JPH01146142A - Two-beam semiconductor laser device - Google Patents

Abstract

PURPOSE:To separatedly monitor each output intensity and to relax the arrangement precision of each element by using a face light emission type semiconductor laser in either of semiconductor laser arrays. CONSTITUTION:One array of a two-beam semiconductor laser 34 consists of the face light emission type semiconductor laser, and a first light intensity monitor photodetector 35 is arranged to face the surface of the two-beam semiconductor laser 34 and a second light intensity monitor photodetector 36 is arranged at right angles to this surface. The light intensity of one light beam 2 is monitored by light 42 emitted in the direction perpendicular to forward emitted light 2 and 3, and backward emitted light 43 is used to monitor the light intensity of the other light beam 3. Thus, light intensities of the reproducing light beam 2 and the recording light beam 3 are monitored and are controlled, and the adjustment of light intensity monitor photodetectors 35 and 36 is facilitated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a two-beam semiconductor laser device for use in an optical recording and reproducing device for recording, reproducing and erasing information on an optical information recording medium. It is.

[Conventional technology]

BACKGROUND ART The optical recording/reproducing family f, which records and reproduces information concentrically or spirally on a rotating disk-shaped information recording medium using optical means, particularly a laser beam, is well known. This German device has the advantage of being capable of higher density recording and larger recording capacity than magnetic disk devices. However, on the other hand, since information recording media have more defects than magnetic disks, they especially require a function to ensure the reliability of recorded information.

For this reason, one possible method is to rotate the information recording medium on which information is recorded once and detect the reproduced signal to determine the presence or absence of an information recording defect. There are some drawbacks.

To prevent this, in recent years, optical recording and reproducing devices that can detect reproduced signals in real time have been proposed.

Similarly, when erasing information recorded on an information recording medium and recording new information, an optical recording/reproducing device that can erase and record information in one rotation of the information recording medium has also been considered. There is.

These are optical recording and reproducing devices that simultaneously irradiate an information recording medium with two or more light spots, and this type of optical recording and reproducing device usually uses a two-beam semiconductor laser that has two light emitting regions. It will be done.

FIG. 3 shows an optical recording and reproducing apparatus described, for example, on pages 107 to 112 of the ``Optical Memory Symposium 85'' collection of papers, and is of a type that can reproduce recorded information in real time. In the figure, a two-beam semiconductor laser (1) having two light emitting sources emits a recording beam (2) and a reproducing beam (3) that are parallel to each other as shown in FIG. 2
A collimator lens (4) is arranged on the beam output side of the beam semiconductor laser (1), and a polarizing beam splitter (5) is arranged on the beam output side of the beam semiconductor laser (1).
) is arranged to receive the beam that has passed through the collimator lens (4).

The reflecting mirror (6) directs the beam transmitted through the polarizing beam splitter (5) upward, and a quarter-wave plate (7) is placed in the optical path.
) and an objective lens (8) are arranged. The information recording medium (9) is placed close to the objective lens (8).

A guide groove (1) is formed along the information recording direction of the information recording medium (9).
o) is formed, and each beam (2) and (3) irradiated along this guide groove (1o) forms a recording slot (11) and a playback slot (12), respectively. .

A half prism (13) is arranged on the side of the polarizing beam splitter (5) to split the beam reflected by the polarizing beam splitter (5) into reflected light and transmitted light, and two light receiving surfaces (14a ) and (14b), and a two-split photodetector (14) that receives the beam transmitted through the half prism (13) is arranged.

The convex lens (15) converges the beam reflected by the half prism (13). The pinhole mirror (16) has a pinhole (17) through which only the reproduction beam (3) among the beams from the convex lens (15) passes. The reproduction beam (3) passing through this pinhole (17) is split by a half prism (18). Half prism (
A knife (19) is arranged on the optical path of the reproduction beam (3) that has passed through the reproducing beam (3), which has two light-receiving surfaces (2
A two-split photodetector (20) having 0a) and (20b) receives the reproducing beam (3) via the knife (19).

