  United States Court of Appeals
      for the Federal Circuit
                ______________________

          SONIX TECHNOLOGY CO., LTD.,
                 Plaintiff-Appellant

                           v.

  PUBLICATIONS INTERNATIONAL, LTD., SD-X
     INTERACTIVE, INC., ENCYCLOPEDIA
   BRITTANNICA, INC., HERFF JONES, INC.,
             Defendants-Appellees
            ______________________

                      2016-1449
                ______________________

   Appeal from the United States District Court for the
Northern District of Illinois in No. 1:13-cv-02082, Judge
Amy J. St. Eve.
                ______________________

               Decided: January 5, 2017
                ______________________

    JONATHAN HANGARTNER, X-Patents, APC, La Jolla,
CA, argued for plaintiff-appellant. Also represented by
STEVEN P. FALLON, Greer, Burns & Crain, Ltd., Chicago,
IL.

    JACOB DANIEL KOERING, Miller, Canfield, Paddock, &
Stone, PLC, Chicago, IL, argued for defendants-appellees.
Also represented by TERRENCE JOSEPH SHEAHAN, Free-
born & Peters, LLP, Chicago, IL.
                ______________________
2                        SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.




        Before LOURIE, O’MALLEY, and TARANTO, Circuit
                         Judges.
LOURIE, Circuit Judge.
    Sonix Technology Co., Ltd. (“Sonix”) appeals from the
district court’s grant of summary judgment following its
determination that claims 9, 25, 35–36, 52–55, 57–60, 62–
64, 66, 68, 71–77, 79–82, and 85–90 (“the asserted
claims”) of Sonix’s U.S. Patent 7,328,845 (“the ’845 pa-
tent”) are invalid as indefinite. See Sonix Tech. Co. v.
Publ’ns. Int’l, Ltd., No. 13-cv-2082, 2015 WL 8153600, at
*9–17 (N.D. Ill. Dec. 8. 2015) (“Opinion”). Specifically, the
district court concluded that the term “visually negligible”
rendered the asserted claims indefinite under 35 U.S.C.
§ 112 ¶ 2. 1 For the reasons that follow, we reverse the
determination of indefiniteness and hence the summary
judgment of invalidity.
                        BACKGROUND
     Sonix owns the ’845 patent, which describes a system
and method for using a “graphical indicator” (e.g., a
matrix of small dots) to encode information on the surface
of an object. See ’845 patent, col. 3 ll. 6–43. The surface
may feature additional information as well; for example,
illustrations or icons in a children’s book. Id. col. 7 ll. 1–6.
The invention also includes an “optical device” that can
read the graphical indicator and output further infor-
mation. Id. col. 7 ll. 18–32. Figure 5 illustrates an
example:



    1   Because the ’845 patent was filed before the en-
actment of the Leahy-Smith America Invents Act, Pub. L.
No. 112-29, § 3, 125 Stat. 284, 285–93 (2011), the prior
version of § 112 governs. See Fleming v. Escort, Inc., 774
F.3d 1371, 1374 n.1 (Fed. Cir. 2014).
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                   3




Id. fig.5. In this example, an icon showing a person riding
a horse (511) is printed on the page of a book (51). Id. col.
7 ll. 1–10. The graphical indicator (512) is printed in the
same area as the icon. Id. col. 7 ll. 18–21. The optical
device (311) captures an image that includes the graph-
ical indicator. Id. col. 7 ll. 21–24. The processing device
(312) retrieves the indicator from the image and outputs
additional information. Id. In this particular example,
holding the optical device over the horse icon could cause
the device to output “audio information, such as pronun-
ciations of horse in English.” Id. col. 7 ll. 27–32.
      Of course, encoding information on the surface of an
object is not new. The ’845 patent admits that infor-
mation has been recorded on the surface of objects
“[d]ating back to ancient time[s],” id. col. 1 ll. 15–16, and
lists a bar code as a “conventional” example of a graphical
4                        SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



indicator, id. col. 9 ll. 46–57. The ’845 patent purports to
improve on conventional methods by rendering the graph-
ical indicator “visually negligible.” Id. col. 3 ll. 5–11. The
patent uses a book cover to illustrate the difference be-
tween a conventional bar code and the claimed indicator:




