5) — The table is a memory storing pulse code values in storage locations and outputting one in response to an address input, and the feature detection circuit comprises combinatorial logic receiving multi-bit pixel values and providing that address input, so that a detected feature pattern indexes an optimized pulse code.

Claim 9 — System (marking engine + buffer + transformation circuit + pulse generator). A system for producing graphic features on paper, the features encoded as an array of pixels each with an associated value, comprising:

• a marking engine producing marks at pixel locations on scan lines in response to driving pulses;
• a memory buffer storing each pixel value as a plurality of binary bits;
• a transformation circuit that receives and determines the value of a first pixel and at least one adjacent pixel and responsively provides a pulse code output;
• a pulse generator receiving that pulse code output and providing the driving pulses to the engine;
• wherein the transformation circuit receives a plurality of values in a feature detection window covering pixels on the same scan line and on adjacent scan lines;
• wherein the driving pulses comprise pulse patterns ranging in duration from a fraction of a pixel period to a full pixel period, positioned within the pixel period responsively to the detected value pattern, at one of (1) the beginning, (2) the center, (3) the end, or (4) both the beginning and end of the pixel period; and
• wherein the resulting marks are adapted to optimally simulate edges, highlights, and shadows, enhancing a simulated gray image.

Claim 10 (dep. on 9) — Adds the charge-region mechanism: the engine produces a charge region per pixel location; the pulse patterns produce charge densities; and marks appear where a predetermined charge density is exceeded.

Claim 11 (dep. on 9) — The transformation circuit includes a look-up table in a memory device.

Claim 12 (dep. on 11) — Adds selection logic receiving and decoding the values and providing an address output to that memory.

I cannot confirm whether any further independent claims (e.g., a second method claim or a calibration-method claim) exist beyond claim 12. The corresponding German family member DE 69532445 T2 shows a counterpart claim set with an additional calibration-type claim (dividing the pixel period into n intervals, encoding pulse codes across positions, selecting the best subset for each graphic feature, and storing the subset in a feature sub-table), but I have not verified whether an equivalent claim appears in the US patent.

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Key technical points from the disclosure (context for claim construction)

• Input is 4-bit-per-pixel gray scale at 300 dpi native resolution; output drives a 300 or 600 dpi laser marking engine.
• The feature detection window is 1×3×1 (a cross): current pixel "PA" plus adjacent pixels "PB," "PC" (same line), "PD," "PE" (adjacent lines) — twenty bits total.
• An 11-bit address indexes a RAM look-up table of 8-bit pulse codes: 2 bits of pulse-position field + 6 bits of duration field (64-step granularity, i.e., 1/64 of the pixel period).
• The four pulse positions map to pulse-code ranges 00–3F Hex (centered), 40–7F Hex (end/right-justified), 80–BF Hex (beginning/left-justified), C0–FF Hex (split).
• Claims are supported by an empirical calibration procedure (print parameter test data covering all 256 position/duration combinations, derive first-approximation table, iterate control images for gamma correction). The specification's worked example is an optimized table for a "Cannon NX 300 dpi laser printer" (spelling as in the patent text — likely a typographical rendering of Canon) in Appendix A, with 2048 addresses broken into 128 sub-tables.

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Litigation / CAFC 2026 docket search

I found no CAFC 2026 docket activity involving patent 5,515,480, and I want to be explicit that this is a negative finding rather than a verified absence. My searches of general web and patent-aggregator sources returned no Federal Circuit appeal, IPR, or district-court matter naming this patent in 2026.

Two contextual points that make 2026 appellate activity implausible (though not impossible):

1. The patent's legal status is Expired – Lifetime, with an anticipated expiration of 2014-06-15 (per Google Patents) or 2014-06-14 (per Unified Patents). A 2014 expiration means any infringement action would relate to pre-2014 conduct and would face laches/damages limitations.
2. The only party records I could locate are the 1994–2011 assignment/reassignment records (DP-TEK → DP-TEK Development → Hewlett-Packard), plus a PlainSite profile for DP Tek, Inc. that lists only the prosecution/assignment documents for application 08/260,085 — no litigation docket entries.

Caveat: I did not have direct access to the CAFC's own docket system (PACER/CM-ECF or the CAFC opinions feed) during this research; my conclusion rests on general and patent-specific web sources. If you need a definitive docket check, the authoritative sources would be the Federal Circuit's PACER docket and the USPTO Patent Trial and Appeal Board / PatentCenter records, which should be searched directly for 5,515,480 and application 08/260,085.

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Explicit uncertainty flags

• Verbatim claim text: not obtained from an official USPTO source; claims 1–4 and any claims beyond 12 are incompletely recovered.
• Independent claim set: I can confirm claims 5 and 9 are independent; claim 1 appears independent but its full text is not recovered. Total claim count is unknown.
• Dates: Google Patents and Unified Patents differ by one day on priority and grant; I did not reconcile against the printed patent front page.
• CAFC 2026: no results found; treat as "no evidence located," not as proof of non-existence.
• The patent text repeatedly refers to a "Cannon NX" printer; I have not auto-corrected this identifier, per your instruction.

I'll search litigation databases for cases naming US 5,515,480 specifically.

Let me run additional targeted checks on docket aggregators and the related DP-Tek cases.

Let me check the DP-Tek corporate litigation history and docket aggregators more directly.

Litigation Involving US Patent 5,515,480

Bottom line: no litigation is known

I found no case — district court, Federal Circuit, ITC, or PTAB — in which US 5,515,480 was named as an asserted patent. Searches keyed to the literal number 5515480 and to the app. no. 08/260,085 returned only prosecution/assignment records and an informational aggregator listing, never a docket entry. Any representation that this patent has been litigated should be treated as unverified.

That is a negative finding, not a certified absence. I could not open PACER/CM-ECF, the CAFC opinions feed, or Docket Alarm's case search directly with the tools available; my searches reached Google Patents, the Unified Patents portal, PlainSite, and general web. Those sources returned no litigation entry for this patent, but the authoritative check remains a docket pull (see "How to confirm" below).

Two threshold points that make litigation searching on this patent mostly moot: (1) it is Expired – Lifetime, anticipated expiration 2014-06-15 (Google Patents) / 2014-06-14 (Unified Patents); (2) even if a pre-2014 suit existed, 35 U.S.C. § 286's six-year lookback from today (2026-04-26) reaches only to 2020-04-26 — roughly six years after the patent died. There is no live accrual window.

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Requested case table

I will not populate this table with numbers or parties I cannot verify. Fabricating a docket entry is worse than an empty row.

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Adjacent matters (NOT '480 litigation — do not conflate)

These surfaced in the search and are the cases a plaintiff might point to as "related." None is confirmed to involve US 5,515,480. I am listing them solely so you can distinguish them.

*1. DP-Tek, Inc. v. AT&T Global Information Solutions Co., 100 F.3d 828 (10th Cir. 1996)*

• Subject: tortious interference — not a patent case. As flagged in the previously generated "Strategic summary" section, the '480 patent's validity and scope were not at issue.
• Fields not recoverable: district jurisdiction, case number, filing date, disposition beyond the 10th Cir. citation.
• Relevance to '480: none. Do not let this be cited as patent litigation on the '480.

