Yukihiro Ohta

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

Proposal of Microjoining Method UsingShock Wave Generated by Femtosecond Laser Irradiation

Femtosecond laser is a type of ultrashort-pulse laser. Ultrashort-pulse laser irradiation generates high-pressure plasma and shock waves at the surface of the target. If the target is irradiated in water, the shock waves are enough to deform the target plastically. The authors proposed a new microjoining method using the shock waves accompanied by femtosecond laser irradiation. A thin wire was mounted in a fit bore drilled in a plate, and the laser was focused around the edge of the wire end face. The wire was deformed by shock waves generated by many laser pulses. After the laser irradiation, the deformed wire prevented the release of the plate, as well as the rivet connection. Some model tests were performed to examine forming properties and joining strength. Laser pulse energy, spot diameter and laser spot position influenced the deformed shape and joining strength. In the case of irradiation close to the wire edge, the deformed shape and joining strength varied. They were made stable by transferring the laser spot intermittently.