JPH0428028A - Optical head device - Google Patents

Abstract

PURPOSE:To miniaturize a device by introducing the emitted light of a laser beam source to a beam splitter again with a reflecting mirror, introducing it to an optical system for signal detection via the beam splitter, and monitoring the emitted light quantity of the laser beam source. CONSTITUTION:The reflecting mirror 6 on which the emitted light of the laser beam source 1 separated with the beam splitter 5 is reflected is provided, and the emitted light of the laser beam source 1 is introduced again to the beam splitter 5 with the reflecting mirror 6, and it is introduced to the optical systems 10-15 for signal detection via the beam splitter 5, and the emitted light quantity of the laser beam source 1 is monitored in the optical systems 10-15. In such a way, a laser emitted beam reflected on the beam splitter 5 is folded at the reflecting mirror 6, and monitored light is detected in the optical systems 10-15. Therefore, the reflecting mirror 6 can be formed integrally with the emission plane of the beam splitter 5, which requires no waste space. Thereby, the miniaturization of the device can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk device that records and reproduces information using light, and particularly to an optical head device thereof.

[Conventional technology]

Among optical disks, magneto-optical disks have been widely put into practical use as they enable recording, reproduction and erasing.

This optical head device for a magneto-optical disk generally has a configuration as shown in FIG. 5, for example.

According to this optical head device, the light emitted from the semiconductor laser l becomes parallel light by the collimating lens 2, and
The light is focused on the recording medium 4 as a minute spot. The reflected light from the recording medium 4 is separated by a beam splitter 5 and guided to a signal detection optical system. Magneto-optical disks generally reproduce information by rotating polarization. In signal detection, 1/
The polarization direction is rotated by approximately 45 degrees by the two-wavelength plate 10, and the polarization direction is rotated by ±45 degrees by the polarization beam splitter 12 through the converging lens 11.
The light is separated into polarized light components in the degree direction and detected by photodetectors 13 and 14. An information signal for magneto-optical recording can be obtained from the differential signals output from the rain detectors 13 and 14. In addition, the photodetector 13 receives a tracking error signal using a push-pull method.
The photodetector 14 is combined with a cylindrical lens 15 to obtain a focus error signal using an astigmatism method.

[Problem to be solved by the invention]

In the above optical head configuration, a portion of the reflected light from the recording medium 4 returns to the semiconductor laser 1, so in a configuration in which the monitor light is taken from the rear emitted light of the semiconductor laser, the forward output must be sufficiently stabilized. is difficult. Therefore, a part of the laser emitted light reflected by the beam splitter is transmitted to the photodetector 16.
The output is stabilized by detecting and monitoring the output.

However, such a photodetector is larger than a photodetector installed inside a semiconductor laser package, and requires extra space in the optical head device.

Further, when an array type semiconductor laser having a plurality of light emitting points is used to realize a function such as playback immediately after recording, the output of each light emitting point cannot be detected independently with this configuration.

An object of the present invention is to provide an optical head device that does not cause the above-mentioned problems.

[Means to solve the problem]

In the present invention, the light emitted from a laser light source is irradiated onto a recording medium as a minute spot using a condensing lens, and a part of the light reflected from the recording medium is separated by a beam splitter installed between the laser light source and the condensing lens. In the optical head device, a reflecting mirror is provided to reflect the laser light source emitted light separated by the beam splitter, and the laser light source emitted light is guided to the beam splitter again by the reflecting mirror to form a beam. It is characterized in that the light is guided to the optical system for signal detection via a splitter, and the amount of light emitted from the laser light source is monitored within the optical system.

In addition, the present invention irradiates the light emitted from the laser light source onto the recording medium as a minute spot using a condensing lens, and uses a beam splitter installed between the laser light source and the condensing lens to split a portion of the reflected light from the recording medium. In the optical head device which separates the light and guides it to an optical system for signal detection, a reflecting mirror is provided to reflect the laser light source emitted light separated by the beam splitter, and a light detection device is provided near the light output part of the laser light source. the laser light source is guided again to the beam splitter by the reflecting mirror,
The light beam is guided to the laser light source via a beam splitter, and the amount of light emitted from the laser light source is detected by the photodetector.

