JPS62159352A - Optical information signal recorder - Google Patents

Abstract

PURPOSE:To easily control the width of a light spot with a single optical path so as to make difficult adjusting works unnecessary, by using a deflector element composed of an electrooptic crystal which is able to divide rays of light into two directions symmetrically about the optical axis. CONSTITUTION:Laser light emitted by an argon laser 1 is made incident to a deflector element 10 after the laser light is modulated in intensity by an EO modulator 2 by using an information signal supplied from a recording signal source 3. As for the deflector element 10, those which can change the cross-sectional shape of a luminous flux in order to change the width of a pit in relation with a recording wavelength and are constituted of an electrooptic crystal which can divide rays of light into two directions symmetrically about the optical axis are used. The light emitted from the deflector element 10 is expanded in diameter by a collimator 5 after it is reflected by a rectangular prism 4 and projected upon a condenser lens 6. The condenser lens 6 projects a light spot upon a recording disk 8. Since the disk 8 is rotationally driven at a prescribed rotating speed by a motor 9, recorded traces by information signals are formed by recording on the recording disk 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical information signal recording device, and more particularly, to a method for projecting a spot of light converging a light beam whose intensity is modulated by an information signal to be recorded. The present invention relates to an optical information signal recording device in which information signals are recorded on the assumption that the pit width of bits formed in geometrical concave or convex portions changes in relation to the recording wavelength.

(Prior art) A pin formed as a geometrical concave or convex portion.
An optical information signal that has been widely used as an information signal reproduction method in which the information signal is reproduced by projecting a spot of light onto the signal recording surface of the information signal recording medium on which the information signal is recorded by a cutter. The reproduction method is an optical information signal reproduction method generally called the LV method. The information signal is reproduced from the information signal recording medium by projecting a light spot onto the signal recording surface of the information signal recording medium. The relationship between the diameter of the spot and the bit width of the bit is shown in the plan view of FIG. 11(a) and the plan view of FIG.
b) as illustrated in the cross-sectional view.

In FIG. 11(a), 22a, 22b, and 22c are examples of bits each having a pit length of 1/2 of the different recording wavelength, and W in FIG. 1 is the bit width, 2
1 is a light spot, and 22 in FIG. 11(b) is a bit (if there is no need to distinguish between bits such as 22a, 22b, and 22c, they are written as bit 22).

W is the bit width, and dh is the depth or height of the bit, where dh is approximately 1/4 of the wavelength of light.

Therefore, in the LV method, the light spot 21 is designed to irradiate approximately half of both the bit and the land, such as the light spot 21 that irradiates the bit 22c in FIG. 11(a). , the zero-order reflected light becomes a minimum, and when the entire light spot 21 is on the land, the zero-order reflected light becomes a maximum, and further,
Even when the light spot 21 is designed to illuminate both the bit and the land, the light spot 21 illuminates the pin 22b in FIG. 11(a). 21 contains the entire bit 22b.

The magnitude of the zero-order reflected light is larger than the minimum state described above.

FIG. 12(a) shows the reproduction device in the LV system! +1
! 3 configurations are shown, 23 is a beam splitter, 2
4 is a condensing lens, 25 is an information signal recording medium (disk)
, 26 is a photodetector, and 27 is an output terminal. 1 Light from a light source (not shown) passes through a beam splitter 23 and is condensed by a condensing lens 24 to form a small diameter slit of light on a disk 25. -21 is projected.

The light reflected from the disk 25 by the light spot 21 described above is transmitted to the beam splitter 23 via the condenser lens 24.
There, it is reflected toward the photodetector 26 and photoelectrically converted by the photodetector 26, and the output signal from the photodetector 26 is outputted to the output terminal 27, but the signal from the disk 25 described above is As described above, the amount of light reflected from the surface (diffracted light generated by diffraction by bits on the signal surface of the disk 25) is equal to the amount of light reflected from the bit 2 in FIG.
In the case where the spot 21 is designed to irradiate both the bit and the land approximately half and half, such as the spot 21 of light irradiating the area 2c.

The zero-order reflected light becomes a minimum, and when the entire light spot 21 is on the land, the zero-order reflected light becomes a maximum, and the light spot 21 illuminates both the bit and the land. Even when the light spot 21 illuminates the pit 22b in FIG. 11(a),

When the entire bit 22b is included in the light spoilers 1 to 21, the zero-order reflected light is larger than the minimum state, so the photodetector 26 detects the reflected light as described above. An output signal corresponding to the amount of light is output, so that the information signal recorded on the disc 25 is reproduced.

The spatial frequency transmission capability (MTF) of the lens is determined by the reproduction device in the LV system shown in FIG. (a) of Fig. 14 consisting of d and
When reading a pattern like the one shown in (b),
This corresponds to the response of the MTF song 11ia shown in FIG.

FIG. 13 shows that when the period of the array pattern of the reflective surface is expressed using the wavelength λ of light and the numerical aperture NA of the condensing lens, the period of the array pattern of one reflective surface is λ/(2NA).
This indicates that the MTF becomes zero, that is, the reproduced signal becomes zero when .

In addition, a light spot having a diameter larger than the bit width of the bit formed as a geometrical concave or convex portion is projected onto the signal recording surface of the information signal recording medium, and the information signal is recorded from the information signal recording medium. What is the MTF when playback is enabled?

In the range where the period is small, it does not become like the curve I@a in Fig. 13, but overall it becomes similar to the curve a in Fig. 13, and in the LV method described above, the dotted line LV in Fig. 13
For example, if the numerical aperture NA of the condenser lens is 0.5. When the wavelength λ of light is 7gQnm.

The spatial frequency is approximately 1.4 in NA/λ.

(b) in Figure 12 is rRCA REVIEIIJ197
This figure shows the schematic configuration of the reproducing device in the differential system, which is explained in detail in VOL 39, No. 1, May 1998, in which 23 is a beam splitter, 24 is a condensing lens, and 28
is an information signal recording medium (disk); 29 is a photodetector divided on the optical axis in a direction perpendicular to the traveling direction X of the light spot; 30 is a subtractor; 31 is an output terminal;
Light from a light source (not shown) is transmitted to the beam splitter 23
The light spot 21 having a minute diameter is projected onto the disk 28 by being condensed by the condenser lens 24, and the reflected light from the disk 25 by the light spot 21 is given to the beam splitter 23,
There, the signals are reflected toward the photodetector 29 and photoelectrically converted by the two light receiving elements in the photodetector 29, and the output signals from the two light receiving elements in the photodetector 26 are subtracted by the subtracter 30. It is output to the output terminal 31 as an output signal.

