US 9891041

I'll search for authoritative information on this specific patent number.

Both queries returned empty. Let me try alternate phrasings to be thorough.

Let me check for litigation/docket activity and confirm the exact bibliographic details.

Search results / data provenance

I was able to run several searches. Important transparency notes:

• Two queries — "9891041" patent and EDTM Inc patent 9891041 litigation — returned zero results.
• A query on CAFC 2026 dockets for this patent returned zero results. I therefore have no authoritative information about any Court of Appeals for the Federal Circuit proceeding, or any district-court litigation, involving U.S. Patent 9,891,041 in 2026. I am not going to speculate about docket numbers or parties.
• The bibliographic and claim data below comes from the full patent text supplied in this prompt (Google Patents, US9891041B2) and corroborating search hits (Google Patents, Justia, Patents Encyclopedia for the A1 publication US2016/0069667).

Caveat on my own search tooling: the two empty result sets may reflect a search limitation rather than the true absence of litigation. Treat "no CAFC/litigation found" as unconfirmed, not as proof there is none.

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Bibliographic summary — US 9,891,041 B2

Abstract (as given): "Methods and apparatuses for measuring the thickness on at least one transparent or translucent medium and detecting the presence and/or location of any conductive coating on a non-conductive medium surface are described."

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Plain-language overview of the independent claims

Claim 1 — Apparatus

An apparatus that measures thickness of at least two transparent/translucent mediums that have matching or similar indices of refraction, and also measures the index of refraction between the two mediums. It requires:

1. At least one light energy source that sends an incident beam to a first medium (having first and second surfaces) and to at least a second medium (having first and second surfaces).
2. At least one light sensor that receives separate reflected beams from each of the first and second surfaces of each medium, and is configured to measure the index of refraction between the two mediums.
3. The sensor is angled at normal or near-normal incidence to those received beams, with a stated physical rationale:
   • at true normal incidence, there is no further reflection of the received beam reaching the sensor;
   • at near-normal incidence, any further reflection essentially stays within the original ray of travel and reinforces the received signal;
   • net effect: reduction of unwanted internal reflections at the sensor.

The core inventive thrust is geometric: orient the detector so reflections off the medium's surfaces arrive normal (or near normal) to the sensor, eliminating stray/internal reflections that otherwise corrupt thickness readings (compare FIG. 3 "near normal" versus FIG. 4 "incident angle" showing multiple unwanted peaks).

Claim 17 — Method

The method counterpart of claim 1, with the same four elements: directing an incident beam at the first and second mediums; providing a light sensor that receives separate surface reflections from each surface of each medium and measures the index of refraction between the two mediums; the sensor positioned at normal/near-normal incidence with the identical "no further reflection" / "stays within the original ray" rationale, thereby reducing unwanted internal reflections.

Drafting note (quote): claim 17 contains the phrase "the light sensor being positioned at an angle is at normal or near normal incidence…" — apparently a residual antecedent/grammar artifact carried over from claim 1. I'm reporting it verbatim rather than correcting it, per instruction.

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Notable observations and uncertainties

• Narrower-on-issue than the specification's stated aspects. The "BRIEF SUMMARY" frames the apparatus/method broadly — e.g., "at least one transparent or translucent medium" and simply "near normal incidence reflected light energy." But the granted independent claims (1 and 17) are narrower: they require (a) at least two mediums, (b) matching or similar indices of refraction, and (c) the sensor configured to measure the index of refraction between the two mediums. That is a meaningful limitation worth flagging for any infringement or validity analysis.
• Dependent-claim support mapping (from the claim set): reflective medium/mirror (cl. 2); movable sensor (cl. 3); housing with first/second mounting fixtures (cl. 4) and independent movement (cl. 5); 2-D array (cl. 6); filter/bandpass or notch (cl. 7–8); CCD/CMOS/photodiode array (cl. 9); three-or-more mediums (cl. 10); gap width (cl. 11); coated-surface reflection (cl. 12); processor correlating gap width (cl. 13); CCD regulating energy carryover between sensor elements (cl. 14); sensor angled in x-/y-/z-axis with redirecting optics (cl. 15); and a capacitive sensor plus processor for detecting conductive coatings (cl. 16). Note the antecedent quirk between cl. 7 ("at least one filter") and cl. 8 ("the filter").
• Cited prior art of record (5 references): US 2008/0068619 A1; US 2007/0074415 A1; US 8,723,944 B1; US 2014/0185060 A1; US 2013/0273237 A1.
• Family follow-on: US 11,067,377 B2 (EDTM, Inc., 2021) appears as a later family member on a capacitance/environmental-capacitance subject, consistent with the capacitive-sensor strand in claim 16.

Bottom line on the current-activity question: the patent itself is live and in force through the 2036 adjusted-expiration date. I could not verify any 2026 CAFC docket or other live litigation for US 9,891,041 with the searches available to me, and I won't fabricate a docket reference. If litigation status is critical to your analysis, it should be confirmed directly against the USPTO PatentCenter litigation portal, PACER/RECAP, or the CAFC docket system.

I'll search for litigation involving US patent 9891041 across litigation-tracking sources.

Initial searches returned unrelated patents. Let me search more specifically.

No litigation hits yet. Let me try more targeted searches on litigation databases.

Known Litigation Involving U.S. Patent No. 9,891,041

Result: No litigation was found involving U.S. Patent No. 9,891,041.

After searching litigation-tracking sources (Unified Patents litigation portal, RPX/Insight, PACER-oriented results, CAFC/Federal Circuit materials, and general web searches) using the exact identifier 9,891,041, I could not identify any district court, ITC, or Federal Circuit case in which this patent was asserted, challenged, or made the subject of a declaratory judgment action.

What the targeted searches returned (and did not return)

• Exact-number searches returned no matches. Queries combining "9891041" / "US 9,891,041" with terms like litigation, lawsuit, defendant, infringement, and complaint produced no relevant results. The hits returned were unrelated patents whose numbers happen to end in "-989" or "-041" (e.g., Transonic v. NMT's '989 and '550 patents; Belanger's '041 patent in Wash World; Crossroads Systems' '041 patent). Per your instruction, I excluded these as similar-but-different numbers.
• The Unified Patents litigation case list was searched for the identifier and returned nothing tied to this patent.
• The patent's own Google Patents record lists "Cited By," "Families Citing this Family," and "Similar Documents" — a "Families Citing" / forward-citation listing that would typically surface later family activity — but the record shows no litigation, ITC, PTAB, or Federal Circuit entries for US 9,891,041.
• No IPR/PGR/reissue/reexam involving this patent appeared in the results either.

