Reflection-type projector

• US 6,457,830 B1
• Filed: 11/03/2000
• Issued: 10/01/2002
• Est. Priority Date: 11/04/1999
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Soon-cheol
• Primary Examiner(s): Perkey, W. B.
• Application Number:
  US09/704,825
• Time in Patent Office: 697 Days
• Field of Search: 353/33, 353/81, 353/99, 353/84, 353/98, 348/743, 348/771
• US Class Current: 353/33
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 27/147 using averaging effects by spatially variable reflectivity on a microscopic level, e.g. polka dots, chequered or discontinuous patterns, or rapidly moving surfaces G02B27/1086 takes precedence
• CPC Class Codes: G02B 5/04 Prisms
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A reflection-type projector includes a light source for generating and emitting light, an optical path changer for changing the traveling path of an incident beam, and an image former. Preferably, the image former is a micro-mirror device having a plurality of movable mirrors provided to correspond to respective pixels, and windows for enclosing the movable mirrors, where the windows transmit most of the incident rays. The micro-mirror device reflects incident rays to form necessary reflected rays and unnecessary reflected rays having reflection paths that differ according to the driven states of the movable mirrors. The reflection-type projector further includes a projection lens unit for magnifying incident rays and projecting the rays. The optical path changer includes a beam separation prism having a first critical surface that is slanted so that incident rays from the light source pass through the first critical surface, and the necessary reflected rays entering from the image former and surface-reflected rays reflected from the window of the image former are reflected by the first critical surface. The beam separation prism further includes an entrance-exit surface that faces the image former and one surface of the projection lens unit, through which entranceexit surface rays enter or exit. The beam separation prism also includes a second critical surface that is slanted with respect to the optical axis of necessary reflected rays reflected from the first critical surface, wherein the second critical surface transmits the unnecessary reflected rays and surface-reflected rays reflected from the first critical surface, and wherein the second critical surface reflects the necessary reflected rays reflected from the first critical surface to the projection lens unit.

Claims

1. A reflection-type projector comprising:

a light source that generates and emits light;

an optical path changer that changes a traveling path of an incident beam;

an image former that has an on-state and an off-state and that reflects a first portion of a plurality of incident rays, emitted from said light source and transmitted through said optical path changer, to form a plurality of necessary reflected rays when said image former is in the on-state and a plurality of unnecessary reflected rays when said image former is in the off-state, wherein the necessary and unnecessary reflected rays have first and second reflection paths, respectively, that differ from each other, said image former comprising a window forming a protective layer, wherein said window reflects a second portion of the plurality of incident rays to form a plurality of surface-reflected rays; and

a projection lens unit that magnifies and projects the necessary reflected rays, wherein said optical path changer comprises a beam separation prism comprising;

a first critical surface that is slanted so that the plurality of incident rays emitted from said light source pass through said first critical surface, and the necessary reflected rays and the surface-reflected rays are reflected by said first critical surface;

an entrance-exit surface that faces said image former and one surface of said projection lens unit, wherein the necessary reflected rays, the unnecessary reflected rays, and the surface-reflected rays enter and the necessary rays exit through said entrance-exit surface; and

a second critical surface that is slanted with respect to an optical axis of the necessary reflected rays reflected from said first critical surface, wherein said second critical surface transmits the unnecessary reflected rays and the surface-reflected rays reflected from said first critical surface, and wherein said second critical surface reflects the necessary reflected rays reflected from said first critical surface to said projection lens unit.

2. The reflection-type projector as claimed in claim 1, wherein said image former comprises a micro-mirror device comprising:

a plurality of movable mirrors corresponding to respective pixels, each movable mirror having an on-state and an off-state and reflecting the incident rays to form the necessary reflected rays corresponding to the on-state of the movable mirror and the unnecessary reflected rays corresponding to the off-state of the movable mirror; and

a plurality of windows, each window enclosing one of said plurality of movable mirrors and transmitting most of the incident rays.

3. The reflection-type projector as claimed in claim 2, wherein the optical path changer further comprises a compensating prism having a compensating surface facing said first critical surface and compensating for deviations of the plurality of incident rays emitted from said light source.

4. The reflection-type projector as claimed in claim 2, further comprising:

a color selector provided on an optical path between said light source and said optical path changer, said color selector comprising;

a color wheel having a plurality of filters selectively transmitting a plurality of rays of red, blue, and green color wavelengths emitted from said light source, and

a driving source for driving said color wheel so that said plurality of filters are positioned alternately on the optical path;

a collimating lens for converging the rays transmitted by said color selector to form a parallel beam; and

a uniform light illuminator comprising a plurality of fly'"'"'s eye lens units that divide the parallel beam from said collimating lens into a plurality of divided beams and converge and mix the plurality of divided beams to form a uniform beam.

5. The reflection-type projector as claimed in claim 1, further comprising:

a color selector provided on an optical path between said light source and said optical path changer, said color selector comprising;

a color wheel having a plurality of filters selectively transmitting rays of red, blue, and green color wavelengths emitted from said light source, and

a driving source for driving said color wheel so that said plurality of filters are positioned alternately on the optical path;

a collimating lens for converging the rays transmitted by said color selector to form a parallel beam; and

a uniform light illuminator comprising a plurality of fly'"'"'s eye lens units that divide the parallel beam from said collimating lens into a plurality of divided beams and converge and mix the plurality of divided beams to form a uniform beam.