Id. figs.12(A) & 12(B). The graphical indicator (10002) in
figure 12(B) stores the same information as the bar code
(10001) in figure 12(A), but in a manner that does not
“interfere with the other main information on the sur-
face.” Id. col. 9 ll. 47–57.
     The “[e]xemplary [d]esign,” id. col. 3 l. 5, of the
claimed indicator “includes multiple graphical micro-units
arranged in a layout.” Id. col. 3 ll. 14–15. In one embod-
iment the micro-units are dots, arranged in a matrix. Id.
col. 3 ll. 15–25. Each cell in the matrix either contains or
does not contain a dot, resulting in a unique pattern that
can store information. Id. col. 3 ll. 38–30, col. 4 ll. 13–41.
     The written description also discloses differentiability,
brightness, and homogeneity “requirements for the graph-
ical indicators being negligible to human eyes.” Id. col. 4
ll. 60–61. First, the indicator must be so small that
“human eyes cannot differentiate one graphical indicator
from others.” Id. col. 4 ll. 61–63. The patent indicates
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                    5



that “[f]or best result, the graphical micro-unit must be so
tiny that only a microscope apparatus can detect it.” Id.
col. 3 ll. 24–25. Second, the patent advises that the
number of micro-units should be reduced based on “the
size of the graphical micro-unit, the pitch between micro-
unit, and the desired visual effect,” so that they “have
little influence on the brightness of the surface of the
object.” Id. col. 4 l. 67–col. 5 l. 1. Finally, the “number of
graphical micro-units of each graphical indicator” should
be “substantially equal to each other,” so that “the graph-
ical indicators look more homogenous to human eyes and
become invisible to human eyes.” Id. col. 5 ll. 1–5.
    The written description also gives two examples of
visually-negligible indicators. In the first, each square
centimeter contains 3,000 matrix cells, of which less than
70% contain graphical micro-units, and where each micro-
unit occupies less than 80% of the cell. Id. col. 5 ll. 6–10.
The second is similar, but requires each square centime-
ter to include 6,000 cells. Id. col. 5 ll. 11–15.
    In 2010, Sonix alleged that children’s books using dot
pattern technology produced by GeneralPlus, a Taiwanese
company, infringed the ’845 patent. In response, SunPlus
Technology Co. Ltd. (“SunPlus”), GeneralPlus’s parent
company, requested ex parte reexamination of the ’845
patent (“the first reexamination”) by the U.S. Patent and
Trademark Office (“USPTO”). On December 27, 2011, the
USPTO confirmed the patentability of, inter alia, asserted
claims 9, 25, and 35–36, and allowed new, and now as-
serted, claims 52–55, 57–60, 62–64, 66, 68, 71–77, 79–82,
and 85–90, among others. J.A. 94–96.
    Less than one month later, GeneralPlus requested
another ex parte reexamination (“the second reexamina-
tion”). J.A. 1937. One of the central disputed issues
during this second reexamination was whether the com-
bination of U.S. Patent 5,416,312 (“Lamoure”) and U.S.
Patent 5,329,107 (“Priddy”) would have led to a visually-
6                       SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



