| 摘要 |
<p>PURPOSE:To make it possible to control light quantity with a simple circuit construction, by providing a frequency divider for dividing the frequency of a basic signal having a fixed period, and a circuit for setting a correction value for lighted time of each light-emitting diode according to a frequency division signal. CONSTITUTION:A circuit of a light quantity controller comprises a frequency dividing circuit A for dividing the frequency of a basic signal with a fixed period for control of ON time and outputting a predetermined timing signal to each of signal lines L1-L4, a circuit B for setting correction values for the lighting time on the basis of the timing signals, and a turning-ON controlling circuit C for controlling LEDs 4n-1, 4n according to the corrected ON times. In the frequency dividing circuit A, clock pulses with a period of (t) are counted as the basic signal by a counter 5, and the timing signal is outputted to each of the signal lines L14-L4. The correction value setting circuit B comprises shift registers 6n-1, 6n supplied with correction data from an external ROM or the like, and when a signal of '01', for example, is inputted as the correction data, a correction signal for the signal line L2 is selected. The signal lines L1-L4 are selected according to the characteristics of each of the LEDs, whereby the quantities of light emitted from the LEDs are controlled uniformly.</p> |