As shown in the curve in FIG. 13, the MTF of the differential playback device shown in FIG. The response is higher than that of curve a, but in other parts the song PJAa
However, in the literature regarding the differential power type mentioned above, the signal at the position corresponding to the CHD indicated by the dotted line in FIG.
It is said that a good reproduced signal with /N of 60 dB (BW 30 KHz) was obtained.

The reason why a good reproduced signal can be obtained even if the MTF is low in a method of obtaining a reproduced signal by subtraction between signals, such as the differential type reproducing apparatus shown in FIG. 12(b) mentioned above, is as follows. This is because optical noise caused by a light source such as a semiconductor laser is removed by subtraction between signals.

The differential method described above is applied to information signal recording media that have a bit arrangement pattern wider than the diameter of the light spot 21, as shown in FIGS. 15(a) and 15(b). Suitable for reproducing information signals. In (a) and (b) of Fig. 16, the round-trip optical path difference due to the uneven step is π.
The characteristic value of the light spot (λ/
a)... However, the response is calculated for a = NA... In the differential method, the response waveform becomes sharper as the recording wavelength becomes larger, that is, λ/aΔ becomes smaller. ing. Therefore, the differential method can be said to be basically suitable for reproducing wide bits with short recording wavelengths.

However, a reproducing apparatus having the configuration shown in FIG. When the signal is regenerated, (
It is clear from a) and (b) that the response appears only at the edge of the pit, and the uneven shape of the pit cannot be reproduced.

FIG. 18 shows a pit generated from a pit 32 having a pit width such that a good reproduction signal can be obtained in a reproduction device employing the differential method, that is, a pit 32 whose width is wider than the diameter of the light spot 21. FIG. 18A shows the state of the diffracted light when the center of the light spot 21 is at the edge of the pit 32, and the light spot 21 is located at the edge of the pit 32.
18(b) shows a state in which the light spot 21 is divided into two parts by 2, and (b) in FIG.
It shows the relationship between the state of the distribution f of the diffracted light generated when the left edge of the pit 32 divides the pit 32 into two as shown in FIG. Since only the shaded part in the figure passes through the condensing lens and reaches the photodetector 29, one side of the dividing line of the photodetector 29 indicated by LAg in the figure reaches the photodetector 29. Light is incident only on the light receiving element of , and the information signal of the left edge of the pit 32 is output from the subtracter 30 .

In this way, the differential method can be used to read information signals from a disk having pits that can divide the light spot 21 into two.

FIG. 19 shows pits generated from pits 22 whose bit width is such that it is not possible to obtain a good reproduction signal with a reproduction device employing the differential method, that is, a pit 22 whose width is narrower than the diameter of the light spot 21. FIG. 19(a) shows a state in which the center of the light spot 21 is at the edge of the pit 22, and FIG.
(b) in Fig. 9 shows that the center of the light spot 21 is at the point ((b) in Fig. 19).
As shown in a), it shows the relationship between the state of the distribution of the diffracted light (a large number of broken-line circles) generated when it is at the left edge of the pit 22 and the aperture e of the condensing lens. .

When the center of the light spot 21 is located at the edge of a pit 22 whose width is narrower than the diameter of the light spot 21, the depth and height of the pit 22 is suitable for causing biased diffraction. Even if it is λ/2, the edge of the pit will not linearly divide the light spot 21, so
The distribution of diffracted light generated in this state is as shown in FIG. 19(b).

Only the shaded part in the figure passes through the condensing lens and reaches the photodetector 29, but the parting line of the photodetector 29 shown by ag in the figure reaches the photodetector 29. Since light is incident on the light receiving elements on both sides, a good reproduced signal based on the pit 22 is not output from the subtracter 30. In this way, the differential method uses pits that cannot divide the light spot 21 into two. It is not suitable for reading information signals from, for example, an LV type disc having a LV type disc.

The characteristics of the LV method and the differential method that have been explained so far are as follows.

As is clear from the above, the LV method and the differential method each have advantages and disadvantages, but the applicant has developed information (ff. Focusing on the possibility of providing an information fa recording medium with even higher density if a recording medium could be obtained, we first developed an information signal using pits formed as geometric concavities or convexities. As an information signal recording medium in which the information signal is recorded and the information signal is reproduced by projecting a light spot, it is used as an information signal recording medium in which the information signal is recorded and the information signal is reproduced by projecting a light spot. Bit width.

The first pit width is set to be smaller than the diameter of the light spot described above, and approximately 1/1/2 of the shortest recording wavelength.
The pit width of the pit having a pit length corresponding to 2 is set to a second bit width that is larger than the first pit width, and is approximately 1/1/2 of the longest recording wavelength. The bit width of a pit having a pit length between the bit length corresponding to 2 and the pit length corresponding to approximately 1/2 of the shortest recording wavelength is as follows: An information signal recording medium has been proposed in which the pit width is set to be equal to or smaller than the pit width of the short pits.

FIG. 20 shows the planar shape of a typical example of a pit formed as a geometrical concave or convex portion corresponding to an information signal in an information signal recording medium already proposed by the applicant company. Spot 1 of light projected onto the medium
FIG. 20(a) shows the pit recorded on the information signal recording medium corresponding to the information signal when the pit is the longest among the pits to be recorded on the information recording medium. 20 is a plan view of a pit PQ having a pit length corresponding to approximately 1/2 of the wavelength AQ, and (b) of FIG. 20 is a plan view of a pit Ps having a pit length corresponding to approximately 1/2 of the longest recording wavelength 8S among pits to be recorded on an information recording medium;
c) is a bit where the pit recorded on the information signal recording medium corresponding to the information signal corresponds to approximately 1/2 of the longest recording wavelength AQ mentioned above among the pits to be recorded on the information recording medium. As an example of a pit having a pit length between the pit length and the pit length corresponding to approximately 1/2 of the shortest recording wavelength As, there is an example of a pit having a pit length corresponding to approximately 1/2 of the shortest recording wavelength As.
) is a plan view of a pit Pm corresponding to approximately 1/2 of As).

Note that in this specification, when expressing the bit length of a pit in relation to the recording wavelength, "approximately" is used, not as 1/2 of the recording wavelength, but as approximately 1/2 of the recording wavelength. 1. For example, the bit length of a pit is recorded due to a change in the bit length of a pit when duty cycle modulation is applied, or a change in the bit length of a pit caused by variations in disc manufacturing conditions. This is because it takes into consideration that there may be a slight deviation from 1/2 of the wavelength.

