US 9651475

I'll search for the specific patent number and check for any litigation/docket activity.

Let me run a few more targeted checks — litigation/PTAB activity, and verification of the patent's bibliographic data.

US 9,651,475 B2 — Summary

Search note / scope of verification. I do not have direct API access to USPTO Patent Public Search, Patent Center, or the CAFC docket system; my checks were run through public web search, which surfaced the Google Patents record (https://patents.google.com/patent/US9651475/en), the granted-PDF copy (https://patentimages.storage.googleapis.com/07/bc/84/f9a0052b0024a7/US9651475.pdf), and the pre-grant publication record (US20150316466A1). The bibliographic data below is consistent across the full patent text supplied and the Google Patents record. I found no litigation, PTAB/IPR, or CAFC 2026 docket activity involving this patent. Treat that as "nothing found in the sources I could reach," not as an affirmative certified clean docket.

Number-similarity caution (per instruction not to auto-correct identifiers): a search result also surfaced US 6,965,147 B2 ("Kurokami et al., 11/2005"). That is a different patent number, not the one requested, and is not treated here.

Bibliographic data

Abstract (verbatim): "An optical sensor apparatus includes a light receiving element configured to produce an output according to a light receiving state, and an optical element including a reflecting layer including a metal film, and being arranged such that at least some of incident light on the light receiving element is light that is reflected by the reflecting layer. The optical element further includes a corrosion resistant layer for suppressing corrosion of the reflecting layer, and the reflecting layer includes a surface covered by the corrosion resistant layer formed by vapor plating."

Plain-language overview of the independent claims

Claim 1 — apparatus (the "core" independent claim). An optical gas sensor in which:

• a light-receiving element produces an output tracking how much light it receives;
• an optical element contains a metal-film reflecting layer and is positioned so that at least some of the light reaching the photodetector is light reflected by that layer;
• there is also a light-emitting element emitting in a predetermined wavelength region;
• a corrosion-resistant layer covers the reflecting layer and was formed by vapor plating (i.e., a gas-phase deposition process, not a painted/applied resin);
• the photodetector's output reflects the received intensity at a specific wavelength selected according to the type of target gas;
• the optical element sits so that the light path between emitter and detector lies in a monitoring space into which the target gas is introduced;
• the optical element is tubular, its wall has an air hole through it, and the reflecting layer is on its inner surface;
• the emitter is coupled at one end and the detector at the other end of the tube, which guides light between them; and
• a filter sits on the outer surface over the air hole, passing gas but blocking solids and/or liquids.

In short: an NDIR-style gas cell, where a vapor-plated corrosion-resistant coating protects the mirrored light guide and a breathable/water-blocking membrane covers the gas inlet.

Claims 4 and 7 — methods of producing the optical element. These are written as method claims that incorporate the apparatus of claim 3 and claim 6 respectively by reference (an unusual cross-class dependency: a method claim referring back to an apparatus claim). Each method comprises:

1. forming the reflecting layer by depositing Al film in the gas phase on the target surface of the optical element's base material; then
2. forming the corrosion-resistant layer comprising Al₂O₃ in the gas phase on the reflecting layer's surface.

Claim 8 — method (dependent on claim 7). Adds the process-efficiency feature: both film formations are done in the same space/chamber; the reflecting layer is deposited in a vacuum atmosphere, and the corrosion-resistant layer in an oxidizing atmosphere with introduced oxygen (allowing Al → Al₂O₃ conversion without swapping deposition material or target).

Dependent claims at a glance

• 2 — corrosion-resistant layer ≥ 100 nm thick.
• 3 — infrared incident light; reflecting layer is Al; corrosion-resistant layer is Al₂O₃.
• 5 — corrosion-resistant layer 125–225 nm thick.
• 6 — same material/IR limitation as claim 3, but depending directly on claim 1 (raised as a fallback to claim 2's thickness limit).
• 9 — the optical element is a pair of half-split bodies each bearing the reflecting and corrosion-resistant layers, with opposing recessed portions forming the air hole when joined, and the filter spanning at least part of the coupling joint (which also reinforces the joint).

Points of uncertainty

• Filing-date presentation: the record lists 2013-11-27, which is the PCT international filing date; the US national-stage application 14/444,000 would have physically been lodged in 2014. I could not independently confirm the exact US §371 filing date without Patent Center access.
• No docket activity found: searches for this patent number in litigation/PTAB/CAFC contexts returned only unrelated matters (e.g., a 2026 Woodway/LifeCORE treadmill petition and a Panasonic imaging-patent document). Given the patent lapsed in 2021 for non-payment of maintenance fees, absence of current litigation is expected but is not something I can certify.
• Everything above is drawn from the patent's own text and the Google Patents/PDF record; I did not verify against the USPTO's official assignment or fee-status databases directly.

I'll research litigation involving US Patent 9,651,475 using multiple sources, including the Unified Patents litigation portal.

Let me search more targeted litigation databases.

Let me check additional litigation databases directly.

Litigation Search: US Patent 9,651,475

Bottom line: I found no evidence of any litigation involving US Patent 9,651,475 in the sources I was able to check. I did not locate a single district court case, ITC investigation, or Federal Circuit / PTAB proceeding naming this patent.

What I checked and what I found

Note: I attempted to query the Unified Patents litigation portal style searches and RPX Insight, but those returned no case records for "9651475." I do not have authenticated, direct access to Docket Navigator or PACER in this session, so I cannot represent my search as an exhaustive PACER sweep. That is a genuine limitation, and I want to be explicit about it rather than fabricate a case list.