2. HP / Xerox dispute over DP-Tek-derived print-resolution chips (D. Kan., Wichita)

• Per Tech Monitor (techmonitor.ai): a US District Court judge in Wichita ordered HP to supply Xerox with 4,000 chips for NC60 color laser printers, with Xerox posting a $250,000 bond; chips came from DP-TEK Development Co LLC (HP-acquired 1996); "the real dispute, over patents, continues."
• ⚠️ Critical caveats: I could not retrieve a case number, filing date, or the identity of the patents-in-suit. US 5,515,480 is not confirmed to be among them. The article as retrieved is undated. Report this as contextual only.
• This is, at most, operating-company vs. operating-company assertion of the acquired DP-Tek portfolio — the inverse of NPE privateering.

3. TPAB / PTAB: As stated in the previously generated "PTAB challenges" section, zero AIA trial proceedings. PGR was unavailable (effective filing 1994-06-15, ~19 years before the 2013-03-16 cutoff); CBM was unavailable (no financial-services nexus, CPC G06K15/1209 / H04N1/4055); IPR's practical window (~2012-09-16 to 2014-06-15) produced no filings. I re-confirmed no AIA proceeding appears on the Unified Patents portal page for US-5515480-A, which shows only bibliographic data, "Patent Art (10)" and "Referenced By (131)" — no litigation or PTAB tab.

4. AU 5515480 A — ⚠️ DO NOT CONFLATE. A search hit returned "AU 5515480 A" (Australian, dated 1980, in a prop argyl-derivatives EPO/PISE document). That is a different document in a different jurisdiction and a different field; it is not US 5,515,480. Flagged because the search string collided. Per your standing instruction, I have not auto-corrected either identifier.

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Confidence and limits

• High confidence: the patent is expired (2014) and no PTAB/AIA proceeding exists. These rest on the structured ODP-style block plus the Unified Patents page.
• Medium confidence: no district-court case ever named this patent. The aggregator sources I reached did not index one, but a 1990s-vintage Kansas case could be poorly indexed in modern aggregators. This is the gap most worth closing.
• Low confidence / unresolved: whether the HP–Xerox Wichita patent dispute involved the '480. I could not obtain the case number or patent list.

How to confirm (recommended before relying on any of this)

1. PACER / CM-ECF — party search "DP-Tek" and "DP-TEK Development" (D. Kan., and nationally); also search the patent number in the "patent" case-type filter.
2. CAFC docket (CM-ECF) and the CAFC opinions RSS — search 5515480 and party names.
3. USPTO Patent Center, application 08/260,085 — the file history will show any §282/reexam or litigation-related papers, and the expiration record.
4. Unified Patents litigation caselist (https://portal.unifiedpatents.com/litigation/caselist) and Docket Alarm — search the literal 5515480.

One flag on a cross-section discrepancy: the "Patent summary" in this file listed four assignment events; the full text and the "Assignment history" section list five (the earlier summary omitted the 2001-01-16 merger). The five-event chain is correct. Also, the previously generated "Obviousness" section recited a task date of April 26, 2026 while other sections said 2026-09-27 — I have used 2026-04-26 per the current instruction, which shifts the § 286 lookback to 2020-04-26 without changing the conclusion.

I'll start by verifying the structured feed's "no proceedings" signal against public sources, since this patent predates the AIA (filed 1994) and expired in 2014 — both factors that shape what's even possible.

Let me run a couple more targeted checks — including CourtListener and any litigation/reexam history — before concluding.

Let me do a final check on the litigation/reexam side, since that history is what usually explains an IPR absence.

PTAB proceedings overview

Total AIA trial proceedings on file: zero. The USPTO Open Data Portal structured record returns no AIA trial proceedings for US 5,515,480, and independent web searching surfaced none — no IPR, no PGR, no CBM. My searches also returned no Federal Circuit appeal from any PTAB decision on this patent, and no evidence of an ex parte reexamination. The bottom-line defensive posture is therefore not "the patent is hardened by surviving IPRs" and not "claims are canceled." It is something more fundamental: the patent is expired (2014-06-15) and, at ~32 years from its 1994-06-15 filing date, was never subjected to a single AIA trial challenge — which means an assertion against you today fails on temporal grounds long before you need a PTAB strategy.

I want to be explicit about the limits of this finding rather than paper over them. Three independent checks agree (ODP structured feed; keyword searches on the patent number, inventor "Frazier," and original assignee "DP-Tek"; and the Unified Patents patent portal page for US-5515480-A, which lists no litigation or PTAB activity), but a negative search result is weaker evidence than a positive one. Treat "no PTAB proceedings" as high-confidence but not certified — the authoritative confirmation is a docket pull on PTAB E2E and USPTO Patent Center for application 08/260,085.

No proceedings to report

Because no petition was ever filed, the per-proceeding template (petitioner, panel, grounds, institution decision, FWD, settlement, appeal) has no entries to populate. I will not invent proceeding numbers, panels, or dispositions to fill it out. For the record, here is why the absence is structural rather than coincidental:

• PGR was never available. Post-Grant Review reaches only patents with an effective filing date on or after 2013-03-16. This patent's effective filing date is 1994-06-15 — roughly 19 years too early.
• CBM was never available. Covered Business Method review (AIA § 18) required a claim directed to a "financial product or service." This is a print-engine halftone/gamma-correction patent (CPC G06K15/1209, H04N1/4055). It has no financial-services nexus, so it could not qualify — independently of CBM's 2020-09-16 sunset.
• IPR was theoretically available for only a narrow window and nobody used it. IPR petitions could be filed against any patent from 2012-09-16 onward, but this patent's term ran out on 2014-06-15. That left a ~21-month practical window, during which the Board could still have reviewed the claims (Sony Corp. v. Iancu confirms expired patents remain IPR-eligible), but the commercial incentive to invalidate a patent with under two years of life left was negligible. No one filed.

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Strategic summary

Claim status: no claims canceled, none sustained — all claims expired. The most important fact for a defendant is that I cannot give you a canceled/sustained/untested claim breakdown, because no tribunal has ever ruled on these claims in a PTAB proceeding. That is not the same as "the claims are strong." It means they were never tested, and now they never will be, because the patent's term expired.

Two independent knockouts precede any PTAB analysis. First, on expiration: Google Patents records an anticipated expiration of 2014-06-15; the Unified Patents portal lists 2014-06-14. That one-day discrepancy is a term-calculation artifact (20 years from the 1994-06-15 filing), not a substantive dispute — either way, the last day on which infringement could have accrued was mid-June 2014. Second, on the statute of limitations: 35 U.S.C. § 286 bars recovery for infringement accruing more than six years before a complaint is filed. As of today (2026-09-27), that six-year lookback reaches back only to 2020-09-27 — roughly six years after the patent died. There is no live accrual window. A demand letter citing this patent today is not a case a rational defendant settles; it is a case that ends on a Rule 12 motion.

Estoppel landscape: § 315(e)(2) is a non-issue in both directions. Statutory estoppel attaches only to a petitioner that obtained an institution decision and a final written decision. Because no petition was ever instituted, there is no estopped petitioner and no estopped privy — no prior-art ground is foreclosed to you, and equally, you cannot rely on any prior winning IPR record. Every invalidity ground that would have been available in 2013 (the Frazier pulse-position/pulse-duration art, the 4-bit sub-pixel pulse-width-modulation references discussed at length in the specification's "Description of the Related Art," and the numerous third-party U.S. patents that cite this one as background) remains fully available as a district-court or ex parte reexam argument. Practically, though, invalidity is a fallback: you should lead with expiration and § 286.

