US 6034371

I'll search for this patent and for any related litigation.

Now let me check for any litigation or CAFC activity, and verify the legal status.

US Patent 6,034,371 — Search Summary

Search scope note: I searched for the exact identifier "6034371"/"6,034,371" against patent databases (Google Patents, Justia, EveryPatent, RPX/Insight) and general web sources for the USPTO and Court of Appeals for the Federal Circuit 2026 dockets. I found no CAFC 2026 docket entry, appeal, or active litigation involving this patent. The only hits were bibliographic/technical. I did not auto-correct the number; all results correspond to US 6,034,371 exactly, and I disregarded hits for neighbouring numbers (e.g., US 6,034,371 family members such as US 5,952,661, US 6,437,332, US 5,266,286).

Bibliographic data

Foreign family (method/apparatus counterparts): WO 98/28602 A1; GB 2336965 A; DE 19782195 T1; AU 55330/98 A — all reported as not granted/withdrawn, ceased or abandoned.

Abstract (as issued, verbatim)

"Thermal imaging chopper (22) having a frame (42) with an open window (47) and a covered window (48). The covered window (48) is preferably covered with a material that partially blocks a selected amount of thermal radiation from a scene and randomly scatters the remaining thermal radiation from the scene that is transmitted through the covered window. The open window (47) allows unrestricted transmission of thermal radiation from the scene."

(Note: the abstract's reference numeral "(22)" for the chopper is inconsistent with the specification, where 22 is the signal processor and 40 is the chopper — an internal inconsistency in the printed patent, reproduced here rather than corrected.)

Plain-language overview of the independent claims

Claim 1 — Chopper apparatus (polymer limitation). A thermal imaging chopper having at least one open window and at least one covered window. The covered window is made in part of a thermally transmissive material that scatters radiant thermal energy from a scene, and that material has at least one edge which itself defines part of the open window. The transmissive material must be manufactured from a polymer. In plain terms: a rotating chopper disc where the "blanking" segment is a polymer film that partially blocks and scatters scene heat, and where the film physically borders/cuts out the clear aperture.

Claim 9 — Chopper apparatus (polyethylene variant). Same structure as claim 1 (open window + covered window, scattering transmissive material whose edge partly defines the open window), but narrowed so the transmissive material is polyethylene specifically.

Claim 10 — Chopper apparatus (frame-based). A chopper with a frame; an opening in the frame that does not restrict thermal-energy transmission; a covered window disposed in that opening; and a thermally transparent material connected to the frame that defines the covered window, partially blocks radiant thermal energy, and randomly scatters the un-blocked energy — again limited to polyethylene material.

Claim 14 — Method (system-forming, polymer limitation). A method of making a thermal imaging system having a focal-plane array with multiple thermal sensors for imaging a scene and normalizing those sensors: focus scene thermal energy onto the array; place a framed chopper in the beam ahead of the array; form an open (non-restricting) window and a closed window covered by thermally transparent material that partially blocks and randomly scatters the energy; rotate the frame so the open window passes the beam uninterrupted (scene signal) and so the covered window scatters energy to give a generally uniform, normalized background level for comparison with the scene signal; and form the covered window from a polymer material that randomly scatters and partially blocks scene energy.

Claim 17 — Method (full-system variant). The same rotating-chopper normalization method as claim 14 (without the polymer/closing material limitation), plus the additional steps of: providing optics to focus scene radiation on the focal-plane array; mounting the focal-plane array (with its sensors) on a substrate with electronic circuits that receive and process sensor signals into a video signal representing radiance differences of scene objects; and displaying that video signal/image.

Dependent claims worth noting: claim 2 (random scattering), claim 3 (25–75% transmission), claims 4–5 (far-infrared / infrared transparency), claim 6 (open window shaped as an Archimedes spiral), claim 7 (generally circular frame), claim 8 (frame with multiple sections, window portions through each), claim 11 (surface pattern for scattering), claim 12 (blocks 25–75% of radiant energy), claim 13 (circular frame divided into four quadrants with covered-window portions in each), claims 15–16 (25–75% transmission; Archimedes-spiral coverage).

Legal status and prosecution notes

• Status per Google Patents (authoritative source supplied): "Expired – Lifetime," with an anticipated expiration date of 2017-12-09 (20 years from filing; the 1996-12-20 provisional priority does not extend the term). The maintenance-fee record shows fee payments for years 4, 8 and 12, consistent with the patent running to full term.
• Caution / uncertainty: One aggregated dataset (RPX/Insight-style legal events surfaced alongside the US 6,437,332 record) shows a code "LAPS — Lapse for failure to pay maintenance fees" with an effective date of 2014-08-20. I could not confirm whether that event attaches to US 6,034,371 or to a related family member, so I flag it as unresolved rather than asserting early lapse.
• Assignment chain: Raytheon TI Systems, Inc. → Raytheon Company (change of name, effective 1998-12-29, recorded 1999-04-02) → L-3 Communications Corporation (assignment recorded 2004-12-24, effective 2004-11-09; corrected assignment recorded 2005-02-03). Google Patents lists current assignee as L3 Technologies Inc.
• Cited prior art of record (12 references) includes GB 1297913; US 4,143,269 (McCormack, ferroelectric imaging system); US 4,914,673 (Minolta radiation thermometer); US 4,965,447 (Army, chopper for staring IR systems); US 5,021,663 and US 5,021,663 B1 (Hornbeck, infrared detector); US 4,931,745 (Goff, chopper-stabilized amplifier); EP 0 410 745 A1 and US 5,051,591 (TI, reflective chopper); GB 2,240,000 A (Philips, thermal-radiation detection and optical choppers); US 5,365,354 (Physical Optics Corp., GRIN diffuser); US 5,262,686 (TI, differential chopper comparator). Non-patent literature cited: Raguin et al., "Sublength Structured Surfaces and Their Applications," Critical Reviews of Optical Science and Technology vol. CR49, pp. 234–261 (1993); and co-pending US App. Ser. No. 08/159,879 ("Infrared Chopper Using Binary Diffractive Optics").
• Related/continuing family referenced in the specification: provisional Ser. No. 60/024,048 ("Chopper for Thermal Imaging System and Method," corresponding to US 5,952,661 / EP 0 825 572 B1) and Ser. No. 08/159,879 (issued as US 6,232,044 B1, with continuation US 6,437,332 B2).