Patent identification confirmed (for the record)

• Patent: U.S. Patent No. 9,891,041 B2
• Title: "Apparatus and method for measuring thickness of transparent and/or translucent mediums using a reflecting signal that is normal or near normal to the mediums"
• Assignee: EDTM, Inc.
• Inventors: Nathan Strimpel; Jed Martens; Mark A. Imbrock; Jeffrey A. Simpson
• App. No.: 14/834,580 | Priority: 2014-09-08 | Filed: 2015-08-25 | Granted: 2018-02-13
• Status: Active; adjusted expiration noted as 2036-01-04

Important caveats

1. Confidence level: I have moderate-to-high confidence that no reported litigation exists as of this date, but I cannot state this with the certainty of a complete PACER/Unified Patents database query, because my searches returned no direct database confirmation for this specific number — only an absence of hits across the sources queried.
2. Why an absence is plausible: This patent is owned by EDTM, Inc., a small Ohio-based instrument manufacturer (small entity; maintenance fees paid at 4th and 8th years). Such patents frequently are not litigated and are instead practiced defensively by the owner. This is consistent with the lack of any litigation record.
3. What I am not asserting: I am not representing that litigation definitively does not exist. If you need a legally reliable negative, the authoritative step is a direct PACER docket search (all U.S. district courts) and a Unified Patents litigation portal query for the exact number, which I was unable to complete before exhausting my search steps.

Bottom line: Based on the sources searched, no case (plaintiff/defendant/jurisdiction/case number/filing date/status) can be reported for U.S. Patent No. 9,891,041 — no known litigation. If you can run or provide a direct PACER/Unified Patents docket lookup for the exact number, I can confirm or update this finding.

I'll verify the ODP's "no proceedings" result against public sources before finalizing.

Proceedings overview

Zero AIA trial proceedings are on file against US 9,891,041. The USPTO Open Data Portal structured feed reports no IPR, PGR, or CBM petitions for this patent, and my independent web checks (queries for "9,891,041" / "US9891041" in combination with IPR/PTAB/petition, and for EDTM as petitioner/patent owner in trial proceedings) surfaced no petition, institution decision, Final Written Decision, or Federal Circuit appeal referencing this patent. There is no proceeding to rank, no claim-level outcome to report, and therefore no claims of this patent have been canceled or held unpatentable by the Board — the bottom-line defensive posture is that the patent stands wholly untested at the PTAB, with all 20 claims intact and no § 315(e) estoppel available to lean on.

A note on confidence: this is a negative finding, and negative findings from public search are weaker than positive ones. I state it directly rather than dress it up. What follows is a null-set report with the verification trail and the strategic implications, not fabricated proceeding entries.

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No proceedings to detail

No {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner} sections are supplied because the canonical source (the ODP "PTAB proceedings on file" block) returns an empty list, and no search result contradicts it. I will not invent petition numbers to fill the template.

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Verification trail

The search results I did retrieve were dominated by unrelated PTAB matters (Netlist '912, HemoSonics '971, YMTC/Micron '974) and by the patent's own Google Patents / USPTO PDF text. None referenced US 9,891,041 as a subject of review.

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Patent posture relevant to a defendant

Pulled from the authoritative patent text you supplied (not from search):

• Independent claims: 1 (apparatus) and 17 (method). All other claims (2–16, 18–20) are dependent. Note that the granted claim 1 is materially narrower than the originally‑filed disclosure — as issued it recites "at least two transparent or translucent mediums that have matching or similar indices of refraction," "separate beams of reflected light energy reflected from each of the first and second surfaces of each the first and second mediums," and "configured to measure the index of refraction between the two mediums." Those limitations are the product of prosecution, and they are the natural target of any future validity challenge.
• Priority / term: priority 2014-09-08 (provisional 62/047,166); filed 2015-08-25; granted 2018-02-13; adjusted expiration 2036-01-04. This is a long-lived asset — roughly nine more years of runway from today (2026-09-29).
• Maintenance fees current: 4th-year fee paid 2021-08-13; 8th-year fee paid 2025-08-13 (both small-entity). The owner is actively maintaining the patent, so an abandonment-based attack is not available.
• Prior-art landscape already on the face of the patent (the five references the examiner cited): US 2008/0068619 A1 (CEA), US 2007/0074415 A1 (Gagnon), US 8,723,944 B1 (EDTM — incorporated by reference and the admitted prior art), US 2014/0185060 A1 (Carl Zeiss SMT), US 2013/0273237 A1 (Johnson). These are cited by the examiner, not by a petitioner, so they do not carry any estoppel baggage and remain fully available to a defendant.
• Family: US 2016/0069667 A1 (pre-grant publication), single U.S. family member in the ODP feed (family ID 55437215). A later EDTM filing, US 11,067,377 B2 (priority 2018-03-20, granted 2021-07-20), cites this family — relevant if your product-accusation touches capacitance-based coating detection, since that is a separate EDTM asset with its own (similarly empty, as far as this record shows) PTAB history.

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Strategic summary

Claim status: all 20 claims UNTESTED. Because no AIA trial has ever been instituted, there is no claim-level adjudication to work from. Claims 1 and 17 (the independents) and every dependent claim remain live, unamended, and presumptively valid under § 282. There has been no certificate of cancellation, no adverse judgment, no disclaimer, and — critically — no PTAB claim construction for a district court to borrow under Phillips or for the parties to argue about under § 315(e). If you received a demand letter or a complaint, you cannot point to a single canceled claim. Any "the patent is already dead" posture is unsupportable on this record.

Estoppel landscape: a clean slate, which cuts both ways. No petitioner has ever triggered § 315(e)(2), so there is no estoppel constraining the patent owner and none constraining a would-be challenger. Conversely, nothing prevents you from filing an IPR so long as you clear § 315(b)'s one-year bar (one year from service of a complaint alleging infringement of this patent on you, your real parties in interest, or your privies). The full universe of prior art remains available: the five examiner-cited references above, the incorporated-by-reference Imbrock '944 disclosure (which the specification itself characterizes as the prior-art baseline — a helpful admission), and anything else you can find. There is no risk that a prior petitioner has already "used up" the good art or that your grounds will be collaterally estopped by a prior FWD.

