JP2014089409A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device capable of correctly detecting luminance of a backlight by a luminance sensor and displaying at appropriate luminance even in high illuminance environment.SOLUTION: An image display device comprises: a transmission type display panel; polarization means provided on the rear surface side of the display panel and transmitting a first polarization component from incident light; a backlight provided on the rear surface side of the polarization means and irradiating the display panel; a luminance sensor provided on the rear surface side of the polarization means; and a polarizer transmitting a second polarization component in a direction orthogonal to the polarization direction of the first polarization component transmitted by the polarization means. The luminance sensor is provided so as to detect the light transmitted by the polarizer.

Description

  The present invention relates to an image display device.

  Conventionally, there is an image display device using a backlight. For example, a liquid crystal display device generally has a structure in which a backlight is disposed on the back surface of a liquid crystal panel. In the liquid crystal display device, the liquid crystal panel itself does not emit light, but is illuminated by a backlight from the back of the liquid crystal panel, and the light is blocked or transmitted to perform display. Therefore, in order to control the brightness of the display screen, it is necessary to accurately control the brightness of the backlight.

  Hereinafter, FIG. 7 will be described. FIG. 7 is a configuration diagram of a conventional general backlight. In a conventional general backlight configuration, a diffusion plate 101 is disposed on a planar light source 100, and a liquid crystal panel 102 is disposed thereon. A luminance sensor 103 that detects the luminance of the backlight is disposed on the planar light source 100. In Patent Document 1, the position of the luminance sensor is described as outside or inside the liquid crystal panel. However, as shown in the conventional backlight configuration diagram of FIG. In general, a plurality of luminance sensors are arranged.

  For example, Patent Document 1 discloses a technology that includes a brightness sensor that detects the brightness of a backlight, and controls and controls the backlight based on the detection result.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for preferentially making light from a backlight enter a luminance sensor in order to improve the accuracy of backlight control.

Japanese Patent Laid-Open No. 11-212056 JP 2008-153014 A

  However, in the conventional technique disclosed in the above-mentioned patent document, when the liquid crystal display device is used in a high illumination environment such as outdoors, external light is incident on the luminance sensor that should originally detect only the luminance of the backlight from the display surface side. In some cases, the backlight brightness is falsely detected. The portion of the backlight that is detected as having a high luminance is surrounded by a high illuminance environment, but the light emission luminance is reduced due to an erroneous detection result, and the visibility of the display screen is reduced.

  Therefore, an object of the present invention is to provide an image display device that can correctly detect the luminance of a backlight and display it at an appropriate luminance even in a high illumination environment.

The present invention includes a transmissive display panel,
A polarizing means provided on the back side of the display panel and transmitting a first polarization component from incident light;
A backlight provided on the back side of the polarizing means and illuminating the display panel;
An image display device comprising:
A luminance sensor provided on the back side of the polarizing means;
A polarizer that transmits a second polarization component in a direction orthogonal to the polarization direction of the first polarization component transmitted by the polarization means;
With
The luminance sensor is an image display device provided to detect light transmitted through the polarizer.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a high illumination environment, the brightness | luminance sensor can detect the brightness | luminance of a backlight correctly, and can provide the image display apparatus which can display with appropriate brightness | luminance.

1 is a configuration diagram of an image display apparatus according to a first embodiment. The figure for demonstrating permeation | transmission and reflection of the light in the backlight of Example 1. FIG. Measurement result of luminance sensor of Example 1 Configuration diagram of image display device of embodiment 2 The figure for demonstrating permeation | transmission and reflection of the light in the backlight of Example 2. FIG. Luminance sensor measurement result of Example 2 Conventional backlight configuration diagram

