JPH0636330A - Optical pickup device - Google Patents

Abstract

PURPOSE:To prevent the disturbance and to properly discriminate the intensity of a laser beam by providing a face, which totally reflects a part of the luminous flux of the laser beam for monitor, and a photodetector and inclining the normal of the reflection face to the incidence direction. CONSTITUTION:The reflected light from the recording face of a magneto-optical disk 14 which is reflected by a separating face 12a passes a half-wave plate 15 and has the plane of polarization rotated at 45 deg.. The signal light which passes the plate 15 is made incident on a beam splitter 16 and is separated into the component transmitted through the separating face 16 and the component reflected by it. The reflected signal light passes a condenser lens 40 and is made incident on a photodetector 41, whose light reception face is divided in the tracking direction, to detect the tracking error. The p-polarized light component of the signal light transmitted through the face 16 has the focusing error detected by a photodetector 23. Only the part made incident on the element 40 is reflected to the detecting optical system side; and therefore, light is not made incident on the other photodetectors by inclining the normal of the reflection face to incident light, and the disturbance is eliminated to properly discriminate the intensity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention monitors a laser beam output from a semiconductor laser element by using a beam splitter, and monitors the laser beam traveling in the direction of a recording medium as signal light and the output level of the semiconductor laser element. The present invention relates to an optical pickup device for forming a monitor laser beam for performing the operation.

[0002]

2. Description of the Related Art Generally, in an optical disc device, a semiconductor laser element is used as a light source in an optical pickup device for recording / reproducing (/ erasing) data. An example of this semiconductor laser device is shown in FIG.

In FIG. 1, a semiconductor laser device comprises a semiconductor laser chip 1, a substrate 2 on which the semiconductor laser chip 1 is mounted, and a monitor light-receiving device 3 for receiving laser light emitted from a cleavage plane behind the semiconductor laser chip 1. To
It is housed in the same envelope 4.

Then, the level of the output light output from the front cleaved surface of the semiconductor laser chip 1 is monitored based on the received light signal from the monitor light receiving element 3, and the semiconductor laser is controlled so that the output light has a constant level. The drive current of the chip 1 is controlled so that stable operation can be performed.

Now, in the optical system of the optical pickup device,
Various signals are obtained by converting the laser light output from the semiconductor laser element into a parallel beam, then focusing it on an optical disc, and guiding the reflected light from the optical disc to a detection optical system. Then, since the focal point of the laser beam on the optical disc and the semiconductor laser element are in an image forming positional relationship with each other, part of the reflected light from the optical disc returns to the semiconductor laser chip 1.

When such return light enters the semiconductor laser device, it becomes impossible to stably control the output of the semiconductor laser device. For example, when there is no returning light, the relationship between the drive current and the light output to the semiconductor laser element, and the relationship between the light output and the light receiving signal (monitor current) of the monitor light receiving element 3 is as shown by the solid line in FIG. At some time, when there is return light, the relationship between the drive current and the optical output for the semiconductor laser element and the relationship between the optical output and the monitor current of the monitor light receiving element 3 fluctuates as shown by the broken line in FIG. .

For this reason, when the drive current is controlled so that the monitor current becomes a predetermined value, and when there is no returning light, the control state becomes the mode shown by point A in FIG. Then, when there is the returning light, the control state becomes the mode shown by point B in FIG. That is, in this case, if there is returning light, the output level of the semiconductor laser device decreases.

In order to eliminate such inconvenience, conventionally, for example, an optical pickup device having an optical system as shown in FIGS. 6A and 6B has been put into practical use. It should be noted that this optical system detects a focusing error using the astigmatism method and a tracking error using the push-pull method. In this case, a magneto-optical disk is used as the recording medium.

In the figure, the laser light output from the semiconductor laser device 10 is converted into a parallel laser beam by a coupling lens 11, and this laser beam is incident on a beam splitter 12 and its separation surface 12a.
Then, it is separated into a component that transmits the separation surface 12a and a component that reflects it.

The laser beam transmitted through the beam splitter 12 is focused on the recording surface of the magneto-optical disk 14 by the objective lens 13. The reflected light from the recording surface of the magneto-optical disk 14 returns to the beam splitter 12 and is separated again into a component that is transmitted and a component that is reflected by the separation surface 12a.

