JP2002342945A - Optical pickup and adjusting method of optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constitution of optical pickup for improving the productivity and its adjusting method. SOLUTION: The optical pickup is provided with a unit having a light source, a photodetector, a beam splitter and a holding member for holding them. A tilting means of the above light source is furnished in the unit for making the normal direction with respect to one reference surface of the holding member to coincide with the center axis of a light emitting angle of light ejected from the light source through the beam splitter, and this optical pickup includes a collimator lens to converge the light from the light source, an objective lens for converging the light to an optical information medium, an actuator for holding the condenser lens and minutely adjusting a relative position between an optical information medium and the condenser lens, and an optical base for holding the actuator and the collimator lens, then the above unit is joined to the optical base at the reference surface of the unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an optical pickup for optically recording and reproducing information on an optical information medium such as an optical disk, and a method of manufacturing the optical pickup.

[0002]

2. Description of the Related Art First, a configuration of a conventional optical pickup will be described with reference to FIG.

In FIG. 6, an optical pickup comprises a semiconductor laser chip 601 and a photodetector 604 for reading information from an optical disk 602 and a semiconductor laser chip 601.
And a unit 620 including a micromirror 615 for reflecting light from a single package 603. In the unit 620, the light emitting point positions of the photodetector 604 and the laser 601 are mechanically positioned in advance with respect to the reference surface of the package 603.

Light emitted from the semiconductor laser chip 601 is reflected by the micromirror 615 of the unit 620 and emitted from the unit 620. This light is transmitted to the collimating lens 6 mounted on the optical base 718 of the optical pickup.
The divergent light is converged after passing through the hologram 605, and is transmitted through the polarizing hologram 606 through the rising mirror 608. A polarizing hologram is formed by forming a lattice having a depth of d on a substrate made of an anisotropic material such as lithium niobate, and filling the groove with an isotropic substance (refractive index n1). Generally, assuming that the phase difference of light passing between the grooves is φ, the transmittance is cos 2 (φ / 2)
It is represented by Assuming that the refractive indices of the substrates are n1 and n2 for polarized light parallel and straight to the grating grooves, respectively, the transmittance is 1 since φ = 0 for polarized light parallel to the grating grooves. On the other hand, for polarized light perpendicular to the grating grooves, φ = 2π (n1-
n2) Since d / λ, if the depth d is set so that φ = π, the transmittance becomes 0 and the light is completely diffracted.

The light transmitted through the polarizing hologram 606 is 1
After being converted into circularly polarized light by the 波長 wavelength plate 607, the light is incident on the objective lens 609 mounted on the actuator 612 and is focused on the signal surface 602 of the optical disk.

The light reflected from the signal surface of the optical disk 602 passes through the objective lens 609 and the quarter-wave plate 607, becomes linearly polarized light having a polarization direction orthogonal to the outward path, is diffracted and branched by the polarization hologram element 606, and rises. 608, return to the unit 620 via the collimating lens 605,
The light is guided to the light detector 604.

With such a unit, the light source, the photodetector, and the optical path switching means are integrally integrated, and the outgoing path and the return path of the optical system can be largely shared, thereby simplifying the configuration of the optical pickup. It can be downsized.

Also, since the optical path length of the portion of the optical system branched between the outward path and the return path is short, it is possible to realize an optical pickup in which the characteristic change of the optical system due to the thermal deformation of the optical pickup with respect to the change in the ambient temperature is small.

Further, there are the following advantages from the viewpoint of assembly adjustment of the optical pickup. In other words, when such a unit is used, assembly of the unit alone can be realized, and the light emitting point of the laser light source 601 is positioned with respect to the reference surface of the package 603. Simply by fitting the optical table 718 on the reference surface and attaching the optical table 718, almost the optical axis accuracy is secured. In addition, since the forward path and the return path of the optical system are almost common, the light returning from the optical disc 602 can be accurately detected by the photodetector 604.
Will come back to.

FIG. 7A shows a method of adjusting a photodetector for returning light branched by a polarization hologram or the like in such a conventional optical pickup.

