JP2008015064A - Illuminator and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminator capable of adjusting an entire image to be easy-to-view with high contrast, and obtaining high utilization efficiency of light rays , and to provide a projector. <P>SOLUTION: The illuminator has a light source part 11R supplying coherent light, and a phase modulation part 13R modulating the phase of the coherent light from the light source part 11R and making it incident on a surface to be irradiated. The phase modulation part 13R changes a phase modulation pattern while generating diffracted light in accordance with the phase modulation pattern of the coherent light, thereby making the light rays, which are adjusted in intensity for every unit area set on the surface to be irradiated, on the surface to be irradiated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lighting device and a projector, and more particularly to a technology of a lighting device used for a projector.

  For a projector that displays an image using projection light corresponding to an image signal, for example, a liquid crystal display device or a DMD (Digital Micromirror Device) is used as a spatial light modulation device that modulates light according to the image signal. In order to display a high-contrast and easy-to-view image, techniques for displaying an image with a dynamic range wider than the dynamic range according to the control of the spatial light modulator have been proposed (for example, Patent Documents 1 and 2). reference).

Special table 2003-3080 publication JP 2003-149730 A

  Patent Document 1 proposes a technique for adjusting the intensity of light incident on the spatial light modulation device from the light source unit by using a light shielding plate. In this case, since the intensity of light is uniformly adjusted with respect to the entire incident surface of the spatial light modulator, for example, when adjustment is performed to increase the intensity of light by focusing on a bright part of the image. In other words, a so-called black float occurs in which a dark display portion is displayed brightly. On the other hand, if the adjustment is made to reduce the light intensity while paying attention to the dark part of the image, the brightness of the part to be displayed brightly becomes insufficient. For this reason, it is very difficult to make adjustments to make the entire image easy to see, particularly for an image in which a bright part and a dark part coexist. The technique proposed in Patent Document 2 is to adjust the intensity of light incident on the spatial light modulator using a light control liquid crystal element provided between the light source unit and the spatial light modulator. By using the light control liquid crystal element, it is possible to make light incident on the incident surface of the spatial light modulator with a desired intensity distribution. However, components other than the component incident on the spatial light modulator out of the light incident on the light control liquid crystal element are scattered or absorbed by the light control liquid crystal element or the like, so the light intensity is adjusted. As a result, the light utilization efficiency decreases. As described above, according to the conventional technique, there is a problem that it is possible to make adjustments to make the entire image easy to see and it is difficult to realize high light utilization efficiency. The present invention has been made in view of the above-described problems, and provides an illumination device and a projector that can be adjusted to make the entire image easy to see with high contrast and realize high light utilization efficiency. With the goal.

  In order to solve the above-described problems and achieve the object, according to the present invention, a light source unit that supplies coherent light and a phase modulation unit that modulates the phase of the coherent light from the light source unit and causes the light to enter the irradiated surface. And the phase modulation unit adjusts the intensity for each unit region set on the irradiated surface by changing the phase of the coherent light while generating diffracted light according to the phase modulation pattern. It is possible to provide an illuminating device characterized in that light is incident on an irradiated surface.

  The phase modulation unit distributes light from the light source unit so that light of a desired intensity is incident on each unit region set on the irradiated surface, for example, the incident surface of the spatial light modulator. By making the coherent light incident on the phase modulator, good diffraction characteristics can be obtained in the phase modulator. By distributing the light using the phase modulation unit, it is possible to make the light having an intensity distribution adapted to the brightness distribution of the image incident on the spatial light modulation device without wasting light from the light source unit. For this reason, it is possible to make adjustments so that the entire image is easy to see with high contrast, and it is possible to effectively use coherent light from the light source unit. By enabling the phase of the coherent light to be modulated by the phase modulation unit, light can be distributed not only for still images but also for moving images. As a result, it is possible to make an adjustment for making the entire image easy to see with high contrast, and to obtain an illumination device for realizing high light utilization efficiency.

  Moreover, as a preferable aspect of the present invention, it is desirable that the phase modulation unit includes a liquid crystal element. By using a liquid crystal element, the phase modulation pattern of coherent light can be easily changed by controlling voltage application.

