JPS6383930A - Light emitting element - Google Patents

Abstract

PURPOSE:To form a spot of an elliptical shape having a sufficient large ellipticity on a recording film of an information storage medium, by varying a proceeding state of a light beam from a light source by a beam state converting member provided in an optical path of the light beam generated from the light source for generating a divergent light. CONSTITUTION:In a beam state converting member 611, its base material 81 is constituted locally of a cylindrical Fresnel lens surface 80 of an aggregation of stripe-shaped planes of a narrow width, and each plane is placed at an angle inclined to each other against each adjacent plane, and also, each stripe plane has an inclination, therefore, at the time of passing through said plane, an erasing laser light Lb generaged from an erasing laser array 61b of a semiconductor laser array (light source) 61 is refracted, and goes into each different direction. Therefore, when the light beam is condensed by an objective lens 18, it is condensed to spots which are shifted slightly from each other on an information storage medium 1, and as a total light by its superposition, an elliptical beam spot is formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides an optical system that changes the progress of light emitted from a light emitting element including a light source having a plurality of light emitting points. Regarding improvements.

(Prior Art) In an information recording device that records, reproduces, and erases information on an information storage medium using focused light, a phase change (
Devices that utilize structural changes (changes between crystalline and non-crystalline states) and structural changes (changes in crystal structure) have a roughly circular focused spot on the recording film and a circular condensed spot that is elongated in the -axis direction. The approximately circular condensed spot is used for recording and reproduction, and the circular spot is used for erasing.

In order to irradiate the recording film with the two spots, conventionally two light sources have been placed at different locations. Separately, semiconductor laser arrays have recently been studied as a single light source having a plurality of light emitting points.

As described above, using an optical system in which the conventional 2IIA light sources are placed at different locations has the disadvantage that the optical system becomes complex and mechanically large, resulting in an increase in the weight of the entire optical system and slow access time. have. On the other hand, when a semiconductor laser array is used, it becomes difficult to create a circular spot on the information storage medium at the same time as a substantially circular condensing spot. It is necessary to make the light emitting point shape of the conventional optical system technology and the IWA of the semiconductor laser array into a circular shape. However, in order to stably emit light from a semiconductor laser, there is a limit to the width of the light-emitting point, and if it is left as it is, an elliptical spot with a sufficiently large inertia will be formed on the recording film of the information storage medium. It was difficult to form.

(Problems to be Solved by the Invention) This invention eliminates the drawback that it is difficult to form an elliptical spot with a sufficiently large inertia on the recording film of an information storage medium, and It is an object of the present invention to provide a light emitting element that can form an elliptical spot having a sufficiently large inertia on a recording film of a storage medium.

[Structure of the Invention] (Means for Solving the Problems) A light emitting element of the present invention is composed of a light source that generates diverging light and a plurality of discontinuous planes having at least a part of the surface in a stripe shape, Furthermore, the beam state converting member is configured such that adjacent planes have mutually inclined angles and change the traveling state of the light generated from the light source.

(Function) The present invention is a beam state changing member provided in the optical path of light emitted from a light source that generates diverging light, and is configured to change the traveling state of light from the light source.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 2 shows an information recording and reproducing apparatus according to the present invention. In this figure, 1 is a disk-shaped information storage medium, which is placed on a turntable 3 that is rotationally driven by a drive shaft 2. It is pressed down by a pressing member 4 from above.

The information storage medium 1 has a recording area on at least one side thereof, which is provided with a recording layer on which information can be recorded, reproduced, and erased using a laser beam or the like. In this recording area, a tracking guide (track) by a pre-group is formed in a spiral shape or a concentric circle shape.

An optical head 5 is provided below the information storage medium 1, and is attached to a slide portion 7 provided on a fixed portion 6 so as to be slidable along the radial direction of the information storage medium 1.

Furthermore, the optical head 5 is movable in the vertical direction with respect to the slide portion 7 (the direction of approaching or moving away from the information storage medium 1).