Pattern signals: none of the usual ones. There is no serial petitioner (in contrast to the repeat-challenger fact patterns the Board polices under General Plastic and § 325(d)/Fintiv), no patent-owner appeal history, and no sign of a defensive aggregator. The Uniform Patents portal page for US-5515480-A appears as an informational listing only, with no challenge activity attributed to Unified Patents or any other aggregator. The patent's lifecycle is instead a corporate-assignment story, not a litigation story: filed by Allen Frazier, assigned to DP-Tek, Inc., then to DP-Tek Development Company, LLC (1996-06-03), then to Hewlett-Packard Company (1997-08-01), then to Hewlett-Packard Development Company, L.P. (2011-09-22). It has been an HP portfolio asset for nearly 30 years and, so far as the public record shows, was never asserted in an AIA-era proceeding. The related DP-Tek litigation — DP-Tek, Inc. v. AT&T Global Information Solutions Co., 100 F.3d 828 (10th Cir. 1996) — was a tortious-interference case, not a patent case, so it tells you nothing about validity or about the '480 claims. Do not let a plaintiff conflate the two.

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Recommended next steps

If you are a defendant receiving an assertion:

1. Lead with expiration, not invalidity. The patent expired 2014-06-15. Confirm the term date via USPTO Patent Center (application 08/260,085) and the maintenance-fee/expiration record. Demand the plaintiff identify the accrual date of the alleged infringement. If every accused act postdates 2014-06-15, there is no infringement as a matter of law.
2. Then apply § 286. Even if the plaintiff points to pre-2014 conduct, any claim accruing before 2020-09-27 is time-barred. The overlap of "expired 2014" and "six-year lookback from 2026" leaves no recoverable window.
3. Note that there is no FWD to cite. I cannot link you to a Final Written Decision for this patent because none exists — no IPR was ever instituted, so there is no disposition, no canceled claim, and no panel reasoning to quote. Any representation to you that this patent "survived PTAB challenges" would be false; it was simply never challenged. Conversely, do not represent to a court that claims were canceled — that would also be false.
4. Preserve the invalidity record anyway. For completeness and to inoculate against a § 282 fight, commission a search of pre-1994 art directed to pulse-width-modulated laser marking engines and multi-bit sub-pixel halftone generation (the specification itself concedes that 4-bit/16-interval centered-pulse schemes were known). This is cheap insurance, not your primary defense.

If you are evaluating this patent for acquisition, licensing, or a freedom-to-operate opinion: the expiration date is the whole analysis. There is no live right to license. See the Google Patents record at patents.google.com/patent/US5515480A/en and the assignment chain on Patent Center.

Confirmation step I recommend before you rely on any of the above in a filing: pull the complete docket from PTAB E2E and the file history from USPTO Patent Center for application 08/260,085. My "zero proceedings" conclusion rests on the ODP structured block plus negative search results, not on a direct E2E docket read, and that distinction is worth preserving in your file.

One caveat on claim-level detail: the authoritative full text provided to me ends before the claims section, so I cannot enumerate the specific claims of 5,515,480 or confirm the independent/dependent structure. That does not affect the analysis above — the expiration and § 286 reasoning applies to every claim regardless of numbering — but if you need the claim set quoted for a brief, pull it directly from the Patent Center "Claims" tab rather than from secondary sources.

I'll research the assignment record for this patent, focusing on reel/frame numbers and correspondents of record.

Let me try to surface the actual assignment record details, including reel/frame and correspondents.

Let me try to retrieve the recorded reel/frame data and correspondent information.

Ownership-Chain Reconstruction — US 5,515,480

Critical verification caveat up front: With the tools available to me I could reach the Google Patents "Legal Events / Reassignment" table and the PlainSite USPTO-derived profile for DP-Tek, Inc., but I could not open USPTO Assignment Center (assignmentcenter.uspto.gov) and read the recorded reel/frame and correspondent fields directly. Google Patents' reassignment table reproduces events and party names but not reel/frame numbers or the correspondent of record. Accordingly:

• Every reel/frame number below is marked "not retrieved." I have not invented any. A fabricated reel/frame is worse than a blank, so I am leaving them blank and telling you exactly where to pull them.
• No correspondent of record could be retrieved for any link in this chain. Signal #3 (repeat correspondent) is therefore reported as unclear, not "absent."

The events themselves are corroborated by three independent sources that all key on application 08/260,085 / patent 5,515,480 (Google Patents legal events; PlainSite DP-Tek profile; Unified Patents patent page), so I am confident about the sequence even though I am not confident about the reel/frame identifiers.

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Inventors

Unusual-pattern check — NOT present. The flagged pattern (all inventors departing the original assignee within 12 months of filing, often preceding a fire-sale) does not appear:

• There is only one named inventor, so there is no multi-inventor exodus to look for.
• Frazier's separation from DP-Tek occurred as part of the 1996 HP acquisition of DP-Tek's technology and patents — roughly 24 months after the 1994-06-15 filing (before the 1996-05-07 grant). His obituary records he "moved to Idaho," matching HP's Boise printer site, to which DP-Tek's developers relocated. That is an acquisition-integration departure, not a pre-fire-sale abandonment.
• Wayne Bradburn is not a named inventor on the '480 patent — the sole named inventor is Frazier. Flagged so the co-founder is not conflated with the inventive entity.

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Original assignee

DP-Tek, Inc. — Wichita, Kansas; incorporated in Kansas; a C-corporation per the PlainSite profile.

• Primary line of business: an operating technology company (not a patent-holding shell). It developed and licensed print-resolution-enhancement and digital-interface technologies — trade names TrueRes, PhotoTone, and RAMSaver. TrueRes provided resolution doubling ~"printing at 400% of standard resolution without hardware modifications" (Frazier obituary). Its '495 and '008 patents (app. 07/610,087 and 07/610,094, filed 1990-11-07) show it was a genuine R&D filer from at least 1990.
• Did it ship a product embodying the claims? DP-Tek was primarily a licensor/integrator, but its technology did reach commerce: the obituary states they "licensed their technologies to large corporations and helped implement the technology into commercially available products," and it was already supplying print-resolution enhancement to Xerox at the time HP acquired it (Tech Monitor). Its TrueRes technology is expressly discussed by name in later third-party patents (e.g., a Ricoh image-forming patent describing "TrueRes technology"). So: yes, embodied in commercial printers via licensees; no, DP-Tek was not itself a mass-market printer OEM.
• Current status: acquired / wound down. HP announced the asset acquisition of DP-Tek's print-resolution enhancement technologies and patents (informedusa.com/t/hp7.11.html, "HP Buys DP-Tek's Resolution Technologies"). Of DP-Tek's ~40 employees, the developers relocated to HP's Boise, Idaho site; the rest were offered severance. The Frazier obituary confirms: "In 1996, laser printer market leader Hewlett Packard purchased DP-Tek."

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Assignment timeline

⚠️ Reel/frame and correspondent are "not retrieved" for every entry (see caveat above). Dates below are recording dates as reproduced in Google Patents' legal-events table (which is derived from USPTO reassignment data). Where Google Patents lists an "executed" date separately I could not confirm execution dates; treat these as recording dates.

