The Isodensitracer is a two-dimensional, scanning microdensitometer which rapidly produces density "contours" by means of a cyclic dropped line code. For more than three years this instrument has proven its utility for making rapid photometric and geometric analyses of photographic imagery for such diverse applications as moon mapping, spectrum analysis, and medical X-ray interpretation.

The properties of zone plates with different boundary shapes are considered. These shapes are discussed as special cases of the super ellipse. For each case the Fresnel-Kirchhoff diffraction integral is numerically evaluated. It is shown that an elliptical zone plate yields an astigmatic image with axial intensity peaks corresponding to the semi-major and semi-minor axes. In the case of the super ellipse, an additional peak proportional to the square of the diagonal length is obtained. The results were experimentally confirmed in the elliptical case.

The high radiometric sensitivity of the image orthicon and the digital video signal processing have made the image tube very valuable for measuring positions versus time, spectral dispersion, and radiometric data on space objects and missiles. In order to derive meaningful data, assessment and calibration of critical tube parameters are necessary. Some examples are given, and test methods and results described.

The spatial frequency response of a CRT flying-spot-scanner system is discussed and film plane modulation response is calculated for response to periodic sine wave, square wave, and isolated Gaussian line signals on the input film. The effects of digital sampling on the spatial frequency response of a digital flying-spot-scanner are also derived from the digital sampling theory. The modulation response is then presented in terms of the film plane parameters for both analog and digital scanning systems and parametric trade-offs are discussed in terms of meeting performance requirements.