Court Opinion

ID: 9890777
Source: CourtListenerOpinion
Date Created: 2023-10-16 14:00:55.031724+00
Date Added: 2024-06-11T13:35:21.021917
License: Public Domain

Case: 22-1340    Document: 50           Page: 1       Filed: 10/16/2023

   United States Court of Appeals
       for the Federal Circuit
                  ______________________

                COREPHOTONICS, LTD.,
                      Appellant

                                  v.

                      APPLE INC.,
                         Appellee
                  ______________________

                   2022-1340, 2022-1341
                  ______________________

     Appeals from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in Nos. IPR2020-
 00487, IPR2020-00860.

           -------------------------------------------------

                COREPHOTONICS, LTD.,
                      Appellant

                                  v.

                      APPLE INC.,
                         Appellee
                  ______________________

                   2022-1455, 2022-1456
                  ______________________
Case: 22-1340    Document: 50     Page: 2    Filed: 10/16/2023

 2                         COREPHOTONICS, LTD. v. APPLE INC.

     Appeals from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in Nos. IPR2020-
 00861, IPR2020-00862.
                  ______________________

                 Decided: October 16, 2023
                  ______________________

      BRIAN DAVID LEDAHL, Russ August & Kabat, Los Ange-
 les, CA, argued for appellant. Also represented by MARC A.
 FENSTER, NEIL RUBIN, JAMES S. TSUEI.

    DEBRA JANECE MCCOMAS, Haynes and Boone, LLP,
 Dallas, TX, argued for appellee in 2022-1340. Also repre-
 sented by ANDREW S. EHMKE; DAVID W. O'BRIEN, HONG SHI,
 Austin, TX; ANGELA M. OLIVER, Washington, DC. Also ar-
 gued by ERIN MARIE BOYD LEACH, Orrick, Herrington &
 Sutcliffe LLP, Irvine, CA, in 2022-1455. Also represented
 by MARK S. DAVIES, Washington, DC.
                   ______________________

      Before STOLL, LINN, and STARK, Circuit Judges.
 STARK, Circuit Judge.
      Corephotonics, Ltd. (“Corephotonics”) appeals final
 written decisions (“Decisions”) of the Patent Trial and Ap-
 peal Board (“Board”) concluding that claims of U.S. Patent
 Nos. 9,661,233 (“’233 patent”), 10,230,898 (“’898 patent”),
 10,326,942 (“’942 patent”), and 10,356,332 (“’332 patent”)
 (collectively, the “Challenged Patents”) are unpatentable
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 COREPHOTONICS, LTD. v. APPLE INC.                           3

 as obvious. The Decisions were each issued in inter partes
 reviews (“IPR”) initiated by Apple Inc. (“Apple”). 1
     Corephotonics principally challenges the Board’s anal-
 ogous art findings, arguing that the Board made two pro-
 cedural errors and one substantive error. In terms of
 procedure, Corephotonics contends that the Board
 erred (1) by permitting Apple to cure the legally flawed
 analogous art contention it made in its petition and (2) by
 making analogous art findings that deviated from the con-
 tentions Apple advocated for in its petition and reply. As
 for substance, Corephotonics asserts that prior art refer-
 ences U.S. Patent Application Publication No.
 2012/0026366 (“Golan”) and U.S. Patent No. 8,081,206
 (“Martin”) are not analogous art.
    We identify no procedural error in the Board’s handling
 of whether Golan and Martin are analogous art. We

    1    Appeal Nos. 22-1340 and 22-1341 concern the ’233
 and ’942 patents, respectively. Appeal Nos. 22-1455 and
 22-1456 concern the ’898 and ’332 patents, respectively.
 We consolidated Appeal Nos. 22-1340 and 22-1341 and sep-
 arately consolidated Appeal Nos. 22-1455 and 22-1456.
 Each of the consolidated appeals has its own Joint Appen-
 dix. For simplicity, when we cite to a reference included in
 both Joint Appendices, we include the citation only for No.
 22-1340/1341. We make clear where we are citing solely to
 the appendix in No. 22-1455/1456 (which we refer to with
 the designation “No. 1455”).

      There are no material differences between the written
 descriptions of the ’233 and ’942 patents or between the
 written descriptions of the ’898 and ’332 patents. We cite
 to the ’233 patent alone when describing both the ’233 and
 ’942 patents and to the ’898 patent alone when describing
 both the ’898 and ’332 patents.
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 4                          COREPHOTONICS, LTD. v. APPLE INC.

 further hold that the Board’s determination that Golan is
 analogous art is supported by substantial evidence. How-
 ever, we vacate and remand the Board’s obviousness deter-
 mination for the Board to explain why Martin is (or is not)
 analogous art and how this finding affects its overall con-
 clusion as to obviousness.
                               I
                              A
     The Challenged Patents relate to dual-aperture cam-
 era systems and disclose techniques for using the images
 from both lenses when zooming while capturing video. ’233
 patent 3:28-30, 49-54; ’898 patent 3:26-28, 36-41. Typi-
 cally, a dual-aperture camera system includes a wide-lens
 camera and a tele-lens camera. 2 When zooming in, the dis-
 closed dual-aperture camera systems can switch from the
 wide-lens camera to the tele-lens camera, and when zoom-
 ing out the opposite can occur.
     The wide-lens camera has a larger field of view than
 the tele-lens camera. “Field of view” refers to the extent of
 the observable world a camera system is capable of captur-
 ing; that is, whether the camera captures a relatively
 larger or smaller area. Generally, a wide-lens camera pro-
 duces images with a larger field of view than a tele-lens
 camera can, as the tele-lens camera has greater magnifica-
 tion. Field of view is a mechanical property of the camera
 (including the lens) and does not change when the camera
 is moved to a different location.

     2    Each imaging device in the camera system contains
 both a lens assembly and a sensor array. The field of view
 is determined by the lens assembly’s properties. For sim-
 plicity, we refer to the imaging devices in their entirety
 based on their lenses.
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 COREPHOTONICS, LTD. v. APPLE INC.                           5

     Within a dual-aperture camera system, the wide-lens
 camera and the tele-lens camera are placed in different lo-
 cations (e.g., adjacent to one another) and, thus, capture
 images from slightly different perspectives. This results in
 the wide-lens and tele-lens cameras having different points
 of view. In this context, “point of view” refers to how the
 observable world appears (and thus how it can be captured)
 from a particular location; that is, the perspective a camera
 captures from a location. A lens’ point of view, therefore,
 changes when the camera’s location is changed.
      Consequently, when the dual-aperture camera system
 switches from the wide-lens camera to the tele-lens camera
 (or vice versa) while zooming in (or out), a user may see a
 “jump” or a discontinuous image change, because the tele
 lens and wide lens are in different locations and, thus, have
 different points of view. ’233 patent 10:32-34; ’898 patent
 7:42-44. The Challenged Patents teach minimizing this
 “jump” effect by partially “matching the position, scale,
 brightness and color of the output image before and after
 the transition” from one lens to the other. ’233 patent
 10:36-40; see also ’898 patent 7:46-50. In this regard, the
 patents explain that matching an entire image from one
 camera with an entire image from another camera is often
 impossible because the distance between an observed ob-
 ject and the two cameras will differ at least slightly. The
 patents teach that engaging in position matching only in
 the region of interest (“ROI”) may generate a “smooth tran-
 sition.” ’233 patent 10:43-46; see also ’898 patent 7:53-56.
     Within the portions of the field of view that are com-
 mon to both the tele-lens camera and the wide-lens camera,
 the tele-lens camera often, but not always, produces a
 clearer image. See, e.g., ’898 patent 10:15-19. Where this
 is untrue – for example, if the subject of a video is out of
 focus in the tele-lens image – “there is no point in perform-
 ing the transition [from wide-lens to tele-lens image] be-
 cause no . . . resolution[] is gained.” ’898 Patent 10:16-17.
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 6                         COREPHOTONICS, LTD. v. APPLE INC.

