JP2010169772A - Projection image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a quality of an image to be projected while suppressing the increase of power consumption. <P>SOLUTION: A laser beam projection part 10 sequentially projects laser beams according to image signals of input images. A horizontal scanning mirror 20 horizontally scans a laser beam. A vertical scanning mirror 30 vertically scans a laser beam. A scanning mirror control unit 40 controls the horizontal scanning mirror 20 and the vertical scanning mirror 30. The laser beam projected from the laser beam projection part 10 is reflected in order of the horizontal scanning mirror 20 and the vertical scanning mirror 30 or its reverse order, and guided to a projection surface 80. The scanning mirror control unit 40 switches a first mode where main scanning of the laser beam is performed by the horizontal scanning mirror 20 and sub-scanning is performed by the vertical scanning mirror 30, and a second mode where main scanning of the laser beam is performed by the vertical scanning mirror 30 and sub-scanning is performed by the horizontal scanning mirror 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection-type video display device that displays an image on a projection surface by scanning a laser beam.

  Development of a laser beam scanning projection display apparatus that displays an image on a projection surface by performing raster scan on the projection surface with laser light corresponding to the value of each pixel included in the image is in progress ( For example, see Patent Document 1). In such an apparatus, it is necessary to provide a mirror for scanning the laser beam.

  In recent years, a resonant mirror using MEMS (Micro Electro Mechanical Systems) technology that can operate at a resonant frequency has been put into practical use, and has become an environment where higher-speed scanning can be realized.

JP 2006-343397 A

The present inventor has succeeded in improving the image quality of a projected image in such a projection-type image display device without reducing energy efficiency as compared with the conventional art.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a projection type video display apparatus capable of improving the image quality of a projected image while suppressing an increase in power consumption.

  A projection-type image display device according to an aspect of the present invention includes a laser light projection unit that sequentially projects laser light according to pixel signals of an input image, a horizontal scanning mirror that scans the laser light in a horizontal direction, and a laser. A vertical scanning mirror that scans light in the vertical direction, a horizontal scanning mirror, and a scanning mirror control unit that controls the vertical scanning mirror are provided. The laser light projected by the laser light projection unit is reflected in the order of the horizontal scanning mirror and the vertical scanning mirror, or vice versa, and guided to the projection surface. The scanning mirror control unit includes a first mode in which main scanning of laser light is performed by a horizontal scanning mirror and sub-scanning is performed by a vertical scanning mirror, main scanning of laser light is performed by a vertical scanning mirror, and sub-scanning is performed by a horizontal scanning mirror. Switch to the second mode to be performed.

  It should be noted that any combination of the above-described constituent elements and a method in which the expression method of the present invention is converted between methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to improve the quality of a projected image while suppressing an increase in power consumption.

It is a figure which shows the basic composition of the projection type video display apparatus concerning embodiment of this invention. It is a figure which shows the circuit structure of the projection type video display apparatus concerning embodiment of this invention. It is a figure for demonstrating a 1st mode. 3A shows an image to be projected, FIG. 3B schematically shows a scanning trajectory of the beam light when the image is projected, and FIG. 3C shows a driving signal for the horizontal scanning mirror. FIG. 3D shows a drive signal for the vertical scanning mirror. It is a figure for demonstrating a 2nd mode. 4A shows an image to be projected, FIG. 4B schematically shows a scanning trajectory of the beam light when the image is projected, and FIG. 4C shows a driving signal for the horizontal scanning mirror. FIG. 4D shows a driving signal for the vertical scanning mirror. It is a flowchart for demonstrating the image analysis process by the image analysis part which concerns on embodiment. It is a figure for demonstrating a black belt area | region. FIG. 6A shows an image in which the black band region is inserted by the pillar box method, and FIG. 6B shows an image in which the black band region is inserted by the letter box method. It is a figure for demonstrating the area | region division | segmentation process of an image, and the specific process of the maximum luminance value of a horizontal band, and the maximum luminance value of a vertical band. It is a flowchart for demonstrating the image correction process by the image correction part which concerns on embodiment. It is a figure which shows the example of calculation of the power distribution P and signal gain G of each band. It is a flowchart for demonstrating the drive process of the scanning mirror by the scanning mirror control part which concerns on embodiment. It is a figure for demonstrating the swing angle (omega) of the scanning mirror in charge of subscanning. It is a figure for demonstrating mode switching which concerns on a modification. 12A shows an image to be projected, FIG. 12B schematically shows a scanning trajectory of the beam light when the image is projected, and FIG. 12C shows a driving signal for the horizontal scanning mirror. FIG. 12D shows a drive signal for the vertical scanning mirror.

