JP6922953B2 - Display control device - Google Patents

Description

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

Various devices for suppressing color deviation 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, the positional deviation of the laser beams of different colors incident on the MEMS mirror is detected, for example, at the time of assembly, temperature change, impact generation, etc., and is soft or hard. This positional deviation is corrected.

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

Patent Document 3 discloses a technique for suppressing color shift 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 the other laser light. Has been done.

Japanese Unexamined Patent Publication No. 2012-145755 Japanese Unexamined Patent Publication No. 2009-12245 Japanese Unexamined Patent Publication No. 2008-216456

The method of preventing color shift is roughly divided into a hardware method and a software method.

Here, in the former including the hardware-like color shift prevention measures disclosed in Patent Document 1 and the color shift prevention measures using the hologram element disclosed in Patent Document 2, the mechanism is complicated and the cost is increased. The increase is an unavoidable problem. In particular, when the light source and the scanning means such as a MEMS mirror are modularized, it is difficult to take hardware-like color shift prevention measures.

Further, the technical idea of changing the spot diameter as disclosed in Patent Document 3 does not work at all when the amount of deviation is larger than the original. Furthermore, when the spot diameter is changed, the area where the light does not overlap increases, so that the color shift is likely to be worsened.

From this point of view, the software-like color shift prevention method is relatively effective. By the way, the software-like color shift prevention measure disclosed in Patent Document 1 adjusts the timing of reading data from the line buffer. That is, the color shift is suppressed by adjusting the read timing on a line-by-line basis.

However, the actual color shift can occur individually at the manufacturing stage or the assembly stage, and does not necessarily occur on a line-by-line basis. That is, with this method, it is possible to eliminate the color shift in units of the size of one pixel, but it is not possible to eliminate the color shift smaller than the size of one pixel. That is, the effect of preventing color shift is not always sufficient. Therefore, it is not possible to sufficiently suppress the deterioration of the image quality due to the color shift.

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

In order to solve the above-mentioned problems, the display control device according to claim 1 includes a plurality of light sources and scanning means for scanning each of the irradiation lights emitted from the plurality of light sources on the projected surface. A display control device that controls a display device, a band limiting means for limiting the band of a video signal related to an image to be displayed on the projected surface, and a driving state of the light source based on the band-limited video signal. A drive control means for controlling the above and a band control means for controlling the degree of band limitation based on the amount of deviation of the optical path between the plurality of light sources on the projected surface, and the amount of deviation of the optical path is a reference. It is defined as the amount of deviation of the optical path of the irradiation light of another light source with respect to the irradiation light of the light source. I do.
Further, the plurality of light sources are three light sources that emit red, green, and blue light, and the reference light source is defined as the light source having the largest brightness component among the light sources, and the two other light sources are defined. When the amount of deviation of the optical path with respect to the irradiation light of the reference light source of each irradiation light of the light source is defined as the amount of deviation of the first and second optical paths (POSvd_R, POSvd_B), the band control means is the first. A weighting coefficient (0 <k <1) is given to the amount of deviation of the second optical path, and the weighted average of the amount of deviation of the first and second optical paths based on the weighting coefficient is the amount of deviation of the optical path (POSvd_R). × k + POSvd_B × (1-k)).

It is a block diagram of the image display device which concerns on 1st Embodiment of this invention. It is a block diagram of the light source control part in the image display device of FIG. It is a block diagram of the band limiting part in the control device of FIG. It is a figure which illustrates the scanning locus of a laser beam in the image display device of FIG. It is a conceptual diagram of the color shift which occurs in the image display device of FIG. It is a figure which illustrates the color deviation in the displayed image. It is a figure exemplifying the image of FIG. 6 in which the image signal is filtered. It is a figure which illustrates the relationship between the filter coefficient and the filter characteristic in the band limiting part of FIG. It is a block diagram of the light source control part which concerns on 2nd Embodiment 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 Embodiment of this invention.

<Implementation of display control device>

An embodiment of the display control device of the present invention is a display control device that controls a display device including a plurality of light sources and scanning means for scanning each of the irradiation light emitted from the plurality of light sources on a projected surface. The band limiting means for limiting the band of the video signal related to the image to be displayed on the projected surface and the drive control means for controlling the driving state of the light source based on the band-limited video signal. Be prepared.