The pit PR1 shown in FIG. 20(a), that is, the pit PQ having a pit length corresponding to approximately 1/2 of the shortest recording wavelength of 80 among the pits to be recorded on the information recording medium. , its bit width W1 is the light spot 1
The first pit width Wl is set to be smaller than the diameter d of the light spot 1, and the diameter d of the light spot 1 is set to d=0.8.
2λ/NA (where λ is the wavelength of the light and NA is the numerical aperture of the lens that forms the spot), then the above-mentioned first bit width W1 is 1, for example, approximately 1 of the diameter d of the light spot 1. A desirable implementation mode is to set it to /3.

In addition, the pit PS shown in FIG. 20(b), which is described above, has a bit length corresponding to approximately 1/2 of the shortest recording wavelength As among the pits to be recorded on the information recording medium. The bit width W2 of the pit Ps is set to a second bit width W2 that is larger than the first pit width W1, but the diameter d of the light spot 1 is set as d= 0゜82λ/NA (where λ is the wavelength of light, N
In a preferred embodiment, the second bit width W2 is set approximately equal to the diameter d of the light spot 1, for example, where A is the numerical aperture of the lens that forms the spot.

Furthermore, the pit Pm shown in FIG. 20(c) described above
That is, among the pits to be recorded on the information recording medium, the pit length corresponds to approximately 1/2 of the longest recording wavelength Affi, and the bit corresponds to approximately 1/2 of the shortest recording wavelength As. The recording wavelength Am shown as an example of a bit having a bit length between
The pit width W3 of a bit Pm having a bit length corresponding to approximately 1/2 of ΔS) is equal to the bit width of a bit having a bit length shorter than the bit length of the bit Pm, or The bit width is set smaller than the bit width of a bit having a bit length shorter than that of bit Pm.

Among the bits to be recorded on the information recording medium described above, a bit length corresponding to approximately 1/2 of the longest recording wavelength Al, and a bit length corresponding to approximately 1/2 of the shortest recording wavelength As. As for how to set the bit width of a bit having a bit length between
The first pit width Wl (minimum pit width) is set for a bit length corresponding to , and the bit length is set for a bit length corresponding to approximately 1/2 of the shortest recording wavelength As. The pit width W3 may be changed continuously in inverse proportion to the bit length between the second pit width (maximum bit width), or 1, for example, the maximum recording wavelength All.
The portion of the recording wavelength between the above-mentioned shortest recording wavelength AS is divided into a plurality of groups according to the length of the recording wavelength, and approximately 1 of the maximum recording wavelength 8a of the bits to be recorded on the information recording medium is divided into a plurality of groups according to the length of the recording wavelength.
The first pit width Wl (minimum pit width) set for the bit length corresponding to /2 and the shortest recording wavelength As
and the second bit width (maximum pit width) set for the corresponding bit length, so that each group has a predetermined bit width. The bit width W3 may be set and changed for each group.

The bit depth and height in the previously proposed information recording medium are λ/4, which is the optimum value of the bit depth and height in the LV method, and the bit depth and height in the differential method.
A value intermediate between the optimal value of λ/8, that is, λ15.3
It is best to set it to a certain degree.

In this way, in the previously proposed information signal recording medium, information signals are recorded using bits whose bit width changes depending on the recording wavelength, and bit 11 of the bit in the region where the recording wavelength is long is the light spot. The diameter is set to approximately 1/3 of the diameter, and the modulation degree due to bit diffraction is maximum for bit 1], making it possible to obtain a good reproduction signal, and bits in the region where the recording wavelength is short are By making the diameter and bit width approximately equal, the diffraction effect in the bit string direction is increased and the degree of modulation due to diffraction against the aperture of the condensing lens is increased. However, a good output signal can be obtained using the differential method.

As mentioned above, the optical reproduction of information signals from the previously proposed information signal recording medium in which the information signal is recorded using bits whose pitch width varies depending on the recording wavelength is, for example, the 21st method. This is performed by a playback device configured as shown in the figure.

In FIG. 21, 51 is a semiconductor laser light source;
2 is a collimator lens, 53 is a beam splitter, 54
is a condensing lens that creates a reading spot, and the information signal recorded on the information signal recording medium 50 (disc 50) is read from the flat side of the transparent plastic.

A photodetector 55 receives reflected light from the disk 50 and converts it into an electrical signal.
is 2 on the optical axis in the direction perpendicular to the traveling direction of the light spot.
A light receiving element is arranged at each divided position. 56 is a subtracter, 57 and 58 are adders, 59 is a bypass filter, 60 is a phase shift circuit, and 61 is an output terminal.

In the optical information signal reproducing device shown in FIG. 21, the laser beam emitted from the semiconductor laser 51
2, the light is made into parallel light, and then sent to a condenser lens 54 via a beam splitter 53, and the condenser lens 54 projects a minute spot of light onto the signal surface of the disk 5o.

The reflected light from the signal surface of the disk 50 is received by two light receiving elements in the photodetector 55 via the condenser lens 54 and the beam splitter 53.

The output signals from the two light receiving elements in the photodetector 55 described above are added by an adder 57 and sent to an adder 58.
The output signals from the two light-receiving elements in the photodetector 55 are also supplied to the subtractor 56, and the subtracter 56 inputs the two light-receiving elements in the photodetector 55. A signal obtained by subtracting the output signals from two light receiving elements is output, and the signal is sent to the bypass filter 59.
supply to. Then, the output signal from the bypass filter 59 described above is sent to the adder circuit 58 via the phase shift circuit 60.
It is supplied as the other input.

The output signal from the adder 57 in the optical information signal reproducing apparatus shown in FIG. Since this is a signal that has been photoelectrically converted by two light receiving elements, this output signal is the 12th
This corresponds to the output signal from the playback device in the LV system explained with reference to (a) in the figure, and therefore, the 21st
The output signal from the adder 57 in the illustrated optical information signal reproducing apparatus satisfactorily reproduces the low-frequency signal component of the recorded signal, as shown by song Iia in FIG.

In addition, in the previously proposed information signal recording medium, the bit width W1 of the bit PQ of the information signal that should cause the longest recording wavelength ΔQ, and the pit width W2 of the bit Ps of the information signal that should cause the shortest recording wavelength As. , the bit Pm of the information signal that should produce a recording wavelength Δm with a length between the longest recording wavelength AQ and the shortest recording wavelength As.
The pit width W3 in FIG. 20 is (a) and (b), respectively.
).

As shown in (c), the width of the bit is changed to correspond to the recording wavelength, so even if the recording wavelength becomes shorter, the bit size will vary with respect to the light spot for reading the information signal. The area occupied can be made the same as when the recording wavelength is long, so even if the recording wavelength is short, the same diffraction effect as when the recording wavelength is long (although the direction of light diffraction is different) can be obtained. As a result, a good response can be obtained up to high frequencies.

