Holographic wavefront sensors

Abstract

A brief historical review of the first designs of holographic wavefront sensors (WFS’s) and the concepts lying in their basis is presented. The main directions in the development of these sensors are highlighted and considered. One of these directions implies a two-stage transition from the use of several separate measuring channels with holograms filtering only one Zernike mode: first to the use of one channel with a multiplexed hologram filtering several first Zernike modes, and then to filtering the entire set of Zernike modes with the aid of one combined multiplexed hologram. Another line of research in this field (related to the first one) is the optimisation of the filter hologram structure in order to reduce cross-modulation interferences, increase multiplexing level, etc. One more line of research implements principles of dynamic holography by introducing spatial light modulators into the WFS composition. Hence, the advantages of time multiplexing of holograms can be used. The approach developed by G. Andersen’s team, aimed at adapting the holographic WFS design for operation as an element of adaptive optical system with a zonal corrector, as well as an approach implying development of hybrid holographic sensors, are considered separately. The results of the authors’ studies of holographic WFS’s with application of the methods of Fourier holography (i.e., holography of focused beams, in particular, using diffuse scatterers in a hologram recording channel) are also reported.

Features and Functionality of the Optical Interference Meter for Measurement of Surface Displacements of Control Objects

“…The scheme of this experimental setup is shown in Figure 2. The experimental setup comprised a coherent optical radiation light source (1) (He-Ne laser, wavelength 0.63 microns), an optical device (2) (optical elements-lenses), a reflector (3) (a simulator of control object surface, an optical mirror with external surface coating), a beam-splitter (4) (a holographic diffraction grating similar to the one used in [33]), a reflector (5) (an optical mirror with external surface coating), a screen (6) (frosted glass), a device for recording the interference pattern (7) (a digital camera, 24 Mpks) and a device (8) for processing the results of the measurements (PC).…”

“…There are many types of wavefront transducers [8] and interferometers; among them, the Fizeau and Twyman-Green configurations should be highlighted. A perfect interferometer must create the image of a 3D optical surface without distortion irrespective of the surface type (flat, spherical or aspherical).…”

Breaking of Wavelength-Dependence in Holographic Wavefront Sensors Using Spatial-Spectral Filtering

“…Currently, wavefront sensors (WFS) are widely used to solve a multitude problems in various fields of physics, namely to control the shape of a wavefront or detect aberrations of the complex field amplitude [ 1 ]. These devices include the well-known Shack–Hartmann wavefront sensor [ 2 , 3 ], curvature sensors [ 4 ], pyramidal sensors [ 5 , 6 ], and holographic WFSs [ 7 , 8 , 9 ]. The principle of the first three sensors is based on analyzing the intensity distribution of an image or set of images using a 2D image sensor.…”

Reconstructing the Spatial Parameters of a Laser Beam Using the Transport-of-Intensity Equation

“…When characterizing conditionally static wave fields of light beams, their complex amplitude is usually represented in the form of two related components-amplitude (intensity) and phase distributions. A reliable estimation of the phase component of the field, often referred to as wavefront reconstruction [1][2][3] or a measurement of its aberrations [4,5], is usually the most difficult procedure. This is because one has to face problems of a possible ambiguity of the phase reconstruction [6], the presence of singular regions [7], a search for optimal boundary conditions [8] and limitations on the admissible dynamic range of phase gradients [9], which is typical for a particular measuring instrument.…”