| 摘要 |
<p>PURPOSE:To eliminate the unevenness of luminance of an illuminating lamp due to a difference of the operating time by providing a compensating circuit, which obtains the time from the start of the operation to the reach of the luminance under the ordinary condition and which controls the driving power at a luminance of the ordinary condition during the obtained time. CONSTITUTION:When an illuminating lamp 5 is changed with a new one, luminance thereof is raised during the time from the starting of operation to a reach of the luminance under the ordinary condition. At this stage, a CPU 13 inside of a compensating circuit 10 outputs the code signal, which is controlled by the crock signal from a timer 12 and corresponds to the time from a start of operation to a reach of the luminance under the ordinary condition, as the digital luminance signal through a memory 14 and an I/O board 15. This output is converted to the analog luminance signal by a D/A converter 17, and applied to a current-resistance converting element 19, and in the case where the luminance is large, the current of a power measuring circuit 6 is controlled small. A result thereof is transmitted to an alternating current circuit 4 through a voltage adjustment circuit 3 to always maintain the illuminating lamp 5 at a constant luminance.</p> |
