Optically efficient polarized projector

A pixel array display system which has an illumination source with a plurality of emitters in a sparse array, collimators in front of the emitters, a condenser lens downstream of the collimators, an optical homogenizing element downstream from the condenser lens, a relay lens downstream from the optical homogenizing element, a pixel array downstream from the relay lens, a rear group of lens elements of a projection lens downstream from the pixel array, a polarization converter stack downstream from the rear group of lens elements and a front group of lens elements of the projection lens downstream from the polarization converter stack, so that light from the emitters is imaged onto input apertures of the polarization converter stack.

FIELD OF THE INVENTION

This invention relates to the field of pixel array display systems. More particularly, this invention relates to optical systems in pixel array display systems.

BACKGROUND OF THE INVENTION

A pixel array display system may modulate light from an illumination source as a function of input image data for each pixel to produce a display. It may be desirable to provide modulated light from the pixel array which is linearly polarized, for example, to enable a three-dimensional (3D) display system which alternates polarization directions between frames. Common methods of providing polarized modulated light from a pixel array may be undesirably inefficient from an optical throughput standpoint. Adding a polarizer to a projection lens discards half of the modulated light, which may add cost and complexity to an illumination source of the display system. Providing a polarized illumination source may require all optical elements to maintain the polarization state of the illumination source, which may add cost and complexity to the optical elements. Additional background information is given in Destain U.S. Pub. No. US 2011/0298842 A1, entitled “Sparse Source Array for Display Pixel Array Illumination with Rotated Far Field Plane.”

SUMMARY OF THE INVENTION

A pixel array display system may have a spatially distributed multiple emitter discrete illumination source. It is not necessary for light from each emitter to have any specific state of polarization. A separate collimator is disposed in front of each emitter. Collimated light from each emitter is directed by a condenser lens, preferably in a telecentric configuration, onto an entrance surface of a light pipe or other optical homogenizing element. Light from the optical homogenizer is relayed onto a pixel array which spatially and temporally modulates the light. Modulated light from the pixel array is directed onto a polarization conversion stack, which has alternating first beamsplitter polarizers and second beamsplitter polarizers combined with polarization rotators, so that an image of the emitters of the illumination source is formed at entrance surfaces of the polarization conversion stack. Unpolarized light entering the first beamsplitter polarizers may be converted to polarized light. The emitters of the illumination source, the optical homogenizer and the polarization converter stack are configured so that substantially all of the light from the emitters is imaged onto the first beamsplitter polarizers. The display system may provide a polarized light output suitable for 3D display systems.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

A pixel array display system may have a spatially distributed multiple emitter discrete illumination source, referred to herein as a sparse source array. The emitters may be, for example, light emitting diodes (LEDs), lasers or high intensity discharge lamps, and may include integrator rods or optical fiber bundles. Each emitter may emit light of a single color or possibly multiple colors. It is not necessary for light from each emitter to have any specific state of polarization. A separate collimator is disposed downstream from each emitter. Collimated light from each emitter is directed by a condenser lens, preferably in a telecentric configuration, onto an entrance surface of a light pipe or other optical homogenizing element. Light from the optical homogenizer is relayed onto one or more pixel arrays which spatially and temporally modulates the light. Modulated light from the pixel array is directed onto a polarization conversion stack, which has alternating first beamsplitter polarizers and second beamsplitter polarizers combined with polarization rotators, so that an image of the emitters of the illumination source is formed at entrance surfaces of the polarization conversion stack. Unpolarized light entering the first beamsplitter polarizers may be converted to polarized light. The emitters of the illumination source, the optical homogenizer and the polarization converter stack are configured so that substantially all of the light from the emitters is imaged onto the first beamsplitter polarizers. The display system may provide a polarized light output suitable for 3D display systems.

For the purposes of this description, the term “substantially” as applied to structures and elements in a display system is understood to mean within tolerances which accrue during fabrication and operation of the display system. The terms “in front of” and “downstream from” as applied to a first optical element in a display system relative to a second optical element in the display system are understood to mean the first optical element is in an optical path of the display system and the first optical element is disposed to receive light from the second optical element during operation of the display system. The term “lens” is understood to mean an optical component which contains one or more lens elements.