Pattern signals: none, and that is the story. There is no repeat petitioner, no serial-IPR campaign, no Unified Patents (or other defensive aggregator) involvement, and no patent-owner appeal activity, because there is no proceeding at all. For a patent that has been on issue since 2018-02-13 and is actively maintained, the absence of any IPR is mildly notable. Two plausible explanations, and I cannot distinguish them on this record: (a) the patent has never been asserted in a way that made the one-year IPR window attractive or that produced a defendant with the incentive and budget to file; or (b) assertions have resolved at the demand-letter stage without litigation. I did not find public litigation filings tying US 9,891,041 to a named defendant, but my search coverage there was thin and I would not treat that as a reliable negative. The patent's field — handheld glass-thickness and low-E coating detectors sold by a small Ohio entity (EDTM, Inc.) — is one where assertions are often against glass fabricators and window manufacturers, i.e., parties that may lack the appetite for a PTAB fight.

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Recommended next steps

If you are a defendant being asserted against:

1. Do not build a defense around invalidated claims — there are none. Before anything else, confirm the live claim set with the USPTO Patent Center "Supplemental Content" / reexamination tab for US 9,891,041 and the patent's public file wrapper at https://patents.google.com/patent/[US9891041B2](/patent/US9891041B2)/en (which lists "Also Published As" and the family). My finding of no PTAB activity is a search-based negative; a file-wrapper pull is the dispositive check.
2. Calendar the § 315(b) deadline immediately. One year from service of the first complaint alleging infringement of the '041 patent. Miss it and IPR is gone permanently. Because the patent issues from a 2015 filing, IPR remains available under § 311(c) (more than nine months post-grant, no PGR pending).
3. Attack the issued claim 1's narrowing limitations. The "matching or similar indices of refraction" and "measure the index of refraction between the two mediums" recitations were added during prosecution and are the most likely weak points. Cross-check them against the provisional (Ser. No. 62/047,166, 2014-09-08) for § 112 written-description support, and against the two prior art references in the record (Optical Device for Measuring the Thickness of an at Least Partially Transparent Medium, US 2008/0068619 A1, and Gagnon, US 2007/0074415 A1).
4. Mine the incorporated-by-reference Imbrock '944 disclosure. The specification expressly calls its own system an "improvement in the Imbrock et al. U.S. Pat. No. 8,723,944" — the prior art's parallel-mount CCD arrangement is admitted background. That admission is useful § 103 material for the "positioned at an angle ... normal or near normal incidence" limitation.
5. Note the § 101 angle is largely foreclosed by Alice step one — the claims recite CCD/CMOS arrays, a light source, mounting fixtures, and a capacitive sensor with opposing plates. This is a hardware-measurement apparatus, not a generic-computer abstract idea. Do not over-invest here.
6. Consider pre-empting the companion asset. If the assertion or your product touches capacitive coating detection, evaluate US 11,067,377 B2 separately; a challenge there is a different proceeding with its own deadline. Do not assume a win on the '041 does anything to the '377.

If you are the patent owner: the absence of PTAB history means your claims and their constructions are unconstrained, but your § 282 validity has also never been stress-tested against a well-funded petitioner with discovery. Expect the narrowing limitations added during prosecution to be challenged first.

If you simply need the canonical record for a filing: the authoritative sources are the USPTO PTAB E2E system at https://ptacts.uspto.gov/ and the ODP endpoint you already queried. For this patent, both point to the same null result. The absence of PTAB activity is itself a data point — but here it reflects an untested patent, not a hardened, IPR-survived one. Treat US 9,891,041 as fully vulnerable and fully live.

I'll research the assignment record for US 9891041, starting with the USPTO Assignment Center and cross-referencing sources.

Let me dig deeper into the assignment record and cross-reference EDTM's status and any litigation.

Let me attempt to access the assignment record directly and check for any litigation or further transfers.

Inventors

Employer determination: The single recorded assignment (reel 036803/0616) is an "ASSIGNMENT OF ASSIGNORS INTEREST" from all four inventors to EDTM, Inc. of Ohio, with inventor signing dates of 2015-10-06 through 2015-10-12 — i.e., contemporaneous with the 2015-08-25 filing. This is a standard employer/employee invention assignment, and the specification identifies the earlier EDTM-owned Imbrock et al. '944 patent as the assignee's own work. All four are therefore treated as EDTM personnel.

Unusual patterns: None observed. There is no evidence of inventors departing the original assignee (no subsequent assignments executed by individual inventors, no re-assignments to third parties). Note that I could not independently confirm each inventor's exact employment title; the employer attribution rests on the recorded assignment plus the common-assignee specification language.

Original assignee

EDTM, Inc. — 745 Capital Commons Drive, Toledo, Ohio 43615.

• Primary line of business: Manufacture and sale of handheld glass-inspection instrumentation for the window/glazing industry — laser and digital glass & air-space thickness gauges, Low-E coating detectors, and window energy profilers. Product line examples: Glass-Chek PRO GC3001, Glass-Chek ELITE GC3200, MG1500 laser thickness gauge, AE2250 Low-E detector, RD1660 ShowerGuard detector, WP4501 energy profiler.
• Did they ship a product embodying the claims? Yes, with high confidence. The patent's stated advance is accurate thickness measurement of laminated inner-layers and of multiple panes with closely matching indices of refraction; EDTM's GC3200 Glass-Chek ELITE is marketed as "Now Detecting Laminated Glass … Identify laminated glass in a window, and measure the thickness of the laminate inner-layer," which matches the improvement described in the specification ("this technique makes it possible to measure more difficult mediums such as laminate inner-layers"). The predecessor MG1500/GC3001 family corresponds to the earlier '944 patent.
• Current status: Operating. No bankruptcy, dissolution, or acquisition is evident in the record; the company advertises current products (edtm.com) and paid maintenance fees on this patent in 2021 and 2025 (see timeline).
• Source: EDTM product pages/manuals (edtm.com), Fine Homebuilding 2025 product coverage, and the patent's own specification.

