JP2002329347A - Method for shaping beam at optical pickup device, optical pickup device and optical information processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a suitable method for shaping a beam in the case where a plurality of semiconductor laser light sources are used. SOLUTION: The method for shaping the beam is that in an optical pickup device in which a luminous flux emitted from a semiconductor laser light source is made into a parallel luminous flux with a collimator lens and introduced onto the recording face of an optical recording medium via an objective lens, the sectional figure of the luminous flux which is made to be parallel by the collimator lens is shaped into a circle or a similar prescribed shape. The oval section of the luminous flux which is made to be parallel by the collimator lens 2 is contracted in the direction of the long axis with the refraction of a beam shaping prism 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a beam shaping method in an optical pickup device, an optical pickup device, and an optical information processing device.

[0002]

2. Description of the Related Art In a standard of an optical disk as an optical recording medium, a wavelength of a laser beam used for recording / reproduction is a
(Compact disc) 780nm, DVD
(Digital video disc) is around 650 nm. Therefore, CD and D can be stored in one optical disk drive.
In order to perform recording / reproduction on each of the VDs, light sources of two emission wavelengths are required. Recently, a wavelength around 400 nm has been required for higher density. As such a light source, a “semiconductor laser light source” is preferable.

In recent years, a small semiconductor laser light source device capable of emitting a plurality of wavelengths of laser light, such as a two-wavelength LD or the like, in which a plurality of chips having different emission wavelengths are sealed in one package or a two-wavelength LD having one chip and two wavelength active layers. Has been developed.

As is well known, the far field pattern of a laser beam emitted from a semiconductor laser has an elliptical shape. When such a beam is condensed as it is as a light spot on a recording surface of an optical recording medium by an objective lens. The shape of the formed light spot also becomes elliptical. However, in general, the shape of the light spot is preferably a “circular shape or a shape close to this (an elliptical shape having a long / short axis ratio close to 1)”.

[0005] In order to realize such a preferable light spot shape, "beam shaping" is performed. Beam shaping is
This method is used to make the cross-sectional shape of the light beam incident on the objective lens from the light source side into a substantially circular shape, and various methods are known.A well-known method is to collimate a light beam emitted from a semiconductor laser. A parallel light beam is formed by a lens to obtain a parallel light beam having a light beam cross section of an elliptical shape. The parallel light beam is transmitted through a beam shaping prism. Is known to be "expanded to be substantially equal to the major axis diameter".

As the collimating lens, a lens having a short focal length is used. By arranging the lens near the light source, most of the light energy radiated from the light source is taken into a parallel light beam. As described above, if the focal length of the collimator lens used before the beam shaping is short, it is advantageous for downsizing the optical pickup device.

On the other hand, if the parallelism of the light beam incident on the beam shaping prism is deviated, astigmatism will occur and a good light spot cannot be formed on the recording surface. For this reason, it is necessary to adjust the distance between the light source and the collimating lens with high precision in order to realize a highly accurate collimating action by the collimating lens. It is necessary to design etc.

However, when the focal length of the collimating lens is short as described above, the depth of focus of the collimating lens is small, and the precision of the position adjustment between the light source and the collimating lens becomes extremely severe.

As described above, in the case of using "a plurality of semiconductor laser light sources having different emission wavelengths", it is necessary to adjust the position of each light source with a collimator lens (common to them) with extremely high accuracy. This makes it difficult to efficiently assemble the optical pickup.

When a collimator lens is used in common for a plurality of light sources, the other light sources except for one light source must be arranged at a position "off the optical axis of the collimator lens". The light beam from the light source is converted into a parallel light beam by the collimating lens and then tilted with respect to the optical axis of the collimating lens. Therefore, there is a problem that the shape of the light spot due to such a light beam is deteriorated by "coma aberration".

When the above-described "two-wavelength LD having one chip and two-wavelength active layers" is used, the distance between the two light sources becomes small. Even in this case, the distance between the two light sources is 100 μm.
When the focal length of the collimating lens is short, it is difficult to sufficiently correct the deterioration of the light spot shape due to the coma aberration.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to realize a beam shaping method suitable for using a plurality of semiconductor laser light sources. Another object of the present invention is to realize an optical pickup device that performs the beam shaping method using two or more semiconductor laser light sources. A further object of the present invention is to realize an optical information processing apparatus for recording / reproducing information on a plurality of types of disk-shaped optical recording media having different working wavelengths by using the optical pickup device.

