Real-time gain correction method using a reference light for an area-parallel-type frame-transfer charge-coupled device with multi-output taps

摘要

The authors propose a technique for performing realtime correction of the gain nonuniformity at output taps in an area-parallel-type frame transfer CCD (FT-CCD) by incorporating a reference optical signal. This technique activates a reference light source every vertical blanking (V-blanking) period, during which time the image sensor is shielded from incident light, and uses that output signal level to automatically adjust the gain of each block. For this method, a color-separation prism with reference light sources has been developed. In addition, to obtain a reference signal from the reference light source emitting for about 11% of the V-blanking period, a new method of accumulating the electron signal generated by the reference light source is described for the CCD. The results of a camera experiment using an 8-million-pixel CCD are described, and the compensation accuracy of this method is discussed.