  FIG. 1 is a diagram showing a basic configuration of a projection display apparatus 100 according to an embodiment of the present invention. The projection type image display apparatus 100 is a two-axis scanning direct drawing type or backlight type laser projector. The projection display apparatus 100 includes a laser light projection unit 10, a horizontal scanning mirror 20, and a vertical scanning mirror 30 as basic elements. The laser light projected by the laser light projection unit 10 is reflected in the order of the horizontal scanning mirror 20 and the vertical scanning mirror 30 or vice versa, and is guided to the projection surface 80 such as a screen or a wall. Hereinafter, in the present embodiment, an example in which the horizontal scanning mirror 20 and the vertical scanning mirror 30 are reflected in the order will be described.

  The horizontal scanning mirror 20 is an element that can swing in the horizontal direction, and scans incident laser light in the horizontal direction. The vertical scanning mirror 30 is an element that can swing in the vertical direction, and scans incident laser light in the vertical direction. The horizontal scanning mirror 20 and the vertical scanning mirror 30 each include a mirror, a magnet, and a current line. The magnet and the current line are disposed at predetermined positions corresponding to the shake direction of the mirror. When a current flows through the current line, Lorentz force is generated, and the mirror moves in a predetermined shake direction. A scanning mirror control unit 40, which will be described later, can control the movement of the horizontal scanning mirror 20 and the vertical scanning mirror 30 by controlling the amount of current flowing through the current line and the direction of the current.

  FIG. 2 is a diagram showing a circuit configuration of the projection display apparatus 100 according to the embodiment of the present invention. The projection display apparatus 100 includes a laser light projection unit 10, a horizontal scanning mirror 20, a vertical scanning mirror 30, a scanning mirror control unit 40, an image analysis unit 50, an image correction unit 60, and a laser light projection control unit 70. The configurations of the scanning mirror control unit 40, the image analysis unit 50, the image correction unit 60, and the laser light projection control unit 70 can be realized by an arbitrary processor, memory, drive element, and other LSI in terms of hardware, and software This is actually realized by a program loaded in a memory or the like, but here, functional blocks realized by their cooperation are depicted. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The laser light projection unit 10 sequentially projects laser light according to pixel signals included in the image signal. More specifically, the laser light projection control unit 70 determines the amount of light to be projected to each pixel position in accordance with each pixel signal included in the image signal corrected by the image correction unit 60, and the amount of light is lasered. Set to the light projection unit 10. The laser light projection unit 10 projects laser light according to the set light amount. Note that the projection direction of the laser light from the laser light projection unit 10 is fixed, and the projection position of the laser light is controlled by the horizontal scanning mirror 20 and the vertical scanning mirror 30.

  The horizontal scanning mirror 20 reflects the laser light projected by the laser light projection unit 10. The vertical scanning mirror 30 reflects the laser light reflected by the horizontal scanning mirror 20 and guides it to the projection plane 80. The light that is instantaneously projected onto the projection surface 80 is for one pixel, but when the light is scanned at a high speed, it can be recognized as a screen due to the afterimage effect of the eyes.

  The scanning mirror control unit 40 performs a first mode in which the main scanning of the laser beam is performed by the horizontal scanning mirror 20 and the sub scanning is performed by the vertical scanning mirror 30, and the main scanning of the laser beam is performed by the vertical scanning mirror 30 and the sub scanning is performed. The second mode performed by the horizontal scanning mirror 20 is switched. In this specification, of the horizontal and vertical directions of an image, the direction of high-speed scanning is referred to as the main scanning direction, the scanning in that direction is referred to as main scanning, and the direction of low-speed scanning is referred to as the sub-scanning direction. This scanning is called sub-scanning.

  The scanning mirror control unit 40 can switch the mode between the first mode and the second mode in accordance with an instruction from the image analysis unit 50. Note that the mode may be switched according to a mode selection signal caused by a user operation from an operation unit (not shown). Moreover, you may switch a mode between both modes for every set time passage.