Context on the patent itself (from the record)

• Patent: US 9,651,475 B2 ("Optical sensor apparatus and method of producing optical element used in optical sensor apparatus")
• Inventors: Takahiko Hirai; Kazuki Yamaguchi
• Original assignee / current assignee: Panasonic Intellectual Property Management Co., Ltd.
• Priority date: 2012-11-30; filed: 2013-11-27; granted: 2017-05-16
• Family: JP 6029073 B2; CN 104797926 B; EP 2927670 A1/A4; WO 2014083847 A1
• Status: Expired – Fee Related. Per the legal events on the face of the record, a maintenance-fee reminder issued 2021-01-04, the patent lapsed for failure to pay maintenance fees on 2021-06-21, and it is recorded as expired (effective 2021-05-16).

This expired status is consistent with — though not proof of — the absence of assertion activity: the patent went abandoned at the first maintenance-fee window (4-year stage), which is typical of patents that are not being enforced or monetized.

Conclusion

Based on the searches performed, no known litigation exists involving US Patent 9,651,475. For each of the requested fields:

• Plaintiff(s): None identified
• Defendant(s): None identified
• Jurisdiction: N/A
• Case number: N/A
• Filing date: N/A
• Outcome / status: N/A

If you need a definitive negative, the reliable next step would be a direct Docket Navigator or PACER "patent number" search (and a PTAB/ITC check), which I was unable to run exhaustively here. I'd rather flag that than assert more than the evidence supports.

I'll verify the structured block's "no proceedings" finding against public sources before writing this up.

Let me run a few more targeted checks before concluding.

One more round to confirm no assertion/litigation trail that would have spawned an IPR.

Proceedings overview

Zero AIA trial proceedings on file. Total count: 0 — 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The USPTO ODP structured block for US 9,651,475 ("PTAB proceedings on file") is empty**, and my independent web sweep (queries below) surfaced no IPR, PGR, or CBM naming 9,651,475 as the challenged patent, and no Federal Circuit appeal from any PTAB proceeding on it. Because that is the case, there is no PTAB record to "harden" or "kill" the patent — the defensive posture is defined almost entirely by the patent's own lapse on 2021-05-16 for nonpayment of maintenance fees, not by any Board ruling. A defendant facing a demand on this patent today should lead with expiration, not with IPR art.

Caveat on confidence. I could not directly query PTAB E2E / PatentCenter in this session (tool access limited to web search), so I am relying on the ODP block as canonical plus negative search results. I rate high confidence that no AIA trial has ever been instituted or even filed on this patent (an IPR petition is a public document and would be indexed within days), and moderate confidence on the absence of any district-court assertion — litigation pleadings are indexed less reliably by general web search.

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No proceedings to report

There are no proceeding entries to detail. I will not construct IPR20XX-XXXXX headers, panels, grounds, or dispositions, because no such proceeding exists on this record. Specifically, the following were not found and should not be assumed:

What I actually searched (2026-09-29):

• US 9651475 IPR inter partes review Panasonic optical sensor — only the Google Patents page and unrelated Panasonic family documents.
• "9651475" PTAB proceedings petition — zero results.
• "IPR2018" OR "IPR2019" OR "IPR2020" Panasonic Optical sensor corrosion resistant layer Al2O3 gas sensor petition — only unrelated Pfizer IPRs (U.S. 8,992,486).
• US9651475 patent Federal Circuit appeal — nothing; returned unrelated CAFC Rule 36 dispositions.
• "9651475" OR "9,651,475" district court lawsuit complaint Panasonic gas sensor — nothing.

Useful negative-check links (no hits for a proceeding):

• PTAB E2E / Patent Trial and Appeal Board: https://ptacts.uspto.gov/ptabweb/
• CourtListener docket search: https://www.courtlistener.com/?q=%229651475%22
• Google Patents (has a "Cited By" but no litigation/PTAB tab entries): https://patents.google.com/patent/US9651475/en

Note: the only "Cited By" entry on the face of the patent, US 11,344,835 B2 (Donaldson Company, Inc., filed 2018-08-21, granted 2022-05-31, "Filter assembly for an enclosure"), is a citing patent, not a proceeding. It is a downstream filter-art citation, not evidence of a challenge.

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Strategic summary

Claim status: wholly UNTESTED, and now largely moot. Claims 1–9 were never subjected to an AIA trial, so nothing has been canceled and nothing has been adjudicated sustained. All nine claims carry the ordinary statutory presumption of validity (35 U.S.C. § 282) — but that presumption is cold comfort for the patent owner, because on 2021-06-21 the USPTO recorded "PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES" with an effective lapse of 2021-05-16, roughly four years after grant (2017-05-16, the 3.5-year maintenance-fee window). The patent is currently listed as Expired – Fee Related, with an anticipated expiration of 2033-11-27 noted only as the nominal end of term. The entire family is dead or dormant: EP 2927670 A4 (Withdrawn), CN 104797926 B (Expired – Fee Related), JP 6029073 B2 (Expired – Fee Related), WO 2014/083847 A1 (Ceased). That pattern — a Panasonic operating-company asset lapsing for fee nonpayment across all jurisdictions — is the signature of an unenforced patent, not an asserted one, and it is consistent with the absence of any PTAB filings.

Estoppel landscape: no estoppel exists. Section 315(e)(2) estoppel attaches only to a petitioner in an IPR/PGR that reached an FWD. With no proceeding, no party is estopped from anything. For a defendant currently on the receiving end of an assertion, every ground is theoretically on the table, including all 17 references cited on the face of the patent and the family-cite references: GB 1559503 A (Bosch, protective coating on reflectors), EP 0266769 A2 and US 4,823,168 (Hitachi flow-through photometer cells), US 4,795,253 (Mobay remote sensing gas analyzer), DE 4002631 A1 (Rosemount analysis cuvette), WO 1994/020013 A1 and US 5,510,895 (Sahagen probe), US 6,486,474 B1 (Minnesota infrared spectrometer), JP 2005-143943 A (Toto, "Processing method of corrosion resistant mirror" — the "Document 2" the specification itself disparages), JP 2005-164303 A (TDK water content instrument), CN 102183482 A, and JP 2012-220351 A / US 2014/0070101 A1 (Panasonic's own "Document 1" gas component detector). Because there is no Board record, there is also no § 315(a)/(b) time bar, no § 325(d) discretion risk, and no IPR "second bite" problem for a challenger — but by the same token, a defendant has no FWD to point to, so invalidity must be litigated de novo if it is litigated at all.

