JPH05114160A - Light emitting device for optical pickup device - Google Patents

Abstract

PURPOSE:To provide a light emitting device which simplifies the constitution of an optical pickup device. CONSTITUTION:A semiconductor laser 11A, a glass plate 14 acting as a beam splitter, a photodetector 21 for reflected light reception, and a photodetector 23 to monitor the intensity of light emitted from the semiconductor laser 11A are provided in a package 40, and an exit window 44 is provided with a glass plate 15 acting as a beam splitter. Glass plates 14 and 15 are inclined to the optical axis of light emitted from the semiconductor laser 11A. The light emitted from the semiconductor laser 11A is emitted to the outside through glass plates 14, 15. The reflected light from the optical disk or a magneto-optical disk is made incident on the inside of the package 40 through the glass plate 15 while being condensed, and a part of this light is reflected by the glass plate 14 and is made incident on the photodetector 21. The light reflected by the glass plate 15 is made incident on a photodetector (omitted in the figure). Thus, a read signal, a focusing error signal, and a tracking error signal are generated based on light reception signals of photodetectors.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a generator preferably used in an optical pickup device for recording / reproducing information on an optical recording medium.

In the present invention, the optical recording medium includes not only an optical recording medium such as an optical disc and an optical card, but also a magneto-optical recording medium such as a magneto-optical disc and a magneto-optical card.

In the present invention, recording / reproducing information includes recording information on an optical recording medium, reproducing information recorded on the optical recording medium, and recording and reproducing.

[0004]

2. Description of the Related Art A conventional optical pickup device is a first optical system for collimating the divergent light from a semiconductor laser, collecting the collimated light on an optical recording medium, and reflecting the light from the optical recording medium. A second optical system for collimating the light, a first polarization beam splitter for polarization separating the reflected light collimated by the second optical system,
A second polarization beam splitter for further separating the polarization-separated light into tracking control light and focusing control light, and further separating the separated light on the light receiving surface of the tracking control photodetector. A third optical system for collecting the separated light, a fourth optical system for collecting the separated light on the light receiving surface of the focusing control photodetector, a third optical system or a fourth optical system for reading a read signal. It is composed of a fifth optical system and the like for guiding light to a photodetector for obtaining.

Since such a conventional optical pickup device uses many optical components, its weight is large,
Therefore, there is a problem that the access time is slow.
In addition, since many optical components are used, the cost of the components is high, and the assembly and adjustment of the components are troublesome and time-consuming, and the final cost is also high from this point.

Therefore, the applicant has proposed an optical pickup device which can be significantly reduced in size, weight and cost.

[0007]

[Explanation of the invention of the prior application] The first invention of the prior application (Japanese Patent Application No. 3-210478) proposed by the applicant is to condense a light emitting element and divergent light emitted from the light emitting element on an optical recording medium. In an optical pickup device including a condensing optical system that condenses reflected light from an optical recording medium, the condensing optical system is provided on an optical path of the divergent light between the light emitting element and the condensing optical system. At least two transparent plates (for example, dielectric plates) which are arranged so as to be inclined with respect to the optical axis of the system and which transmit a part of incident light and reflect a part of the incident light; It is characterized by comprising at least two photodetectors for receiving the light transmitted through the transparent plate or reflected by the transparent plate among the lights condensed by the condensing optical system.

The divergent light emitted from the light emitting element is condensed on the optical recording medium by the condensing optical system. The reflected light from the optical recording medium is condensed by the condensing optical system, a part of which is transmitted through the transparent plate or reflected by the transparent plate and is received by at least two photodetectors. A tracking error signal and a focusing error signal are obtained from the at least two photodetectors. In the case of reproduction, an information read signal is obtained based on the output signal of one or both of the at least two detectors. When the optical recording medium is a magneto-optical recording medium, an analyzer having polarization directions different from each other by 90 degrees is placed in front of the at least two photodetectors, and the polarization plane rotation angle of the reflected light is detected by the recorded information. To be done.

According to the first prior invention, an optical pickup device having a minimum required optical structure is realized by disposing at least two transparent plates between the light emitting element and the condensing optical system. Therefore, it is possible to reduce its size and weight.

The essential optical components in the optical pickup device of the first prior invention are a light emitting element, a condensing optical system, a transparent plate and a photodetector, and in the case of a magneto-optical recording medium, an analyzer is attached thereto. Since it is sufficient to provide it, it is possible to significantly reduce the cost.

