Light source module

Abstract

A light source module includes a light-emitting element, a light guide, a waveplate, and a polarizer. The light-emitting element emits a light beam. The light guide includes a concave curved surface, an output surface, a first convex surface, and a second convex surface. The concave curved surface faces the light-emitting element. The output surface is opposite to the concave curved surface. The first convex surface connects the concave curved surface and the output surface. The second convex surface connects the concave curved surface and the output surface and is opposite to the first convex surface, wherein the light beam enters the light guide through the concave curved surface and exits the light guide through the output surface. The waveplate is disposed in the path of the light beam from the output surface. The polarizer is disposed in the path of the light beam from the waveplate.

Description

Technical Field

[0001] This invention relates to an optical module, and more particularly to a light source module. Prior Technology

[0002] With the development of display technology, projectors were created, which can form large images relative to the screen size. A liquid-crystal-on-silicon panel (LCOS panel) is a key component in a projector, converting the illumination beam into an image beam. However, LCOS panels are not self-emissive, therefore requiring a light source to illuminate them.

[0003] In traditional projectors, a polarizing beam splitter (PBS) is placed in front of the silicon-based liquid crystal panel to filter out beams with unwanted polarization directions. However, the polarizing beam splitter occupies a large space in front of the silicon-based liquid crystal panel, making the optical system overly bulky. Furthermore, when an unpolarized illumination beam propagates to the polarizing beam splitter, only half of the illumination beam is transmitted to the silicon-based liquid crystal panel, resulting in light loss. Summary of the Invention

[0004] This invention provides a light source module that can reduce the size of the optical system and reduce light loss.

[0005] An embodiment of the present invention provides a light source module including a light-emitting element, a light guide, a wave plate, and a polarizer. The light-emitting element is used to emit a light beam. The light guide includes a concave curved surface, an output surface, a first convex surface, and a second convex surface. The concave curved surface faces the light-emitting element. The output surface is opposite to the concave curved surface. The first convex surface connects the concave curved surface and the output surface. The second convex surface connects the concave curved surface and the output surface and is opposite to the first convex surface, wherein the light beam enters the light guide through the concave curved surface and exits the light guide through the output surface. The wave plate is disposed in the path of the light beam from the output surface. The polarizer is disposed in the path of the light beam from the wave plate and is used to allow a first portion of the light beam having a first polarization direction to pass through and reflect a second portion of the light beam having a second polarization direction. The second portion of the light beam passes through the wave plate and the output surface and re-enters the light guide, and then at least a portion of the second portion of the light beam is reflected by at least one of the concave curved surface, the first convex surface, and the second convex surface, thereby returning to the wave plate and the polarizer.

[0006] In the light source module of an embodiment of the present invention, a light guide including a concave curved surface, an output surface, a first convex surface, and a second convex surface is employed, and at least a portion of the second part of the light beam is reflected by at least one of the concave curved surface, the first convex surface, and the second convex surface, thereby propagating the echo plate and the polarizer. Therefore, light loss is reduced due to the light guide recycling, and the volume of the optical system is reduced and a compact structure can be achieved due to the use of the light guide. Simple Explanation of the Diagram

[0007] Figure 1 is a cross-sectional schematic diagram of a front-illuminated silicon-based liquid crystal module according to an embodiment of the present invention. Figure 2A is a rectangular candlestick pattern showing the distribution of the light beam emitted by the light-emitting element in Figure 1 before it passes through the concave curved surface. Figure 2B is a rectangular candlestick pattern showing the distribution of the light beam emitted by the light-emitting element in Figure 1 after passing through the concave curved surface. Figures 3A and 3B are schematic cross-sectional views of a light source module according to another embodiment of the present invention, showing two possible paths for the second part of the light beam, respectively. Figure 4 is a cross-sectional schematic diagram of a light source module according to another embodiment of the present invention. Implementation

