Abstract: Optical imaging system between an object plane (2.2) of a total reflexion prism (2) and an image plane, mainly for a fingerprint reading apparatus, that comprises an optics (3) for imaging the object plane to the image plane, and an electronic image detector (4) in the image plane. The optics defines an optical axis (3.0) and input and output pupils, respectively. The total reflexion prism (2) is arranged in front of the input pupil of the optics (3). The prism has a first surface receiving light for illuminating the object plane through the interior of the prism and a further surface through which light reflected from the object plane passes towards the optics. The object plane closes an angle with the optical axis, which is preferably between 45.degree. and 65.degree. if the refraction index of the prism is between 1.5 and 1.85. The object plane (2.2) of the total reflexion prism (2) is offset relative to the optical axis (3.

Abstract: A method for recording character or marking signals by multi-beam laser technique, in which the characters are recorded in multi-rastered bands in such a way that the character information is inverted, whereby the recording surface is illuminated by the laser beams at each location that do not comprise characters or marks. In character locations the surface is not illuminated. The gaps between adjacent bands are illuminated by separate band gap illuminating laser beams. By using this method the electrophotographic image recording can be solved by means of conventional inexpensive positive copiers in which image reversal does not take place. The apparatus for carrying out the method comprises a Bragg cell, a control unit for producing several raster scanning laser beams, and oscillators for generating additional band gap illuminating laser beams. An inverting unit is inserted in the path between the information source and the control unit to perform electronic image reversal.

Abstract: A circuit arrangement for controlling a multi-beam acousto-optical cell in which Bragg diffraction is used for the generation of a plurality of outgoing laser beams, in which the acousto-optical cell has at least one ultrasonic transducer from which the outgoing laser beams are coming out in a common plane, the circuit arrangement comprises VHF or UHF oscillators coupled through respective control stages to the ultrasonic transducers. The frequency of each oscillator defines the diffraction angle of an associated outgoing laser beam the intensity of which is dependent from the amplitude of the oscillator. The passage of the oscillator outputs towards the respective ultrasonic transducers is controlled by the control stages according to predetermined operational requirements.

Abstract: A laser-operated apparatus for data and signaling recording makes use of a laser-beam source whose laser beam is directed at the Bragg angle into a tellurium dioxide monocrystal provided with an array of ultrasonic transducers, each of which is energized independently by at least one amplitude modulated very high frequency carrier. The individual transducer segments generate respective beams within the body of the crystal which, upon emerging, represent individual information channels which are separately controllable to provide the data and information recordal.