Issue 2                                                                                      April 2001

In this Issue


Invention MiningTM

Patenting your "design around".

Interesting Patent Case

Is patentability protection against infringement?

IP Links

IP Glossary

This is the second issue of Directions, a newsletter from TechRoadmap Inc. discussing intellectual property issues and ideas. We hope to stimulate you to examine and improve your own IP practices. This month's issue has been reformatted to make it more compatible with some e-mail applications. Feel free to share this newsletter (see copyright notice below) and to provide feedback by e-mail to:

Invention MiningTM

Patenting your "design around"

In today's competitive environment we are often faced with the problem of "designing around" prior art. In the patent case discussed below we see an excellent example of how designing around an existing patented product works. In Zygo v. Wyco we also see the value in patenting the design around. Although not a certainty by any means, the patentablility of a design around is a good defense against infringement suits.

Prior art comes in two forms, protected and public. Public prior art is openly revealed information such as the IBM Technical Disclosure Bulletin, whose sole purpose was to put selected technical concepts into the public domain (thereby ensuring IBM's freedom to use). Public prior art bars us from protecting our product with a patent, but does not keep us from incorporating those features in our product. More difficult is protected prior art; that is, an existing unexpired patent. Protected prior art not only keeps us from protecting that aspect of our product but also may bar us from selling it at all. Often the only solution for bringing a product to market is to develop a "design around".

Designing around is best executed early in your design cycle. One of TechRoadmap's Invention Mining activities is guiding your engineers through the forest of prior art to help you avoid the costs of late redesigns and to help deflect infringement suits. Working as a team, your engineers, your patent attorney, and TechRoadmap can identify design arounds that have a high likelihood of patentability. As Wyco learned by experience, not every alternative design escapes the "doctrine of equivalents" and doing a redesign in the middle of an infringement suit is less than pleasant, but a design that is patented over the identified prior art will go a long way to protect you in infringement suits. 

In high tech businesses the need to design around is prevalent. Start-ups entering an established marketplace will surely design their products similar to existing products and established competitors always eyeball each other's products for significant improvements.

If you cannot license the protected prior art, then you must design around. To ease the pain, consider these steps:

  • Track the prior art - particularly patents - continually through your product development cycle. There's no sense in re-inventing someone else's wheel and you might as well know about it as early as possible.

  • Identify the openings for your design - TechRoadmap and your Patent Attorney can help you understand what is actually claimed by the prior art and what regions are left open for you.

  • File a patent covering your design around as early as possible - Again, while not a panacea, patentability is a part of your defense against infringement...but only if the patent has issued by the time you need it.

Remember: overcoming a patent examiner's concern that your design around is "obvious" during the non-adversarial patent prosecution process is likely to be easier and less expensive than fighting the doctrine of equivalents in an adversarial infringement suit.

Nothing in the preceding article should be construed as legal advice. TechRoadmap Inc serves as an interface between companies and their legal counsel.

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Interesting Patent Case
Is patentability protection against infringement?

ZYGO Corp.  v. WYKO Corp. 

DECIDED: March 26, 1996


In this case, Wyko Corporation appealed the judgment of the US District Court for the District of Arizona (Civil Action No. CIV 88-454-T-JLQ), which held Zygo Corporation's US Patent  4,201,473 ("the '473 patent") for an interferometer system not invalid and was infringed by three models of Wyko interferometers. The appeals court held that the district court clearly erred in finding that one model, the Wyko 6000 Redesign, infringed under the doctrine of equivalents but affirmed the finding of infringement on the original Wyko 6000 designs. In this discussion I have only included a review of the infringement issues, based on the published court opinion.


 In 1977, Zygo introduced the Zygo Mark II, based on the invention claimed in the '473 patent. The Mark II has an alignment mode in which the reference and test wavefronts are collected by a series of optical elements and focused as two dots of light onto a stationary diffuse screen. A visible cross-hair reticle is embedded into the screen with intersection of the cross-hairs pre-aligned to the optical axis. An internal TV camera is focused on the screen so an image of the dots and reticle is displayed on a CCTV monitor. An operator moves each of the dots independently to the center of the alignment reticle at which point alignment is achieved (viz., each beam parallel to the optical axis and thereby parallel to each other) .

Five years later Wyko Corporation was founded. In January 1988 the Wyco 6000, an interferometer intended to compete with the Zygo instruments, was introduced. It appears that Wyco tried to design around the '473 patent in the area of the alignment system. The Wyko 6000 included a stationary diffuse screen onto which the reference and test wavefronts were focused as dots of light which were, in turn, imaged onto a television camera, converted into electronic data, and appeared on a computer monitor along with a cross-hair-like reticle that was generated by computer software. During factory setup, the electronic cross-hair was aligned to the system optical axis. An operator moved each dot until they overlapped at the center of the cross-hair, which meant they were aligned.