Example 1
Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of an image display apparatus according to Embodiment 1 of the present invention. This image display device includes a liquid crystal panel 202, an anisotropic polarization separation sheet (hereinafter referred to as DBEF (trademark)) 201 provided on the back side of the liquid crystal panel 202, and a planar light source 200 provided on the back side of the DBEF 201. And having. The liquid crystal panel 202 is a transmissive display panel. A DBEF (Dual Brightness Enhancement Film) 201 transmits a first polarization component from incident light and reflects a second polarization component orthogonal to the polarization direction of the first polarization component. DBEF is also called a reflective polarizing film. The planar light source 200 is a light source in which light emitting elements such as organic EL are arranged in a planar shape, and is a backlight that irradiates the liquid crystal panel 202. A surface light source composed of an organic EL is also called an EL sheet, and the entire surface emits light uniformly. A luminance sensor 204 that detects the luminance of the backlight is provided on the back side of the DBEF 201. In the present embodiment, the brightness sensor 204 is provided with a recess on the light emitting surface of the planar light source 200. An S-wave polarizing plate 203 that is a polarizer that transmits a second polarization component in a direction orthogonal to the polarization direction of the first polarization component transmitted by the DBEF 201 is disposed so as to cover the opening of the recess. That is, with this configuration, the luminance sensor 204 is provided so as to detect light transmitted through the S wave polarizing plate 203.

  Here, the general liquid crystal panel 202 includes a lower polarizing plate that is a P-wave polarizing plate. This is a polarizing plate that allows the DBEF 201 to transmit the same polarization component from incident light. The DBEF 201 has a function of reflecting S-polarized light and transmitting P-polarized light by forming thin films having different refractive indexes into a multilayer structure. The planar light source 200 is preferably capable of uniform surface light emission such as organic EL. The luminance sensor 204 may be an RGB sensor. With respect to the S wave polarizing plate 203 of this embodiment, light incident on the luminance sensor 204 does not necessarily cause the S wave polarizing plate 203 to be covered, for example, by covering the luminance sensor 204 by attaching it as a film to the opening of the luminance sensor 204. Any structure that passes is acceptable. The detection value by the luminance sensor 204 is input to the control unit 210 that controls the light emission of the planar light source 200 of the backlight. The control unit 210 performs backlight brightness control such as unevenness correction based on the brightness detection value input from the brightness sensor 204.

  Next, FIG. 2 is a schematic diagram of the backlight according to the first embodiment of the present invention, in which light vectors are represented by arrows. The direction of the arrow indicates the direction of light, and the letter in the arrow indicates whether it is P-polarized light or S-polarized light.

  The planar light source emitted light 300 emitted from the planar light source 200 is non-polarized light that uniformly includes polarized components in all directions, and emits light from the planar light source 200 toward the liquid crystal panel 202 (display screen side). The planar light source 300 emits the P-polarized component and reflects the S-polarized component by the DBEF 201. The DBEF reflected light 302 reflected by the DBEF 201 is S-polarized light and travels from the DBEF 201 toward the planar light source 200. The DBEF reflected light 302 is reflected by the surface of the planar light source 200. The light source reflected light 304 reflected by the planar light source 200 is scattered at the time of reflection, becomes light including not only the S-polarized component but also the P-polarized component, and proceeds toward the liquid crystal panel 202. In the light source reflected light 304, the P-polarized component is transmitted again by the DBEF 201, and the S-polarized component is reflected. The DBEF reflected light 305, which is the S-polarized component of the light source reflected light 304 reflected by the DBEF 201, is scattered while being repeatedly reflected between the planar light source 200 and the DBEF 201, and the P-polarized component passes through the DBEF 201.

The DBEF transmitted light 301 and 303 transmitted through the DBEF 201 is P-polarized light, passes through the lower polarizing plate provided in the liquid crystal panel 202, and appears on the display screen.

  A part of the DBEF reflected light 302 by the DBEF 201 is transmitted through the S-wave polarizing plate 203 installed in the concave portion provided on the planar light source 200 and is incident on the luminance sensor 204.

  The external light 307 is light such as the sun or illumination. The external light 307 enters from the display screen side of the liquid crystal panel 202 and becomes P-polarized light by the lower polarizing plate of the liquid crystal panel 202. The liquid crystal transmitted external light 308 transmitted through the liquid crystal panel 202 travels in the direction of the DBEF 201 and is transmitted through the DBEF 201. The DBEF transmitted external light 309 transmitted through the DBEF 201 proceeds in the direction of the planar light source 200. Since the DBEF transmitted external light 309 is P-polarized light, it is shielded by the S-wave polarizing plate 203 provided on the luminance sensor 204. As described above, only the light from the planar light source 200 can be incident on the luminance sensor 204, and the external light can be blocked.

