Objective Because of the redshift effect,the deepest and most distant universe has been seen at wavelengths closer to the infrared wavelength.The James Webb Space Telescope(JWST),launched on December 25,2021,focuses its main detector on the infrared detection band.Therefore,infrared observation provides a new technical means for astronomical observation.The core component of infrared payload is infrared focal plane detector.At present,the typical products of mercury cadmium telluride infrared detectors for astronomical applications reported internationally are Hawii-2RG,VIRGO,ALFA(Astronomical Large Focal plane Array),etc.,which have been applied in the European Space Agency(ESA).Projects such as the European Space Agency's Euclid probe and NASA's JWST.Because there is still a big gap between the device performance and the advanced level of foreign countries,the progress of infrared astronomy application is relatively slow,and there are few reports about astronomical application detectors in China.Therefore,a 640×512 HgCdTe focal plane readout circuit for the astronomical application is studied.Methods Because infrared astronomical observation is characterized by extremely low background radiation and low photon flux,low dark current and low read noise are the key array parameters in order to achieve high signal-to-noise ratio(S/N).Some low-flux observations require observation of several photoelectrons in a very long integration time,so the readout circuit needs to achieve a long integration time to complete the detection of small target signals.An effective power management strategy(Fig.5-6)is used to reduce the power consumption,then reduce the influence of glow on the dark current.At the same time,the digital function of non-destructive readout(Fig.9)is studied to achieve long integration time.And as a ramp sampling strategy(Fig.17),the output noise of the circuit is effectively reduced.Results and Discussions The test results of the circuit-coupled shortwave HgCdTe detector are in line with the theoretical design expectation.When the non-destructive readout function of the circuit is turned on,the device can realize ultra-long integral time detection,the dark current of the test device is set to 0.9 e-·pixel-1·s-1(Tab.2,Fig.25-26)when the power consumption of the circuit is reduced to 14.04 MW at the integration time of 6000 s.The readout noise is 50e-(10 fF)and 27e-(5 fF)(Fig.28)with two-step gain,respectively,and the nonlinearity is less than 0.1%.Conclusions The design of the 640×512 readout circuit for astronomical application and the short-wave IRFPA detector show that reducing the power consumption of the readout circuit is conducive to reducing the influence of the glow on the dark current of the device,and turning on the non-destructive readout function of the readout circuit can realize the long integration time of the detection and improve the signal-to-noise ratio of the device.The focal plane of astronomical applications meets the design expectations,meets the use demand of the infrared focal plane of the large optical platform of the space station,and provides a technical basis for the infrared focal plane research of larger scale astronomical applications in the future.
infrared astronomical observationIRFPA ROIClow power consumptionnon-destructive readoutreadout noise
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