JPH07210892A - Optical pickup - Google Patents

Abstract

PURPOSE:To provide an optical pickup in which the reading defect of an optical disk caused by the positional displacement of respective optical element due to temp. change is eliminated. CONSTITUTION:The optical parts 14 of an optical pickup is mounted on a base member 18, on which other optical elements are mounted, through a holding member 14a formed of a material whose coefficient of linear expansion is different from that of the base member 18. Consequently, the positional deviation of the optical elements due to temp. change is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for irradiating a surface of an optical disk used for LD, CD, MD or data storage with a light beam for recording and / or reproducing information. It relates to an optical pickup.

[0002]

2. Description of the Related Art Conventionally, an optical pickup is shown in FIG.
It is configured as shown in. In FIG. 3, an optical pickup 1 includes a laser light source 2 such as a semiconductor laser device.
An objective lens 4 for converging the laser light emitted from the laser light source 2 on the surface of the optical disc 3, a collimator lens 5 and a beam splitter 6 which are sequentially arranged between the light source 2 and the objective lens 4, The beam splitter 6 has a second collimator lens 7 and a photodetector 8 which are sequentially arranged along the optical axis reflected by the reflecting surface 6a and the second reflecting surface 6b. .

Of the above optical elements, the laser light source 2, collimator lens 5, second collimator lens 7 and photodetector 8 are holding members 2a, 5a, 7 respectively.
The beam splitter 6 is directly attached to the base member 9 via a and 8a.

The optical pickup 1 configured as described above
In, the light beam emitted from the laser light source 2 is
After passing through the collimator lens 5 and the beam splitter 6, the light passes through the objective lens 4. At this time, the light beam is collimated by the collimator lens 5, passes through the beam splitter 6, and is refracted by the action of the objective lens 4 to be converged on the surface of the optical disc 3 which is rotationally driven. Will be done.

The reflected light beam reflected on the surface of the optical disk 3 again enters the beam splitter 6 via the objective lens 4. In the beam splitter 6, the reflected light beam is reflected upward in the drawing by the reflecting surface 6a of the beam splitter 6 and further leftward in the drawing by the second reflecting surface 6b. ,
The light is incident on the photodetector 8 via the second collimator lens 7.

Thus, the photodetector 8 detects the focusing control signal, the tracking control signal and the reproduction signal by receiving the reflected light beam.

[0007]

However, in the optical pickup 1 having such a configuration, the collimator lens 5, the beam splitter 6, the second collimator lens 7, the laser light source 2 and the photodetector 8 are common. The position is appropriately adjusted and attached to the base member 9. Further, for example, in the case of the illustration, the collimator lens 5 among the above optical elements is fixedly held in the base member 9 by tightening the fixing screw 5b after the position adjustment in the optical axis direction. Has become.

Therefore, for example, when the temperature of the entire optical pickup 1 rises or falls due to a change in environmental temperature, the base member 9 and the laser light source 2 and the collimator lens 5 due to thermal expansion and contraction of each optical element. Between them, and the distance between the second collimator lens 7 and the photodetector 8 will fluctuate.

For example, the holding member 2a of the laser light source 2 is made of aluminum having a linear expansion coefficient of 23.0 × 10 to the 6th power, and the holding member 5 of the collimator lens 5 is used.
b is made of brass having a linear expansion coefficient of 18.4 × 10 minus 6, and the base member 9 has a linear expansion coefficient of 2
In the case of ZDC (zinc die cast) which is 7.4 × 10 −6, the distance between the laser light source 2 and the collimator lens 5 due to the temperature change Δt is

[0010]

[Equation 1]

[0011] A distance change of ΔL represented by Therefore, for example, if there is a temperature change of 30 ° C., the distance change ΔL becomes 6 μm, and thus a focus shift occurs. As a result, the light beam from the laser light source 2 is not collimated by the collimator lens 5, and therefore the objective lens 4 does not accurately converge on the surface of the optical disc. Thus,
There is a problem in that the performance of the optical pickup is deteriorated.

Further, there is a problem that a similar focus shift occurs due to temperature change between the second collimator lens 7 and the photodetector 8.