The photodetector (21) receives the recording beam (2) reflected by the pinhole mirror (16) and generates a recording beam monitor signal (El).The photodetector (22) is a half prism. The circuit (23) receives the reproduction beam (3) reflected by the circuit (18) and generates the reproduction output (c).
A reproduction signal (
This is a reproduction signal detection circuit for obtaining Dl.

The recording signal generation circuit (24) outputs the recording signal (A) as a pulse train, and the driver circuit (25) outputs the recording signal (A) as a pulse train.
A two-beam semiconductor laser (1) is driven based on Al.

The differential amplifier (26) that detects the output signal (TS) of the two-split photodetector (14) includes each light receiving surface (14a) and (
14b) is input. A differential amplifier (2o) detects the output signal (FS) of the two-split photodetector (2o).
7), output signals from each light receiving surface (20a) and (2ob) are input.

In addition, a two-split photodetector (14) and a differential amplifier (26)
) constitutes a well-known tracking error detection optical system called the push-pull method, and the Naifezi (19), two-split photodetector (20), and differential amplifier (27) constitute a well-known focusing error detection system called the Naifezi method. It constitutes a detection optical system.

Figure 5 shows the spot for F weight (11) on the recording medium (9).
) and reproduction spot (12) are shown in detail.

In addition, each spot (11) is shown here.

(12) is irradiated between the guide grooves (10) to perform recording and reproduction, but recording is performed on the guide grooves (1o).

May be played. In the figure, t is the recording slot) (
11) and the following reproduction spot (12), the arrow indicates the rotational movement direction of the information recording medium (9).

The pits (28) are written on the information recording medium (9) by the recording spots (11).

Although the two-beam semiconductor laser element is shown in FIG. 4, when the intensity of two light beams is to be monitored using the rear emitted light of the semiconductor laser, conventionally the configuration shown in FIG. 6 is used. It had been taken.

In FIG. 6, a light separator block (29) having reflective surfaces (29a) and (29b) is connected to a two-beam semiconductor laser (
The rear emitted light (3) from the semiconductor laser (1) is located close to the semiconductor laser (1).
3a), (33b) as a photodetector (30aL(30b)
) to monitor each. Also, as shown in Figure 7,
The forward emitted light (32aL (32b)) is emitted forward from the active layer (31).

Next, the operation of the conventional device shown in FIGS. 3 to 6 will be explained. First, when a recording signal +Al as shown in FIG. 3 is generated, a two-beam semiconductor laser (1) is driven based on this recording signal (A). The recording beam (2) and the reproducing beam (3) emitted from the two-beam semiconductor laser (1) are turned into parallel beams by a collimator lens (4), and then passed through a polarizing beam splitter (5) and a reflecting mirror (
6), the information recording medium (9) is irradiated through the 1/4 wavelength plate (7) and the objective lens (8), and a recording spora (11) and a reproduction spot (12) as shown in FIG.
).

Recording Spora) (11) is the recording information of the recording signal diagram (
For example, pulse width), and the corresponding shape (B
1 pits (28) are sequentially formed on the information recording medium (9). On the other hand, the reproducing spora (12) that follows the recording spot (11) by a distance t is driven with a constant light intensity, and it moves the written pit (28) for a time tL corresponding to the distance t. (several microseconds) later, it will start playing. That is, the recording spot (11) is reflected at the same time as it forms the pit (2B), and the reproduction spot (12) is reflected at the pit (28) after writing.

In this way, the recording beam (2) and the reproducing beam (3) reflected by the information recording medium (9) pass through the objective lens (8) and the quarter-wave plate (7) again. /
By reciprocating the 4-wave plate (7), the polarization direction is changed to 90
'Because it rotates, it is reflected by the polarizing beam splitter (5).

Next, each of the beams (2) and (3) is reflected by the No. 1-7 prism (13), but a part of it passes through the No. 1-7 prism (13) and is sent to the tracking error detection optical system, which will be described later. It is used for tracking error correction of the input beam and irradiated onto the information recording medium (9).

Each beam (2) reflected by a half prism (13).

