Projection display device

Abstract

A projection display device (100) according to the present embodiment comprises: a light source (101); a reflective liquid crystal display element (106) that is disposed in the light path of light emitted from the light source (101) and optically modulates the light on the basis of image data; a polarizing plate (105) that is disposed at an incline with respect to the light path of the light incident on the liquid crystal display element (106), transmits p-polarized light (L1), and reflects s-polarized light (L2); and a projection optical system (109) that projects, onto a projection surface, the s-polarized light (L2) optically modulated by the liquid crystal display element (106) and reflected by the polarizing plate (105). The projection display device (100) additionally comprises a focusing lens (110) that focuses the light emitted from the light source (101), and an open reflecting plate (111) that is disposed in the light path between the focusing lens (110) and the polarizing plate (105), has a light-reflecting surface (111b) on the polarizing plate (105) side, and has an opening (111a) provided therein at the focal point (F) of the focusing lens (110).

Description

Projection display device

[0001] The present disclosure relates to a projection display device using a liquid crystal display element.

[0002] In general, projection display devices using reflective liquid crystal display elements are known (see, for example, Patent Document 1). In this type of projection display device, for example, after laser light emitted from a light source is split into red, blue, and green color lights, an image obtained by modulating each of these color lights by a reflective liquid crystal display element is enlarged and projected onto a screen.

[0003] Japanese Unexamined Patent Publication No. 2005-227485

[0004] Incidentally, in each pixel of a liquid crystal display element, the alignment of liquid crystal molecules changes depending on an applied voltage, so that the liquid crystal layer functions as a phase plate. For this reason, by controlling the applied voltage to each pixel in accordance with image data, the liquid crystal display element has white pixels that reflect light incident in a first polarization state in a second polarization state obtained by rotating the polarization direction by 90 degrees, and black pixels that reflect light incident in the first polarization state without changing the polarization direction, thereby forming an image pattern including these. In this configuration, among the light emitted from the light source, the light in the first polarization state reflected by the black pixels of the liquid crystal display element returns to the light source side again and is not used as projection light, so there was room for improvement in the utilization efficiency of light source light.

[0005] In view of the above problems, an object of the present disclosure is to provide a projection display device that improves the utilization efficiency of light source light.

[0006] A projection display device according to one aspect of the present disclosure includes: a light source; a reflective liquid crystal display element disposed in an optical path of light emitted from the light source, which optically modulates the light based on image data; a polarizing element disposed obliquely with respect to the optical path of the light incident on the liquid crystal display element, which transmits the light in a first polarization state and reflects the light in a second polarization state; a projection optical system that projects the light optically modulated by the liquid crystal display element and reflected by the polarizing element onto a projection surface; a condensing optical element that condenses the light emitted from the light source; and a reflective optical element disposed in the optical path of the light between the condensing optical element and the polarizing element, having a light reflecting surface on the polarizing element side, and having an opening provided at a condensing focal point of the condensing optical element.

[0007] According to this embodiment, the light-reflecting surface of the reflective optical element reflects light in the first polarization state, thereby improving the utilization efficiency of the light source.

[0008] Figure 1 is a schematic diagram of a projection display device according to this embodiment. Figure 2 is a schematic diagram illustrating the optical path of light in the second polarization state reflected by the white pixels of the liquid crystal display element. Figure 3 is a schematic diagram of an aperture reflector showing how light focused by a condensing lens passes through the opening. Figure 4 is a schematic diagram illustrating the optical path of light in the first polarization state reflected by the black pixels of the liquid crystal display element. Figure 5 is a schematic diagram of an aperture reflector showing how the reflected light in the first polarization state is irradiated onto the light-reflecting surface 111b. Figure 6 is a schematic diagram showing how focused light passes through the mechanism of an aperture reflector according to another embodiment. Figure 7 is a schematic diagram showing how light is reflected by the light-reflecting surface of the aperture reflector in Figure 6.

[0009] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, the embodiments described below will not limit this disclosure.

[0010] (Configuration of the projection display device) Figure 1 is a schematic diagram of the projection display device according to this embodiment. The projection display device is a display device that decomposes light (for example, laser light) emitted from a light source into red, blue, and green light, and then modulates each of these colors of light to display an image that is synthesized. As shown in Figure 1, the projection display device 100 according to this embodiment includes a light source 101, lenses 104R, 104G, 104B, polarizing plates (polarizing elements) 105R, 105G, 105B, liquid crystal display elements 106R, 106G, 106B, a color synthesis prism 108, a projection lens (projection optical system) 109, dichroic mirrors 121 to 122, reflective mirrors 131 to 132, illumination optical system 150, a focusing lens (focusing optical element) 110, an aperture reflector (reflecting optical element) 111, a collimator lens 112, and a diffuser plate (diffusion element) 113. If lenses 104R, 104G, and 104B are not distinguished, they shall be referred to as lens 104. Similarly, if polarizers 105R, 105G, and 105B are not distinguished, they shall be referred to as polarizer 105, and if liquid crystal display elements 106R, 106G, and 106B are not distinguished, they shall be referred to as liquid crystal display element 106.