The reflected light (hereinafter referred to as signal light) from the recording surface of the magneto-optical disk 14 reflected by the separation surface 12a passes through the half-wave plate 15 and has its polarization plane of 4
Rotate 5 degrees. The signal light that has passed through the half-wave plate 15 is
It is incident on the beam splitter 16 and its separating surface 16a
Thus, the light is separated into a component that transmits the separation surface 16a and a component that reflects it. The signal light reflected by the separation surface 16a of the beam splitter 16 is incident on a light receiving element 17 for detecting a tracking error, the light receiving surface of which is divided into two in the tracking direction.

Further, the separation surface 16 of the beam splitter 16
The signal light transmitted through a is incident on the polarization beam splitter 18, and the polarization beam splitter 18 causes the S
The polarization component is reflected and the P polarization component is transmitted.
The signal light of the S-polarized component reflected by the polarization beam splitter 18 is focused by the focusing lens 19 and is incident on the light receiving element 20. The signal light of the P-polarized component that has passed through the polarization beam splitter 18 passes through the condenser lens 21 and the cylindrical lens 22 and then has the detection light receiving element 2 for detecting a focusing error having a four-divided light receiving surface.
It is incident on 3.

Then, a track error signal is formed based on the difference between the light receiving signals obtained from the two light receiving surfaces of the light receiving element 17, and a predetermined calculation is applied to the light receiving signals obtained from the four light receiving surfaces of the light receiving element 23. A focusing error signal is formed. Further, a magneto-optical signal which is a reproduction signal from the user area of the magneto-optical disk 14 is formed based on the difference signal of the total sum of the light receiving signal of the light receiving element 20 and the light receiving signals obtained from the four light receiving surfaces of the light receiving element 23. To be done. Further, a reproduction signal from the preformatted area of the magneto-optical disk 14 is formed based on the sum of the light receiving signals of the light receiving element 20 and the light receiving element 23. In addition, the light receiving element 2 for monitoring
The output level of the semiconductor laser device 10 is controlled based on the light receiving signal output from the semiconductor laser device 5.

On the other hand, of the laser beam incident on the beam splitter 12 from the coupling lens 11, the component reflected by the separation surface 12a of the beam splitter 12 is
Only the P-polarized component is incident on the monitor light-receiving element 25 via the analyzer 24.

Here, the laser beam output from the semiconductor laser device 10 is used for recording / reproducing / erasing data and an LD (laser diode) component used for recording / reproducing / erasing data. There is no LED (light emitting diode) component, LD component is P polarized light, LE
The D component is unpolarized. That is, the P-polarized component and the S-polarized component of the LED component are 50% each. Moreover, the ratio of these LD component and LED component changes with temperature changes and changes over time.

The separation surface 12 of the beam splitter 12
The characteristic of a is set to, for example, a P-polarized light transmittance of 70% and an S-polarized light reflectance of 98%. Therefore, the luminous flux reflected by the separation surface 12a is about 50 times the luminous flux of the LED component.
%, The light flux of the LED component is also received by the monitor light-receiving element 25, and when the ratio of the LD component and the LED component changes due to temperature change or aging, the light beam actually enters the magneto-optical disk 14. The relationship between the intensity of the laser beam to be emitted and the intensity of light received by the monitor light-receiving element 25 changes, which is not preferable.

Then, the separation surface 12 is separated by the analyzer 24.
By transmitting only the P-polarized component of the reflected light from a and making it incident on the monitor light receiving element 25, such a problem can be eliminated.

However, in such a conventional device,
Since the analyzer 24 is used, the device cost is increased, which is a disadvantage.

In order to eliminate such inconvenience, for example,
An optical pickup device as shown in FIGS. 7A and 7B is in practical use. In addition, in FIG.
The same parts as (b) and the corresponding parts are given the same reference numerals.

In the figure, the light beam reflected by the separation surface 12a of the beam splitter 12 is the beam splitter 12
The surface 12b emitted from is inclined by a predetermined angle, and the entire surface of the surface 12b is provided with a reflection enhancing coating surface 12c.

Therefore, of the laser beam incident on the beam splitter 12 from the coupling lens 11, the component reflected by the separation surface 12a of the beam splitter 12 is the entire light flux of the surface 12b, which is the reflection enhancing coating surface 12c.
Is reflected by.