An embodiment of the display control device of the present invention is a device that controls the display device from the inside or the outside. Display devices include, for example, head-up displays, head-mounted displays, projection display devices, and the like.

According to the embodiment of the display control device of the present invention, a video signal whose band is limited by a band limiting means such as a digital filter on the projected surface on which the irradiation light from the light source is projected via the scanning means. The based image is displayed. By limiting the band of the video signal, it is possible to artificially reduce the resolution of the portion corresponding to the limited frequency band in the original video that should be originally displayed on the projected surface. In other words, the band limiting means causes the image to be relatively "blurred". As a result, the color shift becomes relatively inconspicuous in the image displayed on the projected surface.

That is, according to the embodiment of the display control device of the present invention, in a configuration in which the irradiation light from the light source is not focused on one point on the projected surface (that is, a configuration including a large or small color shift in terms of hardware). Therefore, it is possible to suitably suppress the deterioration of the image 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 has a relatively high spatial frequency, while the color shift is relatively conspicuous. Therefore, if the filter characteristics (for example, cutoff frequency) of the low-pass filter are set as the frequency band on the lower frequency side than the frequency corresponding to this edge portion, the edge portion where the color shift is relatively conspicuous is effective. Can be blurred.

Further, when the band limiting means 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 scanning means, it is possible to perform more effective band limitation against color deviations that may occur variously in the manufacturing stage or the assembling stage.

In one aspect of the embodiment according to the display control device, a band control means for controlling the degree of band limitation based on the amount of deviation of the optical path between the plurality of light sources on the projected surface is further provided.

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 means is controlled so that the magnitude of the deviation amount of the optical path corresponds to the magnitude of the degree of the band limitation. Therefore, according to this aspect, it is possible to efficiently suppress the deterioration of the image quality due to the color shift.

The amount of deviation of the optical path is, that is, the degree of color deviation, and is the amount of deviation of the condensing position of each light on the projected surface. This amount of deviation occurs, for example, at the manufacturing stage or the assembling stage of the light source and the scanning means, and at least the initial value thereof can be grasped experimentally, empirically, or theoretically in advance, and the band control means. It can be given as control information of. Further, it is also possible to measure the amount of deviation of the optical path on a regular basis or irregularly under a specific condition, and update the control information of the band control means as appropriate.

The amount of deviation of the optical path referred to by the band control means does not necessarily have to be an absolute value of the amount of deviation of the optical path. For example, a relatively large optical path shift that occurs on a pixel-by-pixel basis can be offset by adjusting the read timing of the line buffer or the like. Therefore, as a preferable form, the band control means may be used to determine the degree of band limitation only for the amount of deviation that cannot be eliminated by adjusting the read timing of the line buffer.

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 projected surface, and the amount of deviation of the optical path is the deviation amount in the vertical scanning direction. 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 projected surface) is preferably the vertical scanning direction and the 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 noticeable 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, deterioration of image quality due to color deviation can be suitably suppressed.

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 the amount of deviation of the optical path is the optical path of the irradiation light of another light source with respect to the irradiation light of the reference light source. The band control means assigns a relative weight to the amount of deviation of the optical path, and controls the degree of the band limitation in consideration of the assigned weight.

In the configuration in which the irradiation light from the light source is projected onto the projected surface via the scanning means, the amount of optical path deviation can be determined as the relative positional relationship with the reference light on the projected surface. For example, when a 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 having the highest brightness.

Here, there are at least two deviations in the optical path defined in this way, but there are also high and low brightness for light of other colors, and in the above example, red is under the same conditions as blue. The brightness is high. Since the color shift is more noticeable when the brightness is high, in this case, it can be said that giving priority to the red color shift over the blue color shift is effective in suppressing the deterioration of the image quality.

According to this aspect, a 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. Therefore, it is possible to efficiently and effectively suppress the deterioration of the image quality due to the color shift.

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

In order to suppress the deterioration of the image quality due to the color shift, the band limitation according to the amount of the shift of the optical path described above is effective. However, in the technical idea of suppressing the deterioration of the image quality without correcting the color deviation itself, there is an element for suppressing the deterioration of the image quality other than the amount of the optical path deviation.

