Abstract: An apparatus for the mounting of semiconductor chips comprises a bondhead with a pick-up tool with a longitudinal drill hole to which vacuum can be applied for the gripping and transport of a semiconductor chip. To detect whether the pick-up tool has gripped the semiconductor chip, a body with a reflecting surface is arranged in the longitudinal drill hole of the pick-up tool which, when passing over the light source on absence of the semiconductor chip deflects light shining from underneath into the longitudinal drill hole of the pick-up tool into a horizontal plane. The pick-up tool has locations which are pervious to the deflected light of the light source. At least one optical element is arranged on the bondhead which concentrates at least part of the deflected light emerging laterally from the pick-up tool onto a photosensor.

Abstract: An apparatus for the mounting of semiconductor chips comprises a bondhead with a pick-up tool with a longitudinal drill hole to which vacuum can be applied for the gripping and transport of a semiconductor chip. To detect whether the pick-up tool has gripped the semiconductor chip, a body with a reflecting surface is arranged in the longitudinal drill hole of the pick-up tool which, when passing over the light source on absence of the semiconductor chip deflects light shining from underneath into the longitudinal drill hole of the pick-up tool into a horizontal plane. The pick-up tool has locations which are pervious to the deflected light of the light source. At least one optical element is arranged on the bondhead which concentrates at least part of the deflected light emerging laterally from the pick-up tool onto a photosensor.

Abstract: A carrier for display fields or value characters, such as a credit card, contains optically readable display fields which can be erased by the effects of heat or which can at least be changed permanently in optical terms, and a storage layer for storing energy for the purpose of producing the thermal energy required for the heating effect at the location of the display field to be erased. In this way, the energy stored in the storage layer, which energy corresponds to at least the erase energy required, is released by the supply of an initial energy which is less than the erase energy. If a photoconductive layer is used additionally, the reading light beam can also serve to produce a local electrical current I in the region of the display field to be erased, wherein the current I produces sufficient thermal energy in the form of initial energy to set in notion the reaction process in the storage layer and to release the thermal energy stored therein.

Abstract: A spectrophotometer useful for measuring absorption or emission bands of a substance irradiated with optical radiation, comprises a light source for producing the optical radiation, a monochromator for isolating light of wavelength (W) from the optical radiation and which modulates the wavelength (W) by a predetermined wavelength amplitude (.delta.W), and a photodetector for detecting the intensity of light passing through the monochromator and for producing a measuring signal in response thereto. The monochromator operates under the control of an electronic control unit which produces a control signal that causes the monochromator to scan across a portion of the spectrum of the optical radiation at a frequency (f.sub.2) to transmit a narrow band of radiation at the wavelength (W). The control unit includes a modulation generator which produces a signal that causes the monochromator to modulate the wavelength (W) by the predetermined wavelength amplitude (.delta.W) at a frequency (f.sub.1).