JP2018146836A - Projector and modulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector of a double modulation system that projects a bright image and has a wide dynamic range, and a modulation method.SOLUTION: A wide dynamic range projector of a double modulation system comprises: a first modulation part that performs optical modulation of light from an excitation laser light source with a DMD, and forms a resulting modulated image on a fluorescent plate; and a second modulation part that forms a fluorescent image formed on the fluorescent plate of the first modulation part on another optical modulator, and performs optical modulation in the another optical modulator. The projector reuses OFF light of the DMD being an optical modulator particularly in the first modulation part to improve efficiency in utilization of light from the excitation laser light source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a projector and a modulation method.

  In recent years, ultra-high-definition large-screen video systems, video systems aimed at improving the frame rate and color reproduction range, and the like have been proposed. In 2020, with the spread of 4K / 8K broadcasting, it is expected that many viewers will share the excitement of sports around the world through television and public viewing. We are on the path of becoming With regard to projectors, high definition has been steadily increased due to the evolution of the micro display which is a spatial light modulator to be used. On the other hand, a projector having a wider luminance dynamic range is desired, and prior arts for realizing the projector are disclosed in Patent Documents 1 to 3, Non-Patent Document 1, and the like.

  In the technologies disclosed in these prior art documents, a liquid crystal, a DMD (Digital Micromirror Device), or a LCOS (Liquid Crystal On Silicon) or the like having a spatial light modulator, as well as a liquid crystal, a DMD, Alternatively, a second light modulation unit having LCOS is provided. Then, the light from the light source is modulated (primary light modulation) based on the image data corresponding to the image to be displayed by the first light modulation unit, and the image light of each color of RGB is output. The image light of each color synthesized by the first light modulation unit is superimposed and formed on the light modulator of the second modulation unit using a relay lens system, and the image light is further modulated by the second modulation unit ( Secondary modulation). Therefore, since light modulation is performed twice, a wide luminance dynamic range can be obtained.

JP 2003-121784 A JP 2002-287250 A JP2015-90496A

Yuichi Kusakabe et al. “Dual Modulation Wide Dynamic Range Projector for Super Hi-Vision”: Journal of the Institute of Image Information and Television Engineers, Vol. 65, no. 7, pp 1045-1056 (2011) Research presentation, Shunsuke Murai (Kyoto University) “Directional light extraction with a plasmonic array: Toward a directional light source” 11th Plasmonic Chemistry Symposium Presentation Material November 11, 2016

  The projector including the two modulation units as described above increases the number of spatial light modulators to be used as much as there are more modulation units than a projector having one modulation unit. In addition, the configuration of the optical system of the projector tends to be complicated.

  A single plate type DLP (Digital Light Processing: registered trademark) projector using a single DMD panel is known. As one form of DLP projector, light from a white light source is separated into three colors of RGB by a color wheel, irradiated to a single DMD display panel in a time-sharing manner, and a synchronously controlled image is enlarged and projected to produce a color image. There is an advantage that there is something to get and the configuration is very simple.

  Here, based on this single plate type DLP projector, it is considered that a projector having a wide dynamic range capable of dual modulation can be configured by adding a second modulation unit.

  By the way, a problem in using DMD for the first modulation section is how to increase the light utilization rate of the light source. In general, in the double modulation system, the contrast is multiplied by the contrast by two modulators, but the optical loss of the optical modulator is considered to be effective by multiplication. Therefore, it is desired to suppress the optical loss in each optical modulator as much as possible. In particular, in the case of DMD, gradation image display is performed by PWM (Pulse Width Modulation) control, and the off-light of the DMD mirror causes light loss. Therefore, if the light loss due to the off-light can be reduced, the light utilization rate of the light source can be improved at a stretch, and a bright and wide dynamic range dual modulation projector can be realized.

  The present invention realizes a bright and wide dynamic range dual modulation type projector and modulation method.

