JP2006171174A - Image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of a multiple image phenomenon even when field frequency is increased to prevent the generation of color breakup in a DLP (Digital Light Processing) type projector. <P>SOLUTION: The field frequency of an input image signal is multiplied by N, the input signal of N-times field frequency is phase-sequentially processed and supplied to a DMD element 4, the DMD element 4 is irradiated with light from a light source 15 through a color wheel 10, and the reflected light thereat is projected to a screen 5. One field of the input image signal is divided into a plurality of light emitting blocks, light quantity is weighted in each light emitting block and a light source driving circuit 16 allows the light source 15 to emit light by a drive current to which the light quantity is weighted in each light emitting block. For instance, the light quantity is weighted in each light emitting block so that the brightness in the vicinity of an intermediate part becomes maximum and the brightness is gradually reduced in accordance with approach to both ends, thereby an image of field around a center is emphasized and inconspicuous in both end fields to suppress the multiple image phenomenon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a video display device using DLP (Digital Light Processing) or the like, and in particular, multiple image phenomenon does not occur even when the field frequency is increased to prevent color breakup. Related to

  In recent years, DLP projectors using DMD (Digital Micromirror Device) elements have been commercialized. The DMD element is a device in which an infinite number of minute mirrors are arranged on the surface and the angle can be changed for each pixel. In the DLP method, light from a light source is irradiated onto a DMD element, the light path is changed according to the angle of a mirror on the surface of the DMD element, light is turned on / off in units of pixels, and image display is performed. A DLP projector performs image display by irradiating the screen with light of image information thus obtained.

  In general, a DLP projector uses a single DMD element. Therefore, in order to obtain three primary colors of R (red), G (green), and B (blue), the rotating color is divided into three colors. Use a wheel. The RGB color display is made possible by converting the video signal into a frame sequence and rotating the color wheel in synchronization with the video display cycle of the DMD element in RGB units.

  DLP projectors display the three colors of RGB in one field of video in order, so there is no problem when still images are displayed or when the viewer's line of sight is fixed. When the viewer's line of sight moves, depending on the pattern, it is detected that the light emission of RGB is shifted in time, and a phenomenon called color breakup, in which an unexpected color appears, appears.

  FIG. 3 illustrates the occurrence of color breakup. When the stationary window W1 in the center of the screen is stationary, no color breakup occurs as shown in FIG. As shown in FIG. 3 (B), the leading edge and the trailing edge of the window W1 have colors that are not supposed to exist. In this example, one edge of the window W1 is colored yellow and red, and the other edge is colored blue and cyan. The width changes according to the amount of movement, and becomes stronger as the movement increases.

  FIG. 4 is a diagram showing the principle of occurrence of color breakup. In FIG. 4, the vertical direction represents time, the horizontal direction represents the position on the screen, and a white window (RGB sequentially emits white light in a frame sequential order) moves rightward at 3 dots / field. To express.

  At this time, the line of sight moves in accordance with the movement of the window, the positions L1 to L3 on the retina correspond to the rear edge of the window, and the positions L4 to L6 on the retina correspond to the front edge of the window. The light emission in the window portion is performed in the order of RGB as shown in the figure, but at the position L3 or L4 on the retina, light of RGB3 color always enters the eye, whereas the position L1, L2 or L5 on the retina. , L6 can be seen to be unbalanced instead. Since only blue is displayed at the position L1 on the retina and only green and blue are displayed at the position L2 on the retina, as a result, as shown in FIG. 3B, blue and cyan colors are attached to one edge of the window W1. It will be. The same applies to the other edge portion. Since the position L5 on the retina is red and green, and the position L6 on the retina is only red, yellow and red are attached, respectively.

  As a countermeasure against this color breakup phenomenon, a method of increasing the image display period of the DMD element to N times or more and simultaneously increasing the rotation of the color wheel is often used.

  FIG. 5 shows an example in which the field frequency is doubled. That is, a field-sequential one-field video signal as shown in FIG. 5A is displayed in the same field twice as shown in FIG. This is a video signal.

  In this way, when the field frequency is doubled, as shown in FIG. 6, the colored range is narrowed, and the color breakup phenomenon is less noticeable. Thus, the higher the video display cycle, the higher the improvement. A technique for reducing the color break-up phenomenon by suppressing such a shift in RGB display time below the human eye detection limit is often used.