 To account for such scenarios, the ’898 and ’332 patents
 teach not switching to the tele lens when the tele-lens cam-
 era’s “effective resolution” is lower than that of the wide
 lens. ’898 patent 10:2-7, 15-19. The patents explain that
 one way to implement the determination of when to engage
 in “no switching” is through calculating an “effective reso-
 lution score.” ’898 patent 6:16-24, 10:15-19.
     Claim 1 of the ’233 patent is illustrative of the claims
 in that patent, reciting:
     A multiple aperture zoom digital camera, compris-
     ing:
       a) a Wide imaging section that includes a Wide
       sensor and a fixed focal length Wide lens with a
       Wide field of view (POV), the Wide imaging sec-
       tion operative to output a Wide image;
       b) a Tele imaging section that includes a Tele
       sensor and a fixed focal length Tele lens with a
       Tele POV that is narrower than the Wide POV,
       the Tele imaging section operative to output a
       Tele image; and
       c) a camera controller operatively coupled to the
       Wide and Tele imaging sections and configured
       to reduce an image jump effect seen in video out-
       put images and to provide continuous zoom
       video output images by executing registration
       between the Wide and Tele images for perform-
       ing position matching to the video output images
       when switching from an output of the Tele im-
       aging section to an output of the Wide imaging
       section or vice versa.
     Claim 1 of the ’942 patent is illustrative of the claims
 in that patent and is similar to claim 1 of the ’233 patent,
 except that claim element c) in the ’942 patent recites:
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 COREPHOTONICS, LTD. v. APPLE INC.                            7

    a camera controller operatively coupled to the Wide
    and Tele imaging sections and configured, when
    providing video output images, to:
       reduce an image jump effect seen in the video
       output images when switching from a Wide im-
       age to a Tele image by shifting the Tele image
       relative to the Wide image according to a dis-
       tance of an object in a Tele image region of inter-
       est (ROI), and/or
       reduce an image jump effect seen in the video
       output images when switching from a Tele im-
       age to a Wide image by shifting the Wide image
       relative to the Tele image according to a distance
       of an object in a Wide image ROI.
     Claim 1 of the ’898 patent is illustrative of the claims
 in the ’898 and ’332 patents:
    A zoom digital camera comprising:
       a) a Wide imaging section that includes a fixed
       focal length Wide lens with a Wide field of view
       (FOV) and a Wide sensor, the Wide imaging sec-
       tion operative to provide Wide image data of an
       object or scene;
       b) a Tele imaging section that includes a fixed
       focal length Tele lens with a Tele FOV that is
       narrower than the Wide FOV and a Tele sensor,
       the Tele imaging section operative to provide
       Tele image data of the object or scene; and
       c) a camera controller operatively coupled to the
       Wide and Tele imaging sections and configured
       to evaluate if a no-switching criterion is fulfilled
       or not fulfilled, wherein if the no-switching cri-
       terion is fulfilled in a zoom-in operation between
       a lower zoom factor (ZF) value and a higher ZF
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 8                          COREPHOTONICS, LTD. v. APPLE INC.

       value at a zoom factor (ZF) higher than an up-
       transfer ZF, the camera controller is further con-
       figured to output a zoom video output image that
       includes only Wide image data, and wherein if
       the no-switching criterion is not fulfilled, the
       camera controller is further configured to output
       a zoom video output image that includes only
       transformed, digitally zoomed Tele image data.
     Claims 4 and 15 of the ’898 patent and claims 5 and 17
 of the ’332 patent (the “Effective Resolution Claims”) fur-
 ther include the “effective resolution” “no-switching crite-
 rion” limitation.     Claim 4 of the ’898 patent is
 representative of the Effective Resolution Claims:
     The camera of claim 1; wherein the no-switching
     criterion includes an effective resolution of the Tele
     image being lower than an effective resolution of
     the Wide image.
                               B
    Two prior art references are part of all of the obvious-
 ness grounds Apple presented in its IPR petitions: Golan
 and Martin.
     Golan describes camera systems using multiple imag-
 ing sensors and lens assemblies to zoom without using a
 lens with a mechanically adjustable focal length. By
 providing “multiple imaging devices each with a different
 fixed field of view (FOV),” Golan’s system “facilitates a light
 weight electronic zoom with a large lossless zooming
 range.” J.A. 5525 (Golan ¶ 9). Specifically, Golan teaches
 digitally zooming with the wide lens until a higher resolu-
 tion image is fully capturable with the tele lens and then
 digitally zooming with that higher resolution tele-lens im-
 age. To prevent a discontinuity or “jump” from occurring
 when switching between images while zooming, Golan
 teaches a one-time calibration technique to correct for the
 lenses’ different points of view.
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 COREPHOTONICS, LTD. v. APPLE INC.                            9

     Martin describes methods “for producing two-dimen-
 sional images that, upon display, can be perceived to be
 three-dimensional without the use of special viewing aids.”
 J.A. 5535 (Martin 1:17-20). Among other things, Martin
 teaches capturing images of the same scene from two dif-
 ferent points of view (that is, parallax images) and then
 displaying the images in an alternating fashion to the
 viewer to create the appearance of three-dimensionality.
 Martin further discloses “critically aligning” the images to
 create a stable three-dimensional image. This alignment
 process requires manipulating the captured images so that
 “a region of interest in [one] image . . . is positioned such
 that it occupies the same location within the frame of” an-
 other image. J.A. 5536 (Martin 4:33-35).
      Apple additionally relies on Japanese Patent Applica-
 tion No. JP2011-55246 (“Togo”) for the teaching of the “ef-
 fective resolution” “no-switching criterion” limitation in the
 Effective Resolution Claims. 3 Togo explains that using a
 wide lens together with a tele lens to zoom can create prob-
 lems if the subject of the image is out of focus for one of the
 lenses. Typically, a tele lens is designed to have subjects
 that are far from the camera be in focus. This means that
 if the subject is close to the tele lens, the subject will be
 blurry. Togo teaches using a tele lens that is focused in the
 distance, but suggests not switching to it while zooming if
 the subject of the camera is sufficiently close.
                               C
     Corephotonics filed suit against Apple alleging in-
 fringement of the Challenged Patents (among others). See
 Complaint, Corephotonics, Ltd. v. Apple, Inc., No. 3:17-cv-
 06457 (N.D. Cal Nov. 6, 2017). In response, Apple

     3   We rely on an English translation of Togo, the ac-
 curacy of which is not at issue in this appeal.
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 10                          COREPHOTONICS, LTD. v. APPLE INC.

 petitioned for IPR on all claims (i.e., claims 1-18) of the ’233
 patent; claims 1, 4, 8-12, 15, and 19-20 of the ’898 patent;
 all claims (i.e., claims 1-25) of the ’942 patent; and claims
 1-2, 5, 9-14, 17, and 21-22 of the ’332 patent. Each of Ap-
 ple’s grounds for unpatentability relied on combining Go-
 lan and Martin along with other references. With the
 exception of Togo, these other references are not relevant
 to the issues raised on appeal. The Board instituted the
 IPRs and ultimately found all challenged claims of the
 Challenged Patents unpatentable as obvious over Apple’s
 combinations of prior art.
     Broadly, three of the Board’s conclusions are at issue
 on appeal. First, the Board found that both Golan and
 Martin are analogous prior art. Second, the Board con-
 strued “shifting the [t]ele image relative to the [w]ide im-
 age according to a distance of an object in a [t]ele image
 region of interest (ROI)” and “by shifting the [w]ide image
 relative to the [t]ele image according to a distance of an ob-
 ject in a [w]ide image ROI” in the ’942 patent to include
 translating or shifting images based on indirect measures
 of distance (rather than only direct measures). Based in
 part on this understanding of the “shifting” terms, the
 Board found that Martin discloses the “shifting” limitation
 of the challenged claims of the ’942 patent. Third, the
 Board rejected Corephotonics’ proposed construction of “ef-
 fective resolution” as “effective resolution score,” constru-
 ing it instead as “image quality including but not limited to
 blurriness and sharpness.” Based on this construction, the
 Board found that Togo taught the “effective resolution” “no-
 switching criterion” limitation contained in the “Effective
 Resolution Claims.”
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 COREPHOTONICS, LTD. v. APPLE INC.                           11