The light beam reflected by the increased reflection coating surface 12c is separated into a component that is transmitted by the separation surface 12a of the beam splitter 12 and a component that is reflected by the separation surface 12a. At this time, the S-polarized component is completely reflected by the separation surface 12a. It is the P-polarized component that is transmitted back to the coupling lens 11 and thus transmitted through the separation surface 12a. The light flux (hereinafter referred to as monitor light) that has passed through the separation surface 12a passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees. 1 /
The monitor light that has passed through the two-wave plate 15 is incident on the beam splitter 16, and is separated by the separation surface 16a into a component that is transmitted through the separation surface 16a and a component that is reflected.

The monitor light transmitted through the separation surface 16a of the beam splitter 16 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18. The monitor light of the P-polarized component that has passed through the polarization beam splitter 18 passes through the condenser lens 21 and the cylindrical lens 22, and then is incident on the monitor light receiving element 25 arranged adjacent to the light receiving element 23.

In this way, the beam splitter 12,
Half-wave plate 15 and polarization beam splitter 18
Is used to extract the necessary monitor light (P-polarized light), and the monitor light is received by the monitor light receiving element 25.
Since it is not necessary to provide the analyzer 24, the device cost can be reduced. Further, since the number of optical components of the optical pickup device can be reduced, the optical pickup device can be downsized.

[0025]

However, the conventional device has the following inconveniences.

That is, since the entire light flux reflected by the separation surface 12a of the beam splitter 12 is reflected by the increased reflection coating surface 12c, there is a light flux that does not pass through the condenser lens 21, and this light flux is diffusely reflected in the optical housing. However, the flare light is incident on the light receiving element 23 and the monitor light receiving element 25, and a detection error of a focusing error occurs, or an accurate monitor signal cannot be obtained. Also,
A part of the monitor light reflected by the separation surface 16a of the beam splitter 16 is incident on the light receiving element 17 for tracking error detection, which causes an inconvenience of causing a tracking error detection error.

Further, in the above-mentioned conventional apparatus, the astigmatism method is used to detect the focusing error. However, when the knife edge method is used to detect the focusing error, the following inconvenience occurs. Occurs.

FIG. 8 shows a conventional example of an optical pickup device for detecting a focusing error using the knife edge method. In the figure, the same parts as those in FIGS. 7A and 7B and the corresponding parts are designated by the same reference numerals.

In the figure, the signal light reflected by the separation surface 12a passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees. The signal light that has passed through the half-wave plate 15 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18.

The signal light of the S-polarized component reflected by the polarization beam splitter 18 is focused by the focusing lens 19 and is incident on the light receiving element 20. Further, the signal light of the P-polarized component that has passed through the polarization beam splitter 18 has 60 to 90% of its light flux after passing through the condenser lens 21.
It is reflected by the splitting mirror 27 forming the knife edge and is incident on the light receiving element 28 for detecting the tracking error, and the remaining portion of the signal light of the P-polarized component is splitting mirror 2.
The light is incident on a light receiving element 29 for detecting a focusing error, the light receiving surface of which is divided into two by a dividing line parallel to the ridge line 27a of FIG.

Then, a tracking error signal is formed based on the difference signal of the light receiving signals output from the two light receiving surfaces of the light receiving element 28, and the tracking error signal is formed from the light receiving signals output from the two light receiving surfaces of the light receiving element 29. A focusing error signal is formed based on the difference signal. Further, based on the sum of the light receiving signals of the light receiving elements 28 and 29 and the difference signal of the light receiving signals of the light receiving element 20, the magneto-optical disk 1
A magneto-optical signal which is a reproduction signal from the user area 4 is formed. Further, the light receiving element 20, the light receiving element 28, and
A reproduction signal from the preformatted area of the magneto-optical disk 14 is formed based on the total sum of the received light signals of the light receiving element 29.

On the other hand, the separation surface 12 of the beam splitter 12
The monitor light transmitted through a passes through the half-wave plate 15 and its plane of polarization is rotated by 45 degrees. The monitor light that has passed through the half-wave plate 15 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18. The monitor light of the P-polarized component that has passed through the polarization beam splitter 18 passes through the condenser lens 21 and then enters the monitor light receiving element 25.