  Using the configuration of the present embodiment, the display device is illuminated from the display screen side with a light source having a constant luminance, and the luminance of the backlight is measured by the luminance sensor 204 with and without the S-wave polarizing plate 203. . The measurement results are shown in the graph of FIG. From the measured value 400 without the S wave polarizing plate 400 and the measured value 401 with the S wave polarizing plate in FIG. 3, the presence of the S wave polarizing plate 203 can suppress the influence of external light on the luminance sensor 204 to 10% or less. I understand that I can do it.

  As described above, by applying the present invention, the incidence of external light to the luminance sensor is suppressed, the light from the backlight is selectively incident on the luminance sensor, and the luminance sensor is Brightness can be detected correctly. Therefore, even in a high illuminance environment, it is possible to display with appropriate luminance by backlight control based on the measurement value by the luminance sensor.

(Example 2)
In Example 2 of the present invention, it will be described that the present invention can be applied even when a point light source that requires a light diffusion structure is used.
The second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a configuration diagram of the image display apparatus according to the second embodiment of the present invention. A DBEF 501 is disposed on the point light source 500, and a diffusion plate 502, a lens sheet 503, and a liquid crystal panel 504 are disposed thereon in that order. The brightness sensor 507 for detecting the brightness of the backlight is provided with a recess on the point light source 500 and disposed therein. S wave polarizing plate 506 so as to cover the recess.
Is arranged.

  Here, the point light source 500 has a plurality of LEDs arranged at equal intervals on the same plane. Unlike the planar light source 200, the point light source 500 has a luminance unevenness in which the luminance is high immediately above the LED and the luminance is low between the LED and the LED. The point light source 500 requires a diffusion structure in order to eliminate uneven brightness. The lens sheet 503 is a sheet having a saw-shaped or kamaboko-shaped prism on the surface, and has a light collecting effect of collecting light forward. The lens sheet 503 is disposed in order to efficiently collect the light diffused by the LEDs on the liquid crystal panel 504. A value detected by the luminance sensor 507 is input to a control unit 510 that controls light emission of the backlight point light source 500. Based on the detected luminance value input from the luminance sensor 507, the control unit 510 performs backlight luminance control such as unevenness correction, for example.

1 differs from the backlight configuration diagram of the first embodiment in FIG. 1 in that the point light source 500 is not a planar light source with uniform brightness and the diffusion plate 502 as a structure for light diffusion between the DBEF 501 and the liquid crystal panel 504. And a lens sheet 503 is disposed.

  Next, FIG. 5 is a schematic diagram of a backlight according to Embodiment 2 of the present invention, in which light vectors are represented by arrows. The direction of the arrow indicates the direction of light, and the letter in the arrow indicates whether it is P-polarized light or S-polarized light.

  The point light source emitted light 600 emitted from the point light source 500 is non-polarized light that uniformly includes polarized light in all directions, and is emitted from the point light source 500 toward the liquid crystal panel 504 (display screen side). The point light source emission light 600 transmits the P-polarized component and reflects the S-polarized component by the DBEF 501. The DBEF reflected light 602 reflected by the DBEF 501 is S-polarized light and travels from the DBEF 501 toward the point light source 500. The DBEF reflected light 602 is reflected by the surface of the point light source 500. The light source reflected light 604 reflected by the point light source 500 is scattered at the time of reflection, becomes light including not only S-polarized light but also P-polarized light, and proceeds toward the liquid crystal panel 504. The light source reflected light 604 again transmits the P-polarized component and reflects the S-polarized component by the DBEF 501. The DBEF reflected light 605 that is the S-polarized component of the light source reflected light 604 reflected by the DBEF 501 is scattered while being repeatedly reflected between the point light source 500 and the DBEF 501, and the P-polarized component passes through the DBEF 501.

The DBEF transmitted light 601 and 603 transmitted through the DBEF 501 is P-polarized light, and the diffusion plate 50
2. It passes through the lens sheet 503. The DBEF transmitted light 601 and 603 are scattered when passing through the diffuser plate 502 and become diffused plate transmitted light 606 including not only P-polarized light but also minute S-polarized light. The diffuser plate transmitted light 606 passes through the lens sheet 503 and is condensed to become lens sheet transmitted light 607. The P-polarized light contained in the lens sheet transmitted light 607 passes through the lower polarizing plate provided in the liquid crystal panel 504 and exits to the display screen.

