JPH0822634A - Laser output controller of optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide the laser output controller of an optical information recording/reproducing device by detecting a forward radiating light beam from a semiconductor laser chip with a simple constitution and using the device for performing the definite control of the laser output. CONSTITUTION:This laser output controller of an optical information recording/ reproducing device is for information recording information reproducing in an information recording medium 9 by using the output light beam from a semiconductor laser 1. A holographic optical element 23 of eccentric converging property is provided on the position on which the peripheral light beam 5 from the laser 1 is received, a photodetector 22 is arranged on the converging position of the peripheral light beam 5 by the holographic optical element 23 and the output control of the semiconductor laser 1 according to the output of the photodetector 22 is performed. The central light beam 2 from the semiconductor laser 1 is used for information recording and information reproducing. By using the holographic optical element 23, the cost down of the device is attained, the device is made light in weight and small and the control operation is excellently and effectively performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser output control device of an optical information recording / reproducing apparatus for recording information on an optical information recording medium and reproducing information from the medium, and in particular,
The present invention relates to a device for controlling the optical output of a semiconductor laser.

[0002]

2. Description of the Related Art The output of a semiconductor laser fluctuates due to changes in temperature and changes in the amount of light returned from an irradiation target. On the other hand,
Since the optical information recording / reproducing apparatus requires a constant laser light output for both recording and reproduction, automatic output control (APC) is performed.

For example, in the conventional optical information recording / reproducing apparatus shown in FIG. 5, out of the forward radiation from the semiconductor laser chip 1, the peripheral light 5 is eliminated by the collimator lens 3 and only the light 2 near the center is collimated. The light enters the lens 3, is converted into a parallel light beam, and enters the beam splitter 4. The beam splitter 4 divides the transmitted light 6 and the reflected light 7, and the transmitted light 6 is condensed by a focusing lens 8 to form a disc,
The light enters the information recording medium 9 such as a card and is irradiated as a minute laser beam spot 10 to record or reproduce information.

The reflected light from the information recording medium 9 travels back in the same path as when it was incident, is converted into a parallel light beam by the focusing lens 8, and the light transmitted through the beam splitter 4 is returned to the semiconductor laser chip 1. Becomes The reflected light 11 from the beam splitter 4 is received by the light receiving element 13 via the light receiving lens 12. In this way, the information signal, the focus control signal, and the tracking control signal are extracted from the light receiving element 13. Then, in the APC operation, a part of the optical output of the semiconductor laser 1 is detected by the monitor light receiving element 14 or 15, and a loop circuit for amplifying the detected output and returning it to the semiconductor laser 1 is provided so that the laser light output is The output is controlled so that it is kept constant.

The monitor light receiving element 14 receives the rearward radiation 16 from the semiconductor laser chip 1 and outputs a signal 17, and the monitor light receiving element 15 receives the reflected light 7 from the beam splitter 4 and obtains a signal 18. It is configured to be.

In such a configuration, the monitor light receiving element 14
A semiconductor laser chip 1 incorporated in a general semiconductor laser chip 1 is used as this, and the rear emission light of the semiconductor laser chip 1 is extracted by this monitor light receiving element 14. However, since there is no perfect correlation between the front emission light and the rear emission light of the semiconductor laser chip 1, there is a problem that the laser light output cannot be controlled to be constant and a good APC operation cannot be performed.

Further, in the case of the monitor light receiving element 15, since the reflected light from the beam splitter 4 is received, there is no choice but to adopt a structure depending on the characteristics of the beam splitter 4. For example, if a polarization beam splitter is used as the beam splitter 4 in order to reduce the transmitted light loss in the beam splitter 4 and improve the light efficiency of the optical system,
Usually, since a quarter wavelength plate is combined to form an optical isolator structure, there is a problem that the reflected light 7 does not exist and a feedback signal cannot be obtained.

Under such a background, as shown in FIG. 6, one that detects the ambient light of the forward radiated light from the semiconductor laser chip to perform the APC operation of the laser output is disclosed in Japanese Patent Laid-Open No. 4-330646. Was proposed in. This is because, as shown in FIG. 6, of the forward radiated light from the semiconductor laser chip 1, the light 2 near the center enters the collimator lens 3, becomes a parallel light beam, and enters the beam splitter 4. Thereafter, similarly to FIG. 5, the information signal, the focus control signal, and the tracking control signal are extracted from the light receiving element 13. Then, a monitor light receiving element 19 for receiving the ambient light 5 in the forward radiated light from the semiconductor laser chip 1 is arranged closer to the semiconductor laser chip 1 than the collimator lens 3, and the output of this monitor light receiving element 19 is applied to the semiconductor. It is fed back to the output control circuit 20 of the laser.

