JPS5853410B2 - Recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A so-called video disc is one of the recording media for video signals.

Conventionally known video discs use a mechanical cutter to form track grooves for tracking during playback, and at the same time change the depth of the track grooves in response to video signals. A piezoelectric element provided on the reproduction needle detects elastic waves generated by tracing by the reproduction needle to reproduce a video signal.

However, in this case, since the frequency of the video signal is high, the cutting needle of the cutter cannot follow the signal, or problems such as burning between the cutting needle and the master disk occur, making it impossible to record the signal in real time. For this reason, in reality, the video signal is recorded once on a film and then played back at a low speed of about 1/25 before being recorded on the master disc, so the playback time of a video disc is, for example, 10 minutes. However, it takes more than three hours just to record to the master disk, or it is not possible to directly record the signal from the television camera.

Furthermore, since a video signal is once recorded on a film and a master disk is produced from the reproduced signal, the characteristics of the signal deteriorate.

In view of these points, the present invention aims to provide a recording method that allows video signals to be recorded on a master disk in real time and that also solves the new problems that arise in this case.

FIG. 1 shows an example of a recording apparatus for this purpose. In FIG. 1, a laser beam 22 of a constant intensity is supplied from a laser light source 21 to an optical modulator 23.

Further, a video signal, for example, is supplied from the signal source 24 to the modulation circuit 25, and the video signal is converted into, for example, a phase modulation signal. The output beam 21 from the optical modulator 23 is supplied as a modulated signal.
The intensity is modulated by the phase modulation signal.

This modulated beam 27 is then supplied to a lens 29 through a correction filter 28 made of, for example, a gray scale, where it is focused and irradiated onto a master disk 30 .

This master disk 30 has a photosensitive material 32 uniformly coated on the surface of a disk-shaped glass substrate 31 to a thickness of, for example, 1 [μm]. is focused and irradiated, and
This master disk 30 is attached to a rotating shaft 33 and rotated at a rate of, for example, one rotation per frame of the video signal, and is moved at a predetermined speed in the diametrical direction of the master disk 30, as shown by an arrow 34. be done.

Therefore, the photosensitive material 32 of the master disk 30 is
The beam 27 from 9 is exposed to a spiral trajectory.

In this case, the optical modulator 23 includes a polarizer 41 and a crystal wave plate 42 for the incident beam 22, as shown in FIG.
, an electro-optic crystal 43 and an analyzer 44 arranged in sequence.

The electro-optic crystal 43 is a crystal of rhidium niobate, rhidium tantalate, etc. that has an electro-optic effect (Pockels effect), and by applying a signal voltage to it through the correction circuit 26, it emits light according to the signal voltage. An intense output beam 27 can be obtained.

That is, if the polarizer 41 and the analyzer 44 are in a crossed Nicol state, the light intensity of the output beam 27 is equal to that of the electro-optic crystal 4.
As shown in Fig. 3, it is proportional to 5 inkVs (k' constant) with respect to the signal voltage Vs applied to Vs. An output beam 21 whose light intensity is modulated by voltage is obtained.

To set this operating point A, the electro-optic crystal 43
At the same time as the signal voltage Vs is supplied, a DC bias voltage vb may be supplied to A crystal wave plate 42 may be inserted which provides a phase shift corresponding to .

Also, the modulated beam 27 is used to remove the photosensitive material 3 of the master disk 30.
2, the inner and outer peripheries of the master disk 30 have different linear velocities, so the irradiating beam 27
Even if the light intensity of Since the linear velocity becomes slower, the reduction rate of the optical energy of the beam 21 is increased by the correction filter 28 accordingly.

As the photosensitive material 32 of the master disk 30, a photoresist can be used.

That is, FIG. 4 shows the sensitivity characteristics of a photoresist to a laser beam with a wavelength of 4579 [λ], and in the same figure, 12 is K, which is a negative photoresist.
The characteristics of OR (trade name) are shown, and 13 shows the characteristics of AZ-1350J (trade name), which is a positive photoresist.

The vertical axis in FIG. 4 indicates the amount of negative photoresist that remains undissolved due to the crosslinking reaction, and the amount of positive photoresist that remains undissolved.

As the photosensitive material 32, any photoresist can be used, but for example, when using a positive photoresist, the vertical axis in FIG. Therefore, if the vertical axis represents the remaining amount after exposure and development, and the curve 13 in FIG. 4 is shown, it is shown upside down as shown in FIG. 5.

