JP2012109989A - Projector and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector capable of obtaining a projected image of high color reproducibility even in a black signal or an image with low brightness.SOLUTION: A projector includes: a dimming unit 103 that reflects light from a light source unit 101 selectively in two directions; and a dimming processing unit 160 that controls the dimming unit 103 on the basis of at least one of a brightness distribution of an image signal and an image average brightness, and the dimming processing unit 160 supplies such an image signal that brightness of light emitted from a liquid crystal type spatial light modulator 110R or the like in accordance with a prescribed level of the image signal during dimming of the dimming unit 103 and that during non-dimming of the dimming unit 103 are approximately equal to each other. The dimming unit 103 reduces the quantity of light made incident on the liquid crystal type spatial light modulator 110R or the like to perform color reproduction for the image signal for black display or low brightness.

Description

  The present invention relates to a projector, and more particularly to a projector using a liquid crystal display device as a liquid crystal spatial light modulator.

  A projector is an image display device that displays an image by projecting light (projection light) representing an image in accordance with an image signal supplied from an image supply device such as a computer. For example, a liquid crystal display device is used as a spatial light modulation device for a projector. The liquid crystal display device controls the amount of light from the liquid crystal display device by changing the transmittance or reflectance using the anisotropy of the liquid crystal molecules. The liquid crystal display device applies a voltage to the liquid crystal molecules inside the panel to displace the liquid crystal molecules. The transmittance or reflectance with respect to incident light is controlled in accordance with the amount of displacement of the liquid crystal molecules. For example, in order to obtain a projected image with high brightness, the applied voltage is increased in order to increase the transmittance of the liquid crystal display device. On the other hand, in order to obtain a black display or a low-brightness projection image, the applied voltage is reduced in order to reduce the transmittance of the liquid crystal display device.

  However, in a region where the applied voltage is small from zero to a predetermined value, it is difficult to accurately control the displacement amount of the liquid crystal molecules with respect to the applied voltage. For this reason, it is difficult to control the transmittance or reflectance of the liquid crystal display device to a desired value in a black display or low luminance region of the projected image. As a result, there arises a problem that accurate color reproduction is difficult in the black display of the projected image or in the low luminance region.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a projector that can obtain a projected image with good color reproduction even in the case of a black signal or an image with low luminance.

  In order to solve the above problems and achieve the object, the present invention includes a light source unit that supplies light, a liquid crystal spatial light modulator that modulates and emits light from the light source unit according to an image signal, A projection lens that projects light modulated by the liquid crystal spatial light modulator; a first state in which light from the light source unit enters the liquid crystal spatial light modulator; and the liquid crystal spatial light modulator. A dimming unit that selectively selects a second state different from the state incident on the liquid crystal, and the liquid crystal spatial light modulation corresponding to a predetermined level of the image signal when the dimming unit performs dimming The luminance of the light emitted from the device and the luminance of the light emitted from the liquid crystal spatial light modulator corresponding to the predetermined level of the image signal when the dimming unit is not dimming are substantially matched. An image signal for supplying the image signal to the liquid crystal spatial light modulator. An adjustment unit; and a dimming processing unit for controlling the dimming unit based on at least one of a luminance distribution of the image signal and an average image luminance, and the dimming unit includes the liquid crystal type space A projector is provided that performs color reproduction when the image signal is displayed in black or has low brightness by reducing the amount of light incident on a light modulation device. In this projector, in the case of a black signal or an image with low brightness, the amount of light incident on the liquid crystal spatial light modulator is reduced. Thereby, the gradation expression value for driving the liquid crystal type spatial light modulation device for setting the transmitted light or reflected light of the liquid crystal type spatial light modulation device to a predetermined luminance is larger than that in the case where the light is not dimmed. As a result, since an area in which the gradation expression value can be controlled is used, a projected image with good color reproduction can be obtained even in the case of a black signal or an image with low luminance. Moreover, since the light control part controls light quantity by reflecting incident light, it can reduce light quantity loss.

  It is desirable to further include a rod integrator for illuminating the liquid crystal type spatial light modulator substantially uniformly with the light from the light source unit, and the dimming unit is provided on the exit side of the rod integrator. Thereby, the uniform illumination light can be dimmed.

  Further, according to a preferred aspect of the present invention, the dimming unit is a tilt mirror device having a plurality of movable mirror elements that can alternatively select the first reflection position and the second reflection position, The movable mirror element reflects light from the light source unit in the first direction to be incident on the liquid crystal type spatial light modulation device at the first reflection position, and at the second reflection position. The light from the light source unit is reflected in the second direction different from the direction in which the light is incident on the liquid crystal type spatial light modulator, and the dimming unit has the plurality of movable mirror elements in the first direction according to an image signal. It is desirable to control the amount of light incident on the liquid crystal spatial light modulator by controlling the time in the state of one reflection position or the time in the state of the second reflection position. Thereby, a light control part can be reduced in size and can be manufactured at low cost. In addition, since the tilt mirror device is used, it is possible to drive with high reliability, durability (long life), low noise, and good response.

  According to a preferred aspect of the present invention, the light that is projected by the projection lens on the second direction different from the direction of incidence on the liquid crystal spatial light modulator by the dimming unit. Auxiliary light element for increasing the luminance of the auxiliary light, a synthesizer for synthesizing the auxiliary light from the auxiliary light element and the modulated light from the liquid crystal spatial light modulator It is desirable to further have. As a result, in an image that is dimmed by the dimming unit and has an overall reduced luminance level, it is possible to obtain a projected image that is dark on the low gradation side and high in contrast, and bright on the high gradation side.

  According to a preferred aspect of the present invention, it is desirable that the auxiliary light element is a liquid crystal display element. The liquid crystal display element does not require pixel unit resolution as in the spatial light modulation device, and the region unit resolution for each predetermined region is sufficient. As a result, the liquid crystal display element can be a low-resolution panel and can be manufactured at low cost. Furthermore, since the scale of the drive circuit of the liquid crystal display element can be reduced, it can be manufactured at low cost.

