Algorithms to Reduce Noise in CCD Using Line Overscan Data
This paper presents a correction algorithm based on line overscan data to solve the testing error produced by drifting image data in a full-frame transfer large-array charge-coupled device(CCD)and the noise introduced by the testing circuit,which prevent the accurate evaluation of the parameters of a CCD device.The effective image data and vertical overscan data were output simultaneously.The drifting image data were suppressed by subtracting the mean value of the vertical overscan data from the image data.In the testing circuit,the analog and digital modules simultaneously acted on a single line of the image data and vertical overscan data.The noise introduced by the testing circuit was eliminated by subtracting the mean value of the vertical overscan data from the image data.Experimental results showed that the proposed algorithm reduced the readout noise of the device by 20％.The ratio for values greater than 15 e-and 25 e-in a dark difference image was reduced by 25％.The algorithm is suitable for a large-area-array CCD device and can correct the errors introduced by the testing circuit to improve the testing efficiency of a full-frame transfer large-area-array CCD device.
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