JP2018101151A - Display control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress degradation of video quality caused by a color shift, while avoiding complication of a mechanism and increase of a cost.SOLUTION: A display control device (100) controlling a display device (1) including a plurality of light sources (20R, 20G, and 20B) and scanning means (30) for scanning respective irradiation lights (21R, 21G, and 21B) applied from the plurality of light sources on a surface to be projected (40) includes: band limitation means (103) for performing band limitation on a video signal on a video to be displayed on the surface to be projected; and drive control means (109) for controlling a driving state of the light sources, on the basis of the video signal on which the band limitation is performed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to the technical field of display control devices.

  Various devices for suppressing color misregistration of images have been conventionally proposed (see, for example, Patent Documents 1 to 3).

  According to the image display device disclosed in Patent Document 1, misalignment of laser beams of different colors incident on a MEMS mirror is detected, for example, at the time of assembly, at a temperature change, at the occurrence of an impact, etc. Therefore, this positional deviation is corrected.

  Patent Document 2 discloses a technique for correcting a color shift of laser light with a hologram.

  Patent Document 3 discloses a technique for suppressing color misregistration in a projection-type color projector by making the spot diameter of at least one of the three colors of laser light different from the spot diameter of other laser lights. Has been.

JP 2012-145755 A JP 2009-122455 A JP 2008-216456 A

  Techniques for preventing color misregistration are broadly divided into hardware techniques and software techniques.

  Here, in the former including the hardware-related color misregistration prevention measures disclosed in Patent Document 1 and the color misregistration prevention measures using the hologram element disclosed in Patent Literature 2, the complexity of the mechanism and the cost are reduced. Increase is an unavoidable problem. In particular, when the light source and the scanning means such as the MEMS mirror are modularized, it is difficult to take a hardware color misregistration prevention measure itself.

  Further, the technical idea of changing the spot diameter as disclosed in Patent Document 3 does not function at all when the amount of deviation is larger than the original. Furthermore, when the spot diameter is changed, the number of areas where light does not overlap increases, so that there is a high possibility that color misregistration will be further deteriorated.

  From this point of view, software-based color misregistration prevention methods are relatively effective. Incidentally, the software-based color misregistration prevention measure disclosed in Patent Document 1 adjusts the data read timing from the line buffer. That is, the color misregistration is suppressed by adjusting the read timing in line units.

  However, actual color misregistration can occur individually in the manufacturing stage and the assembly stage, and does not necessarily occur in line units. That is, with this method, it is possible to eliminate color misregistration in units of the size of one pixel, but it is not possible to eliminate color misregistration less than the size of one pixel. That is, the effect of preventing color misregistration is not always sufficient. Accordingly, it is not possible to sufficiently suppress the deterioration of the video quality due to the color shift.

  That is, the conventional technique has a technical problem that it is difficult to suppress deterioration in video quality due to color misregistration while avoiding complicated mechanism and cost increase. The present invention has been made in view of such technical problems, for example, and provides a display control apparatus capable of suppressing deterioration in video quality while avoiding complicated mechanisms and increased costs. , At least one of the problems to be solved.

  In order to solve the above-described problem, a display control device controls a display device that includes a plurality of light sources and a scanning unit that scans irradiation light emitted from the plurality of light sources on a projection surface. A band limiting unit that limits a band of a video signal related to an image to be displayed on the projection surface; and a drive control unit that controls a driving state of the light source based on the video signal subjected to the band limitation. Is provided.

  In order to solve the above-described problem, a display control method is a display control method in a display device including a plurality of light sources and a scanning unit that scans irradiation light emitted from the plurality of light sources on a projection surface. A band limiting step for limiting a band of a video signal related to an image to be displayed on the projection surface; and a drive control step for controlling a driving state of the light source based on the video signal subjected to the band limitation. .

  In order to solve the above-described problems, a computer program causes a computer system to function as the above-described display control device.

  In order to solve the above-described problems, a recording medium stores the above-described computer program.

1 is a block diagram of a video display apparatus according to a first embodiment of the present invention. It is a block diagram of the light source control part in the video display apparatus of FIG. FIG. 3 is a block diagram of a bandwidth limiter in the control device of FIG. 2. It is a figure which illustrates the scanning locus | trajectory of the laser beam in the video display apparatus of FIG. FIG. 2 is a conceptual diagram of color misregistration that occurs in the video display device of FIG. 1. It is a figure which illustrates the color shift in the image | video displayed. It is a figure which illustrates the image | video of FIG. 6 by which the filter process was performed to the video signal. FIG. 4 is a diagram illustrating a relationship between filter coefficients and filter characteristics in the band limiting unit in FIG. 3. It is a block diagram of the light source control part which concerns on 2nd Example of this invention. It is a block diagram of the light source control part which concerns on 3rd Example of this invention. It is a block diagram of the light source control part which concerns on 4th Example of this invention.

  <Embodiment of Display Control Device>

  An embodiment according to the display control apparatus of the present invention is a display control apparatus that controls a display apparatus that includes a plurality of light sources and a scanning unit that scans irradiation light emitted from the plurality of light sources on a projection surface. A band limiting unit that limits a band of a video signal related to a video to be displayed on the projection surface; and a drive control unit that controls a driving state of the light source based on the video signal subjected to the band limitation. Prepare.

  The embodiment according to the display control device of the present invention is a device that controls the display device from inside or outside. The display device includes, for example, a head-up display, a head-mounted display, a projection display device, and the like.

  According to the embodiment of the display control apparatus of the present invention, the image signal that is band-limited by the band-limiting unit such as a digital filter is projected onto the projection surface onto which the irradiation light from the light source is projected via the scanning unit. The based video is displayed. By subjecting the video signal to band limitation, the resolution of the portion corresponding to the limited frequency band in the original video that should originally be displayed on the projection surface can be reduced. In other words, the video is relatively blurred by the band limiting means. As a result, the color shift is relatively inconspicuous in the video displayed on the projection surface.