In FIG. 7A, light from a unit 720 of the optical pickup passes through a collimator lens 705, a rising mirror 708, a polarization hologram 706, a quarter-wave plate 707, and a disk 702 by an objective lens 709.
It is collected on the surface of. The reflected light from the disk 702 is split by the polarization hologram 706, and each split light returns to the unit 720 by the collimating lens 705, and is received by the photodetector 704 in the unit 720. The adjustment of the photodetector is performed while monitoring this signal. Specifically, while the objective lens 709 is vertically swung by the drive circuit 724 of the actuator, the signal from the photodetector for focus control is flexibly adjusted. The signal is taken out through a plate 722 and processed by a signal processing circuit 723 such as an amplifier circuit or an arithmetic circuit and monitored by an oscilloscope 721 or the like, so that the shape of a focus error signal generally called an S-shape is optimized. .

FIG. 7B shows adjustment of a photodetector in an optical pickup using such a unit. First, as shown in FIG. 7B, if the diffraction direction of the return light is shifted from the photodetector 704 by an angle of θ, the light spot 73
The position of 1,732 is in a positional relationship as shown in the figure with respect to the pattern of the photodetector 704, and no signal is output or a signal of a desired magnitude cannot be obtained. Therefore, by rotating the detector 704, that is, the unit by θ with reference to the light emitting point of the laser light source 701, the light spot 73 of the return light can be obtained.
1,732 and the pattern of the photodetector 704 are aligned. However, the alignment is performed based on the monitoring of the optical output signal from the photodetector 704 as described above.

[0013]

However, such a conventional unit has several problems. In other words, in such a unit, a minute component such as a laser chip is directly mounted on a silicon substrate or the like on which a photodetector is formed, but the object is small and the mechanical accuracy of the mounting is limited. The mounting angle is not always constant with respect to the package reference plane of the unit, and the emission angle center of the light emitted from the laser light source varies within a range of several degrees.

For this reason, even if the laser light source is mounted on the optical bench with the mechanical precision of the package reference plane, its emission angle center axis is inclined with respect to the axis connecting the emission point and the center of the objective lens, that is, the optical axis. If the distribution of the amount of light incident on the objective lens is non-uniform, when the objective lens moves following the track of the optical disk, the transmitted light amount of the objective lens according to the moving direction, that is, the transmitted light amount of the light returning from the optical disk, The change occurs asymmetrically, causing an offset in the signal from the disk.

On the other hand, if the whole unit is tilted and adjusted, the photodetector surface also tilts, and there is a problem that the condensed spot formed on the photodetector surface is deformed from a desired state.

Furthermore, not only in the case of using such a unit but also in the case of adjusting the position of the photodetector from a responsive point of view, such as by adjusting the waveform of a signal actually obtained from an optical disk, the standard varies. There is a problem that the adjustment accuracy is not stable.

The present invention realizes a light source unit that ensures effective light intensity distribution symmetry even in a device that requires spot quality rather than recording a signal on an optical disk. An object is to realize a small optical pickup.

It is another object of the present invention to realize a simple adjustment method for performing high-precision assembly adjustment of an optical pickup simply by monitoring an image with an adjusting device including a simple reference optical system for adjusting a light source unit or an optical pickup. I do.

[0019]

In order to solve this problem, an optical pickup according to the present invention comprises at least one light source, at least one photodetector, light from the light source and light returning from the optical information medium. A unit composed of at least one beam splitter for branching the optical path, a holding member for holding these and having at least one reference surface, a collimating lens for converging light from a light source, and condensing light on an optical information medium An optical pickup comprising an objective lens, an actuator for finely adjusting the position of the objective lens, and an optical bench for holding the objective lens, and a unit joined to the optical bench at a reference plane, the optical pickup being centered on a light emitting point of the light source. The unit is provided with a tilting means for raising a light source.

Alternatively, at least one light source, at least one photodetector, at least one beam splitter for branching an optical path between light from the light source and light returning from the optical information medium, and divergent light from the light source A unit including a collimating lens that converges the light into substantially parallel light, a tilting unit that raises the light source around the light emitting point of the light source, a holding member that holds the light source, and at least one reference surface, and a device that collects light on the optical information medium. The optical pickup includes an objective lens that emits light, an actuator that finely adjusts the position of the objective lens, and an optical bench that holds the actuator, and a unit is joined to the optical bench at a reference plane.

