A 300-kpixel Ultrahigh-Speed Charge-Coupled Device With a Dynamic Range of 48.6 dB at 1 Million Frames per Second

An ultrahigh-speed charge-coupled device (CCD) with an increased dynamic range at a frame rate above 200 kiloframes per second (kfps) was developed. The dynamic range of a CCD operating at extremely high speeds is reduced as a result of rounding of a sharp voltage waveform inside the device. The amount of rounding was estimated by using an equivalent circuit model of one kind of electrodes in a four-phase CCD memory. The simulation showed that the calculated voltage at a quarter period and the measured saturation signal level have similar dependence on the frame rate. To suppress the drop in voltage at a quarter period, the active pixels and the driving circuit were divided, and the resistance of the pixel wiring was reduced. A new ultrahigh-speed CCD, whose active pixels are divided into eight separately driven blocks and that employs dual wirings to each electrode of the four-phase CCD memory, was designed and fabricated. A driving evaluation experiment showed that the ultrahigh-speed CCD had a dynamic range of 48.6 dB at 1 000 000 fps. This range is equivalent to 8-bit digital and is 2.5 times higher than that of a previous ultrahigh-speed CCD.