Then, the CPU 8 creates a program for moving the optical head 5 and accesses when starting recording, reproducing, and erasing information.
/A converter 9 to optical head movement drive circuit 1
0 to move the entire optical head 5 in the direction of arrow a in the figure.

Also, when accessing, the number of tracking guides provided on the information storage medium 1 is counted, and this causes the optical head 5 to
The current location of is now confirmed. That is, the output signal of the track deviation detection circuit 11 is
When the optical head 5 crosses one tracking guide, one pulse is generated from the other circuit 12, and the number of pulses is counted by the counter 13 for counting the number of tracks. It looks like this.

Furthermore, after the access is completed, track deviation correction is started. That is, the photodetector 1 inside the optical head 5 will be described later.
The photoelectric signals obtained from 4 are sent to preamplifier array 1, respectively.
5 and is supplied to the track deviation detection circuit 11 via the arithmetic circuit 16, whereby a track deviation detection signal is obtained.

Then, when the analog switch 17 is activated, the signal is supplied to the optical head movement drive circuit 10,
As a result, the entire optical head 5 is moved to perform track deviation correction.

As described above, the optical head 5 is also capable of moving in the vertical direction of the objective (the axial direction of the objective lens 18), that is, in the uniaxial direction toward and away from the information storage medium 1. The focal position of the objective lens 18 is moved by moving the entire optical head 5 in the direction indicated by the arrow in the figure by an optical head moving drive circuit 20 in response to a signal from a defocus detection circuit 19, which will be described later. . Also, just before the defocus servo loop is closed, the analog switch 21
is switched, thereby activating the automatic retraction circuit 22, and the optical head 5, that is, the objective lens 18, is moved to the initial position.

In addition, the recording light amount setting unit 24 is connected to an external device (not shown).
from the interface 32 and the recording signal processing circuit 2
3, the reproduction light amount setting section 25 outputs an erasure signal, and the reproduction light amount setting section 26 outputs a recording signal corresponding to the information recorded on the information storage medium 1. This outputs the playback signal, and analog switch 2
Reference numeral 7 switches the signals from each of the setting sections described above under the control of the CPU 8 and outputs the signals to the laser light drive circuit 28.

In addition, 29 is an information signal reading circuit, 30 is a binarization circuit,
31 is a reproduction signal processing circuit that performs modulation, demodulation, error correction, etc. of the information signal, and 32 is an interface circuit.

FIG. 3 schematically shows the optical head 5. As shown in FIG. The optical system shown in FIG. 3 is a multi-beam optical system that can form a plurality of focused spots on the information storage medium 1 when focusing, and one of them is used for recording and reproducing the information storage medium. 1 to form a circular condensed spot, and another one for erasing to form an elliptical condensed spot on the information storage medium 1.

That is, as shown in FIGS. 1 and 3, the semiconductor laser array (light source) 61 emits recording and reproducing laser light La.
The recording/reproducing semiconductor laser 61a generates a recording/reproducing laser beam Lb, and the erasing semiconductor laser 61t generates an erasing laser beam Lb. The recording and reproducing laser beam 1-a emitted from the recording and reproducing semiconductor laser 61a of the semiconductor laser array 61 and the erasing laser beam Lb emitted from the erasing semiconductor laser 61b remain as divergent lights at the prism section 63. is incident on the The laser beam entrance surface of this prism portion 63 is a vertical surface 63a perpendicular to the optical axis.

The erasing laser beam Lb generated from the front side of the semiconductor laser array 61 is transmitted to the cylindrical Fresnel lens surface 8.
A beam state changing member 611 made of a base material 81 having a diameter of 0.0 is used to change the traveling direction of the beam or the spot size. Thereby, the divergence and convergence states of the erasing laser beam Lb in one axis direction (a certain specific direction) are changed, and an elliptical focused spot is formed on the information storage medium 1.

The cylindrical Fresnel lens surface 80 of the beam state conversion member 611 is arranged at a position corresponding to the exit of the light emitting point of the erasing laser beam Lb.