Assignment timeline

Caveat on sourcing: the live USPTO Assignment Center query did not return extractable results through the tools available to me, so the record below is reconstructed from the Google Patents legal-events tab for US 9,891,041 (which mirrors the USPTO assignment database entries) plus the patent's own front matter. I could not independently retrieve the recorded correspondent of record for reel 036803/0616, so I am not naming a correspondent rather than fabricating one.

Chronological list of every recorded assignment:

• 2015-10-06 to 2015-10-12 (executed) / recorded 2015-10-15 — Reel 036803/0616
  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Nathan Strimpel; Jed Martens; Mark A. Imbrock; Jeffrey A. Simpson
  • Assignee: EDTM, Inc. (Ohio)
  • Correspondent: Not retrievable with the tools available here. Recorded description is "ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS)." Because there is only one recorded assignment in this chain, there is no recurrence of a correspondent to flag in any event — the "repeat correspondent" tell is inapplicable by construction.
  • Context: Standard inventor-to-employer assignment (internal, pre-issuance); establishes EDTM's clean chain of title from the inventors.

That is the entire recorded assignment record. There are no post-issuance assignments, no security agreements, no mergers, no change-of-name recordings, and no transfers to any third party. Per the Google Patents legal-events feed, EDTM, Inc. remains the current assignee, and the only other recorded events are the 2015-10-15 grant-side publication, the 2018-02-13 grant, and maintenance-fee payments (2021-08-13, 4th year; 2025-08-13, 8th year, both as a small entity — consistent with an independent operating company, not a well-capitalized NPE vehicle).

Timeline diagram

timeline
    title Ownership of US 9891041
    2014 : Provisional filed Sep 8
         : Four inventors named
    2015 : Non-provisional filed Aug 25
         : Inventors assign rights to EDTM Inc
         : Recorded reel 036803 frame 0616
    2016 : Application published
    2018 : Patent granted Feb 13
    2021 : Fourth year maintenance fee paid
    2025 : Eighth year maintenance fee paid

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The only recorded transfer is inventors → EDTM, Inc. (an operating manufacturer, reel 036803/0616). No "IP / Patents / Licensing / Holdings / Ventures" entity appears anywhere in the chain, and no Delaware/Texas single-purpose LLC is a named assignee.

2. Known asserter in the chain — Not present. The current assignee is EDTM, Inc. There is no Acacia, Marathon, Intellectual Ventures, Wi-LAN, Conversant/Mosaid, Vringo, Pendrell, Round Rock, Document Generation Corp, or Spangenberg-linked entity on the record. No Unified Patents / RPX high-frequency-plaintiff match.

3. Repeat correspondent across the chain — Not present / inapplicable. Only one assignment was recorded, so no correspondent can recur. I was unable to retrieve the correspondent name for reel 036803/0616; I flag this as a data gap, not as evidence.

4. Cascading transfers — Not present. A single assignment, executed and recorded in October 2015, with no downstream links and no chained LLCs.

5. Pre-litigation transfer — Not present. No infringement suit naming US 9,891,041 was found, and there is no transfer at all proximate to any litigation.

6. Bankruptcy fire-sale — Not present. No Chapter 7/11 proceeding involving EDTM appears in the record; maintenance fees continued to be paid on schedule through 2025.

7. Privateering — Not present. No transfer to a third-party NPE asserting on EDTM's behalf; EDTM retains ownership and monetizes the patent through product sales (Glass-Chek family).

8. Defensive aggregator (anti-NPE) — Not present. The chain terminates at the operating original assignee, not at RPX, AST, LOT Network, Unified Patents, or OIN.

Verdict

Insufficient data (only the original assignment).

Justification: The complete assignment record consists of a single conveyance — inventors Strimpel, Martens, Imbrock, and Simpson to EDTM, Inc., executed 2015-10-06/12 and recorded 2015-10-15 at reel 036803/0616. There are no post-issuance transfers to analyze, so no NPE behavioral pattern can be constructed from the chain; substantively, the absence of any downstream assignment plus the assignee's continued operation and maintenance-fee payments (2021-08-13 and 2025-08-13) indicates the patent remains with the original operating-company owner, which ships products (e.g., the GC3200 Glass-Chek ELITE measuring laminate inner-layers) that read on the described improvement. All eight NPE signals above are negative on the evidence available.

Verification links:

• USPTO Assignment Center (search by patent number): https://assignment.uspto.gov/patent/index.html#/patent/search
• Google Patents legal events for US 9,891,041: https://patents.google.com/patent/[US9891041B2](/patent/US9891041B2)/en

Confidence note: the "no further assignments" conclusion rests on the Google Patents legal-events mirror of the USPTO assignment database and on the tool limit that prevented me from opening the Assignment Center record directly. If a later recording exists that is not reflected in that feed, it would change the "cascading transfer" analysis — but nothing in the sources consulted suggests one.

I'll research each cited reference to build accurate, grounded prior-art profiles.

USPTO Prior-Art Analysis — U.S. Patent No. 9,891,041 B2

Scope/method. I pulled the authoritative record for U.S. Pat. No. 9,891,041 (App. No. 14/834,580; EDTM, Inc.) from the Google Patents/USPTO data set and cross-checked each of the five examiner-cited references against its own patent record. Below I treat the patent's own "Patent Citations (5)" table as the authoritative citation list for 9,891,041 and analyze each reference literally. Identifiers are quoted exactly as they appear; I have not auto-corrected any.

Patent identity (cross-reference, not repeated): 9,891,041 B2, "Apparatus and method for measuring thickness of transparent and/or translucent mediums using a reflecting signal that is normal or near normal to the mediums," inventors Strimpel, Martens, Imbrock, Simpson; priority 2014-09-08 (prov. 62/047,166); filed 2015-08-25; granted 2018-02-13; source https://patents.google.com/patent/[US9891041](/patent/US9891041)/en.

Critical framing for the § 102 question. Issued independent claim 1 (and mirroring method claim 17) are narrow. They require, in combination: (i) at least two transparent/translucent mediums having matching or similar indices of refraction, with measurement of the index of refraction between the two mediums; (ii) a light sensor receiving separate beams reflected from each of the first and second surfaces of each of the two mediums; and (iii) the sensor positioned at normal or near-normal incidence to those beams, with the recited consequence (no further reflection at normal incidence / near-normal reflection staying within the original ray, "thereby reducing unwanted internal reflections"). Anticipation under § 102 requires every element in a single reference. As shown below, none of the five cited references discloses the near-normal-incidence reflection geometry combined with the two-medium / inter-medium index-of-refraction limitation. They are best characterized as § 103 (obviousness) art and/or art cited against specific dependent-claim features, not as anticipating references.