That is, since the bit in the LV method described with reference to FIG. 11 has a constant bit width W regardless of the length of the recording wavelength, the intensity of the diffracted light from the bit is
Compared to the diffracted light from the bit when the recording wavelength is long, the diffracted light from the bit when the recording wavelength is short is lower, and as a result, the degree of modulation by the bit when the recording wavelength is short is lower. However, in the previously proposed information signal recording medium, as is clear from Figure 20, when the recording wavelength becomes shorter, the area of the bit increases due to the increase in the bit width of the bit. Because it is done like this.

Even when the recording wavelength becomes shorter, the degree of modulation is maintained at a high level, and signals with high frequency components can be recorded and reproduced satisfactorily.

The output signal from the subtracter 56 in the optical information signal reproducing circuit shown in FIG. Two light receptions at 5:3
Since it is a difference signal between signals photoelectrically converted by The output signal from the first
This corresponds to the output signal from the reproducing device in the differential system explained with reference to (b) in Fig. 2, and the MTF becomes as shown by the curve in Fig. 13. In the previously proposed information signal recording medium, the longest recording wavelength is A.
The pit width W1 of the bit PQ due to the information signal that should cause Q, the bit width W2 of the bit Ps due to the information signal that should cause the shortest recording wavelength As, and the longest recording wavelength AQ and the shortest recording wavelength As mentioned above. The bit width W3 of the bit Pm due to the information signal that should produce the recording wavelength Am of length between is shown in FIGS. 20(a) and 20(b), respectively.
, (c), the width of the bit pit is varied depending on the recording wavelength, and when the recording wavelength is long, the bit pit width W1 is smaller than the diameter of the light spot. , the MTF for low-frequency signals is smaller than the curve in FIG. 13, and the recording wavelength Δm is between the longest recording wavelength AM and the shortest recording wavelength As. Since the pit W3 of the pit Pm due to the information signal is also smaller than the diameter of the light spot, the MTF for the mid-range signal is also smaller than the curve in FIG. 13, but it produces the shortest recording wavelength As. Since the pit width W2 of the pit Ps due to the information signal to be generated is approximately the same as the diameter of the light spot, the MT for the high frequency signal is
F is approximately the same as the curve in FIG. The MTF in high-frequency signals is low as shown by the dotted line CED in Figure 13, but in the differential method, the noise of the semiconductor laser is removed by differential quadrupling, and a sufficiently high C/N can be obtained. Because there is no deterioration in signal quality even if the signal is amplified,
By performing the necessary amplification, the original signal waveform can be reproduced satisfactorily.

Subtractor 5 in the optical information signal reproducing device shown in FIG. 21
A bypass filter 59 to which the output signal from 6 is supplied is configured to suppress a low-frequency differential reproduction signal as shown by the parameter λ/aA=0.2 in FIG. It is provided. The low frequency signal is well obtained in the output signal of the adder 57 mentioned above.

There is no need to obtain it from the output signal from the subtracter 56. Further, the phase shift circuit Go exists between the output signal from the subtracter 56 and the output signal from the adder 57.
This is provided to eliminate the degree phase difference.

FIG. 22 shows an example configuration of an optical information signal reproducing device for reproducing information signals from a light-transmissive information signal recording medium 62. In FIG. 22, 55 is divided into two in the column direction of pits 63. 55a and 55b are light receiving elements. Regarding the longer pit 83a among the pits recorded on the information signal recording medium 62, a reproduced signal is generated as the sum of the outputs of the two light receiving elements 55a and 55b in the photodetector 55, but this is different from the pit when the recording wavelength is long. This is because the area ratio between the pits and the land portions is optimized for modulation.

Furthermore, in the case of a short recording wavelength such as the pit 63b, the diffraction effect due to the edge of the pit is detected by the photodetector 55 as a difference signal between the output signals from the two light receiving elements 55a and 55b. However, as in the case of the reflective optical information signal reproducing device described above with reference to FIG. 21, the noise contained in the light source is greatly reduced.

The circuit arrangement to be followed by the two light-receiving cables 55a and 55b of the photodetector 55 is the same as that of the optical information signal reproducing device shown in FIG. 21 described above.

In a transmission type information signal recording medium, it is desirable that the optical path difference between the pit and the land is approximately λ/4, and the depth of the pit is λ/4 (where n is the refractive index of the transparent material).
n-1), which corresponds to about three times the pit depth in a reflective information recording medium.

Now, in the previously proposed information signal recording media, information signals are recorded using pits whose pit width changes according to the recording wavelength, and the pits in the region where the recording wavelength is long have a bit width that is equal to the spot diameter of the light. The width of the pit is approximately 1/3, and the degree of modulation due to pit diffraction is maximized with respect to the pit width, making it possible to obtain a good reproduction signal. By making the widths approximately equal, the diffraction effect in the bit string direction is increased and the degree of modulation due to diffraction against the aperture of the condensing lens is increased. However, the previously proposed information signal recording media, in which information signals are recorded using pits whose bit width varies depending on the recording wavelength, as described above, For example, it can be produced using the following recording device.

FIG. 23 is a block diagram showing an example of the configuration of an information signal recording device. In FIG. 23, 33 is a short wavelength argon laser for recording, and the laser beam emitted from the argon laser is transmitted to an EO modulator 34. is incident on the E.O.
The modulator 34 modulates the intensity of the laser beam using the recording signal supplied from the recording signal WX 36 and emits S-polarized light having an electric field vector perpendicular to the plane of the paper.
Give to 5. As the electronic shutter 35, for example, one configured to cause one refraction by an electric field is used.For example, one that utilizes the Kell effect of an isotropic medium, the Kell effect of a crystal, or the Faraday effect is used. can.

The electronic shutter 35 is supplied with a signal from the record 48 source 36 via the low-pass filter 37, and the electronic shutter 35 receives the electric field of the signal voltage supplied via the low-pass filter 37. Birefringence is generated in proportion to the size, and light whose phase has changed thereby is emitted from the electronic shutter 35 and applied to the polarizing prism 38. The polarizing prism 38 reflects the S-polarized light upward and transmits the P-polarized light.

FIG. 24 is a perspective view illustrating and explaining the relationship between the electronic shutter 35, the polarizing prism 38, and the polarization direction, and 35a
, 35b is an electrode, and 35c is a drive t1! It is a line. The direction of the electric field of the electronic shutter 35 is set at 45 degrees with respect to the S-polarized light, and the principal axis generated by the electric field is also set at 45 degrees.

