Patent ID: 8773544

Claim:
An image sensor, comprising: a pixel array comprising a plurality of pixels arranged in columns and rows, one of the plurality of pixels detecting incident light and generating an analog signal in response to the detected incident light; a reference voltage generation unit configured to generate a reference voltage that changes at a constant rate in a first operation mode and that alternately decreases and increases at the constant rate in a second operation mode; an analog-digital conversion unit configured to convert the analog signal to a digital value a first number of times to generate a first number of digital values using the reference voltage and generate a digital signal by summing the first number of the digital values, the first number corresponding to a total number of decreases and increases of the reference voltage, the analog-digital conversion unit operating at a same speed in the first operation mode and the second operation mode to generate the digital signal; and a control unit configured to control operations of the pixel array, the reference voltage generation unit, and the analog-digital conversion unit.