JPH05234122A - Optical head device - Google Patents

Abstract

PURPOSE:To obtain a smaller converged spot without utilizing efficiency by providing an optical element changing the phase distribution in space of the phase of a parallel laser beam and forming the small converging spot on a convergence optical system. CONSTITUTION:The convergence optical system 9 is formed by the optical components of an objective lens 4, a collimate lens 2, a half mirror 6 and a mirror 3, etc. An integrated optical element 11 is formed with the phase filter 10 of the optical element by the lens 2 of these optical components and the phase distribution in space of the phase of the parallel laser beam is changed by the phase filter 10 and the small converged spot is formed and the smaller converged spot is obtained without the lowering of the utilizing effeiciency of the beam. Further, a similar result is obtained even though other optical element of the convergence optical system is integrated similarly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device for recording and reproducing information on the surface of a recording medium by using light.

[0002]

2. Description of the Related Art In an apparatus for recording and reproducing information on the surface of a recording medium using light, in order to increase the recording density,
It is necessary to make the recording pits smaller and more dense and to have the function of detecting the recording pits. To realize this function, it is necessary to make the focused spot formed on the surface of the recording medium small. There is.

As a method for reducing the focused spot, there is a method using a super-resolution phenomenon in which a light intensity distribution of a laser beam is changed by using a light-shielding band (for example, Hirose, Yamanaka,
Others, "High-density recording of optical disc (I)" by super-resolution 1
1988 (Showa 63) Autumn Proceedings of 49th Annual Meeting of Japan Society of Applied Physics, 4a-ZD-6). When the optical head device using this method is used, the focused spot can be made smaller than that of a normal optical head device, and it becomes possible to perform recording and reproduction with higher density.

FIG. 4 shows an example of the configuration of a conventional optical head device. In the figure, 1 is a laser light source, 2 is a laser light source 1
Collimator lens for converting the light emitted from the laser beam into a parallel laser beam, 3 a reflection mirror for changing the optical path of the laser beam, 4 an objective lens for condensing the laser beam in a spot shape, 5 a recording medium, 6 a reflection mirror 3 and a collimator A half mirror, which is interposed between the lenses 2 and divides the reflected light of the laser beam reflected on the surface of the recording medium 5, and 7 receives the above-mentioned reflected light that has passed through the half mirror 6 and detects its focus state. The focus detection optical system 7 includes, for example, a condenser lens 7 a and a wave plate (polarizing plate) 7.
b and a light receiving element (photoelectric conversion element) 7c such as a CCD. Reference numeral 8 is an optical element having a light-shielding band that changes the spatial distribution of the light intensity of the laser beam made parallel by the collimator lens 2. FIG. 5 is a plan view of the optical element 8 having this light-shielding band, 8a is a light-shielding band, and 9 is a focusing optical system.

FIG. 6 is an explanatory view showing the spatial distribution of the light intensity of the parallel laser beam before and after passing through the optical element 8, and FIG. 6 (a) before entering the optical element 8 and FIG. (B) shows the spatial distribution of the light intensity of the parallel laser beam after passing through the optical element 8. The horizontal axis shows the distance from the center of the parallel laser beam, and the vertical axis shows the light intensity. .. As can be seen from FIG. 6, the spatial distribution of the light intensity is a continuous distribution before passing through the optical element 8, but the laser beam incident on the portion of the light shielding band 8a is blocked, so that FIG. After passing through the optical element 8 as shown in (b), the spatial distribution of the light intensity changes.

In the conventional optical head device having such a structure, the optical element 8 having the light-shielding band distributes the spatial distribution of the light intensity of the laser beam emitted from the laser light source 1 and collimated by the collimator lens 2. The light is changed, transmitted through the half mirror 6, and then reflected by the reflection mirror 3 to form a spot at the focus point of the objective lens 4.

[0007]

The light-shielding band 8a described above
In the optical head device utilizing the super-resolution phenomenon in which the spatial distribution of the light intensity of the laser beam is changed by using the optical element 8 having the There is a problem that the efficiency is lowered and a light source having a higher output than the conventional one is required in order to obtain the light intensity required for recording and reproduction.

Further, there has been a problem that the number of parts is increased and the cost is increased from the conventional case.

An object of the present invention is to provide an optical head device that solves these problems.

[0010]

An optical head device according to the present invention includes a second optical element for changing a spatial distribution of phases without blocking an incident parallel laser beam to reduce a focused spot. It is characterized in that it is provided in the focusing optical system.

Further, the present invention is characterized in that any one of the first optical element and the second optical element constituting the focusing optical system is integrally formed.