Further, the holding members 2a, 8a of the laser light source 2 and the photodetector 8 are usually made of a material different from that of the base member 9. Therefore, the holding members 2a and 8a have different linear expansion coefficients from the base member 9. Therefore, when the temperature is changed, the laser light source and the photodetector 8 may be displaced in the direction perpendicular to the optical axis depending on the supporting positions of the holding members 2a and 8a, so that an accurate optical disc may be obtained. There was a problem that reading could not be performed.

In view of the above points, it is an object of the present invention to provide an optical pickup capable of eliminating a reading failure of an optical disk due to a positional shift of each optical element due to a temperature change.

[0015]

According to the present invention, the above object is to provide a light source and an objective lens which irradiates a surface of an optical disk with a light beam from the light source and receives a reflected light beam reflected by the surface. And a photodetector for receiving the reflected light beam, and an optical component inserted in the optical path,
An optical pickup, wherein the optical component is attached to a base member to which another optical element is attached via a holding member formed of a material having a linear expansion coefficient different from that of the base member. Achieved by pickup.

Here, the optical component is, for example, a collimator lens, but is not limited to this, and may be, for example, a multi-lens.

In the optical pickup according to the present invention, preferably, the optical component is located at a position displaced to the opposite side in the optical axis direction with respect to the optical element whose distance is to be held constant, and the base is provided via the holding member. It is attached to the member.

Further, in the optical pickup according to the present invention, preferably, the light source and the photodetector are attached to a base member via a holding member made of the same material as the base member.

Further, according to the present invention, the above object is to provide a light source, an objective lens for irradiating the surface of an optical disk with the light beam from the light source, and an objective lens for receiving the reflected light beam reflected by the surface, and the light source. And a light separating optical system which is inserted between the objective lens and separates the reflected light beam, a photodetector which receives the separated light beam separated by the light separating optical system, and an optical inserted in the optical path. An optical pickup including a component, wherein the optical component includes a holding member formed of a material having a different linear expansion coefficient from the base member to which a plurality of other optical elements are attached. And the light source and the photodetector are attached to the base member via a holding member made of the same material as the base member. By the pick-up is achieved.

In this case, the optical separation system can be constituted by, for example, a beam splitter or the like so as to separate the reflected light and guide it to the photodetector.

Further, according to the present invention, the above object is to provide a light source, an objective lens which irradiates a light beam from the light source onto a surface of an optical disk and receives a reflected light beam reflected by the surface, and the light source. And a light separating optical system which is inserted between the objective lens and separates the reflected light beam, a photodetector which receives the separated light beam separated by the light separating optical system, and an optical inserted in the optical path. An optical pickup including components, the optical components being housed in a sleeve member provided along an optical path in a base member having other optical elements attached, and the optical components being the sleeve. The sleeve member is attached to the sleeve member via a holding member formed of a material having a linear expansion coefficient larger than that of the member, and the light source and the photodetector are attached to the base member. Through a holding member formed of the same material as the over scan member is attached, also by the optical pickup is achieved.

[0022]

According to the above construction, each optical element is attached to one common base member, and the optical component is made of a material having a coefficient of linear expansion different from that of the base member. .

Here, the base member is made of a material having a relatively small coefficient of linear expansion such as iron, alumina, silicon carbide, silicon nitride and aluminum nitride. In contrast to the base member made of such a material, in the optical pickup according to the present invention, as a holding member for the optical component, synthetic resin such as polyphenylene sulfide PPS, polycarbonate PC, aluminum die cast AlDC, zinc die cast ZDC, Magnesium die cast Mg
It is made of a material having a relatively large linear expansion coefficient such as DC or brass.

As a result, the holding member of the optical component undergoes thermal expansion or contraction so as to relatively cancel the thermal expansion or contraction of the base member when subjected to temperature change. Therefore, in the optical pickup as a whole, variation in the distance between the optical component and the light source, the photodetector, or other optical elements is reduced.

Further, in the case where this optical component is attached to the base member via the holding member at a position shifted to the opposite side in the optical axis direction with respect to the optical element to be held at a constant distance, When the temperature changes, the thermal expansion or contraction of the base member due to the thermal expansion or contraction of the holding member is relatively canceled. As a result, the distance variation between the optical component and the optical element such as the light source or the photodetector that should keep the distance constant is further reduced.

