Image projecting device and method

• US 20060018025A1
• Filed: 07/08/2005
• Published: 01/26/2006
• Est. Priority Date: 01/08/2003
• Status: Active Grant

• Current Assignee: Explay Ltd.
• Original Assignee: Explay Ltd.
• Inventors: Zalevsky, Zeev, Manor, Golan, Kapellner, Yuval, Sharon, IIan
• Granted Patent: US 7,746,559 B2
• Time in Patent Office: Days
• US Class Current: 359/618
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161
• 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

An image projecting device and method are presented. The device comprises a light source system, a spatial light modulator (SLM) unit, and an image projection optics accommodated at the output side of the SLM unit. The SLM unit may be reflective or transmissive. The SLM unit comprises an SLM pixel arrangement enclosed between two glass substrates. The pixel array arrangement is formed by a pixel array assembly and at least one microlens assembly. The microlens assembly includes at least one microlens array accommodated proximate of the pixel array assembly. The light source system may comprise n light sources and a light converting means in optical path of light generated by the n light sources, to thereby produce m light beams of different wavelength ranges, wherein m>n. The light source system may comprise a multi-mode laser, thereby reducing a speckle effect in an integrated speckle pattern produced by the multiple modes, as compared to that of a single mode.

Claims

1. An image projecting device comprising a light source system, a spatial light modulator (SLM) unit, and an image projection optics accommodated at the output side of the SLM unit, the device being characterized in at least one of the following:

(i) said SLM unit includes a pixel array arrangement in the form of a multi-layer structure defining a pixel array assembly and at least one microlens assembly enclosed between two substrates, the microlens assembly including at least one microlens array accommodated proximate of the pixel array assembly at least upstream thereof with respect to a direction of propagation of light from the light source system towards the SLM unit, and operating to condense and focus incident light onto the pixel array;

(ii) said SLM unit including a pixel array assembly and a microlens assembly, the microlens assembly having first and second microlens arrays accommodated in a spaced-apart parallel relationship at least upstream of the pixel array assembly with respect to a direction of propagation of light from the light source system towards the SLM unit, the lenses of said second array located closer to the pixel array assembly being smaller or having different focal length than those of the first array, the lenslet assembly thereby condensing and focusing the incident light to impinge in form of a plurality of parallel light components onto a plurality of pixels, respectively;

(iii) the light source system comprises n light sources and a light converting means in optical path of light generated by the n light sources to thereby produce m light beams of different wavelength ranges, wherein m>

n;

(iv) the light source system comprises a multi-mode laser, thereby reducing a speckle effect in an integrated speckle pattern produced by the multiple modes, as compared to that of a single mode;

(v) the light source system comprises at least one highly polarized light source and a randomly polarized light source.

2. The device of claim 1, wherein the microlens assembly is located within a polymer spacer between the substrate and the pixel assembly.

3. The device of claim 2, wherein the polymer structure is a multi-layer structure.

4. The device of claim 3, wherein the microlens array is defined as a surface relief at an interface between two polymer layers.

5. The device according to claim 1, wherein said SLM unit is of a reflective type and comprises a polarization beam splitter/combiner.

6. The device according to claim 1(ii), wherein the first and second microlens arrays at the same side of the pixel array assembly are spaced from each other a distance equal to a sum of focal lengths of the lenses of the first and second lens arrays.

7. The device according to claim 1, wherein the incident light impinging on to the pixel array arrangement is specifically polarized, the device comprising a polarizer unit accommodated at the output side of the pixel arrangement and having a preferred orientation of a plane of polarization so as to be either substantially the same as of the incident light beam or a 90-degree rotated with respect to that of the incident light beam.

8. The device according to claim 5, wherein the light source system includes at least one high-ratio polarized light source.

9. The device according to claim 7, having one of the following configurations:

(a) the light source system includes at least one high-ratio polarized light source;

(b) an input polarizer is provided at the input side of the pixel arrangement.

10. The device according to claim 1, wherein the light source system comprises an optical arrangement operable to provide substantially uniform intensity distribution within the cross-section of the incident light beam.

11. The device according to claim 10, wherein said optical arrangement includes a diffractive element operable to modify the beam intensity distribution to produce the substantially uniform intensity distribution of the beam within its cross-section.

12. The device according to claim 1 wherein the light source system includes a beam expander affecting the cross section of a light beam generated by the light source system to provide the cross section of the beam substantially of the size of an active surface of the SLM pixel arrangement.

13. The device according to claim 1, wherein the light source system includes a light source generating a light beam of the cross section substantially of the size of the active surface of the SLM pixel arrangement.

14. The device according to claim 1(i), wherein the microlens assembly comprises first and second similar microlens arrays having one of the following configurations:

(a) said first and second similar microlens arrays are configured at opposite sides of the pixel array assembly, respectively, such that each lens in the first array is associated with a corresponding pixel of the pixel array and with the corresponding lens in the second array, each lens being substantially of the pixel size; and

(b) said first and second similar microlens arrays are configured in a spaced-apart parallel relationship upstream of the pixel array assembly, the lenses of the second array located closer to the pixel array assembly being smaller or having different focal length than those of the first lens array.

