JPH10320812A - Astigmatism generating optical element, optical pickup integrated element, optical pickup and optical information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct astigmatism to be generated on an optical information record medium, etc., and to easily perform accurate positioning of the astigmatism generating optical element. SOLUTION: The astigmatism generating optical element 10 is equipped with two transparent optical members 11 and 13, each having a triangle pole shape and a transparent platelike optical member 12 disposed to be held by these two optical members 11 and 13 between them. A refractive index of the optical member 12 is different from refractive indexes of the optical members 11 and 13 respectively. Light from a light source is passed through the optical members 11 and 12, and is reflected by the surface of the optical member 12 on the side of the optical member 13 and passed through the optical members 12 and 11, and is given prescribed astigmatism and then emitted out of the astigmatism generating optical element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element for generating astigmatism which can be used for correcting astigmatism generated in an optical information recording medium and the like, and an optical element for generating astigmatism using the optical element. The present invention relates to an optical pickup integrated device, an optical pickup, and an optical information recording / reproducing device.

[0002]

2. Description of the Related Art In recent years, various optical information recording / reproducing devices for optically recording and / or reproducing information using an optical information recording medium such as an optical disk have been put to practical use.

Incidentally, an optical disc generally has a configuration in which a recording surface is formed on a transparent substrate. Then, the recording or reproducing light is applied to the optical disc so as to be focused on the recording surface via the transparent substrate. Generally, grooves (grooves) for track guidance are formed on the recording surface.

[0004]

As the transparent substrate of the optical disk, for example, a transparent resin such as polycarbonate is used. However, since a transparent substrate made of such a transparent resin has birefringence, astigmatism is generated with respect to incident light. Further, the groove also acts as a diffraction grating for the incident light, and thus generates astigmatism for the incident light. Also, in an optical pickup that irradiates an optical disc with light for recording or reproduction, an optical element such as a laser or a lens as a light source may generate astigmatism in some cases. Such astigmatism is not preferable because it deteriorates signal reading performance, servo performance, and the like in the optical information recording / reproducing apparatus.

Accordingly, the present applicant has proposed an optical pickup provided with a means for correcting astigmatism caused by a transparent substrate, a groove or the like. FIG. 17 conceptually shows a configuration of an example of an optical pickup provided with a means for correcting astigmatism. In this example, as shown in FIG. 17A, light from a light source (not shown) is reflected by a mirror 202, condensed by an objective lens 203, and irradiated onto an optical disc 201. In this example, as a means for correcting astigmatism, an astigmatism generating plate 205 made of a transparent parallel flat plate such as a glass plate is provided obliquely with respect to the optical axis as a means for correcting astigmatism before entering the mirror 202. It is arranged in. FIG. 17 (b) is the same as FIG.
5 shows a state in which the astigmatism generating plate 205 is viewed from the side.

As shown in FIG. 17, astigmatism generating plate 2
In the case where 05 is disposed obliquely with respect to the optical axis, the amount of astigmatism generated by the astigmatism generation plate 205 depends on the angle of the astigmatism generation plate 205. Therefore, in order to obtain a desired amount of astigmatism, it is necessary to accurately position the astigmatism generating plate 205. However, the astigmatism generating plate 2
When the lens 05 is disposed obliquely with respect to the optical axis, it is difficult to accurately position the astigmatism generating plate 205.

Further, providing the astigmatism generating plate 205 as shown in FIG. 17 has a disadvantage that the number of components in the optical pickup and the mounting process are increased.

The present invention has been made in view of the above problems, and a first object of the present invention is to make it possible to correct astigmatism occurring in an optical information recording medium or the like and to facilitate accurate positioning. Another object of the present invention is to provide an optical element for generating astigmatism, an integrated element for an optical pickup, an optical pickup, and an optical information recording / reproducing apparatus using the optical element for generating astigmatism.

[0009] A second object of the present invention is to provide, in addition to the above objects,
Optical element for generating astigmatism capable of preventing an increase in the number of components and the number of component mounting steps, an integrated element for an optical pickup, an optical pickup, and optical information recording / reproducing using the optical element for generating astigmatism It is to provide a device.

[0010]

According to a first aspect of the present invention, there is provided an optical element for generating astigmatism, which has an inclined surface which is inclined with respect to the optical axis of an optical system in which the optical element for generating astigmatism is used. A first optical member having a transparent plate-shaped second optical member joined to the slope of the first optical member and having a different refractive index from the first optical member. .

According to a seventh aspect of the present invention, there is provided an optical element for generating astigmatism, which is bonded to a transparent optical member on which light is incident and one surface of the optical member and generates a predetermined astigmatism with respect to the incident light. And a hologram to be made.

According to a tenth aspect of the present invention, there is provided an optical pickup integrated device comprising: a light source for emitting light for irradiating an optical information recording medium;
A photodetector for detecting return light from the optical information recording medium, a transparent first optical member having an inclined surface arranged to be inclined with respect to the optical axis of the optical system of the optical pickup, and the first optical element An astigmatism generating unit that includes a transparent plate-shaped second optical member having a different refractive index from the first optical member and is bonded to a slope of the member, and that generates predetermined astigmatism with respect to light passing therethrough; An optical element is provided, and a light source, a photodetector, and an astigmatism generating optical element are integrated.

[0013] An integrated device for an optical pickup according to an eleventh aspect is a light source for emitting light for irradiating an optical information recording medium,
A photodetector for detecting return light from the optical information recording medium, a transparent optical member to which light passing through the optical system of the optical pickup is incident, and a surface joined to this optical member, and An optical element for generating astigmatism including a hologram for generating predetermined astigmatism, and a light source, a photodetector, and an optical element for generating astigmatism are integrated.

According to a twelfth aspect of the present invention, there is provided an optical pickup, comprising: a light source for emitting light for irradiating an optical information recording medium; a photodetector for detecting return light from the optical information recording medium; An optical system that irradiates an information recording medium and guides return light from the optical information recording medium to a photodetector; and a transparent first optical system having a slope that is arranged to be inclined with respect to the optical axis of the optical system. A first optical member and a transparent plate-like second optical member having a different refractive index from the first optical member, and having a predetermined astigmatism with respect to light passing therethrough. And an astigmatism generating optical element for generating the astigmatism.

According to a thirteenth aspect of the present invention, there is provided an optical pickup, comprising: a light source for emitting light for irradiating the optical information recording medium; a photodetector for detecting return light from the optical information recording medium; An optical system that irradiates the information recording medium and guides return light from the optical information recording medium to the photodetector, a transparent optical member into which light passing through the optical system is incident, and a joint to one surface of the optical member And an optical element for generating astigmatism including a hologram for generating predetermined astigmatism with respect to the incident light.

An optical information recording / reproducing apparatus according to claim 14 is
An optical pickup emits light for irradiating the optical information recording medium, a light detector for detecting return light from the optical information recording medium, and irradiates the optical information recording medium with light emitted from the light source, An optical system for guiding return light from an optical information recording medium to a photodetector, a transparent first optical member having an inclined surface arranged to be inclined with respect to the optical axis of the optical system, and the first optical system An astigmatism generating unit that includes a transparent plate-shaped second optical member having a different refractive index from the first optical member and is bonded to a slope of the member, and that generates predetermined astigmatism with respect to light passing therethrough; And an optical element.

An optical information recording / reproducing apparatus according to claim 15 is
An optical pickup emits light for irradiating the optical information recording medium, a light detector for detecting return light from the optical information recording medium, and irradiates the optical information recording medium with light emitted from the light source, An optical system that guides the return light from the optical information recording medium to the photodetector, a transparent optical member into which light passing through the optical system is incident, and a surface joined to one surface of the optical member, and An optical element for generating astigmatism including a hologram for generating predetermined astigmatism.

An optical element for generating astigmatism according to claim 1,
An integrated device for an optical pickup according to claim 10, claim 1.
In the optical pickup according to the second aspect or the optical information recording / reproducing apparatus according to the fourteenth aspect, when the light passes through the first optical member and the second optical member, a predetermined astigmatism is generated with respect to the light. You. The first optical member is used for positioning the optical element for generating astigmatism.

