| 摘要 |
PROBLEM TO BE SOLVED: To use the dynamic range of an A/D converter to the maximum by adjusting a target white level depending on the temperature of a lamp when a white level is adjusted. SOLUTION: At first, the tube surface temperature of a lamp is measured (S21). The quantity of light of the lamp is then calculated by making the tube surface temperature of the lamp correspond to a lookup table of the level of quantity of light (S22) thus determining a target white level (S23). A data processing section detects the peak level of a reference white board (S24). A CPU adjusts the gain of an operational amplifier (S25). The CPU makes a decision whether the peak level of the white board is equal to the target white level or not (S26) and if they are not equal to each other (S26; N), the processing is repeated by returning back to S24 until the peak level of the reference white board becomes equal to the target white level. If they are equal to each other (S26; Y), a gain at that time is determined as the final gain of the operational amplifier 2 (S27) thus ending the processing for adjusting the white level. COPYRIGHT: (C)2004,JPO
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