A second prior invention (Japanese Patent Application No. 3-210479) proposed by the applicant is to collect a light emitting element and divergent light emitted from the light emitting element on a magnetooptical recording medium and In an optical pickup device including a condensing optical system for condensing reflected light from the optical system, an optical axis of the condensing optical system is provided on an optical path of the divergent light between the light emitting element and the condensing optical system. At least two transparent plates (for example, dielectric plates) arranged so as to be inclined with respect to and transmitting a part of incident light and reflecting a part of the incident light; At least two photodetectors for respectively receiving the light reflected by the transparent plate among the lights condensed by the optical system are provided, and the one transparent plate is a plane perpendicular to the optical axis. The line segment created by intersecting the transparent plate Characterized in that it is tilted in a direction substantially perpendicular to have.

[0012] Preferably, the inclination angle of the transparent plate is set to a Brewster angle at which a polarization component having a specific polarization plane is completely transmitted.

If necessary, an analyzer having polarization directions different from each other by 90 ° is arranged in front of the photodetector.

The divergent light emitted from the light emitting element is focused on the magneto-optical recording medium by the focusing optical system. The reflected light from the magneto-optical recording medium is condensed by the condensing optical system, a part of which is reflected by the transparent plate and received by at least two photodetectors.

The information recorded on the magneto-optical recording medium is read by detecting the change (Kerr effect) in the rotation angle of the polarization plane of the reflected light from the magneto-optical recording medium.

When light is obliquely incident on one surface of the transparent plate, its reflectance and transmittance have polarization plane selectivity, and the reflectance of light of a specific polarization component is 0% and the transmittance is 100%. There is an incident angle (Brewster angle).

By setting the inclination directions of the two transparent plates as described above, the reflected light of the two transparent plates can contain only or a large amount of polarization components orthogonal to each other.

Therefore, without using the above-mentioned analyzer, or by using it in an auxiliary manner, the above-mentioned photodetector detects the optical components contained in the reflected light from the magneto-optical recording medium and having mutually orthogonal polarization planes. Therefore, the read signal of information can be created based on the output signals of the two photodetectors.

A tracking error signal and a focusing error signal can be obtained from at least two photodetectors.

According to the second prior invention, an optical pickup device having a minimum required optical structure is realized by disposing at least two transparent plates between the light emitting element and the condensing optical system. Therefore, it is possible to reduce its size and weight.

In the optical pickup device of the second prior invention, the essential optical components are a light emitting element, a condensing optical system, a transparent plate and a photodetector. If necessary, an analyzer can be provided. Significant cost reduction can be achieved.

[0022]

The object, structure, operation and effect of the present invention is to provide a light emitting device in the optical pickup device according to the above-mentioned prior invention, in which an optical system such as an optical head can be made compact, lightweight and easy to assemble. The purpose is to provide.

A light emitting device for an optical pickup device according to the first invention comprises a light emitting device, a package of the light emitting device containing the light emitting device therein, and an optical axis of the light emitting device on the optical path of divergent light emitted from the light emitting device. A first transparent plate, which is disposed at an angle with respect to and acts as a beam splitter housed in the package, covers the exit window for the divergent light provided in the package, and tilts with respect to the optical axis. A second transparent plate that functions as a beam splitter arranged, and the first of the light that is contained in the package and that enters the package through the second transparent plate.
The first light receiving element that receives the light reflected by the transparent plate is included.

The light emitting device according to the first invention is applicable to both the first prior invention and the second prior invention described above.

According to the first aspect of the invention, since the two transparent plates that act as beam splitters are provided in the package containing the light emitting element, the minimum beam splitter required in the optical pickup device is integrated with the light emitting device. Have been formed in the same way. Therefore, in principle, the beam splitter is not necessary for the optical pickup device, so that the structure is simplified and the size can be reduced. Since the light emitting element and the two transparent plates are integrally combined in advance, the optical pickup device can be easily assembled.

The light emitting device according to the second invention comprises a light emitting element,
A package of a light emitting device having the light emitting element housed therein, and a beam splitter which is arranged on the optical path of divergent light emitted from the light emitting element with an inclination with respect to the optical axis and is housed in the package. The transparent plate and the light receiving means having two light receiving surfaces for receiving the light reflected on both the front surface and the back surface of the transparent plate among the light incident on the package are provided.

The second invention is suitable as the light emitting device of the first prior invention described above.

According to the second aspect of the invention, the read signal and various error signals are created based on the reflected light from the optical recording medium as well as the transparent plate acting as the beam splitter in the package containing the light emitting element. Since the light receiving means for outputting the signal is built in, the configuration of the optical pickup device is extremely simplified and easy to assemble.

A light emitting device according to a third aspect of the present invention covers a light emitting element that emits divergent light, a package of the light emitting device that houses the light emitting element therein, and an emission window of the divergent light that is opened in the front surface of the package. At the same time, it is provided with a transparent plate which functions as a beam splitter and is arranged to be inclined with respect to the optical axis of the divergent light.