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Summary of the five examiner-cited references

All five published before the 2014-09-08 priority date of 9,891,041 and therefore qualify as prior art (§ 102(a)/(b), or § 102(a) for the 2014 publications), subject to the caveats in the final section.

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Reference-by-reference analysis

1. US 2008/0068619 A1 (US 7,570,372 B2) — Commissariat à l'Énergie Atomique

• Full citation: U.S. Pub. No. 2008/0068619 A1; granted as U.S. Pat. No. 7,570,372 B2. "Optical Device for Measuring the Thickness of an at Least Partially Transparent Medium." Inventors Peltie, Vial, Guiga. Source: https://patents.google.com/patent/US20080068619
• Dates: Priority FR 2004-07-06; PCT filed 2005-06-24 (WO 2006/013247); U.S. pub. 2008-03-20; patent granted 2009-08-04.
• Brief description: A laser 5 emits a collimated beam 4 at an oblique angle of incidence (≈45°) toward a first, at least partially transparent medium 2 covering a second medium 3 (e.g., a water film on asphalt). A reflected beam 6 (from the first-medium free surface) and a scattered beam 7 (from the second medium) are collected by a photosensitive CCD linear array 8. A processing circuit 9 measures the gap between the two beam impacts (δ1, δ2) to derive film thickness (e = k(δ1−δ2)) and corrects the result using the array-to-surface distance H via optical triangulation.
• Relevance under § 102: Discloses a light source + CCD spatial detector for optical thickness determination, arguably touching the "light energy source directing a beam to a medium" and "CCD array" concepts underlying claims 1 and 9. However, it does not disclose: two mediums with matching/similar indices of refraction; measurement of index of refraction between two mediums; detection of separate beams from all four surfaces of two transparent mediums; or normal/near-normal incidence (its geometry is explicitly oblique/triangulation-based). Accordingly it does not anticipate claim 1 or 17, and because every dependent claim depends from claim 1, it does not anticipate any issued claim as a whole. Best treated as § 103/background art.

2. US 2007/0074415 A1 — Gagnon, Robert E.

• Full citation: U.S. Pub. No. 2007/0074415 A1. "Method and Apparatus for Layer Thickness Measurement." Inventor Gagnon, Robert E. Source: https://patents.google.com/patent/US20070074415A1
• Dates: Filed/priority 2005-09-30; published 2007-04-05.
• Brief description: A focused laser beam is aimed at a first spot on a surface; part of the beam refracts through an extant layer (ice, water, etc.), illuminating a region on the underlying surface. Diffuse reflections from the first spot and the illuminated region are imaged (digital camera or diode array), centers are computed, and thickness H is derived from the center separation S using the beam/detector geometry and the index of refraction of the layer. Suited to remote measurement (e.g., aircraft-wing ice).
• Relevance under § 102: Discloses computing layer thickness using an index of refraction and detecting multiple reflections/illuminations from a layer's top and bottom faces — relevant background to the reflection-measuring concept and to dependent claims dealing with layer boundaries (e.g., claim 12's coating/thickness measurement). It does not disclose two glass-type mediums with matching indices of refraction, inter-medium index-of-refraction measurement, or near-normal-incidence reception. Does not anticipate claim 1 or 17.

3. US 8,723,944 B1 — EDTM, Inc. (Imbrock et al.) ← closest art

• Full citation: U.S. Pat. No. 8,723,944 B1. "System for Detecting Conductive Coatings on Non-Conductive Medium Surfaces." Assignee EDTM, Inc. Expressly incorporated by reference into 9,891,041 (see col. spec. "improvement in the Imbrock et al. U.S. Pat. No. 8,723,944"). Source: https://patents.google.com/patent/US8723944
• Dates: Priority 2009-09-28; filed 2010-09-27; granted 2014-05-13.
• Brief description: The antecedent system. A thickness-measuring (reflection) sensor with a light source 52, CCD light-sensing elements 54, and a bandpass/notch filter 70 directs a beam L through a second pane 22, gap 24, and first pane 21, measuring reflections Lr-a…Lr-d from the four glass surfaces, plus a capacitive sensor for LOW-E coating detection. Its CCD array sits parallel to the substrate, so reflections strike the sensor at an angle — the very arrangement 9,891,041 identifies as causing problematic internal reflections (PRIOR ART FIG. 1).
• Relevance under § 102: This is the most pertinent reference and the true antecedent of 9,891,041. It discloses the two-medium reflection architecture, multi-surface reflection sensing, gap-width measurement, index-of-refraction considerations, coating detection, and CCD-array + capacitance combination reflected in dependent claims 6, 7, 9 – 16. Critically, however, it does not disclose the distinguishing element (d) — a sensor at normal or near-normal incidence — and instead teaches the oblique-incidence geometry the '041 patent departs from. It therefore does not anticipate claim 1 or 17 (and cannot anticipate dependent claims, which incorporate claim 1).
• Note (potential § 102 disqualification): The '944 patent shares an inventor (Imbrock) and the same assignee (EDTM) with 9,891,041, so it may be disqualified as prior art for obviousness under the common-ownership provisions (pre-AIA § 103(c)(1); AIA § 102(b)(2)(C)). Its most reliable role is as incorporated background, not as anticipating art.

4. US 2014/0185060 A1 (US 9,250,062 B2) — Carl Zeiss SMT GmbH

• Full citation: U.S. Pub. No. 2014/0185060 A1; granted as U.S. Pat. No. 9,250,062 B2. "Devices for Determining Layer Thickness and/or Contamination Level of a Belt." Assignee Carl Zeiss SMT GmbH (inventors incl. Doerband, Lindner). DE counterpart DE 10 2011 082 793 A1. Source: https://patents.google.com/patent/US20140185060
• Dates: Priority DE 2011-09-15; U.S. pub. 2014-07-03; granted 2016-02-02.
• Brief description: An in-line apparatus for a moving tape/film: a light-generating unit, a beam-shaping unit producing a strip-shaped (line) illumination beam across the tape, a detector unit sensing reflected and/or transmitted illumination (and scattered light for particle contamination), and an evaluation device computing layer thickness and refractive index.
• Relevance under § 102: Discloses optical layer-thickness and refractive-index measurement, relevant background to thickness/refractive-index determination generally. It does not disclose two spaced transparent mediums with matching indices, separate reflections from four surfaces, or near-normal-incidence reception. Does not anticipate claim 1 or 17.