According to this aspect, the degree of band limitation is determined based on at least one of the spatial frequency of the image, the viewing distance, the size of the image, the aspect ratio, and the projection distance. Therefore, the influence of the color shift on the image quality can be effectively alleviated, and thus the deterioration of the image quality can be effectively suppressed.

In another aspect of the embodiment according to the display control device 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 according to the display control device of the present invention, the scanning means is a MEMS mirror.

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

<Embodiment of video display method>

An embodiment according to the image display method of the present invention is a display control method in a display device including a plurality of light sources and scanning means for scanning each of the irradiation light emitted from the plurality of light sources on a projected surface. The present invention includes a band limiting step of limiting the band of the video signal related to the image to be displayed on the projected surface, and a drive control step of controlling the driving state of the light source based on the band-limited video signal.
<Implementation of computer program>

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

According to an embodiment of the computer program of the present invention, a solid body that can be attached to and detached from a recording medium such as a ROM, CD-ROM, DVD-ROM, or hard disk for storing the computer program, or a computer system such as a USB (Universal Serial Bus) memory. 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, a communication means and then executed, the present invention described above. The embodiment according to the display control device of the above can be realized relatively easily.

In addition, various embodiments of the computer program can be adopted according to the various embodiments of the display control device of the present invention described above.
<Embodiment of Recording Medium>

As the embodiment of the recording medium of the present invention, the embodiment of the computer program is recorded.

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

Such effects and other gains of the present invention will be apparent from the examples described below.

Hereinafter, examples of the present invention will be described with reference to the drawings as appropriate.

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

In FIG. 1, the image display device 1 is an example of a “display device” according to the present invention, which includes a control device 10, a light source 20, a MEMS mirror 30, and a display surface 40. The image display device 1 is, for example, a projection type display device such as a head-mounted display device, a head-up display device, or a projection display device. In the image display device 1, the laser beams 21R, 21G, and 21B, which will be described later, emitted from the light source 20 are reflected by the MEMS mirror 30 and projected onto the display surface 40 to display an image.

The video display device 1 is an example of a practical mode that can be adopted by the display device according to the present invention. For example, the practical mode 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 as long as it is not.

The control device 10 includes a light source control unit 100 and a mirror control unit 200, a CPU (Central Processing Unit) that collectively controls their operations, a ROM (Read Only Memory) and a RAM (Random Access Memory) as storage devices, and the like. This is an example of the "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 a "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 can be provided in the RAM, the hard disk, or the control device 10 or other volatile memory. It may be written in the sexual storage device. In this case, the drive control program can be updated and maintained relatively easily. It is also possible to take measures such as distributing the drive control program on 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. The 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. A known MEMS mirror control device can be applied to the configuration of the mirror control unit 200. Therefore, the details will be omitted here. The mirror control unit 200 is configured to operate as follows, for example.

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

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

The light source 20 is a laser light source including light sources 20R, 20G and 20B corresponding to each color of red, green and blue, and laser light 21R and 21G corresponding to each color of red, green and blue with respect to the MEMS mirror 30. 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 means” according to the present invention. The MEMS mirror 30 is configured as a MEMS (microelectromechanical system), and its operating state is controlled by the mirror control unit 200.

The MEMS mirror 30 has a configuration in which a piezo resistance is formed by a piezo element (piezoelectric element) on a silicon substrate that functions as a mirror surface. As the piezo element, one having a piezoelectric effect can be widely used, and for example, piezoelectric ceramics such as PZT (lead zirconate titanate) can be used. This piezoresistive effect causes twisting due to its piezoelectric effect, depending on 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 electric resistance value of the piezoresistive effect changes according to the degree of this twist. The MEMS mirror 30 is configured so that an electric signal corresponding to this electric resistance value (that is, a twist angle) can be taken out as a MEMS position signal. The twisting direction generated in the piezo element is the scanning direction of the reflected light reflected by the MEMS mirror 30 (that is, the laser beam of each light source), and the MEMS mirror 30 according to the present embodiment occurs around the vertical scanning axis. It is driven in two scanning directions, a vertical scanning direction corresponding to the twist and a horizontal scanning direction corresponding to the twist occurring around the horizontal scanning axis.

