Study On Optical Design Of Large Working Area F-Theta Lens

F-Theta lens is one of the most important parts of laser scanning system, and has been widely used in many equipments with high precision, such as laser marking machine, missile tracking and aiming, laser printer, faxes, biochip test and so on. In this dissertation, the optical design and manufacture of F-Theta lens for laser marking machine are investigated. To make the image height of F-Theta lens in proportional to the scanning angle, it is primary to introduce barrel distortion. The key problem of the optical design of F-Theta lens is to achieve the flat field image with high performance as its working area becomes large.Based on the theory of primary aberration, the first-order optical parameters are determined at first through its paraxial analysis, flat-field condition, and aberration characteristics. Secondly, the initial structure parameters of the F-Theta lens are obtained with P-W method. And then a few of optimal F-Theta lenses with different working area and required optical performances are gained with ZEMAX optical design software under practical constrained conditions. The design results and the performance evaluation of F-Theta200 and F-Theta500 are given in detail. The designed lenses are simple and compact and their cost are low. The focusing performances are within diffraction limit, the relative illuminations quite uniform and the distortion relative to the F-Theta linear relation small.Finally, the principle of F-sinθlens is also introduced. The reason that F-sinθlens can avoid the declination of relative illumination as increase of its working area is represented. And its potential application in laser marking machine with larger working area is expected. As an example, an F-sinθlens with the image height of 140mm is given.