In (3), after being converged by a convex lens (15), the recording beam (2) is reflected by a pinhole mirror (16), and the reproduction beam (3) passes through a pinhole (17).
It is reflected by the −7 prism (18). Furthermore, at this time,
Part of the reproduction beam (3) is the No. 1-7 prism (18)
The beam passes through the beam and is input to a focusing error detection optical system, which will be described later, and is used for correcting focusing errors of the beam irradiated onto the information recording medium (9).

The recording beam (
2) is received by the photodetector (21) and detected as a pulse waveform (E) corresponding to the recorded signal diagram, which is used to determine the presence or absence of a failure in the information recording medium (9), optical path, etc.

The reproduction beam (3) reflected by the 1'IJ and half prism (1B) is received by the photodetector (22) and formed into a pit (28) shape (corresponding to Bl) as shown in Figure 5. Output (detected as Q, and further waveform-processed by the reproduction signal detection circuit (23) to produce a pulse train-shaped reproduction signal (D)
Detected as . The reproduced signal (Dl) obtained in this way is compared with the recorded signal (Dl) and used to determine whether there is a defect in the information recording.

Here, we have shown a case where the reflectance of the information recording medium (9) decreases due to the formation of the pits (28), but the information recording medium (9) whose reflectance increases due to the pits (28)
9), the information recording state can be determined in the same way.

Note that the playback signal (Dl is the recording signal (time 1 for Al)
However, since the time 11 is on the order of several microseconds, the presence or absence of a recording defect can be determined in almost real time.

K when reproducing information recorded on the information recording medium (9)
is the reproduction beam (
3) only needs to be emitted and detected by the reproduction signal detection circuit (23).

Further, the rear emitted light (33a) of the semiconductor laser (1) is used to control the light intensity irradiated onto the information recording medium (9).

(33b) is used. This type of equipment requires independent monitoring of the playback beam intensity and recording beam intensity.
Conventionally, a light separator block (29) having two reflecting surfaces (29aL (29b)) is used to separate two backward emitted lights (33a) and (33b), and The emitted light (33a) is made incident on the light intensity monitoring photodetector (30a), and the backward emitted light (33b) relative to the reproduction beam (3) is made incident on the light intensity monitoring photodetector (30b). Based on the photodetector output, the semiconductor laser output can be controlled by a semiconductor laser drive circuit (not shown).

[Problem that the invention seeks to solve]

Since the conventional two-beam semiconductor laser device is configured as described above, it has the following problems.

First, if the interval between the light spots emitted from the two-beam semiconductor laser is (d), then as shown in FIG.
= 50 to 150 μm. Furthermore, since the rear-emitted light is also a light beam with a certain spread angle (100 to 30 degrees), it is necessary to use some means to separate the light beams. When using the block (29) to separate the light beams, the arrangement of each element had to be adjusted to fit within the spot spacing (dl).

This invention was made in order to solve the above-mentioned problems, and it is possible to separately monitor each output intensity from a two-beam semiconductor laser, and the precision of arrangement of each element is greatly reduced. The purpose is to obtain a beam semiconductor laser device.

[Means for solving problems]

In the two-beam semiconductor laser device according to the present invention, either one of the two-beam semiconductor laser arrays is composed of a surface-emitting type semiconductor laser.

[Effect]

In this invention, when monitoring the intensity of light emitted from each semiconductor laser, it is possible to easily separate two light beams. Then, the light intensity of one light beam is monitored using the light emitted in a direction perpendicular to the forward emitted light, and the rear emitted light is used to monitor the light intensity of the other light beam, and the output of each semiconductor laser is monitored. Control light intensity.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In Figure 1, a two-beam semiconductor laser (34
), one of which consists of a surface-emitting semiconductor laser. A first light intensity monitoring photodetector (35) is arranged opposite to the surface of the two-beam semiconductor laser (34), and a second light intensity monitoring photodetector (36) is arranged at right angles to the surface. There is. Two support blocks (38) protrude from a stem (37) to which a second light intensity monitoring light detection tube (36) is attached.

(39) are each attached with a two-beam semiconductor laser (34) and a first light intensity monitoring photodetector (35). Further, a glass window (41) is provided in front of the housing (40) attached to the stem (37).

