JPH04206052A - Optical recording method - Google Patents

Abstract

PURPOSE:To improve data recording density by changing the plane of polarization of a laser beam which is cast into an acoustooptic deflector, and adjusting the ratio of the relative amounts of the emitted rectilinearly propagating light and diffracted light. CONSTITUTION:A laser beam is cast into the modulating element of an acoustooptic deflector 26. An ultrasonic propagating mechanism 32 acts on the acoustooptic deflector 26. The incident laser beam is diffracted into rectilinearly propagating light 28 and diffracted light 30. When the two optical components 28 and 30 are emitted from the acoustooptic deflector 26, the emitted zero-order light 28 and the linear propagating light 30 are exposed on the recording track of a recording medium 36 through one objective lens 34. The objective lens 34 is arranged at a position which is separated from the acoustooptic deflector 26 by a distance (f) so that the diffraction point becomes the position of the focal point. At this time, the respective amounts of the zero-order light 28 and the first order light 30 emitted from the acoustooptic deflector 26 are controlled with the angle of the lattice fringes of a polarizing plate 2. Thus, the recording density and the recording accuracy of the data can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording method for recording a plurality of data in the width direction of a recording track on a recording medium, for example.

[Prior Art] Conventionally, a method for recording data on a recording medium involves forming a plurality of pits at predetermined intervals along the length of a recording track, and encoding various data based on the mutual spacing of these pits. Recording data.

[Problems to be Solved by the Invention] However, when recording more data, the length of the recording track must be increased accordingly, and therefore the recording medium must be made larger. As a result, the entire device becomes larger and the manufacturing cost increases.

Therefore, in order to improve the recording density of data recorded on a recording medium, an optical recording/reproducing apparatus as shown in FIG. 4 has been considered.

FIG. 4 schematically shows a recording optical system for recording a plurality of pits (not shown) in the width direction of a recording track (not shown) of the recording medium 14. This recording optical system includes a laser diode array 12 in which, for example, nine diodes 1o are arranged in parallel above the recording medium 14 along the width direction of the recording track, and a laser beam emitted from the array 1o is exposed onto the recording medium 14. One objective lens 16 is provided. Note that these nine diodes 10 are constructed by combining one diode 1° in the center and a pair of diodes 10 arranged on both sides of this diode 10.

The recording method is performed, for example, by selectively causing a predetermined diode 10 in the array 12 to emit light in accordance with the input data S. That is, the central diode 10 in the array 12 is activated for each data S, for example, and
4. Record the pit on top. Also, the central diode 10
A pair of diodes 10 placed on both sides of the diodes 10 operate simultaneously when recording data S. In this way, a plurality of pits are formed along the width direction of the recording track. Then, data S is encoded and recorded according to the interval between these pits.

However, it is very difficult to maintain the input power to each diode 10 and the amount of laser beam output from each diode 10 constant.

As a result, pits of a predetermined size may not be recorded. In such a case, the change in the size of the pits may become noise, which may affect the data reproduction results.

Furthermore, since ten or more diodes are required, manufacturing costs also increase.

Furthermore, since there is a limit to the fixed arrangement of the diodes 10, there is also a limit to the encoding of data according to the mutual spacing between the pits. As a result, it becomes difficult to improve the data recording density.

This invention was made to solve the above-mentioned problems, and its purpose is to maintain a pit at a predetermined size by keeping the output light amount of a laser beam irradiated onto a recording medium constant in a simple manner. An object of the present invention is to provide an optical recording method that can improve data recording density.

[Means for Solving the Problems] In order to solve these problems, the present invention provides an optical recording method for recording data on a recording medium using an acousto-optic deflector, the acousto-optic deflector The method includes a control step of changing the polarization plane of the laser beam incident on the acousto-optic deflector to change and control the amount of light of the plurality of diffracted lights emitted from the acousto-optic deflector to a predetermined ratio.

[Operation] By changing the plane of polarization of the laser beam incident on the acousto-optic deflector, the mutual light amount ratio of the straight light and the diffracted light emitted from the acousto-optic deflector is adjusted. The recording optical system used in the present invention is based on the one shown in FIG. 1, which will be described later, and the light quantity ratio is approximately constant within a predetermined diffraction angle region of the acousto-optic deflector.

[Example] Hereinafter, an example of the optical recording method of the present invention will be described with reference to FIG.

FIG. 1 schematically shows a recording optical system used in the optical recording method of this embodiment.

For example, a laser beam having a circular polarization plane emitted from the He-Ne laser 20 becomes a parallel beam of light via the collimator 22 and enters the polarizing plate 24 . This polarizing plate 24 is provided with grating stripes (not shown) set at 45@ with respect to the modulation element (not shown) of the acousto-optic deflector 26. Therefore, of the laser beam incident on the polarizing plate 24, only the polarized component having a vibration plane along the grating fringes is transmitted. The transmitted laser beam is incident on the modulation element of the acousto-optic deflector 26.