negligible indicator, as the examiner initially rejected all
pending claims over that combination. See, e.g., J.A.
2328–31. Sonix responded to that rejection with a decla-
ration from Serjer Serjersen (“Serjersen”), an expert with
more than thirty years of experience. J.A. 2337. Ser-
jersen declared that he created graphical indicators using
the processes described by the ’845 patent and by the
cited references, and determined that only the indicator
produced using the process of the ’845 patent was visually
negligible. J.A. 2338–44, 5313–25. The examiner con-
firmed the patentability of the asserted claims on the
basis of Serjersen’s declaration, specifically indicating
that the combination of cited references did not disclose a
visually-negligible graphical indicator. J.A. 2362–65.
    In 2013, Sonix alleged that Publications Internation-
al, Ltd., SD-X Interactive, Inc., Encyclopedia Brittannica,
Inc., and Herff Jones, Inc. (collectively, “Appellees”)
infringed the asserted claims. Appellees’ initial invalidity
contentions identified twenty-six claim limitations that
they believed to be indefinite; however, that list did not
include the term “visually negligible.” See J.A. 2637–41.
In their final invalidity contentions, Appellees contended
that two additional claim limitations were indefinite, but
again did not question “visually negligible.” J.A. 3031.
    During claim construction, Appellees initially asked
the district court to construe “visually negligible,” J.A.
2430, but, when they retained new counsel, proposed that
the term be given its ordinary meaning, J.A. 2434–36.
Sonix agreed with an ordinary-meaning construction, and
so the district court did not construe “visually negligible.”
    Even so, “visually negligible” was used repeatedly in
the expert reports.       For example, Sonix’s expert,
Dr. Ashok, opined that the accused products included
visually-negligible indicators, J.A. 3087–88, and that the
cited prior art did not, J.A. 3539–41, 3547. Appellees’
expert, Dr. Engels, also applied “visually negligible”
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                   7



throughout his reports, and even agreed that “the dot
patterns in the specific products reviewed by Dr. Ashok in
his Report are visually negligible . . . .” J.A. 4210–11. On
validity, Dr. Engels repeatedly opined that the indicators
disclosed in Lamoure and Priddy—the same references at
issue in the second reexamination—were visually negligi-
ble. See J.A. 5348–49, 5355–56, 5418, 5430–31. But Dr.
Engels did not opine that “visually negligible” was indefi-
nite. See id. Elsewhere in his report, Dr. Engels contend-
ed that alternatives to the claimed invention would have
been available because “it would be a simple matter to
ensure that any pattern being used would be printed in a
manner that would be visually negligible compared to the
main information on a page.” J.A. 4228.
     At Dr. Ashok’s deposition, after the close of fact dis-
covery and after the parties agreed to an ordinary mean-
ing for “visually negligible,” he was asked to explain
“what does [‘visually negligible’] mean to you?” J.A. 4755
at 46:25–47:1. Dr. Ashok indicated that he understood it
“to mean that if these dot patterns are imprinted on a
surface, with a cursory look, I will not notice that.” Id. at
47:2–7. Dr. Ashok was then asked whether there was
“any sort of objective standard” for visual negligibility.
J.A. 4756 at 49:11. Dr. Ashok explained that visibility
depended on the ink used, the printing pattern, and the
size of the dot, but that there “is not a universal standard
by any means because it depends on the visual acuity of
the observer.” Id. at 50:24–51:4. Even so, Dr. Ashok
indicated that his “method of determining visual negligi-
bility would be [to] print at the magnification desired and
look at it,” because he “would imagine that would be
representative of most people looking at it.” Id. at 51:5–8.
    In response, Dr. Engels asserted at his deposition that
“visually negligible” was subjective because “there is no
objective test to define the boundary between visually
negligible and visually non-negligible.” Dr. Engels did not
analyze the intrinsic evidence, and did not provide any
8                        SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



