JP3591012B2 - Optical system alignment method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical system centering method. More specifically, the present invention relates to a novel method for aligning the optical axes of small optical elements such as lenses, optical components such as optical fibers, and optical elements such as semiconductor lasers in assembling the optical system of an optical module. Adjustment method.
[0002]
[Prior art]
The use of optical signals is expanding in many fields. However, at present, various kinds of signal processing are performed by converting them into electric signals. Therefore, the electrical / optical converter is used everywhere in the optical system. Therefore, in order to facilitate the construction of a system, a light-emitting element module in which a typical optical fiber as a transmission medium of an optical signal and a light-emitting element as an electric / optical conversion element are integrated is widely used. . In this type of light emitting element module, an optical system including optical elements such as a lens and an isolator is arranged between the light emitting element and the optical fiber in order to converge the light emitted from the light emitting element and efficiently couple the light to the optical fiber. Have been.
[0003]
In the light emitting element module as described above, it is required to couple the limited optical power generated by the light emitting element to the optical fiber as efficiently as possible. On the other hand, coupling efficiency or transmission efficiency of many optical components changes depending on the physical positional relationship with respect to incident light. Therefore, the performance of the light-emitting element module largely depends on the positioning of the parts during assembly, not to mention the individual characteristics of each member.
[0004]
The position adjustment of this kind of optical component in the optical module is performed as follows, for example, as described in “Basics and Application of Optical Coupling System (Hyundai Kogaku)”, page 98. First, while operating the light emitting element, the positions of the lens and the optical fiber disposed immediately thereafter are adjusted, and the lens is first fixed at a position where the optical power coupled to the optical fiber becomes maximum. Next, the position of the optical fiber is adjusted and fixed to the assembly including the light emitting element and the optical system. Actually, a similar adjustment operation is performed again for the positioning of the tip of the optical fiber.
[0005]
As another method of adjusting the position of the optical component, there is a method using a standard optical fiber prepared separately. In this method, a standard optical fiber and an optical component are fixed to each other in an ideal positional relationship to form an assembly, and then assembled with a light emitting element so that the optical power coupled to the assembly is maximized. Adjust the three-dimensional positional relationship to obtain the optimal position.
[0006]
As another more practical method, there is a method in which the optical module is manufactured without adjustment by improving the mechanical accuracy of each member constituting the optical module.
[0007]
[Problems to be solved by the invention]
In order to fix optical components as described above, an accuracy of the order of 10 μm or less is required. Therefore, the positioning is actually a very time-consuming operation, and the person performing the operation requires skill. . Basically, adjustment using an optical fiber also requires an accuracy of 10 μm or less when the optical fiber is a single mode type. On the other hand, non-adjustable light-emitting element modules using high-precision parts are easy to assemble and have high workability. The performance is not improved.
[0008]
Accordingly, it is an object of the present invention to solve the above-mentioned problems of the conventional art and to provide a new centering method capable of easily and reliably positioning a lens with higher working efficiency.
[0009]
[Means for Solving the Problems]
That is, according to the present invention, there is provided a method of performing relative positioning between a light-emitting element and a light-collecting optical component that transmits light emitted from the light-emitting element, wherein the light-emitting element is disposed via the light-collecting optical element. Imaging means for photographing the light-emitting area of the light-emitting element, and an optical component disposed between the light-collecting system optical component and the imaging means for changing a light beam emitted from the light-emitting element through the optical component to collimated light; And adjusting the relative position so that the image displayed on the display means by the imaging means is displayed at a predetermined position on the display means, thereby adjusting the direction perpendicular to the emission optical axis of the light emitting element. Centering, and then adjusting the relative position so that the image is minimized, thereby aligning the light emitting element in the direction of the emission light axis. .
[0010]
[Action]
The main feature of the alignment method according to the present invention is that the alignment is performed while observing the pattern of the radiated light of the light emitting element via the light-collecting optical component whose position is to be adjusted.
