Image display device

• US 20020030660A1
• Filed: 09/12/2001
• Published: 03/14/2002
• Est. Priority Date: 09/12/2000
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Arakawa, Satoshi
• Granted Patent: US 6,952,195 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/36 using liquid crystals

Abstract

The image display device includes a liquid crystal display device having a liquid crystal panel and a backlight and a backlight controller for allowing the backlight of the liquid crystal display device to be bright when environment light is bright and allowing the backlight to be dark when the environment light is dark such that light leak (minimum luminance) which is defined by an extinction ratio of liquid crystal will not grow more than a specified degree. The image display device enables displayed images to be really discernible regardless of brightness of environment light (surrounding light).

Claims

1. An image display device comprising:

a liquid crystal display device having a liquid crystal panel and a backlight; and

a backlight controller for allowing the backlight of the liquid crystal display device to be bright when environment light is bright, and allowing the backlight to be dark when the environment light is dark such that light leak, which is defined by an extinction ratio of liquid crystal, will not grow more than a specified degree.

2. The image display device according to claim 1, wherein

said backlight controller comprises:

a first detector for detecting brightness of the environment light; and

a brightness controller for controlling brightness of the backlight of the liquid crystal display device, and wherein

said backlight controller adjusts the brightness of the backlight corresponding to the brightness of the environment light.

3. The image display device according to claim 2, wherein

said brightness controller comprises:

a second detector for detecting a luminance value of the backlight, being provided at the backlight;

a device for estimating a first luminance value of the light leak of a liquid crystal screen of the liquid crystal display device, with a preset relation between the luminance value of the backlight and the light leak defined by the extinction ratio of the liquid crystal; and

a device for determining a second luminance value accrued by reflection of the liquid crystal screen corresponding to the brightness of the environment light detected by said first detector, based on a predetermined relation between the brightness of the environment light and the second luminance corresponding thereto that is accrued by reflection of the liquid crystal screen;

wherein

said brightness controller controls the brightness of the backlight such that a ratio of the first luminance value to the second luminance value is not more than 2.

4. The image display device according to claim 3, wherein said brightness controller controls the brightness of the backlight such that the brightness of the backlight is 70% or more of a maximum luminance of the backlight in a range in which the ratio of the first luminance value to the second luminance value is not more than 2.

5. The image display device according to claim 3, wherein said brightness controller controls the brightness of the backlight such that said first luminance value is equal to or less than said second luminance value.

6. The image display device according to claim 3, wherein said brightness controller controls the brightness of the backlight such that the brightness of the backlight is 70% or more of a maximum luminance of the backlight in a range in which the first luminance value is equal to or less than the second luminance value.

7. The image display device according to claim 2, wherein

said brightness controller comprises:

a device for estimating a first luminance value of the light leak of a liquid crystal screen of the liquid crystal display device from current brightness of the backlight which is estimated based on a predetermined relation between usage time of the backlight and luminance of emission of the backlight and a predetermined relation between a control signal of the backlight and the luminance of the emission of the backlight, with a preset relation between the luminance value of the backlight and the light leak that is defined by the extinction ratio of the liquid crystal; and

a device for determining a second luminance value accrued by reflection of the liquid crystal screen corresponding to the brightens so of the environment light detected by said first detector, based on a predetermined relation between the brightness of the environment light and the second luminance corresponding thereto that is accrued by reflection of the liquid crystal screen;

wherein

said brightness controller controls the brightness of the backlight such that a ratio of the first luminance value to the second luminance value is not more than 2.

8. The image display device according to claim 7, wherein said brightness controller controls the brightness of the backlight such that the brightness of the backlight is 70% or more of a maximum luminance of the backlight in a range in which the ratio of the first luminance value to the second luminance value is not more than 2.

9. The image display device according to claim 7, wherein said brightness controller controls the brightness of the backlight such that said first luminance value is equal to or less than said second luminance value.

10. The image display device according to claim 7, wherein said brightness controller controls the brightness of the backlight such that the brightness of the backlight is 70% or more of a maximum luminance of the backlight in a range in which the first luminance value is equal to or less than the second luminance value.