5. US 2013/0273237 A1 — David Johnson

• Full citation: U.S. Pub. No. 2013/0273237 A1. "Method to Determine the Thickness of a Thin Film During Plasma Deposition." Inventor David Johnson (Plasma-Therm). Source: https://patents.google.com/patent/US20130273237
• Dates: Priority 2012-04-12; published 2013-10-17 (CN counterpart CN 104246009 A; PCT filed 2013-03-22).
• Brief description: In-situ measurement of thin-film thickness during plasma deposition using optical emission/interference (OEI) at multiple wavelengths; monitors reflected radiation, detects extrema, fits a deposition-thickness-vs-time equation, and calculates film refractive index.
• Relevance under § 102: Discloses multi-wavelength reflectance monitoring and refractive-index calculation — thematic overlap with the multi-wavelength reflection data discussed in 9,891,041's spec (slope relationships of multiple-frequency sources). It does not disclose two glass mediums, four-surface reflection geometry, or near-normal incidence. Does not anticipate claim 1 or 17.

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Overall assessment

• Most relevant prior art to 9,891,041: US 8,723,944 B1 (Imbrock et al., EDTM) — the expressly incorporated antecedent sharing the same assignee/inventor. It discloses nearly the entire reflection-based two-pane architecture and the coating-detection features of claims 1 – 16, but not the claimed near-normal-incidence sensor geometry that is the point of novelty — a distinction the '041 specification itself draws vis-à-vis PRIOR ART FIG. 1. The remaining four references are more remote (§ 103-level) art directed to unrelated measurement contexts (road/ice films, moving tapes, plasma deposition).
• No single cited reference anticipates independent claim 1 or claim 17, because none discloses the combination of (a) two mediums with matching/similar indices of refraction, (b) measurement of the index of refraction between them, and (c) normal/near-normal-incidence reception of the separate surface reflections. Because all 20 issued claims depend from claim 1 or 17, no cited reference anticipates any issued claim in its entirety on the record reviewed.
• Other art of possible interest (from the patent's "Similar Documents" list, not examiner-cited): US 6,683,695 B1 ("detecting properties of reflective transparent surface coatings"); US 9,074,874 B2 ("Coating detection on transparent sheet material"); US 9,304,046 B2 ("Sensor system and method for characterizing a coated body"); WO 2011/007047 A1 ("detecting properties of a reflective transparent object"). These are conceptually closer to reflective coating/thickness sensing and may warrant fuller review if a § 103 challenge were contemplated.

Caveats and confidence

1. "Potentially anticipates" vs. actual prosecution record. The five references appear in the patent's citation table (an examiner citation list), but their citation alone does not establish which statutory section (102 vs. 103) or which claims were relied upon. I mapped each reference to the claim features it discloses based on the reference's own disclosure; I did not have the examiner's office actions, so the specific rejection basis is inferred, not confirmed.
2. Anticipation standard. My conclusion that nothing anticipates claim 1/17 rests on strict element-by-element § 102 analysis using the issued claim language. A reference could still be combined under § 103, but the task specified § 102.
3. Common-ownership issue for the '944 patent (same assignee/inventor as 9,891,041) may remove it as prior art for obviousness; I flagged this rather than treating it as established.
4. Dates are taken as listed in the patent record and the references' own records; I did not independently verify PCT/national-phase filing chains. Where the record shows both a publication and a later grant (references 1 and 4), I listed both.
5. No fabrication: I did not locate any additional examiner-cited reference beyond the five listed, and I am not asserting that the cited list is exhaustive of all art of record (e.g., references cited on the face of the patent versus IDS submissions).

I'll ground this analysis in the prior-art references identified on the patent page. Let me pull details on the five cited references.

Let me pull the foundational Klopfenstein reference (cited within the '944 family) and check whether any art teaches normal-incidence detection to suppress internal reflections.

Obviousness Analysis — U.S. Patent No. 9,891,041 B2 under 35 U.S.C. § 103

Technical analyst assessment, not a legal opinion. Claims and specification text are taken from the patent as supplied in the prompt and from the Justia copy (https://patents.justia.com/patent/9891041). Prior-art content is from the "Prior Art" materials captured on the Google Patents page for US9891041B2 (the five Patent Citations of record) plus the family reference cited within them.

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1. Governing framework and effective filing date

• Effective filing date: 2014-09-08 (provisional 62/047,166; non-provisional 14/834,580 filed 2015-08-25). This is post-AIA, so § 103 is applied as amended, under the KSR framework: whether the differences between the claimed subject matter and the prior art are such that the subject matter as a whole would have been obvious to a person of ordinary skill at the effective filing date. Motivation to combine may come from the references themselves, the knowledge of a POSITA, the nature of the problem, or market/design incentives; the combination need not be "obvious to try" in a narrow sense, and predictable variation of a known technique is enough.
• All five cited references predate the critical date and are available as § 102(a)(1)/(a)(2) art:
  • US 2008/0068619 A1 (Commissariat) — pub. 2008-03-20
  • US 2007/0074415 A1 (Gagnon) — pub. 2007-04-05
  • US 8,723,944 B1 (Imbrock/EDTM) — issued 2014-05-13
  • US 2014/0185060 A1 (Carl Zeiss SMT) — pub. 2014-07-03
  • US 2013/0273237 A1 (Johnson / Plasma-Therm) — pub. 2013-10-17

Threshold flag (common ownership): '944 is the parent that '041 expressly incorporates ("an improvement in the Imbrock et al. U.S. Pat. No. 8,723,944"). Because '944 issued before the '041 effective date, it is § 102(a)(1) "patented" art, and the common-ownership carve-out of § 102(b)(2)(C) (which applies only to § 102(a)(2) art) does not remove it. It remains available for § 103. This is the single most important structural fact in the analysis.

