| 摘要 |
PURPOSE:To attain uniform luminance without hot spot or the like for the screen without increasing the size of this device by providing a variable gain amplifier varying a gain of an output of a clamp circuit taking an output of a waveform circuit synthesis circuit as a control signal. CONSTITUTION:Suppose that the screen is a perfect diffuser for the simplicity in a projecting display, then a luminance Bphi at an optional position on the screen is expressed in the following equation: Bphi=B0 cos<4>phi, where B0 is the luminance of screen on an optical axis, phi is an angle between a ray incident to pupil and the optical axis. Then, the luminance is made constant by making the luminance of the optional position to 1/cos<4>phi or equivalent value thereto at scanning. It is necessary to input the waveform of cos<4>phi and since this waveform is approximated by a parabola waveform in the range of 2phi<90 deg., the parabola waveform is inputted to a synthesis circuit 1 by passing horizontal and vertical deflection voltages of saw tooth waveform respectively through integration circuits 8, 3 and the waveform is inputted also to a control input of a voltage controlled gain amplifier 5 through an inversion circuit 2. |