In this case, the light flux of the monitor light which does not pass through the condenser lens 21 is diffusely reflected inside the optical housing and is incident on the light receiving element 29 and the monitor light receiving element 25 as flare light, causing a detection error of the focusing error. Or, there is a problem that an accurate monitor signal cannot be obtained. Further, a part of the light flux of the monitor light interferes with the split mirror 27 and is reflected, and then is incident on the light receiving element 28 for tracking error detection, which causes an inconvenience of causing a tracking error detection error.

The optical pickup device which detects the focusing error by using the critical angle method has the following disadvantages. FIG. 9 shows a conventional example of an optical pickup device for detecting a focusing error using the critical angle method. In the figure, the same parts as those in FIGS. 7A and 7B and the corresponding parts are designated by the same reference numerals.

In the figure, the signal light reflected by the separation surface 12a passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees. The signal light that has passed through the half-wave plate 15 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18.

The signal light of the S-polarized component reflected by the polarization beam splitter 18 is focused by the focusing lens 19 and is incident on the light receiving element 20. Further, the signal light of the P-polarized component that has passed through the polarization beam splitter 18 is incident on the beam splitter 30, and is separated by the separation surface 30a into a component that is transmitted through the separation surface 30a and a component that is reflected.

The signal light transmitted through the separation surface 30a of the beam splitter 30 is incident on the critical angle prism 31, and the signal light reflected by the surface 31a of the critical angle prism 31 is
The light-receiving surface is incident on a light-receiving element 32 for detecting a focusing error whose light-receiving surface is divided into two. Further, the signal light reflected by the separation surface 30a of the beam splitter 30 passes through the focusing lens 33, and then enters the light receiving element 34 for tracking error detection whose light receiving surface is divided into two.

Then, a tracking error signal is formed based on the difference signal of the light receiving signals output from the respective light receiving surfaces of the light receiving elements 34, and the tracking error signal is formed into the difference signal of the light receiving signals output from the respective light receiving surfaces of the light receiving elements 32. Based on this, a focusing error signal is formed. Further, a magneto-optical signal which is a reproduction signal from the user area of the magneto-optical disk 14 is formed based on the sum of the light-receiving signals of the light-receiving elements 32 and 34 and the difference signal of the light-receiving signals of the light-receiving element 20. Further, the light receiving element 32, the light receiving element 34, and the light receiving element 2
A reproduction signal from the preformatted area of the magneto-optical disk 14 is formed based on the sum of the received light signals of zero.

On the other hand, the separation surface 12 of the beam splitter 12
The monitor light transmitted through a passes through the half-wave plate 15 and its plane of polarization is rotated by 45 degrees. The monitor light that has passed through the half-wave plate 15 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18. The monitor light of the P-polarized component transmitted through the polarization beam splitter 18 is incident on the beam splitter 30 and its separation surface 3
At 0a, the light is separated into a component that is transmitted through the separation surface 30a and a component that is reflected. The monitor light reflected by the separation surface 30 a passes through the condenser lens 33 and then enters the monitor light receiving element 25.

In this case, the component of the monitor light transmitted through the separation surface 30a of the beam splitter 30 enters the critical angle prism 31, is reflected by the surface 31a, and is received by the light receiving element 3
Since two light beams are incident, there is a problem that a detection error occurs in the focusing error. Also, the beam splitter 3
There is also a luminous flux component of the monitor light that did not reach the separation surface 30a of 0, and this luminous flux component is incident on the light receiving element 32 as flare light.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical pickup device capable of preventing disturbance of other signals due to monitor light and appropriately determining the laser beam intensity. Has an aim.

[0042]

According to the present invention, a laser beam output from a semiconductor laser device is split by a beam splitter, and a laser beam that travels toward a recording medium as signal light and an output level of the semiconductor laser device are split. In the optical pickup device for forming a monitor laser beam for monitoring the, a reflecting surface provided on the beam splitter for totally reflecting a part of the light flux of the monitoring laser beam, and a reflected light from the reflecting surface A light receiving element for receiving light is provided, and a normal line of the reflecting surface is inclined with respect to an incident direction of the monitor laser beam.