  That is, according to the embodiment of the display control apparatus of the present invention, in the configuration in which the irradiation light from the light source is not collected at one point on the projection surface (that is, the configuration including a color shift larger or smaller in hardware). Thus, it is possible to suitably suppress the deterioration of the video quality due to the color shift while avoiding the complicated mechanism and the increase in cost.

  The band limiting means is, for example, a low pass filter constructed as a digital filter. For example, the edge portion of the image is a portion where the spatial frequency is relatively high while the color shift is relatively conspicuous. Therefore, if the filter characteristics of the low-pass filter (for example, the cut-off frequency) are set as a frequency band on the lower frequency side than the frequency corresponding to the edge portion, the edge portion that is relatively conspicuous in the color shift is effective. Can be blurred.

  When the band limiting unit is configured as a digital filter, desired filter characteristics can be realized by controlling the filter coefficient. Therefore, in a display device including a light source and a scanning unit, it is possible to perform more effective band limitation on color misregistration that can occur variously in the manufacturing stage or the assembling stage.

  In one aspect of the embodiment according to the display control apparatus, the display control device further includes band control means for controlling the degree of band limitation based on a shift amount of an optical path between the plurality of light sources on the projection surface.

  According to this aspect, the degree of band limitation is controlled based on the amount of deviation of the optical path of the irradiation light emitted from the plurality of light sources by the band control means. That is, the band limiting unit is controlled so that the amount of deviation of the optical path corresponds to the level of the band limitation. Therefore, according to this aspect, it is possible to efficiently suppress deterioration in video quality due to color misregistration.

  The amount of deviation of the optical path is the degree of color deviation, and is the amount of deviation of the condensing position of each light on the projection surface. This amount of deviation occurs, for example, in the manufacturing stage or assembly stage of the light source and scanning means, and at least the initial value can be grasped experimentally, empirically or theoretically in advance, and the band control means It can be given as control information. It is also possible to measure the amount of deviation of the optical path periodically or irregularly under certain conditions and update the control information of the band control means as appropriate.

  The optical path deviation amount referred to by the band control means is not necessarily the absolute value of the optical path deviation amount. For example, a relatively large optical path shift that occurs in units of pixels can be offset by adjusting the read timing of the line buffer. Therefore, as a preferred embodiment, the bandwidth control means may use only the amount of deviation that cannot be eliminated by adjusting the read timing of the line buffer to determine the degree of bandwidth limitation.

  In one aspect of the embodiment including the band control means, each of the plurality of irradiation lights is scanned in the vertical scanning direction and the horizontal scanning direction on the projection surface, and the amount of deviation of the optical path is in the vertical scanning direction. This is the amount of deviation of the optical path.

  The scanning direction of the irradiation light from the light source in the display device (that is, the projection direction of the irradiation light on the projection surface) is preferably a vertical scanning direction and a horizontal scanning when displaying a two-dimensional image on the projection surface. It consists of directions. In such a configuration, the color shift in the vertical scanning direction is more conspicuous than the color shift in the horizontal scanning direction. According to this aspect, since the degree of band limitation is controlled based on the amount of deviation of the optical path in the vertical scanning direction, it is possible to favorably suppress a reduction in video quality due to color deviation.

  In another aspect of the embodiment including the band control means, the display device includes at least three or more of the light sources, and a deviation amount of the optical path is an optical path of irradiation light of another light source with respect to irradiation light of a reference light source. The band control means assigns a relative weight to the deviation amount of the optical path and controls the degree of the band limitation in consideration of the given weight.

  In the configuration in which the irradiation light from the light source is projected onto the projection surface via the scanning unit, the amount of deviation of the optical path can be determined as a relative positional relationship with the reference light on the projection surface. For example, when the plurality of light sources are light sources of the three primary colors of red, green, and blue, the amount of deviation of the optical paths of other colors may be defined with reference to the green light with the highest luminance.

  Here, there are at least two deviations of the optical path defined in this way, but there are also high and low luminances for the light of other colors, and in the above example, red is the same under the same condition as blue. Brightness is high. Since the color shift is more conspicuous when the luminance is high, it can be said that in this case, the priority is given to the red color shift over the blue color shift, which is more effective in suppressing the deterioration of the video quality.

  According to this aspect, the relative weight is given to the amount of deviation of the optical path, and the degree of band limitation is controlled in consideration of the given weight. Accordingly, it is possible to efficiently and effectively suppress a decrease in video quality due to color misregistration.

  In another aspect of the embodiment of the display control apparatus of the present invention, the band control means includes the spatial frequency of the video, the viewing distance of the video, the size of the video on the projection surface, and the projection surface. The degree of band limitation is determined based on at least one of the video aspect ratio and the video projection distance.

  The band limitation according to the amount of deviation of the optical path described above is effective in suppressing the degradation of video quality due to color deviation. However, in the technical idea of suppressing the degradation of the video quality without correcting the color misregistration itself, there are elements for suppressing the degradation of the video quality in addition to the amount of deviation of the optical path.

  According to this aspect, the degree of band limitation is determined based on at least one of the spatial frequency of the video, the viewing distance, the size of the video, the aspect ratio, and the projection distance. Therefore, it is possible to effectively alleviate the influence of color misregistration on video quality, and to effectively suppress the degradation of video quality.

  In another aspect of the embodiment of the display control apparatus of the present invention, the light source is a laser or an LED.

  Lasers and LEDs (Light Emitting Diodes) are suitable as light sources for display devices.

  In another aspect of the embodiment of the display control apparatus of the present invention, the scanning unit is a MEMS mirror.