When the light source and the photodetector are attached to the base member via a holding member made of the same material as the base member, when the temperature and the temperature are changed, This deviation of the light source and the photodetector in the direction perpendicular to the optical axis is eliminated.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows a first embodiment of the optical pickup according to the present invention. In FIG. 1, an optical pickup 10 is a laser light source 1 such as a semiconductor laser device.
1 and an objective lens 13 for converging the laser light emitted from the laser light source 11 on the surface of the optical disc 12.
And a collimator lens 14 and a beam splitter 15 which are sequentially arranged between the light source 11 and the objective lens 13,
The second collimator lens 16 and the photodetector 1 which are sequentially arranged along the optical axis reflected by the reflecting surface 15a of the beam splitter 15 and by the second reflecting surface 15b.
7 and 7.

Among the above optical elements, the laser light source 11, the collimator lens 14, the second collimator lens 16 and the photodetector 17 are respectively holding members 11.
The beam splitter 15 is directly attached to the base member 18 via a, 14a, 16a, and 17a.

Further, the optical pickup 10 of the present embodiment.
The holding member 14a of the collimator lens 14
Is made of a material different from that of the base member 18 and is formed into, for example, a cylindrical shape. Further, the holding member 14a is, for example, an optical element which is to be kept at a constant distance, that is, a laser light source 11, and is slightly longer than the laser light source 11 along the opposite side in the optical axis direction. Thus, the base member 18 is fixedly held.

Further, in the laser light source 11, the holding member 11a is made of the same material as the base member 18.

Here, for example, the holding member 11a of the laser light source 11 and the base member 18 are made of alumina having a coefficient of linear expansion of 8 × 10 to the 6th power. On the other hand, the holding member 14a of the collimator lens 14 is made of brass having a linear expansion coefficient of 18.4 × 10 minus 6.

The optical pickup 10 according to the present embodiment is
It is configured as described above, and its operation is as follows. That is, the light beam emitted from the laser light source 11 is generated by the collimator lens 14 and the beam splitter 1.
After passing through 5, the object lens 13 is passed through. At this time, the light beam becomes parallel light by the collimator lens 14, passes through the beam splitter 15, and is refracted by the action of the objective lens 13,
It will be converged on the surface of the optical disk 12 that is rotationally driven.

The reflected light beam reflected by the surface of the optical disk 12 again enters the beam splitter 15 via the objective lens 13. This beam splitter 1
5, the reflected light beam is reflected upward in the drawing by the reflecting surface 15a of the beam splitter 15,
Further, after being reflected to the left by the second reflecting surface 15b in the drawing, it is incident on the photodetector 17 via the second collimator lens 16.

Thus, the photodetector 17 detects the focusing control signal, the tracking control signal and the reproduction signal by receiving the reflected light beam.

Here, for example, when the temperature of the entire optical pickup 1 rises or falls due to a change in environmental temperature, the holding member 14a of the collimator lens 14 is
Since the base member 18 has a relatively large coefficient of linear expansion, the base member 18 is thermally expanded or contracted so as to cancel out the thermal expansion or contraction of the base member. Therefore, the collimator lens 14 and the laser light source 11
The distance variation between and will be reduced. As a result, the focus shift is reduced within the allowable range.

Moreover, in the illustrated case, the collimator lens 1
Reference numeral 4 is a position displaced to the opposite side in the optical axis direction with respect to the laser light source 11, and is fixedly held by the base member 18 by a fixing screw 14b. Therefore, this fixed position (14b)
Therefore, since the holding member 14a is greatly expanded and contracted on the laser light source 11 side along the optical axis direction,
Therefore, the variation in the distance between the collimator lens 14 and the laser light source 11 due to the temperature change is further reduced.

The laser light source 11 is the base member 1
Since the laser light source 11 is attached to the base member 18 by the holding member 11a made of the same material as that of No. 8, when the laser light source 11 is thermally expanded / contracted due to temperature change,
No displacement occurs in the direction perpendicular to the optical axis. still,
An adhesive may be applied as a fixing means other than the fixing screw 14b. In that case, the assembly becomes easier.

FIG. 2 shows a second embodiment of the optical pickup according to the present invention. In FIG. 2, an optical pickup 20 is a laser light source 1 such as a semiconductor laser device.
1 and an objective lens 13 for converging the laser light emitted from the laser light source 11 on the surface of the optical disc 12.
And a collimator lens 14 and a beam splitter 15 which are sequentially arranged between the light source 11 and the objective lens 13,
The second collimator lens 16 and the photodetector 1 which are sequentially arranged along the optical axis reflected by the reflecting surface 15a of the beam splitter 15 and by the second reflecting surface 15b.
7 and 7.