The projector of the present invention is a projector that further modulates the image light modulated by the first light modulation unit by the second light modulation unit,
A light source;
A polarizing beam splitter on which light from the light source is incident;
A display panel that reflects at least a portion of light from the polarizing beam splitter in a first direction or a second direction;
A fluorescent plate incident by the light reflected by the display panel in the first direction and conjugated with the display panel;
A retardation plate on which light reflected in the second direction by the display panel is incident,
The polarizing beam splitter emits light from the light source and at least part of the light from the retardation plate in the same direction,
The second light modulator is
A color separation prism that color-separates a fluorescent image formed on the fluorescent plate to generate a plurality of color images and emits the images in different directions;
A plurality of light modulators that are in a conjugate relationship with the fluorescent plate and are provided in each of a plurality of color images generated by the color separation prism.

The modulation method of the present invention is a modulation method performed by a projector that further modulates the image light modulated by the first light modulation unit by the second light modulation unit,
A light source;
A polarizing beam splitter on which light from the light source is incident;
A display panel that reflects at least a portion of light from the polarizing beam splitter in a first direction or a second direction;
A fluorescent plate incident by the light reflected by the display panel in the first direction and conjugated with the display panel;
A retardation plate on which light reflected in the second direction by the display panel is incident;
The polarizing beam splitter causes the light from the light source and at least part of the light from the retardation plate to be emitted in the same direction,
In the second light modulator,
A color separation prism that color-separates a fluorescent image formed on the fluorescent plate to generate a plurality of color images and emits the images in different directions;
A plurality of light modulators which are in a conjugate relationship with the fluorescent plate and are provided in each of the plurality of color images generated by the color separation prism.

  In the present invention having the above-described configuration, a bright and wide dynamic range dual modulation type projector and a modulation method are realized.

It is a figure for demonstrating the structure of the 1st Embodiment of this invention. It is a figure for demonstrating the structure of a TIR prism. (A), (b) is a figure for demonstrating the structure of a fluorescent plate. It is a figure for demonstrating the structure of a color separation prism. It is a figure for demonstrating the structure of the 2nd Embodiment of this invention. It is a figure for demonstrating the structure of a fluorescence plate.

First Embodiment Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a first embodiment of a projector according to the present invention.

  In this embodiment, the light source 101, the polarizing beam splitter 102, the lenses 103 and 104, the reflection mirrors 105 and 106, the TIR prism 107, the DMD display panel 108, the reflection mirror 109, the lenses 110 and 111, Phase plate 112, lens 113, reflection mirror 114, lens 115, fluorescent plate 116, lenses 117 and 118, TIR prism 119, three-color separation prism 120, and DMD display panels 121, 122, and 123 And a projection lens 124.

  As the light source 101, a semiconductor laser light source that emits light in a B (Blue) color band was used. As a guide for the wavelength band, 400 nm to 470 nm can be used. Obtaining this type of laser light source is not difficult. Further, although only one laser light source can be used in FIG. 1 for simplicity of explanation, it is needless to say that a plurality of laser light sources can be used.

  The polarizing beam splitter 102 has a cube-shaped outer shape in which the inclined surfaces of two right-angle prisms are bonded to each other, and includes a dielectric multilayer film on the bonding surface. The polarization beam splitter 102 is an optical element having a characteristic of passing P-polarized light that is incident first linearly polarized light and reflecting S-polarized light that is incident second linearly polarized light. In the present embodiment, considering that the light of the B color band is incident on the polarization beam splitter, the transmission and reflection characteristics are designed to be optimal with respect to this band. Such a polarizing beam splitter can be easily designed and manufactured.

  The lenses 103 and 104 are optical lenses. The material may be an optical resin other than glass. The curved surface shape of the lens can be not only a spherical surface but also an aspherical surface or a free curved surface, which is a design matter.

  The reflection mirrors 105 and 106 have a characteristic of reflecting light in the B color band, and can be manufactured by depositing a metal thin film such as aluminum or silver or a dielectric multilayer film on glass.

  FIG. 2 is a diagram showing the configuration of the TIR prism 107 in more detail. The TIR prism 107 is a prism assembly configured to irradiate incident light onto the mirror surface of the DMD display panel 108 to extract on-light and to turn off-light in a different direction from the on-light. The TIR prism 107 is composed of prisms 301, 302, and 303, and has a minute air layer at each joint interface. In general, the three prisms can use the same optical glass.

  The DMD display panel 108 is a two-dimensional MEMS (Micro Electro Mechanical System) mirror array, and has a mirror for the number of pixels. Each mirror has two mirror tilt angles, an on state and an off state, and makes the deflection direction of incident light variable. By controlling the number of times the mirror is turned on / off, it is possible to display a gradation of an image.

  The reflection mirror 109 has a characteristic of reflecting light in the B color band, and can be manufactured by depositing a metal thin film such as aluminum or silver or a dielectric multilayer film on glass.

  The lenses 110 and 111 are optical lenses. The number of sheets to be used, shape specifications, and the like should be appropriately determined by the optical system, and the one-sheet configuration as shown in FIG. 1 is not necessarily optimal.

  The retardation plate 112 can be a half-wave plate. The polarization direction of the linearly polarized light in the B color band is rotated by 90 degrees. Such a wave plate is a well-known technique in the field of projectors.

  The lens 113 is an optical lens. The number of sheets to be used, shape specifications, and the like should be appropriately determined by the optical system, and the one-sheet configuration shown in FIG. 1 is not necessarily optimal.

  The reflection mirror 114 has a characteristic of reflecting light in the B color band. Manufacture is possible by depositing a metal thin film such as aluminum or silver on the glass or by depositing a dielectric multilayer film.

  The lens 115 is an optical lens. The number of sheets to be used, shape specifications, and the like should be appropriately determined by the optical system, and the one-sheet configuration shown in FIG. 1 is not necessarily optimal.

  FIG. 3 is a diagram showing the configuration of the fluorescent plate 116 in detail. The fluorescent plate 115 is a plate-like phosphor, and the phosphor 501 is fixed on the glass substrate 502 as shown in FIG. 3A, or the phosphor 503 is plate-like as shown in FIG. What was sintered to the like can be used. As the phosphor material, a material that fluoresces in G color, Y color, R color, or the like when irradiated with light in the B color band can be used. As such a phosphor material, a material used for a fluorescent wheel used in a white LED or a laser fluorescent projector is known.

  The lenses 117 and 118 are optical lenses. The number of sheets to be used, shape specifications, and the like should be appropriately determined by the optical system, and the two-sheet configuration as shown in FIG. 1 is not necessarily optimal.

  The TIR prism 119 is a prism assembly configured to irradiate incident light onto the mirror surface of the DMD display panel 122 to extract on-light, and at the same time, off-light of the DMD display panel 122 is directed in a different direction from the on-light. Since it is frequently used in single-plate and three-plate DLP projectors, a detailed description is not given here.

  FIG. 4 is a diagram showing the configuration of the three-color separation prism 120 in detail. For example, the three-color separation prism 120 separates white light into three color bands of R, G, and B, and synthesizes light of the three color bands of R, G, and B. The three-color separation prism 120 is an optical component that can be said to be essential in a three-plate type DLP projector.

  The DMD display panels 121, 122, and 123 are two-dimensional MEMS mirror arrays, and have as many mirrors as the number of pixels. Each mirror has two mirror tilt angle states, an on state and an off state, and the deflection direction of incident light is variable. By controlling the number of times the mirror is turned on and off, it is possible to display a gradation of an image. In the first embodiment shown in FIG. 1, three DMD display panels are used for R (Red), G (Green), and B colors.

  The projection lens 124 is a lens that enlarges and projects an image generated by the DMD display panels 121, 122, and 123. In FIG. 1, the projection lens 124 is displayed as a single lens for the sake of simplicity, but actually, a plurality of lenses are used. It consists of a lens system. The projection lens 124 should be designed and manufactured according to the product specifications of the projector device.

  Next, the operation of this embodiment will be described.

  Linearly polarized light is emitted from the B-color semiconductor laser that is the light source 101. Generally, light from a semiconductor laser light source is linearly polarized light, and the polarization axis of linearly polarized light can be arbitrarily adjusted by appropriately arranging the laser beam emission direction around the optical axis.

  When the arrangement of the light source 101 is adjusted so that the P-polarized light is emitted from the light source 101, the emitted P-polarized light travels straight through the polarization beam splitter 102. This is because the polarization beam splitter 102 is arranged so that the polarization separation surface of the polarization beam splitter 102 is 45 degrees with the optical axis of the laser beam. The P-polarized light that has passed through the polarization beam splitter 102 is then refracted and reflected by the lenses 103 and 104 and the reflection mirrors 105 and 106 and enters the TIR prism 107. The lenses 103 and 104 are lenses provided as necessary. It is not necessarily required at the location shown in this figure, and changes depending on the optical design.

  Here, as shown in FIG. 2, incident light to the prism 301 constituting the TIR prism 107 is totally reflected by the inclined surface 31 and reaches the DMD display panel 108. This is because there is a minute air gap between the inclined surface 31 of the prism 301 and the boundary surface of the prism 302. When the pixel mirror of the DMD display panel 108 is in an ON state (indicated by a solid line in FIG. 2), the light reflected from the pixel mirror of the DMD display panel 108 travels from the prism 301 to the prism 302 and is emitted from the TIR prism 107.

  On the other hand, the light reflected when the pixel mirror of the DMD display panel 108 is in the OFF state (indicated by a broken line in FIG. 2) travels from the prism 301 to the prism 303 and is emitted from the TIR prism 107. The inclined surface 31 has a minute air space between it and the prism 303. Thus, the reflected light travels in completely different directions depending on whether the pixel mirror of the DMD display panel 108 is in the on state or the off state.

  Returning to FIG. 1, the description will be continued with respect to the progress of the reflected light of the pixel mirror of the DMD display panel 108. The on-light exiting the TIR prism 107 passes through the lens 113, changes its traveling direction with the reflection mirror 114, and further receives an optical action with the lens 115 and is displayed on the fluorescent plate 116 based on the driving of the DMD display panel 108. Form an image. This is because the shape specifications and arrangement of the lenses 113 and 115 are designed so that the DMD display panel 108 and the fluorescent plate 116 have an optically conjugate relationship, that is, an imaging relationship. Such a conjugate relationship is not difficult and is a well-known technique.

  An image on the DMD 108 is formed on the fluorescent plate 116 to form a fluorescent image on the fluorescent plate 116. The fluorescent plate 116 is formed of a Y-color phosphor, and converts part of the B-color light into the Y-color. Accordingly, a white image that emits light is formed on the fluorescent plate 116 by appropriately designing the concentration and thickness of the fluorescent material forming the fluorescent plate 116. The white image is formed on the DMD display panels 121, 122, and 123 corresponding to the colors R, G, and B, which are placed at conjugate positions by the lenses 117 and 118 (irradiated as illumination light).

  Between the fluorescent plate 116 and the DMD display panels 121, 122, 123, there are a TIR prism 119 and a color separation prism 120. In the color separation prism 120, the white image on the fluorescent plate 116 is separated into R, G, and B colors and formed as illumination light on the corresponding R light DMD 121, G light DMD 122, and B light DMD 123. Thereafter, the light is modulated by each DMD display panel 121, 122, 123. The ON light in each DMD display panel 121, 122, 123 is color-combined by the color separation prism 120 and then emitted from the TIR prism 119 and enlarged and projected by the projection lens 124 to obtain a large screen image.

  Here, regarding the luminance distribution of the illumination light imaged on the three-color DMD display panels 121, 122, and 123, the luminance distribution reflecting the luminance information of the image in advance on the fluorescent plate 116 is the color DMD display panel. , And that the DMD display panels 121, 122, and 123 perform light modulation on the illumination light, the entire image is subjected to two-time modulation and enlarged and projected. Become. Therefore, the contrast of the projected image is very high.

  Next, the off light of the DMD display panel 108 as the first modulation unit will be described. This off-light follows the optical path prepared in a separate system after being emitted from the TIR prism 107 and is reused as illumination light for the DMD display panel 108.

  The off-light of the DMD display panel passes through the reflection mirror 109, the lenses 110 and 111, and further passes through the phase difference plate 112, whereby the polarization light direction is changed from P-polarized light to S-polarized light. This is because the laser beam output from the light source 101 is P-polarized light and the retardation plate 112 is a half-wave plate.

