Abstract: A tracking control apparatus includes an A/D converter, an edge detection circuit, a latch circuit and a ROM to change a tracking error signal having a sinusoidal characteristic representing a relative position of a light beam and a track on a disk to have a sawtooth characteristic representing the relative position. Stable tracking control free from off-tracking due to a disturbance is attained even when amplitudes of the tracking error signal and a tracking sum signal are not equal.

Abstract: A phenolic resin can be obtained by a condensation reaction between a specific trifunctional aromatic compound and a phenolic compound. This resin can be reacted with a curing agent such as a hexamine to give cured articles having excellent heat resistance, electrical properties, wear resistance and chemical resistance, and the phenolic resin is also much more excellent in curing reactivity as compared with conventional techniques.

Abstract: A phase change optical disk in which the thermal conductivity of a first region at an outer peripheral position of the disk is set at a value larger than the minimum value of that of a second region. In the optical disk, in order to provide an output characteristic of a uniform reproduced signal when the disk is rotated at a fixed rotation speed, toward an outer peripheral position thereof, the critical cooling rate of a recording film is set at a larger value or the temperature which the recording film is to reach is set at a lower value. Provided is a method of using the phase change optical disk for recording or erasing information, in which method, the power of the laser beam to be directed to an inner peripheral position of the disk is set larger than that directed to an outer peripheral position thereof.

Abstract: A phenolic resin can be obtained by a condensation reaction between a specific trifunctional aromatic compound and a phenolic compound. This resin can be reacted with a curing agent such as a hexamine to give cured articles having excellent heat resistance, electrical properties, wear resistance and chemical resistance, and the phenolic resin is also much more excellent in curing reactivity as compared with conventional techniques.

Abstract: A method and apparatus for optically recording information in which the phase state of each recording position of the recording film of a recording medium such as an optical disk is reversibly changed between an amorphous phase and a crystalline phase using a single laser beam, thereby optically recording information on the the recording film. The recording position on the recording film is heated to the melting point thereof or more through laser beam irradiation irrespective of the information to be recorded. After completion of the heating, in order to change the phase state of the recording film at the recording position in accordance with the information, the power and/or irradiation time of the laser beam is controlled so as to provide different times required for the temperature of the recording position to pass through the crystallization temperature region of the recording film.

Abstract: Photochlorination of aromatic compounds having at least one alkyl side chain is carried out in the presence of an alkylene polyamine previously mixed with an aromatic compound having at least one chlorinated side chain whereby side reactions are suppressed.Aromatic compounds having a monochlorinated side chain are stabilized with an alkylene polyamine. Stainless steel apparatuses can be used in both cases.

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: Time base fluctuation of a video signal reproduced from a video disc or tape is detected and corrected. Meanwhile, a dropout of such reproduced video signal is also detected. The dropout detection signal thus obtained represents the dropout period during which the time base information is erroneous. Therefore the time base information detected during such dropout period is rendered invalid to consequently eliminate erroneous correction of the time base fluctuation.

Abstract: A digital information recording and reproducing method for significantly improving the transfer rate of digital information, comprises the steps of: forming a plurality of light beam guide tracks on a recording medium capable of multiple light-wavelength recording, the tracks being spaced apart by a predetermined pitch and each of the tracks comprising a series of pre-pits disposed in a scan direction and spaced apart by an interval longer than the diameter of a spot of a light beam for use in recording and reproducing; and recording and reproducing an information bit by changing the light beam to have a different wavelength predetermined n times in a predetermined order while the light beam is scanned by one interval of the pre-pits.

Abstract: In a dynamic optometer, a variation in the direction of a subject's eye, namely, in the direction of gaze is measured by a direction detector to tilt a bi-axial rocking mirror according to the output of the detector, and an actual image of an eyeball formed by a pair of concave spherical mirrors is reflected to an optical system by the rocking mirror varying the direction of incidence. A second actual image which is formed immediately before a light source by the optical system is stably fixated in one direction, so that the eye is irradiated with light constantly from the front side in spite of eye movements. Accordingly, the refractive power can be measured, unaffected by the movement of an eyeball.