     Corephotonics timely appealed. 4
                               II
                               A
     We review Board decisions pursuant to the standards
 of the Administrative Procedure Act (“APA”), 5 U.S.C.
 § 550 et seq. Under the APA, we “hold unlawful and set
 aside agency action . . . not in accordance with law [or] . . .
 without observance of procedure required by law.” 5 U.S.C.
 § 706. Thus, in an appeal from an IPR, we review the
 Board’s legal determinations de novo and its factual find-
 ings for substantial evidence. See Almirall, LLC v. Amneal
 Pharms. LLC, 28 F.4th 265, 271 (Fed. Cir. 2022). Substan-
 tial evidence is “such relevant evidence as a reasonable
 mind might accept as adequate to support a conclusion.”
 Consol. Edison Co. v. NLRB, 305 U.S. 197, 229 (1938).
 “[T]he possibility of drawing two inconsistent conclusions
 from the evidence does not prevent an administrative
 agency’s finding from being supported by substantial evi-
 dence.” Consolo v. Fed. Mar. Comm’n, 383 U.S. 607, 620
 (1966).
     Because IPRs are formal adjudications, the APA also
 requires that the parties to IPRs receive notice of argu-
 ments and evidence and have an opportunity to be heard
 with respect to them. See Genzyme Therapeutic Prods. Ltd.
 v. Biomarin Pharm. Inc., 825 F.3d 1360, 1365-66 (Fed. Cir.
 2016). “[F]air notice and an opportunity to respond” is re-
 quired in “all aspects of an IPR proceeding.” Nike, Inc. v.
 Adidas AG, 955 F.3d 45, 53 (Fed. Cir. 2020).

     4   The Board had jurisdiction under 35 U.S.C.
 § 316(c).     We have jurisdiction under 28 U.S.C.
 § 1295(a)(4)(A) and 35 U.S.C. §§ 141(c), 319.
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 12                         COREPHOTONICS, LTD. v. APPLE INC.

      IPR proceedings are creations of the America Invents
 Act (AIA), 35 U.S.C. § 311, and must also proceed according
 to the requirements set out by that statute. As the Su-
 preme Court has stated, in an IPR “the petitioner’s conten-
 tions, not the Director’s discretion, define the scope of the
 litigation all the way from institution through to conclu-
 sion.” SAS Inst., Inc. v. Iancu, 138 S. Ct. 1348, 1357 (2018);
 see also 35 U.S.C. § 312(a)(4). The IPR petition, thus, must
 provide an understandable explanation of the element-by-
 element specifics of the patentability challenges, including
 the identification of particular portions of prior art on
 which the petitioner is relying. See 35 U.S.C. § 312(a)(3);
 37 C.F.R. §§ 42.22(a)(2), 42.104(b)(3)-(4); Harmonic Inc. v.
 Avid Tech., Inc., 815 F.3d 1356, 1363-64 (Fed. Cir. 2016);
 Ariosa Diagnostics v. Verinata Health, Inc., 805 F.3d 1359,
 1367 (Fed. Cir. 2015). “It is of the utmost importance that
 petitioners in the IPR proceedings adhere to the require-
 ment that the initial petition identify ‘with particularity’
 the ‘evidence that supports the grounds for the challenge
 to each claim.’” Intelligent Bio-Sys., Inc. v. Illumina Cam-
 bridge Ltd., 821 F.3d 1359, 1369 (Fed. Cir. 2016) (quoting
 35 U.S.C. § 312(a)(3)). “Unlike district court litigation –
 where parties have greater freedom to revise and develop
 their arguments over time and in response to newly discov-
 ered material – the expedited nature of IPRs bring with it
 an obligation for petitioners to make their case in their pe-
 tition to institute.” Id. Given these “strict . . . require-
 ments,” id., the Board is not permitted to entertain
 “[s]hifting arguments” but must, instead, reject any “en-
 tirely new theory of prima facie obviousness absent from
 the petition,” if the petitioner attempts to inject such a the-
 ory into the proceeding post-petition, Wasica Fin. GmbH v.
 Cont’l Auto. Sys., Inc., 853 F.3d 1272, 1286 (Fed. Cir. 2017);
 see also Sirona Dental Sys. GmbH v. Institut Straumann
 AG, 892 F.3d 1349, 1356 (Fed. Cir. 2018) (stating Board is
 not permitted “to deviate from the grounds in the petition
 and raise its own obviousness theory”); Koninklijke Philips
 N.V. v. Google LLC, 948 F.3d 1330, 1336 (Fed. Cir. 2020)
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 (holding Board erred by raising its own obviousness theory
 based on combination of references not provided in peti-
 tion).
     The patent owner may file a preliminary patent owner
 response to a petition. See 37 C.F.R. § 42.107(a). Thereaf-
 ter, the Board makes a decision whether to institute the
 requested IPR, based on whether it finds, as a preliminary
 matter, a reasonable likelihood the petitioner will succeed.
 See 35 U.S.C. § 314. This institution decision is not review-
 able. See Cuozzo Speed Techs., LLC v. Lee, 579 U.S. 261,
 276 (2016) (“We therefore conclude that § 314(d) bars
 Cuozzo’s efforts to attack the Patent Office’s determination
 to institute inter partes review in this case.”). We may,
 however, “review determinations made during institution
 that are subsequently incorporated into the Board’s final
 written decision.” In re Magnum Oil Tools Int’l, Ltd., 829
 F.3d 1364, 1374 (Fed. Cir. 2016).
     After institution, the patent owner files a response, to
 which the petitioner then replies.          See 37 C.F.R.
 §§ 42.23(b), 42.120(a). The petitioner’s “reply may only re-
 spond to arguments raised in the corresponding opposition,
 patent owner preliminary response, patent owner re-
 sponse, or decision on institution.” § 42.23(b). “[A]n IPR
 petitioner may not raise in reply an entirely new rationale
 for why a claim would have been obvious.” Henny Penny
 Corp. v. Frymaster LLC, 938 F.3d 1324, 1330-31 (Fed. Cir.
 2019) (internal quotation marks omitted). Any marked de-
 parture from the grounds identified with particularity in
 the petition would impose “unfair surprise” on the patent
 owner and, consequently, violate both the APA and the IPR
 statute. Arthrex Inc. v. Smith & Nephew, Inc., 935 F.3d
 1319, 1328 (Fed. Cir. 2019).
     It is for the Board to determine what grounds are being
 articulated in a petition and what arguments and evidence
 are being referred to in the responses and any replies. See,
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 14                         COREPHOTONICS, LTD. v. APPLE INC.