  A MEMS mirror in which scanning means is constructed by MEMS (Micro Electro Mechanical System) is effective for downsizing and cost reduction of the apparatus. The MEMS mirror is generally scanned bidirectionally in the horizontal scanning direction. Therefore, there is a wide range of color misregistration that cannot be targeted by adjusting the read timing from the line buffer. That is, the effect of the embodiment according to the display control device is likely to appear remarkably.

  <Embodiment of Video Display Method>

An embodiment of the video display method of the present invention is a display control method in a display device including a plurality of light sources and a scanning unit that scans each of irradiation lights emitted from the plurality of light sources on a projection surface. A band limiting step for limiting the band of the video signal related to the video to be displayed on the projection surface, and a drive control step for controlling the driving state of the light source based on the video signal subjected to the band limitation.
<Embodiment of Computer Program>

  An embodiment according to the computer program of the present invention causes a computer system to function as an embodiment of any one of the above display control apparatuses.

  According to the embodiment of the computer program of the present invention, a solid, which can be attached to and detached from a computer system such as a recording medium such as ROM, CD-ROM, DVD-ROM, hard disk, or USB (Universal Serial Bus) memory for storing the computer program. If the computer program is read from the type storage device into the computer system and executed, or if the computer program is downloaded to the computer system via, for example, communication means, the computer program is executed. The embodiment according to the display control apparatus can be realized relatively easily.

Further, according to various aspects that can be taken by the above-described embodiment of the display control apparatus of the present invention, the embodiment according to the computer program can also take various aspects.
<Embodiment of Recording Medium>

  The embodiment according to the recording medium of the present invention records the embodiment according to the computer program.

  According to the embodiment of the recording medium of the present invention, the computer program of the present invention recorded by being attached to or connected to a computer system, or by being inserted into an appropriate reader provided in or connected to the computer system. The embodiment according to the present invention can be read and executed by a computer system, and the embodiment according to the display control apparatus of the present invention described above can be realized relatively easily.

  These effects and other advantages of the present invention will become apparent from the embodiments described below.

  Embodiments of the present invention will be described below with reference to the drawings as appropriate.

<First embodiment>
<Configuration of Example>
First, the configuration of the video display apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the video display device 1.

  In FIG. 1, the video display device 1 is an example of a “display device” according to the present invention that includes a control device 10, a light source 20, a MEMS mirror 30, and a display surface 40. The video display device 1 is, for example, a projection display device such as a head-mounted display device, a head-up display device, or a projection display device. In the video display device 1, laser light 21 </ b> R, 21 </ b> G, and 21 </ b> B (described later) emitted from the light source 20 is reflected by the MEMS mirror 30 and projected onto the display surface 40, thereby displaying a video.

  The video display device 1 is an example of a practical aspect that the display device according to the present invention can take. For example, the practical aspect of the display device according to the present invention deviates from the concept of the display device according to the present invention. It can be changed in any way within the range not to be.

  The control device 10 includes a light source control unit 100, a mirror control unit 200, a CPU (Central Processing Unit) that comprehensively controls these operations, a ROM (Read Only Memory), a RAM (Random Access Memory), and the like as storage devices. 1 is an example of a “display control device” according to the present invention.

  The ROM of the control device 10 stores a drive control program for driving the light source control unit 100 and the mirror control unit 200. This drive control program is an example of the “computer program” according to the present invention. The ROM is an example of the “recording medium” according to the present invention.

  Since the ROM is a non-volatile storage device, in this embodiment, the drive control program is provided in the control unit 110 in advance, but this control program is provided in the RAM, the hard disk, or other volatile data that can be provided in the control device 10. May be written in the volatile storage device. In this case, updating and maintenance of the drive control program can be performed relatively easily. It is also possible to take measures such as distributing the drive control program over a network or distributing a recording medium on which the drive control program is recorded.

  The light source control unit 100 is a control unit that controls the driving state of the light source 20. A detailed configuration of the light source control unit 100 will be described later with reference to FIG.

  The mirror control unit 200 is a control unit that controls the driving state of the MEMS mirror 30. The mirror control unit 200 includes a horizontal waveform generation unit, a horizontal D / A converter, a power amplifier, a clock generation unit, a vertical D / A converter, a vertical waveform generation unit, and the like. In addition, the structure of the mirror control part 200 can apply the well-known MEMS mirror control apparatus. Therefore, the details are omitted here. For example, the mirror controller 200 is configured to operate as follows.

  The horizontal waveform generation unit generates a horizontal drive signal for sweeping the MEMS mirror 30 in the horizontal scanning direction described above. The horizontal drive signal supplied from the horizontal waveform generator is D / A converted by a horizontal D / A converter and amplified by a power amplifier. The horizontal drive signal that has passed through the power amplifier is supplied to the MEMS mirror 30, and the MEMS mirror 30 is driven in the horizontal scanning direction by the horizontal drive signal.

  The vertical waveform generation unit generates a vertical drive signal for sweeping the MEMS mirror 30 in the above-described vertical scanning direction. The vertical drive signal supplied from the vertical waveform generator is D / A converted by a vertical D / A converter and amplified by a power amplifier. The vertical drive signal that has passed through the power amplifier is supplied to the MEMS mirror 30, and the MEMS mirror 30 is driven in the vertical scanning direction by the vertical drive signal.

  The clock generation unit is configured to be able to generate a clock signal at a predetermined period. For example, this predetermined period is set to about 10 ns. The generated clock signal is supplied to the vertical D / A converter. Note that the clock signal having the basic cycle generated by the clock generation unit may be converted into a clock signal having a desired cycle by a frequency divider.

  The light source 20 is a laser light source including light sources 20R, 20G, and 20B corresponding to red, green, and blue colors, and laser light 21R, 21G corresponding to red, green, and blue colors for the MEMS mirror 30, respectively. And 21B can be irradiated.

