What is the range of laser marking airport mirrors? How to choose?
The laser marking airport mirror is installed in the laser marking machine. It is an accessory of the laser marking machine. The plan focusing lens, also called field lens, f-theta focusing lens, is a professional lens system. The laser beam is formed into a uniformly sized focused spot in the entire marking plane, which is one of the most important parts of the laser marking machine.
Field lens can be divided into f-theta lens and telecentric lens.
The field lens is called a plan focusing lens because after the laser passes through it, a focused spot of uniform size and focal depth will be formed in a certain laser marking area. The marking format is related to the focal length of the field lens. The longer the focal length, the larger the format. vice versa.
TELECENTRIC f-THETA SCANNER LENSES：Due to the high cost and expense of telecentric lenses, F-theta lenses are mainly used in laser marking machines for industrial applications. In the absence of deformation, the position of the focus point depends on the focal length of the lens and the tangent of the deflection angle, and the position of the focus point only depends on the focal length and the deflection angle, which simplifies the calculation method of focus positioning.
The main technical parameters of the field lens include: working wavelength, entrance pupil, scanning range (or focal length) and focusing spot diameter.
Working wavelength: It is determined by the laser of the equipment system.
For example, the working wavelength of fiber laser is generally 1064 nanometers, the working wavelength of carbon dioxide laser is generally 10.6 microns, the working wavelength of green laser is 532 nanometers, and the working wavelength of ultraviolet laser is 355 nanometers. Of course, there are other types of lasers that will not be listed. What kind of wavelength the field lens is used for, it is necessary to apply this kind of coating. If the field lens is not used within the given wavelength range, the field lens will be burnt out by the laser.
Entrance pupil: If a single lens is used, the reflector is placed at the entrance pupil, and the diameter of the maximum usable beam is equal to the diameter of the entrance pupil.
Scanning range: The scanning area is determined by the focal length, and the field lens generally only marks the focal length. Focal length and format, tell you an empirical formula: format f=0.7*focal length. For example: the field lens of f=160mm corresponds to a 112mm square format, and our general correction format is 100mm*100mm. The corresponding format of the field lens with f=100mm is 70mm*70mm.
Focus spot diameter D: For laser marking system with incident laser beam diameter d, field lens focal length f, and laser wavelength λ. There is a calculation formula: λ From the formula we can know: the longer the focal length f, the larger the focal spot diameter D. The longer the wavelength λ, the larger the focal spot diameter D. The larger the diameter of the incident spot d, the smaller the focal spot diameter D. Therefore, if you want to get a smaller focused spot, you must choose: a short focal length field lens, a large beam expander to make the incident spot diameter larger and a short-wavelength laser.
Of course, the shorter the focal length of the field lens, the smaller the size of laser marking, this has to be selected according to the actual application. The diameter of the beam expander's exit spot should not be too large, which is determined by the area of the window mirror of the galvanometer motor. If the light spot is too large, the galvanometer window mirror cannot accept all the light spots, and the missed laser will lose energy and easily burn the window mirror and the chuck of the burning surface motor. Therefore, the selection of beam expander magnification is determined by the laser spot, and also by the galvanometer.
Knowing the meaning of the working wavelength, entrance pupil, scanning range, and focusing spot diameter of the field lens, you can know how to choose the type.