Projection display device with optical combiner between first lens group and separate second lens groups

1. A projection display device for enlarging and projecting an image along a projection optical axis, comprising:

a first lens group arranged on the projection optical axis on the enlarging end of the projection display device;

a plurality of display elements, each modulating a different one of a plurality of light beams with image information;

an optical combiner for receiving from at least two different directions light beams modulated by the different display elements, combining the modulated light beams, and directing the combined modulated light beams along an optical axis to the first lens group;

a plurality of second lens groups, each having positive refractive power and each arranged on a separate optical axis so that a different one of the light beams modulated by a different display element is incident on the optical combiner after passing through one of the second lens groups;

wherein the following conditions are satisfied by the projection display device for each of the plurality of second lens groups:

1.0< f 2/ f< 8.0

LVD/{ 4·(1−2·tan θ)}< Bf<LVD /(1−2·tan θ′)+ LVD

0.25< d/f 2<1.0

wherein

f2 is the focal length of the second lens group;

f is the smallest focal length of the combination in optical series of the first lens group and the second lens group;

LVD is the diagonal dimension of the display element;

Bf is the back focal length of the combination in optical series of the first lens group and the second lens group at the smallest focal length of the combination of the first lens group and the second lens group;

θ is the angle for which sin θ=1/(4·F NO );

θ′ is the angle for which sin θ′=1/(2·F NO );

F NO is the f-number at the smallest focal length of the combination in optical series of the first lens group and the second lens group; and

d is the air-converted distance along the optical axis, defined by the combination in optical series of the first lens group and each of the second lens groups, between the first lens group and each of the second lens groups at the smallest focal length of the combination in optical series of the first lens group and the second lens group.

2. The projection display device of claim 1 , wherein:

at least two light beams, each modulated by a different one of the plurality of display elements, are combined and transmitted along a common optical axis before they are incident on a second lens group.

3. The projection display device of claim 2 , wherein the optical combiner consists of a dichroic prism that includes a dichroic surface.

4. The projection display device of claim 1 , wherein:

the optical combiner consists of an X-shaped dichroic prism that includes two dichroic surfaces for combining light beams from three different directions; and

the plurality of second lens groups includes at least three second lens groups.

5. The projection display device of claim 1 , wherein:

the first lens group and each of the plurality of second lens groups define a zoom lens associated with each of the plurality of second lens groups;

the optical axis of each zoom lens is formed by the projection optical axis of the first lens group and the separate optical axis of each of the plurality of second lens groups;

the distance along each separate optical axis between lens components of each of the second lens groups remains fixed during zooming;

the first lens group includes at least two lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming; and

the distances along the optical axis of each zoom lens between the lens component of the first lens group that is closest to the optical combiner and each of the lens components of each of the plurality of second lens groups that is closest to the optical combiner changes during zooming or the first lens group includes at least three lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming.

6. The projection display device of claim 5 , wherein the first lens group includes a lens component that is fixed during zooming and has negative refractive power.

7. The projection display device of claim 1 , wherein each of the plurality of second lens groups is telecentric or nearly telecentric on the side opposite the enlarging side.

8. The projection display device of claim 1 , wherein the first lens group includes a mirror for changing the direction of the projection optical axis of the first lens group.

9. The projection display device of claim 1 , wherein the composition of at least two of the plurality of second lens groups is substantially different in terms of at least one surface shape or lens material of at least one lens element.

10. The projection display device of claim 1 , wherein:

the projection optical axis of the first lens group and each of the separate optical axes of each of the plurality of second lens groups define separate device optical axes, each of which passes through the optical combiner; and

at least one of the plurality of second lens groups is movable along its separate optical axis in order to vary the optical path along its separate device optical axis between the one of the plurality of second lens groups and the first lens group so that the optical path length is different from the optical path length along a different device optical axis between another of the plurality of second lens groups and the first lens group.

11. The projection display device of claim 1 , wherein the projection display device is constructed so that at least one lens component of the first lens group may be readily interchanged with another lens component so that the focal length of the projection display device may be easily changed.