  The MEMS mirror 30 is a scanning mirror that reflects the laser light emitted from each light source and projects it onto the display surface 40, and is an example of the “scanning unit” according to the present invention. The MEMS mirror 30 is configured as a MEMS (micro electro mechanical system), and the operation state is controlled by the mirror control unit 200.

  The MEMS mirror 30 has a configuration in which a piezoresistor is formed by a piezo element (piezoelectric element) on a silicon substrate that functions as a mirror surface. As the piezo element, those having a piezoelectric effect can be widely used. For example, piezoelectric ceramics such as PZT (lead zirconate titanate) can be used. This piezoresistor is twisted by its piezoelectric effect according to the drive voltage applied to the MEMS mirror 30. This twist changes the angle of the mirror surface of the MEMS mirror 30 with respect to the light source 20. That is, scanning in a predetermined scanning direction is realized.

  On the other hand, the electrical resistance value of the piezoresistor changes according to the degree of twist. The MEMS mirror 30 is configured such that an electrical signal corresponding to the electrical resistance value (that is, the twist angle) can be extracted as a MEMS position signal. The direction of twist generated in the piezo element is the scanning direction of the reflected light reflected by the MEMS mirror 30 (that is, the laser light of each light source), and the MEMS mirror 30 according to this embodiment is generated around the vertical scanning axis. Driven in two scanning directions, a vertical scanning direction corresponding to twist and a horizontal scanning direction corresponding to twist generated around the horizontal scanning axis.

  The MEMS mirror 30 is driven by a vertical drive signal that is a sawtooth wave or a triangular wave in the vertical scanning direction, and is resonantly driven by a horizontal drive signal that is a sine wave in the horizontal scanning direction. A basic configuration and a basic driving method relating to the scanning unit of the present invention exemplified as the MEMS mirror 30 are known. Therefore, in this embodiment, the detailed description is omitted for the purpose of preventing the description from becoming complicated.

  The display surface 40 is a display device for displaying images on which laser beams of respective colors scanned by the MEMS mirror 30 are projected. However, unlike the direct-view display device, the display surface 40 is a display device in which a display location and a display area are not fixed as hardware specifications in advance. That is, the position of each pixel constituting the image displayed on the display surface 40 can be freely determined within a range that can be realized by the operation of the MEMS mirror 30.

  Here, the configuration of the light source control unit 100 will be described with reference to FIG. FIG. 2 is a block diagram of the light source control unit 100.

  In FIG. 2, a frame buffer 101, an interpolation processing unit 102, a band limiting unit 103, an offset setting unit 104, a read control unit 105, a timing generation unit 106, an interpolation information generation unit 107, an LPF intensity setting unit 108, and a light source driving unit 109 are shown. Prepare.

  The frame buffer 101 is a buffer configured to be able to store video signals corresponding to three colors of red, green, and blue, which are input from a video signal input terminal (reference number omitted) and are to be projected onto the display surface 40. is there.

  The read control unit 105 is a processor configured to be able to read video signals for a plurality of pixels from the video signals stored in the frame buffer 101. Note that the pixels from which the video signal is read can be different for each color.

  The interpolation processing unit 102 multiplies the video signal of each pixel located around the interpolation center by an interpolation coefficient set in accordance with the scanning position of the laser light on the display surface 40, and adds the original video signal to these interpolation signals. It is a processor comprised so that interpolation processing could be performed by adding the video signal of.

  The interpolation information generation unit 107 is a processor configured to be able to set the interpolation coefficient and the interpolation position in the interpolation processing unit 102 described above.

  As the interpolation process, for example, various known interpolation processes such as bilinear interpolation, bicubic interpolation, B-spline interpolation, and Lanzos3 interpolation are used. In addition, when the number of pixels and the number of lines are different between the input video and the output video, that is, when resolution conversion is necessary, the interpolation coefficient is calculated from the interpolation position information considering the enlargement rate and reduction rate. May be generated. However, this type of interpolation processing is not necessarily required to explain the effect of the display control apparatus according to the present invention.

  The band limiting unit 103 is a digital LPF (low-pass filter) as an example of the “band limiting unit” according to the present invention configured to be able to perform band limiting processing on the video signal output from the interpolation processing unit 102. When the interpolation processing unit 102 adopts a configuration that performs an interpolation process having a band limiting characteristic such as B-spline interpolation or Lanzos3 interpolation, the interpolation process and the band limiting process may be performed together. The video signal that has been subjected to the band limiting process in the band limiting unit 103 is input to the light source driving unit 109.

  Here, the configuration of the band limiting unit 103 will be described with reference to FIG. FIG. 3 is a block diagram of the band limiting unit 103.

  In FIG. 3, the band limiting unit 103 is a 3-tap LPF, and includes line memories 1031 and 1032, multipliers 1033, 1034 and 1035, and an adder 1036. Each line memory is a memory that stores pixel signals (that is, video signals) for one line in the horizontal scanning direction. Multipliers 1033, 1034, and 1035 are multipliers that multiply the input signal by filter coefficients a, b, and c, respectively, and the sum of the filter coefficients a, b, and c is 1.0.

  In FIG. 3, the pixel signal Pb input to the multiplier 1034 is a video signal of the target pixel to be subjected to the band limiting process, and the pixel signal Pa input to the multiplier 1033 is the pixel above the target pixel (that is, , A pixel signal Pc input at a time earlier than the target pixel), and the pixel signal Pc input to the multiplier 1035 is input at a pixel below the target pixel (that is, at a time later than the target pixel). Image signal). When the band limiting process is not performed, the filter coefficient b is set to 1.0, and the filter coefficients a and c are set to 0.0.

  Although the illustrated LPF is a 3-tap LPF, the number of taps may be larger. For example, the band limiting unit 103 may be a 5-tap LPF. In this case, the circuit scale is larger than the 3-tap LPF, but the degree of freedom of the filter characteristics is further increased.