An optical element for generating astigmatism according to claim 7,
An integrated device for an optical pickup according to claim 11, wherein
In the optical pickup according to the third aspect or the optical information recording / reproducing apparatus according to the fifteenth aspect, when the light passes through the hologram, a predetermined astigmatism is generated with respect to the light. The optical member is used for positioning the astigmatism generating optical element.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, the optical element for generating astigmatism according to the present invention will be conceptually described. The astigmatism generating optical element according to the present invention is an astigmatism generating optical element that generates a predetermined astigmatism with respect to light passing therethrough. It is provided in an optical pickup in an optical information recording / reproducing apparatus that performs at least one of recording and reproduction of information, and is used for correcting astigmatism generated in an optical information recording medium or the like. The astigmatism generating optical element according to the present invention is roughly classified into a reflection type and a transmission type.

FIG. 1 shows a main part of an example of an optical pickup including a reflection type astigmatism generating optical element according to a first embodiment of the present invention. The optical pickup shown in this drawing reflects light for recording or reproduction from a light source such as a semiconductor laser (not shown) and generates a predetermined astigmatism with respect to this light. The optical system includes an optical element 10 for generating astigmatism and an objective lens 15 for condensing light reflected by the optical element 10 for generating astigmatism and irradiating the optical disk 16 with the light.

The astigmatism generating optical element 10 is composed of two transparent triangular prism-shaped optical members 11 and 13, and a transparent plate-shaped optical member disposed so as to be sandwiched between the two optical members 11 and 13. And a member 12. Each optical member 1
1 to 13 are formed of, for example, glass.

The optical member 11 has, as three surfaces forming the side surfaces of the triangular prism, a flat surface 11a disposed perpendicular to the optical axis 17 before entering the astigmatism generating optical element 10 in the optical system of the optical pickup. , A plane 11b arranged parallel to the optical axis 17 and a slope 11c arranged inclined at 45 ° to the optical axis 17.

The optical member 13 includes, as three surfaces forming the side surfaces of the triangular prism, a plane 13 a arranged perpendicular to the optical axis 17 and a plane 1 arranged parallel to the optical axis 17.
3b, and a slope 13c which is inclined at 45 ° to the optical axis 17 and is arranged to face the slope 11c of the optical member 11.

The optical member 12 is a slope 11 of the optical member 11.
c and the inclined surface 13c of the optical member 13, and each surface of the optical member 12 is joined to each inclined surface 11c, 13c. As a result, the entire astigmatism generating optical element 10 has a substantially cubic shape.

In this embodiment, the refractive indexes of the optical members 11 and 13 are equal, and the refractive index of the optical member 12 is
It is different from the refractive index of 1,13. Here, the optical member 1
2 is n ₁ , and the refractive indices of the optical members 11 and 13 are n ₂
And The magnitude relationship between the refractive index n ₁ and the refractive index n ₂ is arbitrary.

The surface of the optical member 12 on the side of the optical member 13 (the boundary surface between the optical members 12 and 13) also has a function as a reflecting surface which has a function other than the generation of astigmatism.

Next, the operation of the optical element for generating astigmatism and the optical pickup according to this embodiment will be described. Light from a light source (not shown) is
The light enters the astigmatism generating optical element 10 from 1a, passes through the optical member 11, further passes through the optical member 12, is reflected by the surface of the optical member 12 on the optical member 13 side, and has an optical path of 90 °.
It is bent, passes through the optical member 12 again, further passes through the optical member 11, exits from the plane element 11 b to the outside of the astigmatism generating optical element 10, is condensed by the objective lens 15, and irradiates the optical disk 16. Is done.

A predetermined astigmatism (astigmatic difference) is generated by the astigmatism generating optical element 10 in the light passing through the astigmatism generating optical element 10. Here, the angle of the optical member 12 with respect to the optical axis 17 is θ, and the substantial plate thickness of the optical member 12 as viewed from passing light is T (in the example shown in FIG. Therefore, assuming that the actual plate thickness of the optical member 12 is t, T = 2t.), The refractive indices n ₁ and n ₂ and the relative refractive index n defined as described above.
= N ₁ / n ₂ , the astigmatism generating optical element 10
The astigmatic difference n ₂ Δ in air generated by
It is represented by the following equation (1).

N ₂ Δ = {T · n ₂ / {(n ² −sin ² θ)} · [{n ² cos ² θ / (n ² −sin ² θ)} − 1] (1)

[0032] According to Equation (1), the magnitude relationship between the refractive indexes n _1, n _2, the sign of astigmatism n ₂ delta changes, selecting a magnitude relation between the refractive indexes n _1, n ₂ Thus, the direction of the astigmatic difference n ₂ Δ can be selected.

In the actual design of the optical pickup, the astigmatism generated by the transparent substrate or the groove of the optical disk 16 and the astigmatism generated by the optical element such as a laser or a lens as a light source in the optical pickup are canceled out. Each variable in the equation (1) is determined so that the aberration is obtained by the astigmatism generating optical element 10.

Here, as an example, θ = 45 ° and n ₁ =
1.51, n ₂ = 1.565, t = 0.1 mm (T =
0.2 mm), the astigmatic difference n ₂ Δ is about 38 μm
Becomes This is because when a semiconductor laser is used as a light source, the astigmatic difference in the semiconductor laser is set to, for example, 15 μm, and the NA (numerical aperture) on the semiconductor laser side is set to, for example, 0.1.
This is a value that substantially cancels the astigmatic difference generated by the mini disc as the optical disc.

As described above, according to the present embodiment, it is possible to correct astigmatism occurring in the optical disk 16 or the like, and to improve signal reading performance and servo performance in an optical information recording / reproducing apparatus using an optical pickup. And reliability can be improved.

Further, according to the present embodiment, in the optical system of the optical pickup, the plane arranged perpendicular to the optical axis and the plane arranged parallel to the optical axis are inclined with respect to the optical axis. Member 11, 1 having an inclined surface arranged
Since the plate-like optical member 12 having a different refractive index from the optical members 11 and 13 is joined to the inclined surface in 3 to form the astigmatism generating optical element 10, it is arranged perpendicularly or parallel to the optical axis. The accurate positioning of the optical element for astigmatism generation 10 can be easily performed using the flat surface as a reference plane.
For example, it is possible to accurately position the astigmatism generating optical element 10 only by fixing the plane arranged perpendicularly or parallel to the optical axis to the base member of the optical pickup as it is. Become.

Further, according to the present embodiment, the optical member 1
1 and the refractive index of the optical member 12 are arbitrarily selected, so that the direction and magnitude of the generated astigmatism (astigmatic difference) can be obtained without changing the shape and arrangement of the astigmatism generating optical element 10. Can be set arbitrarily. Also,
When the refractive index of the optical member 12 is smaller than the refractive index of the optical member 13, a further effect can be obtained. This will be described later in detail with reference to FIGS.

Further, according to the present embodiment, the optical member 13 of the optical member 12 in the optical element 10 for generating astigmatism is used.
Since the side surface is integrated with the reflecting surface that reflects light, the number of parts and the number of parts in the component mounting process are smaller than when an optical element for generating astigmatism is provided separately from the mirror that reflects light. The increase can be prevented, and the cost can be reduced and the reliability can be improved.

The present embodiment can be applied to any of the recording / reproducing systems of the read-only type, the write-once type, and the rewritable type.

FIG. 2 is an explanatory view showing a modification of the optical element for generating astigmatism according to the present embodiment. The optical element for astigmatism generation 10A shown in this figure is the same as the optical element for astigmatism generation 10 shown in FIG. 1 except for the optical member 13. Other configurations, operations, and effects of the astigmatism generating optical element 10A are described below.
Is the same as

FIG. 3 is an explanatory view showing another modification of the optical element for generating astigmatism according to the present embodiment. The astigmatism generating optical element 10B shown in FIG. 3 has a predetermined astigmatism instead of the optical member 12 on the slope 11c of the optical member 11 in the astigmatism generating optical element 10A shown in FIG. The reflection type hologram 18 on which a pattern to be generated is formed is joined. In the astigmatism generating optical element 10B, light incident from the plane 11a of the optical member 11 passes through the optical member 11, is reflected by the hologram 18 and generates a predetermined astigmatism. The light passes through and is emitted from the plane 11b. Other configurations, operations, and effects of the astigmatism generating optical element 10B are the same as those of the astigmatism generating optical element 10.

