Document Type
Dissertation
Date of Award
Fall 1-31-1999
Degree Name
Doctor of Philosophy in Electrical Engineering - (Ph.D.)
Department
Electrical and Computer Engineering
First Advisor
Ken K. Chin
Second Advisor
Roy H. Cornely
Third Advisor
Kenneth Sohn
Fourth Advisor
Yun Q. Shi
Fifth Advisor
Hongya Ge
Sixth Advisor
Guang Yang
Abstract
This research was an investigation of a novel readout method for focal plane array (FPA) optical imaging, especially for very sensitive detectors with large dark current. The readout method is based on periodically blocking the optical input enabling the removal of the dark current integration from the output. The research demonstrated that it is feasible to modulate the optical input with the designed readout circuit and thus achieve longer signal integration time to enhance the signal-to-noise ratio.
Study of a proposed circuit model showed that in theory the correlated readout method could increase the output voltage swing and reduce the noise level by attenuating low frequency noise, thereby effectively improving the FPA dynamic range. Circuits based on standard CMOS circuitry were designed, simulated by PSpice, fabricated using Orbit 2µm n-well technology, and tested with a PI-4000 system. In the circuit evaluation, the output noise due to the clock switching phenomena, the gate signal feedthrough and the charge relaxation, was considered to be the critical problem. The most promising design for minimizing this problem had a CMOS current steering circuit at the input of a high CMRR operational amplifier. Simulation and test results showed that a modified capacitive transimpedance amplifier (CTIA) could subtract dark current output and reduce the output signal due to any difference between the frequencies of the optical input modulation signal and the switch modulation signal. In conclusion, the correlated readout circuit was shown to be a promising approach for advancing FPA technology.
Recommended Citation
Qiu, Changqing, "A novel readout method for focal plane array imaging in the presence of large dark current" (1999). Dissertations. 968.
https://digitalcommons.njit.edu/dissertations/968