Here, the semiconductor laser array 61 and the beam state conversion member 611 constitute a light emitting element.

In the beam state conversion member 611, the base material 81 is made of glass or a plastic material such as transparent acrylic or polycarbonate, and locally consists of a cylindrical Fresnel lens surface 80 that is a collection of narrow stripe-shaped planes. has been done.

The planes are arranged at mutually inclined angles with respect to adjacent planes. The erasing laser beam Lb that has passed through one narrow stripe plane is subject to aperture restriction in the narrow width direction. As a result, the spot size of the condensing point condensed by the objective lens 18 is expanded by the amount affected by the aperture restriction.

The spot size of this expanded focal point is approximately:
It is inversely proportional to the width of one stripe plane.

Furthermore, since each stripe plane has an inclination,
When passing through there, the erasing laser beam Lb is refracted,
Each enters in a different direction.

Therefore, when the objective lens 18 is put into service, the light is focused on slightly shifted points on the information storage medium 1, and the total light due to their superposition forms a beam spot of the Japanese system.

Therefore, in order to form an elliptical spot with a clean intensity distribution on the information storage medium 1, the beam state conversion member 611 having the cylindrical Fresnel lens surface 80 as the above-described surface structure is effective.

As a result, the erasing laser beam Lb that has passed through the cylindrical Fresnel lens surface 80 is elongated on the information storage medium 1 in the direction along the plane of the paper, and can form a circle-shaped slot 1-.

The principle of operation of the beam state changing member 611 will be explained using FIG. 4. That is, the recording/reproducing laser beam 1-a generated from the recording/reproducing semiconductor laser 61a is focused onto the information storage medium 1 when it is focused. Further, the cylindrical Fresnel lens surface 80 as the beam state conversion member 611 does not have a light condensing effect in a plane perpendicular to the plane of the drawing. Therefore, the erasing laser beam Lb generated from the erasing semiconductor laser 61b is focused on the information storage medium 1 when focused in the direction perpendicular to the plane of the paper.

On the other hand, when viewed in the plane direction that includes the fourth factor,
Since the cylindrical Fresnel lens surface 80 has a focusing effect on light (an effect of changing the beam state), when focusing, the erasing laser beam Lb is focused at a position closer to the objective lens 18 than the information storage medium 1. Therefore, the erasing laser beam Lb diverged from that point is transmitted to the information storage medium 1.
irradiated on top.

As a result, when focused, the recording/reproducing laser beam 1-a forms a substantially circular focused spot on the information storage medium 1, whereas the erasing laser beam Lb has an elliptical shape with a sufficiently long major axis. Form a shaped spot light.

In other words, the beam-shaped H exchange member 611 shifts the focusing position in a specific direction from the position of the information storage medium 1 at the time of focusing, and places an elliptical spot on the information storage medium 1 (the objective lens 18 having an aspherical curved surface). The feature of FIG. 4 lies in the formation of an ellipse-shaped laser beam near the recording/reproducing semiconductor laser 61a.

Approximately 100% of the laser beams La and Lb incident on the vertical surface 63a of the prism section 63 are reflected by the polarized beam split surface 64 provided on the other surface of the prism section 63.
The light passes through the /4 wavelength plate 70 and becomes circularly polarized light. After passing through the objective lens 18, this circularly polarized light is focused on the information storage medium 1.

The objective lens 18 has an aspherical entrance surface and an exit surface, and is made of a single optical component such as glass or plastic.

The recording and reproducing laser beam 1-a emitted from the recording and reproducing semiconductor laser 61a of the semiconductor laser array 61 and the erasing laser beam 1b emitted from the erasing semiconductor laser 61b have a divergence angle β of the third The direction parallel to the plane of the drawing (trajectory shown by a solid line) is different from the direction perpendicular to the plane of the paper (trajectory shown by a broken line).