  Further, according to a preferred aspect of the present invention, the light storage battery that converts the light reflected in the second direction different from the direction incident on the liquid crystal type spatial light modulation device by the light control unit into electric energy and stores it. And a power supply circuit that uses electrical energy from the photo-electric storage battery as a power source for the projector. Thereby, the stored electrical energy can be used as power consumption when the projector is in a standby state, for example. As a result, low power consumption can be achieved.

  According to a preferred aspect of the present invention, the range of the level of the image signal corresponding to the area where the color reproduction can be performed in the black display or the low luminance area of the liquid crystal spatial light modulator is the input image signal. It is desirable that the amount of light incident on the liquid crystal type spatial light modulator is reduced so that the image signal adjustment unit supplies the image signal to the liquid crystal type spatial light modulator so as to correspond to the range of levels. Thereby, accurate color reproduction can be performed.

  In addition, according to a preferred aspect of the present invention, the image processing device further includes a scene detection circuit that detects a change in a scene based on the image signal, and the dimming unit is configured to perform the above-described operation in a period different from the detected scene period. It is desirable to adjust light so that the amount of light incident on the spatial light modulator becomes a predetermined value. As a result, even if an abrupt image change occurs, it can be prevented from being recognized as flicker.

  Further, according to a preferred aspect of the present invention, it is desirable to extend the dynamic range of the image signal in accordance with the light amount control by the light control unit. Thereby, the dynamic range of an image can always be utilized most effectively. As a result, an image with high contrast can be obtained.

  According to a preferred aspect of the present invention, it is desirable that the dimming unit performs dimming control according to a lighting time of the light source unit or a light emission characteristic unique to the light source unit. As a result, when a lamp is used as the light source unit, the dimming conditions can be controlled in accordance with the change over time of the light emission characteristics depending on the lamp lighting time or the difference in the light emission characteristics unique to the lamp when the lamp is replaced. The light emission characteristics include, for example, a light emission amount. As a result, the light control according to the light source unit can be performed more accurately.

1 is a diagram illustrating a schematic configuration of a projector according to a first embodiment. The figure which shows schematic structure of the light control part in 1st Embodiment. FIG. 6 is a diagram illustrating a schematic configuration of a projector according to a second embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a projector according to a third embodiment. The figure which shows the timing of light control. The figure which shows input gradation, a brightness | luminance, contrast, etc. The figure which shows an input gradation, a brightness | luminance, and target color temperature error rate. The figure which shows the procedure of the light control amount by APL. The figure which shows the procedure of a black-and-white expansion process. The figure which shows the procedure of light control determination. The figure which shows the relationship between light control conditions and a luminance distribution histogram. The figure which shows the procedure of scene detection, dynamic range detection, and light control. The figure which shows the procedure in the case of luminance addition. The figure which shows the area | region and luminance distribution histogram of the image | video in the case of carrying out luminance addition. The figure which shows the procedure in the case of detecting a high gradation area | region and saturation and adding luminance.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.
(First embodiment)
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a projector 100 according to the first embodiment of the present invention. The light source unit 101 includes light including red light (hereinafter referred to as “R light”), green light (hereinafter referred to as “G light”), and blue light (hereinafter referred to as “B light”). Supply. An ultra-high pressure mercury lamp can be used as the light source unit 101. The light from the light source unit 101 is collected at the focal point f. The rod integrator 102 is provided at a position where the focal point f and its incident side end face 102a substantially coincide with each other. The light that has entered the rod integrator 102 travels while being repeatedly reflected, and exits from the exit-side end face 102b. The rod integrator 102 forms a plurality of secondary light source images to illuminate liquid crystal type spatial light modulators 110R, 110G, and 110B described later substantially uniformly. Then, the light emitted from the rod integrator 102 enters the light control unit 103.

  The light control unit 103 is provided on the emission side of the rod integrator 102, and is in a first state that is a first state in which light from the light source unit 101 is incident on liquid crystal type spatial light modulators 110R, 110G, and 110B described later. D1 and the second direction D2, which is a second state different from the direction of incidence on the liquid crystal type spatial light modulators 110R, 110G, 110B, are alternatively selected and reflected. Details of the light control unit 103 will be described later. First, the light reflected in the first direction to be incident on the liquid crystal type spatial light modulators 110R, 110G, and 110B by the light control unit 103 will be described.

  The light reflected in the first direction D1 by the light control unit 103 enters the R light transmitting dichroic mirror 104R. Hereinafter, the R light will be described. The R light transmitting dichroic mirror 104R transmits R light and reflects G light and B light. The R light transmitted through the R light transmitting dichroic mirror 104R enters the reflection mirror M1. The reflection mirror M1 bends the optical path of the R light by 90 degrees. The R light whose optical path is bent is incident on a liquid crystal spatial light modulator 110R for R light that modulates the R light according to an image signal. The liquid crystal spatial light modulator 110R for R light is a transmissive liquid crystal display device that modulates R light according to an image signal. The R light modulated by the liquid crystal spatial light modulator 110R for R light is incident on a cross dichroic prism 120 which is a color synthesis optical system.

  Next, the G light will be described. The light paths of the G light and the B light reflected by the R light transmitting dichroic mirror 104R are bent by 90 degrees. The G light and the B light whose optical paths are bent enter the B light transmitting dichroic mirror 104B. The B light transmitting dichroic mirror 104B reflects G light and transmits B light. The G light reflected by the B light transmitting dichroic mirror 104B is incident on a liquid crystal spatial light modulator 110G for G light that modulates the G light according to an image signal. The liquid crystal spatial light modulator 110G for G light is a transmissive liquid crystal display device that modulates G light according to an image signal. The G light modulated by the liquid crystal type spatial light modulator 110G for G light is incident on the cross dichroic prism 120 which is a color synthesis optical system.

  Next, the B light will be described. The B light transmitted through the B light transmitting dichroic mirror 104B passes through the two relay lenses 105 and the two reflection mirrors M2 and M3, and the B light liquid crystal modulates the B light according to the image signal. It enters the mold spatial light modulator 110B. The liquid crystal spatial light modulator 110B for B light is a transmissive liquid crystal display device that modulates B light according to an image signal.

