A new and simple test structure for evaluating the sectional photo-sensitivity distribution of pixels in a frame-transfer CCD image sensor

A metallic optical shield membrane with a rectangular grid of small apertures was formed on the imaging area of a solid-state frame transfer charge-coupled device (CCD) image sensor. This allowed evaluation of a single pixel. The optical apertures were considerably smaller than a single pixel, with the interval between apertures slightly larger than the spacing between pixels. Thus, each pixel has light impinging on only a very small portion on its surface. With a suitable choice of aperture spacing, the output of the CCD directly represents the sensitivity distribution of pixels in the CCD. The sensitivity distribution can be visualized by displaying the CCD output on a cathode-ray-tube monitor. The evaluation of pixel sensitivity distribution is valuable when designing CCD imaging elements