JP2006337715A - Field sequential image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce color splitting and to improve gradation continuity and white chromaticity tracking, in a field sequential image display device. <P>SOLUTION: Display lumimance/chromaticity, in a prescribed driving time of RGB monochrome and white color to be displayed by field sequence, is measured by a lumimance/chromaticity measurement part 7 and is input to an arithmetic part 10, and a conversion expression for replacing the display by the driving of prescribed time of white color with the driving of RGB display period of time is acquired. An RGB signal processing part 9 detects an achromatic component from an RGB input signal, and subtracts the achromatic component from the RGB input signal, in accordance with the acquired conversion expression. A display element driving control part 8 displays the RGB signal, from which the achromatic component is subtracted and an achromatic signal onto the display element 4 by field sequence. Since the constitution in which the measurement results of the lumimance and the chromaticity of the display image are utilized carries out computation, gradation continuity and white chromaticity tracking of the display image are ensured, without being affected by the tolerance of transmittance and chromaticity characteristics of color filters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a field sequential image display apparatus for displaying a color image by displaying a plurality of color images in a field sequential manner.

  In recent years, a frame sequential image display apparatus has been put to practical use as a method for obtaining a highly efficient display light quantity with a relatively small configuration.

  A conventional frame sequential image display apparatus will be described below.

  Conventionally, as the field sequential image display device, for example, one described in US Pat. No. 6,536,904 (Patent Document 1) is known. The frame sequential image display apparatus is shown in FIG. FIG. 4 is a block diagram of a conventional frame sequential image display apparatus. In FIG. 4, 101 is a light source, 102 is a lens, and condenses light source light. Reference numeral 103 denotes a rotating color wheel, which is configured to be angle-divided by a red color filter 103R, a green color filter 103G, a blue color filter 103B, and a transparent portion (hereinafter, white segment) 103W. The rotating color wheel 103 is rotated by a motor 104. The condensed light source light passes through the rotating color wheel 103, is condensed by the relay lens 105, and enters the display element 106. The color of the light transmitted through the rotating color wheel 103 changes in the frame order. Reference numeral 107 denotes a display element driving circuit which drives the display element 106 by the PWM method. Further, the display element driving circuit 107 performs PWM driving of red, green, blue (hereinafter referred to as R, G, B) and white segments in the surface order in synchronization with the light incident on the display element 106 in the surface order. A projection lens 108 enlarges and projects the output light of the display element 106 onto the screen 109.

  Next, processing in the display element driving circuit 107 will be described with reference to FIG. Reference numeral 110 denotes an achromatic color component detection unit which detects a signal having the smallest amplitude from the RGB signals as shown in FIG. 6A (Y signal in FIG. 5). Reference numeral 111 denotes a limiter circuit that limits the amplitude when the Y signal exceeds a level that can be driven by the transparent portion 103 </ b> W of the rotating color wheel 103. FIG. 6A illustrates that the input (Y signal) and the output (YA signal) of the limiter circuit 111 are equal. The output YA signal of the limiter circuit 111 is output as an achromatic signal output Wout. Reference numerals 112, 113, and 114 denote multiplication circuits that multiply the output YA signal of the limiter circuit 111 by factors CCFR, CCFG, and CCFB, and are input to the subtraction circuits 115, 116, and 117 and subtracted from the RGB signals.

  The RGB signal outputs Rout, Gout, Bout and the achromatic color signal output Wout are expressed by the following formulas by the above arithmetic processing.

  The purpose of the arithmetic processing described above is to counter the color breakup phenomenon, which is an image quality problem of the field sequential display device. The color breakup phenomenon is a defect in which a color stripe pattern is seen at the boundary portion of the image when the line of sight is moved quickly or when the boundary portion of the image moves by switching the images of red, green, and blue in a frame sequence. In the conventional frame sequential image display device, the achromatic signal component is subtracted from the RGB signal by the operations of Equations 2, 3, and 4. As a result, as schematically shown in FIG. 6B, the visibility of red, green, and blue display colors is lowered, and the color break-up phenomenon is reduced.

The factors CCFR, CCFG, and CCFB are multiplied for the following reason. The white chromaticity (130 in FIG. 7) obtained by synthesizing the transmitted light of the red, green, and blue color filters of the rotating color filter 103 and the light intensity are the white chromaticity (FIG. 7) obtained by transmitting the white segment. 131) and the light intensity do not necessarily match, and depend on the spectral transmittance characteristics of the red, green, and blue color filters. If the achromatic color signals to be subtracted in the subtracting circuits 115, 116, and 117 are the same as the RGB signals, the influence of the above white chromaticity and light intensity difference cannot be corrected, and uniform white balance and gradation over all gradations. Linearity cannot be obtained. Therefore, the amount of the achromatic signal to be subtracted from the RGB signal is individually set for each RGB, and white chromaticity and light amount difference are corrected.
US Pat. No. 6,536,904

  The RGB color filter has tolerances for the amount of transmitted light and chromaticity, and an error is superimposed when performing an operation of subtracting the achromatic component from the RGB signal. This error causes gradation discontinuity on the display image. In the prior art, the tolerance of the color filter transmitted light amount and chromaticity is not considered, and the present invention solves this problem.

