Display device capable of measuring an illuminance and widening a dynamic range of the measured illuminance

• US 8,063,866 B2
• Filed: 10/24/2008
• Issued: 11/22/2011
• Est. Priority Date: 11/15/2007
• Status: Active Grant

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Tada, Masahiro, Fuchi, Masayoshi, Nakamura, Hiroki, Nakamura, Takashi, Hayashi, Hirotaka
• Primary Examiner(s): Nguyen; Kimnhung
• Application Number:
  US12/257,778
• Publication Number:
  US 20090128477A1
• Time in Patent Office: 1,124 Days
• Field of Search: 345 87-100, 345/207, 345/102, 250/205, 250/214.R, 313/504, 313/506
• US Class Current: 345/98
• 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 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A capacitor charged beforehand is discharged according to a light surrounding a display unit. A data is decreased similarly to the voltage between the electrodes of the capacitor. A trigger signal is outputted if the data becomes equal to or less than a threshold value. A clock signal whose cycle of changing levels gradually becomes long is generated. A count value is updated at each change of the clock signal'"'"'s level and the updated count value is outputted. The count value is sampled when the trigger signal is outputted.

Claims

1. A display device comprising:

a display unit having pixels;

a light sensor circuit having a capacitor and a light-into-electricity conversion element that discharges the capacitor according to a surrounding illuminance of the display unit;

an arithmetic circuit that decreases a data similarly to a voltage between electrodes of the capacitor and outputs a trigger signal if the data becomes equal to or less than a threshold value;

a clock signal generating circuit that generates a clock signal whose cycle of changing levels gradually becomes long;

a counter circuit that updates a count value at each change of the clock signal'"'"'s level; and

a sampling latch circuit that samples the count value when the trigger signal is outputted.

3. The display device according to claim 1 or claim 2, wherein the light sensor circuit is formed in an area shaped like a picture frame of an array substrate in which the display unit is formed, the picture frame area surrounding the display unit.

2. A display device comprising:

a display unit having pixels;

a light sensor circuit having a capacitor and a light-into-electricity conversion element that discharges the capacitor according to a surrounding illuminance of the display unit;

an arithmetic circuit that decreases a data similarly to a voltage between electrodes of the capacitor and outputs a trigger signal if the data becomes equal to or less than a threshold value;

a clock signal generating circuit that generates a clock signal whose level changes periodically;

a counter circuit that updates a count value at each change of the clock signal'"'"'s level;

a sampling latch circuit that samples the count value when the trigger signal is outputted; and

a value conversion circuit having a map table which has ranges for the sampled count value each associated with an output value, the value conversion circuit being configured to find one of the ranges which includes the sampled count value and outputs the output value associated with the range found;

wherein

a larger output value of the map table corresponds to a narrower range associated with the output value.