[0011] Light source 101 is a light source that generates and emits light. Light source 101 emits light source L0. In this embodiment, three laser light sources are used as the light sources that emit the light source L0. Note that light source 101 may also be configured to use other optical devices (for example, LED light sources) to generate the light source L0.

[0012] Light L0 from the light source 101 is incident on the illumination optical system 150 through a focusing lens 110, an aperture reflector 111, a collimator lens 112, and a diffuser plate 113. This illumination optical system 150 illuminates by distributing the light source light with a uniform intensity distribution and includes a first fly-eye lens 151, a second fly-eye lens 152, a polarization conversion element 153, and a condenser lens 154.

[0013] The first fly-eye lens 151 and the second fly-eye lens 152 each have a plurality of first microlenses 151A and second microlenses 152A arranged in a matrix. There is a one-to-one correspondence between the plurality of first microlenses 151A of the first fly-eye lens 151 and the plurality of second microlenses 152A of the second fly-eye lens 152. The polarization conversion element 153 has, for example, a polarization beam splitter and a phase difference plate, and converts the s-polarized light (light in the second polarization state) of the light source light L0 that has passed through the plurality of second microlenses 152A to p-polarized light (light in the first polarization state), thereby aligning the light source light L0 to p-polarized light. The condenser lens 154 superimposes the light emitted from each of the polarization conversion units into a single light beam and irradiates the dichroic mirror 121 with it.

[0014] The dichroic mirror 121 separates the light source L0 into blue illumination light BL and yellow illumination light YL. The yellow illumination light YL separated by the dichroic mirror 121 is reflected by the reflective mirror 131 and incident on the dichroic mirror 122.

[0015] The dichroic mirror 122 uses a wavelength intermediate between the red and green light bands as a separation boundary, separating the incident yellow illumination light YL into red illumination light RL containing a component in the red band and green illumination light GL containing a component in the green band. Specifically, the dichroic mirror 122 reflects the green band component of the incident yellow illumination light YL to emit green illumination light GL, and transmits the red band component of the incident yellow illumination light YL to emit red illumination light RL.

[0016] The red illumination light RL separated by the dichroic mirror 122 is irradiated onto the polarizer 105R via the lens 104R. The green illumination light GL separated by the dichroic mirror 122 is irradiated onto the polarizer 105G via the lens 104G. The blue illumination light BL separated by the dichroic mirror 121 is reflected by the reflective mirror 132 and irradiated onto the polarizer 105B via the lens 104B.

[0017] The polarizing plates 105R, 105G, and 105B are arranged at an angle to the optical path of the illumination light incident on the liquid crystal display elements 106R, 106G, and 106B, respectively, and have the characteristic of reflecting either s-polarized light or p-polarized light and transmitting the other. In the example in Figure 1, the polarizing plates 105R, 105G, and 105B are shown to reflect s-polarized light (light in the second polarization state) and transmit p-polarized light (light in the first polarization state). The polarizing plates 105R, 105G, and 105B are, for example, wire grid polarizing plates.

[0018] The p-polarized red illumination light RL passes through the polarizing plate 105R and irradiates the liquid crystal display element 106R. The p-polarized green illumination light GL passes through the polarizing plate 105G and irradiates the liquid crystal display element 106G. The p-polarized blue illumination light BL passes through the polarizing plate 105B and irradiates the liquid crystal display element 106B. The liquid crystal display elements 106R, 106G, and 106B have a structure in which, for example, a liquid crystal layer is sandwiched between a silicon substrate and a glass substrate, and are provided corresponding to each color, as described later.

[0019] Liquid crystal display element 106R optically modulates p-polarized red illumination light RL based on image data of the red component to generate s-polarized red image light RM. Liquid crystal display element 106G optically modulates p-polarized green illumination light GL based on image data of the green component to generate s-polarized green image light GM. Liquid crystal display element 106B optically modulates p-polarized blue illumination light BL based on image data of the blue component to generate s-polarized blue image light BM.

