Projector system with hollow light pipe optics

• US 5,902,033 A
• Filed: 08/07/1998
• Issued: 05/11/1999
• Est. Priority Date: 02/18/1997
• Status: Expired due to Fees

• Current Assignee: Torch Technologies LLC
• Original Assignee: Torch Technologies LLC
• Inventors: Levis, Maurice E., Gourley, Helen
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US09/131,267
• Time in Patent Office: 277 Days
• Field of Search: 353/38, 353/99, 353/122, 359/894, 359/900, 359/503, 385/146, 385/132, 385/131, 385/130, 385/147, 385/48, 385/123, 385/133, 362/307, 362/308, 362/311, 362/326, 362/327, 362/328, 362/339, 362/268, 362/32
• US Class Current: 353/122
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• 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
• CPC Class Codes: H04N 9/3152 for shaping the light beam beam shaping per se G02B27/09

Abstract

A projector system includes a light pipe integrator (LPI) between its lamp and its projection lens system. The LPI is hollow, formed from sheet metal, and has an internal cold mirror coating which reflects visible light and passes infra-red radiation. The reflector is a compound reflector having profiles of two ellipses with different eccentricities.

Claims

1. A light engine for an optical projector system comprising:

lamp means to generate light;

collector means to collect and direct the generated light; and

a light pipe having an entrance pupil, a central section, an exit pupil along a straight optical axis, and reflecting walls;

characterized in that

the light pipe is hollow, and with internal walls, the light pipe is double tapered with the exit pupil being rectangular and the area of the entrance pupil being at least 50% larger than a cross-sectional area perpendicular to the optical axis of the center section, and a cold mirror coating is coated on the internal walls.

2. A projector system comprising:

lamp means to generate light;

collector means to gather and re-direct the generated light;

a light pipe having an entrance pupil, an exit pupil, a center section, internal walls and an optical axis, the light from the collector means being directed on the entrance pupil;

an image forming means to form an image and having an image gate, the exit pupil directing light on the image gate; and

a projector lens;

wherein

the light pipe is hollow in shape, the internal walls are mirrors, the internal walls are open to ambient air; and

wherein the mirrors comprise cold mirror means to reflect visible light and transmit infra-red light.

3. A projector system as in claim 2 wherein in at least some of the cross-sections perpendicular to the optical axis of the internal walls form a rectangle.

4. A projector as in claim 2 wherein in a cross-section perpendicular to the optical axis at the entrance pupil the internal walls form a square.

5. A projector system as in claim 2 wherein in all the cross-sections perpendicular to the optical axis the internal walls form a rectangle.

6. A projector system as in claim 2 wherein in a cross-section perpendicular to the optical axis at the exit pupil the internal walls form a rectangle.

7. A projector system as in claim 2 wherein the internal walls are of sheet metal and are flat.

8. A projector system comprising:

lamp means to generate light;

a reflector to gather and re-direct the generated light;

a light pipe having an entrance pupil, an exit pupil, a center section, internal walls and an optical axis, the light from the reflector being directed on the entrance pupil;

an image forming means to form an image and having an image gate, the exit pupil directing the light on the image gate; and

a projector lens;

wherein the light pipe is hollow in shape, the internal walls are mirrors, the internal walls are open to ambient air; and

wherein the reflector is curved and concave in shape in cross-sections through the axis, and the curvature comprises at least two ellipses having different eccentricities and both eccentricities are in the range of 0.60-0.90.

9. A projector system comprising:

(a) a metal halide arc lamp having an arc gap in the range of 1-6 mm;

(b) a reflector having a central axis;

the lamp arc gap being along the reflector'"'"'s axis;

the reflector being circular in cross-sections perpendicular to the central axis and being curved in at least two elliptical curves having different eccentricities in cross-sections through the central axis;

(c) a hollow light pipe having an entrance pupil, a rectangular exit pupil, a center section between the entrance and exit pupils, an optical axis, flat reflecting walls made of metal, and a tapered shape in which the exit pupil is at least 50% larger than the area of a cross-section through the center section taken perpendicular to the optical axis;

(d) a cold mirror coating means on the reflecting walls to reflect visible light and to transmit visible light;

(e) an LCD (Liquid Crystal Display) panel illuminated by light from the exit pupil; and

(f) a projector lens means to project images formed by the LCD panel onto a screen.