In the third aspect of the invention, since the transparent plate that closes the window of the package functions as a beam splitter essential to the optical pickup device, it is possible to omit one beam splitter in the optical system of the optical pickup device. Accordingly, the structure of the optical pickup device can be simplified and the assembling can be facilitated.

A light emitting device according to a fourth aspect of the present invention covers a light emitting device that emits divergent light, a package of the light emitting device that houses the light emitting device therein, and a window for emitting the divergent light that is opened on the front surface of the package. A transparent plate arranged to be inclined with respect to the optical axis of the divergent light, and a signal for receiving the light emitted from the light emitting element and reflected by the transparent plate and controlling the emission intensity of the light emitting element The light receiving element provided in the package for outputting

According to the fourth aspect of the invention, since the light receiving element for monitoring the output light intensity of the light emitting element is provided in the package of the light emitting device, the automatic power control of the light emitting element becomes easy. Moreover, since the transparent plate for obtaining the reflected light incident on the light receiving element also serves as the member for protecting the window of the package, the structure is simplified accordingly. If necessary,
This transparent plate can also be used as a beam splitter required in the optical pickup device.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of the optical pickup device according to the invention of the prior application will be described.

FIG. 1 shows a first embodiment of the first prior invention, showing the structure of an optical pickup device for recording / reproducing information on / from an optical disk.

The optical pickup device includes a semiconductor laser 11
And a condensing optical system that condenses the divergent light emitted from the semiconductor laser 11 onto the optical disc 20. The condensing optical system is a collimating lens 12 that collimates divergent light.
And an objective lens 13 that collects the collimated light.

On the optical path of the divergent light between the semiconductor laser 11 and the collimating lens 12, two glass plates 14 and
15 is arranged in a state of being inclined with respect to the optical axes of the semiconductor laser 11 and the focusing optical system.

The divergent light emitted from the semiconductor laser 11 passes through the two glass plates 14 and 15 and is focused on the optical disk 20 by the focusing optical system. A part of the divergent light emitted from the semiconductor laser 11 is reflected by the glass plate 14 and received by the photodetector 23. The emitted light intensity of the semiconductor laser 11 is controlled based on the light reception signal of the photodetector 23.

The reflected light from the optical disk 20 is condensed by the condensing optical system. A part of the condensed reflected light is reflected by the glass plate 15 and is incident on the photodetector 22, and a part of the light transmitted through the glass plate 15 is further reflected by the glass plate 14 and is detected by the photodetector 21. Incident on.

Since the reflected light from the optical disk 20 is condensed by the condensing optical system, a condenser lens or the like is provided between the glass plate 15 and the photodetector 22 and between the glass plate 14 and the photodetector 21. Need not always be provided.

The output signals of the photodetectors 21 and 22 are used to create a focusing error signal, a tracking error signal and a read signal.

The focusing error signal is created by, for example, the beam size method or the astigmatism method. In the double beam size method, photodetectors 21 and 22 are arranged at positions before and after the focal position of reflected light when focusing is performed correctly. The photodetectors 21 and 22 are configured so as to obtain a signal representing the size of the light beam received by the photodetectors 21 and 22, and the focusing signal is obtained by taking the difference between the output signals of the photodetectors 21 and 22. An error signal is created. Each of the photodetectors 21 and 22 includes, for example, a three-divided photodiode, and the difference between the output signal of the central photodiode and the sum signal of the output signals of the photodiodes on both sides becomes the output signal of the photodetector.

Aberrations including astigmatism occur in the reflected light of the glass plate arranged obliquely with respect to the optical axis. By utilizing this astigmatism, a focusing error signal based on the astigmatism method can be obtained. For example, one of the photodetectors 21 and 22 is composed of a four-divided photodiode, and a focusing error signal is generated by adding and subtracting the output signals of these four photodiodes.

The push-pull method is used to create the tracking error signal. That is, the photodetector
21 or 22 is configured to include a photodiode divided into two or three in a direction perpendicular to the track direction of the optical disc 20, and the difference signal between the output signals of the photodiodes at both ends becomes a tracking error signal.

The read signal of the information recorded on the optical disk 20 can be created by adding the output signals of the photodetectors 21 and 22. Of course, the output signal of either one of the photodetectors 21 and 22 may be used as the read signal.

If necessary, arrange three or more glass plates,
You may make it provide a photodetector corresponding to each glass plate.

The reflectance and the transmittance of the glass plate are appropriately adjusted in advance as needed. In this adjustment, at least one surface of the glass plate may be coated with a non-reflective coating, a semi-mirror surface coating, or the like. The antireflection coating is particularly useful when it is necessary to obtain the reflected light from only one of the two surfaces of the glass plate.