1. 1994-06-15 (recorded) — Reel not retrieved

   • Conveyance: Assignment
   • Assignor: Frazier, Allen
   • Assignee: DP-TEK, INC.
   • Correspondent: not retrieved
   • Context: founder-to-company assignment of the invention, recorded at/around the 1994-06-15 filing.

2. 1996-06-03 (recorded) — Reel not retrieved

   • Conveyance: Assignment
   • Assignor: DP-TEK, INC.
   • Assignee: DP TEK DEVELOPMENT COMPANY, LLC (elsewhere styled "DP-TEK DEVELOPMENT COMPANY, L.L.C.")
   • Correspondent: not retrieved
   • Context: internal reorganization — DP-Tek's patents were moved into a development LLC. Not a shell tell: PlainSite shows this same LLC holding other DP-Tek patents far earlier, e.g. a 1994-12-19 record covering app. 07/610,087 (US 5,134,495) and 07/610,094 (US 5,193,008), and a 1996-06-28 record for app. 07/411,303 (US 4,967,210).

3. 1997-08-01 (recorded) — Reel not retrieved

   • Conveyance: Assignment
   • Assignor: DP-TEK DEVELOPMENT COMPANY, L.L.C.
   • Assignee: HEWLETT-PACKARD COMPANY
   • Correspondent: not retrieved
   • Context: acquisition — HP's purchase of DP-Tek's resolution-enhancement technology/patent portfolio.

4. 2001-01-16 (recorded) — Reel not retrieved

   • Conveyance: Merger
   • Assignor: HEWLETT-PACKARD COMPANY
   • Assignee: HEWLETT-PACKARD COMPANY
   • Correspondent: not retrieved
   • Context: internal reorg / merger housekeeping (same-entity name/merger record filed with USPTO).

5. 2011-09-22 (recorded) — Reel not retrieved

   • Conveyance: Assignment
   • Assignor: HEWLETT-PACKARD COMPANY
   • Assignee: HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P.
   • Correspondent: not retrieved
   • Context: internal reorganization — transfer into the HP subsidiary that holds HP's printer/IP estate.

Cross-check / discrepancy notes:

• The full patent text's legal-events block lists five events (including the 2001-01-16 merger), whereas the earlier "Patent summary" section in this file listed only four (1994-06-15, 1996-06-03, 1997-08-01, 2011-09-22). Not a contradiction — the earlier summary simply omitted the 2001-01-16 merger record. The 2011 assignee can be reconciled either way.
• Unified Patents lists priority/grant/expiration one day earlier (1994-06-14 / 1996-05-06 / 2014-06-14) than Google Patents (1994-06-15 / 1996-05-07 / 2014-06-15). Neither source gives a recorded-assignment date that differs, so this ±1-day issue does not affect the ownership chain.
• The PlainSite DP-Tek profile's own table shows the 1996-06-03 LLC assignment and the 1994-06-15 Frazier assignment, corroborating entries 1 and 2.

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Timeline diagram

timeline
    title Ownership of US 5515480
    1994 : Filed by DP-Tek Inc
         : Frazier assigns to DP-Tek
    1996 : Issued May 7
         : Patents moved to DP-Tek Development LLC
         : HP buys DP-Tek technology
    1997 : Assigned to Hewlett-Packard Company
    2001 : HP merger record at USPTO
    2011 : Assigned to HP Development Co LP
    2014 : Patent expired

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NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The only "LLC-shaped" link is DP TEK DEVELOPMENT COMPANY, LLC (1996-06-03). That is not a licensing-only shell on the evidence: it is the Wichita operating entity's own reorganization vehicle and it demonstrably held multiple other DP-Tek patents years earlier (1994-12-19 record for 5,134,495 and 5,193,008; 1996-06-28 record for 4,967,210 — PlainSite). It also passed the '480 straight to HP ~14 months later. No "IP / Licensing / Ventures" suffix, no anonymous registered-agent posture established.

2. Known asserter in the chain — Not present. No Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or Spangenberg entity appears anywhere in the chain. The terminal assignee is Hewlett-Packard Development Company, L.P., an operating OEM.

3. Repeat correspondent across the chain — Unclear (data not retrievable). I could not obtain any correspondent of record because I could not open Assignment Center's per-record detail. I will not infer a repeat player from names alone. To close this: pull each of the five records above in Assignment Center and read the "Correspondent" column; a recurrence of one attorney/firm across entries 2–5 would be the thing to look for.

4. Cascading transfers — Not present. The transfers are spread over 1994 → 1996 → 1997 → 2001 → 2011. The only sub-24-month adjacency is the 1996-06-03 → 1997-08-01 pair, which is the ordinary two-step structure of a corporate asset purchase (business → affiliate LLC → buyer), not an NPE shell cascade. No shared anonymous correspondent address established (see #3).

5. Pre-litigation transfer — Not present. No assignment is within six months of any infringement suit naming this patent — because no suit naming 5,515,480 was identified at all (see the "Litigation summary" section in this file). Absent an asserted suit there is no transfer "arranged to enable assertion."

6. Bankruptcy fire-sale — Not present. DP-Tek was acquired, not bankrupt, and HP was solvent throughout. There is no Chapter 7/11, no §363 sale, no Kodak/Nortel/Polaroid-style auction in this chain.

7. Privateering — Not present (operating-company dispute, if anything). The relevant adjacent dispute is HP vs. Xerox over DP-Tek-sourced print-resolution chips (Tech Monitor: HP ordered to supply Xerox 4,000 chips from "DP-TEK Development Co LLC," a Wichita company HP acquired in 1996; "the real dispute, over patents, continues"). If anything this is operating-company-vs-operating-company assertion of the acquired DP-Tek portfolio — the inverse of privateering. ⚠️ I could not confirm that US 5,515,480 was one of the patents at issue, and no case number/date was available, so this is contextual only.

8. Defensive aggregator (anti-NPE) — Not present. The chain terminates at HP, an operating company, not at RPX, AST, LOT Network, Unified Patents, or OIN. The patent has not been neutralized by a defensive aggregator.

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Verdict

Operating-company assertion (structural label; see caveat on the "assertion" half)

Justification (2–3 sentences): The chain runs from a genuine operating licensor (DP-Tek, Inc., whose TrueRes technology shipped in commercial printers) through its internal affiliate DP TEK DEVELOPMENT COMPANY, LLC (1996-06-03) into Hewlett-Packard Company (1997-08-01) and finally Hewlett-Packard Development Company, L.P. (2011-09-22) — a true operating company that incorporates the acquired DP-Tek resolution-enhancement technology into its LaserJet line, and not an NPE, a shell, or a defensive aggregator. Zero of the eight NPE signals is affirmatively present; signals #1, #2, #4, #5, #6, #7, and #8 are all "not present," and #3 is "unclear" solely because I could not retrieve correspondent data. Important caveat: I could not confirm any lawsuit naming this patent, so the "assertion" element of the label is unconfirmed — the accurate characterization is an operating-company portfolio asset, never shown to have been asserted — and the patent expired 2014-06-15, so no live assertion is possible today. None of the five verdict categories maps cleanly onto "operating-company-owned, non-asserted, expired"; I chose the operating-company category rather than "Insufficient data" because the ownership record is well-populated (five recorded events), and flagged the mismatch rather than papering over it.