[Effect]

The present invention is based on the principle that the laser emitted light reflected by the beam splitter is returned by a reflecting mirror, and the monitor light is detected within a conventional optical system. Such a reflecting mirror can be integrally formed on the output surface of the beam splitter and does not use extra space, so that the optical head device does not become larger.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 is a diagram showing the configuration of an embodiment. The emitted light from the semiconductor laser 1 becomes parallel light by the collimating lens 2,
The condensing lens 3 condenses the light onto the recording medium 4 as a minute spot. The reflected light from the recording medium 4 is separated by a beam splitter 5 and guided to a signal detection optical system. In signal detection,
The polarization direction is rotated approximately 45 degrees by the 1/2 wavelength plate 10, and the polarization direction is rotated by the polarization beam splitter 12 through the converging lens 11.
The light is separated into polarized light components in the 45 degree direction and detected by detectors 13 and 14.

An information signal for magneto-optical recording can be obtained from the differential signals output from the rain detectors 13 and 14. In addition, the photodetector 13 sends a tracking error signal using a push-pull method to the photodetector 1.
4 is combined with a cylindrical lens 15 to obtain a focus error signal using an astigmatism method.

On the other hand, the laser emitted light reflected by the beam splitter 5 is reflected by the reflection mirror 6 and guided to the signal detection system. In the photodetectors 13 and 14, the angle of the reflection mirror 6 is set so that a light spot is formed at a position different from that of the light reflected from the recording medium.

As the photodetector 14, for example, as shown in FIG. 2, one having a four-division light detection section 20 for detecting the light reflected from the recording medium and a monitor light detection section 21 for detecting the light from the reflection mirror 6 is used. In this way, the forward emitted light of the semiconductor laser 1 can be independently monitored.

Since the photodetector 14 is installed close to the condensing point of the converging lens 11, even if the semiconductor laser 1 is an array type element with multiple light emitting points, the photodetector 14 can be spotted at different positions on the photodetector. Therefore, monitoring light can be obtained independently by simply increasing the number of photodetectors.

FIG. 3 shows the configuration of another embodiment. The basic configuration for detecting magneto-optical signals is the same as in FIG. 1, but the configuration is such that light from a reflecting mirror 6 is guided to a semiconductor laser 1. In a magneto-optical optical head device, the beam splitter 5 functions as a partial reflection mirror for P polarized light, which is the laser emitted light, and as a total reflection mirror for S polarized light, so there is a By installing the /4 wavelength plate 7, a configuration is possible in which all the light from the reflection mirror 6 is guided to the semiconductor laser l.

Inside the semiconductor laser 1, as shown in FIG. 4, a photodetecting element 23 for detecting monitor light may be installed at a position different from that of the semiconductor laser chip 24.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a device that can monitor emitted light from a laser light source without increasing the size of the optical head device.

[Brief explanation of the drawing]

1 and 3 are diagrams showing optical head devices showing embodiments of the present invention, FIG. 2 is a diagram showing an example of a photodetector used in the embodiment of FIG. 1, and FIG. 4 is a diagram showing a third embodiment of the present invention. FIG. 5 is a diagram showing an example of a semiconductor laser used in the embodiment shown in the figure. FIG. 5 is a diagram showing an example of an optical head device according to the prior art. 1... Semiconductor laser 2... Collimating lens 3... Condensing lens 4... Recording medium 5... Beam splitter 6... Reflecting mirror 7 ...1/4 wavelength plate 10...1/2 wavelength plate 11... Converging lens 12... Polarizing beam splitter 13... 14... 15... 16. . . . 20. . . 21. . . 23. . . 24. .・Semiconductor laser output light

Claims (2)

[Claims] (1) The light emitted from the laser light source is irradiated onto the recording medium as a minute spot by a condensing lens, and a part of the reflected light from the recording medium is separated by a beam splitter installed between the laser light source and the condensing lens. In the optical head device, a reflecting mirror is provided to reflect the laser light source emitted light separated by the beam splitter, the reflecting mirror guides the laser light source emitted light to the beam splitter again, and the beam splitter An optical head device characterized in that the light is guided to the optical system for signal detection through the optical system, and the amount of light emitted from the laser light source is monitored within the optical system. (2) The light emitted from the laser light source is irradiated onto the recording medium as a minute spot by a condensing lens, and a part of the reflected light from the recording medium is separated by a beam splitter installed between the laser light source and the condensing lens. In the optical head device, a reflecting mirror is provided to reflect the light emitted from the laser light source separated by the beam splitter, and a photodetector is installed near the light output part of the laser light source. and guide the laser light source emitted light to the beam splitter again by the reflecting mirror,
An optical head device characterized in that the light is guided to the laser light source via a beam splitter, and the amount of light emitted from the laser light source is detected by the photodetector.