JP2001118281A - Optical head and optical information recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and light optical head and optical information recorder by solving a loading problem while satisfying a required optical condition. SOLUTION: A front monitor photodetector 16 is arranged outside the vicinity of an optical axis, a luminous flux part separating means 14 which separates light of the luminous flux peripheral part is arranged, and the separated peripheral luminous flux is guided to the front monitor photodetector 16. Thus, loading is facilitated even when any space for arranging the front monitor photodetector 16 does not exist in the vicinity of the optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head and an optical information recording apparatus, and more particularly to an optical head for detecting the amount of light with a light beam in front of a light source and controlling an optical output by an APC circuit, and an optical information using the same. It relates to a recording device.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of a conventional optical head. 1 is an optical axis, 2 is a laser light source, 3 is a laser chip, 4 is a laser beam, 5 is an auxiliary lens, 6 is a fixed stop,
7 is a prism, 8 is a light beam used for recording and reproduction, 9 is a collimating lens, 10 is a fixed stop, 11 is an objective lens,
2 is an actuator, and 13 is an optical information recording medium such as an optical disk. In the figure, there is a portion where the optical axis changes by 90 degrees due to a mirror or a prism, but is shown on the same plane for explanation (the same applies to other drawings described later).

As shown in FIG. 1, a laser beam 4 emitted from a laser light source 2 passes through an auxiliary lens 5 and is finally narrowed down into a spot by an objective lens 11 to be irradiated onto an optical information recording medium 13.

The recording type optical head uses an external front monitor photodetector for detecting an emitted light beam in order to control the amount of light of a laser light source in detail, and uses an APC (Automatic Power Co.).
ntorol) circuit controls the light output of the laser light source. A
Since the PC circuit is not the gist of the present invention, the description is omitted.

As a method of distributing light to the front monitor photodetector, there is a method of using a light beam which does not contribute to recording and reproduction around the optical axis. However, this method does not lose the light beam used for recording and reproduction. This is a promising method in the future, given the market trend that requires increasing the light intensity on the information recording medium.

[0006]

However, this method has a problem that it is difficult to implement. In order for a light beam to form an image with a required spot size and light intensity on the optical information recording medium 13, the position and power of each optical element are restricted.

FIG. 12 is a diagram in which a front monitor photodetector is applied to a conventional optical head. In the figure, 16 is a front monitor photodetector, and 17 is a light receiving section. When the front monitor photodetector 16 is installed between the laser light source 2 and the auxiliary lens 5 as shown in FIG.
mm, making it difficult to mount the device in consideration of misalignment during holding and assembly.

The front monitor photodetector 16 must not block the light beam 8 used for recording and reproduction. In FIG. 12, the light beam 8 used for recording and reproduction is arranged so as not to be shielded, but at this position, the laser light beam 4 does not enter the light receiving unit 17 and does not function as a front monitor.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the disadvantages of the prior art and to solve the above-mentioned mounting problems while satisfying required optical conditions. A recording device is provided.

[0010]

In order to achieve the above object, a first means is to provide a laser light source for emitting a laser beam, a central portion of an optical axis of a laser beam emitted from the laser light source, and a peripheral portion of the optical axis. And a front monitor photodetector for detecting an outgoing light beam, and an APC circuit for controlling the light output of the laser light source with reference to the output of the front monitor photodetector. A light beam around the optical axis separated by the partial separating means is configured to be guided to the front monitor light detection unit.

The second means is characterized in that the light beam partial separating means is constituted by a specular reflection surface.

The third means is characterized in that the light beam partial separating means is mainly constituted by a curved surface, an ellipsoidal curved surface, a parabolic surface, and a toric surface.

The fourth means is characterized in that a thin metal plate having a thickness of 2 mm or less is used as a substrate of the light beam partial separating means.

The fifth means is characterized in that a bimetal is used for the whole or a part of the light beam partial separating means.

The sixth means is characterized in that the light beam partial separating means is a reflection type diffraction grating.