If necessary, the thickness of the glass plate
On the optical disc 20, the thickness is made thin (for example, about 100 μm or less) so that the influence of the wavefront aberration can be ignored. Alternatively, the shape of the collimator lens 12 or the like may be set to a shape (for example, an aspherical surface or an asymmetrical lens) in which a light spot formed on the optical disc 20 is hardly affected by wavefront aberration.

Further, between the semiconductor laser 11 and the collimating lens 12 of the condensing optical system, a light beam shaping optical system for correcting the light of the elliptical cross section emitted from the semiconductor laser 11 into the light of the circular cross section is provided. You can also In addition, semiconductor laser
An isolator optical system that allows the emitted light of the semiconductor laser 11 to pass therethrough and blocks the reflected light from the optical disc 20 from entering the semiconductor laser 11 may be provided between the glass 11 and the glass 11. If necessary, a condensing optical system can be provided between the glass plate and the photodetector.

FIG. 2 shows a second embodiment of the first prior invention, showing the structure of an optical pickup device suitable for recording / reproducing of a magneto-optical disk. The same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

Analyzers 31 and 32 are provided in front of the light receiving surfaces of the photodetectors 21 and 22, respectively. These analyzers 31 and 32 are arranged so that the polarization directions of light passing therethrough are orthogonal to each other. Further, the polarization direction of the linearly polarized light emitted from the semiconductor laser 11 forms an angle of 45 degrees with the polarization direction of the light passing through the analyzers 31 and 32.

With the above configuration, the change in the polarization plane rotation angle caused by the information recorded on the magneto-optical disk 30 is detected by the difference between the output signals of the photodetectors 21 and 22.

It goes without saying that a polarizer may be provided on the front surface of the semiconductor laser 11.

3 and 4 show an embodiment of the second prior invention.

The optical pickup device includes a semiconductor laser 11
And a condensing optical system for converging the divergent light emitted from the semiconductor laser 11 on the magneto-optical disk 20. The condensing optical system is a collimating lens that collimates divergent light.
It includes an objective lens 13 for condensing the collimated light.

On the optical path of the divergent light between the semiconductor laser 11 and the collimating lens 12, two glass plates 14 and
15 is arranged in a state of being inclined with respect to the optical axes of the semiconductor laser 11 and the focusing optical system.

The divergent light emitted from the semiconductor laser 11 passes through the two glass plates 14 and 15 and is focused on the magneto-optical disk 30 by the focusing optical system. A part of the divergent light emitted from the semiconductor laser 11 is reflected by the glass plate 14 and is detected by the photodetector.
Received by 23. The emitted light intensity of the semiconductor laser 11 is controlled based on the light reception signal of the photodetector 23.

The reflected light from the magneto-optical disk 30 is condensed by the condensing optical system. A part of the condensed reflected light is reflected by the glass plate 15 and is incident on the photodetector 22, and a part of the light transmitted through the glass plate 15 is further reflected by the glass plate 14 and is detected by the photodetector 21. Incident on.

Since the reflected light from the magneto-optical disk 30 is condensed by the condensing optical system, the glass plate 15 and the photodetector 22
It is not always necessary to provide a condenser lens or the like between the glass plate 14 and the photodetector 21.

FIG. 5 shows the incident angle dependence of the reflection coefficient and the transmission coefficient of light when the light is obliquely incident on the surface of the glass plate (refractive index = 1.5).

T _p is the transmission coefficient of the P polarization component, T _s is the transmission coefficient of the S polarization component, R _p is the reflection coefficient of the P polarization component, R _s
Is the reflection coefficient of the S-polarized component. The component parallel to the glass surface is the S-polarized component, and the vertical component is the P-polarized component.

As can be seen from FIG. 5, at a certain angle α _B (this is called Brewster's angle), R _p becomes 0% and T _p becomes 100%. At this time, R _s and T _s take values other than 0 or 100%.

Therefore, if the glass plate is tilted with respect to the incident light at the Brewster angle α _B , the reflected light from the glass plate will be only the S-polarized component. Even if the inclination angle of the glass plate is other than Brewster's angle, the reflected light from the glass plate contains more S-polarized component than P-polarized component.

The glass plates 14 and 15 are arranged so that the line segments formed by intersecting the planes perpendicular to the optical axis of the condensing optical system with these glass plates 14 and 15 are orthogonal to each other,
Moreover, if the incident angle of the reflected light condensed by the condensing optical system is tilted so as to be the Brewster angle, the glass plate 14
The reflected light from 15 and 15 contains only polarization components orthogonal to each other, and only these lights are detected by photodetectors 21 and 22.
Respectively detected by.