  As a preferred embodiment of the present invention, the liquid crystal element is preferably a liquid crystal element of electric field controlled birefringence mode. Thereby, a high-speed response of the phase modulation unit is possible, and sufficient phase modulation can be performed with a low drive voltage.

  As a preferred embodiment of the present invention, it is desirable that the light source unit supplies coherent light whose intensity is adjusted. Thereby, an image can be displayed with a wider dynamic range. Further, power saving can be realized by making it possible to adjust the output of the light source unit in accordance with the intensity of light incident on the spatial light modulator.

  As a preferred aspect of the present invention, it is desirable that the light source unit supplies coherent light having an intensity determined with reference to the average illuminance on the irradiated surface. Thereby, it is possible to simultaneously realize image display and power saving in a wide dynamic range.

  As a preferred aspect of the present invention, it is desirable that the light source unit supplies a plurality of coherent lights, and at least one of the light source unit and the phase modulation unit is controlled according to the intensity difference of the coherent light. As a result, the light intensity distribution can be accurately adjusted according to the intensity difference between the plurality of coherent lights. In addition, when adjusting the intensity of coherent light between colors, a good white balance can be obtained.

  As a preferred embodiment of the present invention, it is desirable that the light source unit supplies coherent light having a substantially constant intensity. In this case, so-called peak luminance control can be performed in which a display with higher luminance than that in the case where light is uniformly emitted to the entire screen with the light source unit as the maximum output. As a result, it is possible to display an image with a wider dynamic range.

  Furthermore, according to the present invention, it is possible to provide a projector characterized in that an image is displayed by modulating light from the above-described illumination device according to an image signal. By using the illumination device described above, it is possible to make adjustments to make the entire image easy to see with high contrast, and it is possible to realize high light utilization efficiency. As a result, it is possible to obtain a projector that can easily display a bright image with high light utilization efficiency and easy to see the entire image.

  In addition, as a preferable aspect of the present invention, a spatial light modulation device that modulates light from the illumination device according to an image signal is provided, and the illumination device is provided for each unit region set on the incident surface of the spatial light modulation device. It is desirable that the light whose intensity is adjusted to be incident on the incident surface. As a result, it is possible to form an easy-to-see image with high contrast as a whole.

  As a preferred embodiment of the present invention, it is desirable that the unit region is smaller than the incident surface and larger than the pixel region in the spatial light modulator. By setting a plurality of unit regions smaller than the incident surface, it is possible to adjust the light intensity for each unit region. Further, in order to make the entire image have high contrast, it is sufficient for the phase modulation unit to adjust the light intensity for each region wider than the pixel. By setting a unit region larger than the pixel region, the configuration and driving of the phase modulation unit can be simplified. As a result, light having an intensity distribution adapted to an image can be incident on the spatial light modulator using a phase modulator that is simple in configuration and drive.

  As a preferred aspect of the present invention, the illumination device includes a phase modulation unit that modulates the phase of the coherent light from the light source unit, and the phase modulation unit corresponds to the phase modulation signal generated based on the image signal. It is desirable to be controlled. Thereby, it is possible to perform control for making the entire image easy to see with high contrast.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a projector 100 according to an embodiment of the present invention. The projector 100 is a front projection type projector that views light by supplying light to the screen 18 and observing light reflected by the screen 18. The projector 100 includes an R light illumination device 10R that supplies red (R) light, a G light illumination device 10G that supplies green (G) light, and a B light illumination device 10B that supplies blue (B) light. Have. The projector 100 displays an image by modulating light from the illumination devices 10R, 10G, and 10B according to an image signal.

  FIG. 2 shows the R light illumination device 10 </ b> R, the R light spatial light modulation device 15 </ b> R, and the cross dichroic prism 16. The R light illumination device 10R includes an R light source unit 11R. The light source unit 11R for R light is a light source unit that supplies laser light that is coherent light. The R light source unit 11R includes five laser light sources 12R that supply R light. The five laser light sources 12R are arranged in parallel in a row. The laser light supplied from the laser light source 12R is polarized light having a specific vibration direction, for example, s-polarized light. For example, a semiconductor laser can be used as the laser light source 12R. All of the five laser light sources 12R supply substantially parallel laser light.

