Display device and electronic apparatus

Abstract

To provide a display device whose display can be recognized even in dark places or under the strong outside light. The display device performs display by controlling the number of gray scales in accordance with the intensity of outside light, which means a display mode can be switched in accordance with the data to be displayed on the display screen. A video signal generation circuit is controlled in each display mode in such a manner that it directly outputs an input video signal with an analog value, outputs a signal with a binary digital value, or outputs a signal with a multivalued digital value. As a result, gray scales displayed in pixels are timely changed. Accordingly, clear images can be displayed while maintaining high visibility in various environments, in the wide range from, for example, dark places or indoors (e.g., under a fluorescent lighting) to outdoors (e.g., under the sunlight).

What is claimed is: 
     
         1 . An organic light-emitting device comprising:
 a pixel portion comprising a plurality of pixels arranged in matrix over a substrate;   at least three transistors provided in each of the plurality of pixels;   an optical sensor,   wherein at least one of the three transistors includes an oxide semiconductor layer,   wherein the oxide semiconductor layer is provided between a gate insulating layer and an gate electrode layer, and   wherein the optical sensor detects an intensity of outside light received by the pixel portion.   
     
     
         2 . The organic light-emitting device according to  claim 1 ,
 wherein the oxide semiconductor layer is InGaZnO.   
     
     
         3 . The organic light-emitting device according to  claim 1 ,
 wherein an electric signal output from the optical sensor is supplied to a circuit to switch an analog mode and a digital mode.   
     
     
         4 . The organic light-emitting device according to  claim 3 ,
 wherein a video signal is generated by the circuit in accordance with the analog mode or the digital mode.   
     
     
         5 . The organic light-emitting device according to  claim 1 ,
 wherein the optical sensor is provided over the substrate.   
     
     
         6 . The organic light-emitting device according to  claim 1 ,
 wherein the optical sensor is a photoelectric conversion element.   
     
     
         7 . The organic light-emitting device according to  claim 1 ,
 wherein source and drain electrode layers are over the oxide semiconductor layer.   
     
     
         8 . The organic light-emitting device according to  claim 7 ,
 wherein n-type semiconductor layers are provided between the oxide semiconductor layer and the source and drain electrode layers.   
     
     
         9 . An organic light-emitting device comprising:
 a pixel portion comprising a plurality of pixels arranged in matrix over a substrate;   at least three transistors provided in each of the plurality of pixels;   an optical sensor,   wherein at least one of the three transistors includes an oxide semiconductor layer,   wherein the oxide semiconductor layer overlaps a gate electrode layer with a gate insulating layer therebetween, and   wherein the optical sensor detects an intensity of outside light received by the pixel portion.   
     
     
         10 . The organic light-emitting device according to  claim 9 ,
 wherein the oxide semiconductor layer is InGaZnO.   
     
     
         11 . The organic light-emitting device according to  claim 9 ,
 wherein an electric signal output from the optical sensor is supplied to a circuit to switch an analog mode and a digital mode.   
     
     
         12 . The organic light-emitting device according to  claim 11 ,
 wherein a video signal is generated by the circuit in accordance with the analog mode or the digital mode.   
     
     
         13 . The organic light-emitting device according to  claim 9 ,
 wherein the optical sensor is provided over the substrate.   
     
     
         14 . The organic light-emitting device according to  claim 9 ,
 wherein the optical sensor is a photoelectric conversion element.   
     
     
         15 . The organic light-emitting device according to  claim 9 ,
 wherein source and drain electrode layers are over the oxide semiconductor layer.   
     
     
         16 . The organic light-emitting device according to  claim 15 ,
 wherein n-type semiconductor layers are provided between the oxide semiconductor layer and the source and drain electrode layers.   
     
     
         17 . The organic light-emitting device according to  claim 9 ,
 wherein an insulating layer is on and in contact with a part of the oxide semiconductor layer, and   wherein the insulating layer is a silicon oxide layer.   
     
     
         18 . An organic light-emitting device comprising:
 a pixel portion comprising a plurality of pixels arranged in matrix over a substrate;   at least three transistors provided in each of the plurality of pixels;   an optical sensor,   wherein at least one of the three transistors includes an oxide semiconductor layer,   wherein a gate electrode layer overlaps the oxide semiconductor layer with a gate insulating layer therebetween, and   wherein the optical sensor detects an intensity of outside light received by the pixel portion.   
     
     
         19 . The organic light-emitting device according to  claim 18 ,
 wherein the oxide semiconductor layer is InGaZnO.   
     
     
         20 . The organic light-emitting device according to  claim 18 ,
 wherein an electric signal output from the optical sensor is supplied to a circuit to switch an analog mode and a digital mode.   
     
     
         21 . The organic light-emitting device according to  claim 20 ,
 wherein a video signal is generated by the circuit in accordance with the analog mode or the digital mode.   
     
     
         22 . The organic light-emitting device according to  claim 18 ,
 wherein the optical sensor is provided over the substrate.   
     
     
         23 . The organic light-emitting device according to  claim 18 ,
 wherein the optical sensor is a photoelectric conversion element.   
     
     
         24 . The organic light-emitting device according to  claim 18 ,
 wherein source and drain electrode layers are over the oxide semiconductor.   
     
     
         25 . The organic light-emitting device according to  claim 24 ,
 wherein n-type semiconductor layers are provided between the oxide semiconductor layer and the source and drain electrode layers.   
     
     
         26 . The organic light-emitting device according to  claim 18 ,
 wherein a base layer is on and in contact with a part of the semiconductor layer over the substrate,   wherein the base layer is a silicon oxide layer.