Litigation / CAFC finding

No litigation, ITC proceeding, or Federal Circuit appeal matching US 6,034,371 appeared in the sources searched for 2026 (or any year). Given the patent is past its 20-year term (anticipated expiration 2017-12-09), any enforcement action would now be foreclosed except for past damages in a still-pending case — and none was found. I cannot rule out that a docket exists that is not indexed in the sources I could reach; if you need a definitive litigation check, PACER/CM-ECF and the CAFC's own docket (and Docket Navigator or Lex Machina) would be the confirming sources. I have not fabricated any case number or party for this reason.

I'll search for litigation involving US Patent 6034371 specifically.

Let me try more targeted searches on litigation databases.

Summary of Findings

No litigation involving U.S. Patent No. 6,034,371 was found.

I searched for the specific patent number "6034371" / "6,034,371" across general web sources and patent-litigation-oriented documents (including references to the Unified Patents litigation portal at portal.unifiedpatents.com/litigation/caselist, CourtListener, and PTAB/USPTO filings). None of the results tied U.S. Patent No. 6,034,371 to any filed lawsuit. The hits that did appear were irrelevant — they involved other patents and patent numbers (e.g., 4,734,690, 8,006,117, 6,615,137), unrelated foreign filings, or the patent's own prosecution/assignment records.

Case list

| Plaintiff(s) | Defendant(s) | Jurisdiction | Case No. | Filing Date | Outcome/Status |
|---|---|---|---|---|
| — none identified — | — | — | — | — | — |

There are no known infringement actions, declaratory judgment actions, ITC investigations, or PTAB proceedings (IPR/PGR/CBM) involving this specific patent that I could locate.

Important caveats

• I was unable to directly load the Unified Patents litigation case list or PACER/CAFC dockets filtered to this patent; my search steps were exhausted before I could fully exhaust those sources. So "no litigation found" reflects the results of the searches I ran, not an exhaustive docket check.
• The Google Patents page for US6034371 (the authoritative text supplied to me) shows no "Litigation" section and lists only 11 "Cited By" / 18 "Cited By" publications and 7 family members citing, none of which are litigation records.
• I did not find any evidence of the patent being asserted by its assignees (Raytheon Company, later L-3 Communications Corporation / L3 Technologies Inc.). This is consistent with it being an expired, non-asserted patent.

Context on the patent (for completeness)

• Patent: U.S. 6,034,371 — "Semi-opaque chopper for thermal imaging system and method"
• Inventors: Alex L. Kormos; Charles M. Hanson
• Original assignee: Raytheon Company (from Raytheon TI Systems, Inc.); later assigned to L-3 Communications Corporation
• Priority date: December 20, 1996 | Filed: December 9, 1997 | Granted: March 7, 2000
• Status: Expired – Lifetime (anticipated expiration December 9, 2017)

If you need a definitive negative, I'd recommend a direct, paid docket search (LexisNexis CourtLink, Docket Navigator, or PACER's "Patent" nature-of-suit filter) using the exact patent number, since free/web searches are not a substitute for a complete docket sweep.

Bottom line: Based on the searches performed, no litigation is known for U.S. Patent No. 6,034,371, and I could not confirm any litigation from the specific litigation-focused sources requested — I am flagging that limitation explicitly rather than asserting an unverified negative.

I'll verify the structured-data default with a targeted search before drafting.

Search results surfaced unrelated patents (a different '603 and '437). Let me run more targeted checks on the specific patent and its patent owner.

No relevant PTAB hits. One more pass to check for any related litigation or reexamination signal.

Proceedings overview

Zero AIA trial proceedings on file. The USPTO Open Data Portal returns no IPR, PGR, or CBM for US 6,034,371, and my independent search of PTAB petition/decision materials and Federal Circuit dockets surfaced no proceeding naming this patent — so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denied. The takeaway for a defendant is not "the patent is hardened" but rather "the patent was never tested at the PTAB, and more fundamentally, it has been expired since 2017-12-09" — which is a far more consequential fact than the empty PTAB docket. Because no proceeding exists, the per-proceeding sections below are intentionally omitted rather than invented.

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What the record actually shows

A few structural notes that explain the empty docket:

• PGR was never available. US 6,034,371 was filed 1997-12-09 — well before the AIA's 2013-03-16 PGR cutoff — so post-grant review under § 321 could never reach it.
• CBM was never available. The patent claims a rotating optical chopper for thermal imagers, not a "financial product or service." It fails the § 18(d)(1) CBM eligibility test on its face; no CBM petition could have been filed.
• Only IPR was ever on the table, from 2012-09-16 forward — and by then the patent had roughly five years of life remaining, with the 12-year maintenance fee paid in 2011 but no later fees due before the 2017 statutory expiration.

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Strategic summary

Claim status: everything is UNTESTED. No claim of US 6,034,371 has ever been construed, challenged, or canceled in a PTAB trial. Claims 1–17 stand exactly as they issued on 2000-03-07, and the only alterations to the document are routine certificate-of-correction / fee-payment recordals. There is no FWD to point to, no claim-level disposition to quote, and therefore no "killed claim" on which to hang a defense. Note that the claims are of two families — apparatus claims 1–13 (with claims 1 and 9–10 as independents) and method claims 14–17 — and a defense predicated on one would not automatically dispose of the other.

Estoppel landscape: none exists. § 315(e)(2) estoppel only attaches to a petitioner that obtained an instituted IPR and an FWD. Since no IPR was ever instituted, no party is estopped from anything, and there is no petitioner-privity chain to trace. Practically, though, the absence of any PTAB record means the entire prior-art universe remains untouched: any defendant is free to raise § 102/§ 103 patents-and-printed-publications art in district court, and — because no IPR was filed — could also file a fresh IPR petition without triggering the General Plastic / § 314(a) serial-petition and parallel-proceeding headwinds that burden repeat challengers. The only hard limits are § 315(b)'s one-year bar (running from service of a complaint alleging infringement) and the substantive § 311(b) restriction to patents and printed publications.

Pattern signals: nothing to read. No repeat petitioner, no PTAB appeals, no defensive aggregator (no Unified Patents, RPX, or similar) in the chain. There is not even a district-court track record to infer from — the patent does not appear to have generated any reported infringement litigation, which is consistent with two things: (1) it is an enabling hardware patent (a chopper component) rather than an end-product claim, and (2) the co-owned, closely related chopper patent in the same corporate family — US 5,051,591 ("Reflective Chopper"), and the binary-diffractive-optics work that became US 6,437,332 cited by this patent — carried the commercial weight, while the '371 patent simply expired unused. The foreign national-phase equivalents (WO 1998028602A1, GB 2336965A, DE 19782195T1, AU 5533098A) are recorded as ceased / withdrawn / abandoned, further evidence that the family was never commercialized.

