US 7557788

Patent Summary: US 7,557,788 B1

Date of Analysis: April 26, 2026

A review of U.S. Patent 7,557,788 B1, titled "Gamma reference voltage generator," has been conducted based on information available from the U.S. Patent and Trademark Office (USPTO). A concurrent search of the 2026 dockets for the Court of Appeals for the Federal Circuit (CAFC) did not yield any results for this patent.

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Patent Overview

Title	Gamma reference voltage generator
Assignee	The assignment history for this patent is complex, with multiple reassignments. As of the latest available records, the assignee is noted as Phenix Longhorn LLC, with a security interest held by BR IP Ventures, LP. The original assignee was Alta Analog Inc.
Inventors	Richard V. Orlando, Trevor A. Blyth
Filing Date	May 1, 2007
Issue Date	July 7, 2009
Abstract	"A programmable buffer integrated circuit which can be programmed to output a set of gamma correction reference voltages to be used in LCD displays. Once programmed, the buffers will continuously output the programmed value. The device incorporates a programming interface to allow the programming of the buffer outputs to the desired values during manufacturing and test of the panel. Multiple sets of values can be programmed to provide different gamma correction curves for different user or application requirements."

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Plain-Language Summary of Independent Claims

This patent contains three independent claims (claims 1, 3, and 5). Below is a simplified explanation of the methods they describe.

Independent Claim 1: This claim outlines a method for calibrating an LCD screen to achieve a specific visual output, known as a "gamma curve." This is done to correct for small inconsistencies that occur from one display panel to another during manufacturing. The process involves:

• Using a display that has a built-in, electrically reprogrammable, and non-volatile (meaning it retains information without power) control for its gamma reference voltages.
• Testing the display's visual output using an external optical sensor.
• Adjusting the gamma voltage levels for the display's columns using an external control circuit.
• Using a separate computing device running a special algorithm to determine the optimal voltage levels based on the sensor's feedback.
• Saving these optimized voltage levels directly into the display's non-volatile gamma control system.

Independent Claim 3: This claim details a method for programming the gamma reference voltage generator chips that are attached to an LCD. The method is iterative and aims to fine-tune the display's visual output. The steps are:

• Selecting one or more columns on the LCD.
• Applying various gamma voltages to these columns.
• Storing these voltages in the reprogrammable, non-volatile cells within the gamma generator chips.
• Using a separate computing device with optimization algorithms to analyze the light coming from the selected columns.
• Modifying the applied gamma voltages based on the results from the optimization algorithms.
• Programming the new, modified voltages into the gamma generator's storage cells.
• Repeating this process of analyzing and modifying until the display's output meets the desired optimization criteria.

Independent Claim 5: This claim describes a comprehensive method for the entire lifecycle of using a liquid crystal display with this technology. It combines the calibration process with the display's normal operation:

• First, providing an LCD that has the electrically reprogrammable and non-volatile gamma control capability.
• Next, calibrating the display through a multi-step process: testing it with an external optical sensor, varying the gamma voltages, optimizing these voltages with an external algorithm based on sensor data, and storing the final voltage levels in the display's gamma control system.
• Then, during normal use, the display retrieves these stored gamma reference voltage levels from its memory.
• Finally, the display uses these retrieved voltage levels to show an image.

In essence, all independent claims describe methods to precisely and permanently tune the visual characteristics of an LCD panel during manufacturing by using external sensors and optimization algorithms, with the resulting settings being saved directly onto the display's hardware.

As a patent attorney, I can provide a summary of the known litigation involving U.S. Patent No. 7,557,788 as of April 26, 2026. This patent has been asserted in multiple legal actions by Phenix Longhorn, LLC.

Here is a list of the known litigation:

District Court Litigation

• Case: Phenix Longhorn, LLC v. AU Optronics Corporation and Hisense Electronica Mexico, S.A. de C.V., et al.

  • Plaintiff: Phenix Longhorn, LLC
  • Defendants: AU Optronics Corporation, Hisense Electronica Mexico, S.A. de C.V., Hisense USA Corporation, and Hisense Visual Technology Co., Ltd.
  • Jurisdiction: U.S. District Court for the Eastern District of Texas
  • Case Number: 2:23-cv-00477-RWS-RSP
  • Filing Date: October 10, 2023
  • Outcome/Current Status: A jury trial concluded in January 2026. The jury found that the defendants did not infringe the asserted patents, including the '788 patent. Additionally, one of the asserted patents was found to be invalid.

• Case: Phenix Longhorn, LLC v. Innolux Corporation

  • Plaintiff: Phenix Longhorn, LLC
  • Defendant: Innolux Corporation
  • Jurisdiction: U.S. District Court for the Eastern District of Texas
  • Case Number: 2:23-cv-00478
  • Filing Date: October 10, 2023
  • Outcome/Current Status: The case was closed on January 5, 2026, following a Stipulation of Voluntary Dismissal by the parties. This type of dismissal often indicates a settlement was reached between the parties.

