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.

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.

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."

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.

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.

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.

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 for litigation involving US patent 5515480 across patent litigation sources.

Let me search more specifically for litigation involving this patent and its original assignee/owner.

Let me search for the specific DP-Tek litigation and check the Unified Patents litigation portal directly.

US Patent 5,515,480 — Litigation Search Results

Bottom line: Based on the patent-litigation sources I was able to search (Unified Patents litigation portal, Google Patents, PACER-oriented opinion databases, and general case-law databases), I found no confirmable litigation record specifically asserting U.S. Patent No. 5,515,480 ("System and method for enhancing graphic features produced by marking engines," Allan Frazier, originally assigned to DP-Tek, Inc., now Hewlett-Packard Development Co. LP). I am stating this as a "not found / not confirmed" result rather than certifying a global negative, because not every 1990s-era docket is fully indexed in the free databases.

What I verified about the patent itself

• Patent number: US 5,515,480 (Application No. 08/260,085), granted May 7, 1996, priority/filing June 15, 1994, anticipated expiration June 15, 2014. — Google Patents: https://patents.google.com/patent/US5515480/en
• Unified Patents entry: https://portal.unifiedpatents.com/patents/patent/US-5515480-A — the entry shows bibliographic data, family members, forward citations, and patent ratings, but no litigation listing. Unified Patents' litigation portal (https://portal.unifiedpatents.com/litigation/caselist) did not return a case tied to this patent number in my searches.
• Assignee chain: DP-Tek, Inc. → DP-Tek Development Co., LLC (1996) → Hewlett-Packard Co. (1997) → Hewlett-Packard Development Co., L.P. (2011). — Per the Google Patents reassignment record above and Plainsite profile: https://www.plainsite.org/profiles/dp-tek-inc/

Related disputes I did find (NOT confirmed to involve the '480 patent)

These are corporate/vicinity disputes involving the patent's original assignee, but I cannot confirm that US 5,515,480 was an asserted patent in them:

1. DP-Tek, Inc. v. AT&T Global Information Solutions Co. (NCR Corp.)

   • Citation: 891 F. Supp. 1510 (D. Kan. 1995), aff'd, 100 F.3d 828 (10th Cir. 1996).
   • Subject matter: This was a tortious-interference action (DP-Tek alleged NCR interfered with DP-Tek's prospective business contract concerning a laser-printer retrofit unit). It was a diversity case appealed to the Tenth Circuit, not the Federal Circuit, and it was not a patent-infringement suit.
   • Outcome: Summary judgment for NCR affirmed.
   • Sources: https://openjurist.org/100/f3d/828 and https://www.courtlistener.com/opinion/[154175](/patent/154175)/dp-tek-inc-v-at-t-global-information-solutions-co/
   • ⚠️ I could not confirm the district-court docket number or that the '480 patent was at issue. No case number for the district court is asserted here.

2. Xerox / Hewlett-Packard dispute over DP-Tek print-resolution-enhancement technology

   • Reported by Tech Monitor: a U.S. District Court judge in Wichita, Kansas ruled HP had to supply Xerox 4,000 chips sourced from "DP-TEK Development Co LLC," the Wichita company HP acquired in 1996; the article states "The real dispute, over patents, continues." — https://www.techmonitor.ai/technology/xerox_wins_one_round_of_its_battle_with_hewlett_packard
   • ⚠️ The article does not name a patent number, case number, or filing date, and I could not confirm that US 5,515,480 was among the patents asserted. This is circumstantial/adjacent information only.

3. HP-Gateway ITC/§ 337 matters and other HP printer patent suits surfaced in searches, but these involve different patents (e.g., the '184, '976, '318 patents) and are not tied to 5,515,480.

Important disambiguation warning

Several search hits referred to "the '548 patent." In every instance I examined, that shorthand referred to a different patent number — e.g., US 6,398,548 (Align Technology/Ormco orthodontic litigation) and the '548 patent in the Alcon/LenSx surgical-system IPR. Those are not US 5,515,480 and must not be conflated with it. No auto-correction or merging has been applied.

