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Desper Products, Inc. And Spatializer Audio Laboratories, Inc. v. Qsound Labs, Inc.
Citations: 157 F.3d 1325; 48 U.S.P.Q. 2d (BNA) 1088; 1998 U.S. App. LEXIS 23324; 1998 WL 643294Docket: 97-1163
Court: Court of Appeals for the Federal Circuit; September 18, 1998; Federal Appellate Court
Desper Products, Inc. and Spatializer Audio Laboratories, Inc. (collectively "Desper") initiated a lawsuit against QSound Labs, Inc. ("QSound") concerning U.S. Patent Nos. 5,105,462 (the '462 patent) and 5,208,860 (the '860 patent), both titled "Sound Imaging Method and Apparatus." Desper sought a declaratory judgment affirming that its "Spatializer" product does not infringe these patents and that the patents themselves are invalid. In response, QSound asserted a counterclaim for patent infringement.
The case was assigned to a special master, who evaluated cross-motions for summary judgment regarding infringement claims, ultimately recommending that the court rule in favor of Desper for non-infringement, except for certain claims where a factual dispute existed. The district court adopted the special master's recommendations, granting summary judgment of non-infringement for all asserted claims, and entered a final judgment favoring Desper.
The patents describe a system that processes monaural sound signals to create a three-dimensional sound image, allowing listeners to perceive individual sounds as originating from different spatial locations. Central to this technology is a "sound processor" that manipulates phase and amplitude of channel signals derived from a monaural input, enabling the illusion of sound sources positioned in three-dimensional space, despite emanating from speakers. The ruling has been appealed by QSound.
A transfer function represents the relationship between the output and input of a system component, and in the preferred embodiment of the patents, it was derived through a detailed empirical process. The patents emphasize the significance of amplitude and phase changes between channel signals, allowing for the potential reduction or elimination of one sound processor by reallocating amplitude alteration and phase shifting to a single channel signal. The transfer functions can be adjusted through position control parameters provided to the sound processors at terminal 1505, enabling users to modify the apparent sound origin, akin to conventional balance or fade controls.
The sound processor's design, illustrated in Fig. 18a, incorporates filters (1610 and 1630) that deliver distinct phase shifts and amplitude changes across multiple frequency bands (40 Hz wide, totaling approximately 500 bands within the 20-20,000 Hz audio spectrum). Individual specification of phase shifts and amplitude changes for each frequency band is crucial for the invention's operation and patentability. The design uses cascaded bandpass filters to achieve these alterations.
Additionally, the sound processor features six potentiometers (1651-1654, 1657, 1658) for enhanced flexibility. Four potentiometers (1651-1654) are controlled by a two-axis joystick, allowing smooth adjustments to sound positioning. Potentiometers 1651 and 1652 operate differentially, while potentiometers 1653 and 1654 manage the outputs of filters 1610 and 1630 respectively, both pairs functioning complementarily. The output from potentiometer 1653 is sent through a buffer amplifier (1655) to potentiometer 1657 and then to a reversing switch (1659) for signal routing to summing elements (1660 and 1670). Finally, the channel signals are directed to output terminals (1688 and 1689), with options for signal selection via switches (1682, 1685, and 1691), though those specifics are not pertinent to the current dispute.
Before the district court, QSound presented four independent claims from two patents: claims 1 and 7 of the '462 patent, and claims 1 and 5 of the '860 patent. A special master provided a detailed interpretation of several disputed terms in these claims, with the district court largely adopting the special master's findings. Although QSound disputed many conclusions, only a few critical phrases were considered significant for the case.
The independent claims include:
1. **'462 Patent**:
- **Claim 1** outlines a method for producing and locating a sound's apparent origin from an electrical signal. This involves separating the signal into first and second channel signals, altering their amplitude and phase across discrete frequency bands while preserving their differential, and applying these modified signals to transducers located in three-dimensional space to create an auditory illusion of sound originating from a specific location.
- **Claim 7** describes a system for conditioning a signal to create an auditory illusion of sound origin using two transducers. It specifies that both transducers receive the same electrical signal, with each channel processing the signal by altering amplitude and shifting the phase in a frequency-dependent manner, ensuring that the channels remain separate before reaching the transducers.
The '860 Patent describes a method for producing and locating a sound's apparent origin using an input monaural signal. The method involves several steps:
1. Separation of the input monaural signal into first and second channel signals.
2. Generation of a sound position control signal, independent of the input signal, to adjust amplitude and phase across discrete frequency bands, determining sound location by azimuth, height, and depth.
3. Alteration of amplitude and phase of at least one channel based on the control signal, with these adjustments varying across frequency bands and ensuring each phase shift is distinct from the previous one, resulting in modified channel signals.
4. Maintenance of the first and second channel signals as distinct after these adjustments.
5. Application of the modified signals to two transducers positioned in three-dimensional space, creating an auditory illusion of sound originating from a predetermined location, separate from the transducers' actual positions.
A system is also outlined, which conditions a single monaural input signal through two channels to achieve the same auditory effect. This system includes sound processing means to manage amplitude and phase adjustments at specified frequency intervals, producing modified signals that maintain a continuous differential between channels.