Patent Trial and Appeal Board (PTAB) Proceedings

• Case: Innolux Corporation v. Phenix Longhorn LLC
  • Petitioner: Innolux Corporation
  • Patent Owner: Phenix Longhorn LLC
  • Jurisdiction: Patent Trial and Appeal Board (PTAB)
  • Case Number: IPR2025-00043
  • Filing Date: October 14, 2024
  • Outcome/Current Status: The PTAB exercised its discretion and chose not to institute an inter partes review for the challenged claims of the related U.S. Patent No. 7,233,305. The outcome for the '788 patent in a similar proceeding is not specified in the provided information.

It is important to note that litigation is a dynamic process, and the status of these cases can change. For the most current information, consulting official court and PTAB records is recommended.

Proceedings Overview

Two inter partes review (IPR) proceedings have been filed against US patent 7,557,788, both of which were denied institution by the Patent Trial and Appeal Board (PTAB). Consequently, all claims of the patent survived these challenges, strengthening its defensive posture against prior-art-based validity attacks that were or could have been raised in those petitions.

IPR2025-01004 — Hisense USA Corporation, et al. v. Phenix Longhorn LLC

• Type: Inter Partes Review
• Filed: 2025-05-14
• Status: Discretionary Denial. This means the PTAB declined to institute a trial, not based on the merits of the invalidity arguments, but for other reasons, likely related to the status of a parallel district court litigation.
• Judge panel: The decision to deny was a Director Decision, a practice that became more common in 2025 where the USPTO Director can issue summary denials.
• Petition grounds: The petition challenged claims of US 7,557,788. Hisense was a defendant in a parallel district court case brought by Phenix Longhorn.
• Institution decision: Denied. Recent PTAB practice under Director Squires has involved issuing summary denials without detailed reasoning, often citing discretionary factors such as parallel litigation or the "settled expectations" of the parties. The denial here falls into that pattern.
• Final Written Decision: Not issued, as the IPR was not instituted.
• Settlement / termination: There is no public record of a settlement specific to this IPR. However, the related district court litigation involving Hisense concluded with a jury verdict of non-infringement and invalidity of one of the asserted patents.
• Appeal: Not applicable, as institution decisions are final and non-appealable.
• Defensive value: This proceeding offers minimal defensive value. The denial was discretionary, not on the merits, meaning the prior art and arguments were not adjudicated by the PTAB. Furthermore, because institution was denied, no statutory estoppel attaches to the petitioner under 35 U.S.C. § 315(e).

IPR2025-00044 — Innolux Corporation v. Phenix Longhorn LLC

• Type: Inter Partes Review
• Filed: 2024-10-15
• Status: Not Instituted - Merits. The PTAB determined that the petitioner did not show a "reasonable likelihood" of prevailing on at least one challenged claim.
• Judge panel: I could not confirm the specific judge panel with high confidence from the available information.
• Petition grounds: The petition challenged claims of US 7,557,788. Innolux was a defendant in a parallel district court case (2:23-cv-00478) filed by Phenix Longhorn.
• Institution decision: Denied. The PTAB found the petition's invalidity arguments unpersuasive on the existing record. The related district court case was voluntarily dismissed on January 5, 2026, which often indicates a settlement between the parties.
• Final Written Decision: Not issued, as the IPR was not instituted.
• Settlement / termination: The parallel district court case was terminated by a stipulation of voluntary dismissal, suggesting a potential settlement, though the terms were not disclosed.
• Appeal: Not applicable.
• Defensive value: This proceeding is also of low defensive value. While the denial was on the merits, which suggests the specific invalidity grounds presented were weak, no estoppel attaches. A new defendant could potentially bring a stronger case with different prior art or arguments before the PTAB.

Strategic Summary

All claims of US 7,557,788 remain valid and enforceable, having survived two IPR institution attempts. No claims have been canceled or amended through a PTAB trial. The patent owner, Phenix Longhorn LLC, has been actively asserting this patent and its family member (US 7,233,305) in the Eastern District of Texas against major display manufacturers and consumer electronics companies, including Innolux, AU Optronics, Hisense, and Samsung.

The key takeaway for a potential defendant is the estoppel landscape. Because both IPRs were denied at the institution stage, statutory estoppel under 35 U.S.C. § 315(e)(2) does not apply. This means a new challenger is free to file their own IPR and may raise the same or different invalidity grounds that were presented in the prior unsuccessful petitions. However, a new petitioner would need to present a significantly more compelling case to persuade the PTAB to institute a trial, given the previous denials. The pattern of litigation and PTAB challenges indicates a well-funded and active assertion entity that defends its portfolio. The district court litigation against AUO and Hisense proceeded to a jury trial, which resulted in a defense verdict of non-infringement, demonstrating that while the patent has survived PTAB scrutiny, it may be vulnerable to non-infringement or invalidity arguments in a district court setting.

Recommended Next Steps

For a defendant facing an assertion of US 7,557,788, the immediate path is not through re-litigating the failed IPR arguments.