Correspondingly, the aspherical curved surface 18a of the objective lens 18,
18b, convergence on the information storage medium 1 is also achieved by changing the curvature in the direction parallel to the plane of the paper in FIG. The angle α is equal in the direction parallel to and perpendicular to the plane of the paper. For this reason, the laser beam La for recording and reproduction is designed to form a substantially circular focused spot on the information storage medium 1.

The divergence angle β of the recording and reproducing laser beam 1a is usually ±1
In contrast, in order to obtain a sufficiently small focused spot on the information storage medium 1, it is necessary to increase the convergence angle α. For this reason, the aspherical curved surface 18b of the objective lens 18 after passing through the quarter-wave plate 70 changes the concave lens curvature and widens the divergence angle further. Thereby, the curvature of the concave lens is changed in a direction parallel to and perpendicular to the plane of the paper in accordance with the difference in the divergence angle β of the recording and reproducing laser beam 1-a, and the degree to which the divergence angle β is widened is changed.

Thereafter, the aspherical curved surface 18a of the objective lens 18 has a convex lens effect and changes the recording/reproducing laser beam 1a and the erasing laser beam Lb into convergent light. The ratio α/β of the divergence angle β and the convergence angle α at this time approximately indicates the imaging lateral magnification.

Laser beams La and Lb focused on the information storage medium 1
is reflected on this information storage medium 1 and is reflected again on the objective lens 1.
8. After passing through the 1/4 wavelength plate 70, the light enters the prism section 63 and returns to the polarized beam splitting surface 64. Here, laser light 1-a.

By reciprocating through the 1/4 wavelength plate 70, Lb has a vibration direction of 9 compared to when it is reflected by the polarized beam split surface 64.
It becomes linearly polarized light rotated by 0 degrees.

Therefore, the laser beams La and Lb returned to the polarized beam splitting surface 64 pass through this polarized beam splitting surface 64, and the light separating and reflecting member 65 that exists behind it and is superimposed on the polarized beam splitting surface 64. A light reflecting plane 65 as two light reflecting surfaces adjacent to each other with an inclination.
a1 reaches the light reflective cylindrical surface 65b.

The laser beam reflected by the light reflecting member 65 passes through the polarized beam splitting surface 64 again and heads toward the photodetector 14. Among the recording and reproducing laser beams La, the light reflected by the light reflective plane 65a becomes a laser beam Lf for defocus detection, and as shown in FIG. The light is focused between 66a and 66b.

Further, the light reflected by the light reflective cylindrical surface 65b becomes a laser beam Lt for detecting track deviation, and when in focus, the sixth
As shown in Figure (a), the photodetection cells 67a and 67b for detecting track deviation on the photodetector 14 are irradiated with light. Since total reflection is used for light reflection between the light reflective plane 65a and the light reflective cylindrical surface 65b, a total reflection gap 65C is provided on the rear side.

Note that the detection sensitivity of the defocus detection using the defocus detection laser beam Lf is proportional to the lateral magnification α/β of the image formed on the photodetector 14 with respect to the information storage medium 1. Therefore, the objective lens 18 having an optical image with a large value of imaging lateral magnification α/β is also useful for improving the sensitivity of defocus detection.

The mechanical frame that holds each of the optical components described above is composed of a semiconductor element mount stand 68 that supports the semiconductor laser array 61 and the photodetector 14, and an optical component mount frame 71 that houses the remaining optical components. . The joint between the two is sealed with a hermetic seal 72 to protect the semiconductor element from environmental resistance.

The inner wall of the optical component mounting frame 71 is machined with high mechanical precision, so that each optical component can be assembled by simply fitting. As a result, by using the structure shown in FIG. 3, the optical head 5 can be significantly downsized, and can be made approximately 7 mm in diameter and 10 mm in length B. - The structure of the photodetector 14 will be explained using FIG. 5. That is, the defocus detection principle uses the so-called Knifezi method, and the defocus detection laser beam Lf is focused on the photodetector 14 at a focused point. In addition, when the distance between the objective lens 18 and the information storage medium 1 becomes too close due to the out-of-focus condition, the defocus detection laser beam Lf
The light converging position is shifted to the rear of the photodetector 14, and the defocus detection laser light is mainly irradiated onto the defocus detection photodetection cell 66b.

