Abstract: Two identical test patterns are overlaid upon each other on a planar substrate of semiconductor material A. Each pattern consists of a plurality of spaced parallel lines. The lines are arranged in two sets of horizontal lines and two sets of vertical lines. The line/space periodicity is known. The lines of the two test patterns are made of two different materials, B and C, respectively. Thus, the target pattern formed by the two test patterns and the substrate has four reflecting regions defined by the different layers in each region: A, AB, AC and ABC. Adjacent the overlaid patterns are four macro-zones each containing a different one of the four layers, A, AB, AC and ABC. Each macro-zone is illuminated by a broad spectrum light, such as that from an incandescent lamp, and the reflected light intensity from each macro-zone is measured. Then, the reflected light intensities from the two sets of horizontal lines are separately measured, as are the reflected intensities from the two sets of vertical lines.

Abstract: Apparatus for producing a line source of a desired shape from a light source such as an excimer laser comprising means for directing the light source along a predetermined path to a cylindrical lens positioned to produce a virtual line image having uniform intensity along its length at a first location. However, the image is intercepted by a cylindrical mirror inclined at an angle so that the beam is transformed into a curved shape and directed onto a quartz diffuser. This apparatus produces a curved self-luminous distribution having uniform intensity over its length. In a specific embodiment, the diffuser is a directional diffuser.

Abstract: This is a vacuum clamp for holding workpieces which assures that the workpiece is held without distortion. This is accomplished by providing a fixed support, with a convex surface, and a flexible seal around the fixed support so that when a vacuum is drawn within the seal the workpiece being held abuts the fixed support tangentially. The convex surface of the support does not force the workpiece to conform to the surface of the support as it would if the surface of the support were flat.