JP2002208164A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the thickness and the number of parts of a condensing system. SOLUTION: The optical pickup is equipped with a condensing element 4 having an objective lens 6 and an immersion lens 7, a hologram 3 for bisecting a reflecting optical flux, a plurality of light receiving elements 9, 10 which are arranged on both sides of an incident optical path 8 and receive two reflecting optical fluxes bisected by the hologram 3 and deflected by a deflecting element 2, while each light-receiving position is made different before and after the convergence. The optical pickup outputs detection signals for focusing and tracking by the output of the light receiving elements 9, 10. In this case, the incident beam and the reflecting optical flux from a medium 1 are deflected nearly at right angles through the deflecting element 2, thereby reducing an optical path length in the direction orthogonal to the medium 1 for reducing the thickness, and also reducing the number of parts and the assembly man-hour of the condensing system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for reading optical information recorded on a medium.

[0002]

2. Description of the Related Art Generally, a compact disk (CD) is used.
An optical pickup system for reading signal information recorded on a medium such as a digital camera includes a servo mechanism for focusing and tracking. This is to make the optical pickup accurately follow mechanical fluctuations such as surface deflection and eccentricity due to rotation of the medium. By the way, in order to improve the followability of the optical pickup and increase the reliability, it is necessary to reduce the size and weight of the optical pickup, and as one of the measures, there is a strong demand for a thinner optical pickup. In addition, there is a demand for an optical pickup to reduce the spot diameter of light applied to a medium.

Therefore, as described in JP-A-11-45455, an objective lens for condensing light emitted from a light source and a solid immersion lens having a high refractive index are provided on one substrate. Optical pickups have been proposed.

[0004]

The above publication discloses a prism provided with a dielectric multilayer film as a means for switching an optical path and a polarizing means provided between the prism and an objective lens to change a polarization state. It is described that the optical component is integrally formed to reduce the size and weight. However, a light source is arranged above a prism provided with a dielectric multilayer film, and an objective is arranged below the prism. In the configuration in which the lens is disposed, the optical path length in the vertical direction from the light source toward the medium becomes long, so that the thickness increases.

[0005] Also, in the above publication, light radiated in a horizontal direction from a light source is deflected in a vertical direction by a prism to irradiate the medium, and a light beam reflected in a vertical direction from the medium is horizontally diverted by the prism. There is also described a configuration in which light is deflected to enter a light receiving element, and a detection signal is obtained from an output of the light receiving element. According to this configuration, the thickness reduction is considered to be superior to the former configuration. However, since the number of prisms for switching the optical path is large, there is a restriction even if the size is reduced, and the cost of parts and assembly adjustment is high. Become.

Further, since it is necessary to provide a detection mechanism for detecting a focus error and a track error in the optical pickup, it is more difficult to reduce the size and thickness of the optical pickup.

An object of the present invention is to provide a small, lightweight and thin optical pickup.

An object of the present invention is to provide an inexpensive optical pickup which can reduce the number of parts and the number of assembly steps.

[0009]

According to the first aspect of the present invention,
A condensing element having an objective lens and an immersion lens arranged on the same optical axis and condensing a beam emitted from a light source on a medium; and a medium arranged near the light source side of the objective lens. A hologram that divides a reflected light beam reflected from the light source into two, and deflects a beam emitted from the light source in a direction substantially perpendicular to the medium, and converts a reflected light beam divided by the hologram into two light beams on an incident optical path from the light source. A deflecting element that deflects toward both sides, and a light receiving position before and after convergence of two reflected light beams that are disposed on both sides of the incident light path and are divided by the hologram and deflected by the deflecting element. And a plurality of light receiving elements that receive light differently.

Therefore, the beam emitted from the light source passes through the incident optical path, is deflected at a substantially right angle by the deflecting element, is condensed by the condensing element and is irradiated on the medium, and the reflected light beam from the medium is divided into two by the hologram. A focus error and a track error can be detected from the output of the light receiving element that has received the reflected light beam before convergence and the output of the light receiving element that has received the reflected light beam after convergence. In this case, the beam from the light source is deflected at a substantially right angle toward the medium, and the reflected light beam from the medium is reflected toward the light receiving elements disposed on both sides of the incident optical path, so that the beam is perpendicular to the plane of the medium. It is possible to shorten the optical path length in the direction and reduce the thickness, and to reduce the number of components and the number of assembling steps of the light collecting system.

Here, it is desirable that the condensing element is a monolithic lens in which an objective lens and an immersion lens are disposed on both sides of the same substrate.

