Projector

• US 5,477,394 A
• Filed: 05/19/1994
• Issued: 12/19/1995
• Est. Priority Date: 06/23/1993
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Shibazaki, Shigeru
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US08/245,899
• Time in Patent Office: 579 Days
• Field of Search: 359/364, 359/365, 359/727, 359/730, 359/731, 359/857, 359/858, 359/859, 359/861, 353/37, 353/50, 353/51, 353/99, 353/64, 353/66, 353/73, 353/77, 353/78, 362/297, 362/298
• US Class Current: 359/858
• CPC Class Codes: G02B 17/0816 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells

Abstract

A projector has a shortened optical path from a light valve to a screen and a reduction in the depth size of its system, and requires less space to mount. Rays of light emitted from a light valve of the projector are refracted by a converging lens and reflected by a plane mirror to converge at the primary focal point of an elliptical mirror, and then travel toward the secondary focal point whereat the focal point of a parabolic mirror also exists and a projection lens is disposed. The light rays pass through the projection lens, are reflected by the parabolic mirror and then are brought to a parallel beam of light that is further collected by a Fresnel lens to finally form an image on a lenticular lens-screen.

Claims

1. A projector, comprising:

an elliptical mirror having a primary focal point and a secondary focal point;

a light valve emitting rays of light converging into the primary focal point of the elliptical mirror through an optical system;

a projection lens disposed at the secondary focal point of the elliptical mirror; and

a parabolic mirror having its focal point at the secondary focal point of the elliptical mirror so as to produce a parallel beam of light, whereby the rays of the parallel beam of light reflected by the parabolic mirror are collected to form an image.

2. The projector of 1, further comprising a light source and a beam spitter, wherein the light valve is a reflection type liquid-crystal display.