Even if the tilt angles of the glass plates 14 and 15 with respect to the incident light are other than Brewster's angle, the glass plates 14 and 15 are
The reflected light from 1 contains more polarization components orthogonal to each other. By disposing analyzers 31 and 32 arranged such that their polarization directions are orthogonal to each other so that only these orthogonal polarization components pass respectively, the polarization components orthogonal to each other are provided. Only are detected by photodetectors 21 and 22, respectively.

The polarization directions of the linearly polarized light emitted from the semiconductor laser 11 are orthogonal to each other (the analyzer 31,
The polarization direction of the light passing through 32) and the angle of 45 degrees.

With the above configuration, the change in the polarization plane rotation angle caused by the information recorded on the magneto-optical disk 30 is detected by the difference between the output signals of the photodetectors 21 and 22.

It goes without saying that a polarizer may be provided on the front surface of the semiconductor laser 11.

The output signals of the photodetectors 21 and 22 are also used for producing the focusing error signal and the tracking error signal, as in the case of the first prior invention.

Each of the photodetectors 21 and 22 includes, for example, a photodiode divided into three, and the difference between the output signal of the central photodiode and the sum signal of the output signals of the photodiodes on both sides is the output signal of the photodetector. Become.

The same modifications as those described in the first prior invention are also applicable to the second prior invention.

FIGS. 6 and 7 show a first embodiment of the first invention. The light emitting device of this embodiment is suitable for the optical pickup device according to the second prior invention described above. FIG. 8 shows an optical system constructed by applying the light emitting device according to this embodiment to the optical pickup device shown in FIG. 3 or 4. In these figures, the same components as those shown in FIGS. 1 to 4 are designated by the same reference numerals to avoid redundant description. This also applies to the other embodiments shown in FIGS. 9 to 16.

Referring to FIGS. 6 and 7, the package 40 of the light emitting device is composed of a base 42 and a tubular portion 41 that is can sealed to the base 42, and an exit window is provided at the tip of the tubular portion 41. 44 is open.

A semiconductor laser 11A as a light emitting element is arranged in the package 40 and attached to a stem 46 fixed to a base 42. Further, the glass plate 14 is arranged in the package 40 obliquely with respect to the optical axis of the laser light emitted from the semiconductor laser 11A, and is fixed by a fixing member 43 provided on the cylindrical portion 41. A glass plate 15 is attached so as to cover the exit window 44. These glass plates
14 and 15 are glass plates 14, whose planes perpendicular to the optical axis are
The line segments formed by intersecting 15 are arranged so as to be orthogonal to each other.

Further, in the package 40, of the reflected light from the magneto-optical disk 30 which is transmitted through the glass plate 15 and enters the package 40, the light reflected by the glass plate 14 is detected. Instrument 21 and analyzer 31 in front of it
Are arranged and fixed to the inner surface of the tubular portion 41.
A photodetector 23 for detecting the light reflected by the glass plate 14 out of the light emitted from the semiconductor laser 11A is also fixed in the package 40.

Driving current of semiconductor laser 11A, photodetector 2
The received light signals of 1 and 23 are input / output through a terminal pin 45 which is provided in the base 42 in a mutually insulated state.

As shown in FIG. 8, such a light emitting device is used for the optical pickup device in the second prior invention. Since the semiconductor laser 11A, the glass plate 14, and the photodetectors 21 and 23 are arranged in the package 40, it is sufficient to provide the photodetector 22, the analyzer 32, the lens 12 and the like outside.

As shown in FIG. 1 or 2, the glass plates 14 and 15 are arranged so that the line segments formed by intersecting the surfaces perpendicular to the optical axis with these glass plates 14 and 15 are parallel to each other. It can also be placed in. In this case, this light emitting device can be used for the optical pickup device according to the first prior invention.

The generation of the read signal, the focusing error signal and the tracking error signal is the same as in the above-mentioned prior invention. Further, the modification examples regarding the formation of the coat film on the glass plate, the thickness of the glass plate, and the like described in the description of the invention of the prior application also apply to this embodiment as they are. These also apply to the other embodiments described below.

FIG. 9 shows a second embodiment according to the second invention. The light emitting device according to this embodiment can be preferably used in the first prior invention.

A light emitting device package 50 for an optical pickup device comprises a base 52 and a cylindrical portion 51.
A semiconductor laser 11A is attached to a stem 56 provided on the base 52.

One glass plate 14 is provided in this package 50.
Is provided and is fixed to the tubular portion 51 by a fixing member 53. A glass plate is provided in the exit window 54 formed in the cylindrical portion 51.
57 is inset.

