Patent Application
20170371113
The present invention relates to an optical axis alignment method and an optical axis alignment apparatus and a method for manufacturing an optical device.
Recently, communication traffic volume in an optical network has gotten increased. Hence, a light communication module with a smaller size is required that has a higher communication capacity and needs less electric power consumption. Patent Document 1, for example, discloses a light communication module including four laser light sources each emitting light of different wavelength and a single optical multiplexer, the laser light sources and the optical multiplexer being connected via four lens, thereby accomplishing a high communication capacity and a small size. In the conventional light communication module the four laser light sources requires to be mounted so that they each have a high coupling efficiency and they have a small variation in a coupling efficiency among the four. In this case, the four laser light sources and the optical multiplexer should be assembled with a high accuracy.
A method for assembling an integrated optical module is discussed below where a plurality of laser light sources are optically coupled by a single optical multiplexer, with reference to conventional prior arts.
Patent Document 1 discloses a method including performing alignment by displacing a lens while detecting a light from a laser light source and fixing the lens via soldering or YAG laser welding. This method including displacing the lens while detecting a light from a laser light source to fix it, which enables tolerances of elements and misaligned positions occurred in one or more previous processes to be compensated, consequently resulting in a high optical coupling efficiency. This method in turn occurs a new problem that an optical coupling efficiency is decreased due to a misaligned position of the lens possibly occurred when the lens is fixed. Optical coupling between the plurality of laser light sources and the single optical multiplexer increases the extent to which the position of the lens is misaligned, which leads to a variation in optical coupling efficiencies among the laser light sources.
Patent Document 2 discloses a method including applying an external force against a lens holder after fixing a lens to plastically deform the lens holder, correcting the position where the lens is fixed for improving an optical coupling efficiency. However, a light communication module having a demanded smaller size and a demanded high integration density possibly occurs an interruption between a tool for applying the external force and a neighbor lens holder, which makes the alignment difficult. Further, when the step of correcting is manually performed, time required to complete the step is elongated.
Patent Documents 3 and 4 each disclose an optical axis alignment method via laser irradiation for occurring melt-solidification of an irradiated portion to shrink it. This method enables a laser irradiation for a cylinder shaped housing accommodating a single light emitter from every direction to conduct a fine alignment. Arranging a plurality of light emitters and a plurality of lens on the same substrate enables the substrate, the emitters and an optical multiplexer to be mounted with an improved accuracy. However, arranging a plurality of lens holder on the same substrate makes it difficult to conduct an alignment via laser irradiation from every direction.
Patent Document 5 discloses a method including plastically deforming a lens holder and correcting a position to which the lens is fixed, by means of YAG laser without direct contact with the lens holder. In the method, YAG laser irradiation is performed from limited range of directions. This enables, when a plurality of lens are mounted in a single light communication module, to correct the position of each of the lens.
Patent Document 1: US 2011/0013869 A
Patent Document 2: JP H2-308209 A
Patent Document 3: JP 2005-43479 A
Patent Document 4: JP 2005-214776 A
Patent Document 5: JP 2013-231937 A
When a plurality of lenses are mounted in an integrated light communication module with an accuracy of sub micrometer order, positional misalignment occurred when the lens are fixed is concerned. Such a misalignment can be compensated by an additional correction of the lens position after it is fixed, which enables the lens to be mounted with an accuracy of sub micrometer order.
However, additional correction process of the lens position occurs longer time required to complete an optical axis alignment, which decreases productivity.
It is an object of the present invention to provide an optical axis alignment method and an optical axis alignment apparatus with a higher accuracy and less time required for the alignment, and a method for manufacturing the optical device.
In order to solve the above problem, an optical axis alignment method for an optical device according to the present invention, where the device includes a lens having an optical axis, a holder for holding the lens and a base member to which the holder is fixed, comprises the steps of:
The method of the present invention preferably, further comprises:
In the method of the present invention, preferably, the step of correcting an irradiation position or an irradiation dose of includes:
In the method of the present invention, preferably, the step of correcting an irradiation position or an irradiation dose includes irradiating with laser light a position between each of opposite two fixing points where the holder and the base member are fixed to each other and the lens, when the lens is to be adjusted downward in the vertical direction.
In the method of the present invention, preferably, the optical device is a light communication module, the module including:
An optical axis alignment apparatus for an optical device according to the present invention, where the device includes a lens having an optical axis, a holder for holding the lens and a base member to which the holder is fixed, comprises:
In the apparatus of the present invention, preferably, the detector includes a light receiving element and an imaging lens for condensing the light beam which exits from the lens into a receiving surface of the receiving element, the imaging lens having a length of infinity in a light incident side.