  The reason why the B light passes through the relay lens 105 is that the optical path length of the B light is longer than the optical path lengths of the R light and the G light. By using the relay lens 105, the B light transmitted through the B light transmitting dichroic mirror 104B can be directly guided to the liquid crystal spatial light modulator 110B for B light. The B light modulated by the liquid crystal spatial light modulator 110B for B light is incident on the cross dichroic prism 120 which is a color synthesis optical system.

  The cross dichroic prism 120, which is a color synthesis optical system, is configured by arranging two dichroic films 120a and 120b perpendicularly to an X shape. The dichroic film 120a reflects R light and transmits G light. The dichroic film 120b reflects B light and transmits G light. As described above, the cross dichroic prism 120 combines the R light, G light, and B light modulated by the liquid crystal spatial light modulators 110R, 110G, and 110B, respectively. The projection lens 130 projects the light combined by the cross dichroic prism 120 onto the screen 140.

  Next, the light control unit 103 will be described. As the light control unit 103, for example, a tilt mirror device can be used. One example of a conventional tilt mirror device is a Texas Instruments DMD. DMD is a trademark of Texas Instruments Incorporated. The tilt mirror device has a plurality of movable mirror elements that can alternatively select the first reflection position and the second reflection position. The movable mirror element reflects the light from the light source unit 101 in the first direction D1 to be incident on the liquid crystal type spatial light modulators 110R, 110G, and 110B at the first reflection position, and at the second reflection position. The light from the light source unit 101 is reflected in a second direction D2 different from the direction in which the light enters the liquid crystal type spatial light modulators 110R, 110G, and 110B. The light control unit 103 controls the time during which the plurality of movable mirror elements are in the state of the first reflection position or the state of the second reflection position in accordance with the image signal, so that the liquid crystal type space The amount of light incident on the light modulation devices 110R, 110G, and 110B is controlled. With this configuration, when a black display or a low-brightness image is projected on the screen 140, the amount of light incident on the liquid crystal spatial light modulators 110R, 110G, and 110B is reduced. As a result, the amount of illumination light of the liquid crystal type spatial light modulators 110R, 110G, and 110B is reduced, so that the brightness of the display can be reduced, and the absolute luminance value can be kept low even in the case of a black signal or an image with low luminance. An image with a high contrast feeling can be projected.

  The DMD that is the light control unit 103 includes a plurality of movable mirror elements 200 as shown in FIG. In the present embodiment, 20 movable mirror elements 200 are arranged in a matrix of 4 rows × 5 columns. The aspect ratio of the reflection region of the light control unit 103 is 3: 4 (for example, length = 15 mm, width = 20 mm). As can be seen from FIG. 2, the size of each movable mirror element 200 can be larger and the number thereof can be smaller than the DMD for image display.

  When the position state of the movable mirror element 200 is selected alternatively, all the movable mirror elements 200 are set to the same state. For example, FIG. 2A shows a case where the movable mirror element 200 is in the first reflection position. In this case, the light control unit 103 reflects the light from the light source unit 101 in the first direction D1 incident on the liquid crystal spatial light modulators 110R, 110G, and 110B. Further, when the movable mirror element 200 is set to the second reflection position, all the movable mirror elements 200 are set to the second reflection position as shown by hatching in FIG. . In this case, the light control unit 103 reflects the light from the light source unit 101 in the second direction D2 different from the direction in which the light enters the liquid crystal spatial light modulators 110R, 110G, and 110B.

  In this way, the light control unit 103 selectively reflects incident light in the first direction D1 and the second direction D2. In addition, the position of the movable mirror element is not partially changed, but the overall position is changed. In other words, the dimming unit 103 has a function of performing surface shielding instead of partial shielding when the light from the light source unit 101 is dimmed and dimmed. Therefore, the light control unit 103 can be designed regardless of the position and size of the secondary light source image formed by the rod integrator 102. For this reason, the freedom degree of design and arrangement | positioning of the tilt mirror device of the light control part 103 becomes large.

  The light control unit 103 is not limited to a tilt mirror device, and may be configured by a grating / light valve or a MEMS (Micro Electro Mechanical Systems). As described above, since the movable mirror element is driven in a surface sequential manner, the shape of the light control unit 103 does not need to be optimized in accordance with the shape of the secondary light source image. Further, the unit element for driving the light control unit 103 is not particularly limited.

  Next, returning to FIG. 1, the operation of the light control unit 103 will be described. The video signal input circuit 150 outputs image signals of R light, G light, and B light to the dimming processing unit 160. In addition, a frame memory 151 is connected to the dimming processing unit 160. The dimming processing unit 160 includes a dimming control circuit 161, a low-pass filter / labeling circuit 162, a scene detection circuit 163, an image average luminance level (hereinafter referred to as “APL”) detection circuit 164, and a histogram detection. Circuit 165. The signal processing procedure of these circuits will be described later. The image signal from the light control processing unit 160 is sent to the video signal modulation circuit 170. The video signal modulation circuit 170 performs sharpness processing, color processing, and black and white expansion processing. The dimming processing unit 160 also controls the luminance of each color light emitted by the liquid crystal spatial light modulators 110R, 100G, and 110B in accordance with a predetermined level of the image signal when the dimming unit 103 performs dimming, and dimming The liquid crystal type spatial light modulator 110R so that the luminance of each color light emitted by the liquid crystal type spatial light modulators 110R, 110G, and 110B substantially corresponds to the predetermined level of the image signal when the unit 160 is not dimmed. , 110G, and 110B also serve as an image signal adjustment unit that supplies image signals.

  The image signal from the video signal modulation circuit 170 is sent to the liquid crystal spatial light modulator driving circuit 171. The liquid crystal spatial light modulator driving circuit 171 drives the liquid crystal spatial light modulators 110R, 110G, and 110B for each color light according to the image signal. For the sake of simplicity, FIG. 1 shows the connection between the liquid crystal spatial light modulator driving circuit 171 and the liquid crystal spatial light modulator 110R for R light, and liquid crystal spatial light for G light and B light. Connection with the modulators 110G and 110B is omitted.