12. The projection display device of claim 1 , further including a polarization sensitive beam splitter on the side opposite the enlarging side of one of the plurality of second lens groups for separating a light beam illuminating a display element from the light beam modulated by the display element;

the projection display device being constructed so the polarization sensitive beam splitter may be easily interchanged with another polarization sensitive beam splitter; and

at least one lens component of at least one of the first lens group and the second lens group on the enlarging side of the polarization sensitive beam splitter being readily interchangeable with another lens component in order to correct changes in imaging performance resulting from changing the polarization sensitive beam splitter being used in the projection display device.

13. The projection display device of claim 1 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

14. The projection display device of claim 1 , further comprising an illuminator including:

a light source, an integrator optical system for integrating light from the light source;

an illumination optical system for guiding light from the integrator optical system to the plurality of display elements;

wherein the light from the illuminator is modulated by the plurality of display elements and projected by the projection display device along the projection optical axis to form a projected image.

15. The projection display device of claim 1 , wherein the first lens group, the optical combiner, and the plurality of second lens groups are movable together as a unit in a direction orthogonal to the projection optical axis.

16. The projection display device of claim 1 , wherein the optical combiner and the plurality of second lens groups receive light from the light source before the light is modulated by a display element.

17. The projection display device of claim 2 , wherein:

the first lens group and each of the plurality of second lens groups define a zoom lens associated with each of the plurality of second lens groups;

the optical axis of each zoom lens is formed by the projection optical axis of the first lens group and the separate optical axis of each of the plurality of second lens groups;

the distance along each separate optical axis between lens components of each of the second lens groups remains fixed during zooming;

the first lens group includes at least two lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming; and

the distances along the optical axis of each zoom lens between the lens component of the first lens group that is closest to the optical combiner and each of the lens components of each of the plurality of second lens groups that is closest to the optical combiner changes during zooming or the first lens group includes at least three lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming.

18. The projection display device of claim 3 , wherein:

the first lens group and each of the plurality of second lens groups define a zoom lens associated with each of the plurality of second lens groups;

the optical axis of each zoom lens is formed by the projection optical axis of the first lens group and the separate optical axis of each of the plurality of second lens groups;

the distance along each separate optical axis between lens components of each of the second lens groups remains fixed during zooming;

the first lens group includes at least two lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming; and

the distances along the optical axis of each zoom lens between the lens component of the first lens group that is closest to the optical combiner and each of the lens components of each of the plurality of second lens groups that is closest to the optical combiner changes during zooming or the first lens group includes at least three lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming.

19. The projection display device of claim 4 , wherein:

the first lens group and each of the plurality of second lens groups define a zoom lens associated with each of the plurality of second lens groups;

the optical axis of each zoom lens is formed by the projection optical axis of the first lens group and the separate optical axis of each of the plurality of second lens groups;

the distance along each separate optical axis between lens components of each of the second lens groups remains fixed during zooming;

the first lens group includes at least two lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming; and

the distances along the optical axis of each zoom lens between the lens component of the first lens group that is closest to the optical combiner and each of the lens components of each of the plurality of second lens groups that is closest to the optical combiner changes during zooming or the first lens group includes at least three lens groups that are movable relative to one another along the projection optical axis of the first lens group during zooming.

20. The projection display device of claim 2 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

21. The projection display device of claim 3 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

22. The projection display device of claim 4 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

23. The projection display device of claim 5 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

24. The projection display device of claim 6 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

25. The projection display device of claim 7 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

26. The projection display device of claim 8 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

27. The projection display device of claim 9 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

28. The projection display device of claim 10 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

29. The projection display device of claim 11 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.

30. The projection display device of claim 12 , wherein:

at least one of the modulated light beams incident from different directions on the optical combiner is a modulated light beam that is linearly polarized and transmitted by the optical combiner; and

the transmittance of the optical combiner is greater for a light beam having the direction of linear polarization of the modulated light beam than for a light beam having a direction of linear polarization orthogonal to the direction of linear polarization of the modulated light beam.