JP2009109711A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field sequential image display device capable of displaying a color image in which luminance unevenness is not conspicuous. <P>SOLUTION: The display device includes: backlight means 2 and 3 for transmitting and illuminating a liquid crystal display device 6 composed of a plurality of light emitting elements 2a, 2b, 2c, 3a, 3b and 3c having different light emitting colors; and a control means for controlling luminance of the light emitting elements 2a, 2b, 2c, 3a, 3b and 3c. The display device displays an image by a field sequential system which turns on the light emitting elements 2a, 2b, 2c, 3a, 3b and 3c for each field. The control means 17 controls the luminance of the light emitting elements 2a, 2b, 2c, 3a, 3b and 3c, according to transmittance of a liquid crystal display element 6, and makes luminance of the liquid crystal display element 6 approximately uniform. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device that displays an image by a field sequential method.

  Conventionally, various field sequential image display devices for displaying a color image using illumination light of a color corresponding to unit color image data as a liquid crystal display element for each subfield into which a field is divided have been proposed. It is disclosed. Such a field sequential image display device sequentially selects a plurality of pixel rows of a liquid crystal display element from the first row for each subfield obtained by dividing one field for displaying a color image composed of a plurality of colors into at least two parts, One unit color image data of two or more colors is written to the pixels in these rows, and illumination light of a color corresponding to the unit color image data written to the liquid crystal display element is supplied from the surface light source for each subfield. The light is emitted.

A field sequential image display device displays a color image using a liquid crystal display element having no color filter, and a unit of two or more colors is provided on a liquid crystal display element having a display area in which pixels are arranged in a plurality of rows. By sequentially writing the color image data and emitting the illumination light of the color corresponding to the unit color image data from the surface light source, two or more unit color images are sequentially displayed on the liquid crystal display element, and the visual of each color is displayed. A color image is displayed by mixing.
JP 2005-77474 A

However, the field sequential image display device that sequentially selects the pixel rows of the liquid crystal display element from the first row and writes the unit color image data to the pixels of these rows has two colors displayed for every two or more fields. The above unit color image is darker at the top and bottom than the brightness at the center of each unit, and the luminance unevenness of the color image displayed by visual mixing of unit color images of two or more colors is noticeable Had.
The present invention has been made in view of this problem, and provides a field sequential image display device capable of displaying a color image with inconspicuous luminance unevenness.

  As described in claim 1, the present invention comprises a liquid crystal display element 6 and a plurality of light emitting elements 2a, 2b, 2c, 3a, 3b, and 3c having different emission colors, and transmissively illuminates the liquid crystal display element 6. Backlight means 2 and 3, and control means 17 for controlling the luminance of the light emitting elements 2a, 2b, 2c, 3a, 3b and 3c, and the light emitting elements 2a, 2b, 2c, 3a, 3b and 3c. In a display device that displays an image by a field sequential method in which each field is turned on, the control means 17 controls the light emitting elements 2a, 2b, 2c, 3a, 3b, 3c according to the transmittance of the liquid crystal display element 6. The luminance is controlled to make the luminance of the liquid crystal display element 6 substantially uniform.

  Further, according to the present invention, as described in claim 2, the control means 17 includes a first control unit 4 a that controls the luminance of the upper part of the liquid crystal display element 6, and the luminance of the central part of the liquid crystal display element 6. And a third control unit 4c for controlling the brightness of the lower portion of the liquid crystal display element 6.

  Further, according to the present invention, as described in claim 3, the first control unit 4a, the second control unit 4b, and the third control unit 4c are configured such that the light emitting element 2a, The current supplied to 2b, 2c, 3a, 3b, 3c is controlled.

  Further, according to the present invention, temperature detecting means 16 for detecting the temperature in the vicinity of the liquid crystal display element 6 is provided.

  Further, according to the present invention, the control unit 17 controls the backlight means 2 and 3 based on the temperature data output from the temperature detecting means 16.

  In a field sequential image display device that displays images by turning on light-emitting elements at each timing for each field, the luminance distribution of the backlight means is controlled according to the transmittance of the liquid crystal display elements, and the luminance of the liquid crystal display elements is substantially uniform. By maintaining the above, the luminance unevenness can be made inconspicuous.

  Hereinafter, an embodiment in which the present invention is applied to a head-up display device will be described with reference to the accompanying drawings. In the description of this embodiment, “right”, “left”, and “down” are directions in FIG.

