B. Bates

Liquid-crystal television optical gates applied to real-time speckle metrology

Abstract The performance of several optical logic gates implemented with liquid-crystal televisions (LCTVs) is discussed. A description is given of an optical OR gate constructed with three LCTVs which has potential for speckle metrology. Using this optical gate together with a standard optical processor, the fringes produced by an in-plane displacement of an object are displayed on an additional LCTV and the correlation spots which result may be observed directly. Examples are given of the application of the system to the real-time (video rate) display of object motion.

Astronomical spectrophotometry with an acoustooptic filter photometer.

A novel astronomical spectrophotometer has been constructed which uses an acoustooptic filter under the programmable control of a microcomputer for spectral scanning. A brief outline of the spectrophotometer and relevant filter characteristics is given, and results of first astronomical trials are used to discuss instrument performance and the relative merits of the technique for application to astronomical spectrophotometry.

The determination of element abundances in the solar neighborhood from B-type stellar spectra. I: Argon

The coude spectrograph and CCD camera on the coude feed telescope at the Kitt Peak National Observatory, have been used to obtain high-resolution (0.09 A FWHM), high signal-to-noise (200) observations of weak A II absorption lines formed in the atmospheres of main-sequence early-type stars. These have been analyzed using LTE model atmosphere techniques to derive a mean argon-to-hydrogen abundance ratio of 6.49, which is believed to be accurate to + or - 0.1 dex. As the stellar atmospheres should be uncontaminated by the products of interior reactions, this abundance should be that of the interstellar medium from which the stars formed some 1-10 million yrs ago, and hence reflects the current chemical composition of the solar neighborhood. The result is compatible with that of Veck and Parkinson (1981). 45 refs.

Interferometer-grating spectrograph for high resolution astronomical spectroscopy in the middle uv

A high resolution spectrograph is described, which is to be used for a program of uv astronomical spectroscopy from a moderately stabilized, star pointing balloon-borne platform. A spectral resolving power >10(5) is achieved using an optically contacted Fabry-Perot interferometer in crossed dispersion with a grating order sorter.

Programmable liquid-crystal TV spatial light modulator: modified drive electronics to improve device performance for spatial-light-modulation operation

Liquid crystal television (LCTV) continues to play a useful role as a spatial light modulator in the development and evaluation of systems for optical image processing. We outline new addressing electronics developed for a commercially available LCTV that permit writing to individual pixels at an improved display up-date rate and allow the input video signal to cover a much greater transmittance range of the TV display for black and white pixels. We illustrate this by measuring the diffraction efficiency for gratings written onto the display. For vertical gratings written along the display columns the diffraction efficiency is increased significantly, but there is no improvement for horizontal gratings. Some merits of the modified LCTV modulator for optical processing applications are considered briefly.

Binary phase modulation properties of a programmable liquid-crystal television display.

Programmable display electronics developed for a commercial liquid-crystal television resulted in an improved binary phase diffraction efficiency performance for spatial light modulation applications.

Acoustooptic filters for astronomical photometry: design and fabrication

Using calculations based on the acoustooptic properties of the crystal material a procedure is outlined for the design of filters having a particular bandwidth specification and reduced sensitivity to the incidence angle of the input beam. Relevant aspects of the fabrication techniques are given. The optical performance of a prototype filter having a 0.5-2-nm bandwidth over the 400-700-nm tuning range based on the design methods outlined is satisfactory for the chosen application, but it is not optimum. Analysis of experimental and design data shows that this can be accounted for by an error in the specified angle of the crystal axis which is required to accuracy of some +/-0 5 degrees .

Optical properties of multilayer overcoated aluminum films in the uv (2000–2500 Å)

Optical properties of high reflectance, low absorptance coatings consisting of aluminum films overcoated with multilayers of Al(2)O(3) and MgF(2) are reported in the far ultraviolet. Coating design considerations and preparation techniques are described and the potential of such reflectors for multiple-beam interferometry is considered. Transmission characteristics of experimental Fabry-Perot type interference filters constructed from these Al-multilayer coatings are discussed.

H i and optical spectroscopy towards the M15 intermediate-velocity cloud

We present echelle spectrograph observations in NaD, at resolutions of 6.2-8.5 km/s, for 11 stars located in the line-of-sight to the M15 intermediate velocity cloud, which has a radial velocity of 70 km/s. This cloud is a part of IVC Complex gp. The targets range in magnitude from V=13.3-14.8. Seven of the observed stars are in the M15 globular cluster, the remaining four being field stars. Column density ratios of log(N cm^-2)=11.8-12.5 are derived. Combining the current sightlines with previously-existing data, we find the NaD/HI ratio in the IVC varies by upto a factor of 25. One cluster star, M15 ZNG-1, was also observed in Calcium. We find N(CaI)/N(CaII)<0.03 and NaI/CaII=0.25, similar to values seen in the local ISM. Finally, we detect tentative evidence for IV absorption in KI towards 3 cluster stars.

Liquid crystal TVs in speckle metrology: optimum conditions for bipolar phase modulation

Operating conditions for using a LCTV in the bipolar phase mode are discussed showing that optimum performance is obtained when the interpixel transmitted light contribution is effectively reduced to zero.