Imaging apparatus having image sensor to reduce column noise
A plurality of analog-to-digital (AD) conversion units is provided in a column signal line connecting commonly to vertical pixel columns. A signal of one pixel is digitized by the plurality of AD conversion units and averaged to achieve noise reduction. Operations for reading signals from a plurality of pixels are performed in parallel for alleviating the decrease of the frame rate.
1. An imaging apparatus comprising:
an image pickup device having a pixel array in which a plurality of pixels is arranged in a matrix form, a plurality of column signal lines provided for each column of the pixel array and receiving input of signals of the plurality of pixels of the column, a plurality of AD conversion units provided in parallel on one side of each of the plurality of column signal lines, and an averaging unit that averages output signals of the plurality of AD conversion units; and
a drive unit that selectively drives the image pickup device in one driving mode of a first driving mode in which output signals of a plurality of different pixels, which are arranged in different rows and a same column in the pixel array, are AD converted by each of the plurality of AD conversion units and a second driving mode in which an output signal of a same pixel in the pixel array is AD converted by the plurality of AD conversion units in parallel,
wherein the averaging unit averages the AD converted output signals of the same pixel in the second driving mode.
2. The imaging apparatus according to claim 1 , wherein the image pickup device further has an output unit that outputs averaging results from the averaging unit in a predetermined order.
3. The imaging apparatus according to claim 1 , wherein, in the first driving mode, a period in which a signal of one of the plurality of pixels is processed and a period in which a signal of another of the plurality of pixels is processed overlap at least partially.
4. The imaging apparatus according to claim 3 , wherein, in the first driving mode, a period in which a signal of one of the plurality of pixels is AD converted by one of the plurality of AD conversion units and a period in which a signal of another of the plurality of pixels is AD converted by another of the plurality of AD conversion units overlap at least partially.
5. The imaging apparatus according to claim 3 , wherein in the first driving mode, a signal of one of the plurality of pixels is read out to one of the column signal lines in a period in which a signal of another of the plurality of pixels is AD converted by one of the plurality of AD conversion units.
6. The imaging apparatus according to claim 3 , wherein in the first driving mode, a signal of one of the plurality of pixels is read out to one of the column signal lines in a period in which a signal of another of the plurality of pixels is output from one of the plurality of AD conversion units.
7. The imaging apparatus according to claim 3 , wherein in the first driving mode, a signal of one of the plurality of pixels is AD converted by one of the plurality of AD conversion units in a period in which a signal of another of the plurality of pixels is output from another of the plurality of AD conversion units.