Abstract:
A detection system of vertical and horizontal position using a Quadrant
Photodetector (QPD) has been designed and made. The system consists of four level, i.e a QPD, an integrator circuit as current to voltage converter, summing and divider circuits, and a circuit of signal output X and Y. A quadrant photodetector is placed on a translation stage than can be arranged vertically (y) and horizontally (x) in a interval of millimeter. Positions of the laser beam are varied vertically and horizontally on the QPD so that output voltage of each segment of the QPD, integrator and output voltage X and
Y can be observed. The positions of X and Y measured are plotted to x and y that are
varied manually. The relation indicated a linear. For all segment of QPD the bigger segment of QPD that is irradiated by the laser beam then the larger output voltage is
generated. The values of output voltage and will decrease when x position
increasingly towards the negative, while the values of output voltage and
will be increased. This is due to the laser beam diameter on the surface of A and B it gets smaller while on the surface C and D it gets larger when the x position is changed
manually from the position -1,5 mm x 1,5 mm. The position of y is changed
manually from the position -1,5 mm y 1,5 mm then the values of output voltage and will decrease when y position increasingly towards the negative, while the value
an output voltage and
will increase because the laser beam on surface of C and B it gets larger while on the surface A and D ist gets smaller