  Laser light from the laser light source 12R enters the phase modulation unit 13R. The phase modulation unit 13 </ b> R is a liquid crystal panel including the liquid crystal element 20. The phase modulation unit 13R arranges the liquid crystal element 20 corresponding to the laser beam supplied from the R light source unit 11R. The phase modulation unit 13R modulates the phase of the laser light from each laser light source 12R and makes it incident on the incident surface of the R light spatial light modulation device 15R. The incident surface of the R light spatial light modulator 15R is an irradiated surface of the R light illumination device 10R.

  The phase modulation unit 13 </ b> R generates diffracted light corresponding to the phase modulation pattern formed by the liquid crystal element 20. The diffracted light from the phase modulation unit 13R enters the field lens 14R. The field lens 14R collimates the light from the phase modulation unit 13R and causes the light to enter the R light spatial light modulation device 15R. The field lens 14R is provided obliquely in front of the phase modulation unit 13R and at a position other than the position where the zero-order light from the phase modulation unit 13R is incident.

  The spatial light modulator 15R for R light is a transmissive liquid crystal display device that modulates R light according to an image signal. A liquid crystal panel (not shown) provided in the R light spatial light modulator 15R encloses a liquid crystal layer for image display between two transparent substrates. The s-polarized light incident on the liquid crystal panel is converted into p-polarized light by modulation according to the image signal. The spatial light modulator for R light 15R emits R light converted into p-polarized light by modulation. The R light modulated by the R light spatial light modulator 15R is incident on the cross dichroic prism 16 which is a color synthesis optical system.

  Returning to FIG. 1, the G light illumination device 10G and the B light illumination device 10B both have the same configuration as the R light illumination device 10R. The G light illumination device 10G includes a G light source 11G. The light source unit 11G for G light is a light source unit that supplies laser light that is coherent light. The G light source unit 11G includes five laser light sources 12G that supply G light. The laser light from the laser light source 12G passes through the phase modulator 13G and the field lens 14G, and then enters the G light spatial light modulator 15G. The G light spatial light modulation device 15G is a transmissive liquid crystal display device that modulates G light according to an image signal. The spatial light modulator for G light 15G emits G light converted into p-polarized light by modulation. The G light modulated by the G light spatial light modulator 15G enters the cross dichroic prism 16 from a side different from the R light.

  The B light illumination device 10B includes a B light source 11B. The light source unit 11B for B light is a light source unit that supplies laser light that is coherent light. The B light source unit 11B includes five laser light sources 12B that supply B light. The laser light from the laser light source 12B passes through the phase modulator 13B and the field lens 14B, and then enters the B light spatial light modulator 15B. The B light spatial light modulator 15B is a transmissive liquid crystal display device that modulates the B light according to an image signal. The B light spatial light modulator 15B emits B light converted into p-polarized light by modulation. The B light modulated by the B light spatial light modulator 15B enters the cross dichroic prism 16 from a side different from the R light and the G light.

  The cross dichroic prism 16 has two dichroic films 16a and 16b arranged so as to be substantially orthogonal to each other. The first dichroic film 16a reflects R light and transmits G light and B light. The second dichroic film 16b reflects B light and transmits R light and G light. The cross dichroic prism 16 combines the R light, G light, and B light incident from different sides and emits the light toward the projection lens 17. The projection lens 17 projects the light combined by the cross dichroic prism 16 onto the screen 18.

  The phase modulators 13R, 13G, and 13B are not limited to the configuration that allows light to enter the field lenses 14R, 14G, and 14B provided at positions other than the position where the zero-order light is incident. The phase modulators 13R, 13G, and 13B only need to be able to cause the diffracted light to enter the field lenses 14R, 14G, and 14B, and to the field lenses 14R, 14G, and 14B provided at positions where the zero-order light is incident. Light may be incident. The projector 100 is not limited to a configuration using a transmissive liquid crystal display device as a spatial light modulator. As the spatial light modulation device, a reflective liquid crystal display device or DMD may be used.

  The illumination devices 10R, 10G, and 10B use the light source units 11R, 11G, and 11B including the laser light sources 12R, 12G, and 12B, so that the configuration for color separation and the polarization for supplying polarized light in a specific vibration direction are used. The separation element can be omitted. Since laser light has a single wavelength, it has the characteristics of high color purity and high coherence. Further, since ultraviolet light is not included, there is an advantage that deterioration of the liquid crystal element can be reduced. Further, there is an advantage that the laser light sources 12R, 12G, and 12B can be miniaturized, so that the projector 100 can be miniaturized and the laser light sources 12R, 12G, and 12B can be turned on instantaneously.

