Abstract: A tracking servo system includes in addition to a composite servo system composed of a push-pull track deviation detecting loop operative with pregrooves formed in an optical disc and a wobbling track deviation detecting loop operative with intermittently provided wobbled tracking marks, an offset correcting loop for detecting offset component possibly produced due to tilt, deformation and eccentricity of a recording medium or change in optical and mechanical parameters in the course of time lapse to drive forcibly a light spot by applying an electrical offset to cancel out the offset component. In the offset correcting loop, light reflected by wobbled tracking marks provided intermittently or mirror areas formed by interrupting intermittently the pregroove is utilized for detecting the offset component.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation to provide a sector, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in the header field in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted by the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot traversing the wobbled track marks. The push-pull tracking error signal is corrected on the basis of the wobbled tracking error signal to attain the tracking control with higher accuracy, thereby eliminating an undesirable track offset attributable to tilting or eccentricity of the optical disc.

Abstract: In an optical disk, one turn of a recording track is divided into a number of sectors. Each of these sectors is composed of a servo field, which is stored in advance with servo information for tracking, and a data recording area which is to be written with data. A predetermined number of these sectors are joined together to form a plurality of blocks. Each of these blocks is recorded at the data recording areas of its predetermined sectors with identification information for identifying the blocks and phase synchronization loop pull-in information for read out clocks.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in each of the header fields in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted from the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot passing the wobbled track marks. After attenuating the gain of the wobbled tracking error signal by a low-pass filter so that the gain of the wobbled tracking error signal becomes equal to that of the push-pull tracking error signal at a frequency fe satisfying the relation1/50.multidot.N.multidot.fd<fe<1/5.multidot.N.multidot.

Abstract: In electron-beam lithography, and similar operations, to achieve good drawing accuracy on a sample, it is necessary to detect the position of a mark on the sample with high accuracy. To accomplish this, a mark signal amplifier is provided including a first circuit for taking maximum and minimum values out of a mark signal detected by causing an electron beam to scan a mark area provided on a sample. A second circuit determines a peak-to-peak value of an amplitude of the detected mark signal in accordance with the maximum and minimum values, and a third circuit produces an output signal of a constant amplitude level as an input to a binary-coding circuit in accordance with the peak-to-peak value. The output signal of the third circuit remains constant in spite of fluctuations of the detected mark signal, so that a higher accuracy is obtained in detecting the mark for positioning.

Abstract: This invention relates to a method of detecting a mark by an electron beam, the mark being provided on a sample, which includes the steps of scanning the electron beam over an area of the mark in such a manner that the electron beam is subjected to chopping by sampling pulses having a higher frequency than the scanning frequency, eliminating a component of noise from a detected signal representative of the mark, synchronously rectifying the detected mark signal, binary-coding the detected mark signal as compared with a suitable threshold value, and detecting a position of the mark by using the binary-coded signal.

Abstract: In an apparatus for driving a motor wherein a carrier or stage carrying a sample thereon is located and moved to a predetermined position by controlling the slow-up and slow-down speed of the motor at the start and prior to the stopping thereof, respectively, this invention provides for speed control of the motor in accordance with a function of arbitrary characteristic slope, the function being stored in the form of a succession of digital values which may be sequentially accessed by a counter control circuit responsive to a control command signal representing the on-off condition for the motor.

Abstract: This invention relates to a driving signal control circuit, in which at least four detecting points (or detectors) are arranged for detecting the position of the working table, which is repeatedly reciprocated between the detecting points.

Abstract: A variable inductor wherein two closed magnetic circuits each having a predetermined gap in one place are constructed of a movable magnetic core and a fixed magnetic core. When the movable magnetic core is moved, the opposite area between both the magnetic cores in one of the closed magnetic circuits increases, while the opposite area between both the magnetic cores in the other closed magnetic circuit decreases. Thus, the inductances of coils wound around parts of the respective closed magnetic circuits vary complementarily.

Abstract: A digital displacement sensor includes a plurality of zigzag coils provided with projecting or convex portions having different pitches and arranged on the surface of a flat plate. A magnetic head consisting of a magnetic body and a coil is wound around part of the magnetic body, the magnetic head being supported so as to be moved, while maintaining a given gap from the surface of the flat plate, whereby a digital signal corresponding to the displacement of the magnetic head is sensed by means of a plurality of zigzag coils.