  The S-polarized light that has passed through the phase difference plate 112 joins the traveling path of the P-polarized laser beam before being reused from the light source 101 by the polarization beam splitter 102 and travels. Therefore, thereafter, the light is used as illumination light for the DMD display panel 108, and the on-light forms a light source image on the fluorescent plate 116, which is further optically modulated and projected on the DMD display panels 121, 122, 123.

  As described above, in this embodiment, the off-light in the DMD display panel 108 is reused as illumination light for the DMD display panel 108 again without loss of light. The light utilization rate is increased in each stage, and highly efficient light modulation is possible. The place where the wave plate 112 is disposed may be either between the off-light of the DMD display panel 108 and the polarization beam splitter 102 in the optical path before being reused except for the polarization beam splitter 102.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the configuration of the projector according to the second embodiment of the invention.

  The difference between this embodiment and the first embodiment is that the first embodiment is a three-plate type DLP projector, whereas the present embodiment has a configuration of a three-plate type liquid crystal projector. Is a point. In other words, it can be said that the same wide dynamic projector can be configured regardless of whether the projector of the present invention is a DMD display panel or a liquid crystal display panel.

  In FIG. 5, the same reference numerals are given to the same components and operations as those in FIG. 1. Differences in configuration include dichroic mirrors 201 and 203, reflection mirrors 202, 205, and 206, lenses 204 and 206, a liquid crystal panel for R color 208, a liquid crystal panel for G color 209, and a liquid crystal panel for B color 210. A cross dichroic prism 211 and a projection lens 212. Both components are well-known techniques. Similarly, regarding the operation, the white light source image formed on the fluorescent plate 116 is separated into three colors of R, G, and B, and formed on the corresponding liquid crystal panels 208, 209, and 210, respectively. Here, since illumination light having illumination information reflecting the luminance distribution of the display image is imaged in advance on each liquid crystal panel, images that are further light-modulated by three liquid crystal panels are finally displayed. Since the image is magnified and projected, the image is very excellent in contrast. In addition, regarding the image modulation of the excitation light applied to the fluorescent plate 116, not only the on-light of the DMD display panel 108 but also the off-light is reused to increase the light utilization rate of the semiconductor laser as the light source 101. Highly efficient light modulation is realized.

  By the way, in this method, the image formed on the fluorescent plate 116 is fluorescent, and the directivity which is the light emission characteristic is isotropic. Therefore, in order to suppress light loss and use light efficiently, it is effective to devise the configuration of the fluorescent plate 116. As described in Non-Patent Document 2, it has been reported that fluorescence emission characteristics can be controlled by introducing the most advanced fine processing such as photonic crystal technology and surface plasmonics technology.

  As shown in FIG. 6, by adopting a configuration in which aluminum nanorods 602 are periodically formed on a YAG (Yttrium Aluminum Garnet) phosphor plate, the emission directionality of the depression angle fluorescence with respect to the excitation light irradiation can be obtained. There is a suggestion. By applying this structure, light loss in the optical system of the second modulator is reduced, and a more efficient projector can be realized.

  In the first embodiment, the light source is a laser light source in the B color band. However, a laser light source other than the B color can be used. For example, a white modulated image can be obtained by forming a fluorescent material that emits both B and Y colors on a fluorescent plate using an ultraviolet laser light source.

  As described above, the projector according to the present invention is a dual modulation type projector having the first modulation unit and the second modulation unit. In particular, the first modulation unit is equipped with a DMD. As the light source, a laser light source of B color band was used. The B color laser light is optically modulated by the DMD display panel in the first modulation section, and then imaged on the fluorescent plate to form a fluorescent image on the fluorescent plate. B color laser light is excitation light.

  In general, a DMD display panel displays an image by PWM modulation. The on-light that is incident when the MEMS mirror constituting one pixel is on is used for the projection image. However, the off-light that is incident when the MEMS mirror is off does not go to the projection lens after reflection and becomes a light loss. That is, it is difficult to use all light rays incident on the DMD display panel for the projection image. If all incident light is available, the highest light utilization can be achieved.

  In the projector of the present invention, during the light modulation of the DMD display panel of the first modulation unit, off-light is guided using an optical path of another system, and the light is reused as light incident on the DMD display panel again. As a result, the reused light is also optically modulated by the DMD display panel and irradiated onto the fluorescent plate. Therefore, the light from the light source is efficiently used for modulation, so that a bright image is obtained on the fluorescent plate.