• Focus on District Court Defenses: The successful defense by AUO and Hisense, which resulted in a jury verdict of non-infringement, is the most significant data point. A defendant should analyze the public filings and trial record from that case (likely 2:23-cv-00477-RWS-RSP) to understand the prevailing non-infringement arguments.
• Evaluate New Prior Art: Since no estoppel attaches from the denied IPRs, a new validity challenge at the PTAB is still possible. However, it would require identifying prior art or developing invalidity theories that are substantially different and stronger than those presented by Innolux and Hisense.
• Monitor Litigation Activity: The patent owner is an active plaintiff. Monitoring ongoing cases against other parties can provide valuable intelligence on claim construction, infringement theories, and potential settlements. The voluntary dismissal in the Innolux case suggests the patent owner may be willing to settle.

Here is the patent ownership analysis for US 7,557,788.

Inventors

• Richard V. Orlando
• Trevor A. Blyth

Both inventors assigned their interest to Alta Analog, Inc. at the time of the original filing on May 1, 2007. There are no unusual patterns, such as immediate departure from the assignee, evident from the record.

Original assignee

• Alta Analog Inc (California)

Alta Analog was a fabless semiconductor company focused on developing analog and mixed-signal integrated circuits. The patented invention, a programmable gamma reference voltage generator, was central to their product line, including the "AG1818" chip described in the patent's detailed description. The company appears to be defunct; the patent assets were transferred out via a security agreement starting in 2014, suggesting financial distress.

Assignment timeline

Chronological list of every recorded assignment for US patent 7,557,788.

• 2007-04-19 (executed) / recorded 2007-05-01 — Reel 019233/0515

  • Conveyance: Assignment
  • Assignor: Richard V. Orlando, Trevor A. Blyth
  • Assignee: Alta Analog, Inc.
  • Correspondent: Thomas T. Gordon, Esq., The Gordon Law Firm, LLP, Los Altos, CA 94023
  • Context: Standard inventor assignment to employer at time of filing.

• 2010-06-30 (executed) / recorded 2010-07-02 — Reel 024630/0270

  • Conveyance: Security Agreement
  • Assignor: Alta Analog, Inc.
  • Assignee: Comerica Bank
  • Correspondent: Alta Analog, Inc., San Jose, CA 95131
  • Context: Securitization of assets; the patent was pledged as collateral for a loan.

• 2014-06-27 (executed) / recorded 2014-07-18 — Reel 033360/0474

  • Conveyance: Security Interest
  • Assignor: Alta Analog Inc
  • Assignee: AVM Capital LP and Richard Orlando
  • Correspondent: AVM Capital, LP, San Jose, CA 95125
  • Context: A second securitization, suggesting Alta Analog was taking on more debt. Richard Orlando is one of the patent's inventors.

• 2014-11-05 (executed) / recorded 2015-07-13 — Reel 036067/0288

  • Conveyance: Release
  • Assignor: Comerica Bank
  • Assignee: Alta Analog, Inc.
  • Correspondent: Comerica Bank, Detroit, MI 48226
  • Context: Release of the original 2010 security agreement, clearing the title.

• 2014-06-27 (executed) / recorded 2015-07-16 — Reel 036142/0214

  • Conveyance: Assignment ("Delivery and Receipt of Collateral")
  • Assignor: Alta Analog, Inc.
  • Assignee: AVM Capital LP and Richard V. Orlando
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Transfer of the patent from the original assignee to its creditors (including an original inventor) in satisfaction of the 2014 security interest. This suggests a default or dissolution of Alta Analog.

• 2014-06-27 (executed) / recorded 2015-07-16 — Reel 036114/0576

  • Conveyance: Assignment
  • Assignor: AVM Captial LP [sic]
  • Assignee: Maury Domengeaux
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Part of a rapid chain of transfers on the same day. The correspondent is the next assignee in the chain, Phenix LLC.

• 2015-01-08 (executed) / recorded 2015-07-16 — Reel 036114/0930

  • Conveyance: Assignment
  • Assignor: Richard V. Orlando and Maury Domengeaux
  • Assignee: Phenix LLC
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Consolidation of title into a new entity, Phenix LLC.

• 2016-03-11 (executed) / recorded 2016-03-11 — Reel 037960/0875

  • Conveyance: Nunc Pro Tunc Assignment
  • Assignor: Alta Analog, Inc.
  • Assignee: AVM Capital L.P. and Richard V. Orlando
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: A "nunc pro tunc" (now for then) assignment is corrective, likely to clean up chain-of-title defects from the previous year's transfers.

• 2016-03-09 (executed) / recorded 2016-03-12 — Reel 037961/0726

  • Conveyance: Nunc Pro Tunc Assignment
  • Assignor: AVM Capital L.P.
  • Assignee: Maury Domengeaux
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Another corrective assignment in the chain.

• 2016-03-11 (executed) / recorded 2016-03-12 — Reel 037961/0718

  • Conveyance: Nunc Pro Tunc Assignment
  • Assignor: Richard V. Orlando and Maury Domengeaux
  • Assignee: Phenix, LLC
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Final corrective assignment to solidify title in Phenix, LLC.

• 2016-12-22 (executed) / recorded 2017-01-04 — Reel 040834/0069

  • Conveyance: Assignment
  • Assignor: Phenix, LLC
  • Assignee: Phenix Longhorn, LLC
  • Correspondent: Phenix, LLC, Sacramento, CA 95814
  • Context: Transfer to a new LLC, likely for assertion purposes.