FIG. 1depicts a pixel array display system formed according to an embodiment. The display system (100) has an illumination source (102) which includes a sparse array of emitters (104). The emitters (104) may be, for example, LEDs or lasers. The emitters (104) may include integrator rods, optical fibers or other optical elements which may increase a light emission area of the emitters (104).

In one version of the instant embodiment, every emitter (104) may emit light of a same color, for example red. In such a case, the display system (100) may include a second illumination source, not shown, with emitters which all emit light of a second color, for example, blue, and may further include a third illumination source, not shown, with emitters which all emit light of a third color, for example, green. Light from the illumination sources may be combined optically, for example with prism beamsplitters, not shown.

In another version of the instant embodiment, every instance of a first plurality of the emitters (104) may emit light of a first color, for example red, every instance of a second plurality of the emitters (104) may emit light of a second color, for example blue, and every instance of a third plurality of the emitters (104) may emit light of a third color, for example green. During operation of the display system (100), instances of the emitters (104) which emit the first color may be turned on during a first time period, while remaining emitters are not turned on during the first time period. Subsequently, instances of the emitters (104) which emit the second color may be turned on during a second time period, while remaining emitters are not turned on during the first second period, and similarly for instances of the emitters (104) which emit the third color.

In a further version of the instant embodiment, at least a portion of the emitters (104) may be operational to emit light of two or more colors, one color at a time. During operation of the display system (100), the emitters (104) may emit a first color during a first time period, a second color during a second time period, and so on.

In yet another version, the illumination source (102) may simultaneously provide light of more than one color, such as from a high intensity discharge lamp. The display system (100) may include a color wheel (144) disposed, for example, between the condenser lens (108) and the optical homogenizing element (112) so as to provide a single color of light to the pixel array (120).

A plurality of collimators (106) is disposed in front of the emitters (104) such that a separate collimator (106) is disposed in front of each emitter (104) so that light from each emitter (104) is collimated by a separate collimator (106). The collimators (106) are configured such that principal axes of the collimated light from each emitter (104) are substantially parallel to each other exiting the collimators (106). In one version of the instant embodiment, each collimator (106) may be disposed at a distance from its respective emitter (104) which is between70percent and130percent of a focal length of the collimator (106). The emitters (104) and collimators (106) are depicted in perspective inFIG. 1to more clearly indicate their spatial configuration.

A condenser lens (108) is disposed downstream from the collimators (106) at a first distance (110) which is between60percent and130percent of a focal length of the condenser lens (108). The collimated light from each emitter (104) is directed by the condenser lens (108) onto an entrance surface of an optical homogenizing element (112) such as a light pipe. The optical homogenizing element (112) is disposed downstream from the condenser lens (108). The entrance surface of the optical homogenizing element (112) is at a second distance (114) from the condenser lens (108) which is between 85 percent and 115 percent of a back focal length of the condenser lens (108). The optical homogenizing element (112) may have, for example, parallel sides and a rectangular optical cross section.

An optional source diaphragm (116) may be disposed in an optical path of the display system (100), for example between the collimators (106) and the condenser lens (108). An optional anamorphic lens element (118) may be disposed in an optical path of the display system (100), for example between the collimators (106) and the condenser lens (108). The anamorphic lens element (118) may provide a desired aspect ratio of the collimated light from the emitters (104).

Light from the exit surface of the optical homogenizing element (112) is directed through a relay lens (122), and possibly reflection/transmission prisms (124), onto one or more pixel arrays (120). The relay lens (122) is disposed downstream from the optical homogenizing element (112), and the pixel arrays (120) are disposed downstream from the relay lens (122). In versions of the instant embodiment with two or more pixel arrays (120), beamsplitter prisms (126) may be used to direct light to the pixel arrays (120), for example directing red light to a first pixel array (120), blue light to a second pixel array (120) and green light to a third pixel array (120).

The pixel arrays (120) spatially and temporally modulate the light from the relay lens (122) and direct it toward a pixel array output optical cone. A rear group of lens elements (128) of a projection lens directs the output optical cone onto a polarization converter stack (130) disposed downstream from the rear group of lens elements (128) of the projection lens.

