Often meet friends when choosing laser structure light, the depth of field of line laser measurement range and imaging system will have a lot of confusion, this chapter focuses on structure light laser line laser, for example, the specific definition of depth of field and should pay attention to when using,
1. The definition of the depth of field
As shown in the figure below, the laser focal length (common working distance location) minimum line width, set to w0, with the change of working distance, the line width to increase, to the square root of 2 w0, corresponds to the change of the distance to plus or minus ZR, and + ZR is line width corresponding to the depth of field,
2. The change of the depth of field
In 660 nm wavelength laser, for example, by excited by semiconductor diode laser is elliptically polarized light as shown in the figure below, in order to keep the line width, and depth of field, the elliptically polarized light into linear polarized, so the corresponding there are two types, one is long axis type of linear polarized, large depth of field (dashed line), is a short axis line polarized light, to focus on (solid line)
By above knowable, therefore, generally the light power requirements, we are all with a dotted line corresponds to the type of laser, such as if the working distance of 20 cm, corresponding to the line width is 200 um, its corresponding to the depth of field is about 70 mm,
3. The choice of the depth of field
The choice of depth of field related to line width, and line width is related to light energy and rate of system respectively, thus for low reflectivity, the object to be tested the choice of the appropriate line width (about 1 mm), large depth of field (200 mm), but high light intensity type effect will be better,
We often use the friends of superfine line width, actually fine line width is not the goal, the purpose is in unit of CCD pixel can form the obvious contrast distribution, so the unit pixel light energy density is when use should pay attention to the problem,
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