Pattern signals. (i) Same petitioner, multiple IPRs: no petitioner has ever filed on this patent at all. (ii) Patent owner PTAB appeals: none — Panasonic has never appealed a Board loss on this patent because it has never had one; the file history's appellate activity is ordinary ex parte prosecution (the PCT/JP 2013/006974 international search report and written opinion mailed 2014-02-10; the EESR dated 2015-09-25 in EP 13857877.8; a Chinese First Office Action mailed 2016-08-18 in CN 201380060256.5). (iii) Defensive aggregator: none in the chain — no Unified Patents, RPX, or similar entity appears anywhere on this patent. (iv) One structural detail worth noting for claim scope: the granted US claim 1 was narrowed relative to the disclosure by pulling in the FIG. 6 filter embodiment — the filter "provided on an outer surface of the optical element so as to cover the air hole" that "caus[es] gas to pass through the air hole and prevent[s] at least one of a solid body and a liquid body from passing through the air hole." That is a meaningful limitation absent from the general inventive concept, and its all-elements structure (combined with the "at least one of a solid body and a liquid body" alternative-form recitation) is the natural first front for both non-infringement and § 112(b) attacks if this patent is ever actually asserted.

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Recommended next steps

1. Lead with expiration, not with prior art — and check the damages clock immediately. The patent lapsed on 2021-05-16 and was formally recorded as expired on 2021-06-21. Under 35 U.S.C. § 286, a plaintiff suing today (2026-09-29) may recover damages only for infringement occurring on or after 2020-09-29 — and because the patent expired 2021-05-16, the entire recoverable universe is roughly a 7.6-month window (2020-09-29 → 2021-05-16). That window closes permanently on 2027-05-16: after that date, no suit can reach any pre-expiration conduct within the six-year lookback, and post-expiration conduct is simply not infringement. There is also no injunctive relief available for a expired patent. Demand-letter response should therefore demand, first, the accused instrumentality's dates of manufacture/sale, and second, production of the maintenance-fee payment record and any 37 C.F.R. § 1.378 petition to revive. Absent a successful revival (which after 2023-05-16 would require a showing that the entire delay was unintentional, plus surcharges), the demand is substantially a historical-damages play. If revival is ever attempted, consider intervening rights under 35 U.S.C. § 41(c)(2) for substantial preparations or sales made during the lapse period.

2. If this patent is nonetheless asserted, treat it as untested and prepare a full invalidity case from scratch. With no FWD and no estoppel, the classic IPR-centric defense plan is unavailable; instead, build the § 102/§ 103 record directly on the face-cited art, starting with JP 2005-143943 A (Toto) against the vapor-plated corrosion-resistant-layer concept, GB 1559503 A (Bosch) on protective coatings for optical reflectors, and Panasonic's own JP 2012-220351 A / US 2014/0070101 A1 (Document 1) plus the EP 0266769 A2 / US 4,823,168 Hitachi flow-through cell family on the tubular light-guide-with-air-holes architecture. Because there is no Board record, you are free to raise any ground, in any forum, without § 315(e)(2) risk.

3. Do not expect a PTAB option to open on the current record — verify, then plan around it. With the patent expired since 2021-05-16, an IPR/PGR filing is of doubtful practical value (and PGR is time-barred regardless, since PGR must be filed within nine months of grant, i.e., by 2018-02-16). Before spending on any challenge, have counsel re-run PTAB E2E (https://ptacts.uspto.gov/ptabweb/) and PatentCenter by patent number and by application number 14/444,000, plus a CourtListener name search for Panasonic Intellectual Property Management Co., Ltd. on this patent, since ODP ingest can lag and my session could not reach those systems directly.

4. Treat the "no PTAB activity" default as confirmed, with one live caveat. The absence here is a weak signal of non-assertion (well-asserted patents usually attract IPRs), but the strong signal is the fee lapse across the entire family. The residual risk is a recently-filed petition or a recently-filed district-court case that is not yet web-indexed, or a revival petition under 37 C.F.R. § 1.378. That is the only scenario in which anything in this report would need revising.

Bottom line for a defendant: there is no PTAB proceeding to exploit and no FWD to quote — but you likely don't need one. On the record as of 2026-09-29, US 9,651,475 is an expired, never-challenged, never-adjudicated patent with a shrinking historical-damages tail ending 2027-05-16, and its entire international family has been abandoned or allowed to lapse.

I'll start by verifying the assignment record and ownership status through available sources.

Let me attempt to pull the primary assignment record and check for any litigation or later transfers.

Let me try to locate the actual recorded assignment documents and any correspondent of record.

Assignment Record Reconstruction — US 9,651,475 B2

Verification basis / limitation on sources. I was able to reach the patent's full text and Google Patents' legal-events table (the authoritative copy supplied in this thread), but I was unable to complete a live query of USPTO Patent Assignment Search (assignmentcenter.uspto.gov) / legacy-assignments.uspto.gov for application 14/444,000 and could not retrieve the underlying assignment instrument or its recorded correspondent of record. Where I rely on the Google Patents legal-events entry, I say so. I have not fabricated any reel/frame, date, or correspondent.

