Моделювання та дослідження параметрів концентраторів світлових променів

Abstract

Now, in many fields of applied optics, the focusing Fresnel lenses are used. Mostly, such devices are created for tracking different objects; they are used also for forming the precise visual images, even with a changing focal distance, for solar concentrators, and for many other applications. Different methods have been proposed for designing such optics. The flat focusing Fresnel structures were manufactured by the photolithography methods or by the adjustable direct laser recording with photoresists. Such methods allow the formation of known stepped structures [10–15] but the optical quality of images obtained with such aspherical surfaces is not very good. The high-quality images are not practically realized due to the defects of created aspherical surfacesHowever, for some light signal processing systems it is necessary to convert a parallel circular light beam into a uniformly illuminated light circle instead of focusing. Such transforming Fresnel lenses are often used in the optical sensor systems for imaging and optoelectronic integration or in the monitoring devices for automatically adjusting the output signal from the four-quadrant photodetectors. These structures can be easily made by a diamond cutting method [16–17]. This method provides a manufacture of Fresnel optics with refractive surfaces having minimum of optical defects due to the almost mirror-like quality of the working surfaces of the diamond cutting tools. The quality of formed images, in turn, is also very high.However, the refractive angles for sequential microprisms in the lens made but a diamond cutting can be changed only discretely, and only the discrete images can be formed. The value of above discreteness is determined by the width of the circular focusing zones, so the size of such zones should not be too large. It is proposed the method for simulating microrelief structures with the flat conical working faces for creating transforming Fresnel devices that form an almost uniformly illuminated light circle in the focal plane. The geometrical parameters of the relief for circular light beam concentrators are calculated. Some samples of such focusing microprismatic devices having been manufactured according to our simulation results were investigated experimentally. Fig.: 13. Refs: 8 titles.