FIG. 4 shows a main part of an example of an optical pickup including a transmission type astigmatism generating optical element according to a second embodiment of the present invention. The optical pickup shown in this drawing transmits light for recording or reproduction from a light source (not shown) and generates a predetermined astigmatism with respect to this light. An optical element 20 and an objective lens 15 for condensing light transmitted through the astigmatism generating optical element 20 and irradiating the optical disk 16 with the light are provided. Optical element 20 for generating astigmatism
Has the same configuration as the astigmatism generating optical element 10 shown in FIG.

In this embodiment, light from a light source (not shown) is incident on the astigmatism generating optical element 20 from the plane 13b of the optical member 13, and passes through the optical member 13, the optical member 12, and the optical member 11 in this order. And the plane 11b of the optical member 11
The light is further emitted outside the astigmatism generating optical element 20, condensed by the objective lens 15, and irradiated on the optical disc 16.

A predetermined astigmatism (astigmatic difference) is generated by the astigmatism generating optical element 20 in the light passing through the astigmatism generating optical element 20. The astigmatism difference n ₂ Δ generated by the astigmatism generating optical element 20 is obtained by using T as the actual plate thickness t of the optical member 12 in Expression (1).

Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.

FIG. 5 is an explanatory view showing a modification of the optical element for generating astigmatism according to the present embodiment. The astigmatism generating optical element 20A shown in this figure is the one obtained by removing the optical member 11 from the astigmatism generating optical element 20 shown in FIG. Other configurations, operations, and effects of the astigmatism generating optical element 20A are described below.
Is the same as

FIG. 6 is an explanatory view showing another modification of the optical element for generating astigmatism according to the present embodiment. The astigmatism generating optical element 20B shown in this figure applies a predetermined astigmatism instead of the optical member 12 to the slope 13c of the optical member 13 in the astigmatism generating optical element 20A shown in FIG. A transmission type hologram 19 on which a pattern to be generated is formed is joined. In the astigmatism generating optical element 20B, light incident from the plane 13b of the optical member 13 passes through the optical member 13 and further passes through the hologram 19, where a predetermined astigmatism is generated and the astigmatism is generated. The light is emitted from the generating optical element 20B. Other configurations, operations, and effects of the astigmatism generating optical element 20B are the same as those of the astigmatism generating optical element 20.

Here, in the astigmatism generating optical element as shown in FIG. 1, FIG. 2 or FIG. 4, the refractive index of the inner optical member 12 is smaller than that of the outer optical members 11 and 13. Further effects obtained in this case will be described in detail with reference to FIGS.

For example, in an optical disk apparatus using a mini disk, which is a kind of magneto-optical disk, as an optical disk, the optical disk is so arranged that the polarization direction (the vibration direction of the electric field) coincides with the tracking direction (the cross-track direction) of the optical disk. It is designed to emit light.

FIG. 7 shows a simplified optical system of an optical pickup in the case where the polarization direction of the light irradiated on the optical disk is defined as described above. FIG. 1 shows a semiconductor laser 21 as a light source, and an objective lens 15 which collects light from the semiconductor laser 21 and irradiates the signal recording surface of an optical disk 16 with the light. here,
The direction of the track on the optical disc 16 is 1 in the figure.
The direction is perpendicular to the paper surface as shown by 6a, and the tracking direction is the up and down direction in the figure as shown by the symbol T in the figure. Therefore, the semiconductor laser 21 is arranged such that the polarization direction of the emitted light is in the vertical direction in the figure as indicated by reference numeral 21a in the figure.

Here, as shown in FIG. 7, a transparent parallel flat plate 22 is arranged obliquely with respect to the optical axis 23 in the optical path from the semiconductor laser 21 to the objective lens 15, and Considering the generation of astigmatism that cancels the astigmatism generated in the optical pickup and by the optical disc 16 including the astigmatism generated by the optical pickup 16. In this case, as shown in FIG.
It is necessary to make the arrangement such that it turns from a state perpendicular to the optical axis 23 about an axis perpendicular to the paper surface.

The objective lens 15 is driven in the tracking direction T by the tracking servo. Therefore, the relative positional relationship between the parallel plate 22 and the objective lens 15 changes in the tracking direction T. However, in the arrangement as shown in FIG. 7, the parallel plate 22 is asymmetric about the optical axis 23 in the tracking direction T. Therefore, when the position of the objective lens 15 in the tracking direction T changes from its center position, the astigmatism generated by the parallel plate 22 with respect to the light applied to the optical disc 16 changes asymmetrically with respect to the center position. Phenomenon appears. As a result, as shown in FIG.
When the reading performance of the optical pickup with respect to the position of the objective lens 15 in the tracking direction is represented by some parameter, in the arrangement shown in FIG.
As shown in FIG. 4, there is a problem that the reading performance becomes asymmetric with respect to the center position of the lens, and the reliability is deteriorated.

On the other hand, an astigmatism generating optical element 20 as shown in FIG. 4 is provided in place of the parallel plate 22 in FIG. 7, and the refractive index of the inner optical member 12 is changed to the outer optical member. When the refractive index is smaller than 11 and 13, the astigmatism generating optical element 20 is arranged as shown in FIG. Note that FIG.
1 shows a state of the astigmatism generating optical element 20 when viewed from above in the figure. In this case, as shown in FIG.
3, it is arranged so as to rotate about the axis in the tracking direction T. In this case,
The optical member 12 is symmetric about the optical axis 23 in the tracking direction T. Therefore, even if the position of the objective lens 15 in the tracking direction T changes from the center position, the astigmatism generated by the astigmatism generating optical element 20 with respect to the light irradiated on the optical disc 16 is the center position. Changes symmetrically with respect to position. As a result, as indicated by reference numeral 25 in FIG. 9, the reading performance is symmetric with respect to the center position of the lens, and the reliability is improved. Note that the astigmatism generating optical element 10 shown in FIG. 1 or the astigmatism generating optical element 10A shown in FIG. 2 may be used instead of the astigmatism generating optical element 20 shown in FIG. The same is true.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 10 is an explanatory diagram showing a configuration of a magneto-optical type optical pickup including the optical element for generating astigmatism according to the present embodiment. The optical pickup 30 includes a semiconductor laser 31 that emits a laser beam, an objective lens 35 arranged to face the magneto-optical disk 40, and a semiconductor laser 31 between the semiconductor laser 31 and the objective lens 35. Diffractive elements (gratings) 32 arranged in order, and a beam splitter 3 as an astigmatism generating optical element according to the present embodiment.
3. A collimator lens 34 is provided. The optical pickup 30 further includes a three-beam Wollaston prism 36, a multi-lens 37, and a photodetector 38, which are sequentially arranged on the side of the beam splitter 33 from the beam splitter 33 side.
It has. The optical pickup 30 further includes an actuator 39 which can drive the objective lens 35 in a focus direction (a direction perpendicular to the surface of the magneto-optical disk 40) F and a tracking direction (track traverse direction) T.
The optical pickup 30 includes a base member (not shown) supported so as to be movable in the radial direction of the magneto-optical disk 40 along a guide (not shown). Each component of the optical pickup 30 except the objective lens 35 is attached to the base member. It is fixed for.

The semiconductor laser 31 is a light emitting element utilizing recombination light emission of a semiconductor, and emits a linearly polarized laser beam that becomes P-polarized light (linearly polarized light whose polarization direction is parallel to the plane of incidence) to a beam splitter 33. It is supposed to. The diffraction element 32 diffracts the light from the semiconductor laser 31 and
It is designed to generate three diffracted lights of zero-order diffracted light and ± first-order diffracted light.