detail explaining his conclusion. J.A. 3709. On the basis
of the two expert depositions, Appellees amended their
invalidity contentions and moved for summary judgment
of indefiniteness.
    The district court ultimately held that the claims are
invalid as indefinite. Opinion, 2015 WL 8153600, at *9–
17. Reasoning that “visually negligible” is “purely subjec-
tive” and that the claim language does not provide guid-
ance on its meaning, the court turned to the other
intrinsic evidence. Id. at *13. The court determined that
the written description does not provide a person of
ordinary skill in the art “with a meaning that is reasona-
bly certain and defines objective boundaries” of the claim
scope. Id. The court rejected Sonix’s argument that
“visually negligible” means “something that may be
visible, but does not interfere with the user’s perception of
other visual information on a surface,” concluding that
defining the term “as reliant on the user’s perception
provides no objective standard by which to measure the
scope of the term—the user’s perception becomes the
measure and this is insufficient.” Id. (citing Datamize,
LLC v. Plumtree Software, Inc., 417 F.3d 1342, 1351 (Fed.
Cir. 2005)).
     The district court also rejected Sonix’s attempts to re-
ly on other portions of the written description. For exam-
ple, the court determined that the instruction that the
graphical micro-units “must be so tiny that only a micro-
scope apparatus can detect it,” ’845 patent, col. 3 ll. 24–25,
failed to provide reasonable certainty because the written
description “contains no information . . . regarding what
type of microscope apparatus or what level of magnifica-
tion the user would need.” Opinion, 2015 WL 8153600, at
*14. The court similarly rejected Sonix’s reliance on the
differentiability, brightness, and homogeneity require-
ments because they lacked “the necessary detail to make
[them] meaningful.” Id. Finally, the court rejected the
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                  9



prosecution and reexamination history as not providing
additional guidance. Id. at *15.
    Although the district court determined that it was
“not necessary” to consult the extrinsic evidence, it none-
theless concluded that the extrinsic evidence “highlights
the problem with the subjective nature of the ‘visually
negligible’ claim term.” Id. The court noted, for example,
that although the experts applied the term to the prior
art, they did not provide any standard by which to meas-
ure negligibility aside from their “subjective belief.” Id.
     The district court then reviewed recent cases from the
Supreme Court and this court, and determined that the
present case was more similar to those concluding that
claims were invalid as indefinite than to those holding
otherwise. See id. at *15–17 (citing Nautilus v. Biosig
Instruments, Inc., 134 S. Ct. 2120, 2129 (2014); Interval
Licensing LLC v. AOL, Inc., 766 F.3d 1364, 1368–74 (Fed.
Cir. 2014); Enzo Biochem, Inc. v. Applera Corp., 599 F.3d
1325, 1336 (Fed. Cir. 2010); Datamize, 417 F.3d at 1349–
54).
   The district court therefore entered judgment against
Sonix and for Appellees on December 8, 2015. J.A. 1–2.
Sonix timely appealed. We have jurisdiction pursuant to
28 U.S.C. § 1295(a)(1).
                           DISCUSSION
    At the outset, there is a dispute relating to the stand-
ard of review to be applied to the present case. Sonix
argues that our review is entirely de novo, because the
district court indicated that it was unnecessary to address
the extrinsic evidence and did not make any factual
findings based thereon. Appellees respond that the
district court made underlying findings that “visually
negligible” is subjective and that it lacks an objectively-
measurable standard.
10                      SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



    We agree with Sonix that we review a district court’s
determination that a claim is invalid as indefinite under
35 U.S.C. § 112 ¶ 2 de novo, although, as with claim
construction, any factual findings by the district court
based on extrinsic evidence are reviewed for clear error.
Cox Commc’ns, Inc. v. Sprint Commc’n Co., 838 F.3d
1224, 1228 (Fed. Cir. 2016) (citing Teva Pharm. USA, Inc.
v. Sandoz, Inc., 135 S. Ct. 831, 840–42 (2015) (“Teva I”)).
To trigger clear error review, “it is not enough that the
district court may have heard extrinsic evidence during a
claim construction proceeding—rather, the district court
must have actually made a factual finding . . . .” Card-
Soft, LLC v. VeriFone, Inc., 807 F.3d 1346, 1350 (Fed. Cir.
2015) (citations omitted). Moreover, “[a] party cannot
transform into a factual matter the internal coherence
and context assessment of the patent simply by having an
expert offer an opinion on it. The internal coherence and
context assessment of the patent, and whether it conveys
claim meaning with reasonable certainty, are questions of
law.” Teva Pharm. USA, Inc. v. Sandoz, Inc., 789 F.3d
1335, 1342 (Fed. Cir. 2015) (“Teva II”).
     The district court expressly explained that the extrin-
sic evidence was “not necessary for [its] consideration” of
the indefiniteness issue. Opinion, 2015 WL 8153600, at
*15. Moreover, the district court’s conclusions of subjec-
tivity and lack of an objective standard are not findings
subject to clear error review; instead, they are conclusions
relating to the meaning of the intrinsic evidence, and
whether it conveys claim meaning with reasonable cer-
tainty. See Teva II, 789 F.3d at 1342. Such conclusions
cannot be transformed into factual matters “simply by
having an expert offer an opinion on [them].” Id.
                   I.   INDEFINITENESS
    Sonix argues that the district court erred in conclud-
ing that “visually negligible” renders the asserted claims
invalid as indefinite. Specifically, Sonix argues that the
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                11



