JPH06167677A - Optical pickup and its assembling and adjusting method - Google Patents

Abstract

PURPOSE:To provide an optical pickup which allows a large assembly permissible error of a hologram laser unit itself, enables the assembly error of the optical pickup to speedily and securely be corrected, and greatly contributes to the improvement of mass-productivity. CONSTITUTION:A hologram laser unit 10 and a collimator lens 1 are moved in a radial direction in one body, and consequently an adjustment is made while the intensity distribution center L1 of a beam 8 made incident on an objective 4 is deviated by a distance e2 from the center of the objective 4. As a result of this adjustment, the intensity distribution center L1' of return light 8' from a disk 5, i.e. return light 8' to a hologram pattern 13 is nearly aligned with the division line l1 of a hologram pattern 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup in which a semiconductor laser light source and a servo signal detector are integrated as a hologram laser unit and a method of assembling and adjusting the same, and more specifically, an assembly tolerance of the hologram laser unit can be increased. The present invention relates to an optical pickup capable of efficiently performing adjustment work and an assembly adjustment method thereof.

[0002]

2. Description of the Related Art Optical discs capable of recording a large amount of information with high density have been used in many fields in recent years. Since such an optical disc is an optical information recording medium which has an excellent feature that information can be recorded and reproduced in a contactless manner and the medium can be exchanged, it is particularly noted as an optical file or an external storage medium of a computer. ing.

In an optical disc, information is recorded or reproduced by an optical pickup using, for example, a semiconductor laser as a light source, and the recorded information is erased or rewritten depending on the medium. This kind of optical pickup
Many optical components such as a lens, a prism, and a photodetector are used in order to narrow down a light beam from a semiconductor laser on an optical disc to a diffraction limit and follow a recording track of the optical disc with high accuracy.

By the way, in such an optical pickup, it is necessary to carry out an adjusting work such as an assembling accuracy adjustment of the above-mentioned optical parts at the time of assembling, but since the number of parts is large, the adjusting work becomes complicated and accuracy is required. Therefore, it takes a lot of time for the adjustment work, which is a hindrance to mass production of the optical pickup.

In order to solve such a problem, recently, a signal detecting section such as a light receiving element for detecting a focus error and a tracking error of a focused beam focused on an optical disk is integrated with a semiconductor laser package, Holographic laser units have been developed that realize a significant reduction in the number of parts and simplification of adjustment work.

11 and 12 show an optical pickup equipped with a hologram laser unit. The hologram laser unit 10 has a semiconductor laser 11, and a servo error detector 14 is integrated with a semiconductor laser package. The beam 8 emitted from the semiconductor laser 11 is collimated by the collimator lens 1 and then shaped by the compound prism 2 to be guided to the 45-degree rising mirror 3.

The composite prism 2 comprises a polarization beam splitter 2a, a Wollaston prism 2b, and a spot lens 2c. The rising 45-degree mirror 3 changes the optical path of the incident laser light by 90 degrees and guides the reflected light to the objective lens 4 provided above it. The objective lens 4 collects the incident light and irradiates the information recording surface of the disk 5 located above the incident light with the condensed beam.

The objective lens 4 is driven by an actuator 6 in a radial direction which is a radial direction of the optical disk 5 and a focus direction which moves toward and away from the disk 5. The actuator 6 is driven by a radial servo signal and a focus servo signal.

The laser light focused on the disk 5 is reflected by the information recording surface, the reflected light is transmitted through the objective lens 4, is reflected by the 45 ° mirror 3 for raising, and then returns to the composite prism 2. . This return light is the composite prism 2
A part of the light is reflected by the polarized beam splitter 2a, and the rest is transmitted through the compound prism 2 and returns to the hologram laser unit 10 through the collimator lens 1.

