JPS6325408B2 - - Google Patents

Description

[Detailed Description of the Invention] A recording medium in which TV signals are recorded on a disk-shaped recording medium is known as a video disk, and the signal recording method is a method of recording with a mechanical cutter like a normal audio record. , a method of recording signals by focusing light from a high-intensity light source such as a laser into a fine pattern using a lens and irradiating it onto a recording medium, and a method of recording with an electron beam have been reported. Among these, a recording method using a laser and an electron beam is considered to be a promising recording method because it has the advantage of being able to record a signal in the same time as the reproduction time.

Conventionally, in the method of recording signals using laser or electron beam, a polymer photosensitive material such as a photoresist is used as the recording medium, and the uneven relief obtained after development processing after irradiation with light or electron beam was recording the signal. Although recording media such as photoresists have excellent recording density (i.e. resolution), they have the trouble of having to be developed after being irradiated with light or electron beams. However, the development process must be maintained under appropriate conditions, and the recording state cannot be determined until the development process is completed.

However, in recent years, heat mode recording media have been developed that can record signals by melting or evaporating them using heat energy, such as metal thin films such as rhodium, bismuth, gold, and chromium, or chalcogen substances proposed by the present inventors. has been developed.

In particular, chalcogen substances have high resolution and can be used satisfactorily as recording media for high-density signal recording.

Such a heat mode type recording medium does not require development processing, and has the advantage that a signal can be reproduced immediately after being irradiated with thermal energy rays.
Therefore, the recording condition can be observed immediately, and a good recording plate can be manufactured by always maintaining a good recording condition.

The present invention proposes a method for determining the optimum value of the recording light intensity in a signal recording method using a heat mode type recording medium as described above, with the aim of always performing good recording. .

Description will be made below with reference to the drawings. Figure 1 shows
This figure shows how signals are recorded on a heat mode recording medium. In FIG. 1, for example, light 1 from a laser light source is modulated in brightness and darkness by an electrical signal sent from a signal source 3 to the optical modulator 2 by an optical modulator 2. Thereafter, the light 1 is converted into a light beam 5 having an appropriate cross-sectional shape by an optical system 4, and a heat beam coated on a substrate 8 by a recording lens 6.
The light is focused on the mode type recording medium 7 as a minute light spot. This light spot is usually 1 μm or less in size, and all the thermal energy of the laser beam is concentrated in this light spot, so that enough thermal energy to melt or evaporate the recording medium 7 is applied to the recording medium 7.
can be given to

Therefore, if the recording medium 7 is now run in the direction of the arrow A as shown in FIG. FIG. 1b shows the relationship between the signal to be recorded and the uneven relief recorded on the heat mode recording medium 7. FIG. (b-
1) is an example of the electrical signal to be recorded.
When a pulse signal with a wave height V _R is sent from the signal source 3 to the optical modulator 2 at times t ₁ to _{t 2} , t ₃ to t ₄ , t ₅ to t ₆ , and t ₇ to t ₈ , the laser beam 1 _t1 ~ _t2 , _t3 ~ _t4 , t5 _{~ t6} , _t7
At ~ _t8 , since the light is configured to pass through the optical modulator 2, it is modulated in brightness, and when the pulse enters, strong optical energy irradiates the recording medium 7, causing the recording medium 7 to melt or evaporate. As shown in (b-2), the surface becomes uneven and a signal is recorded.

Also, at this time, the recording depth d of the recording medium 7
is proportional to the intensity I of the light that irradiates the recording medium, and in a configuration where the optical modulator 2 uses the electro-optic effect, the intensity I of the light is proportional to the wave height V _R of the electric signal and I∝sin There is a relationship of ² V _R /V〓 _/2 .

However, V〓 _/2 is called a half-wavelength voltage here.