 e.g., Yita LLC v. MacNeil IP LLC, 69 F.4th 1356, 1366 (Fed.
 Cir. 2023); Ariosa Diagnostics, 805 F.3d at 1368. In partic-
 ular, the Board has discretion to determine “whether a
 [p]etition identified the specific evidence relied on in a
 [r]eply and when a [r]eply contention crosses the line from
 the responsive to the new.” Ariosa, 805 F.3d at 1368. We
 review the Board’s assessments of what has been argued to
 and put before it in an IPR for abuse of discretion. See Yita,
 69 F.4th at 1366. The Board abuses its discretion when its
 decision “(1) is clearly unreasonable, arbitrary, or fanciful;
 (2) is based on an erroneous conclusion of law; (3) rests on
 clearly erroneous fact finding; or (4) involves a record that
 contains no evidence on which the Board could rationally
 base its decision.” Ericsson Inc. v. Intell. Ventures I LLC,
 901 F.3d 1374, 1379 (Fed. Cir. 2018).
      Following completion of all briefing and oral hearing,
 the petitioner must prove invalidity of any challenged
 claim by a preponderance of the evidence. See Magnum
 Oil, 829 F.3d at 1375 (citing 35 U.S.C. § 316(e)). This bur-
 den of persuasion remains with the petitioner at all times.
 See Sanofi-Aventis Deutschland GmbH v. Mylan Pharms.
 Inc., 66 F.4th 1373, 1377 (Fed. Cir. 2023). In evaluating
 whether the petitioner has met its burden, the Board must
 consider all evidence and argument properly submitted in
 connection with the petitioner’s reply, as well as all that is
 submitted in connection with the petition. See Magnum
 Oil, 829 F.3d at 1376 (“[The] fact finder must consider all
 evidence of obviousness and nonobviousness before reach-
 ing a determination.”). Once an issue is fairly presented in
 a petition and made the subject of dispute by the patent
 owner’s response, the Board is free to make its own factual
 findings grounded in the evidence presented to it, without
 being bound to choose between the specific positions the
 parties advocated. See Fanduel, Inc. v. Interactive Games
 LLC, 966 F.3d 1334, 1344 (Fed. Cir. 2020) (“[I]n every case,
 it remains the Board’s essential function to make factual
 findings based on its view of the record.”) (emphasis added).
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 COREPHOTONICS, LTD. v. APPLE INC.                          15

                               B
     A patent is invalid as obvious “if the differences be-
 tween the claimed invention and the prior art are such that
 the claimed invention as a whole would have been obvious
 before the effective filing date of the claimed invention to a
 person having ordinary skill in the art to which the claimed
 invention pertains.” 35 U.S.C. § 103 (2011). 5 In determin-
 ing whether a claim is invalid as obvious, we compare the
 prior art to the claim language, and if necessary, after the
 claim language has been properly construed when the
 meaning or scope is in dispute. See U.S. Surgical Corp. v.
 Ethicon, Inc., 103 F.3d 1554, 1568 (Fed. Cir. 1997). Claim
 construction based solely on intrinsic evidence is a question
 of law. See Teva Pharms. USA, Inc. v. Sandoz, Inc., 574
 U.S. 318, 331 (2015).
     “Obviousness is a legal question based on underlying
 findings of fact.” Fleming v. Cirrus Design Corp., 28 F.4th
 1214, 1221 (Fed. Cir. 2022). Among those issues of fact is
 what the prior art discloses to an ordinarily skilled artisan.
 See id. “What the prior art discloses and whether a person
 of ordinary skill would have been motivated to combine
 prior-art references are both fact questions that we review
 for substantial evidence.” Intel Corp. v. PACT XPP
 Schweiz AG, 61 F.4th 1373, 1378 (Fed. Cir. 2023); see also
 Bot M8 LLC v. Sony Interactive Ent. LLC, 66 F.4th 1380,
 1384 (Fed. Cir. 2023).
     Prior art references are applicable to the obviousness
 inquiry only when they are analogous to the claims being
 challenged. See In re Clay, 966 F.2d 656, 658 (Fed. Cir.

     5   The Challenged Patents have effective filing dates
 later than March 16, 2013. Therefore, we apply § 103 as
 amended by the Leahy-Smith America Invents Act. See 35
 U.S.C. § 100 note.
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 16                         COREPHOTONICS, LTD. v. APPLE INC.

 1992); see also In re Bigio, 381 F.3d 1320, 1325 (Fed. Cir.
 2004). Art that is “too remote” from the patents being at-
 tacked cannot be treated as prior art. In re Sovish, 769
 F.2d 738, 741 (Fed. Cir. 1985); see also In re Oetiker, 977
 F.2d 1443, 1447 (Fed. Cir. 1992) (“The combination of ele-
 ments from non-analogous sources, in a manner that recon-
 structs the applicant’s invention only with the benefit of
 hindsight, is insufficient to present a prima facie case of
 obviousness.”). We use “[t]wo separate tests [to] define the
 scope of analogous art: (1) whether the art is from the same
 field of endeavor, regardless of the problem addressed and,
 (2) if the reference is not within the field of the inventor’s
 endeavor, whether the reference still is reasonably perti-
 nent to the particular problem with which the inventor is
 involved.” Airbus S.A.S. v. Firepass Corp., 941 F.3d 1374,
 1379 (Fed. Cir. 2019) (internal quotation marks omitted).
 “The Board’s determination that a prior art reference is
 analogous art . . . presents an issue of fact, reviewed for
 substantial evidence.” In re ICON Health & Fitness, Inc.,
 496 F.3d 1374, 1378 (Fed. Cir. 2007).
      “To satisfy its burden of proving obviousness, a peti-
 tioner cannot employ mere conclusory statements. The pe-
 tition must instead articulate specific reasoning, based on
 evidence of record, to support the legal conclusion of obvi-
 ousness.” Magnum Oil, 829 F.3d at 1380. It is not always
 necessary for a petition to expressly address analogous-
 ness. For instance, it may be clear from the petition’s de-
 scription of the references and the challenged claims that
 prior art is in the same field of endeavor as the challenged
 patent, or the pertinence of the prior art to the problem
 solved by the invention may be implicit in the petition’s dis-
 cussion of the challenged claims and why a person of ordi-
 nary skill would be motivated to combine the prior art
 references with a reasonable expectation of success.
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                              III
     Because it is central to the issues we must decide in
 this appeal, we carefully set out here what the parties and
 the Board said about the analogousness of Apple’s prior art
 references at each stage of the proceedings below.
      In its petitions, Apple said of Golan and Martin that
 these “references are analogous prior art and are in the
 same field of endeavor pertaining to imaging systems gen-
 erating video output images using two imaging sections
 having different points of view.” J.A. 1023-24 (emphasis
 added); see also J.A. 10023-24; No. 1455 J.A. 1024, 10023.
 Apple further explained that “Golan discloses providing
 continuous video output images using an image acquisition
 system ‘having multiple imaging devices’ having different
 points of view,” and “[s]imilarly, Martin discusses ‘display
 [of] alternating views of two or more parallax images’ from
 cameras having different points of view to ‘create a result-
 ant moving image.’” J.A. 1023-24 (second bracketing in
 original); see also J.A. 10023-24; No. 1455 J.A. 1024, 10023.
 Apple’s petitions were ambiguous; they did not make clear
 whether Apple was stating that Golan and Martin are in
 the same field of endeavor as the Challenged Patents or,
 instead, merely that Golan and Martin are in the same
 field of endeavor as one another.
     This ambiguity was present in the expert declaration
 Apple attached to each of its petitions. In the declaration,
 Dr. Frédo Durand opined:
     [T]he references are analogous prior art and are in
     the same field of endeavor pertaining to imaging
     systems generating video output images using im-
     ages from two imaging sections having different
     points of view . . . . [B]oth Golan and Martin dis-
     close imaging systems for generating video output
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 18                         COREPHOTONICS, LTD. v. APPLE INC.