Verify at: USPTO Assignment Center → https://assignmentcenter.uspto.gov/ (and the legacy index at https://assignment.uspto.gov/patent/index.html) — search patent number 5515480 or application 08/260,085 to read the reel/frame and correspondent I could not retrieve.

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What remains to be pulled to complete this record

1. Reel/frame for all five recorded assignments (Assignment Center, per record).
2. Correspondent of record for each entry — specifically, whether one attorney/firm recurs across entries 2–5 (the unreported signal #3).
3. Execution dates as distinct from recording dates (Assignment Center shows both; Google Patents collapses them).
4. DP-Tek's state corporate records (Kansas SOS) to confirm DP-Tek, Inc. and DP-Tek Development Company, LLC share the same registered office/principals in Wichita — the evidence here says they do, but it is aggregator-derived, not secretary-of-state-verified.
5. The Xerox/HP D. Kan. docket — to determine definitively whether 5,515,480 was among the asserted DP-Tek patents (signal #7).

Reminder — no fabrication: every reel/frame and correspondent field above is marked as unretrieved because I could not read them. Do not cite a reel/frame for this patent from this memo; pull them from Assignment Center.

I'll research US Patent 5515480 and its cited prior art references.

Let me look specifically at the "Patent Citations" section of US5515480.

Let me retrieve the actual patent document to read its "References Cited" section.

Scope, method, and verification caveat (read first)

I ran the searches against the Google Patents full-text record for US 5,515,480 A (which mirrors the USPTO's public data) plus secondary aggregators (Unified Patents, EveryPatent, EPO/Google cross-citation tables). I was not able to open USPTO PatentCenter/PTAB full-text directly with the tools available, so the citation list below is assembled from the Google Patents citation tables and cross-citation pages.

Important honesty flag: the front-page "References Cited" block could not be parsed line-by-line from the fetched HTML. What I could positively retrieve is (a) a set of pre-1994 references carried in the citation table associated with this record, and (b) a list of forward-citing patents. I mark clearly below which items are prior art (usable under §102) and which are forward citations (not prior art at all, and therefore incapable of anticipating). Where a specific column/line cite is not verifiable from what I retrieved, I say so rather than inventing one.

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1. Identification (interpreted literally)

The effective prior-art cutoffs are therefore §102(b): before 1993-06-15 (publication more than one year before filing), plus §102(a)/(e) for anything in the 1993-06-15 → 1994-06-15 window. Every reference listed in Section 3 predates the filing date by years, so §102(b) is the operative subsection.

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2. The claims that must be mapped (for §102 purposes)

From the claim text retrieved (EveryPatent/Google):

• Claim 1 (independent, system): a pulse generator providing an energization pulse for a current pixel in a current pixel period to an energizing element in response to a pulse code indication; a table containing a plurality of pulse code values optimized to enhance graphic features; and a feature detection circuit decoding multi-bit value patterns for each of a plurality of pixels in the raster source and responsively indexing a pulse code value in the table.
• Claim 6: detecting highlight and shadow features by detecting first/second threshold values in the pixels adjacent the current pixel → indexing respective sub-tables.
• Claim 7: detecting right and left edges by comparing multi-bit values of adjacent pixels → indexing respective sub-tables.
• Claim 8: table = memory providing stored values on an address input; feature detection circuit = combinatorial logic.
• Claim 9 (independent, system): marking engine + memory buffer storing multi-bit pixel values + transformation circuit receiving the value of a first pixel and at least one adjacent pixel → pulse code output; pulse patterns ranging from a fraction of a pixel period to a full pixel period and positioned within the pixel period (beginning / end / both) responsively to the window pattern; marks simulating edges, highlights, and shadows.
• Claims 10–12: charge-region/charge-density dependent mark formation; look-up table in a memory device; selection logic generating an address.
• Claim 13 (independent, method) and dependent claim(s) 14: method steps of determining a current-pixel value and transforming it (with neighboring values) into driving pulses.

The dispositive novelty is the combination of (i) a multi-bit, multi-pixel feature-detection window driving (ii) an indexed pulse-code table that selects both position (centered / left-justified / right-justified / split) and sub-pixel duration of the energizing pulse. A §102 reference must disclose all of that in one document to anticipate.

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3. Prior art for US 5,515,480 — retrieved references

All seven below are pre-1993 publications and thus §102(b) art as to the 1994-06-15 filing. Column/line citations are given only where the citation table itself supplied passages; otherwise the mapping is based on the reference's stated subject matter, and I flag it as inferred.

R1 — US 3,725,574 A

• Citation: US 3,725,574 A, "Method and apparatus for recording rastered continuous-tone pictures in printed graphics."
• Date: granted 1973-04-03 (pre-1993 → §102(b)).
• Description: Classic raster-recording reference; converts continuous-tone image values into modulated exposure of a rastered recording beam to produce the printed graphic. Establishes the general "grey value → modulated beam drive signal" art.
• §102 exposure: Potentially anticipates the broadest concept recited in claims 1/13 (grey values transformed into marking-engine drive signals). It does not disclose a multi-pixel feature-detection window, an indexed pulse-code table, or selectable pulse position within the pixel period, so it cannot anticipate claims 1, 6–9, 12 in full.
• Note: this reference also appears on the face of EP 0 291 300 A2, and in Google's cross-citation data the "Apparatus for producing an image" record is linked to US 5,515,480 — i.e., it is consistent with being citation-level art here. Attribution flagged as not independently line-verified.

R2 — US 4,040,047 A

• Citation: US 4,040,047 A (Thomson-CSF), "Erasable thermo-optic storage display of a transmitted image."
• Date: 1977-08-02 (§102(b)).
• Description: Thermo-optic erasable image storage/display; image formation by controlled localized heating of a medium.
• §102 exposure: Barely relevant. Addresses image storage/display rather than halftone pulse modulation of a laser marking engine; it does not disclose the claim-1 pulse-generator/table/feature-detection architecture. No anticipation of any claim of US 5,515,480.

R3 — US 4,198,154 A

• Citation: US 4,198,154 A (Canon Kabushiki Kaisha), "Image recording apparatus capable of representing half-tones on an image."
• Date: 1980-04-15 (§102(b)).
• Description: Recording apparatus that reproduces half-tones — i.e., tone reproduction on a binary/monotone recorder, the general problem addressed in the '480 background.
• §102 exposure: Relevant to the purpose and possibly to the general method of converting tone data into recording drive signals (claims 1/13, broadly). Does not disclose the feature-detection window or the two-bit position / six-bit duration pulse code, so no full anticipation.

R4 — US 4,553,172 A

• Citation: US 4,553,172 A (Dainippon Screen Mfg. Co., Ltd.), "Picture scanning and recording method."
• Date: 1985-11-12 (§102(b)).
• Description: Scanning/recording method for producing screened (halftone) reproductions using controlled exposure — the classic Dainippon Screen halftone-dot generation line of art.
• §102 exposure: The closest of the older references on the screening concept; potentially anticipatory of a broad claim reciting "transforming pattern value data into marking-engine drive signals to simulate grey levels," but silent on the specific pulse-position (centered/left/right/split) and neighbor-window indexing. No anticipation of claims 1, 8, 9, 12 as issued.

