A Wide DR and Linear Response CMOS Image Sensor With Three Photocurrent Integrations in Photodiodes, Lateral Overflow Capacitors, and Column Capacitors

A 1/3-inch, 800^H x 600^v pixels, 5.6 x 5.6 mum² color CMOS image sensor with three photocurrent integrations in pixel photodiodes, pixel lateral overflow capacitors and column capacitors fabricated in a 0.18 mum 2P3M CMOS technology has been reported. The image sensor operates using photodiode integrations and lateral overflow integrations in low light condition and achieves a wide dynamic range (DR) performance of around 100 dB in its one exposure. The wide DR performance in one exposure makes high S/N ratios at the signal switching points in the multiple exposures. The CMOS image sensor also operates using the column capacitor integration in very bright light condition. In the column capacitor integration, the photocurrents generated at the photodiodes are directly integrated at the column capacitors in each column line. The combination of two exposures using the photodiode integrations and the lateral overflow integrations and one exposure using the column capacitors leads to the whole linear photo-electric conversion responses from low light to very bright light region. The fabricated image sensor achieves a high S/N ratio, a fully linear response and over 180 dB DR in the incident light ranging from about 1.4 x 10^-2 lx to about 2.4 x 10⁷ lx.