Methods of reducing blooming in the drive of charge-coupled image sensors

Abstract

Signal charges are accumulated in photosensitive elements of an integrated semiconductor imaging matrix, the charges being divided into two parts. Responsive to first and second pulse signals, the first or preceding part of the charge from each of the elements is drawn out via a charge transfer device, as a non-information signal. The second or following part is drawn out, as an information signal, responsive to transfer pulse signals and shift pulse signals. Therefore, even in the presence of intense light, the information signal charges are stored in the photosensitive elements for only a short period of time between the ending time of the first pulse signal and the beginning time of the transfer pulse signal. Thus, the storage will not overflow the capacity of the photosensitive elements. The intensity of light used in this invention is considerably higher than the intensity of light which may be used in the conventional system; therefore, a satisfactory control can be achieved without lowering the sensitivity of the photosensitive elements. It is not necessary to provide charge sinks close to the photosensitive elements for absorbing the signal charge overflowing the elements. As a result, there is a high density of photosensitive elements and a higher resolution of stored information. Alternatively, by designing a wider area of photosensitive elements, an image sensor of higher sensitivity may also be achieved.