  Next, the basic operation of the light control unit 103 will be described with reference to FIG. Note that increasing or decreasing the amount of light incident on the liquid crystal spatial light modulators 110R, 110G, and 110B by the light control unit 103 is hereinafter referred to as “light control”. As described above, the dimming unit 103 performs so-called time-division driving for controlling the time during which the movable mirror element is in the first reflection position or the second reflection position. The amount of light incident on the liquid crystal type spatial light modulators 110R, 110G, and 110B is controlled. The dimming processing unit 160 sends a signal for driving the dimming unit 103 to the movable mirror element control circuit 181. Further, the movable mirror element control circuit 181 sends a signal for driving the movable mirror element of the light control unit 103 to the movable mirror element drive circuit 182. Further, the light control processing unit 160 is controlled by the CPU 180.

Consider a case in which the amount of light in one frame of video is dimmed with 8 gradations (3 bits). When dimming with 3 bits, three subframe pulses P0 (= 2 ⁰ ) and P1 (= 2 ¹ ) having a weight corresponding to each bit of the 3-bit gradation display as shown in FIG. , P2 (= 2 ² ). When the video signal A is displayed within the display period of one frame shown in FIG. 5A, the dimming unit 103 has the movable mirror element in the first reflection position state at all subframe pulses. In this case, all the light from the light source unit 101 is incident on the liquid crystal type spatial light modulators 110R, 110G, and 110B. When the video signal B is displayed, the movable mirror element is in the first reflection position state at the subframe pulse P1, and is in the second reflection position state at the other subframe pulses P0 and P2. As a result, as shown in FIG. 5C, the amount of light incident on the liquid crystal spatial light modulators 110R, 110G, 110B of the video signal B is reduced to about 30% compared to the video signal A. Is done. The luminance distribution histograms of the video signals A and B are shown in FIGS. 5 (d) and 5 (e), respectively. The luminance distribution histogram is a graph showing the relationship between the input gradation level (horizontal axis) and the distribution frequency (vertical axis).

  In the light control by partial light shielding by, for example, shutter blades as in the prior art, the secondary light source image of the light source unit is partially shielded. For this reason, in the light shielding by the prior art, light from the secondary light source image shielded by the shutter blades among the secondary light source images formed on the integrator is shielded. Thereby, only a part of the light of the secondary light source image that is not shielded by the shutter blades is irradiated to the liquid crystal spatial light modulator. As a result, the amount of light incident on the top and bottom of the liquid crystal type spatial light modulator or on the left and right is partially different. In the liquid crystal type spatial light modulator, the distribution of the regions having different amounts of incident light depends on the structure of the shutter blades, that is, the direction and size of the light shielding region. As a result, luminance unevenness occurs. Furthermore, in the case of a configuration in which the polarization directions of the R light and B light are different from the polarization direction of the G light, the light energy of the portion where the luminance unevenness occurs is not 1: 1: 1 between the color lights. For this reason, color unevenness similarly occurs. On the other hand, in the present embodiment, the light control unit 103 performs light control by driving the movable mirror element in the subframe as described above. For this reason, it is possible to prevent the projected image from flickering even when a sudden luminance change occurs in the video signal.

  FIG. 6 shows the relationship between the input gradation n of the liquid crystal spatial light modulators 110R, 110G, and 110B, the contrast (solid line), the luminance (one-dot chain line), and the target color temperature error rate (dotted line). A target color temperature error rate is set to 0% when a desired color reproduction is performed. As the color reproduction shifts from the desired value, the target color temperature error rate increases. As is clear from FIG. 6, the target color temperature error rate increases in the region where the input gradation of the liquid crystal spatial light modulators 110R, 110G, 110B is small, for example, the region smaller than 32 gradations, and the color reproduction is accurate. Difficult to do. In the present embodiment, even in a low-brightness region where it is difficult to accurately perform conventional color reproduction, color reproduction can be performed favorably by dimming with the light control unit 103. The reason why the color can be reproduced well by dimming will be described with reference to FIG.

  FIG. 7A shows the luminance (vertical axis) of light emitted from the liquid crystal spatial light modulators 110R, 110G, and 110B and the input gradation n (horizontal axis) of the liquid crystal spatial light modulators 110R, 110G, and 110B. Shows the relationship. The luminance curve La when the light from the light source unit 101 is incident on the spatial light modulators 101R, 110G, and 110B by the dimming unit 103 and the luminance curve Lb when dimmed by the dimming unit 103 are shown side by side. In the case of the luminance curve La, as shown in FIG. 7B, for example, it is assumed that it is difficult to control color reproduction when the input gradation n is 32 gradations or less. Further, in order to obtain a predetermined luminance I0 in the absence of dimming, it is assumed that the input gradation n is 32 gradations. Next, when the light is dimmed by the light control unit 103, the luminance is lowered and a luminance curve Lb is obtained. In this case, in order to obtain the predetermined luminance I0, the input gradation n increases to 64 gradations. Thus, by dimming, the input gradation n for obtaining the same luminance I0 changes from 32 gradations to 64 gradations. As described in FIG. 7B, it is difficult to accurately perform color reproduction in an area smaller than 32 gradations. On the other hand, in the region where the input gradation n is about 64 gradations, the target color temperature error rate is substantially zero in FIG. 7B, so that color reproduction can be performed accurately. As a result, it is possible to perform color reproduction in the case of a black display or a dark image with low brightness by dimming with the light control unit 103. As a result, when dimming, the target color temperature error rate becomes substantially zero over almost all gradations as shown in FIG. 7C. However, as shown in FIG. 7A, the dynamic range DR3 of the image signal in the case of dimming is the dynamic range DR2 in which color reproduction control is possible before dimming (the dynamic range DR1 is the full range before dimming). Compared to the dynamic range).

