A simple phase shifting (PS) technique without moving element in lateral shearing (LS) interferometer is presented. This method uses Murty’s simple LS interferometer with a wedge plate and adds only two identical transmission gratings. The two gratings can make three (or odd number of) equally separated identical test wavefronts. The wedge plate changes the optical path difference between the original wavefront and the sheared wavefront along the wedge direction. So three (or odd number of) interferograms having different phase shift quantity can be obtained simultaneously and 3-step PS interferometry algorithm can be applied.
A holographic polymer-dispersed liquid crystal (HPDLC) thin film is composed of multifunctional acrylate monomer blended with the nematic liquid crystal mixture, and then investigated the real-time diffraction efficiencies for various physical parameters of amount of liquid crystals and applied AC electric fields. It is experimentally shown that the holographic gratings recorded in HPDLC film can be reversibly erased and reconstructed by switching on and off of appropriate applied AC electric field. By using these electro-optic properties we have developed bifocal holographic lenses having two different focal lengths of 300 mm and 400 mm.
In order to use phase shifting interferometry(PSI) in lateral shearing interferometer, piezoelectric transducer(PZT) is mainly used. But because PZT has many error sources and the moving distance for required phase shifting is very short, the phase shifting quantity has always considerable errors. We present a simple phase shifting technique without PZT. Moving the wedge plate parallel to the first wedge surface changes the phase difference between the original wavefront and the sheared wavefront. This method makes the shearing interferometer very simple in spite of using PSI technique. We derive the phase shifting relations originated from the moving wedge and discuss some error factors.
Bessel beams are a special class of diffraction-free solutions of the wave equation which are of practical interest, for example, in precision alignment, laser machining and laser surgery. Therefore efficient methods for the transformation of a Gaussian laser beam into a Bessel beam are needed. We design and fabricate computer generated holograms(CGH) to generate this Bessel beam. Designed CGH is recorded onto the photopolymer which is used as a volume hologram material making CGHOE(computer generated holographic optical element). The principle of the CGH and the propagation characteristics of the Bessel beam are explained. The binary mask designed for generating Bessel beam is copied on photopolymer by the contact copy method. The axial intensity is measured for the beam propagation distances. The propagation property and the intensity profile of the Bessel beam are analyzed.