Optical multifrequency complex holograms

Abstract

A two-channel system for synthesizing two-dimensional optical multifrequency complex holograms of rotating objects was developed. In the object irradiation (longitudinal) direction, a hologram is synthesized due to multifrequency laser radiation, and in the transverse direction, the synthesis is provided by object rotation. The resolution of the synthesized hologram in the longitudinal direction is determined by the frequency bandwidth of the laser radiation, and in transverse direction, the resolution is determined by the initial laserradiation frequency and the angle of object rotation during the time of hologram synthesis. Using a digital simulation, the degree of isoplanarity of the multifrequency system for synthesizing holograms of rotating objects and its noise immunity under conditions of phase noises were analyzed.The known long-wave holography methods for measuring the parameters of rotating objects are based on the synthesis of holograms with the use of multifrequency coherent RF radiation illuminating the object [1] or using the Doppler change in the frequency when observing a rectilinearly moving and simultaneously rotating object [2], which is illuminated by pulse single-frequency coherent radiation. The data on the rotating object in the optical range can be obtained either by synthesizing holograms by scanning the object along angular coordinates with a laser beam [3] or receiving the laser radiation reflected by the object at several spatial points [4]. This makes it possible to obtain a three-dimensional (3-D) image and determine both the rotation frequency and the orientation ofthe rotating object.This work describes a multifrequency holographic system for synthesizing images of rotating object (Fig. 1), which uses a principle of synthesizing complex optical holograms with the help of combined receiving and transmitting point aperture. In the object irradiation (longitudinal) direction, a hologram is synthesized due to the presence of multiple frequencies in the laser radiation, and in the object's rotation determines the synthesizing of a hologram in the transverse direction. The resolution of the hologram in these directions is determined, respectively, by the laser-radiation frequency bandwidth and the angle through which the object rotates during the hologram synthesis time, being independent of the distance to the object. Using a digital simulation technique, we analyze the properties of 2-D optical multifrequency complex holograms of rotating objects synthesized on an aperture of (128x256) discrete elements, including the degree of isoplanarity of the system considered [5].Multifrequency holograms of rotating objects are, synthesized with the system considered to the following procedure. The radiation of the frequency-turned laser I is directed by a telescopic system, which is formed by the lenses 6 and 8, diaphragm 7, and semitransparent mirror 9, to the holographed object 10 rotating around the center of rotation 11 using the object control unit 12. The duration of each frequency-turned...