  Next, a procedure for determining the light control amount of the light control unit 103 using APL will be described with reference to FIG. In step S800, the low-pass filter / labeling circuit 162 removes high-frequency noise from the video signal by performing low-pass filtering (LPF) processing. In step S801, the APL detection circuit 164 calculates an APL value of the video signal of one frame. If the APL value is large, the dimming processing unit 160 performs control so as not to dim the light in step S802. In this case, all the light reflected by the light control unit 103 is guided to the liquid crystal type spatial light modulators 110R, 110G, and 110B. If the APL value is intermediate, in step S803, the dimming processing unit 160 controls the amount of light to be dimmed between a small amount and an intermediate amount. Further, when the APL value is small, that is, when the signal is a black signal or a signal with low luminance, the dimming processing unit 160 performs control so as to increase the amount of light to be dimmed in step S804. In step S805, black and white expansion processing is performed on the video signal. In step S806, the movable mirror element driving circuit 182 drives the movable mirror element of the light control unit 103 in accordance with a control signal from the movable mirror element control circuit 181 to control the light control amount. Details of steps S805 and S806 will be described later. In step S807, the liquid crystal spatial light modulators (abbreviated as “LCD” in the drawing) 110R, 110G, and 110B are driven. In step S808, the dimmer 103 is driven in the above-described subframe. In the sub-frame driving, since pulse width modulation is performed, it is abbreviated as “PWM driving” in step S808.

  FIG. 9 is a flowchart for explaining in more detail the procedure of the black and white expansion processing in step S805 in FIG. In step S900, the histogram detection circuit 165 calculates a minimum value Min (J), a maximum value Max (K), and a contrast CR of the luminance of the video signal. It should be noted that the brightness is not limited to the maximum value and the minimum value. For example, the value may be 0.9 times the maximum value, 0.9 times the minimum value, or a region where the frequency of the brightness distribution is 10,000 or more. good. In step S901, the dynamic range DR is maximized while keeping the contrast condition constant. In step S <b> 902, it is determined whether or not there is data of a region that is difficult to accurately perform color reproduction in a dark region with black display or low luminance (abbreviated as “black temperature non-control region” in the drawing). If the determination result in step S902 is true, in step S903, the minimum luminance value (Min value) is displayed in a black display area or an area where color reproduction can be accurately performed in a dark area with low luminance ("black control" in the figure). It is set to the lowest limit value N of “Area”. In step S904, the dynamic range is maximized again. Further, after step SS904 or when the determination result in step S902 is false, the process proceeds to step S905. In step S905, the liquid crystal type spatial light modulators 110R, 110G, and 110B and the light control unit 103 are controlled to perform the result of the above processing.

  Next, a processing procedure for determining the light control amount will be described with reference to FIG. In step S1000, the minimum luminance value Min of the above-described black and white expansion process is calculated. In step S1001, the brightness value P at the minimum value Min (J) of the gradation expression value of the original image (image before reducing the brightness) is calculated from the look-up table (LUT). In this LUT, the relationship between the gradation expression value and the luminance is recorded in a table format. In step S1002, the luminance value Q at the minimum value Min (N) of the gradation table original value of the image subjected to the expansion / contraction processing is calculated from the LUT. In step S1003, the dimming amount for the luminance value Q = P is calculated from the LUT. In step S1004, the dimming processing unit 160 determines the dimming amount. In step S1005, a dimming control condition is calculated. In step S1006, the light control unit 103 is driven so that the determined light control amount is obtained.

  Next, the relationship between the light intensity to be dimmed and the luminance distribution histogram will be described with reference to FIG. FIG. 11A shows a case where there is an area where black is difficult to reproduce (black non-control area) in a dark area where black display or luminance is low, and there is no intermediate luminance area. In this case, as shown in FIG. 11E, the light adjustment unit 103 reduces light by 97%, for example. Then, white expansion is performed on the brighter area side. Thus, the target color temperature achievement rate T can be set to 100% and the apparent contrast CR change rate can be set to 134% by avoiding the black non-control region.

  FIG. 11B shows a case where there is a region (black non-control region) in which color reproduction is difficult in a dark region where black display or luminance is low, and there is an intermediate luminance region. In this case, as shown in FIG. 11 (f), the light adjustment unit 103 attenuates, for example, 30%. Then, white expansion is performed on the brighter area side. Thus, the target color temperature achievement rate T can be set to 134%, and the apparent contrast CR change rate can be set to 100% by avoiding about half of the black non-control region.

  FIG. 11C shows a case where there is no region (black non-control region) where color reproduction is difficult in a dark region where black display or luminance is low. In this case, as shown in FIG. 11 (g), the light control unit 103 does not perform light control (light control amount = 0%). Then, black expansion is performed on the side of the dark area. Thus, the target color temperature achievement rate T can be set to 100%, and the apparent contrast CR change rate can be set to 200%.

  FIG. 11D shows a case where there is no region (black non-control region) where color reproduction is difficult in a dark region where black display or luminance is low. In this case, as shown in FIG. 11 (h), the light adjustment unit 103 attenuates 33%. Then, both the black extension on the darker area side and the white extension on the brighter area side are performed. Thereby, the target color temperature achievement rate T can be set to 100%, and the change rate of the apparent contrast CR can be set to 250%.

  Next, a dimming amount determination procedure in which scene detection and dynamic range detection are added to the dimming procedure described in FIG. 10 will be described with reference to FIG. In step S1200, the low-pass filter / labeling circuit 162 removes high-frequency noise from the video signal by performing low-pass filtering (LPF) processing. In step S1201, the APL detection circuit 164 calculates the APL value of the video signal of one frame. If the APL value is large, in step S1202, the dimming processing unit 160 performs control so that dimming is not performed. In this case, all the light reflected by the light control unit 103 is guided to the liquid crystal type spatial light modulators 110R, 110G, and 110B. After step S1202, in step S1207, the black and white expansion process described with reference to FIG. 9 is performed. In step S1208, the light control amount determination process described in FIG. 10 is performed. If the APL value is intermediate, in step S1203, the histogram detection circuit 165 calculates the dynamic range of the video signal based on the luminance distribution histogram. If the dynamic range is wide, the process proceeds to step S1207.

  If the dynamic range is an intermediate value in step S1203, the process proceeds to step S1205. In step S1205, the light control processing unit 160 controls the amount of light to be controlled between a small amount and an intermediate amount. Step S1205 is processing that emphasizes contrast. In particular, it is preferable to compress a bright video signal with high luminance. Then, the black and white expansion process in step S1207 is performed. If the dynamic range is narrow in step S1203, the process proceeds to step S1206. In step S <b> 1206, the dimming unit 103 reduces the amount of light reduced by dimming from an intermediate amount to a large amount. Step S1206 is processing that places importance on reproduction of the black temperature. Then, the processes in steps S1207 and S1208 are performed.