[0012]

The second optical element allows the laser beam to pass therethrough without blocking, and changes the spatial distribution of the phase so that the light spot becomes small when condensed.
A small focused spot can be obtained without lowering the light utilization efficiency as in the conventional optical head device.

Also, any one of the first optical element and the second optical element
Since it is integrated with the optical element of, the increase in the number of parts can be prevented.

[0014]

【Example】

Example 1. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, and 1, 2, 7 and 9 are exactly the same as the conventional device of FIG. Reference numeral 10 denotes a second optical element that changes the spatial spatial distribution of the phase of the parallel laser beam that is collimated by the collimator lens 2. For example, (Kinugawa, Sakamoto, Ototake, Nai, Uchiyama, Tanaka, "Phase or amplitude" Mastering with filters ”Autumn 1991 (No. 52)
Proceedings of the 12th JSAP Academic Lecture Meeting, 11a-SZP
-12) is a phase filter in which a strip-shaped phase shift portion is formed. The phase filter 10 is integrated with the collimator lens 2 to form an integrated optical element 11. FIG. 2 is a plan view of the integrated optical element 11.
The phase filter 10 is the other area 2a of the collimator lens 2.
The phase of the light is delayed from the light transmitted through.

According to the first embodiment, the laser beam emitted from the laser light source 1 is changed by the integrated optical element 11 into a parallel laser beam having a changed spatial phase distribution, passes through the half mirror 6, and is reflected. After being reflected by the mirror 3, a spot is formed at the focal point of the objective lens 4.

In this embodiment, the integrated optical element 1
Since the light is not blocked at 1, the light intensity of the laser beam before and after passing through the integrated optical element 11 is the same. As a result, it is possible to reduce the laser focused spot diameter when the laser beam is focused on the surface of the recording medium 5, and it is possible to use the optical output of the laser light source with high efficiency to increase the recording density. ..

Embodiment 2. FIG. 3 is a schematic diagram showing the configuration of a second embodiment of the present invention, in which 1 to 4 and 9, 10 are the same as those of the conventional apparatus of FIG. The integrated optical element 12 integrally formed with the element 10 is provided, and the structure of the integrated optical element 12 is the same as the integrated optical element 11 of the first embodiment.

According to the second embodiment, the laser beam emitted from the laser light source 1 becomes parallel by the collimator lens 2, passes through the half mirror 6, is reflected by the reflection mirror 3, and then is integrated by the integrated optical element 12. , A spot is formed at the focal point.

Also in this embodiment, the integrated optical element 12 is used.
Since the light is not blocked by, the light intensity of the laser beam before and after passing through the optical element 12 is the same. As a result, it is possible to reduce the laser focused spot diameter when the laser beam is focused on the surface of the recording medium 5, and it is possible to increase the recording density by using the laser beam with high efficiency.

By the way, in the above-mentioned Examples 1 and 2, the optical head device having the integrated optical elements 11 and 12 in which the collimator lens 2 or the objective lens 4 and the second optical element 10 are integrated is described. It goes without saying that the same effect can be obtained even with an integrated optical element integrated with any one of the first optical elements constituting the focusing optical system 9, such as a half mirror, a reflection mirror, or a beam shaping prism.

[0021]

As described above, according to the present invention, the focusing optical system is provided with the second optical element for changing the spatial phase distribution of the phases of the parallel laser beams to form a small focused spot. Therefore, when the laser beam is focused, it is possible to obtain a smaller focused spot without lowering the light utilization efficiency as compared with a normal optical head device.

Further, since any one of the first optical element and the second optical element forming the focusing optical system is integrally formed, it is possible to prevent an increase in the number of parts and suppress an increase in cost. There is.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an optical head device according to a first embodiment.

FIG. 2 is a schematic plan view of an integrated optical element 11 used in the optical head device of Example 1.

FIG. 3 is a schematic diagram showing a configuration of an optical head device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing an example of a configuration of a conventional optical head device.

FIG. 5 is a plan view of an optical element 8 having a light-shielding band used in a conventional optical head device.

FIG. 6 is a spatial distribution diagram of light intensity before and after transmission through an optical element 8.