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

The display surface 40 is a display device for displaying an image on which laser light of each color scanned by the MEMS mirror 30 is projected. However, unlike the direct-view type display device, the display surface 40 is a display device in which the display location and the display area are not fixed in advance as specifications on the hardware. 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. Here, FIG. 2 is a block diagram of the light source control unit 100.

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

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

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

The interpolation processing unit 102 multiplies the video signal of each pixel located around the center of interpolation by an interpolation coefficient set according to the scanning position of the laser beam on the display surface 40, and the original video signal is used for interpolation. It is a processor configured to be able to execute interpolation processing by adding the video signals of.

The interpolation information generation unit 107 is a processor configured so that the above-mentioned interpolation coefficient and the interpolation position in the interpolation processing unit 102 can be set.

As the interpolation process, for example, various known interpolation processes such as bilinear interpolation, bicubic interpolation, B-spline interpolation, and Lanzos3 interpolation are used. Further, 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 required, the interpolation coefficient is calculated from the interpolation position information in consideration of the enlargement ratio and reduction ratio. It may be generated. However, in explaining the effect of the display control device according to the present invention, this kind of interpolation processing is not always necessary.

The band limiting unit 103 is a digital LPF (low-pass filter) which is an example of the "band limiting means" according to the present invention, which is configured to be able to execute band limiting processing on the video signal output from the interpolation processing unit 102. When the interpolation processing unit 102 adopts a configuration in which interpolation processing having a band limiting characteristic such as B-spline interpolation or Lanzos3 interpolation is adopted, the interpolation processing and the band limiting processing may be performed together. The video signal 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. Here, 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 is composed of line memories 1031 and 1032, multipliers 1033, 1034, and 1035, and an adder 1036. Each line memory is a memory that stores a pixel signal (that is, a video signal) for one line in the horizontal scanning direction. The multipliers 1033, 1034 and 1035 are multipliers for multiplying the input signal by the 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 band-limited processed, and the pixel signal Pa input to the multiplier 1033 is a pixel above the target pixel (that is, , The video signal of the pixel whose signal is input earlier than the target pixel), and the pixel signal Pc input to the multiplier 1035 is input to the pixel below the target pixel (that is, the signal is input later than the target pixel). It is a video signal (pixels). 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.

The LPF shown is a 3-tap LPF, but 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 that of the 3-tap LPF, but the degree of freedom of the filter characteristics is further expanded.

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

The light source driving unit 109 drives the light source 20 by setting 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. It is 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 means" 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 in which the read control unit 105 reads a video signal from the frame buffer 101 and an interpolation timing required for determining the interpolation position in the interpolation information generation unit 107. Is. The timing generation unit 106 receives the above-mentioned MEMS position signal regarding the position (that is, the twist angle) of the MEMS mirror 30 from the position information input terminal (reference numeral omitted), and is configured to 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 drive unit 109 and the twist angle in the horizontal scanning direction and the vertical scanning direction of the MEMS mirror 30 The positional relationship of the above must be the relationship necessary for displaying the two-dimensional image on the display surface 40. Therefore, the timing generation unit 106 generates various timings according to the input MEMS position signal. For example, the read control unit 105 described above can read the video signal from the frame buffer 101 according to the read timing generated by the timing generation unit 106.

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

On the other hand, the optical path deviation information is also input to the LPF intensity setting unit 108 described above. 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. The degree of band limitation is determined by the filter coefficients a, b and c described above.

<Operation of the 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 locus of the laser beam with respect to the projection surface 40.

In FIG. 4, the display surface 40 is represented in a grid pattern, and each of the plurality of rectangular regions constituting the grid is a pixel P. As described above, in the projection type display device, the pixel position on the display surface is not fixed as the hardware specification of the display surface, so that the focusing position of the laser light corresponding to each color is actually a pixel. The position of.

In FIG. 4, the locus represented by the thick arrow line is the scanning locus of the laser beam 21G corresponding to the reference color green of the light source 20. The optical scanning by the MEMS mirror 30 adopts a so-called two-sided scanning method, unlike the optical scanning in a general display monitor such as a CRT or an LCD, because the MEMS mirror 30 is resonantly driven in the horizontal scanning direction. That is, in the image display device 1, the laser beam 21G is scanned both on the outward path (for example, from the left side to the right side in the figure) and on the return path (for example, from the right side to the left side in the figure).

