| 摘要 |
<p>PURPOSE:To keep the brightness of a screen constant by detecting the brightness of the screen, performing the feedback of it, comparing obtained value with set value and adjusting the magnitude of an input power which is supplied to a light source in a direction where the difference between the above-mentioned value becomes zero. CONSTITUTION:A current control loop 3 consisting of a projecting light source 4, a light source DC amplifier 5 and a current detection resistance 6 (R1) processes a current command 8 and a current feedback value 9 given from a luminance control loop 7 in an adder 10 so as to apply a light source current corresponding to the command 8. When the detection value of luminance lowers, a luminance controller 15 increases the command 8 to increase the input current to the light source 4. Then, the increase of the power is obtained and the light source 4 is operated to increase its luminance. The above-mentioned operation is performed so as to control to keep the luminance constant according to a luminance command 11. Projected luminous flux having specified luminance from the light source 4 passes through a projecting lens 16 and an optical image plane modulator 17 and is reflected on a screen 2 to project the image plane there. Thus, the brightness can be always kept constant.</p> |