[0020] The red image light RM, which is s-polarized light generated by the liquid crystal display element 106R, is reflected by the polarizer 105R and irradiated onto the color synthesis prism 108. The green image light GM, which is s-polarized light generated by the liquid crystal display element 106G, is reflected by the polarizer 105G and irradiated onto the color synthesis prism 108. The blue image light BM, which is s-polarized light generated by the liquid crystal display element 106B, is reflected by the polarizer 105B and irradiated onto the color synthesis prism 108.

[0021] The color synthesis prism 108 reflects the red image light RM and the blue image light BM respectively, transmits the green image light GM, and irradiates the projection lens 109 with each of the respective image lights.

[0022] The red image light RM, the green image light GM, and the blue image light BM are projected onto a screen or the like (not shown) via the projection lens 109. The red image light RM, the green image light GM, and the blue image light BM display a visible light image.

[0023] Incidentally, the liquid crystal display element 106 described above controls the applied voltage to each pixel of the liquid crystal display element 106 based on image data of each color component by a video signal processing circuit (not shown). In each pixel of the liquid crystal display element 106, the arrangement of liquid crystal molecules changes due to the applied voltage, and the liquid crystal layer comes to act as a phase plate. By controlling the applied voltage, the liquid crystal display element 106 can form a state in which the polarization direction of the incident polarized light is rotated by 90 degrees before emission, and a state in which the polarization direction of the incident polarized light is emitted without changing it. Here, pixels in the state where the polarization direction is rotated by 90 degrees are called white pixels, and pixels in the state where the polarization direction is not changed are called black pixels. That is, the liquid crystal display element 106 forms an image pattern that includes white pixels that reflect p-polarized light incident in the first polarization state as a second polarization state (s-polarized light) with the polarization direction rotated by 90 degrees, and black pixels that reflect p-polarized light incident in the first polarization state without changing it.

[0024] In the above configuration, of the light emitted from the light source 101, the p-polarized light (light in the first polarization state) reflected by the black pixels of the liquid crystal display element 106 is returned to the light source 101 side by passing through the polarizing plate 105 and is not used as projected light irradiated onto the projection lens 109. For this reason, in this embodiment, a structure is realized that utilizes the p-polarized light (light in the first polarization state) reflected by the black pixels of the liquid crystal display element 106 to improve the utilization efficiency of the light emitted from the light source 101.

[0025] In this embodiment, the condensing lens 110, aperture reflector 111, collimator lens 112, and diffuser plate 113 are arranged in the optical path between the light source 101 and the illumination optical system 150. The condensing lens 110 focuses the light emitted from the light source 101. The aperture reflector 111 has a light-reflecting surface 111b on the side opposite to the condensing lens 110 in the optical path (the polarizer plate 105 side), and an aperture 111a is provided at the focal point (point of focus) of the condensing lens 110. In this configuration, the light irradiated from the light source 101 is focused by the condensing lens 110 and passes through the aperture 111a of the aperture reflector 111. The collimator lens 112 converts the light that has passed through the aperture 111a of the aperture reflector 111 into parallel light. The diffuser plate 113 diffuses the incident light before it is emitted.

[0026] Next, the operation of the projection display device 100 according to this embodiment will be described. Figure 2 is a schematic diagram illustrating the optical path of light in the second polarization state reflected by the white pixels of the liquid crystal display element. Figure 3 is a schematic diagram of an aperture reflector showing how light focused by a focusing lens passes through the opening. Figure 4 is a schematic diagram illustrating the optical path of light in the first polarization state reflected by the black pixels of the liquid crystal display element. Figure 5 is a schematic diagram of an aperture reflector showing how the reflected light in the first polarization state is irradiated onto the light reflecting surface 111b. In Figures 2 and 4, the areas drawn in white on the liquid crystal display element 106 represent white pixels WT, and the areas filled in black represent black pixels BL.

[0027] As shown in Figure 2, the light source L0 from the light source 101 is focused by the focusing lens 110 and passes through the aperture reflector 111, which has an opening 111a at the focal point (point of focus) F of the focusing lens 110. As shown in Figure 3, the aperture area of ​​the opening 111a of the aperture reflector 111 is formed to be slightly larger than the light source L0 focused at the focal point F (Figure 2) of the focusing lens 110, so the light source L0 passes through this opening 111a. In this embodiment, a laser light source is used as the light source 101. A laser light source can reduce the light emission area of ​​the light source L0, so the focusing area at the focal point F can be reduced, and consequently, the aperture area of ​​the opening 111a can be formed to be smaller.

[0028] As shown in Figure 2, the light source L0 that passes through the opening 111a of the aperture reflector 111 is converted into parallel light by the collimator lens 112 and illuminates with a uniform intensity distribution through the first fly-eye lens 151, the second fly-eye lens 152, the polarization conversion element 153 (Figure 1), and the condenser lens 154 of the illumination optical system 150, and is converted into p-polarized light (light in the first polarization state) L1 with aligned polarization directions.