The monitor light receiving element 19 has such a shape as to be able to receive all or part of the ambient light 5 in the forward radiation light from the semiconductor laser chip 1, and is a donut as shown in FIG. 8 (a). Type element 19-1 or the like in FIG.
An element 19-2 such as a square or a rectangle having a hole at the center as shown in (b), and further, an element 19-3 or 19 divided into a plurality as shown in FIG. 9 (c) or (d). -4
Etc.

As shown in FIG. 7, instead of FIG. 6, a concave mirror 21 having a hole through which the light 2 near the center passes is arranged at the position of the monitor light receiving element 19, and the reflected focused light from this mirror 21 is arranged. The light receiving element 22 may be configured to receive light.

[0011]

However, in the above-mentioned Japanese Patent Laid-Open No. 4-330646, for example, as shown in FIG.
When the light receiving elements 19-1 to 19-4 as in (a) to (d) are to be used, the light receiving element needs a large area light receiving surface. Therefore, there is a problem that the cost becomes high and a sufficient response speed cannot be obtained. Further, as another means, if the concave mirror 21 is used as shown in FIG.
A hole for the center light 2 must be formed at the center of the circle, it is difficult to use all of the peripheral light 5, and the amount of light that can be received becomes minute. In addition, an aspherical surface is required as a concave mirror for focusing the incident light at one location by shifting the light receiving element 22 from the optical axis, and there is a problem that the fabrication is not easy and the cost is high.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to detect the forward radiation light from the semiconductor laser chip with a simple structure and control the laser output to be constant. Another object of the present invention is to provide a laser output control device for an optical information recording / reproducing device used in.

[0013]

A laser output control device of an optical information recording / reproducing apparatus of the present invention which achieves the above object,
In a laser output control device of an optical information recording / reproducing apparatus for recording information on an optical information recording medium and reproducing information from the medium by using output light of a semiconductor laser, a peripheral light in forward emission light from the semiconductor laser is An eccentric condensing hologram optical element is provided at a light receiving position, the light receiving element is arranged at a position where the hologram optical element collects the peripheral light, and output control of the semiconductor laser is performed according to the output of the light receiving element. It is characterized by being performed.

In this case, the hologram optical element may be integrally provided in the output window of the package accommodating the semiconductor laser, and the light receiving element may be mounted in the package.

A reflection type hologram can be used as the hologram optical element. In this case, the hologram optical element has a transparent portion at which the central light in the forward emission light from the semiconductor laser is incident. Alternatively, it is desirable that a passage hole be provided in that portion.

[0016]

In the present invention, a hologram optical element having an eccentric focusing property is provided at a position for receiving the peripheral light in the forward radiated light from the semiconductor laser, and the light receiving element is provided at the position for collecting the peripheral light by the hologram optical element. Since it is arranged to control the output of the semiconductor laser according to the output of the light receiving element,
The center light of the front emission light from the semiconductor laser is used for information recording and information reproduction from the optical information recording medium, and the peripheral light is incident on the light receiving element and a signal corresponding to the emission output of the semiconductor laser is generated. It is output and this signal is given to the output control circuit of the semiconductor laser through the feedback circuit,
Even if the output of the semiconductor laser fluctuates due to a change in temperature or a change in the amount of light returned from the information recording medium or the like, the control is constantly performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser output control device of an optical information recording / reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an optical system according to an embodiment of the present invention, in which the same reference numerals as those in FIGS. 5 to 7 represent the same elements. Of the forward radiated light from the semiconductor laser chip 1, only the light 2 near the center enters the collimator lens 3, is converted into a parallel light beam, and enters the beam splitter 4. The transmitted light 6 of the beam splitter 4 is focused by a focusing lens 8
Then, the light is focused on, enters the information recording medium 9 such as a disk or a card, and is irradiated as a minute laser beam spot 10 to record or reproduce information.