The reflected light from the optical disk 20 or the magneto-optical disk 30 is condensed by the condensing optical system and is a glass plate.
Enter package 50 through 57. The incident light is reflected by the front surface of the glass plate 14 and is received by the photodetector 22, and is reflected by the rear surface and is received by the photodetector 21. These photo detectors 21,
22 is also provided in the package 50. Magneto-optical disk
When the reflected light from 30 is received, analyzers 31 and 32 are provided in front of the photodetectors 21 and 22, respectively.

In this embodiment, since the reflected light from the front and back surfaces of the glass plate 14 is received, the glass plate 15 is unnecessary. The reflectance of the front and back surfaces of the glass plate 14 is adjusted by forming a coat film or the like so that the amounts of light incident on both photodetectors 21 and 22 are substantially equal. It is preferable that each of the photodetectors 21 and 22 is divided into three, as in a third embodiment described later (application example shown in FIG. 12).

A photodetector 23 is also provided in the package 50. The terminal pin 55 is for driving the semiconductor laser 11A and for reading output signals of the photodetectors 21, 22, 23.

FIG. 10 shows a third embodiment according to the third invention. The light emitting device according to this embodiment includes the first and second
It is applicable to the optical pickup device according to the invention of the earlier application.

The package 60 of the light emitting device comprises a base 62 and a cylindrical portion 61, and a stem 66 fixed to the base 62.
The semiconductor laser 11A is fixed to.

An exit window 64 is opened at the tip of the tubular portion 61, and the glass plate 14 is provided there. The glass plate 14 is tilted with respect to the optical axis of the semiconductor laser 11A.

A photodetector 23 is provided in the package 60. The received light signal of the photodetector 23 is led to the outside through the pin 65. The semiconductor laser 11A is also driven by the current supplied via the pin 65.

FIG. 11 is a diagram in which the light emitting device of the third embodiment is applied to the optical pickup device according to the second prior invention of FIG. 3 and FIG. As can be seen from the comparison with FIG. 3, the semiconductor laser 11, the glass plate 14, and the photodetector 23 are replaced with the package 60 of the light emitting device.

FIG. 12 shows the light emitting device of the third embodiment applied to the optical pickup device of the first prior invention shown in FIG. 1 or 2. Also in this embodiment, as in the second embodiment shown in FIG. 9, the reflected light from the front and back surfaces of the glass plate 14 is used. Therefore, the glass plate 15 becomes unnecessary.

Further, in this embodiment, the photodetector 21 is composed of a 6-division photodiode. The photodetector 22 is unnecessary. If the photodetector 21 is divided into the photodetectors 21A and 21B, it can be considered that the photodetectors 21A and 21B correspond to the photodetectors 21 and 22 in the invention of the prior application. When reading the recorded information on the magneto-optical disk 30, the photodetectors 21A and 21B
An analyzer 31A, which allows the transmission of polarized components orthogonal to each other,
31B are arranged respectively.

FIG. 13 shows the photodetector 21 (or the photodetector 21A).
And 21B), and a concrete example of a circuit for producing a tracking error signal, a focusing error signal and a read signal based on the output signal of this photodetector.

Each of the photodetectors 21A and 21B is composed of a three-divided photodiode. The photodetector 21 is
As mentioned above, it can be said that the photodiode is composed of six-division photodiodes.

The photodetector 21A is composed of three photodiodes 21a, 21b and 21c which are electrically insulated from each other, and the width of the central photodiode 21b is set to be the smallest. Photodiodes 21a, 21b and 21c
The straight line that divides the line extends in the track direction of the optical disk or magneto-optical disk.

The photodetector 21B similarly has three electrically isolated photodiodes 21d, 21e and 21.
The photodiode 21e at the center is set to have the smallest width. Photodiodes 21d, 21e
A straight line dividing 21f and 21f extends in the track direction of the optical disk or the magneto-optical disk.

The spots SP1 and SP2 formed on the photodiodes 21a to 21f by the reflected light from the front and back surfaces of the glass plate 14 are the photodiodes 21a to 21f.
Photodetector 21 so that it is arranged along a straight line dividing f
A and 21B are arranged.

The push-pull method is used to detect tracking errors, and the double-pull method is used to detect focusing errors.
The beam size method is used respectively. As described above, in the case where the focusing is performed correctly due to the double beam size method, as described above, the photodetector 21A
Is in front of the focal position of the reflected light from the surface of the glass plate 14,
The photodetectors 21B are arranged behind the focal point of the reflected light from the back surface of the glass plate 14, respectively.

