JP3477922B2 - Optical guide member and optical pickup - Google Patents

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 recording or reproducing information on a recording medium such as an optical disk.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for miniaturization of an optical disc device for recording and reproducing information on an optical recording medium such as an optical disc using a laser beam. Attempts have been made to realize reduction in weight and weight, facilitation of adjustment, and cost reduction.

As such an attempt, optical functional elements such as a beam splitter film having a polarization selectivity, a diffraction grating, and a reflection mirror are made into glass by making full use of semiconductor manufacturing technologies such as photolithography technology, film formation technology, and etching technology. An integrated pickup mounted on a member substrate has been proposed.

In this integrated optical pickup, the light beam is guided while being reflected and transmitted through the inside of each glass member on which the optical functional element is mounted, enters the recording surface of the optical disk, and the reflected light from the optical disk is emitted. The light is guided to the photodetector by the optical path opposite to the above.

Each optical functional element is mounted on a glass member substrate by making full use of semiconductor manufacturing techniques such as photolithography technique, film forming technique and etching technique. Further, it is possible to adopt a method of manufacturing a large number of identical optical pickups by finally cutting a substrate made of a plurality of glass members and formed with a large number of identical elements. This allows
It is possible to realize an optical pickup that has the same functions as conventional products, and can be made smaller and lighter, and it is possible to manufacture many same elements at the same time with a small number of manufacturing processes.
Further, since the number of adjusting units is small, the productivity can be improved and the cost can be reduced.

In order to read the information on the optical disk, the imaging spot of the light beam is tracking-controlled so as to move along the information track provided on the optical disk. As a tracking error detecting method for this tracking control, an imaging spot of a main beam (0th order diffracted light) formed by a diffraction grating is positioned so as to be symmetric with respect to a center line in a traveling direction of an information track. A so-called "three-beam method" is used in which two side beams (± first-order diffracted light) are imaged on both sides of the main beam in directions opposite to each other with respect to the information track with slight deviation.

The structure of a conventional integrated optical pickup will be described below. Conventional integrated optical pickup 40
0 indicates a substrate 401, a submount 402, a semiconductor laser 403, and a light guide member 405, as shown in FIG.
And a light detection element 409 and a light blocking plate 410.

The submount 402 is arranged on the substrate 401, and the semiconductor laser 403 is arranged on the substrate 401 via the submount 402. Also,
The light guide member 405 is formed by laminating transparent glass sheet thin materials, and has a plurality of parallel inclined surfaces 405a to 405c. Of these slopes, the slope 405a has
A beam splitter film 406 is formed.

With the above structure, the semiconductor laser 4 mounted on the substrate 401 via the submount 402.
The laser light horizontally emitted from 03 is shaped into a circular light beam by the light shielding plate 410, and enters the light guide member 405 through the surface 400a. The light beam incident on the light guide member 405 reaches the slope 405a inside the light guide member 405, then advances while reflecting inside the light guide member 405, and reaches the beam splitter film 406.

A part of the light incident on the beam splitter film 406 is reflected by the beam splitter film 406,
The reflected laser light passes through the surface 400b and passes through the objective lens 40.
7 and is imaged on the information recording surface S of the optical disc D by the condensing action of the objective lens 407.

The return light reflected by the information recording surface S of the optical disc D passes through the objective lens 407, the surface 400b of the optical pickup 400, and the optical guide member 40 again.
Beam splitter film 4 formed on slope 405a in
It is incident on 06.

The light transmitted through the beam splitter film 406 is received by the photodetector element 409, and the information recorded on the optical disk is converted into an electric signal. Further, similarly, a focus error signal for focus servo control can be obtained by another slope in the light guide member 405.

Therefore, as described above, an optical functional element such as a beam splitter film having a polarization selectivity, a diffraction grating and a reflection mirror is formed on a glass member substrate by making full use of photolithography technology, film formation technology and etching technology. By properly mounting, it is possible to mass-produce various integrated pickups used in a method such as magneto-optical recording or phase change recording.

In order to read the information recorded on the optical disk, the optical pickup uses a servo signal detection mechanism for making a spot of a light beam narrowed down to a micron order follow the recording surface, and records the information as a minute recording mark. -It is necessary to provide a mechanism for emitting and detecting the light beam for reproduction and erasing.