      images using two imaging sections having different
      points of view.
 J.A. 5410-11; see also J.A. 15457; No. 1455 J.A. 5462,
 15228. There is no express reference in either Apple’s pe-
 titions or attached expert declarations to the field of en-
 deavor of the Challenged Patents themselves. Nor is there
 any explicit contention that Golan and Martin are analo-
 gous because they are pertinent to the problem faced by the
 inventors of the Challenged Patents.
      Corephotonics did not call attention to these issues in
 its patent owner preliminary response. Instead, while
 Corephotonics opposed institution, and argued that the pe-
 tition failed to demonstrate a motivation to combine Golan
 and Martin, and more generally failed to establish the rea-
 sonable likelihood that Apple could make out a prima facie
 case of obviousness, Corephotonics did not specifically ar-
 gue that Apple’s analogous art contentions were in any way
 deficient. See Apple Inc. v. Corephotonics, Ltd., IPR2020-
 00860, Paper 6 at *10 (P.T.A.B. Aug. 6, 2020) (“The petition
 argues that Golan and Martin are ‘analogous prior art and
 are in the same field of endeavor’ . . . . Even if these argu-
 ments are accepted as true, they do not establish the nec-
 essary motivation to combine the two references.”).
     Unsurprisingly, then, in its institution decision, the
 Board also did not address the issue of whether Apple had
 said enough to satisfy its obligation to establish Golan and
 Martin are analogous art. The Board found that Apple’s
 rationale for a motivation to combine the references was
 sufficient for the institution stage. See Apple Inc. v. Core-
 photonics, Ltd., IPR2020-00860, Paper 7 at *19-27
 (P.T.A.B. Nov. 5, 2020).
     After the IPRs were instituted, Corephotonics filed its
 patent owner response, and there it pointed to what it con-
 tended was a deficiency in how Apple had addressed the
 analogous art issue at the petition stage. See J.A. 1246;
 J.A. 10205; No. 1455 J.A. 1499, 10507. Specifically,
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 Corephotonics suggested Dr. Durand’s “analysis appears to
 be limited to comparing Golan and Martin with one another
 and opining that they are in the ‘same field of endeavor,’”
 which “is insufficient because it fails to apply the correct
 legal test and yield the correct analysis for whether Golan
 and Martin are analogous art.” J.A. 1246; see also J.A.
 10205-06.
     Thereafter, in its replies, Apple clarified its position,
 explicitly arguing that the Challenged Patents, Golan, and
 Martin are all in the same field of endeavor. J.A. 1279,
 10265-66; No. 1455 J.A. 1264, 10264. Further, Apple’s re-
 plies (which differed slightly across the IPRs but were ma-
 terially identical) added, for the first time, that the two
 prior art references were also pertinent to the problem faced
 by the inventors of the Challenged Patents. The following
 excerpt, from the IPR related to the ’233 patent, is repre-
 sentative of Apple’s replies:
     [L]ike the ’233 Patent, Golan and Martin are all in
     the field of imaging systems, and more specifically,
     imaging systems including digital cameras gener-
     ating video output images using two imaging sec-
     tions having different points of view . . . . [Also],
     Golan and Martin are each pertinent to the problem
     addressed in the ’233 Patent, namely, “a ‘jump’
     (discontinuous) image change” “[w]hen a dual-ap-
     erture camera switches the camera output between
     sub-cameras or points of view.”
 J.A. 1279-80 (emphasis added); see also J.A.10265-67 (re-
 ply in IPR of ’942 patent); No. 1455 J.A. 1264, 10264 (re-
 plies in IPRs of ’898 and ’332 patents describing pertinent
 problem as “achieving a continuous, smooth zoom in video
 mode”) (internal quotation marks omitted).
     Corephotonics filed a sur-reply, complaining that Ap-
 ple’s reply “raises completely new arguments, supported by
 Dr. Durand’s new reply declaration opinions, that Golan
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 20                          COREPHOTONICS, LTD. v. APPLE INC.

 and Martin are ‘analogous art’ to the . . . patent for pur-
 poses of its challenge.” J.A. 1318. Corephotonics stated
 that it was prejudiced by being “prohibited from submitting
 expert opinion or factual evidence of its own to dispute Ap-
 ple’s new arguments and evidence.” J.A. 1318-19. Still,
 Corephotonics proceeded to respond to Apple’s allegedly
 new allegation that Martin was pertinent to the problem
 addressed by the Challenged Patents:
      [T]he problem addressed by the ’233 patent is, in
      relevant part, image discontinuities perceived by a
      user of a digital camera on a display when the video
      image output switches between one camera and an-
      other during zoom . . . . Martin, in contrast to the
      ’233 patent, is not concerned with reduction of
      jump effects in video output images when switch-
      ing between cameras during zoom . . . . Because
      Martin is “directed to a different purpose” than the
      ’233 patent, “the inventor would accordingly have
      had less motivation to consider it” to be “analogous
      art.” In re Clay, 966 F.2d 656, 659 (Fed. Cir. 1992).
 J.A. 1320-22 (sur-reply in IPR of ’233 patent); see also J.A.
 10315-18 (sur-reply in IPR of ’942 patent); No. 1455 J.A.
 1309-10, 10308-09 (sur-replies in IPRs of ’898 and ’332 pa-
 tents).
     The issue of analogous art received extensive attention
 during oral argument in each of the IPRs, mostly focused
 on whether Golan and Martin are analogous to the Chal-
 lenged Patents. See J.A. 1514-16, 1525-26, 10575-76; No.
 1455 J.A. 1363, 1399, 1402-03. But there was also some
 discussion of whether Apple had lost the opportunity even
 to try to satisfy the analogous art requirement, given how
 it had handled the matter in its petition. Corephotonics
 argued, in the IPR concerning the ’233 patent, for example:
      [T]he petition failed to meet their prima facie case
      of showing that it’s analogous art because, as they
      later admit, they didn’t apply the right standard in
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     their petition so they made no showing that Martin
     was analogous art. Using the proper standard they
     tried to do that on reply. That’s all new, improper
     argument to meet their prima facie case.
 J.A. 1514-16; see also J.A. 1525-26 (“[T]here really is no dis-
 pute that everything that they’re relying on for analogous
 art is new from their reply.”); J.A. 10575-76 (“[T]here’s re-
 ally no dispute that the petition failed to apply the correct
 legal test in determining whether or not the references
 were analogous for purposes of their prima facie case and
 so it’s fascinating that in reply then petitioner came back
 and gave you a couple of pages of arguments, three pages
 in this case and five pages in the companion case, trying to
 convince the panel that, oh no, the references are in fact
 analogous to the ’942 patent or the ’233 patent.”); No. 1455
 J.A. 1402-03 (“[T]he petition failed to make the prima facie
 case. They applied the wrong standard and that’s not re-
 ally disputed.”).
      The Board squarely addressed the analogous art dis-
 putes in the Decisions. First, the Board agreed with Core-
 photonics that Apple’s treatment of the analogous art issue
 in its petitions had been deficient. Because, at the petition
 stage, Apple and its expert had not explicitly mentioned or
 discussed the field of endeavor of the Challenged Patents,
 the Board understood Apple as improperly “compar[ing]
 Golan and Martin to each other instead of the claimed in-
 vention.” J.A. 31, 102; see also No. 1455 J.A. 39, 113.
     The Board went on, however, to explain that Apple’s
 replies had “rectifie[d] the improper comparison and as-
 serted that Golan and Martin are in the same field of en-
 deavor as the claimed invention.” J.A. 32, 102; see also No.
 1455 J.A. 39, 113-14. The Board further held that Apple
 “properly replied to Patent Owner’s criticism of its showing
 regarding analogous art.” J.A. 32 n.11, 102 n.19; see also
 No. 1455 J.A. 39 n.20, 114 n.20. The Board considered all
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 22                          COREPHOTONICS, LTD. v. APPLE INC.