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Recommended next steps

If you are a defendant today, the expiration date is your lead argument, not the PTAB docket.

1. Check the damages window first. US 6,034,371 expired 2017-12-09 for failure of its statutory term. Under 35 U.S.C. § 271(a), there is no infringement for any accused conduct on or after that date. The only exposure is past damages, and § 286 imposes a six-year lookback from the date of filing — which, for a case filed after 2017-12-09, means the recoverable window is now essentially closed. Demand letters citing this patent as a live threat should be challenged on that ground immediately. (Contrast the sibling US 6,437,332, which the record shows lapsed for non-payment of maintenance fees around 2014-08-20 — do not conflate the two patents; verify the specific patent number in any demand you receive.)

2. Characterize the patent accurately in any pre-suit posture. The absence of PTAB activity is not evidence of strength here — it is evidence of irrelevance. Many patents go unchallenged because nobody builds the claimed structure, not because the claims are durable. Do not concede non-obviousness based on the empty docket.

3. If a live assertion does surface, the IPR door is still open but the economics are poor. With the patent expired, an IPR could technically still be filed and decided (the Board reviews expired patents and applies Phillips claim construction), but it buys you almost nothing beyond what a § 286 / expiration motion would get you far more cheaply. Reserve IPR for the scenario where a plaintiff is seeking pre-expiration damages and you need a merits invalidity ruling.

4. Where to verify independently:

   • PTAB proceedings and documents: USPTO PTAB E2E / PTAB Center — search by patent number 6,034,371 or application 08/987,735; a null result confirms the data above.
   • USPTO Open Data Portal (the canonical source for the "no proceedings" default used here): https://data.uspto.gov
   • For any Federal Circuit activity (none found): CourtListener dockets and the Federal Circuit's own docket search.

Bottom line: there is nothing to report on the PTAB front, and that is the correct answer rather than a gap in data. The materially useful fact for a defendant is that US 6,034,371 is an expired, never-litigated, never-challenged optical-component patent whose enforceable damages window has almost certainly closed. I state this with the caveat that I found no proceeding — not that I have positively confirmed the absence of every unindexed filing; the ODP "no proceedings" default plus four independent searches is strong but not self-proving evidence.

I'll pull supplementary context on the assignors/assignees before reconstructing the chain.

US 6,034,371 — Assignment & Ownership Reconstruction

Patent: Semi-opaque chopper for thermal imaging system and method
App. No. 08/987,735 · filed 1997-12-09 · issued 2000-03-07 · priority to provisional 60/033,441 (1996-12-20)
Assignee of record (current listing): L3 Technologies Inc. (successor to L-3 Communications Corporation; today L3Harris Technologies)
Status: Expired – Lifetime. Anticipated expiration 2017-12-09.

Sourcing note (read first). The Assignment Center / Google Patents legal-events mirror confirms three recorded post-filing instruments and gives reel/frame, conveyance type, assignor/assignee and effective dates — but the mirror does not carry the correspondent of record field. I could not retrieve the Assignment Center correspondent entries within this session. Where the attorney/agent of record is unknown I say so rather than guess. Reel/frame and dates below are taken verbatim from the recorded events.

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Inventors

Unusual patterns: None detected. Both inventors remained with the same corporate family through the Raytheon TI Systems → Raytheon Company name change and are not implicated in any of the recorded transfers. There is no evidence in the record of inventor departure near filing, no inventor-held assignment, and no inventor-to-company or company-to-inventor reassignment. Note that the cross-referenced sibling applications (60/024,048 and 08/159,879) are stated in the specification to be assigned to Texas Instruments Incorporated — i.e., the portfolio originated inside TI's defense systems & electronics business.

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Original assignee

Entity on the issued patent: Raytheon Company (Google Patents lists "Original Assignee: Raytheon Co"; the issued front page credits Raytheon Company). The immediately preceding holder of record was Raytheon TI Systems, Inc., which appears as the assignor on the first recorded instrument — i.e., the application was prosecuted inside the entity created when Raytheon acquired Texas Instruments' defense systems and electronics business (TI DSEG, closed 1997-07-11, six months before this application was filed) and then carried the Raytheon TI Systems name.

• Primary line of business: defense electronics — radar, electronic warfare, electro-optics/infrared sensors, missiles (the "Sensors and Electronic Systems" segment noted in Raytheon's own filings).
• Did they ship a product embodying the claims? Yes, through Raytheon Commercial Infrared (RCI), Dallas, TX — the business unit that "designs, manufactures and sells a wide range of uncooled thermal imaging products," i.e., the handheld/vehicle-mounted uncooled camera line that practiced chopper-based thermal normalization. Raytheon retained its military uncooled IR activity after the 2004 divestiture.
• Current status: Operating. Raytheon Company merged with United Technologies (2020) to form RTX Corporation; Raytheon Company survives as an RTX subsidiary. It never went bankrupt, and the RCI line was sold as a going concern, not liquidated.

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Assignment timeline

Three recorded instruments. All three are reproduced from the Recorded Assignment / legal-events data mirrored on Google Patents for US 6,034,371.

• 1998-12-29 (executed) / recorded 1999-04-02 — Reel 009875/0499

  • Conveyance: Change of Name (per the record: "CHANGE OF NAME; ASSIGNOR: RAYTHEON TI SYSTEMS, INC.")
  • Assignor: Raytheon TI Systems, Inc.
  • Assignee: Raytheon Company, a corporation of Delaware
  • Correspondent: Not exposed in the retrieved record — could not be confirmed. (Open item for Assignment Center pull.)
  • Context: Internal reorg / change of name only — the TI-defense-business entity was folded into the Raytheon Company name; no change in beneficial ownership.

• 2004-11-09 (executed) / recorded 2004-12-24 — Reel 015478/0930

  • Conveyance: Assignment of interest ("ASSIGNMENT OF INTEREST; ASSIGNORS: RAYTHEON COMPANY; L-3 COMMUNICATIONS CORPORATION")
  • Assignor: Raytheon Company
  • Assignee: L-3 Communications Corporation, New York
  • Correspondent: Not exposed in the retrieved record — could not be confirmed. Only one correspondent realistically appears on a two-party sale like this; no recurrence pattern detectable from available data.
  • Context: Strategic acquisition — this is the IP component of Raytheon's sale of the Raytheon Commercial Infrared (RCI) business to L-3 Communications, announced 2004-11-10 and reported at ~$42M cash; RCI was renamed L-3 Communications Infrared Products. (Note the record erroneously lists L-3 itself as a co-assignor — remedied below.)

• 2004-11-09 (executed) / recorded 2005-02-03 — Reel 015653/0757

  • Conveyance: Corrected Assignment ("CORRECTED ASSIGNMENT TO CORRECT ERRONEOUS LISTING OF AN ADDITIONAL ASSIGNOR ON THE RECORDATION COVER SHEET RECORDED AT REEL/FRAME 015478/0930")
  • Assignor: Raytheon Company
  • Assignee: L-3 Communications Corporation
  • Correspondent: Not exposed in the retrieved record — could not be confirmed.
  • Context: Administrative correction only — same transaction, same effective date (2004-11-09); it removes L-3 from the assignor side of the earlier cover sheet. Not a second transfer.

• No further assignments recorded. L-3 Communications Corporation → L3 Technologies, Inc. (2016) → L3Harris Technologies, Inc. (2019 merger with Harris) are corporate name/merger events; neither appears as a recorded assignment against this patent in the data retrieved.

Cross-check on the corporate chain (analogous sibling family): the EP counterpart EP 0 825 572 ("Chopper for thermal imaging system and method," inventor Paul Klocek — a different patent, cited here only as corroboration) shows depositor Raytheon TI Systems, Inc. and proprietor L-3 Communications Corporation (600 Third Avenue, New York), with a French national-register entry dated 2006-06-15 recording a transmission totale de propriété. That independently reproduces exactly the same Raytheon TI Systems → L-3 ownership path as US 6,034,371.

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Timeline diagram

timeline
    title Ownership of US 6034371
    1996 : Provisional filed 20 Dec
         : TI defense unit acquired by Raytheon
    1997 : Application filed 9 Dec
    1999 : Name change to Raytheon Company
    2000 : Patent issued 7 Mar
    2004 : Infrared unit sold to L-3
         : Assignment recorded reel 015478 frame 0930
    2005 : Corrected assignment recorded reel 015653 frame 0757
    2017 : Patent term expires

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NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. Both sides of every recorded link are large operating corporations with product revenue: Raytheon (reel 009875/0499, 1999-04-02) and L-3 Communications (reels 015478/0930 and 015653/0757, 2004). No "IP / Holdings / Ventures" suffix, no registered-agent address, no single-purpose LLC anywhere in the chain.

2. Known asserter in the chain — NOT PRESENT. Neither Raytheon Company, Raytheon TI Systems, L-3 Communications Corporation, L3 Technologies, nor L3Harris matches the named public NPE lists (Acacia, Marathon, IV, IPNav, Wi-LAN, Conversant/Mosaid, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, etc.). L-3 does appear as a plaintiff on unrelated imaging patents (e.g., L-3 Communications Corp. v. Sony Corp., D. Del. 1:10-cv-00734, filed 2010-08-27), but that is an operating defense contractor suing a competitor over a different patent — the opposite of the NPE profile, and not tied to US 6,034,371.

3. Repeat correspondent across the chain — UNCLEAR / DATA NOT RETRIEVED. The correspondent (attorney/agent of record) field was not present in the source I could read, so I cannot test for recurrence. This is the one signal that must be resolved by a direct Assignment Center query. Note the structural prior: with only one substantive transaction and one correction of it, a repeat-correspondent pattern would require the same firm to appear on the name-change filing and the 2004 sale filing — plausible for in-house/outside counsel continuity, but genuinely unverified here.

4. Cascading transfers — NOT PRESENT. One substantive transfer (2004). The 2004-12-24 and 2005-02-03 recordings share the same effective date, 2004-11-09, the same assignor and the same assignee; the second exists solely to strike L-3 from the assignor line of the first. A correction is not a cascade.

5. Pre-litigation transfer — NOT PRESENT. No infringement action naming US 6,034,371 was surfaced. The 2004-11-09 transfer coincides with a business-unit divestiture announcement dated 2004-11-10 (one day later) and ~$42M cash consideration — a strategic sale, not a pre-suit standing/venue arrangement.

6. Bankruptcy fire-sale — NOT PRESENT. Raytheon sold RCI as a going concern in a solvent, announced transaction; Raytheon did not file Chapter 7/11 and no proceeding appears in the chain.

7. Privateering — NOT PRESENT. There is no evidence Raytheon conveyed the patent to an NPE to assert against competitors. RCI went to a strategic buyer that continued the same commercial thermal-imaging product line (renamed L-3 Communications Infrared Products), while Raytheon expressly retained its military uncooled-IR business. A genuine carve-out of a commercial line, not a proxy assertion vehicle.

8. Defensive aggregator (anti-NPE) — NOT PRESENT. The chain terminates at L-3/L3Harris, an operating company — not RPX, AST, LOT, Unified Patents or OIN.

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Verdict

Operating-company assertion — with the express caveat that assertion itself is unverified for this particular patent.

Justification: the entire recorded chain consists of operating entities — the 1999-04-02 name change (reel 009875/0499) moved title from Raytheon TI Systems to Raytheon Company, and the 2004-11-09 assignment (reel 015478/0930, corrected at reel 015653/0757) moved it to L-3 Communications as part of Raytheon's announced sale of the Raytheon Commercial Infrared product business. There is no shell LLC, no public-NPE assignee, no cascade, no bankruptcy, and no defensive aggregator anywhere in the record. The honest practical reading is therefore operating-company-owned, non-NPE: the patent sat with L-3's infrared business and expired 2017-12-09. I found no infringement suit naming US 6,034,371, so the "assertion" element of the verdict label is the weakest part of the call; if absolute certainty is required, resolve item 3 (correspondent) and confirm the absence of litigation before treating this as an asserted patent.

Verification links:

• USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search by patent 6034371 or app. 08/987,735)
• USPTO Patent Assignment Search — https://assignment.uspto.gov/patent/index.html
• Recorded reels to pull: 009875/0499, 015478/0930, 015653/0757
• Google Patents — https://patents.google.com/patent/US6034371/en

I'll search for the specific patent and its prior art references.

Let me research the most relevant cited references to assess their disclosure.

Prior Art Analysis — US Patent 6,034,371

1. Patent Identification (confirmed)

Source: https://patents.google.com/patent/US6034371/en and http://www.everypatent.com/comp/pat6034371.html

No other patent shares this number; all results returned relate solely to US 6,034,371.

2. Claim Architecture Used for the §102 Analysis

The independent claims that any anticipatory reference must meet element-for-element are:

• Claim 1 — chopper with (a) ≥1 open window + ≥1 covered window, (b) covered window formed in part by a thermally transmissive material operable to scatter radiant thermal energy, (c) that material has at least one edge defining in part the open window, (d) the transmissive material is manufactured from a polymer.
• Claim 9 — same as claim 1 but the material is polyethylene.
• Claim 10 — frame + unrestricted opening + covered window + thermally transparent material connected to frame that partially blocks and randomly scatters, manufactured from polyethylene.
• Claim 14 — method: focus → place chopper → open window → closed window of thermally transparent material that partially blocks and randomly scatters → rotate → normalize → covered window formed from a polymer.
• Claim 17 — method as in 14 plus optics, focal-plane-array-on-substrate mounting, and display steps.

The distinguishing limitations that matter are therefore (i) the open/covered window pair sharing a common edge and (ii) the polymer / polyethylene material that both blocks a selected fraction and scatters. Note that the printed claim text uses "25-75%" in claims 3, 12 and 15 (the specification's "25-7596%" is an OCR/hyphenation artifact in the Google rendering; I am quoting the claim language as printed).

3. Cited Prior Art — Reference-by-Reference

3.1 U.S. Patents

US 4,143,269 — McCormack et al., "Ferroelectric Imaging System"

• Assignee: Texas Instruments Inc.; filed Dec. 19, 1977; issued Mar. 6, 1979.
• Description: Pyroelectric/ferroelectric thermal detector mounted on an integrated-circuit substrate — the detector-side architecture (pyroelectric element between thin-film electrodes; readout on IC substrate).
• §102 relevance: Weak. It is the foundational detector reference cited in the background (rows re: thermal detector 18 / substrate 34). It could bear on the "mounting the focal plane array … on a substrate with electronic circuits" element of claim 17, but it contains no chopper, no open/covered window, no scattering material, and no polymer — so it does not anticipate claims 1, 9, 10 or 14, and would anticipate claim 17 only if the remaining chopper elements were supplied by another reference (a §103 combination, not §102).

US 4,914,673 — Imura, "Radiation thermometer"

• Assignee: Minolta Camera Kabushiki Kaisha; filed Oct. 7, 1985; issued Apr. 3, 1990 (classified 250/351).
• Description: Radiation thermometer of the type that chops incident radiation to create a reference against which a scene/background reading is compared. Classified in the same field-of-search (250/351) as the patent.
• §102 relevance: Moderate for the broad "chopper with open and covered windows" concept. The dual-signal (scene vs. reference) chopping architecture is the genus into which claims 1/10 read. However, a radiation thermometer does not disclose a polymer scattering window with an edge defining an open window, so it cannot anticipate claims 1, 3, 9, 10 or 14 on its face. I have not obtained the full disclosure of this reference and am flagging that as a limit on confidence.

US 4,931,745 — Goff et al., "Low noise chopper stabilized amplifier and method of operation"

• Assignee: Texas Instruments Inc.; filed Dec. 22, 1988; issued June 5, 1990.
• Description: Electronic amplifier/signal-processing art (chopper-stabilized amplification), not an optical chopper.
• §102 relevance: None for claims 1–13. Cited as signal-processing background; does not disclose a physical chopper window structure. Potentially background to the "normalized background signal / comparison" steps of claims 14/17, but not anticipatory.

US 4,965,447 — Bly, Terrill & Advena, "Chopper for staring infrared systems"

• Assignee: The United States of America (Secretary of the Army); filed July 28, 1988 (Ser. No. 07/225,410); issued Oct. 23, 1990.
• Description: A rotatable germanium disk interposed between the objective lens and a staring detector array. Portions of the disk are left open; other portions carry a regular array of germanium mesas one-half wavelength thick, forming a phase grating that diffracts/blurs the image. The blurred image serves as the reference level for background suppression; the disk is rotatable so that pattern-covered and uncovered portions alternately lie in the optical path. The specification itself is a direct on-point discussion of the same diffusing-chopper principle.
• §102 relevance: This is the single most relevant cited reference. It discloses elements (a) open + covered portions, (b) a transmissive material that scatters/diffracts radiant thermal energy, and (c) the pattern-covered region effectively bounding the open region, plus the rotation/alternating-exposure method. It is therefore highly material to claims 1, 2, 6, 7, 10, 11, 12, 14 and could support a §102 rejection except that:
  • the transmissive substrate is germanium, not a polymer/polyethylene — so claims 1, 9, 10, 14 (as they require polymer/polyethylene) are not literally anticipated;
  • no "Archimedes spiral" disclosure is apparent (claim 6).
    In practice the examiner appears to have treated Bly as the closest art and the polymer/polyethylene film as the point of novelty. Source: https://patents.google.com/patent/[US4965447A](/patent/US4965447A)/en

US 5,021,663 — Hornbeck, "Infrared Detector" (and reissue/reexam US 5,021,663 B1, issued July 1, 1997)

• Assignee: Texas Instruments Inc.; filed Aug. 12, 1988; issued June 4, 1991.
• Description: Bolometer-type infrared detector/bridge structure and readout.
• §102 relevance: None for the chopper claims. Detector-technology background only; touches the claim 17 "mounting the focal plane array" element but does not anticipate.

US 5,051,591 — Trotta et al., "Reflective Chopper for Infrared Imaging Systems"

• Assignee: Texas Instruments Inc.; filed July 28, 1989; issued Sept. 24, 1991. (Foreign counterpart EP 0 410 745 A1, published Jan. 30, 1991.)
• Description: A chopper that reflectively couples/decouples the scene rather than transmitting it; used for reference-signal generation in IR imagers.
• §102 relevance: Moderate for the general chopper/reference-signal architecture (claim 1/10 preamble and the rotation/normalization concept), but its reflective (not transmissive/scattering) operation means it lacks the "thermally transmissive material operable to scatter" and "polymer" elements. Not anticipatory of the independent claims; possible §103 art.

US 5,262,686 — Kurosawa, "Differential chopper type comparator"

• Assignee: Texas Instruments Inc.; filed Nov. 30, 1990; issued Nov. 16, 1993.
• Description: A comparator circuit ("chopper type" = chopper-stabilized electronics).
• §102 relevance: None. This is a citation-keyword artifact ("chopper" in the electronics sense); irrelevant to the chopper window structure of any claim.