  Returning to FIG. 2, the LPF intensity setting unit 108 is a processor as an example of a “band control unit” according to the present invention configured to be able to set the above-described filter coefficients a, b, and c of the band limiting unit 103.

  The light source driving unit 109 sets the voltage and current according to the characteristics of the red, green, and blue light sources provided in the light source 20 according to the video signal output from the band limiting unit 103, and drives the light source 20. A processor that generates a drive signal. The light source 20 is driven and controlled by this drive signal. The light source driving unit 109 is an example of the “drive control unit” according to the present invention.

  The timing generation unit 106 is a processor configured to be able to generate various timings such as a read timing at which the read control unit 105 reads a video signal from the frame buffer 101 and an interpolation timing necessary for determining an interpolation position in the interpolation information generation unit 107. It is. The timing generation unit 106 is configured to receive the above-described MEMS position signal related to the position (that is, the twist angle) of the MEMS mirror 30 from a position information input terminal (reference number omitted), and generate these timings.

  Supplementally, in the projection-type image display device 1 including the light source 20 and the MEMS mirror 30, the image corresponding to the drive signal supplied from the light source driving unit 109 and the twist angle of the MEMS mirror 30 in the horizontal scanning direction and the vertical scanning direction. Must be in a relationship necessary for displaying a two-dimensional image on the display surface 40. For this reason, the timing generation unit 106 generates various timings according to the input MEMS position signal. For example, the above-described read control unit 105 can read a video signal from the frame buffer 101 in accordance with the read timing generated by the timing generation unit 106.

  The offset setting unit 104 determines an offset amount of a horizontal scanning direction line for reading a video signal from the frame buffer 101 based on optical path deviation information (described later) input from an optical path deviation information input terminal (reference numeral omitted). This offset amount is a relative offset amount of other colors with respect to the reference color. In this embodiment, it is assumed that the reference color is green.

  On the other hand, the optical path deviation information is also input to the above-described LPF intensity setting unit 108. The LPF intensity setting unit 108 determines the degree of band limitation in the band limiting unit 103 based on the input optical path deviation information, and controls the filter characteristics of the band limiting unit 103. Note that the degree of band limitation is determined by the filter coefficients a, b, and c described above.

<Operation of Example>
Next, the operation of the embodiment will be described.

<Basic operation of MEMS mirror 30>
First, the basic operation of the MEMS mirror 30 will be described with reference to FIG. Here, FIG. 4 is a diagram for explaining the scanning trajectory of the laser light with respect to the projection surface 40.

  In FIG. 4, the display surface 40 is expressed in a lattice shape, and each of a plurality of rectangular regions constituting the lattice is a pixel P. As described above, in the projection type display device, since the pixel position on the display surface is not fixed as the hardware specification of the display surface, the condensing position of the laser beam corresponding to each color is actually the pixel. Is the position.

  In FIG. 4, a locus represented by a thick arrow line is a scanning locus of the laser light 21 </ b> G corresponding to green as the reference color of the light source 20. Optical scanning by the MEMS mirror 30 employs a so-called double-sided scanning method, unlike the optical scanning in a general display monitor such as a CRT or LCD, because the MEMS mirror 30 is driven to resonate in the horizontal scanning direction. That is, in the video display device 1, the laser light 21G is scanned both in the forward path (for example, from the left side to the right side in the figure) and in the return path (for example, from the right side to the left side in the figure).

  Next, with reference to FIG. 5, a color shift that occurs on the display surface 40 will be described. FIG. 5 is a conceptual diagram of color misregistration. In the figure, the same reference numerals or names are assigned to the same portions as those in FIG. 4 and the description thereof is omitted as appropriate.

  In FIG. 5, in addition to the laser beam 21G corresponding to the light source 20G, the scanning locus (see the broken arrow line) of the laser beam 21R corresponding to the light source 20R is shown. As shown in the figure, a color shift of one pixel occurs in the vertical scanning direction between them (see white circles in the figure). This color shift is a kind of individual difference caused by, for example, a shift of the optical path of each laser beam (optical path shift) generated in the manufacturing stage or the assembly stage of the video display device 1. The optical path deviation may be referred to as an optical axis deviation.

  Here, the absolute value of the optical path deviation in the vertical scanning direction between the laser beams may reach several tens of pixels depending on the case, but it affects the quality of the image projected on the display surface 40. Is a maximum of one pixel in the video display device 1 that employs the double-side scanning method. With respect to more color misregistration, when the video signal is read out from the frame buffer 101 described above, it is only necessary to offset the readout line in pixel units in the vertical scanning direction. For example, when the optical path deviation in the vertical scanning direction is 20.5 pixels, the actual color deviation may be 0.5 pixels if the readout line is offset by 20 pixels. The band limitation of the video signal by the band limiting unit 103 according to the embodiment is to suppress the deterioration of the video quality due to the minute color misregistration generated for the maximum one pixel.

<Effect of bandwidth limitation processing>
Next, with reference to FIG. 6 and FIG. 7, the effect of the band limiting process by the band limiting unit 103 will be described. Here, FIG. 6 is a diagram illustrating an image in which color misregistration has occurred, and FIG. 7 is a diagram illustrating the image in FIG. 6 in which band limitation processing has been performed on the video signal.

  In FIG. 6, (a) is an image in which no color misregistration occurs (that is, an original image that should be displayed originally). On the other hand, (b) is a diagram illustrating a state in which a color shift of x (x <1) pixels occurs in the vertical scanning direction, and (c) is y (x <y <) in the vertical scanning direction. 1) This is an example of a state in which color misregistration for pixels has occurred. Note that the images illustrated in FIGS. 6B and 6C show a state where the interpolation processing by the interpolation processing unit 102 has already been performed.