The claim construction section notes that the primary claims in question are method and system claims. The special master interpreted "being maintained separate and apart" literally and differentiated between "following" in claims of the '462 and '860 patents and "prior to" in another claim, indicating a nuanced understanding of the claims' language.
The special master distinguished between the terms 'prior to' and 'following' in relation to signal separation in the accused Spatializer device. 'Prior to' requires the signals to be kept separate immediately before they reach the loudspeakers, while 'following' demands separation immediately after the signals are altered. The Spatializer combines signals after phase and amplitude adjustments but separates them before speaker input. Consequently, the special master concluded that the Spatializer likely does not infringe the 'following' claims but could infringe the 'prior to' claims. The district court accepted the special master's recommendations regarding 'following' claims but ruled in favor of Desper on 'prior to' claims, granting summary judgment on non-infringement for both. QSound appealed the district court's interpretations.
The excerpt outlines the legal standards for summary judgment, asserting that it is applicable in patent cases when there are no genuine material facts in dispute. It describes the two-step infringement determination process: first, claim construction to ascertain meaning and scope, and second, comparison of the accused product to the construed claim. In cases where the composition of the allegedly infringing product is undisputed, infringement analysis may simplify to claim construction. The excerpt also emphasizes that claim interpretation involves examining the claim language, specification, and relevant prosecution history, with extrinsic evidence permissible only to aid understanding, not to alter clear claim meanings. Claim interpretation is a legal question subject to de novo review on appeal.
The claim language of the '462 and '860 patents stipulates that the system must "maintain" the separation of the first and second channel signals following the alteration of amplitude and phase. The term "following" is defined as occurring after a given event, but the specific timing for maintaining separation is unclear. Specifications suggest that this separation should commence immediately after the initial alterations. Although the term "following" appears infrequently in the descriptions and does not explicitly reference channel signals, accompanying diagrams indicate that once separated, the signals remain distinct.
QSound's argument relies on a passage discussing potential circuit elements in the sound processor, asserting that maintenance of separation occurs only after alterations are complete; however, this passage does not clarify the timing. The prosecution history supports the interpretation that the requirement for maintaining separation was not in the original claims but was added after the initial application was rejected for obviousness. A preliminary amendment highlighted that once the monaural signal is split, the channel signals must remain isolated and not be recombined, distinguishing the invention from prior art. The applicant's attorney emphasized that the amended claims describe a unique method that is not suggested by existing references.
Applicants conducted a personal examiner interview instead of waiting for a formal response regarding their patent claims. The Examiner Interview Summary Record noted that the amended claims distinguished from previous prior art but introduced a new reference for rejection. Despite this, the examiner allowed two dependent claims if rewritten in independent form. Consequently, the applicants abandoned their original independent claims and adopted the examiner's suggestions, leading to the issuance of the '462 patent.
The prosecution history of the '860 patent similarly shows that, after a prior rejection based on a British patent, the applicants amended independent claims to specify that channel signals be kept separate. An office action later rejected these claims as obvious, but further amendments and distinctions made by the applicants overcame this rejection, resulting in the issuance of the '860 patent. Both patents included the separate channel signals limitation to address the prior art rejections.
QSound did not contest the limiting nature of the attorney's comments on appeal but claimed these remarks should not interpret the disputed claim language, asserting they were erroneous and extraneous. The court disagreed, stating that QSound's argument misinterpreted the patent's teaching. Specifically, QSound argued that signals cross and commingle at a certain point in a figure, contradicting the written description and the established operation of a switch. The notation used in the figure indicates that the signals are not connected, allowing the switch to reroute signals rather than commingle them. Thus, the switch's operation aligns with its intended function, countering QSound's claims about the attorney's statements being misleading or inaccurate.
Following oral arguments, QSound attempted to reinforce its position using expert testimony submitted under Fed. R.App. P. 28(j), which only permits supplemental authorities, not arguments. Consequently, this submission was deemed inappropriate and did not support QSound’s claims regarding reversible switch 1659 commingling channel signals. QSound also sought to undermine the prosecuting attorney’s statements, arguing they were irrelevant to the claim. However, the court found that QSound's reliance on the case Intervet America, Inc. v. Kee-Vet Labs, Inc. was misplaced, as that case involved limitations not present in QSound's claims. In contrast, QSound's case focuses on interpreting explicit claim language, specifically the terms "following" and "prior to," and the attorney’s remarks were considered accurate rather than erroneous. QSound's assertion that the attorney’s comments should not influence claim interpretation because they did not lead to claim allowance was rejected. The remarks were relevant as they aimed to address prior rejections, maintaining their significance regardless of the prosecution's focus shifting.