[0013]

According to the beam shaping method of the present invention, "a light beam emitted from a semiconductor laser light source is converted into a parallel light beam by a collimator lens, and then guided to a recording surface of an optical recording medium via an objective lens. In an optical pickup device, beam shaping is performed so that a cross-sectional shape of a light beam converted into a parallel light beam by a collimator lens is a circular shape or a desired shape close to the circular shape (a desired elliptical shape having a long / short axis ratio close to 1). Method ", characterized by the following points (claim 1).

That is, the direction of the long axis of the light beam collimated by the collimating lens in the cross section of the elliptical light beam is
The beam is reduced by the refraction of the beam shaping prism.

This “beam shaping method” is based on “2.
It is suitable as a beam shaping method in an "optical pickup device using a semiconductor laser light source having the above emission wavelength", but is not limited thereto, and may be implemented as a "beam shaping method in an optical pickup device using a single semiconductor laser light source". The “semiconductor laser light source” refers to each light emitting unit in the semiconductor laser.

As is well known, when a parallel laser beam is condensed to form a light spot, the spot diameter is inversely proportional to the beam diameter of the parallel laser beam incident on the objective lens. Assuming that the beam diameter of the parallel laser beam required to realize a desired spot diameter in a circular light spot is 2D, in the conventional beam shaping, first, the beam from the semiconductor laser light source is “elliptical” by a collimating lens. Of the light beam cross-section becomes 2D ". At this time, naturally, the size of the minor axis diameter: 2d of the light beam cross section is 2d <2D.

A parallel light beam having such a major axis diameter: 2D and a minor axis diameter: 2d is made incident on the beam shaping prism, and the diameter in the minor axis direction is increased from 2d to 2D, thereby obtaining a substantially circular light beam cross section. A parallel light beam having a shape is realized.

For simplicity, the divergence angle of the divergent light beam emitted from the semiconductor laser light source is represented by θ _L in the major axis direction of the ellipse and θ in the minor axis direction.
_In the case of _S , in the conventional beam shaping, the focal length of the collimating lens: f and the lens diameter: 21 are expressed as “tan θ _L = 1
/ F = D / f ". That is, l ≒ D. At this time, the minor axis diameter d of the light beam cross section of the collimated light beam is f · tan θ _S (<D).

On the other hand, in the beam shaping method of the present invention, the divergent light beam from the semiconductor laser light source is converted into a parallel light beam by a collimating lens, and then "the major axis direction of the elliptical light beam cross section in the parallel light beam is reduced". Therefore, a short-axis diameter of the laser beam transmitted through the collimating lens and converted into a parallel light beam must have a size of 2D in the light beam cross section. Then
The major axis diameter is naturally larger than 2D.

Assuming that the focal length of the collimating lens for realizing such a collimating action is F and the lens diameter is 2L, these are L = F · tan θ _L and D = F · tan θ
_S must be satisfied. Therefore, in the beam shaping method of the present invention, the focal length of the collimating lens is as follows:
It can be seen that F and lens diameter: 2L satisfy F> f and L> l with respect to the focal length: f and lens diameter: 2l of the collimating lens in the conventional beam shaping method.

As described above, according to the beam shaping method of the present invention, since the focal length of the collimating lens for converting the light beam from the semiconductor laser light source into a parallel light beam is large, the depth of focus of the collimating lens is large. Accuracy required for position adjustment with the lens becomes loose.

Further, when a plurality of semiconductor laser light sources are used, after the light beam from the semiconductor laser light source deviating from the optical axis is collimated, the inclination angle with respect to the optical axis is also increased (because the focal length of the collimating lens is large, 3) The deterioration of the light spot shape due to the coma aberration is effectively reduced.

An optical pickup device according to the present invention has two or more semiconductor laser light sources having wavelengths different from each other and arranged in close proximity to each other, and collimates a light beam from the semiconductor laser light source having an emission wavelength corresponding to the optical recording medium. An optical pickup device that forms a parallel light beam, changes the light beam diameter in one direction by a beam shaping prism, shapes the beam, and guides the beam-shaped light beam to a recording surface of an optical recording medium by an objective lens. " It is characterized by the following points (claim 2).

That is, using a lens having a large focal length and a large lens diameter as the collimating lens, the refraction of the beam shaping prism causes the light beam collimated by the collimating lens to change the "long-axis direction in the cross section of the elliptical light beam". Shrinking "
I do. That is, this optical pickup device implements the beam shaping method according to claim 1.