  Note that, as described above, in the projection-type image display device 1, since the condensing position of the laser light of each color is the pixel position, the color misregistration is defined as a deviation of the condensing position relative to the reference color. be able to. Here, since green generally has a larger luminance component than red and blue, it is suitable as a reference color. 6B and 6C show, for example, that there is no color misalignment between green and blue (note that the optical path misalignment is not always zero in this case as well), and green and red A state in which the color misregistration corresponding to the x or y pixels is generated during the period is shown. As shown in the figure, the larger the color deviation, the lower the quality of the video.

  FIG. 7 shows a state in which the band limiting process by the band limiting unit 103 is performed on the video signal related to each video illustrated in FIG. Note that FIG. 6A and FIG. 7A corresponding to an image with no color shift are the same.

  FIG. 7B and FIG. 7C both show an image obtained by subjecting the video signal to band limitation processing, and FIG. 7 corresponds to an image in which a color shift of x (x <1) pixels has occurred. FIG. 7C corresponding to an image in which color misregistration corresponding to y (x <y <1) pixels has occurred has a greater degree of band limitation than (b). That is, the image illustrated in FIG. 7C has a lower resolution at the boundary portion of the image than the image illustrated in FIG. 7B, and is visually blurred. ing.

  Thus, in the present embodiment, the degree of band limitation is controlled based on the magnitude of color misregistration, that is, the magnitude of the optical path misregistration amount. Thus, by increasing the degree of band limitation relative to a relatively large color shift, the influence of the color shift on the video can be mitigated. That is, according to the present embodiment, the deterioration of the video quality due to the color shift is preferably suppressed.

  In addition, when considering only the effect of color misregistration, the degree of band limitation is better, but as shown in the figure, increasing the band limitation degree lowers the resolution of the video and has another meaning. In this case, the quality of the image may be degraded. Therefore, a reduction in video quality is suitably suppressed by changing the band restriction degree according to the degree of color misregistration.

<Operation of Band Limiting Unit 103>
Next, the filter characteristics of the band limiting unit 103 will be described with reference to FIG. FIG. 8 is a diagram illustrating the relationship between the filter coefficient and the filter characteristic in the band limiting unit 103.

  In FIG. 8, the vertical axis represents the signal passing amount (dB), and the horizontal axis represents the frequency index value. The frequency index value is a value that is normalized with a half of the sampling frequency as 1.0. That is, from the sampling theorem, the point where the frequency index value is 1.0 corresponds to the maximum frequency of the video to be displayed.

  FIG. 8A illustrates filter characteristics when the filter coefficient b = 0.875 and a = c = 0.0625. With this filter characteristic, a passing amount of 50% (−3.0 dB) or more is ensured in the entire frequency range. That is, FIG. 8A corresponds to the filter characteristic when the degree of band limitation is small.

  FIG. 8B illustrates filter characteristics when the filter coefficient b = 0.750 and a = c = 0.125. In this filter characteristic, the cut-off frequency is set near the frequency index value 0.6, and the mid-high frequency band is limited.

  FIG. 8C illustrates filter characteristics when the filter coefficient b = 0.500 and a = c = 0.250. In this filter characteristic, the cut-off frequency is set in the vicinity of the frequency index value 0.35, and the mid-high frequency band is greatly limited. That is, FIG. 8C corresponds to the filter characteristic when the degree of band limitation is large. Further, in comparison with FIGS. 8A and 8C, it can be said that FIG. 8B corresponds to a filter characteristic with a medium degree of band limitation.

  As described above, the band limiting unit 103 can change the degree of band limitation of the video signal by the filter coefficients a, b, and c set by the LPF intensity setting unit 108. Therefore, as shown in FIG. 7, band limiting processing according to the degree of color misregistration is possible.

<Operation of LPF Strength Setting Unit 108>
Next, the operation of the LPF intensity setting unit 108 will be described.

  First, the position in the vertical scanning direction of each of the laser beams 21R, 21G, and 21B in a state where the MEMS mirror 30 is stationary and the MEMS mirror 30 and the display surface 40 that is the projection surface face each other. These are POSv_R, POSv_G, and POSv_B, respectively.

  Next, the distance from the center position of the laser beam 21G, which is the reference color, to the center position of the laser beam 21R, the provisional optical path shift amount POSvd_Rtmp, and the center position of the laser beam 21B from the center position of the laser beam 21G. When the distance to the position is the provisional optical path deviation amount POSvd_Btmp, the following equations (1) and (2) are established.

POSvd_Rtmp = POSv_R-POSv_G (1)
POSvd_Btmp = POSv_B-POSv_G (2)
For example, when the image display capability of the MEMS mirror 30 is 1280 pixels in the horizontal scanning direction and 720 lines (lines for 720 pixels) in the vertical scanning direction,
POSv_G = 360.0
POSv_R = 363.0
POSv_B = 365.9
If
POSvd_Rtmp = 3.0
POSvd_Btmp = 5.9
It becomes.

  Here, the provisional optical path deviation amount is expressed because, as described above, in the video display apparatus 1 that employs the double-sided scanning method, the maximum value of the optical path deviation of each laser beam is one pixel. That is, for example, an optical path shift that occurs on the upper side in the vertical scanning direction by 1.9 pixels can be treated equally with an optical path shift that occurs on the lower side in the vertical scanning direction by 0.1 pixel. Considering this point, when the final optical path deviation amount is defined, the optical path deviation amount POSvd_R between the laser light 21G and the laser light 21R, and the optical path deviation amount POSvd_B between the laser light 21G and the laser light 21B are: They are expressed by the following equations (3) and (4), respectively.

POSvd_R = ABS (ABS (POSv_R-POSv_G) -2n) (3)
POSvd_B = ABS (ABS (POSv_B-POSv_G) -2n) (4)
Here, ABS represents an absolute value, and n is a natural number that can minimize each value or zero.