[0011]
That is, when the radiated light of the light emitting element passes through the condensing optical components such as a lens, a predetermined pattern including concentric bright lines is formed. Since the shape and size of this pattern image change depending on the relative position between the light emitting element and the optical component, the change in the relative position between the light emitting element and the optical component can be determined by observing the image with an imaging means such as a CCD camera. be able to. Further, in general, since the imaging means is provided with an optical system for enlarging and photographing the observation target, the centering operation for fine elements or components can be easily and reliably performed.
[0012]
Further, the shape, size, position on the display means, etc. of the image pattern obtained when the relative position between the light emitting element and the lens to be fixed was optimized were recorded at the time of the next adjustment work. By referring to the pattern, the adjustment can be performed with the same accuracy as that of a skilled person even if a person who is not particularly skilled works.
[0013]
Hereinafter, the present invention will be described more specifically with reference to the drawings. However, the following disclosure is merely an example of the present invention, and does not limit the technical scope of the present invention.
[0014]
【Example】
FIG. 1 is a diagram schematically showing a configuration of equipment when the centering method according to the present invention is performed.
[0015]
As shown in FIG. 1, the apparatus includes a chuck 4 for gripping an adjustable lens 2 to be aligned with a light emitting element 1 fixed on a base, and an observation gripping by the chuck 4 together with the lens 2. And a CCD camera 5 capable of observing the light-emitting surface of the light-emitting element 1 via the adjusted lens 2 and the observation lens 3, and a light beam pattern photographed by the CCD camera 5 is displayed as an image. It mainly comprises a CRT monitor 6. However, both the lens to be adjusted 2 and the observation lens 3 can be individually opened from the chuck 4. Note that the light emitting element 1 is fixed to a stage that can move in each of the X, Y, and Z directions.
[0016]
A procedure for positioning the lens 2 with respect to the light emitting element 1 using the device configured as described above will be described. Note that the adjustment performed here is intended to position the object point in the image forming system by the lens 2 so as to coincide with the light emitting portion of the light emitting element 1.
[0017]
In this embodiment, a collimating lens is used as the observation lens 3. First, the observation lens 3 is formed so that the collimated light is formed when the positional relationship between the lens 2 to be adjusted and the light emitting element 1 reaches a design value. The relative position between the lens and the lens to be adjusted 2 is determined, and these lenses are fixed by the chuck 4 while maintaining the relative position. Although the relative position is determined by relying on the mechanical accuracy of the chuck 4, a general device of this kind has sufficient mechanical accuracy for adjustment at this stage.
[0018]
FIG. 2 is a diagram showing an image displayed on a monitor when adjusting a relative position with respect to a light emitting element for performing the following operation.
[0019]
As shown in each figure, the image appearing on the monitor at this time is composed of a bright circular image formed by the light beam itself and a plurality of concentric interference images formed inside and outside near the end of the circular image. This is a circular image as a whole formed from stripes.
[0020]
When the image as described above appears on the monitor, first, the light emitting element 1 is moved horizontally so that the emission optical axis of the light emitting element 1 and the optical axis of the lens 2 to be adjusted coincide. At this time, it is preferable to perform the centering so that the center of the image coincides with a specific position on the monitor that has been checked in advance.
[0021]
Next, the distance between the light emitting element 1 and the optical system including the lens to be adjusted 2 and the observation lens 3 is adjusted. That is, first, the image 7 on the screen of the monitor 6 is set so that the light beam 8 is most narrowed and the outer diameter of the high-brightness area is the same as the image obtained when the collimated light is captured. Adjust the position of the optical system.
[0022]
More specifically, when the distance x between the light emitting element 1 and the lens to be adjusted 2 is smaller than the optimum distance a, the light beam 8 emitted from the lens 3 diverges, as shown in FIG. The image 7 on the monitor becomes large. Next, when the distance x is gradually increased, the light beam 8 is gradually narrowed, and becomes the smallest when it coincides with the optimum distance a as shown in FIG. Further, when the distance x is larger than the optimum distance a, the light beam 8 emitted from the lens 3 is focused before the camera 5, and as shown in FIG. The image 7 displayed on top is again larger.
