Obviousness

Analysis of Obviousness for U.S. Patent No. 7,557,788

Date of Analysis: May 14, 2026

Patent at Issue: U.S. Patent No. 7,557,788 (hereinafter "'788 patent")

Statutory Basis for Analysis: 35 U.S.C. § 103

I. Introduction

This analysis examines the patentability of the claims of the '788 patent in view of prior art, focusing on the legal standard of obviousness. Under 35 U.S.C. § 103, an invention is unpatentable if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (a "PHOSITA"). This analysis will consider combinations of prior art references cited within the '788 patent itself to determine if they would render the claimed invention obvious.

II. Understanding the '788 Patent

The '788 patent, titled "Gamma reference voltage generator," discloses a programmable buffer integrated circuit designed to output a set of gamma correction reference voltages for liquid crystal displays (LCDs). A key feature of the invention is the use of non-volatile, programmable memory to store these voltage values, allowing for automated and reprogrammable gamma adjustment. This is presented as an improvement over the prior art method of using "Select-On-Test-Resistors," which required manual testing and selection of resistors, a costly and inflexible process.

The claims of the '788 patent are directed towards a method of calibrating an LCD. For example, Claim 1 recites a method comprising:

• Providing the display with electrically reprogrammable and non-volatile gamma reference control.
• Testing the display with an external optical sensor.
• Varying gamma reference voltage levels with an external control circuit.
• Optimizing these levels using an external algorithm based on sensor data.
• Storing the optimized levels in the non-volatile gamma reference control.

Claim 3 outlines a similar method of programming one or more gamma reference voltage generator integrated circuits.

III. Prior Art References

The '788 patent cites several prior art references, including:

• U.S. Patent No. 6,593,934 (Lin, et al.) titled "Automatic gamma correction system for displays" (hereinafter "'934 patent").
• U.S. Patent No. 5,754,150 (Chun, et al.) titled "Liquid crystal luminance adjusting apparatus" (hereinafter "'150 patent").
• U.S. Patent No. 6,373,478 (Weitbruch, et al.) titled "Liquid crystal display driver supporting a large number of gray-scale values" (hereinafter "'478 patent").
• U.S. Patent No. 7,233,305 (Orlando, et al.) which is the parent application of the '788 patent.

For the purpose of an obviousness analysis, we will focus on combinations of the '934 patent and the '150 patent.

IV. Obviousness Analysis: Combination of '934 and '150 Patents

A strong argument for the obviousness of the claims of the '788 patent can be made by combining the teachings of the '934 patent and the '150 patent.

A. Teachings of the Prior Art

• The '934 Patent: This reference discloses an automatic gamma correction system for a display. It explicitly teaches the use of an optical sensor to measure the luminance of the display, a control unit to compare this with a desired gamma curve, and a gamma correction circuit to adjust the gamma values accordingly. The system aims to automate the gamma correction process to compensate for variations in display characteristics. The '934 patent, however, does not explicitly detail the use of non-volatile memory for storing the optimized gamma values.

• The '150 Patent: This reference describes a liquid crystal luminance adjusting apparatus that includes a non-volatile memory (specifically an EEPROM) to store luminance adjustment data. The purpose is to maintain the desired luminance settings even after the device is powered off.

B. Motivation to Combine

A person of ordinary skill in the art at the time of the invention would have been motivated to combine the teachings of the '934 and '150 patents for several reasons:

1. Solving a Known Problem: The '788 patent itself identifies a long-standing problem in the field: the need for a cost-effective, automated, and reprogrammable method for gamma correction. The prior art method of using selectable resistors was cumbersome and did not allow for easy recalibration. The '934 patent provides the automation and feedback mechanism (optical sensor and control unit) to address this, while the '150 patent provides the means to make the adjustments permanent and non-volatile.

2. Predictable Results: The combination of a sensor-based automatic adjustment system with non-volatile memory is a well-established engineering principle. A PHOSITA would have reasonably expected that storing the output of the '934 patent's automatic correction system into the non-volatile memory taught by the '150 patent would result in a display that retains its calibrated gamma curve after power cycling. There would be no technical uncertainty or unpredictable results from this combination.

3. Analogous Art: Both patents are in the same field of endeavor: display technology and specifically, luminance and color characteristic adjustment. A designer working on improving gamma correction would naturally look to solutions for similar problems, such as luminance adjustment, and find the use of non-volatile memory as a readily applicable technique.

C. Mapping the Combination to the Claims

The combination of the '934 and '150 patents appears to teach all the elements of at least claims 1 and 5 of the '788 patent:

• "providing said display with gamma reference control capability which is electrically reprogrammable and non-volatile": This is taught by the combination of the '934 patent's adjustable gamma correction circuit with the '150 patent's non-volatile memory.
• "testing said display with at least one sensor with optical input, wherein said sensor is separate from said display": This is explicitly taught by the '934 patent.
• "varying gamma reference voltage levels on columns of said display by a control circuit, wherein said control circuit is separate from said display": The '934 patent discloses a control unit for this purpose.
• "optimizing said gamma reference voltage levels using means for executing a predetermined algorithm according to a predetermined criteria and data sensed by said at least one sensor, wherein said means for executing said predetermined algorithm is separate from said display to achieve the desired gamma curve": This is the core function of the control unit in the '934 patent.
• "storing said gamma reference voltage levels in said gamma reference control capability": This is the contribution from the '150 patent, which a PHOSITA would have been motivated to add to the system of the '934 patent to make the calibration persistent.

V. Conclusion

The claims of U.S. Patent No. 7,557,788 are likely obvious under 35 U.S.C. § 103 in light of the combination of U.S. Patent No. 6,593,934 and U.S. Patent No. 5,754,150. A person of ordinary skill in the art, faced with the problem of creating a more efficient and flexible gamma correction system, would have been motivated to combine the automated, sensor-based adjustment system of the '934 patent with the non-volatile storage taught by the '150 patent. This combination would have yielded the claimed invention with a reasonable expectation of success. The asserted novelty of the '788 patent appears to be the application of a known technique (non-volatile storage) to a known system (automated gamma correction) to achieve a predictable and desirable result.