Further, the laser beam output from the semiconductor laser device is split by using a beam splitter, and a laser beam that advances toward the recording medium as signal light and a monitor laser for monitoring the output level of the semiconductor laser device are split. In an optical pickup device that forms a beam and detects a focus error of the laser beam with respect to the recording medium by a knife edge method, a reflection that is provided in the beam splitter and totally reflects a part of the light beam of the monitoring laser beam. A surface and a light-receiving element for receiving the reflected light from the reflecting surface. The reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam and reflects from the reflecting surface. The shape is set so that the light does not interfere with the split mirror forming the knife edge.

Further, the laser beam output from the semiconductor laser element is split using a beam splitter, and a laser beam that advances toward the recording medium as signal light and a monitor laser for monitoring the output level of the semiconductor laser element are split. In an optical pickup device that forms a beam and detects a focus error of the laser beam with respect to the recording medium by an astigmatism method, it is provided in the beam splitter and totally reflects a part of the light beam of the monitor laser beam. A reflecting surface and a light receiving element for receiving the reflected light from the reflecting surface are provided. The reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam, and The shape is set so that the reflected light is composed of only the light flux component incident on the light receiving surface of the light receiving element. .

Further, the laser beam output from the semiconductor laser device is split using the first beam splitter,
A laser beam that travels toward the recording medium as signal light,
In an optical pickup device for forming a monitor laser beam for monitoring the output level of a semiconductor laser element and detecting a focus error of the laser beam with respect to the recording medium by a critical angle method, the optical pickup device is provided on the first beam splitter. A reflecting surface for totally reflecting a part of the light flux of the monitor laser beam, a second beam splitter for splitting the reflected light from the reflecting surface and the reflected light from the recording medium, and the second beam A light receiving element for receiving reflected light from the reflecting surface contained in one of the light beams split by the splitter is provided, and the reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam. At the same time, the shape thereof is set so that the reflected light from the reflecting surface consists only of the light flux component incident on the light receiving surface of the light receiving element. It is. Further, the inclination angle of the reflecting surface is such that the incident angle of the reflected light from the reflecting surface included in the other light beam split by the second beam splitter to the critical angle prism is the reflected light from the recording medium. It is advisable to set the size so that the value becomes smaller than the incident angle on the critical angle prism. Further, the inclination angle of the reflecting surface is such that the incident angle of the reflected light from the reflecting surface included in the other light beam split by the second beam splitter to the critical angle prism is near the Brewster angle. The size should be set to.

[0046]

Therefore, of the luminous flux of the monitor laser beam (monitor light), only the portion incident on the light receiving element for monitoring is reflected to the detection optical system side, so that a part of the monitor light becomes flare light. It is possible to prevent a situation in which the light is incident on another light receiving element.

[0047]

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

1A and 1B show an optical pickup device according to an embodiment of the present invention. This optical pickup device detects a focusing error by using the astigmatism method and a tracking error by using the push-pull method, as shown in FIG.
The same parts as (b) and corresponding parts are designated by the same reference numerals.

In the figure, the light reflected from the recording surface of the magneto-optical disk 14 (hereinafter referred to as signal light) reflected by the separation surface 12a passes through the half-wave plate 15 and its polarization plane is 45 degrees. Rotate. The signal light that has passed through the half-wave plate 15 is incident on the beam splitter 16, and the separation surface 16
At a, the light is separated into a component that transmits the separation surface 16a and a component that reflects it. The signal light reflected by the separation surface 16a of the beam splitter 16 passes through the focusing lens 40 and then,
The light is incident on a light receiving element 41 for detecting a tracking error whose light receiving surface is divided into two in the tracking direction.

Further, the separation surface 16 of the beam splitter 16
The signal light transmitted through a is incident on the polarization beam splitter 18, and the polarization beam splitter 18 causes the S
The polarization component is reflected and the P polarization component is transmitted.
The signal light of the S-polarized component reflected by the polarization beam splitter 18 is focused by the focusing lens 19 and is incident on the light receiving element 20. The signal light of the P-polarized component that has passed through the polarization beam splitter 18 passes through the condenser lens 21 and the cylindrical lens 22 and then has the detection light receiving element 2 for detecting a focusing error having a four-divided light receiving surface.
It is incident on 3.

