JPS59178635A - Optical recording device - Google Patents

Abstract

PURPOSE:To prevent the loss of the quantity of light and monitor a light spot well by dividing a luminous flux, whose intensity of light is reduced from the center toward the peripheral part, into two and placing parts of maximum intensities of light of two divided luminous fluxes in positions symmetrical with respect to the center of a recording lens. CONSTITUTION:The laser light from a laser light source 1 is made incident to an acoustooptic optical modulator 7 using Bragg diffraction through a reflective mirror 2, an optical modulator 3, etc., and a laser light 20 is divided into two by the modulator 7, and parts 20am and 20bm of maximum intensities of light of laser lights 20a and 20b are placed in positions symmetrical with respect to a center O of a recording lens 13, and a line L connecting their incidence points is made coincident with the advance direction of a recording medium 16 to perform high-density recording. In this system, the light loss which is a problem in case of a lens having a ring band aperture is not generated. The spot state of the light is monitored well by a general monitor device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording device capable of optically recording various information signals onto a recording medium.

(Prior Art and Problems) In an optical recording device for optically recording various information signals onto a recording medium, when it is necessary to reduce the diameter of the light spot used during recording, It is common to use measures such as using short wavelength light for recording or using lenses with large numerical apertures for optical recording devices. 5 For example, if the wavelength is shorter than that of visible light, it may be difficult to monitor the state of the light spot during recording, or the optical components used in the configuration of the device may be difficult to monitor. Because of the problems such as being expensive, optical recording devices usually use light with a short wavelength within visible light when recording. In addition, there is a limit to the large numerical aperture of the I-mens used, so conventional optical recording devices are required to record information signals on the recording medium at an even higher recording density. Even if the diameter of the light spot needs to be reduced, it is difficult to achieve this.

And, conventionally, to solve the above-mentioned No. 4 problem.

The lenses used in optical recording devices are lenses with a so-called annular aperture, ie with a circular center. Attempts have been made to create a lens that is light-shielding with the original plate, but when this solution is applied, the light that is incident on the center of the lens is not used. Light loss is a problem, especially
Light whose intensity in the cross section of the light beam continuously decreases from the center to the periphery, for example, laser light whose intensity distribution in the cross section of the light beam has a Gaussian distribution, is optically When used for recording, there is a disadvantage that the central part of the luminous flux with the greatest energy is not utilized, resulting in a large loss of light.In addition, when a lens with an annular aperture is used, This method has the disadvantage that it is difficult to properly monitor the state of the light spot on the recording medium even if a conventional monitoring device with a general configuration is used. A single recording lens is used to focus the first beam of light that should produce a spot on the recording medium and the second beam of light that should produce a relatively large spot of light on the recording medium. When a lens with an annular aperture is used as a recording lens in a conventional optical recording device (for example, see Japanese Patent Application Laid-Open No. 56-58139), in addition to the above-mentioned drawbacks, Second
Another problem arises in that it becomes difficult to form a light spot using the luminous flux.

(Means for Solving the Problems) The present invention provides a method for controlling a luminous flux in which the intensity of the light continuously decreases from the center to the periphery of the cross section of the luminous flux.
In an optical recording device such as the one used for optically recording information signals, a light splitting means for splitting the above-mentioned light beam into two, and two light fluxes obtained by the light splitting means are provided.
an optical system comprising: means for causing the maximum light intensity in each of the two light beams to be incident on the recording lens such that the portion thereof is located at a symmetrical position with the center of the lens as the axis of symmetry; The present invention provides a recording device that solves the above-mentioned conventional problems.

(Example) Hereinafter, specific contents of the optical recording device of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of an embodiment of the optical recording apparatus of the present invention. In FIG. 1, 1 is a laser light source, and the laser light from the laser light source 1 is transmitted to is applied to the optical modulator 3 via.

The optical modulator 3 intensity-modulates the laser beam based on the information signal (4-) supplied to the terminal 4. The laser beam 20 outputted from the optical modulator 3 is reflected by a reflecting mirror 5 and then passed through a lens 6 to an optical modulator 7 that utilizes an acousto-optic effect (the same applies to an optical deflector that utilizes an acousto-optic effect). Below,
It will be described as an acousto-optic optical modulator 7. ).

The above-mentioned acousto-optic light modulator 7 has a light beam incident on it.
This is a light splitting means for splitting the laser beam 20 of a book into two and emitting them as two laser beams. type optical modulator 7 may be used.

The acousto-optic light modulator 7 splits one laser beam 20 incident thereon into two laser beams 20a and 20b, a 0th-order diffracted beam 20a and a 1st-order diffracted beam 20b, and emits the two laser beams 20a and 20b.

