Reserch And Design Of Short-range Hand-held Laser Range Finder

With the birth of the laser ranging technology, the rapid development of modern electronic technology and the constant improvement of the photoelectric device performance, laser range finder become the main instrument of distance measurement and soon be applied to the measurement field. Because of the laser range finder does not depend on the distance under test and the experience of the user, error only depends on the precision of the instrument itself, the research of laser range finder is not only plays an important role in the field of national defense, but also occupies a very important position in the national application.By comparing the characteristics of several common laser ranging methods, the paper choose the phase laser ranging principle which can achieve a high precision to solve the precision problems often encountered in the civil domain of short distance measurement. The project mainly includes five modules:the signal generating module, the signal emitting module, the receiving and amplifing module, the signal mixing and sampling module and the control module.To meet the requirements of miniaturization, this design mainly choose to use the components with small volume, low power consumption, high reliability such as a sensitive PIN as the photoelectric diode detector. Put forward to use the advanced DDS (Direct Digital Synthesizer) to obtain the required precision and a phase difference frequency measuring technique to decrease the requirement of the components and parts in the signal mixing and sampling circuit. Considering the safety of human eyes in civil field, the laser chose a650nm red light semiconductor laser which can provide a corresponding protection by the blink of eyes. In order to increase the power of the optical output, effectively adjust the bandwidth of the laser modulation and reduce the relaxation oscillation at the same time, the paper also designed a bias current provide circuit consist of a triode and a operational amplifier to provide a appropriate bias current for the semiconductor laser diode. Finally, the paper put forward a corresponding algorithm of the data combination.