| 摘要 |
PURPOSE:To shorten a time for forming an image by supplying a voltage corresponding to a data value based on a generating digital data to a light source and providing a light quantity control means which decides a bit value in accordance with a quantity of light determined by a photoelectricity detecting means and changes the data, so as to quickly and correctly adjust a quantity of light of irradiation light which optically reads a position of a recording paper. CONSTITUTION:A D/A converter 31 converts a data (a) of a set value of a light source application voltage to be outputted by dimmer function of a CPU 30 into a corresponding analog signal. A driver 32 converts it into a drive voltage corresponding to the signal and supplies it to a light source 14. When a light source lighting voltage is supplied to the light source 14 by the driver 32, current flows to the light source 14 which heats by itself due to Joule heat caused by the current and a time delay of several tens msec generates until it heats, i.e., quantity of light is stabilized. Corresponding to the quantity of generating light from the light source 14, a quantity of reflected light from a recording paper changes, level of an output voltage (c) of a CCD sensor 12 which receives the reflected light changes, and the output voltage (c) of the sensor 12 is compared with a reference voltage (d) at a comparator 34. |