A method for manufacturing an optical device according to the present invention comprises the steps of:
According to the present invention, by obtaining two sets of location information about the light path of the light beam both before and after the step of laser irradiation to adjust the position of the lens, the laser irradiation condition can be correlated to the transitional light path of the light beam. This allows the laser irradiation condition to be optimized when the lens position is adjusted, which subsequently enables to perform the optical axis alignment with a higher accuracy and less time required for the alignment.
The light communication module may include four laser light sources 1, four lens holders 4, an optical multiplexer 10 and a carrier substrate 6. In this embodiment, for the purpose of easier understanding, a first direction in which an optical axis of the laser light source 1 extends is referred to as Z direction, a second direction which is perpendicular to the optical axis and parallel to a main surface of the carrier substrate 6 is referred to as X direction, and a third direction which is perpendicular to the optical axis and parallel to the main surface of the carrier substrate 6 is referred to as Y direction.
The laser light sources 1, which may be a semiconductor laser, each emit light having a central wavelength different from each other among the sources 1, the central wavelength being in a range between 1,300 nm and 1,500 nm when wavelength-division multiplexing is employed. The laser light source 1 is adhered on a submount (not shown) via soldering or adhesive bonding and the submount is fixed on the carrier substrate 6 via soldering or adhesive bonding. The laser light source 1 is connected to a circuit such as a drive circuit and/or a modulation circuit, which allows the source 1 to emit light pulse modulated in a high frequency based on a digital signal received from one or more external devices. In
The lens holder 4 holds a collimating lens 2, which is configured to convert a laser beam emitted from each of the laser light sources 1 into collimated light ray 11. Laser light in the form of the collimated light rays 11 is ideally collected to one spot on XY plane by means of the optical multiplexer 10 and in turn focused in a spot-like way by the focus lens 12 to be connected to an optical fiber (not shown). Practically, the collimated light rays 11, which are generated after the light beams from the laser light sources 1 are converted by the collimating lens 2, may not coincide to an extent with each other in their locations in XY plane due to tolerances of the laser light sources 1 and the optical multiplexer 10 and due to variations in mounted positions thereof. The extent to which the collimated light rays 11 are not coincident is preferably small such that they are combined to the optical fiber by the condensing lens 12 and they exit from the optical fiber with their light intensity being maintained.
The lens cylinder 3 may be fixed to the lens holder 4 via soldering, adhesive bonding or YAG laser welding. When the soldering is employed, gold plating is preferably applied on a bonding surface defined between the lens cylinder 3 and the lens holder 4. When the adhesive is applied, gold plating should not be applied. Also, when the YAG laser welding is employed, the lens cylinder 3 and the lens holder 4 are preferably made of a material such as stainless steel or silicon steel plate, which has a high absorbance for YAG laser light having a range of wavelength. Alternatively, either the lens cylinder 3 or the lens holder 4 may be made of a material such as stainless steel or silicon steel plate. When the collimating lens 2 is directly held by the lens holder 4 without the lens cylinder 3 provided therebetween, the YAG laser welding should not be used and the soldering or the adhesive bonding is preferably used.
In this embodiment, the lens cylinder 3 and the lens holder 4 are fixed via the YAG laser welding and they are made of a material having a high absorbance for the YAG laser light.
The lens holder 4 includes a horizontal member 41 extending in X direction and two vertical members 42a, 42b each extending in Y direction from both ends of the horizontal member 41, thereby forming a U shape. The collimating lens 2 is housed in the lens cylinder 3 and fixed to the horizontal member 41 of the lens holder 4 so that the optical axis of the lens 2 is aligned with Z direction. The vertical members 42a, 42b and the holder base 5 working as a base member, to which the members 42a, 42b are fixed, constitute a lens unit 7 as a whole. The lens holder 4 is welded to the holder base 5 to be fixed thereto. Hence, a lower end surface of the lens holder 4 and a lateral surface of the holder base 5 each preferably have a margin for welding.
The lens unit 7 is fixed to the carrier substrate 6. The collimating lens 2 fixed to the lens holder 4 may have a cuboid shape such that the lens 2 conform to the inner shape of the lens holder 4 without the lens cylinder 3 being used. In this example, the lens 2 and the lens holder 4 are fixed to each other via the soldering or the adhesive bonding. The lens unit 7 and the carrier substrate 6 may be fixed to each other via the soldering, the adhesive bonding or the YAG laser welding. When the soldering is employed, gold plating is preferably applied to the bonding surface defined between the carrier substrate 6 and the lens unit 7, i.e. an upper surface of the carrier substrate 6 and the bottom surface of the holder base 5. When the adhesive bonding is employed, the gold plating is not applied. When the YAG laser welding is employed, the holder base 5 and the carrier substrate 6 are preferably made of a material such as stainless steel or silicon steel plate, which has a high absorption for light emitted from the YAG laser. Alternatively, among the two, only the holder base 5 may be made of such a material while the carrier 6 may be made of a material such as copper-tungsten, which has a low absorption for light emitted from the YAG laser.