The polarization converter stack (130) includes an array of pairs of adjacent polarizing beamsplitters (132). A first polarizing beamsplitter (132) of a pair provides an input aperture for incoming light into the polarization converter stack (130). A portion of the incoming light with a first polarization orientation is passed through the first polarizing beamsplitter (132) into a polarized output optical cone, with the first polarization orientation unchanged. A second portion of the incoming light into the polarization converter stack (130), having a second polarization orientation which is perpendicular to the first polarization orientation, is reflected by the first polarizing beamsplitter (132) to an adjacent second polarizing beamsplitter (132) of the pair. The second polarizing beamsplitter (132) reflects the second portion of the incoming light into a half wave plate (134) which rotates the polarization orientation of the second portion of the incoming light to the first polarization orientation and transmits the rotated second portion into the polarized output optical cone. Thus, both the first portion and the second portion of the incoming light are polarized in the first polarization orientation and transmitted into the polarized output optical cone.

Incoming light into the polarization converter stack (130) which directly enters the second polarizing beamsplitter (132) of the pair may be transmitted by the polarization converter stack (130) with the second polarization orientation. Maintaining substantially all the light in the polarized output optical cone with the first polarization orientation is accomplished by configuring the emitters (104) so as to be imaged onto the first polarizing beamsplitter (132) of each beamsplitter pair of adjacent polarizing beamsplitters (132). Exemplary configurations of the emitters (104) will be discussed in reference to subsequent figures.

The polarization converter stack (130) may further include an optional input mask (136) which reduces, by at least50percent, or blocks incoming light from directly entering the second polarizing beamsplitter (132) of each beamsplitter pair of adjacent polarizing beamsplitters (132). In one version of the instant embodiment, the input mask (136) may include metal thin film areas which are substantially opaque to block incoming light from directly entering the second polarizing beamsplitter (132) of each beamsplitter pair.FIG. 1depicts the input mask (136) spatially separated from the array of pairs of adjacent polarizing beamsplitters (132) to more clearly indicate the arrangement of the polarizing beamsplitters (132). The input mask (136) may directly contact the polarizing beamsplitters (132).

The polarized light from the polarization converter stack (130) passes through a front group of lens elements (138) of the projection lens disposed in front of the polarization converter stack (130). The front group of lens elements (138) may focus the light in the polarized output optical cone onto a display screen, not shown. The display system (100) may further include an optional cleanup polarizer (140) which may desirably increase a degree of polarization of the light in the polarized output optical cone. In an alternate version of the instant embodiment, the cleanup polarizer (140) may be disposed between the polarization converter stack (130) and the front group of lens elements (138) of the projection lens.

In versions of the instant embodiment used in 3D displays, the display system (100) may also include a polarization modulator (142), disposed downstream from the polarization converter stack (130), which may vary a polarization state of light from the polarization converter stack (130) in sequential frames. In one version of the instant embodiment, the polarization modulator (142) may be disposed in front of the front group of lens elements (138) of the projection lens. In an alternate version, the polarization modulator (142) may be disposed between the polarization converter stack (130) and the front group of lens elements (138) of the projection lens.

FIG. 2depicts a first exemplary configuration of a polarization converter stack which may be used in a pixel array display system formed according to an embodiment. The polarization converter stack (200) includes pairs of adjacent polarizing beamsplitters (202), configured in columns (204). The pairs (202) are outlined in a bold linewidth inFIG. 2to more clearly indicate their spatial configuration. Each beamsplitter pair (202) includes a first polarizing beamsplitter (208), labeled with a numeral “1” on an input aperture of the first polarizing beamsplitter (208). Each beamsplitter pair (202) also includes an adjacent second polarizing beamsplitter (210), laterally adjacent to the first polarizing beamsplitter (208), labeled with a numeral “2.” A polarization rotator plate, not shown, is disposed behind each instance of the second polarizing beamsplitters (210). In the instant embodiment, a vertical projection (212) of the principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the polarization converter stack (200) bisects an instance of the second polarizing beamsplitters (210) in one instance of the columns (206). A horizontal projection (214) of the principal axes of the homogenizing optical element is perpendicular to the vertical projection (212). The projections (212) and (214) of the principal axes are depicted with hatched lines. Emitters in an illumination source which are used with the polarization converter stack (200) of the instant embodiment are imaged onto the input aperture of the first polarizing beamsplitters (208), labeled with numeral “1.”