For example, Patent Document 1 and Patent Document 2 propose changing the amount of light in order to expand the dynamic range.
JP-A-11-65528 JP 2001-1000069 A

  As described above, in a DLP projector using a DMD element, the field frequency is increased to prevent color breakup. However, when the field frequency is increased with a DLP projector, there arises a problem that a multiple image phenomenon occurs.

  That is, FIG. 7 shows a state where a white character “X” is displayed on a black background. When the character is stationary, it is displayed normally as shown in FIG.

  However, if the field frequency is set to 100 Hz as in the case of a projector with a measure against color breakage, the same image in a certain field is displayed twice when it starts to move to the right or left.

  FIG. 8 shows a state in which an image having a width of 1 dot moves to the right by 2 dots. The line of sight moves with the movement on the screen as before. However, since the image of the same field is displayed twice, the same image appears again at the position L1 on the retina immediately next to the position L2 on the retina. However, since the position on the retina has already shifted from the first display, it is recognized as an image shifted to the left.

  In the vicinity of the positions L1 and L2 on the retina in FIG. 8, the previous color breakup phenomenon is observed, but since the width is shortened, it is not conspicuous, so the description is omitted. Although omitted in the figure, there is actually a blackout period between each display when the speed is doubled or higher, so positions L1 and L2 on the retina. Are recognized as two separate images.

  As described above, when the field frequency is increased with a DLP projector, a multiple image phenomenon occurs. The multiple image phenomenon becomes worse as triple field and quadruple images as the field frequency is increased to prevent color breakup.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a video display device in which multiple image phenomenon does not occur even when the field frequency is increased in order to prevent color breakup in a DLP projector. And

  In order to solve the above-mentioned problem, the video display device according to the invention of claim 1 writes the input video signal at the field frequency of the input video signal, and N times the field frequency of the input video signal (N is a positive integer). A field speed increasing means for forming an image signal having a field frequency of N times the field frequency of the input video signal, a field-sequencing means for field-sequentially converting the image signal having a field frequency of N times, A display element to which a video signal having a field frequency of N times that is serialized is supplied, a color wheel that is rotated in synchronization with the video signal having a field frequency of N times that is frame-sequentially, and is separated into RGB, Light source control means for dividing the light emission period into a plurality of light emission blocks and weighting the light quantity for each light emission block, and light whose light quantity is controlled by the control of the light source control means With the door, the projection light from a light source is projected to the display device via the color wheel, it is characterized in that so as to project a video that a projected light transmitted or is reflected by the display element.

  According to a second aspect of the present invention, in the first aspect of the invention, the light source control means sets the light emission block having a period shorter than the one field period in synchronization with the one field period of the input video signal. Features.

  According to a third aspect of the present invention, in the first aspect of the invention, the light source control means is configured such that the light amount at the predetermined block among the light emitting blocks is maximized, and the light amount decreases as the distance from the predetermined block increases. The amount of light is weighted.

  According to the invention of claim 4, in the invention of claim 3, the light quantity is weighted so that the light quantity at the intermediate block is maximized among the respective light emitting blocks, and the light quantity decreases as it goes to both end blocks. It is characterized by that.

  In the invention of claim 5, in the invention of claim 4, the light source control means weights so that the total amount of light after weighting each block is equal to the total amount of light before weighting. It is characterized by that.

  According to the present invention, the occurrence of color breakup is prevented by increasing the input video signal to N times speed, and one field of the input video signal is divided into a plurality of light-emitting blocks. The light quantity is weighted for each light-emitting block so that the brightness decreases as it goes to both ends. For this reason, the amount of light from the light source changes so that the brightness near the middle is maximum and the brightness decreases as it goes to both ends, the image in the field near the center is emphasized, the image in the fields at both ends becomes inconspicuous, The image phenomenon can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, the video signal from the input terminal 1 is supplied to the N-times speed increasing circuit 2. The N-times speed increasing circuit 2 includes an image memory. The N-time speed increasing circuit 2 writes an input video signal to the image memory at the field frequency of the input video signal and reads it from the image memory at the N-times field frequency. The field frequency of the video signal is increased to N times (N is a positive integer).

  The output signal of the N-times speed increasing circuit 2 is supplied to the frame sequential signal forming circuit 3. The RGB signals are sequentially framed sequentially by the frame sequential signal forming circuit 3. An output signal of the frame sequential signal forming circuit 3 is supplied to the DMD element 4. The DMD element 4 is a device in which countless minute mirrors are arranged on the surface, and the angle can be changed for each pixel.