Here, of the above optical elements, the second collimator lens 16 and the photodetector 17 are provided on the base member 18 via the holding members 16a and 17a, respectively. It is installed.

Further, the holding member 14a is, for example, an optical element for keeping the distance constant, that is, the laser light source 11.
On the other hand, it extends toward the opposite side in the optical axis direction, and is fixed and held to the base member 18 by the fixing screw 14b at this extended portion. The holding member 11 a of the laser light source 11 is made of the same material as the base member 18.

The above construction is similar to that of the optical pickup 10 in the first embodiment shown in FIG.
In the optical pickup 20, the laser light source 11 and the collimator lens 14 are attached to the holding members 11 a and 14 thereof.
It is attached via a to a cylindrical sleeve 18a which defines the inner wall of the optical path inserted into the base member 18. In this case, the material of the base member 18 is arbitrarily selected, and the sleeve 18a thereof is made of a material having a relatively small linear expansion coefficient. On the other hand, the holding member 14a of the collimator lens 14 is made of a material having a relatively large linear expansion coefficient, which is different from the sleeve 18a of the base member 18.

Here, for example, the holding member 11a and the sleeve 18a of the laser light source 11 have a linear expansion coefficient of 8 × 10.
The holding member 14a of the collimator lens 14 has a linear expansion coefficient of 18.4.
It is made of brass, which is the minus 6th power of x10.

According to the optical pickup 20 having such a configuration, the distance variation between the laser light source 11 and the fastening position (14b) of the collimator lens 14 due to the temperature change Δt and the collimator lens 14 and its fastening position (14b). The distance variation between

[0045]

[Equation 2]

[Equation 3]

Will be represented by Therefore, the distance variation Δ between the laser light source 11 and the collimator lens 14
L is canceled by the above two distance fluctuations, and becomes substantially zero. Thus, the variation in distance between the collimator lens 14 and the laser light source 11 is substantially eliminated. As a result, the focus shift is reduced within the allowable range.

Moreover, in the illustrated case, the collimator lens 1
4 is a position displaced from the laser light source 11 on the opposite side in the optical axis direction and is fixedly held by the sleeve 18a of the base member 18 by the fixing screw 14b. The distance variation between the two will be further reduced.

The laser light source 11 is the base member 1
Holding member 11a made of the same material as the sleeve 18a of FIG.
Since it is attached to the sleeve 18a of the base member 18, the laser light source 11 will not be displaced in the direction perpendicular to the optical axis when the laser light source 11 thermally expands or contracts due to temperature change.

In this case, as compared with the embodiment shown in FIG. 1, only the sleeve 18a needs to be formed of a relatively expensive material having a small linear expansion coefficient, so that the overall cost can be reduced accordingly. Become.

As described above, according to the above-described embodiment, each optical element is attached to one common base member, and the optical components such as the collimator lens and the like have a coefficient of linear expansion larger than that of the base member. It is made of a large material. Therefore, the holding member of the optical component undergoes thermal expansion or contraction so as to relatively cancel the thermal expansion or contraction of the base member when subjected to a temperature change. Variations in distance between the light source, photodetector and other optical elements are reduced. As a result, the light beam from the light source is focused on the surface of the optical disc, so that the reliability of the optical pickup due to the temperature change is improved.

Further, this optical component is attached to the base member via the holding member at a position displaced to the opposite side in the optical axis direction with respect to the optical elements such as the light source and the photodetector which should be kept at a constant distance. If it is attached, distance variation due to temperature change will be further reduced. Therefore, the reliability of the optical pickup due to the temperature change is further improved.

When the light source and the photodetector are attached to the base member via the holding member formed of the same material as the base member, when the temperature is changed, This deviation of the light source and the photodetector in the direction perpendicular to the optical axis is eliminated. Therefore, accurate reading of the optical disc can be performed.