  Part of the DBEF reflected light 602 from the DBEF 501 is transmitted through the S wave polarizing plate 506 provided in the concave portion provided on the point light source 500 and is incident on the luminance sensor 507.

The external light 609 is light such as the sun or illumination. The external light 609 enters from the display screen side of the liquid crystal panel 504 and becomes P-polarized light by the lower polarizing plate of the liquid crystal panel 504. The liquid crystal transmitted external light 610 transmitted through the liquid crystal panel 504 proceeds in the direction of the lens sheet 503 and is transmitted through the lens sheet 503. The lens sheet transmitted external light 611 that has passed through the lens sheet 503 travels in the direction of the diffusion plate 502 and passes through the diffusion plate 502. The lens sheet transmitted external light 611 is scattered when transmitted through the diffuser plate 502 and becomes diffused plate transmitted external light 612 including not only P polarized light but also minute S polarized light. The diffuser plate transmitted light 612 travels in the direction of the DBEF 501 and passes through the DBEF 501. The DBEF transmitted external light 613 transmitted through the DBEF 501 travels in the direction of the point light source 500. Since most of the DBEF transmitted external light 613 is P-polarized light, most of the DBEF transmitted external light 613 is shielded by the S wave polarizing plate 506 provided on the upper part of the luminance sensor 507. As described above, the light from the point light source 500 is preferentially incident on the luminance sensor 507, and most of the external light incident from the outside of the display screen can be shielded from the luminance sensor 507.

  Using the configuration of this embodiment, the display device is illuminated from the display screen side with a light source having a constant luminance, and the luminance of the backlight is measured by the luminance sensor 507 with and without the S-wave polarizing plate 506. . The measurement results are shown in the graph of FIG. From the measured value 700 without S wave polarizing plate 700 and the measured value 701 with S wave polarizing plate 701 in FIG. 6, the presence of the S wave polarizing plate 506 can suppress the influence of external light on the luminance sensor 507 to 50% or less. I understand that I can do it.

  According to the present embodiment, even when a point light source that requires a light diffusing structure is used, the incidence of external light to the luminance sensor is suppressed, and light from the backlight is selectively transmitted to the luminance sensor. The luminance sensor can detect the luminance of the backlight correctly even in a high illumination environment. Therefore, even in a high illuminance environment, it is possible to display with appropriate luminance by backlight control based on the measurement value by the luminance sensor.

100, 200 Planar light sources 102, 202, 504 Liquid crystal panels 103, 204, 507 Luminance sensors 201, 402, 501, 704 DBEF
203, 506 S wave polarizing plate

Claims (13)

A transmissive display panel;
A polarizing means provided on the back side of the display panel and transmitting a first polarization component from incident light;
A backlight provided on the back side of the polarizing means and illuminating the display panel;
An image display device comprising:
A luminance sensor provided on the back side of the polarizing means;
A polarizer that transmits a second polarization component in a direction orthogonal to the polarization direction of the first polarization component transmitted by the polarization means;
With
The brightness display is provided so as to detect light transmitted through the polarizer. The luminance sensor is disposed in a recess provided on the light emitting surface of the backlight,
The image display device according to claim 1, wherein the polarizer is provided so as to cover an opening of the concave portion.   The image display device according to claim 1, wherein the polarizer is provided so as to cover the luminance sensor.   4. The image display device according to claim 1, wherein the display panel has a polarizing plate on the back side that transmits the first polarization component from incident light. 5.   The image display device according to claim 1, wherein the backlight includes a planar light source.   The image display device according to claim 1, wherein the backlight includes a plurality of point light sources.   The image display apparatus according to claim 1, further comprising a light diffusing unit between the display panel and the polarizing unit.   The image display device according to claim 1, wherein the backlight includes an organic EL as a light source.   The image display device according to claim 1, wherein the backlight includes an LED as a light source.   The image display device according to claim 1, wherein the polarization unit reflects the second polarization component.   The image display apparatus according to claim 1, wherein the polarization unit is an anisotropic polarization separation sheet.   The image display apparatus according to claim 1, wherein the luminance sensor is an RGB sensor.   The image display device according to any one of claims 1 to 12, further comprising a control unit that controls light emission of the backlight based on a detection value by the luminance sensor.

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