  Each light source part 11R, 11G, and 11B is not restricted to the structure provided with five laser light sources, What is necessary is just a structure provided with one or several laser light sources. The light source units 11R, 11G, and 11B are not limited to the configuration in which the plurality of laser light sources 12R, 12G, and 12B are arranged in parallel in one direction, and may be arranged in an array. By supplying laser light from the plurality of laser light sources 12R, 12G, and 12B, each of the light source units 11R, 11G, and 11B can have high output. Moreover, there is an advantage that speckle noise can be reduced by supplying a plurality of laser beams from the light source units 11R, 11G, and 11B. Each light source part 11R, 11G, 11B is good also as a structure provided with the laser light source which has a some light emission part instead of the structure provided with a some laser light source.

  Each of the light source units 11R, 11G, and 11B may be configured to use a wavelength conversion element that converts the wavelength of the laser light from the semiconductor laser, for example, a second-harmonic generation (SHG) element. As the laser light source, a semiconductor laser pumped solid state (DPSS) laser, a solid laser, a liquid laser, a gas laser, or the like may be used instead of the semiconductor laser.

  FIG. 3 shows a cross-sectional configuration of the liquid crystal element 20 provided in the phase modulators 13R, 13G, and 13B. The liquid crystal element 20 is configured by sealing a liquid crystal layer 32 with a first transparent substrate 21 and a second transparent substrate 24. A first transparent electrode 22 is formed between the first transparent substrate 21 and the liquid crystal layer 32. The 1st transparent electrode 22 can be comprised by ITO and IZO which are metal oxides, for example. A light shielding layer 23 is provided in a partial region between the first transparent electrode 22 and the liquid crystal layer 32. In addition, an alignment film (not shown) subjected to a rubbing process is formed.

  In a partial region on the second transparent substrate 24, a semiconductor layer 25, a gate insulating film 26 formed on the semiconductor layer 25, and a gate electrode 27 formed on the gate insulating film 26 are provided. Such a portion constitutes a thin film transistor (TFT) having a part of the semiconductor layer 25 as a source and a drain. An insulating film 28 made of silicon oxide or the like is formed on the second transparent substrate 24 and the TFT. A signal line 29 is provided on the TFT via an insulating film 28. The signal line 29 is connected to the source of the TFT. A scanning line (not shown) is connected to a gate electrode 27 that is a gate of the TFT.

  A PSG (Phosphosillicate glass) film 30 is formed on the insulating film 28, the signal line 29, and the scanning line. A second transparent electrode 31 is provided on a portion of the PSG film 30 other than the portion corresponding to the TFT. Similar to the first transparent electrode 22, the second transparent electrode 31 can be made of ITO or IZO. The TFT and the second transparent electrode 31 are formed for each pixel. In addition, an alignment film is also formed on the second transparent substrate 24 side. The rubbing direction of the alignment film on the second transparent substrate 24 side is parallel and opposite to the rubbing direction of the alignment film on the first transparent substrate 21 side. Thereby, the liquid crystal element 20 can obtain a uniform alignment state as a whole.

  The liquid crystal element 20 causes the second transparent substrate 24 to emit light that sequentially passes through the first transparent substrate 21, the liquid crystal layer 32, and the second transparent electrode 31. The liquid crystal element 20 is arranged so that the polarization direction of the laser light incident on the first transparent substrate 21 coincides with the alignment direction of the liquid crystal molecules on the first transparent substrate 21 side. Thereby, the laser beams from the light source units 11R, 11G, and 11B can be efficiently incident on the liquid crystal element 20.

