Photoelectric conversion apparatus and image capturing system

Abstract

In a first sensitivity level, an AD converter performs AD conversion selectively using, in accordance with the level of the analog signal, any one of a first reference signal and a second reference signal that have mutually different slopes, and in a second sensitivity level that is different from the first sensitivity level, the AD converter performs AD conversion only using a third reference signal.

1 . (canceled) 
     
     
         2 . A photoelectric conversion apparatus in which a sensitivity level is settable, the photoelectric conversion apparatus comprising:
 a ramp signal supply unit configured to supply a ramp signal; and   an analog-to-digital (AD) converter into which an analog signal based on light incident on a pixel and the ramp signal are input, and configured to perform analog-to-digital (AD) conversion on the analog signal by comparing the analog signal and the ramp signal,   wherein in the AD conversion in a first sensitivity level, the ramp signal supply unit outputs a first number of ramp signals having different slopes to the AD converter, and   wherein in the AD conversion in a second sensitivity level different from the first sensitivity level, the ramp signal supply unit outputs a second number, smaller than the first number, of ramp signals having different slopes or only one ramp signal to the AD converter.   
     
     
         3 . The photoelectric conversion apparatus according to  claim 2 , wherein the second sensitivity level is higher than the first sensitivity level. 
     
     
         4 . The photoelectric conversion apparatus according to  claim 3 , wherein a ramp signal to be used for the AD conversion in the second sensitivity level includes a ramp signal having a smallest slope among the first number of ramp signals. 
     
     
         5 . The photoelectric conversion apparatus according to  claim 3 , wherein a ramp signal to be used for the AD conversion in the second sensitivity level includes a ramp signal having a smaller slope than a slope of any of the first number of ramp signals. 
     
     
         6 . The photoelectric conversion apparatus according to  claim 5 ,
 wherein the second sensitivity level is n times as high as the first sensitivity level, and   wherein the ramp signal to be used for the AD conversion in the second sensitivity level includes a ramp signal having a slope that is 1/n times as large as a slope of a ramp signal having a smallest slope among the first number of ramp signals.   
     
     
         7 . The photoelectric conversion apparatus according to  claim 2 , wherein the second sensitivity level is lower than the first sensitivity level. 
     
     
         8 . The photoelectric conversion apparatus according to  claim 7 , wherein ramp signals to be used for the AD conversion in the first sensitivity level include a ramp signal having a smallest slope among ramp signals to be used for the AD conversion in the second sensitivity level. 
     
     
         9 . The photoelectric conversion apparatus according to  claim 7 , wherein ramp signals to be used for the AD conversion in the first sensitivity level include a ramp signal having a smaller slope than a slope of any of ramp signals to be used for the AD conversion in the second sensitivity level. 
     
     
         10 . The photoelectric conversion apparatus according to  claim 9 ,
 wherein the first sensitivity level is n times as high as the second sensitivity level, and   wherein the ramp signals to be used for the AD conversion in the first sensitivity level include a ramp signal having a slope that is 1/n times as large as a slope of a ramp signal having a smallest slope among the ramp signals to be used for the AD conversion in the second sensitivity level.   
     
     
         11 . The photoelectric conversion apparatus according to  claim 2 ,
 wherein, in the first sensitivity level, in a case where a signal level of the analog signal is smaller than a predetermined value, the AD converter performs AD conversion on the analog signal, using a ramp signal having a first slope among the first number of ramp signals, and in a case where the signal level of the analog signal is larger than the predetermined value, the AD converter performs AD conversion on the analog signal, using a ramp signal having a second slope larger than the first slope among the first number of ramp signals.   
     
     
         12 . The photoelectric conversion apparatus according to  claim 2 ,
 wherein, in the second sensitivity level, in a case where a signal level of the analog signal is smaller than a predetermined value, the AD converter performs AD conversion on the analog signal, using a ramp signal having a first slope among the second number of ramp signals, and in a case where the signal level of the analog signal is larger than the predetermined value, the AD converter performs AD conversion on the analog signal, using a ramp signal having a second slope larger than the first slope among the second number of ramp signals.   
     
     
         13 . The photoelectric conversion apparatus according to  claim 12 , further comprising:
 a correction unit configured to correct an error in change rates of first and second ramp signals.   
     
     
         14 . The photoelectric conversion apparatus according to  claim 2 , wherein the AD converter includes a comparator configured to compare the ramp signal and the analog signal and a selection circuit configured to output, to the comparator, a ramp signal selected from the first number of ramp signals output by the ramp signal supply unit. 
     
     
         15 . The photoelectric conversion apparatus according to  claim 2 , wherein the first sensitivity level is a first ISO speed, and the second sensitivity level is a second ISO speed. 
     
     
         16 . An imaging system comprising:
 the photoelectric conversion apparatus according to  claim 2 ;   an optical system configured to form an image on a plurality of pixels: and   a video signal processing unit configured to process a signal output from the photoelectric conversion apparatus and generate image data.   
     
     
         17 . The imaging system according to  claim 16 , further comprising:
 a sensitivity level selection unit,   wherein the sensitivity level selection unit selects a sensitivity level of the photoelectric conversion apparatus.