  The head-up display device 1 includes backlight means 2 and 3 arranged at a predetermined interval. The backlight means 2 and 3 are arranged so that their optical axes are substantially orthogonal to each other, one backlight means 2 emits red light R downward, and the other backlight means 3 is green. Light G is emitted toward the left. The backlight means 2 is composed of light emitting diodes 2a, 2b, 2c (light emitting elements), and the backlight means 3 is composed of light emitting diodes 3a, 3b, 3c (light emitting elements).

  A lighting controller 4 is connected to each of the light emitting diodes 2a, 2b, 2c, 3a, 3b, 3c. The lighting control unit 4 includes a control unit 4a that controls the luminance of the light emitting diodes 2a and 3a by a PWM method or a constant current method, a control unit 4b that controls the luminance of the light emitting diodes 2b and 3b, and the luminance of the light emitting diodes 2c and 3c. And a controller 4c for controlling the light-emitting diodes 2a, 2b, 2c, 3a, 3b, and 3c by sequentially switching the light-emitting diodes 2a, 2b, 2c, 3a, 3b, and 3c so as to perform a field-sequential method using additive color mixing by time division. It has become. Thereby, a plurality of colored lights composed of mixed colors of the respective light emitting diodes 2a, 2b, 2c, 3a, 3b, 3c including the primary colors of the respective light emitting diodes 2a, 2b, 2c, 3a, 3b, 3c can be visually recognized. It has become.

  The traveling direction side of the red light R emitted from the light emitting diodes 2a, 2b, 2c and the green light G emitted from the light emitting diodes 3a, 3b, 3c, the optical axes of the light emitting diodes 2a, 2b, 2c, and the light emitting diode 3a , 3b, 3c, a dichroic mirror 5 is disposed at a position where the optical axes intersect. The dichroic mirror 5 reflects the red light R emitted from the light emitting diodes 2a, 2b and 2c to the left, and transmits the green light G emitted from the other light emitting diodes 3a, 3b and 3c. ing. Thereby, the light R, G of each light emitting diode 2a, 2b, 2c, 3a, 3b, 3c travels in the same direction.

  A liquid crystal display element 6 is disposed on the traveling direction side of the red light R reflected by the dichroic mirror 5 and the green light G transmitted through the dichroic mirror 5. The upper part of the liquid crystal display element 6 is transmitted and illuminated by the light emitting diodes 2a and 3a, the central part of the liquid crystal display element 6 is transmitted and illuminated by the light emitting diodes 2b and 3b, and the lower part of the liquid crystal display element 6 is illuminated by the light emitting diodes 2c and 3c. Is transmitted and illuminated.

  The liquid crystal display element 6 is a monochrome liquid crystal display panel not equipped with a color filter, and transmits or blocks light R and G guided from the light-emitting diodes 2a, 2b, 2c, 3a, 3b, and 3c. The color image is formed. Therefore, unlike a conventional liquid crystal display panel with a color filter, the transmittance is high and the brightness of a color image can be improved. In addition, the colored layer for the purpose of toning may be arrange | positioned.

  As the liquid crystal display element 6, a polysilicon type TFT liquid crystal display element is used. In the liquid crystal display element 6, it is desirable that the non-display portion other than the pixel portion is sufficiently shielded by the black matrix. As the black matrix as the light shielding film, a resin or metal one is used, but a metal film is preferable from the viewpoint of the degree of light shielding and the film thickness. The liquid crystal mode is preferably an OCB mode with excellent responsiveness.

  A drive control unit 7 is connected to the liquid crystal display element 6, and the drive control unit 7 performs on / off control of the liquid crystal drive voltage in synchronization with the lighting control unit 4. A temperature sensor 8 such as a thermistor for detecting the temperature of the liquid crystal display element 6 is installed in the vicinity of the liquid crystal display element 6. A concave mirror 9 is disposed on the traveling direction side of the display light L transmitted through the liquid crystal display element 6, and the display light L from the liquid crystal display element 6 is guided to the windshield 10 by the concave mirror 9. Yes. The display light L is reflected by the windshield 10, and the driver D can visually recognize the virtual image V (see FIG. 3).