15. The device according to claim 1(ii), wherein the lenses of the second array closer to the pixel array are substantially of the pixel size.

16. The device according to claim 1(ii), wherein the SLM unit is transmissive, and said pixel arrangement comprises an additional microlens assembly formed by an additional pair of microlens arrays accommodated in a spaced-apart parallel relationship at the opposite side of the pixel array assembly.

17. The device of claim 16, wherein the two pairs of the microlens arrays are oriented substantially symmetrically identical with respect to the pixel assembly;

or oriented substantially identical to each other.

18. The device according to claim 16, wherein the lenses of the array closer to the pixel array assembly are substantially of the pixel size.

19. The device of claim 17, wherein the microlens arrays at one side of the pixel assembly face each other by their convex surfaces.

20. The device of claim 17, wherein the microlens arrays at one side of the pixel assembly face the respective substrate of the SLM unit by their convex surfaces and face the pixel assembly by their substantially planar surfaces;

and the microlens arrays at the other side of the pixel assembly face the pixel assembly by their convex surfaces and face the other substrate by their substantially planar surfaces.

21. The device according to claim 1, wherein the light source system is configured and operable to produce several light beams of several different wavelength ranges, the device being configured for projecting a colored image, and having one of the following configurations:

(a) comprises a wavelength-selective periscope structure allowing transparency for given wavelengths and reflecting other wavelengths, accommodated between the light source system and the SLM unit;

(b) comprises additional SLM units, each in the optical path of the corresponding one of said light beams, and a wavelength combiner accommodated in the optical paths of modulated light beams emerging from the SLM units.

22. The device according to claim 21, wherein the light source system comprises several light sources for generating, respectively, said several light beams of different wavelength ranges.

23. The device according to claim 22, wherein at least some of said light sources are highly polarized light sources.

24. The device according to claim 21, wherein said light source system comprises n light sources and a light converting means to thereby produce m light beams of different wavelength ranges, wherein m>

n.

25. The device according to claim 24, wherein the light source system has one of the following configurations:

(a) comprises a laser diode emitting a light beam of the non-visible range, said light converting means comprising a splitter assembly for splitting said emitted light beam into at least two spatially separated light components, at least two crystals accommodated so as to be pumped by said at least two light components to produce two light beams, respectively, of different wavelengths and different from those of the pumping light components, and an assembly operable apply harmonic generation to said two light beams, to thereby produce two light outputs of different wavelengths in the visible range;

(b) comprises a laser diode emitting a light beam including at least two light components of different wavelengths within the non-visible range, said light converting means comprising a splitter assembly for spatially separating said at least two light components of the emitted light beam and an assembly operable to apply second harmonic generation to said at least two light components, to thereby produce at least two light outputs of different wavelengths in the visible range.

26. The device according to claim 25, wherein said splitter assembly has one of the following configurations:

comprises a beam splitter and a mirror;

or comprises an optical switch.

27. The device according to claim 25, wherein said assembly operable to apply harmonic generation comprises at least two crystals.

28. The device according to claim 24, wherein the light source system comprises at least one LED.

38. The method of claim 27, wherein the first and second microlens assemblies are oriented substantially symmetrically identical with respect to the pixel assembly, or oriented substantially identical with respect to each other.

39. The method of claim 38, wherein the microlens arrays at one side of the pixel assembly face each other by their convex surfaces.

40. The method of claim 38, wherein the microlens arrays at one side of the pixel assembly face the respective substrate of the SLM unit by their convex surfaces and face the pixel assembly by their substantially planar surfaces;

and the microlens arrays at the other side of the pixel assembly face the pixel assembly by their convex surfaces and face the other substrate by their substantially planar surfaces.

29. A method for projecting an image comprising:

creating at least one incident light beam having a predetermined cross section corresponding to a size of an active surface of a spatial light modulator (SLM) unit defined by its pixel array assembly, and directing the incident light towards the pixel array assembly;

operating the pixel assembly with an imaging signal representative of an image to be projected, thereby causing modulation of the light passing through the pixel assembly;

passing the modulated light through an image projecting optics to a projecting surface;

the method comprising;

(a) passing said incident light beam, while propagating towards the pixel array assembly inside the SLM unit, and the modulated light, while propagating from the pixel array assembly inside the SLM unit, through at least one microlens array that condenses and focuses a plurality of light components of the incident light to the centers of a plurality of said pixels, respectively, and converts the condensed beams of the modulated light the pixel array assembly into substantially parallel beams;

(b) said incident light beam, propagating towards the pixel array assembly, passes through first and second microlens arrays accommodated in a spaced-apart parallel relationship, wherein the lenses of said second array located closer to the pixel array assembly are smaller or have different focal length than those of the first array, the incident light being thereby condensed and focused to impinge onto a plurality of pixels in form of a plurality of parallel light components, respectively;

(c) m light beams of different wavelength ranges are created by a light source system including n light sources and a light converting means in optical path of light generated by the n light sources, wherein m>

n;

(d) a speckle effect in a projected image is reduced by using a multi-mode laser for the creation of said at least one incident light beam.