• 2023-08-25 (executed) / recorded 2023-11-01 — Reel 065421/0893

  • Conveyance: Security Interest
  • Assignor: Phenix Longhorn LLC
  • Assignee: BR IP Ventures, LP
  • Correspondent: Buether Joe & Counselors, LLC, Dallas, TX 75201
  • Context: The asserting entity is pledging the patent as collateral, likely for litigation financing. This was recorded shortly after the first lawsuits were filed.

Timeline diagram

timeline
    title Ownership of US 7557788
    2007 : Filed by Alta Analog
    2009 : Issued to Alta Analog
    2010 : Pledged to Comerica Bank
    2014 : Pledged to AVM Capital
    2015 : Transferred to AVM/Orlando
         : Transferred to Domengeaux
         : Transferred to Phenix LLC
    2017 : Transferred to Phenix Longhorn LLC
    2023 : Lawsuits filed vs multiple cos
         : Pledged to BR IP Ventures
    2024 : More lawsuits filed

NPE / troll-pattern signals

1. Shell-entity transfer — Present.
   The patent was transferred from an operating company (Alta Analog Inc.) to a series of non-operating LLCs, culminating in Phenix Longhorn, LLC. The name "Phenix Longhorn, LLC" and the subsequent assertion campaign confirm its status as a licensing/assertion entity. The final transfer is a security interest to "BR IP Ventures, LP," another name indicative of a patent monetization firm.

2. Known asserter in the chain — Present.
   Phenix Longhorn LLC is the plaintiff in multiple lawsuits filed in 2023 and 2024, including case numbers 2:23-cv-00477 and 2:24-cv-01077 in the Eastern District of Texas. Unified Patents also lists litigation involving Phenix Longhorn, LLC.

3. Repeat correspondent across the chain — Present.
   The entity "Phenix, LLC" of Sacramento, CA is the correspondent of record for a cascade of six separate assignments executed between 2014 and 2016 (Reels 036142/0214, 036114/0576, 036114/0930, 037960/0875, 037961/0726, 037961/0718, and 040834/0069). This demonstrates a single controlling hand behind the series of title transfers.

4. Cascading transfers — Present.
   The patent was transferred three times in rapid succession, with the transfers all being recorded on the same day, July 16, 2015. This was followed by a series of three corrective "nunc pro tunc" assignments in March 2016 to perfect the chain of title, culminating in the transfer to Phenix Longhorn, LLC in early 2017.

5. Pre-litigation transfer — Not present.
   The key transfer to the asserting entity, Phenix Longhorn, LLC, occurred in late 2016 / early 2017. The first infringement suits were filed over six years later, in late 2023.

6. Bankruptcy fire-sale — Unclear.
   While there is no explicit record of a bankruptcy filing for Alta Analog Inc., the transfer of its core patent asset to its creditors (AVM Capital and inventor Richard Orlando) via a "Delivery and Receipt of Collateral" (Reel 036142/0214) strongly indicates a default or dissolution event analogous to a fire-sale.

7. Privateering — Not present.
   The original assignee, Alta Analog Inc., appears to be defunct and is not participating in or benefiting from the current assertion campaign.

8. Defensive aggregator (anti-NPE) — Not present.
   The patent is held by an active plaintiff and has not been transferred to any known defensive aggregator.

Verdict

NPE — high confidence

The ownership history of US 7,557,788 displays multiple strong signals of NPE activity. The patent was transferred from its original operating-company assignee, Alta Analog Inc., through a rapid cascade of assignments (e.g., three transfers recorded on July 16, 2015) orchestrated by a single correspondent ("Phenix, LLC"). The chain terminates at Phenix Longhorn, LLC, a known patent asserter that has filed multiple infringement suits. The entire history is a textbook example of transferring a distressed asset into a special-purpose vehicle for litigation.

Verification link: USPTO Patent Assignment Search for US 7557788

Analysis of Prior Art for U.S. Patent 7,557,788: Gamma Reference Voltage Generator

Washington D.C. – April 26, 2026 – A detailed analysis of the prior art cited in U.S. Patent 7,557,788, titled "Gamma reference voltage generator," reveals a landscape of existing technologies aimed at calibrating and controlling gamma correction in liquid crystal displays (LCDs). The patent, granted on July 7, 2009, to inventors Richard V. Orlando and Trevor A. Blyth, addresses the need for a programmable and non-volatile solution to compensate for panel-to-panel manufacturing variations. This report outlines the most relevant prior art and its potential impact on the claims of the '788 patent.

The core of the '788 patent lies in its method for calibrating an LCD by providing it with electrically reprogrammable and non-volatile gamma reference control. This process involves testing the display with an external optical sensor, varying the gamma reference voltage levels, optimizing these levels with an external control circuit and algorithm, and finally storing the optimized values in the non-volatile gamma reference control.

An examination of the prior art cited by the patent examiner indicates that while the concept of gamma correction was well-established, the specific combination of features claimed in the '788 patent, particularly the use of external calibration with non-volatile analog memory, was considered novel.

Key Prior Art and Potential Anticipation:

Below is a review of the primary prior art references cited against U.S. Patent 7,557,788 and an analysis of which claims they could potentially anticipate under 35 U.S.C. § 102.

