Patent ID: 8400543

Claim:
An imaging system comprising: an image sensing apparatus configured to sense an object to acquire an image signal; and a supply unit configured to supply a power supply voltage to the image sensing apparatus, the image sensing apparatus including a pixel array in which a plurality of pixels are arrayed in a row direction and a column direction, a row selection unit configured to select one row in the pixel array, and a readout unit configured to read out and output signals from the pixels of at least some columns from the plurality of pixels of a row, which is selected by the row selection unit, in a 1-line period from when the row selection unit selects one row until the row selection unit selects the next row, the readout unit including a plurality of A/D converting units provided according to respective columns of the pixel array, a transfer unit configured to transfer signals from the pixels of the respective columns of the pixel array to the plurality of A/D converting units, an adding unit configured to add signals from the pixels of two or more columns in the pixel array, a plurality of holding units which are arranged between the adding unit and the plurality of A/D converting units and are configured to temporarily hold signal from each column in the pixel array before the signal is converted to digital signal by the A/D converting unit, and a transfer gate which is arranged for each column between the adding unit and the plurality of holding units and is configured to transfer signals of pixels of each column in the pixel array to the plurality of holding units respectively, wherein the supply unit supplies a power supply voltage to an A/D converting unit which, of the plurality of A/D converting units, receives the sum signal obtained by the adding unit, and does not supply a power supply voltage to an A/D converting unit which, of the plurality of A/D converting units, does not receive the sum signal obtained by the adding unit, in the 1-line period, wherein the readout unit A/D-converts the signals from the pixels in the pixel array using the A/D converting unit supplied with the power supply voltage by the supply unit, and outputs a digital image signal, and wherein the transfer gate which is arranged in a column to which the A/D converting unit which receives the sum signal is arranged is turned on, and the transfer gate which is arranged in a column to which the A/D converting unit which does not receive the sum signal is arranged is not turned on.