US 4610541

I'll search for the specific patent number and any litigation references.

Let me search for the claim text and any litigation involving this patent.

Let me try to retrieve the actual claim text.

Search scope and results

I searched for the exact number 4610541 (US 4,610,541) and for any 2026 CAFC/Federal Circuit docket referencing it.

• USPTO/patent‑office record: located. Authoritative full text retrieved from Google Patents (https://patents.google.com/patent/US4610541/en), with corroborating copies at FreePatentsOnline (https://FreePatentsOnline.com/4610541.html) and Justia (https://patents.justia.com/patent/4610541).
• CAFC 2026 docket: no hit. No 2026 Federal Circuit docket entry, opinion, or briefing referencing 4610541 was found. Two apparent numeric matches in search results were unrelated non‑patent records — an Argentine trademark filing "Acta 4610541" (class 35, INPI Argentina bulletin) and a Florida entity FEI number "47‑4610541" (Sunbiz annual report). Neither is a patent litigation reference. I therefore cannot confirm any litigation, PTAB proceeding, or appeal for this patent, and I am not asserting one exists — the negative result may simply reflect that no such 2026 docket exists, or that it is not indexed in the sources I could reach.

Bibliographic data (per the Google Patents record)

Related family item: The specification cites the inventors' own earlier application, Ser. No. 343,552, filed Jan. 28, 1982, now U.S. Pat. No. 4,468,120 (issued Aug. 28, 1984). Note the strict rule: I am reading "4,468,120" literally as it appears in the text, not re‑deriving it.

Abstract (verbatim from source)

"An inspecting apparatus for precisely detecting foreign substances or scars present on a translucent planar article such as a photomask at a high speed with a laser beam entering from face of the article, comprises first photoelectric means for receiving the scattered light generated in a space on a face of the photomask, second photoelectric means for receiving the scattered light generated in a space on the other face of the photomask, comparator means for comparing the photoelectrically converted signals from the first and second photoelectric means to identify one of predetermined plural magnitude relationships to which the magnitudes of the signals belong, and inspecting means for generating, in response to the detection output signal of the comparator means, a detection signal allowing to identify the approximate difference in the shape of the foreign substance, for example either a tall foreign substance or a short one."

Plain‑language overview

Problem. Photomasks/reticles and wafers used for LSI fabrication get contaminated by dust and by scratches ("scars"). The prior art (the inventors' own '120 patent) could tell whether a foreign substance sat on chromium (opaque) areas versus clear (translucent) glass, and which face it was on — but it could not tell the shape/attachment state (tall loosely‑adhered dust vs. a low, flattened deposit) nor distinguish a scratch from a particle.

Core insight. Illuminate the photomask obliquely with a laser; place photoreceptors on both the front (laser‑incident) and rear faces. Because tall loosely‑adhered particles scatter mostly into free space above the surface while low adherent deposits and scratches couple light into the glass, the ratio of front‑face to rear‑face scattered light is a signature of the object's shape. Comparing that ratio against thresholds (a simple one, e1 > e2, and a scaled one, e1 > K·e2, with K typically 1.5–2.5, e.g. 2) yields separate detection signals for tall particles versus low particles/scars. Additionally, a scanning‑position‑dependent "slicing voltage" compensates for the changing collection solid angle as the beam sweeps.

Hardware. 3rd/4th embodiments add redundant photoreceptors (lenses 10/20/30, elements 11/21/31 front; 12/22/23 rear) arranged at ~30–45° to each other and ~10–30° to the mask plane, letting the logic pick the less saturated channel — the one least affected by directional diffraction from dense circuit patterns. FIG. 18's circuit uses K ≈ 1.0 and a beam entering the rear face and focused on the patterned face, allowing both‑face inspection from one‑side illumination (no optical path switching mirror), producing signals SP (pattern‑bearing face) and SG (rear face).

Independent claims — plain‑language summary

Important caveat. I was not able to retrieve the verbatim, numbered claim text for this patent from the sources I reached (the fetched Google Patents and Justia text include the Definitions/summary and description but not the "What is claimed is" block, and my claim‑text searches returned other patents). The descriptions below are reconstructed from the patent's own "Definitions"/Summary‑of‑the‑Invention language and the described embodiments. The wording is therefore not verbatim and the exact number of independent claims is uncertain. I recommend verifying against the USPTO PatentCenter/Patent Public Search full‑text documents (patent number 4610541) before relying on it.

Based on that summary language, the patent appears to contain independent claims of roughly three kinds:

1. Broad apparatus claim. An apparatus for inspecting a translucent planar article (e.g., a photomask) scanned by a light beam entering one face, comprising: first photoelectric means for receiving scattered light generated in a space on one face of the article; second photoelectric means for receiving scattered light generated in a space on the other face; comparator means for comparing the photoelectrically converted signals from the first and second means to identify one of a plurality of predetermined magnitude relationships into which those signals fall; and inspecting means responsive to the comparator output for generating a detection signal that identifies the approximate shape difference of the foreign substance (e.g., tall vs. short).

2. Two‑comparator shape‑discrimination claim. An embodiment‑specific claim reciting a first comparator circuit that determines whether the first photoelectric signal is larger than the second, and a second comparator circuit that determines whether the first signal is larger than K times the second signal, the detection outputs of the two comparator circuits together enabling a determination as to the shape of the foreign substance.

3. Both‑face identification claim. A claim directed to detecting foreign substances on both faces of the photomask by laser irradiation onto one face and identifying whether the substance is on the pattern‑bearing face or the other face.

Dependent claims (per the description) would add such features as the position‑dependent slicing voltage synchronized with the scanning clock, the selected amplifying factor K in the 1.5–2.5 range, the redundant/paired photoreceptor geometry at specified angles, and the logic gating that produces the SA/SB (or SP/SG) detection signals. I cannot state their exact count or wording.

Uncertainties I want to flag explicitly

1. Claim text and claim count are unverified. Do not treat the above independent‑claim descriptions as literal claim language.
2. Priority document. A 1983‑04‑07 priority date with a Japanese‑origin assignee strongly suggests a JP priority application, but the source text I retrieved does not state the foreign application number, so I am not asserting one.
3. No 2026 CAFC activity found. Absence of a hit is not affirmative proof of absence; it means the sources I could reach surfaced nothing. Given the patent expired in 2004 and its legal status is "Expired – Fee Related," current 2026 appellate activity involving this number is unlikely.
4. I did not auto‑correct any identifier; "4610541," "US 4,610,541," application "06/596,440," and prior patent "4,468,120" are reproduced exactly as they appear in the source.

I'll search for litigation involving US patent 4610541 across patent litigation databases.

Let me search more targeted patent litigation sources.

Let me search dedicated litigation databases and dockets more specifically.

Search Results: Litigation Involving U.S. Patent No. 4,610,541

Conclusion: No litigation found

Based on my searches of patent litigation resources (including Google Patents' litigation listings, RPX/Unified Patents-style litigation portals, CourtListener, Justia, and general web sources), I found no litigation — no district court cases, ITC investigations, PTAB proceedings, or Federal Circuit appeals — involving U.S. Patent No. 4,610,541.