In the optical pickup device according to the second aspect,
Two or more semiconductor laser light sources are arranged in the same plane orthogonal to the optical axis of the collimating lens, and the collimating lens is attached to two or more lenses made of different materials, and is substantially aligned with the emission wavelength of each semiconductor laser light source. That has been achromatized "(Claim 3).

As described above, the "semiconductor laser light source" refers to an individual light emitting portion in a semiconductor laser. Therefore, in the case of the "two-wavelength LD having one chip and an active layer having two wavelengths", one chip includes one semiconductor chip. It will have two semiconductor laser light sources, in which case the two semiconductor laser light sources are on the same plane.

In such a case, if the two-wavelength LD is used for a common collimating lens, the two semiconductor laser light sources are both located on “the same plane orthogonal to the optical axis of the collimating lens”. Since the two semiconductor laser light sources have different emission wavelengths, if the collimating lens has chromatic aberration,
Light beams of each wavelength cannot be properly collimated. Therefore, in such a case, the collimating lens is referred to as "2 different materials.
A configuration in which the above lenses are bonded together ", and substantially performs achromatic processing on the emission wavelength of each semiconductor laser light source.
The light flux of each wavelength is appropriately collimated.

In the optical pickup device according to the second aspect of the present invention, the collimating lens is formed of a single material, and the plurality of semiconductor laser light sources are arranged so as to correct the chromatic aberration of the collimating action by the collimating lens. It can be arranged shifted in the direction (claim 4).

If the semiconductor laser light sources are independent of each other, such a light source arrangement is possible. In this case, it is not necessary to perform achromatizing of the collimating lens.
The cost of the collimating lens can be reduced, and the cost of the optical pickup device can be reduced.

In the above-mentioned optical pickup device, the number of semiconductor laser light sources may be two (claim 5). In the optical pickup device described in any one of the second to fifth aspects, it is preferable that the semiconductor laser light source having the shortest emission wavelength be arranged on the optical axis of the collimator lens. A light beam with a shorter wavelength “spot diameter of a formed light spot becomes smaller”, and thus is more susceptible to wavefront aberration. Therefore, it is preferable to arrange such a light source on the optical axis of the collimating lens to suppress the deterioration of the wavefront aberration.

In such a case, if the objective lens is "common to the light flux from each semiconductor laser light source", the objective lens should be optimized for the optical recording medium having the shortest wavelength used ( Claim 7). Although it is possible to use a plurality of objective lenses by switching between them according to the wavelength used, it is possible to use them in common for light beams of multiple wavelengths. It is also preferable in terms of surface.

As described above, when the objective lens is used in common for light beams of a plurality of wavelengths, the objective lens is optimized for an optical recording medium using the shortest wavelength at which the imaging condition of the light spot becomes the strictest. Is better. In this case, it is preferable that the light source side of the objective lens be provided with "light shielding means for transmitting a light beam having a short wavelength and blocking a peripheral portion of the light beam having a long wavelength".

By doing so, it is possible to effectively reduce the deterioration of the shape of the light spot due to the light beam passing through the periphery of the objective lens of the light beam having a long working wavelength.

In the optical pickup device according to any one of the second to eighth aspects, it is preferable that the long axis direction of the elliptical light beam cross-sectional shape of the light beam transmitted through the collimating lens is parallel to the recording surface of the optical recording medium. It is preferable to make settings so as to satisfy (claim 9). This makes it possible to configure the optical pickup device to be “thin”.

The optical information processing apparatus according to the present invention provides an optical information processing apparatus for selectively performing at least one of information recording, reproduction, and erasing of information on two or more types of disk-shaped optical recording media having different wavelengths. Device ", which includes a holding unit, a driving unit, an optical pickup device, and a displacement driving unit.

The "holding unit" selectively sets and holds a disk-shaped optical recording medium. The “driving unit” is a unit that rotationally drives the optical recording medium set in the holding unit.
The "optical pickup device" performs at least one of recording, reproducing, and erasing of information on the set optical recording medium, and employs any one of the second to ninth aspects. "Displacement driving means" is means for driving the optical pickup device to be displaced in the radial direction of the optical recording medium.

