Abstract: A cemented carbide end mill has three or more cutting edges formed on its periphery and flutes each provided between adjacent cutting edges. The land width of each cutting edge and the flute width has a ratio of 1:1.5 to 1:4. Each flute has a helix angle of 35°-60° and, when viewed in a cross section perpendicular to the end mill axis, is in a shape smoothly concave radially inwardly. The core of the end mill has a diameter which is 62%-68% of the outer diameter of the end mill. The cutting edges have a base material of ultra-fine cemented carbide and are coated with a titanium-aluminum nitride hard film. The end mill is good at chip discharging in groove cutting and provides less inclination of cut grooves and less corner wear of the end mill.

Abstract: An improved twist drill is provided which reduces wear or chippings of the major cutting edges (3) and those of the leading edges (7) of land (9) and which has a long service life and stays sharp. A twist drill has a pair of chip discharge flutes (6), a pair of chisel edges (1), a pair of inner cutting edges (2) and a pair of major cutting edges (3) extending from each outer end of the inner cutting edges (2). Further, the drill has a pair of outer cutting edges (4) each receding from each of the major cutting edges (3) at an angle (&agr;1), and a pair of leading edges (7) of lands (9) each formed by the land (9) and the outer cutting edge (4) and has a linear or curved rake face (8). Wherein, an angle (&agr;4) of the leading edge (7) of land (9) between the leading edge (7) of the land (9) between the leading edge (7) of the land (9) and the linear or curved rake face (8) is an obtuse angle.

Abstract: An optical recording apparatus for automatically compensating for focus offset which cannot be compensated for with a conventional focus servo circuit. A plurality of auxiliary signals differing from one another in the frequency domain is generated, a rotational synchronism signal is generated by detecting an index mark put on the optical disk in advance to indicate the reference point of the rotational phase, and a switching signal is generated in response to the rotational synchronism signal. In response to the switching signal, a plurality of auxiliary signals and an information signal are consecutively outputted and recorded onto a track of the optical disk.

Abstract: An apparatus for optically recording/reproducing data to/from a disc including a focus servo circuit which initially sets an objective lens of an optical head to a predetermined setting. This predetermined setting is such that a laser beam passing through the lens is focused on the disc at a point inside of the disc in the thickness direction. Then, the focus servo circuit fine tunes the objective lens position until the laser beam is focused onto a recording film located inside of the disc.

Abstract: An optical recording apparatus for automatically compensating for focus offset which cannot be compensated for with a conventional focus servo circuit. A plurality of auxiliary signals differing from one another in the frequency domain is generated, a rotational synchronism signal is generated by detecting an index mark put on the optical disk in advance to indicate the reference point of the rotational phase, and a switching signal is generated in response to the rotational synchronism signal. In response to the switching signal, a plurality of auxiliary signals and an information signal are consecutively outputted and recorded onto a track of the optical disk.

Abstract: An apparatus and method for recording and reproducing information onto or from a rotating magnetooptic disc such that optimal laser power is maintained throughout the recording process. A test recording laser beam undergoes stepwise power changes as the recording position along a track of the disc changes. The recording signal is read out by a reproducing mechanism corresponding to the stepwise power change. A correcting mechanism utilizes the read-out signal to obtain the optimal power of the recording laser beam. Then, routine recording is carried out utilizing the optimal laser power. As routine recording is carried out, the optimal laser power is corrected depending upon the radial distance of the track being recorded from the center of the disc. As a result, optimal laser power is maintained regardless of the track position on the magnetooptic disc.

Abstract: A laser beam control circuit for an optical recording/reproducing apparatus, which controls the intensity of a laser beam striking a magneto-optical disc. The control circuit controls the injection current to a laser diode to provide high intensity for recording and low intensity for reproducing, providing a smooth transition between the high and low intensity states, and avoiding any excessive transition current. The control circuit monitors the output power of the laser diode and maintains it at a first value in the reproducing mode and a second value in the recording mode, and further controls the output power so that even during switching, the output power does not exceed the second level. This is done by supplying a compensating reference voltage to the recording power control loop during the reproducing mode, so that the output of the recording error amplifier does not change abruptly when the operating mode is switched to the recording mode.