The tracking error signal is created by the subtracter 77 taking the difference between the output signal of the photodiode 21a of the photodetector 21A and the output signal of the photodiode 21c. Photodetector 21B photodiode 21d
The tracking error signal can also be created by taking the difference between the output signals of and 21f.

Photodiodes 21a, 21b, 21c, 21
The output signals of d, 21e and 21f are respectively a, b, c,
Represented by d, e and f. Adders 74 and 75 and subtractor 76
Then, a focusing error signal is generated by calculating (a + c + e)-(b + d + f).

By the adders 71 and 72 and the subtractor 73,
A read signal is created by calculating (a + b + c)-(d + e + f).

FIG. 14 shows a fourth embodiment according to the fourth invention. The light emitting device of this embodiment is applicable to both the first and second prior inventions.

The package 80 of the light emitting device comprises a base 82 and a cylindrical portion 81, and a stem fixed to the base 82.
A semiconductor laser 11A is provided at 86. The front surface of the cylindrical portion 81 is opened as an emission window 84, and a glass plate 87 is provided in the emission window 84 obliquely with respect to the optical axis of the semiconductor laser 11A.

The photodetector 23 is arranged in the package 80. Most of the light emitted from the front end face of the semiconductor laser 11A passes through the glass plate 87 and is emitted to the outside, but part of the light is reflected by the glass plate 87 and enters the photodetector 23.
The level of the received light signal of the photodetector 23 represents the emitted light intensity of the semiconductor laser 11A, and feedback control is performed based on this received light signal so that the emitted light intensity of the semiconductor laser 11A becomes constant. In this way, the FAPC (Fro
nt Automatic Power Control) is realized.

Laser light is also generated from the rear end face of the semiconductor laser chip 11A. The laser light that goes to the rear is the base
82 A shield plate 88 is provided to prevent the light from being reflected by the surface or the like and entering the photodetector 23. The shield plate 88 is provided on the entire cross-section of the cylindrical portion, except for the portion through which the light directed forward of the semiconductor laser 11A passes.

FIG. 15 shows the light emitting device package 80 described above applied to the first prior invention.

As will be apparent from comparison with FIG. 2, a light emitting device package 80 is provided in place of the semiconductor laser 11. Further, in FIG. 15, the collimating lens 12 is omitted. The glass plate 87 of the package 80 can be used as a beam splitter and the glass plate 14 can be omitted.

FIG. 16 shows an example in which the light emitting device package 80 is applied to the second prior invention. As is clear from comparison with FIG. 4, a package 80 is provided in place of the semiconductor laser 11 and the photodetector 23.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the first prior invention, and shows a configuration of an optical pickup device suitable for recording / reproducing of an optical disc.

FIG. 2 shows a second embodiment of the first prior invention, showing the configuration of an optical pickup device suitable for recording / reproducing of a magneto-optical disk.

FIG. 3 shows an embodiment of the optical pickup device according to the second prior invention, and is a plan view of the optical configuration of the optical pickup device.

FIG. 4 is a perspective view showing an embodiment of the optical pickup device according to the second prior invention, and showing a part of the optical system shown in FIG.

FIG. 5 is a graph showing the incident angle dependence of the reflection coefficient and the transmission coefficient of a glass plate.

FIG. 6 shows a first embodiment of the first invention,
It is sectional drawing of a light-emitting device.

7 is a side view of the light emitting device shown in FIG.

FIG. 8 is a perspective view showing a configuration of an optical pickup device using the light emitting device according to the first embodiment.

FIG. 9 shows a second embodiment of the second invention,
It is sectional drawing of a light-emitting device.

FIG. 10 shows a third embodiment of the third invention and is a cross-sectional view of a light emitting device.

FIG. 11 shows a configuration of an optical pickup device using the light emitting device of the third embodiment.

FIG. 12 shows another example of an optical pickup device using the light emitting device of the third invention.

FIG. 13 is a circuit diagram showing a circuit that creates a read signal, a focusing error signal, and a tracking error signal.

FIG. 14 is a sectional view of a light emitting device, showing a fourth embodiment of the fourth invention.

FIG. 15 shows a configuration of an optical pickup device using the light emitting device of the fourth embodiment.

FIG. 16 is a perspective view showing another example of an optical pickup device using the light emitting device of the fourth embodiment.