FIG. 3depicts a first spatial configuration of emitters in an illumination source which may be used, according to an embodiment, with the polarization converter stack discussed in reference toFIG. 2. The illumination source (300) includes a sparse array of emitters (302) which are disposed in populated columns (304) separated by empty columns (306). In the instant embodiment, a vertical projection (308) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the sparse array of emitters (302) bisects one instance of the empty columns (306). A horizontal projection (310) of the principal axes of the homogenizing optical element may, for example, bisect instances of the emitters (302). The projections (308) and (310) of the principal axes are depicted with hatched lines.

During operation of a pixel array display system, formed according to an embodiment and containing the illumination source (300), images of light from each emitter (302) will be reflected across the projections (308) and (310) of the principal axes so as to form columns of light which may be imaged onto the input aperture of the first polarizing beamsplitter (208) in each beamsplitter pair of adjacent polarizing beamsplitters (202) inFIG. 2. Configuring the sparse array of emitters (302) to image onto the input apertures of a polarization converter stack in the pixel array display system may provide an advantageous optical efficiency of conversion of light from the emitters (302) to a desired polarization orientation.

FIG. 4AandFIG. 4Bdepict a second spatial configuration of emitters in an illumination source which may be used, according to an embodiment, with the polarization converter stack discussed in reference toFIG. 2. Referring toFIG. 4A, the illumination source (400) includes a sparse array of emitters (402) which are disposed in offset populated columns (404) separated by empty columns (406). In the instant embodiment, a vertical projection (408) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the sparse array of emitters (402) bisects an instance of the empty columns (406). A horizontal projection (410) of the principal axes of the homogenizing optical element may, for example, bisect instances of the emitters (402). The projections (408) and (410) of the principal axes are depicted with hatched lines.

FIG. 4Bdepicts the horizontal reflections (412) of the emitters (402) across the vertical projection (408) of the principal axes after passing through the homogenizing optical element; the reflections are shown in hatched line inFIG. 4B. Reflection arrows (414) indicate correspondence between emitters (402) and horizontal reflections (412). Horizontal reflections (412) fill gaps in the populated columns (404) so as to provide light to the input aperture of the first polarizing beamsplitter (208) in each beamsplitter pair of adjacent polarizing beamsplitters (202) inFIG. 2. Vertical reflections (416) also occur, and may help to fill gaps in the populated columns (404).

FIG. 5AandFIG. 5Bdepict a third spatial configuration of emitters in an illumination source which may be used, according to an embodiment, with the polarization converter stack discussed in reference toFIG. 2. Referring toFIG. 5A, the illumination source (500) includes a sparse array of emitters (502) which are disposed in alternating emitter populated columns (504) and reflection populated columns (506) which are separated from each other by empty columns (508). In the instant embodiment, a vertical projection (510) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the sparse array of emitters (502) bisects an instance of the empty columns (508). A horizontal projection (512) of the principal axes of the homogenizing optical element may, for example, bisect instances of the emitters (502). The projections (510) and (512) of the principal axes are depicted with hatched lines.

FIG. 5Bdepicts the reflections (514) of the emitters (502) across the projections (510) and (512) of the principal axes after passing through the homogenizing optical element; the reflections (514) are shown in hatched line inFIG. 5B. Reflection arrows (516) indicate correspondence between emitters (502) and reflections (514). Reflections (514) fill gaps in the emitter populated columns (504) and fill in the reflection populated columns (506) so as to provide light to the input aperture of the first polarizing beamsplitter (208) in each beamsplitter pair of adjacent polarizing beamsplitters (202) inFIG. 2.