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Inventors

• No co-inventors are named; it is a two-inventor, single-assignee chain (Google Patents, US9651475B2 front page and legal events: ASSIGNORS: HIRAI, TAKAHIKO, YAMAGUCHI, KAZUKI).
• Unusual-pattern check: I found no evidence that either inventor left Panasonic within 12 months of filing, and no successor inventor-owned filings that would indicate a spin-out. I could not confirm current employment status of either inventor — unclear, not a finding either way.
• No inventorship challenge, derivation proceeding, or § 256 correction appears in the record.

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Original assignee

• Panasonic Intellectual Property Management Co., Ltd. (PIPM), 1-61 Shiromi 2-chome, Chuo-ku, Osaka 540-6207, Japan — named as original assignee on the issued patent US 9,651,475 B2 and as the assignee in the only recorded assignment.
• Who this is: a wholly-owned captive subsidiary of the Panasonic group, not an arm's-length third party. Panasonic Holdings' disclosed IP structure places PIPM under its IP shared-service organization (PEX); PIPM consolidates group patents — often via an intra-group trust transfer under Art. 51 of the Japanese Trust Business Act — and handles group licensing and co-creation. It is Panasonic's own patent-management arm, not an NPE. (Secondary source: Panasonic Holdings IP-strategy analysis, techno-producer.com, Nov 2025 — analyst commentary, treat as corroborating rather than primary.)
• Product embodying the claims: the patent claims an NDIR-type gas sensor with a tubular light guide, an Al reflecting layer, an Al₂O₃ vapor-plated corrosion-resistant layer, air holes and a filter. Panasonic is a long-standing supplier of infrared/optical sensor modules for appliances and building equipment, and the specification's own framing (carbon-dioxide detection at 3.9 / 4.3 µm) matches a shipped product family. Whether a unit practicing claim 1 specifically (filter + split half-bodies) was commercialized is not something I can confirm from the record — unclear.
• Current status: Panasonic group is an operating, going concern (not acquired, not dissolved, not in bankruptcy). Panasonic IP Management remains an active patent holder.
• Patent status: expired 2021-05-16 for failure to pay maintenance fees (USPTO event code LAPS, 2021-06-21; FP, 2021-07-13), so the asset was abandoned by its owner before the 3.5-year window closed. Related family members: JP 6029073 B2, CN 104797926 B, WO 2014083847 A1, EP 2927670 A4 (EP file withdrawn).

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Assignment timeline

Only one assignment is recorded against this patent. There is no post-issuance transfer of any kind — no sale, no security interest, no license recordation, no change of name.

• 2015-03-09 (executed / USPTO effective date) / recorded 2015-06-22 — Reel 035879 / Frame 0573

  • Conveyance: Assignment (USPTO event code AS) — "ASSIGNMENT OF ASSIGNORS INTEREST"
  • Assignor: Hirai, Takahiko; Yamaguchi, Kazuki (the two named inventors)
  • Assignee: Panasonic Intellectual Property Management Co., Ltd.
  • Correspondent: Not retrieved. I could not obtain the recorded correspondent of record (attorney/firm) for reel 035879/0573. I am flagging this as a gap rather than guessing; a Panasonic corporate assignment form from the same era on the legacy assignment site names the US associate firm by code ("WLP"), but that document is for a different application (13/400,896) and must not be imputed to this patent.
  • Context: ordinary captive-subsidiary IP consolidation — inventors assign their rights to Panasonic's in-house IP management company in connection with US national-phase entry of PCT/JP2013/006974. Not a fire-sale, not a transfer to an asserter.

• No further recorded assignments. The chain terminates at Panasonic IP Management through the 2021 lapse. Google Patents' legal-events table for US9651475B2 contains exactly one AS entry; the remaining entries are STCF (grant), FEPP (fee reminder), LAPS, and FP (expiration). The single "Cited By" item (US 11,344,835 B2, Donaldson Company) is a citation, not an assignment.

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Timeline diagram

timeline
    title Ownership of US 9651475
    2012 : JP priority application filed
    2013 : PCT application filed
    2014 : US national phase entered
    2015 : Inventors assign to Panasonic IP Management
    2017 : Patent granted
    2021 : Expired for failure to pay maintenance fees

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NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. The only recorded transfer runs from the inventors to Panasonic Intellectual Property Management Co., Ltd. (reel 035879/0573, recorded 2015-06-22). No LLC with an "IP / Patents / Licensing / Holdings / Ventures" suffix; no registered-agent service address; the assignee address is Panasonic's Osaka HQ block. PIPM is a captive subsidiary of an operating group, which is the opposite of an arm's-length shell.

2. Known asserter in the chain — NOT PRESENT. Neither assignor nor assignee matches any name on the Acacia / Marathon / Intellectual Ventures / IPNav / Wi-LAN / Conversant / Vringo / Pendrell / Innovatio / MPHJ / Lumen View / Round Rock list, nor any Unified Patents or RPX high-frequency-plaintiff entry I could surface. Nothing in the chain touches those entities. (Generic note: Panasonic does delegate enforcement of certain portfolios to external licensing vehicles — e.g., battery patents via Tulip Innovation, and 2025 sales to CosMX per Korean trade press. That is portfolio-specific and there is no evidence it reaches US 9,651,475.)

3. Repeat correspondent across the chain — NOT PRESENT / NOT ASSESSABLE. With a single recorded link there is no recurrence to measure, and I was unable to retrieve the correspondent of record for reel 035879/0573. Flagging as a data gap, not as a clean bill of health.

4. Cascading transfers — NOT PRESENT. One assignment, zero chained LLCs, zero transfers inside any 24-month window. The patent sat with Panasonic IP Management from 2015 until it lapsed in 2021 — a six-year static hold.

5. Pre-litigation transfer — NOT PRESENT. No infringement action naming US 9,651,475 appears in my searches. There is no litigation to be "pre" to, and the nearest assignment predates expiration by six years.

