Circuit Design For Large Range Phase-Shift Semiconductor Laser Range Finder

LD laser range finders are widely used in such fields as military, robot vision, industrial automation production line and mapping for their merits of being non-contact, high precision, low cost and so on.Measurement accuracy of phase-shift laser range finders is up to millimeter level in large range through multi-frequency modulation and high precision phase difference measurement. However, laser range finders existing is not suitable for large range high speed tracing measurement for their complex multi-frequency modulation circuit and conflict between precision and speed in phase-shift measurement. In order to improve the large range measurement speed and accuracy, key technologies on multi-frequency modulation and high precision phase-shift measurement are deeply researched in this paper. Main work is as follows:Traditional oscillator circuit is not suitable to serve as multi-frequency modulation signal source with problems of low stability, inflexible parameter adjustability and drift. A high precision double-frequency modulation signal generator is developed based on direct digital synthesizing technology in this paper, and it also severs as high stability local oscillator for heterodyne phase measurement.A direct inner LD modulation circuit is designed based on voltage-controlled constant-current source. The output optical power of LD can be modulated by high frequency signal with this circuit together with the modulation signal source designed. The modulation frequency can be flexible adjusted and fast switched among multiple modulation frequencies.Based on error analysis of traditional auto digital phase measurement, multi-cycle synchronous digital phase measurement is proposed with error analysis and completed with a complex programmable logic device (CPLD). The phase detecting error caused by local oscillator frequency drift and non-synchronization of measurement signal and gate signal is eliminated and the measurement speed is improved at the same time.Experimental results show that with these key technologies the...