  The image on the fluorescent plate is used as illumination light for a micro display display panel such as a DMD or a liquid crystal panel of the second modulation unit. The DMD display panel, which is the modulator of the first modulator, and the fluorescent plate are arranged in a conjugate relationship. The fluorescent plate of the first modulation unit and the modulator of the second modulation unit are optically conjugate. Accordingly, illumination information reflecting the luminance distribution of the image displayed on the DMD display panel of the first modulation unit is formed on the fluorescent plate, and this forms an image as illumination light of the modulator of the second modulation unit 2. This is a configuration of multiple modulation.

  In the double modulation method, the contrast of multiplication of the first modulation unit and the second modulation unit is obtained. Therefore, the projection image realizes a very wide dynamic range. In addition, since the DMD off-light of the first modulation unit that has conventionally lost light can be reused, it is possible to provide a projector with a very high light utilization rate and a wide dynamic range.

  In the description of the embodiments, the light source is a laser, but the same effect can be realized by using an LED.

  The polarization beam splitter has been described as passing the linearly polarized light from the light source and reflecting the linearly polarized light from the phase difference plate, but these may be reversed, and they are emitted in the same direction. Any configuration may be used.

101 Light source 102 Polarizing beam splitter 103, 104, 113, 110, 111, 113, 115, 117, 118, 204, 206 Lens 105, 106, 109, 114, 202, 205, 207 Mirror 107 TIR prism 108, 121, 122 , 123 DMD display panel 112 Retardation plate 116 Fluorescent plate 119 TIR prism 120 Color separation prism 124, 212 Projection lens 201, 203 Dichroic mirror 208, 209, 210 Liquid crystal panel 211 Dichroic prism 301, 302, 303, 401, 402, 403 Prism 31 Slope 501, 503, 601 Phosphor Phosphor 502 Substrate 602 Al nanorod

Claims (6)

A projector that further modulates the image light modulated by the first light modulator by the second light modulator,
A light source;
A polarizing beam splitter on which light from the light source is incident;
A display panel that reflects at least a portion of light from the polarizing beam splitter in a first direction or a second direction;
A fluorescent plate incident by the light reflected by the display panel in the first direction and conjugated with the display panel;
A retardation plate on which light reflected in the second direction by the display panel is incident,
The polarizing beam splitter emits light from the light source and at least part of the light from the retardation plate in the same direction,
The second light modulator is
A color separation prism that color-separates a fluorescent image formed on the fluorescent plate to generate a plurality of color images and emits the images in different directions;
A projector comprising: a plurality of light modulators that are conjugated with the fluorescent plate and provided in each of a plurality of color images generated by the color separation prism. The projector according to claim 1, wherein
The projector, wherein the plurality of light modulators are DMD display panels. The projector according to claim 1, wherein
The projector, wherein the color separation prism is a cross dichroic prism, and the plurality of light modulators are liquid crystal panels. A modulation method performed by a projector that further modulates the image light modulated by the first light modulation unit by the second light modulation unit,
A light source;
A polarizing beam splitter on which light from the light source is incident;
A display panel that reflects at least a portion of light from the polarizing beam splitter in a first direction or a second direction;
A fluorescent plate incident by the light reflected by the display panel in the first direction and conjugated with the display panel;
A retardation plate on which light reflected in the second direction by the display panel is incident;
The polarizing beam splitter causes the light from the light source and at least part of the light from the retardation plate to be emitted in the same direction,
In the second light modulator,
A color separation prism that color-separates a fluorescent image formed on the fluorescent plate to generate a plurality of color images and emits the images in different directions;
A modulation method comprising: a plurality of light modulators provided in each of a plurality of color images that are conjugated with the fluorescent plate and generated by the color separation prism. The modulation method according to claim 4, wherein
A modulation method using a DMD display panel as the plurality of optical modulators. The modulation method according to claim 4, wherein
A modulation method in which a cross dichroic prism is used as the color separation prism, and the plurality of light modulators use liquid crystal panels.

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