6. Bankruptcy fire-sale — NOT PRESENT. Panasonic has not filed Chapter 7/11; no § 363 sale of this asset. The patent was instead abandoned — the owner declined to pay the maintenance fee (USPTO LAPS, 2021-06-21; effective lapse 2021-05-16). Non-payment is the clearest possible evidence that no monetization plan existed.

7. Privateering — NOT PRESENT. No transfer, license, or enforcement delegation to an NPE is recorded for this patent, and the asset expired before any could occur. Panasonic's known external-enforcement arrangements concern its cellular-SEP and battery portfolios, not gas-sensor patents.

8. Defensive aggregator — NOT PRESENT. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates in abandonment by the original owner.

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Verdict

Insufficient data — the chain consists of only the original assignment (inventors → Panasonic Intellectual Property Management Co., Ltd., executed 2015-03-09 / recorded 2015-06-22, reel 035879/0573), with no post-issuance transfers, no litigation, and expiration for non-payment of maintenance fees on 2021-05-16. This is the textbook "no NPE involvement" fact pattern: a major operating company assigned its inventors' rights to its captive IP-management subsidiary and then let the patent lapse, rather than moving it into an assertion vehicle. The one unresolved item is the correspondent of record on reel 035879/0573, which I could not retrieve — that gap does not change the verdict, but it is the item to close on re-verification.

Verify at:

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent 9651475 / application 14/444,000)
• Legacy assignment viewer: https://assignment.uspto.gov/patent/index.html
• Google Patents record: https://patents.google.com/patent/US9651475/en

I'll research the prior art citations for US Patent 9,651,475. Let me start by verifying the patent record and key references.

Let me verify additional prior art references and the USPTO record.

Prior Art Analysis — US Patent 9,651,475 B2

1. Patent record verification (searched literally as "9651475")

I verified the number 9651475 literally against the USPTO/Google Patents record. It resolves to US 9,651,475 B2:

This is the exact patent — I did not substitute any similar number. (Note: my prior litigation scan for this same patent found no litigation; nothing here changes that.)

Method / limitation note (stated up front): The references below are the citations that appear on the face of US 9,651,475 ("References Cited / Patent Citations"). Those front-page citations do not record the examiner's statutory basis (whether each was used under §102 or §103), so the "§102 potential" column is my own technical assessment, not a reproduction of an Office Action. I retrieved full text for only a subset of these references before exhausting my search budget; where I did not retrieve full text, the description is based on the reference's title/abstract and is flagged [title-based]. Descriptions should be treated accordingly.

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2. The patent citations of record for US 9,651,475 (17 references)

Ordered as listed on the patent. "Pub. date" is the publication date; "Prio." is the priority date.

A. Closest art — the two references the specification itself names

1. JP 2012-220351 A — "Gas component detector" — Panasonic Corp. — prio. 2011-04-11; pub. 2012-11-12 (specification "Document 1")

• Description: A gas sensor in which a space for introducing a detection-target gas sits between a light emitting unit and a light receiving unit, with a light guide body arranged between them. The inside of the light guide body carries a reflecting layer (reflecting mirror) formed by a metal such as aluminum, made as a metal plate or metal film. Gas concentration is derived from wavelength-specific absorption.
• U.S. sibling: US 2014/0070101 A1 — "Gas component detection device" — Panasonic Corp. — prio. 2011-04-11; pub. 2014-03-13 (also cited).
• §102 potential: This is the strongest single-reference candidate for the apparatus claim, because it discloses the light emitting element + light receiving element + tubular light guide with a metal reflecting layer monitoring a gas. It does not disclose (a) a corrosion-resistant layer covering the reflecting layer, formed by vapor plating, or (b) the filter of granted claim 1. Therefore it does not anticipate granted claim 1, but it is squarely relevant to the air-hole/light-guide structure of claim 1 and to the "pair of halves" concept of claim 9, and would support a §103 combination.

2. JP 2005-143943 A — "Processing method of corrosion resistant mirror" — TOTO Ltd. — prio. 2003-11-18; pub. 2005-06-09 (specification "Document 2")

• Description (verified): Relates to a mirror whose reflective metal film (Ag/Cu) is protected by a corrosion-resistant coating. The conventional corrosion-resistant layer is a synthetic resin (epoxy edge-coat) applied to the reflective film's exposed regions. The document is concerned with applying a resin coating of adequate, uniform thickness.
• §102 potential: Directly relevant to the "corrosion resistant layer for suppressing corrosion of the reflecting layer" element (claim 1) and to the anti-corrosion concept of claims 4/6/7/8. Because it teaches a resin (liquid-applied) coating rather than vapor plating, it does not anticipate the vapor-plated corrosion-resistant layer recited in claim 1 or the method claims — indeed the patent uses exactly this distinction (resin application vs. vapor plating) as its stated point of novelty.

B. Anti-corrosion coatings on optical/analysis surfaces

3. GB 1 559 503 A — "Method of producing a protective coating on the surface of optical reflectors and reflectors manufactured in accordance with this method" — Robert Bosch GmbH — prio. 1976-06-05; pub. 1980-01-23

• Description [title-based]: A method of forming a protective (anti-corrosion/anti-degradation) coating on the surface of an optical reflector, and the resulting reflector.
• §102 potential: The concept of a protective coating over a reflecting surface of an optical element is highly relevant to the "corrosion resistant layer" of claims 1/4/6/7/8. If the coating is produced by vacuum/vapor techniques it would bear directly on the "formed by vapor plating" limitation; on the title alone I cannot confirm the deposition technique. Even so, it lacks a gas-monitoring space and the claim-1 filter, so it cannot anticipate claim 1 as granted.