To narrow down the spot on the optical disk surface,
A light source having coherence (coherence) is required, and therefore, a semiconductor laser light source that is small and capable of direct modulation is used. A semiconductor laser utilizes light emission from an active layer formed on a joint surface portion where an n-type semiconductor clad layer and a p-type semiconductor clad layer are joined, and a light beam propagates through the active layer and is emitted from an end face. To be done. However, the emission pattern of the semiconductor laser is different in the vertical direction and the horizontal direction with respect to the junction surface of the semiconductor laser, and the emission beam is an elliptical shape with the ratio of the minor axis length to the major axis length of the ellipse being about 0.25 to 0.5. is there. As a beam shaping method for obtaining a circular light beam from such an elliptical emission light beam, a method of blocking the end portion of the light beam in the long axis direction, or shaping the beam shape by adding a prism or a cylindrical lens Methods etc. are known.

FIG. 5 shows the configuration of a conventional example of an optical pickup using the latter method. As shown in FIG. 5, the optical pickup 500 includes a semiconductor laser 501, a beam shaping prism 502, a condenser lens 503, a beam splitter 504, an objective lens 505, and a photodetector element 50.
It is configured with 7.

With the above structure, the semiconductor laser 5
The laser light emitted from 01 is reflected by the beam shaping prism 5
The light beam on the cross section perpendicular to the optical axis is shaped into a substantially circular shape. This method effectively utilizes the power of the light beam emitted from the semiconductor laser 501, which is a light source, in comparison with the method of cutting a part of the elliptical light beam into a circular light beam and effectively using the power of the light beam. Can be reached on S.

[0018]

However, when the method of circularly shaping the light beam emitted from the semiconductor laser without blocking the light beam as described above is used, the number of optical components and the adjustment process are To increase. Therefore, there is a problem that the advantages of downsizing, integration, and no adjustment in the integrated pickup or the like are lost.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical pickup which can be miniaturized, integrated, and unadjusted.

[0020]

In order to solve the above-mentioned problems, an optical pickup according to the first invention of the present invention is arranged such that a semiconductor laser and radiated light which is a light beam emitted from the semiconductor laser are incident on the semiconductor laser. An optical pickup comprising: a light guide member that internally reflects incident light that is an incident light beam and emits the light toward an optical recording medium side, the optical pickup being a surface of the light guide member on which the emitted light is incident. The normal of the first surface forms a first angle with respect to the second surface, which is a surface including the major axis of the elliptical light intensity distribution of the emitted light and the optical axis of the emitted light, and It is characterized in that the normal line of one surface is arranged so as to form a second angle with respect to the optical axis of the incident light.

An optical pickup according to a second aspect of the present invention is a semiconductor laser and radiated light, which is a light beam from the semiconductor laser, is made incident from a third surface, which is one of the surfaces, and the incident light is made incident. Is an optical pickup having an optical guide member that internally reflects light and emits the light toward the optical recording medium side. The optical pickup is provided on a fourth surface that is provided inside the optical guide member and that reflects or transmits the incident light. A hologram element for diffracting and reflecting or transmitting a light beam at a diffraction angle different from the incident angle of the incident light on the guide member is provided.

[0022]

According to the present invention having the above structure, the first surface or the third surface which is the incident surface of the optical pickup, or the fourth surface which is the reflective surface or the transmissive surface of the light guide member on which the hologram element is provided. The light beam shape in the cross section perpendicular to the optical axis can be shaped into a substantially circular shape without blocking the light beam emitted from the semiconductor laser.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an optical pickup which is a first embodiment of the present invention. As shown in the figure, the optical pickup 100 includes a substrate 101, a submount 102, a semiconductor laser 103, a light guide member 105, and a photodetector element 109.

The submount 102 is arranged on the substrate 101, and the semiconductor laser 103 is arranged on the substrate 101 via the submount 102. Also,
The light guide member 105 is formed by laminating transparent glass sheet thin materials and has a plurality of parallel inclined surfaces 105a to 105c. Of these slopes, the slope 105a has
The beam splitter film 106 is formed. The light guide member 105 has a surface 100a and a surface 100b, and the surface 100a corresponds to the first surface on which the laser light is incident, and the projection shape of the incident laser light beam on the surface 100a is the optical axis thereof. On the other hand, it is inclined at a predetermined angle so as to have a substantially circular shape.

Laser light horizontally emitted from the semiconductor laser 103 mounted on the substrate 101 via the submount 102 enters the light guide member 105 through the surface 100a. Here, regarding the emission angle of the laser light emitted from the semiconductor laser 103, the angle (θp) in the direction parallel to the joint surface (not shown) of the semiconductor laser 103 is 8 °. Bonding surface of 103 (not shown)
The angle (θs) in the direction perpendicular to the direction is 20 °, and the light intensity distribution of the cross section has a minor axis in the parallel direction (θp) to the bonding surface of the semiconductor laser 103 and a vertical direction (θs).
) Is the elliptical shape having the major axis (hereinafter, simply referred to as the “minor axis” and the “major axis”, respectively).

