Reflection type projector

• US 6,666,557 B1
• Filed: 04/09/1998
• Issued: 12/23/2003
• Est. Priority Date: 04/09/1997
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Soon-cheol
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US09/057,585
• Time in Patent Office: 2,084 Days
• Field of Search: 353/20, 353/31, 353/33, 353/34, 353/37, 353/81, 349/8, 349/7, 349/5, 348/742, 348/743, 348/771
• US Class Current: 353/31
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A reflection type projector including a critical angle prism for changing the path of light. The reflection type projector includes a light source for generating and emitting light, an image forming unit having a multiplicity of pixels in a two-dimensional array structure, each of the pixels being independently driven, for forming and reflecting an image from the input light, a critical angle prism having a transmission/reflection surface disposed along an optical path of the light, to transmit the light input from the light source and reflect the light re-entering from the image forming unit, and a projection lens unit for enlarging and transmitting the light reflected from the transmission/reflection surface of the critical angle prism onto a screen.

Claims

1. A reflection type projector comprising:

a light source for emitting an input light;

a first dichroic mirror, disposed along an optical path of the input light, for dividing the input light into a first transmitted light beam and a first reflected light beam, the first dichroic mirror transmitting the first transmitted light beam and reflecting the first reflected light beam according to a wavelength;

a first optical path changing unit for changing the path of the first transmitted light beam from the first dichroic mirror, the first optical path changing unit including only one prism;

a first image forming unit for forming an image from the first transmitted light beam passing through the first optical path changing unit;

a second dichroic mirror, disposed along an optical path of the first reflected light beam from the first dichroic mirror, for dividing the first reflected light beam into a second transmitted light beam and a second reflected light beam, the second dichroic mirror transmitting the second transmitted light beam and reflecting the second reflected light beam according to a wavelength;

a second optical path changing unit for changing the path of the second reflected light beam from the second dichroic mirror, the second optical path changing unit including only one prism;

a second image forming unit for forming an image from the second reflected light beam passing through the second optical path changing unit;

a third optical path changing unit for changing the path of the second transmitted light beam from the second dichroic mirror;

a third image forming unit for forming an image from the second transmitted light beam passing through the third optical path changing unit, the third optical path changing unit including only one prism;

a dichroic beam splitter having a first and a second mirror surface for selectively transmitting and reflecting the input light passing through the first, second and third optical path changing units in one direction according to wavelength; and

a projection lens unit for enlarging and transmitting the input light from the dichroic beam splitter.

2. The reflection type projector of claim 1, wherein the first optical path changing unit comprises:

a converging lens for converging input light; and

a prism having a transmission/reflection surface for transmitting the input light from the converging lens and total internal reflecting the light reflected from the first image forming unit.

3. The reflection type projector of claim 2, wherein the transmission/reflection surface is disposed at an angle with respect to the optical axis of light reflected from the first image forming unit which is greater than a critical angle.

4. The reflection type projector of claim 1, wherein the first image forming unit comprises:

a polarizer for linearly-polarizing input light;

a ferroelectric liquid crystal display device for linearly polarizing light transmitted from the polarizer and passed through the first optical path changing unit, into linearly polarized light having a polarization direction independently selected according to respective regions; and

an analyzer, disposed along the optical path of the light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting light of one polarization direction.

5. The reflection type projector of claim 2, wherein the first image forming unit comprises:

a polarizer, disposed along the optical path of the light between the converging lens and the prism, for linearly polarizing input light;

a ferroelectric liquid crystal display device having a plurality of pixels for linearly-polarizing the input light transmitted from the polarizer and the prism into linearly-polarized light having a polarization direction independently selected according to each pixel, and reflecting the linearly-polarized light toward the prism; and

an analyzer, disposed along the optical path of light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting the light of one polarization direction of the input light reflected from the ferroelectric liquid crystal display device and the prism.

6. The reflection type projector of claim 1, wherein the first image forming unit is a digital mirror device including a plurality of reflection mirrors of a two-dimensional array structure, each of the plurality of mirrors being independently driven.