  The phase modulators 13R, 13G, and 13B are driven by an active matrix method, for example, similarly to the spatial light modulators 15R, 15G, and 15B. As the liquid crystal element 20, a liquid crystal in an electric field control birefringence mode, for example, a ferroelectric liquid crystal can be used. By using a ferroelectric liquid crystal having a low molecular weight and a relatively high birefringence, the phase modulators 13R, 13G, and 13B can respond at high speed, and sufficient phase modulation can be performed with a low driving voltage. The liquid crystal element 20 may be a liquid crystal other than the ferroelectric liquid crystal, for example, a nematic liquid crystal or a twisted nematic liquid crystal as long as it is a liquid crystal in an electric field control birefringence mode. The phase modulation units 13R, 13G, and 13B can obtain a large diffraction angle by using the liquid crystal element 20 having a narrow pixel interval. In order to obtain good diffraction characteristics, the pixel pitch of the liquid crystal element 20 is preferably 10 μm or less.

  Each of the phase modulation units 13R, 13G, and 13B splits the laser light by generating diffracted light in the liquid crystal element 20, respectively. The phase modulators 13R, 13G, and 13B distribute the laser light using the liquid crystal element 20, thereby allowing the incident light to be incident on each unit region 41 set on the incident surface 40 so as to be hatched in FIG. Change the intensity. For example, the unit region 41 can be set as one obtained by equally dividing the incident surface 40 into 64 (= 8 × 8).

The following formula is established between the phase modulation pattern Φ formed on the incident surface 40 that is a predetermined distance z away from the phase modulators 13R, 13G, and 13B and the light wave T of the diffracted light on the incident surface 40.
T (x, y, z) = a (x, y, z) · exp [−iΦ (x, y, z)]

  Here, (x, y) is a coordinate in a plane orthogonal to the optical axis, and a (x, y, z) is the amplitude of the light wave. The intensity of the light wave is given by the square of the amplitude a (x, y, z). A phase modulation pattern optimized for obtaining a target intensity distribution can be obtained by using a predetermined calculation method (simulation method) such as an iterative Fourier transform. By making it possible to modulate the phase of the laser beam by the phase modulators 13R, 13G, and 13B, it is possible to distribute light corresponding to not only a still image but also a moving image. Note that the illumination devices 10R, 10G, and 10B cause light having substantially uniform intensity to enter the incident surface 40 when the phase modulation patterns of the phase modulation units 13R, 13G, and 13B are in the reference state. The phase modulation units 13R, 13G, and 13B change the phase modulation pattern with reference to a state in which light having substantially uniform intensity is incident.

  FIG. 5 shows a block configuration for driving the projector 100. A portion surrounded by a broken line in the figure is a portion for driving the illumination devices 10R, 10G, and 10B in the projector 100. The AD converter 50 switches an image signal input as an analog signal from an external device or the like to a digital signal. The DSP (1) 51, which is a digital signal processing circuit, extracts a brightness parameter for controlling the brightness of the image from the image signal converted into the digital signal.

  The brightness parameter is extracted for each unit region 41 (see FIG. 4). As the brightness parameter, for example, using the appearance number distribution (histogram) for each number of gradations of the pixel data included in the frame of interest, the number of appearances is a certain ratio from the maximum gradation, for example, 1%. The number of gradations can be extracted. For example, when the maximum gradation is extracted as the brightness parameter, it is conceivable that the reliability as the brightness parameter is lowered because the maximum gradation is caused by noise or an unexpected gradation peak. Therefore, by using information that allows a certain number of appearances from the maximum gradation as the brightness parameter, high reliability is ensured and accurate brightness control is possible. The ratio from the maximum brightness is not limited to 1%, and can be determined as appropriate within a range of 0 to 50%, for example.

  The DSP (2) 52, which is a digital signal processing circuit, determines the illuminance distribution on the incident surface 40 (see FIG. 4) using the brightness parameter extracted by the DSP (1) 51. The illuminance is determined for each unit region 41 based on the brightness parameter. For example, an LUT (look up table) can be used for the conversion from the brightness parameter to the illuminance. The phase modulation signal generation unit 56 generates a phase modulation signal in accordance with the output from the DSP (2) 52.