[0029] The p-polarized light L1 passes through the lens 104 and the polarizing plate 105 and is irradiated onto the liquid crystal display element 106. When the p-polarized light L1 is irradiated onto the white pixel W of the liquid crystal display element 106, the white pixel W converts the p-polarized light L1 into s-polarized light L2 by rotating its polarization direction by 90 degrees and reflects it. This s-polarized light L2 is reflected by the polarizing plate 105 and projected onto a screen or the like (not shown) via the projection lens 109.

[0030] On the other hand, as shown in Figure 4, when p-polarized light L1 is irradiated onto the black pixel B of the liquid crystal display element 106, the p-polarized light L1 is reflected by the black pixel B without changing its polarization direction. As a result, the reflected p-polarized light L1 passes through the polarizer plate 105, lens 104, and illumination optical system 150, is diffused by the diffuser plate 113, and then focused by the collimator lens 112 to reach the aperture reflector plate 111. In this case, because the p-polarized light L1 is diffused once by the diffuser plate 113, the outer diameter of the p-polarized light L1 is larger than the size of the opening 111a of the aperture reflector plate 111, as shown in Figure 5. Therefore, the p-polarized light L1 is reflected by the light-reflecting surface 111b surrounding the opening 111a, and passes through the illumination optical system 150, lens 104, and polarizer plate 105 again to irradiate the liquid crystal display element 106. Here, when p-polarized light L1 is irradiated onto the white pixel W of the liquid crystal display element 106, it is converted into s-polarized light L2 by the white pixel W, reflected by the polarizing plate 105, and projected onto a screen or the like via the projection lens 109. In this way, an aperture reflector 111 is provided, which is positioned in the optical path between the condensing lens 110 and the polarizing plate 105, has a light-reflecting surface 111b on the polarizing plate 105 side, and has an opening 111a at the focal point F of the condensing lens 110. As a result, the p-polarized light L1 irradiated onto the black pixel B of the liquid crystal display element 106 can be reflected by the light-reflecting surface 111b of the aperture reflector 111, thereby improving the utilization efficiency of the light source L0. Furthermore, since a laser light source is used as the light source 101, and the aperture reflector 111 has an opening 111a at the focal point F of the condensing lens 110, the size of this opening 111a can be made as small as possible, and the amount of light reflected by the light-reflecting surface 111b can be increased accordingly.

[0031] Next, another embodiment will be described. Figure 6 is a schematic diagram showing how focused light passes through the mechanism of an aperture reflector according to another embodiment. Figure 7 is a schematic diagram showing how light is reflected by the light-reflecting surface of the aperture reflector in Figure 6. In this other embodiment, the first microlens 151A of the first fly-eye lens 151 and the second microlens 152A of the second fly-eye lens 152 function as focusing optical elements, and as shown in Figure 6, an aperture reflector 211 is provided on the optical path between the second fly-eye lens 152 and the diffuser plate 213, having a light-reflecting surface 211b on the polarizing plate 105 side, and each of the second microlenses 152A corresponding to each focal point (focusing point) F of the first microlens 151A has an opening 211a on the rear side (diffuser plate 213 side). These openings 211a are formed in a matrix shape corresponding to the plurality of first microlenses 151A described above. In another embodiment, a diffuser plate 213 is placed between the aperture reflector plate 211 and the polarizing plate 105.

[0032] In this configuration, the light source L0 from the light source 101 is focused by each first microlens 151A of the first fly-eye lens 151, and passes through the focal point (focus point) F of these first microlenses 151A, which is located near each second microlens 152A of the second fly-eye lens 152, for example, through an aperture reflector 211 with an opening 211a on the back side of the second microlens 152A. Then, as in the embodiment described above, it is converted into p-polarized light (light in the first polarization state) L1, and then passes through the polarizing plate 105 and irradiates the liquid crystal display element 106 (Figure 2). Here, when the p-polarized light L1 is irradiated onto the black pixel B (Figure 2) of the liquid crystal display element 106, the p-polarized light L1 is reflected by this black pixel B without changing the polarization direction. As a result, the reflected p-polarized light L1 passes through the polarizing plate 105, is diffused by the diffuser plate 213, and then reaches the aperture reflector 211, as shown in Figure 7. In this case, the p-polarized light L1 is diffused once by the diffuser plate 213, so the outer diameter of the p-polarized light L1 is larger than the size of the opening 211a of the aperture reflector plate 211. Therefore, the p-polarized light L1 is reflected by the light-reflecting surface 211b surrounding the opening 211a, thereby improving the utilization efficiency of the light source L0.

