Study On The Relationship Between The PRNU And Wavelength Of Backside-illuminated CCD/CMOD

CCD(charge coupled devices)and sCMOS(scientific CMOS)are widely used in astronomical observation because of their high quantum efficiency,large dynamic range,low noise and good linearity.In the process of detector testing,we found that the photon response non-uniformity of detector always changes with wavelength,which is very obvious in some detectors.Based on the CCD imaging process,this paper studies the source of response difference between pixels,and proposes a physical model to predict the change of response difference between pixels with wavelength.Because the distribution of photoelectron with depth varies with the wavelength of incident light,and the capture ability of photoelectron varies with the position and depth of each pixel,the response images at different wavelengths are different.Based on this consideration and the difference of the size and thickness of each pixel,the relationship between the photon response non-uniformity and the wavelength of incident light is studied.In order to study the validity of the model,we selected the backside-illuminated EMCCD camera i Xon Ultra DU-888U3-CS0-#BV produced by andor and the sCMOS camera Dhyana 95 produced by Fuzhou Xintu Optoelectronics(TUCSEN)to obtain the pixel response images with high signal-to-noise ratio at several wavelengths from ultraviolet to infrared.It is found that the fitting standard deviation and the photon noise level are similar by fitting the wavelength of each pixel response of the two detectors.It is shown that this model can well explain the phenomenon that the photon response non-uniformity varies with wavelength.Compared with the commonly used interpolation algorithms,it is found that the prediction ability of the response image predicted by this model is equivalent to that of piecewise linear interpolation and piecewise cubic Hermite interpolation in most bands,and is better than that of piecewise cubic spline interpolation.And when the photon response non-uniformity of the detector varies greatly with wavelength,the prediction ability of this model is significantly better than the commonly used interpolation algorithm.