| 摘要 |
<p>PURPOSE:To prevent a erroneous read caused by time aging, in photoelectric converting efficiency, by comparing the magnitude of a signal of a storing circuit corresponding to a photoelectric converting element, and an output signal of the photoelectric converting element, so that binary information is outputted. CONSTITUTION:A photoelectric converting circuit 1 irradiates light to a recording medium 9, photodetects its reflected ray, and outputs an analog signal A corresponding to the photodetecting quantity. Also, this circuit 1 is provided with a light source for irradiating a light beam to the recording medium 9, and a photodetector for photodetecting the reflected ray from the recording medium 9. In this example, this photodetector is an image sensor which has arranged N pieces of photoelectric converting elements in one row, and this image sensor is driven by a clock signal B1 inputted from a controlling circuit 8, and serially outputs the analog signal A converted by each photoelectric converting element. This analog signal A is supplied to the second comparing circuit 7 mentioned in the latter part, also is converted to a digital signal in an A/D converting circuit 2, and after that, is supplied to the first comparing circuit 3 and a selecting circuit 4, too.</p> |
