In January 1984, a United Kingdom Joint Opto-Electronics Research Scheme (JOERS) on LiNbO3 technology for integrated optics commenced. This 65 man-year programme, which ended in April 1987, was undertaken jointly by four industrial companies and four universities, representing almost all of the LiNbO3 integrated optics expertise in the U.K. at that time. The aim of the programme was twofold: to develop high quality LiNbO3 wafers for integrated optics applications through close collaboration between the material manufacturers and the material users and to establish a strong technology base in device design and fabrication. This paper outlines some of the main achievements of the programme. Topics covered include work on LiNbO3 material optimisation, waveguide fabrication technology (Ti-indiffused, proton-exchanged, and ion-implanted waveguides), and waveguide interconnection technology (low loss curves, modal profile variation), and fibre-guide coupling.

Equation (2) should read as follows: (SNR)2 = K1Are + K2 .

The Optical Engineering editorial schedule for 1988, which appears on this page, lists the titles of the special issues that have been lined up at the present time. As can be seen, these special issues will once again address a variety of important and timely topics. This issue leads off 1988 with a special issue reporting on industrial optics in the U.K., with co-guest editors Chris Dainty and Lionel Baker. The February issue, which will be a somewhat smaller version of an issue that had originally been intended for November of 1987, will address the subject of optomechanical engineering, and Dan Vukobratovich will act as guest editor.

Image Recovery: Theory and Application-Reviewed by Andrew G. Tescher; Gas Flow and Chemical Lasers-Reviewed by R.A. Meinzer; Elements of Solid State Physics-Reviewed by H.Y. Fan

A coherent optical radar is described. The transmitter is a continuous wave (cw) carbon dioxide laser scanned over a 25 mrad x 25 mrad field of view. Radiation scattered by targets within the field is coherently detected by the system, allowing Doppler shifts to be measured. After processing, the detected signals are displayed on a monitor, with target velocity colour coded. Examples of the images obtained to date are given, along with typical detector output signals. The results of some preliminary work on frequency-modulated continuous wave techniques, which allow both target range and velocity to be extracted, are also given.

Projection TV sets for the consumer market, with picture diagonals of 37 to 50 in., are being significantly improved in brightness and resolution by advances in the optical components. In the longer term, the cathode ray tube projector is likely to be replaced by a system using liquid crystal light valves.

The wavelength-dependent transmission characteristics of optical fibre sensor systems are analyzed and measured experimentally, and conditions under which they may be reduced to a minimum are established.

In this paper we consider digital and analogue implementations of optical associative memories. Both techniques rely on the holographic manipulation of optical information. In the digital scheme, which is based on an optical version of the Hopfield model, computer-generated holograms achieve this, whilst for the analogue processor, Fourier transform holograms are used. We discuss how these primitive associative memory systems could be extended to incorporate the learning algorithms required by the more flexible, and useful, neural network architectures.

High efficiency optical logic devices and interconnect elements are required for digital optical experiments. Nonlinear interference filters, capable of acting as optical gates, have been demonstrated to switch with ~2 mW input power and ~50 us recovery time. Switch contrast of 20:1 has been achieved with multicavity designs. Switch energies for micrometre-dimension transversely isolated pixels of <25 pJ are predicted. Holographic input and interconnect components with >90% diffraction efficiencies have been fabricated in dichromated gelatin and assessed.

We report a characterisation technique for both amplitude and phase variations of polished fibre half-couplers in the proximity of variable index bulk overlays. Experimental results are compared with simple theoretical models. In addition, simple derivative fibre-based devices are reported. Amplitude measurements were performed using a single fibre embedded in a block with a 25 cm radius groove, polished to within 1um of the core. A linear (in decibels) change in attenuation resulted for overlay indices greater than the effective mode index. An attenuation change of 40 dB was observed for a 0.0026 change in index. To observe phase changes, an interferometric approach was taken. Two fibres were embedded, one above the other, in a block identical to that above. The core of the top fibre only was exposed by polishing. Low loss 50:50 fused taper couplers were spliced to both sides of the block, forming a fibre Mach-Zehnder interferometer. For overlay indices less than the effective mode index, a phase change of rad was observed for an index change of 0.0045, with an interaction length of 700um.

A new optical method for determining film thickness is described in which a set of measured transmittance values for a sample of unknown thickness is correlated with sets of transmittance values predicted for different known thicknesses. A reiterative calculation is used to determine the thickness for which the predicted and measured values yield an optimum correlation. The method is particularly suited to on-line use in a film production process, where the sample is moving and cannot be contacted. The predicted transmittance values may be based on a model involving either absorption or interference. A simple, robust optical system can be used, even when using an interference-based model capable of X/100 accuracy. Criteria for selection of measurement wavelengths and bandwidths are outlined, and strategies for the reiterative calculation sequence are explained.

Holography has recently achieved new importance as a means of providing the data necessary for the development and validation of computer models. Increasingly, design work is being performed through the application of complicated three-dimensional models to gas flow prediction and the use of finite-element models for investigation of mechanical behaviour and stress. This paper reviews the many applications of holography that have been developed at Rolls-Royce over the past 20 years. These cover all of the major fields within holographic interferometry; flow visualisation, nondestructive testing, vibration analysis, and holographic contouring. Of equal interest with the techniques themselves are the problems encountered and overcome in applying these techniques in a demanding and at times hostile industrial environment away from the laboratory. The extensive use of high-power pulsed lasers has greatly facilitated this move and has allowed holography to be used routinely in normal component test areas.

A Fabry-Perot interferometric system coupled to an image intensifier camera has been evolved for the imaging spectroscopy of extended astronomical objects. The instrument is compact, lightweight, and ideally suited for small telescopes. Details of the instrument are discussed, its performance is evaluated, and preliminary results are presented.

We describe a real-time method for measuring the spatial frequency response of a phase-modulating spatial light modulator (SLM). The measurement involves illuminating the SLM with a chirp test signal. Data extraction is done with a linear CCD array after spatial filtering of the readout light. The method was tested on a deformable elastomeric SLM, and the results show good agreement with those obtained by the conventional point-by-point method. We present the mathematical formulation of the method and describe the experimental setup and results.

The extended infrared celestial emission is due to three main sources: zodiacal dust, large discrete objects in the galaxy, and inter-stellar dust. As viewed from earth orbit, the thermal reradiation of sunlight absorbed by dust in the solar system produces a pervasive IR background that peaks roughly along the ecliptic plane, where the density of dust is highest. Much-smaller-scale structure has also been ob-served in both the visual and infrared. Between 7 and 30 Am, H II regions are the brightest discrete objects in the galaxy. Dust mixed with and sur-rounding gas ionized by the embedded hot star(s) absorbs the visible and ultraviolet stellar radiation and re-emits the energy in the infrared. These regions are large and if close to the sun can subtend significant angular areas of sky. The emission from the interstellar dust produces a filamentary background that is consistent with dust in thermal equilibrium with the interstellar radiation field at far-IR wavelengths. An additional emission mechanism is needed, however, to account for the shorter-wavelength observations. The galactic sources combine along the line of sight to produce an intense band of emission, centered on the galactic plane. Structure in all of these backgrounds creates a clutter problem for an orbiting IR telescope.

Measurement of the line spread function of a black slit against an extended illuminated background detects the existence of stray light in the measured system. This method is useful for imaging systems since it is directly related to the modulation transfer function. The method is described in detail, a figure of merit is introduced, and an example of the use of the method is shown.