JPS60214437A - Optical video tape recorder - Google Patents

Abstract

PURPOSE:To attain a recording/reproducing section free from maintenance by mounting a minimum number of a recording/reproduction laser device, a rotary polygon mirror scanning a laser light onto a magnetic tape and a photodetector and recording/reproducing a video signal through the laser light to eliminate the deterioration of the service life due to the wear of a magnetic head. CONSTITUTION:A video signal is processed by modulating a magnetic field made by a magnetic field generating coil 24 fitted to a tape guide 22. Since the tape guide 22 is made of a nonmagnetic substance, the magnetic field reaches a tape and the vicinity of a magnetic field generation coil 24 is arranged unidirectionally. In scanning the laser light to it, the video signal is recorded. The laser light 20 is subject to linear polarization by a polarizer 25, the light is converged on the tape 1 via the rotary polygon mirror 21 so as to detect the rotary angle of the polarized plane of the reflected at reproduction. The optical path of the reflected light whose polarized plane is turned in response to the state of magnetization is changed by a half mirror 26 and enters a photodetector 28. Since the strength of the transmitted light changes according to the rotary angle of the polarized plane, it is converted into an electric signal by the photodetector 29.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to the recording of image information (by scanning a laser beam on a magnetic tape (hereinafter referred to as tape)) and the recording of image information by scanning a laser beam on a magnetic tape. The present invention relates to an optical video tape recorder that reproduces image information by detecting the magnetic polarization angle of reflected light.

[Prior art]

A basic diagram of the tape running system of a conventional popular video tape precoder is shown in FIG. Tape 14-supply reel 2
The tape runs at a constant speed from the tape to the take-up reel 3 (2#) and is controlled by the carburetor Tanabata.The tape is also controlled by changing the position of the tension post 5 so that a constant tension is always applied to the tape. ing. A full-width erasing head 6 and a sound F/control head 8 are arranged on the running surface.

The video signal is recorded and reproduced by a video head B12 attached to the cylinder 10. FIG. 2 shows the positional relationship between the tape, cylinder, and video heads A and B. The video head A11 and the video head B12 are fixed to the upper cylinder 13 and rotated at 1800 rpm by a cylinder motor directly connected thereto to scan the tape surface.

As a result, the video signal is recorded diagonally, and the video head A
The video track recorded by the video head B11 and the friend video track recorded by the video head B12 are arranged alternately. Third
The figure shows the recording pattern on the tape. 16 is a video track, 17 is an audio track, and 18 is a control track.

As described above, since the video head scans the tape surface at high speed during recording and reproduction, the contact surface with the tape is extremely worn and has a short lifespan. As long as a recording/reproducing method using a video head is adopted, this is a fateful problem and cannot be avoided.

〔the purpose〕

The present invention was made in order to eliminate the fatal disadvantages of the conventional technology, and its purpose is to eliminate the decrease in the life of the magnetic head due to wear and to make the recording/reproducing unit maintenance-free.

〔overview〕

The present invention relates to a recording/reproducing laser device, a rotating polygon mirror that scans a part of the laser beam onto a magnetic tape, guides reflected light from the magnetic tape to a photodetector, and detects the magnetic polarization angle of the reflected light to generate an electrical signal. Equipped with a minimum number of photodetectors that convert into
This is an optical video tape recorder that records and reproduces video signals using laser light.

[laughing]

FIG. 4 shows a laser driving device 1 showing a specific example of the present invention.
A laser beam 20 emitted from a rotating polygon mirror 21 scans one surface of the tape, and serves as the basis for recording and reproducing video signals. The laser beam 20 is reflected by a rotating polygon (fi 211) and reaches one surface of the tape, but the tape guide 2
2 causes the tape 1 to be curved. This tape guide 22 has a scanning hole 23 formed along the scanning line so that the laser beam reaches the tape surface, and a magnetic field generating coil 24 is arranged around the scanning hole 23. FIG. 5 shows the positional relationship among the tape 1, tape guide 22, and magnetic field generating coil 24. Laser drive device 19 and rotating polygon #! Between 21 and 21 are Bikoko 25.7 -Forer 26 and focusing lens 27
etc. are arranged, and the reflected light from the half mirror 26 is passed through an analyzer 28. The light is guided to a photodetector 29. Photodetector 29 and signal amplifier 150 are electrically coupled.

The present invention is completely different from conventional recording and reproducing systems, and the magnetic layer of the tape must be a perpendicularly magnetized film. The basic principles of recording and reproduction will be described below.

The coercive force (minimum magnetic field required to cause reversal of S-conversion) Ha of a magnetic material changes depending on temperature. Two typical temperature dependencies are shown in FIGS. 6 and 7.

