Photodiode-type pixel for global electronic shutter and reduced lag

• US 6,667,768 B1
• Filed: 02/17/1998
• Issued: 12/23/2003
• Est. Priority Date: 02/17/1998
• Status: Expired due to Term

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Fossum, Eric R.
• Primary Examiner(s): MOE, AUNG SOE
• Application Number:
  US09/025,079
• Time in Patent Office: 2,135 Days
• Field of Search: 348/308, 348/309, 348/301, 348/302, 348/303, 348/313, 348/314, 348/362, 348/296, 348/297, 257/292, 257/291, 257/237, 257/239, 257/216, 250/208.1
• US Class Current: 348/308
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H04N 25/62 Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels
• CPC Class Codes: H04N 25/626 Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
• CPC Class Codes: H04N 25/672 between adjacent sensors or output registers for reading a single image

Abstract

Operation for global electronic shutter photodiode-type pixels. In a first mode of operation, lag is reduced through global reset of the photodiode array and fixed pattern noise is eliminated through comparison of the photosignal level and the reset level of the floating drain. In a second mode of operation, simultaneous integration and readout processes are achieved through cessation of spill charges over the transfer gate. In a third mode of operation, regulation of the reset photodiode and transfer gate enables voltage gain between the photodiode and the sense node.

Claims

1. A method, comprising:

initially, resetting a plurality of photodiodes in image sensing array, by initially flooding each of said photodiodes with charge, and then allowing each of said photodiodes to spill to a common initial value;

after said resetting, integrating for the desired integration, in each of said photodiodes, and allowing charge to trickle continuously into a collection node during said integrating;

after said integrating, sampling a signal level by determining a level of charge on said collection node;

again filling and spilling said plurality of photodiodes in said image sensing array, after said sampling;

second sampling a level of said photodiodes as a reset level; and

taking a difference between said signal level and said reset level as an output value from each pixel.

2. A method as in claim 1, wherein said first sampling and said second sampling are carried out by transferring a voltage on to a capacitor.