US 7404644

Patent Overview: US 7,404,644 B2 — "Time-sequential colour projection"

Source: https://patents.google.com/patent/US7404644/en

Bibliographic data (from the supplied text)

• Patent number: US 7,404,644 B2
• Title: Time-sequential colour projection
• Application number: US 11/127,710
• Inventors: Allan Evans; Grant Bourhill; Marina V. Khazova
• Assignee: Sharp Corp (Sharp Kabushiki Kaisha)
• Priority date: 2004-05-12; Filed: 2005-05-12
• Published (application): US 2005/0254127 A1, 2005-11-17
• Granted/Published (patent): 2008-07-29
• Legal status: Expired – Fee Related; adjusted expiration 2026-05-05
• Classifications: notably G02B27/10, G02B27/102, G02B27/1046, G02B27/1053 (single light modulator for all colour channels), G02B27/12, G02B27/14, G02B27/149 (crossed beamsplitting surfaces, e.g. cross-dichroic cubes)

Purpose
The invention relates to a time-sequential colour projector, with applications including video/data projectors, front and rear projectors, cinema and home entertainment, head-up displays in vehicles, business and conference projectors, and miniature portable projectors.

Plain-language scope
The background explains that monochrome light valves (transmissive liquid crystal panels, reflective liquid crystal panels, micromirror devices) can produce colour either via a three-panel system (dichroic combining optics) or a time-sequential system (rapid red/green/blue illumination of one valve). The text notes drawbacks of the time-sequential approach — flicker or colour artefacts, need for fast (often costlier) light valves, and low optical efficiency since less than one-third of white light is used at any time — and of the three-panel approach, which needs three panels, colour separating/combining optics, and precise image convergence.

The excerpt then describes known alternatives (U.S. Pat. No. 5,161,042 and EP1089115) using dichroic mirrors to send red, green and blue to different angles, with microlens arrays directing colours to different pixels. It notes limits: microlenses need low f-numbers; as panels shrink, lens-to-pixel separation becomes small, while typical liquid crystal light valves sit on ~0.5 mm glass substrates, imposing a lower limit on achievable separation — so lenses may need integrating into the panel, requiring specially manufactured, costlier light valves.

What the excerpt does not establish
The supplied excerpt is incomplete: it does not include the claims, the full detailed description, or the complete wording of the "angular time-sequential colour" passage (which is cut off). Therefore the precise claimed scope cannot be determined from this text alone. No litigation, ownership-transfer, validity or prior-art conclusions are drawn here.