7. The reflection type projector of claim 1, wherein the second optical path changing unit comprises:

a converging lens for converging input light; and

a prism having a transmission/reflection surface for transmitting the input light from the converging lens and total internal reflecting the light reflected from the second image forming unit.

8. The reflection type projector of claim 7, wherein the transmission/reflection surface is disposed at an angle with respect to the optical axis of the light reflected from the second image forming unit which is greater than a critical angle.

9. The reflection type projector of claim 1, wherein the second image forming unit comprises:

a polarizer for linearly-polarizing input light;

a ferroelectric liquid crystal display device for linearly-polarizing light transmitted from the polarizer and passed through the second optical path changing unit, into light having a polarization direction selected independently according to each region and for reflecting the linearly-polarized light; and

an analyzer, disposed along the optical path of the light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting light of one polarization direction.

10. The reflection type projector of claim 7, wherein the second image forming unit comprises:

a polarizer, disposed along the optical path of the light between the converging lens and the prism;

a ferroelectric liquid crystal display device having a plurality of pixels for linearly-polarizing input light transmitted from the polarizer and the prism into light having a polarization direction independently selected according to each pixel, and reflecting the linearly-polarized light; and

an analyzer, disposed along the optical path of light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting light of one polarization direction of the input light reflected from the ferroelectric liquid crystal display device and the prism.

11. The reflection type projector of claim 1, wherein the second image forming unit is a digital mirror device having a plurality of reflection mirrors in a two-dimensional array structure, each of the plurality of mirrors being independently driven.

12. The reflection type projector of claim 1, wherein the third optical path changing unit comprises:

a converging lens for converging input light; and

a prism having a transmission/reflection surface for transmitting the light input from the converging lens and total internal reflecting the light reflected from the third image forming unit.

13. The reflection type projector of claim 12, wherein the transmission/reflection surface has an angle with respect to input light reflected from the third image forming unit which is greater than a critical angle.

14. The reflection type projector of claim 1, wherein the third image forming unit comprising:

a polarizer for linearly-polarizing input light;

a ferroelectric liquid crystal display device for linearly polarizing input light transmitted from the polarizer and passed through the third optical path changing unit, into linearly-polarized light having a polarization direction independently selected according to respective regions; and

an analyzer, disposed along the optical path of the light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting light of one polarization direction.

15. The reflection type projector of claim 12, wherein the third image generation unit comprises:

a polarizer, disposed along the optical path of the light between the converging lens and the prism, for linearly polarizing input light;

a ferroelectric liquid crystal display device having a plurality of pixels for linearly polarizing the input light transmitted from the polarizer and the prism into linearly polarized light having a polarization direction independently selected according to each pixel, and reflecting the linearly-polarized light toward the prism; and

an analyzer, disposed along the optical path of light between the ferroelectric liquid crystal display device and the dichroic beam splitter, for transmitting light of one polarization direction of the input light reflected from the ferroelectric liquid crystal display device and the prism.

16. The reflection type projector of claim 1, wherein the third image forming unit is a digital mirror device including a plurality of reflection mirrors of a two-dimensional structure, each of the plurality of mirrors being independently driven.

17. The reflection type projector of claim 1, comprising:

a light mixing unit disposed along the optical path of the input light between the light source and the first dichroic mirror, for making the input light from the light source into uniform light by at least one of diverging, converging, diffusing and reflecting the input light from the light source.

18. The reflection type projector of claim 17, wherein the light mixing unit comprises:

a first and a second fly-eye lens disposed adjacent to each other, each having a plurality of convex portions at on of an input surface and an output surface thereof, each of the convex portions converging input light; and

a converging lens for converging the light transmitted from the second fly-eye lens to form parallel light beams.

19. The reflection type projector of claim 17, wherein the light mixing unit is a scrambler fabricated from glass and having a hexahedron shape with an input surface and an output surface that are perpendicular to the optical path of the light to make the input light uniform by diffusing and reflecting the input light.

20. The reflection type projector of claim 1, comprising a correction prism formed on an outer surface of the dichroic beam splitter, for correcting an aberration of input light.

21. The reflection type projector of claim 1, wherein each one of the first, second, and third image forming units receives light having wavelengths that are not received by the other two image forming units.