The district court's claim construction for claim 1 of the '462 patent and the '860 patent is affirmed as correct. Claims 7 of the '462 patent and 5 of the '860 patent include "sound processor means," which use means-plus-function language under 35 U.S.C. § 112, p 6. The interpretation of such elements is a legal question subject to independent review on appeal. QSound contends that the district court misinterpreted the term "prior to" in the context of maintaining two channel signals separate before they reach the transducers. While QSound argues for a broader interpretation of "prior to," supported by dictionary definitions indicating it means "preceding in time," the district court's construction aligns with the written description and prosecution history. The specification indicates that the channel signals must be separated initially and maintained as such after their phase and amplitude are altered, prior to being fed into the transducers. This interpretation is consistent with the preferred embodiment of the invention, reinforcing the district court's conclusion.
The district court determined that the prosecution history favors interpreting the term "prior to" in a manner consistent with "following" as used in claim 1 of the patent. Prosecution history serves as intrinsic evidence critical for claim interpretation, reflecting the interaction between the applicant and the patent examiner. This relevance extends to claims articulated in means-plus-function language. During the prosecution of claim 7 of the '462 patent, QSound treated claims 1 and 7 (previously claim 8) as having a similar scope despite their different language. QSound emphasized that the first channel signal is always kept distinct from the second channel signal after certain alterations, indicating that it regarded the claims as comparable in this context.
The public is entitled to rely on the applicants' statements made during prosecution. Just as prosecution history estoppel can limit equivalence arguments, positions taken before the PTO can restrict inconsistent claim construction under 112, p 6. The court agreed with the interpretation that "prior to" means after the alteration of amplitude and phase has commenced.
In assessing infringement, the properly construed claim must be compared to the accused device. For a method claim to be literally infringed, the accused device must meet all claim limitations, and for means-plus-function claims, it must perform the claimed function identically. The structure of the accused device, the Spatializer, is undisputed; it splits a monaural signal into two channel signals and creates a third signal by summing these. The phase and amplitude of this third signal are altered and then combined with one of the channel signals. The court found that the two channel signals in the Spatializer are not maintained separately as interpreted, since they are mixed after the phase alteration, contradicting the claim's requirements.
The two channel signals are not kept separate after their amplitude is altered and phase shifted, leading to the conclusion that the Spatializer does not literally infringe claims 1 of the '462 patent or claim 1 of the '860 patent. Claims 7 of the '462 patent and 5 of the '860 patent were interpreted to align with a "following" limitation, indicating that these claims are also not literally infringed because the Spatializer does not perform the same function. The district court's summary judgment affirming that the Spatializer does not literally infringe is upheld.
While a device that does not literally infringe may still infringe under the doctrine of equivalents if the differences are deemed insubstantial, prosecution history estoppel prevents a patentee from claiming protection for subject matter surrendered during prosecution for claim allowance. This estoppel applies to features amended to avoid prior art rejections and trivial variations of those features. Filing a continuing application with narrowed claims does not circumvent this estoppel, nor can unequivocal assertions made during prosecution. Estoppel can exist even if the claim at issue was not amended.
The application of prosecution history estoppel is a legal question reviewed without deference to the trial court, with the standard being what a reasonable competitor would perceive as surrendered from the prosecution history. In this case, amendments made to address prior art rejections and clear assertions by the applicants create an estoppel that legally precludes infringement under the doctrine of equivalents. The British patent referenced describes a circuit for deriving pseudo-stereophonic signals from a monaural signal, where the monaural signal is split into two channel signals and their amplitudes manipulated to form a difference signal.
A difference signal is added to and subtracted from an attenuated monaural signal to create two pseudo-stereophonic signals, which are then sent to speakers for sound reproduction. The original patent application (Ser. No. 07/398,988) was rejected under 35 U.S.C. 103 for being obvious in light of a British patent. Instead of appealing, the applicants filed a File Wrapper Continuation and submitted a Preliminary Amendment that altered claims 1 and 8 to clarify that the first and second channel signals are kept strictly separate after processing. The applicants emphasized that their invention maintains isolation of the channel signals, contrasting it with the British patent, which combines signals after processing. They acknowledged that they surrendered any subject matter, including the technique used in the accused Spatializer device, which also processes a conditioning signal that is added to and subtracted from input signals, failing to maintain separation post-processing. Consequently, the Spatializer's topology aligns with the disclaimed subject matter, and any minor differences do not alter this conclusion. This leads to a legal determination that infringement under the doctrine of equivalents is precluded.
QSound contends that estoppel should not apply because there are multiple ways to distinguish the claimed invention from the British reference, beyond the separation of signals. Citing *Conroy v. Reebok Int'l*, QSound argues that the case is inapplicable, as it involved a summary judgment of non-infringement based solely on prior art without considering whether that art invalidated the "hypothetical claim." The court clarifies that, unlike in *Conroy*, it found the applicants actively distinguished their invention from prior art, establishing a case for prosecution history estoppel. The possibility of distinguishing the British reference on different grounds is deemed irrelevant. The court emphasizes that the public relies on patent applicants' assertions, and post-litigation arguments cannot reclaim subject matter that has been abandoned in the patent office record. The court concludes that summary judgment of non-infringement under the doctrine of equivalents is affirmed, highlighting that QSound’s challenges regarding claim interpretations are moot given their established meanings. The estoppel applies equally to similar language in a related patent application.