According to a second aspect of the present invention, in the first aspect, the light source, a collimating element for collimating a light beam of a beam emitted from the light source, the deflecting element,
The light collecting element, the hologram, and the light receiving element are hermetically supported by a housing.

Therefore, since all the optical system components are sealed in the housing, it is possible to protect them from the environment or mechanical external force. Further, since all the optical components are maintained in a constant positional relationship by the housing, the accuracy of focusing and tracking performed by moving the housing can be improved.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the plurality of light receiving elements are disposed in parallel with the surface of the medium, are divided into two by the hologram, and are deflected by the deflecting element. A pair of left and right second deflecting elements for deflecting the reflected light beam substantially at right angles toward the light receiving element are provided on both sides of the incident light path.

Therefore, when a plurality of light receiving elements disposed on both sides of the optical path from the light source to the deflection element are supported by one supporting member, it is possible to prevent the beam in the incident optical path from being interrupted by the supporting member. Thus, the degree of freedom in the shape and arrangement of the support member can be increased.

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in any one of the above, the light receiving element and the light source are supported by the same member.

Accordingly, it is possible to reduce the number of parts and the number of assembling steps of the supporting member for supporting the plurality of light receiving elements and the light sources.

The invention described in claim 5 provides the invention according to claims 1 to 4
In the invention according to any one of the above, the deflection element is a prism.

Therefore, the flat surface of the hologram can be accurately and easily fixed to the flat surface of the prism in a contact or adhesive state. Further, it becomes easy to totally reflect the light on the deflecting surface of the prism, so that the use efficiency of the light can be easily increased at lower cost and easily than when a mirror is used, and stable signal detection can be performed.

According to a sixth aspect of the present invention, in the third or fourth aspect, the deflecting element and the second deflecting element are formed by one prism.

Therefore, it is possible to reduce the number of parts and the number of assembling steps for deflecting light. further,
It becomes easy to totally reflect the light on the deflecting surface of the prism, and it is possible to increase the light use efficiency at lower cost and more easily than when a mirror is used, and to perform stable signal detection.

[0022] The invention according to claim 7 is the invention according to claims 3 to 6.
In the invention described in the above, the light source and the light receiving element that receives the reflected light flux deflected by the second deflection element are provided on a support surface on a side of the housing that supports them in a sealed state and that is away from the medium. It is supported by.

Therefore, the heat radiating area of the supporting surface of the housing close to the medium is reduced by at least the amount corresponding to the support of the light-collecting element. However, the light source is supported on the supporting surface having a large heat radiating area away from the medium. The heat of the light source can be efficiently dissipated. In this case, since the light source and the light receiving element are supported by the support surface on the same side of the housing, it is possible to enhance the heat radiation effect of the light source while satisfying the condition for maintaining the mutual positional relationship accurately. .

[0024] The invention described in claim 8 is the invention according to claims 1 to 7.
In the invention according to any one of the above, the light receiving element is divided into a light receiving portion so as to receive light in at least four divided regions in the tangential direction and the radial direction of the medium in the spot of the reflected light flux. ing.

Therefore, as a method of extracting the track error signal from the output of the light receiving unit divided into four or more, a phase difference detection method having high detection accuracy other than the push-pull method can be adopted.

According to the ninth aspect of the present invention, there are provided the first to eighth aspects.
In the invention according to any one of the above, a polarization hologram is used as the hologram, and a quarter-wave plate is provided between the polarization hologram and the light-collecting element.

Therefore, the use of the deflection hologram and the quarter-wave plate makes it possible to prevent the generation of stray light when the beam is incident on the medium.

[0028]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. 1 is a side view showing an internal structure of an optical pickup, FIG. 2 is a plan view thereof, FIG. 3 is a front view showing an arrangement state of light receiving elements, and FIG. 4 shows a relationship between the light receiving element and a spot of a reflected light beam incident thereon. Illustrated diagram, FIG.
FIG. 4 is an explanatory diagram showing one mode of processing the output of the light receiving element.

First, the configuration of the optical pickup will be described with reference to FIGS. Reference numeral 1 denotes a disk-shaped medium such as a CD. The medium 1 is supported by a turntable (not shown), and is rotationally driven together with the turntable. Above the medium 1, a light source (not shown)
A mirror 2, which is a deflecting element for deflecting a beam emitted in the horizontal direction at a substantially right angle toward a medium 1 below, a flat hologram 3, and a monolithic lens 4 as a condensing element are sequentially directed downward. Are arranged.

