Measuring a distance with laser triangulation
| Autor: | S Y El-Zaiat |
|---|---|
| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | European Journal of Physics. 18:126-127 |
| ISSN: | 1361-6404 0143-0807 |
| DOI: | 10.1088/0143-0807/18/2/014 |
| Popis: | A plane mirror and a half-silvered mirror can be used with a laser source to measure distance, instead of moving the laser source itself. R?sum?. Un miroir de surface plane et un miroir a-demi argent? peuvent ?tre untilis?s avec une source laser afin de mesurer la distance, au lieu de d?placer la source laser elle-m?me. An experiment for measuring a distance by laser triangulation has been demonstrated [1], in which a laser source is set inclined, with an angle, to a base line where its beam is directed to a distant object. Then the laser source is moved, along the base line, to another position and its beam is directed again to the distant object. The distances from the two laser locations to the distant object are determined by measuring the two angles of inclination to the base line and the distance moved. Moving a laser source along a base line and realignment takes some time and is not advisable. There is also a doubt whether the laser spot in the second position is incident on the distant object at exactly the same place as the laser spot in the first position. A modification of the original experiment is performed by adding a half-silvered mirror and a plane reflecting mirror. With this modification the laser source is not moved and the two spots of the laser beam are seen on the distant object at the same instant. Figure 1 shows the optics of the experiment. S is a He - Ne laser source of power 2 mW and wavelength is a half-silvered mirror to divide the incident laser beam into two beams, one of them being directed to the distant object. is a plane reflecting mirror to reflect the laser beam to the distant object. and are fixed to two rotating stages with angle scales. O is a distant object. From the triangle in figure 1 we obtain Rearranging the last equation we obtain ? Figure 1. ?Optical set-up for measuring a distance with laser triangulation. The experiment is performed as follows. The two mirrors, and , are fixed to two rotating stages, at a known distance, and adjusted to reflect the unexpended laser beam back along itself to the laser source. Then and are rotated to reflect the laser beam to a distant object such that the two laser spots coincide on the same area. Then their angles of rotation, and , are measured. Substituting by the mean measured values of and in equations (2) and (3), and can be found. Table 1 shows the experimental result for measuring the distance between the optical table and the wall of our laboratory by the suggested method. ? Table 1. Experimental results for measuring a distant object. The relative error in measuring can be written The relative error in measuring is In our measurements, and which approximately gives . References [1] Kallard T 1977 Exploring Laser Light (New York: Optosonic) pp 18 - 19 |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|