When the disk 5 is a magneto-optical disk, the light reflected by the polarization beam splitter 2a is divided into different polarization components by the Wollaston prism 2b, and then is spotted on the two-divided detector 7 by the spot lens 2c. It is condensed and reproduced as a magneto-optical signal.
On the other hand, the return light that has passed through the polarization beam splitter 2a and returned to the hologram laser unit 10 is guided to the servo signal detection system. In the figure, 12 is a glass substrate.

Next, the principle of servo signal detection will be described with reference to FIG. The return light returning to the hologram laser unit 10 is diffracted in the direction of the servo error detector 14 by the hologram pattern 13 having a three-division structure formed on the glass substrate 12 provided on the hologram laser unit 10. . Servo error detector 14
Is divided into three parts, that is, the detectors 14b and 14c and the detector 14a, and the detector 14a is divided into two parts 14a-1 and 14a-2. That is, the servo error detector 14 is a four-divided structure detector as a whole.

The hologram pattern 13 has an elliptical shape in accordance with the beam shape of the return light returning from the disk 5 through the composite prism 2. The hologram pattern 13 is divided into three areas. That is, the dividing line l extending in the direction corresponding to the radial direction of the disk 5
_{By 2} , it is first divided into two areas. One of these areas is the focus division area 13a. The remaining area is further divided into two tracking division areas 13b and 13c by a division line l ₁ extending in a direction corresponding to the track direction of the disk 5.

The return light diffracted by the tracking division regions 13b and 13c enters detectors 14b and 14c, respectively. Further, the return light diffracted by the focus division region 13a is arranged so as to be incident on the division line l _{1 of the} two-division detectors 14a-1 and 14a-2.

Here, the detectors 14b, 14a-1, 14a
When the output from -2,14c and _{S 1, S 2, S 3} , S 4 respectively, the focus error signal (focus error signal)
FES is detected by the Foucault method as FES = (S ₃ −S ₂ ).

Further, the radial error signal (radial error signal) RES is detected by the push-pull method as RES = (S ₄ −S ₁ ).

Incidentally, these detections are specifically shown in FIG.
It is performed by the subtracters 15f and 15r shown in FIG.

As shown in FIG. 14, the hologram laser unit 10 includes a semiconductor laser 11 in both the radial direction (see FIG. 14A) and the track direction (see FIG. 14B).
After adjusting the assembling position of the glass substrate 12 with respect to the hologram laser unit 10 so that the intensity distribution centers L ₁ and L ₂ of the outgoing beam from and the division lines l ₁ and l _{2 of the} hologram pattern 13 are aligned, an adhesive is applied. Using glass substrate 1
Fix 2

Since the optical pickup of the present invention is characterized by adjusting the position of the hologram laser unit in the radial direction as will be described later, a method of adjusting the position in the radial direction in the conventional hologram laser unit 10 will be described below.

As shown in FIG. 15, when the hologram laser unit 10 is assembled to the optical pickup, the adjustment method is as follows: the center L ₁ of the intensity distribution of the beam 8 collimated by the collimator lens ₁ becomes the center of the objective lens 4. The collimator lens 1 and the hologram laser unit 10 are integrally adjusted in the radial direction within a plane perpendicular to the optical axis so that they coincide with each other, and then they are screwed together.

Here, the dividing line l ₁ of the hologram pattern 13 and the intensity distribution center L _{1 of the} light emitted from the semiconductor laser 11
, The return light 8 ′ from the disk 5 travels exactly the same path when the center of the intensity distribution is made to coincide with the center of the objective lens 4 and returns to the hologram laser unit 10. The center L ₁ ′ of the intensity distribution of the return light and the dividing line l ₁ of the hologram pattern 13 also match.

FIG. 16 shows the diffraction pattern of the returning light 8'on the hologram pattern 13 at this time. As shown by the diagonal lines in FIG. 16, the diffraction pattern generated by the groove of the disk 5 is symmetrical with respect to the dividing line l ₁ , that is, the same pattern with respect to the tracking dividing regions 13b and 13c. Regions 13b, 13
Radial error signal RE generated by the light amount difference of c
No offset occurs in S.