The beam splitter 3 according to the present embodiment
Reference numeral 3 has both a beam splitting function and an astigmatism generation function. This beam splitter 33
The optical system includes two transparent optical members 41 and 43 having a triangular prism shape, and a transparent plate-shaped optical member 42 disposed so as to be sandwiched between the two optical members 41 and 43. Each of the optical members 41 to 43 is formed of, for example, glass.

The optical member 41 has three surfaces forming the side surfaces of the triangular prism, and is formed by the semiconductor laser 31 and the objective lens 35.
The optical system has a plane arranged perpendicular to the optical axis, a plane arranged parallel to the optical axis, and a slope arranged at 45 ° to the optical axis. doing. Similarly, the optical member 43 includes, as three surfaces forming the side surfaces of the triangular prism, a plane arranged perpendicular to the optical axis, a plane arranged parallel to the optical axis, and a plane arranged parallel to the optical axis. It has a slope inclined at 45 ° and arranged so as to face the slope of the optical member 41.

The optical member 42 is disposed between the slope of the optical member 41 and the slope of the optical member 43, and the surface of the optical member 42 on the optical member 41 side is joined to the slope of the optical member 41. The surface of the optical member 42 on the optical member 43 side and the optical member 43
A dielectric multilayer film 33a formed by vapor deposition or sputtering is formed between the inclined surface of the optical member 43 and the inclined surface of the optical member 43 and the inclined surface of the optical member 43 through the dielectric multilayer film 33a. Have been. As a result, the entire beam splitter 33 has a substantially cubic shape.

In the beam splitter 33, the refractive indexes of the optical members 41 and 43 are equal, and the refractive index of the optical member 42 is different from the refractive indexes of the optical members 41 and 43. In the present embodiment, in particular, the semiconductor laser 31 is arranged so that the polarization direction of the light emitted from the semiconductor laser 31 coincides with the tracking direction T as indicated by reference numeral 31a in the drawing. Therefore, the beam splitter 33 generates astigmatism that cancels the astigmatism generated in the optical pickup 30 and the magneto-optical disk 40 except for the beam splitter 33, including the astigmatism generated by the semiconductor laser 31. Thus, the refractive index of the optical member 42 is set to be larger than the refractive indexes of the optical members 41 and 43.

Since the dielectric multilayer film 33a is formed between the surface of the optical member 42 on the optical member 43 side and the slope of the optical member 43, the surface of the optical member 42 on the optical member 43 side is: This means that it is integrated with the beam splitting surface which has a function other than the generation of astigmatism.

The dielectric multilayer film 33a has, for example, a transmittance of about 1 S-polarized light (linearly polarized light whose polarization direction is perpendicular to the plane of incidence).
0% or less, the transmittance of the P-polarized component is about 63%, the reflectance of the S-polarized component is about 90%, and the reflectance of the P-polarized component is about 35%.
%.

The collimator lens 34 converts the light from the beam splitter 33 into a parallel light beam. The objective lens 35 condenses the light from the collimator lens 34 and converges the light on the magneto-optical disk 4 so that it converges on the signal recording surface.
0 is irradiated. The return light from the magneto-optical disk 40 passes through the objective lens 35 and the collimator lens 34 in order, and then enters the beam splitter 33, and is partially reflected by the dielectric multilayer film 33a. The light passes through the lens 37 in order and enters the photodetector 38.

The three-beam Wollaston prism 36 separates the incident light into three light beams having different polarization directions. Of the three light beams separated by the three-beam Wollaston prism 36, the upper and lower two light beams are linearly polarized light whose polarization directions are orthogonal to each other.

The multi-lens 37 is a lens having both a cylindrical lens function and a concave lens function, and obtains a focus error signal by the astigmatism method for the light from the three-beam Wollaston prism 36 by the cylindrical lens function. And a concave lens function to extend the optical path length of the three light beams from the three-beam Wollaston prism 36 to the photodetector 38 to facilitate separation of the three light beams. ing. The photodetector 38 has a plurality of light receiving sections for detecting a focus error signal, a tracking error signal, and a magneto-optical reproduction signal.

FIG. 11 shows the arrangement of the light receiving section of the photodetector 38 in FIG. As shown in this figure, the photodetector 38 has four light receiving sections 3 each having a shape obtained by dividing a square into four parts by the upper and lower center lines and the left and right center lines.
8A to 38D, light receiving units 38F and 38E arranged on the left and right of the light receiving units 38A to 38D, and light receiving units 38I and 38J arranged above and below the light receiving units 38A to 38D. Of the return light from the magneto-optical disk 40, light corresponding to the 0th-order diffracted light from the diffraction element 32 is separated into three light beams by a three-beam Wollaston prism 36, and each of the light beams is received by a light receiving unit of a photodetector 38. 38I and light receiving unit 3
8A to 38D and the light receiving unit 38J. Also, of the return light from the magneto-optical disk 40,
Light corresponding to the ± 1st-order diffracted light from the diffraction element 32 is separated into three light beams by the three-beam Wollaston prism 36, and the central light beam among them is received by the light receiving portion 38E of the photodetector 38. , 38F.

Here, each of the light receiving sections 38A to 38F, 38
When each output signal of I, 38J is represented by A to F, I, J,
Focus error signal FE, tracking error signal T
E and the magneto-optical reproduction signal MS are expressed by the following equation (2), respectively.
To (4).

FE = (A + C)-(B + D) (2) TE = EF (3) MS = IJ (4)

The optical pickup 30 has a subtractor 45 that performs the operation of the above equation (2) and outputs the focus error signal FE, and a subtractor 46 that performs the operation of the above equation (3) and outputs the tracking error signal TE. And a subtractor 47 that performs the operation of the above equation (4) and outputs a magneto-optical reproduction signal MS.

Next, the operation of the optical pickup 30 will be described. The recording or reproducing laser light emitted from the semiconductor laser 31 is split into three light beams by the diffractive element 32, enters the beam splitter 33, passes through the optical members 41 and 42 in order, and then reduces the amount of light. Part of the light passes through the dielectric multilayer film 33a, passes through the optical member 43, and is emitted from the beam splitter 33. Here, predetermined astigmatism (astigmatic difference) is generated by the optical members 41 to 43 in the light passing through the beam splitter 33.

The light emitted from the beam splitter 33 is converted into a parallel light beam by a collimator lens 34, condensed by an objective lens 35, and applied to a magneto-optical disk 40 so as to converge on a desired track on a signal recording surface. You. The output of the semiconductor laser 31 is set to a high output for recording during recording, and is set to a low output for reproduction during reproduction.

At the time of reproduction, the light applied to the magneto-optical disk 40 is reflected by rotating the polarization direction in a different direction in accordance with the magnetization direction on the signal recording surface of the magneto-optical disk 40 by the Kerr effect. Become. Therefore, the return light has a P polarization component and an S polarization component. This return light passes through the objective lens 35 and the collimator lens 34 in order, then enters the beam splitter 33, is partially reflected by the dielectric multilayer film 33a, and passes through the three-beam Wollaston prism 36 and the multi-lens 37 in this order. Then, the light enters the photodetector 38. Then, based on the output signal of the photodetector 38, a focus error signal, a tracking error signal, and a magneto-optical reproduction signal are detected.

FIG. 12 is a block diagram showing a configuration of an optical disk device as an optical information recording / reproducing device according to the present embodiment having the optical pickup 30 shown in FIG.
The optical disk device 50 includes, in addition to the optical pickup 30, a spindle motor 51 for rotating and driving the magneto-optical disk 40, a feed motor 52 for driving the optical pickup 30 in the radial direction of the magneto-optical disk 40, The servo control circuit 53 controls the actuator 39 of the pickup 30, the spindle motor 51 and the feed motor 52.