  The scanning mirror control unit 40 controls the horizontal scanning mirror 20 or the vertical scanning mirror 30 that is responsible for the main scanning of the laser light to swing regularly. For example, it is operated at the resonance frequency. Since it is necessary to operate the mirror surface at high speed in the main scanning direction, fine control such as changing the amplitude of the mirror surface for each line in the image is not performed on the scanning mirror responsible for main scanning.

  The scanning mirror control unit 40 is a ratio between the representative luminance values in each of the plurality of strip-like regions obtained by dividing the horizontal scanning mirror 20 or the vertical scanning mirror 30 responsible for the sub scanning of the laser light in the sub scanning direction of the image. Control is performed so that the direction of the mirror surface is changed at a time ratio according to. This time ratio can be set from the image correction unit 60. In the sub-scanning direction, it is only necessary to perform one scan within the time of the synchronization signal section of the image (for example, 16.6 milliseconds). Therefore, finer control is performed on the scanning mirror responsible for the sub-scan. Details of the control applied to the scanning mirror responsible for sub-scanning will be described later.

  The image analysis unit 50 analyzes an image signal input from a recording medium or communication medium (not shown) through a buffer (not shown), and obtains a brightness distribution in the image generated by the image signal, thereby Select either mode 1 or mode 2. Here, the brightness may be a brightness value, brightness, or an input video signal itself (RGB maximum value or the like). Then, the selected mode is set in the scanning mirror control unit 40 and the image correction unit 60. For example, the image analysis unit 50 specifies the direction in which the brightness (for example, the luminance level) is more leveled out of the horizontal direction and the vertical direction of the image, and the brightness is leveled in the horizontal direction of the image. If the brightness is leveled in the vertical direction, the second mode is selected. Here, the direction in which the leveling is performed may be a direction in which blackening is performed. Hereinafter, an example will be described in which the direction in which the brightness is more blackened out of the horizontal direction and the vertical direction of the image is specified.

  As an example for specifying the blackened direction, the image analysis unit 50 determines whether pixels having a luminance value equal to or lower than a predetermined reference value in the image are spread in the horizontal direction or the vertical direction. Is identified. The reference value is set to zero or a value close to zero. That is, it is specified whether substantially black pixels in the image continuously spread in the horizontal direction or continuously in the vertical direction.

  In order to identify this, the image analysis unit 50 divides the image into a plurality of band-like regions (hereinafter referred to as bands) in the horizontal direction and the vertical direction, and represents the representative values ( For example, the maximum luminance value) is specified. For each direction, a minimum value of representative values of a plurality of bands is calculated, and the minimum value in the horizontal direction is compared with the minimum value in the vertical direction. When the former is greater than the latter, the second mode is selected, and when the former is less than or equal to the latter, the first mode is selected.

  The image analysis unit 50 compares a display area, which is an area that can be projected onto the projection plane, with a significant image area in the image, and a signal corresponding to an insignificant image area in the image (hereinafter referred to as a black belt area). Signal). The black belt area signal is a signal for adjusting a significant image area aspect ratio and a display area aspect ratio in the image. The input image signal may include the black belt region signal. When the image analysis unit 50 detects the black band region signal in the input image signal, the image analysis unit 50 uses the scanning mirror control unit 40 and the image correction information to identify the position of the black band region signal in the image signal. Notification to the unit 60.

  The image correction unit 60 corrects the input image signal and supplies it to the laser light projection control unit 70. When the second mode is selected, the image correction unit 60 changes the order of the pixel signals included in the input image signal. In the normal image signal, the pixel signals are arranged in the order in which the horizontal direction is the main scanning direction and the vertical direction is the sub-scanning direction. That is, it is assumed that scanning is performed as in the first mode. Therefore, when the first mode is selected, it is not necessary to change the pixel signals included in the image signal. However, when the second mode is selected, the order of the pixel signals according to the scanning order. Need to be reconfigured.

  Further, when the image correcting unit 60 is notified of the information for specifying the position of the black band region signal from the image analyzing unit 50, the image correcting unit 60 deletes the black band region signal from the input image signal, and the laser beam This is supplied to the projection control unit 70.

  The image correction unit 60 calculates each power distribution to be distributed to each of the plurality of bands determined in the sub-scanning direction, and sets the power distribution in the scanning mirror control unit 40. Details of this power distribution calculation method will be described later.