  According to a first aspect of the present invention, there is provided a frame sequential image display apparatus, a plane sequential illumination light generating unit that generates a plurality of monochromatic lights and white light in a plane sequence, a display unit that receives plane sequential illumination light, and a plane sequential illumination. Display control means for obtaining a color image by display control synchronized with light; the display control means detects detection means for detecting an achromatic color signal from RGB signals; calculation means for subtracting the achromatic color signal from RGB signals; brightness of a display image; Consists of measuring means for measuring chromaticity, and calculating means for calculating the amount of achromatic signal component to be subtracted from RGB signals from luminance and chromaticity measurement values, and displays the amount by which the achromatic signal is subtracted from the RGB signal by the calculating means Since the calculation is based on the measurement results of brightness and chromaticity of the image, the gradation of the displayed image is not affected by the tolerance of the transmittance and chromaticity characteristics of the color filter. Continued resistance, and white chromaticity tracking is ensured.

  Note that the colors of the plurality of monochromatic lights are red, green, and blue. The surface sequential illumination light generating means is composed of a light source, a light source output light condensing means, and a rotating color wheel. The color wheel is divided into a plurality of single color filters and a transparent part without color filters to condense the light source light. Or a method that uses light transmitted through the color wheel, or a combination of multiple light sources and a white light source, and means for condensing and synthesizing the output light of each light source. The same effect can be obtained in any of the methods for obtaining the surface sequential light.

  The drive PWM of the display element is optimized so as to correct the tolerance of the amount of light transmitted through the color filter and the chromaticity, and the gradation continuity of the display image and the white chromaticity tracking are improved, and the color breakup is also improved.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

(Embodiment 1)
FIG. 1 is a block diagram of a frame sequential image display apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a light source, and 2 denotes a rotating color wheel, which is divided into a color filter portion for three primary colors of red, green, and blue and a white segment portion to which no color filter is attached. Reference numeral 3 denotes a reflection mirror, 4 denotes a display element, 5 denotes a projection lens, and 6 denotes a screen. The output light of the light source 1 is collected and transmitted through the rotating color wheel 2 and reflected by the reflection mirror 3 to the display element 4. The output light of the display element 4 is enlarged by the projection lens 5 and displayed on the screen 6. Note that the rotary color wheel 2 requires a motor for rotational driving, but is omitted in the drawing. Reference numeral 8 denotes a display element drive control unit, 9 denotes an RGB signal processing unit, 7 denotes a luminance / chromaticity measuring unit, and 10 denotes an arithmetic unit. The configuration of the RGB signal processing unit 9 is shown in FIG. Reference numeral 11 denotes an achromatic color signal detection unit that outputs the achromatic color signal component of the RGB input signals (Rin, Gin, Bin) (Wout). A multiplication circuit 12 multiplies the achromatic signal component Wout by factors Fr, Fg, and Fb and inputs the result to the subtraction circuit 13 to be subtracted from the RGB signal. The outputs Rout, Gout, Bout and the achromatic signal component output Wout of the subtracting circuit 13 are output to the display element drive control unit 8 and are displayed in the order of frames in synchronism with the RGB and white light input to the display element 4 in the order of the planes. The element 4 is PWM driven.

  The multiplication factors Fr, Fg, and Fb are generated in the arithmetic unit 10 based on the measurement result of the luminance / chromaticity measuring unit 7 and input to the RGB signal processing unit 9. Specific calculation processing for obtaining the multiplication factors Fr, Fg, and Fb will be described in detail below with reference to FIGS.

  First, a PWM drive pattern having a predetermined time width T is input from the display element drive control unit 8 to the display element 4 during the R color filter period of the rotating color wheel 2 (FIG. 3A). The display image brightness Lr and chromaticity (xr, yr) are measured and input to the calculation unit 10. Next, a PWM drive pattern having a predetermined time width T is input from the display element drive control unit 8 to the display element 4 during the G color filter period of the rotating color wheel 2 (FIG. 3B). The display image brightness Lg and chromaticity (xg, yg) are measured and input to the calculation unit 10. Similarly, a PWM drive pattern having a predetermined time width T is input from the display element drive control unit 8 to the display element 4 during the B color filter period of the rotating color wheel 2 (FIG. 3C). The display image brightness Lb and chromaticity (xb, yb) are measured and input to the calculation unit 10. Further, a PWM drive pattern having a predetermined time width T is input from the display element drive control unit 8 to the display element 4 during the white segment period of the rotating color wheel 2 (FIG. 3D), and the display image is displayed by the luminance / chromaticity measurement unit 7. Luminance Lw and chromaticity (xw, yw) are measured and input to the calculation unit 10. Using the above measured values as constants, the unit time PWM drive bit of the achromatic portion is represented by the sum of the unit time PWM drive bit display of each RGB color.