The optical disk device 50 is further disposed at a position facing the optical pickup 30 with the magneto-optical disk 40 interposed therebetween, and a recording magnetic head 54 for applying a predetermined magnetic field to the magneto-optical disk 40, and the recording magnetic head 54. Magnetic head 54
, A signal modulation / demodulation / error correction unit 56 connected to the optical pickup 30 and the head drive circuit 55, and a working RAM (random) connected to the signal modulation / demodulation / error correction unit 56. (Access memory) 57, and system controller 5 for controlling servo circuit 53 and signal modulation / demodulation / error correction unit 56
8 is provided. The signal modulation / demodulation / error correction unit 56
A signal modulator for modulating a signal input from the outside to record on the magneto-optical disk 40, a signal demodulator for demodulating a signal reproduced from the magneto-optical disk 40, and an error for a signal recorded on the magneto-optical disk 40. An error correction unit is provided for adding a correction code and for correcting an error of a signal reproduced from the magneto-optical disk 40 using the error correction code.

If the optical disk device 50 is for data storage, for example, the signal modulation / demodulation / error correction unit 5
6 for connecting an external computer 61 to an external computer 61. For audio, for example, an audio input / output unit 63 for inputting / outputting an audio signal and an output signal of a signal modulation / demodulation / error correction unit 56 are further provided. It is converted from digital to analog (hereinafter referred to as D / A) and sent to the audio input / output unit 63, and the audio signal input at the audio input / output unit 63 is converted from analog to digital (hereinafter referred to as A / D). And a D / A / A / D conversion section 64 for sending to the signal modulation / demodulation / error correction section 56.

Next, the operation of the optical disk device 50 will be described. The spindle motor 51 is controlled by a system controller 58 and a servo control circuit 53, and rotates at a predetermined rotation speed.

At the time of recording, the optical pickup 30 irradiates the signal recording surface of the magneto-optical disk 40 with a high-power laser beam for recording. At the time of recording, a signal input from the outside via the interface 62 and the audio input / output unit 63 is modulated for recording on the magneto-optical disk 40 by the signal modulation unit of the signal modulation / demodulation / error correction unit 56, and further error-free. An error correction code is added by the correction unit. The head drive circuit 55 is driven based on this signal, and the magneto-optical disk 40 is driven by a magnetic field modulation method.
The information is recorded on the signal recording surface.

On the other hand, at the time of reproduction, a low-output laser beam for reproduction is applied to the magneto-optical disk 4 by the optical pickup 30.
The information is reproduced by irradiating the signal recording surface of No. 0 and detecting the return light. The magneto-optical reproduction signal output from the optical pickup 30 is subjected to error correction processing by an error correction unit of a signal modulation / demodulation / error correction unit 56, and
The signal is demodulated by the signal demodulation unit and sent to the external computer 61 via the interface 62, or D / A / A /
It is D / A converted by the D conversion unit 64 and output from the audio input / output unit 63.

As described above, the beam splitter 3 as the astigmatism generating optical element according to the present embodiment
3. According to the optical pickup 30 and the optical disk device 50, as in the first embodiment, the magneto-optical disk 40
And the like can be corrected, the signal reading performance and the servo performance in the optical disc device 50 can be improved to improve reliability, and the optical element for generating astigmatism can be used. The accurate positioning of the beam splitter 33 can be easily performed.

Further, according to the present embodiment, by arbitrarily selecting the refractive indices of the optical members 41 and 43 and the optical member 42 of the beam splitter 33, the shape and arrangement of the beam splitter 33 can be changed. It is possible to arbitrarily set the direction and magnitude of the generated astigmatism (astigmatic difference).

Further, according to the present embodiment, since the beam splitter 33 has both the original function of the beam splitter and the function of generating astigmatism, the beam splitter and the optical element for generating astigmatism are separately provided. Compared with the case where the components are provided, it is possible to prevent an increase in the number of components and the number of component mounting steps, and it is possible to reduce costs.

In the present embodiment, the optical member 4
Instead of 2, a transmission type hologram having a pattern for generating a predetermined astigmatism may be provided, and the same effect can be obtained in this case.

FIG. 13 is an explanatory view showing the structure of an optical pickup including an optical element for generating astigmatism according to a fourth embodiment of the present invention. This optical pickup 70 includes an integrated element 71. This integrated element 71 is formed integrally with a semiconductor laser, a photodetector, and an optical system that forms a light beam for detecting a reproduction signal, a focus error signal, and a tracking error signal. The integrated element 71 emits light from the semiconductor laser downward in the figure. The optical pickup 70 further reflects the light emitted from the integrated element 71 in the right direction in the figure, and generates a predetermined astigmatism with respect to the light. A mirror 73 for reflecting light reflected by the optical element 72 for generating astigmatism upward in the figure, and condensing the light reflected by the mirror 73 to form an optical disk 75
And an objective lens 74 for irradiating the light.

The astigmatism generating optical element 72 is a triangular prism-shaped transparent optical member 76, a trapezoidal quadrangular prism-shaped transparent optical member 78, and is sandwiched between these optical members 76, 78. And a transparent plate-shaped optical member 77 provided. Each of the optical members 76 to 78 is formed of, for example, glass.

The optical member 76 includes, as three surfaces forming the side surfaces of the triangular prism, a plane 76 a disposed perpendicular to the optical axis in the optical system from the astigmatism generating optical element 72 to the mirror 73. It has a flat surface 76b arranged parallel to the optical axis and a slope 76c inclined at 45 ° to the optical axis. The optical member 78 includes, as four surfaces forming side surfaces of the quadrangular prism, a plane 78a arranged perpendicular to the optical axis, two planes 78b and 78c arranged parallel to the optical axis, It has a slope 78d inclined at 45 ° to the axis and arranged so as to face the slope 76c of the optical member 76. Optical member 77
Are the slope 76c of the optical member 76 and the slope 7 of the optical member 78.
8d, each surface of which is provided with an optical member 76, 78.
Are joined to the inclined surfaces 76c and 78d. As a result, the entire astigmatism generating optical element 72 has a rectangular parallelepiped shape.

In the astigmatism generating optical element 72, the refractive indexes of the optical members 76 and 78 are equal, and the refractive index of the optical member 77 is different from the refractive indexes of the optical members 76 and 78. In the present embodiment, in particular, the polarization direction of the emitted light of the semiconductor laser in the integrated device 71 is in the direction perpendicular to the plane of FIG. 13, and the astigmatism including the astigmatism generated by this semiconductor laser is included. The refractive index of the optical member 77 is such that the astigmatism that cancels the astigmatism generated in the optical pickup 70 and the optical disk 75 except for the optical element 72 for generating astigmatism is generated in the optical element 72 for generating astigmatism. Is set to be larger than the refractive indexes of the optical members 76 and 78.

In the optical pickup according to the present embodiment,
Light emitted from the semiconductor laser in the integrated element 71 is transmitted from the plane 78 b of the optical member 78 to the astigmatism generating optical element 7.
2, passes through the optical member 78, and further passes through the optical member 77.
Passes through the optical member 77, is reflected by the surface of the optical member 77 on the optical member 76 side, the optical path is bent by 90 °, passes through the optical member 77 again, further passes through the optical member 78, and astigmatism from the plane 78a. The light is emitted outside the generating optical element 72. A predetermined astigmatism (astigmatic difference) is generated by the astigmatism generating optical element 72 in the light passing through the astigmatism generating optical element 72. The light emitted from the astigmatism generating optical element 72 is reflected by the mirror 73, condensed by the objective lens 74, and irradiated on the optical disc 75. The return light from the optical disc 75 is condensed by the objective lens 74, reflected by the mirror 73, further reflected by the astigmatism generating optical element 72, and incident on the integrated element 71, where the photodetector in the integrated element 71 Is detected by

The optical information recording / reproducing apparatus using the optical pickup according to the present embodiment can be configured, for example, in the same manner as in FIG.

In this embodiment, as shown in FIG. 14, the optical element 76 in the astigmatism generating optical element 72 is replaced by the optical element 76 in place of the astigmatism generating optical element 72 shown in FIG. The astigmatism generating optical element 72A formed in this way may be used. In the present embodiment,
Instead of the optical member 77, a reflection hologram having a pattern for generating a predetermined astigmatism may be provided. In these cases, the same effects as in the above embodiment can be obtained. Other functions and effects of the present embodiment are the same as those of the first or third embodiment.