The reflected light from the information recording medium 9 goes through the same path as when it was incident, is converted into a parallel light beam by the focusing lens 8, and the light transmitted through the beam splitter 4 is returned to the semiconductor laser chip 1. Becomes The reflected light 11 from the beam splitter 4 is received by the light receiving element 13 via the light receiving lens 12. An information signal, a focus control signal, and a tracking control signal are taken out from the light receiving element 13.

The structure up to this point is the same as the conventional one shown in FIG. Further, according to the present invention, a reflection-type eccentric light-concentrating hologram is provided at the position where the front emission light from the semiconductor laser chip 1 is incident and around the collimator lens 3 or on the side closer to the semiconductor laser chip 1 than that. Optical element 23
To place. The hologram optical element 23 is shown in FIG.
As shown in (b), the hologram sensitive material layer 26 is provided on the transparent substrate 25, and a portion 28 other than the portion 27 through which the light 2 near the center passes and the peripheral light 5 enters is reflected and eccentric. It is provided with a condensing hologram. This hologram optical element 23 focuses the ambient light 5 diverging from the semiconductor laser chip 1 onto the light receiving element 22 arranged off the optical axis, similarly to the concave mirror 21 in FIG.
It has a function of diffracting and entering.

The output of the light receiving element 22 is fed back to the output control circuit 20 of the semiconductor laser so that the output of the laser light can be kept constant even if the temperature or the amount of light returned from the information recording medium 9 or the like changes. Output control.

Regarding the central portion 27 of the hologram optical element 23, a hole may be formed in the substrate 25 through which the central light 2 incident on the collimator lens 3 passes. Further, as shown in FIGS. 2A and 2B, the entire shape thereof may be square or round, and only the central portion 27 through which the central light 2 passes is made transparent. It should be perforated.

In order to create such a reflection type eccentric light converging hologram optical element 23, for example, an optical arrangement as shown in FIG. 3 is used. That is, the hologram sensitive material layer 26
A light shielding body 38 is arranged on the central portion 27 of the transparent substrate 25 provided with, and light 36 diverging from a point A corresponding to the arrangement position of the semiconductor laser chip 1 and the arrangement position of the light receiving element 22 from both sides thereof. The light 37 to be condensed is made incident on the point B
Holographic recording is performed at the intersection of both lights. Therefore, the light from the laser 30 is transmitted to the beam expander 31.
Is converted into a thick parallel light by means of a beam splitter 32, which is bisected by a beam splitter 32, and each of the light beams is redirected by a mirror 33. Just convert it.

As described above, the ambient light 5 of the front emission light from the semiconductor laser chip 1 is diffracted and condensed by the hologram optical element 23 and detected by the light receiving element 22, so that the APC operation of the laser output is performed. In this case, the hologram optical element 23 can be easily duplicated and made by making one original plate, so that the cost of the apparatus can be reduced and the hologram optical element 23 can be made light and small. Further, since the hologram optical element 23 can be produced with high diffraction efficiency, most of the ambient light 5 can be used, and an efficient one can be constructed.

In the case of FIG. 1, it is assumed that the semiconductor laser and the hologram optical element are formed separately, and they are combined when the pickup of the optical information recording / reproducing apparatus is assembled. Then, attach the hologram optical element 23 integrally with the semiconductor laser package,
The light receiving element 22 is incorporated in the semiconductor laser package.
In FIG. 4, a semiconductor laser package 40 comprises a stem 41 and a cap 42, the semiconductor laser chip 1 is attached to the center of the stem 41, and the light receiving element 22 is attached to a position deviated from the center. The cap 42 is put on. An output window 43 is provided in a portion of the cap 42 facing the semiconductor laser chip 1, and the central light 2 and the peripheral light 5 are emitted from the package 40. The hologram optical element 23 is attached to the outside or inside of the window 43 (in the case of the figure,
Outside the output window 43), the central light 2 diverging from the semiconductor laser chip 1 is transmitted, and the collimator lens 3 (not shown)
On the other hand, the ambient light 5 is diffracted to be converted into the focused light 24, which is focused and incident on the light receiving element 22 arranged off the optical axis. In this case, the hologram light-sensitive material layer 26 may be provided directly on the output window 43 so that the window 43 itself can also serve as the hologram optical element 23. As described above, when the hologram optical element 23 is provided integrally with the semiconductor laser package 40, the labor for position adjustment and assembly can be saved and the cost of the pickup can be reduced. The semiconductor laser package 40 shown in FIG. 4 can be used to control the output of the laser light at a constant level even when it is used for other purposes besides the pickup of the optical information recording / reproducing device.