The seventh means is characterized in that the light beam partial separating means is integrally formed on a part of the surface of the optical device including the lens and the prism.

The eighth means is that the light beam partial separating means comprises:
It is configured to guide the light intensity center of the light beam separated at the periphery of the optical axis to outside the light receiving unit center of the front monitor photodetector,
Assuming that the radius of a circle inscribed in the light receiving portion of the front monitor photodetector is r, the light intensity center of the separated light beam is outside the circle that is 0.1 r from the light receiving portion center of the front monitor photodetector, It is configured to be located inside the circle of 0.3r.

The ninth means is that the light beam partial separating means has a light collecting function, and the absolute value of the distance between the light receiving surface of the front monitor light detector and the focal point of the condensed light is 0.1 mm or less. It is characterized in that it is set within a range of 5.0 mm.

An optical information recording apparatus according to the present invention is characterized in that the optical head of the first to ninth means is used.

As described above, according to the present invention, the front monitor photodetector is disposed near the optical axis, the light beam partial separating means for separating the light around the light beam is disposed, and the light beam is separated by the light beam partial separating means. By guiding the peripheral light beam to the front monitor photodetector, mounting is easy even when there is no space for arranging the flot monitor photodetector near the optical axis.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of the optical head according to the first embodiment. 1 is an optical axis, 2 is a laser light source, 3 is a laser chip, 4 is a laser beam, 5 is an auxiliary lens, 6 is a fixed stop, 7 is a prism, 8 is a light beam used for recording and reproduction, and 9 is a collimating lens. , 10 is a fixed aperture, 1
1 is an objective lens, 12 is an actuator, 13 is an optical information recording medium such as an optical disk, 14 is a mirror as a light beam partial separating means, 15 is a separated light beam separated by a mirror 14, 16 is a front monitor photodetector, 17 is It is a light receiving unit.

As shown in FIG. 1, a light beam emitted from the laser light source 2 is emitted from the laser chip 3. The center of the optical axis of the laser beam 4 forward passes through the auxiliary lens 5, sequentially passes through the optical device, and is guided to the collimating lens 9 as a beam 8 used for recording and reproduction. Thereafter, the light passes through the opening of the fixed stop 12, is condensed by the objective lens 11, and is irradiated onto the optical information recording medium 13.

Most of the laser beam 4 emitted from the laser chip 3 around the optical axis does not contribute to recording / reproduction even if it is captured by the auxiliary lens 5, and is reflected by the outer wall or the like. It becomes stray light. A part of the light beam around the optical axis is reflected by the mirror 14 as a light beam partial separating means, and is incident on the light receiving unit 17 of the front monitor photodetector 16.
The current is photoelectrically converted by the front monitor photodetector 16 and the current of the laser light source 2 is controlled by an APC circuit (not shown), so that the required optical power can be obtained.

The reflector of the mirror 14 is made of a sufficiently thin material such as a metal plate, and has a thickness of, for example, about 0.15 mm. Further, it is easy to form a bent shape as shown in FIG. 1 and can be fixed to a fixing member such as a casing. The overall thickness of the mirror 14 is suitably about 2 mm or less from the viewpoint of mounting and mechanical strength.

When a reflection type light beam partial separating means is used, the reflection surface is preferably made of a material having a high reflectance such as Al, Ag, Au or the like. . For example, there is a method of forming an anti-oxidation film on the reflection surface to protect it. When a material having low reflectance is used, there is a method of using a front monitor photodetector 16 having high sensitivity or increasing the amplification factor of the detection signal.
If high reflectance is not required, relatively inexpensive materials such as stainless steel can be used.

FIG. 2 shows a second embodiment of the present invention. FIG. 2 is a top view of an example in which the light beam partial separation element is reinforced [FIG.
(A)] and a side view (FIG. 2 (B)). The shape of the mirror 141 is different from that of the first embodiment, and the left and right edges 141a of the metal plate are bent and reinforced. The deflection of the reflecting surface due to external vibration and the like is reduced, and the holding property is further ensured. There is also a method in which the bent portion is further reinforced by welding or bonding to a horizontal portion or another bent portion. The reinforcing means by bending can be applied to other embodiments of the present invention.