Figure 2 is an enlarged view of the two-beam semiconductor laser (34), showing a beam for monitoring the optical output intensity (42) for the reproducing optical beam (2), and an optical beam for monitoring the optical output intensity for the recording optical beam (3) K. (43) is emitted. In this case, a surface-emitting semiconductor laser is used as the semiconductor laser that generates the reproducing light beam (2).

The surface-emitting semiconductor laser used in this example is published by the Institute of Electronics and Communication Engineers, Materials of the Photon Quantum Electronics Study Group, 0Q
E86-165 (1987)''AlGaAs/GaAs DBR laser using MQW active/inactive waveguide or the same study group material 0QE86-152 (19B?
)"Surface-emitting GaAs/AtGaAs DFB -
It has a structure that allows light to be obtained in a direction perpendicular to the active layer, as shown in TJS v-The. Incidentally, a surface emitting type semiconductor laser also naturally provides backward emitted light, but in the surface emitting type semiconductor laser according to the present invention, the rear emitted light is completely blocked.

With the above configuration, the light intensity is monitored using the surface emitting light (42) for the reproducing light beam (2) and the rear emitting light (43) for the recording beam (3) K. The intensity can be controlled. Since the emission directions of these two monitor lights are 90' different from each other, there is no need for special separation means such as a conventional optical separator block, and the photodetector can be arranged as shown in Figure 1. .

In the above embodiment, a surface-emitting semiconductor laser was used as the semiconductor laser that generates the reproduction light beam, and light emitted in a direction perpendicular to the active layer was used to monitor the light intensity. A surface emitting semiconductor laser may be used as the semiconductor laser that generates the beam. In addition, although each output of the two-beam semiconductor laser is used for reproduction and recording, these may be a recording light beam and an erasing light beam, or an erasing light beam and a reproduction light beam, The same effects as in the embodiment are achieved.

〔Effect of the invention〕

As described above, according to the present invention, a surface-emitting semiconductor laser is used as one of the two-beam semiconductor lasers, and the light intensity is monitored using the light emitted in the direction perpendicular to the active layer. Therefore, there is no need for means for separating two adjacent beams, and the adjustment of the light intensity monitoring photodetector is facilitated, and the accuracy of the apparatus can be improved.

[Brief explanation of the drawing]

FIGS. 1 and 2 show an embodiment of the present invention, with FIG. 1 being a sectional side view of a main part, and FIG. 2 being a perspective view of a semiconductor laser element. 3 to 7 show a conventional two-beam semiconductor laser device, FIG. 3 is a perspective view, FIG. 4 is a perspective view of a semiconductor laser element, and FIG. 5 is a partial perspective view for explaining operation. FIG. 6 is a plan view of the main part, and FIG. 7 is a partial perspective view for explaining the operation. (34) @@2 beam semiconductor laser, (21# (31
...Front emitted light, (35), (36') - Photodetector for monitoring working light intensity, (42)... Surface emitted light, (43)... Rear emitted light. In each figure, the same reference numerals indicate the same or corresponding parts. 34: 2 Hi + 9 pieces - Tee 35. 36: Moninu round book sword condyle and main flood 2 Figure 2.3: Collapse momme starting standing Asahi 42: Surface emitting light 43: Rear momme emitting light

Claims (4)

[Claims] (1) A two-beam semiconductor laser including a two-beam semiconductor laser array having two light-emitting sources, a drive circuit connected to each of the light-emitting sources, and a photodetector for monitoring the intensity of the light output emitted from the light-emitting sources. A two-beam semiconductor laser device, wherein either one of the two-beam semiconductor laser arrays is a surface-emitting semiconductor laser. (2) A two-beam semiconductor laser device according to claim 1, in which the intensity of the light output emitted from the side having the surface-emitting semiconductor laser is controlled using surface-emitting light. (3) A two-beam semiconductor laser device according to claim 1, in which the intensity of the light output emitted from the side without the surface-emitting semiconductor laser is controlled using rear emitted light. (4) A two-beam semiconductor laser device according to claim 1, wherein the forward emitted light emitted from the surface-emitting semiconductor laser is one of a reproducing beam, a recording beam, and an erasing beam.