[0008] Figure 1 is a schematic cross-sectional view of a front-lit liquid-crystal-on-silicon module according to an embodiment of the present invention. Referring to Figure 1, the front-lit liquid-crystal-on-silicon module 200 in this embodiment includes a light source module 100, a waveguide 220, a liquid crystal panel 230, and a polarizer 240. The light source module 100 includes a light-emitting element 110, a light guide 120, a waveplate 150, and a polarizer 160. The light-emitting element 110 is used to emit a light beam 111. In this embodiment, the light-emitting element 110 includes a plurality of light-emitting diodes (LEDs) 112 and a window plate 114 disposed on these LEDs 112. These LEDs 112 may include multiple LEDs having multiple emission colors. For example, these LEDs 112 may include red LEDs, green LEDs, and blue LEDs.

[0009] The light guide 120 includes a concave curved surface 124, an output surface 128, a first convex surface 122, and a second convex surface 126. The concave curved surface 124 faces the light-emitting element 110. The output surface 128 is opposite to the concave curved surface 124. In this embodiment, the output surface 128 is, for example, a planar surface. The first convex surface 122 connects the concave curved surface 124 and the output surface 128. The second convex surface 126 connects the concave curved surface 124 and the output surface 128 and is opposite to the first convex surface 122, wherein the light beam 111 enters the light guide 120 through the concave curved surface 124 and exits the light guide 120 through the output surface 128. In this embodiment, the light beam 111 emitted from the light-emitting diode 112 passes through the window plate 114 and reaches the concave curved surface 124. A waveplate 150 is disposed on the path of the light beam 111 from the output surface 128. A polarizer 160 is positioned in the path of the beam 111 from the waveplate 150, allowing a first portion 113 of the beam 111 with a first polarization direction P1 to pass through, and reflecting a second portion 115 of the beam 111 with a second polarization direction. In this embodiment, the second polarization direction is perpendicular to the first polarization direction P1. The second portion 115 of the beam 111 passes through the waveplate 150 and the output surface 128 and re-enters the light guide 120, whereby at least a portion of the second portion 115 is reflected by at least one of the concave curved surface 124, the first convex surface 122, and the second convex surface 126, thus propagating back to the waveplate 150 and the polarizer 160. In this embodiment, the waveplate 150 is a quarter-wave plate, and because the second portion 115 of the beam 111 returning to the polarizer 160 passes through the waveplate 150 twice, the polarization direction of the second portion 115 of the beam 111 becomes the first polarization direction P1. In this way, the second portion 115 of the light beam 111, having the first polarization direction P1, passes through the polarizer 160, and the second portion 115 of the light beam 111 is recycled, thus reducing light loss in the light source module 100. In one embodiment, the light source module 100 can recycle 30% of the light.

[0010] In the light source module 100 of this embodiment, a light guide 120 is employed, comprising a concave curved surface 124, an output surface 128, a first convex surface 122, and a second convex surface 126. At least a portion of the second part 115 of the light beam 111 is reflected by at least one of the concave curved surface 124, the first convex surface 122, and the second convex surface 126, thereby propagating the echo plate 150 and the polarizer 160. Therefore, light loss is reduced due to the light guide 120 circulating the light, and the size of the optical system (e.g., the front-illuminated silicon-based liquid crystal module 200) is reduced due to the use of the light guide 120, allowing for a compact structure. Furthermore, in this embodiment, the light guide 120 is used to reflect (e.g., by reflection from the concave curved surface 124) at least a portion of the second part 115 of the light beam 111 to prevent it from illuminating the light-emitting element 110. In this way, this portion of the second part 115 of the light beam 111 is not absorbed by the light-emitting element 110, further reducing light loss.

[0011] In one embodiment, the polarizer 160 is, for example, a wire grid polarizer film. The waveguide 220 has a first surface 222, a second surface 224 opposite to the first surface 222, and an incident surface 226 connecting the first surface 222 and the second surface 224, wherein a light beam 111 from the polarizer 160 enters the waveguide 220 via the incident surface 226. A silicon-based liquid crystal panel 230 is disposed below the second surface 224 to convert the light beam 111 having a first polarization direction P1 into a polarized image beam 231 having a second polarization direction P2. A polarizer 240 is disposed on the first surface 222 to allow the polarized image beam 231 having the second polarization direction P2 to pass through, wherein the polarized image beam 231 from the silicon-based liquid crystal panel 230 sequentially passes through the second surface 224, the first surface 222, and the polarizer 240. In this embodiment, the first polarization direction P1 is perpendicular to the second polarization direction P2.