FIG. 6depicts a second exemplary configuration of a polarization converter stack which may be used in a pixel array display system formed according to an embodiment. The polarization converter stack (600) includes pairs of adjacent polarizing beamsplitters (602), configured in rows (604) and staggered columns (606). The pairs (602) are outlined in a bold linewidth inFIG. 6to more clearly indicate their spatial configuration. Each beamsplitter pair (602) includes a first polarizing beamsplitter (608), labeled with a numeral “1” on an input aperture of the first polarizing beamsplitter (608). Each beamsplitter pair (602) also includes an adjacent second polarizing beamsplitter (610), labeled with a numeral “2.” A half wave plate, not shown, is disposed behind each instance of the second polarizing beamsplitters (610). Configuring the beamsplitter pairs (602) in staggered columns (606) results in instances of the first polarizing beamsplitters (608) being laterally and vertically adjacent to instances of the second polarizing beamsplitters (610), and vice versa, so that the first polarizing beamsplitters (608) and the second polarizing beamsplitters (610) have a “checkerboard” pattern.

In the instant embodiment, a vertical projection (612) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the polarization converter stack (600) bisects instances of the first polarizing beamsplitters (608) and instances of the second polarizing beamsplitters (610) in one instance of the staggered columns (606). A horizontal projection (614) of the principal axes of the homogenizing optical element bisects instances of the first polarizing beamsplitters (608) and instances of the second polarizing beamsplitters (610) in one instance of the rows (604). The projections (612) and (614) of the principal axes of a homogenizing optical element, not shown, on the polarization converter stack (600) are depicted with hatched lines.

FIG. 7depicts a fourth spatial configuration of emitters in an illumination source, which may be used, according to an embodiment, with the polarization converter stack discussed in reference toFIG. 6. The illumination source (700) includes a sparse array of emitters (702) which are configured in a checkerboard pattern, so that each row (704) of emitters (702) and each column (706) of emitters (702) has alternating emitters (702) and empty spaces.

In the instant embodiment, a vertical projection (708) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the sparse array of emitters (702) bisects the emitters (702) in an instance of the columns (706). A horizontal projection (710) of the principal axes of the homogenizing optical element bisects the emitters (702) in an instance of the rows (704). The projections (708) and (710) of the principal axes meet in, and bisect, an empty space between emitters (702). The projections (708) and (710) of the principal axes are depicted with hatched lines.

During operation of a pixel array display system, formed according to an embodiment and containing the illumination source (700), images of light from each emitter (702) may be imaged onto the input aperture of the first polarizing beamsplitter (608) in each beamsplitter pair of adjacent polarizing beamsplitters (602) inFIG. 6. Configuring the sparse array of emitters (702) to image onto the input apertures of a polarization converter stack in the pixel array display system may provide an advantageous optical efficiency of conversion of light from the emitters (702) to a desired polarization orientation.

FIG. 8AandFIG. 8Bdepict a fifth spatial configuration of emitters in an illumination source which may be used, according to an embodiment, with the polarization converter stack discussed in reference toFIG. 6. Referring toFIG. 8A, the illumination source (800) includes a sparse array of emitters (802) which are disposed in staggered dual columns (804) separated by empty columns (806).

In the instant embodiment, a vertical projection (808) of principal axes of a homogenizing optical element, not shown, in the pixel array display system, on the sparse array of emitters (802) bisects a portion of the emitters (802) in an instance of the staggered dual columns (804). A horizontal projection (810) of the principal axes of the homogenizing optical element bisects instances of the emitters (802) and intersects the vertical projection (808) in an empty space between emitters (802). The projections (808) and (810) of the principal axes are depicted with hatched lines.

FIG. 8Bdepicts the reflections (812) of the emitters (802) across the vertical projection (808) of the principal axes after passing through the homogenizing optical element; the reflections are shown in hatched line inFIG. 8B. Reflection arrows (814) indicate correspondence between emitters (802) and reflections (812). Reflections (812) fill in the empty columns (806) so as to provide light to the input aperture of the first polarizing beamsplitter (608) in each beamsplitter pair of adjacent polarizing beamsplitters (602) inFIG. 6.