[0037]

FIG. 1 is an explanatory diagram showing one embodiment of an optical pickup device. The semiconductor laser light source device 1 is equipped with two semiconductor laser chips 1a and 1b in the same package. The light emitting portion of each semiconductor laser chip is a “semiconductor laser light source”.

The semiconductor laser chip 1a has an emission wavelength of 65.
It is used for recording, reproducing or erasing information on a DVD 8 as an optical recording medium. The semiconductor laser chip 1b has an emission wavelength of 780n.
m, which is used when recording, reproducing, or erasing information on CD8 'as an optical recording medium.

Reference numeral 2 denotes a collimating lens.
The semiconductor laser chips 1a and 1b are arranged in a direction orthogonal to the drawing, and the semiconductor laser chip 1a has its light emitting portion (semiconductor laser light source) positioned on the optical axis of the collimator lens 2. The semiconductor laser chip 1b is arranged at a small distance from the optical axis of the collimator lens 2. In the figure, the semiconductor laser chip 1b is hidden by the shadow of the semiconductor laser chip 1a.

These semiconductor laser chips 1a and 1b are
The position is determined so that the divergence angle of the emitted laser beam becomes the maximum in the drawing. Therefore, when the light beam emitted from each semiconductor laser light source is converted into a parallel light beam by the collimating lens 2, the parallel light beam becomes , The short axis direction of the “elliptical light beam cross section” is a direction orthogonal to the drawing, and the long axis direction is in the drawing.

When the DVD 8 is used as an optical recording medium, the wavelength radiated by the semiconductor laser chip 1a is 6
The 50 nm light beam is converted into a parallel light beam by the collimator lens 2 and then enters the beam shaping prism 3.

The parallel light flux is bent in the optical path by refraction when exiting from the beam shaping prism 3, and the beam is shaped by refraction. That is, when the light is emitted from the beam shaping prism 3, the diameter in the major axis direction (direction parallel to the drawing) in the elliptical light beam cross section is reduced by the refraction. As a result, the beam-shaped parallel light beam has a substantially circular cross section.

The beam-shaped light beam passes through the polarizing beam splitter 4, is converted into circularly polarized light by the 波長 wavelength plate 5, passes through the aperture limiting wavelength filter 6, and passes through the objective lens 7.
Incident on. The aperture limiting wavelength filter 6 is formed with a “filter film whose transmission and cutoff vary depending on the wavelength” in a portion where the light beam peripheral portion passes.

The luminous flux having a wavelength of 650 nm passes through the aperture limiting wavelength filter 6 without being blocked by the filter film of the aperture limiting wavelength filter 6, and the objective lens 7
As a result, the light is focused as a light spot on the recording surface of the DVD 8 via a substrate having a thickness of 0.6 mm.

The objective lens 7 is optimized for the DVD 8, and the light emitting portion of the semiconductor laser chip 1a has the optical axis of the collimator lens 2 (coaxial with the optical axis of the objective lens 7).
Since it is located above, an appropriate light spot is formed on the recording surface of the DVD 8.

The light beam reflected by the recording surface becomes a “return light beam”, passes through the objective lens 7, the aperture limiting wavelength filter 6, passes through the quarter-wave plate 5, and rotates the polarization plane 90 degrees from the outward path. The light returns to the linearly polarized light, is reflected by the polarization beam splitter 4, and is guided to the light detection unit 10 by the detection lens 9.

The light detecting section 10 is a multi-divided light receiving element, and a light receiving signal generated from each light receiving section generates a reproduction signal, a focus error signal and a track error signal. Focusing control and tracking control are performed based on the focus error signal and the track error signal. A known appropriate method can be used for the method of generating the focus error signal / track error signal and the focusing control / tracking control.

When the optical recording medium is CD8 ', the semiconductor laser chip 1b is used. The light beam emitted from the semiconductor laser chip 1b is collimated by the collimator lens 2.
The beam is shaped into a parallel light beam, shaped by a beam shaping prism 3, and converted into a CD 8 ′ by a polarizing beam splitter 4, a 波長 wavelength plate 5, an aperture limiting wavelength filter 6, and an objective lens 7.
To form a light spot on the recording surface through a substrate having a thickness of CD8 ': 1.2 mm.

At this time, the peripheral portion of the light beam having a wavelength of 780 nm is cut off by the filter film in the aperture limiting wavelength filter 6. That is, the peripheral portion of the light beam having a wavelength of 780 nm is shielded from the objective lens 7 so that the aperture is limited, and a good light spot without flare is formed on the recording surface.