Then, a track error signal is formed based on the difference between the light receiving signals obtained from the two light receiving surfaces of the light receiving element 41, and a predetermined calculation is applied to the light receiving signals obtained from the four light receiving surfaces of the light receiving element 23. A focusing error signal is formed. Further, a magneto-optical signal which is a reproduction signal from the user area of the magneto-optical disk 14 is formed based on the difference signal of the total sum of the light receiving signal of the light receiving element 20 and the light receiving signals obtained from the four light receiving surfaces of the light receiving element 23. To be done. Further, a reproduction signal from the preformatted area of the magneto-optical disk 14 is formed based on the sum of the light receiving signals of the light receiving element 20 and the light receiving element 23. In addition, the light receiving element 2 for monitoring
The output level of the semiconductor laser device 10 is controlled based on the light receiving signal output from the semiconductor laser device 5.

On the other hand, the separation surface 12 of the beam splitter 12
A surface 12b from which the light beam reflected by a is emitted from the beam splitter 12 is inclined at a predetermined angle, and a part of the surface 12b is provided with a reflection enhancing coating surface 12d.

Therefore, of the laser beam incident on the beam splitter 12 from the coupling lens 11, a part of the light beam of the component reflected by the separation surface 12a of the beam splitter 12 is the reflection-increasing coated surface 1 of the surface 12b.
It is reflected at 2d.

The light flux reflected by the increased reflection coating surface 12d is separated into a component that is transmitted by the separation surface 12a of the beam splitter 12 and a component that is reflected by the separation surface 12a, and the light flux that is transmitted through this separation surface 12a (hereinafter referred to as monitor light ) Passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees. 1 /
The monitor light that has passed through the two-wave plate 15 is incident on the beam splitter 16, and is separated by the separation surface 16a into a component that is transmitted through the separation surface 16a and a component that is reflected.

The monitor light transmitted through the separation surface 16a of the beam splitter 16 is incident on the polarization beam splitter 18, and the S polarization component is reflected and the P polarization component is transmitted by the polarization beam splitter 18. The monitor light of the P-polarized component that has passed through the polarization beam splitter 18 passes through the condenser lens 21 and the cylindrical lens 22, and then is incident on the monitor light receiving element 25 arranged adjacent to the light receiving element 23.

At this time, all the light flux reflected by the increased reflection coating surface 12d passes through the condenser lens 21 and is incident on the monitor light receiving element 25, so that flare light is generated as in the conventional device. Therefore, it is possible to avoid a situation in which the light receiving elements 23 and 25 are made incident, and it is possible to obtain an accurate focusing error signal. Further, the reliability of the light receiving signal from the monitor light receiving element 25 is also improved, and the output level of the semiconductor laser element 1 can be appropriately controlled.

Further, the separation surface 16 of the beam splitter 16
The monitor light reflected by a does not enter the light receiving element 41 because it is focused by the condenser lens 40. Therefore, the light receiving signals output from the two light receiving surfaces of the light receiving signal 41 include the monitor light of the monitor light. Since no component is included, an accurate tracking error signal can be obtained.

FIG. 2 shows an optical pickup device according to another embodiment of the present invention. This optical pickup device detects a focusing error by using the knife edge method, and the same portions as those in FIGS. 8 and 1 and the corresponding portions are denoted by the same reference numerals.

In the figure, in the laser beam incident on the beam splitter 12 from the coupling lens 11, a part of the light beam of the component reflected by the separation surface 12a of the beam splitter 12 has an increased reflection coating on the surface 12b. Surface 1
It is reflected at 2d.

The light beam reflected by the increased reflection coating surface 12d is separated into a component that is transmitted and a component that is reflected by the separation surface 12a of the beam splitter 12, and the beam splitter 1
The monitor light transmitted through the second separation surface 12a passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees.

The monitor light that has passed through the half-wave plate 15 is
The light enters the polarization beam splitter 18, and the polarization beam splitter 18 reflects the S polarization component and transmits the P polarization component. Polarizing beam splitter 1
The monitor light of the P-polarized component that has passed through 8 is collected by the condenser lens 21.
After passing through, the light is incident on the monitor light receiving element 25.

