José J. Lunazzi

Holophotography with a diffraction grating

Color encoding of depth is shown to occur naturally in images of objects observed through diffraction gratings under common white light illumination. A synthetic image is then obtained from a single point of view, a phenomenon that can be applied to stereophotography. The image can be recorded in a common color photograph, providing a simple method of visual decoding by means of ordinary colored 3-D spectacles. The fundamental equa- tions and the photographic procedure for maximum fidelity in three-dimen sional reproduction are described. The result is a photograph that has the capability of registering all of the views of an object in a continuous sequence, which is called holophotography and was previously obtained by means of a hologram. By eliminating the need for a laser and holographic film, a new technique for holography in white light is foreseen.

Pseudoscopic imaging in a double diffraction process with a slit

Pseudoscopic images that keep a continuous parallax are shown to be possible due to a double diffraction process intermediated by a slit. One diffraction grating acts as a wavelength encoder of views while a second diffraction grating decodes the projected image. The process results in the enlargement of the image under common white light illumination.

Three-dimensional photography by holography

Colorencoding of depth is shown to occur naturally in holograms that are reconstructed under white light illumination. It can be registered in a common color photograph, allowing a simple method of visual decoding by means of ordinary colored 3-D spectacles. The fundamental holographic equations and the photographic procedure required for maximum fidelity in threedimensional reproduction are described. The result is a new kind of photograph that shows all of the views of the object in a continuous sequence. It permits an animated photographic representation and also makes it possible to adjust the degree of depth visualization when observed as a stereoscopic representation.

Fabry-Perot laser interferometry to measure refractive index or thickness of transparent materials

By introducing a transparent plane parallel plate into an open Fabry-Perot cavity and counting the change in the interference order while the plate is rotated, it is possible to measure the thickness or refractive index of the material with a high degree of accuracy. The method of multipass interferometry can be applied by using a He-Ne laser of 632.8 nm wavelength.

One-step technique for enlarging straddling holographic images by white-light projection onto a diffractive screen

We demonstrate a simple holographic technique that permits enlargement of the holographic image at the reconstruction stage. The technique employs a spherical mirror to generate an image that straddles the hologram to produce the maximum depth. The holographic image is projected with a white-light reconstruction beam, a lens, and a transmission diffractive screen to an enlargement of up to 5× linear magnification. Wavelength encoding of views is a new process that projects the holographic image by using all the visible spectrum and low-f -number lenses and allows for 18 simultaneous observers.

Holo-television system with a single plane

We show a system capable of projecting a video scene onto a white-light holographic screen to obtain a kind of image that results in a plane in front of the screen. This holographic screen is mainly a diffractive lens and is constructed by holography. The image plane can be located at any azimuth angle and seen with continuous parallax and without the use of goggles or any special visualization equipment. The image is not volumetric, but when the plane is oblique to the observer its appearance looks very close to a real volumetric image.

Construction of white-light holographic screens

Abstract In this paper we describe one setup employed for the recording of two types of holographic screens that can be used in white-light applications. We show how to obtain holographic screens with areas up to 1370 cm 2 and diffraction efficiency of 17%. We analyze the holographic screens in their relevant aspects as to focal lengths, theoretical approach, sizes and diffraction efficiencies specifying when each type is appropriate for particular applications.PACS 090.0090 090.1970 090.2890Keywords: holography, holographic screen, three-dimensional imaging 1. Introduction The holographic screen 1 is a diffractive optical element (DOE) constructed by holographic techniques in order to obtain the highest directionality such that one projected image can be seen in strictly one direction, while many images can be seen projected simultaneously. It is primarily a holographically-made lens where the vertical and/or horizontal observers field is extended, allowing for a more comfortable posture of the observer. The term “holographic screen” is used sometimes in a popular way to designate translucent screens that are used for image projections which produce a phantasmagoric two-dimensional image at the plane of the screen. These screens can be holographically constructed or by other methods. The holographic screens that we will describe here are

Pseudoscopic white-light imaging by means of two bi-dimensional diffracting elements and a pinhole

Diffracted images with inverted depth were first reported by the authors where a lens or slit intermediated the white-light double diffraction process. The diffracting elements were simple straight line diffraction gratings and the image could be seen but not projected due to its strong astigmatism. The generalization of the symmetry properties to bi-dimensionally defined diffracting elements allows to produce projected images with circular gratings intermediated by a pinhole. Acting as a focusing element, the possibility of enlargement is reported here with experimental results.

Volume Images Vector Display Based on a Diffractive Screen

A white light system based on a 65 cm × 35 cm diffractive screen is demonstrated to be capable of displaying three-dimensional figures with continuous horizontal parallax. Three computer-controlled mirrors and a diffractive-refractive optical system are employed for positioning each element of the figure. No visual accessories are necessary and more than one observer can watch it simultaneously.

Imaging with two spiral diffracting elements intermediated by a pinhole.

A pseudoscopic (inverted depth) image made with spiral diffracting elements intermediated by a pinhole is explained by its symmetry properties. The whole process is made under common white light illumination and allows the projection of images. The analysis of this projection demonstrates that the images of two objects pointing away longitudinally have the main features of standard pseudoscopic image points. An orthoscopic (normal depth) image has also been obtained with the breaking of the symmetry conditions.