The monolithic lens 4 has an objective lens 6 integrally on the upper surface of the same substrate 5 and an immersion lens 7 on the lower surface of the substrate 5 and is manufactured by a semiconductor manufacturing process or the like. The lens 6 and the immersion lens 7 are arranged on the same optical axis. The surface of the monolithic lens 4 on the side of the objective lens 6 is a flat surface, and since the hologram 3 can be fixed to the flat surface in a contact or adhesive state, the assembling work of the monolithic lens 4 and the hologram 3 and the adjustment thereof are performed. The work is easy.

As is apparent from FIG.
Light receiving elements 9 and 10 are provided on both sides of the optical path 8 of the beam incident on the right and left sides. These light receiving elements 9,
Although the semiconductor substrate 11 supporting 10 is orthogonal to the incident optical path 8, an opening 12 is formed so as to pass a beam. The hologram 3 reflects the reflected light flux 2
The reflected luminous flux split by the hologram 3 is deflected by the mirror 2 and enters the light receiving elements 9 and 10.

Here, FIG. 1 and FIG.
The light beam incident on the hologram 3 is indicated by a solid line, the reflected light beam directed to one of the light receiving elements 9 is indicated by a dotted line, and the reflected light beam directed to the other light receiving element 10 is indicated by a dashed line. In the present embodiment, the hologram 3 is designed so as to divide the reflected light beam from the medium 1 into two and focus on the light receiving elements 9 and 10 at different distances. That is, as is apparent from the reflected light beams classified by line type, the light receiving element 9 is configured to receive the reflected light beam before convergence, and the light receiving element 10 is configured to receive the reflected light beam after convergence. In this case, preferably, the left and right light receiving elements 9 and 10 are arranged in the same vertical plane orthogonal to the incident optical path 8 so that the spot diameters of the reflected light beams incident on the left and right light receiving elements 9 and 10 are equal (see FIG. 3). (See Figure 2)
It can be supported by the common semiconductor substrate 11, thereby reducing the number of parts and the number of assembly steps. Of course, the spot diameters of the reflected light beams incident on the left and right light receiving elements 9 and 10 are different, but the left and right light receiving elements 9 and 10 may be arranged on different vertical planes so that the distance to the hologram 3 changes. Absent.

The light receiving elements 9 and 10 are divided into light receiving portions so as to receive light in each of four areas of the medium 1 where the spot S of the reflected light beam is divided in the tangential direction. In FIGS. 4 and 5, a1, b1, c1, and d1 are divided light receiving portions of the light receiving element 9, and a2, b2, c2, and d2 are divided light receiving portions of the light receiving element 10. Note that the tangential direction is a longitudinal direction of a groove formed in the medium 1, in other words, a tangential direction on the circumference of the medium 1.

In such a configuration, the beam emitted from the light source is collimated by a collimator lens (not shown), travels toward the mirror 2, is deflected downward by the mirror 2, passes through the hologram 3, and then passes through the monolithic lens 4. And is radiated to the medium 1. The light beam reflected from the medium 1 passes through the monolithic lens 4 and is split into two by the hologram 3, reflected by the mirror 2 and received by the light receiving elements 9 and 10.

In this case, when the medium 1 is at the in-focus position with respect to the monolithic lens 4, the diameters of the spots S incident on the light receiving elements 9 and 10 are equal as shown in FIG. When the medium 1 moves away from the monolithic lens 4, as shown in FIG.
The diameter of the spot S incident on the lens becomes smaller than that at the time of focusing,
The diameter of the spot S incident on the light receiving element 10 after the convergence becomes larger than that at the time of focusing. When the medium 1 approaches the monolithic lens 4, as shown in FIG. 4C, the diameter of the spot S incident on the light receiving element 9 before convergence becomes larger than that at the time of focusing, and the light receiving element 10 after convergence. Is smaller than that at the time of focusing.

Therefore, referring to FIG.
The output of each light receiving section of the light receiving elements 9 and 10 is calculated as (a1 + d1 + b2 + c2)-
By performing calculation based on the calculation formula (b1 + c1 + a2 + d2), a focus error signal can be obtained.

The output of the light receiving element 9 is calculated as (a1 + b1)-(c1 + d
A track error signal can be obtained by calculating based on the calculation formula 1) or calculating the output of the light receiving element 10 based on the calculation formula (a2 + b2)-(c2 + d2).
This method of calculating the track error signal is a method called a push-pull method.