  If the APL value is low in step S1201, the process proceeds to step S1204. In step S1204, the histogram detection circuit 165 calculates the dynamic range of the video signal based on the luminance distribution histogram. If the dynamic range is wide, the process proceeds to step S1205. If the dynamic range is intermediate or narrow, the process proceeds to step S1206. Then, the processes in steps S1207 and S1208 are performed. Finally, the processes in steps S1209 and S1210 are performed. Since the contents of these processes are the same as those in steps S807 and S808 described above, redundant description is omitted.

  Furthermore, a dimming procedure taking scene detection into consideration will be described. In step S1220, it is determined whether the APL value has changed to a certain value or more. If the determination result is true, it is determined in step S1221 that there is a scene change. If the determination result is false, it is determined in step S1222 that there is no scene change. If it is determined in step S1221 that there is a scene change, the process advances to step S1223. In step S1223, the amount of light dimming or dimming is determined. Then, after step S1223 or after setting no scene change in step S1222, the processes of steps S1209 and S1210 described above are performed. Here, when a scene change is detected based on the image signal, the dimming unit 103 performs the spatial light modulators 110R and 110G in a period different from the detected scene period, for example, in a period of at least several frames. , 100B is desirably dimmed so that the amount of light incident on it becomes a predetermined value. As a result, even if an abrupt image change occurs, it can be prevented from being recognized as flicker.

  In addition, it is desirable that the light control unit 103 performs light control according to the lighting time of the light source unit 101 or the light emission characteristics unique to the light source unit 101. As a result, when an ultra-high pressure mercury lamp is used as the light source unit 101, for example, the light emission characteristics change over time due to the lighting time (life) of the ultra-high pressure mercury lamp, or the light emission unique to the ultra-high pressure mercury lamp when the ultra-high pressure mercury lamp is replaced. The dimming conditions can be controlled in accordance with the difference in characteristics. The light emission characteristics include, for example, a light emission amount. As a result, the light control according to the light source unit can be performed more accurately.

(Second Embodiment)
FIG. 3 shows a schematic configuration of a projector 300 according to the second embodiment of the present invention. This embodiment is different from the first embodiment in that light reflected from the light source unit 101 in the second direction D2 by the light control unit 103 is reused and incident on the projection lens 130. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The light emitted from the rod integrator 102 enters the polarization converter 301. The polarization conversion unit 301 converts the light from the light source unit 101 into polarized light having a specific vibration direction, for example, s-polarized light and emits it. The light converted into s-polarized light is incident on the light control unit 103. The light control unit 103 reflects incident light in the first direction D1 or the second direction D2.

  The light reflected in the first direction D1 travels on the same optical path as described in the first embodiment, and enters the liquid crystal spatial light modulators 110R, 110G, and 110B for each color. The liquid crystal spatial light modulators 110R, 110G, and 110B for each color modulate the incident light into p-polarized light according to the image signal and emit it. The modulated light is synthesized by the cross dichroic prism 120 and emitted. The modulated light synthesized by the cross dichroic prism 120 enters the polarization beam splitter 304. The polarizing film of the polarizing beam splitter 304 transmits p-polarized light and reflects s-polarized light. Therefore, the modulated light passes through the polarization beam splitter 304 and is emitted to the projection lens 130 side. The projection lens 130 projects the modulated light onto the screen 140.

  Next, light reflected by the light control unit 103 in the second direction D2 will be described. In the first embodiment, the light reflected in the second direction D2 by the light control unit 103 is discarded without being projected on the screen 140. On the other hand, in the present embodiment, the light reflected in the second direction D2 by the light control unit 103 is light for increasing the luminance of the image projected on the screen 140 (hereinafter referred to as “auxiliary light”). .) Is different from the first embodiment in that it is reused.

  The light reflected in the second direction D2 by the light control unit 103 is reflected by the reflection mirrors M4 and M5 and the optical path is bent. The light whose optical path is bent is incident on the half-wave retardation plate 302. The s-polarized light is converted into p-polarized light by passing through the half-wave retardation plate 302. The p-polarized light is incident on the luminance liquid crystal panel 303, which is an auxiliary light element. The brightness liquid crystal panel 303 emits the incident p-polarized light as s-polarized light by controlling the transmittance in the procedure described later. The auxiliary light whose light intensity is controlled by the luminance liquid crystal panel 303 is incident on the polarization beam splitter 304 which is a combining unit. The polarizing film of the polarizing beam splitter 304 reflects the auxiliary light that is s-polarized light and emits it to the projection lens 130 side. As a result, the polarization beam splitter 304 combines the auxiliary light from the luminance liquid crystal panel 303, which is an auxiliary light element, and the modulated light from the liquid crystal spatial light modulators 110R, 110G, and 110B. The projection lens 130 projects auxiliary light on the screen 140. As a result, it is possible to obtain a projected image that is dimmed by the dimming unit 103 and has a high brightness level on the low gradation side and a bright contrast on the high gradation side in an image whose luminance level is generally lowered.

  Next, a procedure for supplying auxiliary light by the luminance liquid crystal panel 303 will be described with reference to FIG. In step S1300, the low pass filter / labeling circuit 162 removes high frequency noise from the video signal by performing low pass filtering (LPF) processing. In step S1301, the APL detection circuit 164 calculates the APL value of the video signal of one frame. If the APL value is large, in step S1302, the dimming processing unit 160 performs control so as not to perform dimming. In this case, all the light reflected by the light control unit 103 is guided to the spatial light modulators 110R, 110G, and 110B. If the APL value is intermediate or low, in step S1303, the histogram detection circuit 165 determines whether high gradation video signal data exists based on the luminance distribution histogram. If the determination result is true, in step S1305, the dimming unit 103 changes the amount of light reduction from a small amount to an intermediate level by dimming, and the luminance (Y) is increased by the auxiliary light. The increase in luminance due to the auxiliary light will be further described later. The light reflected in the second direction D <b> 2 by the light control unit 103 is guided to the luminance liquid crystal panel 303. In step S1306, the transmission region and the transmitted light amount of the luminance liquid crystal panel 303 are determined. In step S1307, the luminance liquid crystal panel 303 is driven.

  If the determination result in step S1303 is false, in step S1304, the light control unit 103 increases the amount of light reduction due to light control. In step S1308, expansion processing or the like is performed on the video signals of the liquid crystal spatial light modulators 110R, 110G, and 110B. Further, in step S1309, control processing of the light control unit 103 is performed.

  FIG. 14A is a diagram schematically showing a projected image. The projected image has, for example, a bright region BR having a high luminance, a region MD having a middle luminance, and a region BK having a low luminance. FIG. 14B shows a brightness distribution histogram of the projected image shown in FIG. The luminance distribution Yh corresponds to the high luminance region BR.

  The luminance liquid crystal panel 303 transmits auxiliary light only in the high-luminance region BR. At this time, the luminance liquid crystal panel 303 may be a low-resolution panel, as long as it can illuminate the substantially area BR. Further, the number of display gradations of the luminance liquid crystal panel 303 may be smaller than that when displaying an image. Therefore, the luminance liquid crystal panel 303 can be manufactured at low cost. In addition, the scale of the drive circuit of the luminance liquid crystal panel 303 can be reduced.

  Furthermore, the observer of the projected image on the screen 140 tends to gaze near the center of the projected image. For this reason, it is more effective to increase the luminance when the high luminance image is distributed near the center of the projected image. Moreover, it is not restricted to the brightness increase by the auxiliary light to a high-intensity area | region, You may irradiate auxiliary light to the area | region of achromatic color or light chromatic color. In this case, there is an effect that fading of the projected image can be reduced. When controlling the light control amount, as shown in FIG. 14C, the target light control amount is not achieved at once, but the light control amount is increased step by step to a% and b%. It is desirable to reach the target light control amount. Thereby, a sudden light quantity change can be reduced.

  Next, a procedure for detecting and adding a high gradation region and color saturation when increasing the luminance will be described with reference to FIG. In FIG. 15, steps S1100 and S1102 to S1108 are the same as steps S1300 to S1309 in FIG. First, in step S1101, one block of data in the MPEG4 standard, that is, a so-called object is calculated and labeled. In step S1110, a histogram is calculated for each labeling. In step S1111, it is determined whether or not the maximum luminance value max is greater than a predetermined value Q. If the determination result in step S1111 is true, it is determined in step S1113 that luminance (Y) is added. If the determination result of step S1111 is false, the process proceeds to step S1112. In step S <b> 1112, it is determined whether or not the total number of pixels (lumps of pixels) whose luminance is in a range from R% (R is 100 or less) to max of the maximum value max is larger than a predetermined pixel number S. In the processing after this step, if there is a luminance area of a certain gradation or higher, the gradation of the bright area with high luminance of the original video signal (before image processing) is not reduced by dimming by dimming. Is to do. If the determination result of step S1112 is true, the process proceeds to step S1113. If the determination result in step S1112 is false, it is determined in step S1114 that luminance (Y) is not added.

  Next, a procedure for proceeding to step S1120 after labeling an object in step S1101 will be described. In step S1120, a chromatic color and an achromatic color are determined for each labeling. In step S1121, it is determined whether the color is achromatic. If the determination result in step S1121 is true, it is determined in step S1123 that luminance (Y) is added. If the determination result in step S1121 is false, it is determined in step S1122 whether the color is light chromatic. If the determination result of step S1122 is true, the process proceeds to step S1123. If the determination result in step S1122 is false, it is determined in step S1124 that luminance (Y) is not added.

  In step S1125, in the case where luminance addition is performed based on the contents determined whether or not luminance (Y) is added in steps S1113, 1114, 1123, and 1124, in step S1126, the transmission region of the luminance liquid crystal panel 303 is displayed. And the amount of transmitted light is determined. In step S1127, the luminance liquid crystal panel 303 is driven. If the luminance is not added in step S1125, the process proceeds to step S1106, which is a normal dimming process. As a result, the brightness of an achromatic or light chromatic area can also be increased while maintaining a high contrast in a dark area. In addition, the luminance of an area of an aggregate of pixels whose chromatic color data cluster (object) is a predetermined value or less can also be increased. Further, if the luminance (Y) component is simply added later to the light modulated by the liquid crystal type spatial light modulators 110R, 110G, and 110B, the projected image may fade. For this reason, when luminance (Y) is added by auxiliary light, it is desirable to add only to image data that does not have fading.

(Third embodiment)
FIG. 4 shows a schematic configuration of a projector 400 according to the third embodiment of the present invention. The present embodiment is different from the first embodiment in that light reflected from the light source unit 101 in the second direction D2 by the light control unit 103 is reused and guided to the photovoltaic battery 401. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The light emitted from the rod integrator 102 enters the light control unit 103. The light control unit 103 reflects incident light in the first direction D1 or the second direction D2. The light reflected in the first direction D1 travels on the same optical path as described in the first embodiment and is projected on the screen 140.

  Next, light reflected by the light control unit 103 in the second direction D2 will be described. In the first embodiment, the light reflected by the light control unit 103 in the second direction D2 is discarded without being projected on the screen 140. On the other hand, the present embodiment is different from the first embodiment in that electric energy is stored in the photovoltaic battery 401 using the light reflected in the second direction D2 by the light control unit 103.

  The light reflected in the second direction D <b> 2 by the light control unit 103 enters the photovoltaic battery 401. The light storage battery 401 converts the light reflected in the second direction D2 into electric energy and stores it. The optical storage battery 401 includes a portion that converts light energy into electrical energy using the photoelectric effect, and a portion that stores electrical energy. The part that converts light energy into electrical energy is, for example, a pn junction photovoltaic cell using a single crystal such as a selenium photovoltaic cell, a cuprous oxide photovoltaic cell, germanium, or silicon. The power supply circuit 402 uses the electrical energy from the photo storage battery 401 as a power source for the projector 400. For example, when the projector 400 is in a standby state, it functions only to the extent that it can receive a remote control. For this reason, the power consumption when the projector 400 is in the standby state is smaller than the power consumption in the projection state. For this reason, by using the electrical energy stored in the photovoltaic battery 401 when the projector 400 is in a standby state, the power consumption can be reduced as much as when the projector 400 is powered off.