Abstract: Disclosed is a magneto-optic recording/reproducing apparatus capable of detecting small size defects in a magneto-optic recording disk in the order of tens of microns in size, and capable of reliably compensating for signal defects of a video image recorded on the disk. In the apparatus first and second photodetectors are provided for detecting information signals of two luminous fluxes into which a luminous flux emitted from a laser oscillator is divided by light splitting means. The photodetectors are arranged on the part of light reflected or emitted by the surface of a magneto-optic recording medium when it is irradiated with the luminous flux from the laser oscillator. According to the invention, the signals produced by the photodetectors are processed to produce a highly sensitive defect signal or a plurality of highly sensitive defect signals which may be summed together.

Abstract: A tape address synchronizing apparatus for synchronizing the tape position of a video tape recorder to another tape recorder or to a reference has a tape address generating circuit, a reference address generating circuit, comparators for comparing the tape addresses to the reference addresses, a circuit for generating an acceleration signal or a deceleration signal and a capstan servo circuit controlling a motor which in turn controls the speed of the magnetic tape in the tape recorder which is to be synchronized. When the tape addresses match the reference addresses, the phases of a reference signal used for generating the reference addresses and the phase of a CTL signal recorded on the magnetic tape are compared to one another to further synchronize the phases of the signals to one another.

Abstract: A tape synchronizing apparatus for synchronizing tape addresses corresponding to tape locations of a tape which is being played back and reference addresses produced in the apparatus. The apparatus includes a capstan for rotating the tape at a controllable speed and a circuit for producing the tape addresses. The tape address generator circuit includes a circuit for detecting the direction of movement of the tape being played back, a shaping circuit for detecting a control signal from the tape which indicates each successive address and an up-down counter for producing the actual tape addresses. The reference addresses are produced in a reference address counter. The reference addresses are produced and updated at a rate corresponding to the frequency of a frequency reference. The clock rate of the frequency reference is adjustable by means of a frequency dividing circuit.

Abstract: A tape timer apparatus is disclosed. Apparatus is provided for producing frame pulses indicating a frame period in a running tape and for producing a tape direction signal. An up/down counter counts up or down, as determined by the tape direction signal, in response to the frame pulses. A detecting circuit generates a detection signal indicating whether the frequency of the frame pulse has exceeded a predetermined frequency. A circuit is also provided for dividing the frame pulses by a predetermined number and generating a single frequency divided pulse each time the predetermined number of frame pulses is generated. A selection circuit selects, in accordance with the detection circuit, either the frame pulse or the frequency divided pulse. A microcomputer receives the pulse from the selecting means as an interruption demand pulse and calculates the tape time on the basis of the value counted by the up/down counter.

Abstract: An apparatus for synchronizing the playback of magnetic tape, use in a VTR, to a reference signal. Reference addresses which are synchronized to the reference signal and tape addresses which are derived from and correspond to video frames located on the tape are generated. The playback speed of the tape is controlled by a capstan servo to select a speed at which the tape addresses and the reference addresses are synchronized. Each tape section corresponding to a single tape address is further subdivided into auxiliary segments which are identified by an auxiliary address. After a reference address and a tape address have been synchronized, the auxiliary address is compared against a predetermined value and the tape is momentarily accelerated or decelerated to further align the tape to the reference signal.

Abstract: A scan tracking apparatus for a helical scan tape recorder, comprising a movable tape head (11), a detector (13) detecting the envelope of the tape signal to produce a reproduced signal, sampling means (15) for sampling the reproduced signal at fixed points of the helical scan, memory (17) for storing the reproduced signal and correction signals from different tracks of the helical scan, computation means (2) for computing a correction signal to return the tape head to the center of the track, a sawtooth generator (2, 4) for producing a signal related to the tape speed (v), and a head driving mechanism (9) for moving the tape head in response to the sawtooth and correction signals.