Abstract: The present invention is directed to an optical system for measuring the rotation angle of rotatable object having a rotation shaft (2), which system comprises a reflective diffraction element (6) mounted on said shaft and a module that includes a radiation source (8) emitting a monochromatic beam (bo) towards this element and a radiation-sensitive detection structure (14, 16), the diffraction element is configured to project diffraction order images (18) of its pattern onto associated sections (50(1)-54(2)) of an annular grating structure forming part of the detection structure and the surface size of the diffraction element is smaller than 20% of the surface size of the annular grating structure.

Abstract: The present invention is directed to an optical system for measuring the rotation angle of rotatable object having a rotation shaft (2), which system comprises a reflective diffraction element (6) mounted on said shaft and a module that includes a radiation source (8) emitting a monochromatic beam (bo) towards this element and a radiation-sensitive detection structure (14, 16), the diffraction element is configured to project diffraction order images (18) of its pattern onto associated sections (50(1)-54(2)) of an annular grating structure forming part of the detection structure and the surface size of the diffraction element is smaller than 20% of the surface size of the annular grating structure.

Abstract: A method for removing residues of molding material from metal parts of plastic packages of semiconductor devices includes applying first and second pulsed laser radiations to at least one surface region of a metal part covered with residues of molding material. The first pulsed laser radiation has a first wavelength that is absorbed by residues of molding material having a thickness greater than a prescribed thickness. The intensity and the duration of the first pulsed laser radiation causes the residues to be directly attacked. The second pulsed laser radiation has a second wavelength so that residues of molding material having a thickness less than the prescribed value are at least partially transparent and the metal parts are at least partially absorbent. The intensity and the duration of the second pulsed laser radiation causes the formation of plasma at the point of impact with the metal part.