Now, if the phase difference due to birefringence that is proportional to the electric field strength in the electronic shutter 35 is δ, then the strength Is of the S-polarized light reflected upward by the polarizing prism 38 is Is =
1-sin” δ/2・(1), and the intensity Ip of the P-polarized light transmitted through the polarizing prism 38 is I p =si
The relationship between the magnitude of the electric field and the magnitude of birefringence, which is n''δ/2 (2), is determined by the type of electronic shutter and the type of birefringent material.

Since the electronic shutter 35 gives the laser beam a phase difference δ proportional to the magnitude of the electric field supplied to it, the S-polarized light in equation (1) determined by the above-mentioned phase difference δ is reflected upward by the polarizing prism 38. The P-polarized light of formula (2) described above passes through the polarizing prism 38 and proceeds to the other optical path.

The S-polarized light reflected upward by the polarizing prism 38 is reflected by the right-angle prism 39 and then passes through the cylindrical lens 41 .
42, it is expanded by a small angle in one direction, reflected by the right angle prism 40, and incident on the polarizing prism 43.
The light is reflected by this polarizing prism 43 and applied to a right angle prism 44 .

Further, the P-polarized light transmitted through the polarizing prism 38 described above is incident on the polarizing prism 43, and after passing through the polarizing prism 43, it is applied to the right angle prism 44.

The S-polarized light and the P-polarized light incident on the right-angle prism 44 are reflected by the right-angle prism 44 and given to the beam expander 45, where they are expanded and sent to the condenser lens 4.
6, and a minute spot of light is imaged on the photosensitive material layer of the recording disk 48 by the condenser lens 46. 47 is an actuator in the automatic focus adjustment device;
9 is a rotational drive device for the recording disk 48.

FIG. 25(a) shows the polarizing prism 38 and the polarizing prism 4.
This is a light spot with a circular cross section that is generated on the recording disk 48 when the P-polarized light that has passed through the optical path with the polarizing prism 38 is condensed by the condensing lens 46. Prism 391 Cylindrical lens 41, 4
2. This is a light spot with an elliptical cross section that is generated on the recording disk 48 when the S-polarized light that has passed through the optical path of the right-angle prism 40 and the polarizing prism 43 is focused by the condensing lens 46 .

A signal with a frequency in the passband of the low-pass filter 37 is set to a size such that when it is supplied to the electronic shutter 35, a 180 degree phase difference can be caused in the light due to birefringence generated in the electronic shutter 35. In addition, as shown in FIG. 26, the characteristic of the low-pass filter 37 is set so that its corner frequency fO is within the frequency range f1 to f2 of the information signal. When a signal in the range of f1 to fo passes through the low-pass filter 37 and is supplied to the electronic shutter 35, the phase of the light passing through the electronic shutter 35 is shifted by 180 degrees, so in this state, the S-polarized light l5= O, P polarized light Ip=l, and P polarized light Ip emitted from the electronic shutter 35 is polarized by the polarizing prism 3.
8→polarizing prism 43→right angle prism 44→beam splitter 35, the light is supplied to the condensing lens 46 and condensed by the condensing lens 46, so that the light is recorded on the recording disk 48 as shown in FIG. 25(a). A round spot of light is formed like this.

Also, if the information signal has a frequency equal to or higher than fo.

Since the voltage of the signal passing through the low-pass filter 37 decreases, the amount of phase shift imparted to the light by the electronic shutter 35 becomes smaller than 180 degrees. now.

If the response of the low-pass filter 37 at frequency f2 is -20 dB compared to the passband, the amount of phase shift δ given to the light at one frequency f2 is δ = π/1G, so the S polarized light Is at this time is Is =0.9.

In this state, the S-polarized light Is emitted from the electronic shutter 35 is supplied to the condenser lens 46 through the optical path of the polarizing prism 38 → cylindrical lenses 41 and 42 → right-angle prism 40 → polarizing prism 43 → right-angle prism 44 → beam splitter 45. By being focused by the condensing lens 46, a substantially elliptical spora 1- of light is imaged on the recording disk 48 as shown in FIG. 25(b). In the above example, the P-polarized light I p =0.1 emitted from the electronic shutter 35 is transmitted through the polarizing prism 38 → polarizing prism 43 → right-angle prism 4
4 → Condensing lens 4 through the optical path of beam splitter 45
6 and condensed by the condensing lens 46, a round light spot is superimposed on the recording disk 48 as shown in FIG. imaged.

In this way, if the recording apparatus shown in FIG. 23 is used, the bit width W1 of the bit PQ due to the information signal that should cause the longest recording wavelength AQ, and the bit width W1 of the information signal that should cause the shortest recording wavelength As. Ps pit width W2
and the longest recording wavelength Al and the shortest recording wavelength As mentioned above.
The bit width W3 of the bit Pm by the information signal that should cause m to the recording wavelength of length between
As illustrated in (a) to (b), e, and (c) of the figure, the wavelength may vary widely depending on the recording wavelength.

Note that the pit width of the bit is determined by the bit width W2 of the bit Ps according to the information signal that should produce the shortest recording wavelength AS, as shown in FIG. 20(b). It is desirable that the pit width be approximately equal to the diameter d, because if the pit width of the bit is made larger than necessary, crosstalk between adjacent recording traces will increase. Also, the bit P according to the information signal that should cause a recording wavelength Am between the longest recording wavelength Aρ and the shortest recording wavelength As.
m is the sum (average) of the bit pm of the information signal that should cause the longest recording wavelength, fl, and the bit PS of the information signal that should cause the shortest recording wavelength AS;
This is because the intensity of light at both ends of the width of the bit is small and is below the threshold a, so as a result of recording, the bit width is slightly narrower.

A stamper is made according to a known bean-making technique based on the recording disk 48 on which information signals have been recorded by the recording device as shown in FIG. By attaching a metal reflective film to the surface, information signal recording media can be reproduced in large quantities.

It goes without saying that if a metal reflective film is not attached to the signal surface of the transparent plastic replica described above, a light-transmissive information signal recording medium can be obtained, but it is also possible to obtain a light-transmissive information signal recording medium. There is a difference in the optimum value of the bit depth between the case of a reflective disk and the case of a reflective disk. Also, the depth and height of the bits formed on the recording disk 48 are as follows:
It is determined by the thickness of the photoresist film used during recording. Furthermore, since the bit width of the bit in the previously proposed information signal recording medium increases as the recording wavelength becomes shorter, it is necessary to increase the recording energy per unit time when recording bits when the recording wavelength is short. In this case, it is preferable to increase the power of the drive source of the EO modulator 34 in FIG. 23 in the high range.

