Projection-type display devices with reduced speckle

Abstract

Described herein are display devices that provide projection-type video output and use lasers to generate light. To reduce any speckle effects for a projected image cast by a projector onto of a non-specular surface, the present invention decreases coherence of the laser-generated light. Coherence reduction is accomplished by introducing a coherence diffuser in a light path of the laser light. Arranging the coherence diffuser in an unfocused light beam reduces both temporal and spatial coherence in the light. Arranging the rotating diffuser at the focus of a beam reduces only the temporal coherence while maintaining the spatial coherence.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority under U.S.C. §120 from co-pending U.S. patent application Ser. No. 10 / 891,840, filed Jul. 15, 2004 and entitled, “POSITIONABLE PROJECTION DISPLAY DEVICES”, which is incorporated herein for all purposes; the patent application Ser. No. 10 / 891,840 also claimed under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60 / 487,868 filed Jul. 16, 2003, which is incorporated by reference herein for all purposes; the patent application Ser. No. 10 / 891,840 also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60 / 487,871 filed Jul. 16, 2003, which is incorporated by reference herein for all purposes; the patent application Ser. No. 10 / 891,840 also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60 / 487,691 filed Jul. 16, 2003, which is incorporated by reference herein for all purposes; the patent appl...

AI Technical Summary

Benefits of technology

[0007] The present invention relates to display devices that provide projection-type video output and use diode lasers to generate light. For example, one set of diode lasers may produce red light, while a second set produces blue light. One or more lenses may be employed to reduce divergence in the laser light generated by each diode laser. Optics are employed to expand laser light from its small generated or transmitted flux area to a size suitable for transmission onto an optical modulation device.

[0011] Another aspect of the invention relates to a redundant laser set to generate light. The laser set produces a desired amount of light, e.g., for a primary color. A redundant laser set includes more lasers than that needed to produce the desired amount of light. For example, a set of six lasers may only need five lasers to generate and emit the desired amount of light. The sixth laser allows failure of one laser in the set to not compromise operability of the entire set—and the display device. In addition, extra lasers in a laser set also allow the lasers to be cycled for heat purposes and to extend longevity of individual lasers in the set.

[0015] To reduce any speckle effects for a projected image cast by a projector onto of a non-specular surface, the present invention may decrease coherence of laser-generated light. In one embodiment, coherence reduction is accomplished by introducing a coherence diffuser in a light path of the laser light. Arranging the coherence diffuser in an unfocused light beam reduces both temporal and spatial coherence in the light. Arranging the rotating diffuser at the focus of a beam reduces only the temporal coherence while maintaining the spatial coherence.

Problems solved by technology

One problem with a white-light emitting lamp is lifetime.

Not only does a lamp burn out after about two thousand hours, but luminous power consistency often declines with lamp age.

The high price of currently available projectors—and the cost of replacement lamps—compromises market acceptance and projector sales.

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