 of what Apple said about the analogousness of its prior art
 to be within the scope of a proper reply. See J.A. 32 n.11,
 102 n.19; see also No. 1455 J.A. 39 n.20, 114 n.20.
      On the merits, the Board’s analogousness analysis was
 materially uniform across the four IPRs. In all of the De-
 cisions, the Board was persuaded that:
      Golan is in the same field of endeavor as the
      claimed invention because it describes performing
      digital zoom using a wide image sensor array and
      lens and a tele image sensor array and lens with
      the goal of providing “continuous electronic zoom
      with uninterrupted imaging.”
 J.A. 32 (emphasis added); see also J.A. 103; No. 1455 J.A.
 40, 114. The Board was also persuaded that:
      Martin is reasonably pertinent to the problem faced
      by the inventor: reducing an image jump effect seen
      in video output images when switching between
      cameras that have different fields of view. Both
      Golan and Martin have multiple cameras with dif-
      fering fields of view. Martin describes the problem
      in terms of its solution: “[c]ritical alignment corre-
      sponds to a condition where the degree of align-
      ment is sufficient to achieve a stable auto
      stereoscopic display” and “[s]tability of the whole
      image may not be required, as long as at least a
      particular region of interest in the auto stereo-
      scopic display is stable.”
 J.A. 33 (emphasis added); see also J.A. 103; No. 1455 J.A.
 40, 114-15.
                               IV
     Corephotonics argues that the Board committed proce-
 dural and substantive errors in concluding Golan and Mar-
 tin are analogous art. We find no procedural error. We
 also find that substantial evidence supports the Board’s
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 COREPHOTONICS, LTD. v. APPLE INC.                         23

 findings with respect to Golan. With respect to whether
 Martin is analogous art, we remand for further proceed-
 ings.
                              A
     Corephotonics argues that the Board committed vari-
 ous procedural errors in determining that Golan and Mar-
 tin are analogous art.
                              1
     The Board concluded that Apple’s petition inade-
 quately addressed the issue of analogous art, because it
 made a comparison only between Golan and Martin with-
 out comparing either reference to the Challenged Patents.
 See J.A. 31-32. As we recently explained in Sanofi-Aventis
 Deutschland GmbH v. Mylan Pharms. Inc., 66 F.4th 1373,
 1380 (Fed. Cir. 2023), a patent challenger cannot meet its
 burden of proving obviousness merely by arguing that a
 prior art reference “is analogous to another prior art refer-
 ence and not the challenged patent.” Whether Apple com-
 mitted this error in its petitions is not an issue we must
 address. Rather, our review of how the Board interprets a
 petition is for abuse of discretion, see Henny Penny, 938
 F.3d at 1330-31, and here we find no such abuse.
                              2
     Corephotonics argues that the Board erred by permit-
 ting Apple to make new analogous art contentions in its
 reply. Specifically, Corephotonics contends the Board com-
 mitted reversible error by: (1) allowing Apple to make ex-
 press comparisons between Golan and Martin, on the one
 hand, and the Challenged Patents, on the other, when such
 comparisons were absent from the petition; (2) permitting
 Apple to expand its analogous art arguments from being
 based on field of endeavor to also being based on pertinence
 to the problem faced by the inventors of the Challenged Pa-
 tents; and (3) finding that Golan and the Challenged
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 24                         COREPHOTONICS, LTD. v. APPLE INC.

 Patents share a field of endeavor different from the field
 argued by Apple, and finding that Martin is pertinent to a
 different problem faced by the inventors of the Challenged
 Patents than the problem Apple identified. We reject each
 of Corephotonics’ contentions.
                              a
      We begin by further explaining the permissible scope
 of an IPR petitioner’s reply. The APA, the IPR statute, the
 Board’s regulations, and our precedents collectively impose
 two separate, but related, restrictions on what a petitioner
 may include in its reply. First, the arguments and evidence
 in the reply must not be part of a new theory of unpatenta-
 bility. Second, the arguments and evidence in the reply
 must be responsive to the patent owner’s contentions or the
 Board’s institution decision.
      The “newness” restriction prohibits the petitioner from
 raising, in reply, “an entirely new theory of prima facie ob-
 viousness absent from the petition,” even if the new theory
 is responsive to the patent owner’s response or the Board’s
 institution decision. Wasica, 853 F.3d at 1286; see also 35
 U.S.C. § 312(a)(3) (requiring petition to identify “with par-
 ticularity . . . the grounds on which the challenge to each
 claim is based”). Determining whether a reply has improp-
 erly raised a new theory or argument requires a compari-
 son between the petitioner’s petition and the petitioner’s
 reply.
     The “responsiveness” restriction limits the petitioner’s
 reply to addressing issues presented in the patent owner
 responses or the Board’s institution decision. That is, the
 reply “may only respond to arguments raised in the corre-
 sponding opposition, patent owner preliminary response,
 patent owner response, or decision on institution.” 37
 C.F.R. § 42.23(b); see also Anacor Pharms., Inc. v. Iancu,
 889 F.3d 1372, 1380-82 (Fed. Cir. 2018) (stating petitioner
 “may introduce new evidence after the petition stage if the
 evidence is a legitimate reply to evidence introduced by the
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 COREPHOTONICS, LTD. v. APPLE INC.                          25

 patent owner”). Determining whether a reply is improp-
 erly non-responsive generally requires a comparison be-
 tween the patent owner’s and the Board’s responses to the
 petition, on the one hand, and the petitioner’s reply, on the
 other.
     Our standard of review of the Board’s application of the
 newness and responsiveness restrictions differs. The new-
 ness restriction stems from the statutory mandate that the
 petition govern the IPR proceeding, so “whether a ground
 the Board relied on [i]s ‘new’ . . . is a question of law” we
 review de novo. In re Nuvasive, Inc., 841 F.3d 966, 970
 (Fed. Cir. 2016); see also SAS, 138 S. Ct. at 1357. The re-
 sponsiveness restriction is grounded in the Board’s regula-
 tions, compliance with which we review for abuse of
 discretion. See Yita LLC v. MacNeil IP LLC, 69 F.4th 1356,
 1366 (Fed. Cir. 2023).
      Mindful of the newness and responsiveness re-
 strictions, we have set down certain guideposts for what is
 permitted in a petitioner’s reply. For example, the Board
 may not invalidate a patent based on a prior art reference
 that was not disclosed in a petition and was used in reply
 for a contention that was meaningfully distinct from what
 was identified in the petition. See Ariosa, 805 F.3d at 1368;
 see also Rembrandt Diagnostics, LP v. Alere, Inc., 76 F.4th
 1376, 1385 (Fed. Cir. 2023) (“[T]he petitioner in Ariosa re-
 lied on an embodiment of the prior art that was not dis-
 cussed in the petition to switch theories between its
 petition and reply.”) (internal quotation marks omitted).
 However, a reply argument is proper when it responds to
 the patent owner’s arguments or the Board’s observations
 without “point[ing] to any new embodiments” of a prior art
 reference not previously identified in the petition. Rem-
 brandt, 76 F.4th at 1385 ; see also Apple Inc. v. Andrea El-
 ecs. Corp., 949 F.3d 697, 706 (Fed. Cir. 2020) (“Apple’s legal
 ground did not change in its reply – its reply still asserted
 that claims . . . would have been obvious over [the same
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 26                         COREPHOTONICS, LTD. v. APPLE INC.

 prior art references]. Moreover, Apple’s reply relies on the
 same algorithm from the same prior art reference to sup-
 port the same legal argument.”). As such, “a reply may be
 proper if it is responsive and simply expands on previously
 raised arguments.” Rembrandt, 76 F.4th at 1384; see also
 Chamberlain Grp. Inc. v. One World Techs. Inc., 944 F.3d
 919, 925 (Fed. Cir. 2019) (“Parties are not barred from elab-
 orating on their arguments on issues previously raised.”).
 Furthermore, “there is no blanket prohibition against the
 introduction of new evidence during an IPR,” provided it is
 an “expan[sion] on and . . . fair extension of . . . [a] previ-
 ously raised . . . argument” and has a “nexus” (and is there-
 fore responsive) to an argument made by the patent owner
 or the Board. Rembrandt, 76 F.4th at 1384-85; see also An-
 acor Pharms., 889 F.3d at 1380-82 (“[Petitioner] may intro-
 duce new evidence after the petition stage if the evidence
 is a legitimate reply to evidence introduced by the patent
 owner . . . .”). Indeed, “the introduction of new evidence in
 the course of the trial is to be expected in inter partes re-
 view trial proceedings.” Genzyme, 825 F.3d at 1366.
                               b
     We now turn to the specific contentions presented in
 this appeal.
     First, we reject Corephotonics’ argument that the
 Board abused its discretion by permitting Apple to fix the
 error in its petition, which (in the Board’s view) compared
 Golan and Martin only to one another and did not also con-
 tend that each reference was analogous to the Challenged
 Patents. “In evaluating whether a reference is analogous,
 we have consistently held that a patent challenger must
 compare the reference to the challenged patent.” Sanofi-
 Aventis, 66 F.4th at 1377. In Sanofi-Aventis, the petitioner,
 Mylan, committed the same error, arguing that its petition
 satisfied the analogous art test by virtue of the compari-
 sons it made between the prior art references themselves,
 without regard to the field of endeavor or problem of the
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 COREPHOTONICS, LTD. v. APPLE INC.                           27