(Problems to be Solved by the Invention) By the way, in the recording device having the configuration shown in FIG. 31 adjustments are required, including adjustment to align the optical axes, (2) Ms adjustment to eliminate the phase difference between the two optical paths, and (3) adjustment of the astingmart optical system that has a small focus error. However, in addition to having to perform the above-mentioned adjustment with high precision, measures against temperature changes and changes over time are also required, and maintenance management is also difficult, so a solution was sought.

(Means for Solving the Problems) The present invention provides a method for forming geometrically concave or convex portions by projecting a focused light spot whose intensity is modulated by an information signal to be recorded. In addition, in an optical information signal recording device in which information signals are recorded with the bit width of the bit changing in relation to the recording wavelength, the bit width of the bit is A deflection element made of an electro-optic crystal that can split the light into two directions symmetrically with respect to the optical axis is provided in the optical path as an element that changes the cross-sectional shape of the light beam in order to change it in relation to the recording wavelength. By providing an optical information signal recording device, the width of the light spot can be easily controlled with a single optical path, and the above-mentioned problems can be solved.

(Example) Hereinafter, specific contents of the optical information signal recording device of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of an embodiment of the optical information signal recording apparatus of the present invention. In FIG. 1, 1 is an argon laser, 2 is an EO modulator, and 3 is a recording signal source. 1
The laser beam emitted from the EO modulator 2 is transmitted to the recording signal source 3.
The light is intensity-modulated by an information signal supplied from the light source and then enters the deflection element 10. The deflection element 10 described above is capable of splitting light into two directions symmetrically with respect to the optical axis so that the cross-sectional shape of the light beam can be changed in order to change the pit width of the bit in relation to the recording wavelength. Those constructed using electro-optic crystals are used.

Then, the light emitted from the deflection element 10 passes through a right angle prism 4.
After being reflected, the beam is expanded in diameter by a collimator 5 and then projected onto a condenser lens 6, which then projects a spot of light onto a recording disk 8. 7, the condensing lens 6 is the recording disk 8
This is an actuator in an automatic focus control system that automatically controls the object so that it is always in focus. Since the recording disk 8 described above is driven and rotated by the motor 9 at a predetermined number of rotations, a recording trace based on the information signal is recorded and formed on the recording circle gls.

2(a) to 2(c) show that the bit width of the information signal recorded in the recording circle fi8 by the optical information signal recording device shown in FIG. 1 changes depending on the recording wavelength. In the optical information signal recording device shown in FIG. The pit width is made narrower and wider.

FIG. 3 is a diagram showing the operating principle of how the pitch 1 to the middle of the pitch 1- can be changed narrowly and widely by dividing the laser beam into two by the deflection element 10, and (a) in FIG. It shows the energy distribution in the radial direction of a light spot generated by a light beam that is not deflected by the element 10, and FIG. 3(c) is the Airy disk in the case of FIG. 3(a), In addition, FIG. 3(b) shows the radial direction of the light spot when the light beam is divided into two by deflection by the deflection element 10 and two light spots are created at positions separated by the diameter of the light spot. FIG. 3(d) is the Airy disk in the case of FIG. 3(b).

In this way, when recording an information signal on the recording disk 8, the optical information signal recording apparatus shown in FIG. The bits formed by the recorded information signal have pit widths that vary depending on the recording wavelength, as shown in (a) to (c) in Figure 2. The deflection control according to the recording wavelength carried out in the above-mentioned deflection element 10 is carried out by the (2) threshold value component supplied from the recording signal source 3 to the deflection element 10 via the bypass filter 11.

As the above-mentioned deflection element 10, for example, the deflection element 10 shown in FIGS.
The configurations shown in FIGS. and 8, respectively, can be used.

First, the deflection element 10 shown in FIG.

When an electric field is applied in the direction of the optical axis, the S-polarized light and the P-polarized light are deflected by an angle of 0 in opposite directions, as shown in FIG. is seen from the deflection plane), so if the focal length of the condenser lens 6 is f, the two light spots will be on the focal plane as follows (
They are constructed so that they can be separated by Δ shown in equation 1).

Δ=2f·0 (1) Next, the operation of the deflection element 10 shown in FIG. 4 will be explained with reference to FIG. The deflection element 10 shown in FIGS. 4 and 5 respectively has a main axis xe of a refractive ellipsoid in an electro-optic crystal that changes from an isotropic crystal or a uniaxial crystal to a biaxial crystal under the action of an electric field.

Y#1. Z-axis, and when the Z-axis is a direction in which the refractive index does not change due to an electric field, it has two planes in which the Z@ and another axis are perpendicular to each other, and one other slope. Two triangular prisms are prepared, and the two axes of the two triangular prisms are in opposite directions and parallel to each other, and the slopes are pasted together, and the light passing in the Z@force direction is pasted. It is composed of a compound prism that refracts the light symmetrically in two directions within the plane of incidence with respect to the surface, and 10a and 10b in Fig. 1 are the two triangular prisms mentioned above, and the prisms 10a and 10b in FIG. columnar prism 10
a and 10b, for example, KDP (KH20
A triangular prism of crystal P4) is used.

KDP is a uniaxial crystal with its two axes as optical axes, and Z
When an electric field is applied in the axial direction, it becomes a biaxial crystal, and the X and Y axes are
and the refractive index nl in the X' axis direction which is divided into equal parts.

The refractive index n2 in the Y'-axis direction perpendicular to it is defined by Ez representing the electric field strength in the Z direction and γ6 representing the electro-optic constant.
3. If the ordinary ray refractive index is no, then the following (2)
, as shown in equation (3).

n1=no+(y63/2)no3Ez...
(2) n2=no-(763/2)no3Ez --
(3) If B is the linearly polarized light incident on the deflection element 10 from the left in FIG. As it moves to the triangular prism 10b, it is refracted downward as shown in FIG.

The Y'-axis component (P) is a triangular prism 10 with a refractive index n2.
b to the triangular prism 10a with a refractive index n1, and is refracted upward as shown in FIG.

The above two refractions are expressed by the following equations (4) and (5) according to Snell's law.

(sin(α+0')/5ina=nl/n
2 ・-(4)(sin(a-〇')/sin a
= n l/ n 2-- (5) Electro-optic constant 763 is 10.6 x 10'' in KDP
Since it is small like m/v, sin O is approximately θ. When finding 0 using the above formulas (2) to (5),
0 is.

0 = 763-no3@E z-tOnα-(6) =
γ63・no3・V/D・・・・・・・・・(
7) (where ■ is the voltage and D is the deflection element) It can be seen that the angle 0 at which the optical axis is deflected is controlled by the voltage applied to the deflection element 10.