The optical multiplexer 10 is configured to collect the collimated light rays 11 from the collimating lens 2 into ideally a single position in XY plane at an exit side of the optical multiplexer 10 and to allow the collimated light rays 11 to be consistent in their beam orientations with each other, so that the light rays 11 are incident on the condensing lens 12. As described above, the optical multiplexer 10 may allow a plurality of collimated light rays 11 to be incident on the condensing lens 12 at an identical orientation or align orientations of the collimated light rays 11 incident on the optical multiplexer 10, so that they exit from the optical multiplexer 10 at an identical orientation. In other words, the collimating light rays 11 may be incident on the optical multiplexer 10 at the identical orientation and may be collected to the single position XY plane at the exit side of the optical multiplexer 10 with orientations of the collimating light rays 11 being maintained. Alternatively, the optical multiplexer 10 may be configured to compensate variations in the orientations of the collimated light rays incident on the optical multiplexer 10 and allow the rays 11 to exit with the identical orientation with each other. In this embodiment, the optical multiplexer 10 is configured to allow the collimating light rays 11 incident on the multiplexer 10 to emit it so that the rays 11 are collected to a single position on XY plane with orientations of the rays 11 being maintained.
In step S2, a position of the lens unit 7 is adjusted in X, Y and Z directions with respect to a plurality of laser light sources 1 which are mounted on the carrier substrate 6 to perform an optical axis alignment such that the light emitted from the laser light source 1 is shaped into collimated light rays 11. Orientation of the collimated light rays 11 are preferably adjusted so that the adjusted rays 11 are parallel to a direction around the X-axis of the carrier substrate 6 and are perpendicular to a direction around the Y-axis thereof.
In step S3, the lens holder 4 is fixed to the holder base 5. The lens holder 4 may be fixed to the holder base 5 via soldering, adhesive bonding or YAG laser welding, and in this embodiment, the YAG laser welding is employed. When the soldering or the adhesive bonding is employed, surface treatment such as gold plating should be applied to the bonding surface between the lens holder 4 and the holder base 5 as described above. An optical axis alignment assembling apparatus for performing this assembling process should have a unit for applying the solder or the adhesive and a unit for hardening the bonding materials (e.g. a means for heating or ultra violet irradiation). When the lens holder 4 is fixed to the holder base 5, the adjusted collimating lens 2 is subject to a fine misalignment. Hence, in this process, an extent of the misalignment occurred is preliminarily estimated and an adjustment position is preferably offset based on the extent.
In step S4, the lens unit 7, which is fixed as described above, is subject to the optical axis adjustment again. Because the lens holder 4 and the holder base 5 were already fixed, preventing from adjusting the optical axis in Y direction, the optical axis adjustment is performed only in X and Z directions.
In step S5, the lens unit 7 is fixed on the carrier substrate 6. The lens unit 7 may be fixed on the carrier substrate 6 via the means for fixing the lens holder 4 and the holder base 5 to each other including the soldering, the adhesive bonding and the YAG laser welding as described above, and in this embodiment, the YAG laser welding is employed. In this process, surfaces of the holder base 5 and the carrier substrate 6 are preferably aligned with each other.
Finally, in step S6, the holder base 5 is fixed on the carrier substrate 6 to compensate for a misalignment of the collimating lens 2 occurred when the holder base 5 is fixed. In this step, the lens holder 4 which holds the collimating lens 2 and the holder base 5 are irradiated with YAG laser light for thermal deformation, thereby correcting the position of the collimating lens 2.
One optical axis adjustment method using laser irradiation is disclosed in Patent Document 5 (JP2013-231937A) and one embodiment thereof is discussed below. When the position of the collimating lens 2 is to be corrected in +Y direction or upward in a vertical direction, a position denoted by A (shown in
When the position of the collimating lens 2 is to be corrected in X direction or horizontal direction, a position denoted by C (shown in
As described, the lens holder 4 and the holder base 5 have the positions different from each other irradiated with the YAG laser light 13, which enables the position of the collimating lens 2 to be corrected in ±X and ±Y directions. Further, changing a irradiation dose for the YAG laser light 13 enables to adjust an extent to which the position of the collimating lens 2 is corrected with sub micrometer order.