TbFe, DyFe, Or02, etc. show temperature dependence as shown in Figure 6, and GdO'o, GdFe
etc. show temperature dependence as shown in Figure 75.In a ferromagnetic material such as TbFe, when the Curie temperature approaches 1fTCK, H
c becomes very small. In addition, a ferrimagnetic material such as G(10o) has a large Hc at the compensation temperature Tcomp, but T
When it deviates from comp, Ha decreases rapidly. Magneto-optical recording is an fc recording method that utilizes the phenomenon that when the temperature of a magnetic material rises, the Ha conversion is easily reversed by a small externally applied magnetic field. FIG. 8, which uses Tc or TcOmp and is called Curie temperature recording or compensated temperature recording, respectively, shows how recording is performed on the magnetic thin film 31 one bit at a time.

In advance, the magnetization of the magnetic thin film 31 is aligned in one direction over the entire surface by applying a strong magnetic field Kl, and then the laser beam 20 is irradiated onto the surface for a short time to cause a local temperature rise. decreases and reversal of fluorination occurs due to the external magnetic field. In this way, an inverted magnetic pressure having a diameter on the order of microns is formed in the magnetic thin film, and this corresponds to one bit.

When linearly polarized light is incident on a magnetic body, the plane of polarization of the reflected light rotates in accordance with the magnetization state of the magnetic body.

The rotation of the polarization plane of reflected light is called the Kerr effect.

FIG. 9 is an explanatory diagram of the Kerr effect. , the polarization plane 35 of the reflected light is shifted by an angle φ with respect to the polarization plane 64 of the incident light. By utilizing these phenomena, it is possible to reproduce the information recorded on a magnetic material.

Recording and reproduction of a specific example of the present invention shown in FIG. 4 will be described. The video signal is generated by modulating the magnetic field generated by a magnetic field generating coil 24 attached to the tape guide 22. Since the tape guide 22 is made of a non-magnetic material, the magnetic field reaches the tape and the area near the magnetic field generating coil 24 is aligned in one direction. When a laser beam is scanned here, a video signal can be recorded according to the principle shown in FIG.

In reproduction, the laser beam 20 is linearly polarized by the polarizer 25 and converged onto the tape 1 through the rotating polygon mirror 21, and the rotation angle of the plane of polarization of the reflected light is detected. The plane of polarization rotates according to the state of magnetization, and the reflected light becomes a half mirror.
At 26, the optical path is changed and the light enters an analyzer 28''.The intensity of the transmitted light changes in accordance with the rotation angle of the plane of polarization, so it is converted into an electrical signal by a photodetector 29.

As described above, the present invention allows recording and reproduction of video signals to be performed in a non-contact manner using laser light, completely eliminates the problems caused by wear of the video head as in the past, and enables recording and reproduction of video signals. The basic diagram of the tape running system Figure 2: Positional relationship diagram of the tape, cylinder, and video head in Figure 1 Figure 3: Recording pattern on the tape Figure 4 Figure 2 Explanatory diagram showing a specific example of the present invention Figure 5: Positional relationship diagram of the tape, tape guide, and magnetic field generating coil in Figure 4 Figure 6: Temperature dependence of coercive force of magnetic material Graph Figure 7 2a
Temperature dependence graph of anti-4a force of a sexual body Figure 8: Diagram of the principle of ii recording Figure 9m: Explanatory diagram of the Kerr effect Figures 1 to 913? The text numbers marked IK indicate the following:

1... Tape 2... Supply reel 3... Take-up reel 4... Capstan shaft 5... Tension post 6
・・・Full width erase・Bed 7・Audio erase head 8・
・・Audio control head 9・Pinch roller 10・Cylinder f-11・・
・Video head A 12...Video head B13...
・Upper cylinder 14...Lower cylinder 15...Conical guide 16...Video track 17...Audio track 18...Control track 19...Laser drive device 20...Laser light 21...Rotating polygon mirror 22...
・Tape guide 25...Scanning hole 24...Magnetic field generating coil 25...Polarizer 26...Half mirror 27
...Focusing lens 28...Analyzer 29...Photodetector 50...Signal amplifier 51...A thin film 32...
・Recorded bit 33...Magnetic field generating coil 34...Polarization plane of incident light 35...Polarization plane of reflected light z 714 2nd concave figure 5 degree A 1 figure 76 humidity 77 figure 78 figure

Claims (2)

[Claims] (1) A recording/reproduction laser device, a polygon mirror that scans the laser beam from the laser device onto a magnetic tape, and guides the reflected light of the laser beam obtained via the magnetic tape to a photodetector; An optical video tape recorder characterized in that it is equipped with at least the above-mentioned photodetector that detects the magnetic polarization angle of light and converts it into an electrical signal. (2) The magnetic tape area to be scanned by the laser beam is positioned by a tape guide, and the tape guide is provided with a scanning hole for the laser beam to scan the 8-tape surface. 2. An optical video tape recorder according to claim 1, further comprising a $ field generating coil for recording.