requirements and examples in the written description
would have allowed a skilled artisan to know the scope of
the claimed invention with reasonable certainty and
establish that the term depends on human perception, not
opinion. This conclusion is supported, Sonix contends, by
the consistent manner in which “visually negligible” has
been applied during initial examination, both reexamina-
tions, and the majority of the district court litigation.
    Appellees respond that visual negligibility does not
have an objective standard because it depends on the
“vagaries of any one person’s opinion,” Datamize, 417 F.3d
at 1350, and is therefore indefinite. Appellees contend
that the written description would not allow a skilled
artisan to understand the scope of the claims with rea-
sonable certainty, and that the ability of experts to apply
the term does not provide an objective standard.
    We agree with Sonix that a skilled artisan would un-
derstand, with reasonable certainty, what it means for an
indicator in the claimed invention to be “visually negligi-
ble.” The intrinsic evidence supports, and the extrinsic
evidence is consistent with, this conclusion.
    Section 112 requires that a patent specification “con-
clude with one or more claims particularly pointing out
and distinctly claiming the subject matter which the
applicant regards as his invention.” The Supreme Court
has read this provision to require that “a patent’s claims,
viewed in light of the specification and prosecution histo-
ry, inform those skilled in the art about the scope of the
invention with reasonable certainty.” Nautilus, 134 S. Ct.
at 2129. Indefiniteness must be proven by clear and
convincing evidence. See Teva II, 789 F.3d at 1345.
    The § 112 ¶ 2 requirement strikes a “delicate balance”
between “the inherent limitations of language” and
providing “clear notice of what is claimed.” Nautilus, 134
S. Ct. at 2129 (internal citations omitted). Even so, the
Supreme Court has recognized that “absolute precision is
12                     SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



unattainable.” Id. “[T]he certainty which the law re-
quires in patents is not greater than is reasonable, having
regard to their subject-matter.” Id. (quoting Minerals
Separation, Ltd. v. Hyde, 242 U.S. 261, 270 (1916) (inter-
nal quotation marks omitted)).
    Because language is limited, we have rejected the
proposition that claims involving terms of degree are
inherently indefinite. Interval Licensing, 766 F.3d at
1370. Thus, “a patentee need not define his invention
with mathematical precision in order to comply with the
definiteness requirement.” Invitrogen Corp. v. Biocrest
Mfg., L.P., 424 F.3d 1374, 1384 (Fed. Cir. 2005) (citation
omitted). Indeed, “[c]laim language employing terms of
degree has long been found definite where it provided
enough certainty to one of skill in the art when read in
the context of the invention.” Interval Licensing, 766 F.3d
at 1370 (citing Eibel Process Co. v. Minn. & Ont. Paper
Co., 261 U.S. 45, 65–66 (1923)).
    Accordingly, we have held that the clause “not inter-
fering substantially” did not render a claim invalid as
indefinite. Enzo, 599 F.3d at 1336. 2 In that case, we
reasoned that the intrinsic evidence provided guidance as
to the scope of the claims, including, inter alia, examples
of noninterfering structures and criteria for their selec-
tion. Id. at 1334–35. This guidance allowed a skilled
artisan to compare a potentially infringing product “with
the examples in the specification to determine whether
interference . . . is substantial.” Id. at 1336.
   We have found terms of degree indefinite, however,
when such guidance is lacking. For example, Datamize