[Explanation of symbols]

 1 Laser Light Source 2 Collimator Lens 3 Reflection Mirror 4 Objective Lens 5 Recording Medium 6 Half Mirror 7 Focus Detection Optical System 9 Focusing Optical System 10 Second Optical Element (Phase Filter) 11 Integrated Optical Element 12 Integrated Optical Element

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[Procedure amendment]

[Submission date] July 30, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

As a method for reducing the focused spot, there is a method using a super-resolution phenomenon in which a light intensity distribution of a laser beam is changed by using a light-shielding band (for example, Hirose, Yamanaka,
Other, "high density recording of optical disks that by the super-resolution (I)" 1
1988 (Showa 63) Autumn Proceedings of 49th Annual Meeting of Japan Society of Applied Physics, 4a-ZD-6). When the optical head device using this method is used, the focused spot can be made smaller than that of a normal optical head device, and it becomes possible to perform recording and reproduction with higher density.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

FIG. 4 shows an example of the configuration of a conventional optical head device. In the figure, 1 is a laser light source, 2 is a laser light source 1
A collimator lens for collimating the laser beam light emitted from the three reflection-mirror changing an optical path of the laser beam, an objective lens for converging the laser beam in a spot shape is 4, 5 recording medium, 6 reflected Mirror 3 and interposed between the collimator lens 2, the half mirror over which divides the reflected light of the laser beam reflected on the surface of the recording medium 5, 7 its focus by receiving the reflected light of the above that through the half mirror -6 This is a focus detection optical system for detecting the state. The focus detection optical system 7 includes, for example, a condenser lens 7a, a wave plate (polarizing plate) 7b, and a light receiving element (photoelectric conversion element) such as a CCD.
7c and. Reference numeral 8 is an optical element having a light-shielding band that changes the spatial distribution of the light intensity of the laser beam made parallel by the collimator lens 2. FIG. 5 is a plan view of the optical element 8 having this light-shielding band, 8a is a light-shielding band, and 9 is a focusing optical system.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

In the conventional optical head device having such a structure, the optical element 8 having the light-shielding band distributes the spatial distribution of the light intensity of the laser beam emitted from the laser light source 1 and collimated by the collimator lens 2. varied, is reflected by the reflecting-mirror 3 after passing through the half <br/> mirror 6,
A spot is formed at the focal point of the objective lens 4.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

EXAMPLES Example 1. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, and 1 to 7 and 9 are exactly the same as the conventional device of FIG. Reference numeral 10 denotes a second optical element that changes the spatial spatial distribution of the phase of the parallel laser beam that is collimated by the collimator lens 2. For example, (Kinugawa, Sakamoto, Ototake, Nai, Uchiyama, Tanaka, "Phase or amplitude" Mastering using filters "Proceedings of the 52nd Annual Meeting of the Japan Society of Applied Physics, 1991 (1991), 11a-SZP-1
Position phase shift unit that is shown in 2) is a phase filter formed with. This phase filter 10 includes a collimator lens 2
And the integrated optical element 11 are integrated. FIG. 2 is a plan view of the integrated optical element 11, in which the phase filter 10 delays the phase of the light transmitted through the other region 2a of the collimator lens 2.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

According to this first embodiment, the laser beam emitted from the laser light source 1 is transmitted through the half mirror -6 changed into a parallel laser beam changes in the spatial distribution of the phase by integrating the optical element 11, to form a spot in the focal point of the objective lens 4 after being reflected by the reflecting-mirror 3.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Embodiment 2. FIG. 3 is a schematic diagram showing the configuration of a second embodiment of the present invention. 1 to 7 and 9 are the same as those of the conventional apparatus of FIG. 4, and in this embodiment, the objective lens 4 and second optical element 10 are used. And the integrated optical element 12 integrally formed with each other.
This is the same as the integrated optical element 11 of.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

According to this second embodiment, the laser beam emitted by the laser light source 1 is converted into a parallel by the collimator lens 2, passes through the half mirror -6, integrated optical element after being reflected by the reflecting-mirror 3 12, a spot is formed at the converging point.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

By the way, in the above-mentioned Examples 1 and 2, the optical head device having the integrated optical elements 11 and 12 in which the collimator lens 2 or the objective lens 4 and the second optical element 10 are integrated is described. half mirror over,
It can be obtained similar effects in integrated optics integrated with either of the first optical element constituting the converging optical system 9, such as the reflection-mirror or beam shaping prism course.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Reference Numerals] 1 laser light source 2 a collimator lens 3 reflected Mirror 4 objective lens 5 recording medium 6 half mirror -7 focus detecting optical system 9 focusing optics 10 and the second optical element (phase filter) 11 integrated optics element 12 integral Optical element

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (2)

[Claims] 1. An optical head device for condensing a laser beam to record / reproduce information on the surface of a recording medium, the first optical element constituting an optical system for converging the laser beam into a light spot. 2. An optical head device comprising a second optical element which is formed integrally with any one of the above to change the spatial distribution of the phase of the laser beam to form a small light spot. 2. The optical head device according to claim 1, wherein the optical head device is a phase filter that shifts the phase of a parallel laser beam transmitted by the second optical element.