Showing papers on "Aerial image published in 1977"

High precision pattern registration and overlay measurement system and process

Abstract: A system for measuring the lateral displacement between edges located on two spaced apart objects, with a precision in the order of 1 microinch, generates and analyses the diffraction pattern produced by the physical edge on one object and the aerial image of the edge on the other object. The system can be used for the alignment of the objects or the comparison of patterns located on the objects.

Horizon projection device for aircraft simulator

Abstract: An horizon projection device for an aircraft simulator. The device comprises an aerial image 4 of a part of the Earth's surface, an optical image projector comprising a variable magnification system 13, an optical scanning device 18 and a wide angle projection lens 17. The optical system 13 forms in the focal plane of the wide angle lens 17 an intermediate image whose dimensions depend on the magnification. Controls responsive to the altitude, to the attitude and to the heading simulated by the pilot act on the magnification of the optical system 13, particularly to correct an apparent altitude variation due to the shift between the eyes of the pilot and the wide angle lens, during simulation of the aircraft going over on to its back.

Techniques And Applications Of Nonlinear Processing With Halftones

Abstract: Optical analog systems which are capable of doing nonlinear processing have potential application in several areas including equidensitometry and analog-to-digital conversion. One approach to nonlinear optical processing is derived from the idea of halftone printing. This approach to nonlinear processing requires custommade halftone screens. It is important to be able to produce such screens accurately and reproducibly. This paper describes a technique of making a binary-coded halftone screen. The desired continuous-tone screen is obtained as an aerial image by spatial filtering the binary mask. Techniques of microlithography have been advanced to such a state that it is possible to produce binary masks which cannot be adequately imaged by lenses. This paper discusses a method of circumventing this limitation. This is done by a means of self-imaging which incorporates the equivalent of low-pass spatial filtering.