Laser range finder measurement method has the following advantages.

  ① based on the energy to the object, there is no blind area (Missing part).

  ② the surface properties of the object (color, texture, texture) without restrictions.

  ③ can be directly measured.

  ④ no need to obtain images and analysis of the image processing.

  The disadvantage of this method is that the system is complex, the measurement accuracy is low, the measurement time is long, only suitable for the measurement of large objects.

  In 1969, Hildebrand and Haines, from the point of view of coherent optics, proposed a full-information technique with dual-wavelength light sources. It can generate contours on the object, the contour of the resolution depends on the wavelength of light, and can not be any change. Another approach proposed by Hildebrand and Haines is to generate contour lines on two objects by the interference fringes generated by two light sources with different wavelengths. Compared with the first method, the contours produced by the second method The resolution can be changed from the wavelength level to the meter level. For dual light systems, the main problem is that if there are some "swirl patterns" on the object, the specific area will not be able to clearly depict the holographic contour. The relevant measurement method is extremely demanding on the measurement environment, generally only in the laboratory conditions, and is not easy to achieve automation.

 Triangulation has always been paid attention to because of the shortcomings of the barimeter 0 and the coherence measurement of laser range finder. Triangle measurement system can be further divided into active systems (Activesystem) and passive system (Passing system).