| 摘要 |
PURPOSE:To make a high-precision adjustment according to an optional fluorescent lamp by adjusting white balance with the signal generated by detecting a ripple of a fluorescent lamp light source stored in an object light source and color temperature information from a color temperature detecting means. CONSTITUTION:Signals iR and iB of red and blue detected by a milk white diffusing plate 8 are amplified logarithmically and the difference between both logarithmic signals is obtained by a differential amplifier 12, whose output signal is led to a ripple detecting circuit 21 and an LPF26. The circuit 21 extracts a ripple component with a period twice as long as that of the commercial frequency and makes it into a direct current to output logic 1 to a coincidence circuit 25 when a fluorescent lamp is used as a light source 4. The LPF26 supplies a window comparator CP27 with a signal obtained by excluding the ripple component from the output signal of the amplifier 12. The CP27 impresses logic 1 to a circuit 25 when the input signal is within the set color temperature range of the fluorescent lamp, and the circuit 25 outputs logic 1 to a white balance adjusting circuit 7 when both input signals coincide with each other. The circuit 7 controls the gains of amplifiers 4 and 6 for the signals of R and B to correct the deviation of adjustment of the white balance. |