  The LPF intensity setting unit 108 determines the degree of band limitation in the band limiting unit 103 based on the optical path deviation amount defined by the above equations (3) and (4). Specifically, the filter coefficients a, b, and c described above are determined.

  Note that the filter coefficient determination method based on the optical path deviation amount corresponds to the magnitude of the optical path deviation quantity corresponding to the magnitude of the filter coefficient b and the magnitudes of the filter coefficients a and c (in other words, the magnitude of the optical path deviation quantity corresponds to the band). It is not limited as long as it corresponds to the degree of restriction.

  For example, the maximum value and the minimum value of the cutoff frequency in the band limiting unit 103 are determined, the optical path deviation amount is divided into a plurality of stages, and the magnitude of the optical path deviation amount corresponds to the low and high cutoff frequencies, respectively. Further, a cut-off frequency may be assigned according to the divided stage. The maximum value of the cut-off frequency is preferably the cut-off frequency when there is no band limitation (filter coefficient b = 1.0).

  By the way, when the optical path deviation amount is defined as a relative deviation amount with respect to the laser beam 21G as the reference light, two types of optical path deviation amounts, a value corresponding to the laser beam 21R and a value corresponding to the laser beam 21B, are determined. . Since there is no correlation between these optical path deviation amounts, it is difficult to perform band limiting processing that effectively suppresses both. Therefore, the LPF intensity setting unit 108 is configured to assign weights to the two optical path deviation amounts and to determine final filter coefficients in consideration of the assigned weights.

  Here, one of the simplest and most effective weighting modes is to match the band limitation degree to one of the other color lights other than the reference light. That is, in this case, the weight given to one side corresponds to 100% and the weight given to the other corresponds to 0%. Here, in particular, when comparing red and blue, the luminance component of the laser beam 21B is smaller than that of the laser beam 21R. That is, the red color shift is more noticeable than the blue color shift. Therefore, in this case, the filter coefficient can be determined based on POSvd_R which is the optical path deviation amount of the laser light 21R.

  In general, when the weighting coefficient is k (0 <k <1), the optical path deviation amount POSvd ′ for determining the filter coefficient can be defined as in the following equation (5).

POSvd ′ = POSvd_R × k + POSvd_B × (1-k) (5)
Note that the optical path deviation amount referred to when the LPF intensity setting unit 108 determines the degree of band limitation (which is uniquely related to the filter coefficient in this embodiment) is the optical path deviation information in advance as described above. Input from the optical path deviation information input terminal.

  Here, in view of the fact that the optical path deviation of the light source 20 can occur at the manufacturing stage or the assembly stage, the optical path deviation information can be given as initial setting information of the video display device 1. On the other hand, in view of the fact that the provisional optical path deviation amount described above is caused by the deviation amount of the condensing position in the case where the MEMS mirror 30 and the display surface 40 are in a direct-facing relationship, each time the operation condition or the operation environment changes. In addition, the provisional optical path deviation amount may be measured, and the optical path deviation information may be appropriately updated. In this way, it is possible to easily adapt to changes in the amount of optical path deviation due to temperature changes and changes with time. In this case, the video display device 1 needs to include a provisional means for measuring the amount of provisional optical path deviation. For this type of measurement means, for example, a known measurement means using a photodetector or the like can be suitably applied.

<Second embodiment>
In the first embodiment, the filter coefficient corresponding to the degree of band limitation of the band limiting unit 103 is determined by the LPF intensity setting unit 111 based on the optical path deviation information described above. However, in the concept of the display control device of the present invention having the technical idea of suppressing the deterioration of the image quality without adjusting the color shift itself generated on the display surface 40, the degree of band limitation is determined in addition to the optical path shift information. There may be a reference element in doing so. A second embodiment of the present invention along such a purpose will be described with reference to FIG. FIG. 9 is a block diagram of the light source control unit 110 according to the second embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 2, and the description thereof will be omitted as appropriate.

  In FIG. 9, the light source control unit 110 is different from the light source control unit 100 according to the first example in that an LPF intensity setting unit 111 is provided instead of the LPF intensity setting unit 108.

  The LPF intensity setting unit 111 is configured to determine the degree of band limitation (that is, the filter coefficient) in the band limiting unit 103 based on the band control information input from the band control information input terminal (reference number omitted).

  Here, as the band control information input from the band control information input terminal, a projection plane size, a viewing distance, an aspect ratio, and the like can be used.

<Band limitation processing according to the projection surface size>
If the screen size of the display surface 40 that is the projection surface of each laser beam is large, the color shift is conspicuous accordingly. Therefore, by controlling the degree of band limitation according to the size of the screen size of the display surface 40, it is possible to suitably suppress deterioration in video quality due to color misregistration.

  Since the configuration of the display surface 40 hardly changes in the video display device 1, the band control information (screen size) in this case can be given in advance as initial setting information. That is, in this case, the degree of band limitation (that is, the degree of reference) with respect to the reference screen size is determined, and the degree of this reference is determined according to the magnitude relationship between the display surface 40 and the reference screen size. May be corrected to be larger or smaller.

<Band limit processing according to viewing distance>
The viewing distance is a physical distance between the user who uses the video display device 1 and the display surface 40. If the viewing distance is short, the user can recognize the image finely. Inevitably, color shift will be noticeable if the viewing distance is short.

  Therefore, by controlling the degree of band limitation to a small or large size according to the viewing distance, it is possible to suitably suppress a decrease in video quality due to color shift.

  Note that the viewing distance, which is the distance between the video display device 1 and the user, can change according to the usage environment each time. Therefore, in this case, the viewing distance may be input as reference information from the outside. Further, a means for measuring the viewing distance may be provided, and the viewing distance measured as the initial setting may be input as band control information.

