ISBN: 978-981-09-5471-0 DOI: 10.18178/wcse.2015.04.071
An Active Gain Control System of Avalanche Photo-Diodes for Phase-Shift Laser Range Finder
Abstract— In time fight phase-shift laser range finder, it is noticed that unwanted phase delay in
avalanche photo-diodes (APD) between the incident light and the output current. When the
modulation frequency is higher and the incident light is weaker, the phase delay is becoming larger.
The measurement resolution of laser range finder by the optical modulation method is strongly
influenced by the undesirable phase delay. In order to solve the problem, the relationships among
the phase delay, the reverse bias voltage and the multiplication factor of APD were investigated at
different modulation frequency respectively. An active gain control system was proposed by
controlling the reverse bias acting on the APD according to different incident light power. Given the
high light intensity, the reverse bias voltage was adjusted to keep APD operating at optimal M
factor, and the phase delay was compensated by software, on the condition that the low light
intensity, the reverse bias voltage is decreased to reduce the phase delay. The experiment results
show that for a modulation frequency of 75MHz and incident light intensity of 0.5uW，the phase
delay can be reduced from 4.8013° to less than 0.04°.
Index Terms— avalanche photodiode, multiplicatoin factor, control system, laser range finder.
Jia Fang-xiu, YIN Ting-ting, ZHAI Meng, WANG Xiao-ming
ZNDY of Ministerial Key Laboratory, Nanjing University of Science and Technology, CHINA
Cite: Jia Fang-xiu, YIN Ting-ting, ZHAI Meng, WANG Xiao-ming, "An Active Gain Control System of Avalanche Photo-Diodes for Phase-Shift Laser Range Finder," 2015 The 5th International Workshop on Computer Science and Engineering-Information Processing and Control Engineering (WCSE 2015-IPCE), pp. 430-436, Moscow, Russia, April 15-17, 2015.