Design and fabrication of a hybrid diffractive optical device for multiple-line generation over a wide angle

Abstract

A new hybrid optical device that is capable of splitting a monochromatic laser beam into an arbitrary number of lines over a wide angle is presented. It consists of a binary surface-relief computer-generated phase hologram and a continuous parabolic surface-relief grating. In this device the phase hologram serves to generate three small, parallel lines while the continuous parabolic surface-relief phase grating acts as an array of diverging parabolic lenses to widen these lines. The binary surface-relief was generated into one side of a quartz substrate through a plasma-etching process, and the parabolic profile was generated into a thick photoresist deposited on the other side of the quartz substrate. Calculations showed that a diverging parabolic lens with a f-number of 0.5 would deliver the desired optical pattern of multiple beams distributed over 90 degrees . A surface-relief depth of 6.0 mum was calculated with consideration of the phase distributions of such lens. The parabolic profiles were fabricated in a 10-mum-thick photoresist, by use of a contact exposure through a mask with a space pattern of repetitive 4- and 6-mum lines. He-Ne laser light was passed through a device that generated three parallel lines over a 90 degrees angle. The resulting diffraction patterns were characterized, and a satisfying result was obtained. The resulting multiple-line pattern can be used in robot vision and other applications.

Fabrication of hybrid optical line generator by direct machining

“…Lithographical processes are conventionally used in making diffractive gratings and even hybrid diffractive phase element for line generator [14] but they lack the ability to pattern three-dimensional surfaces. In this work, we attempt to overcome this limitation by generating diffractive gratings on a cylindrical lens array with ultra-precision diamond machining.…”

Image quality enhancement and computation acceleration of 3D holographic display using a symmetrical 3D GS algorithm

“…A pure-phase CGH (or kinoform) is a hologram whose amplitude is constant, and this kind of hologram has a high light efficiency. As a result, research on kinoform has drawn much attention [3,4].…”

Microlens Array Fabricated by Gray-Scale Lithography Maskless System

“…Among the several applications of MLAs one can find: in the enhancement of the efficiency of detector arrays (1); in the fabrication of optical components with non-Gaussian imaging properties (2); they are also of interest in digital optical processing where they might be used in array illuminators (3), in various forms as interconnects, in couplers and multiplexers with optical fibers, in retro-reflective screens and to sampling an optical wavefront for adaptive optics and Shack-Hartmann wavefront sensors (4). There are several techniques to implement microlens array such as photoresist melting (5-8), e-beam lithography (9), grayscale lithography (10), optical lithography operating in proximity mode (11,12), UV exposure directly on photosensitive hybrid glass (13,14), anisotropic etching of silicon in a KOH water solution (15), among others. Each technique has its advantages and limitations.…”