An ultrasonic propagation mechanism 32 acts on this acousto-optic deflector 26, and the incident laser beam is diffracted into straight light and diffracted light. In this embodiment, straight light, ie, O-order light 28, and diffracted light, ie, first-order light 30 are used, and these two light components 28 and 30 are emitted from the acousto-optic deflector 26. The emitted zero-order light 28 and first-order light 30 are focused on one objective lens 34, which is placed at a distance f from the acousto-optic deflector 26, so that the emitted zero-order light 28 and the first-order light 30 become a diffraction point or a focal point.
A recording track (not shown) of the recording medium 36 is exposed to light through the recording medium 36. As a result, a pair of pits are formed along the width direction of the recording track.

Zero-order light 28 and first-order light 3 emitted from the acousto-optic polarizer 26
The amount of light with respect to 0 is controlled by the angle of the lattice fringes of the polarizing plate 24. In this example, by setting the angle of the grating stripes to 45 degrees, the acousto-optic polarizer 2
The amount of light of the primary light 30 passing through the diffraction angle region 38 of 6 and 0
The ratio of the amount of light of the secondary light 28 can be maintained at a 1:1 ratio.

When the light intensity ratio of the 0th order light 28 and the 1st order light 30 is 1:1, that is, 50% as in this embodiment, pits created by the 0th order light 28 and pits created by the 1st order light 30 can be made to be approximately the same size.

In the above embodiment, the angle of the grid pattern of the polarizing plate 24 with respect to the angle of the modulation element of the acousto-optic deflector 26 is set to 45.
This shows that when the setting is set to 1, the light amount ratio is constant at 1:1. However, even when these angles are different, the light amount ratio is not 1:1 (although it will be explained with reference to FIG. 2 that the light amount ratio is constant within the diffraction angle region as in one embodiment).

The graph in FIG. 2 is for explaining the relationship between diffraction angles when the light amount ratio is constant.

Note that the vertical axis indicates the light intensity ratio of the primary light 30 to the sum of the output lights of the 0th-order light 28 and the 1st-order light 30 (1st-order light/(0th-order light + 1st-order light) [%], and the horizontal axis represents the 1st order light 3 relative to 0th order light 28
The diffraction angle of 0 [°] is shown. And curve A-D
1 and 2 respectively show the characteristics of the light amount ratio versus the diffraction angle when the angle of the grating edge of the polarizing plate 24 is varied with respect to the angle of the modulation element of the acousto-optic deflector 26, and the curve A is 0°. ,
Curve B shows the characteristics when the curve is 30 degrees, curve C is 45 degrees (corresponding to the above embodiment), and the curve is 60 degrees.

As is clear from curves A-D of this graph, when the diffraction angle is about 2.5 to 4@, that is, the diffraction angle region 38 is about 1.
Within the range of 56, there is almost no change in the amount of light due to a change in the diffraction angle. That is, the light amount ratio is constant. By using this constant portion, the recording medium 36
It is possible to keep the output light amount ratio of the laser beam irradiated to the area constant. As a result, the mutual sizes of the pair of pits can be maintained in an optimal state.

In this state, the ultrasonic propagation mechanism 32 is activated to
By changing the diffraction angle of the secondary light 30, a pair of pits having a constant size and a predetermined interval can be formed along the width direction of the recording track. As a result, data recording density and recording accuracy can be improved.

Note that the recording optical system used in the optical recording method of the present invention is not limited to the configuration of the above-described embodiment. For example, as a modification of the above-mentioned embodiment, as shown in FIG. It is also possible to adopt a configuration in which the He-Ne laser 20 itself that emits laser light is rotated to change the angle of the polarization plane of the emitted laser beam. In this case, an objective lens is not necessarily required.

In the above-described embodiment, the polarizing plate 24 is arranged so that the angle of the grating fringes is 45'' with respect to the angle of the modulation element of the acousto-optic deflector 26.
However, a means for rotating the polarizing plate 24 may be provided to set an arbitrary angle. In this way, the light amount ratio can be set arbitrarily.

[Effects of the Invention] According to the optical recording method of the present invention, by changing the polarization plane of the laser beam incident on the acousto-optic deflector, the output light amount ratio of the laser beam irradiated onto the recording medium is changed. At the same time, by keeping it constant,
The pits recorded on the recording medium can be maintained at a predetermined size, and the data recording density and recording accuracy can be improved.

Furthermore, since the recording optical system used in the optical recording method of the present invention has a simple structure, the manufacturing cost is also low.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of a recording optical system used in an optical recording method according to an embodiment of the present invention, and FIG. 2 shows a 0th-order light and a first-order light obtained by the recording optical system of FIG. Figure 3 shows the relationship between the diffraction angle and the light intensity ratio when the light amount ratio is constant.
The figure schematically shows a modification of the recording optical system used in the optical recording method according to the embodiment of the present invention, and FIG. 4 schematically shows a conventional recording optical system. 24... polarizing plate, 26... acousto-optic deflector, 28...
・0th order light, 30...1st order light, 36...recording medium. Applicant's representative Patent attorney Atsushi Tsuboi Angle Figure 2 Figure 3 Figure Cow

Claims (1)

[Claims] An optical recording method for recording data on a recording medium using an acousto-optic deflector, the method comprising: changing the plane of polarization of a laser beam incident on the acousto-optic deflector; An optical recording method that includes a control step of controlling the mutual light intensity of a plurality of diffracted lights emitted from a deflector by changing them to a predetermined ratio.