[0022]

However, as shown in FIG.
As shown in, when the intensity distribution center L ₁ of the beam 8 emitted from the semiconductor laser 11 and the dividing line l ₁ are deviated by a minute amount e ₁ , an optical pickup is assembled by the above-mentioned conventional adjustment method. Then, the intensity distribution center L ₁ of the return light 8 ′ reflected from the disk 5 through the objective lens 4
Then, the dividing line l ₁ is also displaced by e ₁ .

FIG. 18 shows the hologram pattern 1 in this case.
3 shows the diffraction pattern of return light 8'on top of FIG. FIG.
As indicated by the slanted line, the diffraction pattern of the return light generated by the groove of the disk 5 is also asymmetric with respect to the dividing line l ₁ . Therefore, in this case, an offset occurs in the radial error signal RES generated by the light amount difference between the tracking division areas 13b and 13c.

Even when the hologram laser unit 10 itself has no assembly error, the intensity distribution center L of the incident beam of the objective lens 4 is assembled at the time of assembling the optical pickup.
Even if the center of ₁ and the center of the objective lens 4 are slightly deviated from each other, an offset is similarly generated in the radial error signal RES.

For the above reason, in the conventional optical pickup, it is necessary to increase both the assembly error accuracy of the hologram laser unit itself and the assembly error accuracy of the optical pickup, and it takes a lot of time for the adjustment work, resulting in an efficient operation. It was not possible to assemble a simple optical pickup, which was one of the causes of the cost increase.

The present invention solves the drawbacks of the prior art as described above. The offset of the radial error signal can be remarkably reduced, the assembly tolerance of the hologram laser unit itself can be increased, and the assembly error of the optical pickup can be increased. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical pickup assembling / adjusting method capable of promptly and surely correcting the above.

Further, according to the present invention, the position of the center of the intensity distribution of the incident beam of the objective lens can be finely adjusted, and the assembling adjustment can be performed quickly.
It is an object of the present invention to provide an optical pickup that can be surely performed, can greatly contribute to the improvement of mass productivity, and can be expected to greatly reduce the cost.

[0028]

A method for assembling and adjusting an optical pickup according to the present invention comprises a semiconductor laser light source, an optical system including an objective lens, a diffractive element and a light receiving element, and a laser emitted from the semiconductor laser light source by the optical system. While condensing light on a recording medium having a plurality of tracks, the return light from the recording medium is guided to the diffraction element, and the light receiving element detects at least a tracking error based on the return light diffracted by the diffraction element. At least the semiconductor laser light source, the diffraction element, and the light receiving element are integrated as a hologram laser unit, and the diffraction element is divided by at least a dividing line extending in a direction corresponding to the track direction of the recording medium. While having two regions, at least the light receiving element receives the return light diffracted by the divided regions of the diffractive element, respectively. In a method for assembling and adjusting an optical pickup having two light receiving regions, after provisional assembly, the intensity distribution center of return light from the recording medium is incident on the objective lens such that the center of the intensity distribution of the returned light coincides with the dividing line of the diffraction element. The method includes the step of adjusting the position of the intensity center of the incident light beam and the step of fixing it after the adjustment, whereby the above object is achieved.

Further, the optical pickup of the present invention comprises a semiconductor laser light source, an optical system including an objective lens, a diffractive element and a light receiving element, and the optical system records the laser light from the semiconductor laser light source in a plurality of tracks. The semiconductor laser is configured such that the return light from the recording medium is guided to the diffraction element while being condensed on a medium, and the light receiving element detects at least a tracking error based on the return light diffracted by the diffraction element. The light source, the diffractive element and the light receiving element are integrated as a hologram laser unit, and the diffractive element has at least two regions divided by a dividing line extending in a direction corresponding to the track direction of the recording medium, At least two light receiving elements each receive the return light diffracted by the divided regions of the diffraction element.
In an optical pickup having two light receiving regions, the intensity center of the incident light beam incident on the objective lens is adjusted so that the intensity distribution center of the return light from the recording medium coincides with the dividing line of the diffraction element. An adjusting mechanism is provided to achieve the above object.

