Abstract: Compound surfaces of a test object are interferometrically measured by a multi-beam probe. One of two measuring beams emerges from the probe at a fixed angle for measuring one of the compound surfaces, and the other measuring beam emerges from the probe at a variable angle for measuring a plurality of other compound surfaces.

Abstract: A double mirror objective lens system uses a three optical surface refractor incorporating a convex mirror into a right surface thereof that reflects incident light to a concave mirror, which reflects the light back through the refractor and on toward a focal point of the system. This arrangement yields better resolution images with low spherical aberration, minimal chromatic aberration, and long working distance. A variation of the invention includes another refractor, a right surface of which carries the concave mirror to form a Mangin mirror. This variation on of the invention has even less aberration over increased wavelength range due to better corrected chromatic aberration.

Abstract: A moiré interferometer has an illumination system and an imaging system that share a common focusing optic, which preferably takes the form of a concave mirror. Within the illumination system, the common focusing optic collimates light en route to a test surface. Within the imaging system, the common focusing optic telecentrically images a grating pattern appearing on the test surface onto a fringe pattern detector.

Abstract: A speckle reduction system divides pulses of coherent radiation into successions of temporally separated and spatially aberrated pulselets. One or more beamsplitters divide the pulses into the successions of pulselets that are circulated through delay lines. Spatial aberrators located along the delay lines modify wavefront shapes of the pulselets. Together, the temporal separation and spatial aberration of the pulselets produce a succession of different speckle patterns that can be averaged together within the integration interval of a detector to reduce speckle contrast.

Abstract: Toric surfaces are mounted on a transparent support plate and measured at grazing incidence using a pair of leading and following diffractive optics for diffracting a test beam with respect to a reference beam. The leading diffractive optic diffracts rays of the test beam through various diffraction angles so that after passing through the transparent support plate, the rays strike the toric surface at a constant grazing angle. The following diffractive optic further diffracts the rays of the test beam through other diffraction angles into realignment with the reference beam.

Abstract: Toric surfaces are mounted on a transparent support plate and measured at grazing incidence using a pair of leading and following diffractive optics for diffracting a test beam with respect to a reference beam. The leading diffractive optic diffracts rays of the test beam through various diffraction angles so that after passing through the transparent support plate, the rays strike the toric surface at a constant grazing angle. The following diffractive optic further diffracts the rays of the test beam through other diffraction angles into realignment with the reference beam.

Abstract: A reduction photolithographic scanning system uses a reduction lens with a circular image field that is shaped to an irregular hexagonal configuration affording different effective scanning widths so that the full area of a microcircuit image can be scanned onto a substrate in an integer number of overlapping scans. This minimizes the number of scans required for each image area and maximizes the total image area that can be scanned per time unit.

Abstract: A grazing incidence interferometer includes an extended light source for limiting spatial coherence of reference and test beams. A test plate is oriented at a grazing incidence to the test beam so that a first portion of the test beam is reflected from the front surface of the test plate, a second portion of the test beam is reflected from the back surface of the test plate, and the two test beam portions are sheared with respect to each other. The spatial coherence of the test beam is related to the lateral shear between the first and second test beam portions to significantly reduce contrast of an interference fringe pattern between the front and back surfaces of the test plate.

Abstract: Thickness variations of semiconductor wafers are measured by interfering two beams of infrared light that are relatively modified by reflections from opposite side surfaces of the wafers. Non-null interferometric measurements are made by illuminating the wafers with diverging beams and subtracting errors caused by varying angles of incidence. Null interferometric measurements are made of both thickness variations and flatness. Infrared light, which can transmit through the wafers, is used for measuring thickness variations; and visible light, which cannot transmit through the wafers, is used for simultaneously measuring flatness.

Abstract: An interferometer (10) employs diffractive optics (30 and 40) for measuring errors in test surfaces (14) that differ from planes and spheres. A beam of light (28) having a planar shape is separated into two portions (32 and 34). One of the diffractive optics (30) can be used to reshape the second portion (34) of a beam of light (28) into a non-planar shape along a path of grazing incidence to the test surface (14), and the other diffractive optic (40) can be used to further reshape the second portion (34) back into a planar shape in common with the first portion (32) of the beam of light (28). The two planar beam portions (32 and 34) are recombined to produce an interference pattern (44) representing the errors in the test surface (14).

Abstract: Toric surfaces are mounted on a transparent support plate and measured at grazing incidence using a pair of leading and following diffractive optics for diffracting a test beam with respect to a reference beam. The leading diffractive optic diffracts rays of the test beam through various diffraction angles so that after passing through the transparent support plate, the rays strike the toric surface at a constant grazing angle. The following diffractive optic further diffracts the rays of the test beam through other diffraction angles into realignment with the reference beam.

Abstract: Compound diffractive optics are used in an interferometer for simultaneously measuring multiple surfaces, making multiple measurements of individual surfaces, conveying test beams multiple times, and aligning pairs of the diffractive optics with each other. Typically, the compound optics have multiple diffraction zones that reshape test beams for reflecting from test surfaces or for combining with reference beams. The multiple diffraction zones can also exhibit different optical qualities such as transmission and reflection for conveying the test beams to and from the test surfaces.

Abstract: Cylindrical surfaces of a test cylinder are measured with a grazing incidence interferometer. Separate measures of a test cylinder's cylindrical surface and a master cylinder's surface are made and compared to obtain absolute measures of the test cylinder's surface. Surface fitting techniques are used to discount the effects of positioning errors, and a separate measurement is used to resolve remaining ambiguities for extending the range of test cylinder sizes that can be measured with absolute dimensions.

Abstract: A catadioptric imaging system for an interferometer includes a beamsplitter plate for reflecting a beam of light to a concave mirror for transmitting reflected light from the mirror. The beamsplitter reflections and transmissions produce opposite sign spherical aberrations. A refractive optic is located between the beamsplitter plate and a convex test surface for removing residual spherical aberrations and for permitting more variability in the positioning of the beamsplitter plate. Design variables for both the refractive optic and the position of the beamsplitter plate can be used to adjust a numerical aperture of the beam approaching the test surface. The refractive optic can also be used as a Fizeau objective to further reduce errors in the imaging system.

Abstract: An object fringe pattern is distinguished from other fringe patterns in an interferogram produced by an interferometer using a pair of diffraction gratings for separating and recombining test and reference beams. The object on which a test beam is grazingly incident is moved in X and Y directions in a plane perpendicular to an optical axis of the interferometer to change the brightness regions of the object fringe pattern. A computer identifies pixels whose irradiance changes in response to object movement, and then only irradiance data from the identified pixels is used in analyzing the interferogram to produce a measurement of a surface of the object.

Abstract: Test surfaces are measured at grazing incidence with an interferometer using diffractive optics for manipulating reference and test beams. A leading diffractive optic separates the reference and test beams, and a following diffractive optic recombines the beams after the test beam is reflected from the test surface. Extraneous light, including light from other orders of diffraction, is isolated and blocked from combining with test and reference wavefronts.

Abstract: An object fixturing system applies to an interferometer having a pair of diffraction gratings arranged to produce and recombine test and reference beams. The fixturing system positions an object between the diffraction gratings so that a test beam is incident on a surface of the object at a grazing incidence angle. A positioning fixture engages the object and a reference surface of the interferometer in moving the object to a measurement position on a window platform that transmits the test and reference beams. The fixture is then removed for a simultaneous measurement of an entire surface of the object, which can be clamped in place if necessary by a clamping window that also transmits the test and reference beams.

Abstract: An interferometer (10) employs diffractive optics (30 and 40) for measuring errors in test surfaces (14) that differ from planes and spheres. A beam of light (28) is separated into two portions (32 and 34). One of the diffractive optics (30) can be used to reshape the second portion (34) of a beam of light (28) into a form that is different than the first portion (32) along a path of grazing incidence to the test surface (14), and the other diffractive optic (40) can be used to further reshape the second portion (34) into a form in common with the first portion (32) of the beam of light (28). The two beam portions (32 and 34) are recombined to produce an interference pattern (44) representing the errors in the test surface (14).

Abstract: A catadioptric reduction system operating in the deep ultraviolet range projects a reduced image of a mask on a substrate. A reducing optic made of a material transmissive to deep ultraviolet light has a concave front face covered by a partially reflective surface and a convex back face covered by a concave reflective surface surrounding a central aperture. The partially reflective surface transmits a portion of the light passing through the mask to the concave reflecting surface, which returns a portion of the transmitted light to the partially reflective surface. A portion of the returned light is reflected by the partially reflective surface on a converging path through said central aperture for producing a reduced image of the mask on the substrate.

Abstract: An interferometer (10) includes a prism extender (50) appended to a prism (32) for directing a beam of light (42) into a recess (44) of a test piece (34). A first portion (42a) of the beam (42) refracts from a reference surface (54) of the prism extender (50) to an angle (.alpha.) of grazing incidence on a bottom surface (46) of the recess (44), and a second portion (42b) of the beam (42) reflects from the reference surface (54). The two portions (42 aand 42b) of the beam (42) recombine at the reference surface (54) forming an interference pattern indicative of differences between the reference surface (54) and the bottom surface (46) of the recess (44).