Table of results (as found)

Recommendation / caveat

• To get a definitive answer, the authoritative checks would be PACER (the district-court dockets for D. Kan., N.D. Cal., D. Del., E.D. Tex., etc.), the USPTO Patent Assignment and Patent Center records, and Lex Machina / Docket Navigator patent modules, which index patent assertions by patent number. My free-source searches did not surface a case asserting the '480 patent, but I cannot rule out an unindexed 1990s docket.
• I do not know with high confidence that any litigation exists specifically asserting US 5,515,480, and I have not fabricated any case numbers or filing dates to fill that gap. If you need certainty, I'd recommend the paid docket search noted above.

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.

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.

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.

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.

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."

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.

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

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.

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.

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.

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.

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.

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.

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.

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 analysis in verifiable prior art rather than relying on memory. Let me search for the relevant references.

Good — I've located several probative references. Let me verify bibliographic details on the most important ones before relying on them.

Scope, inputs, and flagged discrepancies

Before the analysis, three input problems that affect how you should read what follows:

1. No separate "Prior Art section" was supplied. The materials I was given contain only two previously generated sections — "Patent summary" and "Litigation summary" — neither of which is a prior-art reference list. The only prior-art data actually present in the record is (a) the Google Patents header field "Prior art keywords: pixel / pulse / marking engine / value / pulse code", and (b) the patent's own "Description of the Related Art" in the full text. I have used both, and supplemented them with my own searches. If a curated prior-art list existed on "this page," it did not reach me — treat that as a gap rather than an omission on my part.

2. Conflicting "current date." This task says April 26, 2026; the previously generated sections and the fetched patent text both say 2026-09-27. Immaterial to §103 (the patent expired 2014-06-15), but flagged per the standing instruction.

3. The verbatim claim set is still not in hand. The prior sections state that claims 1–4 and anything above claim 12 were only partially recovered, and that the total claim count is unknown. My analysis below is therefore claim-by-claim on claims 1, 5–12 as reconstructed, and I mark where the reconstruction (not the art) is the weak link. I have not auto-corrected "Cannon NX," "CO Hex" (the patent's OCR of "C0 Hex"), or any patent number.

Legal framework and the level of ordinary skill

Under Graham v. John Deere, 383 U.S. 1 (1966), and KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), the analysis turns on scope/content of the prior art, differences from the claims, PHOSITA level, and secondary considerations. Two doctrines do most of the work here:

• Applicant admissions as prior art. A patent's own specification can supply the prior art. In re Fout, 675 F.2d 297 (CCPA 1982); MPEP 2129. The '480 specification contains unusually damaging admissions (below).
• Combination of known elements. Where a known technique has been used to improve a similar device in the same way, the combination is likely obvious. KSR, 550 U.S. at 417.

POSITA (proposed): a B.S.-level engineer with 2–4 years in electrophotographic raster-output-scanner (ROS) design, familiar with pulse-width modulation, digital halftoning, LUT-based tone reproduction, and hardware implemented between a printer formatter and a laser driver. This is if anything a high level of skill for 1994 — which helps the patentee, and I account for that below.

Claim-construction anchors (limitations that drive the analysis)

Prior-art inventory (with verification status)

I have flagged every bibliographic fact I could not independently confirm. Do not let an unverified date silently become a §102 date.

The patent's own admissions (usable prior art under In re Fout)

These are the most efficient §103 ammunition, because no reference needs to be produced for them:

• Sub-pixel PWM was known: "several implementations have divided the pixel period of the laser by 16, and have attempted to provide 16 different dot sizes … the pulse being centered in the pixel period interval."
• The marking-limit problem was known: "most marking engines will not create a mark or dot when the centered pulse width is less than a certain duration, such as 7/15 or 8/15 of the pixel period."
• Mark-overlap physics was known: "marks or spots that can be 2-3 times as large as the specified pixel region"; charge regions "exceed the boundaries of a given pixel region, overlapping with adjacent pixel regions," and the effect "is additive in the overlapping regions."
• Gamma correction, halftone cells, and the ~10-usable-of-33-grays problem were all known.