R5 — US 4,622,595 A

• Citation: US 4,622,595 A (Fuji Xerox Co., Ltd.), "Image display unit capable of tone reproduction."
• Date: 1986-11-11 (§102(b)).
• Description: Tone-reproduction image unit; gradation rendering.
• §102 exposure: Background art on tone reproduction; no teaching of a marking-engine pulse-code table or feature-detection window. No anticipation.

R6 — EP 0 207 246 A1

• Citation: EP 0 207 246 A1 (Dainippon Screen Mfg. Co., Ltd.), "Halftone image recording method and apparatus therefor."
• Date: published 1987-01-07 (§102(b) — foreign printed publication).
• Description: Halftone image recording method and apparatus; dot-formation control for screened output.
• §102 exposure: Relevant to the halftone-recording framework and to claims 1/13 in their broadest reading; does not disclose the claimed multi-bit adjacent-pixel feature-detection window indexing a pulse code that carries an explicit 2-bit position + 6-bit duration encoding. No anticipation.

R7 — US 4,661,859 A ← most on-point reference

• Citation: US 4,661,859 A (Xerox Corporation), "Pulse width modulation greyscale system for halftone printer."
• Date: 1987-04-28 (§102(b)).
• Description: A halftone printer in which greyscale is produced not by clustered dot growth but by modulating the width (duration) of the marking pulse for each pixel location. This is the single reference most directly aimed at the "sub-pixel mark sized by pulse duration" concept that the '480 specification identifies as the starting point of the art ("...several implementations have divided the pixel period of the laser by 16...").
• §102 exposure: This is the reference with genuine §102 bite. It can plausibly anticipate a claim limited to "drive the marking engine with pulses of fractional pixel-period duration to obtain more grey levels." However, on its face it does not disclose (a) a feature-detection window comprising the current pixel plus its four orthogonal neighbors' multi-bit values, (b) a look-up table indexed by the detected value pattern returning an optimized pulse code, or (c) selectable pulse position within the pixel period (centered / beginning / end / split) chosen according to adjacent-pixel values. Because claims 1, 8, 9 and 12 each expressly require those elements, R7 does not anticipate them; it is better characterized as §103 (obviousness) art. Note also that US 4,661,859 appears on the face of EP 0 291 300 A2.
• Caution: I could not verify an examiner-applied passage citation for R7 in the record I retrieved; the mapping above is from the reference's title/subject matter.

Summary table

No reference in this set discloses all elements of claims 1, 6–9, 12 or 13. On the retrieved record, no single reference anticipates the issued claims; the closest is R7 (US 4,661,859), and even it omits the feature-detection window, the indexed pulse-code table, and pulse-position selectivity.

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4. Items that are NOT prior art (forward citations) — do not use for §102

The cross-citation tables also surfaced patents that cite US 5,515,480 (i.e., they post-date it). These are §102(a) irrelevant because they are later in time, and they cannot anticipate:

• US 6,184,916 B1 — Xerox, "Multiple-pulse, pulse width and position modulation systems and methods" (2001) — interestingly a descendant of the '480 concept.
• US 5,959,656 A — Korea Electronics Technology Institute, "Method and apparatus for enhancing laser printer resolution by using a laser beam modulation technique" (1999).
• US 5,630,026 A — Compaq Computer Corp., "Toner saver using anti-aliasing apparatus and methodology" (1997).
• US 5,657,430 A — Hewlett-Packard Co., "Software-based procedure for conversion of a scalable font character bitmap to a gray level bitmap" (1997).
• US 5,742,708 A — Xerox Corp., "Method and system for performing perspective projection conversion" (1998).
• US 5,786,994 A — Imation Corp., "Performance monitoring system and method for a laser medical imager" (1998).

Also worth noting for the record (not prior art, but same-field linkage): the Google/EPO cross-citation table for EP 0 291 300 A2 ("Apparatus for producing an image") lists US 5,515,480 A among its citing documents, which is consistent with EP 0 291 300 A2 being cited by (and therefore being prior art to) US 5,515,480. If that cross-link is accurate, EP 0 291 300 A2 should be added to the §102(b) list and analyzed on the same footing as R1/R4/R6 — I could not verify its full citation list or publication date from the retrieved content, so I am reporting it as a flag, not as a confirmed citation.

Aggregator counts (for completeness): Unified Patents shows "Patent Art (10)" and "Referenced By (131)" for this record; Google's tables in one cross-linked view showed "Cited By (32)". The discrepancy means my list of 7 positively-dated references is likely incomplete — expect roughly 3 additional pre-1994 references (possibly including EP 0 291 300 A2) on the actual front page.

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5. Bottom line

1. Patent identified literally: US 5,515,480 A / App. 08/260,085 / filed 1994-06-15 / granted 1996-05-07 / DP-Tek → HP / Expired-Lifetime.
2. Prior-art cutoff: §102(b) before 1993-06-15; §102(a)/(e) for 1993-06-15 to 1994-06-15. All seven retrieved references fall under §102(b).
3. Most relevant prior art: US 4,661,859 A (Xerox, "Pulse width modulation greyscale system for halftone printer," 1987-04-28) is the single most pertinent reference and the only one with realistic §102 potential — but only against a claim directed to bare PWM greyscale. US 4,553,172 A (Dainippon Screen, 1985) and EP 0 207 246 A1 (Dainippon Screen, 1987) are the next most relevant as halftone-screening art.
4. No retrieved reference, alone, anticipates claims 1, 6, 7, 8, 9, 12 or 13, because none discloses the combination of a multi-bit four-neighbor feature-detection window + indexed pulse-code table + selectable pulse position (centered/left/right/split) within the pixel period. Those references are properly §103 art, not §102 art, as to the issued claims.
5. Verification caveat: because I could not line-parse the printed "References Cited" block from the fetched pages, the exact examiner-cited list (reported as ~10 references) should be confirmed against the granted patent's front page or USPTO PatentCenter before this is used in any §102/§103 chart. The seven references above are the pre-1994 references I positively retrieved with dates; EP 0 291 300 A2 is a probable additional citation that I could not confirm.

I'll ground this obviousness analysis by verifying the key references and probing for the specific missing claim elements (window-indexed LUT; selectable pulse position).

Obviousness Analysis — US 5,515,480 under 35 U.S.C. § 103

Analyst note on method. Per the operating rules, I treated the Prior Art section of this file as the base reference set, then ran targeted verification searches because that section itself flagged that its citation list was incomplete (it positively retrieved only 7 pre-1994 references against an expected ~10, and could not line-parse the printed "References Cited" block). The searches materially changed the analysis: they confirmed R7 in full and surfaced several §102(b) references the prior-art section did not have, including the applicant's own earlier DP-Tek patent (US 5,134,495). I flag every reference below as either "[prior-art section]" or "[verified this session]".

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0. Two contradictions to flag before anything else

1. Claim 1's statutory category is inconsistent across sections. The "Patent summary" section describes claim 1 as a method claim ("Method (pulse-position method)"), while the "Prior art" section describes claim 1 as an independent system claim ("a pulse generator… a table… a feature detection circuit"). These cannot both be right. Everything below is written against an element inventory (§2) rather than against a claim number, so the analysis survives either reading — but if you are filing anything, pull the claim set from Patent Center's Claims tab first.
2. Claim count is inconsistent. The "Patent summary" section said it could not confirm any claim beyond 12 and did not know the total; the "Prior art" section asserts a method claim 13 and dependent claim 14, and the "Patent summary" section independently noted that the German family member (DE 69532445 T2) carries a calibration-type claim. Those are reconcilable (a US method + calibration claim set matching the DE counterpart), but neither section retrieved the US claims from an official source. Treat claims 13–14 as probable but unverified.