  The synchronizing circuit 7 is supplied with the horizontal synchronizing signal HSync and the vertical synchronizing signal VSync of the input video signal. The horizontal synchronizing signal HSync and the vertical synchronizing signal VSync from the synchronizing circuit 7 and the horizontal synchronizing signal NHSync and the vertical synchronizing signal NVSync having the N times frequency are supplied to the N speed increasing circuit 2.

  Further, the N-fold vertical synchronization signal NVSync from the synchronization circuit 7 is supplied to the control circuit 8. The control circuit 8 forms a motor control signal for rotating the color wheel 10 and a light source control signal for controlling the light source.

  The color wheel 10 is painted with RGB colors. The color wheel 10 is rotated by a motor 11. The control circuit 8 outputs a motor control signal in synchronization with the N-fold vertical synchronization signal NVSync, and this motor control signal is supplied to the motor 11 via the motor drive circuit 12. As a result, the color wheel 10 is rotated in synchronization with the N-fold vertical synchronization signal NVSync.

  The light source 15 projects light onto the DMD element 4 via the color wheel 10. The light quantity of the light source 15 is controlled by the drive current of the light source drive circuit 16. As will be described later, one field of the input video signal is divided into a plurality of light emission blocks by the drive current from the control circuit 8, and the drive current of the light source 15 is weighted for each light emission block.

  The projection light from the light source 15 is applied to the DMD element 4 through the color wheel 10. Reflected light from the DMD element 4 is applied to the screen 5, and an image is displayed on the screen 5.

  The operation of the embodiment of the present invention will be described with reference to FIG. FIG. 2 shows an example when the input video signal is speeded up to 6 times. As shown in FIG. 2A, the field frequency of the input video signal is, for example, 60 Hz (for example, NTSC system). The video signal is increased, for example, by 6 × in the N × speed increasing circuit 2. In this case, the video signal is speeded up 6 times by the N-times speed-up circuit 2 and a video signal having a field frequency of 360 Hz is formed. This video signal is subjected to frame sequential processing by the frame sequential signal forming circuit 3, and a 6 × speed frame sequential video signal as shown in FIG. 2B is output from the frame sequential signal forming circuit 3.

  In FIG. 2, a period F1 indicates the field period of the input video signal, and periods f1, f2,..., F6 indicate field periods that are 6 times faster. For example, when the input video signal is speeded up 6 times, the same image is repeatedly displayed 6 times in the fields f1 to f6.

  In this example, each color of RGB is painted on the color wheel 10 so that the same color appears twice in one turn. One rotation of the color wheel 10 corresponds to two fields of N-times video signal. As shown in FIG. 2 (C), the color wheel 10 is rotated at 180 Hz once in two fields of a 6 × video signal and in synchronization with a 6 × vertical synchronization signal 6VSync.

  As shown in FIG. 2D, the light source 15 is divided into a plurality of light-emitting blocks B0, B1, B2, B3, B4, B5, and B6 during a field F1 of the input video signal. Of B1, B2, B3, B4, B5, and B6, the drive current is weighted so that the vicinity of the middle is the maximum and the brightness decreases toward both ends. Therefore, the light quantity of the light emitted from the light source 15 changes in a mountain shape as shown in FIG. 2E with respect to the frame-sequential video signal at 6 × speed as shown in FIG. .

  A frame-sequential video signal as shown in FIG. 2B is supplied to the DMD element 4, and light having a variable amount of light is projected from the light source 15 as shown in FIG. As shown in C), the DMD element 4 is irradiated through the rotating color wheel 10, and the reflected light from the DMD element 4 is irradiated onto the screen 5.

  Thus, in the embodiment of the present invention, the field frequency of the input video signal is increased by, for example, 6 times. For this reason, generation | occurrence | production of a color break can be prevented.

  Along with this, as shown in FIG. 2D, the light source 15 is divided into a plurality of light-emitting blocks B0, B1, B2, B3, B4, B5, and B6 during one field period F1 of the input video signal. Among the light emitting blocks B0, B1, B2, B3, B4, B5, and B6, the driving current is weighted so that the vicinity of the middle is maximum and the brightness decreases toward both ends. As a result, the occurrence of multiple image phenomenon can be suppressed.