  The phase modulation signal generation unit 56 determines a phase modulation pattern using a calculation method such as iterative Fourier transform. As the phase modulation signal generation unit 56, a configuration capable of high-speed arithmetic processing, for example, a GPU (Graphics Processing Unit) or an ASIC (Application Specific Integrated Circuit) is used, so that real-time calculation according to the output from the DSP (2) 52 Processing can be enabled. Thereby, data that needs to be stored in advance can be reduced, and the memory capacity can be reduced. In addition, the phase modulation signal generation unit 56 may be configured to refer to data stored in advance in the LUT and output a calculation result. In this case, the arithmetic processing in the phase modulation signal generation unit 56 can be simplified. Further, by eliminating the need for high-speed arithmetic processing, the circuit configuration of the phase modulation signal generation unit 56 can be simplified.

  The phase modulation driver 57 drives the phase modulators 13R, 13G, and 13B according to the phase modulation signal from the phase modulation signal generator 56. The phase modulation units 13R, 13G, and 13B are controlled according to the phase modulation signal generated based on the image signal. The phase modulation units 13R, 13G, and 13B cause the light whose intensity is adjusted for each unit region 41 to enter the incident surface 40 by changing the phase modulation pattern according to the phase modulation signal.

  The DSP (2) 52 calculates the amount of light from the light source units 11R, 11G, and 11B necessary for realizing the illuminance distribution of light determined based on the brightness parameter. The light quantity of each light source part 11R, 11G, 11B is determined on the basis of the average illumination intensity of the light in the entrance plane 40 of a spatial light modulator. A pulse width modulation (PWM) signal generator 58 generates a PWM signal whose pulse width is modulated based on the output from the DPS (2) 52. The light source drive unit 59 drives the light source units 11R, 11G, and 11B in accordance with the PWM signal from the PWM signal generation unit 58. The light source units 11R, 11G, and 11B supply light modulated according to the PWM signal. As a result, the light source units 11R, 11G, and 11B supply laser light with adjusted intensity. While the relative intensity of light for each unit region 41 is determined by the control of the phase modulation units 13R, 13G, and 13B, the light intensity of the entire incident surface 40 is determined by the control of the light source units 11R, 11G, and 11B. The

  When the average illuminance on the incident surface 40 is m, the phase modulators 13R, 13G, and 13B distribute the diffracted light from the unit area 41 having an illuminance lower than the average illuminance m to the unit area 41 having an illuminance higher than the average illuminance m. . Further, assuming that the light source units 11R, 11G, and 11B have the maximum output L and the illuminance when uniformly illuminating the entire incident surface 40 is n, the outputs of the light source units 11R, 11G, and 11B are m / n of the maximum output L. Can be doubled. For example, when the average illuminance m is 1 and the illuminance n at the maximum output L is 2, the outputs of the light source units 11R, 11G, and 11B can be reduced to L / 2. By making the output of the light source units 11R, 11G, and 11B adjustable according to the intensity of light incident on the incident surface 40, the projector 100 can realize power saving.

  The DSP (3) 53, which is a digital signal processing circuit, expands the gradation range of the image signal based on the brightness parameter from the DSP (1) 51. By extending the gradation range, it is possible to display a high-contrast image that makes the best use of the dynamic range of the spatial light modulators 15R, 15G, and 15B. The DA converter 54 converts the image signal that has been decompressed by the DSP (3) 53 into an analog signal. The spatial light modulation driving unit 55 drives the spatial light modulation devices 15R, 15G, and 15B in accordance with the image signal converted into the analog signal. The spatial light modulators 15R, 15G, and 15B modulate light from the illumination devices 10R, 10G, and 10B according to the image signal.

  By adopting a configuration in which laser light that is coherent light is incident on the phase modulators 13R, 13G, and 13B, favorable diffraction characteristics can be obtained in the phase modulators 13R, 13G, and 13B. By distributing the light using the phase modulation units 13R, 13G, and 13B, the light with the illuminance distribution adapted to the image is incident on the incident surface 40 without wasting light from the light source units 11R, 11G, and 11B. Is possible. For this reason, it is possible to make adjustment so as to make it easy to see the entire image with high contrast, and it is also possible to effectively use the laser light from the light source unit.

  Furthermore, by adjusting the output of the light source units 11R, 11G, and 11B according to the intensity of light incident on the incident surface 40, an image can be displayed with a wider dynamic range. As a result, it is possible to make adjustments to make the entire image easy to see with high contrast, and to achieve high light utilization efficiency. The projector 100 can display a bright image with high contrast and high light utilization efficiency.