The invention is not limited to the embodiments described above. That is, in the above-described embodiments, the case where the distance variation between the collimator lens 14 and the laser light source 11 due to the temperature variation is reduced has been described, but for example, between the photodetector 17 and the second collimator lens 16. The present invention can be applied to the case where the distance variation due to the temperature change is reduced. In this case, the holding member 16a of the collimator lens 16 is formed of a material having a relatively large linear expansion coefficient, the fastening position of the holding member 16a is shifted to the side opposite to the photodetector 17, and the holding position of the photodetector 17 is increased. It is realized by forming the holding member 17a and the base member 18 with a material having a relatively small linear expansion coefficient.

Further, in the above embodiment, the case where brass and alumina were used for the materials of the holding member 14a of the collimator lens 14 and the holding member of the laser light source 11, and the base member 18 or the sleeve 18a, respectively, was explained. It is not limited to these materials.

As a material of the holding member 14a of the collimator lens 14, a material having a relatively large linear expansion coefficient, for example, PPS having a linear expansion coefficient of 19 to 62, 13 to 71 of the same.
Which is a synthetic resin such as PC, aluminum die cast AlDC having a linear expansion coefficient of 23, zinc die cast ZDC and magnesium die cast Mg of 27.4.
Brass, which is DC or 18.4, is used.

Further, the holding member 11a of the laser light source 11
As the material of the base member 18 or the sleeve 18a, a material having a relatively small linear expansion coefficient, such as iron Fe having a linear expansion coefficient of 11.7 and alumina Al having the same coefficient of 6 to 8 is used.
2 O3, linear expansion coefficient 4. To 5 silicon carbide Si
C, silicon nitride SiI3 N having a linear expansion coefficient of 2 to 3
4. Aluminum nitride AlN having a linear expansion coefficient of 3.9 is used.

[0057]

As described above, according to the optical pickup of the present invention, the displacement of each optical element does not occur due to the environmental change of the apparatus, especially the temperature change. Therefore, it is possible to eliminate writing on the optical disk and reading failure of the disk.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of an optical pickup according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the optical pickup according to the present invention.

FIG. 3 is a schematic plan view showing the configuration of an example of a conventional optical pickup.

[Explanation of symbols]

 10 Optical Pickup 11 Laser Light Source 11a Holding Member 12 Optical Disc 13 Objective Lens 14 Collimator Lens 14a Holding Member 15 Beam Splitter 16 Collimator Lens 16a Holding Member 17 Photodetector 17a Holding Member 18 Base Member 18a Sleeve 20 Optical Pickup

Claims (5)

[Claims] 1. A light source, an objective lens for irradiating a surface of an optical disk with a light beam from the light source and receiving a reflected light beam reflected by the surface, and a photodetector for receiving the reflected light beam. An optical pickup including an optical component inserted in an optical path, wherein the optical component is formed of a material having a linear expansion coefficient different from that of a base member to which another optical element is attached. An optical pickup which is attached via a holding member. 2. The optical component at a position displaced to the opposite side in the optical axis direction with respect to an optical element whose distance should be kept constant,
The optical pickup according to claim 1, wherein the optical pickup is attached to the base member via the holding member. 3. The light source and the photodetector are attached to a base member via a holding member formed of the same material as the base member. Optical pickup. 4. A light source, an objective lens for irradiating a surface of an optical disk with a light beam from the light source and receiving a reflected light beam reflected by the surface, and the objective lens inserted between the light source and the objective lens. An optical pickup including a light splitting optical system for splitting the reflected light beam, a photodetector for receiving the split light beam split by the light splitting optical system, and an optical component inserted in the optical path. The optical component is attached to a base member to which another optical element is attached via a holding member formed of a material having a larger linear expansion coefficient than the base member, and the light source and An optical pickup characterized in that a photodetector is attached to a base member via a holding member made of the same material as the base member. 5. A light source, an objective lens for irradiating the surface of an optical disk with a light beam from the light source and receiving a reflected light beam reflected by the surface, and the objective lens inserted between the light source and the objective lens. An optical pickup including a light splitting optical system for splitting the reflected light beam, a photodetector for receiving the split light beam split by the light splitting optical system, and an optical component inserted in the optical path. The optical component is housed in a sleeve member provided along the optical path in a base member to which another optical element is attached, and the optical component is made of a material having a larger linear expansion coefficient than the sleeve member. Attached to the sleeve member via a holding member, and the light source and photodetector are formed of the same material as the base member with respect to the base member. An optical pickup, which is attached via a holding member that is attached.