Image sensor

Abstract

The image sensor of the present invention performs two exposures of differing exposure times, holds the signal charge that is generated in photodiode 1 in the first exposure period in pixel interior capacitance 4 that is provided inside pixels and integrates the signal charge that is generated in photodiode 1 in the second exposure period with the first signal charge inside the pixels and executes readout, whereby the white (overexposed) portions that occur in the first exposure period are compensated by information of the second exposure period, and black (underexposed) portions that occur in the second exposure period are compensated by information of the first exposure period, and an image is obtained having wide dynamic range with respect to the amount of light in which underexposure and overexposure are mitigated.

What is claimed is:  
     
         1 . An image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed within said semiconductor region having the opposite conductivity of said semiconductor region, that, after discharging carrier in said diffusion layer of said semiconductor device, causes light to be irradiated into said diffusion layer to generate carrier inside said diffusion layer, that outputs a signal to an output section based on the surface potential of the generated carrier, and measures the amount of incidence of said light; comprising: 
 a timing generation means for creating:    a first exposure period for, when irradiating light into said diffusion layer and generating carrier inside said diffusion layer, irradiating said light into said diffusion layer and generating a first carrier inside said diffusion layer;    a storage period after said first exposure period for moving said first carrier to a storage section;    a second exposure period after said storage period for irradiating said light into said diffusion layer and generating a second carrier inside said diffusion layer; and    a readout period after said second exposure period; and    a carrier integration means for, when outputting to an output section a signal based on the surface potential of carrier that is generated by said timing generation means and measuring the amount of incidence of said light, integrating said first carrier and said second carrier in said readout period and reading out the integrated carrier.    
     
     
         2 . An image sensor according to  claim 1  wherein: 
 said first exposure period generates said first carrier inside said diffusion layer with said diffusion layer and said storage section in a conducting state; and  
 said storage period moves said first carrier to said storage section by cutting off said diffusion layer and said storage section.  
 
     
     
         3 . An image sensor according to  claim 1  wherein: 
 said first exposure period generates said first carrier inside said diffusion layer with said diffusion layer and said storage section in a cut off state; and  
 said storage period moves said first carrier to said storage section by conduction of said diffusion layer and said storage section.  
 
     
     
         4 . An image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed within said semiconductor region having the opposite conductivity of said semiconductor region; that, after discharging carrier in said diffusion layer of said semiconductor device, causes light to be irradiated into said diffusion layer to generate carrier inside said diffusion layer, that outputs a signal to an output section based on the surface potential of the generated carrier, and that measures the amount of incidence of said light; comprising: 
 a timing generation means for creating:    a first exposure period for, when irradiating light into said diffusion layer and generating carrier inside said diffusion layer, irradiating said light into said diffusion layer and generating a first carrier inside said diffusion layer;    a storage period after said first exposure period for moving a portion of said first carrier to a storage section and leaving said first carrier inside said diffusion layer;    a second exposure period after said storage period for irradiating said light into said diffusion layer and generating a second carrier inside said diffusion layer; and    a readout period after said second exposure period; and    a carrier integration means for, when outputting to an output section a signal based on the surface potential of said generated carrier and measuring the amount of incidence of said light, reading out carrier that is the sum of said second carrier and said first carrier that is left in said diffusion layer during a readout period.    
     
     
         5 . An image sensor according to  claim 1  wherein carrier that is contained in said diffusion layer and said storage section is discharged before said first exposure period by a reset transistor that is included in said semiconductor region and connected to the power supply.  
     
     
         6 . An image sensor according to  claim 4  wherein carrier that is contained in said diffusion layer and said storage section is discharged before said first exposure period by a reset transistor that is included in said semiconductor region and connected to the power supply.  
     
     
         7 . An image sensor according to  claim 1  wherein the period from said first exposure period to said second exposure period is positioned within a preceding readout period.  
     
     
         8 . An image sensor according to  claim 4  wherein the period from said first exposure period to said second exposure period is positioned within a preceding readout period.  
     
     
         9 . An image sensor according to  claim 1  wherein said first exposure period is longer than said second exposure period.  
     
     
         10 . An image sensor according to  claim 4  wherein said first exposure period is longer than said second exposure period.  
     
     
         11 . An image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed inside said semiconductor region and having the opposite conductivity of said semiconductor region; that, after discharging carrier in said diffusion layer of said semiconductor device, causes light to be irradiated into said diffusion layer to generate carrier inside said diffusion layer, that outputs a signal to an output section based on the surface potential of generated carrier, and measures the amount of incidence of said light is measured; comprising: 
 a timing generation means for creating:    when irradiating light into said-diffusion layer and generating carrier inside said diffusion layer, a plurality of exposure periods that do not mutually overlap for irradiating said light into said diffusion layer and generating carriers corresponding to said plurality of exposure periods inside said diffusion layer;    a storage period for moving a preceding carrier that was generated inside said diffusion layer in the one preceding exposure period of said plurality of exposure periods that relatively preceded to a storage section after said preceding exposure period;    a succeeding exposure period after said storage period for irradiating said light into said diffusion layer after said preceding exposure period and generating a succeeding carrier in said diffusion layer; and    a readout period after said succeeding exposure period; and    a carrier integration means for, when outputting to an output section a signal based on the surface potential of said generated carrier and measuring the amount of incidence of said light, integrating, in the readout period after the last exposure period of said plurality of exposure periods, the carrier that was stored in said storage section up to the exposure period immediately preceding said last exposure period and the carrier that was generated inside said diffusion layer in said last exposure period.    
     
