Abstract: A wavefront tilt measurement system for measuring the wavefront tilt of light passing through transmitting or receiving optical systems, the optical systems including a primary aperture and internal optical elements defining an optical system focal plane. A light source emits light at the optical system focal plane towards the internal optical elements such that light from the light source emerges from the primary aperture. A plurality of tilt sensors are disposed adjacent to the primary aperture to receive light emerging from the primary aperture. Each tilt sensor includes a sensor focal plane and a plurality of detector elements. Each tilt sensor generates at the focal plane a plurality of overlapping regions of zero and first order images of light emerging from the primary aperture. The measured intensity of light in the overlapping regions is used to determine the wavefront tilt of light emerging from the primary aperture.

Abstract: A wavefront tilt measurement system for measuring the wavefront tilt of light passing through transmitting or receiving optical systems, the optical systems including a primary aperture and internal optical elements defining an optical system focal plane. A light source emits light at the optical system focal plane towards the internal optical elements such that light from the light source emerges from the primary aperture. A plurality of tilt sensors are disposed adjacent to the primary aperture to receive light emerging from the primary aperture. Each tilt sensor includes a sensor focal plane and a plurality of detector elements. Each tilt sensor generates at the focal plane a plurality of overlapping regions of zero and first order images of light emerging from the primary aperture. The measured intensity of light in the overlapping regions is used to determine the wavefront tilt of light emerging from the primary aperture.

Abstract: A high speed high resolution spectral sensor is formed by placing a cascade of chained wide field-of-view Mach-Zender interferometers inside a dispersive sensor between the sensor's grating and the focusing lens. Also is disclosed an optical filter with wide field-of-view capabilities. Such a filter is formed by inserting a plurality of gap plates of certain thicknesses and refractive indices. The invention provides formulas for calculation of optimal dimensions for such gap plates.

Abstract: A hardware system is disclosed for detecting alignment marks on a substrate in connection with electron beam lithography. The system is considerably faster than prior software approaches. A scanning signal derived from backscattered electrons as the beam scans the substrate is stored and updated in a set of shift registers as scanning proceeds. The signals in the scanning shift registers are compared with a predetermined reference signal, corresponding to the expected scanning signal when the beam traverses an edge of an alignment mark, stored in another set of shift registers. A correlation is obtained between the scanning and reference signals by multiplying the values of the corresponding cells in the scanning and reference registers, and accumulating and weighting the result. The locations of the maximum positive and negative correlations, and hence the locations of the opposed edges of the alignment mark, are obtained by means of a timing mechanism coordinated with the scanning.

Abstract: A surface acoustic wave device wherein a reflective array is disposed on a surface of material capable of supporting propagating surface acoustic wave energy, the array including a plurality of spaced, parallel elements having longitudinal axes angularly oriented with respect to the direction of a beam path of propagating straight crested phase fronts, the device also including matching structures disposed adjacent the leading and trailing ends of the elements for converting the normal mode, straight crested phase front outside the reflective array region to the normal mode, sawtoothed shaped, phase front within the reflective array region, and the reverse thereof, and thereby avoid diffractive effects at the entry and exit points of the reflective array.

Abstract: A surface acoustic wave device for use as an amplifier or convolver, or the like, and incorporating a plurality of parallel, spaced rails disposed between and separating a semiconductor slab and a surface acoustic wave propagating planar surface of a piezoelectric substrate a relatively small but finite distance apart, the rails having longitudinal axes aligned with the propagation beam path by and between a pair of spaced electro-acoustic transducers disposed on the substrate.

Abstract: A surface acoustic wave device including a synchronous reflection array disposed in a delay line between the input and output transducers, the synchronous reflection array having a synchronous reflection frequency that distorts the beam profile of propagating surface acoustic wave energy in the delay line so that when the beam profile is amplitude averaged at the output transducer, the transducer output signal has a relatively deep notch in amplitude at the synchronous reflection frequency.

Abstract: A temperature stable surface acoustic wave device utilizing reflective gratings in a material such as Y-cut quartz having two propagation directions in which the temperature coefficients of delay are of opposite sign, the gratings reflecting the Rayleigh waves in the two propagation directions along suitable path lengths to provide a total linear zero temperature coefficient of delay. A temperature stable oscillator is formed by providing an amplifier in a feedback path from the output transducer to the input transducer of the surface acoustic wave device.

Abstract: Signal processing apparatus wherein true correlation or convolution of signals is obtained by a third order nonlinear parametric acoustic wave interaction in a piezoelectric medium.