In this case, the tracking error signal, the focusing error signal, the magneto-optical signal, and the reproduction signal can be formed in the same manner as in the conventional device shown in FIG.

At this time, since all the light flux reflected by the increased reflection coating surface 12d passes through the condenser lens 21 and is incident on the monitor light receiving element 25, flare light is not generated. Further, since the light flux reflected by the increased reflection coating surface 12d does not interfere with the separation mirror 27, the light receiving element 28
No ambient light is incident on the.

Therefore, the reliability of the tracking error signal, the focusing error signal, and the light receiving signal from the monitor light receiving element 25 is improved, and the tracking control, the focusing control, and the output level control of the semiconductor laser element 1 are properly performed. Can be done.

FIG. 3 shows an optical pickup device according to still another embodiment of the present invention. This optical pickup device detects a focusing error using the critical angle method, and the same parts as those in FIGS. 9 and 1 and the corresponding parts are denoted by the same reference numerals.

In the figure, in the laser beam incident on the beam splitter 12 from the coupling lens 11, the component reflected by the separation surface 12a of the beam splitter 12 has a part of its light flux which is reflected by the surface 12b. Surface 1
It is reflected at 2d.

The light beam reflected by the increased reflection coating surface 12d is separated into a component that is transmitted and a component that is reflected by the separation surface 12a of the beam splitter 12, and the beam splitter 1
The monitor light transmitted through the second separation surface 12a passes through the half-wave plate 15 and its polarization plane is rotated by 45 degrees.

The monitor light that has passed through the half-wave plate 15 is
The light enters the polarization beam splitter 18, and the polarization beam splitter 18 reflects the S polarization component and transmits the P polarization component. Polarizing beam splitter 1
The monitor light of the P-polarized component that has passed through 8 enters the beam splitter 30 and is separated by the separation surface 30a.
Is separated into a component that transmits and a component that reflects. The monitor light reflected by the separation surface 30 a passes through the condenser lens 33 and then enters the monitor light receiving element 25.

In this case, the tracking error signal, the focusing error signal, the magneto-optical signal, and the reproduction signal can be formed in the same manner as in the conventional device shown in FIG.

In this case, the monitor light transmitted through the separation surface 30a of the beam splitter 30 has the surface 3 of the critical angle prism 31.
The incident angle at which the signal light is incident on the surface 31a is set to a value sufficiently smaller than the incident angle at which the signal light is incident on the surface 31a. Therefore, the incident angle at which the monitor light is incident on the surface 31a is always smaller than the critical angle. Becomes As a result, the monitor light is reflected on the surface 31.
Therefore, the monitor light does not enter the light receiving element 32, and the focusing error does not cause a detection error.

Further, if the incident angle when the monitor light is incident on the surface 31a of the critical angle prism 31 is set to a value near the Brewster angle at which the P polarized light can be completely transmitted, the monitor light at this time is the P polarized light. Almost all the luminous flux of the monitor light incident on the critical angle prism 31 can be emitted from the surface 31a, and the adverse effect of the monitor light can be further suppressed.

The size of the increased reflection coating surface 12d is
By setting the total light flux of the monitor light to be incident on the monitor light receiving element 25, it is possible to prevent the flare light from being generated and suppress the adverse effect of the monitor light.

In the above-described embodiment, the present invention is applied to the optical pickup device for recording / reproducing / erasing data on the magneto-optical disk, but the present invention records other optical recording media. The same applies to an optical pickup device used as a medium.

[0074]

As described above, according to the present invention,
Of the luminous flux of the monitor laser beam (monitor light), only the portion that is incident on the light receiving element for monitoring is reflected to the detection optical system side, so that part of the monitor light becomes flare light and the other light receiving element. It is possible to obtain an effect that it is possible to prevent a situation such as being incident on the.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical system of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an optical system of an optical pickup device according to another embodiment of the present invention.

FIG. 3 is a schematic diagram showing an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a configuration example of a semiconductor laser device.

FIG. 5 is a graph for explaining the influence of return light.

FIG. 6 is a schematic diagram showing an example of an optical system of a conventional optical pickup device.

FIG. 7 is a schematic diagram showing another example of the optical system of the conventional optical pickup device.

FIG. 8 is a schematic diagram showing still another example of the optical system of the conventional optical pickup device.