     2   Although Enzo was decided before the introduc-
tion of the “reasonable certainty” standard, we have relied
on it in our post-Nautilus decisions. See, e.g., Interval
Licensing, 766 F.3d at 1370.
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                  13



involved claims to an “aesthetically pleasing” look and feel
for interface screens. 417 F.3d at 1348–49. We deter-
mined that such language rendered the claim indefinite
because, although the written description did detail
various elements that might affect whether a screen was
aesthetically pleasing (such as button styles and sizes), it
“provide[d] no guidance to a person making aesthetic
choices such that their choices will result in an ‘aestheti-
cally pleasing’ look and feel of an interface screen.” Id. at
1352. Without such guidance, the claim did “not just
include a subjective element, it [wa]s completely depend-
ent on a person’s subjective opinion.” Id.
    Similarly, Interval Licensing involved a claim related
to displaying content “in an unobtrusive manner that does
not distract a user.” 766 F.3d at 1368. We observed that
the term was “a term of degree,” id. at 1370, “purely
subjective,” id. at 1371, and that the claim language
offered “no objective indication of the manner in which
content images are to be displayed to the user,” id. We
refused to limit the “facially subjective claim term” to the
single example in the written description because, with-
out more information, “a skilled artisan is still left to
wonder what other forms of display are unobtrusive and
non-distracting . . . thus leaving the skilled artisan to
consult the ‘unpredictable vagaries of any one person’s
opinion.’” Id. at 1373–74 (quoting Datamize, 417 F.3d at
1350).
    As indefiniteness analysis involves general claim con-
struction principles, we begin with the language of the
claims of the ’845 patent. See Enzo, 599 F.3d 1332. We do
agree with the district court that the claim language itself
does not unmistakably make clear the scope of “visually
negligible”; however, we disagree with the conclusion, and
Appellees’ argument, that the term is “purely subjective,”
Opinion, 2015 WL 8153600, at *13, in the same manner
as “aesthetically pleasing” in Datamize and “in an unob-
14                     SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



trusive manner that does not distract a user” in Interval
Licensing.
    Datamize and Interval Licensing involved terms that
were subjective in the sense that they turned on a per-
son’s tastes or opinion. “Aesthetically pleasing” impli-
cates matters of taste or preference; whether something is
aesthetically pleasing is a value judgment that inherently
varies from person to person. “In an unobtrusive manner
that does not distract” similarly implicates a person’s
individual focus, concentration, attentiveness, or similar
mental state at a given moment, or even opinions, affect-
ing what is or is not distracting. The question whether
something is “visually negligible” or whether it interferes
with a user’s perception, however, involves what can be
seen by the normal human eye. This provides an objec-
tive baseline through which to interpret the claims. See
Warsaw Orthopedic, Inc. v. NuVasive, Inc., 778 F.3d 1365,
1371 (Fed. Cir. 2015), cert. granted, judgment vacated sub
nom. Medtronic Sofamor Danek USA, Inc. v. NuVasive,
Inc., 136 S. Ct. 893 (2016), and opinion reinstated in
relevant part, 824 F.3d 1344, 1346 (Fed. Cir. 2016). Thus,
although the term may be a term of degree, it is not
“purely subjective.”
    We turn next to the written description, to determine
whether there is some standard in the written description
for measuring visual negligibility. See Enzo, 599 F.3d at
1332. Our prior cases establish that the written descrip-
tion is key to determining whether a term of degree is
indefinite. In Enzo, for example, the written description
included examples of noninterfering structures and the
procedures for selecting them; we reasoned that the
examples and procedures provided guidance and points of
comparison for skilled artisans. Id. at 1335–36. The one
example provided in the written description at issue in
Interval Licensing, in contrast, was not accompanied by
sufficient detail to render the claim scope reasonably
certain. 766 F.3d at 1372. In Datamize, the written
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                   15



