Laser beam expander is also called collimator, the most commonly used beam expander is the Galileo telescope system, the system is usually composed of a negative lens and a positive lens, the laser beam expander negative lens is the system negative lens, the two lenses are confocal. This kind of beam expander has the advantages of simple structure, low cost, small size, etc., and has been widely used in laser marking.
A laser beam expander can expand the diameter of the collimated input beam to a larger collimated output beam. Beam-expanding mirrors are often used in applications such as laser scanning, interferometry, or telemetry. Today's laser beam extenders are all focus-free system designs developed from the fundamentals of sound optical telescopes. In such systems, object light enters the optical axis of the internal optical element in a parallel manner and exits in a parallel manner
Laser beam expander has two main uses: one is to expand the diameter of the laser beam; The second is to reduce the divergence Angle of the laser beam. Therefore, it is used for remote lighting or projection, as well as focusing systems. The divergence Angle of an expanded beam varies inversely to the beam expansion ratio. The expanded beam can be focused much smaller than the unexpanded beam. The magnification of the laser beam expanding collimator is the magnification of the beam diameter. The product of the spot size and divergence Angle of the laser beam output from the laser is an optical invariant, which is approximately a certain value. When the waist radius of the beam is expanded x times, its divergence Angle is compressed to the original 1/x, and the compression divergence Angle is actually the collimation of the laser. Compression of divergence Angle does not improve beam quality, which is the product of beam waist radius and divergence Angle. When the divergence Angle of compression is accompanied by the increase of the waist radius, the spot size increases. The laser marking machine is usually used in conjunction with the flat field focusing lens.
Usually, we take the beam divergence parameter as the characteristic of a perfect Gaussian laser beam. Divergence means that light waves spread at a certain Angle during space propagation. Due to the diffraction effect, even perfect light rays without any anomalies will experience some beam divergence. Diffraction refers to the bending effect of light when it is cut by an opaque object, such as a blade. Expand the array of secondary wave fronts emitted from the edge of the incision. These secondary and primary waves will interfere with each other, and at the same time they will interfere with each other, and in some cases will form complex diffraction patterns. Diffraction prevents the beam from being perfectly collimated and from focusing the beam to an infinitesimal point. Fortunately, diffraction effects can be calculated. Therefore, there is a theory that can predict the collimation and spot size of any line-limiting lens.
YAG laser wavelength of 1064nm, invisible laser wavelength. The 10.64um wavelength is the CO2 laser wavelength. So how can these two wavelength expanders be distinguished? First check to see if the appearance of the beam expander is marked. In general, the beam expander manufacturer will standardize the appearance of its beam expander over the wavelength range of the beam expander. If there is no standard, it can be distinguished by the color of the beam expanding mirror. The lens color of the 1064nm beam expander is dark blue, while the 10.64μm beam expander is gold.