Noise characteristic of CCD image sensor with cooling device

Abstract

According to the improvement on large-scale integration of semiconductor devices, an advanced application for medical equipment make it possible to design a retinal prosthesis system. We have developed the image sensor on chip. We focused CCD image sensor that commonly used as device of image acquisition for medical equipment. Since CCD image sensor is able to enlarge its pixel size, high resolution and wide dynamic range become possible. The development of CCD image sensor will contribute to provide more highresolution for medical image. In addition to above useful characteristics, however, one of disadvantage is the presence of noise. While CCD image sensor is working, it may produce heat that causes the generation of noise. The noise is processed in different ways by DSP. On the occasion of processing, the DSP processing will be given that processing time and the limitation of memory size and so on. Therefore, It is important issue to reduce the noise on analog data form. We demonstrated the shift of noise level during cooling and heating CCD image sensor with the Peltiert device for cooling. The effect of heating was recorded the range between -10 and 32 degrees centigrade, exposure time was 10 seconds in the dark place. Moreover, we also prepared the photograph data that processed a reduction of the dark current. A dark current conform a Shockley-Read-Hall model. Thus, we made a simulation model according to SRH model and compared with experiment results. The examination result was shown exponential curve characteristic in response to thermal change, and to reduce almost of noise in comparing with the data corrected the dark current. As a result, it has been proved that most of the noise origin a dark current. From experimental results, we confirmed that the noise property could be influenced in response to thermal change.