description did not contain any examples of an “aestheti-
cally pleasing” interface, nor did it “explain what factors a
person should consider when selecting a feature” to lead
to an aesthetically pleasing result. 417 F.3d at 1352.
     On the other hand, the ’845 patent contains consider-
ably more detail than Datamize or Interval Licensing. As
explained previously, the written description of the ’845
patent includes: (1) a general exemplary design for a
visually-negligible indicator, ’845 patent, col. 3 ll. 13–20;
(2) “requirements for the graphical indicators being
negligible to human eyes,” id. col. 4 l. 60–col. 5 l. 5; and
(3) two specific examples of visually-negligible indicators,
id. col. 5 ll. 6–15. That there are examples at all distin-
guishes this case from Datamize, and that the written
description contains an additional example and specific
requirements distances this case from Interval Licensing.
Instead, the level of detail provided in the written de-
scription is closer to that provided in Enzo: These are
statements that provide guidance on how to create visual-
ly-negligible indicators, and specific examples that pro-
vide points of comparison for the result.
     Appellees criticize what they see as the written de-
scription’s low level of detail. Specifically, they argue that
the examples and requirements in the written description
cannot be translated to an objective standard for the
claim’s scope because they, too, are subjective. We disa-
gree. Just as the patent in Enzo included “examples of
suitable linkage groups,” 599 F.3d at 1334, the ’845 pa-
tent includes examples of visually-negligible indicators,
’845 patent, col. 5 ll. 6–15. Just as the patent in Enzo
provided “some criteria for selecting [linkage groups that
did not substantially interfere],” 599 F.3d at 1334, the
’845 patent includes the differentiability, brightness, and
homogeneity “requirements for the graphical indicators
being negligible to human eyes,” ’845 patent, col. 4 l. 60–
col. 5 l. 5. The guidance in Enzo allowed a skilled artisan
to compare a potentially infringing product “with the
16                       SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



examples in the specification to determine whether inter-
ference . . . is substantial,” 599 F.3d at 1336; similarly, an
accused infringer could compare the examples and criteria
from the written description of the ’845 patent to deter-
mine whether an indicator is visually negligible. Moreo-
ver, Appellees have not provided evidence that human
perception varies so significantly that reliance on it as a
standard renders the claims indefinite. See Warsaw, 778
F.3d at 1371. Thus, as in Enzo, the written description of
the ’845 patent supports the conclusion that a skilled
artisan would have understood the term with reasonable
certainty.
    Other aspects of this case also make reversal compel-
ling. The prosecution history of the ’845 patent, which
includes the reexamination history, see Info-Hold, Inc. v.
Applied Media Techs. Corp., 783 F.3d 1262, 1266 (Fed.
Cir. 2015), supports that conclusion. No one involved in
either the first or the second reexamination had any
apparent difficulty in determining the scope of “visually
negligible.” During the first reexamination, SunPlus
repeatedly argued that the prior art disclosed visually-
negligible graphical indicators without any apparent
uncertainty as to the meaning or scope of the term, and no
apparent difficulty applying it to the references at issue.
See, e.g., J.A. 795, 800, 801, 811, 823, 835, 844, 849–50,
854, 864, 876. During the second reexamination, the
examiner was able to understand and apply the term in
performing a search for prior art and make an initial
rejection. See J.A. 2312–13. Moreover, Serjersen was
able to understand both the claims and written descrip-
tion with sufficient certainty to (1) replicate the claimed
indicator; and (2) opine regarding whether it, and the
indicators of Lamoure and Priddy, were visually negligi-
ble. See J.A. 2338–44, 5313–25. Thus, he was readily
able to differentiate between which indicators were and
which were not visually negligible. Finally, the examiner
understood the import of Serjersen’s results well enough
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.                 17



