| 摘要 |
<p>PURPOSE:To correctly detect a light position by a method wherein light position signals to indicate the position in the X direction and light position signals to indicate the position in the Y direction are so contrived as not to interfere with each other, and at the same time, the amount of light is controlled in such a way that the sum total of the light position signals in the X direction or the Y direction becomes constant. CONSTITUTION:Photocurrents IX+, IX-, IY+ and IY- which are outputted from each electrode 9-1, 9-2, 3-1 and 3-2 of a light position detecting element 1 are each converted into voltages V1-V4 by operational amplifiers 11a-11d for current-voltage conversion corresponding to the electrodes. The output voltage V1 of the operational amplifier 11a and the output voltage V2 of the operational amplifier 11b are inputted to a light source driving circuit 20 and these voltages V1 and V2 are added to the inversion input terminals of an operational amplifier 22 of the driving circuit 20 and added. Driving current ID which is outputted from the output terminal by this operational amplifier 22 is controlled so as to prevent the fluctuation at the time the sum of the voltages V1 and V2 fluctuates, that is, at the time the sum of the photocurrent IX+ and the photocurrent IX- fluctuates.</p> |
