Image sensor

An image sensor performing normal operation to read out imaging signals from a grid of a plurality of pixel circuits arranged in columns and rows, the imaging signals having a voltage level proportional to an exposure on photoelectric conversion elements in the pixel circuits, and calibration operation to generate a correction value to be applied equally to the imaging signals output from the pixel circuits aligned in the same rows, the image sensor comprising:

• a plurality of vertical readout lines coupled to the pixel circuits aligned in the same columns;
• a pixel clipping circuit provided to each of the vertical readout lines, and supplying a calibration voltage to the associated vertical readout line;
• a timing generator controlling the pixel clipping circuit and the pixel circuits to output the imaging signals from the pixel circuits in numeric order of the rows;
• a plurality of analog-digital converter circuits each generating imaging data having a digital value corresponding to a voltage level of the imaging signal input through the associated vertical readout line and generating calibration data having a digital value corresponding to a voltage level of the calibration voltage;
• a pixel data generation unit generating pixel data by applying the correction value to the imaging data;
• and
• a correction value generation unit accumulating the calibration data, generating an updated correction value using a predetermined number of the accumulated calibration data pieces, and updating the correction value to the updated correction value,
• wherein the pixel circuits are arranged in an effective pixel area that is exposed to incident light through lenses,
• wherein, in the calibration operation, the timing generator
• categorizes the pixel circuits by row into an imaging pixel circuit group and a calibration pixel circuit group, and controls the pixel circuits belonging to the imaging pixel circuit group to output the imaging signals, and, at the time when the pixel circuits belonging to the calibration pixel circuit group are read, electrically cuts off the pixel circuits belonging to the calibration pixel circuit group from the vertical readout lines, and controls the pixel clipping circuit to supply the calibration voltage to the vertical readout lines.