[0023]
When the lens to be adjusted 2 is positioned at the optimum position as described above, only the lens to be adjusted 2 is fixed to a common substrate with the light emitting element at that position, and then the lens 2 to be adjusted is released from the chuck 4 and adjusted. The core work ends.
[0024]
In contrast to the conventional alignment method using an optical fiber, which took 30 minutes or more for one alignment, a series of alignment operations according to the present invention as described above took about 10 minutes. Ended with
[0025]
In actual work, the light adjusting lens 2 must be fixed after the alignment. Considering this point, in the method according to the present invention, the distance between the lens 2 and the camera 5 can be made sufficiently large, so that a reliable fixing method such as soldering or YAG laser welding can be freely selected. Can be implemented. In this regard, in a method that relies on a magnifying optical system such as a microscope, the distance between the lens to be adjusted and the objective lens of the magnifying optical system becomes extremely short when an optical system with a high magnification is used to increase accuracy. . Therefore, in this type of method, if the accuracy of the adjustment is increased, the lens to be adjusted must be fixed by a fixing method with low reliability such as resin fixing.
[0026]
In the present embodiment, the alignment operation between the light emitting element and the lens has been described as an example.However, for example, by injecting light from the other end or by using a light beam from a separately prepared light source, The alignment method of the present invention can also be applied to alignment of an optical component which does not emit light itself, such as an optical fiber and a lens or between lenses.
[0027]
In the above description, the case where the object point in the imaging system by the light adjustment lens 2 and the light emitting element are adjusted is described. However, a lens having different characteristics may be used as the observation lens 3, By changing the observation pattern to be referred to, the optical components can be positioned in an arbitrary positional relationship.
[0028]
Further, an observation image obtained when the position is adjusted to the optimum position in the series of procedures as described above is recorded, and by using this image as a reference, even an unskilled worker has the same quality as an expert. In addition to performing accurate alignment, it can also be applied to automation of alignment work.
[0029]
【The invention's effect】
As described above in detail, according to the alignment method according to the present invention, the positioning of the lens with respect to the light emitting element can be performed easily and in a short time. In addition, the method according to the present invention can perform highly accurate adjustment even by an unskilled worker, so that it is easy to secure personnel. Therefore, according to the present invention, the productivity of the optical module is significantly improved.
[0030]
Furthermore, in the method according to the present invention, the distance between the lens to be aligned and the image pickup means can be made sufficiently wide while maintaining the alignment accuracy, so that an appropriate fixing method such as soldering or YAG laser welding can be used. Can be arbitrarily selected.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of equipment when a method according to the present invention is performed.
FIG. 2 is a diagram for explaining an operation when performing a method according to the present invention.
[Explanation of symbols]
1 ... light-emitting element,
2. Adjustable lens
3 ... observation lens,
4 ... Chuck,
5 ... camera,
6 monitor
7 ... high brightness image,
8 ... Light beam

Claims (4)

A method for performing relative positioning between a light emitting element and a light collecting system optical component that transmits emitted light of the light emitting element,
Imaging means for photographing the light-emitting region of the light-emitting element through the light-collecting system optical component; and light emitted from the light-emitting element via the optical component disposed between the light-collecting system optical component and the imaging means. Using an optical component that changes the light beam into collimated light ,
By adjusting the relative position so that the image displayed on the display means by the imaging means is displayed at a predetermined position on the display means, the alignment in the direction perpendicular to the emission optical axis of the light emitting element is performed. And adjusting the relative position of the light emitting element in the direction of the emission light axis by adjusting the relative position so that the image is minimized. 2. The alignment method according to claim 1, wherein said imaging means is a CCD camera, and said display means is a CRT monitor connected to said CCD camera. 3. The alignment method according to claim 1, wherein an image of the set of light-emitting elements and light-collecting system optical components after alignment is recorded, and the other light-emitting element and light-collecting system are recorded. A method of aligning an optical component, wherein the aligning operation is performed so as to match the recorded image when aligning the optical component. 4. The centering method according to claim 1, wherein an enlargement optical element for enlarging a pattern formed by the radiated light is inserted immediately before the imaging unit. 5. Characteristic alignment method.

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