  Further, the image correction unit 60 can compress or expand the image signal in accordance with the deletion of the black band region signal or the calculated power distribution. More specifically, the image signal is compressed or expanded by thinning or interpolation processing of pixel signals in the image signal. For example, in order to compensate for the deletion of the black band region signal, the image signal after the deletion is expanded. Further, since the band to which large power is distributed is scanned in the sub-scanning direction at a low speed and the speed in the main scanning direction is constant, the light beam is reciprocated in the main scanning direction more times than the actual number of pixel lines. There is a need. In this case, the image correction unit 60 expands the image signal of the band in the sub scanning direction. For a band to which a small power is allocated, the image correcting unit 60 compresses the image signal of the band in the sub-scanning direction based on the reverse principle.

  Further, the image correction unit 60 calculates each signal gain for amplifying the luminance value of the image signal included in each of the plurality of bands determined in the sub-scanning direction, and each corresponding band is calculated based on each signal gain. The luminance value of the image signal is amplified. This amplification process is a process for canceling the brightness change of each band in the sub-scanning direction, which occurs according to the power distribution, by amplification of the luminance value of the image signal of each band. Therefore, when it is important to increase the contrast, it is not necessary to perform this amplification process. Further, the luminance value of the image signal of each band may be amplified with a signal gain that only cancels a part of the brightness change of each band. Details of this signal gain calculation method will be described later.

  FIG. 3 is a diagram for explaining the first mode. FIG. 3A shows an image 111 to be projected. This image 111 is an image in which the luminance value is more blackened in the horizontal direction, and substantially black pixels are relatively widened in the horizontal direction. Therefore, the scanning of the image 111 is executed in the first mode. FIG. 3B schematically shows the scanning trajectory 112 of the light beam when the image 111 is projected. Here, a scanning trajectory 112 in which the beam light has moved from the bottom to the top is shown.

  FIG. 3C shows a drive signal 113 for the horizontal scanning mirror 20, and FIG. 3D shows a drive signal 114 for the vertical scanning mirror 30. The horizontal axis represents time, and the vertical axis represents the current value supplied to each scanning mirror. The vertical axis may be considered as the swing angle of each scanning mirror controlled by the current value. “1V” depicted in FIG. 3D indicates one frame period. The drive signal 113 for the horizontal scanning mirror 20 is a current value that changes at the resonance frequency.

  The inclination of the current value of the drive signal 114 of the vertical scanning mirror 30, that is, the shake speed of the vertical scanning mirror 30, is switched twice in one frame period. Among one frame period, the speed of the first period is the fastest, the speed of the second period is the slowest, and the speed of the third period is the speed between them. The two speed changes are reflected in the scanning locus 112 shown in FIG. In the image 111, the lower area where the substantially black pixels spread in a strip shape in the horizontal direction is scanned at the fastest speed in the sub-scanning direction, and the central area where the sun is drawn is the most in the sub-scanning direction. It can be seen that the scanning is performed at a slow speed.

  FIG. 4 is a diagram for explaining the second mode. FIG. 4A shows an image 121 to be projected. This image 121 is an image in which the luminance value is more blackened in the vertical direction, and is substantially an image in which black pixels are relatively spread in the vertical direction. Therefore, the scanning of the image 121 is executed in the second mode. FIG. 4B schematically shows the scanning trajectory 122 of the beam light when the image 121 is projected. Here, a scanning locus 122 in which the beam light moves from left to right is shown.

  4C shows the driving signal 123 for the horizontal scanning mirror 20, and FIG. 4D shows the driving signal 124 for the vertical scanning mirror 30. FIG. The inclination of the current value of the drive signal 123 of the horizontal scanning mirror 20, that is, the shake speed of the horizontal scanning mirror 20, is switched once in one frame period. In one frame period, the speed of the first period is high and the speed of the second period is low. The drive signal 124 of the vertical scanning mirror 30 is a current value that changes at the resonance frequency.

  This change in speed is reflected in the scanning locus 122 shown in FIG. In the image 121, in the left region in which substantially black pixels spread in a strip shape in the horizontal direction, the image is scanned at a high speed in the sub-scanning direction, and in the region from the center where the fireworks are drawn to the right side, It can be seen that scanning is slow in the sub-scanning direction.