[0012] In this embodiment, the front-illuminated silicon liquid crystal module 200 further includes a plurality of micromirrors 250 spaced apart along the first surface 222, for reflecting the light beam 111 onto the silicon liquid crystal panel 230. In one embodiment, each micromirror 250 is a polarizing beam splitter film, which is capable of reflecting the light beam 111 having a first polarization direction P1 and allowing the polarized image beam 231 having a second polarization direction P2 to pass through.

[0013] In this embodiment, the concave curved surface 124, the first convex surface 122, and the second convex surface 126 can be described using a one-dimensional polynomial. However, in another embodiment, the concave curved surface 124, the first convex surface 122, and the second convex surface 126 can be described using a two-dimensional polynomial. Alternatively, the concave curved surface 124, the first convex surface 122, and the second convex surface 126 can be described using mesh data. In this embodiment, the refractive index of the light guide 120 falls within the range of 1.3 to 2.3. Furthermore, in this embodiment, the light source module 100 also includes at least one coupling lens (two coupling lenses 130 and 140 are exemplarily shown in FIG. 1) disposed between the light guide 120 and the waveplate 150 to couple the light beam 111 to the waveplate 150. For example, each of the coupling lenses 130 and 140 is a lens array. However, in other embodiments, each of the coupling lenses 130 and 140 can be a single lens.

[0014] Figure 2A is a rectangular candlestick pattern of the light beam emitted by the light-emitting element in Figure 1 before passing through the concave curved surface, and Figure 2B is a rectangular candlestick pattern of the light beam emitted by the light-emitting element in Figure 1 after passing through the concave curved surface. In Figures 2A and 2B, the curves labeled 0.0, 45.0, 90.0, and 135.0 represent curves located in planes with directions of 0.0 degrees, 45.0 degrees, 90.0 degrees, and 135.0 degrees, respectively, where each plane contains the optical axis of the light-emitting element 110, and the plane with a direction of 0.0 degrees is the plane of Figure 1. As can be seen from Figures 2A and 2B, the light guide 120 is used to convert the light beam 111 emitted by the light-emitting element 110 from a Lambertian profile to a profile with two or more intensity peaks (two intensity peaks are exemplarily shown in Figure 2B).

[0015] Figures 3A and 3B are schematic cross-sectional views of a light source module according to another embodiment of the present invention, showing two possible paths for the second portion of the light beam. Referring to Figures 3A and 3B, the light source module 100a is similar to the light source module 100 in Figure 1, with the main differences as follows. In this embodiment, the light source module 100a further includes a first reflector 172 configured to face the first convex surface 122 and a second reflector 174 configured to face the second convex surface 126. The second portion 115 of the light beam 111 reflected by the polarizer 160 may have multiple possible loop paths; two paths are given as examples below, as shown in Figures 3A and 3B.

[0016] Referring to Figure 3A, the second portion 115 of the light beam 111 reflected by the polarizer 160 is sequentially reflected by the first convex surface 122, reflected by the concave curved surface 124, refracted by the first convex surface 122, diffusely reflected by the carrier plate 50 carrying the light-emitting element 110, refracted by the first convex surface 122, refracted twice by the concave curved surface 124, reflected by the second convex surface 126, and passes through the polarizer 160. Referring to Figure 3B, the second portion 115 of the light beam 111 reflected by the polarizer 160 is sequentially refracted by the first convex surface 122, reflected by the first reflector 172, refracted by the first convex surface 122, refracted twice by the concave curved surface 124, refracted by the second convex surface 126, reflected by the second reflector 174, refracted by the second convex surface 126, and passes through the polarizer 160. In other possible loop paths, the second portion 115 of the beam 111 may be reflected or refracted multiple times by the surface of the light guide 120, the first reflector 172, or the second reflector 174.

