Before Mayer, Chief Judge, Rich, *fn1 Circuit Judge, and Smith, Senior
The opinion of the court was delivered by: Per Curiam.
Essilor International (Essilor) appeals the judgment of the United States District Court for the Eastern District of New York, No. 95-CV-1243, of non-infringement of United States Patent No. 4,596,091 (the '091 patent) which is directed to a machine for automatically grinding a bevel on the edge of an eyeglass lens. Nidek Co., Ltd. (Nidek) and Santinelli International, Inc. (Santinelli) cross-appeal the court's judgment that the '091 patent is not invalid, that Essilor did not engage in unfair competition, and that laches and equitable estoppel do not apply. We affirm the district court's judgment in all respects.
We begin with infringement. Step (f) of claim 1, the only independent claim at issue, requires the claimed invention to have (emphasis added):
a control means including
means for storing a collection of predetermined bevelling or grooving paths and
means for comparing first and second reference paths with the collection of predetermined paths and for selecting one of the bevelling or grooving paths which is intermediate the first and second reference paths from the collection of predetermined paths whereby said control means controls the displacement of said lens in accordance with the selected intermediate path to form the edge of the lens. '901 patent, col. 10, ln. 67 to col. 11 ln. 8.
The district court found that the accused devices did not satisfy the three means limitations relating to the predetermined bevelling or grooving paths, namely the means for storing, means for comparing, and means for selecting limitations. In reaching this Conclusion, the court construed a predetermined bevelling and grooving path as meaning an actual beveling path that has already been stored in the control unit and not covering pre-stored equations that are used to calculate the beveling path, such as the equations used in the accused devices. Essilor argues that the district court erred in its claim construction and that under a proper construction, a predetermined beveling path would include the equations that are stored in the control unit of the accused devices and that the accused devices literally infringe the claim.
Claim construction is a question of law which we review de novo. See Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1455-56, 46 USPQ2d 1169, 1173-74 (Fed. Cir. 1998) (en banc). We agree with the district court's claim construction. Contrary to Essilor's assertions, the plain meaning of a predetermined bevelling path is a beveling path that has been set previously. A bevelling path represented by an equation which needs the input of additional information before the path can be determined, such as the equations used in the Nidek devices, is not a predetermined bevelling path.
Essilor argues that to those skilled in the art, a typical bevelling path can be described by equations such as ratios or by diopter values for the spheres on which the paths lie. We disagree. As the district court found, ratios and diopters are not the only parameters used to calculate a bevelling path. Additional information is needed before the beveling path can be determined.
There is nothing in the written description or prosecution history that changes the plain meaning of the term. The passage in the written description that states that the control unit is arranged so that the path can be reconstructed for the point of contact of the lens with the bevelling wheel does not support Essilor's argument that reconstruction of a path necessarily implies the use of equations that require additional data to calculate a bevelling path. Essilor does not argue that the accused devices infringe under the district court's claim construction. Therefore, we affirm the district court's finding of no literal infringement.
Essilor also contends that even if the district court's claim construction is correct, it erred in finding that Nidek's devices do not infringe under the doctrine of equivalents. Essilor asserts that the district court should have analyzed whether the equations used by the Nidek devices are equivalent to the predetermined beveling paths required by the claims.
To infringe under the doctrine of equivalents, an accused device must meet every limitation of the claim either exactly or by a substantial equivalent. See Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 29 (1997). One test used to determine if the accused device is a substantial equivalent is to ask whether the element performs substantially the same function in substantially the same way to obtain substantially the same result as the claim limitation. See Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 608 (1950). Equivalence is a question of fact, which we review under the clearly erroneous standard. See id. at 609-10.
Even if we agree with Essilor's argument that in some instances an equation may be the equivalent of a predetermined beveling path, we cannot say that the district court erred when it found that in this case, the accused devices do not perform the comparing and selecting functions required by the claim in the same way. Specifically, the district court found that the accused devices do not perform an equivalent of the "means for comparing" and the "means for selecting" limitations because the accused devices operate in a different way.
The comparing function requires the control means to compare the first and second reference paths with the collection of predetermined paths. Essilor contends that the Nidek devices perform this function when the control unit in the accused devices asks "is the minimum lens thickness 1.5 mm?" The district court found that although the accused devices do compare information from the lens to data stored in the computer such as ratios and diopters, the comparison performed by the accused devices is not equivalent to the comparison required by the ...