In the above, the hologram optical element may be of any type such as Lippmann type, relief reflection type and transmission type. Further, the arrangement of the hologram optical element is not limited to the arrangement shown in FIGS. 1 and 4,
It may be at any position where ambient light is incident. Further, it need not be concentric with the optical axis or be perpendicular to the optical axis. Further, the hologram optical element may be of a transmissive type, which is eccentric and condensing, instead of the reflective type, and the light receiving element may be arranged at the condensing position.

[0026]

According to the present invention, a holographic optical element having an eccentric focussing property is provided at a position for receiving the peripheral light in the forward radiated light from the semiconductor laser, and the hologram optical element receives the peripheral light at the position for collecting the peripheral light. Since the elements are arranged so that the output of the semiconductor laser is controlled according to the output of the light receiving element, the central light of the forward emission light from the semiconductor laser is used for information recording on the optical information recording medium and information from the medium. Used for reproduction, the ambient light is incident on the light receiving element and a signal corresponding to the emitted light output of the semiconductor laser is output. This signal is given to the output control circuit of the semiconductor laser through the feedback circuit, so that temperature change or Even if the output of the semiconductor laser changes due to a change in the amount of light returned from the information recording medium or the like, the control is constantly performed.

Since the hologram optical element can be easily duplicated by making one original plate, the cost of the apparatus can be reduced and the hologram optical element can be made light and small. Furthermore, since the hologram optical element can be made to have high diffraction efficiency, most of the ambient light can be used, and a device for performing the automatic output control operation of the semiconductor laser favorably and efficiently can be realized. .

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical system of a laser output control device of an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a form of a hologram optical element used in the apparatus of FIG.

FIG. 3 is a diagram showing an optical arrangement for exposing the hologram optical element of FIG.

FIG. 4 is a sectional view of a semiconductor laser package used in another embodiment.

FIG. 5 is a diagram showing a configuration of an optical system of a conventional optical information recording / reproducing apparatus.

FIG. 6 is a diagram showing a configuration of an optical system of another conventional optical information recording / reproducing apparatus.

FIG. 7 is a diagram showing a configuration of a main part of an optical system which is a modification of FIG.

8 is a diagram showing a configuration example of a light receiving element used in the optical system of FIG.

[Explanation of symbols]

 1 ... Semiconductor laser chip 2 ... Center light 3 ... Collimator lens 4 ... Beam splitter 5 ... Peripheral light 6 ... Transmitted light 8 ... Focusing lens 9 ... Information recording medium 10 ... Micro laser light spot 11 ... Reflected light 12 ... Light receiving lens 13 ... Light receiving element 20 ... Output control circuit 22 ... Light receiving element 23 ... Reflective eccentric light converging hologram optical element 24 ... Focused light 25 ... Transparent substrate 26 ... Holographic light-sensitive material layer 27 ... Center light passing portion 28 ... Ambient light incident portion 30 ... laser 31 ... beam expander 32 ... beam splitter 33 ... mirror 34 ... lens 35 ... lens system 36 ... diverging light 37 ... converging light 38 ... shading body 40 ... semiconductor laser package 41 ... stem 42 ... cap 43 ... output window

Claims (4)

[Claims] 1. A laser output control device of an optical information recording / reproducing apparatus for recording information on an optical information recording medium and reproducing information from the medium by using output light of a semiconductor laser, wherein forward emission light from the semiconductor laser is used. An eccentric light converging hologram optical element is provided at a position for receiving peripheral light, a light receiving element is arranged at a position where the peripheral light is condensed by the hologram optical element, and the semiconductor is provided according to the output of the light receiving element. A laser output control device for an optical information recording / reproducing device, characterized in that a laser output control is performed. 2. The hologram optical element according to claim 1, wherein the hologram optical element is integrally provided in an output window of a package accommodating the semiconductor laser, and the light receiving element is attached in the package. A laser output control device for a characteristic optical information recording / reproducing device. 3. The laser output control device for an optical information recording / reproducing apparatus according to claim 1, wherein the hologram optical element is a reflection type hologram. 4. The hologram optical element according to claim 3, wherein a portion of the front emission light from the semiconductor laser, on which the central light is incident, is transparent, or a passage hole is provided in the portion. A laser output control device for an optical information recording / reproducing device characterized in that