From two tables can be seen that the pulsed laser ranging system due to the application, its performance parameters vary greatly. For the measurement range of the lower end of the tanks, artillery and long-range laser rangefinder military pulsed laser ranging system ranging accuracy is not high, the wavelength is gradually transformed into eye-safe direction; pulsed laser ranging equipment in the missile system and The small laser ranging radar range accuracy than ordinary military ranging system. Selected after considering the pulsed laser parameters: the launch of the optical system design. Emission optical system consists of a collimation system, rectangular prism group and the fiber coupler. Also, the customer can use this kind of green laser pointer for the astronomy purpose.
As the beam output aperture of a certain size, and the radio beam divergence angle, which coupled into the fiber coupler before beam propagation distance increases, the spot size will be larger, so the need for collimation. The collimation system structure: beam after a rectangular prism group by the coupling lens into single-mode fiber, the beam divergence angle DA fiber core diameter of a coupling lens focal length f relations: DA = a / f. Therefore, only the beam divergence angle is satisfied, can be coupled into the fiber. Coupling lens schematic: the incident beam after collimation system required in the rectangular prism group reflection, and then coupled into the fiber coupler on the optical path as shown in Figure. For example, the stargazer can use this piece of laser pointer to point at the star they want to observe or show the star to others very easily.
Collimation system diameter of D, the coupler coupling lens effective aperture d, the collimation system and the coupling between the beam propagation distance l, the beam transmission distance in a rectangular prism, the beam divergence angle is, the spot after a rectangular prism The diameter d: receiving optical system design. Detection beam divergence angle and beam intensity spatial distribution of the laser spot imaging infrared CCD image processing to calculate the beam radius, divergence angle calculated by the formula, ring through the gray value obtained beam intensity The spatial distribution of information. Be detected beam divergence angle within a certain range, the focal length the greater the CCD acquisition of the spot occupied pixel more, such a detection spot radius is more accurate. The customer can find and show the star to others by using green laser .
Focusing optical system selection of telephoto-type structure, can reduce the structure size of the optical system. Focusing optical system block diagram: receiver circuit design. The choice of the photodetector. The photodetector is to convert optical signals to facilitate the measurement of electrical signals, and then zoom processing circuit, the photoelectric conversion principle is the photoelectric effect. Common photoelectric detectors: photoelectric tube, PMT (photomultiplier tube), silicon photocell, photodiode, APD (avalanche photodiode), the PIN photodiode. Accurate measurement of the laser pulse time-of-flight laser ranging system, the response time of the photoelectric detection sensors a very high demand. It is for the laser beam light emitted by green laser pointer .
In addition, because the sensor to receive the optical signal is reflected back, it must be sensitive to weak optical signal. According to these two requirements, the choice of the photoelectric sensor PMT PIN photodiode and avalanche photodiode APD. Which PMT high gain and low noise, but the relatively large size, resistance to external magnetic fields, dynamic range is small and the need of multiple voltage, it seldom used in pulsed laser ranging system. Comparison of PIN and APD. Based on the above considerations, to select the APD avalanche photodiode. green laser pointer can easily points at the star.