When the collimating lens 2 is to be corrected in −Y direction or downward in a vertical direction, the YAG laser light may be radiated for the adjustment to a region between each of the opposite two welding positions 8 to which the holder and the base member are fixed and the collimating lens 2, the region being contacted to the lens holder 4 and the holder base 5 as shown in
The assembling process above includes allowing the Y-axis stage 113 to move in Y-axis direction when the holder base 5 is fixed to the carrier substrate 6 so that the holder base 5 is pushed against the carrier substrate 6. Hence, the lens gripper 110 preferably includes a tactile sensor 16 for detecting when the holder base 5 contacts with the carrier substrate 6. When the holder base 5 contacts with the carrier substrate 6, the slide system 115 displaces in a direction opposite to that of the stage movement. The tactile sensor 116 is configured to detect the displacement. The tactile sensor 116 may include, but not limited to a contact displacement sensor for measuring the displacement.
Referring back to
The YAG laser head aligning unit 130 is positioned on a stage which allows the position of the YAG laser head to be adjustable in one or more directions, preferably X, Y and Z directions. A plurality of the YAG laser heads are symmetrically positioned with respect to the lens gripper 110.
The light detector 140 may include light receiving elements each having a high sensitivity to light emitted from the laser light source (e.g. infrared light) and being arranged in two dimensions. The light detector 140 may further include an imaging lens focusing the collimated light rays 11 formed by the collimating lens 2 on a light receiving surface of the light receiving element, an translation stage for adjusting a location of the light receiving element and the imaging lens in X, Y and Z directions, and a rotation stage for adjusting an orientation around X, Y and Z directions. The imaging lens has a focal length of infinity in an incident side with respect to the imaging lens where the collimated light ray 11 is incident, so that orientations of the collimated light rays 11 are detectable.
The workpiece recognizer 150, which is positioned on the Y-axis stage 113 of the lens gripper 110, includes a camera 151 for taking an image of the lens holder 4 and the holder base 5 as a workpiece from the upper side. The image taken by the camera 151 is transmitted to the controller 101 of the optical axis alignment apparatus 100 and processed so that a position to which the workpiece is fixed is determined. Preliminarily obtained is a first relation between the workpiece position and the YAG laser irradiation position and a second relation among the YAG laser irradiation condition (an irradiation dose and a YAG laser irradiation position), the extent to which the workpiece should be corrected and the direction in which the workpiece should be corrected. These relations are stored in a database accommodated in the controller 101. The transmission of the image to the controller 101 as well as the calculation of the workpiece position may be a dedicated image processor and the calculated workpiece position may be only transmitted to the controller 101.
In step Q3, the controller 101 operates so that at least one of the holder and the base member is irradiated with laser light to plastically deform them depending on a particular laser irradiation condition (e.g. an irradiation position and an irradiation dose), which enables a position of the collimating lens 2 to be adjusted within XY surface perpendicular to the optical axis. The position of the lens is adjusted to correct an irradiation position or an irradiation dose for a subsequent laser irradiation. In Step Q4, the camera 151 is used to take an image of the lens holder 4 and the holder base 5 to obtain new contour information after the laser irradiation and the obtained information is stored in a database. Then, in step Q5, the light detector 140 is used to detect new location information about the light path of the light beam which exits from the collimating lens 2 and then the new information is saved in a database.
Then, in step Q6, whether the accuracy, which is obtained as a result of the optical axis alignment for the collimating lens 2, is within predetermined allowable limits is determined by the controller 101 based on the detected light beam location information. If the accuracy is within the predetermined allowable limits, the optical axis alignment step is finished. Otherwise, following step Q7 is performed. The lens position is adjusted based on the contour information and the location information about the light path which are obtained in steps Q1 and Q2.
In step Q7, the laser irradiation condition (e.g. an irradiation position or an irradiation dose) for the lens position adjustment is now corrected by the controller 101 based on the contour information and/or the location information obtained both before and after the laser irradiation and then the corrected condition is stored in a database. Moving back to Q3, the optical axis alignment is performed again. As such, the optical axis alignment may be performed for the collimating lens 2 for each assembling or manufacturing of the light communication module.
As described above, detecting the collimated light rays 11, which are generated by the laser light sources 1 and the collimating lens 2, by means of the imaging lens having a focal length of infinity enables to measure an extent and a direction of misalignment of the collimated light rays 11, without the external force to be applied against the collimating lens 2 as taught in Patent Document 2 (H2-308209 A), which subsequently allows a direction in which the collimating lens 2 should be corrected to be easily determined.
Further, taking an image of the position, to which the workpiece is fixed, by means of the camera 151 of the workpiece recognizer 150 in order to automatically determine the YAG laser irradiation condition, based on the predetermined relation between the condition and the extent and the direction for the correction for the workpiece, enables to easily align the optical axis of the collimating lens 2.
The present invention is industrially useful in that it allows an optical axis alignment to be performed with a high accuracy and less time required for the alignment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-009324 | Jan 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/051155 | 1/15/2016 | WO | 00 |
