In a recent decision, the U.S. Court of Appeals for the Federal Circuit reversed the Patent Trial and Appeal Board’s (PTAB) finding that certain patent claims were not unpatentable, holding that the Board relied on an erroneous, implicit claim construction. The case is Sigray, Inc. v. Carl Zeiss X-Ray Microscopy, Inc., Case No. 23-2211 (Fed. Cir. May 23, 2025) (Dyk, Prost, JJ.; Goldberg, Chief Dist. J., sitting by designation).
Background
Carl Zeiss X-Ray Microscopy, Inc. owns a patent covering X-ray imaging systems that use projection magnification. Sigray, Inc. petitioned for inter partes review (IPR) of all claims in the patent. After institution, the PTAB issued a final written decision declining to invalidate any of the challenged claims. Sigray appealed the Board’s decision.
Disputed Claim Construction
On appeal, Sigray argued that the challenged claims were anticipated or rendered obvious by a single piece of prior art—Jorgensen. According to the Federal Circuit, Jorgensen “describes a system that uses an X-ray source to generate an X-ray beam, which then passes through a sample before being received by a detector.”
The dispute focused on whether Jorgensen inherently disclosed a limitation found in the independent claim—specifically, “a magnification of the projection X ray stage . . . between 1 and 10 times.” The parties did not dispute that Jorgensen disclosed all other claim limitations.
Federal Circuit Finds Implicit Construction Flawed
The Federal Circuit agreed with Sigray’s contention that the PTAB applied a flawed, implicit construction of the magnification limitation. In particular, Sigray argued that “the Board implicitly and incorrectly construed the limitation ‘between 1 and 10’ to exclude unspecified, small divergence resulting in projection magnifications only slightly greater than 1.” This was evident, according to Sigray, from the Board’s finding that Sigray “failed to show that the . . . X-ray beam in Jorgensen diverges enough to result in projection magnification between 1 and 10 times.”
The Federal Circuit found the Board’s use of the phrase “enough” telling. The Court concluded that this language revealed an acknowledgment that some beam divergence was present in Jorgensen, but that the Board improperly imposed a threshold for divergence without supporting that threshold through proper claim construction or analysis.
As the Court explained, because the prior art beam was not completely parallel, “some magnification necessarily resulted,” and even “a miniscule amount (as disclosed in the prior art)” would fall within the claimed range of 1 to 10 times magnification.
Reversal and Remand
Given that the Board made only one supported finding relevant to anticipation, the Federal Circuit reversed the Board’s determination with respect to the independent claim and two dependent claims, finding them unpatentable. The Court declined to remand those claims.
However, the Court did remand the case with respect to the three remaining dependent claims, which included additional material limitations. The Federal Circuit instructed the PTAB to determine whether those claims would have been obvious in light of the prior art.