  The temperature detection means 16 is composed of a temperature sensor 8 and an A / D converter 11. The analog data output from the temperature sensor 8 is converted into digital data by the A / D converter 11, and the temperature data is sent to the microcomputer 12. Is output. The control means 17 is composed of the microcomputer 12 and the lighting control section 4, and based on the temperature data output from the temperature detection means 16, the control section 4a, the control section 4b, and the control section 4c of the lighting control section 4 The brightness of the light emitting diodes 2 and 3 that illuminate the upper part, the center part, and the lower part of the liquid crystal display element 6 is controlled so that the brightness of the liquid crystal display element 6 becomes a predetermined value.

  FIG. 4 is a diagram showing a data writing sequence to the liquid crystal display element 6 and a lighting sequence of the light emitting diodes 2 and 3. As soon as data writing to the liquid crystal display element 6 starts, the liquid crystal of the first line starts to rise, and as data writing to the liquid crystal display element 6 progresses, the liquid crystal also rises in synchronization with this, and the liquid crystal display element 6 The liquid crystal on the last line starts to rise immediately after the data writing is completed. At this time, the lighting sequence of each of the light emitting diodes 2 and 3 is such that the liquid crystal in the vicinity of the first line and the last line has a long liquid crystal rising period in a period in which the light emitting diodes 2 and 3 are not turned on. The transmittance is lower than near the middle line.

  In particular, since the temperature characteristics of the liquid crystal deteriorate at a low temperature, the rising sequence of the liquid crystal becomes a dotted line. Therefore, the difference in transmittance between the upper part, the lower part, and the central part of the liquid crystal display element becomes more remarkable at low temperatures than at normal temperature. The microcomputer 12 controls the brightness of the light emitting diodes 2a, 2c, 3a, and 3c via the control unit 4a, the control unit 4b, and the control unit 4c of the lighting control unit 4 so that the brightness of the liquid crystal display element 6 becomes substantially uniform. The luminance is higher than that of the light emitting diodes 2b and 2b.

  According to the present embodiment, the luminance of the light emitting diodes 2a, 2b, 2c, 3a, 3b, 3c can be controlled according to the transmittance of the liquid crystal display element 6, and the luminance of the liquid crystal display element 6 can be kept uniform. . Although the present embodiment is a head-up display device, the present invention may be applied to a direct-view type on-vehicle display device such as a combination meter or a navigation device.

  The temperature sensor 8 is typically a thermistor or temperature IC, but the temperature detection means senses a change in temperature indirectly by looking at a change in the optical characteristics of the liquid crystal display element with an optical sensor or the like. There may be. Each of the light emitting diodes 2a, 2b, 2c, 3a, 3b, and 3c may be provided with light emitting diodes of three colors of R (red), B (blue), and B (green). In particular, when full-color display is not required, it is desirable to mount only a single color light emitting diode group in preference to luminance.

Sectional drawing which shows embodiment of this invention. The block diagram which shows embodiment same as the above. The general-view figure which shows embodiment same as the above. The timing diagram which shows embodiment same as the above.

Explanation of symbols

2 Backlight means 2a Light emitting diode (light emitting element)
2b Light emitting diode (light emitting element)
2c Light emitting diode (light emitting element)
3 Backlight means 3a Light emitting diode (light emitting element)
3b Light emitting diode (light emitting element)
3c Light emitting diode (light emitting element)
4a 1st control part 4b 2nd control part 4c 3rd control part 6 Liquid crystal display element 17 Control means

Claims (5)

A liquid crystal display element, a backlight unit composed of a plurality of light emitting elements having different emission colors, and transmitting and illuminating the liquid crystal display element; and a control unit for controlling the luminance of the light emitting element. In a display device that displays an image in a field-sequential system that is lit on
The display device according to claim 1, wherein the control means controls the luminance of the light emitting element in accordance with the transmittance of the liquid crystal display element to make the luminance of the liquid crystal display element substantially uniform.   The control means controls a first control unit that controls the luminance of the upper part of the liquid crystal display element, a second control unit that controls the luminance of the central part of the liquid crystal display element, and the luminance of the lower part of the liquid crystal display element. The display device according to claim 1, further comprising a third control unit.   The display device according to claim 2, wherein the first control unit, the second control unit, and the third control unit control a current supplied to the light emitting element by a PWM method or a constant current method. .   2. The display device according to claim 1, further comprising temperature detection means for detecting a temperature in the vicinity of the liquid crystal display element.   The display device according to claim 4, wherein the control unit controls the backlight unit based on temperature data output from the temperature detection unit.

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