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2. The independent claims (1 and 17), decomposed

Both independent claims recite the same six elements (17 being the method twin of 1):

The specification frames E6 as the whole reason for E5: in the '944 arrangement the CCD "inside the enclosure … positioned in parallel to the substrate surface" causes reflected energy entering the bandpass filter and CCD cover glass "at an angle," producing extra internal reflections that corrupt the legitimate surface peaks (contrast FIG. 3 near-normal vs. FIG. 4 oblique).

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3. What each reference of record actually teaches

US 8,723,944 B1 — Imbrock et al. (EDTM) — the closest art. (https://patents.google.com/patent/US8723944; https://insight.rpxcorp.com/patent/[US8723944B1](/patent/US8723944B1))

• Same field, same assignee, same problem. Discloses a dual-pane assembly with a first and second medium, each having two surfaces, illuminated by a light source that directs a beam through the second medium, the gap, and the first medium, with reflections Lr-a, Lr-b, Lr-c, Lr-d returned from those four surfaces to a CCD linear image array.
• Discloses a filter in the beam path (bandpass or notch), a processor, and computation of medium thickness and gap width from reflections.
• Expressly discusses index of refraction: "different mediums and/or gaps will result in different indexes of refraction that will … shift or alter the reflecting angle."
• Expressly discloses the capacitive-measuring sensor + processor for conductive coatings (its claims 18 et seq.), and the CCD "energy carryover" regulation / intensity / sensitivity / shutter-speed / anti-saturation features (its claims 34/44) — i.e., the subject matter of '041 claims 14 and 16.
• Critical deficiency: the CCD array is "positioned in a linear plane parallel to the substrate surface," so reflections strike the sensor at an angle — the exact condition '041 says causes the internal-reflection problem.

US 2008/0068619 A1 — Commissariat à l'énergie atomique (https://patents.google.com/patent/US20080068619; https://uspto.report/patent/app/20080068619)

• Optical device measuring the thickness of a first medium that covers a second medium (water film over asphalt), using a collimated laser beam at a "predetermined angle of incidence," a CCD photosensitive array, and a processing circuit that computes thickness from the gap between the reflected and scattered beam impacts (e = k(δ1−δ2)) and corrects for the standoff distance H by triangulation.
• Supplies: two-layer transparent-medium thickness measurement by a CCD array with geometric/optical processing — but it is explicitly oblique (triangulation requires it).

US 2007/0074415 A1 — Gagnon (https://patents.google.com/patent/US20070074415A1)

• Method/apparatus for measuring a layer on a surface (ice/water) by detecting reflections from the top and bottom faces, computing their centers/separation, and computing thickness using the separation, the beam/surface geometry, and the index of refraction of the layer. Works for transparent and diffuse layers; multi-point pan/tilt.
• Supplies: explicit teaching that the index of refraction of the medium is used in the thickness computation, and that separate top/bottom reflections are resolved — again at oblique angles.

US 2014/0185060 A1 — Carl Zeiss SMT (https://patents.google.com/patent/US20140185060)

• Determines layer thickness and/or contamination of a tape from illumination radiation reflected and/or transmitted at the tape, using a light-generating unit, beam-shaping unit, detector unit, and evaluation device; also determines refractive index of the tape/individual layers; multi-layer stack; in-situ/inline.

US 2013/0273237 A1 — Johnson / Plasma-Therm (https://patents.google.com/patent/US20130273237)

• Determines thin-film thickness during deposition by monitoring reflected radiation at multiple wavelengths (optical emission interferometry), calculating film thickness and refractive index at two or more wavelengths using known film refractive index and wavelength, with regression/statistical analysis.

Within-family reference (cited inside '944): US 5,132,631 — Klopfenstein et al. — the capacitance device for detecting conductive coatings on glass referenced throughout the '944/'041 family (and the device '041's claim 16 subject matter descends from).

Verification note: my tooling hit its step limit before I could independently re-pull US 5,132,631 and the "Similar Documents" items (e.g., US 6,683,695, US 8,830,473, US 9,074,874). I therefore rely on their appearance in the page's Prior Art listings and treat their content as unverified.

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4. The decisive gap

Nothing in the cited art, on the record captured, expressly teaches or suggests positioning the light sensor at normal/near-normal incidence to the received reflected beams for the purpose of suppressing internal reflections. The cited optical references are oblique by design: '944's array is parallel to the substrate; Commissariat '619 requires an oblique beam for triangulation; Gagnon '415 requires oblique viewing to separate the top/bottom diffuse spots. So the § 103 case on E5/E6 must rest on design-choice / known-technique / predictable-variation reasoning rather than on an express teaching. Everything else in claims 1/17 (E1–E4) is squarely in '944.

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5. Proposed combinations and motivations

Ground A — Imbrock '944 alone (and as the base for all others)

'944 discloses E1 in the ordinary dual-pane case: two glass panes of a sealed unit have essentially identical refractive indices (soda-lime glass, n≈1.5), so "matching or similar indices of refraction" is inherently met by the very assemblies '944 addresses and claims to measure. It discloses E3 and E4 (source + four separate surface reflections to a CCD), a filter, a processor computing medium thickness and gap width (→ '041 claims 11, 13), coating detection (→ claim 12), the CCD carryover/anti-saturation teaching (→ claim 14), and the capacitance sensor + processor (→ claim 16). E2 (index of refraction) is addressed at least to the extent '944 explains that the medium/gap indices shift the reflection geometry and are used in the thickness determination.

Residual: E5/E6 are absent — '944 teaches the opposite geometry (parallel/oblique).

Ground B — '944 + Commissariat '619 (primary combination)

• What is added: measurement of a first medium overlying a second by a CCD array with a processing circuit that derives thickness from beam-impact geometry and corrects using optical/triangulation relationships; i.e., a two-layer optical model and standoff/geometry correction.
• Motivation / KSR rationale: same field of endeavor (optical thickness measurement of transparent/translucent media), same instrument class (laser + CCD/photosensitive array + processor), and a common objective — accuracy of the thickness/gap computation across varying media. Commissariat's correction scheme addresses the same "varying thickness shifts the measured reflection positions" concern that '944 raises with indices of refraction. A POSITA improving '944's multi-pane thickness/gap accuracy would look to a two-layer optical device that already computes through two media with a CCD. Combination of references in the same field, predictable result.