As shown in FIG.
f:J! so that the portions 20am and 20bm of maximum light intensity in each of 20a and 20b are located at symmetrical positions with the lens center O of the recording lens 13 as the axis of symmetry. In this manner, the light is made incident on the recording lens 13.

In addition, the direction of extension of the straight line connecting the two laser beams 20a and 20b, which are incident on the recording I-nons 13 as described above, and the portions 20am and 20b of the maximum light intensity in the soft beams is defined as the recording medium 16. If the light spot is imaged on the recording medium 16, the smaller size of the spot will be generated in the direction of extension of the recording trace formed on the recording medium, which is suitable for high-density recording. It can be easily realized.

Two laser beams 2Qa split into two by the acousto-optic light modulator 7 and emitted from the acousto-optic light modulator 7,
20b and the part 20a of maximum light intensity in them.
m, 20bm is the lens center 0 of the recording lens 13
It is easy to make the ultrasonic waves incident on the recording lens 13 in such a manner that they are located at symmetrical positions with respect to the axis of symmetry by appropriately setting the frequency and amplitude of the ultrasonic waves given to the acousto-optic optical modulator 7. can be done.

In the optical recording apparatus shown in FIG. 1, a lens 8 that converts laser beams 20a and 20b emitted from the acousto-optic modulator 7 into parallel beams is provided between the acousto-optic modulator 7 and the recording lens 13. ．． Although a half mirror 9° reflecting mirror 12 and the like are provided, in practice, the laser beams 20a and 20b emitted from the acousto-optic optical modulator 7 are applied directly to the recording lens 13. Good too.

In FIG. 1, a recording medium 16 is rotated integrally with a turntable 15 driven by a motor 14, and laser beams 20a and 20b applied to the recording lens 13 via the optical path described above are The light is focused and imaged onto the recording medium 16 as a spot of light. In addition,
In FIG. 1, 11 is a monitoring device, and 10 is a photodetector. The signal generated by the photodetector 10 is used, for example, to generate a signal for automatic control of optical components installed in the optical path. In the embodiment shown in FIG. 1, the acousto-optic optical modulator 7 is used as a light splitting means. However, as a light splitting means, a parallel A flat plate 21 may also be used.

As described above, in the optical recording device of the present invention, a light beam whose intensity continuously decreases from the center to the periphery of the cross section of the light beam (in the example shown in the first figure, a laser beam) is used. 20) into two, resulting in two luminous fluxes (first
In the illustrated example, the laser beams 20a, 20b) are
As shown in figure a, the part of the maximum light intensity in each of the two luminous fluxes described above (20
am.

20bm) is the lens center O in the recording lens 13.
The light incident on the recording lens 13 of the optical recording apparatus of the present invention is made to enter the recording lens 13 in such a manner that it is located at a symmetrical position with respect to the axis of symmetry. The change mode of the light intensity in the second
Regarding the direction of the straight line 8-L in a of the figure, for example, the curve ■(20
).

The curve I (20) in b in FIG. 2 described above represents the change in light intensity in the radial direction of the cross section of the two lights 20a and 2'Ob incident on the recording lens 13 [Curve 1 in b in FIG. (
20a) and I (20b)].

In this way, in the optical recording device of the present invention, the intensity change of the light incident on the recording lens 13 in one direction of its cross section is similar to that of the light transmitted through the annular aperture lens described above. By making the recording lens 13 similar to the mode of intensity change in the cross section, for example, as shown in FIG. In the case of the present invention, it is possible to generate a light spot with a small diameter on the recording medium 16 by the recording lens 13, but in the case of the present invention,
Unlike the case where the lens with the annular aperture described above is used, a part of the light incident on the recording lens is not blocked by a light shielding plate, so in the optical recording apparatus of the present invention, , the large loss of light quantity that was a problem in the case of the rotational aperture lens described above does not occur, and as described above, in the optical recording device of the present invention, the operation is similar to that of the rotational aperture lens described above. This operation is performed with light also passing through the center of the recording lens, so even if a conventional tank bottom-type monitoring device is used as a monitoring device for an optical recording device, recording will not be possible. The state of the light spot on the medium can be well monitored, and furthermore, as described above, the optical recording device of the present invention can
Since the operation similar to the operation of the rotational aperture lens described above is performed with light also passing through the center of the recording lens, the first light beam that should produce a small diameter light spot on the recording medium is The present invention is applied to an optical recording device in which focusing of a second beam of light to produce a light spot of a relatively large diameter on a recording medium is performed by a single recording lens. Also, the second
According to the present invention, the above-mentioned conventional problems can be satisfactorily solved by the present invention, such as being able to form a light spot on a recording medium by a luminous flux of .

FIG. 4 shows the focusing of the first beam to produce a light spot with a small diameter on the recording medium, and the focusing of the second beam to produce a light spot I~ with a relatively large diameter on the recording medium. In an optical recording device that performs both of these operations using a single recording lens, an optical recording device to which the present invention is applied is capable of forming a spot of light from the second beam on the recording medium. 4 is a block diagram of an exemplary configuration of a recording device. In FIG. 4, components corresponding to those in the optical recording device shown in FIG. The same drawing numbers are given.

In FIG. 4, among the laser light emitted from the laser light source 1, the light transmitted through the half mirror 21 is transmitted through the reflecting mirror 2 to an optical modulator 17 for adjusting the light amount (e.g., JP-A-52-7
The laser light emitted from the light intensity adjusting optical modulator 17 described above is transmitted to the optical modulator 3 which performs intensity modulation according to the first information signal supplied to the terminal 4. It is incident.

Further, the light reflected by the half mirror 21 described above is incident on the optical modulator 22 which performs intensity modulation using the second information signal supplied to the terminal 23. The first laser beam whose intensity is modulated by the optical modulator 3 described above is
The laser beam is to be caused to form a small diameter optical spot on the recording medium 16 by the recording lens 13, and the second laser beam whose intensity has been modulated by the optical modulator 22 is to be formed by the recording lens 13 on the recording medium 16. This is a laser beam that should form a light spot with a relatively large diameter on the top.

The first laser beam 20 described above is given to the acousto-optic optical modulator 7 via the reflection 1115 and the lens 6, and the two laser beams 20a are transmitted by the acousto-optic optical modulator 7 described above.
, 20b, then the cylindrical lens 2
9, 30, the slit member 31, the lens 32, etc. to the polarizing prism 33, and the above-mentioned second laser light is given to the polarizing prism 33 via the lens 24, the slit member 25, the lens 26,
The light is applied to the aforementioned polarizing prism 33 via a reflecting mirror 27 or the like.

12- The first light emitted from the polarizing prism 33 described above. The second laser beam is incident on the recording lens 13 via the half mirror 9, the reflecting mirror 12, etc., as in the case of the apparatus according to the first embodiment shown in FIG. In addition, in the figure, 28 is a lens.

In the embodiment shown in FIG. 4, the first laser beam is imaged by the recording lens 13 as a light spot with a small diameter on the recording medium 16, and the second laser beam is imaged by the recording lens 13 as a light spot with a small diameter. An image is formed on the recording medium 16 as a light spot with a relatively large diameter.

(Effects) Second, as is clear from the detailed explanation, in the optical recording device of the present invention, the intensity of light continuously decreases from the center to the periphery of the cross section of the light beam. The two luminous fluxes obtained by dividing the luminous flux of By making the light incident on the recording lens in such a manner, in the optical recording device of the present invention, the large loss of light amount that was a problem in the case of the lens with the annular aperture described above does not occur. As described above, in the optical recording device of the present invention, an operation similar to that of the annular aperture lens described above is performed with light also passing through the center of the recording lens. Even if a conventional monitoring device with a general configuration is used as a monitoring device provided in a recording device, the state of a light spot on a recording medium can be satisfactorily monitored. In an optical recording device, an operation similar to the operation of the lens with the a-band opening described above is performed with light passing through the center of the recording lens, so a small diameter spot of light is applied to the recording medium. The first thing to occur
The present invention is applied to an optical recording device in which a single recording lens is used to focus a second beam of light and to focus a second beam of light that is to produce a light spot with a relatively large diameter on a recording medium. However, according to the present invention, all of the problems of the conventional art described above can be satisfactorily solved, such as the ability to form a light spot by the second light beam on the recording medium.

[Brief explanation of the drawing]

1 and 4 are block diagrams of an embodiment of the optical recording device of the present invention, FIG. 2 is a diagram showing the relationship between a recording lens and two lights incident thereon, and the intensity distribution of the light; FIG. 3 is a side view of the parallel plane plate.

Claims (1)

[Claims] 1. A luminous flux in which the intensity of the light continuously decreases from the center to the periphery of the cross section of the luminous flux. In an optical recording device such as the one used for optically recording information signals, a light splitting means for splitting the above-mentioned light beam into two, and two light fluxes obtained by the light splitting means are provided.
means for causing the maximum light intensity in each of the two light beams to be incident on the recording lens such that the portion thereof is located at a symmetrical position with the center of the lens as an axis of symmetry. Optical recording device 2, a patent claim in which two light beams incident on a recording lens are configured such that the extension direction of a straight line connecting the maximum light intensity portion of each of the light beams coincides with the traveling direction of the recording medium. The optical recording device 3 according to item 1 above, as a light splitting means for splitting a luminous flux into two. An optical recording device according to claim 1, which uses an acousto-optic optical modulator that utilizes Bragg diffraction.