to withdraw the rejections in response, indicating that he
was able to differentiate between indicators as well. J.A.
2363–65. Again, GeneralPlus, Sonix, and the USPTO did
not express any uncertainty as to the scope of “visually
negligible,” or encounter any apparent difficulty in apply-
ing the term to the references.
    Appellees challenge this evidence as well, arguing
that the fact that the experts applied the term does not
mean that they used or could determine an objective
standard. Although Appellees are correct that application
by the examiner and an expert do not, on their own,
establish an objective standard, they nevertheless provide
evidence that a skilled artisan did understand the scope
of this invention with reasonable certainty.
     The extrinsic evidence, to the extent that it is neces-
sary in this case, does not counsel otherwise. Appellees
apparently understood the meaning of “visually negligi-
ble” from the beginning of the litigation. Their initial
invalidity contentions did not argue that the “visually
negligible” was indefinite, and neither did their final
contentions. Indeed, at no point before Dr. Ashok’s depo-
sition did they contend that “visually negligible” was
indefinite, even though they contended that twenty-eight
other terms were indefinite. That Appellees themselves
did not question the clarity of “visually negligible” in the
first several years of litigation supports the conclusion
that the term could be understood with reasonable cer-
tainty.
    Appellees’ other actions during litigation also reflect
that they understood “visually negligible.” They initially
argued for a specific construction of the term, but later
abandoned their attempt in favor of an ordinary-meaning
construction. The parties’ experts also had no difficulty in
applying “visually negligible.” Dr. Ashok and Dr. Engels
repeatedly applied the term to the references and the
accused products. Although Appellees again argue that
18                      SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.



this does not establish an objective standard, continued
application by the experts in this case further supports
the conclusion that a skilled artisan did understand the
term with reasonable certainty.
    Appellees’ repeatedly cite Dr. Ashok’s responses dur-
ing his deposition. Appellees asked Dr. Ashok to define
“visually negligible,” a term for which he had given no
previous definition, and which Appellees had previously
agreed did not need a construction. But it is unsurprising
that Dr. Ashok indicated that he was unaware of a “tech-
nical standard” for the term, J.A. 4756 at 51:9–11; as
Appellees had agreed to an ordinary-meaning construc-
tion, there was no reason for him to attempt to determine
one. Even so, Dr. Ashok did not opine that a skilled
artisan would have any trouble understanding the term
or that the claims were indefinite, and he observed that
he thought that his assessment of what was visually
negligible would likely be representative. See J.A. 4755–
56. Dr. Engels, Appellees’ own expert, also did not opine
that the claims were indefinite or that a skilled artisan
would not have understood the term; instead, he provided
a one-sentence statement that “visually negligible” is
subjective and that there was no objective test to define it.
See J.A. 3709. Dr. Engels did not detail any basis for this
conclusion, instead simply stating that it was “based on
Dr. Ashok’s testimony.” Id. In light of the intrinsic
evidence, this ambiguous testimony is not persuasive.
     Our holding in this case does not mean that the exist-
ence of examples in the written description will always
render a claim definite, or that listing requirements
always provide sufficient certainty. Neither does the fact
that an expert has applied a contested claim term without
difficulty render a claim immune from an indefiniteness
challenge. As always, whether a claim is indefinite must
be judged “in light of the specification and prosecution
history” of the patent in which it appears. Interval Li-
censing, 766 F.3d at 1369. We simply hold that “visually
SONIX TECH. CO.   v. PUBL’NS INT’L, LTD.               19



negligible” is not a purely subjective term and that, on
this record, the written description and prosecution
history provide sufficient support to inform with reasona-
ble certainty those skilled in the art of the scope of the
invention. The examiner’s knowing allowance of claims
based on the term that is now questioned, plus the ac-
ceptance of the term by both parties’ experts, force us to
the conclusion that the term “visually negligible” is not
indefinite. Accordingly, we reverse the district court’s
conclusion that the asserted claims are invalid as indefi-
nite.
    Because we hold that the district court erred in con-
cluding that the asserted claims are indefinite, we need
not, and do not, reach Sonix’s alternative arguments for
reversal.
                          CONCLUSION
    We have considered the remaining arguments, but
find them unpersuasive. For the foregoing reasons, the
decision of the district court is reversed.
                          REVERSED
