Abstract: A personal identification system, which uses a vein pattern of a finger, optimizes the amount of light of a light source based on a captured finger image and emphasizes the vein pattern during image processing for identification.

Abstract: A feature extraction system comprises first and second memory circuits and a control circuit for controlling a storing period of time when signals are stored in the first memory circuit. The first and the second memory circuits comprise capacitor memory circuits, the time constant of the second memory circuit being larger than that of the first memory circuit. First and second comparators are coupled to the first and the second memory circuit, respectively. Signals supplied to the first memory circuit are compared with the contents thereof by the first comparator, so that the maximum signal thereof within a predetermined period of time controlled by the control circuit is stored in the first memory circuit. After the predetermined period of time, the contents of the first memory circuit are supplied to the second memory circuit and then the first memory circuit operates to store the maximum signal of the signals supplied to the first memory circuit within a next predetermined period of time.