  That is, conventionally, as shown in FIG. 2F, the same drive current is supplied to the light source, and the light quantity of the light source is constant. On the other hand, in the embodiment of the present invention, as shown in FIG. 2D, one field of the input video signal is divided into a plurality of light-emitting blocks, the maximum near the middle, and the brightness increases toward both ends. Weighted to decrease.

  The multiple image phenomenon occurs because an image in the same field is displayed a plurality of times. In the embodiment of the present invention, the same image is displayed in the fields f1 to f6, but the amount of light from the light source 15 is maximum near the middle and changes so that the brightness decreases toward both ends. The image in the nearby field is emphasized, and the image in the field at both ends becomes inconspicuous. For this reason, the multiple image phenomenon can be suppressed.

  In the embodiment of the present invention, when the total light amount is weighted so that the brightness near the middle is maximum and the brightness decreases toward both ends, the total light amount itself does not change from that before weighting even after weighting. Is weighted. For this reason, multiple images can be reduced while maintaining the brightness of the video.

  In the above-described example, the light amount is weighted so that the vicinity of the middle is the maximum and the brightness decreases toward the both ends. However, the present invention is not limited to this. In short, the light amount of the light source for one field of the input video signal is controlled by dividing it into a plurality of light emission blocks so that the light amount at the predetermined light emission block is maximized and the light amount decreases as the distance from the predetermined light emission block increases. , Weighting.

  In this example, the input video signal is speeded up 6 times, and the light emission block is divided into 6 blocks corresponding thereto. However, the speed of the input video signal and the number of light emission blocks need not necessarily correspond to each other. . The light emitting block may be set in any way as long as it is synchronized with the input video signal and is shorter than the period of one field of the input video signal.

  In the above example, the projector is configured such that the projection light from the light source is reflected by the DMD element and displayed on the screen. However, the present invention provides a light source for the display element modulated by the video signal. Any projector can be applied as long as it transmits or reflects the projection light from the projector.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the gist of the present invention.

  The present invention is a DLP projector using a DMD element and can be used to prevent the generation of multiple images when the field frequency is increased in order to suppress the occurrence of color breakup.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a timing chart used for operation | movement description of one Embodiment of this invention. It is explanatory drawing of generation | occurrence | production of a color break. It is explanatory drawing of generation | occurrence | production of the color break in the DLP projector using a DMD element. It is explanatory drawing of the improvement of the color breakup in the DLP projector using a DMD element. It is explanatory drawing of improvement of color breakup. It is explanatory drawing of generation | occurrence | production of a multiple image. It is explanatory drawing of generation | occurrence | production of the multiple image in the DLP projector using a DMD element.

Explanation of symbols

2 N-times speed increasing circuit 3 Frame sequential signal forming circuit 4 DMD element 5 Screen 10 Color wheel 15 Light source 16 Light source driving circuit

Claims (5)

An input video signal is written at a field frequency of the input video signal, read at a field frequency N times (N is a positive integer) the field frequency of the input video signal, and a field N times the field frequency of the input video signal. A speed-up means for forming a frequency image signal;
A field-sequentialization means for field-sequentially processing the video signal having the N-fold field frequency;
A display element to which the image signal having the field frequency of N times the field sequence is supplied;
A color wheel that rotates in synchronization with the image signal of N times the field frequency that has been frame-sequentially and is color-coded in RGB;
A light source control unit that divides a light emission period into a plurality of light emission blocks and weights the amount of light for each of the light emission blocks;
A light source whose light amount is controlled by the control of the light source control means,
An image display apparatus, wherein projection light from the light source is projected onto the display element via the color wheel, and the projection element transmits or reflects the projection light to project an image.   2. The video display according to claim 1, wherein the light source control unit sets a light emission block of a period shorter than the period of the one field in synchronization with a period of one field of the input video signal. apparatus.   The light source control means weights the light amount so that the light amount at the predetermined block among the light emitting blocks is maximized and the light amount decreases as the distance from the predetermined block increases. The video display device according to claim 1.   The light quantity is weighted so that the light quantity in the intermediate block is maximized among the light emitting blocks, and the light quantity decreases as it goes to both end blocks. Video display device. 2. The video according to claim 1, wherein the light source control unit performs weighting so that a total amount of light after weighting the light amount for each block is equal to a total amount of light before weighting. Display device.

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