Claim-by-claim §103 analysis

Claim 1 (method — energizing pulses at selected positions in a pixel period)

Anticipated or obvious over WO 91/13512 alone. WO '512 discloses a driver that creates "independently-locatable signal transitions … with great precision within a cell print area," "zero, one, two or three … times per cell print area," locatable "to the precision of at least 1/64th … of the cell scan time." Zero/one/two/three transitions per cell is, respectively: no pulse; a left- or right-justified pulse; a centered pulse; and a split pulse — the exact four positions the '480 claim recites. To the extent the '480 claim requires the selection among those positions responsive to data, WO '512's "reproduce the center of gravity of the input image data within a cell" and "displace the printed halftone dot horizontally or diagonally" supply it.

Secondary combination: US 4,800,442 (variable-duration PWM pulses in a pixel period, admittedly centered) + WO '512 (positioning). Motivation: combining known duration control with known position control is the predictable use of two known techniques to improve gray-level fidelity and edge placement — precisely KSR's "arrangement of old elements" with "predictable results." Both are in laser-ROS imaging.

Claim 5 (system: pulse generator + optimization table + feature-detection circuit; pulse code encodes duration and at least one position)

This is the strongest independent claim and the hardest to reach with one reference. Three-way combination:

1. US 4,847,641 (Tung) — supplies the architecture verbatim: a feature-detection window (central bit + neighbors), a logic array matching the window against stored patterns, and an index matching table outputting a replacement value for the center pixel, interposed between the formatter and the laser. A POSITA would substitute multi-bit gray values for Tung's binary bits as a matter of routine engineering, because the '480 input (4-bit gray) and multi-bit gray halftone sources such as US 5,124,802 were already in the field.
2. US 4,800,442 (or US 4,873,537) — supplies a memory LUT whose stored values are chosen to correct the engine's non-linear tone response, i.e., "pulse code values optimized to enhance graphic features produced by the marking engine." US 4,800,442's express statement that linear mapping is unacceptable supplies the motivation to populate the table empirically rather than linearly.
3. WO 91/13512 — supplies the position half of the pulse code (independently-locatable transitions, 1/64 precision).

Motivation to combine (articulable, MPEP 2143): (i) same field (enhanced ROS printing); (ii) same problem (insufficient usable gray levels plus poor edge fidelity — expressly recited in US 5,124,802 and WO '512); (iii) Tung's binary template substitution cannot place a partial mark within a pixel, whereas WO '512's transition modulation can — thus a finite number of prior-art elements combines to yield the claimed arrangement; (iv) all three are physically combinable between formatter and laser driver, and Tung teaches precisely that location for such circuitry.

Claims 6 and 7 (highlight/shadow sub-tables; right/left-edge sub-tables)

Claim 6: US 5,124,802 names the highlight defect ("highlight portions become too white") and US 4,847,641 discloses organizing empirically derived patterns and their compensation signals into an "index matching table" — dividing that table into feature-specific sub-tables is a design choice with no new technical effect. US 5,479,263 (if it qualifies under §102(e)) adds that the pixel "decode tables" are modifiable per printer process control. Claim 7: US 4,544,264 and US 4,625,222 are directed to exactly edge enhancement via modulated dot size/position; combining them with Tung's window logic yields the recited "compare values of adjacent pixels → index an edge sub-table."

Claim 8 (memory + combinatorial logic producing the address)

US 4,847,641 + US 4,800,442. Tung's "index matching table implemented in a high speed parallel logic array" is a memory addressed by pattern-match logic; US 4,800,442/4,873,537 use a ROM/RAM look-up table addressed by digital video. Combining an addressed memory with combinatorial address-generation logic is the definition of the admitted art. EP 0 592 775 A2 independently discloses window-comparison logic substituting an enhanced center-pixel representation — a second, independent route to claim 8.