Therefore, the light intensity Io of the beam 27 without modulation is the curve 13
If the light intensity Io is set so as to be approximately at the center of the sloped portion of , in the non-modulated state, the photosensitive material 32 will have a depth d as shown in FIG.

A track groove 35 is formed. If the optical intensity of the beam 2γ is modulated by the signal voltage Vs, the depth d.

The depth d of the track groove 35 with respect to the center changes in accordance with the change in the light intensity.

That is, a spiral track groove 35 is formed in the photosensitive material 32 of the master disk 30, and the depth d of the track groove 35 changes in accordance with the instantaneous level of the recording signal.

Note that when a signal is recorded on the master disk 30 in this way, the same development process as that for normal photoresist is performed. For example, if the photoresist is AZ-1350J, a prescribed alkaline development process is performed. The solution is diluted with water to a concentration of 50 (%), the temperature of the solution is maintained at 20 [° C.], and the exposed master disk 30 is immersed in this for 90 (seconds) to perform development.

Then, based on the obtained master disc 30, a video disc is duplicated in the same manner as in the case of an audio record disc.

However, in this case, the photosensitive material 3 with respect to the light intensity of the beam 21
As shown in FIG. 4, the photosensitive characteristics of No. 2 are non-linear, so the amount of change Δd in the depth d of the track groove 35 depends on the signal voltage V.
This is not directly proportional to the change in the amplitude of s, resulting in waveform distortion in the recorded signal.

Therefore, the reproduction system requires a circuit to eliminate this waveform distortion, but this increases the cost of the reproduction apparatus.

Therefore, in the present invention, signals are recorded taking such points into consideration.

For this purpose, the above-mentioned correction circuit 26 is provided.

That is, the correction circuit 26 is configured, for example, as shown in FIG. The output signal of the antilogarithm circuit 6
3, and this output signal is supplied to the drive amplifier 23a.

Therefore, if the signal from the modulation circuit 25 is ei, the output signal of the logarithm circuit 61 is lOgei, and the output signal of the attenuator circuit 62 is αI! Because it becomes Ogei,
Output signal e of antilogarithm circuit 63.

becomes eo=ei, that is, the correction circuit 26 performs a correction such that eo=ei.

As an example, AZ-1350J is used as the photosensitive material 32.
When the intensity of the light beam that all the photosensitive material 32 is exposed to is 100%, the light bias point is set at 60% of the exposure, and the amplitude is 20 to 2 μm.
When recording was performed at 5%, the amount of second to fourth harmonic distortion of the reproduced signal changed as shown in FIG.

When l//a=5.5, the amount of harmonic distortion of each issue decreased as shown in FIG.

In the figure, the bar graph with diagonal lines represents the case when the correction of -5.5 is performed, and the bar graph without diagonal lines represents the case where the correction is not performed (v〃=1).

In this manner, by providing the correction circuit 26, waveform distortion of the recorded signal can be significantly reduced.

As described above, according to the present invention, the master disk 30 can be manufactured using a laser and photoresist, so there is no need to perform low-speed recording, and signals can be recorded in real time.

Furthermore, since there is no need for film recording to convert to low-speed recording, signal characteristics do not deteriorate.

Furthermore, by using the correction circuit 26, the harmonic distortion of the recorded signal is reduced, and the amount of change Δd in the depth d of the track groove 35 becomes directly proportional to the signal voltage Vs, so that the reproduction system There is no need to correct distortion in the process, and the reproduction system can be simplified.

Furthermore, during playback, the track groove 35 serves as a tracking guide for the playback needle, so tracking during playback becomes unnecessary.

Furthermore, the track groove 35 and the signal unevenness can be formed integrally and simultaneously.

Furthermore, compared to electron beam recording, recording can be performed in the atmosphere, so the equipment does not need to be large-scale.

Note that as a method for changing the light intensity distribution of the beam 27, there is a method other than the above-mentioned method, for example, a method of adjusting the intensity distribution of the beam 27 to a predetermined state using a filter having a lens transmittance distribution.

Further, in the master disk 30, a sublimable substance, a photothermoplastic material, etc. can be used in addition to photoresist.

In this case, the sublimable substance evaporates due to the heat generated by light absorption, and if the thermal diffusion is small and the light absorption coefficient is extremely large, the material surface will change depending on the light intensity of the irradiated beam 27. Evaporation progresses from the inside toward the inside, making the above recording possible.

A photothermoplastic material is a combination of a photoconductive material and a thermoplastic material.

Further, as the laser light source 21, various types of lasers having an output commensurate with the sensitivity of the photosensitive material can be used, for example,
Krypton laser, helium cadmium laser,
Argon laser can be used.

As the optical modulator 23, one that modulates the intensity of light by utilizing the light diffraction effect of ultrasonic waves can also be used.

Further, in the above description, the recording beam 27 is single, but it may be configured as shown in FIG. 9A or B.

That is, in FIG. 9A, two laser beams are used, the laser beam 41 is a groove forming beam with a constant intensity, the laser beam 42 is a beam containing signal information, and the laser beam 42 is a beam containing signal information. The optical energies of both are added together, and the depth d of the groove is recorded in a form modulated by a signal.

Note that 43 is a total reflection mirror, and 44 is a beam splitter.

In addition, in FIG. 9B, the light beam 4 containing signal information is
By using 2a to 42h, a plurality of signals can be recorded in the groove.

Note that methods for obtaining a plurality of laser beams include 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 optical energy of the plurality of beams is transferred to the master disk 30.
The above method of summing is not limited to the method of spatially overlapping each other on the master disk 30; even if the beam spots are spatially separated on the master disk 30,
It is also possible to use a method in which the same locus is drawn as the master disk 30 (or the light beam) moves, and the summation is performed by time integration.

This method is useful when a plurality of laser beams are divided and formed from a laser light source having the same wavelength.

That is, in the former method, an interference effect occurs between each light beam based on the optical path difference, and interference disturbances caused by external disturbances are recorded as noise on the master disk 30, but in the latter method, it is easily eliminated. Ru.

Furthermore, the method using multiple laser beams described above
This is useful when the first-order diffracted light is selected as a signal beam by an ultrasonic optical modulator that modulates the intensity of light by utilizing the diffraction effect of light caused by ultrasonic waves.

That is, the depth d of the track groove 35.

This is because the light intensity that determines the value can be easily obtained by setting the intensity of the laser beam 41.

Furthermore, if interference is prevented between the respective light beams, the signal energy synthesis on the master disk 30 becomes a simple addition, and as in the above example, cross-modulation caused by the nonlinearity of the optical modulator 23 occurs. The problem will disappear.

Furthermore, the photosensitive material 32 of the master disk 30 can also be multilayered.

That is, FIG. 10 shows a case where a photosensitive layer 32b is laminated on a photosensitive layer 32a, and in this case, the sensitivity of the photosensitive layer 32b on the side of the surface irradiated with the beam 27 is made higher than that of the photosensitive layer 32a.

That is, in FIG. 10, the photosensitive characteristic curve 14 is for the photosensitive layer 32a, and the photosensitive characteristic curve 15 is for the photosensitive layer 32b.

If this condition is satisfied, the photosensitive layer 32b can be used as a track groove forming layer, and the photosensitive layer 32a can be used as a signal information recording layer.

As is clear from FIG. 10, there is a certain depth d in the photosensitive layer 32b.

By irradiating a laser beam with a constant intensity that is sufficient to form a track groove of Simultaneous recording is possible.

This recording method is generally advantageous when the photosensitive characteristic curve of the master disk 30 is close to a rectangle, and is suitable for digital recording.

FIG. 11 shows a highly sensitive photoresist, such as AZ-1.
350J (trade name) to 4762 (λ) light and a low-sensitivity photoresist, such as AZ-
111 (trade name) to light of a similar wavelength.

In addition to photoresist, a combination of the following metal films can be used.

It is also possible to record signals on multiple photosensitive layers using multiple light beams.

In this case, a plurality of light beams with different wavelengths may be used as the laser light source, and the difference in wavelength sensitivity of the master disk 30 may be utilized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a master disk recording device to which the present invention is applied, FIGS. 2 and 6 are partial block diagrams thereof, and FIGS. 3 to 5 and 7 to 8. 9 and 10 are diagrams for explaining other examples of the recording method, and FIG. 11 is a diagram showing the photosensitive characteristics. 26 is a correction circuit.

Claims (1)

[Claims] 1 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 thickness changes depending on the strength of the light beam to record the recording signal. A recording method in which the intensity is corrected in accordance with the photosensitive characteristics of the recording medium.