I want to be explicit that I was unable to retrieve a dedicated docket hit, and I hit a tooling/step limit before exhausting every database. So I cannot state with 100% certainty that no case ever existed, but I can state that nothing in the sources searched identifies U.S. Patent No. 4,610,541 as an asserted or challenged patent.

Why this is the expected result (contextual analysis)

• The patent issued in 1986 and expired (fee-related) around 2004-04-03, giving a real-world enforcement window of roughly 1986–2004.
• It was owned by Nikon (Nippon Kogaku) — an operating company with no history of wielding an expired 1980s inspection-tool patent as an assertion vehicle.
• It belongs to an early-generation photolithography equipment / mask-inspection area. The well-known Nikon-versus-ASML/Zeiss patent disputes (e.g., the 2001 ITC action and the 2017 suits in the Netherlands, Germany, and Japan, and related U.S. actions) involved different, later patents — for example, Nikon's "off-axis illumination" U.S. Patent No. 6,2xx,041 (note the similar trailing digits "'041") and the immersion-lithography EP 2 937 734 family. Those are distinct patents and should not be conflated with U.S. 4,610,541.

Important caution on false positives

Several search hits referenced a "'541 patent," but each refers to a different U.S. patent number, not 4,610,541. For example:

• Headwater Research LLC v. Verizon — the "'541 patent" there is a 2009-era network-capacity patent (U.S. 10,xxx,541-type).
• SK nexilis v. Solus Advanced Materials (E.D. Tex. 2:23-cv-00539) — a "'541 patent" in the copper-foil/CFL art.
• Various Chinese proceedings citing CN application/publication numbers.

None of these is U.S. Patent No. 4,610,541.

Bottom line

There is no known litigation involving U.S. Patent No. 4,610,541. The patent expired for failure to pay maintenance fees circa April 2004 and, consistent with its age, owner profile, and subject matter, does not appear in litigation, PTAB, or ITC records.

If you need a definitive negative, I recommend a direct paid-database check (Docket Navigator, Lex Machina, or RPX) and the USPTO Patent Center / assignment record for U.S. 4,610,541, since those are the authoritative sources for complete enforcement history.

I'll verify the structured-data default against live sources before writing anything up.

Proceedings overview

Zero AIA trial proceedings on file against US 4,610,541. The structured "PTAB proceedings on file" block (USPTO Open Data Portal, most recent ingest) returns no IPR, PGR, or CBM for this patent, and my independent web sweeps of Google Patents, Justia, FreePatentsOnline, and open Docket Alarm/PTAB document indices surfaced no petition, institution decision, Final Written Decision, or PTAB appeal naming this patent. Breakdown: active 0 / claims invalidated 0 / claims sustained 0 / settled 0 / institution denied 0.

The bottom-line defensive posture: this is not a "hardened patent" story — it is an abandoned-arsenal story. US 4,610,541 issued 1986-09-09, its 17-year term ran from the 1984-04-03 filing date, and it reached anticipated expiration on 2004-04-03 with a fee-related/expired legal status. There is no live patent right to attack, and no PTAB activity because there was never an economic reason to file one — the AIA trial regime did not exist until 2012-09-16, roughly eight years after this patent expired.

No proceedings to report

Because the canonical count is zero, the per-proceeding template (### {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner}) has no entries. I will not manufacture docket numbers to fill it. For the record, I checked and rejected the following near-misses, which are different patents with confusable shorthand:

I flag these because a naive "'541 IPR" docket search will hand you the Arthrex or Headwater proceedings and invite a serious mis-citation in a brief.

Verification and its limits

• Structured source (controlling): the ODP block in this prompt — no AIA trial proceedings.
• Live web searches run: US4610541 IPR PTAB proceeding; "4610541" inter partes review; "US 4,610,541" IPR petition PTAB; "foreign substance inspecting apparatus" 4610541 litigation/IPR; docketalarm PTAB "Patent 4,610,541". All returned zero proceedings against this patent.
• Caveat I want to be explicit about: Docket Alarm's case pages and PTAB E2E are dynamic/paywalled, so I could not run an exhaustive full-text query inside them. My negative finding rests on the ODP ingest plus these open-web sweeps. If a proceeding were filed in the last few weeks it could in principle be unindexed — but see the date math below, which makes that possibility negligible.

Strategic summary

Claim status: everything is UNTESTED — and moot. US 4,610,541 has never been construed, never been the subject of an IPR/PGR/CBM, and never been the subject of a published PTAB Final Written Decision. There is therefore no canceled-claim list to hand you and no sustained-claim list to worry about. The patent's own claim set (drawn to a scattered-light foreign-substance inspecting apparatus with paired photoreceptors, a K-factor comparator, and a scan-position-dependent slicing-voltage generator) is academic: per the Google Patents bibliographic data, the patent expired 2004-04-03 and carries status "Expired – Fee Related." Note the invention's own lineage — the specification credits the inventors' earlier US 4,468,120 (Ser. No. 343,552, filed 1982-01-28) as the prior improvement, so any historical family analysis should look there, not here.

Estoppel landscape: § 315(e)(2) is irrelevant here. There is no petitioner, so no estoppel attaches, and equally no petitioner-side record to mine for winning art. Nor do the usual IPR-side constraints help a defendant: an IPR of this patent is effectively unavailable for practical purposes, since the patent's term ended over two decades ago. An expired patent cannot support prospective infringement relief, and the practical motive to invalidate it — clearing a demand letter or an EDVA/EDTX count — is nil. If someone is citing US 4,610,541 to you today, the correct first question is not "what did the PTAB do?" but "under what legal theory is an expired 1986 apparatus patent being asserted at all?" — which usually indicates a patent-number transcription error in the demand or a scraped-portfolio citation.

Pattern signals: none to read. No serial petitioner, no patent-owner aggressive PTAB practice (Nikon Corporation, the current assignee via the 1988 name change from Nippon Kogaku K.K., appears nowhere in the PTAB record for this patent), and no defensive aggregator (Unified Patents or similar) in the chain. The absence of activity is not the ambiguous "well-asserted patents eventually attract IPRs" signal — here the absence is fully explained by expiration predating the AIA trial regime by eight years. Do not over-read it as evidence the patent was too strong to challenge.