4. DE 39 42 325 A1 — "Coating for the surface of an analyzing cuff [cuvette] and method for producing the coating" — Rosemount GmbH & Co. — prio. 1989-12-21; pub. 1991-06-27 (family-cited, listed under "Family Cites Families")

• Description [title-based]: A protective/functional coating applied to the surface of an analysis cuvette, plus its production method.
• §102 potential: Strongest conceptual match for the combination of (i) an optical analysis cell and (ii) a surface coating on it. Relevant to claims 1/4/6/7/8. No filter, no gas-sensor architecture → no anticipation of claim 1.

5. JP 2005-164303 A — "Water content measuring instrument" — TDK Corp. — prio. 2003-11-28; pub. 2005-06-23

• Description [title-based]: An optical water/moisture measuring instrument (typically NDIR-type with a reflective cell).
• §102 potential: General NDIR/optical-measurement context; weak, background-type reference. No anticipation of any claim identified.

C. Tubular / multi-part optical cells (relevant to claim 9 and the tubular optical element)

6. EP 0 266 769 A2 — "Flow cell for photometer" — Hitachi, Ltd. — prio. 1986-11-07; pub. 1988-05-11
7. US 4,823,168 A — "Flow-through cell for a photometer formed using a pair of cell body members" — Hitachi, Ltd. — prio. 1986-11-07; pub. 1989-04-18

• Description [title-based]: A photometer flow cell built from a pair of cell body members that mate to form the fluid passage.
• §102 potential: These are the most relevant references to the "pair of half-split bodies" structure of claim 9 (two body halves joined to define the through-passage). Relevant to claim 9 and to the tubular optical element of claim 1. They do not disclose a metal reflecting layer, a vapor-plated corrosion layer, gas sensing at a target wavelength, or the filter → no anticipation of claims 1–9 as granted, but useful §103 art for the cell geometry.

8. DE 40 02 631 A1 — "Analysis cuvette for absorption spectral analysis of gases" — Rosemount GmbH & Co. — prio. 1990-01-30; pub. 1991-08-01

• Description [title-based]: A cuvette/cell for absorption spectroscopic gas analysis.
• §102 potential: Relevant to the "monitoring space into which the detection target gas is introduced" of claim 1. No corrosion-resistant vapor-plated layer, no filter → no anticipation.

9. WO 1994/020013 A1 — "Probe for monitoring a fluid medium" — Armen N. Sahagen — prio. 1993-03-05; pub. 1994-09-15
10. US 5,510,895 A — "Probe for monitoring a fluid medium" — Armen N. Sahagen — prio. 1993-03-05; pub. 1996-04-23
11. JP H08-510829 A — national-phase counterpart of the Sahagen "Probe for monitoring a fluid medium" — prio. 1993-03-05; pub. 1996-11-12

• Description [title-based]: An optical probe for monitoring a fluid medium, generally using reflective/optical surfaces to convey light through the medium.
• §102 potential: Background art on optical probes with reflective paths; weak to moderate. No anticipation identified.

D. IR / NDIR gas analyzers with reflective optics

12. US 4,795,253 A — "Remote sensing gas analyzer" — Mobay Corporation — prio. 1987-04-24; pub. 1989-01-03
13. JP S64-78134 A — "Remotely measuring gas analyzer" — Mobay Corp. — prio. 1987-04-24; pub. 1989-03-23

• Description (verified, US): Detects gaseous materials by collecting background IR (and visible) radiation, analyzing it with a spectrometer, and displaying results. Claim 42 recites "the radiation collection device is a concave diamond-turned mirror with a rhodium surface." Broad IR-gas-analysis and reflective-mirror disclosure.
• §102 potential: Relevant to the IR reflecting element of claim 1/3/6 (metallic mirror for IR). It is a remote open-path analyzer — no enclosed tubular cell, no vapor-plated corrosion layer, no filter → no anticipation.

14. US 6,486,474 B1 — "Infrared spectrometer for the measurement of isotopic ratios" — Regents of the University of Minnesota — prio. 1999-08-13; pub. 2002-11-26

• Description [title-based]: An IR spectrometer configured to measure isotopic ratios (a filter-based NDIR-type optical measurement).
• §102 potential: Background IR-measurement art; relevant at most to the "received light intensity at a specific wavelength" element of claim 1. No anticipation.

15. CN 102183482 A — "Non-disperse infrared multi-component flue gas analyzer" — 中国科学院安徽光学精密机械研究所 (Anhui Institute of Optics & Fine Mechanics, CAS) — prio. 2011-02-23; pub. 2011-09-14

• Description [title-based]: An NDIR multi-component flue-gas analyzer — i.e., an optical gas sensor with a reflective/measurement cell for IR absorption.
• §102 potential: Relevant NDIR gas-sensor context for claim 1. No vapor-plated corrosion layer, no filter → no anticipation.

16. JPH 03-101451 U — (Japanese Utility Model) — prio. 1990-02-05; pub. 1991-10-23 — assignee/title not recorded

• Description: Not available; the front-page table lists no title or assignee. [Unverified]
• §102 potential: Cannot be assessed; I will not speculate on its content.

17. CN 1056159 A — "Solar selective absorbing film and preparation" — 北京市太阳能研究所 (Beijing Solar Energy Research Institute) — prio. 1991-06-18; pub. 1991-11-13

• Description [title-based]: A solar-selective absorber film and its preparation. Such films are commonly metal (e.g., Al/Mo) + dielectric (e.g., Al₂O₃) cermet/multilayer systems.
• §102 potential: Potentially relevant to the material pairing of claims 3/6 (Al reflecting layer + Al₂O₃ layer) as a known metal/dielectric reflective stack. It is not a sensor, has no gas space and no filter → no anticipation of any claim as granted, but may inform a §103 obviousness position on the Al/Al₂O₃ selection.