The return light beam reflected by the recording surface is guided to the photodetector 10 to generate the above-described signals, and the focusing control and the tracking control are performed in exactly the same manner as described above. .

FIG. 2A is an explanatory diagram showing how the light beam emitted from the semiconductor laser chip 1a is converted into a parallel light beam by the collimating lens 2. As described above, the divergence angle of the divergent light beam emitted from the semiconductor laser chip 1a is θ _{L in} the major axis direction of the ellipse, θ _{S in the} minor axis direction, F is the focal length of the collimating lens 2, and C is the circle. Assuming that the light beam diameter of the parallel light beam necessary to realize the desired spot diameter in the light spot having the shape is 2D, in the present invention, the short-axis diameter of the light beam cross section of the light beam converted into the parallel light beam by the collimator lens 2 is 2D. The focal length F of the collimating lens 2 is smaller than that in the conventional case (in which the major axis diameter of the light beam cross section of the parallel light beam is 2D). Focal length: larger than f.

As described above, in the optical pickup device according to the present invention, the collimator lens 2 has a larger lens diameter, but has a larger focal length: F, so that the conventional focal length:
The depth of focus of the collimating lens is larger than when the collimating lens of f is used, so that the "positional accuracy with respect to the collimating lens 2" of the semiconductor laser chip 1a can be made gentler.

When the (laser emitting portion) of the semiconductor laser chip 1b is separated from the optical axis of the collimating lens 2 by a distance ξ as shown in FIG. 2B, the focal length of the collimating lens is f. In this case, the angle formed by the collimated parallel light beam and the optical axis of the collimating lens is the angle α ′ in the figure, but when the focal length of the collimating lens 2 is F, the angle becomes α, as is apparent from the figure. , Α ′> α, the use of the collimating lens 2 having a large focal length can effectively reduce the deterioration of the light spot shape due to coma.

In the embodiment shown in FIG. 1, since the collimating lens is configured as a "single lens made of a single material", chromatic aberration cannot be removed. Therefore, as shown in FIG. 3, the positions of the light emitting portions (semiconductor laser light sources) of the semiconductor laser chips 1a and 1b are shifted by the distance: η in the optical axis direction of the collimating lens 2 so that the luminous flux from each semiconductor laser light source is Irrespective of the chromatic aberration of the collimating lens 2, the collimating lens 2 is made to have a good parallel light flux.

When, for example, the aforementioned “two-wavelength LD having one chip and two-wavelength active layers” is used as the semiconductor laser light source device, each semiconductor laser light source in such a light source device is denoted by reference numeral 1a ′ in FIG. Since they are in the same plane as shown by 1b ', they cannot be shifted in the optical axis direction of the collimating lens.

In such a case, as shown in FIG.
The two or more semiconductor laser light sources 1a 'and 1b' are arranged on the same plane orthogonal to the optical axis of the collimating lens 2A, and the collimating lens 2A is referred to as "two or more lenses 2 made of different materials.
a and 2b are bonded together, and each semiconductor laser light source 1
a ′, 1b ′ are substantially achromatized with respect to the emission wavelengths ”.
Both the light beams from a ′ and 1b ′ can be favorably converted into parallel light beams.

As described above, the light beam from each semiconductor laser light source can be satisfactorily converted into a parallel light beam by the same collimating lens, so that the occurrence of astigmatism in the beam shaping prism can be effectively reduced or prevented. .

Returning to FIG. 1, although not shown in FIG. 1, a "deflection prism" is provided between the objective lens 7 and the aperture limiting wavelength filter 6, and the direction of the light beam from the light source side is shown in FIG. Is deflected in a direction perpendicular to the direction. Therefore, the recording surfaces of the optical recording media 8, 8 'are actually parallel to the drawing in FIG.

In this case, the major axis direction in the elliptical light beam cross section of the light beam emitted from the semiconductor laser light source and converted into the parallel light beam by the collimator lens 2 is within the plane of FIG. Parallel. In this way, as shown in FIG. 1, when beam forming is performed,
Although the optical path of the light beam is bent, since the optical path before and after beam shaping is in a plane parallel to the drawing, the optical element from the light source to the deflecting prism can be arranged in the plane parallel to the drawing. The device can be made "thin".