Preferably, as the adjusting mechanism, a parallel flat plate glass provided in the optical path of the parallel beam incident on the objective lens and rotatable about the rotation axis of the recording medium in the track direction is used.

Further, preferably, as the adjusting mechanism,
An objective lens driving device is used which is capable of adjusting the neutral position of the objective lens in a direction orthogonal to the track of the recording medium.

Further, preferably, as the adjusting mechanism,
A 45-degree rising mirror that is movable in a direction orthogonal to the track of the recording medium is used.

[0033]

As described above, the intensity center of the incident light beam incident on the objective lens is adjusted so that the intensity distribution center of the return light from the recording medium coincides with the division line (hologram division line) of the diffraction element. When the adjustment mechanism is provided, the offset of the radial error signal RES can be quickly and surely eliminated by performing the adjustment work using this adjustment mechanism.

[0034]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an optical pickup to which the method for assembling and adjusting the optical pickup according to the present invention is applied. This optical pickup is provided with a hologram laser unit 10 in which a servo signal detecting section is integrated with a semiconductor laser light source in order to reduce the number of parts and simplify adjustment, and the overall configuration is the same as that of the conventional example described above. Therefore, only the parts shown below will be described.

The hologram laser unit 10 has a semiconductor laser 11 and is constructed by integrating a servo error detector (not shown) in a semiconductor laser package. The beam 8 emitted from the semiconductor laser 11 is focused on the information recording surface of the disk 5 via the collimator lens 1, the objective lens 4 and the like.

A part of the reflected light from the information recording surface, that is, the returned light, returns to the hologram laser unit 10 along a path opposite to the above. Hologram laser unit 1
The return light 8 ′ that has returned to 0 is a servo error detector having a four-division structure similar to the conventional example due to the three-division structure hologram pattern 13 formed on the glass substrate 12 provided on the hologram laser unit 10. Is diffracted in the direction of.

As shown in FIG. 2, the hologram pattern 1
3 is the return light 8'which is reflected back from the disk 5 and returned.
It has an elliptical shape in accordance with the beam shape of. The hologram pattern 13 is divided into three areas. That is, first, the disc 5 is divided into two regions by the dividing line l ₂ extending in the direction corresponding to the radial direction of the disc 5. One of these areas is the focus division area 13a.
It has become. The remaining area is further divided into two tracking division areas 13b and 13c by a division line l ₁ extending in a direction corresponding to the track direction of the disk 5.

The return light diffracted in each region of the hologram pattern 13 is detected by each detector of the servo error detector in the same manner as the above-mentioned conventional example, and the focus error signal FES and the radial error signal R are detected based on the detection results.
ES can be obtained.

In the hologram laser unit 10, in the temporarily fixed state, an error e _{1 in the} lateral direction between the intensity distribution center L ₁ of the laser beam emitted from the semiconductor laser 11 and the dividing line l ₁ of the hologram pattern 13 is shown. Occurs, and the error e ₁ is adjusted as follows in the method of the present invention.

The hologram laser unit 10 and the collimator lens 1 are integrally moved in the radial direction corresponding to the lateral direction in the figure, whereby the intensity distribution center L ₁ of the laser light incident on the objective lens 4 is moved to the objective lens 4. Adjust with a distance of e ₂ from the center. By this adjustment, the intensity distribution center L of the return light 8 ′ from the disk 5, that is, the return light 8 ′ returning to the hologram pattern 13
₁ ′ and the dividing line l ₁ of the hologram pattern 13 are made to substantially coincide with each other.

In this way, as shown in FIG. 2, the diffraction pattern of the returning light 8'on the hologram pattern 13 becomes substantially symmetrical with respect to the dividing line l ₁ . Therefore, according to the method of the present invention, the offset of the radial error signal RES can be reliably corrected. At this time, the intensity distribution center L ₁ of the laser light incident on the objective lens 4 deviates from the center of the objective lens 4 by e _2, but such an error is almost due to the condensing characteristics of the objective lens 4. It doesn't matter. When this adjustment work is completed, a predetermined portion is screwed and fixed, and the optical pickup is finally assembled.