Neither contradiction affects the §103 bottom line, because the same combination disposes of the system claims, the method claims, and the calibration claim.

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1. Legal framework and the person of ordinary skill

Framework: Graham v. John Deere Co., 383 U.S. 1 (1966) (scope/content of prior art; differences; PHOSITA level; secondary considerations), as recalibrated by KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), and applied through the exemplary rationales of MPEP § 2143. A combination is obvious where a reference teaches or suggests the claimed element, or where the element is a known design choice, a predictable variation, or the product of routine experimentation (KSR, 550 U.S. at 417, 421, 427).

PHOSITA (as of June 1994): a B.S. in electrical engineering or computer science (or equivalent), with 2–4 years designing raster image pipelines for electrophotographic laser printers — specifically pulse-width modulation of laser diodes, halftone screening, and look-up-table-based image transformations. This is a mature art: by 1994 the field had a decade-plus of patents on PWM halftoning (R7 alone dates to a 1981 priority), and the specification's own Background confirms the artisan was expected to know sub-pixel PWM, gamma-correction tables, and dot-gain/overcoverage phenomena.

Critical admission in the specification (usable as prior art): The '480 Background concedes the state of the art:

"several implementations have divided the pixel period of the laser by 16, and have attempted to provide 16 different dot sizes… Usually, such dots are centered on the pixel region location… most marking engines will not create a mark or dot when the centered pulse width is less than a certain duration."

That admission establishes (a) sub-pixel, pulse-duration-controlled laser marking was known; (b) a per-pixel duration code driving the laser was known; and (c) the known failure mode was that centered small pulses fail to mark and long pulses over-cover. That is precisely the problem the '480 purports to solve — and it frames the obviousness question as: was it obvious, by 1994, to shift pulse position based on neighboring pixels and to implement the mapping as an indexed look-up table?

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2. Claim-element inventory (as reconstructed)

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3. Reference set and element-by-element teaching

3.1 The base set from the prior-art section [prior-art section]

3.2 R7 — US 4,661,859 ("Pulse width modulation greyscale system for halftone printer") — the primary reference [verified this session]

Formerly the prior-art section could only map R7 from its title. The verified text changes R7's weight substantially. R7 discloses:

• A six-bit greyscale data word per pixel, conveyed to a counter and converted into a variable-width laser pulse — i.e., a duration code per pixel.
• "Each pixel is divided up into 64 states" via a "divide by sixty four circuit" — precisely the '480's 6-bit duration field / 1-64 granularity (E4, E6). This is a direct, numerical identity, not an analogy.
• The laser is on for the first N/64 of the pixel period (data word 63 → on for 1 of 64 periods), i.e., a pulse anchored at the beginning of the pixel period — the '480's "beginning-positioned / left-justified" mode (E7, first position).
• A step wedge generator 62 that "provides a sequence of greyscale signals to develop a test pattern for monitoring system operation," plus a manual switch to insert a particular greyscale value — i.e., calibration/test-pattern infrastructure (E10 in kind).
• A raster output scanner driven from a controller with a video rate and a 64× carrier — the architecture the '480 physically plugs into.

What R7 does not teach: multi-bit adjacent-pixel pattern detection, a LUT indexed by such a pattern, or pulse position selected among plural discrete positions as a function of neighbors. R7 therefore does not anticipate E2/E3/E7 — but it supplies E4, E5, E6, E10 and half of E7 outright.

Source: https://patents.google.com/patent/US4661859 (claims 1–4; PDF at patentimages.storage.googleapis.com/e1/88/3b/1557e052f80920/US4661859.pdf)

3.3 US 5,134,495 — DP-Tek/Frazier, "Resolution transforming raster-based imaging system" — the closest art, and it is the applicant's own [verified this session — NOT in the prior-art section's list]

This is the single most important finding of this session, and its absence from the prior-art section's seven-item list is itself a red flag (see §7).

• Filed 1990-11-07; issued 1992-07-28 — more than one year before the '480's 1994-06-15 filing. It is therefore §102(b) prior art ("patented… more than one year prior to the date of the application") regardless of the common inventor/assignee. Pre-AIA §103(c)'s common-ownership safe harbor does not reach §102(b) patents or printed publications — it reaches subject matter qualifying "only under… (e), (f), and (g)." A DP-Tek engineer analyzing this claim set in 1994 could not have screened out the company's own '495 on common-ownership grounds.
• Its abstract recites modifying a laser printer so that "overlap areas… exceed the device threshold" to produce dots at non-native positions, achieved by "modifying the duration that the energy source is activated, by the placement of less-than-full-extent energy actuation within the pixel extent, by activating the energy source multiple times within a pixel extent, by modulating the intensity… and by modulating the shape of the energy cluster." That sentence alone covers E4 (duration + placement), E6 (fractional to full), E7's "split" (multiple activations within one pixel extent), and E9 (threshold-exceeding overlap charge = the '480's claim 10).
• FIG. 11–13 disclose a three-by-three template structure and a "Modulation Table" mapping template states to pulse widths, with state-dependent pulse widths selected from the template contents — e.g., the "P2" interleaved-line state uses 7/16 pulse width at some neighbor positions and 8/16 at others, depending on which scan line is evaluating the dot. That is: a table of pulse-duration codes, indexed by a multi-pixel neighborhood pattern (E2, E3, E5).
• It is expressly directed to producing halftone screens on angles and interleaved dots — the same §101 subject matter as the '480.

Source: https://www.freepatentsonline.com/[5134495](/patent/5134495).html; US 5,193,008 ("Interleaving vertical pixels in raster-based laser printers," same DP-Tek family) is its sibling. Caveat: I could not open US 5,193,008's front page this session; its issue date should be verified before it is cited, though it is at least §102(e) art and likely §102(b).

3.4 Additional references verified this session

Explicitly NOT prior art (do not use in this chart): US 7,064,859 B1 ("generating a table for enhancing print quality… position information indicating a justification of the sub-pel region within the pel") and US 6,184,916 B1 (multiple-pulse PWPM). Both are HP/Xerox descendants that cite the '480. They are the best evidence that the industry regarded the '480's approach as the natural next step — but as post-1994 documents they cannot be used under §102. Their proper use is as objective evidence that the claimed subject matter was the predictable next design step, which cuts against nonobviousness, not for it.

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4. The combinations, and why a PHOSITA would have made them

Combination A (primary): R7 + US 5,134,495

Coverage: E2, E3, E4, E5, E6, E7, E9, E10 — everything except the express word "split" and the express highlight/edge/shadow sub-table labels.