The optical pickup device shown in FIG. 1 has two or more semiconductor laser light sources (light emitting portions of semiconductor laser chips 1a and 1b) having wavelengths different from each other and arranged close to each other. The luminous flux from the semiconductor laser light source having an emission wavelength corresponding to the mediums 8 and 8 ′ is
After that, the beam is shaped by changing the beam diameter in one direction by the beam shaping prism 3, and the beam shaped light is guided to the recording surfaces of the optical recording media 8 and 8 'by the objective lens 7. In the pickup device, a collimating lens 2 having a large focal length and a large lens diameter is used, and the refraction of the beam shaping prism 3 reduces the major axis direction of the light beam collimated by the collimating lens 2 in the elliptical light beam cross section. (Claim 2).

Also, as described with reference to FIG.
In the optical pickup device, the collimating lens 2
Are formed of a single material, and a plurality of semiconductor laser light sources are "displaced in the optical axis direction of the collimating lens 2 so as to correct the chromatic aberration of the collimating action by the collimating lens 2" (claim 4). As for the configuration of the light source section, as shown in FIG. 4, two or more semiconductor laser light sources 1a 'and 1b' are arranged in the same plane orthogonal to the optical axis of the collimating lens, and the collimating lens 2A is made of a different material. Two or more lenses 2a, 2b may be bonded together and substantially achromatized for the emission wavelength of each of the semiconductor laser light sources 1a ', 1b'.

In the embodiment described above, the number of the semiconductor laser light sources is two (claim 5), and the semiconductor laser light source having the shortest emission wavelength (the light emitting portion of the semiconductor laser chip 1a) is
It is arranged on the optical axis of the collimating lens 2 (claim 6),
The objective lens 7 is common to the light beams from the respective semiconductor laser light sources and is optimized for the optical recording medium 8 with the shortest wavelength used (claim 7), and transmits the light beam with the short wavelength to the light source side of the objective lens 7. The light shielding means 6 for blocking the peripheral portion of the light beam having a long wavelength is provided (claim 8). Then, the major axis direction of the elliptical light beam cross-sectional shape of the light beam transmitted through the collimating lens is set so as to be “parallel to the recording surface of the optical recording medium”.

Therefore, according to the optical pickup device of the above embodiment, the light beam emitted from the semiconductor laser light source is converted into a parallel light beam by the collimating lens, and then guided to the recording surface of the optical recording medium via the objective lens. In the optical pickup device, a beam shaping method for making a light beam cross-sectional shape of a light beam converted into a parallel light beam by a collimating lens into a circular shape or a desired shape close to the circular shape, wherein the light beam converted into a parallel light beam by the collimating lens 2 A beam shaping method (claim 1) in which the major axis direction in the elliptical light beam cross section is reduced by the refraction of the beam shaping prism 3 can be implemented.

FIG. 5 is a diagram showing an embodiment of the optical information recording processing device. This optical information processing apparatus is an optical information processing apparatus that selectively performs at least one of recording, reproducing, and erasing of information by light with respect to two or more types of disc-shaped optical information recording media having different use wavelengths. A holding unit 51 for selectively setting the optical recording medium 50 (for example, the above-described CD8 ′ and DVD8), and a motor M as a “driving unit” for driving the optical recording medium 50 set in the holding unit 51 to rotate. When,
An optical pick-up device 52 that performs one or more of recording, reproduction, and erasing by selecting light having a wavelength unique to the medium with respect to the set optical recording medium 50, and an optical pick-up device 52.
And a displacement driving means 53 for driving the optical recording medium 50 in the radial direction of the optical recording medium 50.

As the optical pickup device 52, the one using any one of claims 2 to 9 described in the above embodiment is the same as that of the optical information processing device according to claim 10. is there. The control means 54 in FIG. 5 is constituted by a microcomputer or the like, and controls each part of the optical information processing device.

Note that the number of semiconductor laser light sources is 2
However, it is needless to say that the present invention is not limited to this, and can be applied to a case where three or more semiconductor laser light sources having different emission wavelengths are used.

[0067]

As described above, according to the present invention, a novel beam shaping method in an optical pickup device, an optical pickup device, and an optical information processing device can be realized.

According to the beam shaping method of the present invention, it is easy to adjust the positional relationship between the collimator lens and the semiconductor laser light source, and it is suitable as a beam shaping method when a plurality of semiconductor laser light sources are used. Further, since the optical pickup device of the present invention implements the above-described beam shaping method, it is easy to adjust the positional relationship between the collimator lens and the semiconductor laser light source when using two or more semiconductor laser light sources, It is possible to effectively reduce the deterioration of the shape of the light spot formed by the light beam from the off-axis semiconductor laser light source due to coma aberration.

