Arl Travis

The display of three-dimensional video images

Three-dimensional images can be pixellated in three distinct ways: volumetric, holographic, and autostereoscopic. The latter excels if images of opaque objects are to be displayed with wide fields of view, and the quality of view-sequential displays with 1/spl deg/ per view now appears adequate for general applications. Although in principle autostereoscopic pixellation gives a true three-dimensional image, 1/10/spl deg/ per view is needed to avoid flaws in a typical display. This approximately equals the diffraction limit, and the information content is no less than that of a hologram. A hybrid of holographic views and view-sequential multiplexing promises images with the field of view of autostereoscopic images but the significantly greater resolution and depth of holograms. Light valves and high-frame-rate arrays already have the space-bandwidth product needed to display such images, and further advances in photonic switches and gigahertz telecommunications look set to promote the display of such high-quality three-dimensional video images.

Time-multiplexed three-dimensional video display

A true 3D image is synthesised from many 2D views of the original. The views are presented in rapid succession on a CRT whose field of view is restricted to a different zone for each view. This restriction is achieved by using optical fourier transforms which result in a 3D image that is especially sharp and clear. The display is bulky but inherently robust and flexible. It is therefore well adapted for the design of novel 3D systems.

Optically addressed spatial light modulators using the twisted smectic C* liquid crystal effect

Abstract This paper investigates the possible use of the twisted smectic C* liquid crystal effect (TS) in OASLMs. An averaging uniaxial model of the TS using the Jones Calculus is described, which can qualitatively and, to a certain extent, quantitatively simulate and account for the optical throughput in the transmission and reflection modes of such grey scale liquid crystal modulators. Three samples of different thicknesses namely, 1.38, 2.6 and 3.05μm in the transmission mode and a sample thickness of approximately 2.0μm in the reflection mode have been simulated.

Passive quadrature detection using speckle rotation on a multisegment photodetector

In coherent optical transmission systems and sensors, passive quadrature detection1 is frequently used as it facilitates unambiguous measurement of amplitude and phase and avoids the need for an optical phase-locked loop. This requires the use of some kind of multiport network with the appropriate phase shifts. A network to produce three outputs 120° apart is easily implemented in a three-fiber fused coupler.2 However, this arrangement is not the optimum tor sensitivity or rejection of local oscillator intensity noise. Implementation of a multiport network to produce true quadrature (90°) and balanced outputs has proved more difficult, requiring precise control of differential phase delays.1 Various techniques have recently been proposed3,4 which achieve this by birefringence or mode coupling in a multiport coupler, and in all these the phase relationship of the outputs is determined by coupling in the fiber system.

Illuminating a Scanning Ripple for Flat-Panel 3-D

A surface ripple moving across a sheet of reflective film can be illuminated by a one-line video projector in order to create a flat panel pixelated image. The concept can be extended to create 3-D autostereoscopic images on large screens with wide fields of view. The initial results of two prototypes are presented.

A software interface for an industrial control network using the CAN protocol

The band period of a controller area network (CAN) interface written in software cannot be less than the time taken for a bit move, bit comparison and count with branch. Such an interface has been demonstrated, and baud rates of 0.5 MHz may be possible.

Parallel image generation for a 3D display

Two viewing models for an experimental three-dimensional display are presented. Two alternative projections were tried. These are parallel oblique and perspective oblique, and they place different requirements on the 3-D display hardware. The parallel oblique projections may produce a jagged effect when P is small but will correctly maintain the horizontal parallax effect for a range of distances between screen and viewer. With the aid of parallel processing the time required to change the 3-D image will be comparable with the time taken to alter the image on a conventional display.<<ETX>>

Overmoded Fibre For Multiport Coherent Detection

Combining appropriate zero-order and first-order fields in an overmoded optical fibre, produces an offset intensity distribution whose radial position varies with their relative phase and polarization. This may be used to achieve phase (or polarization) diversity detection in a coherent optical receiver, by detection of this intensity distribution on a four segment photodetector. In-phase and Quadrature signals (or orthogonally polarized signals) are produced from each diametrically opposed pair of photodiode segments.