FIG. 15 is an explanatory view showing the structure of an optical pickup integrated device according to the fifth embodiment of the present invention. The optical pickup integrated element 80 includes a semiconductor substrate 81, a semiconductor laser substrate 82 fixed on the semiconductor substrate 81, a semiconductor laser 83 provided on the semiconductor laser substrate 82, and a semiconductor laser substrate. And a composite prism 84 fixed on the semiconductor substrate 81 on the side of 82. Photodetectors 88 and 89 are formed on the semiconductor substrate 81 below the composite prism 84.

The semiconductor laser 83 emits light in the horizontal direction toward the composite prism 84. The compound prism 84 is a transparent optical member 85 having a triangular prism shape.
And a transparent optical member 87 having a trapezoidal quadrangular prism shape in cross section,
A transparent plate-shaped optical member 86 is provided so as to be sandwiched between these optical members 85 and 87. Each of the optical members 85 to 87 is formed of, for example, glass.

The optical member 85 is arranged as three surfaces forming the side surfaces of the triangular prism, and a plane 85a arranged perpendicular to the optical axis of the light emitted from the semiconductor laser 83 and a plane 85a arranged parallel to the optical axis. It has a flat surface 85b and an inclined surface 85c that is arranged to be inclined at a predetermined angle with respect to the optical axis. The optical member 87 includes, as four surfaces forming side surfaces of the quadrangular prism, a flat surface 87a arranged perpendicular to the optical axis,
Two planes 87b, 87 arranged parallel to the optical axis
c, and a slope 8 inclined at a predetermined angle with respect to the optical axis and arranged so as to face the slope 85 c of the optical member 85.
7d. The optical member 86 is arranged between the inclined surface 85a of the optical member 85 and the inclined surface 87d of the optical member 87, and the respective surfaces are inclined surfaces 85c, 87 of the optical members 85, 87.
d. As a result, the entire composite prism 84 has a rectangular parallelepiped shape.

In the composite prism 84, the optical member 8
The refractive indexes of the optical members 86 are equal to each other.
The refractive index of the optical members 85 and 87 is different. In the present embodiment, in particular, the polarization direction of the light emitted from the semiconductor laser 83 is a direction perpendicular to the plane of FIG.
Including the astigmatism generated by the semiconductor laser 83, the astigmatism that cancels the astigmatism generated in the optical pickup and the optical disk except for the compound prism 84 is generated in the compound prism 84,
The refractive index of the optical member 86 is set to be larger than the refractive indexes of the optical members 85 and 87.

Next, the operation of the optical pickup integrated device 80 according to the present embodiment will be described. The light emitted from the semiconductor laser 83 enters the composite prism 84 from the plane 85a of the optical member 85, passes through the optical member 85,
Part of the light amount passes through the optical members 86 and 87 in order, and is emitted out of the composite prism 84 from the plane 87a of the optical member 87. A predetermined astigmatism (astigmatic difference) is generated by the compound prism 84 in the light that has passed through the compound prism 84. The light emitted from the compound prism 84 passes through an optical system including an objective lens and the like (not shown), and is applied to an optical disk (not shown).

The return light from the optical disk passes through an optical system including an objective lens and the like (not shown), and while converging, enters the composite prism 84 from the flat surface 87b of the optical member 87, passes through the optical member 87, and receives one light amount. The parts are optical members 86 and 87
Is reflected at the boundary surface of. This light is partially reflected by the plane 87c of the optical member 87, and the reflected light is
Further, the light is reflected by the plane 87b and enters the plane 87c.
At the time of focusing on the optical disk, the light passing through the optical member 87 converges so as to have the smallest diameter on the plane 87b, and the two light beams incident on the plane 87c of the optical member 87 have the same diameter. ing. Semiconductor substrate 81
The upper photodetectors 88 and 89 are provided on the plane 87c of the optical member 87.
Is disposed at a position for receiving two light beams incident on the. Each of the photodetectors 88 and 89 has a plurality of light receiving units for detecting the diameter of the incident light beam. Then, a reproduction signal, a focus error signal and a tracking error signal are detected based on the output signals of the respective light receiving sections of the photodetectors 88 and 89.

The integrated device for optical pickup according to the present embodiment is applied to, for example, an optical pickup and an optical disk apparatus using a read-only optical disk.
Further, in the present embodiment, instead of the optical member 86, a transmission type hologram having a pattern for generating a predetermined astigmatism may be provided. In this case, the same effect can be obtained. Other functions and effects of the present embodiment are the same as those of the second embodiment.

FIG. 16 is an explanatory view showing the structure of an integrated device for an optical pickup according to a sixth embodiment of the present invention. The optical pickup integrated device 100 is applied to an optical pickup for a magneto-optical disk and an optical disk device. The integrated device 100 for optical pickup includes a composite prism 101 having a rectangular parallelepiped shape, a semiconductor substrate 102 bonded to the bottom of the composite prism 101, and a composite prism 1.
01 bonded to one side of the semiconductor laser substrate 103
And a semiconductor laser 104 provided on the upper surface of the semiconductor laser substrate 103. Semiconductor laser 10
Numeral 4 emits light in the horizontal direction toward the composite prism 101 side.

The composite prism 101 has six substrates 111
To 116. The substrates 111 to 116 have a shape obtained by dividing a rectangular parallelepiped by five planes parallel to each other that are inclined at a predetermined angle, for example, 45 ° with respect to the optical axis of the light emitted from the semiconductor laser 104. 16
Are arranged in the order of the substrates 111 to 116 from the upper right to the lower left. The substrate 111 and the substrate 116 are formed in a triangular prism shape, and the other substrates 112 to 115 are formed in a plate shape.

The substrate 111 has, as three side surfaces of the triangular prism, a plane 111a arranged perpendicular to the optical axis of the light emitted from the semiconductor laser 104, a plane 111b arranged parallel to the optical axis, and A predetermined angle to the axis,
For example, it has a slope 111c that is arranged to be inclined at 45 °.

The substrate 116 has, as three side surfaces of a triangular prism, a plane 116a arranged perpendicular to the optical axis of the light emitted from the semiconductor laser 104, a plane 116b arranged parallel to the optical axis, A predetermined angle to the axis,
For example, it has a slope 116c which is arranged to be inclined at 45 °.

The substrates 112 to 115 are respectively
11 and two slopes parallel to the slope 116c of the substrate 116.

A transparent plate-shaped optical member 120 is provided between the inclined surface 111c of the substrate 111 and the substrate 112 opposed thereto.
Is provided. The six substrates 111 to 116 and the optical member 120 are integrated by joining surfaces facing each other.

The refractive index of the optical member 120 is different from the refractive index of the substrate 112. In the present embodiment, in particular, the polarization direction of the light emitted from the semiconductor laser 104 is perpendicular to the plane of FIG.
In addition to the astigmatism generated by the substrate 112 and the optical member 120, the astigmatism that cancels out the astigmatism generated in the optical pickup and the optical disk, excluding the astigmatism generated by the substrate 112 and the optical member 120, including the astigmatism generated by the optical member 120 as generated by the optical member 1
The refractive index of 20 is set to be larger than the refractive index of the substrate 112.

On the inclined surface 111c of the substrate 111, a three-beam diffraction grating 122 for generating three beams for tracking error signal detection is formed. Substrate 1 of substrate 112
An NA conversion hologram 121 for converting NA (numerical aperture) and a first beam splitter film 123 are formed on the surface on the 13th side. On the surface of the substrate 113 on the substrate 112 side, an astigmatism hologram 131 for generating astigmatism for detecting a focus error signal is formed. A half mirror 124 and a second beam splitter film 127 are formed on the surface of the substrate 113 on the substrate 114 side. A reflection film 125 is formed on the upper surface of the substrate 113 in FIG.

The substrate 115 is a polarization separation substrate that separates incident light into a P-polarized component and an S-polarized component. The substrate 115 has, for example, a slanted film surface at an angle of 45 ° between the incident polarization plane and the incident plane, transmits a P-polarized component, and reflects an S-polarized component, It has a reflection film that reflects the S-polarized component reflected by the polarization separation film downward in FIG.

