PTAB

IPR2021-00432

Platinum Optics Technology Inc v. Viavi Solutions Inc

Log In
Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Optical Interference Filters
  • Brief Description: The ’526 patent describes optical interference filters for near-infrared (NIR) sensing systems. The technology uses alternating layers of a high-refractive-index material (hydrogenated silicon, or Si:H) and a lower-refractive-index material to create filters that exhibit reduced center wavelength shift when the angle of incident light changes.

3. Grounds for Unpatentability

Ground 1: Obviousness of Claims 9-13 and 16-18 over Tsai-133 in view of Yoda

  • Prior Art Relied Upon: Tsai-133 (Patent 5,398,133) and Yoda (a 2004 Applied Optics journal article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Tsai-133 discloses the core structure of the challenged claims: an optical filter comprising a plurality of hydrogenated silicon (a-Si:H) layers alternating with a plurality of lower-refractive-index layers (a-SiNx:H). Tsai-133’s disclosed filter designs also meet the limitation that at least one Si:H layer is thicker than a lower-refractive-index layer. The distinguishing feature of independent claim 9, which the examiner found patentable, was the requirement that the Si:H layers have a refractive index greater than 3.65 at a wavelength of 800 nm. Petitioner contended that the Yoda reference, which was not before the examiner, explicitly teaches an a-Si:H material with a refractive index of approximately 3.85 at 800 nm, satisfying this limitation.
    • Motivation to Combine: A POSITA would combine the teachings of Tsai-133 and Yoda for two primary reasons. First, it was well-known that using materials with a higher refractive index, like the Si:H in Yoda, reduces the center wavelength shift of a filter, a known desirable property. Second, using higher-index materials allows for thinner layers or a reduced number of layers to achieve the same optical performance, which reduces manufacturing cost and complexity, a benefit explicitly taught in both Tsai-133 and Yoda.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because the proposed modification was merely the substitution of one known Si:H material (from Yoda) for another (from Tsai-133) to predictably achieve the known benefits of a higher refractive index.

Ground 2: Obviousness of Claims 20, 21, and 25 over Tsai-133 in view of Yoda and Hirai

  • Prior Art Relied Upon: Tsai-133 (Patent 5,398,133), Yoda (a 2004 Applied Optics journal article), and Hirai (Patent 6,115,180).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Tsai-133 discloses the structure of independent claim 20: a first filter stack on one side of a substrate and a second filter stack on the opposite side. The limitation that allowed claim 20 was the requirement that the second filter stack include "at least two, different oxides." Petitioner argued it would have been obvious to first substitute the lower-refractive-index a-SiNx:H material of Tsai-133 with an oxide like SiO2 (as taught by Yoda) and then to use a blend of at least two different oxides for the layers of the second stack, as taught by Hirai. Hirai discloses using blends of SiO2 and TiO2 to create layers with specific, intermediate refractive indices.
    • Motivation to Combine: A POSITA would have been motivated to incorporate Hirai’s teachings to gain greater design flexibility. Hirai teaches that blending oxides allows for the creation of filters with tailored refractive indices, enabling improved optical characteristics such as reduced interference and better passband/blocking performance. This technique would allow a designer to optimize the performance of the second filter stack in Tsai-133’s design.
    • Expectation of Success: The process of creating blended oxide layers via techniques like dual-target sputtering was known. A POSITA would have been able to characterize the resulting materials and predict the filter's performance using standard simulation software.

Ground 3: Obviousness of Claims 27-30 over Tsai-133 in view of the Tsai Paper

  • Prior Art Relied Upon: Tsai-133 (Patent 5,398,133) and the Tsai Paper (a 1993 Applied Optics journal article).

  • Core Argument for this Ground:

    • Prior Art Mapping: Independent claim 27 was allowed for requiring an optical filter with a passband center wavelength that shifts by less than 13 nm as the incidence angle changes from 0° to 30°. While Tsai-133 describes filter designs, it only provides refractive index data at a single wavelength (500 nm), making it difficult to determine this property. However, Tsai-133 explicitly refers to the Tsai Paper for further details. The Tsai Paper provides more comprehensive refractive index data over the relevant NIR spectrum for the same materials. Petitioner’s expert performed a simulation of the filter design described in Tsai-133’s Table 3 using the material data from the Tsai Paper. The simulation showed a center wavelength shift of only 6 nm, well within the claimed <13 nm limit.
    • Motivation to Combine: A POSITA seeking to build or analyze the filter designs in Tsai-133 would have been directly motivated to consult the Tsai Paper. Tsai-133 explicitly cites the Tsai Paper, and a skilled artisan would naturally seek out such a reference to obtain more complete material data necessary for accurate simulation and manufacturing.
    • Expectation of Success: Simulating a filter’s performance based on its physical design and the known optical properties of its constituent materials is a standard and predictable task for a POSITA in the field of optical coating design.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including that claims 27-30 are obvious over Pilgrim (Application # 2012/0224061) in view of Tsai-133 and the Tsai Paper, where Pilgrim provides an explicit motivation for designing a low-shift NIR filter for use in imaging systems.

4. Key Claim Construction Positions

  • "center wavelength": Petitioner proposed this term means "the average of the two half-power wavelengths (i.e., FWHM) in a passband," citing consistency with the patent and Patent Owner’s prior positions.
  • "passband": Petitioner adopted Patent Owner's prior construction, meaning "a wavelength range within which a signal can pass through a filter and outside of which the signal is blocked."

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv would be inappropriate. The petition was filed over five months before the scheduled claim construction hearing in a co-pending district court case, and discovery in that case was in its infancy. Petitioner also noted that a stay of the litigation pending IPR was likely and that this petition challenges claims that were not asserted in the litigation, further favoring institution.

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 9-14, 16-18, 20-21, 25, and 27-30 of the ’526 patent as unpatentable.