(e) a colored image is projected by creating the incident light beams of different wavelength ranges by at least one-highly polarized light source and a randomly-polarized light source.

30. The method of claim 29, wherein said passing of the incident and modulated light through at least one microlens assembly comprises providing said at least one microlens assembly within a pixel array arrangement of the SLM unit such that said at least one microlens assembly is made in a polymer spacer between the pixel assembly and a glass substrate of the SLM unit.

31. The method according to claim 29, comprising passing the incident light beam propagating towards the SLM pixel arrangement and the reflected modulated light emerging from the SLM pixel arrangement, through a polarization beam splitter.

32. The method according to claim 29, wherein the first and second microlens arrays are spaced from each other a distance equal to a sum of focal lengths of the lenses of the first and second lens arrays.

33. The method according to claim 29, comprising providing specific polarization of the incident light, and passing the modulated light emerging from the SLM pixel arrangement through a polarizer having a preferred orientation of a plane of polarization so as to be either substantially the same as of the incident light beam or a 90-degree rotated with respect to that of the incident light beam.

34. The method according to claim 29, comprising providing substantially uniform intensity distribution within a cross-section of the incident light beam.

35. The method according to claim 29, wherein said incident and modulated light pass through, respectively, first and second similar microlens arrays at opposite sides of the pixel array assembly, respectively, such that each lens in the first array is associated with a corresponding pixel of the pixel array and with the corresponding lens in the second array, each lens being substantially of the pixel size.

36. The method according to claim 29, wherein said incident and modulated light pass through first and second microlens arrays accommodated in a spaced-apart parallel relationship upstream of the pixel array assembly with respect to a direction of propagation of the incident light, the lenses of the second array located closer to the pixel array assembly being smaller or having different focal length than those of the first lens array.

37. The method according to claim 29, wherein the SLM unit is transmissive, the incident and modulated light passing through, respectively, the first microlens assembly formed by first and second microlens arrays accommodated in a spaced-apart parallel relationship upstream of the pixel array assembly with respect to a direction of propagation of the incident light, and a second microlens assembly formed by first and second microlens arrays accommodated in a spaced-apart parallel relationship downstream of the pixel array assembly.

41. The method according to claim 29, providing for projecting a colored image, the method comprising producing several incident light beams of several different wavelength ranges, and passing these light beams, on their ways to the SLM pixel arrangement, through a wavelength-selective periscope structure allowing transparency for given wavelengths and reflecting other wavelengths.

42. The method according to claim 29, providing for projecting a colored image, the method comprising producing several light beams of several different wavelength ranges, passing these light beams through the SLM units, respectively, and passing the modulated light beams through a wavelength combiner.

43. The method according to claim 42, wherein at least some of said light beams are highly polarized light beams.

44. The method according to claim 29(c), wherein said producing of m light beams by n light sources comprises emitting a light beam of the non-visible range, and converting said light beam into at least two light beams of different wavelengths in the visible range.

45. The method according to claim 44, wherein said converting comprises splitting said emitted light beam into at least two spatially separated light components for pumping at least two laser crystals, respectively, to thereby produce two light beams, respectively, of different wavelengths and different from those of the pumping light components, and applying harmonic generation to said two light beams to produce two light outputs of different wavelengths in the visible range.

46. The method according to claim 44, wherein said emitted light beam includes at least two light components of different wavelengths within the non-visible range, said converting comprises spatially separating said at least two light components of the emitted light beam and applying second harmonic generation to said at least two light components, to thereby produce at least two light outputs of different wavelengths in the visible range.

47. The method according to claim 29(d), wherein the speckle effect in the projected image is reduced by sequentially pulsing the laser light source while creating the incident light beam, such that independent speckle patterns of the pulses result in an integrated speckle pattern of the projected image that is time averaged by a human eye faster than the human eye sensitivity.

48. A spatial light modulator (SLM) for use in an image projecting device, the SLM comprising two spaced-apart substrates enclosing therebetween a multi-layer structure configured to define a pixel array arrangement formed by a pixel array assembly and at least one microlens assembly at either side of the pixel assembly, the microlens assembly including at least one microlens array spaced from the pixel array assembly a predetermined distance to thereby condense and focus incident light such that substantially the entire incident light impinge onto an active pixel area of the pixel array assembly.

49. The SLM according to claim 48, comprising a polymer spacer between the substrate and the pixel array assembly, the microlens assembly being made in said polymer spacer.

50. The SLM according to claim 49, wherein the polymer spacer is a multi-layer structure, said microlens assembly being made as a surface relief at an interface between two polymer layers.

51. The SLM according to claim 48, wherein said microlens assembly comprises first and second microlens arrays accommodated in a spaced-apart parallel relationship at one side of the pixel array assembly, the lenses of said second array located closer to the pixel array assembly being smaller or having different focal length than those of the first array, the incident light being thereby condensed and focused to impinge onto a plurality of pixels in form of a plurality of parallel light components, respectively.