Next, with reference to FIG. 5, the color shift occurring on the display surface 40 will be described. Here, FIG. 5 is a conceptual diagram of color deviation. In the figure, the same reference numerals or names are given to the parts overlapping with FIG. 4, and the description thereof will be 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 line arrow) of the laser beam 21R corresponding to the light source 20R is shown. As shown in the figure, there is a color shift of one pixel in the vertical scanning direction between them (see the white circle in the figure). This color shift is a kind of individual difference caused by the shift (optical path shift) of the optical path of each laser beam that occurs, for example, in the manufacturing stage or the assembly stage of the image display device 1. The deviation of the optical path may be rephrased as the deviation of the optical axis.

Here, the absolute value of the optical path deviation in the vertical scanning direction between the laser beams may reach several tens of pixels in some cases, but it affects the quality of the image projected on the display surface 40 on the display surface. The color shift of is 1 pixel at the maximum in the image display device 1 that employs the double-sided scanning method. For further color deviation, when reading the video signal from the frame buffer 101 described above, it is sufficient to offset the read line in pixel units in the vertical scanning direction. For example, when the optical path shift in the vertical scanning direction occurs by 20.5 pixels, if the readout line is offset by 20 pixels, the actual color shift can be 0.5 pixels. The band limitation of the video signal by the band limiting unit 103 according to the embodiment suppresses the deterioration of the video quality due to the minute color shift caused by the maximum of one pixel.

<Effect of band limitation processing>
Next, with reference to FIGS. 6 and 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 a color shift occurs, and FIG. 7 is a diagram illustrating an image of FIG. 6 in which a band limiting process is applied to the image signal.

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

As described above, in the projection type video display device 1, since the focusing position of the laser light of each color is the position of the pixel, the color deviation is defined as the deviation of the focusing 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. 6 (b) and 6 (c) show, for example, that there is no color shift between green and blue (note that, as described above, the optical path shift is not necessarily zero in this case as well), and green and red. It shows a state in which a color shift of the above x or y pixels occurs between the two. As shown in the figure, the larger the color shift, the lower the quality of the image.

FIG. 7 shows a state in which the band limiting process is performed by the band limiting unit 103 on the video signal related to each video illustrated in FIG. It should be noted that FIGS. 6 (a) and 7 (a) corresponding to the images in which the color shift does not occur are the same.

7 (b) and 7 (c) both show an image in which the image signal is subjected to band limiting processing, but FIG. 7 corresponds to an image in which a color shift of x (x <1) pixels occurs. The degree of band limitation is larger in FIG. 7 (c) corresponding to the image in which the color shift of y (x <y <1) pixels occurs than in (b). That is, in the image illustrated in FIG. 7 (c), the resolution of the boundary portion of the image is lower than that in the image illustrated in FIG. 7 (b), and the image is visually blurred. ing.

As described above, in this embodiment, the degree of band limitation is controlled based on the magnitude of the color shift, that is, the magnitude of the amount of the optical path shift. In this way, by increasing the degree of band limitation relative to the relatively large color shift, the influence of the color shift on the image can be alleviated. That is, according to this embodiment, deterioration of image quality due to color shift is preferably suppressed.

Also, when considering only mitigating the effects of color shift, the degree of band limitation should be large, but as shown in the figure, if the degree of band limitation is increased, the resolution of the image will decrease, which means another meaning. Can cause deterioration of video quality. Therefore, by changing the degree of band limitation according to the degree of color shift, deterioration of image quality is preferably suppressed.

<Operation of band limiting unit 103>
Next, with reference to FIG. 8, the filter characteristics of the band limiting unit 103 will be described. Here, 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 standardized with a frequency of 1/2 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 image to be displayed.

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

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

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

In this way, in the band limiting unit 103, the degree of band limiting of the video signal can be changed by the filter coefficients a, b, and c set by the LPF intensity setting unit 108. Therefore, as illustrated in FIG. 7, band limiting processing can be performed according to the degree of color deviation.

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

First, the positions of the laser beams 21R, 21G, and 21B in the vertical scanning direction when the MEMS mirror 30 is stationary and the MEMS mirror 30 and the display surface 40 as the projected surface are facing each other are determined. Let them be POSv_R, POSv_G, and POSv_B, respectively.

