Yasuo Wakamori

A wide dynamic range CMOS image sensor with multiple exposure-time signal outputs and 12-bit column-parallel cyclic A/D converters

A wide dynamic range CMOS image sensor with a burst readout multiple exposure method is proposed. In this method, maximally four different exposure-time signals are read out in one frame. To achieve the high-speed readout, a compact cyclic analog-to-digital converter (ADC) with noise canceling function is proposed and arrays of the cyclic ADCs are integrated at the column. A prototype wide dynamic range CMOS image sensor has been developed with 0.25-/spl mu/m 1-poly 4-metal CMOS image sensor technology. The dynamic range is expanded maximally by a factor of 1791 compared to the case of single exposure. The dynamic range is measured to be 19.8 bit or 119 dB. The 12-bit ADC integrated at the column of the CMOS image sensor has DNL of +0.2/-0.8 LSB.

An ultra wide dynamic range CMOS image sensor with a linear response

An ultra wide dynamic range (WDR) CMOS image sensor (CIS) and the details of evaluation are presented. The proposed signal readout technique of extremely short accumulation (ESA) enables the dynamic range of image sensor to be expanded up to 146dB. Including the ESA signals, total of 4 different accumulation time signals are read out in one frame period based on burst readout technique. To achieve the high-speed signal readout required for the multiple exposure signals, column parallel A/D converters are integrated at the upper and lower sides of pixel arrays. The improved 12-bits cyclic ADCs with a built-in correlated double sampling (CDS) circuit has the differential non-linearity (DNL) of ±0.3LSB.

A 142dB Dynamic Range CMOS Image Sensor with Multiple Exposure Time Signals

An ultra wide dynamic range image sensor with a linear response is presented. The proposed extremely short accumulation (ESA) signal readout technique enables the dynamic range of image sensor to be expanded up to 142dB. Including the ESA signals, total of 4 different accumulation time signals are read out in one frame based on burst readout mode. To achieve the high-speed readout required for the multiple exposure signals, column parallel A/D converters are integrated at the upper and lower sides of pixel array. The improved column parallel cyclic 12-b ADC with a built-in CDS circuit has the differential non-linearity of plusmn0.3LSB

A new active pixel structure with a pinned photodiode for wide dynamic range image sensors

A wide dynamic range CMOS image sensor based on a new active pixel structure with a pinned photodiode is proposed and evaluated with device simulations. The proposed pixel device has a linear and a logarithmic characteristics in low and high illumination region, respectively. The technique of direct detection of photodiode potential leads to a wide logarithmic response compared with the conventional linear-log wide DR image sensor with pinned photo diode.