FIG. 2 shows the principle of reproducing a signal from the recording medium 7 recorded as described above.
In FIG. 2a, for example, a linearly polarized laser beam 9 for signal reproduction passes through a polarizing beam splitter 10, and then becomes a light beam 12 with an appropriate cross-sectional shape, for example, circular, in an optical system 11. The polarized light is circularly or elliptically polarized, and is focused by the reproducing lens 14 as a minute spot on the surface of the recording medium 7 on which the signal has been recorded. The energy of the laser beam 9 at this time is smaller than that of the laser beam during recording, and it goes without saying that it is not so large that the recording medium 7 will melt or evaporate. The positional relationship between the minute spot and the recorded unevenness relief is as shown in FIG. 2b. Here, a part 7' (hatching part) forming a rectangular shape
is a concave part of the recording medium 7, that is, a place where the recording medium melts or evaporates during recording, and 12' indicated by circular hatching is a minute spot for reading. After the light beam 12 is focused on a minute spot 12' on the recording medium 7, it is reflected on the surface of the recording medium, passes through the reproduction lens 14, the λ/4 plate 13, and the optical system 11 again, and enters the polarizing beam splitter. 10 and enters the photodetector 15. When the reflected light flux passes through the λ/4 plate 13 again, its polarization state becomes a linear polarization state having an angle of 90 degrees with respect to the incident state, and the light beam is effectively transmitted to the photodetector 15 by the polarizing beam splitter 10. is incident on .

Now, the relationship between the signal recorded on the recording medium 7 and the size of the reading laser beam spot is as shown in Figure 2b, that is, the laser beam spot is larger than the area where the recording medium has melted or evaporated. In this case, the light reflected from the recording medium 7 and incident on the photodetector 15 is interference light between the surface of the recording medium 7 and the reflected light from the bottom of the concave portion that has been dissolved or evaporated. Now, when the depth of the recess is zero, that is, when the light spot is not placed in the recess, the phase difference between the two lights is zero, and the amount of light entering the photodetector 15 is large, but the light spot entering the recess and both When a phase difference occurs in the light, the amount of light entering the photodetector 15 decreases in accordance with the phase difference. That is,
It is clear that the electrical signal obtained by the photodetector 15 is related to the signal waveform during recording as shown in FIG. 2c. Photodetector 15 in FIG. 2a
The P-P value of the output of This is when the depth d of the recess is an odd multiple of 1/4 of the wavelength of the recording laser beam (d=(2n-1)λ/4). Therefore, by recording a signal on a heat mode recording medium and reproducing the signal at the same time, and controlling the intensity of the recording laser beam so that the signal output from the photodetector 15 is maximized during reproduction, it is possible to always achieve optimum results. The signal can be recorded at a depth (d=(2n-1)λ/4).

FIG. 3 shows an example of a recording apparatus configured to carry out the signal recording method of the present invention. Light 21 emitted from a high-intensity light source, such as a laser light source 20, is split into two beams by a beam splitter 22, one beam 23 for signal recording and the other beam 24 for reproduction. Here, the beam splitter 22 is used so that the light 24 does not have enough energy to melt or evaporate the recording medium 30.
The reflectance is set. light 23
After being modulated in brightness and darkness by the optical modulator 25 according to the signal to be recorded and passing through the beam splitter 33, its cross-sectional shape is changed by an appropriate optical system 26 (for example, a beam expander), and the mirror 34 The light passes through an optical coupler (for example, a beam splitter, a polarizing beam splitter, etc.) 27, and is focused by a lens 28 onto the surface of a recording medium 30 coated on a substrate 29, depending on the signal to be recorded. Recording is performed by melting or evaporating the recording medium 30. A signal source 31 generates a signal to be recorded, an amplifier 32 amplifies the signal, and an optical modulator 2
5 to modulate the light 23. Optical modulator 25
A part of the light modulated by the beam splitter 33 is taken out by the mirror 35.
is sent to the photodetector 36 via. Photodetector 36
is a photoelectric conversion element, which has the function of converting optical signals into electrical signals. The electrical signal obtained by the photodetector 36 is transferred to a known p-p value measuring electrical system 37.
and its P-P value is read. On the other hand, the light 24 for reproduction is reflected by a mirror 38, passes through a polarizing beam splitter 39, has its cross section changed to an appropriate shape and size by an optical system 40, and passes through a λ/4 plate 41. The light is then combined with the light 23 by the optical coupler 27, and focused by the lens 28 onto the recording medium 30 as a minute light spot.
The optical path of the light 24 entering the lens 28 is adjusted by the optical coupler 27, mirror 38, or beam splitter 22 so that it has a slight angle with the optical path of the light 23, and the positional relationship between the spots of the two condensed lights is adjusted. is constructed as shown in FIG. 3b.
In Fig. 3b, 42 is a recess where the recording medium has melted or evaporated, 43 is a spot of reproduction light, and 44
is the recording light spot. Light 24 for signal reproduction
is reflected on the surface of the recording medium 30 and returns to the original optical path again by the polarizing beam splitter 39.
The light is taken out to be incident on the photodetector 45.