Recommended next steps

1. Treat this as a null-result and pivot to the real dispute. There is no FWD to link to and no disposition to quote. If a counterparty has asserted US 4,610,541, respond by demanding the asserted claim numbers and an accounting of the patent's live term; the Google Patents record showing anticipated expiration on 2004-04-03 is the dispositive citation (https://patents.google.com/patent/US4610541/en).
2. Do not file, and do not threaten, an IPR. A petition against an expired patent invites a § 315(b)/standing fight and a discretionary-denial order for zero defensive benefit. If you genuinely need an administrative record on this disclosure, ex parte reexamination (which, unlike AIA trials, can address an expired patent's claims and is not subject to the one-year § 315(b) bar) is the correct vehicle — but confirm there is a live, asserted claim worth the expense first.
3. Sanity-check the patent number before doing any of this. The most likely explanation for this task is a transcription or docket-scrape error: confirm whether the assertion actually points to US 4,610,541, to the sibling US 4,468,120, or to one of the confusable " '541" patents identified above (Arthrex's 8,821,541; the Headwater '541). If the number resolves to one of those, the entire PTAB picture changes, and you should re-run this analysis against the correct patent.
4. If (and only if) a live patent in this family is identified, then run the standard four searches I was unable to complete inside the paywalled tools: PTAB E2E by patent number, Docket Alarm PTAB case search keyed to the exact patent number (not the " '541" shorthand), CourtListener RECAP for co-pending district court actions, and the CAFC docket for any appeal from a FWD. That is where a real estoppel and institution-decision narrative would come from — and it cannot exist for a patent that expired in 2004.

I'll attempt to retrieve the assignment record details, including reel/frame numbers and correspondent info, from the USPTO Assignment Center and cross-references.

Good — I found a concrete reel/frame lead on a sibling Nikon patent. Let me verify whether the same recording applies to US 4,610,541 specifically.

I hit the tool-step limit mid-verification, so one datapoint (the exact reel/frame for US 4,610,541's own 1988 recording) could not be confirmed for this patent. Everything below is stated with that caveat and nothing is invented.

Inventors

• Both are listed as the assignors in the original assignment of inventors' interest to Nippon Kogaku K.K. (Google Patents legal events: "Assignors: IMAMURA, KAZUNORI, TANIMOTO, AKIKAZU"), which is the ordinary signature of an employee-invention assignment, not a startup-founder transfer. There is no evidence either inventor held ownership personally at issue.
• No departure pattern. Nothing in the reachable record shows either inventor leaving the assignee within 12 months of the 1983‑04‑07 priority / 1984‑04‑03 filing. The opposite indicator is present: Tanimoto and Imamura are the same pair named on the inventors' earlier U.S. Pat. No. 4,468,120 (Ser. No. 343,552, filed 1982‑01‑28), cited in this very specification — a continuing R&D team at Nippon Kogaku, not a fire-sale precursor.
• Prosecution was handled by the U.S. firm Shapiro and Shapiro (listed as "Law Firm" on the published patent front page / Justia "Patent History"). Note the distinction the task asks me to draw: this is prosecution counsel of record, not an assignment-record correspondent. I could not retrieve assignment-correspondent fields (see caveat below).

Original assignee

• Entity on the issued patent: Nippon Kogaku K.K., a corporation of Japan, Tokyo (front page: "Assignee: Nippon Kogaku K. K. (Tokyo)").
• Primary line of business: optics and precision instruments — cameras, lenses, microscopes, and (critically here) semiconductor reduction-projection exposure equipment ("steppers"). Nikon shipped the NSR‑1010G, its first commercial ultra-LSI reduction projection aligner, in November 1980, i.e. before this application. This is a practising operating company, not a patent-holding vehicle.
• Product embodying the claims: the claimed subject matter is a foreign-substance/scatter inspection apparatus for photomasks and reticles — an inspection/metrology tool for mask and wafer manufacturing. Nikon's精機 (Precision Equipment) division was the business line; the invention sits in the same internal ecosystem as the stepper business.
• Current status: operating / solvent. Nippon Kogaku K.K. changed its corporate name to Nikon Corporation effective 1988‑04‑01 (recorded 1988‑06‑17). Nikon remains a publicly listed (Tokyo Stock Exchange), going concern with 80+ consolidated subsidiaries. No bankruptcy, no dissolution, no acquisition.

Assignment timeline

Two recorded chain events exist. A third listed legal event is a lapse, not an assignment.

• 1984‑04‑03 (execution date not separately stated) / recorded 1984‑04‑03 — Reel/Frame not retrievable from the sources reached (see caveat).

  • Conveyance: Assignment (assignment of inventors' interest)
  • Assignor: Akikazu Tanimoto; Kazunori Imamura
  • Assignee: NIPPON KOGAKU K.K., a corp. of Japan
  • Correspondent: not retrievable. Prosecution counsel of record was Shapiro and Shapiro; I do not assert they were the recording correspondent.
  • Context: standard employee-invention assignment taken at filing by the original operating-company assignee.

• 1988‑06‑17 (effective 1988‑04‑01) / recorded 1988‑06‑17 — Reel 004935 / Frame 0584 (⚠ see caveat — verified for sibling patent US 4,135,790, not yet confirmed for US 4,610,541)

  • Conveyance: Change of Name ("CHANGE OF NAME; ASSIGNOR: NIPPON KOGAKU, K.K.; REEL/FRAME:004935/0584")
  • Assignor: Nippon Kogaku, K.K.
  • Assignee: NIKON CORPORATION, 2‑3, Marunouchi 3‑chome, Chiyoda‑ku, Tokyo, Japan
  • Correspondent: not retrievable — this is the field the task flags as the key tell, and it is exactly the field I could not extract. No repeat-player attorney pattern can therefore be established either way.
  • Context: internal corporate reorganization / change of name only. This is not a transfer of ownership to a new party — the same legal person renamed itself. Google Patents labels it "CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE APR. 1, 1988."

• 2004‑04‑03 — anticipated expiration (legal-status event; not an assignment). Status: Expired – Fee Related. The patent lapsed for failure to pay maintenance fees; it was never transferred to any third party.

Correspondent caveat (explicit): The USPTO Assignment Center / Assignment Search application (https://assignmentcenter.uspto.gov/, https://assignment.uspto.gov/patent/index.html) is a JavaScript interface that the retrieval method available to me could not render. I therefore obtained the chain from Google Patents legal events and, for the 1988 recording, an Espacenet INPADOC legal-status record. The reel 004935 / frame 0584 citation comes from INPADOC for US 4,135,790 — a different Nippon Kogaku patent recorded on the identical date with identical assignor/assignee and the identical "CHANGE OF NAME" wording. Because Nikon recorded its mass 1988‑06‑17 name-change across a single reel per recording batch, reel 004935 is likely shared with US 4,610,541, but the frame would differ and I have not verified it for 4,610,541. Do not cite 004935/0584 as this patent's record without confirming in Assignment Center.

Timeline diagram

timeline
    title Ownership of US 4610541
    1984 : Application filed by Nippon Kogaku KK
         : Inventors Tanimoto and Imamura assign rights
    1986 : Patent issued to Nippon Kogaku KK
    1988 : Change of name only to Nikon Corporation
    2004 : Term expired for fee non-payment

NPE / troll-pattern signals

Score: zero strong signals, zero weak signals established; one field (correspondent) unresolved.

Verdict

Defensive / non-asserting.

Justification: the ownership chain contains no NPE signals whatsoever — the sole post‑1984 event is a name change only (Nippon Kogaku K.K. → Nikon Corporation, effective 1988‑04‑01, recorded 1988‑06‑17), so the patent never left the original operating company, and it terminated by fee lapse on 2004‑04‑03, not by transfer to any asserting entity. Explicit definitional caveat: the prescribed "Defensive / non-asserting" label is defined as a chain terminating at a defensive aggregator, which is not literally the case here; the chain terminates at an operating company. I am selecting this label as the only category that correctly captures the substantive finding — an operating-company-held, never-asserted, expired patent — and I flag the mismatch rather than force the facts into "Operating-company assertion" (no competitor suit exists) or "Insufficient data" (the chain is determinable).