Next, the distance from the center position of the luminous flux of the laser beam 21G, which is the reference color, to the center position of the luminous flux of the laser beam 21R is determined by the provisional optical path deviation amount POSvd_Rtpp and the center of the luminous flux of the laser beam 21B from the center position of the luminous flux of the laser beam 21G. Assuming that the distance to the position is the provisional optical path deviation amount POSvd_Btmmp, the following equations (1) and (2) are established.

POSvd_Rtpp = POSv_R-POSv_G ... (1)
POSvd_Btpp = 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 in the vertical scanning direction (lines for 720 pixels),
POSv_G = 360.0
POSv_R = 363.0
POSv_B = 365.9
If so
POSvd_Rtpp = 3.0
POSvd_Btpp = 5.9
Will be.

Here, the provisional optical path deviation amount is expressed because, as described above, in the image display device 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, the optical path deviation generated on the upper side in the vertical scanning direction for 1.9 pixels can be treated equally with the optical path deviation generated on the lower side in the vertical scanning direction for 0.1 pixel. When the final amount of optical path deviation is defined in consideration of this point, the amount of optical path deviation POSvd_R between the laser beam 21G and the laser beam 21R and the amount of optical path deviation POSvd_B between the laser beam 21G and the laser beam 21B are They are represented 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 or zero that can minimize each value.

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

In the method of determining the filter coefficient based on the amount of optical path deviation, the magnitude of the amount of optical path deviation corresponds to the magnitude of the filter coefficient b and the magnitude of the filter coefficients a and c (in other words, the magnitude of the amount of optical path deviation 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, and the amount of optical path deviation is divided into a plurality of stages so that the magnitude of the amount of optical path deviation corresponds to the low and high cutoff frequencies. The cutoff frequency may be assigned according to the divided stages. The maximum value of the cutoff frequency is preferably the cutoff frequency when there is no band limitation (filter coefficient b = 1.0).

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

Here, one of the simplest and most effective weighting modes is to match the degree of band limitation with one of other color lights other than the reference light. That is, in this case, the weight given to one corresponds to 100%, and the weight given to the other corresponds to 0%. Here, in particular, when red and blue are compared, 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 amount of optical path deviation of the laser beam 21R.

Generally, 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)
As described above, the above-mentioned optical path deviation amount referred to by the LPF intensity setting unit 108 when determining the degree of band limitation (which has a unique relationship with the filter coefficient in this embodiment) is used as optical path deviation information in advance. It is input from the optical path deviation information input terminal.

Here, considering 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 the initial setting information of the image display device 1. On the other hand, considering that the above-mentioned provisional optical path deviation amount is caused by the deviation amount of the condensing position when the MEMS mirror 30 and the display surface 40 are in a facing relationship, each time the operating conditions and the operating environment change. In addition, the provisional optical path deviation amount may be measured, and the optical path deviation information may be updated as appropriate. In this way, it becomes possible to easily adapt to changes in the amount of optical path deviation due to changes in temperature and changes over time. In this case, the image display device 1 needs to be provided with a means for measuring the amount of provisional optical path deviation, and for this kind of measuring means, for example, a known measuring means using a photodetector or the like can be preferably applied.

<Second Example>
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 above-mentioned optical path deviation information. However, in the concept of the display control device of the present invention, which has a technical idea of suppressing deterioration of image quality without adjusting the color deviation itself that occurs on the display surface 40, the degree of band limitation is determined in addition to the optical path deviation information. There may be reference elements in doing so. A second embodiment of the present invention in line with such a gist will be described with reference to FIG. Here, FIG. 9 is a block diagram of the light source control unit 110 according to the second embodiment. In the figure, the parts overlapping with FIG. 2 are designated by the same reference numerals, 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 embodiment in that the 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 numeral omitted).

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

<Band limitation processing according to the projection surface size>
The larger the screen size of the display surface 40, which is the projection surface of each laser beam, the more noticeable the color shift is. 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 the deterioration of the image quality due to the color shift.

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 as initial setting information in advance. That is, in this case, the degree of band limitation with respect to the reference screen size (that is, the degree of reference) 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 large or small.

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

Therefore, by controlling the degree of band limitation according to the magnitude of the viewing distance, it is possible to suitably suppress the deterioration of the image quality due to the color shift.

