Honda Giken Kogyo Kabushiki Kaisha

Citizen Tokei Kabushiki Kaisha

Honda Giken Koygo Kabushiki Kaisha

Toshio Imai

Sukeyuki Shinotsuka

Toshiaki Tanaka

Tomoyuki Kamiyama

Katsuhiko Takebe

Nobuhiro Fueki

A photosensor circuit comprises a photodiode PD, which converts a light signal into electricity, an n-channel MOS transistor QDwhich has a logarithmic characteristic in its weakly reversed condition and converts a sensor current generated by the photodiode PD into a detection voltage which has a logarithmic characteristic, and a capacitor which is connected to a detection terminal of this transistor QD. A resetting voltage VG=VS is applied to the gate G of the transistor QDto lower the impedance between the drain and the source of the transistor for resetting the transistor to an initial condition. As the n-channel MOS transistor QDis a depletion type n-channel MOS transistor, when this transistor QDdoes not receive any gate voltage, the transistor stays in a weakly reversed condition and has a logarithmic characteristic. This photosensor circuit has a high SN ratio and is capable of detecting minute light signals in high precision. Furthermore, it shows no after-image phenomenon and requires a relatively small number of power sources.

Photosensor circuit capable of detecting minute light signal in high precision and image sensor utilizing photosensor circuit

A photosensor signal processing apparatus is used in combination with an image sensor comprised of a matrix of pixels or photosensors capable of producing an output as a linear function and a logarithmic function of incident illumination. The apparatus includes a correction data storage device which stores therein a set of data about the respective photosensors for the correction of individual outputs of the photosensors, and a correcting device for correcting the respective output values of the photosensors on the basis of the correction data. Thus, even when the individual outputs of the photosensors generate have different characteristics, the output characteristic variation between the photosensors are corrected such that the output characteristics of all the photosensors agree with a reference output characteristic. A fixed pattern noise resulting from the pixel-to-pixel output characteristic variation can be suppressed.

Photosensor signal processing apparatus

Growing community of inventors

Tokorozawa, Japan

Toshio Imai