According to the method of assembling and adjusting the optical pickup of the present invention, when the hologram laser unit 10 is assembled, the intensity distribution center L ₁ of the outgoing beam 8 and the dividing line l ₁ of the hologram pattern 13 are slightly displaced. Even if there is, the offset of the radial error signal RES can be reliably adjusted (reduced) by fine adjustment at the time of assembling the optical pickup, unlike the above-mentioned conventional example.

However, according to the above adjusting method, it is necessary to perform fine adjustment manually by the operator, which requires skill, and the hologram laser unit 10 is required for screw fixing.
Semiconductor laser as a light source, which may move a minute amount
However, there is a problem that the emission angle of the laser beam may shift because 1 is moved.

Therefore, in the optical pickup of the present invention, in order to solve such a problem, the optical pickup is provided with an adjusting mechanism capable of adjusting the intensity distribution center of the laser light incident on the objective lens 4 independently of the light source. By doing so, adjustment work can be performed quickly and reliably. Hereinafter, each embodiment of the adjusting mechanism targeted by the optical pickup of the present invention will be described step by step.

(Embodiment 1) FIG. 3 shows Embodiment 1 of the adjusting mechanism. In the first embodiment, a transparent parallel plate glass 20 is used as the adjusting mechanism. That is, in the first embodiment, the parallel beam 8 between the collimator lens 1 and the objective lens 4 is
The parallel flat plate glass 20 is inserted therein, and the parallel flat plate glass 20 is rotated in the vertical direction, whereby the beam 8 is translated in the horizontal direction.

A mechanism shown in FIG. 4 may be used as a mechanism for rotating the parallel flat plate glass 20. That is, in the illustrated example, as shown in FIG. 4B, the parallel plate glass 20 is fixed in the cylindrical holder 21, and the cylindrical holder 21 is provided on the pickup base 22 as shown in FIG. 4A. Inserted into the holder mounting hole 22a. The outer peripheral surface of the cylindrical holder 21 is cut out except for the portions where both ends of the parallel plate glass 20 are fixed, and a long hole 21a that is long in the axial direction is formed in the portion that partially remains. Therefore, for example, when the eccentric pin (see FIG. 6) in which the tip shaft portion is inserted into the elongated hole 21a is rotated about its central axis and the cylindrical holder 21 is rotated about the central axis corresponding to the track direction, Along with this, the parallel plate glass 20 is rotated and the beam 8 is moved in the radial direction.

The structure of the pickup base 22 will be described below. The pickup base 22 has a U-shape with its upper end opened, and a 45-degree mirror 3 is set up at both ends corresponding to the left-right direction in the figure.
The hologram laser unit 10 is fixedly arranged.
The hologram laser unit 10 includes a semiconductor laser 1
1, the servo error detector 14 and the like are mounted, and the collimator lens 1 is arranged on the emission side of the laser light emitted from the semiconductor laser 11.

The beam 8 collimated by the collimator lens 1 is guided to the parallel plate glass 20 through the compound prism 2, and the parallel plate glass 20 is rotated to move the beam 8 in the radial direction. Raise 45
Degree is guided to the mirror 3.

That is, a holder mounting hole 22a is formed between the compound prism 2 on the pickup base 22 and the rising 45-degree mirror 3, and the parallel plate glass 2 is formed therein.
A cylindrical holder 21 in which 0 is fixed is inserted. The holder mounting hole 22a has a radius of curvature that is substantially the same as the radius of curvature of the cylindrical holder 21, and smoothly guides the rotation of the cylindrical holder 21.