Further, the photodetector may be a unit having a plurality of photodetecting elements, and further including a light splitting element for splitting light returning from the optical information medium in the direction of each photodetecting element.

Alternatively, there is provided an optical pickup having moving means for moving the polarizing beam splitter in the optical axis direction.

Further, as the tilting means, a light source holding member which holds the light source and has a concave or convex spherical surface centered on the light emitting point of the light source, and a member having a convex or concave spherical surface fitted with the light source holding member is provided. An optical pickup, or a light source holding member having a concave or convex spherical surface centered on the light emitting point of the light source, holding a light source as a tilting means, and a convex or concave spherical portion fitted with the light source holding member. An optical pickup having a unit having a spherical seat having a flat portion along one plane of a holding member.

Further, as an adjustment method of the optical pickup,
In an optical pickup having at least one light source, at least one photodetector, and at least one beam splitter for branching an optical path between light from the light source and light returning from the optical information medium, a light emitting point of the light source and light This is an adjustment method for an optical pickup in which each detection element of a detector is simultaneously observed by the same observation system via a beam splitter, and the relative position between the light source and the light detection element is adjusted based on the image. Specifically, the photodetector has a plurality of points or linear mark patterns for positioning, and the mark pattern is aligned with the reference mark displayed on the observation screen to position the photodetector. Is an adjustment method.

Alternatively, the adjustment method is characterized in that the pattern of the photodetector that receives the return light from the optical information medium is matched with the reference mark displayed on the observation screen.

Alternatively, an optical pickup is a method for adjusting the position of a photodetector using a semiconductor laser as a light source and using a line of an active layer of the semiconductor laser chip as a reference mark.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1A is a top view showing a configuration example of a unit having a laser light source and a photodetector which is a part of the configuration of an optical pickup according to an embodiment of the present invention. And a side view. FIG. 1B is a diagram showing a configuration of an optical pickup having this unit. In addition,
A detailed description of the elements that fulfill the same functions as those of the conventional example will be omitted.

In FIG. 1A, a unit comprises a holding member 101 having a mechanical reference, a laser light source 104 attached via a photodetector 102 attached to the holding member 101 and a tilting means 103, and a laser light source 104. And a polarization beam splitter 105 that transmits the light from the optical path as it is and reflects light on the return path orthogonal to the polarization direction. Here, the reference surface A1 is a bonding surface of the optical pickup with the optical bench.

The tilting means 103 is a laser holding member 106 having a spherical surface centered on the light emitting point of the laser light source 104.
And a spherical seat 107 having a spherical surface joined to the spherical surface. The tilt of the laser chip can be adjusted two-dimensionally along the spherical surface by the tilting means 103, and the center of the emission angle coincides with the normal direction of the reference plane A1 of the holding member 101. Further, by sliding the spherical seat 107 along the mounting surface C1 of the holding member 101, the light emitting point can be adjusted in the xy plane of the drawing without changing the distance between the surface C1 and the light emitting point.

The polarization beam splitter 105 has a holder 108 for holding the polarization beam splitter
The polarizing beam splitter 105 moves along an axis passing through the light emitting point in the normal direction of the reference plane A1. The polarizing beam splitter 105 is moved by moving the polarizing beam splitter 105. Light source 104 and photodetector 10 from the branch point of the round-trip light passing through
The relative optical distance between the two can be adjusted.

Further, the light detector 102 slides along the mounting surface of the holding member with respect to light traveling toward the light detector 102 having an optical axis coincident with the axis passing through the light emitting point in the normal direction of the reference plane A1. And positioning.

FIG. 1B is a top view and a side view showing the structure of an optical pickup using such a unit. The optical table 113 holds an actuator 112 on which a collimating lens 109 for collimating light from the laser light source 104, a rising mirror 110, and an objective lens 111 are mounted.