The display brightness of red, green, and blue in Equation 5 is

If the sum of tristimulus values is Sr, Sg, and Sb, the white chromaticity generated by the red, green, and blue three-color composition is equal to the chromaticity xw and yw of the white segment.

It is necessary to satisfy the relational expression. Also,

By solving Equation 7 to Equation 9 for Yr / Yg, Yb / Yg,

Is obtained. As is clear from Equations 10 and 11, Yr / Yg and Yb / Yg are constants represented by chromaticity measurement values of RGB and white segments.

After that, the subsequent calculation is performed. By solving Equation 5, Equation 6, and Equation 12 for coefficients A, B, and C,

Is obtained. As is clear from the equations, A, B, and C are constants represented by the luminance and chromaticity measurement values of RGB and white segments.

  The calculation unit 10 uses multiplication factors Fr, Fg, and Fb of the RGB signal processing unit 9 as follows:

Is output. The RGB signal processing unit 9 performs an operation with the factor of Expression 16 and reflects it in the display element drive control.

  By the arithmetic processing described above, even if the RGB color filter portion display bits of the rotating color wheel 2 are replaced with the display bits of the white segment portion, luminance and chromaticity fluctuations do not occur, and the gradation continuity of the display image, And white chromaticity tracking is maintained. In addition, since the display light quantity and chromaticity of the achromatic color part and the RGB display part on the screen are measured and used, the display image can be displayed without being affected by the tolerance of the transmittance and chromaticity characteristics of the color filter. Gradation continuity and white chromaticity tracking are ensured.

  Note that the present invention is not limited to the scope of the above-described embodiment, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention. Specifically, in the first embodiment and FIG. 1, the light source 1 may be configured to synthesize the output of a plurality of light sources, and the rotating color wheel 2 is not limited to the RGB color filter and the transparent part divided into four parts, such as yellow. The color of the filter may be a division number other than four, the reflection mirror 3 is not essential and may be another optical component such as a relay lens, the display element 4 may be a transmission type as well as a reflection type, and the screen 6 Can be either built-in or non-built-in in the apparatus, and is not limited to the surface sequential method using a rotating color filter, and the same processing is possible even in a method of sequentially emitting a color light source and a white light source.

  The image display apparatus according to the present invention has the effect of correcting the white / RGB light intensity ratio tolerance by driving control in the field sequential display method to obtain good gradation continuity, and can be applied to a liquid crystal / DLP projector. is there.

1 is a configuration diagram of a frame sequential image display apparatus according to Embodiment 1 of the present invention. The block diagram of the RGB signal processing part in Embodiment 1 of this invention Signal processing explanatory diagram in Embodiment 1 of the present invention Configuration of conventional frame sequential image display device Configuration diagram of display element driving circuit of conventional frame sequential image display device Operation explanatory diagram of conventional frame sequential image display device White chromaticity diagram of conventional frame sequential image display device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Rotating color wheel 3 Reflection mirror 4 Display element 5 Projection lens 6 Screen 7 Luminance and chromaticity measurement part 8 Drive control part 9 RGB signal processing part 10 Arithmetic part 11 Achromatic color signal detection part 12 Multiplication circuit 13 Subtraction circuit 13

Claims (4)

A surface sequential illumination light generating means for generating a plurality of monochromatic light and white light in a field sequential manner, a display means for receiving the surface sequential illumination light, and a display control means for obtaining a color image by display control synchronized with the surface sequential illumination light. The display control means includes a detecting means for detecting an achromatic signal from the RGB signal, a calculating means for subtracting the achromatic signal from the RGB signal, a measuring means for measuring the luminance and chromaticity of the display image, and a luminance and chromaticity measurement value A frame sequential image display device comprising an arithmetic means for calculating an achromatic signal component amount to be subtracted from RGB signals. The frame sequential image display device according to claim 1, wherein the colors of the plurality of monochromatic lights are red, green, and blue. The surface sequential illumination light generating means includes a light source, a light source output light condensing means, and a rotating color wheel, and the rotating color wheel divides the light source light by a plurality of single color filters and a transparent part without the color filter. 2. The frame sequential image display device according to claim 1, wherein the light is incident on a color wheel that is condensed and rotated, and uses light transmitted through the color wheel. The surface sequential illumination light generating means comprises a plurality of light sources, a white light source, a condensing means for each light source output light, and a combining means, and each surface light source is sequentially time-divided to obtain surface sequential light. Item 1. A field sequential image display device according to Item 1.

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