Claim 9 (marking engine + buffer + transformation circuit + window across scan lines; fraction-to-full pulse patterns at beginning/center/end/both)

US 4,847,641 + WO 91/13512 + US 4,800,442.

• Buffer storing multi-bit pixel values across lines: Tung's FIFO storing "successive lines of the bit map"; US 5,124,802's page memory/line buffer.
• Window covering the same and adjacent scan lines: Tung's sample window; the '480's 1×3×1 cross is an obvious sizing choice.
• Pulse patterns "from a fraction of a pixel period to a full pixel period": US 4,661,859 (64 states per pixel), US 4,800,442 (PWM), US 5,124,802.
• Four positions including split: WO 91/13512 ("zero, one, two or three" transitions).

Claim 10 (charge region per pixel; marks where a predetermined charge density is exceeded)

This claim is largely an admission. The '480 specification itself states that energization creates "a substantially circular" charge region, that regions "overlap with adjacent pixel regions," that the charge effect "is additive in the overlapping regions," and that toner is attracted "wherever the charge density exceeds a given threshold." Add US 5,387,985 (residual/fringe energy at the periphery of an adjacent pixel) and US 5,134,495 (multiple sub-threshold exposures cumulating) for the same physics, and claim 10 adds no patentable weight.

Claims 11 and 12 (LUT in memory device; selection logic providing the address)

US 4,800,442 / US 4,873,537 (gamma ROM/RAM LUT) + US 4,847,641 (parallel logic array producing the index) + EP 0 592 775 A2 (comparison logic). Straightforward.

Where the patent retains non-trivial argument (a balanced view)

I do not want to overstate the case. The following are real weaknesses in a §103 attack:

1. No single verified reference discloses indexing a LUT with a window of multi-bit gray values to output a combined position+duration code. Tung uses binary bits; WO '512 doesn't use a neighborhood window; US 5,479,263 and US 5,387,985 — the closest on the code structure — both issued in 1995 and their filing dates are unverified, so they may not be §102(e) art at all. A patentee will argue this is the point of novelty.
2. US 5,479,263 and US 5,387,985 must be date-cleared first. If either was filed after 1994-06-15, it drops out entirely. This is the single highest-value verification step remaining, and I could not complete it.
3. Claim 6's "first and second threshold values" (the spec's 0 and F) is narrower than a generic comparator; a reference using a magnitude comparison (e.g., PB ≥ PC) may not literally meet it.
4. Teaching away, in theory: US 5,124,802 teaches that narrow pulses fail to develop — a patentee could argue this discourages sub-pixel marks rather than the '480's "growing" approach. In practice this argument is weak, because the '480 patent itself asserts the same problem and solves it with the same family of techniques (position + neighbors), so the reference confirms rather than negates the motivation.
5. Secondary considerations are largely unavailable: the record before me shows no evidence of commercial success, licensing, or copying tied to these claims, and the patent expired in 2014.

Bottom line

Claims 4–12 of US 5,515,480, as reconstructed, are strong §103 candidates on the combination:

US 4,847,641 (Tung) + WO 91/13512 + US 4,800,442 (or US 4,873,537), optionally adding US 4,544,264 / US 4,625,222 for the edge claims, US 5,124,802 for the highlight claims, and US 5,387,985 / US 5,134,495 for the charge-density claim — with the specification's own admissions supplying the balance of the obviousness case under In re Fout.

The strongest single-reference attack is WO 91/13512 against claim 1 (position-selected pulses with 1/64 precision and 0–3 transitions per cell) and US 4,847,641 against claims 8 and 12 (window + logic array + index table + interrogation between formatter and laser).

The weakest link in the attack is claim 5's combination of (a) a multi-bit feature window and (b) a single code that encodes both position and duration. Clearing the dates on US 5,479,263 and US 5,387,985 would materially strengthen that attack; I could not clear them, and I have not assumed they qualify. Likewise, if the actual granted text of claim 1 differs from my reconstruction, the claim-1 conclusion should be re-run before it is relied upon.