When the optical bench 113 is mounted on the apparatus, the optical bench 113 has a reference plane E orthogonal to the light of the optical axis in the direction coinciding with the normal direction of the optical disk. The unit 1a is joined and bonded to the reference surface A1 of the holding member 101 of the unit. Further, positioning pins 114 and 115 are formed on the optical bench 113, and the position of the laser emission point in the xy plane is defined by pressing the unit against the positioning pins 114 and 115. As a result, a state equivalent to the optical axis adjustment of the optical pickup is performed.

In the optical pickup, the photodetector 1
When the collimator lens 109 is shared between the forward path and the return path of the optical system, the size of the spot on the laser light source 10
4 and the photodetector 102 are determined by the relative position in the optical axis direction, but as in the present embodiment, the polarization beam splitter 105
By moving in the optical axis direction, the relative position can be adjusted.

With such a unit, as in the conventional example,
Since the photodetector, the laser light source, and the polarizing beam splitter are integrated, the size of the optical pickup can be reduced, and the three-dimensional relative position between the laser light source and the photodetector is adjusted in advance. In addition to simplifying the assembly of the optical pickup, by joining the optical pickup to the optical pickup at the reference plane, it is possible to realize an optical pickup in which the center of the light intensity distribution stably comes to the center of the objective lens.

In general, when a high-output semiconductor laser is used, the light output with respect to the current changes due to a temperature rise due to heat generation. In order to reduce the degree of this change as much as possible, it is necessary to devise a means for efficiently releasing heat from the laser package. According to the configuration of the present invention, the laser holding member 1
06, the spherical seat 107 and the holding member 101 of the unit are made of a heat dissipating material, so that they are all in surface contact, so that the heat of the laser is efficiently transmitted to the optical bench, so that the heat dissipating property is high.

(Embodiment 2) FIG. 2A shows an example of the configuration of a unit including a collimating lens for converging light from a laser light source as another embodiment of the present invention. In the figure, the collimating lens 214 has its holder 215
At the same time, the spring 219 is pressed against the inner walls B2 and D2 of the holding member 201, so that the collimator lens 214 can move along an axis passing through the light emitting point in the normal direction of the reference plane A1.

FIG. 2B shows the structure of an optical pickup using such a unit. The optical bench 213 holds an actuator 212 on which a rising mirror 210 and an objective lens 211 are mounted.

When the optical bench 213 is mounted on the apparatus, the optical bench 213 has a surface F orthogonal to the optical axis when a light beam having an optical axis in a direction coinciding with the normal direction of the optical disk passes through the optical system. This surface F and the reference surface A1 of the holding member 201 of the unit shown in FIG. In addition, positioning pins 214 and 215 are formed on the optical bench 213, and the unit is connected to the positioning pins 21 respectively.
4 and 215, the position of the laser emission point in the xy plane is defined, and a state equivalent to the optical axis adjustment of the optical pickup is performed.

According to such a configuration, the optical pickup can be assembled only by mounting a unit whose relative position in the optical axis direction between the laser light source and the collimator lens has been adjusted in advance to the optical table. Simplified.

(Embodiment 3) FIG. 3 schematically shows the structure of a unit according to another embodiment of the present invention. In the present embodiment, a branch element 321 for branching the light from the return light is included in each detection element of the photodetector 302 in the unit.

Thus, the unit in which the relative position between the light spot branched by the light branching element 321 on the return path and the light detecting element of the light detector 302 is mounted on the optical base of the optical pickup simply by mounting the unit. Since assembly can be performed, the assembly adjustment process is further simplified.

(Embodiment 4) FIG. 4A is a view schematically showing an assembling / adjusting apparatus for assembling such a unit. In FIG. 4A, the adjusting device has a reference surface G, and the optical axis of the optical system of the adjusting device is adjusted in the normal direction of the reference surface G in advance. The reference plane G of the adjusting device is
The positioning pins 415 and 416 are provided to define the position of the ideal light emitting point position of the optical system in the xy plane.

The reference surface G is joined to the reference surface A1 of the holding member of the unit, and two reference surfaces orthogonal to the reference surface A1 are pressed against the positioning pins 415 and 416.

The adjustment optical system will be described. This optical system converts collimated light from a laser light source into a collimated lens, observes an image of a photodetector and a laser chip via a polarizing beam splitter, and a half mirror 410 as an optical system for observing an image. , Imaging lens 41
1. a CCD camera 412; Further, an imaging lens 414 for observing a far-field image of light from a laser light source transmitted through the half mirror 410, a CCD
An optical system including a camera 417 is provided.