The angle θ between the surface 102a of the submount 102 on which the semiconductor laser 103 is mounted and the normal line of the incident surface 100a is set to 72 °, and the semiconductor laser 103 has the major axis direction of the laser light and the submount 102 of the semiconductor laser 103. The semiconductor laser chip mounting surface 102a is mounted in parallel.
The angle (φ) formed by the normal line of the light beam incident surface 100a of the light guide member 105 and the optical axis of the incident light after entering the light guide member 105 is formed to be inclined at 39 °.

The relationship between these is that the refractive index of the incident medium (such as air) through which light passes before entering the light guide member 105 is no (no = 1.0), and the glass material forming the light guide member 105. Since the refractive index of n is n (n = 1.52), the angles θ and φ are (θs / θp) = [1-{(no / n) sin θ} ² ] ^1/2
cos θ φ = sin ⁻¹ {(no / n) sin θ}

The light beam that has entered the light guide member 105 reaches the slope 105a inside the light guide member 105, travels while reflecting inside the light guide member 105, and reaches the beam splitter film 106. Beam splitter film 1
The light beam reflected by the beam splitter film 106 out of the light incident on 06 is transmitted through the surface 100b such that the optical axis of the light beam and the normal line of the surface 100b are parallel to each other, enters the objective lens 107, and An image is formed on the information recording surface S of the optical disc D which is an optical recording medium by the condensing action of the lens 107.

The light beam that has entered the light guide member 105 has a substantially circular shape on a cross section perpendicular to the optical axis, and the image formation spot on the information recording surface S of the optical disc D by the objective lens 107 is: The emission power of the semiconductor laser 103 is efficiently transmitted to the optical disc D by narrowing down to the diffraction limit to an ideal size, and information can be easily recorded or reproduced.

The return light reflected by the optical disk D passes through the surface 100b through the objective lens 107, and then enters the beam splitter film 106 formed on the inclined surface 105a of the light guide member 105 again. The light transmitted from the beam splitter film 106 is received by the photodetector element 109, and the information on the optical disc D is converted into an electric signal. Similarly, a focus error signal for focus servo control can be obtained by another slope of the light guide member 105. The light detection element 109 and the mechanism for obtaining the focus error signal constitute a light detection mechanism.

Next, a second embodiment of the present invention will be described. As shown in FIG. 2, this optical pickup 200 is
Substrate 201, submount 202, and semiconductor laser 2
03, a light guide member 205, and a light detection element 209 which is a light detection mechanism.

The submount 202 is arranged on the substrate 201, and the semiconductor laser 203 is arranged on the substrate 201 via the submount 202. Also,
The light guide member 205 described above has a surface 200a that is the third surface.
And has a surface 200b. In addition, the light guide member 20
5 is formed by laminating thin transparent glass plates and has a plurality of parallel inclined surfaces 205a to 205c. Of these slopes, the slope 205a corresponds to the fourth surface, and the slope 2
A beam splitter film 206 and a hologram element 210 are formed on 05a.

Laser light emitted from the semiconductor laser 203 mounted on the substrate 201 via the submount 202 enters the light guide member 205 from the surface 200a. Here, the emission angle of the incident light after entering the light guide member 205 is 5.3 ° at an angle (θp) in the direction parallel to the joint surface (not shown) of the semiconductor laser 203. The angle (θs) in the vertical direction with respect to the joint surface (not shown) of 203 is 13 °.

The incident angle θ _L at which the light beam incident on the light guide member 205 enters the hologram element 210 on the slope 205a inside the light guide member 205 is set to 73.2 °. Further, φ _L is set to 45 ° between the normal line of the inclined surface 205a and the optical axis of the light beam reflected and diffracted by the hologram element 210.

The light beam entering the light guide member 205 reaches the hologram element 210 on the slope 205a inside the light guide member 205 and is diffracted and reflected. Reach 206. Of the light that has entered the beam splitter film 206, the laser light that has been reflected by the beam splitter film 206 passes through the surface 200b, enters the objective lens 207, and is condensed by the objective lens 207 so that an optical disk that is an optical recording medium. An image is formed on the information recording surface S of D.