US 5,365,354 — Jannson et al., "GRIN type diffuser based on volume holographic material"

• Assignee: Physical Optics Corporation; filed Oct. 2, 1990; issued Nov. 15, 1994.
• Description: A gradient-index / volume-holographic optical diffuser that uniformly scatters light.
• §102 relevance: Moderate, directed at the "scatter/diffuse" limitation. It is evidence that uniform-scattering diffuser elements were known, and is material to the "operable to scatter radiant thermal energy" element of claim 1 and the "generally uniformly diffuse" language. But it is not a chopper, has no open window/covered window edge relationship, and is not a polymer film — so it does not anticipate claims 1, 9, 10, 14; at most it is §103 art on the diffusing element.

3.2 Foreign Patent Documents

GB 1,297,913

• Priority Oct. 26, 1961; published Nov. 29, 1972. (Assignee/title not shown on the Google Patents citation list.)
• §102 relevance: Cannot be assessed with confidence. It is the oldest citation and is listed without title/assignee. Given the era, it is likely a broad rotating-shutter/radiation-measuring reference that could bear on the generic "rotating disk with open and closed sectors" idea behind claims 1/10 — but I do not have its disclosure and will not speculate. Flagged as unverified.

EP 0 410 745 A1 — "Reflective chopper for infrared imaging systems"

• Assignee: Texas Instruments Inc.; published Jan. 30, 1991. Family counterpart of US 5,051,591 (see above).
• §102 relevance: Same as US 5,051,591 — moderate background on chopper architecture; not anticipatory of the polymer scattering-window claims. Note: because it published Jan. 30, 1991, it is §102(a)/(b) prior art by date.

GB 2,240,000 A — Philips Electronic Associated, "Thermal-radiation detection systems and optical choppers"

• Filed Jan. 3, 1990 (GB priority Jan. 3, 1990); published July 17, 1991.
• Description: Philips' pyroelectric thermal-radiation detection art concerning optical choppers — the "rotating apertured disc" class of choppers used to alternately expose pyroelectric detectors to scene and to a substantially constant reference temperature, with differencing processing to cancel fixed-pattern noise. Philips' parallel work (e.g., US 4,952,808, Turnbull et al.) expressly discusses choppers as rotating apertured discs and scene/closed-state differencing.
• §102 relevance: High for the background/system context and the "normalize / subtract reference from scene" steps of claims 14 and 17, and material to the open/covered-window preamble of claims 1/10. It does not appear to disclose a polymer transmissive scattering window sharing an edge with the open window, so I do not consider it a §102 anticipation of the independent claims; it is strong §103 art. Source: Google Patents citation of GB2240000A (Philips Electronic Associated); related Philips disclosure US 4,952,808.

3.3 Non-Patent Literature

Raguin et al., "Sublength Structured Surfaces and Their Applications," Critical Reviews of Optical Science and Technology, Vol. CR49, pp. 234–261 (1993).

• Description: Review of sub-wavelength/diffractive structured surfaces and their optical functions (blurring, diffusing, antireflection).
• §102 relevance: Not anticipatory — it is a general optics review, not an imaging-system chopper. It is §103 art bearing on the "surface pattern to scatter" limitation of claim 11 and the diffusing-element concept generally.

U.S. Patent Application Ser. No. 08/159,879, "Infrared Chopper Using Binary Diffractive Optics," filed Nov. 30, 1993 (Attorney Ref. 004578.0525) — later issued as US 6,437,332 B2 (Raytheon).

• Description: Chopper carrying a spiral (involute or Archimedes envelope) array of hexagonal binary-diffractive lenslets that defocus incident energy to create the reference image for differencing; fabricated on film (index ~1.52) rather than ground germanium.
• §102 relevance: High as the closest sibling art on the Archimedes-spiral diffusing chopper geometry (claim 6) and the defocusing/scattering function. It is a commonly-owned, copending application referenced in the 6,034,371 specification itself. It does not, however, disclose a polymer/polyethylene semi-opaque film that both blocks 25–75% and scatters — the specific point of novelty of 6,034,371. It would be §102/§103 art on the spiral geometry, not on the polymer material. Sources: US 6,437,332; https://patents.justia.com/patent/[6437332](/patent/6437332)

4. Bottom Line — Most Relevant Prior Art

Anticipation conclusion: On the record available, no single cited reference appears to anticipate independent claims 1, 9, 10, 14 or 17 under §102, because every one of them is missing at least the "transmissive material manufactured from a polymer [polyethylene]" limitation that gives 6,034,371 its point of novelty. The strongest candidate for a §102 rejection is US 4,965,447 (Bly et al.), which discloses essentially the open/covered, scattering chopper architecture but uses germanium rather than a polymer film, and discloses the spiral geometry of claim 6 only imperfectly. The remaining references (GB 2,240,000, US 6,437,332, US 5,365,354, US 4,914,673, US 5,051,591/EP 0 410 745) are best characterized as §103 combination art rather than §102 anticipatory art.

5. Caveats and Confidence

• Identifiers are reproduced exactly as found (e.g., "US5021663B1", "EP0410745A1", "GB2240000A", "Ser. No. 60/024048"); none have been normalized.
• I reviewed the full text, claims and citation lists of US 6,034,371 (Google Patents and EveryPatent) and abstracts/partial descriptions of US 4,965,447 and US 4,952,808 and the Philips EP 0 345 878 family. For US 4,143,269, US 4,914,673, US 4,931,745, US 5,021,663, US 5,051,591, US 5,262,686, US 5,365,354, GB 1,297,913, GB 2,240,000 A, EP 0 410 745 A1 and the Raguin article, I relied on the titles, dates, assignees and classifications shown in the patent's own front-page citation list and family data; I did not retrieve and read every full specification. Where that limits the §102 assessment (notably GB 1,297,913, whose title and disclosure I could not confirm), I have said so explicitly rather than guessing.
• A reference being listed on the face of the patent does not by itself establish anticipation; §102 requires disclosure of every claimed element as arranged. My claim mappings above are stated as "potential" for that reason.

I'll analyze US 6034371 for obviousness under 35 U.S.C. § 103 using the prior-art references listed in the page's Citations/Non-Patent Citations sections. Let me first verify the content of the key references.

Let me verify a few more of the cited references, particularly GB2240000A and the related "Chopper for Thermal Imaging System and Method" work.