On the other hand, when the distance between the objective lens 18 and the information storage medium 1 increases, the focus position of the laser beam for defocus detection shifts to the front of the photodetector 14, and the light detection cell 66a for defocus detection shifts to the front of the photodetector 14. The out-of-focus detection laser light is irradiated more toward the object.

However, the defocus became too large and the objective lens 18
When the distance between the information storage medium 1 and the information storage medium 1 becomes further, the focal position of the defocus detection laser beam 66f shifts significantly,
For example, it may shift to the γ point shown in FIG. Then, as shown in FIG. 6(b), the spot state of the laser light on the photodetector 14 is such that the out-of-focus detection cell 66b is exposed more. In this state, the objective lens 18
The situation remains the same as when the two are too close. Therefore, in order to distinguish between the above state and the state in which the objective lens 18 has moved out of focus and has slightly approached the information storage medium 1, it is necessary to
) A photodetection cell 69 for abnormality detection as shown in (b) is provided.

Therefore, either one of the two types of laser beams Lf and Lt is detected by the defocus or track deviation light detection center/L, 6.
6a, 66b, 67a, 67b and reaches the abnormality detection light detection cells 69 arranged around them, it is assumed that the focus has become significantly out of focus, the defocus correction is temporarily interrupted, and the focus is refocused. Try searching for the location again. When defocus and track deviation are detected by each of the photodetection cells 66a, 66b, 67a, and 67b. optical head 1
Corrections are made by moving the entire image up and down and left and right.

In addition, 14 photodetection cells 66a166b, 6 of the photodetector
The portion other than 7a and 67b is a non-sensing area 14a.

A prism 81 and a photodetector 82 are provided on the back side of the semiconductor laser array 61 to adjust the amount of laser light 1a, lb emitted by the semiconductor laser array 61. Since this light emission amount control is explained in Japanese Patent Application No. 61-40710, the details thereof will be omitted here.

Further, the semiconductor element mount table 68 includes a photodetector 1.
While taking out the output of 4.82, the semiconductor laser 61a
, 61 drive signals are supplied to the electrical terminal connector 68a.
is provided.

Next, a method of assembling and adjusting the optical system shown in FIG. 3 will be explained. That is, the important part during adjustment is the occurrence of comatic aberration in the objective lens 18 due to the deviation of the optical axis. For this reason, as described above, a frame is created with high precision and each optical component is fitted into the frame. Therefore, if the light emitting point of the semiconductor laser array 61 is set at the ideal position,
This ensures that coma aberration does not occur.

For this reason, first, the far field pattern of laser light 1-all-b emitted from the semiconductor laser array 61 is measured, and those whose patterns have an asymmetric intensity distribution are rejected as defective products. Next, a mirror is placed near the position where the information storage medium 1 is to be set through a transparent substrate having birefringence, and the mirror is moved up and down. During focusing, a portion of the laser light returns to the semiconductor laser array 61 through the transparent substrate with birefringence, making the light emission of the semiconductor laser array 61 unstable. As a result, noise is added to the light emission from the semiconductor laser array 61, and when the light is unstable, it is considered to be in focus.

As shown in FIG. 3, there are three directions in which the semiconductor element mount table 68 can be adjusted: X, Y, and .theta..

That is, by moving in the X direction, the light m ratio between the laser beam Lf for defocus detection and the laser beam Lt for tracking deviation detection can be changed. By moving in the Y direction, the optical detection cells 67a and 67b for detecting track deviation are
The upper track deviation detection laser beam Lt moves.