     
         12 . An image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed inside said semiconductor region and having the opposite conductivity of said semiconductor region; that, after discharging carrier in said diffusion layer of said semiconductor device, causes light to be irradiated into said diffusion layer to generate carrier inside said diffusion layer, that outputs a signal that is based on the surface potential of the generated carrier to an output section and measures the amount of incidence of said light; comprising: 
 a timing generation means for creating:    when irradiating light into said diffusion layer and generating carrier in said diffusion layer, a plurality of exposure periods that do not mutually overlap for irradiating said light into said diffusion layer and generating carriers that correspond to said plurality of exposure periods in said diffusion layer;    a storage period, which follows the relatively preceding exposure period of said plurality of exposure periods, for moving to a storage section a portion of preceding carrier that was stored in said diffusion layer in exposure periods up to said preceding exposure period;    a succeeding exposure period for simultaneously leaving said preceding carrier in said diffusion layer and, after said storage period, irradiating said light into said diffusion layer after said preceding exposure period and generating a succeeding carrier in said diffusion layer; and    a readout period after said succeeding exposure period; and    a carrier integration means for, when outputting to an output section a signal based on the surface potential of said generated carrier and measuring the amount of incidence of said light, reading out carrier, in the readout period that follows the last exposure period of said plurality of exposure periods, said carrier being the sum of preceding carrier that remained in said diffusion layer until the exposure period immediately preceding said last exposure period and the succeeding carrier that was generated in said diffusion layer in said last exposure period.    
     
     
         13 . An image sensor according to  claim 11  wherein a preceding exposure period among said plurality of exposure periods is a longer period than exposure periods that are positioned later.  
     
     
         14 . An image sensor according to  claim 12  wherein a preceding exposure period among said plurality of exposure periods is a longer period than exposure periods that are positioned later.  
     
     
         15 . An image sensor according to  claim 11  wherein the period that extends over said plurality of exposure periods is positioned within a preceding readout period.  
     
     
         16 . An image sensor according to  claim 12  wherein the period that extends over said plurality of exposure periods is positioned within a preceding readout period.  
     
     
         17 . An image sensor according to  claim 1  wherein said diffusion layer constitutes pixels of an image sensor and said storage section is provided inside said pixels corresponding to said diffusion layer.  
     
     
         18 . An image sensor according to  claim 4  wherein said diffusion layer constitutes pixels of an image sensor and said storage section is provided inside said pixels corresponding to said diffusion layer.  
     
     
         19 . An image sensor according to  claim 11  wherein said diffusion layer constitutes pixels of an image sensor and said storage section is provided inside said pixels corresponding to said diffusion layer.  
     
     
         20 . An image sensor according to  claim 12  wherein said diffusion layer constitutes pixels of an image sensor and said storage section is provided inside said pixels corresponding to said diffusion layer.  
     
     
         21 . An image sensor having unit pixels comprising: 
 a photodiode of a structure that converts irradiated light to electrons, has an anode connected to ground, and extracts said electrons from a cathode;    an amplification transistor having gate connected to the cathode of said photodiode, drain connected to a power supply line, and source connected to the drain of a readout transistor;    a reset transistor having source connected to the cathode of said photodiode, gate connected to a reset line, and drain connected to said power supply line,    a pixel interior capacitance selection transistor having drain connected to the cathode of said photodiode, gate connected to a pixel interior capacitance selection line, and source connected to pixel interior capacitance;    pixel interior capacitance having one end grounded and the other end connected to the source of said pixel interior capacitance selection transistor; and    a readout transistor having drain connected to the source of said amplification transistor, gate connected to a horizontal selection line, and source connected to a vertical readout line.    
     
     
         22 . An image sensor according to  claim 21  having a construction wherein said pixel interior capacitance is constituted by an MOS transistor, the source and drain of said MOS transistor are short-circuited and grounded, and the gate is connected to the source of said pixel interior capacitance selection transistor.  
     
     
         23 . An image sensor according to  claim 21  wherein said reset transistor and said pixel interior capacitance selection transistor are both depletion-type MOS transistors.  
     
     
         24 . An image sensor according to  claim 23  wherein the potential of said reset transistor when OFF is higher than the potential of said pixel interior capacitance selection transistor when OFF.