| 摘要 |
PURPOSE:To eliminate inconvenience caused by a variation of quantity of light of a light source, by providing a light quantity detecting means for detecting the quantity of light of the light source, and varying a slice level of a slice level setting device by an output of this detecting means. CONSTITUTION:An original 1 is irradiated by a light source 2, and the reflected light from the original 1 is converted to an electric signal by a photoelectric converting circuit 3 and is supplied to a variable gain amplifying circuit 4. Its level is adjusted automatically by this circuit 4, and it is applied to a binary- coding circuit and is binary-coded to two values showing black and white. Also, the electric signal from the circuit 3 is inputted to one terminal of a comparing circuit 7, a variation of quantity of light of the light source 2 is detected by a photoelectric converting element 9, is inputted to a variable voltage generating circuit 10, and a level of a slice level setting device 6 is adjusted by an output of the circuit 10, and it is provided to the other input of the comparator 7. Subsequently, voltage corresponding to a variation of quantity of light from the comparator 7 is applied to a correcting circuit 8 to which a binary-coded signal of the circuit 5 is inputted, thus the inconvenience caused by a variation of quantity of light of the light source 2 is eliminated. |