Beam 8 guided to a 45 ° mirror 3
Is converted right above the optical path, is condensed by the objective lens 4, and is condensed on the information recording surface of the disk 5. Then, the return light reflected by the information recording surface returns to the hologram laser unit 10, and the servo error detector 14 detects the servo signal. In the figure, 6 is an actuator.

In such a structure, when the cylindrical holder 21 is rotated about the central axis by the eccentric pin, the beam 8 incident on the objective lens 4 is moved in the radial direction, and thus the method of the present invention has been described above. Adjustment work is performed. According to the first embodiment, the above-mentioned simple mechanism allows fine adjustment of the intensity distribution center while actually observing the servo signal without moving the light source, that is, the radial error signal RE.
Since the offset of S can be adjusted, there is an advantage that the adjustment work can be performed quickly and reliably.

(Second Embodiment) FIGS. 5 and 6 show a second embodiment of the adjusting mechanism. In this Example 2, the parallel flat plate glass 2
0 is not provided, and the offset of the radial error signal RES is adjusted by adjusting the position of the objective lens 4 itself.

In FIG. 5, the actuator 6 is fixed on a rectangular actuator base 23.
A focus drive coil 6c and a radial drive coil 6d are attached to the actuator 6. A magnetic circuit composed of a permanent magnet 6a and a yoke 6b is fixed on the actuator base 23. The objective lens holder 6f is supported by four elastic wires 6e, and has a structure in which the objective lens 4 is driven in the focusing direction and the radial direction by passing a current through the coils 6c and 6d. In order to adjust the center position of the objective lens 4 in the radial direction with respect to the beam 8 incident thereon, the actuator base 23 may be movable in that direction.

FIG. 6 shows an adjusting mechanism for making the actuator base 23 movable in the radial direction. The actuator base 23 is configured as follows by the pickup base 22.
Is rotatably attached to. That is, the positioning pin 24 fixed to the pickup base 22 is inserted into the hole 23a formed at one end of the actuator base 23 in the longitudinal direction, and the positioning of the both is performed. On the other hand, on the other end side of the actuator base 23,
An elongated hole 23b into which the tip shaft portion 25a of the eccentric pin 25 provided on the other end side of the pickup base 22 is inserted is formed.

Here, the tip shaft portion 25a is eccentric with respect to the central axis of the eccentric pin 25, and the eccentric pin 25 itself is rotatable about the central axis. Therefore, when the eccentric pin 25 is rotated, the actuator base 23 rotates in the radial direction indicated by the arrow with the positioning pin 24 as a fulcrum according to the amount of eccentricity of the tip shaft portion 25a. The objective lens 4 will rotate in the same direction. At this time, the movement amount of the objective lens 4 in the track direction is small and can be ignored.

Reference numeral 23c in the drawing denotes a hole penetratingly formed in the central portion of the actuator base 23.
The beam 8 whose optical path has been changed by the 45 ° mirror 3 which has been set up is guided to the objective lens 4.

Also in the case of the second embodiment, since the adjusting mechanism capable of finely adjusting the offset of the radial error signal RES is provided, there is an advantage that the assembly and adjustment of the optical pickup can be performed quickly and surely as in the first embodiment.

In addition, according to the second embodiment, since it can be realized only by adding a simple adjusting mechanism to the existing parts, it is advantageous in reducing the number of parts, simplifying the apparatus structure and reducing the cost. become.

(Third Embodiment) FIGS. 7 to 10 show a third embodiment of the adjusting mechanism. However, FIG. 7 shows an overall schematic configuration of an optical pickup in which an adjusting mechanism detailed in FIGS. 8 to 10 is mounted. Since this configuration itself is the same as the conventional example shown in FIG. 11, it is the same as the corresponding portion. No. and the detailed description is omitted.

In the third embodiment, the offset of the radial error signal RES is adjusted by moving the rising 45 ° mirror 3 in parallel in the radial direction. 8 to 10 show an adjusting mechanism for moving the rising 45-degree mirror 3 in parallel in the radial direction. In the figure, start up 45
The degree mirror 3 is fixed to a rectangular mirror base 26. The mirror base 26 is fixed on the pickup base 22 by a leaf spring 27.

