Rambus’ Jay Endsley, Thomas Vogelsang and Michael Guidash, along with Jiaju Ma of the Thayer School of Engineering at Dartmouth College, have published a new article about CMOS imaging in Sensors.
Titled “Reduction of CMOS Image Sensor Read Noise to Enable Photon Counting,” the open access article explores recent activity in photon counting CMOS image sensors (CIS) which has been directed to reduction of read noise.
“Many approaches and methods have been reported. This work is focused on providing sub 1 e− read noise by design and operation of the binary and small signal readout of photon counting CIS,” the abstract reads.
“Compensation of transfer gate feed-through was used to provide substantially reduced correlated double sample (CDS) time and source follower (SF) bandwidth. SF read noise was reduced by a factor of 3 with this method. This method can be applied broadly to CIS devices to reduce the read noise for small signals, enabling use as a photon counting sensor.”
More specifically, the article experimentally shows that reduced CDS time and dominant time constant of the SF readout is capable of providing significant read noise reduction.
“The ratio of noise reduction will depend on the baseline characteristics of the CIS device. We achieved a factor of three reduction in the average SF read noise for the device used in this study (246 μVrms to 79 μVrms),” the researchers explained.
According to Endsley, sensor noise performance of existing sensor array architectures can easily be enhanced to use this method with small changes to the array drivers and timing control.
“The reduction in CDS time can enable improved readout rate and faster sensor operation,” he added.
Interested in learning more? The full text of “Reduction of CMOS Image Sensor Read Noise to Enable Photon Counting” can be read here.
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