[0017] Figure 4 is a cross-sectional schematic diagram of a light source module according to another embodiment of the present invention. Referring to Figure 4, the light source module 100b in this embodiment is similar to the light source module 100 in Figure 1, with the main differences as follows. In the light source module 100 of this embodiment, the output surface 128b of the light guide 120b is a concave surface, thereby making the light guide 120b a hollow tube.

[0018] In summary, the light source module of the embodiments of the present invention employs a light guide comprising a concave curved surface, an output surface, a first convex surface, and a second convex surface. At least a portion of the second part of the light beam is reflected by at least one of the concave curved surface, the first convex surface, and the second convex surface, thereby propagating the echo plate and the polarizer. Therefore, light loss is reduced due to the light guide recirculating the light, and the volume of the optical system is reduced due to the use of the light guide, resulting in a compact structure.

[0019] 50: Carrier board 100, 100a, 100b: Light source modules 110: Light-emitting element 111: Beam 112: Light Emitting Diode 113: Part One 114: Window panel 115: Part Two 120, 120b: Light guide tube 122: First convex surface 124: Concave curved surface 126: Second convex surface 128, 128b: Output surface 130, 140: Coupler lenses 150: Wave plate 160: Polarizing film 172: First Reflector 174: Second Reflector 200: Front-illuminated silicon-based liquid crystal module 220: Waveguide 222: First Surface 224: Second Surface 226:Light incident surface 230: Silicon-based LCD panel 231: Image Beam 240: Polarizing film 250: Micromirror P1: First polarization direction P2: Second polarization direction

Claims

1. A light source module, comprising: Light-emitting elements, used to emit light beams; The light guide includes: a concave curved surface facing the light-emitting element; an output surface opposite the concave curved surface; a first convex surface connecting the concave curved surface and the output surface; and a second convex surface connecting the concave curved surface and the output surface and opposite the first convex surface, wherein the light beam enters the light guide via the concave curved surface and exits the light guide via the output surface; a waveplate disposed in the path of the light beam from the output surface; and a polarizer disposed in the path of the light beam from the waveplate and configured to allow a first portion of the light beam having a first polarization direction to pass through and reflect a second portion of the light beam having a second polarization direction, wherein the second portion of the light beam passes through the waveplate and the output surface and re-enters the light guide, and then at least a portion of the second portion of the light beam is reflected by at least one of the concave curved surface, the first convex surface, and the second convex surface, thereby propagating back to the waveplate and the polarizer.

2. The light source module as claimed in claim 1, wherein the concave curved surface, the first convex surface, and the second convex surface are described by a one-dimensional polynomial.

3. The light source module as claimed in claim 1, wherein the concave curved surface, the first convex surface, and the second convex surface are described by a two-dimensional polynomial.

4. The light source module as claimed in claim 1, wherein the light guide is used to convert the light beam emitted by the light-emitting element from a Lambertian distribution to a distribution of two or more intensity peaks.

5. The light source module as claimed in claim 1, wherein the light guide is used to reflect at least a portion of the second portion of the light beam to prevent it from illuminating the light-emitting element.

6. The light source module as claimed in claim 1, wherein the refractive index of the light guide tube is in the range of 1.3 to 2.

3.

7. The light source module as claimed in claim 1, wherein the output surface is a concave surface, thereby making the light guide tube a hollow tube.

8. The light source module as claimed in claim 1 further includes a first reflector configured to face the first convex surface and a second reflector configured to face the second convex surface.

9. The light source module as claimed in claim 1 further includes at least one coupling lens disposed between the light guide and the waveplate.

10. The light source module as claimed in claim 9, wherein the coupling lens is a lens array.

11. The light source module as claimed in claim 1, wherein the waveplate is a quarter-wave plate.

12. The light source module as claimed in claim 1, wherein the light-emitting element comprises a plurality of light-emitting diodes.

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