First, a mate lens 409, a half mirror 410, an imaging lens 411, a CCD camera 412
The image of the laser light source 401 using the observation optical system
The image is displayed on the image monitor 418 by the CD camera 412, and the xy with respect to the holding member 403 of the laser light source 401 is set so that the light emitting point position of the laser light source 401 is located at a predetermined position on the screen.
Adjust the position in the plane. Next, the far-field image of the light emission pattern of the laser light source 401 is converted to an objective lens 409,
The far field image is projected on the monitor 418 using an optical system including a half mirror 410, an imaging lens 414, and a CCD camera 417, and the laser light source 401 is held by the holding member 40 so that the center of the light amount distribution coincides with a predetermined position on the screen.
Adjust the tilt for 3. Thereby, in the ideal optical system, the laser light source 401 can be fixed in a state where the optical axis and the far field center coincide.

Since the ideal optical system is calibrated so that the optical axis is the direction normal to the reference surface of the holding member, the normal direction of the reference surface of the holding member of the unit coincides with the center of the emission angle. The position of the light emitting point is accurately positioned with respect to the xy reference plane of the holding member.

Next, the pattern of the photodetector 402 is observed by the above-mentioned observation optical system via the polarization beam splitter 406. Here, the relative distance between the photodetector 402 and the laser light source 401 with respect to the polarization beam splitter 406 is determined by design.
While observing 18, the image of the light emitting point of the laser light source 401 and the image of the photodetector 402 are both brought into focus, and the polarization beam splitter 406 is adjusted by moving a predetermined amount in the optical axis direction of the optical system from this state. it can. Next, the photodetector 40
The position of the photodetector 402 is adjusted with respect to the holding member 403 in the xz plane so that the center position of the pattern 2 is at a predetermined position on the screen of the monitor 418.

At this time, for example, the alignment marker 421 provided on the photodetector 402 and the reference mark 423 on the screen may be aligned like the image on the monitor screen shown in FIG. The arrangement and shape of the elements 422 may be matched with the reference marks 423 on the screen. Alternatively, the alignment marker 421 of the photodetector 402 may be added to the line of the active layer 424 of the laser chip 426 shown in FIG.
Alternatively, the patterns of the light detection elements 422 may be matched.

According to the above-described method, the light emitting point of the laser 401 and the photodetector 402 are set to 3 with respect to the optical axis of the ideal optical system.
This means that the relative position can be adjusted dimensionally. That is, a unit in which the light emission point and the light emission angle of the laser and the relative position of the photodetector are adjusted based on the holding member of the unit by such an adjustment method is completed.

The signal from the photodetector can be monitored by assembling an optical pickup by joining this unit to a reference surface on the optical bench side on which optical components such as a collimator lens are mounted at its reference surface. The optical pickup can be adjusted using only a simple optical system and a system for observing the image.

(Embodiment 5) FIG. 5 shows the configuration of an adjustment apparatus in a case where the adjustment of Embodiment 4 is further applied and the optical adjustment of the entire optical base of the optical pickup instead of the unit is performed only with an image. .

In this adjustment apparatus, the adjustment optical system is calibrated with the surface of the optical base 513 of the optical pickup 513 having the ideal optical axis as a normal line as a reference surface.

As shown in FIG. 5, the optical table 51 of the optical pickup 51
The light emitted from the rising mirror 506 attached to the third mirror is split via the half mirror 510, and the fourth embodiment is hereinafter described.
Similarly, the adjustment of the optical system of the optical pickup can be completed by the image by guiding the optical system to the adjustment optical system described in (1).

[0056]

As described above, according to the present invention, it is possible to realize an optical pickup in which a signal offset change is small in accordance with the lens shift direction of the objective lens, and the structure thereof can be simplified.

Further, the adjustment of the light source unit or the optical pickup can be performed with high accuracy by simply monitoring the image with an adjusting device having a simple reference optical system, thereby simplifying the assembly process of the optical pickup. Is done.