  Conventionally, a film-like diffractive optical element in which fine irregularities are formed is used as an element for generating diffracted light. Compared with the case where a film-like diffractive optical element is used, the phase modulation units 13R, 13G, and 13B using the liquid crystal element 20 have an advantage that the phase modulation pattern can be easily changed by controlling voltage application. . In addition, the film-like diffractive optical element becomes difficult to manufacture as the number of gradations increases. For example, when a diffractive optical element is manufactured through an exposure process using a mask, more masks are required as the number of gradations increases. On the other hand, the phase modulators 13R, 13G, and 13B can obtain an advantage that the increase in the number of gradations can be handled relatively easily by using the liquid crystal element 20.

  When the difference in light intensity between adjacent frames in a certain unit region 41 is significant, it may give the viewer a sense of discomfort as flickering. The adjustment of the light intensity by the phase modulators 13R, 13G, and 13B is desirably a change within, for example, 2% in a time during which light is integrated as an afterimage, for example, two frame periods. In addition, even when the difference in light intensity between adjacent unit regions 41 is significant, the viewer may feel uncomfortable such as unnaturalness of the image. Even within the spatial range in which the light is integrated, the adjustment of the light intensity by the phase modulators 13R, 13G, and 13B is desirably a change within 2%, for example. In this way, by relaxing the change in light intensity temporally or spatially, it is possible to reduce a sense of incongruity and allow comfortable image observation.

  The phase modulators 13 </ b> R, 13 </ b> G, and 13 </ b> B may be configured to use, as the liquid crystal element 20, a scattering type liquid crystal in addition to the liquid crystal in the electric field control birefringence mode. However, when the scattering type liquid crystal is used, the light utilization efficiency may be reduced due to light scattering. The phase modulation units 13R, 13G, and 13B may be configured to perform phase modulation according to a digital signal in addition to a configuration that performs phase modulation according to an analog signal. As a configuration for performing phase modulation according to a digital signal, for example, a MEMS (Micro Electro Mechanical System) device can be used. However, in the case of digital modulation, since the gradation expression is discontinuous, if the phase modulation pattern cannot be reproduced finely, it is difficult to sufficiently control the diffraction angle. The configuration of performing phase modulation according to an analog signal has an advantage that an accurate illuminance distribution can be obtained by fine reproduction of the phase modulation pattern and sufficient control of the diffraction angle since continuous gradation expression is possible.

  The illumination devices 10R, 10G, and 10B are not limited to the configuration in which the laser light whose intensity is adjusted based on the image signal is supplied by the light source units 11R, 11G, and 11B. The light source units 11R, 11G, and 11B may supply laser light having a substantially constant intensity. In this case, so-called peak luminance control can be performed in which a display with higher luminance than that in the case of irradiating light uniformly over the entire screen with the light source units 11R, 11G, and 11B as the maximum output. Conventionally, peak luminance control has been a feature of CRT displays and plasma displays. As a result, the liquid crystal projector 100 can display an image with a wider dynamic range.

  Furthermore, the DSP (2) 52 may perform adjustment according to a control signal directly input from the outside, as indicated by a dashed arrow in FIG. The control signal directly input to the DSP (2) 52 is for setting according to the difference in intensity of each laser beam. For example, output variation due to individual differences among the laser light sources 12R, 12G, and 12B. Is to correct. The light sources 11R, 11G, and 11B are controlled according to a PWM signal that is set based on the intensity difference between the laser light sources 12R, 12G, and 12B. The phase modulators 13R, 13G, and 13B are controlled according to the phase modulation signal set based on the intensity difference between the laser light sources 12R, 12G, and 12B. Thereby, effective control according to the output difference of a several laser light source can be performed. Also, good white balance can be obtained by adjusting the intensity of the laser light between the colors. Note that any one of the light source units 11R, 11G, and 11B and the phase modulation units 13R, 13G, and 13B may be controlled in accordance with the intensity difference of the laser light.