10. A projector system as in claim 9 wherein the elliptical curves each have a different focal point.

11. A projector system as in claim 9 wherein each of the elliptical curves are formed around the same apex point.

12. An elongated light pipe having an optical axis, an entrance pupil and an exit pupil, for use in a projector system, characterized in that:

(a) the light pipe is hollow and has internal mirror walls and is not filled with a dielectric;

(b) the mirror walls are flat and of metal;

(c) a cold mirror coating means is coated on the mirror walls to reflect visible light and transmit infra-red light.

13. A light pipe as in claim 12 wherein the entrance pupil is square or octagonal and the exit pupil is rectangular in a cross-section perpendicular to the optical axis.

14. A light pipe as in claim 12 wherein the light pipe is a tapered shape and in which the exit pupil is at least 50% larger than the area of a cross-section through the center section taken perpendicular to the optical axis.

15. A light engine for an optical projector system comprising:

(a) lamp means to generate light;

(b) a reflector which is circular in cross-sections perpendicular to a central axis and having first and second curved sectors, the sectors in profile having two different curvatures, the reflector producing a first beam from the first reflector sector and a second beam from the second reflector sector, each beam having a free end focus spot;

(c) a hollow light pipe integrator having a tapered entry section with an entry pupil, a central section, an exit pupil and internal mirror walls, a cross-section of the entry pupil being at least 50% larger in area than a cross-section of the center section; and

(d) reflector means to focus the first beam so that it does not reflect from the walls of the entry section and its free end spot is within the entry section.

16. A light engine as in claim 15 wherein the curvatures of the first and second reflector sectors are ellipses.

17. A light engine as in claim 15 wherein the light pipe integrator comprises metal walls having an internal cold mirror coating.

18. A light engine as in claim 15 and second reflector means to focus the second beam so that its free end focus spot is within the center section.

19. A light engine for an optical projector system comprising:

(a) lamp means to generate light;

(b) a reflector which is circular in cross-sections perpendicular to a central axis and having first and second curved sectors, the sectors in profile having two different curvatures, the reflector producing a first beam from the first reflector sector and a second beam from the second reflector sector, each beam having a free end focus spot;

(c) a hollow light pipe aligned in sequence along an optical axis, a tapered entry section having an entry pupil and an exit pupil and internal mirror walls, the entry pupil being at least 50% larger in area than the section exit pupil; and

(d) reflector means to focus the first beam and second beam to substantially overlap at the exit pupil.

20. A light engine as in claim 19 wherein the curvatures of the first and second sectors are ellipses.

21. A light engine as in claim 19 wherein the light pipe comprises metal walls having an internal cold mirror coating.

22. A light engine for an optical projector system comprising:

(a) lamp means to generate light;

(b) a reflector which is circular in cross-sections perpendicular to a central axis and having first and second curved sectors, the sectors in profile having two different curvatures, the reflector producing a first beam from the first reflector sector and a second beam from the second reflector sector, each beam having a free end focus spot;

(c) a hollow light pipe integrator having a tapered entry section with an entry pupil, a central section, an exit pupil and internal mirror walls, a cross-section of the entry pupil being at least 50% larger than a cross-section of the center section; and

(d) the free end focus spot of the first beam being focus point F1 and the free end focus spot of the second beam being focus point F2 which is separated from F1 in the range of 10-40 mm.

23. A light engine as in claim 22 wherein the curvatures of the first and second reflector sectors are ellipses.

24. A light engine as in claim 22 wherein the light pipe integrator comprises metal walls having an internal cold mirror coating.