Regents of the University of Michigan v. Leica Microsystems — Filtered Light Does Not Meet “Entire Spectrum” Patent Claim

Background

The University of Michigan accused Leica’s fluorescence-detection microscopes of infringing U.S. Patent No. 7,277,169. The patent claims systems in which a supercontinuum white-light pulse “comprising an entire spectrum of white light” excites fluorophores in a sample. Leica’s accused products instead filter a white-light pulse before it reaches the sample and use selected wavelengths to excite the fluorophores. The Northern District of California construed the claims to require the entire spectrum to perform that excitation and granted Leica summary judgment of noninfringement.

The Court’s Holding

The Federal Circuit affirmed. Judge Prost explained that the phrase “said supercontinuum white light pulse” refers back to the previously recited pulse comprising the entire spectrum. Other claim language separately refers to “a portion” of the pulse, showing that the drafter knew how to claim only part of the spectrum when that was intended.

The specification reinforced that reading by describing the entire spectrum as reaching the sample and by contrasting the invention with filtered systems. The prosecution history was especially direct: to overcome prior art, Michigan told the Patent Office that the prior art selected discrete wavelengths, while the claimed invention used the entire white-light spectrum to excite the fluorophores. Because Michigan’s infringement theory depended on a broader construction, the undisputed filtering in Leica’s products defeated infringement.

Key Takeaways

• “Said” ordinarily carries the full antecedent limitation forward; it does not silently discard the “entire spectrum” requirement.
• Contrasting “entire” and “portion” within the same claim can strongly signal that the terms have different scopes.
• Statements used to distinguish prior art during prosecution can later foreclose a broader infringement theory.

Why It Matters

The decision is a compact example of claim construction operating across the claim text, specification, and prosecution history. Patent owners should be precise when distinguishing prior art: a successful narrow argument at the Patent Office may become the decisive limitation in later infringement litigation.