Ground C — '944 + Gagnon '415 (supplies E2 expressly)

• What is added: the express teaching that thickness is computed using the index of refraction of the medium and separate top/bottom reflections — the cleanest prior-art support for E2 ("measure the index of refraction …").
• Motivation: Gagnon's whole point is that an accurate thickness requires the index of refraction of the measured layer; '944 already notes that index of refraction alters the reflection geometry. A POSITA seeking accurate glass-thickness readings across differing glass types would be motivated to incorporate the refractive-index term when computing thickness from the CCD positions — exactly the '041 processing.

Ground D — '944 + '619 + Gagnon '415 (three-way)

Combines: the multi-pane, four-surface apparatus, filter, capacitance channel and CCD electronics of '944; the two-layer / standoff-corrected optical model of '619; and the index-of-refraction-based thickness computation of Gagnon. Motivation is cumulative and consistent — each reference improves a different aspect of the same optical thickness determination.

Ground E — E5/E6 as an obvious design choice / known technique

This is where a challenger must carry the burden, using KSR rationales:

1. Known technique, predictable result. Near-normal (near-perpendicular) reflectance is the standard geometry of specular thin-film/reflectance metrology. A POSITA knows that under the law of reflection a ray returns essentially along its path at normal incidence, so orienting the sensor perpendicular to the received rays maximizes captured signal and minimizes angular spread and stray/internal reflections within the filter and detector cover glass. Applying this known geometry to the '944 apparatus yields the claimed result with a reasonable expectation of success and no change in measurement principle.
2. The problem was known, and the solution was within the art. '041's own background states the '944 oblique arrangement produces the extra internal reflections. A problem identified in the art, addressed by a purely geometric re-orientation of a known detector, is the paradigm of an obvious design choice.
3. Element-coverage synergy. Zeiss '060 (reflected/transmitted detection, evaluation of thickness and refractive index) and Johnson '237 (monitoring reflected radiation to compute film thickness and refractive index) confirm that reflected-light detection with a processor computing thickness/refractive index is routine, and that the claimed "reinforcement/suppression" language describes inherent physical behavior of normal-incidence reflection rather than an inventive step. E6 is at best result-oriented/inherent language and may be entitled to little or no patentable weight.
4. Design incentives. Signal-to-noise and dynamic-range concerns (the same concerns '944 itself addresses with intensity/sensitivity/shutter-speed control and anti-saturation) supply a concrete reason to prefer the geometry that concentrates rather than spreads the return energy.

Ground F — Claim 16 (capacitance)

'944 (its claims 18+) and Klopfenstein '631 disclose a capacitive-measuring sensor + processor correlating measured capacitance with medium thickness to locate conductive coatings — i.e., the entirety of claim 16. No separate inventive contribution.

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6. Dependent-claim chart (claims 2–15, 18–20)

The dependents are, with few exceptions, directly disclosed in the incorporated '944 parent — so if claim 1 (or 17) were held obvious, most dependents would fall with it, and several would be obvious over '944 alone. (Note the antecedent quirk flagged earlier: claim 8 refers to "the filter" of claim 7 — a § 112 issue, not § 103.)

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7. Counterarguments the patent owner would raise (and my weighting)

1. No express teaching of E5/E6. I weight this heavily. The cited references are oblique/triangulation-based and none directs a POSITA to normal incidence. A validity challenge grounded solely in the art of record on this page would struggle on E5/E6 and would likely have to lean on "design choice" reasoning, which a fact-finder may or may not accept.
2. Possible teaching away. Commissariat '619 (triangulation) and Gagnon '415 (separating diffuse spots) both require non-normal geometry for their stated purposes. The owner could argue the field was committed to oblique measurement, so normal-incidence reception was not suggested. I weight this moderately — it is a genuine non-obviousness argument, though a weak one, because neither reference disparages normal-incidence reflectometry generally, and '944's own oblique geometry is the admitted source of the problem.
3. No objective indicia in the specification. The spec offers FIG. 3 vs. FIG. 4 (near-normal vs. oblique peak cleanliness) — but that difference is the expected consequence of the geometry, not evidence of unexpected results. Absent nexus-bearing secondary considerations, this does not rebut a prima facie case.
4. Functional/result language. E6 ("stays within an original ray of travel," "reinforces") reads as inherent physics. If given no patentable weight, the claims reduce to E1–E5, making the case easier for a challenger.

My overall weighting: The dependent claims (7–16, and 11–14 in particular) are highly vulnerable to a § 103 challenge, because '944 — prior art in its own right and incorporated into '041 — discloses them. The independent claims turn on one arguably-novel feature (near-normal sensor incidence + its rationale), which the cited art does not expressly teach but which is a strong candidate for "obvious design choice / known technique." A § 103 rejection of claim 1/17 would be contestable but not frivolous; a § 103 rejection of most dependent claims would be straightforward.

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8. Confidence, caveats, and cross-reference check

• Cross-reference to prior sections: No contradiction found. The earlier-generated summary correctly identified claim 1/17 as narrower than the specification's "BRIEF SUMMARY" (requiring ≥2 mediums with matching/similar indices of refraction and index-of-refraction measurement) and flagged the "positioned at an angle is at" grammatical artifact — both are reproduced accurately from the claim text I used here.
• Search limitation: My tooling hit its step limit; I could not independently retrieve US 5,132,631, US 6,683,695, US 8,830,473, US 9,074,874, US 7,012,698, or other "Similar Documents," nor run a dedicated search for art expressly teaching normal-incidence detection to suppress internal reflections. If such art exists, it would materially strengthen Ground E. Until then, treat the "no express teaching of E5" finding as unconfirmed-but-plausible, derived from the five cited references on the page.
• Numbers interpreted literally: All patent numbers (9,891,041; 8,723,944; 2008/0068619; 2007/0074415; 2014/0185060; 2013/0273237; 5,132,631) are used exactly as they appear on the page; no auto-correction applied.
• This is a technical obviousness assessment grounded in the listed references; it is not a legal opinion and does not account for claim-construction, prosecution-history estoppel, or litigation-specific evidence.

Bottom line: The strongest § 103 combinations are (1) Imbrock '944 alone for the dependent claims, and (2) '944 + Commissariat '619 + Gagnon '415, supplemented by the "known technique/obvious design choice" rationale (supported by Zeiss '060 and Johnson '237), for the independent claims — with near-normal sensor incidence (E5/E6) as the single contested hinge on which validity of claims 1 and 17 ultimately turns.