  FIG. 5 is a flowchart for explaining image analysis processing by the image analysis unit 50 according to the embodiment. First, when the black belt region is included in the image generated by the input image signal, the image analysis unit 50 excludes the black belt region from the subsequent processing targets (S101). Next, the image analysis unit 50 divides the image into n (n is an integer of 2 or more) horizontal bands (S102). Here, it is preferable to divide so that the area of each horizontal band becomes equal. The image analysis unit 50 identifies the maximum luminance value Yh (1, 2,..., N) of each horizontal band from the luminance values of the pixels included in each horizontal band (S103).

  Similarly, the image analysis unit 50 divides the image into m (m is an integer of 2 or more) vertical bands (S104). Here, it is preferable to divide so that the area of each vertical band becomes equal. The image analysis unit 50 identifies the maximum luminance value Yv (1, 2,..., M) of each vertical band from the luminance values of the pixels included in each vertical band (S105). It is preferable that m and n are proportional to the screen aspect ratio of the image.

  The image analysis unit 50 calculates the minimum value of the maximum luminance value Yh (1,2, ..., n) of each horizontal band and the maximum luminance value Yv (1,2, ..., m) of each vertical band. The minimum value is compared (S106). When the former is equal to or less than the latter (Y in S106), the image analysis unit 50 determines the horizontal direction as the main scanning direction (S107). When the former is larger than the latter (N in S106), the image analysis unit 50 determines the vertical direction as the main scanning direction (S108).

  That is, the minimum value of the maximum luminance value Yh (1,2, ..., n) of each horizontal band is a value representing the brightness of the band that is estimated to be the darkest in the horizontal direction of the image. The minimum value of the maximum luminance value Yv (1,2, ..., m) of the vertical band is a value representing the brightness of the band that is estimated to be the darkest in the vertical direction of the image. Accordingly, the smaller value is determined as a direction in which a darker area is widened, and the direction is determined as the main scanning direction.

  FIG. 6 is a diagram for explaining the black belt region. Images have different screen aspect ratios depending on the standard. For example, images with a screen aspect ratio of 4: 3 or 16: 9 are standardized. Some image signals have a fixed resolution at any screen aspect ratio in order to absorb the difference in screen aspect ratio. When the screen aspect ratio is fixed, a black belt region is inserted in an image with insufficient resolution.

  FIG. 6A shows an image 141 in which the black belt region BW is inserted by the pillar box method. The pillar box method is a method for making a vertically long image fit within a horizontally long image. FIG. 6B shows an image 142 in which the black belt region BW is inserted by the letter box method. The letterbox method is a method for keeping a horizontally long image within a vertically long image. In a scanning type laser projector, it is possible to display an image more efficiently when the projection is performed without the black belt region.

  FIG. 7 is a diagram for explaining region division processing for the image 150 and processing for specifying the maximum luminance value Yh of the horizontal band HB and the maximum luminance value Yv of the vertical band VB. The image 150 is divided into N horizontal bands HB. Among the luminance values of the pixels included in each horizontal band HB (1,2, ..., n), the highest luminance value is the maximum luminance value Yh of each horizontal band HB (1,2, ..., n). Let (1,2, ..., n). Similarly, the image 150 is divided into m vertical bands VB. Among the luminance values of the pixels included in each vertical band VB (1,2, ..., m), the highest luminance value is the maximum luminance value Yh of each vertical band VB (1,2, ..., m). (1,2, ..., m).

  FIG. 8 is a flowchart for explaining image correction processing by the image correction unit 60 according to the embodiment. First, the image correction unit 60 determines whether the main scanning direction determined by the image analysis unit 50 is the vertical direction or the horizontal direction of the image (S201). If it is the vertical direction (Y in S201), the target image signal is transposed (S202). More specifically, it is transposed from an array that outputs each pixel column in the horizontal direction in order to an array that outputs each pixel column in the vertical direction in order. When the result of the determination is in the horizontal direction (N in S201), the process in step S202 is skipped.

  Next, when the image includes a black belt region (Y in S203), the image correction unit 60 deletes the black belt region signal. Then, in order to fill a blank portion corresponding to the deleted black belt region, the image signal is expanded in the main scanning direction (S204). Specifically, the pixel signal is interpolated in the main scanning direction according to the expansion ratio. As a pixel signal to be interpolated, an average value of each pixel signal of a plurality of pixels adjacent to the pixel can be used. When the black band area is not included in the image (N in S203), the process in step S204 is skipped.

