Abstract: A method and apparatus for repetitively imaging a mask pattern (C) on a substrate (W) are described. Various parameters of the apparatus and the projection lens system (PL) can be measured accurately and reliably and measuring devices of the apparatus can be calibrated by measuring a latent image of a mark by means of a scanning microscope (LID) forming a diffraction-limited radiation spot (Sp) on the photoresist layer on the substrate (W), in which layer the latent image is formed by means of a projection beam (PB).

Abstract: An optical reader for record carriers of a two types adapted for scanning with radiation beams. The information structures of the respective types are arranged in tracks. The structure of the second type has a phase structure in which effect areas alternate with intermediate areas, and is adapted for scanning with radiation of a wavelength longer than that for the first type. This reader scans both types with radiation of the first wavelength. An analog read signal is detected from radiation received from a scanned track. For reading the second type, first and second comparators supply respective detection signals if the differences between values of the read signals, separated by a given time interval, are greater than a given positive threshold or more negative than a given negative threshold. A signal recovery circuit derives a binary information signal from the first and second detection signals.

Abstract: An apparatus for writing and reading a magneto-optical record carrier (1) with an increased information density are described. Information areas (4) which are smaller than the write spot (V.sub.w) supplied by a first diode laser (40) can be written by a switched magnetic field. The areas can be read with a read spot (V.sub.r) which is smaller than the write spot, which read spot is formed by radiation from, for example an assembly of a second diode laser (42) and a frequency doubler (43).

Abstract: An optical information carrier comprising a substrate, an auxiliary layer bounded by dielectric layers, a thin reflection layer, a dielectric layer, a phase-change layer, a dielectric layer, a tight metal reflection layer and a protective layer. The information carrier is recordable and erasable by a laser-light beam and can be played in a conventional CD player. The auxiliary layer consists of selenium or AlGaAs, and has the property that the absorption increases substantially at temperatures above 70.degree. C. An information carrier comprising this auxiliary layer can be recorded with a lower laser power as compared to information carrier which does not comprise the auxiliary layer.

Abstract: The disclosed information reading system comprises a record carrier (1) having at least two parallel tracks (2a, 2b) whose mutual distance is so small that the radiation beam (10) is modulated by the information patterns of the two tracks (2a, 2b) when the tracks are scanned by a focused radiation beam (10) along a line (18) indicating the center between the tracks (2a, 2b). The tracks comprise elementary areas, with the positions of the boundaries (80) of the elementary areas of the two tracks, viewed in the track direction, corresponding to each other. The information patterns in the tracks comprise elementary areas occupied by a mark and unoccupied elementary areas. The occupied elementary areas have a different influence on the radiation than the unoccupied elementary areas. When the two tracks (2a, 2b) are scanned, the center (17) of the scanning spot (14) is directed onto a line (18) which is located centrally between the tracks (2a, 2b).

Abstract: Recording and/or reading of information on an optical record carrier is effected by scanning such record carrier with a radiation beam which is focussed by an objective lens into a scanning spot of a size which is diffraction-limited by the aperture of the objective lens. The effective size of the scanning spot is considerably reduced by including a layer of non-linear optical material in the record carrier, such material having an optical characteristic which changes with changes in intensity of the radiation incident thereon. The read/write resolution of information on the record carrier is thereby substantially increased.

Abstract: A method is revealed for recording an information signal (Vi) on a record carrier (1). The information signal (Vi) is converted into code words (200), which comprise a variable number of bits of a first logic value ("1") and a variable number of bits of a second logic value ("0"). The number of successive bits of the first logic value ("1") is at least equal to P. The number of successive bits of the second logic value, situated between the bits of the first logic value, is at least equal to Q, Q being greater than P. A pattern of recording marks (8;54) corresponding to the code signal (Vc) is recorded on the record carrier (1) in such a way that bits of the first logic value ("1") are represented by recording marks (8;54). Moreover, an information recording device (FIG. 17), an information read device, and a decoding device (FIG. 18) are revealed.

Abstract: A method and device are disclosed for recording information represented by a code signal Vd on an optically readable record carrier (1) by means of optically detectable recording marks (8). Outside the areas (30) of the record carrier (1) which are used for recording the information signal reference marks (33) are formed. When the record carrier is read a detection signal Vd is generated, from which the code signal is derived by comparison of the detection signal Vd with a decision level Vref. The decision level Vref is derived from those portions (34) of the detection signal Vd which are representative of the reference marks (33).

Abstract: A method of and device for recording an information signal (Vc) on a record carrier (1) are revealed. The information words of the information signal are converted into code words (200) comprising a variable number of bits of a first logic value ("1"). The number of consecutive bits of the first logic value is at least equal to P. the number of consecutive bits of the second logic value ("0") is at least Q, P being an integer greater than or equal to 1 and Q being an integer greater than P. the code words are selected in such a way that for information words of successive values the associated code words differ for only one bit. During recording an elementary mark (54) is formed on the record carrier for every bit of the first logic value. Moreover a read device for the record carrier thus obtained is described.

Abstract: The invention relates to a method and system for determining an image of a nuclear magnetization distribution in a body. In known methods, particularly in nuclear spin echo techniques, a resonance signal is generated which has high dynamics. In the method according to the invention dephasing is effected which is non-linear place-dependent or which is frequency-dependent within a spectroscopy distribution, as a result of which the generated resonance signal will have a much smaller amplitude. Since the non-linear dephasing applied within the distribution is known, a correction can be made for this after the determination of the measuring signals.

Abstract: The invention proposes a method and a device in which resonance signals (generated for NMR imaging) are sampled in the presence of a static or semi-static and time modulated gradient magnetic field with the gradient direction of the fields applied being mutually perpendicular. The resonance signals are conditioned prior to the start of sampling. The sampled signals are associated with spatial frequencies (i.e. points in a spatial frequency space (k.sub.x, k.sub.y) which is the (2-D) Fourier transform of the actual (s, y) space), which are determined by the applied gradient fields. The static or semi-static gradient field always produces an increase (for example, in k.sub.x), while the time modulated gradient field always produces an image frequency which lies between two limits (k.sub.y and k.sub.y +k.sub.y). Consequently, the invention enables determination of NMR spectroscopy data in an entire band in the (k.sub.x, k.sub.y) space.

Abstract: During measurement cycles for generating and sampling FID signals in NMR imaging devices, a 180.degree. pulse and subsequently a 90.degree. excitation pulse are added to the pulse sequence. The 180.degree. pulse produces an additional echo signal. During (the maximum of) the echo signal, the 90.degree. pulse is generated. The waiting period occurring before the beginning of a next measurement cycle can thus be substantially reduced without giving rise to a significant signal loss in the echo signals to be generated during said cycle. In addition to a reduction of the measurement time, NMR images with different contrasts (other intensity distribution) can be provided.

Abstract: The invention proposes a method and a device in which resonance signals (generated for NMR imaging) are sampled in the presence of a (semi-) static and a time modulated gradient magnetic field, the gradient direction of the fields applied being mutually perpendicular. The resonance signal is conditioned prior to the start of sampling. The sampled signals are associated with spatial frequencies (i.e. points in a spatial frequency space (k.sub.x, k.sub.y) which is the (2-D) Fourier transform of the actual (x, y) space), which are determined by the applied gradient fields. The (semi-) static gradient field always produces an increase (for example, in k.sub.x), while the time modulated gradient field always produces an image frequency which lies between two limits (k.sub.y and k.sub.y +k.sub.y). Consequently, the invention enables the determination of data in an entire band in the (k.sub.x, k.sub.y) space; this is in contrast with the present state of the art (DE 26.11.