FIG. 3 shows a third embodiment of the present invention. The figure shows an example in which the light beam partial separating means is composed of a substrate and a reflection film.
The mirror 142 uses a low-reflection material as a substrate, and forms a reflection film 19 at a necessary portion by aluminum evaporation or the like, thereby constituting a light beam partial separation unit.

In this way, since the reflection surface has a high reflectance, it is possible to use a material that does not expect high reflection for the substrate of the light beam partial separating means. Substrate materials are inexpensive,
A stronger one can be used. As a material of the reflection film 19, a material having a high reflectance such as Al, Ag, or Au is used. The reflection film 19 is formed by vapor deposition, but may be etched or pasted with another material.

FIG. 4 shows a fourth embodiment of the present invention. This figure shows an example in which a bimetal material is used for the substrate of the light beam partial separating means. The mirror 143 uses a bimetal material for the substrate,
As in the third embodiment, a high reflection film is applied to the reflection surface. When the mirror 143 expands and contracts due to a change in ambient temperature, the position of the reflection surface changes.

Due to the change in the position of the reflecting surface, the reflected light beam may not be guided to the expected position of the front monitor photodetector 16. For this reason, there is a method of controlling the reflection angle by using a plurality of materials having different coefficients of thermal expansion, such as a bimetal element, as in the present embodiment, so as not to change the position of the reflection surface due to a temperature change. FIG.
Although the thickness of the temperature compensating mirror 143 is slightly exaggerated in FIG.
The thickness is equivalent to 4.

FIG. 5 shows a fifth embodiment of the present invention. In this example, the film 144 is used as a light beam partial separating means, and a reflection effect is obtained by stretching the film 144 with two supporting pillars 20 provided above and below so that the supporting pillar 20 is not loosened. ).

The film 144 may be a thin sheet such as an aluminum foil or a laminated film, and may obtain a reflection effect without separately forming a reflection film.
You can use a tape-like film. As long as the film 144 and the support column 20 are securely fixed, they may be fixed with an adhesive or may be heat-welded.

FIG. 6 shows a sixth embodiment of the present invention. FIG. 2 shows an example in which the light beam partial separating means is constituted by an arc. First
In the mirror constituted by a flat surface as in the embodiment described above, there is a limit to the light flux that can be guided to the front monitor photodetector 16. The more the mirror is tilted forward, the more the space between the front and rear devices is required, and the more the mirror is made vertical, the more light beams are blocked by the housing of the laser 2.

Therefore, if an arc-shaped mirror 145 is used for the light beam partial separating means as in this embodiment, more light beams can be guided to the front monitor photodetector 16 than in the case where a plane mirror is adopted. . Further, the shape may be parabolic, or may be an ellipsoidal curved surface or a toric surface.
However, if the light is condensed, the carrier does not escape from the light receiving surface 17 of the front monitor photodetector 16 and the response frequency may be deteriorated. In order to suppress the influence of the non-uniformity of the light receiving portion sensitivity depending on the light receiving position, If possible, it is better to make the light uniformly incident on the light receiving unit so as to reduce the amount of light per unit area.

FIGS. 7 and 8 show a seventh embodiment. FIG.
FIG. 8 shows an example in which the light beam partial separating means is constituted by a ring-shaped reflector. FIG. 8 is a top view of FIG. In the first to sixth embodiments, the front monitor light detector 1
The light flux not used for recording / reproduction exists in a ring shape around the optical axis.

In the present embodiment, the light beam 8 used for recording / reproduction is light within about ± 11 deg from the light emitting point, and the laser light beam 4 is light within 27 deg at an angle looking up the emission window of the laser 2 from the laser chip 3. is there. At this time, the light beam 8 used for recording and reproduction in the laser light beam 4 is about 25%, and if the light beam partial separating means is devised, the remaining 75% of the light beam can be guided to the front monitor photodetector 16. Effective use of the laser beam around the optical axis also has the effect of simultaneously reducing stray light that adversely affects recording / reproduction due to reflection on the housing or the like.