The Wyko 6000 Redesign made its debut about one year after initiation of this lawsuit. In the Redesign a further design around of the alignment system is included. No reticle is displayed for alignment. Instead, a prism is used which is factory-positioned so that its axis is parallel to the optical axis of the interferometer. When so positioned, the prism deflects light that is not parallel to its axis. If the wavefronts are not in alignment, the prism creates a split-image of the test and reference wavefronts such that four dots (two for each wavefront) are projected onto the diffuse screen. This image is transferred to a TV monitor. Both pairs of dots are moved together. When properly aligned, the four dots coalesce into a single spot, which means they are aligned along the optical axis of the interferometer.

Procedural History - The court entered its Findings of Fact and Conclusions of Law on March 3, 1993, holding the '473 patent was neither invalid nor was the patent unenforceable (two claims made by Wyco). While none of the accused Wyko devices were found to literally infringe the '473 patent, the court concluded that all versions of the accused Wyko devices infringed under the doctrine of equivalents. In this appeal, Wyko alleged the district court erred in the finding that the accused devices infringed the '473 patent under the doctrine of equivalents.

INFRINGEMENT UNDER THE DOCTRINE OF EQUIVALENTS (or did Wyco adequately design around the Zygo patent)

The infringement dispute in this case centers on the claim language "means for collecting said two wavefronts and focusing them as spots onto a diffuse screen containing an integral alignment reticle having a marked center." The court construed the emphasized language to mean the alignment reticle and the diffuse screen were "one piece." Literal infringement is not an issue. No Wyko device contains a unitary screen and an alignment reticle as required by the claim. The only issue is infringement under the doctrine of equivalents.

The appeals court stated that infringement under the doctrine of equivalents may be found where those limitations of a claim not found exactly in the accused device are met equivalently. Additionally, the court said it is well settled that each element of a claim is material and essential, and that in order for a court to find infringement, the plaintiff must show the presence of every element or its substantial equivalent in the accused device. Infringement may not be found under the doctrine of equivalents if a limitation is missing, that is, not replaced with an equivalent substituent. But the substituent need not be in the exact same location specified by the claim. If, in the context of the invention, the substituent substantially performs the same function to achieve the same result in the same way as the required limitation, that limitation is satisfied.

Now, in the original Wyko 6000 devices, a reticle which coincided with the location of the optical axis, in the words of the claim, an "alignment reticle," was generated by hardware or software and appeared on a monitor together with the two dots imaged by the camera from the diffuse screen. Thus, the image on the Wyko monitor duplicated the required image on the monitor in the alignment mode of the Zygo invention. The court had no difficulty agreeing that the image of the reticle generated on the monitor is the equivalent of the physical reticle on the screen which is also imaged on the monitor in the Zygo invention. While the alignment reticle has been moved within the alignment leg of the accused interferometers, the function of alignment is accomplished in the same way, by moving the two spots to coalesce at the center of a reticle which coincides with the optical axis of the interferometer. Similarly, the point at which the crosshairs cross is at least equivalent to a marked spot.

Thus, the court found that Wyco's first attempt to design around a Zygo feature "failed" because the approach was equivalent to the patented approach.

Turning to the Wyko 6000 Redesign, the court reached the opposite conclusion. In these devices, an image inverting prism is placed in the path of the wavefronts that emerge from the diffuse screen. Each portion of the wavefronts that passes around the prism is projected as a spot on the camera. Each part of the wavefront passing through the prism is deflected and projected as a separate spot on the camera. The spots are mirror images. When these four spots coincide, the positions of which can be adjusted by the operator, alignment is achieved. In the Redesign, there is no substitute "alignment reticle," that is, crosshairs defining the optical axis of the interferometer. The "alignment aid" is the prism structure which splits each of the beams on its way to the camera into two so that four dots appear on the monitor. These four dots are moved so as to coalesce into one, at which point the beams are centered on the axis of the interferometer. Thus, to find infringement, the prism structure must be found an equivalent of an alignment reticle placed on the optical axis, a finding which is not supportable. That both can be labeled "alignment aids," as Zygo terms them, does not answer the question whether they are equivalent within the concept of infringement. That the substituent performs the same general function to achieve the same result as the required element also does not establish their equivalency. The result must be achieved in substantially the same way.

Thus, just incorporating the same general function, was not enough to trigger infringement.

Finally, the court pointed out that for purposes of infringement under the doctrine of equivalents, the differences between the claimed device and the accused device must be insubstantial. According to Wyko, the fact that the Wyko 6000 Redesign alignment system was patented demonstrates the substantiality of the differences between the claimed and accused devices. [emphasis added] Wyko's patent, which cited the '473 patent as prior art, is thus presumed nonobvious in view of the '473 patent until proven otherwise.

Thus, the court implied a logical imperative that a patented device cannot be simultaneously non-obvious (as determined by the USPTO) and insubstantial (required by the doctrine of equivalents).

As a footnote, remember that patent examinations are not adversarial while infringement suits are. It should be easier to make your non-obviousness case at the patent office than your substantiality case in the court.

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IP Links
US Patent office Searchable database of all US Patents and, now, published patent applications.
The Patent Cafe - an on-line source of interesting insights into current IP issues.
EKMS Inc. - a company with whom we've worked that provides a range of IP management services including portfolio analysis, deal-making, and process improvement.

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IP Glossary

Industry's Best Glossary

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