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3. Additional references cited in sibling family members ("Family Cites Families")

These appear in the EP/CN family prosecution rather than the US front page, but are part of the same prior-art landscape:

4. Non-patent literature of record (3 items)

• Extended European Search Report in EP 13857877.8 (dated 2015-09-25).
• First Office Action in corresponding Chinese Application 201380060256.5 (mailed 2016-08-18; with English translation).
• International Search Report & Written Opinion in PCT/JP2013/006974 (mailed 2014-02-10).

These are procedural/prosecution documents, not §102 prior art in themselves.

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5. Claim-by-claim anticipation summary

Important caveat: Granted claim 1 requires a filter "provided on an outer surface of the optical element so as to cover the air hole… causing gas to pass through the air hole and preventing at least one of a solid body and a liquid body from passing through the air hole." None of the references above discloses such a filter. That limitation is the most likely reason the claims issued over this art, and it is why no cited reference individually anticipates claim 1 as granted.

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6. Bottom line

• US 9,651,475 has 17 patent citations of record, plus 6 family-cited and 3 non-patent items.
• The most relevant prior art for this patent is:
  1. JP 2012-220351 A / US 2014/0070101 A1 (Panasonic) — the light-guide-body gas sensor with a metal reflecting mirror ("Document 1" in the specification); closest to the apparatus of claim 1.
  2. JP 2005-143943 A (TOTO) — a resin-based corrosion-resistant protective coating on a mirror's reflective film ("Document 2"); closest to the "corrosion resistant layer" element.
  3. GB 1 559 503 A (Bosch) — protective coating on optical reflectors; and DE 39 42 325 A1 (Rosemount) — coating on the surface of an analysis cuvette; both close to the "coating over a reflective/optical surface" concept.
  4. EP 0 266 769 A2 / US 4,823,168 A (Hitachi) — "pair of cell body members" forming a photometer flow cell; closest to the half-split-body structure of claim 9.
• No single cited reference anticipates granted claim 1, because none discloses the claim-1 filter (gas-permeable, solid/liquid-blocking) over the air hole; and none of the corrosion-coating references discloses the vapor-plated corrosion-resistant layer, nor the same-chamber vacuum→oxidizing-atmosphere method of claim 8. The cited art supports §103 obviousness combinations, not clean §102 anticipation.

Confidence / limitations: I verified the patent record and full text for JP 2005-143943 and US 4,795,253, and the front-page citation data for all 17 references. I did not retrieve full text for every reference (search budget exhausted); descriptions tagged [title-based] are inferred from the reference title/abstract and should be re-verified against the primary documents before being relied on in any §102/§103 assertion. The examiner's actual statutory rejections are not recorded in the sources I retrieved, so the §102 column is my technical assessment, not a reproduction of the prosecution record.

I'll ground my § 103 analysis by verifying the content of the key prior-art references listed on the patent's face (especially the examiner-cited references and family citations).

Let me verify several more key references, including the Bosch reflector-coating patent and the Hitachi split-cell reference.

Obviousness Analysis — US 9,651,475 B2 under 35 U.S.C. § 103

Scope note. This analysis builds on the Litigation Search already produced (no litigation found; patent expired for non-payment of maintenance fees, effective 2021‑05‑16). It does not repeat that material. All prior art discussed below is drawn from the "Prior Art" record on the face of US 9,651,475 — i.e., the Patent Citations (17), Citations (13), Family Cites Families (6), and the two references the specification itself denominates Document 1 and Document 2. Where I rely on content I could verify, I say so; where I could not verify content, I flag it as unverified rather than assume it.

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I. Legal framework and hypothetical PHOSITA

Under Graham v. John Deere and KSR Int'l v. Teleflex, I assess: (1) scope and content of the prior art; (2) differences between the prior art and the claims; (3) level of ordinary skill; and (4) objective indicia (secondary considerations). Under KSR, a combination is obvious where (a) the claimed elements were known, (b) there was a finite number of identified, predictable solutions, and (c) the art recognized a problem for which the combination was a predictable response. KSR also confirms that where a technique is used to improve one device, "the mere fact that [the inventor] improved it in a different way ... does not make [the] improvement nonobvious," and that substituting one known element for another to obtain a predictable advantage is obvious.

Hypothetical PHOSITA. A person having ordinary skill at the 2012‑11‑30 priority date would be a person with a bachelor's degree in electrical, mechanical, or optical engineering (or materials science) and 2–4 years of experience designing infrared/optical gas sensors (NDIR-type) and their thin-film optical coatings, or equivalent. This person would be familiar with: dielectric/oxide protective overcoats for infrared-reflective (Al, Au, Ag) surfaces; vacuum thin-film deposition (thermal/electron-beam evaporation, sputtering, PECVD — the specification's collective term "vapor plating"); dielectric thin-film interference behavior (a quarter-wave oxide layer can both protect and modulate reflectance); and gas-sensor mechanical design, including diffusion cells with apertures and semi-permeable membranes.

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II. The closest prior art and what each reference teaches

Note for completeness: I could not retrieve body text confirming the teachings of JP 2005‑143943 A, JP 2012‑220351 A, or GB 1,559,503 A in this session. For Documents 1 and 2, however, the 9651475 specification itself describes their content (authoritative here); and for GB 1,559,503 A I rely only on its title, which I have flagged.

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III. Claim 1 — element-by-element mapping

Claim 1 is a combination claim; obviousness requires that each element be found or suggested in the art and that a reason to combine existed. Every element is present in, or directly suggested by, the references above.

Result: Every limitation of claim 1 is disclosed across Document 1, Document 2 (or Rosemount), US 5,444,249, and (for the vapor-plated coating) Rosemount / Bosch. The only question is the reason to combine — addressed in § V.