In this embodiment, the curvature of the reflection surface of the ring mirror 146 is different between the front and back sides of the sheet of FIG. For example, if the unit is mm, the back side of the paper is the X axis, the upper side of the paper is the Y axis, the left side of the paper is the Z axis, and the light receiving unit position is (0, -2.6, 2.5), The inside of each of the circle having a center (0.4, -2) radius of 4.1 on the YZ plane and the center (1.7, 0) having a radius of 2.8 on the XZ plane is a reflection surface. .

FIG. 9 shows a light beam partial separating means according to the eighth embodiment. This figure shows an example in which the light beam partial separating means is a twin mirror. The twin mirror 147 has a concave surface with respect to the light source, and has a shape such that the left and right sides of the ring mirror 146 of the seventh embodiment are deleted and the upper and lower parts are divided into two. Generally, the laser light source used in the optical head is a semiconductor laser, but the spread angle of the light beam emitted from the laser chip 3 is different in the semiconductor laser. For example, in FIG. 1 showing the first embodiment, the divergence angles of the laser light source in the front and back directions of the paper surface and the vertical direction of the paper surface are different.

In the semiconductor laser of the present embodiment, the polarization plane is the front and back direction of the figure, and the divergence angle of the light beam is ± 15 d in the vertical direction of the paper.
± 20 deg from eg, and the full width at half maximum from ± 5 deg to ± 10 deg in the front and back direction of the drawing. In the seventh embodiment, the luminous flux used for recording / reproduction is ± 11 deg. Therefore, when the ring-shaped luminous flux partial separating means is used, the luminous flux around the optical axis in the front and back directions of the paper surface hardly exists. bad. Therefore, there is a method in which the light beam partial separating means is not ring-shaped as in the present embodiment, but two light beam partial separating means are vertically separated from each other. Then the upper and lower mirrors 1
47 can be held, so that the holding is ensured.

FIG. 10 shows a light beam partial separating means according to the ninth embodiment. This figure shows an example in which the light beam partial separating means is realized integrally with the lens element and by a reflection type diffraction grating. The difference from the first embodiment is that a mirror serving as a light beam partial separating means and an auxiliary lens are integrated, and a diffraction grating is applied to a portion immediately below the optical axis of a light source side lens surface of the auxiliary lens 51. When such a light beam partial separating means is integrally formed with other elements, the number of components can be reduced, and the installation space is advantageous.

Although the grating spacing of the diffraction grating is exaggerated in FIG. 10, it is actually on the order of μm. In this example, only the portion immediately below the optical axis is provided with a diffraction grating, but may be formed in a ring shape as in the seventh embodiment. Further, a blazed diffraction grating may increase the diffraction efficiency on a required side. In this example, the diffraction grating is integrated with the auxiliary lens. However, the diffraction grating may be integrated with the prism, or the light beam partial separating means may be a reflection film instead of the diffraction grating.

Although it is applicable to the first to eighth embodiments, when the light beam to be separated is guided to the front monitor photodetector by the light beam partial separating means, the separation is performed in consideration of the temperature change of the housing and the like. The center of the intensity of the light beam is preferably located not at the center of the front monitor photodetector but at a position off the center in advance. Specifically, assuming that the radius of a circle inscribed in the front monitor photodetector light receiving portion is r, the radius of the circle is 0.1 r from the center of the light receiving portion of the front monitor photodetector.
The center of the light intensity of the separated light beam is preferably arranged so as to be located inside the circle r.

When the light beam partial separating means has a light condensing function, the focus of the condensed light and the light received by the front monitor light detector are used in order to avoid deterioration of the response characteristics of the front monitor light detector and non-uniform light receiving sensitivity. The distance from the surface is preferably set to an absolute value within a range of 0.1 mm to 5.0 mm.

