Light emitting device and electronic apparatus using the same

• US 20070097038A1
• Filed: 12/20/2006
• Published: 05/03/2007
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Jun Koyama, Shunpei Yamazaki
• Original Assignee: Jun Koyama, Shunpei Yamazaki
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 7,688,291 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0828 forming a digital to analog [D/A] conversion circuit
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes

Abstract

Providing a light emitting device capable of suppressing the variations of luminance of OLEDs associated with the deterioration of an organic light emitting material, and achieving a consistent luminance. An input image signal is constantly or periodically sampled to sense a light emission period or displayed gradation level of each of light emitting elements of pixels and then, a pixel suffering the greatest deterioration and decreased luminance is predicted from the accumulations of the sensed values. A current supply to the target pixel is corrected for achieving a desired luminance. The other pixels than the target pixel are supplied with an excessive current and hence, the individual gradation levels of the pixels are lowered by correcting the image signal for driving the pixel with the deteriorated light emitting element on as-needed basis, the correction of the image signal made by comparing the accumulation of the sensed values of each of the other pixels with a previously stored data on a time-varying luminance characteristic of the light emitting element.

Claims

1. A method for driving a light emitting device comprising:

calculating an accumulation of light emission periods of each of a plural light emitting elements based on image signals;

correcting a current supplied from a current source to the plural light emitting elements based on the accumulation of light emission periods of the plural light emitting elements and on a data on time-varying luminance characteristic of the plural light emitting elements; and

correcting image signals so as to correct gradation levels of at least a part of the plural light emitting elements.

2. A method for driving a light emitting device comprising:

calculating an accumulation of gradation levels of each of a plural light emitting elements based on image signals;

correcting a current supplied from a current source to the plural light emitting elements based on the accumulation of gradation levels of the plural light emitting elements and on a data on time-varying luminance characteristic of the plural light emitting elements; and

correcting image signals so as to correct gradation levels of at least a part of the plural light emitting elements.

3. A method for driving a light emitting device, comprising

detecting a presence or absence of light emissions from each of a plural light emitting elements by sampling image signals over several times;

counting a number of light emissions of the each of the plural light emitting elements;

correcting a current supplied from a current source to the plural light emitting elements based on a ratio of the number of light emissions versus a number of total detections and on a data on a time-varying luminance characteristic of the plural light emitting elements; and

correcting image signals so as to correct gradation levels of at least a part of the plural light emitting elements.