As described above, the beam from the light source is
And the reflected light flux from the medium 1 is reflected toward the light receiving elements 9 and 10 disposed on both sides of the incident light path 8, so that the light path in the vertical direction orthogonal to the plane of the medium 1 The length can be shortened and the thickness can be reduced. Further, since the beam is focused on the medium 1 by the monolithic lens 4 in which the objective lens 6 and the immersion lens 7 are integrally formed via the substrate 5, the number of components and the number of assembling steps of the focusing system can be reduced. .

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment and other embodiments that follow it, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted. 6 is a vertical sectional side view showing the optical pickup, and FIG. 7 is a horizontal sectional view taken along the line AA in FIG.

In the present embodiment, a semiconductor laser 13 as a light source, a collimating lens 14 as a collimating element for collimating a light beam of a beam emitted from the semiconductor laser 13, a mirror 2 as a deflecting element, a hologram 3, Monolithic lens 4 as light collecting element, light receiving elements 9 and 10
Is supported by the housing 15 in a sealed state. A part 15a of the housing 15 functions as a semiconductor substrate for mechanically supporting the semiconductor laser 13 and connecting to an external circuit.

In such a configuration, the semiconductor laser 1
The beam emitted from 3 is collimated by a collimator lens 14 and travels toward a mirror 2, is deflected downward by the mirror 2, passes through a hologram 3, is condensed by a monolithic lens 4, and irradiates the medium 1. The light beam reflected from the medium 1 passes through the monolithic lens 4 and is split into two by the hologram 3, reflected by the mirror 2 and received by the light receiving elements 9 and 10.

In this embodiment, all the optical components such as the semiconductor laser 13, the collimating lens 14, the mirror 2, the hologram 3, the monolithic lens 4, and the light receiving elements 9, 10 are hermetically sealed in the housing 15. It is possible to protect from environmental or mechanical external forces. Also,
These optical components have a mutual positional relationship with the housing 15.
, The accuracy of focusing and tracking performed by moving the housing 15 can be improved.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a side view showing the internal structure of the optical pickup, and FIG. 9 is a plan view thereof.

In the present embodiment, the light receiving elements 9 and 10 are disposed in parallel with the surface of the medium 1 and split the reflected light flux by the hologram 3 and deflected by the mirror 2 as a deflecting element. Second mirrors 16 and 17 as a pair of left and right second deflecting elements that deflect at a substantially right angle toward 10
Are disposed on both sides of the incident optical path 8.

In such a configuration, when the plurality of light receiving elements 9 and 10 arranged on both sides of the optical path 8 from the light source to the mirror 2 are supported by one semiconductor substrate (support member) 11, the semiconductor substrate 11 prevents the beam in the incident light path 8 from being interrupted. Thus, it is not necessary to form the opening 12 as shown in FIG. 2 in the semiconductor substrate 11, and the degree of freedom in the shape and arrangement of the semiconductor substrate 11 can be increased.

In this case, the second mirrors 16 and 17 are not limited to the example in which the reflected light beam is reflected downward, and is not limited to the example shown in FIG.
It is needless to say that the same effect as described above can be obtained even if provided in a direction reflecting upward as shown in FIG. In this case, the light receiving elements 9 and 10
Is disposed above the second mirrors 16 and 17.

FIG. 10 is a side view showing the internal structure of an optical pickup according to a modification of the present embodiment, and FIG. 11 is a plan view thereof.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
It will be described based on. FIG. 12 is a vertical sectional side view of the optical pickup.

Semiconductor laser 13, collimating lens 1
4, mirror 2, hologram 3, monolithic lens 4,
The light receiving elements 9 and 10 and the second mirrors 16 and 17 are hermetically supported by a housing 15.

Accordingly, the beam emitted from the semiconductor laser 13 is collimated by the collimating lens 14 and travels toward the mirror 2, is deflected downward by the mirror 2, is transmitted through the hologram 3, is condensed by the monolithic lens 4, 1 is irradiated. The light beam reflected from the medium 1 passes through the monolithic lens 4 and is then split into two by the hologram 3, deflected by the mirror 2 and the second mirrors 16 and 17, and received by the light receiving elements 9 and 10.

Here, in the present embodiment, the light receiving elements 9 and
The semiconductor laser 10 and the semiconductor laser 13 are supported by a housing 15 as the same member.

Therefore, it is possible to reduce the number of parts and the number of assembling steps of the supporting member for supporting the plurality of light receiving elements 9 and 10 and the semiconductor laser 13.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 13 is a side view showing the internal structure of the optical pickup, and FIG. 14 is a vertical sectional side view of the optical pickup.