On the semiconductor substrate 102, a monitoring photodetector 126, a P-polarized component detecting photodetector 128, an S-polarized component detecting photodetector 129, and the servo photodetector 13 are provided.
2 are formed.

Next, the operation of the optical pickup integrated device 100 according to the present embodiment will be described. The light emitted from the semiconductor laser 104 enters the substrate 112 from the side surface of the substrate 112, is converted by the NA conversion hologram 121 so as to reduce the NA, is reflected, and enters the optical member 120. This light passes through the optical member 120, enters the three-beam diffraction grating 122, is split into three beams and is reflected, passes through the optical member 120 again, further passes through the substrate 112, and passes through the first beam splitter film. 123
Then, a part of the light amount is reflected and emitted from the upper surface of the substrate 112 to the outside of the composite prism 101. Light that has passed through the substrate 112 and the optical member 120 is subjected to predetermined astigmatism by the substrate 112 and the optical member 120. The light emitted from the composite prism 101 passes through the cover glass 106, is condensed by an objective lens (not shown), and is applied to a signal recording surface of a magneto-optical disk (not shown).

A part of the light amount of the light incident on the first beam splitter film 123 is reduced by the first beam splitter film 12.
3, the light passes through the substrate 113, and passes through the half mirror 12
At 4, a part of the light amount is reflected, and further reflected at the reflection film 125. This light enters the half mirror 124 again,
A part of the light amount is transmitted, sequentially transmitted through the substrates 114, 115, and 116 and received by the monitoring photodetector 126, whereby the output of the semiconductor laser 104 is monitored.

The return light from the magneto-optical disk is
2 enters the substrate 112 from the upper surface, and a part of the light amount
The light passes through the beam splitter film 123, enters the substrate 113, enters the second beam splitter film 127, and a part of the light amount is transmitted and a part is reflected. The light transmitted through the second beam splitter film 127 passes through the substrate 114, enters the substrate 115, and is separated into a P-polarized component and an S-polarized component. The P-polarized component passes through the substrate 116 and is received by the P-polarized component detecting photodetector 128, and the S-polarized component passes through the substrate 116 and is received by the S-polarized component detecting photodetector 129. . Then, a reproduced signal is detected based on the output signals of the photodetectors 128 and 129.

The light reflected by the second beam splitter film 127 passes through the substrate 113 and passes through the astigmatism hologram 13
At this point, astigmatism for detecting a focus error signal is given and reflected, passes through the substrates 113 and 114 in order, and is received by the servo photodetector 132. The servo photodetector 132 has a plurality of light receiving units,
Based on the output signals of these light receiving sections, a focus error signal is obtained by the astigmatism method, and a tracking error signal is obtained by the three-beam method.

As described above, according to the integrated device 100 for an optical pickup according to the present embodiment, the optical member 120 is provided in the composite prism 101 having various functions to generate a predetermined astigmatism. Therefore, as compared with the case where an optical element for generating astigmatism is provided separately from the compound prism 101, the number of parts and the number of parts mounting steps can be prevented from increasing, and the cost and reliability can be reduced. It becomes possible to plan. In particular, in the present embodiment, the optical member 120 is arranged in parallel with the slope that performs other functions besides generation of astigmatism in the compound prism 101.
Is provided, the fabrication of the composite prism 101 is facilitated. In the present embodiment, the substrate 1 of the optical member 120 is used.
The surface on the 11th side has a function other than the generation of astigmatism 3
Since it is integrated with the surface of the beam diffraction grating, it is possible to prevent an increase in the number of components and the number of component mounting steps as compared with the case where an optical element for generating astigmatism is provided separately from the three-beam diffraction grating. Thus, it is possible to reduce cost and improve reliability.

The optical information recording / reproducing apparatus using the optical pickup integrated device 100 according to the present embodiment can be configured, for example, in the same manner as in FIG.

In this embodiment, the optical member 1
Without providing 20, instead of the three-beam diffraction grating 122,
A reflection hologram having a function of generating three beams and a function of generating predetermined astigmatism may be formed.
Further, a transparent plate-shaped optical member having a different refractive index from the substrate 112 may be provided on the front surface of the NA conversion hologram 121 without providing the optical member 120, and instead of the NA conversion hologram 121, an NA conversion hologram 121 may be provided. A reflection type hologram having a function and a function of generating a predetermined astigmatism may be formed. In these cases, effects similar to those of the above embodiment can be obtained. Other functions and effects of the present embodiment are the same as those of the first or third embodiment.

The present invention is not limited to the above embodiments. For example, the astigmatism generating optical element according to the present invention is not limited to the position shown in each embodiment, but may be configured as an optical pickup. Can be arranged at an appropriate position according to the conditions.

[0114]

As described above, the optical element for generating astigmatism according to any one of claims 1 to 6, and claim 10.
According to the integrated device for optical pickup described in the above, the optical pickup according to the twelfth aspect or the optical information recording / reproducing apparatus according to the fourteenth aspect, the optical element for astigmatism generation is tilted with respect to the optical axis of the optical system in which it is used. A transparent first optical member having an inclined surface disposed and arranged; and a transparent plate-shaped second optical member joined to the inclined surface of the first optical member and having a different refractive index from the first optical member. And a first optical member and a second optical member.
Since a predetermined astigmatism is generated for the light passing through the optical member, it is possible to correct the astigmatism generated in the optical information recording medium and the like,
Since the optical member can be used for positioning the astigmatism generating optical element, there is an effect that accurate positioning of the astigmatism generating optical element can be easily performed.

Further, according to the optical element for generating astigmatism according to the fifth aspect, one surface of the second optical member is integrated with a surface that performs a function other than the generation of astigmatism. ,
Furthermore, as compared with the case where an optical element for generating astigmatism is provided separately from a member that performs other functions other than the generation of astigmatism, the number of parts and the number of parts mounting steps can be prevented from increasing, and the cost can be reduced. This leads to an effect of reducing the number and improving the reliability.

Further, according to the optical element for generating astigmatism according to the sixth aspect, the inclined surface which is integrated with the first optical member and the second optical member and has a function other than the generation of astigmatism. Since the inclined surface of the first optical member and the second optical member are arranged in parallel to the inclined surface of the prism, an optical element for generating astigmatism is provided separately from the prism. As compared with the case where the optical element is provided, it is possible to prevent an increase in the number of components and the number of component mounting steps, and to easily manufacture an optical element for generating astigmatism including a prism, thereby reducing costs and improving reliability. This has the effect that it becomes possible.

An optical element for generating astigmatism according to claim 7,
An integrated device for an optical pickup according to claim 11, wherein
According to the optical pickup according to the third aspect or the optical information recording / reproducing apparatus according to the fifteenth aspect, a transparent optical member on which light is incident, and a predetermined astigmatism with respect to the incident light, which are joined to one surface of the optical member. A hologram for generating aberration is provided, and a predetermined astigmatism is generated for the incident light. Therefore, it is possible to correct astigmatism generated in an optical information recording medium and the like, and Since the member can be used for positioning the astigmatism generating optical element, there is an effect that accurate positioning of the astigmatism generating optical element can be easily performed.

According to the optical element for generating astigmatism according to the eighth aspect, the optical member has a function other than the generation of astigmatism, and the optical element for generating astigmatism is used. Since the hologram has a slope that is arranged to be inclined with respect to the optical axis of the optical system, and the hologram is joined to the slope of the optical member, the hologram further has a function that performs other functions than astigmatism. Separately, compared to the case where an optical element for astigmatism generation is provided,
It is possible to prevent an increase in the number of parts and the number of parts mounting steps, thereby achieving an effect of reducing costs and improving reliability.

