Invalidity dossier
US 5050946
Faceted light pipe
Current assignee: Hewlett Packard Development Co LP
Added 9/23/2026, 3:10:21 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US 5,050,946 — "Faceted Light Pipe"
Title: Faceted light pipe
Patent Number: US 5,050,946 A
Inventors: Kevin J. Hathaway; Richard M. Knox, Jr.; Douglas A. Arego; Gaylon R. Kornfuerhrer
Original Assignee: Compaq Computer Corp. (current assignee listed as Hewlett Packard Development Co LP)
Priority/Filing Date: 1990-09-27
Publication (Grant) Date: 1991-09-24
Legal Status: Expired – Lifetime (anticipated expiration 2010-09-27)
Purpose: The invention relates to backlighting systems for liquid crystal displays (LCDs), specifically light pipe systems. LCDs act as light valves and require a light source; conventional monochrome LCDs are only ~12% transmissive and color LCDs only ~2% transmissive, so relatively large amounts of uniform light are needed. Prior designs trade off backlight uniformity against space or efficiency, using scattering means and a final diffuser that cause light loss. The invention aims to improve transmission efficiency and reduce space.
Plain-Language Scope (from the supplied excerpt): A faceted, parallel-surface light pipe. Light sources (preferably reflector or apertured fluorescent lamps, alternatively uniform lamps) supply light to one or both ends. The front surface (carrying a low-loss diffuser in contact with the LCD) is planar; the back surface is generally parallel but has a stair-stepped or faceted surface. Facets are angled so injected light reflects off them through the front surface. Facet pitch/step length keeps the faceting invisible to the human eye; step height is preferably in the micron range and may increase with distance from the lamp. A planar, white, diffuse reflector (highly reflective and high-scattering) sits parallel to the back surface; it may have a sawtoothed/grooved surface whose ridge axis is slightly askew to the facet axis to reduce moiré. A conventional pre-LCD diffuser is not required; a low-loss diffuser between light pipe and display overcomes moiré.
Source: https://patents.google.com/patent/US5050946/en
What the excerpt does not establish: The full claim language and exact claim scope; complete description, figures (FIGS. 1–5 referenced, only FIG. 5 partially described), and embodiments; any prosecution history; specific numeric dimensions, materials, or performance data.
Generated 10/1/2026, 9:51:46 PM
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Litigation summary
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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