This embodiment is an example in which a prism 18 is used as a deflection element instead of the mirror 2 described above. That is, a beam emitted from a light source such as the semiconductor laser 13 is deflected by the prism 18 toward the medium 1,
In this configuration, a light beam reflected from the medium 1 is deflected by the prism 18 toward the light receiving elements 9 and 10. The configuration of FIG. 13 causes the reflected light beam deflected by the prism 18 to directly enter the light receiving elements 9 and 10, and the structure of FIG. 14 further transmits the reflected light beam deflected by the prism 18 to the second mirrors 16 and 17.
This is an example in which the light is deflected by the light and made incident on the light receiving elements 9 and 10.

As described above, by using the prism 18 in place of the mirror 2, the flat surface of the hologram 3 can be easily and accurately fixed to the flat surface of the prism 18 in a contact or adhesive state. Further, it becomes easy to totally reflect the light on the deflecting surface 19 of the prism 18, so that the use efficiency of the light can be increased more easily and cheaply than when the mirror 2 is used, and stable signal detection can be performed.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
18 will be described with reference to FIG. 15 is a side view showing the internal structure of the optical pickup, FIG. 16 is a plan view thereof, FIG. 17 is a longitudinal sectional side view of the optical pickup, and FIG. 18 is a horizontal sectional view taken along line AA in FIG.

The present embodiment is characterized in that the mirror 2 serving as the deflecting element and the second mirrors 16 and 17 serving as the second deflecting element described above are formed by one prism 20. That is, this prism 20
A deflecting surface 21 that functions as a deflecting element that deflects a beam emitted from a light source such as a semiconductor laser 13 and collimated by a collimating lens 14 toward the medium 1 at a substantially right angle.
And the reflected light flux reflected from the medium 1 and divided by the hologram 3 and deflected by the deflecting surface 21 is received by the light receiving elements 9 and 1
Deflection surfaces 22 and 23 functioning as a second deflection element that deflects toward zero are integrally provided.

With this configuration, it is possible to reduce the number of components and the number of assembly steps for deflecting light. Further, similarly to the above-described embodiment, the flat surface of the hologram 3 can be easily and accurately fixed to the flat surface of the prism 20 in a contact or adhesive state. further,
It becomes easy to totally reflect the light on the deflection surfaces 21, 22, 23 of the prism 20, and the mirror 2 and the second mirror 1
The use efficiency of light can be easily increased at lower cost and more easily than in the case of using 6, 17, and stable signal detection can be performed.

Next, a seventh embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. In this embodiment, FIG.
This is an example in which a prism 24 having an additional function is used in place of the prism 20 used in the embodiment of FIGS.

That is, the prism 24 includes a collimating lens unit 25 for collimating a beam emitted from a light source such as the semiconductor laser 13 and the collimating lens unit 2.
A deflecting surface 21 for deflecting the beam collimated by 5 toward the medium 1 at a substantially right angle to the medium 1 and a reflected light flux reflected from the medium 1 and divided by the hologram 3 and deflected by the deflecting surface 21 to the light receiving elements 9 and 10. Deflecting surfaces 22, 2 deflecting toward
3 are integrally provided. In addition, the collimating lens unit 2
In step 5, an optimal shape for an optical pickup, such as a spherical lens, an aspherical lens, or a hologram lens, may be selected.

As described above, by providing the prism 24 with the function of the collimating lens unit 25, the number of parts and the number of assembling steps can be further reduced.

Next, an eighth embodiment of the present invention will be described with reference to FIG.
It will be described based on. FIG. 21 is a vertical sectional side view of the optical pickup.

The semiconductor laser 13,
Hologram 3, monolithic lens 4, light receiving elements 9, 1
0, the prism 27 is supported in a sealed state. In the present embodiment, the prism 27 has a collimating lens unit 25 for collimating a beam emitted from a light source such as the semiconductor laser 13, and the beam collimated by the collimating lens unit 25 is directed at a substantially right angle toward the medium 1. And a deflecting surface 22 and 23 for deflecting the reflected light flux reflected from the medium 1 by the hologram 3 and deflected by the deflecting surface 21 toward the light receiving elements 9 and 10. I have.

The monolithic lens 4 is supported on a support surface 28 on the side of the housing 26 near the medium 1, and the semiconductor laser 13 and the light receiving elements 9 and 10 are on the side of the housing 26 on the side away from the medium 1. Support surface 2
9 supported. For this purpose, the deflecting surfaces 22 and 23 formed as the second deflecting elements on the prism 27 transmit reflected light beams deflected by the deflecting surface 21 to the upper light receiving elements 9 and 9.
It is formed so as to deflect toward 10.

In such a configuration, the housing 26
The supporting surface 28 close to the medium 1 has a smaller heat radiation area by supporting the monolithic lens 4, but the upper supporting surface 29 which is separated from the medium 1 has a larger heat radiation area. Since the semiconductor laser 13 is supported on the support surface 29 having a large heat radiation area, the heat of the semiconductor laser 13 can be efficiently radiated.

In this case, since the semiconductor laser 13 and the light receiving elements 9 and 10 are supported by the support surface 29 on the same side of the housing 26, the semiconductor laser 13 and the light receiving elements 9 and 10 satisfy the condition for maintaining the mutual positional relationship accurately. The heat radiation effect of the laser 13 can be enhanced.

The present invention, when deflecting the reflected light beam to the light receiving elements 9 and 10 arranged on the side away from the medium 1 together with the semiconductor laser 13, provides the second mirrors 16 and 17 as shown in FIG. The present invention can also be applied to an optical pickup that is deflected by the optical pickup.

Next, a ninth embodiment of the present invention will be described with reference to FIG.
It will be described based on. FIG. 22 is a front view of the light receiving element 9. The light receiving element 9 is an area obtained by dividing the spot S of the reflected light beam into eight in the tangential direction and the radial direction of the medium 1.
The light receiving unit is divided so as to receive light for each of a1, b1, c1, d1, e1, f1, g1, and h1.

Here, the tangential direction refers to the tangential direction of the circumference of the disk-shaped medium 1, in other words, the longitudinal direction of the groove formed in the medium 1, and the radial direction refers to the radial direction of the medium 1. Point to. Referring to FIG. 22, a plurality of dividing lines 30 are divided in the tangential direction, dividing line 3
1 is a dividing line in the radial direction.

By dividing the light receiving portion of the light receiving element 9 as described above, it is possible to employ a phase difference detection method with high detection accuracy other than the push-pull method as a method of extracting a track error signal from the output of each area. . Since the phase difference detection method is well-known, the description is omitted. The other light receiving element 10 may be similarly divided and output a track error signal.

Next, a tenth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 23 is a side view showing an internal structure of the optical pickup, and FIG. 24 is a longitudinal side view of the optical pickup.

FIG. 23 shows a state in which a beam emitted from a light source is collimated by a collimator lens (not shown),
To deflect the light toward the medium 1 and deflect the light beam reflected from the medium 1 by the mirror 2 to enter the light receiving elements 9 and 10.

FIG. 24 shows that the beam emitted from the semiconductor laser 13 is collimated by the collimating lens unit 25 of the prism 24, and the collimated beam is deflected toward the medium 1 by the deflecting surface 21 of the prism 24. Of the light reflected from the prism 24 into the deflecting surfaces 21 and 22 and 23 of the prism 24.
And the light is incident on the light receiving elements 9 and 10.

Even if the hologram 3 described in the above embodiments is designed so that the reflected light beam is divided into two and condensed at an appropriate position, the hologram 3 may not pass when the incident light beam passes without considering ordinary polarized light. Unnecessary diffraction occurs and unintended stray light is generated. The stray light causes deterioration of the focus error signal and the track error signal.

Therefore, the present embodiment is different from FIGS.
As shown in FIG. 7, a polarization hologram 32 is used in place of the hologram 3 described so far, and a quarter-wave plate 33 is provided between the polarization hologram 32 and the monolithic lens 4.

In such a configuration, the configuration shown in FIG.
In the configuration of FIG. 24 as well, a beam from a light source such as the semiconductor laser 13 is incident on the polarization hologram 32 while being directly polarized into p-polarized light. The polarization hologram 32 transmits the beam as it is without having a diffraction effect for p-polarized light.
The transmitted beam enters the quarter-wave plate 33 and becomes circularly polarized light. The beam condensed by the monolithic lens 4 is reflected by the medium 1, and the reflected light flux becomes a substantially parallel reflected light flux when passing through the monolithic lens 4 again.
The light passes through the four-wavelength plate 33 and changes from circularly polarized light to s-polarized light. Since the polarization hologram 32 has a diffraction effect on the s-polarized light, the reflected light beam is diffracted, split into two as designed, and enters the light receiving elements 9 and 10 as desired converged light.

As described above, by providing the polarization hologram 32 and the quarter-wave plate 33 on the light source side of the monolithic lens 4, generation of stray light can be prevented.

[0078]

According to the first aspect of the present invention, a light-collecting element having an objective lens and an immersion lens disposed on the same optical axis, and a light-receiving element arranged near the light source side of the objective lens and reflected from a medium. A hologram that divides the reflected light beam into two, a deflection element that deflects the beam passing through the incident light path in a direction substantially perpendicular to the medium, and deflects the reflected light beam divided by the hologram into both sides of the incident light path, and an incident light path And a plurality of light-receiving elements that receive two reflected light beams that are divided by a hologram and deflected by a deflecting element at different light-receiving positions before and after convergence, respectively. The beam passing through the medium is irradiated on the medium, the reflected light beam from the medium is divided into two by the hologram, the output of the light receiving element receiving the reflected light beam before convergence and the light receiving light receiving the reflected light beam after convergence It is possible to detect a focus error and track error by the output of the child. In this case, the beam passing through the incident optical path is deflected at a substantially right angle toward the medium,
Since the reflected light flux from the medium is reflected toward the light receiving elements arranged on both sides of the incident optical path, the optical path length in the vertical direction perpendicular to the plane of the medium is shortened to reduce the thickness, and the light collecting system The number of parts and the number of assembly steps can be reduced.

According to a second aspect of the present invention, in the first aspect, a light source, a collimating element for collimating a light beam of a beam emitted from the light source, a deflecting element, the condensing element, Since the hologram and the light receiving element are hermetically supported by the housing, it is possible to protect all optical components from the environment or mechanical external force,
In addition, since all the optical components are maintained in a constant positional relationship by the housing, the accuracy of focusing and tracking performed by moving the housing can be improved.

According to a third aspect of the present invention, in the first or second aspect, the plurality of light receiving elements are arranged in parallel with the surface of the medium, and are reflected by the hologram and are deflected by the deflection element. A pair of left and right second deflecting elements for deflecting the light at substantially right angles toward the light receiving element are disposed on both sides of the incident light path, so that a plurality of light receiving elements disposed on both sides of the incident light path from the light source to the deflecting element are provided. When the element is supported by one supporting member such as a semiconductor substrate, it is possible to prevent the incident light beam in the incident optical path from being blocked by the supporting member, thereby increasing the degree of freedom in the shape and arrangement of the supporting member. .

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in any one of the above, since the light receiving element and the light source are supported by the same member, the number of components and the number of assembling steps of the supporting member for supporting the plurality of light receiving elements and the light source can be reduced.

The fifth aspect of the present invention provides the first to fourth aspects.
In the invention according to any one of the above, since the deflecting element is a prism, the flat surface of the hologram can be easily and accurately fixed to the flat surface of the prism in a contact or adhesive state, and further, the deflection surface of the prism Makes it easy to totally reflect the light, and it is possible to easily and inexpensively increase the light use efficiency and to perform stable signal detection at a lower cost than when a mirror is used.

According to a sixth aspect of the present invention, in the third or fourth aspect, since the deflecting element and the second deflecting element are formed by one prism, the number of components for deflecting light and the number of parts for deflecting light are reduced. The number of assembling steps can be reduced, and it is easy to totally reflect light on the deflecting surface of the prism. The efficiency of light utilization can be increased more easily and cheaply than when a mirror is used, and stable signal detection can be performed. .

The invention described in claim 7 is the invention according to claims 3 to 6
In the invention described, the light source and the light receiving element that receives the reflected light flux deflected by the second deflecting element are supported on a support surface of the housing that supports them in a sealed state on a side away from the medium. Since the supporting surface of the housing close to the medium has a smaller heat radiation area by at least as much as the light collecting element is supported, the light source is supported by the supporting surface having a large heat radiation area away from the medium. Heat can be efficiently dissipated. In this case, since the light source and the light receiving element are supported by the support surface on the same side of the housing, the heat radiation function of the light source can be enhanced while satisfying the condition for maintaining the mutual positional relationship accurately.

The invention described in claim 8 is the first invention to the seventh invention.
In the invention described in any one of the above, the light-receiving element is divided into a light-receiving portion such that the light-receiving portion receives the light in at least four divided regions in the tangential direction and the radial direction of the medium in the spot of the reflected light beam. Therefore, as a method of extracting the track error signal from the output of the light receiving unit divided into four or more, a phase difference detection method with high detection accuracy other than the push-pull method can be adopted.

According to the ninth aspect of the present invention, there are provided the first to eighth aspects.
In the invention according to any one of the above, a polarization hologram is used as the hologram, and a quarter-wave plate is provided between the polarization hologram and the condensing element. Accordingly, it is possible to prevent the generation of stray light when the beam is incident on the medium.

[Brief description of the drawings]

FIG. 1 is a side view showing an internal structure of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a front view showing an arrangement state of light receiving elements.

FIG. 4 is an explanatory diagram showing a relationship between a light receiving element and a spot of a reflected light beam incident thereon.

FIG. 5 is an explanatory diagram showing one mode of processing the output of the light receiving element.

FIG. 6 is a vertical sectional side view showing an optical pickup according to a second embodiment of the present invention.

FIG. 7 is a horizontal sectional view taken along the line AA in FIG. 6;

FIG. 8 is a side view showing an internal structure of an optical pickup according to a third embodiment of the present invention.

FIG. 9 is a plan view thereof.

FIG. 10 is a side view showing an internal structure of an optical pickup according to a modified example of the third embodiment.

FIG. 11 is a plan view thereof.

FIG. 12 is a vertical sectional side view of an optical pickup according to a fourth embodiment of the present invention.

FIG. 13 is a side view showing an internal structure of an optical pickup according to a fifth embodiment of the present invention.

FIG. 14 is a vertical sectional side view of the optical pickup.

FIG. 15 is a side view showing an internal structure of an optical pickup according to a sixth embodiment of the present invention.

FIG. 16 is a plan view thereof.

FIG. 17 is a vertical sectional side view of the optical pickup.

18 is a horizontal sectional view taken along line AA in FIG.

FIG. 19 is a vertical sectional side view of an optical pickup according to a seventh embodiment of the present invention.

FIG. 20 is a horizontal sectional view taken along the line AA in FIG. 19;

FIG. 21 is a vertical sectional side view of an optical pickup according to an eighth embodiment of the present invention.

FIG. 22 is a front view of a light receiving element according to a ninth embodiment of the present invention.

FIG. 23 is a side view showing the internal structure of the optical pickup according to the tenth embodiment of the present invention.

FIG. 24 is a vertical sectional side view of the optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Medium 2 Deflection element 3 Hologram 4 Condensing element 6 Objective lens 7 Immersion lens 8 Incident optical path 9, 10 Light receiving element 13 Light source, semiconductor laser 14 Parallelizing element 15 Housing 16, 17 Second deflection element 18 Deflection element, prism 20 Prism 21 Deflection element 22, 23 Second deflection element 26 Housing 29 Support surface 32 Polarization hologram 33 Quarter-wave plate

Claims (9)

[Claims] 1. A condensing element having an objective lens and an immersion lens disposed on the same optical axis and condensing a beam emitted from a light source on a medium, and a condensing element near the light source side of the objective lens. A hologram arranged to divide a reflected light beam reflected by the medium into two, a light beam emitted from the light source being deflected in a substantially right-angle direction toward the medium, and a reflected light beam divided by the hologram into two light sources; A deflecting element for deflecting the light toward both sides of the incident light path from the hologram;
An optical pickup comprising: a plurality of light receiving elements for receiving two reflected light beams which are divided and deflected by the deflecting element at different light receiving positions before and after convergence, respectively. 2. The light source, a collimating element for collimating a light beam of a beam emitted from the light source, the deflecting element, the condensing element, the hologram, and the light receiving element are hermetically sealed by a housing. The optical pickup according to claim 1, which is supported in a state. 3. A plurality of said light receiving elements are disposed in parallel with the surface of said medium, and deflect a reflected light beam, which is divided by said hologram into two and deflected by said deflecting element, at a substantially right angle toward said light receiving element. 3. The optical pickup according to claim 1, wherein a pair of left and right second deflection elements are disposed on both sides of the incident optical path. 4. The optical pickup according to claim 1, wherein the light receiving element and the light source are supported by the same member. 5. The method according to claim 1, wherein the deflecting element is a prism.
An optical pickup according to any one of claims 1 to 4. 6. The optical pickup according to claim 3, wherein said deflecting element and said second deflecting element are formed by one prism. 7. A supporting surface on a side of a housing for supporting the light beam deflected by the second deflecting element and receiving the reflected light beam deflected by the second deflecting element in a hermetically sealed state with respect to the medium. The optical pickup according to claim 3, wherein the optical pickup is supported by the optical pickup. 8. The light-receiving element has a light-receiving portion divided so as to receive light in each of at least four divided areas of the spot of the reflected light beam in the tangential direction and the radial direction of the medium. 8. The optical pickup according to any one of 1 to 7. 9. The light according to claim 1, wherein a polarization hologram is used as the hologram, and a quarter-wave plate is provided between the polarization hologram and the light-collecting element. pick up.