FIG. 9throughFIG. 14depict exemplary sparse emitter arrays which may be used in pixel array display systems according to embodiments. Referring toFIG. 9, an illumination source (900) includes an array of lasers (902) configured in a sparse array. An array of integrator rods (904) is disposed in front of the array of lasers (902), so that one integrator rod (904) is disposed in front of each laser (902) so as to provide a desired uniformity of light at an exit surface of the integrator rod (904). Exit surfaces (906) of the integrator rods (904) provide emitters for the illumination source (900). The integrator rods (904) are configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (900). The integrator rods (904) may be configured, for example, to provide a sparse array of emitters as described in reference toFIG. 3,FIG. 4A,FIG. 5A,FIG. 7orFIG. 8A. In one version of the instant embodiment, instances of the lasers (902) may emit different colors. For example, a first portion of the lasers (902) may emit red light, a second portion of the lasers (902) may emit blue light, and a third portion of the lasers (902) may emit green light, as depicted inFIG. 9. During operation of the display system containing the illumination source (900), instances of the lasers (902) emitting a same color may be turned on and off in sequence with instances of lasers (902) emitting a different color. In another version of the instant embodiment, all of the lasers (902) may emit light of substantially a same color.

Referring toFIG. 10, an illumination source (1000) includes an array of lasers (1002) which may be spatially configured independently of a desired illumination pattern at a polarization converter stack, not shown, in a pixel array display system containing the illumination source (1000). For example, the lasers (1002) may be spatially configured to provide a desired level of heat dissipation. Optical fibers (1004) are disposed in front of the lasers (1002) so that at least one optical fiber (1004) is disposed in front of each laser (1002). Instances of the optical fibers (1004) may be single optical fibers or may include bundles of optical fibers. The optical fibers (1004) are configured so as to collect light emitted from the lasers (1002) with a desired level of optical efficiency. In one version of the instant embodiment, exit surfaces (1006) of the optical fibers (1004) may provide emitters for the illumination source (1000). The exit surfaces (1006) of the optical fibers (1004) are spatially configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (1000).

In another version, the optical fibers (1004) are further configured so that the exit surfaces (1006) of the optical fibers (1004) provide light from the lasers (1002) to integrator rods (1008) disposed in front of the exit surfaces (1006) of the optical fibers (1004). Exit surfaces (1010) of the integrator rods (1008) provide emitters for the illumination source (1000). The exit surfaces (1010) of the integrator rods (1008) are spatially configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (1000).FIG. 10depicts a single column of lasers to more clearly indicate the spatial configuration of the lasers (1002), the optical fibers (1004) and the integrator rods (1008).

The illumination source (1000) may be configured, for example, to provide a sparse array of emitters as described in reference toFIG. 3,FIG. 4A,FIG. 5A,FIG. 7orFIG. 8A. In one version of the instant embodiment, instances of the lasers (1002) may emit different colors. For example, a first portion of the lasers (1002) may emit red light, a second portion of the lasers (1002) may emit blue light, and a third portion of the lasers (1002) may emit green light, as depicted inFIG. 10. During operation of the display system containing the illumination source (900), instances of the lasers (1002) emitting a same color may be turned on and off in sequence with instances of lasers (1002) emitting a different color. In another version of the instant embodiment, all of the lasers (1002) may emit light of substantially a same color.

Referring toFIG. 11, an illumination source (1100) includes a first plurality of lasers (1102). A first plurality of optical fibers (1104) is disposed in front of the first plurality of lasers (1102) so that at least one optical fiber (1104) is disposed in front of each laser (1102). Instances of the optical fibers (1104) may be single optical fibers or may include bundles of optical fibers. The optical fibers (1104) are configured so as to collect light emitted from the lasers (1102) with a desired level of optical efficiency. The optical fibers (1104) are further configured so that exit surfaces (1106) of the first plurality of optical fibers (1104) provide light from the first plurality of lasers (1102) to a first integrator rod (1108), disposed in front of the exit surfaces (1106) of the first plurality of optical fibers (1104), with a desired level of optical efficiency. An exit surface (1110) of the first integrator rod (1108) provides a first emitter in a sparse array of emitters of the illumination source (1100).

The illumination source (1100) further includes a second plurality of lasers (1112), a second plurality of optical fibers (1114) and a second integrator rod (1116), similarly configured, so that an exit surface (1118) of the second integrator rod (1116) provides a second emitter in the sparse array of emitters of the illumination source (1100). The illumination source (1100) may include additional pluralities of lasers, optical fibers and integrator rods, not shown, which provide additional emitters in the sparse array of emitters.