[Explanation of symbols]

 11, 11A Semiconductor laser 12 Collimating lens 13 Objective lens 14, 15 Glass plate 20 Optical disc 21, 22 Photodetector 30 Magneto-optical disc 31, 32 Analyzer 40, 50, 60, 80 Light emitting device package 44, 54, 64 , 84 exit window

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironobu Kiyomoto 10 Odoron-cho, Hanazono, Ukyo-ku, Kyoto City Omron Corporation

Claims (21)

[Claims] 1. A light emitting device, a package of a light emitting device having the light emitting device housed therein, arranged on the optical path of divergent light emitted from the light emitting device at an angle with respect to the optical axis, and in the package. A first transparent plate that acts as a contained beam splitter, a second transparent plate that acts as a beam splitter that covers the exit window for the divergent light provided in the package and that is arranged at an angle with respect to the optical axis. , And the first of the light that is contained in the package and enters the package through the second transparent plate.
A light emitting device for an optical pickup device, comprising: a first light receiving element for receiving the light reflected by the transparent plate. 2. The first and second transparent plates are arranged such that line segments generated by a plane perpendicular to the optical axis intersecting these transparent plates are inclined in directions substantially orthogonal to each other. Item 2. The light emitting device according to item 1. 3. The first and second transparent plates are arranged so as to be inclined in a direction in which line segments generated by a plane perpendicular to the optical axis intersecting these transparent plates are substantially parallel to each other. The light emitting device according to claim 1. 4. The first light emitted from the light emitting element and the first light emitting element.
2. The light emitting device according to claim 1, wherein a light detector that receives the light reflected by the transparent plate and outputs a signal for controlling the emission intensity of the light emitting element is provided in the package. 5. The light emitting device according to claim 1, further comprising a second light receiving element for receiving the light reflected by the second transparent plate out of the light incident on the second transparent plate from the outside. apparatus. 6. An analyzer is arranged between the first transparent plate and the first light receiving element and between the second transparent plate and the second light receiving element, respectively. The light-emitting device according to. 7. The light emitting device according to claim 5, wherein at least one surface of at least one of the first and second transparent plates is coated with a coating for adjusting a reflectance. 8. A light emitting device, a package of a light emitting device having the light emitting device housed therein, arranged on the optical path of divergent light emitted from the light emitting device, inclined with respect to the optical axis thereof, and within the package. Light including a transparent plate that acts as a beam splitter housed therein, and a light-receiving means having two light-receiving surfaces that receive light that is reflected on both the front and back surfaces of the transparent plate among the light incident on the package. A light emitting device for a pickup device. 9. The light-emitting device according to claim 8, wherein the two light-receiving surfaces of the light-receiving means are arranged so as to be respectively located in front of and behind a focal position of reflected light from the front and back surfaces of the transparent plate. apparatus. 10. The light emitting device according to claim 8, wherein the two light receiving surfaces of the light receiving means are each divided into three. 11. A photodetector is provided in the package, which receives light emitted from the light emitting element and reflected by the transparent plate and outputs a signal for controlling the light emission intensity of the light emitting element. The light emitting device according to claim 8. 12. The light emitting device according to claim 8, wherein analyzers are respectively arranged between the transparent plate and the two light receiving surfaces of the light receiving means. 13. The light emitting device according to claim 8, wherein at least one of a front surface and a back surface of the transparent plate is coated with a coating for adjusting a reflectance. 14. A light emitting device that emits divergent light, a package of a light emitting device that houses the light emitting device therein, and an emission window of the divergent light that is opened in the front surface of the package and an optical axis of the divergent light. A light emitting device for an optical pickup device, which comprises a transparent plate which is arranged so as to be inclined with respect to the beam splitter. 15. A photodetector is provided in the package for receiving the light emitted from the light emitting element and reflected by the transparent plate and outputting a signal for controlling the emission intensity of the light emitting element. 15. The light emitting device according to claim 14, which is present. 16. The coating for adjusting the reflectance is applied to at least one surface of the transparent plate.
14. The light emitting device according to 14. 17. A light receiving means having two light receiving surfaces for respectively receiving light reflected from both the front surface and the back surface of the transparent plate out of light incident on the transparent plate of the package from outside, is further provided. 15. The light emitting device according to claim 14. 18. The light-emitting device according to claim 17, wherein the two light-receiving surfaces of the light-receiving means are arranged so as to be located in front of and behind the focal position of the reflected light from the front and back surfaces of the transparent plate, respectively. apparatus. 19. The light emitting device according to claim 17, wherein the two light receiving surfaces of the light receiving means are each divided into three. 20. A light emitting device for emitting divergent light, a package of a light emitting device having the light emitting device housed therein, an emission window of the divergent light provided on the front surface of the package, and an optical axis of the divergent light. In the package, the transparent plate arranged to be inclined with respect to the light emitting device, and the light emitted from the light emitting device and reflected by the transparent plate are received and a signal for controlling the light emission intensity of the light emitting device is output. A light-emitting device including a light-receiving element provided in. 21. The light emitting device according to claim 20, further comprising a shield plate that prevents light emitted from the rear end surface of the light emitting element from entering the light receiving element.