JPH06131677A - Optical head device - Google Patents

Abstract

PURPOSE:To relax the mounting precision of a bisected photodetector and to suppress track aberration. CONSTITUTION:A half mirror 6a is employed as a rising mirror 6 arranged at the front stage of an objective lens 7, and furthermore, the bisected photodetector 2a is arranged at the back of the half mirror 6a. Light transmitting the half mirror 6a out of reflected light from a magneto-optical disk 8 is received by the bisected photodetector 2a, and a tracking error can be detected by the output signal of the photodetector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used in a magneto-optical recording / reproducing apparatus, and more particularly to an optical head device capable of effectively detecting a tracking error and controlling the light amount of a light emitting element.

[0002]

2. Description of the Related Art In recent years, a demand for a small-sized and large-capacity memory has remarkably increased, and various products have been developed. Among them, what is greatly expected is a magneto-optical recording / reproducing apparatus (hereinafter, also referred to as “magneto-optical disk apparatus”) that records / reproduces by using interaction between light and magnetism (Kerr effect). .

The magneto-optical disk device is currently under intensive development and improvement. The most important elemental technology among them is
It is a part of an optical head device (hereinafter, also simply referred to as “optical head”) for reading and writing data on the magneto-optical disk.

FIG. 7 is a diagram showing a first system configuration example of a conventional optical head. Light output from a semiconductor laser (LD) 1 is converted into parallel light by a collimator lens 4, and a beam splitter 5 is used. Through the objective lens 7 to form a spot on the magneto-optical disk 8.

The reflected light from the magneto-optical disk 8 passes through the objective lens 7, is reflected by the rising mirror 6, is reflected by the beam splitter 5, passes through the half-wave plate 9 and the converging lens 10, and is a polarized beam splitter 11. The polarized light is separated by, and one is incident on the 4-division photodetector 3 and the other is incident on the 2-division photodetector 2.

The tracking error detection related to the present invention is performed by the push-pull method using the two-division photodetector 2.

The signals from the two-division photodetector 2 and the four-division photodetector 3 are differentially detected to reproduce information, and
A focus error is detected by the 4-division photodetector 3.

FIG. 8 is a diagram showing a second system configuration example of a conventional optical head, which is an example of a separation type optical head.
The parts corresponding to those of the conventional example in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

In the separation type optical head of FIG. 8, the optical head is divided into two parts between the part where the light beam becomes parallel light, that is, between the beam splitter 5 and the rising mirror 6.

That is, the objective lens 7 and the rising mirror 6
The movable part 20 is constituted by only the other part, and the other optical elements are arranged on the fixed part 30. Further, the movable portion 20 is configured to be movable in both directions as indicated by an arrow a. In this separation type optical head device, the movable part is significantly lightened, and the access performance to the magneto-optical disk 8 is improved.

Also in this conventional example, the tracking error is detected by the push-pull method using the two-division photodetector 2.

FIG. 9 is a diagram showing a third system configuration example of a conventional optical head device, which is an example of a separation type optical head. Note that the portions corresponding to those in the conventional example in FIG. 8 are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

In the conventional example of FIG. 9, the beam splitter 5a is used.
Partially reflects the light from the semiconductor laser (LD) 1, and the partially reflected light irradiates the light quantity monitoring photodetector 12. That is, the light quantity monitor (monitoring) photodetector 12 detects the light emission quantity of the semiconductor laser (LD) 1, and the light quantity control output signal from the light quantity detection photodetector 12 causes the light quantity of the semiconductor laser (LD) 1 to be emitted. To control.

Also in this conventional example, the tracking error is detected by the push-pull method using the two-division photodetector 2.

[0015]

The above-described state of detecting the tracking error in the conventional optical system is shown in FIG. 10 for explaining the tracking error detection. The two-division photodetector 2 has two light receiving elements PDa and PDb.
The reflected light from the magneto-optical disk 8 connects the beam spots on the boundary lines X1 and X2 via the polarization beam splitter 11 (portions indicated by circles in the figure).
Then, the tracking error is detected by the push-pull method based on the detection signals of the light receiving elements PDa and PDb.

However, in the conventional configuration, the light receiving element PD
Since the beam spot diameters on a and PDb are small, the positional accuracy of the light receiving elements PDa and PDb is strictly required, and it takes a lot of time for adjustment. In addition, there is a problem that a track shift occurs due to a position shift due to a change in temperature.

Further, in the case of the separation type optical head shown in the conventional example of FIGS. 8 and 9, the light emitted from the fixed portion 30 and
The problem that the track deviation occurs due to the deviation of the optical axis of the reflected light from the movable portion 20 is added to the problem.

Further, in the separation type optical head shown in the conventional example of FIG. 9, the light emission amount of the semiconductor laser (LD) 1 is detected by the beam splitter 5a in the fixed portion 30 and the light amount monitor photodetector 12. However, the amount of light actually irradiated onto the magneto-optical disk could not be accurately monitored.

The present invention has been made in view of the above problems, and it is a first object of the present invention to provide an optical head device capable of reducing the mounting accuracy of a light receiving element for detecting a tracking error and shortening the adjustment time. A second object is to provide an optical head device capable of accurately monitoring the irradiation light to the magneto-optical disk.

[0020]

According to another aspect of the present invention, there is provided an optical head device which reflects light from a light emitting element received through an optical system in the head toward an objective lens and reflects light received from the objective lens. In an optical head device including an optical element that reflects toward an optical system in a head, a first optical element that partially reflects and partially transmits incident light through the optical element.
In addition to the half mirror 6a as the optical element, the two-division photodetector 2a or the light quantity monitor photodetector 12a as the first light receiving element for detecting the light transmitted through the first optical element is provided. Characterize.

In the optical head device according to the second aspect, the two-divided photodetector 2a as the first light receiving element receives the light reflected by the optical recording medium and transmitted through the half mirror 6a as the first optical element. The optical head device according to claim 1, which receives light.

An optical head device according to a third aspect of the present invention detects a tracking error based on an output signal of a two-divided photodetector 2a as a first light receiving element. It is a device.

In the optical head device according to the fourth aspect, the light quantity monitor photodetector 12a as the first light receiving element is the incident light from the light emitting element, and the half mirror 6a as the first optical element is used. The optical head device according to claim 1, wherein the transmitted light is received.

An optical head device according to a fifth aspect of the present invention uses a semiconductor laser (LD) 1 as a light emitting element based on an output signal of a light quantity monitor photodetector 12a as a first light receiving element.
5. The optical head device according to claim 4, wherein the light emission amount of the optical head device is controlled.

An optical head device according to a sixth aspect of the present invention is an optical head including a fixed portion 30 as a fixed optical system and a movable portion 20 as a movable optical system for track access. Half mirror 6a as an optical element of the above, and a two-split photodetector 2 as a first light receiving element
6. The optical head device according to claim 1, wherein a or the light quantity monitor photodetector 12a is disposed in the movable portion 20.

[0026]

In the optical head device having the structure described in claim 1, the rising mirror located in front of the objective lens 7 is a half mirror 6a, and the light transmitted through the half mirror 6a is divided into two photodetectors 2a or a light quantity monitor. It is detected by the optical detector 12a.

By doing so, the two-divided photodetector 2a can detect a beam having a large spot diameter, and the mounting accuracy is relaxed. Further, since the light quantity monitor photodetector 12a monitors the quantity of light immediately before it is irradiated onto the magneto-optical disk 8, the irradiation light on the magneto-optical disk 8 can be accurately monitored.

In the optical head device of the second aspect of the present invention, the rising mirror positioned in front of the objective lens 7 is the half mirror 6a, and the light reflected from the magneto-optical disk 8 that is transmitted through the half mirror 6a. 2 split photodetector 2a
Detect with.

By doing so, the two-divided photodetector 2a can detect a beam having a large spot diameter, and the mounting accuracy thereof is relaxed.

In the optical head device of the third aspect of the invention, the rising mirror located in front of the objective lens 7 is the half mirror 6a, and the light reflected from the magneto-optical disk 8 that is transmitted through the half mirror 6a. 2 split photodetector 2a
Then, the tracking error is detected from the output signal of the two-division photodetector 2a.

By doing so, the two-divided photodetector 2a can detect a beam having a large spot diameter, the mounting accuracy is relaxed, and the tracking error can be easily detected. Become.

According to another aspect of the optical head device of the present invention, the rising mirror located in front of the objective lens 7 is a half mirror 6a, and the amount of light transmitted from the light emitting element that passes through the half mirror 6a is monitored. It is detected by the optical detector 12a.

By doing so, the light quantity monitor photodetector 12a can monitor the irradiation light to the magneto-optical disk 8 immediately before it, so that the irradiation light to the magneto-optical disk 8 can be accurately monitored.

In the optical head device having the structure described in claim 5, the rising mirror positioned in front of the objective lens 7 is the half mirror 6a, and the half mirror 6a of the light from the semiconductor laser (LD) 1 is transmitted. The emitted light is detected by the light amount monitor photodetector 12a, and the light emission amount of the semiconductor laser (LD) 1 is controlled by the light amount control output signal of the light amount monitor photodetector 12a.

By doing so, the light quantity monitor photodetector 12a can monitor the irradiation light to the magneto-optical disk 8 immediately before it, so that the irradiation light to the magneto-optical disk 8 can be accurately controlled.

In the optical head device having the structure described in claim 6, the present invention is applied to the separation type optical head, and the objective lens 7, the half mirror 6a, the two-divided photodetector 2a or the light quantity monitor photodetection is used. The container 12a to the movable part 20
To place. With such a configuration, the following effects can be obtained in addition to the good access performance to the magneto-optical disk 8 as the separation type optical head.

(1) In the case of using the two-division photodetector 2a, the two-division photodetector 2a can detect a beam having a large spot diameter, and its mounting accuracy is relaxed. Further, it becomes easy to detect the tracking error. Further, the track shift due to the change in the relative positional relationship between the movable portion 20 and the fixed portion 30 is eliminated.

(2) When the light quantity monitor photodetector 12a is used, the quantity of light is monitored immediately before the irradiation on the magneto-optical disk 8, so that the irradiation light on the magneto-optical disk 8 can be accurately monitored and controlled. .

[0039]

1 is a diagram showing a system configuration of a first embodiment of an optical head device according to the present invention.
It is an embodiment commonly corresponding to the described invention. Note that FIG.
The same reference numerals are attached to the portions corresponding to the conventional example of
The description will be omitted as appropriate.

In the embodiment of FIG. 1, the rising mirror is a half mirror 6a (first optical element) which is a semi-transparent mirror, and a two-split photodetector 2a (first light receiving element) is arranged behind the half mirror 6a. To do.

The reflected light from the magneto-optical disk 8 is condensed by the objective lens 7 to become parallel light, and the half mirror 6a.
Is partially transmitted to illuminate the two-division photodetector 2a. A tracking error is detected by the output signal of the 2-split photodetector 2a.

FIG. 2 is a diagram for explaining the effect of the present invention, showing the state of the beam spots generated on the two light receiving elements PDa and PDb forming the two-divided photodetector 2a. is there.

FIG. 2A shows the case of the conventional example (FIG. 7), and the spot diameter of the beam spot (the portion indicated by a circle in the figure) is small, and the boundary line (X1, X1) between the two light receiving elements PDa and PDb. It is quite difficult to perform the alignment so that the center of the beam spot is located on X2).

FIG. 2B shows the case of this embodiment, in which the spot diameter is larger than that of the conventional example and two light receiving elements PD are provided.
It is not so difficult to adjust so that the center of the beam spot is located on the boundary line (X1, X2) of a and PDb. For example, if the spot diameter in this embodiment is 10 times the conventional spot diameter, the positional accuracy of the light receiving element is relaxed 10 times.

Therefore, the time for adjusting the attachment of the two-divided photodetector 2a is shortened, and the cost can be reduced. Also,
The permissible displacement range of the light receiving element due to environmental changes such as temperature also increases.

FIG. 3 is a diagram showing a system configuration of a second embodiment of the optical head device of the present invention, which is an embodiment commonly corresponding to the inventions described in claims 1, 2 and 3. The present embodiment is an example in which the present invention is applied to a finite optical system using an objective lens 7a which is an aspherical lens and a half mirror 6b.

Of the reflected light from the magneto-optical disk 8, the light that passes through the half mirror 6b is detected by the two-division photodetector 2a to obtain the tracking error, and the effect is the first embodiment (FIG. This is the same as in 1).

FIG. 4 is a diagram showing the system configuration of a third embodiment of the optical head device of the present invention.
6 is an embodiment commonly corresponding to the inventions described in Nos. 6 and 6, and is an embodiment in which the present invention is applied to a separation type optical head. In addition,
The parts corresponding to those in the conventional example of FIG.

In the example of FIG. 4, the two-division photodetector 2a is arranged behind the half mirror 6a in the movable part 20 to obtain the tracking error.

Although the basic operation and effect are the same as in the case of the first embodiment of FIG. 1, in this example, the emitted light from the fixed part 30 and the movable part, which have been a serious problem in the conventional example, are present. It is possible to avoid the problem of track deviation due to the deviation of the optical axis of the reflected light from 20.

FIG. 5 is a diagram showing a system configuration of a fourth embodiment of the optical head device of the present invention.
6 is an embodiment commonly corresponding to the inventions described in Nos. 6 and 6, and is an embodiment in which the present invention is applied to a separation type optical head. In addition,
The parts corresponding to those in the conventional example of FIG.

In this example, the structure of the fixed part 30 is partly different from that of the example of FIG. 4, but the movable part 20 to which the present invention is applied.
Have the same configuration. Therefore, the effect is the same.

Although the structure of the fixing portion 30 is not directly related to the present invention, a brief description will be given.
Is arranged in front of the beam splitter 5, and the reflected light from the magneto-optical disk 8 is reflected by the polarization beam splitter 11a.
The separated light is irradiated onto the four-division photodetector 14a and the photodetector 14b on the composite photodetector 14, respectively. The composite photodetector 14 is a package of a 4-division photodetector 14a and a photodetector 14b.

FIG. 6 is a diagram showing a system configuration of a fifth embodiment of the optical head device of the present invention, which is an embodiment commonly corresponding to the inventions described in claims 1, 4, 5 and 6 of the present invention. Is. Further, it is an embodiment in which the present invention is applied to a separation type optical head. Note that the portions corresponding to those of the conventional example in FIG. 9 are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

In the embodiment of FIG. 6, the light quantity monitor photodetector 12a is provided on the lateral side of the half mirror 6a (the position shown in FIG. 6).
To place. The light amount monitor photodetector 12a receives the light from the semiconductor laser (LD) 1 that has passed through the half mirror 6a. Then, the light emission amount of the semiconductor laser (LD) 1 is controlled by the output signal of the light amount monitor photodetector 12a.

In the embodiment shown in FIG. 6, the light quantity monitor photodetector 12a monitors the quantity of light immediately before it is irradiated onto the magneto-optical disk 8, so that the irradiation light on the magneto-optical disk 8 can be controlled accurately. In addition, the problem of the shift of the optical axes of the movable portion 20 and the fixed portion 30 in the separation type optical head is not affected.

[0057]

According to the optical head device having the structure described in claim 1, since the rising mirror 6 of the conventional example is the half mirror 6a, various controls are performed by utilizing the light partially transmitted through the half mirror 6a. It can be used for.

According to the optical head device of the second aspect, since the rising mirror 6 of the conventional example is the half mirror 6a, and the two-divided photodetector 2a is arranged behind it, the magneto-optical disk 8 is used. Reflected light can be detected with a large spot diameter, and the mounting accuracy of the two-division photodetector 2a can be relaxed.

According to the optical head device of the third aspect, the rising mirror 6 of the conventional example is the half mirror 6a, and the two-split photodetector 2a is arranged behind the half mirror 6a. Since the tracking error is detected by the output signal, the mounting accuracy of the two-divided photodetector 2a can be relaxed and the accurate tracking control can be easily performed.

According to the optical head device having the structure described in claim 4, the rising mirror 6 of the conventional example is the half mirror 6a, the photodetector 12a for light quantity monitor is arranged on the side thereof, and the magneto-optical disk 8 is provided. Since the amount of light immediately before irradiating the optical disk is monitored, the irradiation light to the magneto-optical disk 8 can be accurately monitored.

According to the optical head device having the structure described in claim 5, the rising mirror 6 of the conventional example is a half mirror 6a, and a photodetector 12a for light quantity monitor is arranged on the side of the half mirror 6a. Since the amount of light emitted from the semiconductor laser (LD) 1 is controlled by the output signal of the photodetector 12a for use, the amount of light immediately before being irradiated onto the magneto-optical disk 8 can be monitored, and the irradiation light on the magneto-optical disk 8 can be accurately measured. Can be controlled.

According to the optical head device having the structure described in claim 6, the objective lens 7, the half mirror 6a, the two-divided photodetector 2a, or the photodetector 12a for monitoring the light amount is provided in the movable part 20.
In addition to the good access performance with respect to the magneto-optical disk 8 as the separation type optical head,
It is possible to avoid the problem that the track shift occurs due to the optical axis shift between the emitted light from and the reflected light from the movable portion 20, and further, in the case of using the two-division photodetector 2a, the two-division photodetection is performed. The device 2 can detect a beam having a large spot diameter, and its mounting accuracy is relaxed. When the light quantity monitor photodetector 12a is used, the quantity of light immediately before being irradiated on the magneto-optical disk 8 is monitored, so that the irradiation light on the magneto-optical disk 8 can be controlled accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing a system configuration of a first embodiment of an optical head device of the present invention.

FIG. 2 is a diagram for explaining the effect of the present invention.

FIG. 3 is a diagram showing a system configuration of a second embodiment of the optical head device of the present invention.

FIG. 4 is a diagram showing a system configuration of a third embodiment of the optical head device of the present invention.

FIG. 5 is a diagram showing a system configuration of a fourth embodiment of the optical head device of the present invention.

FIG. 6 is a diagram showing a system configuration of a fifth embodiment of the optical head device of the present invention.

FIG. 7 is a diagram showing a first system configuration example of a conventional optical head device.

FIG. 8 is a diagram showing a second system configuration example of a conventional optical head device.

FIG. 9 is a diagram showing a third system configuration example of a conventional optical head device.

FIG. 10 is a diagram illustrating detection of a tracking error.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 semiconductor laser (LD) 2 2-split photodetector 2a 2-split photodetector (first light receiving element) 3 4-split photodetector 4, 4a Collimator lens 5, 5a Beam splitter 6a, 6b Half mirror (first Optical element) 7, 7a Objective lens 8 Magneto-optical disk 9 1/2 wavelength plate 10 Converging lens 11, 11a Polarization beam splitter 12 Light quantity monitor photodetector 12a Light quantity monitor photodetector (first light receiving element) 13 Light Detector 14 Composite photodetector

Claims (6)

[Claims] 1. The light from a light emitting element received through an optical system in the head is reflected toward an objective lens, and
In an optical head device including an optical element that reflects light received from an objective lens toward an optical system in the head, the optical element is a first optical element that partially reflects incident light and partially transmits it. And an optical head device comprising a first light receiving element for detecting light transmitted through the first optical element. 2. The optical head device according to claim 1, wherein the first light receiving element receives the light reflected by the optical recording medium and transmitted through the first optical element. 3. Based on the output signal of the first light receiving element,
The optical head device according to claim 2, wherein a tracking error is detected. 4. The optical head device according to claim 1, wherein the first light receiving element receives the incident light from the light emitting element and the light transmitted through the first optical element. 5. Based on the output signal of the first light receiving element,
The amount of light emitted from the light emitting element is controlled.
The optical head device described. 6. An optical head comprising a fixed optical system and a movable optical system for track access, wherein an objective lens, a first optical element and a first light receiving element are arranged in the movable optical system. The optical head device according to claim 1, 2, 3, 4, or 5.