As described above, in the present invention, the light beam emitted from the laser light source 2 is mainly used for recording or reproduction at the central portion of the light beam. A part or most of the peripheral portion of the light beam is warped from the main optical axis by the thin light beam portion separating means 14,
The light is guided to the front monitor photodetector 16. The front monitor photodetector 16 is connected to an APC circuit, which feeds back the optical output of the laser 2, so that light emission to the optical information recording medium 13 can be controlled to a constant level without sacrificing the recording / reproducing power. Even if there is no room to install the front monitor photodetector 16 in the vicinity of the optical axis, the light beam partial separating means 14 can be used.

[0045]

According to the present invention, a compact and lightweight optical head and an optical information recording apparatus can be provided by solving the above-mentioned mounting problems while satisfying required optical conditions.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical head according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a mirror according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical head according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical head according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical head according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical head according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of an optical head according to a seventh embodiment of the present invention.

FIG. 8 is a top view of FIG. 7;

FIG. 9 is a view showing a twin mirror according to an eighth embodiment of the present invention.

FIG. 10 is a configuration diagram of an optical head according to a ninth embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional optical head.

FIG. 12 is a diagram showing an example in which a front monitor photodetector is applied to a conventional optical head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical axis 2 Laser light source 3 Laser chip 4 Laser beam 5 Auxiliary lens 6 Fixed aperture 7 Prism 8 Light flux used for recording / reproduction 9 Collimator lens 10 Fixed aperture 11 Objective lens 12 Actuator 13 Optical information recording medium 14 Mirror 15 Light beam partial separation means 16 Front monitor photodetector 17 Light receiving unit 18 Glass mirror 19 Reflective film 20 Support pillar 51 Diffraction grating auxiliary lens 141 Reinforcement mirror 141a Reinforcement mirror edge 142 Reflection film mirror 143 Temperature compensation mirror 144 Film 145 Arc mirror 146 Ring Mirror 147 Twin mirror

Claims (10)

[Claims] 1. A laser light source that emits a laser beam, a light beam partial separating unit that separates an optical axis center portion and an optical axis peripheral portion of a laser light beam emitted from the laser light source, and a front monitor light detection that detects an emitted light beam And an APC circuit for controlling the light output of the laser light source with reference to the output of the front monitor photodetector. The front monitor light detection detects the light flux around the optical axis separated by the light flux partial separation means. An optical head configured to be guided to a section. 2. An optical head according to claim 1, wherein said light beam partial separating means has a specular reflection surface. 3. The light beam partial separating means according to claim 1, wherein said light beam partial separating means has a light beam partial separating surface formed of any one of a curved surface, an ellipsoidal curved surface, a parabolic surface, and a toric surface. Item 3. The optical head according to Item 2. 4. A substrate having a thickness of 2
2. A thin metal plate having a thickness of not more than 1 mm.
An optical head according to claim 3. 5. The optical head according to claim 1, wherein a bimetal is used for all or a part of the light beam partial separating means. 6. The light beam partial separating means includes a reflection type diffraction grating.
An optical head according to claim 5. 7. The light beam partial separating means is integrated with a part of the surface of an optical device including a lens or a prism. Light head. 8. The light beam splitting means for guiding the center of the light intensity of the light beam separated at the periphery of the optical axis to outside the center of the light receiving section of the front monitor photodetector. Assuming that the radius of a circle inscribed in the portion is r, the center of the light intensity of the separated light beam is outside the circle that is 0.1 r from the center of the light receiving portion of the front monitor photodetector, and
The optical head according to any one of claims 1 to 7, wherein the optical head is configured to be located inside a circle that is 3r. 9. The light beam partial separating means having a light condensing function, wherein an absolute value of a distance between a light receiving surface of a front monitor photodetector and a focal point of the condensed light is 0.1 mm to 5.0 m.
9. The image processing apparatus according to claim 8, wherein the distance is set within a range of m.
Optical head as described. 10. An optical information recording apparatus using the optical head according to claim 1. Description: