Abstract: Method and apparatus for forming an image of an object by optical projection with a focusing system comprising the steps of collimating a set of at least two mutually incoherent light beams from the light source to fall on the object from directions that makes the non-diffracted components intersect the aperture stop at a set of points that are distributed over the surface of the stop, attenuating in a spatial filter the zero diffraction order of each beam relative to diffraction orders diffracted in directions towards the centre of the aperture stop, and adding the images formed by the light beams.

Abstract: In an ellipsometric method and apparatus which, in order to increase the degree of measuring accuracy, uses the principle of comparative ellipsometry in measuring a characteristic such as a layer thickness, a reference surface is divided into first and second equal surface portions with respectively different reflection characteristics which are in substantially symmetrical relationship to the reflection characteristics of the testpiece, the surface portions preferably comprising two different tapering surface layers extending in parallel relationship to each other.

Abstract: An ellipsometric method and apparatus for studying physical properties of a testpiece provides that during the measuring operation the angular positions of a polarizing means and an analyzing means disposed upstream and downstream of the testpiece remain fixed. Two or more discrete, mutually different predetermined states of polarization of the radiation employed are produced between the polarizing means and the testpiece and/or between the testpiece and the analyzing means, by polarization modulating elements which are disposed in the path of the radiation. In each discrete state of polarization, the intensity of the radiation which is polarized in the analyzer is measured and evaluated for determining the polarization properties of the testpiece in a computer.

Abstract: In a method and apparatus for studying surface properties of a testpiece, such as refractive index or thickness of a layer or film on said surface, electromagnetic radiation is directed on to the test surface or a reference surface which has known properties, and reflected on to the other surface. The angle of incidence in respect of the incident radiation, in relation to the respective surfaces, are the same, and the surfaces are so arranged that when the radiation is reflected from one surface on to the other, the parallel polarization component of the first reflection is the perpendicular component of the second reflection. Radiation in the same state of polarization as before the first reflection is extinguished by an analyzer, providing for point-to-point comparison between the two surfaces.