[Brief description of the drawings]

FIG. 1A shows a schematic configuration of a unit according to a first embodiment of the present invention. FIG. 1B shows a schematic configuration of an optical pickup including the unit according to the first embodiment of the present invention.

2A is a diagram showing a schematic configuration of a unit according to a second embodiment of the present invention. FIG. 2B is a diagram showing a schematic configuration of an optical pickup including the unit according to the second embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a unit according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a unit adjustment method according to the embodiment of the present invention.

FIG. 5 is a diagram showing a method of adjusting the optical pickup according to the embodiment of the present invention.

FIG. 6 is a diagram showing an optical system configuration of a conventional optical pickup.

FIG. 7 is a diagram showing a conventional optical pickup adjustment method.

[Explanation of symbols]

 101, 201 holding member 102 photodetector 103 tilting means 104 laser light source 105 polarization beam splitter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoichi Saito 1006, Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5D117 AA02 CC07 HH01 HH11 KK01 KK08 KK17 KK25 5D119 AA29 AA38 BA01 EC30 EC35 FA05 FA28 FA35 JA10 PA04

Claims (10)

[Claims] At least one light source, at least one photodetector, at least one beam splitter for branching an optical path between light from the light source and light returning from the optical information medium, the light source and the light detection A unit comprising a holder and a holding member having at least one reference surface for holding a beam splitter, a collimating lens for converging light from the light source, an objective lens for condensing light on an optical information medium, and An optical pickup comprising an actuator for finely adjusting the position of an objective lens, and an optical bench holding the actuator and the collimating lens, and the unit being joined to the optical bench at the reference surface, An optical pickup characterized in that the unit is provided with a tilting means for raising the light source around a light emitting point of the light source. 2. At least one light source, at least one photodetector, at least one beam splitter for branching an optical path between light from the light source and light returning from the optical information medium, and divergent light from the light source A collimating lens that converges the light into substantially parallel light, a tilting unit that raises the light source around a light emitting point of the light source, and holds at least the light source, the photodetector, the beam splitter, the collimating lens, and the tilting unit. A unit including a holding member having one reference surface, an objective lens for condensing light on the optical information medium, an actuator for finely adjusting the position of the objective lens, and an optical table for holding the actuator, An optical pickup formed by joining the unit to the optical bench at the reference surface. 3. The unit according to claim 1, wherein the photodetector has a plurality of photodetectors, and further includes a unit for splitting light returning from the optical information medium in the direction of each photodetector. The optical pickup according to claim 2. 4. A light source holding member having a concave or convex spherical surface centered on a light emitting point of the light source as a tilting means, and a member having a convex or concave spherical surface fitted with the light source holding member. The optical pickup according to claim 1. 5. A light source holding member holding a light source as a tilting means and having a concave or convex spherical surface centered on a light emitting point of the light source, and a convex or concave spherical portion fitted to the light source holding member and one of the holding members. The optical pickup according to claim 4, further comprising a unit having a spherical seat having a plane portion along the plane. 6. An optical pickup comprising: a unit having a moving means for moving a polarizing beam splitter along an optical path from a light source; and an optical pickup or a polarizing beam splitter, which moves along the optical path from the light source. A method for adjusting an optical pickup, comprising changing a size of a spot on a detector surface. 7. An optical pickup comprising at least one light source, at least one photodetector, and at least one beam splitter for branching an optical path between light from the light source and light returning from the optical information medium. An optical pickup adjustment method for observing the light-emitting point and each detection element of the photodetector with the same observation system via a beam splitter, and adjusting the relative position between the light source and the photodetection element based on the observation image. 8. The photodetector has a plurality of position or linear mark patterns for positioning, and aligns the mark pattern with a reference mark displayed on an observation screen to position the photodetector. The method for adjusting an optical pickup according to claim 7, wherein: 9. The method for adjusting an optical pickup according to claim 7, wherein a pattern of a photodetector for receiving return light from the optical information medium is matched with a reference mark displayed on an observation screen. 10. The method for adjusting an optical pickup according to claim 8, wherein the light source is a semiconductor laser, and the position of the photodetector is adjusted using the line of the active layer of the semiconductor laser chip as a reference mark.