[0033] As described above, the projection display device 100 according to this embodiment includes a light source 101, a reflective liquid crystal display element 106 arranged in the optical path of light irradiated from the light source 101 and which modulates the light based on image data, a polarizing plate 105 arranged at an angle to the optical path of light incident on the liquid crystal display element 106, which transmits p-polarized light L1 and reflects s-polarized light L2, and a projection device that projects the s-polarized light L2, which has been modulated by the liquid crystal display element 106 and reflected by the polarizing plate 105, onto the projection surface. The device comprises a projection lens 109, a focusing lens 110 (first microlens 151A) that focuses light irradiated from a light source 101, and an aperture reflector 111 (211) that is arranged in the optical path between the focusing lens 110 (first microlens 151A) and the polarizing plate 105, has a light reflecting surface 111b (211b) on the polarizing plate 105 side, and has an opening 111a (211a) at the focal point F of the focusing lens 110 (first microlens 151A). With this configuration, for example, when p-polarized light L1 is irradiated onto a black pixel B of a liquid crystal display element 106, the p-polarized light L1 is reflected by the black pixel B without changing its polarization direction. As a result, the reflected p-polarized light L1 passes through the polarizing plate 105, reaches the aperture reflector 111 (211), and is reflected by the light-reflecting surface 111b (211b) around the opening 111a (211a) of the aperture reflector 111 (211), thereby improving the utilization efficiency of the light source L0.

[0034] Furthermore, in the projection display device 100 according to this embodiment, since the diffuser plate 113 (213) is arranged in the optical path of light between the aperture reflector plate 111 (211) and the polarizing plate 105, the p-polarized light L1 that passes through the polarizing plate 105 and is returned to the light source 101 is diffused by the diffuser plate 113 (213), thereby increasing the area of ​​light irradiated onto the light reflective surface 111b (211b) of the aperture reflector plate 111 (211), and improving the utilization efficiency of the light source L0.

[0035] Furthermore, in the projection display device 100 according to this embodiment, since the light source 101 is a laser light source that emits laser light, the light emission area of ​​the light source L0 can be reduced, and consequently the light collection area at the focal point F can be reduced, and thus the aperture area of ​​the aperture 111a (211a) can be made smaller. Therefore, the amount of light reflected by the light reflective surface 111b (211b) of the aperture reflector 111 (211) can be increased, and the utilization efficiency of the light source L0 can be improved.

[0036] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above.

[0037] The projection display device of this embodiment can be used, for example, in light projection technology that improves the utilization efficiency of light from a light source.

[0038] 100 Projection display device 101 Light source 104, 104B, 104G, 104R Lens 105, 105B, 105G, 105R Polarizing plate (polarizing element) 106, 106B, 106G, 106R Liquid crystal display element 108 Color synthesis prism 109 Projection lens (projection optical system) 110 Focusing lens (focusing optical element) 111, 211 Aperture reflector (reflecting optical element) 111a, 211a Aperture 111b, 211b Light reflecting surface 113, 213 Diffuser plate (diffusing element) 150 Illumination optical system 151 First fly-eye lens 151A First microlens (focusing optical element) 152 Second fly-eye lens 152A Second microlens (focusing optical element) 153 Polarization conversion element 154 Condenser lens B Black pixel F Focal point (point of convergence) L0 Light source L1 p-polarized light (light in the first polarization state) L2 s-polarized light (light in the second polarization state) W White pixel

Claims

1. A projection display device comprising: a light source; a reflective liquid crystal display element positioned in the optical path of light irradiated from the light source and modulating the light based on image data; a polarizing element positioned at an angle to the optical path of light incident on the liquid crystal display element, transmitting the light in a first polarization state and reflecting the light in a second polarization state; and a projection optical system that projects the light modulated by the liquid crystal display element and reflected by the polarizing element onto a projection surface; a focusing optical element that focuses the light irradiated from the light source; and a reflective optical element positioned in the optical path of the light between the focusing optical element and the polarizing element, having a light-reflecting surface on the polarizing element side and an opening at the focusing point of the focusing optical element.

2. The projection display device according to claim 1, wherein a diffusion element is arranged in the optical path of the light between the reflective optical element and the polarizing element.

3. The projection display device according to claim 1 or 2, wherein the light source is a laser light source that emits laser light.

4. The projection display device according to claim 1 or 2, wherein the light-gathering optical element is composed of a fly-eye lens having a plurality of microlenses, and the reflective optical element has the aperture at each focal point of the microlenses.

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