Verification link: search patent number 4610541 at the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (mirror: https://assignment.uspto.gov/patent/index.html) — and confirm the 1988‑06‑17 change-of-name reel/frame and its correspondent directly, since that is the one entry I could not read for this patent.

I'll search for the USPTO record and the cited prior art references for this patent.

Let me pull the citation lists from dedicated patent databases.

I found the cited-references list. Let me verify each reference's details.

Prior Art Analysis — U.S. Patent No. 4,610,541

0. Scope, method, and a hard caveat

What I searched. I queried for the exact number 4610541 (US 4,610,541) and for its front‑page citation list. Retrieval came from mirrors of the USPTO front page rather than a direct PatentCenter full‑text pull:

• Google Patents (authoritative full text): https://patents.google.com/patent/US4610541/en
• Justia (front page incl. "Referenced Cited"): https://patents.justia.com/patent/4610541
• FreePatentsOnline: https://FreePatentsOnline.com/4610541.html
• Cross‑check search on US3814946A: https://patents.google.com/patent/US3814946A/en
• Cross‑check on 4,468,120 (cited in the 4610541 specification itself): https://www.freepatentsonline.com/4468120.html

I deliberately did not substitute or "correct" any number. Everything below is keyed strictly to 4610541 / US 4,610,541, application 06/596,440, filed 1984‑04‑03, priority 1983‑04‑07, issued 1986‑09‑09.

Two caveats you must carry into any § 102 conclusion:

1. The claim text of 4610541 is still unverified. The previously generated sections flagged this, and it remains true: neither the Google Patents nor Justia text I reached exposed the "What is claimed is" block. I therefore cannot cite claim numbers with confidence. Below I map references to the reconstructed claim types (broad apparatus claim; two‑comparator K‑threshold claim; both‑face identification claim) already described in the prior section. Flagging this as a contradiction‑risk item: any statement here about "which claim" is provisional until the numbered claims are pulled from USPTO Patent Public Search. If you have the claim block, I will redo the mapping precisely.
2. The citation list I retrieved appears to contain the U.S. patent documents only. The Justia front‑page snippet showed the "U.S. Patent Documents" sub‑table; it did not surface any "Foreign Patent Documents" or "Other Publications" sub‑table. A 1983‑priority, Japanese‑assignee application (Nippon Kogaku K.K.) very commonly carries JP citation(s) too, so I am not asserting the list below is the complete Rule 1.56/IDS‑style citation set. Treat it as the U.S.‑document subset.

Also note the citation direction. The references below are prior art cited against 4610541. Separately, 4610541 is itself cited by later Nikon patents (e.g., US 5,017,798, US 5,245,403, US 6,396,579) — those are forward citations and are not prior art; I exclude them from the § 102 analysis.

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1. Front‑page references cited (U.S. Patent Documents)

Source for the list: https://patents.justia.com/patent/4610541 ("Referenced Cited → U.S. Patent Documents").

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2. Reference‑by‑reference analysis

Reference 1 — US 3,814,946

• Full citation: U.S. Patent No. 3,814,946, "Method of detecting defects in transparent and semitransparent bodies," Takahashi et al., issued June 4, 1974. (Title and date confirmed independently at https://patents.google.com/patent/US3814946A/en; date also appears as "1974.6.4" in the citation list of CN 100590426 C.)
• Description (verified from the patent text): A light beam (collimated, from a slit) is directed at a transparent/semi‑transparent plate such as glass; a photodetector (condenser lens + photocell/photomultiplier) is positioned so it does not catch the direct beam but does catch light scattered by a defect inside the plate. Multiple photodetectors are arranged in a line for band illumination, and a second light source/geometry is used for defects in the smooth surface that the first source cannot see. Defects can be bubbles, inclusions, or surface defects.
• § 102 relevance: This is a classic scattered‑light, off‑axis photodetection disclosure. It is relevant to the "first/second photoelectric means for receiving scattered light" element of 4610541's broad apparatus claim. However, it has no second photoreceptor on the opposite face with a comparison of the two scattered‑light signals, and no comparator means identifying one of plural predetermined magnitude relationships, nor any shape ("tall vs. short") discrimination.
  • Potential § 102(b): could arguably anticipate only a hypothetical claim drawn to nothing more than "irradiate a transparent body and photoelectrically detect scattered light from a defect" — i.e., it is not anticipatory of any of the three reconstructed independent claim types of 4610541. More realistically it is a § 103 glue reference (single‑side scattered‑light detection is old).
  • Claim numbers: cannot be assigned — claim text unverified.

Reference 2 — US 3,984,189

• Full citation: U.S. Patent No. 3,984,189, Seki et al., issued Oct. 5, 1976 (as listed).
• Description: Not independently verified in this session. I did not retrieve this patent's own text or title in the searches performed, and I will not guess its title. Based on the assignee/inventor field alone I can only say it is a 1974–76‑era optical inspection patent by a Japanese‑named inventor.
• § 102 relevance: Provisionally, low/uncertain. Given its vintage and the company it sits next to in the citation list, it is most likely surface‑flaw/foreign‑matter detection by scattered or reflected light, which would make it relevant to the generic photoelectric‑detection element only. Because it issued more than one year before Apr. 3, 1984 (the 4610541 U.S. filing date), it falls in the § 102(b) window if its disclosure is enabling for the element at issue.
• Action item: I recommend a direct pull of US 3,984,189 to confirm title, disclosure, and whether it teaches any two‑face comparison. I am explicitly flagging this as an unresolved gap rather than inventing a description.

Reference 3 — US 4,173,441

• Full citation: U.S. Patent No. 4,173,441, Wolf, issued Nov. 6, 1979 (as listed).
• Description: Not independently verified in this session. Title and disclosure unretrieved; I will not fabricate them.
• § 102 relevance: Issued well over one year before the Apr. 3, 1984 filing → § 102(b) window if enabling. On the face of the citation list it sits in the general surface‑inspection/scattered‑light art useful against the photodetection element, and is unlikely by itself to disclose the front/rear ratio comparison or the plural‑magnitude‑relationship comparator.
• Action item: direct pull recommended; flag as unresolved.

Reference 4 — US 4,342,515

• Full citation: U.S. Patent No. 4,342,515, Akiba et al., issued Aug. 3, 1982 (as listed).
• Description: Not independently verified in this session. The "Akiba et al." / 1982 optical‑inspection profile is consistent with foreign‑matter or pattern inspection art, but I will not state a title or disclosure I have not read.
• § 102 relevance and the one timing point worth making: Aug. 3, 1982 is less than one year before the Apr. 3, 1984 U.S. filing date, so this reference does not qualify under § 102(b) on its issue date. Its relevance would run through § 102(a) (if its disclosure predates the April 7, 1983 priority/invention date) and/or § 102(e) (its own U.S. filing date predating the 4610541 invention date, and being "by another"). Given the one‑year priority window and the foreign‑priority (1983‑04‑07) situation, this is the reference whose § 102 subsection most needs careful handling.
• Action item: confirm title/disclosure and, importantly, its filing date, since § 102(e) turns on that date.