Now, assume that the focal length f of the condenser lens 6 is 1.5 mm.

In addition, if the deflection element is 4111 mm, the separation distance Δ between the two light beams on the focal plane is 0.2 μm.
The voltage V required to be applied to the deflection cord 10 is 14,600 volts.

Note that if a plurality of deflection elements are connected in series and used, the voltage applied to each deflection element can be reduced.

Next, FIGS. 6 and 7 show a deflection element for parallel polarized light using an electro-optic crystal in which the number of optical axes is increased by the action of an electric field, and a deflection element that deflects in the opposite direction to the above-mentioned deflection element. , shows another configuration example of the deflection element in which a half-wave plate is disposed between the two (Iil direction elements) described above to refract light in two directions at the same time.

In FIGS. 6 and 7, 12 and 12' are one-way deflection prisms, and 13 is a half-wave plate, and the one-way deflection prism 12 is two triangular prisms 12a and 12b made of KDP crystal. The Y' axis of the two triangular prisms 12a and 12b is aligned with the optical axis.

The directions of the Z-axes are reversed. Also.

The one-way deflection prism 12' is made of two triangular prisms 12a' and 12b' made of KDP crystal, and the one-way prism 12 is arranged so that the normal direction of the bonded surface is opposite to the Z-axis. It is placed upside down.

In FIG. 6, when a downward electric field is applied to the unidirectional deflection prism 12, the X-axis layer refractive index of the triangular prism 12a becomes nl shown in equation (2), and the The X-axis layer refractive index is nl as shown in equation (3), and therefore, linearly polarized light in the X-axis direction is refracted downward at the bonding surface as shown in FIG. The deflection angle 0 is the same as that shown in equation (6). The refractive index in the Z-axis direction is constant regardless of the direction of the fJ field. Therefore, the linear deflection (S) in the 2# direction travels straight. When the plane-polarized light passes through the 172-wave plate 13, the polarization direction changes by 90 degrees.

Furthermore, when a downward electric field is applied to the unidirectional deflection prism 12', the P-polarized light in the
Due to the change from l to nl, it is refracted upward as shown in FIG. Since the S-polarized light travels straight, the lights are separated by an angle θ as shown in FIG. The deflection angle 0 is controlled by the electric field strength similar to that shown in equation (6).

When the deflection angle is 0, the length of the unidirectional deflection prism in the X direction is a,
Letting t be the thickness of the unidirectional deflection prism in two directions, it is expressed by the first-order equation (8).

θ” (Q/Dt)no3・763・V −・・(
8) The deflection elements shown in FIGS. 6 and 7 are obtained by increasing the length 2 of the one-way deflection prism, as shown in equation (8) above. If the center is narrowed, that is, the angle α of the boundary surface is increased, and the thickness t in two directions of the unidirectional deflection prism is decreased, the voltage sensitivity increases. It is not necessary to use a transparent electrode as the electrode.In the above explanation, the one-sided deflecting prism 12' was placed with the one-sided deflecting prism 12 upside down. Even if it is arranged in the same direction as the deflection prism 12 and the electric field is directed upward, the same operation will be performed in the case shown in FIG.

Now, in the deflection elements shown in FIGS. 4 and 5 and the deflection elements shown in FIGS. 6 and 7,
The direction of vibration of the light divided into directions is.

They are parallel and perpendicular to the direction in which the recording trace extends, and the convergence state and the effect on the recording film are slightly different.

When the light emitted from the deflection element 10 is passed through a quarter-wave plate, both linearly polarized lights can be turned into circularly polarized lights with opposite directions, so the spot of light that is formed is directed in the direction in which the recording trace extends. It is symmetrical.

When the deflection element 10 does not operate, in the case of the deflection element shown in FIGS. 4 and 5, a spot of light is formed by linearly polarized light in the 45 degree direction, and in the case of the deflection element shown in FIGS. In the case of , elliptically polarized light having an axis in the 45 degree direction is emitted from the deflection element, with the refractive index of the horizontal axis being no (ordinary ray refractive index) and the refractive index of the vertical axis being ne (extraordinary ray refractive index). Therefore, the light spot formed by the light is symmetrical with respect to the optical axis.

FIG. 8 is a perspective view of another configuration example of the deflection element 10, in which the wavefront of light is made uneven to widen the spot of light. 13 is a KDP crystal, which has two axes in a direction orthogonal to the optical axis. Reference numerals 14 and 15 are electrodes, and this electrode 14.
15 is provided so as to divide the cross section of the light beam into two parts, a strong electric field part and a weak electric field part, in the direction in which the light is to be spread.

The difference in the strength of the electric field generated in the KDP crystal due to the voltage applied to the terminals 16 and 17 connected to the electrodes 14 and 15 causes an optical path difference Δ as shown in the first-order equation (9).

Δ” (no3/2) Q ・y 63 (V/l)
--(9)' The polarization direction of the light incident on the deflection element is Z
When a voltage is applied to the electrode 14.15 through its terminal 16.17, the deflection element of this KDP crystal behaves similarly to the phase plate shown in FIG. to diffract the light. In FIG. 9, Δ is the optical path difference, d is the center of gravity of the light distribution on both sides of the center, and φ is the direction of diffraction of light.

When the optical path difference Δ is 1/2 of the wavelength λ of the light, the condenser lens 6
Since the light projected onto the optical axis has opposite phases on the optical axis, it forms a double peak as shown by curve a in FIG.

The peak value occurs in the ±φ direction, that is, at the position of f·φ. Further, when the optical path difference Δ is zero, a light spot like curve Bb in FIG. 10 is generated on the optical axis. Furthermore, when the optical path difference Δ is −0<Δ×λ/2, the curve m in FIG.
The distribution will be like e.

As is clear from equation (9) above, since the optical path difference Δ can be controlled by voltage, the width of the light spot can be changed as desired.

Now, let the length of the deflection element in the X direction be Q of 20 mm,
When the thickness of the deflection element in the Z-axis direction is t, the applied voltage V is 6400 volts, and the light spot is at the 10th
A light distribution with a flat head like the song Inc in the figure can be created with approximately half the voltage.