Further, according to the optical element for generating astigmatism according to the ninth aspect, there is provided a prism having a slope integrated with the optical member and performing a function other than the generation of astigmatism,
The optical member has a slope arranged parallel to the slope of the prism, and the hologram is joined to the slope of the optical member. Therefore, separately from the prism, an optical element for generating astigmatism is provided. As compared with the case where the optical element is provided, it is possible to prevent an increase in the number of components and the number of component mounting steps, and to easily manufacture an optical element for generating astigmatism including a prism, thereby reducing costs and improving reliability. The effect that it becomes possible is produced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a main part of an example of an optical pickup including a reflection-type astigmatism generating optical element according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a modification of the astigmatism generating optical element according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing another modification of the astigmatism generating optical element according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a main part of an example of an optical pickup including a transmission type astigmatism generating optical element according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a modification of the astigmatism generating optical element according to the second embodiment of the present invention.

FIG. 6 is an explanatory view showing another modification of the astigmatism generation optical element according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a simplified optical system of an optical pickup when a polarization direction of light applied to an optical disk is defined.

8 is an explanatory diagram showing a simplified optical system of an optical pickup when an astigmatism generating optical element as shown in FIG. 4 is provided instead of the parallel flat plate in FIG. 7;

FIG. 9 is an explanatory diagram showing the reading performance of the optical pickup in the cases of FIGS. 7 and 8;

FIG. 10 is an explanatory diagram showing a configuration of a magneto-optical type optical pickup including an optical element for generating astigmatism according to a third embodiment of the present invention.

11 is an explanatory diagram showing an arrangement of a light receiving section of the photodetector in FIG.

FIG. 12 is a block diagram showing a configuration of an optical disk device having the optical pickup shown in FIG.

FIG. 13 is an explanatory diagram showing a configuration of an optical pickup including an astigmatism generating optical element according to a fourth embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a modification of the astigmatism generation optical element in FIG. 13;

FIG. 15 is an explanatory diagram showing a configuration of an optical pickup integrated device according to a fifth embodiment of the present invention.

FIG. 16 is an explanatory diagram showing a configuration of an optical pickup integrated device according to a sixth embodiment of the present invention.

FIG. 17 is an explanatory view conceptually showing a configuration of an example of an optical pickup provided with a means for correcting astigmatism.

[Explanation of symbols]

10 optical elements for generating astigmatism, 11 to 13 optical members, 16 objective lenses.

Claims (15)

[Claims] 1. An astigmatism generating optical element for generating predetermined astigmatism with respect to light passing therethrough, wherein the optical element is inclined with respect to the optical axis of an optical system in which the astigmatism generating optical element is used. A transparent first optical member having an inclined surface disposed and arranged; and a transparent plate-shaped second member joined to the inclined surface of the first optical member and having a different refractive index from the first optical member. An optical element for generating astigmatism, comprising: an optical member. 2. The optical system according to claim 1, wherein the first optical member has a plane arranged perpendicular to the optical axis and a plane arranged parallel to the optical axis. Optical element for generating astigmatism. 3. A transparent plate having a plane arranged perpendicular to the optical axis, a plane arranged parallel to the optical axis, and a slope arranged parallel to a slope of the first optical member. A third optical member, wherein the second optical member is arranged and joined between a slope of the first optical member and a slope of the third optical member which are arranged to face each other. The optical element for generating astigmatism according to claim 1, wherein: 4. The optical element for generating astigmatism according to claim 1, wherein a refractive index of said second optical member is smaller than a refractive index of said first optical member. 5. The astigmatism generating optical system according to claim 1, wherein one surface of the second optical member is integrated with a surface that performs a function other than generation of astigmatism. element. 6. A prism having a slope integrated with the first optical member and the second optical member and performing a function other than the generation of astigmatism, the slope of the first optical member. 2. The optical element for astigmatism generation according to claim 1, wherein the second optical member is disposed in parallel with a slope of the prism. 3. 7. An astigmatism generating optical element for generating a predetermined astigmatism with respect to light passing therethrough, comprising: a transparent optical member on which light is incident; A hologram that generates a predetermined astigmatism with respect to the incident light. 8. The optical member fulfills a function other than the generation of astigmatism, and includes a slanted surface arranged at an angle to the optical axis of an optical system in which the astigmatism generating optical element is used. The optical element for generating astigmatism according to claim 7, wherein the hologram is joined to the slope of the optical member. 9. A prism having a slope integrated with the optical member and performing a function other than generation of astigmatism, wherein the optical member is arranged in parallel with the slope of the prism. The optical element for generating astigmatism according to claim 7, wherein the hologram is joined to the inclined surface of the optical member. 10. An optical pickup for irradiating an optical information recording medium with light for recording or reproduction and detecting return light from the optical information recording medium, and irradiating the optical information recording medium. A light detector for detecting return light from the optical information recording medium, and a transparent first optical member having an inclined surface arranged to be inclined with respect to the optical axis of the optical system of the optical pickup. And a second optical member which is bonded to the inclined surface of the first optical member and has a refractive index different from that of the first optical member and has a predetermined astigmatism with respect to light passing therethrough. An optical element for generating astigmatism that generates aberration, and the light source,
An integrated device for an optical pickup, wherein the photodetector and the astigmatism generating optical element are integrated. 11. An optical pickup for irradiating an optical information recording medium with light for recording or reproduction and detecting return light from the optical information recording medium, and irradiating the optical information recording medium. A light detector for detecting return light from the optical information recording medium; a transparent optical member to which light passing through the optical system of the optical pickup is incident; and a surface joined to one surface of the optical member. An optical element for generating astigmatism including a hologram that generates a predetermined astigmatism with respect to incident light, and the light source, the photodetector, and the optical element for astigmatism generation are integrated. An integrated device for an optical pickup, comprising: 12. An optical pickup for irradiating an optical information recording medium with recording or reproduction light and detecting return light from the optical information recording medium, wherein the light irradiating the optical information recording medium is provided. A light detector that detects return light from the optical information recording medium; and a light that emits light emitted from the light source to the optical information recording medium and returns light from the optical information recording medium. To the photodetector, a transparent first optical member having a slope arranged to be inclined with respect to the optical axis of the optical system, and joined to the slope of the first optical member. An optical element for generating astigmatism that includes a transparent plate-shaped second optical member having a different refractive index from the first optical member, and that generates predetermined astigmatism with respect to light passing therethrough. An optical pickup characterized in that: 13. An optical pickup for irradiating recording or reproduction light to an optical information recording medium and detecting return light from the optical information recording medium, wherein the light irradiating the optical information recording medium is provided. A light detector that detects return light from the optical information recording medium; and a light that emits light emitted from the light source to the optical information recording medium and returns light from the optical information recording medium. An optical system that guides the light to the photodetector; a transparent optical member that receives light passing through the optical system;
And an optical element for astigmatism generation including a hologram that is bonded to one surface of the optical member and generates predetermined astigmatism with respect to incident light. 14. An optical pickup for irradiating an optical information recording medium with light for recording or reproduction and detecting return light from the optical information recording medium, controlling the optical pickup, and An optical information recording / reproducing apparatus for optically recording and / or reproducing information using an information recording medium, wherein the optical pickup comprises: a light source for emitting light for irradiating the optical information recording medium; A photodetector for detecting return light from the information recording medium; and an optical element for irradiating the light emitted from the light source to the optical information recording medium and guiding the return light from the optical information recording medium to the photodetector. A transparent first optical member having a slope disposed to be inclined with respect to the optical axis of the optical system; and a first optical member joined to the slope of the first optical member. Is the refractive index It includes different transparent plate of the second optical member, the optical information recording and reproducing apparatus characterized by having a astigmatism generating optical element for generating a predetermined astigmatism to light that passes through. 15. An optical pickup for irradiating an optical information recording medium with light for recording or reproduction and detecting return light from the optical information recording medium, controlling the optical pickup, and An optical information recording / reproducing apparatus for optically recording and / or reproducing information using an information recording medium, wherein the optical pickup comprises: a light source for emitting light for irradiating the optical information recording medium; A photodetector for detecting return light from the information recording medium; and an optical element for irradiating the light emitted from the light source to the optical information recording medium and guiding the return light from the optical information recording medium to the photodetector. A transparent optical member to which light passing through the optical system is incident;
And an optical element for generating astigmatism including a hologram that is bonded to one surface of the optical member and generates predetermined astigmatism with respect to incident light.