Reference 5 — US 4,468,120 (the closest reference — the inventors' own earlier patent)

• Full citation: U.S. Patent No. 4,468,120, "Foreign substance inspecting apparatus," Tanimoto et al., Nippon Kogaku K.K.; application Ser. No. 343,552 filed Jan. 28, 1982; issued Aug. 28, 1984. This is the very application the 4610541 specification names: "The present inventors already proposed, in the U.S. patent application Ser. No. 343,552 filed Jan. 28, 1982, now Pat. No. 4,468,120, issued Aug. 28, 1984…"
• Description (corroborated from the 4,468,120 text): Discloses exactly the two‑face architecture that 4610541 builds on. Independent claim 17 of 4,468,120 reads: "An apparatus for detecting the presence of a foreign substance adhering to a planar substrate having a light‑transmitting property, comprising: …" and the specification states, for its second embodiment, that there are provided "first photoelectric means disposed so as to look to said one surface and to receive the scattered light emitted to said one surface side, second photoelectric means disposed so as to look to the other surface … and a detecting device for comparing the photoelectric signals of said first and second photoelectric means and producing a detection signal corresponding to the adherence conditions of the foreign substance." It thereby distinguishes opaque‑area vs. translucent‑area foreign matter and which face the substance is on.
• § 102 relevance: This is the most relevant prior art and the only reference that comes close to 4610541's independent‑claim core.
  • Against the broad apparatus claim, 4,468,120 discloses: (i) light‑beam scanning of a translucent planar article; (ii) first photoelectric means for scattered light at one face; (iii) second photoelectric means for scattered light at the other face; and (iv) a detecting/comparing device. What it does not appear to disclose is the element 4610541 stresses — "comparator means for comparing … to identify one of predetermined plural magnitude relationships to which the magnitudes of said signals belong" — nor "inspecting means … allowing to identify the approximate difference in the shape of the foreign substance (tall vs. short)." On that reading, 4,468,120 is anticipatory only of a claim that is not limited to the plural‑magnitude/shape feature; against the claim 1 actually described in the 4610541 specification, it is best characterized as the admitted starting point under § 103, not a § 102 anticipation.
  • § 102 subsection caveat — the "by another" problem: 4,468,120 issued After the Apr. 3, 1984 filing date, so it is not a § 102(a) reference by issue date. Its § 102(e)-type force rests on its Jan. 28, 1982 filing date, but § 102(e) requires the reference to be "by another." Because 4610541's inventors are Tanimoto and Imamura and 4,468,120 is likewise a Tanimoto et al. Nippon Kogaku filing, the "by another" (distinct inventive entity) question must be checked against the 4,468,120 inventor list before this reference is relied on under § 102(e). Note also common assignee to Nippon Kogaku. This is a genuine open issue, not a settled point.
  • Claim numbers: cannot be assigned — claim text unverified.

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3. Consolidated § 102 picture

Bottom line. No single listed reference, on the record retrieved, discloses all elements of 4610541's independent claims — specifically the combination of (a) front‑face and rear‑face scattered‑light photoelectric means, (b) comparator means identifying one of a plurality of predetermined magnitude relationships, and (c) inspecting means emitting a shape‑discriminating (tall vs. short / scar vs. particle) detection signal. US 4,468,120 is the closest and is the reference the specification itself admits as the starting point; the patentable distinction 4610541 asserts over it is precisely the plural‑magnitude comparison (e1 > e2, and e1 > K·e2, K ≈ 1.5–2.5) and the resulting shape discrimination. That makes the likely examiner posture § 103 over 4,468,120 (optionally combined with a single‑side scattered‑light reference such as 3,814,946) rather than clean § 102 anticipation.

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4. What I could not establish (stated plainly)

1. Verbatim claims and claim numbering of 4610541 — not retrieved; all claim identifications above are provisional and keyed to the reconstructed claim types.
2. Titles/disclosures of US 3,984,189, US 4,173,441, and US 4,342,515 — not retrieved in this session; I have not described them and will not guess.
3. Completeness of the citation list — the retrieved list appears to be the U.S. patent documents only; foreign patent documents and other publications were not surfaced.
4. Inventor identity on US 4,468,120 — needed to resolve whether it qualifies as "by another" for § 102(e).
5. Foreign priority document number for 1983‑04‑07 — still not stated in the sources retrieved.

If you supply the numbered claims (or authorize a direct Patent Public Search pull), I can convert the provisional mapping in § 2–3 into a claim‑by‑claim § 102(a)/(b)/(e) chart.

I'll ground the prior-art universe before analyzing. The fetched page text does not include Google Patents' "Citations" or "Similar Documents" lists, so let me try to retrieve them, plus the admitted prior art US 4,468,120.

Two very important findings surfaced. Let me verify the admitted prior art's detecting circuit and try once more for the verbatim claims of US 4,610,541.

Obviousness Analysis — U.S. Patent No. 4,610,541 under 35 U.S.C. § 103

Prepared: 2026-04-26 · Patent: US 4,610,541 (US4610541A), "Foreign substance inspecting apparatus" · Priority: 1983-04-07 · Filed: 1984-04-03 · Issued: 1986-09-09

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0. What this section adds, and what changed from the earlier sections

The earlier sections established the bibliographic record, the substantive disclosure, and the (null) litigation/PTAB posture. This section is new work on the prior-art record, and it materially changes one earlier characterization. Three things to flag at the outset:

1. The Google Patents page as fetched did not include a standalone "Citations" or "Similar Documents" list. The only prior art named on the page itself is the reference in the specification's own background section: the inventors' earlier application Ser. No. 343,552, filed Jan. 28, 1982, now U.S. Pat. No. 4,468,120 (issued Aug. 28, 1984). I therefore built the prior-art universe from (a) that express admission and (b) live retrieval of US 4,468,120's full text, claims, and family. Read the combinations below accordingly.

2. Correction/refinement to the earlier "Patent summary." The earlier section called '120 "the inventors' own earlier application." Retrieved bibliographic data indicate '120's named inventor of record is Akikazu Tanimoto alone (see https://idiyas.com/patent/badge/4468120), whereas '541 names Tanimoto and Kazunori Imamura. This is not a trivial detail: it affects the pre-AIA §102(e) "by another" analysis (discussed in §3.1), and it makes '120 stronger as prior art against '541 than the "own earlier work" gloss implies.

3. The claim-text caveat from the earlier section still stands. I attempted again to retrieve the verbatim "What is claimed is" block for '541 and hit a tool/step limit. The analysis below is therefore keyed to the three claim archetypes reconstructed in the earlier section from the specification's Summary and Definitions language. I mark every place where verbatim text would change the conclusion.

Cross-reference: the Google Patents record's own "Prior art keywords" for this patent are foreign substance, substrate, photoreceptor, face, comparator — i.e., the examiner's art groupings are coextensive with the '120 disclosure. That is consistent with everything that follows.

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1. Governing standard and level of ordinary skill

Legal framework. Pre-AIA § 103(a); Graham v. John Deere Co., 383 U.S. 1 (1966) (scope/content of art; differences; PHOSITA level; secondary considerations); KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) (expansive motivation analysis and the enumerated rationales); MPEP §§ 2141–2144.04. Because '541's effective filing date is 1984-04-03, the pre-AIA framework governs, and the reference must qualify under pre-AIA § 102(a)/(b)/(e).

KSR rationales relied on below (I label them for traceability):

POSITA (1983 vintage). A worker with a bachelor's degree in optics, applied physics, or electrical engineering and about two to four years' experience in dark-field laser-scanning inspection of photomasks/reticles and wafers — familiar with (i) oblique-incidence laser scanning and galvanometer/polygon-mirror scanners, (ii) condenser-lens/photomultiplier collection of omnidirectional scattered light at low take-off angles, (iii) the directivity difference between pattern-edge scattering and particle scattering, and (iv) routine analog threshold and logic-circuit design (comparators, AND/OR gates, slice-level generators). This is a mature, predictable art — which matters, because in a predictable art the KSR "obvious to try" and "predictable variation" rationales carry substantial weight.

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2. The prior art of record

2.1 US 4,468,120 — the primary reference (and the only reference named on the '541 page)

Bibliographic (as retrieved): "Foreign substance inspecting apparatus," Nippon Kogaku K.K.; inventor Akikazu Tanimoto; filed 1982-01-28 (Ser. No. 343,552); issued 1984-08-28. Sources: https://patents.google.com/patent/US4468120 · https://www.freepatentsonline.com/4468120.html · https://patents.justia.com/patent/4468120 · https://patentimages.storage.googleapis.com/44/86/9e/1bc1feaf8f7076/US4468120.pdf

Disclosure inventory (I cite by figure/embodiment, since I could not verify column/line numbers):

Two points of enormous significance:

• The '541 and '120 detecting circuits appear to share reference numerals. '120's sixth embodiment uses preamplifiers 110, 111 and comparators 150–152; '541's Fig. 13 uses amplifiers 110, 111, 112, 113, 140 and comparators 114, 115, 141, 118, 119, 130, 135, 136. '120's fragments show comparator 104 and the relation e₁ < Ke₂; '541's Fig. 8 uses comparator 104 comparing e1 with Ke2. This overlap suggests '541 is, in large part, the same disclosure with additional comparators and logic gates bolted on — an important § 103 (and potential § 102) datum.
• '120 already claims the "position-dependent slice level" + "compare the two channels" architecture (claim 17), and already claims selection of the minimum-intensity channel (claim 10).

2.2 The published Japanese counterpart (flagged, unverified as to date)

US 4,586,822 (Tanimoto, Nippon Kogaku, filed 1984-06-15) states that '120 corresponds to Japanese Patent Application laid open No. 62543/1983 (i.e., JP 58-62543). Source: https://uspto.report/patent/grant/[4,586,822](/patent/4586822). If that laid-open publication bears a date before '541's 1983-04-07 priority date, it is a § 102(a) printed publication against '541 independent of '120's § 102(e) status; if it published only after that date but more than one year before 1984-04-03, it is § 102(b) art. I did not verify the publication date and do not assert it. Note also that US 4,586,822 itself (filed 1984-06-15) post-dates '541's filing date and is therefore not § 102/§ 103 prior art, despite being in the same family.

2.3 Secondary/background art — candidates, flagged as unverified

I identified the following as pre-1984 art cited on the face of later, same-field U.S. patents, but I did not retrieve their contents, and I do not rely on them for any limitation:

I list these for completeness and as a search roadmap, not as asserted combinations. Any of them may be developed into a formal combination if their full texts are pulled.

2.4 References that are not available as prior art (explicitly flagged to prevent mis-citation)

• US 4,740,079 (Koizumi et al., Hitachi) — "Method of and apparatus for detecting foreign substances." Filed 1985-10-28; JP priorities 1984-10-29 and 1984-11-14. Both dates post-date '541's 1983-04-07 priority and 1984-04-03 filing. It is therefore not § 102(a), (b), or (e) art against '541. It is useful only as evidence of the field. Source: https://patentimages.storage.googleapis.com/16/a8/a1/03680b8c3f3bdb/US4740079.pdf
• US 4,586,822 (Tanimoto) — filed 1984-06-15; not prior art (see §2.2).
• Later Nikon patents that cite '120 as the foundational reference — US 5,363,187 (Nikon; inventors Hagiwara & Hayano) and US 5,436,464 (Hayano et al.) — are post-dating and serve only to demonstrate that '120 is the base reference of this art. Source: https://patents.searchlight.law/doc/US5363187; https://patentimages.storage.googleapis.com/c7/1f/f5/0e8990ad342205/US5436464.pdf

Why this matters: every later patent in this lineage treats '120 as the starting point. That is strong evidence that a POSITA in 1984 would likewise have started from '120 and modified it — precisely the KSR "known device ready for improvement" posture (Rationale D).

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3. Status of '120 as prior art against '541 (three independent routes)

This threshold question matters more than usual here, so I address it before the merits.

1. Admission in the specification. '541 states: "The present inventors already proposed, in the U.S. patent application Ser. No. 343,552 filed Jan. 28, 1982, now Pat. No. 4,468,120, issued Aug. 28, 1984, an improvement on such apparatus…." A patent's own characterization of the prior art is usable as prior art for § 103 purposes regardless of whether it independently qualifies under § 102 (MPEP § 2129; the applicant's admission defines the problem and the state of the art). Critically, '541 then admits the gap: "It is however not yet possible to identify the attaching state of the foreign substance, namely the shape thereof or the status thereof on the surface, nor to distinguish a scar on the glass surface from the foreign substance." That sentence is a binding admission of the known problem and supplies the motivation element by itself.

2. Pre-AIA § 102(e). '120's application was filed 1982-01-28, which precedes '541's 1983-04-07 priority date. Under pre-AIA § 102(e), a U.S. patent granted on an application "by another" filed before the applicant's invention is prior art as of its filing date. The "by another" requirement is satisfied here because the inventive entities differ: '120 names Tanimoto alone; '541 names Tanimoto and Imamura. Where the entities differ, the reference is § 102(e) art as to that differing subject matter (see In re Land, 368 F.2d 866 (CCPA 1966); In re DeBaun, 687 F.2d 459 (CCPA 1982)). Caveat: I have verified '120's inventorship only from secondary bibliographic sources (idiyas) and its front page ("Tanimoto et al."); confirm '120's face-of-patent inventorship before relying on this route.

3. Pre-AIA § 102(a)/(b) printed publication. If JP 58-62543 (§2.2) issued as indicated, the same disclosure is a printed publication as of 1983. Unverified — do not brief it without checking.

Even if routes 2 and 3 were defeated, route 1 makes '120 fully available for the § 103 analysis. The claim-by-claim analysis below therefore stands on the admission alone.

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4. Claim chart: the '541 claim archetypes mapped against '120

Legend: ✔ = disclosed in '120; ◐ = partially disclosed / disclosed in a different but analogous context; ✗ = not found in '120.

Archetype 1 — broad apparatus claim (first/second photoelectric means; comparator means identifying one of plural predetermined magnitude relationships; inspecting means emitting a detection signal identifying the approximate shape difference)

Net: Archetype 1 differs from '120 essentially only in the characterization of the output — the same two-channel ratio comparator, applied to a further threshold, now reported as a shape classification rather than a face/localization classification.

Archetype 2 — the two-comparator shape claim (first comparator: e1 > e2; second comparator: e1 > K·e2; shape inferred from the pair of outputs)

Net: If the retrieved fragment is accurate, Archetype 2 may be anticipated by '120 rather than merely obvious over it. This is the single highest-value verification item (see §8).

Archetype 3 — both-face identification from single-side irradiation (SP = pattern-bearing face; SG = rear face)

Dependent-feature map (redundant receptors, angles, slice-voltage reversal)

Observation: Several dependent features of '541 appear to be literal carry-overs from '120's claims 3, 6, 7, 8, 10, 13, 16, 17, 18 and its fifth/sixth embodiments. If so, those dependent claims are anticipated, not merely obvious. This should be checked figure-by-figure against the '120 PDF.

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5. Combinations rendering the '541 claims obvious

For each combination I state (a) the differences from '120, (b) the KSR rationales, (c) predictability/reasonable expectation of success, and (d) the resulting conclusion.

Combination I — '120 alone (or '120 in view of the POSITA's ordinary creativity): Archetype 1 obvious

Differences. Only the output characterization: '120 classifies by where the particle is (chromium vs. glass; front vs. rear face); '541 classifies by how tall/adherent it is. The physical quantity being compared (the front-to-rear scattered-intensity ratio) is identical in both.

Motivation.

• Rationale F (design incentive). '120 itself articulates the economic driver: detecting needlessly small particles "would … re-clean a reticle or a mask usable for exposure," causing "time loss." The very next incremental improvement a mask-inspection engineer would demand is a false-positive discriminator — a way to separate a worrying particle from a harmless flat deposit or a scratch. '541's admitted problem ("nor to distinguish a scar on the glass surface from the foreign substance") is that demand stated in words.
• Rationale D (known device ready for improvement). '120 is the acknowledged base apparatus, and '120's own Summary flags "adherence conditions" as its object. A device built to classify adherence conditions is manifestly "ready for improvement" into a device that classifies shape.
• Rationale A (predictable result). Adding a second comparator to an existing ratio-comparing circuit changes nothing in the optics, the scan, the collection geometry, or the principle of operation; it merely subdivides an existing analog ratio into more bins.
• Rationale G (predictable variation / mere change in degree). Subdividing a measured value into three or four outcome classes rather than two by adding thresholds is a textbook change in degree with a predictable result. See In re Aller, 220 F.2d 454, 456 (CCPA 1955) ("where the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation").

Predictability. Total. The only question is whether the ratio actually correlates with shape — and '541's own specification answers that it does, using data obtained by routine experiment ("the ratio … is generally 2 to 8"; "the threshold ratio … is experimentally determined in relation to the shape of the foreign substance").

Conclusion. Archetype 1 obvious under § 103 over '120, at minimum in view of the specification's admission of the known problem. A § 102 challenge is also colorable if the actual claim language does not add a structural limitation absent from '120.

Combination II — '120 alone: Archetype 2 obvious (and possibly anticipated)

Differences. The recitation of two named comparator circuits (e1 > e2; e1 > K·e2) with the K factor recited.

Motivation.

• Rationales A + G. '120 already discloses (i) a two-channel comparison (claim 17(e)) and (ii) a K-scaled comparison (the "e₁ < Ke₂" relation with amplifier/comparator 104). Adding a further, un-scaled comparator that performs the identical comparison against a different reference is a duplication of parts with no change in function — the paradigm of Rationale A.
• Rationales D + F. Once the POSITA accepts that the front/rear ratio encodes particle character (which '120's apparatus measures and '120's spec links to particle size), the ratio test is "ready for improvement" by a scale factor.
• Rationale E + routine optimization. '541 recites K ∈ [1.5, 2.5], "for example 2," and calls the threshold "experimentally determined." Selecting a numeric multiplier within a disclosed, narrow, empirically located window, where the spec supplies no evidence of criticality, is routine optimization (In re Boesch, 617 F.2d 272 (CCPA 1980); In re Geisler, 116 F.3d 1465 (Fed. Cir. 1997) (no criticality without evidence of unexpected results)).

Predictability. High. The claim recites a threshold comparison — a purely deterministic, predictable operation on a measured ratio.

Conclusion. Archetype 2 obvious over '120 alone; potentially anticipated if '120's Fig. 14/16 circuit is as the retrieved fragment indicates. This combination is the strongest and simplest in the whole analysis and needs no secondary reference at all.

Combination III — '120 alone (claims 13(e) and 17(d)): the position-dependent slicing-voltage features obvious

Differences. '541's slicing-voltage generator varies Vs in synchronization with the scanning clock so the threshold tracks the changing collection solid angle as the spot sweeps.

Motivation. '120 claim 17(d) recites exactly this ("slice level output which … changes according to said position of incidence"); '120 claim 13(e) recites position-responsive amplification; '120's description discloses converters 58, 59, 60 driven by controller 61. '541's own explanation ("the distance from said position to the photoreceptor element 11 varies according to the scanning of the laser beam 1, thus varying the steric angle of the lens 10") is an explanation of why '120's disclosed feature works, not a new structure. Discovering the reason a known expedient works does not confer patentability on the known expedient.

Conclusion. Obvious (indeed anticipated, if the claim language tracks '120 claim 17(d)). Note this is not a mere dependent-claim issue: if '541's independent claim recites the slice-level generator, Combination III knocks it out on its own.

Combination IV — '120 alone (claim 10 + fifth/sixth embodiments): the redundant-photoreceptor/lesser-channel architecture obvious

Differences. '541's Fig. 12/13 uses five detectors in a redundancy scheme in which the lesser of two front-side channels is selected for the ratio test, and a third, oppositely-directed front-side channel (element 31) is used with a reversed-tendency slice voltage to veto pattern-edge false positives.

Motivation.

• '120 claim 10(d)–(e) already claims "means for detecting the light-receiving means having detected a minimum intensity of light" and comparing that channel with its counterpart — which is '541's comparator 130 / inverter 131 / ANDs 132–133 / OR 134 function.
• '120's fifth embodiment already discloses the oppositely-directed third receptor with a reversed-tendency slice voltage.
• '120's sixth embodiment already discloses two slice voltages per channel separated by a predetermined difference.
• Rationale C/D. Using a third, oppositely-directed detector to suppress directional pattern-edge scattering is the very technique '120 teaches to improve its own device; '541 uses it in the same way for the same purpose.

Conclusion. Obvious; and if '541's dependent claims recite these geometries, they are likely anticipated by '120's claims 6–8, 10 and fifth/sixth embodiments. The specification's asserted advantage ("selecting the smaller … prevents disabled comparison … due to saturation of the signal processing system") is an advantage the POSITA would expect from claim 10's disclosed minimum-intensity selection — a predictable benefit, not an unexpected one.

Combination V — '120 in view of the known single-side/both-face expedient: Archetype 3 (SP/SG) obvious

Differences. '541 detects both faces with a beam entering only one face (Fig. 17/18), with K ≈ 1.0 and the beam focused on the pattern-bearing face, producing SP and SG.

Motivation.

• Rationale F. '541's own justification is inspection throughput ("reducing the time required for inspection). '120's own stated objects include quickly detecting adherence conditions on both surfaces. Time-saving in a scanning inspection tool is a classic design incentive.
• Rationale C + B. The alternative that '541 itself identifies — "an optical path switching mirror or the like for obliquely introducing the laser beam 1 into the rear face" — is a known, disclosed-in-the-spec expedient; replacing it with the equivalent one-pass approach is a simple substitution of one known mode of illuminating the mask for another (Rationale B), yielding an expected result.
• Rationales D + G. Focusing the beam on the pattern-bearing face (rather than on the rear face) merely moves the focal plane; '541 admits the sensitivity tradeoff "may be regulated by the adjustment of said focus point," which is the language of a predictable, tunable parameter — Routine optimization.
• Setting K = 1.0 is a degenerate substitution of a value within, and at the boundary of, the already-disclosed range — Rationale G. If a claim recites K ≈ 1.0 as inventive, the response is In re Aller/In re Geisler.

Conclusion. Archetype 3 obvious over '120 in view of the POSITA's ordinary knowledge plus the admitted expedient.

Combination VI — secondary references (Jablonowski '293; Heebner '124) as substitutes for the optical/scanning elements

Status: NOT asserted. I have not verified the contents of these references (§2.3). I include them only to mark where a formal combination could be built if a challenge ever materialized: the scanning/scatter-collection elements of '541 are the most conventional part of the disclosure, and either reference could substitute for or supplement '120 on those elements under Rationale B. Do not brief these until full texts are pulled and their dates confirmed (note the date risk on Heebner, 4/1984 vs. '541's 1984-04-03 filing).

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6. Secondary considerations

There is no objective evidence of non-obviousness in the record. The earlier sections established that this patent was never litigated, never IPR'd, and never construed; consequently there is no testimony, no commercial-success evidence with a proven nexus, and no unexpected-results data. What the specification does supply cuts against patentability:

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7. The § 102 exposure the § 103 analysis does not fully capture

With the claim text unavailable, the single most consequential point is this: the retrieved fragments and claims of '120 suggest that several '541 limitations are not merely suggested by the prior art but literally disclosed in it — most importantly:

• the K-multiplier comparison (amplifier with factor K feeding a comparator: "e₁ < Ke₂"),
• the position-responsive slice level ('120 claim 17(d)),
• the two-channel comparison ('120 claim 17(e)),
• the minimum-intensity channel selection ('120 claim 10(d)–(e)),
• the oppositely-directed third receptor with reversed-tendency slice voltage ('120 fifth embodiment), and
• two slice voltages per channel separated by a predetermined difference ('120 sixth embodiment).

If those disclosures are confirmed, the corresponding '541 claims should be analyzed as anticipated under § 102(a)/(e), not merely obvious under § 103 — a materially easier challenge that avoids all Graham-factor balancing.

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8. Verification checklist — what could change this analysis

Ranked by impact:

1. Retrieve the verbatim '541 claims (USPTO PatentCenter / Patent Public Search, or FPO/Justia claim block). Everything above is keyed to the three spec-derived archetypes. If, e.g., the independent claim recites a specific structure — the redundant third-side receptor, the reversal of the slice-voltage tendency, or particular angular ranges — then Combinations IV and the dependent-feature map become the controlling analysis, and Combination I may become moot.
2. Retrieve '120's Fig. 14/16 detecting circuit in full (the PDF at patentimages.storage.googleapis.com/…/US4468120.pdf) to confirm the exact presence and configuration of the K amplifier, comparators 103/104/107, AND 105/108, and inverter 109. This determines whether Archetype 2 is anticipated or "merely" obvious, and whether the sharing of reference numerals between the two patents is genuine.
3. Confirm '120's inventorship of record from the patent's own front page (not from idiyas) to firm up the pre-AIA § 102(e) "by another" argument.
4. Verify JP 58-62543's publication date before relying on § 102(a)/(b).
5. Verify the Heebner '124 and Jablonowski '293 dates/contents if Combination VI is ever needed.
6. Confirm the truncated tail of the '541 specification (the fetched text ends mid-sentence in the Fig. 18 discussion, "…to divide the detection signal SP for the pattern bearing face into a detection…"), in case the missing text contains an additional claim-supporting limitation.

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9. Bottom line

• The § 103 case against US 4,610,541 is strong, and unusually simple, because it reduces almost entirely to a single reference — US 4,468,120 — which the '541 specification itself names and which the retrieved record shows to disclose the same oblique-scanning, dual-face, ratio-comparing, position-compensated, lesser-channel-selecting architecture. The '541 and '120 detecting circuits appear to use the same reference numerals for the same components.
• Archetype 2 (the two-comparator, K-factor shape claim) is the cleanest knock-out: '120 indisputably claims the two-channel comparison with a position-responsive slice level ('120 claim 17), and the retrieved fragment shows the K-scaled comparison in '120's own circuit. The only addition is a further comparator against a different reference — Rationales A, G, and routine optimization of K.
• Archetype 1 is obvious because the sole difference is the name given to the output classification (shape vs. face/localization); '120's stated object is already the detection of "adherence conditions," and '541 expressly admits the residual problem, which is the motivation.
• Archetype 3 (both faces from one-side irradiation) is obvious over '120 in view of the time-saving incentive and the admitted optical-path-switching alternative; K = 1.0 is a boundary value of the disclosed range.
• The dependent features (redundant receptors, angular geometry, reversed slice-voltage tendency, lesser-channel selection) appear to be carried over from '120's claims 6–8, 10, 13, 16–18 and its fifth/sixth embodiments and are candidates for outright § 102 anticipation.
• No secondary consideration supports patentability, and the specification's own admissions (empirical thresholds, "experimentally determined" ratio, focus-point adjustability, "may be vertically displaced") supply the routine-optimization and predictable-variation rationales.
• Strategic caveat carried forward from the earlier sections: this patent expired 2004-04-03 and has no litigation or PTAB history. This § 103 analysis is therefore a defensive/academic exercise unless a counterparty actually asserts US 4,610,541 — in which case the first question remains whether the asserted claim is live at all, and the second is whether the number resolves to '541 or to one of the confusable " '541" patents identified earlier. If a challenge is ever needed notwithstanding expiration, ex parte reexamination — not an AIA trial — is the correct vehicle.