## Facts

- Alpex owned U.S. Patent No. 4,026,555, directed to a microprocessor-based home video game system using replaceable ROM cartridges and a RAM-based, bit-mapped video display that outputs pixel data as a television raster is scanned.
- Claims at issue (including claims 12 and 13) used means-plus-function limitations for generating video signals depicting game images, including rotation of an image.
- During patent prosecution, the applicant distinguished prior art (including a reference using shift-register display technology) by emphasizing the patented system’s RAM bit-mapped display structure.
- Nintendo manufactured the Nintendo Entertainment System (NES), which used a picture processing unit and a shift-register-based, “on-the-fly” display approach that modified portions of the screen rather than storing a full-screen bit map in RAM.
- A jury verdict found the patent not invalid and willfully infringed, and the district court entered judgment for Alpex with a damages and interest award exceeding $253 million; Nintendo appealed and Alpex cross-appealed on damages.

## Issues

1. How should the means-plus-function limitations in claims 12 and 13 be construed under 35 U.S.C. § 112 ¶ 6 (now § 112(f)): limited to the specification’s disclosed structure and its equivalents, or broad enough to cover Nintendo’s different display architecture?
2. Whether prosecution history statements distinguishing shift-register display systems from the claimed bit-mapped RAM display bar Alpex from asserting infringement under the doctrine of equivalents.
3. Whether substantial evidence supported the jury’s findings rejecting invalidity (anticipation and obviousness).
4. What effect reversal of infringement has on the damages award and willfulness finding.

## Decision

- The Federal Circuit affirmed the judgment that the ’555 patent was not invalid.
- The court reversed the infringement judgment and entered judgment of noninfringement for Nintendo.
- Because infringement was reversed, the damages award and willfulness finding could not stand.

## Legal Principles

- Means-plus-function limitations under § 112 ¶ 6 are confined to the corresponding structure disclosed in the specification and equivalents; they cannot be treated as covering any structure performing the stated function.
- Claim construction of means-plus-function elements must identify the disclosed structure; here, the relevant structure was a RAM-based, bit-mapped display as described in the patent.
- Prosecution history statements made to overcome prior art can limit claim scope and create prosecution history estoppel, barring a patentee from recapturing surrendered subject matter through the doctrine of equivalents.
- Where the accused device uses a materially different structure from the disclosed structure, and estoppel forecloses treating that structure as an equivalent, a verdict of infringement cannot be sustained.

## Conclusion

The court upheld the patent’s validity but held that Alpex’s means-plus-function claims were limited to the patent’s RAM bit-mapped display structure and its permissible equivalents, and that prosecution history estoppel prevented treating Nintendo’s shift-register-based NES display as an equivalent; infringement, and thus damages and willfulness, were reversed.


Alpex Comput. Corp. v. Nintendo Co., 102 F.3d 1214 (Fed. Cir. 1996)