| 摘要 |
PURPOSE:To enable detection of positions in two-dimensional directions by photo-detectors, by connecting the photo-detectors so that the photo-detectors in the same group have the same signal circuit, aud operating illuminating means so as to illuminate a number of the photo-detectors which number is equal to the number of groups including the photo-detector corresponding to each of the illuminating means. CONSTITUTION:A plurality of photo-detectors 26-28 each of which comprises a pair of a-Si thin films are provided in an array on a substrate 25, and the photo-detectors in the same group are connected by the same signal lines. LEDs 26A-28A are disposed opposite to the photo-detectors 26-28, respectively, and each of the LEDs projects light on the photo-detector opposed thereto and the adjacent photo-detectors. For instance, the position of an ink drop 2C in a direction Y perpendicular to the arranging direction of nozzles is detected by turning ON the LED 27A and detecting the difference between photocurrent outputs from the pair of thin films of the photo-detector 26, which outputs are varied according to a shadow 13 cast on the thin films by the ink drop 2C. |