Explaining a little now, the leaf spring 27 has a rectangular shape as a whole, and the horizontal portion 27a on one side has the screws 270,2.
It is fixed on the pickup base 22 by 70 and has a leaf spring portion 27b on the opposite side. The leaf spring portion 27b is notched in the middle portion in the longitudinal direction so as to exhibit springiness.
The leaf spring portion 27b is in contact with one end of the mirror base 26, so that the mirror base 26 is fixed to the pickup base 2.
The second horizontal guide surface 22b and the vertical guide surface 22c are fixed (temporarily fixed) in a state of being pressed.

In addition, a long hole 29 which is long in the width direction orthogonal to the longitudinal direction is formed in the central portion of the mirror base 26 in the longitudinal direction, which is located below the rising 45 ° mirror 3. And the pickup base 2 below that
An adjusting hole 30 shown in FIG. 10 is provided at a position corresponding to 2. An eccentric pin 28 is inserted into the adjustment hole 30, and a tip shaft portion 28a of the eccentric pin 28, which is eccentric to the center of the eccentric pin 28, is inserted into the elongated hole 29. The eccentric pin 28 itself is rotatable about the central axis.

In such a structure, when the eccentric pin 28 is rotated, the mirror base 26 moves in the radial direction against the biasing resistance of the leaf spring 27. That is, the 45-degree mirror 3 is moved along with this in the radial direction,
Offset adjustment of the radial error signal RES is performed.

When the adjustment work is completed, the screws 271 and 27 are
In step 1, the mirror base 26 is fixed onto the pickup base 22, and the final assembly process is performed.

In the case of the third embodiment as well, the same effects as those of the first embodiment can be obtained, and as in the case of the second embodiment, it can be realized by adding a simple adjusting mechanism to the existing parts. This is advantageous in reducing the number of points, simplifying the device configuration, and reducing the cost.

[0067]

According to the optical pickup assembling / adjusting method of the first aspect, the position of the incident light beam of the objective lens is adjusted so that the center of the intensity distribution of the returning light from the disk coincides with the dividing line of the hologram pattern. Therefore, even if the assembly error of the hologram laser unit itself is large, the offset of the radial error signal RES, which has occurred in the conventional adjustment method, can be significantly reduced in the process of incorporating this hologram laser unit into the optical pickup. . Therefore, there is an advantage that the allowable error of the hologram laser unit can be increased and the adjustment work can be efficiently performed.

Further, according to the optical pickups of claims 2 to 5, since the optical pickup is provided with an adjusting mechanism capable of finely adjusting the position adjustment of the center of the intensity distribution of the beam, that is, the offset adjustment of the radial error signal RES, There is an advantage that the pickup can be assembled quickly and surely and it can greatly contribute to the mass production of the optical pickup.

In particular, according to the optical pickups of claims 4 and 5, the optical pickup can be realized only by adding a simple adjusting mechanism to the existing parts. Therefore, the number of parts is reduced, the device configuration is simplified, and the cost is reduced. It will be advantageous for the purpose.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of an optical pickup to which an optical pickup assembling and adjusting method of the present invention is applied.

FIG. 2 is an explanatory diagram showing a beam intensity distribution on a hologram pattern.

FIG. 3 is a schematic front view showing a first embodiment of the optical pickup of the present invention having an adjusting mechanism.

4A is a side cross-sectional view of the optical pickup of Embodiment 1, and FIG. 4B is a perspective view of a cylindrical holder 21.

FIG. 5 is a perspective view showing a second embodiment of the optical pickup of the present invention having an adjusting mechanism.

FIG. 6 is an exploded perspective view showing an adjusting mechanism mounted on the optical pickup according to the second embodiment.

FIG. 7 is a side view showing a third embodiment of the optical pickup of the present invention having an adjusting mechanism.

FIG. 8 is a perspective view of an adjusting mechanism mounted on the optical pickup according to the third embodiment.

