Opinion ID: 779640
Heading Depth: 3
Heading Rank: 2

Heading: selectively controlling the durations of the time intervals of activation

Text: 48 Claims 1 and 3 of both the '481 and '561 patents include the limitation selectively controlling the durations of time intervals of activation. In its Markman ruling, the district court explicitly refused to provide a distinct definition for this limitation, deeming the phrase sufficiently defined. 49 Telegenix contended before the district court, and reiterates on appeal, that this limitation means specifically controlling the length of time that individual pulses are activated to vary the amount of light emitted from a light source. Telegenix argues that by his disclosure in the specification, the inventor limited the claims to varying color using pulse width modulation (PWM), a technique that varies the duration of individual pulses. Telegenix further contends that the inventor limited the asserted claims to PWM by statements and amendments during prosecution of the patents in suit. 50 TDS responds that the claims are not limited to the particular PWM technique suggested by Telegenix. TDS urges that the claim language uses the plural form of both durations and time intervals and thus is consistent with an interpretation in which color is controlled with more than one pulse and includes multiple activations of the same LED within the repetition period. In other words, TDS urges a claim construction that would cover devices which change perceived light intensity by varying either the width of the pulses or the number of pulses. 51 The words of the claim require controlling the durations of the time intervals of activation. The plain meaning of controlling the durations indicates that the claimed invention requires variation of the duration of individual time intervals, or controlling the width of pulses, during which the LEDs are activated, e.g., PWM. This plain meaning is consistent with the specification of the '481 and '561 patents. The structures shown in Figures 9 and 11 of the '481 patent and Figure 1 of the '561 patent depict circuitry for driving the LEDs using PWM. As shown in Figure 9 of the '481 patent, the circuitry includes at least one counter 71f for each color connected to a corresponding memory 76 containing data regarding the amount of primary color activation required to produce the desired color. '481 patent, col. 4, ll. 24-59. The counter and corresponding memory are connected to a flip-flop 73 which provides the appropriate output to generate the desired color. Id. According to the specification, the output of the flip flop 73 will be at a high logic level for a period of time proportional to the data loaded into the counter 71f from the memory 76. Id. at col. 4, ll. 51-52. Thus, the circuitry controls color by setting the output at a high logic level for a period of time proportional to the desired color data. 52 Moreover, the prosecution history is consistent with this interpretation of the claim language. During prosecution of the '481 patent, the inventor distinguished prior art on the basis of PWM. The Patent Office initially rejected all claims in the application as obvious in view of the Kaelin reference, which taught that LED color display elements can be varied by applying variable timed pulses to the individual diodes. The applicant responded by submitting new claims and arguing that the invention control[s] the durations of the pulses that are applied to the primary color light sources in the selected display areas to control the portions of the primary color light signals, to thereby control the color of the exhibited display unit. 53 On the basis of our review of the ordinary meaning of the words themselves, we conclude that this limitation requires control of pulse width. This is entirely consistent with the intrinsic record. Contrary to TDS's argument, introducing multiple pulses of identical duration during the repetition period does not effect control of pulse duration. Where multiple pulses of identical duration are introduced during a single repetition period, pulse duration remains constant and color is controlled not by varying the durations of the time intervals of activation of pulses, as called for in the claims themselves, but by varying the number of constant duration pulses applied. Such a technique does not set the output at a high logic level for a period of time proportional to the desired color data nor does it control the durations of the pulses, and thus is inconsistent with the specification and prosecution history. 54 We conclude that selectively controlling the durations of the time intervals of activation means controlling the width of pulses during repetition periods. 55