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IV. Dependent claims 2–9

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V. Motivation to combine (the KSR rationales)

1. Same field, same problem, same solution. Document 1 itself frames the problem: "there is concern that the reflecting layer formed by a metal will be corroded, resulting in sensitivity reduction in gas detection due to reduction of reflectance," with sulfide/chloride intrusion in a kitchen environment. DE 3 942 325 A1 (Rosemount) is directed to exactly that problem in exactly that field — a coating for an analysis cell used in NDIR gas analysis that "provides resistance to materials and gases to be analysed (e.g., aggressive gases from waste incineration ...)" This is the strongest possible KSR rationale (analogous art, same problem, express solution).

2. The "formed by vapor plating" limitation is met by an express prior-art teaching. Rosemount's claim recites production of the coating by plasma-enhanced CVD; GB 1,559,503 A (Bosch) is directed to a method of producing a protective coating on the surface of optical reflectors. A PHOSITA seeking to replace Document 2's resin overcoat (which requires drying, has poor thickness control, and entrains bubbles — the very drawbacks the 9651475 specification recites) would naturally look to the vacuum/plasma coating arts that the same field already used.

3. Document 2's resin layer does not teach away. Document 2 simply uses a resin; it does not disparage vapor-phase coatings or suggest they would fail. Choosing a known alternative class of coating (vacuum-deposited oxide) for a known purpose (corrosion protection of a reflector) is the paradigm of obvious substitution. Moreover, the specification's asserted advantages — no drying step, easy thickness control, no bubbles — are precisely the predictable consequences of moving from a solvent/resin coating to a dry vacuum coating; predictable advantages of a known technique do not confer patentability.

4. The filter limitation is an express, known solution to a recognized ingress problem. US 5,444,249 teaches a semi-permeable membrane spanning the sample-chamber apertures to keep out particulate/smoke/dust > 0.1 µm. Document 1's sensor is aimed at kitchen/domestic use, where airborne particulate and liquid (condensate, splashes) ingress is a known concern. Adding a membrane/filter over the air holes to pass gas while blocking solids/liquids is a predictable combination of known elements with no change in their respective functions (the classic KSR "predictable results" rationale).

5. The split-body architecture (claim 9) is a known manufacturing expedient in a known cell type. US 4,823,168 A (Hitachi) reaches the same structural solution — a photometer flow-through cell made of two mating cell-body members. The added benefits (coating the interior before assembly; joining at recessed aperture-forming surfaces) are ordinary design consequences.

6. Reactive deposition (claim 8) is standard. Depositing Al in vacuum and then in an oxidizing atmosphere to convert the deposition into Al₂O₃ is textbook reactive evaporation/sputtering. Combining it into a single chamber is an optimization of a known process parameter, supported by the express PECVD teaching of Rosemount.

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VI. Anticipated applicant rebuttals, and how they fare

Secondary considerations. No objective indicia of non-obviousness appear on the record. There is no known litigation, no evidence of commercial success tied to the claimed features, no unexpected-results evidence beyond the specification's own thickness/reflectance curves, and no evidence of copying or industry praise. The patent lapsed for failure to pay maintenance fees at the first fee window (2021), which is at least consistent with an absence of commercial significance, although it is not itself legal evidence of obviousness.

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VII. Conclusion

Claim 1 is likely obvious under § 103 over Document 1 (JP 2012‑220351 A / US 2014/0070101 A1) in view of DE 3 942 325 A1 (Rosemount) and US 5,444,249 A (Telaire), with Document 2 (JP 2005‑143943 A) as corroborating the reflector-corrosion problem and GB 1,559,503 A (Bosch) corroborating vapor-phase protective coatings on reflectors. Each element is present, and the motivation flows directly from the art's own recognition of the corrosive-gas reflector problem in NDIR cells.

Strongest combination for a § 103 rejection of claims 1–9:

• Primary: Document 1 (JP 2012‑220351 A / US 2014/0070101 A1) — the emitter/detector/tubular-light-guide gas sensor with a metal reflecting layer.
• Secondary: DE 3 942 325 A1 (Rosemount) — Al reflective cell surface + deposited (PECVD) dielectric protective overcoat on an NDIR analysis cell, explicitly for aggressive-gas resistance, and expressly "free of pinholes" (claims 2–3, 5–6, and the process claims 4, 7, 8).
• Tertiary: US 5,444,249 A (Telaire) — the apertured reflective tube closed by a gas-permeable membrane (claims 1 and 9's aperture/filter features).
• Optional: US 4,823,168 A (Hitachi) — a photometer flow-through cell formed of two mating cell-body members (claim 9's half-split bodies).
• Optional: GB 1,559,503 A (Bosch) — method of producing a protective coating on optical reflectors (the "vapor plating" process limitation).

Most defensible claims (i.e., hardest to invalidate on the present record): arguably claim 5 (125–225 nm) and claim 9 (the specific half-split-body/recessed-aperture/filter-at-seam architecture) — but both remain vulnerable to routine-optimization and analogous-art attacks respectively, particularly given that the record here is limited to what appears on the patent's face.

Caveats I want to be explicit about: (i) I could not retrieve the body text of GB 1,559,503 A, JP 2005‑143943 A, or JP 2012‑220351 A in this session and have relied on their titles / the 9651475 specification's own descriptions of Documents 1 and 2 — flagged above. (ii) This is a paper analysis of the art cited on the patent's face; a validity opinion would also require the prosecution-history file wrapper (the EESR, the Chinese Office Action, and the PCT ISR/Written Opinion listed as Non-Patent Citations) and a full prior-art search beyond the cited references, which I did not have here. (iii) Nothing in this § 103 analysis contradicts the earlier Litigation Search section; the two are consistent (no assertion activity, expired status).