1. U.S. Patent 6,593,934: "Automatic gamma correction system for displays"

• Full Citation: US Patent 6,593,934 B1
• Publication Date: July 15, 2003
• Filing Date: November 16, 2000
• Brief Description: This patent discloses an automatic gamma correction system that uses a light-sensing device to measure the brightness of a display. The system then adjusts the gamma values in a lookup table to match a desired gamma curve. The adjusted values are stored in a memory.
• Potential Anticipation of Claims: This reference appears to be the most significant prior art. It discloses several key elements of the '788 patent's claims, including testing a display with an optical sensor (claim 1b, 5a), varying gamma reference voltage levels (claim 1c, 5b), and optimizing those levels (claim 1d, 5c). However, the '934 patent primarily focuses on a digital approach using a lookup table stored in a memory that may not be explicitly non-volatile in the same manner as the analog floating gate memory cells described in the '788 patent. The distinction between digital lookup tables and the directly programmable, non-volatile analog voltage storage is a key differentiator for the '788 patent. Therefore, while it teaches the general concept of external optical feedback for gamma correction, it may not fully anticipate the "electrically reprogrammable and non-volatile" gamma reference control capability as claimed.

2. U.S. Patent 6,373,478: "Liquid crystal display driver supporting a large number of gray-scale values"

• Full Citation: US Patent 6,373,478 B1
• Publication Date: April 16, 2002
• Filing Date: March 26, 1999
• Brief Description: This patent describes an LCD driver that can generate a large number of gray-scale voltages. It includes a gamma correction circuit that can be adjusted. The focus is on the driver architecture to achieve a high number of gray levels.
• Potential Anticipation of Claims: The '478 patent discusses adjustable gamma correction but does not explicitly describe a method of calibrating the display using an external optical sensor and storing the optimized values in a non-volatile manner to compensate for manufacturing variations. Its primary contribution is the driver circuit design. Therefore, it is unlikely to anticipate the core method claims (1, 3, and 5) of the '788 patent, which are centered on the calibration process with external feedback and non-volatile storage.

3. U.S. Patent 5,754,150: "Liquid crystal luminance adjusting apparatus"

• Full Citation: US Patent 5,754,150 A
• Publication Date: May 19, 1998
• Filing Date: February 17, 1995
• Brief Description: This patent details an apparatus for adjusting the luminance of a liquid crystal display. It includes a mechanism for setting the gamma characteristic of the display.
• Potential Anticipation of Claims: The '150 patent, being an earlier reference, describes methods for adjusting display luminance and gamma characteristics. However, it does not appear to disclose the combination of an external optical sensor for feedback-based calibration and the use of electrically reprogrammable, non-volatile memory to store the resulting gamma correction values for individual panel compensation. Its teachings are more general to the adjustment of display parameters.

4. U.S. Patent 7,233,305: "Gamma reference voltage generator"

• Full Citation: US Patent 7,233,305 B1
• Publication Date: June 19, 2007
• Filing Date: December 23, 2003
• Brief Description: This patent is a parent to the '788 patent and shares the same inventors. It describes a programmable buffer integrated circuit with non-volatile storage for gamma correction voltages.
• Potential Anticipation of Claims: As this is a parent application from which the '788 patent claims priority, it does not constitute prior art under 35 U.S.C. § 102. The '788 patent is a continuation, which typically involves claims to a different aspect of the invention disclosed in the parent application. The disclosure of the '305 patent provides the foundational description of the programmable gamma reference generator hardware that is utilized in the calibration methods claimed by the '788 patent.

In conclusion, while the prior art establishes the general principles of gamma correction and the use of feedback for display calibration, the claims of U.S. Patent 7,557,788 are distinguished by their specific combination of using an external optical sensor, an external control circuit and algorithm for optimization, and, crucially, storing the optimized analog gamma reference voltages in an electrically reprogrammable and non-volatile memory integrated with the display. This allows for a streamlined, automated, and permanent calibration process to address manufacturing variability on a per-panel basis. The '934 patent comes closest to anticipating the claims but its focus on a digital lookup table approach likely provides a sufficient distinction to support the novelty of the '788 patent's claims.

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.

Term and Application History of Patent US 7,557,788 B1

Date of Analysis: May 14, 2026

An analysis of the prosecution and family history of U.S. Patent 7,557,788 B1 ("the '788 patent") reveals the following details regarding its term, related applications, and expiration.

Patent Term Adjustments (PTA) and Extensions (PTE):
There is no record of any Patent Term Adjustment (PTA) or Patent Term Extension (PTE) for the '788 patent. PTA is typically granted to compensate for delays caused by the U.S. Patent and Trademark Office (USPTO) during the examination process. The absence of PTA suggests the application's prosecution proceeded without significant administrative delays attributable to the USPTO.

Application History and Family Members:
The '788 patent is a continuation of an earlier application, which establishes its relationship to a broader patent family.

• Continuation Application: The application for the '788 patent (Ser. No. 11/743,014), filed on May 1, 2007, is a continuation of U.S. patent application Ser. No. 10/746,333, which was filed on December 23, 2003.
• Parent Patent: The parent application (Ser. No. 10/746,333) matured into U.S. Patent No. 7,233,305 B1, also titled "Gamma reference voltage generator."
• Provisional Application: The parent application, in turn, claims priority from U.S. Provisional Application Ser. No. 60/477,680, filed on June 11, 2003.

The '788 patent does not have any divisional applications.

Projected Expiration Date:
The term of a U.S. patent is generally 20 years from the filing date of the earliest U.S. or international (PCT) application to which priority is claimed (excluding provisional applications). For the '788 patent, the relevant priority date is the filing date of the parent application (Ser. No. 10/746,333), which is December 23, 2003.

Therefore, the projected expiration date for US 7,557,788 B1 was December 23, 2023. According to available records, the patent is now expired.

Defensive Disclosure Document for US 7,557,788

Publication Date: May 14, 2026
Subject: Derivative Methods and Implementations for In-Situ Calibration of Emitter and Modulator Arrays.
Scope: This document discloses a series of derivative inventions and technical variations based on the core principles outlined in US Patent 7,557,788. The purpose is to place these variations into the public domain, thereby establishing them as prior art. The core principle involves a closed-loop system where an external sensor and control algorithm are used to program and permanently store optimized operational parameters in non-volatile memory integral to an electronic device, compensating for manufacturing variations.

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Derivatives Based on Claims 1 & 5: Method of Calibrating an Emitter/Modulator Array

Axis 1: Material & Component Substitution

• Derivative 1.1: Quantum Dot Color Filter Calibration

  • Enabling Description: The calibration method is applied to displays employing Quantum Dot (QD) color filters. The external optical sensor is a spectrometer calibrated to the narrow-band emission characteristics of the specific QDs used (e.g., CdSe/ZnS core-shell structures). The optimization algorithm adjusts gamma reference voltages to correct for minor center-wavelength shifts and full-width at half-maximum (FWHM) variations inherent in the QD synthesis and deposition process. This ensures the display's primaries precisely match a target color space, such as Rec. 2020, by compensating for per-panel material variations. The resulting color-corrected gamma curve is stored in the device's non-volatile memory.
  • Mermaid Diagram:

    graph TD
        A[Display with QD Filters] -- Emitted Light --> B{External Spectrometer};
        B -- Spectral Data --> C[Control Computer w/ Colorimetric Algorithm];
        C -- Control Signals --> D{External Voltage Control Circuit};
        D -- Vary Gamma Voltages --> A;
        C -- Store Final Curve --> E[On-Chip Non-Volatile Memory];
        E -- Provides Operating Voltages --> A;
    

• Derivative 1.2: Memristor-Based Analog Voltage Storage

  • Enabling Description: The non-volatile gamma control capability is implemented using an array of analog-programmable memristors (e.g., TiO₂-based). Instead of storing a digital value, the resistance of each memristor is tuned to an analog level that, through an op-amp buffer, produces the desired gamma voltage. The external control circuit uses a sequence of precise voltage/current pulses to incrementally adjust the memristor's resistance. The closed-loop feedback from the optical sensor guides this tuning process until the desired light output is achieved, at which point the resistance value is permanently stored. This allows for a higher-resolution, lower-power implementation of the non-volatile storage.
  • Mermaid Diagram:

    sequenceDiagram
        participant Optical Sensor
        participant Control Algorithm
        participant Gamma IC (Memristor Array)
        Optical Sensor->>Control Algorithm: Luminance Data
        Control Algorithm->>Gamma IC (Memristor Array): Select Memristor (Gamma Point)
        Control Algorithm->>Gamma IC (Memristor Array): Apply Tuning Pulse
        Gamma IC (Memristor Array)-->>Control Algorithm: Feedback (A_OUT or Resistance)
        Control Algorithm->>Control Algorithm: Compare to Target
        Control Algorithm->>Gamma IC (Memristor Array): Store Final Resistance State
    

Axis 2: Operational Parameter Expansion

• Derivative 2.1: Cryogenic Display Calibration

  • Enabling Description: The calibration method is performed on displays designed for cryogenic operation (e.g., 77 Kelvin), such as those used in quantum computing control interfaces or deep-space instrumentation. The display panel, optical sensor, and control circuitry are placed within a cryogenic test chamber. The optimization algorithm is parameterized to account for the altered electro-optical response of the liquid crystal or OLED emitters at cryogenic temperatures. Multiple gamma curves, each corresponding to a specific temperature range (e.g., 77K, 100K), are generated and stored in separate "banks" in the non-volatile memory, as described in the original patent. An on-board temperature sensor selects the appropriate curve during operation.
  • Mermaid Diagram:

    graph TD
        subgraph Cryogenic Chamber (77K)
            A[Display Panel]
            B[Cooled Optical Sensor]
        end
        A -- Light Output --> B;
        B -- Sensor Data --> C{External Control Computer};
        C -- Control Signals --> D{Voltage Control Circuit};
        D -- Drives Panel --> A;
        C -- Store Temp-Specific Curves --> E[On-Chip NVM];
    

• Derivative 2.2: High-Frequency Micro-LED Per-Pixel Calibration

  • Enabling Description: The method is adapted for Micro-LED (µLED) displays operating at refresh rates above 1 kHz. The "columns" are individual µLED pixels, and the "gamma reference voltage" is the analog driving voltage or PWM duty cycle for each pixel. The optical sensor is a high-speed photodiode array synchronized with the pixel driving sequence. The algorithm creates a per-pixel correction map to normalize light output, compensating for variations in epitaxial growth that cause non-uniformity in quantum efficiency. This map of micro-corrections is stored in the non-volatile memory and accessed by the display driver IC to ensure uniformity at extreme frame rates.
  • Mermaid Diagram:

    flowchart LR
        subgraph Calibration System
            controller[Control PC / Algorithm]
            sensor[High-Speed Photodiode Array]
            driver[External µLED Driver]
        end
        subgraph Display Assembly
            uLED_Panel[Micro-LED Panel]
            NVM[On-Chip NVM]
        end
        controller -- Optimize Drive Signal --> driver;
        driver -- Drives Individual µLEDs --> uLED_Panel;
        uLED_Panel -- Emitted Light --> sensor;
        sensor -- Per-Pixel Luminance Data --> controller;
        controller -- Store Per-Pixel Correction Map --> NVM;
        NVM -- Provides Correction Data to internal driver --> uLED_Panel;
    

Axis 3: Cross-Domain Application

• Derivative 3.1: Aerospace - Electrochromic Window Uniformity Calibration

  • Enabling Description: The method is used to calibrate large, segmented electrochromic "smart windows" for aircraft cabins. Each addressable segment of the window is a "column". An array of external photometers measures the optical transmission of each segment. The control circuit varies the voltage applied to the electrochromic layer of each segment. The optimization algorithm generates and stores a voltage correction map in non-volatile memory to ensure all segments tint uniformly and that all windows across the aircraft exhibit identical tinting characteristics, compensating for manufacturing variations in the electrochromic material.
  • Mermaid Diagram:

    stateDiagram-v2
        [*] --> Calibrating
        Calibrating: For each window segment...
        Calibrating --> Optimizing: Segment optical transmission acquired
        Optimizing: Algorithm calculates ideal voltage for target opacity
        Optimizing --> Storing: Optimal voltage found
        Storing: Write voltage to NVM for that segment
        Storing --> Calibrating: Move to next segment
        Calibrating --> Calibrated: All segments complete
        Calibrated --> [*]
    

• Derivative 3.2: AgTech - Spectral Tuning of LED Grow Lights

  • Enabling Description: The method calibrates multi-channel, programmable LED grow light arrays. Each "column" is a string of LEDs of a specific color (e.g., deep red, far-red, blue). The sensor is a spectrometer that measures the spectral power distribution (SPD) of the combined output. Based on a target plant growth recipe (e.g., maximizing the photosynthetically active radiation), the optimization algorithm iteratively adjusts the current supplied to each color channel. It stores the final current settings in the driver's non-volatile memory to produce the exact target spectrum, compensating for variations in LED binning, thermal droop, and lens optics.
  • Mermaid Diagram:

    graph TD
        A[Multi-Channel LED Array] -- Light Output --> B{Spectrometer};
        B -- Spectral Data --> C[Control PC w/ Plant Growth Algorithm];
        C -- Adjust Channel Currents --> D{Multi-Channel LED Driver};
        D -- Drives LEDs --> A;
        C -- Store Optimized Current Settings --> E[Driver's NVM];
        E -- Provides Drive Currents --> D;
    

• Derivative 3.3: Medical - Phased-Array Ultrasound Transducer Homogenization

  • Enabling Description: The method calibrates the individual piezoelectric elements of a medical phased-array ultrasound transducer. Each element is a "column". A calibrated hydrophone, acting as the sensor, measures the acoustic pressure and phase of the output from each element. The control circuit varies the amplitude and phase of the driving voltage. The optimization algorithm adjusts these parameters for each element to normalize the acoustic output across the array, compensating for manufacturing variations in the piezoelectric material. The final table of per-element amplitude and phase corrections is stored in non-volatile memory on the transducer probe.
  • Mermaid Diagram:

    sequenceDiagram
        participant Hydrophone
        participant Controller
        participant Transducer Element Array
        Controller->>Transducer Element Array: Excite element N with voltage V, phase P
        Transducer Element Array->>Hydrophone: Acoustic Pulse
        Hydrophone->>Controller: Measured Acoustic Pressure/Phase
        Controller->>Controller: Compare to desired uniform response
        Controller->>Transducer Element Array: Store optimized (V', P') for element N in NVM
    

Axis 4: Integration with Emerging Tech

• Derivative 4.1: AI-Driven Perceptual Quality Optimization

  • Enabling Description: The "predetermined algorithm" is replaced by a pre-trained Convolutional Neural Network (CNN) that models human visual perception. The optical sensor (a high-resolution camera) captures test patterns displayed on the screen. The CNN analyzes these images for artifacts that are difficult to quantify with simple metrics, such as mura, backlight bleed, and color banding. The network's output guides the control circuit in adjusting gamma levels to minimize these perceived flaws. The resulting gamma correction map, optimized for human perception rather than pure colorimetric accuracy, is stored in the non-volatile memory.
  • Mermaid Diagram:

    flowchart TD
        A[Display Panel] -- Shows Test Pattern --> B(High-Resolution Camera);
        B -- Captured Image --> C(AI Inference Engine - Perceptual CNN);
        C -- Generates Perceptual Score & Correction Vector --> D(Optimization Loop);
        D -- New Gamma Values --> E(External Control Circuit);
        E -- Applies Voltages --> A;
        D -- Final Perceptually-Tuned Gamma Map --> F(On-Chip NVM);
    

• Derivative 4.2: IoT-Enabled Real-Time Environmental Compensation

  • Enabling Description: The display unit is augmented with an IoT sensor module that measures ambient light color temperature, intensity, and display operating temperature. During manufacturing, the calibration process is repeated under various simulated environmental conditions, and a unique gamma curve for each condition is stored in a separate bank within the non-volatile memory. In the field, the IoT module reports the current environment to an onboard microcontroller, which then dynamically selects the appropriate pre-calibrated gamma curve from memory, ensuring optimal image quality regardless of viewing conditions.
  • Mermaid Diagram:

    classDiagram
        Display {
            +Panel
            +GammaControlIC
            +selectGammaCurve(environment)
        }
        GammaControlIC {
            -NonVolatileMemory
            -storedCurves[]
            +retrieveCurve(index)
        }
        IoTSensorModule {
            +ambientLightSensor
            +temperatureSensor
            +getCurrentEnvironment()
        }
        Display "1" *-- "1" GammaControlIC
        Display "1" *-- "1" IoTSensorModule
        IoTSensorModule ..> Display : reports environment
    

• Derivative 4.3: Blockchain-Verified Calibration Provenance

  • Enabling Description: After the calibration process is complete, a cryptographic hash of the final stored gamma voltage data is generated. This hash, along with the display's serial number, the calibration date, and the sensor equipment ID, is recorded as an immutable transaction on a manufacturing blockchain. This provides an auditable and tamper-proof record of calibration for each specific panel, which is essential for devices requiring certified performance, such as medical diagnostic displays or avionics controls.
  • Mermaid Diagram:

    sequenceDiagram
        participant Calibration Station
        participant Display
        participant Manufacturing Blockchain
        Calibration Station->>Display: Perform Calibration
        Display-->>Calibration Station: Final Gamma Data
        Calibration Station->>Calibration Station: Generate Hash(Gamma Data + Serial#)
        Calibration Station->>Manufacturing Blockchain: Create Provenance Transaction
        Blockchain-->>Calibration Station: Transaction Confirmed
    

Axis 5: "Inverse" or Failure Mode

• Derivative 5.1: Failsafe Default Gamma from ROM
  • Enabling Description: The gamma reference generator IC is designed with a hardware-masked, read-only memory (ROM) section that contains a generic, failsafe gamma curve. Upon device power-on, a checksum of the primary reprogrammable non-volatile memory is performed. If the checksum fails, indicating data corruption, the device's control logic automatically bypasses the corrupted data and loads the default gamma curve from the ROM. This ensures the display remains operational with a usable, albeit non-optimized, image, preventing a critical failure.
  • Mermaid Diagram:

    stateDiagram-v2
        [*] --> PowerOn
        PowerOn --> CheckingNVM: Boot Sequence
        CheckingNVM --> LoadingCustomCurve: NVM Checksum OK
        CheckingNVM --> LoadingDefaultCurve: NVM Checksum FAILED
        LoadingCustomCurve --> DisplayActive: Using Optimized Curve
        LoadingDefaultCurve --> DisplayActive: Using Failsafe Curve
        DisplayActive --> [*]: PowerOff
    

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Combination Prior Art Scenarios with Open Standards

1. Combination with VESA DisplayHDR Standard: The iterative method of Claim 3 is employed to ensure compliance with the open VESA DisplayHDR standard. The "optimization criteria" are the specific test parameters of a target HDR level (e.g., DisplayHDR 1000). The external sensor and control algorithm execute the official VESA tests, iteratively adjusting the gamma and tone-mapping reference voltages until the panel passes. The resulting compliant voltage curves are stored in the non-volatile memory, effectively using the patented method as the means to achieve an open-standard certification.

2. Combination with MIPI DSI-2 Protocol: The dedicated parallel programming interface (A0-A2, R/W) of the gamma generator is replaced by a command-based interface accessible via the open MIPI Display Serial Interface 2 (DSI-2) bus. The external calibrator sends standardized Display Command Set (DCS) commands to select and program the non-volatile gamma registers. This integrates the calibration function into the primary display communication bus, reducing pin count and cost, and standardizing the programming method according to an open protocol.

3. Combination with Open-Source Hardware (Raspberry Pi/Arduino): The external calibration system (sensor, control circuit, and algorithm execution) is implemented using widely available, low-cost, open-source hardware, such as a Raspberry Pi and an Arduino. The Pi runs an optimization script (e.g., in Python) that processes data from a compatible open-source color sensor and controls an Arduino board, which in turn generates the necessary analog voltages and digital control signals for programming the gamma IC. This demonstrates that the method is readily implemented using non-proprietary, open-source tools, establishing a low threshold for what a person skilled in the art could obviously achieve.