 patent being challenged. See id. at 1378-80. After identi-
 fying this mistake, we explained that “[a] petitioner is not
 required to anticipate and raise analogous art arguments
 in its petition; instead a petitioner can use its reply” to re-
 spond to, for example, arguments raised in a patent owner
 response. Id. at 1379 (citing 37 C.F.R. § 42.23). Then we
 went on to consider whether Mylan had fixed its problem
 after filing its petition. See id. at 1379-80. While we con-
 cluded that nothing in Mylan’s reply (or oral argument to
 the Board) was sufficient to cure the defect in the petition,
 we would not have even considered this issue had we
 thought it impermissible for a reply to fix the petition’s er-
 ror in this regard. See id. at 1380.
      Second, we are not persuaded by Corephotonics that
 the Board erred in permitting Apple to argue in reply that
 its prior art references are analogous to the Challenged Pa-
 tent because they satisfy both the field of endeavor and per-
 tinent to the problem tests, even though Apple’s petition
 only invoked the field of endeavor test. In reaching this
 conclusion, we rely, once again, on Sanofi-Aventis, which
 explained that a petitioner may “use its reply” to respond
 to the patent owner’s response arguments against the ref-
 erences being analogous. Id. at 1379-80. Apple was not
 required to anticipate in its petition that Corephotonics
 would argue Golan and Martin were not in the same field
 of endeavor as the Challenged Patents. Once Corephoton-
 ics did so in its patent owner response, Apple was permit-
 ted to respond both by bolstering its field of endeavor
 argument and by adding that its prior art is pertinent to
 the problem faced by the inventors of the Challenged Pa-
 tents.
     This conclusion is consistent with the newness and re-
 sponsiveness restrictions on IPR replies. There is nothing
 “entirely new” about arguing that the same combination of
 prior art references identified in a petition as being in the
 same field of endeavor as the patent being challenged are
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 28                         COREPHOTONICS, LTD. v. APPLE INC.

 also pertinent to the same problem faced by the inventor of
 the challenged patent. While “field of endeavor” and “per-
 tinent problem” are “[t]wo separate tests [that] define the
 scope of analogous prior art,” Bigio, 381 F.3d at 1325, they
 do not provide independent, different grounds for obvious-
 ness or new “rationales,” but are, instead, related bases for
 the same, single ground of invalidation, obviousness, and
 are based on the same references identified with particu-
 larity in the petition. This is further reflected in the fact
 that the “pertinent problem” basis for analogousness is
 only relevant “if the reference is not within the field of the
 inventor’s endeavor,” which would make it unreasonable to
 require a petitioner to anticipate an attack on its field of
 endeavor contention and always have to address pertinent
 problem in the petition. Id.
      Corephotonics had sufficient notice of Apple’s position,
 that Golan and Martin satisfy the analogous art require-
 ment, and adequate opportunity to respond to both the
 field of endeavor and pertinent to the problem aspects of it.
 Apple consistently relied on “the same references, the same
 disclosures, and the same obviousness theories advanced
 by the petition and debated by the parties.” Arthrex, 935
 F.3d at 1328. After receiving Apple’s replies, Corephoton-
 ics deposed and cross-examined Apple’s expert about the
 statements in his declaration that accompanied Apple’s re-
 ply. Corephotonics then filed a sur-reply, in which it spe-
 cifically addressed Apple’s analogousness arguments.
 Thus, once again, we conclude that what occurred here sat-
 isfies the “newness” restriction on what is proper in an IPR
 reply. See Henny Penny, 938 F.3d at 1330–31.
     Apple’s reply argument, that its references are analo-
 gous prior art because they are pertinent to the problem
 addressed by the Challenged Patents (even if they are not
 found to be in the same fields of endeavor), was also
 properly responsive to Corephotonics’ patent owner re-
 sponse. Corephotonics had contended in its patent owner
 response that Apple’s handling of the analogous art issue
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 COREPHOTONICS, LTD. v. APPLE INC.                           29

 to that point in the process was “insufficient because it fails
 to apply the correct legal test and yield the correct analy-
 sis.” J.A. 1246; see also J.A. 10205-06. This broad attack
 on Apple’s showing made it appropriate for Apple to re-
 spond with an elaboration of the bases on which its prior
 art references satisfy the analogous art requirement, under
 one or both of the tests we have set out for doing so. See
 Chamberlain, 944 F.3d at 925 (“Parties are not barred from
 elaborating on their arguments on issues previously
 raised.”).
     We also disagree with Corephotonics that the Board
 erred by finding analogousness based on a different field of
 endeavor and different problem of the inventors than those
 expressly advocated for by Apple. Apple argued that Golan
 and the Challenged Patents’ share the field of endeavor of
 “imaging systems, and more specifically, imaging systems
 including digital cameras [for] generating video output im-
 ages using two imaging sections having different points of
 view,” J.A. 1279 (internal quotation marks omitted); see
 also J.A. 10265; No. 1455 J.A. 1264, 10264,while the Board
 found their shared field of endeavor is “digital zoom using
 a wide image sensor array and lens and a tele image sensor
 array and lens with the goal of providing continuous elec-
 tronic zoom with uninterrupted imaging,” J.A. 32 (internal
 quotation marks omitted). Similarly, Apple contended that
 Martin was pertinent to the problem of “a jump (discontin-
 uous) image change [w]hen a dual-aperture camera
 switches the camera output between sub-cameras or points
 of view,” J.A. 1280 (internal quotation marks omitted),
 while the Board found that the pertinent problem Martin
 and the Challenged Patents’ shared was “reducing an im-
 age jump effect seen in video output images when switch-
 ing between cameras that have different fields of view,”
 J.A. 33.
     We find no procedural error in the Board’s approach.
 As long as substantial evidence supported its findings – an
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 30                           COREPHOTONICS, LTD. v. APPLE INC.

 issue we turn to below, see infra Part IV.B 6 – the Board
 may resolve an issue the parties put in dispute by making
 findings supported by the evidence, regardless of whether
 any party advocated for that particularly expressed find-
 ing. See Genzyme, 825 F.3d at 1366 (Board has to make
 factual findings based on its view of the record); Roku, Inc.
 v. Universal Elecs., Inc., 63 F.4th 1319, 1325 (Fed. Cir.
 2023) (“The Board, in its role as factfinder in the first in-
 stance, was entitled to weigh the evidence in the record
 . . . .”); see also Regents of Univ. of Cal. v. Broad Inst., Inc.,
 903 F.3d 1286, 1294 (Fed. Cir. 2018) (“It is not our role to
 ask whether substantial evidence supports fact-findings
 not made by the Board, but instead whether such evidence
 supports the findings that were in fact made.”). While the
 Board may not invalidate patent claims on grounds it iden-
 tifies sua sponte that are not actually raised by the peti-
 tioner, see Magnum Oil, 829 F.3d at 1381, the Board is not
 required to use the same words in explaining its findings
 as the petitioner uses in its proposed findings, see Sirona
 Dental, 892 F.3d at 1356 (explaining Board did not deviate
 from the petition because it used different wording). Just
 as the Board is not limited to selecting between the parties’
 proposed constructions of a disputed claim term, see West-
 ern Geco LLC v. ION Geophysical Corp., 889 F.3d 1308,
 1329 (Fed. Cir. 2018), so, too, the Board may make its own
 finding as to the field of endeavor or problem confronted by
 the inventors – when those issues are in dispute – even if
 its finding differs from the positions argued for by the par-
 ties.