  As described above, in each of the above embodiments, since the light control unit 103 is provided on the exit side of the rod integrator 102, the light control unit 103 can be reduced in size and cost. In addition, since light adjustment is performed using a tilt mirror device as the light control unit 103, the light use efficiency is approximately 100% and the loss is small. Furthermore, the response speed of the light control unit 103 is fast, the life is long, and the reliability (color unevenness and deterioration against light resistance) is high. In addition, it can easily cope with high image quality processing of video signals. Moreover, the light control part 103 can be easily manufactured by a semiconductor process. Furthermore, it is advantageous from the viewpoint of durability and life because no organic material such as a polarizing plate or a retardation plate is used. Furthermore, since the light source unit 101 itself is not controlled at the time of light control, a load is not applied to the lamp that is the light source unit 101, and the life of the light source unit 101 can be extended. Further, as described above, the light control unit 103 is not limited to the tilt mirror device, and GLV, MEMS, and a shutter mechanism may be used.

  DESCRIPTION OF SYMBOLS 101 ... Light source part, 102 ... Rod integrator, 103 ... Light control part, 104R, 104B ... Dichroic mirror, M1, M2, M3 ... Reflection mirror, 105 ... Relay lens, 110R, 110G, 110B ... Liquid crystal type spatial light modulator, DESCRIPTION OF SYMBOLS 130 ... Projection lens, 140 ... Screen, 120 ... Cross dichroic prism, 120a ... Dichroic film | membrane, 150 ... Video signal input circuit, 160 ... Dimming processing part, 161 ... Dimming control circuit, 162 ... Low-pass filter labeling circuit, 163 ... Scene detection circuit, 164 ... APL detection circuit, 165 ... Histogram detection circuit, 170 ... Video signal modulation circuit, 171 ... Liquid crystal type spatial light modulator driving circuit, 181 ... Movable mirror element control circuit, 182 ... Movable mirror element drive circuit , 200 ... movable mirror element, 300 ... professional Ekuta, 301 ... polarization conversion section, 302 ... 1/2-wave plate, 303 ... liquid crystal panel for luminance, 304 ... polarizing beam splitter, 400 ... projector 401 ... optical storage battery, 402 ... power supply circuit.

Claims (10)

A light source unit for supplying light;
A liquid crystal spatial light modulator that modulates and emits light from the light source unit according to an image signal;
A projection lens for projecting light modulated by the liquid crystal type spatial light modulator;
A first state in which light from the light source unit is incident on the liquid crystal type spatial light modulator and a second state different from a state in which the light is incident on the liquid crystal type spatial light modulator are alternatively selected. A light control unit;
A dimming processing unit for controlling the dimming unit based on at least one of a luminance distribution of the image signal and an average image luminance;
The brightness of the light emitted from the liquid crystal spatial light modulator corresponding to a predetermined level of the image signal when the light control unit performs light control, and the image signal when the light control unit does not perform light control. An image signal adjusting unit for supplying the image signal to the liquid crystal type spatial light modulator such that the luminance of light emitted from the liquid crystal type spatial light modulator corresponding to a predetermined level substantially matches;
A light control processing unit for controlling the light control unit based on at least one of a luminance distribution of the image signal and an average image luminance;
The projector according to claim 1, wherein the light control unit performs color reproduction when the image signal is displayed in black or has a low luminance by reducing a light amount incident on the liquid crystal type spatial light modulator. A rod integrator for substantially uniformly illuminating the liquid crystal spatial light modulator;
The projector according to claim 1, wherein the light control unit is provided on an emission side of the rod integrator. The dimming unit is a tilt mirror device having a plurality of movable mirror elements that can alternatively select the first reflection position and the second reflection position,
The movable mirror element reflects light from the light source unit in the first direction to be incident on the liquid crystal type spatial light modulation device at the first reflection position, and at the second reflection position. The light from the light source part is reflected in the second direction different from the direction in which the light enters the liquid crystal spatial light modulator,
The light control unit controls the time during which the plurality of movable mirror elements are in the state of the first reflection position or the state of the second reflection position in accordance with an image signal, so that the liquid crystal type The projector according to claim 2, wherein the amount of light incident on the spatial light modulator is controlled. Light that is reflected by the dimming unit in the second direction different from the direction that is incident on the liquid crystal type spatial light modulation device is used as auxiliary light that increases the luminance of light projected by the projection lens. An auxiliary light element;
The said auxiliary | assistant light from the said element for auxiliary | assistant light, and the synthetic | combination part for synthesize | combining the light modulated from the said liquid crystal type spatial light modulation apparatus are further provided, The Claim 2 or 3 characterized by the above-mentioned. projector.   The projector according to claim 4, wherein the auxiliary light element is a liquid crystal display element. A light storage battery that converts the light reflected in the second direction different from the direction of incidence to the liquid crystal type spatial light modulator by the light control unit into electrical energy and stores the electric energy;
4. The projector according to claim 2, further comprising a power supply circuit that uses electric energy generated by the light storage battery as a power supply of the projector. 5.   The range of the level of the image signal corresponding to the black display of the liquid crystal spatial light modulator or the region where color reproduction can be performed in the low luminance region corresponds to the level range of the input image signal. 2. The projector according to claim 1, wherein the amount of light incident on the liquid crystal spatial light modulator is reduced, and the image signal adjustment unit supplies the image signal to the liquid crystal spatial light modulator. A scene detection circuit for detecting a scene change based on the image signal;
The dimming unit performs dimming so that the amount of light incident on the spatial light modulator becomes a predetermined value in a period different from the period of the detected scene. The projector according to any one of the above.   The projector according to any one of claims 1 to 3, wherein the dynamic range of the image signal is expanded in accordance with control of the amount of light by the light control unit.   The projector according to claim 1, wherein the light adjustment unit performs light adjustment control according to a lighting time of the light source unit or a light emission characteristic unique to the light source unit.

Images