Next, the image correction unit 60 calculates the power distribution P and the signal gain G of the band determined in the sub-scanning direction (S205). This specific calculation method will be described later.
Next, 1 is substituted as an initial value setting of the variable i (S206). When the variable i exceeds the number of bands (Y in S207), the entire process is terminated. When not exceeding (N of S207), the process after step S208 is performed. Note that the number of bands is m when the sub-scanning direction is the horizontal direction, and n when the sub-scanning direction is the vertical direction.

  The image correction unit 60 compresses or expands the band (i) image signal by P (i) times in the sub-scanning direction (S208). When the value of P (i) is larger than 1, the image signal is expanded, and when smaller than 1, the image signal is compressed. The image signal can be expanded by using the same method as the image signal expansion in the main scanning direction described above. In the compression of the image signal, pixel signals in the sub-scanning direction of the band (i) are thinned out according to the compression ratio.

  The image correcting unit 60 amplifies the luminance value of the image signal of band (i), more specifically, the luminance value of the plurality of pixel signals included in the image signal by G (i) times (S209). After this process is completed, the variable i is incremented (S210), and the process proceeds to the determination process in step S207.

  FIG. 9 is a diagram illustrating a calculation example of the power distribution P and the signal gain G of each band. Here, an example in which the sub-scanning direction is determined as the vertical direction will be described. The target image is divided into n horizontal bands, and the maximum luminance value Yh (1,2, ..., n) of these horizontal bands HB (1,2, ..., n) is 128, 192, 255,... The average value of these maximum luminance values Yh (1, 2,..., N) is 192.

  The power distribution P includes the maximum luminance value Yh (i) of each horizontal band HB (i) and the maximum luminance value Yh (1,2, ...) of the horizontal band HB (1,2, ..., n). , n) divided by the average value. The power distribution P (1,2, ..., n) of these horizontal bands HB (1,2, ..., n) is 0.67, 1.0, 1.33,. 17 The signal gain G is the maximum value of the power distributions P (1,2, ..., n) of the n horizontal bands HB (1,2, ..., n). ) Divided by the power distribution P (i). The signal gain G may be adjusted by multiplying by a predetermined coefficient.

  FIG. 10 is a flowchart for explaining the driving process of the scanning mirrors 20 and 30 by the scanning mirror control unit 40 according to the embodiment. First, when the target image includes a black belt region (Y in S301), the scanning mirror control unit 40 changes the swing angle of the scanning mirror responsible for the main scanning direction to an angle excluding the black belt region. (S302). If the target image does not include a black belt region (N in S301), the process in step S302 is skipped.

  The scanning mirror control unit 40 resonates and drives the scanning mirror that is in charge of main scanning (S303). The scanning mirror control unit 40 drives the scanning mirror responsible for sub-scanning according to the power distribution P (S304). The speed at which the light beam passes through each of the plurality of bands in the sub-scanning direction is determined by the value of the power distribution P.

  FIG. 11 is a diagram for explaining the swing angle ω of the scanning mirror in charge of sub-scanning. The horizontal axis indicates time t, and the vertical axis indicates the swing angle ω. FIG. 11 is based on the calculated values of FIG. The time for passing each band in the sub-scanning direction is determined by the power distribution P (1, 2,..., N) of each band. ω / n indicates the swing angle of the scanning mirror necessary for projecting the image signal of each band. As can be seen from FIG. 11, the third band is assigned more power than the first and second bands.

  As described above, according to the present embodiment, by appropriately switching between the first mode and the second mode, it is possible to improve the image quality of the projected image while suppressing an increase in power consumption. That is, by assigning the direction in which the luminance distribution in the image is blackened to the main scanning direction, which requires high-speed operation and is difficult to finely control, the direction in which the luminance distribution changes is finer. It can be assigned in the sub-scanning direction that can be controlled. Therefore, in the sub-scanning direction, part of the power that should be distributed to the dark area can be transferred to the bright area. That is, light can be efficiently collected in an area where the amount of light is required. Therefore, it is possible to increase image quality, particularly contrast, without increasing power consumption.

  The present invention has been described based on some embodiments. It is understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way.