FIG. 9 is a plan view of an adjustment mechanism mounted on the optical pickup according to the third embodiment.

10 is a cross-sectional view taken along line XX of FIG.

FIG. 11 is a side view showing a conventional example of an optical pickup.

FIG. 12 is a plan view showing a conventional example of an optical pickup.

FIG. 13 is a perspective view showing a hologram laser unit.

14A and 14B are diagrams showing a conventional method for adjusting a hologram laser unit, wherein FIG. 14A shows a radial direction and FIG. 14B shows a track direction.

FIG. 15 is a front view showing a conventional adjusting method when a hologram laser unit is assembled to an optical pickup.

FIG. 16 is an explanatory diagram showing the intensity distribution of a beam on a hologram pattern.

FIG. 17 is a front view showing a case where a center of an intensity distribution of laser light emitted from a semiconductor laser and a dividing line are deviated from each other by a minute amount.

FIG. 18 is an explanatory view showing the intensity distribution of laser light on the hologram pattern in the case of FIG.

[Explanation of symbols]

 1 collimator lens 2 composite prism 3 rising 45 degree mirror 4 objective lens 5 disk 6 actuator 8 beam 8'return light 10 hologram laser unit 11 semiconductor laser 12 glass substrate 13 hologram pattern 14 servo error detector 20 parallel plate glass 21 cylindrical holder 22 pickup base 22a holder mounting hole 23 actuator base 23b oblong hole 24 positioning pin 25 eccentric pin 26 mirror base 27 leaf spring 28 eccentric pin 29 oblong hole

Claims (5)

[Claims] 1. A semiconductor laser light source, an optical system including an objective lens, a diffractive element and a light receiving element are provided, and the laser light from the semiconductor laser light source is focused on a recording medium having a plurality of tracks by the optical system. A configuration is provided in which return light from the recording medium is guided to the diffraction element, and the light receiving element detects at least a tracking error based on the return light diffracted by the diffraction element. The light receiving element is integrated as a hologram laser unit, and the diffractive element has at least two regions divided by a dividing line extending in a direction corresponding to the track direction of the recording medium, while the light receiving element is the diffractive element. A method for assembling and adjusting an optical pickup having at least two light receiving areas for receiving return light diffracted in divided areas. After the temporary assembly, the position of the intensity center of the incident light beam incident on the objective lens is adjusted so that the intensity distribution center of the return light from the recording medium coincides with the dividing line of the diffraction element. A method for assembling and adjusting an optical pickup, which comprises a step of fixing after adjustment. 2. A semiconductor laser light source, an optical system including an objective lens, a diffractive element and a light receiving element are provided, and the laser light from the semiconductor laser light source is focused on a recording medium having a plurality of tracks by the optical system. A configuration is provided in which return light from the recording medium is guided to the diffraction element, and the light receiving element detects at least a tracking error based on the return light diffracted by the diffraction element. The light receiving element is integrated as a hologram laser unit, and the diffractive element has at least two regions divided by a dividing line extending in a direction corresponding to the track direction of the recording medium, while the light receiving element is the diffractive element. In an optical pickup having at least two light receiving areas for receiving return light diffracted in the divided areas, the recording is performed. Intensity distribution center of the return light from the body to match the split line of the diffraction element, an optical pickup including an adjusting mechanism for adjusting the intensity center of the incident light beam entering the objective lens. 3. The parallel plate glass, wherein the adjusting mechanism is provided in an optical path of a parallel beam incident on the objective lens and is rotatable about a rotation axis of the recording medium in the track direction. The optical pickup described in 2. 4. The optical pickup according to claim 2, wherein the adjusting mechanism is an objective lens driving device that can adjust a neutral position of the objective lens in a direction orthogonal to the track of the recording medium. 5. The optical pickup according to claim 2, wherein the adjusting mechanism is a rising 45-degree mirror that is movable in a direction orthogonal to the track of the recording medium.