  In this case, the degree of band limitation (that is, the degree of reference) with respect to the reference viewing distance is determined, and this reference degree may be corrected to be large or small according to the actual viewing distance.

<Bandwidth limit processing according to aspect ratio>
In the MEMS mirror 30, the vertical scanning position (twisting angle) and the horizontal scanning position (twisting angle) can be controlled independently. Accordingly, it is possible to easily project an image having an aspect ratio different from that of the original image onto the display surface 40.

  Here, when the image is relatively enlarged in the vertical scanning direction with the change in the aspect ratio, for example, when the aspect ratio of 16: 9 is changed to 16:18, the screen size of the display surface 40 is exemplified. Even if it is small, the color shift that occurs in the vertical scanning direction is relatively conspicuous. On the other hand, when the image is relatively reduced in the vertical scanning direction in accordance with the change of the aspect ratio, for example, when the aspect ratio of 16: 9 is changed to 16: 4, the screen size of the display surface 40 is an example. Even if it is large, the color shift occurring in the vertical scanning direction is relatively inconspicuous.

  Therefore, by controlling the degree of band limitation in accordance with the aspect ratio of the display surface 40, it is possible to suitably suppress deterioration in video quality due to color misregistration.

<Third embodiment>
A third embodiment based on the same purpose as the second embodiment will be described with reference to FIG. FIG. 10 is a block diagram of the light source control unit 120 according to the third embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 2, and the description thereof will be omitted as appropriate.

  In FIG. 10, the light source control unit 120 includes an image analysis unit 121 and is different from the light source control unit 100 according to the first embodiment in that an LPF intensity setting unit 122 is provided instead of the LPF intensity setting unit 108.

  The video analysis unit 121 is a processor that analyzes the spatial frequency of video based on the video signal input from the video signal input terminal. The LPF intensity setting unit 122 controls the degree of band limitation (that is, the filter coefficient) in the band limiting unit 103 based on the spatial frequency analyzed by the video analysis unit 121.

  The color shift on the display surface 40 is easily noticeable at a color boundary portion in the projected image, particularly at a boundary portion between white and black. Also, color misregistration is conspicuous even at the boundary between pixels with high and low luminance components of the three primary colors of red, green, and blue.

  Here, the spatial frequency of the image is high at the boundary portion where such color misalignment is relatively conspicuous. Therefore, by controlling the degree of band limitation according to the level of the spatial frequency, it is possible to suitably suppress the deterioration of the video quality due to the color shift.

  Various known methods can be applied to the method of analyzing the spatial frequency. For example, the video analysis unit 121 may perform first-order differential processing on the video signal for peripheral pixels adjacent to the target pixel in the vertical scanning direction, and calculate the intensity of the spatial frequency based on the absolute value.

<Fourth embodiment>
Next, a fourth embodiment based on the same purpose as the second and third embodiments will be described with reference to FIG. FIG. 11 is a block diagram of the light source control unit 130 according to the fourth embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 2, and the description thereof will be omitted as appropriate.

  In FIG. 10, the light source control unit 130 includes a projection distance measurement unit 131 and is different from the light source control unit 100 according to the first embodiment in that it includes an LPF intensity setting unit 132 instead of the LPF intensity setting unit 108. .

  The projection distance measurement unit 131 receives the projection distance of the laser light from the MEMS mirror 30 to the display surface 40 based on the projection angle or the maximum twist angle as the band control information input from the band control information input terminal (reference number omitted). It is a processor that measures. The LPF intensity setting unit 132 controls the degree of band limitation (that is, the filter coefficient) in the band limitation unit 103 based on the projection distance measured by the projection distance measurement unit 131.

  The projection distance in the present embodiment is a distance from the MEMS mirror 30 to the display surface 40. When the projection distance changes, the scale of color shift on the display surface 40 also changes. Specifically, as the projection distance increases, the scale of color misregistration also increases.

  By the way, the optical path shift amount described with reference to the equations (3) and (4) in the first embodiment is based on the premise that the MEMS mirror 30 and the display surface 40 are facing each other. However, in actuality, the MEMS mirror 30 changes the twist angle θh in the horizontal scanning direction and the twist angle θv in the vertical scanning direction in the scanning process of the laser light.

  When the twist angle is in the range of 0 ° to 90 °, the distance from the MEMS mirror 30 to the display surface 40 (projection distance) increases as the twist angle increases, and as a result, the color shift increases. Such a problem can occur basically unchanged even if a correction measure such as a bobbin correction is taken on the system side. Further, the relationship between the projection distance and the color shift can occur in the same manner when the laser light is projected on the display surface 40 from an oblique direction.

  Therefore, in this embodiment, information on the projection angle and the maximum twist angle of the MEMS mirror 30 is input as the band control information, and the projection distance measurement unit 131 measures or calculates the projection distance based on these information. Further, the filter coefficient of the band limiting unit 103 is determined based on the measured or calculated projection distance. The projection angle as the band control information is grasped by the mirror control unit 200 as the drive control amount of the MEMS mirror 30. The maximum twist angle is a value unique to the MEMS mirror 30.

  Therefore, according to the present embodiment, it is possible to suitably suppress the deterioration of the video quality due to the color shift caused by the projection distance.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. A display control apparatus with such a change is also applicable. Moreover, it is included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Video display apparatus, 10 ... Control apparatus, 20 ... Light source, 30 ... MEMS mirror, 40 ... Display exemption, 100 ... Light source control part, 103 ... Band-limiting part, 108 ... LPF intensity setting part 108, 200 ... Mirror control part .

Claims (1)

A display control device that controls a display device including a plurality of light sources and a scanning unit that scans irradiation light emitted from the plurality of light sources on a projection surface,
Band limiting means for limiting the band of the video signal related to the video to be displayed on the projection surface;
And a drive control means for controlling the drive state of the light source based on the video signal subjected to the band limitation.

Images