FIG. 9 is a schematic view showing still another example of the optical system of the conventional optical pickup device.

[Explanation of symbols]

 12 Beam splitter 12b surface 12d Enhanced reflection coated surface

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[Procedure amendment]

[Submission date] December 11, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical system of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an optical system of an optical pickup device according to another embodiment of the present invention.

FIG. 3 is a schematic diagram showing an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a configuration example of a semiconductor laser device.

FIG. 5 is a graph for explaining the influence of return light.

FIG. 6 is a schematic diagram showing an example of an optical system of a conventional optical pickup device.

FIG. 7 is a schematic diagram showing another example of the optical system of the conventional optical pickup device.

FIG. 8 is a schematic diagram showing still another example of the optical system of the conventional optical pickup device.

FIG. 9 is a schematic view showing still another example of the optical system of the conventional optical pickup device.

[Explanation of Codes] 12 Beam Splitter 12b Surface 12d Enhanced Reflection Coated Surface

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 4]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

[Figure 9]

Claims (6)

[Claims] 1. A laser beam output from a semiconductor laser device is split using a beam splitter, and a laser beam that advances toward a recording medium as signal light and a monitor laser for monitoring the output level of the semiconductor laser device are provided. In an optical pickup device for forming a beam, the beam splitter is provided with a reflecting surface for totally reflecting a part of the light flux of the monitoring laser beam, and a light receiving element for receiving the reflected light from the reflecting surface. An optical pickup device characterized in that the reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam. 2. A laser beam output from a semiconductor laser device is split using a beam splitter, and a laser beam that advances toward a recording medium as signal light and a monitor laser for monitoring the output level of the semiconductor laser device are split. In an optical pickup device that forms a beam and detects a focus error of the laser beam with respect to the recording medium by a knife edge method, a reflection that is provided in the beam splitter and totally reflects a part of the light beam of the monitoring laser beam. A surface and a light-receiving element for receiving the reflected light from the reflecting surface. The reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam and reflects from the reflecting surface. An optical pick characterized in that its shape is set so that the light does not interfere with the split mirror forming the knife edge. Up device. 3. A laser beam output from a semiconductor laser device is split using a beam splitter, and a laser beam that travels in the direction of a recording medium as signal light and a monitor laser for monitoring the output level of the semiconductor laser device are split. In an optical pickup device that forms a beam and detects a focus error of the laser beam with respect to the recording medium by an astigmatism method, it is provided in the beam splitter and totally reflects a part of the light beam of the monitor laser beam. A reflecting surface and a light receiving element for receiving the reflected light from the reflecting surface are provided, and the reflecting surface has a normal line inclined with respect to the incident direction of the monitor laser beam,
The optical pickup device is characterized in that the shape thereof is set so that the reflected light from the reflecting surface is composed of only the light flux component incident on the light receiving surface of the light receiving element. 4. A laser beam outputted from a semiconductor laser device is split by using a first beam splitter, and a laser beam traveling toward a recording medium as signal light and an output level of the semiconductor laser device are monitored. In an optical pickup device that forms a monitor laser beam and detects a focus error of the laser beam with respect to the recording medium by a critical angle method, the optical pickup device is provided in the first beam splitter and Included in one of the light beams split by the second beam splitter, a reflecting surface that totally reflects the light, a second beam splitter that splits the reflected light from the reflecting surface and the reflected light from the recording medium. A light receiving element for receiving the reflected light from the reflecting surface is provided, and the reflecting surface is arranged in the incident direction of the monitor laser beam. On the other hand, its normal line is inclined, and its shape is set so that the reflected light from the reflecting surface is composed of only the light flux component incident on the light receiving surface of the light receiving element. apparatus. 5. The inclination angle of the reflecting surface is such that the incident angle of the reflected light from the reflecting surface included in the other light beam split by the second beam splitter to the critical angle prism is from the recording medium. 5. The optical pickup device according to claim 4, wherein the size of the reflected light is set to be a value smaller than the angle of incidence of the reflected light on the critical angle prism. 6. The tilt angle of the reflecting surface is such that the incident angle of the reflected light from the reflecting surface contained in the other light beam split by the second beam splitter to the critical angle prism is near the Brewster angle. 5. The optical pickup device according to claim 4, wherein the size is set so that