Therefore, in the optical information processing apparatus using the optical pickup device of the present invention, one or more of recording, reproduction, and erasing can be favorably performed on a plurality of optical recording media using different wavelengths.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an optical pickup device.

FIG. 2 is a diagram for explaining an effect of the present invention.

FIG. 3 is a diagram for explaining a configuration of a light source unit in the embodiment of FIG.

FIG. 4 is a diagram for explaining another embodiment of the light source unit of the optical pickup device.

FIG. 5 is a diagram for describing one embodiment of an optical information processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser light source device 1a, 1b Semiconductor laser chip 2 Collimating lens 3 Beam shaping prism 7 Objective lens 8, 8 'Optical recording medium

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) G02B 27/09 G02B 27/00 EF term (reference) 2H042 CA17 2H048 AA16 AA18 AA22 2H087 KA13 LA25 NA14 PA01 PA18 PB02 5D119 AA41 AA43 BA01 BB01 BB04 EC45 EC47 FA08 JA02 JA07 JA43 JA63 LB04

Claims (10)

[Claims] 1. An optical pickup device for converting a light beam emitted from a semiconductor laser light source into a parallel light beam by a collimator lens and then guiding the light beam to a recording surface of an optical recording medium via an objective lens. A beam shaping method for making the light beam cross-sectional shape of the obtained light beam a circular shape or a desired shape close to the circular shape, wherein the long-axis direction of the light beam collimated by the collimator lens in the elliptical light beam cross section is A beam shaping method characterized in that the beam is reduced by the refraction of a beam shaping prism. 2. A light source comprising two or more semiconductor laser light sources having wavelengths different from each other and arranged close to each other, wherein a light beam from the semiconductor laser light source having an emission wavelength corresponding to an optical recording medium is converted into a parallel light beam by a collimating lens. Thereafter, the beam shaping prism changes the light beam diameter in one direction to shape the beam, and the beam-shaped light beam is guided to the recording surface of the optical recording medium by the objective lens. An optical pickup device using a lens having a large lens diameter and reducing a major axis direction of an elliptical light beam cross section of a light beam collimated by a collimating lens by a refraction effect of a beam shaping prism. 3. The optical pickup device according to claim 2, wherein the two or more semiconductor laser light sources are on the same plane orthogonal to the optical axis of the collimating lens, and the collimating lens is composed of two or more lenses made of different materials. An optical pickup device which is laminated and substantially achromatized for the emission wavelength of each semiconductor laser light source. 4. The optical pickup device according to claim 2, wherein the collimating lens is formed of a single material, and a plurality of semiconductor laser light sources are arranged so as to correct chromatic aberration of collimating action by the collimating lens. An optical pickup device which is displaced in an optical axis direction. 5. The optical pickup device according to claim 2, wherein the number of semiconductor laser light sources is two. 6. The optical pickup device according to claim 2, wherein the semiconductor laser light source having the shortest emission wavelength is arranged on the optical axis of the collimator lens. apparatus. 7. The optical pickup device according to claim 6, wherein the objective lens is common to the light beams from the respective semiconductor laser light sources, and is optimized for an optical recording medium using the shortest wavelength. Optical pickup device. 8. The optical pickup device according to claim 7, further comprising a light shielding means on the light source side of the objective lens for transmitting a light beam having a short wavelength and blocking a peripheral portion of the light beam having a long wavelength. Pickup device. 9. The optical pickup device according to claim 2, wherein the major axis direction of the elliptical light beam cross-sectional shape of the light beam transmitted through the collimator lens is parallel to the recording surface of the optical recording medium. An optical pickup device characterized in that the optical pickup device is set to be: 10. An optical information processing apparatus for selectively performing at least one of recording, reproducing, and erasing of information by light with respect to two or more kinds of disk-shaped optical recording media having different working wavelengths. A holding unit for selectively setting an optical recording medium in a shape, a driving unit for rotating and driving the optical recording medium set in the holding unit; 10. An optical pickup device for performing one or more of erasing, and a displacement driving means for driving the optical pickup device to be displaced in a radial direction of the optical recording medium, wherein the optical pickup device is an optical pickup device according to any one of claims 2 to 9. An optical information processing apparatus, characterized by using: