KR800000202B1 - Linear method of optically recording a video or other signal - Google Patents

Abstract

An optical recording medium for recording a high-density video or other signal is disclosed. The intensity of light beam is modulated elec. by recording signals, and the modulated light beam is irradiated on the medium surface being changeable depending on a quantity of light reaction products which also is changed according to a quantity of irradiation light. The recording groove portion of the signal and the tracking is formed on the medium at the same time by predetg. the intensity of light beam when the signal is not modulated.

Description

Optical record carrier

1 is a schematic diagram for explaining an example of a recording medium.

2 is a block diagram of a recording apparatus used in the practice of the present invention.

3 is a diagram showing a photosensitive characteristic curve of a recording medium.

4 is a configuration diagram of an example of an optical modulator

Figure 5 is a schematic diagram for explaining the operation

6 is a schematic diagram for explaining one embodiment of a recording method.

7 through 8 are schematic diagrams for explaining another embodiment.

9 is a photosensitive characteristic curve with different sensitivity

The present invention relates, for example, to an optical recording medium adapted to record video signals.

As a recording medium using mechanical tracking, it is formed in the groove 1 via a piezoelectric conversion element 3 attached to the needle 2 which scans the groove 1 as well as a conventional audio disc, as shown in FIG. There has been proposed a video disc for reading uneven information. If one record of a TV signal is recorded at one rotation rate on this video disk, it is necessary to rotate the disk at 1,800 r.p.m during playback. The player with such a high speed rotation has technical difficulties in many points than in the case of a conventional audio disc. On the other hand, from the standpoint of recording signals, it is very difficult to increase the recording speed in conventional mechanical cutting. Do. That is, even if the shape corresponding to the groove and the signal is written on the disk for high-speed rotation of about 1800 r.pm, the needle burns due to the frictional heat generated between the cutting needle and the recording medium. A problem arises in that a limit point arises in the recording of the high frequency characteristics of the signal converter.

Thus, in practice, mechanical cutting of video discs is performed at about one-tenth the speed of rotation. For this reason, a video disc with a playback time of 10 minutes is consumed and recorded for about 3 hours to produce it, which is undesirable in the disc production process. Moreover, since the recording speed is lowered, it is impossible to directly record the signal of the video camera, and an intermediate recording medium having excellent characteristics between the signal source and the recording apparatus is required.

In order to control the above-mentioned drawbacks in mechanical cutting, the present invention is to realize that the optical groove can be used to record the track groove and the signal at the same time with high density.

One embodiment of the invention is described below. 2 shows the configuration of the recording apparatus used in the practice of the present invention. In FIG. 2, 4 denotes a laser light source, and the predetermined intensity from the laser beam 5 is supplied to the optical modulator 6, and modulated to the intensity corresponding to the signal of the optical modulator 6. 7 is a modulated signal source such as a video signal, and the signal from this is supplied to the optical modulator 6 via a correction circuit 8. The correction circuit 8 is for correcting the nonlinearity of the photosensitive characteristic and the modulation characteristic of the optical modulator with respect to the intensity of the laser beam described later. The laser beam obtained from the optical modulator 6 is irradiated through the correction filter 9 and the condenser lens 10 onto the photosensitive recording medium 12 uniformly coated with a thickness of about 1 μm on the surface of the glass substrate 11 on the disc. The glass substrate 11 is fixed to the rotating shaft 13, for example, rotates at high speed at 1,800 rpm, one frame is recorded in one rotation, and the rotating shaft 13 is moved in the radial direction as indicated by the arrow, and a spiral signal groove is formed. do. In this case, since the linear velocities are different on the inner circumferential side and the outer circumferential side of the photosensitive recording medium 12, the light intensity is substantially changed when viewed on the photosensitive recording medium 12 even though the irradiated light intensity is constant. In order to correct this, a correction filter 9 is designed. That is, since the linear velocity is faster toward the outer periphery than the inner periphery, the rate at which the light energy is reduced in the correction filter 9 is correspondingly smaller.

As an example of the photosensitive recording medium 12, a photoresist can be used.