  In the above embodiment, an example in which switching between the first mode and the second mode is performed in units of frames has been described. In the modification, switching is performed in units smaller than the frame. The scanning mirror control unit 40 according to the modification switches between the first mode and the second mode between one frame in the image.

  FIG. 12 is a diagram for explaining mode switching according to the modification. FIG. 12A shows an image 131 to be projected. In this image 131, a window 131a is opened. This image 131 is an image in which the upper right is relatively bright and the lower left is relatively dark. Therefore, the scanning of the image 111 is performed in the first mode in the first half of one frame period, and is performed in the second mode in the second half of the period. FIG. 12B schematically shows the scanning trajectory 132 of the light beam when the image 131 is projected. Here, a scanning trajectory 132 in which the beam light moves from bottom to top and then from left to right is shown.

  FIG. 12C shows a drive signal 133 for the horizontal scanning mirror 20, and FIG. 12D shows a drive signal 134 for the vertical scanning mirror 30. It can be seen that the horizontal scanning mirror 20 operates at the resonance frequency in the first half of one frame period, and operates in a time corresponding to the power distribution in the second half. On the other hand, it can be seen that the vertical scanning mirror 30 operates at a time corresponding to the power distribution in the first half of one frame period and operates at a resonance frequency in the second half. If the scanning speed in the sub-scanning direction is doubled as compared with the example shown in FIG. 3 or FIG. 4, scanning of the beam light of the scanning locus 132 shown in FIG. 12B can be performed in one frame period.

  DESCRIPTION OF SYMBOLS 10 Laser light projection part, 20 Horizontal scanning mirror, 30 Vertical scanning mirror, 40 Scanning mirror control part, 50 Image analysis part, 60 Image correction part, 70 Laser light projection control part, 80 Projection surface, 100 Projection type video display apparatus.

Claims (6)

A laser light projection unit that sequentially projects laser light according to the pixel signal of the input image;
A horizontal scanning mirror that scans the laser beam in a horizontal direction;
A vertical scanning mirror that scans the laser beam in a vertical direction;
A scanning mirror controller for controlling the horizontal scanning mirror and the vertical scanning mirror,
The laser light projected by the laser light projection unit is reflected in the order of the horizontal scanning mirror and the vertical scanning mirror, or vice versa, and guided to the projection surface,
The scanning mirror control unit includes a first mode in which main scanning of the laser light is performed by the horizontal scanning mirror and sub-scanning is performed by the vertical scanning mirror, and main scanning of the laser light is performed by the vertical scanning mirror and sub-scanning thereof. A projection-type image display device that switches between a second mode in which scanning is performed by the horizontal scanning mirror.   By analyzing the image signal and obtaining the brightness distribution in the image generated by the image signal, either the first mode or the second mode is selected, and the selected mode is selected as the scanning mirror. The projection display apparatus according to claim 1, further comprising an image analysis unit set in the control unit.   The image analysis unit specifies a direction in which the brightness is more blackened in the horizontal direction and the vertical direction of the image, and when the brightness is more blackened in the horizontal direction of the image, The projection type image display apparatus according to claim 2, wherein when the first mode is selected and the brightness is more blackened in the vertical direction, the second mode is selected. The image analysis unit divides the image into a plurality of band-shaped regions with respect to the horizontal direction and the vertical direction, and specifies a representative value of brightness of each region,
The scanning mirror control unit controls the horizontal scanning mirror or the vertical scanning mirror that is responsible for the main scanning of the laser light to be regularly shaken, and the horizontal scanning mirror that is responsible for the sub scanning of the laser light or the The vertical scanning mirror is controlled so as to change the orientation of the mirror surface at a time ratio corresponding to the ratio between the representative values of brightness in each of the plurality of band-like regions obtained by dividing the image in the sub-scanning direction. The projection-type image display device according to claim 2 or 3, An image correction unit for correcting the input image signal is further provided.
The image analysis unit compares a display area, which is an area that can be projected onto a projection plane, with a significant image area in the image, and identifies a signal corresponding to an insignificant image area in the image;
The projection image display apparatus according to claim 2, wherein the image correction unit deletes a signal corresponding to the insignificant image region from an input image signal.   6. The projection type video display device according to claim 1, wherein the scanning mirror control unit switches between the first mode and the second mode between one frame in the image.