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An autofocus system has been developed that automatically detects the presence of fringes in a white-light interference microscope and adjusts the vertical position of the microscope objective such that the focus error is minimal. The system consists of a motorized stage, a beam splitter, an optical detector, and associated electronics. In order for the interference microscope to provide accurate measurements of the optical wavefront, the error in the focus position must be small. The goal of this paper is to calculate the rms noise produced by the detector and electronics and use the results to predict the positioning error of the autofocus system.

A fog chamber, developed to support measurement of the performance of electrooptical devices in the presence of fog, is discussed. Rationale for the fog chamber concept is presented. Emphasis is placed on the theory of operation of the chamber, an optical method for assessing fog particle characteristics, and the optical properties of the different types of fog produced.

The authors have previously called attention to the importance of atmospheric and aerosol emission in IR imaging device performance. The present paper derives a more precise and general result than the empirically derived expressions in the earlier paper. The same general conclusion, that atmospheric and aerosol emissions are an important factor in IR imaging performance, is supported, assuming that the system is photon noise-limited.

Measurements of beams of ~1 μm in diameter are presented. Three approaches, one using a Ronchi ruling, the other two based on knife-edge scan techniques are compared experimentally. Effects of Ronchi ruling accuracy and nonconstant scan velocity are discussed. Included are results of theoretical studies on the effect of imperfect scanning edges and non-Gaussian beam profiles on measurement results.

The use of an astigmatic lens to generate a position error signal (PES) suitable for servo control is discussed. A simple computer model was written that can predict adequately the performance of an astigmatic system. The effect of various system parameters on the PES is presented.

This paper reviews various techniques for measuring the diameter of Gaussian beams and, in particular, those of ~1-μm diam. A description of measurement techniques for nonideal conditions is also included. A novel ruling used for beam-size measurement is discussed.

Fog spectral transmission data generated in the Electro-Optical Test Facility and propagation models usedm by the authors are presented. Preliminary results of a modeling effort are presented that support the following conclusions: (1) atmosphere emission is a major factor in IR system performance despite the fact it is commonly omitted; (2) the 3.5-4.1-microm interval offers superior performance to the 3-5 band at both relatively short and long ranges; and (3) the longer wavelength 9.5-11.5-microm band is superior to either the 3-5 or 3.5-4.1 bands in the presence of fog.