The light flux after entering the light guide member 205 has a substantially circular shape on the cross section perpendicular to the optical axis, and the image forming spot on the information recording surface S of the optical disc D by the objective lens 207 is The emission power of the semiconductor laser 203 is efficiently transmitted to the optical disc D by narrowing down to the diffraction limit to an ideal size, and information can be easily recorded or reproduced.

The return light reflected by the optical disk D passes through the surface 200b through the objective lens 207 and again enters the beam splitter film 206 formed on the inclined surface 205a of the light guide member 205. The light transmitted from the beam splitter film 206 is received by the photodetector 209, and the information on the optical disc D is converted into an electric signal. Similarly, the other slope of the light guide member 205 provides a focus error signal for focus servo control. The light detection element 209 and the mechanism for obtaining the focus error signal constitute a light detection mechanism.

FIG. 3 shows the optical pickup 200 shown in FIG.
The detailed shape of the hologram element 210 used in FIG. As shown in the figure, the surface of the hologram element 210 is provided with concentric concavities and convexities. This uneven pattern has an optical distance l1 to an arbitrary point on the pattern surface and a light source, and a distance l to a point on the pattern surface and a virtual wavefront (a spherical wavefront in this embodiment) set on the diffraction space.
The sum of the two, l1 + l2, is the wavelength of the light source λ (68
(0 mm), the contours are connected so that the remainders are equal. With this configuration,
The hologram element 210 diffracts a light beam incident on the internal slope 205a at an angle θL (73.2 °) into a diffraction angle φL (4
Diffract and reflect at 5 °. The light intensity distribution of the cross section perpendicular to the optical axis of the diffracted and reflected light beam has a substantially circular shape.

The hologram element 210 of the second embodiment has a diffraction reflection angle (for example, 45 °) when diffracting a light beam.
However, the light beam is diffracted so as to be smaller than the incident angle (for example, 73.2 °) of the light beam incident on the slope 205a of the light guide member 205. However, the light guide member 20
The surface (sixth surface) including the minor axis and the optical axis of the elliptical light intensity distribution of the light beam incident on the light beam 5 is at a predetermined angle (with respect to the normal to the incident surface (fourth surface) of the light guide member 205 ( If it is arranged to be inclined by a fifth angle), the hologram element 210
By providing the hologram element 210 that diffracts the light beam so that the diffraction angle thereof is larger than the incident angle of the light beam on the surface (fourth surface) of the light guide member 205, the optical axis of the diffracted light beam is The light intensity distribution in the vertical cross section can be shaped into a substantially circular shape.

The present invention is not limited to the above embodiment. The above-mentioned embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to the present invention. It is included in the technical scope of the invention.

The present invention can be changed according to the recording system of the optical disc. For example, in the case of a magneto-optical disk,
A light detection mechanism that detects the polarization state of the return light may be provided in the light guide member. Further, a light detection mechanism such as a focus error signal detection mechanism or a tracking error signal detection mechanism may be provided.

[0042]

According to the present invention having the above structure, the first surface or the third surface which is the incident surface of the optical pickup, or the fourth surface which is the reflecting surface of the light guide member provided with the hologram element, The light beam shape in a cross section perpendicular to the optical axis can be shaped into a substantially circular shape without blocking the light beam emitted from the semiconductor laser.

Further, the power of the semiconductor laser light source can be effectively used without complicating the adjustment process of the optical axis and the like and without adding an extra optical element, and the size of the optical disk device and the number of optical parts can be reduced. Easy adjustment by reducing
It is possible to improve productivity and reduce costs.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical pickup that is a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an optical pickup that is a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a hologram element in the optical pickup shown in FIG.

FIG. 4 is a diagram showing a configuration of a conventional optical pickup.

FIG. 5 is a diagram showing a configuration of a conventional optical pickup.

[Explanation of symbols]

100 optical pickup 100a, 100b side 101 substrate 102 submount 102a side 103 Semiconductor laser 105 Light guide member 105a slope 106 Beam splitter film 107 Objective lens 109 Photodetector 200 optical pickup 200a, 200b side 201 substrate 202 submount 202a Semiconductor laser mounting surface 203 Semiconductor laser 205 Light guide member 205a slope 206 Beam splitter film 207 Objective lens 209 Photodetector 210 hologram element 400 optical pickup 400a side 400b side 401 substrate 402 submount 402a Semiconductor laser chip mounting surface 403 Semiconductor laser 405 Light guide member 405a slope 406 Beam splitter film 407 Objective lens 409 Photodetector 410 light shield 500 optical pickup 501 semiconductor laser 502 beam shaping prism 503 condenser lens 504 beam splitter 505 Objective lens 507 Photodetector D optical disc S information recording surface