A portion of the electrical signal from the photodetector 45 is reproduced on a display device 46, allowing the recording device operator to visually observe the signal. Further, the electrical signal from the photodetector 45 is used to measure the P-P value of the reproduced waveform, that is, the waveform shown in FIG. 2c.
The PP value of the reproduced waveform is sent to the value measurement electrical system 47 and is displayed on the display section 47' at the same time.

At the beginning of signal recording, a test pattern waveform is sent from the signal source 31, and at the same time, the amplification degree of the amplifier 32 is gradually changed to change the peak value, that is, the PP value of the electrical signal sent to the optical modulator 25. Depending on this value, the recesses are recorded on the recording medium 30 with different depths.

As explained earlier, the P-P value of the reproduced waveform obtained by the photodetector 45 (displayed on the display section 47') is related to the depth d of the recess, and the P-P value is the maximum. The P-P value measurement electrical system 37 measures the P-P value of the signal waveform obtained from the photodetector 36 corresponding to the
The value is determined as the optimum value for switch S-1.
is stored in the memory 48 by opening S-2 and closing S-2. After this state is set, switch S-1 is closed and switch S-2 is opened to start signal recording. -P value is compared in the electric system 49, and by controlling the amplification degree of the amplifier 32 using the difference signal, signal recording can always be performed under optimal conditions.

FIG. 4 shows another example of an apparatus using the method of the invention, in which a separate light source 50 is provided to obtain light for reproduction. The functions of the other systems are exactly the same as explained in Figure 3, but the advantage of using a separate light source is
Since the reflectance of heat mode recording media such as chalcogen-based materials differs depending on the wavelength, it is possible to more effectively receive the reflected light from the recording medium by appropriately selecting the wavelength of the light for reproduction. It's all about what you can do.

In addition, in the examples shown in FIGS. 3 and 4, the lens for condensing light for signal recording and the lens for condensing light for reproduction are the same, but as shown in FIG. A dedicated condensing lens may be used for each light. In FIG. 5, 51 is light for signal recording, 52 is light for reproduction, 53 is a lens for condensing the light for signal recording, and 54
is a lens for condensing light for reproduction, 5
5 is a recording medium.