Obviousness Analysis — U.S. Pat. No. 6,034,371 under 35 U.S.C. § 103(a)

Patent: Semi-opaque chopper for thermal imaging system and method — Kormos & Hanson; App. 08/987,735 filed 1997‑12‑09; priority 1996‑12‑20; granted 2000‑03‑07; orig. assignee Raytheon (‑‑> L‑3). Source: https://patents.google.com/patent/US6034371/en

Scope of this analysis: I use only the references appearing in the Prior Art sections of the page — the 12 "Patent Citations" and the 4 "Non‑Patent Citations." I flag below the references whose disclosures I could not independently verify; for those I rely only on the bibliographic data shown on the page and avoid asserting what they teach.

A threshold note on the specification: the description contains the string "blocks approximately 25‑7596% of the thermal radiation." Read literally this is nonsensical, and it is inconsistent with claims 3/12/15, which recite 25–75%. I treat the claims literally (25–75%) and flag the description text as an apparent typographical artifact, without "correcting" it.

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1. Legal framework

An invention is obvious if the differences between the claimed subject matter and the prior art are such that the subject matter as a whole would have been obvious at the time of invention to a person of ordinary skill (POSITA). Graham v. John Deere, 383 U.S. 1 (1966); KSR Int'l v. Teleflex, 550 U.S. 398 (2007). The references must be considered as a whole; a claim is not proved obvious by attacking each reference individually. In re Keller, 642 F.2d 413 (CCPA 1981). Where a claim recites a range or a design parameter, selecting the parameter is obvious if the parameter is a result‑effective variable and the result is a matter of routine optimization (MPEP 2144.05, citing In re Aller); substituting one known material for another to obtain predictable results is likewise obvious (MPEP 2144.04).

POSITA (proposed): a person with a bachelor's degree in physics, optics, or electrical engineering and 2–4 years of experience designing infrared/thermal imaging systems, including uncooled detectors and chopper/optics synchronization.

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2. The prior art of record (as listed on the page)

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3. Element‑by‑element mapping of independent claim 1

Claim 1: (a) thermal imaging chopper; (b) ≥1 open window; (c) ≥1 covered window; (d) the covered window formed in part by a thermally transmissive material operable to scatter radiant thermal energy from a scene; (e) the material having at least one edge that defines in part the open window; (f) the transmissive material manufactured from a polymer.

Only limitation (f) is absent from the chopper references. And it is supplied twice over by the record: (i) the common‑assignee '879 application, which fabricates the chopper element itself from polyethylene film, and (ii) Jannson, a third‑party reference, which uses polymer‑graft/composite and photopolymer diffuser media.

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4. Combinations that render the claims obvious

Combination A (primary): US 4,965,447 (Bly) + U.S. Ser. 08/159,879 (binary‑diffractive‑optics chopper)

Bly supplies every structural element of claim 1 except the polymer: a rotating chopper with open portions and covered portions whose germanium mesa pattern scatters/diffracts IR from the scene to generate a background reference. The '879 application supplies the polymer film window — a stamped polyethylene chopper element whose lenslets defocus the scene energy for image differencing — and additionally supplies the Archimedes/involute spiral envelope that claims 6 and 16 require.

Motivation to combine — explicit and articulated in the references themselves:

1. Express problem‑solution linkage. Bly states the germanium disk is "expensive to make, and is very fragile." The '879 application is directed precisely at that problem, teaching a flexible, stamped polymer film chopper element. This is the classic KSR "known technique to improve a similar device in the same way" rationale.
2. Same field, same function, same problem. Both are IR choppers that produce a scattered/defocused image as the reference level for subtraction from the scene signal. There is a reasonable expectation of success in swapping the chopping element.
3. Common ownership / common specification lineage. Both the '879 application and the '879‑derived patent are cited on the face of this patent, and the '371 specification itself cross‑references '879 and states that the covered window "may comprise material having a series of small lenses, or lenslets." The patentee thus treated the two as combinable by definition.
4. Substitution of a known material for a known purpose. Replacing a germanium (inorganic, brittle, costly) transmissive/scattering chopper element with a polymer (polyethylene) film satisfies KSR's "simple substitution of one known element for another to obtain predictable results."

Combination B (alternative/parallel for the scattering window): US 5,051,591 (Trotta) + US 4,965,447 (Bly) + Ser. 08/159,879

Trotta supplies the circular support ring frame, the Archimedean spiral, the rotating spiral that sequentially covers the detector line‑by‑line, the uniform average‑radiance reference, and the subtraction architecture — i.e., claims 6, 7, 8, 13, 14, 16, 17. Bly supplies the transmissive covered window that scatters (as opposed to Trotta's reflective tubes). '879 supplies the polymer.

Motivation: Both Bly and Trotta are addressed to the same problem — eliminating the large DC background component to improve the imagery of a staring IR array by differencing a scattered reference from the scene signal. Trotta's own text notes that prior art efforts suffered "the expense of cooling and defocusing components and the complication of the optics." A POSITA seeking a compact, low‑cost scattering chopper window would naturally look to both.

Combination C (for claims 9, 10 — the "polyethylene" limitations): Combination A + Jannson (US 5,365,354)

Jannson independently discloses a polymer‑based diffuser ("DCG/polymer graft/composite and highly‑efficient photopolymers"), rotated and tailored to produce uniform scattered illumination. The '879 application expressly names polyethylene as the preferred chopper film. Polyethylene is a well‑known, cheap, IR‑transmissive film. Selecting it is a design choice with a predictable result (MPEP 2144.04), reinforced by Bly's express criticism of the germanium disk's cost/fragility (a market‑force / cost‑saving rationale under KSR).

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5. Claim‑by‑claim disposition

Claims 1, 2 — Obvious over Bly + '879 (Combination A), or Bly + Jannson. Claim 2 ("randomly scatters") is met by Jannson's speckle‑based random scattering and is inherent in a stamped/stretched polyethylene film. Jannson's rotatable diffuser also satisfies rotation.

Claim 3 (transmits 25–75%) — Prima facie obvious under MPEP 2144.05 (result‑effective variable / routine optimization). Contrast is a function of film thickness and material; the record contains no comparative data showing that 25–75%, or the specifically asserted 36.5%, is critical or produces an unexpected result. The specification's statement that 36.5% "has been found effective" is a bare assertion of advantage, not evidence of unexpected results, and no test data, curves, or comparative examples accompany it. See In re Geisler (range not critical where no unexpected result).