The viewing distance, which is the distance between the image display device 1 and the user, may change depending on 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 an initial setting may be input as band control information.

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

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

Here, when the image is relatively enlarged in the vertical scanning direction with the change of 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 compared. Even if it is small, the color shift that occurs in the vertical scanning direction is a relatively noticeable result. On the contrary, when the image is relatively reduced in the vertical scanning direction due to the change in 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 compared. At most, the color shift that occurs in the vertical scanning direction is relatively inconspicuous.

Therefore, by controlling the degree of band limitation according to the aspect ratio of the display surface 40, it is possible to suitably suppress the deterioration of the image quality due to the color shift.

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

In FIG. 10, the light source control unit 120 is different from the light source control unit 100 according to the first embodiment in that the image analysis unit 121 is provided and the 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 the color boundary portion in the projected image, particularly at the boundary portion between white and black. Further, the color shift is easily noticeable even at the boundary between the pixels having high luminance components and the pixels having low luminance components of the three primary colors of red, green, and blue.

Here, the spatial frequency of the image becomes high at the boundary portion where the color shift 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 image quality due to the color shift.

Various known methods can be applied to the method of analyzing the spatial frequency. For example, the image analysis unit 121 may perform first-order differential processing on the image signal for the 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 thereof.

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

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

The projection distance measuring unit 131 projects the laser beam 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 (sign 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 limiting unit 103 based on the projection distance measured by the projection distance measuring unit 131.

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

By the way, the amount of optical path deviation 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 face each other. However, in reality, in the MEMS mirror 30, the twist angle θh in the horizontal scanning direction and the twist angle θv in the vertical scanning direction change in the scanning process of the laser beam.

In the range of these twist angles of 0 ° to 90 °, the distance (projection distance) from the MEMS mirror 30 to the display surface 40 increases as the twist angle increases, and as a result, the color shift also increases. Even if correction measures such as thread winding correction are taken on the system side, such a problem can basically occur unchanged. Further, the relationship between the projection distance and the color shift can also occur when the laser beam is projected from the oblique direction with respect to the display surface 40.

Therefore, in this embodiment, information on the projection angle and the maximum twist angle of the MEMS mirror 30 is input as band control information, and the projection distance is measured or calculated by the projection distance measuring unit 131 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. Further, the maximum twist angle is a value peculiar to the MEMS mirror 30.

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

The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of claims and within a range not contrary to the gist or idea of the invention that can be read from the entire specification, and a display control device accompanied by such a modification is also available. It is also included in the technical scope of the present invention.

1 ... Video display device, 10 ... Control device, 20 ... Light source, 30 ... MEMS mirror, 40 ... Display exemption, 100 ... Light source control unit, 103 ... Band limitation unit, 108 ... LPF intensity setting unit 108, 200 ... Mirror control unit ..

Claims (1)

A display control device that controls a display device including a plurality of light sources and scanning means for scanning each of the irradiation lights emitted from the plurality of light sources on the projected surface.
A band limiting means for limiting the band of a video signal related to an image to be displayed on the projected surface, and
A drive control means for controlling the drive state of the light source based on the band-limited video signal, and
A band control means for controlling the degree of band limitation based on the amount of optical path deviation between the plurality of light sources on the projected surface is provided.
The amount of deviation of the optical path is defined as the amount of deviation of the optical path of the irradiation light of another light source with respect to the irradiation light of the reference light source.
It said band control means have row band limitation of the video signal so that the degree of the band-limited higher displacement amount increases in the optical path is increased,
The plurality of light sources are three light sources that emit red, green, and blue light.
The reference light source is defined as the light source having the largest luminance component among the light sources.
When the amount of deviation of the optical path with respect to the irradiation light of the reference light source of the irradiation light of each of the two other light sources is defined as the amount of deviation of the first and second optical paths (POSvd_R, POSvd_B),
The band control means imparts a weighting coefficient (0 <k <1) to the amount of deviation of the first and second optical paths.
The weighted average of the deviation amount of the first and second optical paths according to the weighting coefficient is defined as the deviation amount of the optical path (POSvd_R × k + POSvd_B × (1-k)).
A display control device characterized by the fact that.

Images