FIG. 6 shows an embodiment in which the present invention is applied to a video disk recording apparatus that records TV signals on a disk-shaped recording medium. 60 is a laser light source for signal recording, and the laser light 61 is modulated in brightness and darkness by an optical modulator 62. A TV signal from a TV signal generator 63 is subjected to, for example, FM modulation in a modulation system 64, appropriately amplified in an optical modulator driver amplifier 65, and sent to an optical modulator 62. Part of the modulated laser beam 61 passes through a beam splitter 66
and enters the photodetector 67. Laser light 61 passed through beam splitter 66
is bent toward the front perpendicular to the plane of the paper by a mirror (not shown) located behind mirror 68 in the figure, further bent to the left by mirror 68 as shown in the figure, expanded by beam expander 69, and then mirror 70 The recording medium 7 is bent downward by the lens 72, passes through the optical coupler 71, and is
The light is focused on tiny spots on three sides. Further, a laser beam 75 from a laser light source 74 for signal reproduction is bent in the front direction perpendicular to the plane of the paper by a mirror (not shown) located behind a mirror 76 in the figure, and further bent to the left by the mirror 76, so that it becomes a polarized beam. After passing through the splitter 77, the beam is expanded by the beam expander 78, passes through the λ/4 plate 79, is bent downward by the optical coupler 71, and is bent downward by the lens 72.
As a result, the light is focused on a minute spot on the recording medium 73, further reflected by the recording medium 73, returns to the original optical path, and is extracted by the polarizing beam splitter 77 toward the photodetector 80. A moving member 81 carrying each optical element 68-72, 76-80
is moved in a direction perpendicular to the plane of the paper by means of a guide hole 83 movably connected to a guide rod (not shown) provided perpendicular to the plane of the paper, and a female screw 82 that engages with a male feed screw provided parallel to the guide bar; A disk-shaped recording medium 73 is rotationally driven by a motor 84, and signals are recorded in a spiral or concentric pattern. A part of the reproduced signal from the photodetector 80 enters a demodulation system 85 and returns it to a TV signal based on the FM signal.
Display on TV86. A portion is also sent to the P-P value measurement system 87 of the reproduced signal waveform, and
The P value is measured and displayed on the display section 87'. now,
When the amplification degree of the driver amplifier 65 is gradually changed and the P-P value of the reproduced signal waveform, that is, the display section 87' reaches its maximum, the light detection is performed by opening the switch S-3 and closing the switch S-4. P of the signal waveform obtained by the device 67 - P of the output signal from the P value measurement system 88
The P value is stored in memory 89.

When recording a signal, by closing switch S-3 and opening switch S-4, the P-P value of the signal waveform obtained by the P-P value measurement system 88 and the P of the optimal signal waveform stored in the memory 89 are sequentially calculated. -P values are compared in a comparator circuit 90, and the difference between the two is used as a signal to control the amplification degree of the driver amplifier 65, so that the signal is always recorded in the best condition.

As described above, in the signal recording method of the present invention, a signal is first recorded while changing the intensity of the recording light, and the recorded signal is reproduced to obtain the optimal value of the recording light intensity so that the reproduced signal is in the best condition. After determining the recording light intensity, the signal recording is performed while controlling the recording light intensity to the optimum value, so that signal recording can always be performed in the best condition.

[Brief explanation of the drawing]

Fig. 1a is a schematic diagram showing the main parts of an optical signal recording device, Fig. 1b is a diagram showing the correlation between the recorded signals and the recording medium, and Fig. 2a shows the main parts of the information reading device from the recording medium. FIG. 2b is a top view showing the relationship between the recording medium and reproduction light, FIG. 2c is a waveform diagram showing the reproduction output, and FIG. 3a is an apparatus using the signal recording method of the present invention. The schematic diagram shown in Figure 3b shows the recording medium and recording light.
4 is a diagram showing another signal recording device using the present invention; FIG. 5 is a side view of main parts showing another configuration example of the device using the present invention; FIG.
FIG. 6 is a diagram showing a signal recording device according to still another embodiment of the present invention. Here, 20, 50, 60, 74 are laser light sources, 25, 62 are optical modulators, 28, 53, 54 are lenses, 30, 55, 73 are recording bodies, 45, 67
is a photodetector, 46, 47, 87, 88 is a P-P value measurement electrical system; 48, 89 is a memory, 49, 90 is a comparison circuit, 32 is an amplifier, 65 is an optical modulation driver amplifier, 31, 64 is a modulation It is a vessel.

Claims (1)

[Claims] 1 In a method of recording information signals by irradiating a recording medium with recording light, the signal is first recorded while changing the intensity of the recording light, and then this recorded signal is reproduced to find the best reproduced signal. 1. A signal recording method, comprising: determining an optimum value of the recording light intensity for a state, and then performing signal recording while controlling the recording light intensity to the optimum value.