A lens that works near the focal plane of the objective lens and can effectively reduce the size of the detector is called a field lens.

To be precise, the field lens should work on the image plane of the objective lens. On the one hand: The object plane of the field lens coincides with the main plane. The characteristics of the main plane show that its magnification is 1, so it has no contribution to the magnification of the system; On the one hand, the field lens should project the aperture surface of the objective lens on the entrance pupil of the eyepiece. For a single lens, the aperture surface is also the exit pupil, so you can Ensure that the light emitted from the objective lens can pass through the eyepiece as much as possible.

If used in a scanning system, the detector replaces the entrance pupil of the eyepiece.

　　 Generally speaking, the laser beam in the marking system will produce off-axis deflection after passing through the focusing lens system. Relative to an ideal plane, it will

An abnormal image or distortion appears on the surface. Plan focusing lens, also called field lens, f-theta focusing lens, is a professional lens system,

The purpose is to form the laser beam in the entire marking plane The uniformly sized focused spot is one of the most important parts of the laser marking machine. Field lens can be divided into f-theta lens and telecentric lens. Due to the high cost and expense of telecentric lenses, F-theta lenses are mainly used in laser marking machines for industrial applications. Without distortion, the position of the focus point depends on the focal length of the lens and the tangent of the deflection angle. The position of the focus point only depends on the focal length and the deflection angle, so Simplify the calculation method of focus positioning.

　　Choosing field lens, the main technical parameters considered are working wavelength, entrance pupil, scanning range and focusing spot diameter.

　　 Working wavelength: It mainly depends on the wavelength of the laser. The field lens is coated at a given laser wavelength. If it is not within the given wavelength range

　　Use a field lens, the field lens will be burned by the laser.

　　Entrance pupil: If a single lens is used, the reflector is placed at the entrance pupil, and the maximum usable beam diameter is equal to that of the entrance pupil

　　 diameter.

　　 Scanning range: The larger the range that the field lens can scan, the more popular it is of course. However, if the scanning range is increased, the focus spot

　　 becomes larger, and the distortion degree also increases. In addition, to increase the scanning range, the focal length and working distance of the field lens must also be increased. The lengthening of the working distance will inevitably lead to the loss of laser energy. Also, the diameter of the focused spot is proportional to the focal length, which means that the scanning range is increased, and the focused spot is straight. The power density drops very quickly (the power density is inverse to the 2nd power of the spot diameter

　　 ratio), which is not conducive to processing. Therefore, the user should choose the most suitable field lens according to the different processing area, or spare several field lenses with different scanning range

　　.

　　 Focus spot diameter: For a scanning system with incident laser beam diameter D, field lens focal length F and beam quality factor Q, the focus spot diameter

　　d u003d 13.5QF/D (μm). Therefore, a beam expander can be used to obtain a smaller focused spot.

　　Model naming rule: STY-xxxx-yyy-zzz-A

　　STY STY series laser field lens

　　xxxx---laser wavelength, 1064 is 1064nm, 10.6 is 10.6um.

　　yyy scanning range, yyy x yyy mm

　　zzz Focal length mm

　　A Other

　　1. Nd:YAG Laser wavelength scanning focusing lens

　　STY series laser field lens is composed of three focusing lens and a protective lens. The protective lens is coated on both sides, and the field lens transmittance is greater than 99%.

　　(1) STY series Nd:YAG laser field lens (scanning focus lens)

　　1064nm laser wavelength field lens< /p>

　　Sweep angle incident light diffuse spot

　　Focus working distance Marking area mm D1 D2 Threaded connection shape

　　 model degree diameter diameter

　　mm mm round/square mm mm

　　θmax mm μm

　　STY-1064-35-63 63 58 Φ50/35x35 ±22o 12 10 31