3 shows the photosensitive characteristics of the photoresist for a laser beam with a wavelength of 4,579 GHz, i.e., the relationship between the amount of light irradiation and the amount of light product. 14 is a negative photoresistor, e.g. The characteristic of KOR (brand name) is shown, and 15 shows the characteristic of positive type photoresist, for example, AZ-1,350J (brand name) of Shipply Campney. The abscissa of FIG. 3 is the amount of light irradiated, and the ordinate represents the negative photoresist with the photo products produced by photosensitivity. Display amount. It can be seen that this photosensitive characteristic has a predetermined inclined region.

4 shows the structure of an example of the optical modulator 6, in which the polarizing element 16, the plate 17 of the crystal wavelength, the electro-optic crystal 18 and the detector 19 are sequentially arranged with respect to the incident light. Electro-optic crystal 18 has an electro-optic effect (PEM effect) and consists of crystals such as lithium niobate, lithium tantalate, and the like, by applying a signal voltage at signal source 7 to the corresponding light intensity. You can get a casting mine. In other words, when the polarization element 16 and the detection element 19 are orthogonal to each other, the modulation curve indicating the relationship between the output light intensity and the signal voltage V applied to the electro-optic crystal has an output light intensity proportional to SinKV as shown in FIG. It is known to be. Where K is an integer. Here, if the point A on the modulation curve is selected as the operating point (photosensitivity I) and the signal voltage is applied to the crystal, output light modulated with the photosensitivity by the signal voltage is obtained. In determining this point, a predetermined DC voltage V _B may be applied to the electro-optic crystal 18, and since the electro-optic effect is a modulation of the refractive index and thus phase modulation of the light, the DC voltage V as shown in FIG. _You may insert the plate 17 of the crystal wavelength which gives the phase corresponded to _B.

In addition, when the positive photoresist is used as the photosensitive recording medium 12, the photosensitive material is removed and developed in response to the intensity of the modulated light beam as shown in FIG. 6 having the photosensitivity described above in FIG. Is changed to a predetermined inspection area, and the depth of the groove portion formed on the photosensitive recording medium 12 is changed corresponding to the intensity of the modulated light beam. In this case, the light intensity I of the unmodulated laser beam from the laser light source 4 is selected at approximately the center portion (point B) of the good portion of the inclined portion of the photosensitive characteristic, and at the same time as shown in FIG. The maximum strength and the minimum strength of are chosen to be within this slope region. When the photoresist is removed after image development and the thickness of d ₁ becomes d ₂ , the photosensitive recording medium 12 has a groove having a depth of d ₁ -d ₂ and the bottom of the groove. Unevenness (i.e., signal) can be recorded at the same time. For example, the groove width can be 3 to 10 m, the groove depth d _1- d ₂ is 0.5 m, and the signal amplitude can be ± 0.3 m.

In the recording medium recorded in this way, the video disk can be copied in a large amount in the same manner as in the case of an audio disk. Such a video disc is reproduced by the method shown in FIG. 1. In addition, signals are detected capacitively and optically.

According to the present invention described above, since it is a non-contact type recording method, the recording speed can be greatly improved, and the speed can be the same as or higher than the reproduction speed. In addition, since the groove and the signal are recorded at the same time, unlike when the signal is recorded with the groove formed in advance, the tracking of the groove is unnecessary at the time of recording. Compared to mechanical cutting, high frequency recording is easier, the width of the groove can be narrowed, and high density recording can be realized. Furthermore, there is an advantage that the apparatus is not enlarged by recording in the air as compared with recording in the electron beam.

In addition, the cross-sectional shape of the grooves may be spherical, approximate to parabolic, regular distributed, or triangular.

As an optical method for this purpose, it is conceivable to shape the light intensity distribution in a predetermined form in the cross section of the light beam by, for example, a filter having a lens transmittance distribution.

The materials to be applied to the recording medium are sublimable materials and photothermal plastic materials other than the photoresist. Sublimable materials are photoreaction products evaporated by heat generated by the absorption of light and evaporate. They have a low thermal diffusion and a very large light absorption coefficient, and evaporate inward from the surface of the material in response to the light intensity of the irradiated beam Recording becomes possible. Photothermal plastic material is a combination of a photoconductive material and a thermal plastic material.

As the laser light, various kinds of lasers having an output corresponding to the sensitivity of the photosensitive material can be used. Specifically, krypton laser, helium-cadmium laser, and argon laser are used.