Motivation, articulated:

• Same field, same problem, same hardware. Both address a 300 dpi laser marking engine; both exploit the additive overlap of charge regions; both are the same company's work product on the same product line (DP-Tek's TrueRes/PhotoTone technology).
• R7 supplies the duration half; the '495 supplies the context half. R7's six-bit/64-state duration code (E4, E6) is structurally coincident with the '480's duration field. The '495 supplies the neighbor-context selection (its 3×3 template/Modulation Table with position-dependent 7/16 vs. 8/16 widths). A PHOSITA with R7's data word in hand and the '495's template look-up in hand has, in combination, the claimed pulse code — the only thing an artisan need do is concatenate a position field to a duration field, which is a known data-formatting choice (MPEP 2143 rationale (A), and KSR's "predictable results").
• The references supply the reason. R7's own test-pattern/step-wedge facility exists to characterize the engine's marking limits — the same problem the '480's calibration procedure addresses. The '495 expressly motivates selective activation below threshold in some pixels and above threshold in others precisely because single-pixel full pulses over-cover.

Assessment: Strong. Claims E4/E5/E6 are met almost verbatim by R7; E2/E3/E7/E9 are met by '495; the difference is a formatting/housekeeping difference with no unexpected result.

Combination B: R7 + EP 0 564 868 A2 (or WO 91/13512) + US 5,185,852

Coverage: E2, E3, E4, E6, E7, E10.

Motivation, articulated: This is the cleanest three-reference combination, each element sourced from a reference that expressly states the deficiency it cures:

1. R7 — 64-step sub-pixel PWM duration (E4, E6).
2. EP 0 564 868 — explicitly identifies the defect of centered PWM ("white spots are caused and the sharpness of the image is lowered") and cures it by displacing the pulse position according to the density of the objective pixel and its adjacent pixel (E2, E7). This is the strongest, most explicit motivation-to-modify in the entire set: the reference's stated purpose is the '480's left/right-justified and split modes.
3. US 5,185,852 — teaches implementing the neighborhood→value mapping as a look-up table whose values are derived from a "learning pattern" (E3, E10), which is the '480's calibration procedure in substance.

Assessment: Strong, and it independently corroborates Combination A. Note the 1.131 swearing-behind vulnerability of EP 0 564 868 (within one year of filing) — which is why Combination A (all §102(b) art) is the primary theory.

Combination C: WO 91/13512 + R7 (+ US 4,661,859 alone for E4)

WO 91/13512 already teaches displacement of a halftone dot from the cell center as a function of the neighboring pixels' center of gravity, implemented from a lookup table — the inventive core of the '480, published in 1991 and thus §102(b). Adding R7 for the 64-step duration encoding yields E1–E7. Assessment: strong, and useful because WO 91/13512 is §102(b) art that the applicant cannot swear behind.

Combination D: EP 0 533 299 / EP 0 216 462 + R7 + US 5,134,495

For E10 specifically ("optimized"/calibrated codes): EP 0 216 462 (1987) teaches a digital LUT for gamma-correcting video data before PWM comparison into a print engine. A PHOSITA combining that with R7's step-wedge test pattern and '495's Modulation Table has the "optimized pulse code table" as a matter of routine engineering. Assessment: strong for E10.

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5. Rationales (MPEP § 2143 / KSR)

"Optimized" (E10) is not a patentable distinction. "Optimized"/"near-optimum" is a result-oriented limitation entitled to no separate weight (In re Trovato), and the pulse-code values stored in the LUT are non-functional descriptive material — a data set whose particular numeric contents cannot render an otherwise obvious memory-plus-logic structure patentable (In re Lowry). The structural elements the claims rely on (memory, combinatorial address logic, pulse generator) are all in '495, '852 and '985.

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6. Claim-by-claim conclusion

No element of the reconstructed claim set is missing from the combined prior art. The only limitations for which I cannot point to explicit disclosure are (i) the "split" pulse as a specifically labeled mode (though '495's "activating the energy source multiple times within a pixel extent" is the same thing) and (ii) the exact suite of highlight/midtone/shadow sub-table names. Both are labeling/optimization differences, not technical ones.

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7. Where this analysis is vulnerable — and one issue that is not obviousness

Vulnerabilities to be honest about:

1. Claim text is unverified. All mapping is against reconstructed claims. If the issued claims contain a limitation I have not seen (e.g., a specific structural relation between the position field and the duration field, or a specific "first and second threshold" numeric relation in claim 6), the mapping must be re-run. Pull the claims from Patent Center before using this chart.
2. The '495 is the applicant's own work and 103(c) may be argued (incorrectly). Expect a plaintiff to assert common ownership defeats reliance on DP-Tek's own patents. That argument fails for the '495 because it is §102(b) art (issued 1992-07-28, >1 year pre-filing), and pre-AIA §103(c) reaches only art qualifying "only under (e), (f), and (g)." But be ready to brief it.
3. Two of my strongest secondary references are provisionally dated. US 5,390,263 and US 5,387,985 depend on filing dates I could not confirm this session; if either was filed after 1994-06-15 it is not §102(e) art. Verify before relying on them. The primary theory (Combination A) does not depend on them.
4. EP 0 564 868 A2 is §102(a) art (published within one year of filing) and is swearable-behind under 37 CFR 1.131. Do not build the case on it alone; use it as corroboration for Combination A.

An issue separate from §103 that the record raises: The prior-art section retrieved seven pre-1994 references and flagged that the list was likely incomplete, yet the list contains neither US 5,134,495 nor US 5,193,008 — two DP-Tek/Frazier patents directly on point and more than one year before the '480 filing. Either the examiner did not cite them (raising a § 102(b) and, potentially, inequitable-conduct question in a 1996-vintage prosecution) or the secondary-source retrieval simply missed them. This should be resolved from the '480's official file wrapper before any of the above is used in a filing — it is the kind of omission that changes how a defendant frames the case, and it is not something an aggregator page can settle.

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8. Bottom line

1. The claimed advance over the art is narrower than the prior-art section's bottom line suggested. That section concluded "no reference, alone, anticipates claims 1, 6–9, 12 or 13." That remains true reference-by-reference — but § 103 does not require a single reference, and the combination closes every element.
2. R7 (US 4,661,859) is stronger than the prior-art section could show. It discloses a six-bit, 64-state pulse duration — numerically identical to the '480's duration field — anchored at the beginning of the pixel period, with a test-pattern generator. It supplies E4, E5, E6 and one of E7's four positions outright.
3. US 5,134,495 (DP-Tek/Frazier, issued 1992-07-28) is the closest art in existence and is §102(b) prior art against the '480 despite common ownership. It discloses the 3×3 template, a "Modulation Table" of neighbor-dependent pulse widths, multiple activations within one pixel extent, and threshold-exceeding charge overlap (the '480's own claim 10 mechanism).
4. The motivation to combine is unusually well documented. EP 0 564 868 A2 and WO 91/13512 each state the purpose of the '480 — displacing the PWM pulse from the pixel center based on adjacent pixel density to eliminate edge white-spots — years before the '480 was filed.
5. "Optimized" pulse codes carry no patentable weight. The LUT contents are non-functional data (Lowry); "optimized" is result-oriented (Trovato); and the calibration procedure is a method of making, not a claim limitation.
6. The practical consequence is the same as the earlier sections': this is an academic exercise. With expiration in June 2014 and the § 286 lookback now reaching only September 2020, no §103 chart will ever be litigated on this patent. Its value is (a) completeness of the invalidity record under § 282, and (b) the file-wrapper question in §7 about the uncited DP-Tek patents — which is the only loose thread here that a court or an acquirer could still care about.