In one version of the instant embodiment, instances of the lasers in the first plurality of lasers (1102) may emit different colors, and instances of the lasers in the second plurality of lasers (1112) may also emit different colors. For example, a first portion of the first plurality of lasers (1102) may emit red light, a second portion of the first plurality of lasers (1102) may emit blue light, and a third portion of the first plurality of lasers (1102) may emit green light, and a first portion of the second plurality of lasers (1112) may emit red light, a second portion of the second plurality of lasers (1112) may emit blue light, and a third portion of the second plurality of lasers (1112) may emit green light, as depicted inFIG. 11. During operation of the display system containing the illumination source (1100), instances of the lasers (1102) emitting a same color may be turned on and off in sequence with instances of lasers (1102) emitting a different color.

In another version of the instant embodiment, all the lasers (1102) in the first plurality of lasers (1102) may emit light of a first color, for example red, and all the lasers (1112) in the second plurality of lasers (1112) may emit light of a second color, for example blue, and so on for additional pluralities of lasers. During operation of the display system containing the illumination source (1100), instances of the lasers (1102) emitting a same color may be turned on and off in sequence with instances of lasers (1102) emitting a different color.

In a further version of the instant embodiment, all the lasers (1102) in the first plurality of lasers (1102) and all the lasers (1112) in the second plurality of lasers (1112), and additional pluralities of lasers in the illumination source (1100), may emit light of a same color.

Referring toFIG. 12, an illumination source (1200) includes an array of LEDs (1202) which may be spatially configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (1200). The illumination source (1200) may be configured, for example, to provide a sparse array of emitters as described in reference toFIG. 3,FIG. 4A,FIG. 5A,FIG. 7orFIG. 8A. In one version of the instant embodiment, instances of the LEDs (1202) may emit different colors. For example, a first portion of the LEDs (1202) may emit red light, a second portion of the LEDs (1202) may emit blue light, and a third portion of the LEDs (1202) may emit green light. During operation of the display system containing the illumination source (900), instances of the LEDs (1202) emitting a same color may be turned on and off in sequence with instances of LEDs (1202) emitting a different color. In another version of the instant embodiment, all of the LEDs (1202) may emit light of substantially a same color.

Referring toFIG. 13, an illumination source (1300) includes a high intensity arc discharge lamp (1302) and a reflector (1304) which direct light of multiple colors into an array of fiber optics (1306). Exit surfaces (1308) of the optical fibers (1306) may provide emitters for the illumination source (1300). The exit surfaces (1308) of the optical fibers (1306) are spatially configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (1300).

Referring toFIG. 14, an illumination source (1400) includes a first array of emitters (1402) which emit light of a first color, for example, red, a second array of emitters (1404) which emit light of a second color, for example, green, and a third array of emitters (1406) which emit light of a third color, for example, blue. The first array of emitters (1402), the second array of emitters (1404), and the third array of emitters (1406) are disposed around a crossed dichroic filter (1408) which includes a first dichroic filter element (1410) and a second dichroic filter element (1412). A condenser lens (1414) is disposed in front of the crossed dichroic filter (1408). During operation of a display system containing the illumination source (1400), light from the first array of emitters (1402) is transmitted through the first dichroic filter element (1410) and reflected off the second dichroic filter element (1412) into the condenser lens (1414). Light from the second array of emitters (1404) is transmitted through the first dichroic filter element (1410) and transmitted through the second dichroic filter element (1412) into the condenser lens (1414). Light from the third array of emitters (1406) is transmitted through the second dichroic filter element (1412) and reflected off the first dichroic filter element (1410) into the condenser lens (1414). Each of the first array of emitters (1402), the second array of emitters (1404), and the third array of emitters (1406) are spatially configured so as to provide a desired light pattern on a polarization converter stack, not shown, in a display system containing the illumination source (1400).

It will be recognized that the emitters described in reference toFIG. 9throughFIG. 14may have square, rectangular, circular, ellipsoidal, hexagonal, octagonal or other shapes.