Furthermore, the light modulator uses the diffraction effect of light by ultrasonic waves to cause intensity modulation of the light. The above-described embodiment is recorded as a single light beam, but may be as shown in Figs. 7A or 7B. FIG. 7A shows a case where two light beams are used, an optical beam 20a is a beam for constituting a groove of a certain intensity, an optical beam 20b is a beam containing signal information, and two light energies are summed on the recording medium 12. The depth of the grooves is recorded in the form modulated by the signal. In FIG. 7, 21 denotes a total reflector and 22 denotes a beam splitter.

In this manner, as shown in FIG. 7B, the plurality of signals can be recorded and formed in the groove by using the optical beams 20b ₁ and 20b ₂ ... 20b _n including the signal information. In the case shown in FIG. 7B, the total energy of the light beams 20b ₁ , 20b ₂ ... 20b _n needs to be within a certain range.

As a method of obtaining a plurality of light beams, there is a method of dividing an output beam of the same light source (same wavelength), a method of using a plurality of light sources (not limited to the same wavelength), and the like.

In addition, the method of adding the light energies of the plurality of light beams onto the recording medium is not limited to the method of spatially polymerizing on the recording medium, and even if the beam spots of the respective beams are spatially separated on the recording medium (and the optical beams). It is also possible to use the method of adding by visuals, such as drawing the same trajectory with the movement of). This latter method is useful when dividing a laser light source of the same wavelength to form a plurality of light beams. That is, in the premise method, the interference effect due to the optical path difference between the respective light beams is generated, and the interference due to external disturbance is recorded as noise on the recording medium, but this disadvantage is easily eliminated by the latter method.

In the method using the plurality of light beams described above, it is useful to select the first diffracted light as a signal beam by using an ultrasonic light modulator that modulates the intensity of light by using the diffraction effect of light by ultrasonic waves. In other words, the light intensity I for determining the depth of the groove is easily obtained by setting the intensity of the light beam 20a. Furthermore, if there is no interference between the respective light beams, the synthesis of the signal energy on the recording medium becomes a simple addition. As in the above-described embodiment, there is an advantage that the problem of mixed modulation resulting from nonlinearity of the optical modulator 6 is eliminated.

In the third embodiment, recording with a single light beam is the same as in the first embodiment, except that a plurality of recording media having different sensitivitys are used for the use of photosensitive recording media. 8 shows a case where the photosensitive layer 12b is laminated on the photosensitive layer 12a. In this case, it should be noted that the photosensitive layer 12b on the light beam irradiation surface side should be higher than the sensitivity of the photosensitive layer 12a. That is, the photosensitive characteristic curve 23 in FIG. 8 is that of the photosensitive layer 12a, and the photosensitive characteristic curve 24 is that of the photosensitive layer 12b. If this condition is satisfied, the photosensitive layer 12b can be used for the groove formation layer and the photosensitive layer 12a for signal information recording. As can be clarified in FIG. 8, the photosensitive layers are irradiated with a light intensity of a constant intensity I sufficient to form a groove of a predetermined depth in the photosensitive layer 12b, and the depth of the photosensitive layer 12a is changed in correspondence with the signal information. Investigating the light beam with sufficient amplitude allows simultaneous recording of grooves and signals. This third embodiment is generally advantageous in that the photosensitive characteristic curve of the photosensitive recording medium is close to a spherical shape and is suitable for digital recording.

9 is a high sensitivity photoresist, for example, 4,762 kPa of AZ-1,350J (trade name). A photosensitive characteristic curve 25 for light and a low photoresist, for example AZ-1111 (trade name), are shown for the photosensitive characteristic curve 26 for light of the same wavelength.

Moreover, it is not limited to a photoresist, It can use combining the predetermined | prescribed among the following metal films.

Although not shown, a method of recording with a plurality of light beams for a plurality of photosensitive layers by combining the embodiments of FIGS. 2 and 3 is also conceivable. In this case, a plurality of light beams having different wavelengths may be used as the laser light source, and those having different wavelength sensitivity of the photosensitive recording medium may be used.

Claims (1)

As shown in the figure and described in detail in the text, the intensity of the light beam is electrically modulated by a recording signal, and the modulated light beam is irradiated onto a recording medium whose amount of photoreaction product changes in response to the amount of light irradiation. Wherein the recording groove portion of the signal and the groove portion for tracking are integrally formed by selecting the brightness of the light beam when there is no modulation by the signal.

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