  The unit region 41 set on the incident surface 40 of the spatial light modulators 15R, 15G, and 15B may be smaller than the incident surface 40 and larger than the pixel region in the spatial light modulators 15R, 15G, and 15B. By setting a plurality of unit regions 41 smaller than the incident surface 40, it is possible to adjust the light intensity for each unit region 41. In addition, in order to obtain a high contrast for the entire image, it is sufficient for the phase modulation units 13R, 13G, and 13B to adjust the light intensity for each region wider than the pixel. By setting the unit region 41 larger than the pixel region, the configuration and driving of the phase modulation units 13R, 13G, and 13B can be simplified. Thereby, the light of the intensity distribution adapted to the image can be incident on the spatial light modulators 15R, 15G, and 15B using the phase modulators 13R, 13G, and 13B that are simple in configuration and driving.

  The projector 100 is not limited to a front projection type projector. A so-called rear projector may be used in which light is supplied to one surface of the screen and an image is viewed by observing light emitted from the other surface of the screen. Further, the present invention may be applied to a direct view type display using a liquid crystal display device.

  As described above, the illumination device according to the present invention is suitable for use in a projector that projects light according to an image signal.

1 is a diagram showing a schematic configuration of a projector according to an embodiment of the invention. The figure which shows an illuminating device, a spatial light modulator, and a cross dichroic prism. The figure which shows the cross-sectional structure of a liquid crystal element. The figure which shows the unit area | region set to the entrance plane of a spatial light modulator. The figure which shows the block structure for driving a projector.

Explanation of symbols

  100 projector, 10R R light illumination device, 10G G light illumination device, 10B B light illumination device, 11R R light source unit, 11G G light source unit, 11B B light source unit, 12R, 12G, 12B Laser light source, 13R, 13G, 13B phase modulation unit, 14R, 14G, 14B field lens, 15R R light spatial light modulation device, 15G G light spatial light modulation device, 15BB light spatial light modulation device, 16 cross dichroic Prism, 16a first dichroic film, 16b second dichroic film, 17 projection lens, 18 screen, 20 liquid crystal element, 21 first transparent substrate, 22 first transparent electrode, 23 light shielding layer, 24 second transparent substrate, 25 semiconductor layer , 26 Gate insulating film, 27 Gate electrode, 28 Insulating film, 29 Signal line, 30 PSG film, 3 DESCRIPTION OF SYMBOLS 1 2nd transparent electrode, 32 Liquid crystal layer, 40 Incidence surface, 41 Unit area | region, 50 AD converter, 51 DSP (1), 52 DSP (2), 53 DSP (3), 54 DA converter, 55 Spatial light modulation drive part 56 phase modulation signal generation unit, 57 phase modulation drive unit, 58 PWM signal generation unit, 59 light source drive unit

Claims (11)

A light source for supplying coherent light;
A phase modulation unit that modulates the phase of the coherent light from the light source unit and enters the surface to be irradiated; and
The phase modulation unit changes the phase of the coherent light while generating diffracted light according to a phase modulation pattern, thereby adjusting light whose intensity is adjusted for each unit region set on the irradiated surface, An illumination device that is incident on the irradiated surface.   The lighting device according to claim 1, wherein the phase modulation unit includes a liquid crystal element.   The lighting device according to claim 2, wherein the liquid crystal element is an electric field controlled birefringence mode liquid crystal element.   The illumination device according to claim 1, wherein the light source unit supplies the coherent light whose intensity is adjusted.   The lighting device according to claim 4, wherein the light source unit supplies the coherent light having an intensity determined with reference to an average illuminance on the irradiated surface. The light source unit supplies a plurality of the coherent lights,
6. The illumination device according to claim 1, wherein at least one of the light source unit and the phase modulation unit is controlled according to an intensity difference of the coherent light.   The said light source part supplies the said coherent light of substantially constant intensity | strength, The illuminating device as described in any one of Claims 1-3 characterized by the above-mentioned.   A projector that displays an image by modulating light from the illumination device according to claim 1 in accordance with an image signal. A spatial light modulator that modulates light from the illumination device according to the image signal;
The projector according to claim 8, wherein the illumination device causes light having an intensity adjusted for each unit region set on the incident surface of the spatial light modulator to be incident on the incident surface.   The projector according to claim 9, wherein the unit region is smaller than the incident surface and larger than a pixel region in the spatial light modulation device. The illumination device has a phase modulation unit that modulates the phase of coherent light from the light source unit,
The projector according to claim 8, wherein the phase modulation unit is controlled according to a phase modulation signal generated based on the image signal.

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