JPH0612696A - Optical pickup - Google Patents

Abstract

PURPOSE:To enhance the detective accuracy of a monitor beam and to reduce the light quantity of an incident stray beam on a reproducing light receiving system by receiving the converged monitor beam. CONSTITUTION:By an optical pickup 1, the beam L1 is reflected partially by a mirror 18 and the monitor beam LM is generated by inserting half mirror 18 between a collimate lens 12 and an objective lens 14. By the pickup 1, the monitor beam LM is made incident on a photodetector 20 and the light quantity of the beam L1 is monitored by the output signal of the detector. In the photodetector 20, a diode chip 22 is formed into a small shape and a circular arc shape projecting part 24 is formed integrally on the front surface of the package of the chip 22. Thus, the projecting part 24 plays the role of a lens and the monitor beam LM is converged by the projecting part 24 and made incident on the chip 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup, and more particularly to an optical pickup which can be applied to a front monitor system to improve the light amount detection accuracy of a light beam applied to an optical recording medium.

[0002]

2. Description of the Related Art Conventionally, in an optical pickup such as a magneto-optical disk device, the light amount of a light beam emitted from a laser diode is monitored and the light amount of the light beam is kept at a constant value.

In the front monitor system in which a part of the light beam is separated to monitor the amount of light, a beam splitter is arranged on the optical path of the light beam to separate a part of the light beam at a constant ratio. .

Further, in this front monitor system, the separated light beam (hereinafter referred to as monitor light) is incident on a light receiving element to detect the light amount of the monitor light.

Thus, in the front monitor system, the light quantity of the light beam is controlled to a constant value based on the detection result of the monitor light quantity.

[0006]

By the way, in order to properly control the light amount of the light beam in the front monitor system, the light amount of the monitor light incident on the light receiving element is always adjusted with respect to the light beam emitted from the laser diode. It is necessary to maintain a fixed ratio.

Therefore, as shown in FIG. 2, in the conventional front monitor system, the monitor light LM is received by using the light receiving element 1 having a sufficiently large light receiving area M with respect to the beam diameter L of the monitor light LM. Thus, even if the beam diameter L of the monitor light LM changes with the change of the beam diameter of the light beam, the monitor light LM can be reliably received.

However, in the light receiving element 1 having a large light receiving area M as described above, since the electrostatic capacitance becomes large,
There is a problem that the frequency characteristic of the spectral quantity detection result cannot be improved and the frequency characteristic of the light quantity control is deteriorated.

Further, the reflected light beam reflected by the incident surface of the light receiving element 1 becomes stray light and is incident on a light receiving system (hereinafter referred to as a reproduction light receiving system) for receiving the reflected light from the optical recording medium, whereby the reproduction signal is reproduced. There is also a problem that the SN ratio deteriorates.

One method for solving this problem is shown in FIG.
As shown in FIG. 3, there is a method of arranging the aperture 2 on the optical path of the monitor light LM and generating the monitor light LM1 having a smaller beam diameter from the monitor light LM.

According to this method, the light receiving element 4 having a small light receiving area M can be used, and the frequency characteristic of the spectral quantity control can be improved.

In this method, however, when the beam position of the monitor light LM changes and deviates from the aperture of the aperture 2, the light amount ratio of the monitor light LM1 to the light beam cannot be held at a constant value, and the light amount of the light beam is eventually reduced. It cannot be detected correctly.

Further, the monitor light LM incident on the aperture 2
Even when the beam diameter L of the light beam changes, the light amount ratio of the monitor light LM1 to the light beam cannot be maintained at a constant value, and the light amount detection accuracy of the light beam deteriorates. Also in this case, stray light from the aperture 2 and the light receiving element 4 cannot be prevented.

The present invention has been made to solve the above problems, and provides an optical pickup capable of improving the detection accuracy of monitor light and reducing the amount of stray light incident on the reproduction light receiving system. The purpose is to

[0015]

According to the present invention, the above object is to irradiate an optical recording medium with a light beam emitted from a laser diode, and to separate the light beam to form monitor light. In an optical pickup for detecting the light quantity of the light beam via the monitor light, light including light collecting means for collecting the monitor light and light receiving means for receiving the monitor light collected by the light collecting means. Achieved by pickup.

The light receiving means can be formed integrally with the light collecting means by forming the package on the incident surface side of the monitor light into a lens shape.

Further, the light receiving means may be configured so that the lens-shaped portion of the package is inserted into a predetermined through hole to position and hold it.

[0018]

For convenience of understanding, an example of the operation will be described with reference to the reference numerals of the embodiments. According to the configuration described above, the monitor light LM formed from the light beam L1 can be received by the light receiving means 22 having a small shape without leakage.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

The examples described below are preferred specific examples of the present invention, and therefore, various technically preferable limitations are attached thereto. However, the scope of the present invention is particularly limited in the following description. These aspects are not limited unless otherwise stated.