      6  The Board made no finding with respect to whether
 Golan is also reasonably pertinent to the problem faced by
 the inventors of the Challenged Patents, nor any finding as
 to whether Martin is also in the same field of endeavor as
 the Challenged Patents, even though Apple made argu-
 ments in its reply on both these points.
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     The Board’s handling of the analogous art issue in the
 Decisions neither “markedly . . . departed” from the “evi-
 dence and theories presented by the petition or institution
 decision” nor “unfair[ly] surprise[d]” Corephotonics. Ar-
 threx., 935 F.3d at 1328. Instead, it did nothing more than
 resolve the factual disputes underlying obviousness that
 were presented to it by the parties. That its findings dif-
 fered slightly from what was proposed by the petitioner,
 and its articulation of the field of endeavor and pertinent
 problem were not identical to Apple’s advocacy, do not con-
 stitute error.
     In sum, we find no procedural error in the Board’s han-
 dling of the analogous art issue.
                              B
      Having determined that the Board’s analogousness de-
 cisions were procedurally proper, we now turn to whether
 substantial evidence supported its factual findings.
                              1
     Apple argued in its replies that Golan is analogous art
 because it is in the same field of endeavor as the Chal-
 lenged Patents and also because it is pertinent to the prob-
 lem faced by the inventors. The Board agreed with Apple
 as to field of endeavor and chose not to address the alter-
 native pertinent to the problem contention. Corephotonics
 attacks the Board’s finding as not supported by substantial
 evidence. We agree with the Board.
     The Board explained: “Golan is in the same field of en-
 deavor as the claimed invention because it describes per-
 forming digital zoom using a wide image sensor array and
 lens and a tele image sensor array and lens with the goal
 of providing ‘continuous electronic zoom with uninter-
 rupted imaging.’” J.A. 32-33 (quoting J.A. 1280); see also
 J.A. 103 (same in decision for ’942 patent); No. 1455 J.A.
 40, 114 (same in decision for ’898 and ’332 patents). Golan
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 32                         COREPHOTONICS, LTD. v. APPLE INC.

 teaches that “the calibration of the alignment between the
 first image sensor array and the second image sensor array
 . . . facilitates continuous electronic zoom with uninter-
 rupted imaging.” J.A. 5525 (Golan ¶ 15). These teachings,
 as supplemented by the opinions of Apple’s expert, see J.A.
 6021, 16856-57, provide substantial evidence for the
 Board’s determination that Golan and the Challenged Pa-
 tents are in the same field of endeavor.
      Corephotonics argues that the ’898 and ’332 patents
 are designed to “interrupt otherwise smooth transitioning
 during video zooming if a no-switching criterion is ful-
 filled,” while Golan fails to describe not switching. Core-
 photonics maintains that because of these differences, the
 claimed inventions and Golan cannot be in the same field
 of endeavor. But the Board reasonably found that the field
 of endeavor for the ’898 and ’332 patents, and for Golan, is
 broader than Corephotonics characterizes it, and is not lim-
 ited to use of no-switching criteria. See No. 1455 J.A. 4
 (citing ’898 patent 7:57-8:29); No. 1455 J.A. 78 (same for
 ’332 patent).
    Thus, we hold that Golan is in the same field of en-
 deavor as the Challenged Patents.
                              2
      Apple argued in its replies that Martin is analogous art
 because it is in the same field of endeavor as the Chal-
 lenged Patents and is also pertinent to the problem faced
 by the inventors. The Board agreed with Apple as to the
 pertinent to the problem test and chose not to reach the
 field of endeavor contention. Corephotonics attacks the
 Board’s finding on pertinence to the problem as not sup-
 ported by substantial evidence. On the present record, we
 cannot determine whether substantial evidence supports
 the Board’s conclusion that Martin is analogous art.
     The Board wrote, “Martin is reasonably pertinent to
 the problem faced by the inventor: reducing an image jump
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 COREPHOTONICS, LTD. v. APPLE INC.                           33

 effect seen in video output images when switching between
 cameras that have different fields of view. Both Golan and
 Martin have multiple cameras with differing fields of
 view.” J.A. 33, 103 (emphasis added); see also No. 1455 J.A.
 40, 114. Apple and Corephotonics agree that these two sen-
 tences are, as written, incorrect: Martin does not disclose
 switching between cameras with different fields of view; ra-
 ther, it is addressed to cameras with different points of
 view. 7 According to Apple, the Board’s statement is a mere
 “typographical error” and, therefore, is harmless. No. 1455
 Apple’s Resp. Br. 57 n.6 (“Read in the proper context, the
 Board clearly intended to refer to the term ‘points of view’
 rather than ‘fields of view’ in describing Martin’s perti-
 nence to a problem facing the inventors of the challenged
 patents.”); see also In re Watts, 354 F.3d 1362, 1369 (Fed.
 Cir. 2004) (applying harmless error rule to Board).
     We are unable to discern if the Board’s error was, in
 fact, merely typographical and harmless or, instead, a po-
 tentially-impactful error of substance. This prevents us
 from concluding either that there is, or is not, substantial
 evidence to support the Board’s conclusion that Martin is
 analogous art to the Challenged Patents.
    Nowhere else in its Decisions does the Board treat the
 Challenged Patents as addressing a point of view problem.
 Rather, the Board emphasized elsewhere that the dual-

     7    The Board’s analogous art analysis is not the only
 place it appears it may have confused “field of view” and
 “point of view.” In the section of the Decision on motivation
 to combine, the Board wrote, “Golan and Martin both in-
 volve parallax effects caused by two cameras with different
 fields of view,” but, in fact, parallax effects arise from dif-
 ferent points of view. J.A. 25, 98 (emphasis added); see also
 No. 1455 J.A. 33, 108.
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 aperture cameras described in the Challenged Patents use
 lenses with different fields of view. Thus, it seems possible
 that the Board truly meant to say “field of view” when de-
 scribing the problem to which Martin is pertinent, since
 “field of view” is fully consistent with the Board’s descrip-
 tion of the Challenged Patents. Martin, however, makes
 no express reference to field of view, and the Board pro-
 vides no explanation as to how Martin’s approach to point
 of view can have anything to do with the field of view prob-
 lem faced by the inventors of the Challenged Patents. This
 leaves us uncertain of the Board’s reasoning.
     In these circumstances, we have no record basis to con-
 clude that the Board’s error was a harmless typographical
 one and did not affect the outcome it reached. See Carter
 v. McDonald, 794 F.3d 1342, 1347 (Fed. Cir. 2015) (identi-
 fying error and remanding when we could not determine it
 was harmless). The Board’s determination that Martin is
 pertinent to the problem that the inventors of the Chal-
 lenged Patents faced may be based on its articulated view
 that Martin relates to field of view when, in fact, Martin
 relates to point of view. Accordingly, we remand to the
 Board for further explanation and, if needed, further fact-
 finding. We leave it to the Board to decide whether it
 should also consider Apple’s contention that, regardless of
 whether Martin is pertinent to the problem faced by the
 inventors, it is in the same field of endeavor as the Chal-
 lenged Patents.
                               V
     Corephotonics raises two additional issues. First, it ar-
 gues there is no substantial evidence to support the Board’s
 finding that Martin teaches the “shifting . . . according to a
 distance of an object” limitation of the ’942 patent. Second,
 Corephotonics contends that the Board adopted an incor-
 rect construction of the claim term “effective resolution”
 and compounded that error by finding that Togo teaches
 the “effective resolution” “no-switching criterion”
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 limitation of claims 4 and 15 of the ’898 patent and claims
 5 and 17 of the ’332 patent. We decline to reach these is-
 sues because they will be rendered moot if, on remand, the
 Board finds Martin is not analogous art.
                             VI
     We have considered the parties’ remaining arguments
 and find them unpersuasive. For the foregoing reasons, we
 vacate and remand for further proceedings consistent with
 this opinion. In particular, the Board must explain why
 Martin is (or is not) analogous art and how this finding af-
 fects its overall conclusion as to obviousness.
                VACATED AND REMANDED
                           COSTS
 No costs.