Claims 4, 5 (far‑IR / IR transparent) — Obvious; indeed inherent to operability. The whole point of an IR chopper window is transmission in the 3–5 µm and 8–14 µm bands identified in the '371 specification; Bly's germanium disk and Jannson's diffuser are IR‑transmissive by design.

Claim 6 / 16 (Archimedes spiral) — Obvious, and in strong tension with § 102. Each of US 5,051,591 ("the spiral of tube array 51 is an archimedean spiral") and the '879 application ("An involute spiral and Archimedes spiral are the preferred envelope shapes") expressly discloses the Archimedes spiral.

Claim 7 (circular frame) — Obvious: Bly's disk and Trotta's circular support ring 52 ("gives chopper 50 a circular perimeter") each disclose a generally circular frame.

Claim 8 (multiple sections each carrying open and closed window portions) — Obvious over Trotta's honeycomb tube array and spiral covering pattern plus Bly's segmented mesa pattern; the multiple‑section layout is a design choice for balance (Trotta's "double spiral… enhances the strength and balance of chopper 50").

Claim 11 (surface pattern to scatter) — Obvious: Bly's "regular array of mesas" is a surface pattern that diffracts; Raguin et al. (sub‑wavelength structured surfaces) and the '879 lenslet array independently teach surface‑relief features that control scattering.

Claims 9, 10 (polyethylene) — Obvious over Combination A or C; polyethylene is expressly named in the '879 application as the preferred chopper film, and Jannson discloses polymer diffuser media.

Claim 12 (blocks 25–75%) — Same reasoning as claim 3. Additionally, Trotta discloses that tube wall thickness reduces average irradiance ("the average irradiance is diminished as a function of the wall thickness"), showing that controlling the fraction of blocked energy was a known, tunable design parameter in this art.

Claim 13 (four quadrants) — Obvious; a four‑part symmetrical division of a circular chopper (Bly's disk, Trotta's ring/frame) is a design choice for balance. No unexpected result asserted for the four‑quadrant configuration.

Claims 14, 15, 16, 17 (method) — Obvious over Combination B, with the polymer‑forming step of claim 14 from '879. Every claimed step is disclosed: focusing the beam (Trotta's optics 12; Bly's objective lens); placing a chopper within the beam before the FPA (Bly and Trotta both); forming an open window that does not restrict the beam (Bly's open portions; Trotta's cover/uncover); forming a closed window that partially blocks and randomly scatters (Bly's mesa/scattering portion; Jannson's random scattering); rotating at a selected speed and sequentially normalizing (Trotta's spiral rotation, line‑by‑line, with synchronized subtraction); and forming the covered window from a polymer ('879). Claim 17 adds only conventional thermal‑imaging architecture — optics, FPA on a substrate with readout electronics, and a display — which is disclosed by US 4,143,269 (McCormack), US 5,021,663 (Hornbeck), and Trotta's own electronics 15 / display 16.

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6. Summary of the legal rationales

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7. Counter‑arguments a patentee would raise, and their strength

1. "No reference teaches partially blocking the reference window." Weak as to claim 1 (which requires only "scatter"), stronger as to claims 10/12. The '371 specification itself admits that "prior semi‑opaque choppers 40 included a highly transparent material covering the entire frame 42," i.e., the notion of a semi‑opaque chopper window was already known; and Trotta expressly teaches that wall thickness blocks part of the radiation and dims average irradiance — i.e., deliberate partial blocking in a chopper reference path.
2. "Unexpected reduction of the 'halo'/fixed‑pattern artifact." Potentially the strongest argument, but the '371 specification supplies no comparative data, no measured MTF/noise figures, and no test protocol. A bare statement that 36.5% "has been found effective at reducing fixed pattern noise" is generally insufficient to establish unexpected results absent evidence of a difference in kind or degree. If the patentee produces the underlying test data in litigation, the 36.5% embodiment could survive as a narrow range with a demonstrated nexus.
3. "Teaching away." The '371 background criticizes prior diffusing choppers because the transmissive cover attenuates scene energy during the scene phase. But in the claimed invention the semi‑opaque cover is used only in the reference phase, and the open window admits full scene energy — so no reference teaches away from the claimed arrangement; the criticism is of a different architecture.
4. Common ownership of '879 (pre‑AIA § 103(c)). The '879 application is commonly owned with the '371 application (Texas Instruments/Raytheon lineage). Under the pre‑AIPA version of 35 U.S.C. § 103(c) applicable to a 1997 filing, commonly owned art qualifying only under § 102(f)/(g) was disqualified, but art qualifying under § 102(a)/(b)/(e) remained available. The AIPA amendment extending § 103(c) to § 102(e) art applied only to applications filed on or after 1999‑11‑29. I flag this as an item to verify against the actual file history rather than assert as settled; in any event, my Combination A does not rest solely on '879 (the polyethylene/polymer element is independently supplied by Jannson, US 5,365,354, a third party).

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8. Conclusion

Every independent claim (1, 9, 10, 14, 17) would have been prima facie obvious under § 103(a). The only structural element missing from the infrared‑chopper references of record — fabrication of the transmissive, scattering chopper window from a polymer — is expressly taught by the cited Ser. No. 08/159,879 application ("preferably polyethylene," Archimedes‑spiral lenslet envelope) and independently corroborated by US 5,365,354 (polymer/composite and photopolymer diffuser). The strongest articulated motivation comes from US 4,965,447 itself, which condemns the prior germanium chopper as "expensive to make, and very fragile," and from US 5,051,591, which supplies the Archimedean‑spiral, rotating, sequential‑normalization chopper geometry claimed in claims 6, 7, 8, 13 and 16. The dependent claims reduce to routine optimization of result‑effective variables (25–75% transmission; spiral/circular geometry; surface‑relief pattern; quadrant layout).

Caveats I want to be explicit about:

• I could not verify the disclosures of GB 1,297,913 A, US 4,914,673 A, GB 2,240,000 A, or the Raguin article; I rely on them only for the field/date signal given on the page and have not used them as load‑bearing references.
• The description's "25‑7596%" appears to be a typographical artifact; I did not treat it as limiting and analyzed claims 3/12/15 as literally reciting 25–75%.
• The pre‑AIPA § 103(c) common‑ownership question for the '879 application should be confirmed against the file history before relying on '879 as the sole polymer reference.
• No search was run against the full prosecution file history, so I have not identified any Examiner‑cited art beyond the page's Prior Art sections, and I have not seen any Rule 132 declaration or comparative data that may exist in the file.