FIG. 1 is a schematic diagram showing an optical pickup of a magneto-optical disk device according to a preferred embodiment of the present invention.

In the figure, in the construction of the optical pickup 8,
Since the parts denoted by the same reference numerals as those in the conventional example have the same configuration as this, duplicate description will be omitted.

The optical pickup 8 emits a light beam L1 having a predetermined plane of polarization from the laser diode and converts it into parallel rays by the collimator lens 12.

Further, the optical pickup 8 includes the objective lens 1
This light beam L1 is focused on the information recording surface of the magneto-optical disk 16 via 4 and the resulting reflected light beam L2 is received by the objective lens 14 and guided to the light receiving system.

As a result, in the optical pickup 1,
With the light beam L1 condensed on the magneto-optical disk 16,
A predetermined modulation magnetic field is applied by means (not shown), and predetermined information determined by this modulation magnetic field can be thermomagnetically recorded.

On the other hand, during reproduction, the record information can be reproduced on the basis of the output signal of the light receiving system.

Further, in this embodiment, the optical pickup 1 inserts a half mirror 18 between the collimator lens 12 and the objective lens 14, and the half mirror 18 partially reflects the light beam L1 to generate the monitor light LM.

The optical pickup 1 allows the monitor light LM to be incident on the light receiving element 20, so that the light amount of the light beam L1 can be monitored via the output signal of the light receiving element 20.

Here, the light receiving element 20 is formed of a photodiode, and the diode chip 22 forming the photodiode is formed in a small shape. In the present embodiment, the diode chip 22 has an arc shape on the front surface of the package. The protrusion 24 is integrally formed. This allows
Since the arcuate projection 24 plays the role of a lens, the arcuate projection 24 collects the monitor light LM and makes it incident on the diode chip 22.

As a result, in the optical pickup 1,
The monitor light LM1 reflected by the half mirror 18 enters the diode chip 22 without leakage.

Therefore, the light receiving element 20 can receive the monitor light LM held at a constant ratio determined by the reflectance of the half mirror 18 with respect to the light quantity of the light beam L1. Can be monitored.

Further, when the beam diameter of the light beam L1 is changed by changing the beam diameter of the monitor light LM by collecting and receiving the light beam L1, the monitor light LM is further changed.
Reliable diode chip 2 even if the beam position changes
The light can be received at 2, and the detection accuracy of the spectral amount can be improved.

In particular, if the light beam L1 is collected and received as described above, the shape of the diode chip 22 can be reduced,
Capacitance can be reduced. Thereby, the high frequency characteristics of the light receiving element 20 can be improved, and the detection accuracy can be improved.

Further, since the shape of the diode chip 22 can be miniaturized, the amount of extraneous light incident on the diode chip 22 can be reduced, and the monitoring accuracy of the light beam L1 can be improved.

Further, in the optical pickup 1, since the front surface of the package is formed in an arc shape, the light beam reflected on the front surface of the package can be held so as not to go backward in the optical path of the monitor light LM. As a result, the amount of stray light can be reduced, and the SN ratio of the reproduced signal can be improved.

Further, in this embodiment, the optical pickup 1 is formed by arranging optical components such as the laser diode 10 on a predetermined metal base. At this time, in the light receiving element 20, the front projection 24 is formed on the metal base. After it is inserted into the through hole and positioned, it is bonded and held by a predetermined adhesive.

As a result, in the optical pickup 1,
The front projection 24 of the light receiving element 20 is effectively used for positioning and holding, which simplifies the assembly work and simplifies the overall configuration.

[0038]

As described above, according to the present invention, since the monitor light can be reliably received by using the semiconductor chip having a small shape, the accuracy of detecting the light amount of the light beam can be improved, and the light can be generated on the front surface of the package. Since stray light can be prevented in advance, it is possible to reduce the amount of stray light that enters the reproduction light receiving system.

[Brief description of drawings]

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

FIG. 2 is a schematic view showing an example of a monitor light receiving unit of a conventional optical pickup.

FIG. 3 is a schematic view showing another example of a monitor light receiving unit of a conventional optical pickup.

[Explanation of symbols]

 1, 4, 20 Light receiving element 10 Laser diode 18 Half mirror 22 Projection 24 Diode chip

Claims (3)

[Claims] 1. Light for irradiating an optical recording medium with a light beam emitted from a laser diode, separating the light beam to form monitor light, and detecting the light amount of the light beam via the monitor light. An optical pickup, comprising: a light collecting means for collecting the monitor light, and a light receiving means for receiving the monitor light collected by the light collecting means. 2. The optical pickup according to claim 1, wherein the light-receiving unit is formed integrally with the light-collecting unit by forming a package on the incident surface side of the monitor light into a lens shape. 3. The optical pickup according to claim 2, wherein the light receiving unit is positioned and held by inserting a lens-shaped portion of the package into a predetermined through hole.