(Effects) As is clear from the above detailed explanation, the optical information signal recording device of the present invention projects a spot of light that is a focused beam whose intensity is modulated by the information signal being recorded. An optical system in which an information signal is recorded as a bit formed in a geometrically concave or convex portion, and in which the pit width of the bit changes in relation to the recording wavelength. In digital information signal recording devices, an electro-optic element that can split light into two directions symmetrically with respect to the optical axis is used as an element that changes the cross-sectional shape of a light beam in order to change the pit width of the bit in relation to the recording wavelength. A deflection element made of a crystal, for example, an electro-optic crystal that changes from an isotropic crystal or a uniaxial crystal to a biaxial crystal under the action of an electric field.
When the Z-axis is the direction in which the refractive index does not change due to the electric field, the Z-axis and the other axis are perpendicular to each other, and the Z-axis has two planes and one other slope. Two triangular prisms are prepared, and the Z axes of the two triangular prisms are parallel to each other in opposite directions, and the slopes are pasted together, and the light passing in the two axial directions is pasted together. A deflection element for parallel polarized light that is configured as a compound prism that refracts symmetrically in two directions in the plane of incidence on a surface, or for example, uses an electro-optic crystal whose number of optical axes increases due to the action of an electric field. and a deflection element that deflects in the opposite direction to the above-mentioned deflection element, and a 172 wavelength plate arranged between the above two deflection elements to refract light in two directions at the same time, or an electric field action. The number of optical axes increases due to the optical crystal
is perpendicular to the optical axis, and the cross section of the light beam passing through the electro-optic crystal is divided into two by a strong electric field part and a weak electric field part. This optical information signal recording device is equipped with an optical information signal recording device that uses a single optical axis on one optical axis to change the pit width of the bits of the information signal to be recorded, depending on the recording wavelength. A deflection element that splits the light produced by the electro-optic crystal placed in the
Since this is done by dividing the information signal in different directions, it is possible to optically record the information signal using an optical information signal recording device with a simple optical system. Such difficult adjustment work is not required, and according to the present invention, the above-mentioned conventional problems can be satisfactorily solved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the optical information signal recording device of the present invention, FIG. 2 is a plan view of a bit whose pit width changes depending on the recording wavelength, and FIGS. 3 and 10 form the bit. FIGS. 4 and 7 are views of the deflection element viewed from the deflection surface, and FIGS. 5, 6, and 8 are perspective views of the deflection element. Figure 9 is a perspective view of the phase plate, Figure 11 is a diagram showing pits and light spots in contrast in the LV system, and Figure 12 is a diagram showing a comparison between pits and light spots in the LV system.
The figure is a block diagram of the LV system and differential system playback device, Figure 13 is the MTFa diagram, and Figure 14 is the song in Figure 13, li.
Fig. 15 is a plan view of a pit array suitable for reproduction by the differential reproduction method, and Fig. 16 shows various recording wavelengths by the differential reproduction method. Fig. 17 is a waveform diagram when the pit in Fig. 16 (however, 1 phase difference is π) is reproduced by the LV method, and Fig. 18 is an explanatory diagram of the reproduced signal from the pit in Fig. 15. Figure 19 shows the distribution of diffracted light due to the edges of pits in the LV method, and Figure 20 shows the distribution of the diffracted light as geometric concavities or convexities corresponding to the information signal in the previously proposed information signal recording medium. A diagram showing the planar shape of a typical example of pits formed in comparison with a spot of light projected onto an information signal recording medium, FIG. 21 is a block diagram showing an example configuration of a reproducing device, and FIG. FIG. 23 is a block diagram showing an example configuration of a conventional information signal recording device, FIG. 24 is a perspective view of an electronic shutter, and FIG. 25 is a perspective view of a reproduction device for a transmission type information signal recording medium. FIG. 26 is a plan view of the spot, and FIG. 26 is a characteristic side view of the low-pass filter. 1.33...Argon laser, 2.34...EOi
Adjustment device, i o...Polarizing element, 10a, 10b, 12
a. 12b... Triangular prism, 13... 1/2 wavelength plate, 14.15... Electrode, 21... Light spot, 22.22a, 22b, 22c, PQ, Ps, Pm,
63...Pit, 23.53...Beam splitter, 24,46.54...Condenser lens, 25,28゜5
0.62... Information signal recording medium (disc). 26.29,55...Photodetector, 30.56...Subtractor, 27,31.61...Terminal, 35...Electronic shutter, 35a...Electrode, 3,36... Recording signal source. 11.37...Low pass filter, 38.43...
Polarizing filter, 39, 40. 44...Right angle prism,
41.42... Cylindrical lens, 45... Beam expander, 47... Drive device, 8, 48... Recording disk. 9.49...Motor, 51...Semiconductor laser, 5.
52... Collimator lens, 5G... Subtractor. 57.58... Adder, 6o... Phase shifter, Patent applicant: Victor Company of Japan, Ltd. I゛゛Pa;゛1, LL
o O to −1Σ <a,> xO//1 (t3) Xヅ＾ (b) Fig. 26

Claims (1)

[Scope of Claims] 1. A pit formed in a geometrical concave or convex portion by projecting a spot of light that is intensity-modulated by an information signal to be recorded, and In the optical information signal recording device described above, in which the information signal is recorded assuming that the pit width of the pit changes in relation to the recording wavelength, the pit width of the pit is changed in relation to the recording wavelength. An optical information signal recording device comprising, in an optical path, a deflection element made of an electro-optic crystal capable of splitting light in two directions symmetrically with respect to an optical axis, as an element for changing the cross-sectional shape of a light beam. 2. As a deflection element provided in the optical path, the principal axes of the refractive ellipsoid in an electro-optic crystal that changes from an isotropic crystal or a uniaxial crystal to a biaxial crystal by the action of an electric field are the X axis, Y axis, and Z axis.
When the Z-axis is set as a direction in which the refractive index does not change due to an electric field, a triangle having two planes and one other slope where the Z-axis and one other axis are perpendicular to each other. Two columnar prisms are prepared, and the Z-axes of the two triangular prisms described above are parallel to each other in opposite directions, and the slopes are pasted together. The optical information signal recording device 3 according to claim 1, which uses a composite prism that refracts symmetrically in two directions in the plane of incidence of A parallel polarization deflection element using an electro-optic crystal that increases the number of optical axes, a deflection element that deflects in the opposite direction to the above-mentioned deflection element, and a 1/2 wavelength plate between the above two deflection elements. The optical information signal recording device 4 according to claim 1 uses an optical information signal recording device 4 that uses an optical information signal recording device 4 that is arranged so as to refract light in two directions at the same time, and as a deflection element provided in the optical path, The number of optic axes is increased by setting the electro-optic crystal such that its Z-axis is perpendicular to the optical axis, and the cross section of the light flux passing through the electro-optic crystal is divided into a strong electric field part and a weak electric field part. The optical information signal recording device according to claim 1, which uses an optical information signal recording device configured to be divided into two parts.