Level detection/elimination system for dark current signal of solid state image pickup element

Abstract

Abstract PURPOSE:To ensure a detection for the dark current of the solid state image pickup element, by selecting the output signal of the 1st photoelectric converting element having a light receiving screen which is masked partially and the output signal of the 2nd photoelectric converting element having a different masking area from the 1st element and then carrying out an operation. CONSTITUTION:The photoelectric converting parts S1-Sn of the solid state image pickup element are set to the same area, and the elements S1 and S2 have a partial masking of light each. Among the electric charge converted at the photoelectric converting part, the electric charge produced by the exposure are CS1-CSn, and the electric charge by the dark current are CD1- CDn each. The voltage caused by the above charge CS1-CSn plus CD1-CDn which are read out through the shift register are referred to as VC1-VCn and VD1-VDn respectively, and the reference voltage is defined as VK respectively. The electric charge caused by the dark current is equal at each converting part to obtain VD1=VD2=VD, and X=VC2/VC1 is obtained, where X is the ratio of the exposed parts between the parts S1 and S2. As a result, the dark current signal level VD becomes as shown in the equation (A), and thus the dark current signal level can be detected from the output voltage given from the parts S1 and S2 plus X.

Inventors

• 👤 Tokuichi Tsunekawa

Bibliographic Details