In this case, the center of rotation of the semiconductor element mount table 68 is made to coincide with the recording/reproducing laser light emitting point of the semiconductor laser array 61. Furthermore, when the semiconductor element mount base 68 is rotated in the θ direction, the defocus detection laser light moves relatively on the defocus detection photodetection cells 66a and 66b. Note that the optical detection cell 67 for detecting track misalignment is installed so that the track misalignment detection system is not adversely affected during rotation in the θ direction.
The boundary line between a167b has a structure in which an arc is drawn around the recording and reproducing laser emission point.

Therefore, adjustment is completed only by movement in the X-Y-θ directions. Finally, information storage medium 1 that can be moved vertically and horizontally
Confirmation is performed by placing the fragment at the location of the information storage medium 1.

As a result, the fragments of the information storage medium 1 are moved up and down using the defocus detection signal, and a servo for defocus correction is applied. Also, shake the pieces of information storage medium 1 further left and right,
Check the status of the track deviation detection signal.

Therefore, except when erasing information on the information storage medium 1, that is, when recording or reproducing, the recording and reproducing semiconductor laser 6
Only 1a lights up, and each cell 66a, 66b of the photodetector 14
, 67a, 67b are irradiated with only the recording/reproducing laser beam 1a, which is used for defocus detection and track deviation detection.

As described above, by utilizing the action of the cylindrical Fresnel lens, the size of the erasing spot on the information storage medium at the time of focusing can be expanded in only one direction. As a result, one of the constituent parts of the cylindrical Fresnel lens
Since the light that passes through the striped planes (stripe planes) of the plate is subject to aperture restrictions in the width direction, the spot size can be expanded in that direction at the condensing point. Furthermore, since the plane of each stripe is inclined, the spot size can be further increased by refracting at the boundary surface and converging in directions slightly shifted from each other.

Further, the ellipticity of the erasing laser spot irradiated onto the recording film can be arbitrarily changed according to the characteristics of the recording film of the information storage medium.

In addition, the erasing laser beam on the recording film of the information storage medium can be applied very easily and precisely on a regular basis.

Furthermore, since the beam state conversion means with a very small shape is placed near the semiconductor laser array, the optical system becomes conspicuous by directing the erasing laser beam onto the recording film of the information storage medium. You can prevent it from getting bigger. Furthermore, the beam state converting means can direct (fix) the semiconductor laser array with mechanical dimensional accuracy, which facilitates assembly and adjustment of the optical head in subsequent processes such as optical axis adjustment.

In addition, in the above embodiment, a light source that generates a laser beam for recording and reproduction and a laser beam for erasing was explained, but the present invention is not limited to this. The same operation as described above can be carried out when using a light source changed to a recording laser.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a light emitting element that can form a circular spot having a sufficiently large ellipticity on the recording film of an information storage medium.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a perspective view showing the configuration of the main parts of the optical system, Fig. 2 is a block diagram showing the schematic structure of the information recording and reproducing device, and Fig. 3 is the optical 4 is a cross-sectional view showing the overall configuration of the head, FIG. 4 is a diagram for explaining the working principle of the beam state conversion member, FIG. 5 is a plan view showing the semiconductor laser array and photodetector, and FIG. 6 is a photodetector. FIG. 3 is a plan view showing the configuration of the container. la... Laser light for recording and reproduction, Lb... Laser light for erasing, 1... Information storage medium, 14... Photodetector,
18... Objective lens, 61... Semiconductor laser array (light source), 61a... Recording and reproducing laser, 61b...
... Erasing laser, 611... Beam state conversion member,
80... Cylindrical Fresnel lens surface, 81...
・Base material. Applicant's agent Patent attorney Takehiko Suzue @1 Figure 3 Figure 4 Figure 5 (a) (b) Figure 6

Claims (2)

[Claims] (1) A light source that generates diverging light; At least a part of the surface is composed of a plurality of discontinuous planes in a stripe shape, and adjacent planes have inclined angles to each other, and the light source generates diverging light. A light emitting element comprising: a beam state conversion member that changes the state of progress of light; and a light emitting element. (2) The light emitting device according to claim 1, wherein the beam state conversion member is constituted by a cylindrical Fresnel lens.