Abstract: Light beam emitted from a laser light source is focused by an objective lens and applied in this state to an optical information recording medium. In the optical path between the laser light source and the objective lens is disposed a diffraction grating inclinedly with respect to the optical axis. This diffraction grating not only reflects the light beam emitted from the laser light source but also separates it into zero order as well as +1st order and -1st order diffracted light beams. Thus, this diffraction grating functions not only as a diffraction grating but also as a mirror. The thus-separated light beams are applied to an optical disc and the reflected light beams from the optical disc are converted to electric signals by means of a photo detector. The .+-.1st order diffracted light beams are used as track servo beams for following the track on the disc. The zero order diffracted light beam is used for reproducing information signals provided from the track on the disc.

Abstract: In the case where an information signal is optically recorded on the tracks of a disc-like recording medium, the apparatus of the invention confirms that no information signal is recorded on the track prior to recording the information signal in order to prevent the overlap recording of the information signal. This apparatus has a track jump pulse generating circuit and an RF signal detecting circuit and the light spot sequentially moves to the adjacent tracks by a plurality of times during one rotation of the track. The presence or absence of an RF signal is detected from each track and the presence or absence of the recorded track is checked at a high speed.

Abstract: A information recording medium has characteristics of high sensitivity and high density. The medium has a double layer formed on a transparent substrate, the double layer comprising a highly transparent recording layer, for example, Sb.sub.2 Se.sub.3 layer and a highly reflective layer, for example, Bi layer. The highly transparent recording layer includes Bi so as to set a minimum value of a reflection factor in prerecording 8 to 16 percentages.

Abstract: A servo circuit for a signal reproducing apparatus for reproducing signals from a record medium such as a disc utilizing an optical pickup, wherein a variable gain amplifier is arranged in a servo loop between a pickup and an actuator so that the pickup is caused to track a signal track in accordance with a servo error signal produced by the variable gain amplifier. A playback condition of a disc is discriminated by detecting the number of errors in a signal reproduced from a recorded signal on the disc by the pickup, and a gain of the variable gain amplifier is controlled by the discrimination output so that the variation of the servo error signal caused by a difference in reflectance between individual discs is eliminated and a loop gain appropriate to an individual disc is automatically set.

Abstract: A method of visually representing output data on a screen by deflecting a laser beam in both horizontal and vertical directions for scanning, and an indicating device for performing the above method. The laser beam is first divided into two polarized waves which are, after being modulated in accordance with the output data, combined into a first synthesized laser beam. The two polarized waves are alternately extinguished synchronously with a predetermined simple harmonic oscillation. The synthesized laser beam is then horizontally deflected by means of a sinusoidally oscillating mirror so that the angular displacement of the deflection oscillates in synchronism with the predetermined simple harmonic oscillation. The resultant deflected beam is again divided into two polarized waves, one of which is then inverted. The resulting two polarized waves are combined to obtain a second synthesized laser beam whose angular displacement in deflection is unidirectional at any phase.

Abstract: A tracking system for optically tracking information tracks formed on a recording medium, comprising a comparator which generates a trigger signal when the light beam scanning the information track is located over an information pit, and a sample holding circuit which samples a deviation signal caused by the difference of reflection light intensities on two photo detectors at that time. The deviation signal obtained when the light beam is located over the information pit includes smaller error component caused by the displacement of the object lens during the tracking control, whereby the accurate tracking control can be achieved.

Abstract: A high frequency heating apparatus is provided with a hood so constructed as to limit infrared ray energy reaching an infrared ray detecting element for detecting infrared rays radiated from an object to be heated within a heating chamber. In heating apparatus, the influence by the reflection of infrared rays is minimized by making the absorption factor approach to about "1" with blackening the inner surface of the hood. Also, the rotation of a chopper to detect infrared rays radiated from the object through chopping operation is detected by a mechanical switch. The output signal from the infrared ray detecting element is synchronous-rectified in synchronism with the switching operation of the mechanical switch.

Abstract: An inverter circuit comprises a reactor and a capacitor connected in series to a load to supply the load with a series resonance high-frequency power, a secondary winding provided at the reactor, and means for feeding a voltage generated in the secondary winding back to a power supply through switching means of a thyristor. The switching means is made conductive to feed the voltage generated in the secondary winding back to the power supply when supply voltage detecting means detects that a supply voltage exceeds a predetermined voltage.