Patent Document ID: 20170026595
Application ID: 15216496
Patent Status: 0

Claim One:
1. An active pixel image sensor comprising a matrix of pixels organized in rows and columns and a read circuit comprising a distinct read pathway for each column of pixels, in which each pixel comprises: a photodiode, a storage node for the electrical charges integrated by said photodiode, a transfer transistor for selectively allowing the transfer of said electrical charges from the photodiode to the storage node, a storage node reset transistor for selectively linking said storage node to a source of reset voltage, a row select transistor for selectively connecting said pixel to the read pathway of the column to which it belongs, and a transistor mounted as voltage follower for transferring to said read pathway the voltage at the terminals of the storage node via said row select transistor; wherein each read pathway comprises a subtraction block having two inputs and one output, said subtraction block being connected to receive, on a first input, the voltage at the terminals of the storage node of one of the pixels of the corresponding column via the transistor mounted as voltage follower and via the row select transistor of said pixel and, on a second input, a reference voltage external to said matrix, of value substantially equal to the reset voltage of the pixels of the matrix seen at the input of the read pathway, and to supply, at its output, a signal representative of a difference in the voltage levels present at its inputs; and wherein said sensor also comprises a controller configured for driving the transistors of the pixels and the read circuit to: perform a global reset of the photodiodes; perform a reset of the storage nodes of the pixels of the matrix and acquire a first digital image, called black image; then perform a global charge transfer from the photodiodes to the storage nodes of said pixels; then acquire a second digital image, called integration image; so as to perform an image acquisition in global shutter mode with subtraction of the reset noise and reading of the pixels that does not destroy the integrated charges.