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 12-7/22

Claims (6)

(57) [Claims] 1. Optical recording of emitted light from a semiconductor laser
The light returned from the optical recording medium is guided to the medium.
It is guided to the detection element and is formed so as to be inclined with respect to the substrate.
Toward the first surface on which the incident light is incident and the optical recording medium
A plurality of slopes parallel to the inside of the second surface through which the emitted light passes
And a light guide member mounted on the substrate.
Te, wherein the first inclined surface of the plurality of inclined surfaces (105a) beam
A splitter film is formed so that the emitted light is directed to the first surface.
When incident at an angle to the line,
Converted to a radiant light flux having a circular shape,
The second slope (105b), the first slope, and the
To reflect the emitted light between the beam splitter film and
In the direction normal to the second surface toward the optical recording medium,
A light sensor characterized by being formed so as to transmit radiated light.
Id member. 2. Optical recording of emitted light from a semiconductor laser
The light returned from the optical recording medium is guided to the medium.
A first surface on which the emitted light is incident and which is guided to a detection element, and the light.
Second surface through which the radiant light is transmitted toward the biological recording medium,
It is a light guide member that has a plurality of slopes parallel to the inside.
Te, wherein the first inclined surface of the plurality of inclined surfaces (205a) beam
By forming a splitter film and a hologram element, the radiation
When light is incident at an angle with respect to the normal to the first surface
Converts to a radiant light flux having a substantially circular shape with respect to its optical axis
The converted radiant light flux to the hologram element
Therefore, it diffracts and reflects, and further,
Between the slope (205b) and the beam splitter film
It reflects the diffracted reflected light and travels toward the optical recording medium.
So that the diffracted and reflected light is transmitted in the direction normal to the second surface.
A light guide member characterized by being formed. 3. The diffraction reflection angle of the hologram element is the
Set at 45 ° to the normal of the first slope (205a)
The light guide member according to claim 2, wherein 4. A substrate and an optical beam tilted with respect to the substrate.
Through a submount on the substrate to radiate
And the semiconductor lasers placed on the substrate
Radiation of the semiconductor laser having a plurality of slopes parallel to the
The passed through the objective lens and guides the objective lens return light
And a light guide member that guides light to the photodetector , and formed on the substrate.
Light detecting element and the light emitted through the light guide member.
The objective lens for converging the emitted light on the optical recording medium,
An optical pickup having the light guide , wherein the emitted light is incident on the light guide member.
The first surface of the member is formed to be inclined with respect to the substrate.
And the emitted light is inclined with respect to the normal to the first surface.
The first slope of the plurality of slopes of the light guide member is arranged so as to be incident.
A beam splitter film is formed on the surface (105a), and the emitted light is directed to the optical axis when entering the first surface.
Is converted into a radiant light flux having a substantially circular shape,
Of the slopes of the first slope and the second slope (105b)
And between the beam splitter film and the
Toward the lens, the direction normal to the second surface of the light guide member
An optical pickup , wherein the radiated light is arranged to be transmitted through the optical pickup. 5. A substrate and an optical beam tilted with respect to the substrate.
Through a submount on the substrate to radiate
And the semiconductor lasers placed on the substrate
Radiation of the semiconductor laser having a plurality of slopes parallel to the
Light to the objective lens and return light passing through the objective lens
And a light guide member that guides light to the photodetector , and formed on the substrate.
Light detecting element and the light emitted through the light guide member.
The objective lens for converging the emitted light on the optical recording medium,
An optical pickup having the normal to the first surface of the light guide member on which the emitted light is incident.
So that the emitted light is obliquely incident on the semiconductor.
Body laser is arranged and the first slope of the plurality of slopes of the light guide member is arranged.
The surface (205a) has a beam splitter film and a hologram element.
And the emitted light is coupled to the optical axis of the first surface when it is incident on the first surface.
Converted into a radiant light flux having a substantially circular shape,
The emitted light beam is diffracted and reflected by the hologram element.
And further, a second slope (205) of the plurality of slopes.
b) between the beam splitter film and
A normal line of the second surface of the light guide member toward the objective lens
An optical pickup which is arranged so as to transmit the diffracted and reflected light in a predetermined direction . 6. The diffraction reflection angle of the hologram element is the
Set at 45 ° to the normal of the first slope (205a)
The optical pickup according to claim 5, wherein: