JP6448497B2 - Wavefront sensor, wavefront measuring method, and optical module positioning method - Google Patents

Description

  The present invention relates to an optical axis adjustment of an optical module, and more particularly to a technique for measuring a wavefront of irradiation light of an optical module.

An optical module in an optical communication system is an important optical component as a light source. As an optical system of the optical module, there are a single lens system and a compound lens system. Among these, in the compound lens system, the laser light emitted from the light source is converted into a parallel beam by a collimator lens, is again stopped by the lens, and is coupled to an optical fiber as a transmission means. Conventionally, various collimator lens positioning methods have been proposed.
For example, in Patent Document 1, a photodiode having a light receiving diameter that is the same diameter as the parallel beam converted by the collimator lens is disposed at the tip of the light source and the collimator lens, and the collimator has a maximum light receiving current. A positioning adjustment method for positioning a lens is disclosed.

  Further, in Patent Document 2, the light spot position of a fixed optical module is measured with a photodetector, and the incident end of an optical fiber fixed at the position for optical axis alignment with the photodetector at the measured light spot position. An optical axis adjusting device is disclosed in which the optical module is moved by an amount corresponding to the correction of the relative position to the optical axis, and the optical axes of the optical module and the incident end of the optical fiber are aligned.

JP-A 64-21409 Japanese Patent Laid-Open No. 9-43456

  However, the techniques described in Patent Document 1 and Patent Document 2 described above are based on the premise that the relative angle between the optical module and the apparatus for adjusting the optical axis is constant. In the manufacturing process, for example, according to manufacturing tolerances. When it is desired to change the angle of the entire optical module flexibly, there is a problem that it is impossible to measure the wavefront of the irradiation light of the optical module based on the arrangement angle of the optical module necessary for positioning the collimator lens. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to detect a wavefront of irradiation light of an optical module based on an arrangement angle of the optical module.

The wavefront sensor according to the present invention is installed in an optical module that irradiates a light beam to be measured at a preset angle, transmits at least part of the incident light beam, and reflects at least part of the incident light beam. A reference beam irradiation optical system that irradiates the beam splitting unit with a first reference beam in a direction opposite to the irradiation direction of a reference beam that is an angle reference of the wavefront sensor, and a first beam irradiated by the reference beam irradiation optical system A wavefront detector that measures a wavefront inclination of a second reference light beam obtained by reflecting the reference light beam at the light beam splitter, and calculates a relative angle with the optical module from the measured wavefront inclination ; a light beam splitter and a wavefront detector; An optical system is provided between the optical system and the light splitting unit and the wavefront detecting unit are arranged on the pupil plane of the optical system .

  According to the present invention, even when the arrangement angle of the optical module is used as a reference, the wavefront of the irradiation light of the optical module can be detected and the focus deviation and the optical axis deviation of the optical module can be accurately measured.

1 is a diagram illustrating a configuration of a wavefront sensor according to Embodiment 1. FIG. It is a figure which shows the structure which adjusts before the optical axis measurement of the wavefront sensor of Embodiment 1. FIG. 3 is a flowchart showing the operation of the wavefront sensor according to the first embodiment. FIG. 3 is a schematic diagram showing a light ray angle of the wavefront sensor according to the first embodiment. 4 is a diagram illustrating a configuration example of a first light beam splitting unit of the wavefront sensor according to Embodiment 1. FIG. 4 is a diagram illustrating a configuration example of a first light beam splitting unit of the wavefront sensor according to Embodiment 1. FIG. 6 is a diagram illustrating a configuration of a wavefront sensor according to Embodiment 2. FIG. FIG. 5 is a diagram illustrating a configuration of a wavefront sensor according to a third embodiment. 10 is a flowchart showing the operation of the wavefront sensor according to the third embodiment.

Embodiment 1 FIG.
1 is a diagram showing a configuration of a wavefront sensor according to Embodiment 1 of the present invention.
The wavefront sensor includes a first light beam splitting unit 1, a light source 2, a collimator 3, a beam splitter 4, a wavefront detection unit 5, and a reference light source 6. In the following, a case where the laser module 20 is used as an optical module will be described as an example, but other optical modules may be used.
The first light beam splitting unit 1 is attached to the laser module 20 to be adjusted at a preset angle, and transmits a part of the incident light beam and reflects a part thereof. The light source 2 is a reference light irradiation optical system that irradiates the first light beam splitting unit 1 with the first reference light beam 102. The collimator 3 includes a lens 3a and a fiber end 3c of a single mode fiber 3b separated by a focal length of the lens 3a.

  The beam splitter 4 separates the first reference light beam 102 irradiated from the collimator 3 onto the first light beam splitting unit 1 and the second reference light beam 103 reflected by the first light beam splitting unit 1. Although not shown, the wavefront detection unit 5 is configured to include at least a microlens array, an image sensor, and wavefront calculation means in the case of a Shachk-Hartmann wavefront sensor. The wavefront detection unit 5 includes a wavefront of a light beam (hereinafter referred to as a measured light beam) emitted from the laser light source 21 of the laser module 20, a wavefront of the second reference light beam 103 reflected by the first light beam splitting unit 1, and A wavefront of a reference light beam 104, which will be described later by a reference light source 6, is detected. The wavefront detection unit 5 is realized by a processing circuit, which is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP, for example) that executes a program stored in a memory. Say).

  The reference light source 6 is a light source serving as an angle reference between the wavefront detection unit 5 and the first reference light beam 102. Further, the wavefront sensor includes an optical system 7 that expands and contracts the measured light beam 101 in accordance with the opening of the wavefront detection unit 5, and a second light beam splitting unit 8 that separates the reference light beam 104 emitted from the reference light source 6. It may be provided. As shown in FIG. 1, the optical system 7 is disposed between the beam splitter 4 and the first light beam splitting unit 1.

  The laser module 20 includes a laser light source 21 and a collimator lens 22. The laser light source 21 irradiates the measured light beam 101. The collimator lens 22 is a lens that converts the measured light beam 101 emitted from the laser light source 21 into parallel light. The first beam splitting unit 1 is attached to the rear stage of the collimator lens 22 at a predetermined angle with respect to the substrate (not shown) of the laser module 20.

Next, the operation of the wavefront sensor will be described.
First, the optical axis adjustment performed before the wavefront sensor performs the optical axis measurement process will be described with reference to FIG.
FIG. 2 is a diagram showing a configuration for performing adjustment before measuring the optical axis of the wavefront sensor according to Embodiment 1 of the present invention.
In the adjustment before the optical axis measurement, the angles of the wavefront detection unit 5 and the first reference light beam 102 are adjusted using the reference light beam 104 emitted from the reference light source 6. The reference light beam 104 irradiated by the reference light source 6 is separated by the second light beam dividing unit 8, enlarged or reduced by the optical system 7, and divided by the beam splitter 4. One reference light beam 104 divided by the beam splitter 4 is applied to the wavefront detector 5, and the other is applied to the collimator 3. The wavefront detection unit 5 stores the wavefront of the irradiated reference light beam 104 as a reference wavefront. The wavefront sensor measures the wavefront with a relative value to the reference wavefront. Therefore, the stored reference wavefront serves as a reference for the wavefront sensor, and at the same time is used to calibrate aberrations of the optical system 7 and arrangement distortion of the microlens array constituting the wavefront detection unit 5.

  The collimator 3 irradiated with the other of the reference light beam 104 divided by the beam splitter 4 collects the reference light beam 104 by the lens 3a and makes it incident on the fiber end 3c. When the reference light beam 104 is incident on the fiber end 3c, the angle of the reference light beam 104 or the position of the fiber end 3c is adjusted so that the light intensity coupled to the single mode fiber 3b becomes the highest. The adjustment of the angle of the reference beam 104 or the position of the fiber end 3c is performed with the target at the position where the light intensity coupled to the single mode fiber 3b is the highest, but the coupled light intensity is not necessarily the highest. What is necessary is just to obtain high light intensity. Further, since the light beam coupled to the single mode fiber 3b always faces each other, the optical axis of the first reference light beam 102 irradiated from the fiber end 3c and the optical axis of the reference light beam 104 incident on the fiber end 3c are coaxial and Adjust to the opposite direction.

  As a method of coupling the reference light beam 104 to the single mode fiber 3b, generally, the power meter 9 is connected to the other of the single mode fiber 3b, and the fiber end 3c is set so that the light intensity indicated by the power meter 9 is maximized. Apply the adjustment method to translate. Note that an adjustment mechanism for translating the fiber end 3c is not shown in FIG. Note that the method of coupling the reference light beam 104 to the single mode fiber 3b is not limited to the above-described method, and any means for adjusting the reference light beam 104 to be incident on the single mode fiber 3b can be applied as appropriate. is there.

  For example, any of angle adjusting means (not shown) of the reference light beam 104, angle adjusting means (not shown) of the beam splitter 4, and adjusting means (not shown) for moving the lens 3a in parallel may be used. The angle adjusting means for the reference light beam 104 is a means that combines these, for example, a gimbal mount that holds the reference light source 6, a kinematic mount, a rotary stage, or a gonio stage. The angle adjusting means of the beam splitter 4 is a means that combines these, for example, a gimbal mount, a kinematic mount, a rotary stage, or a gonio stage that holds the beam splitter 4. The adjusting means for moving the lens 3a in parallel is, for example, a linear motion stage that holds the lens 3a. The angle adjusting means for the reference beam 104, the angle adjusting means for the beam splitter 4, or the adjusting means for moving the lens 3a in parallel can be configured to be removed from the wavefront sensor after the adjustment is completed.

Next, a process for acquiring the wavefront inclination based on the arrangement angle of the laser module 20 will be described with reference to FIGS.
FIG. 3 is a flowchart showing the operation of the wavefront sensor according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram showing the light ray angle of the wavefront sensor according to Embodiment 1 of the present invention.
First, the process of acquiring the relative angle between the laser module 20 and the wavefront sensor is shown in steps ST1 to ST5.
The wavefront sensor extinguishes the laser light source 21 of the laser module 20 and causes the light source 2 to emit light (step ST1). The first reference light beam 102 irradiated from the light source 2 in step ST1 is irradiated from the collimator 3, reflected by the beam splitter 4, and irradiated to the first light beam splitting unit 1 (step ST2). The first light beam splitting unit 1 reflects the first reference light beam 102, and the reflected second reference light beam 103 passes through the second light beam splitting unit 8, the optical system 7, and the beam splitter 4 to be a wavefront detection unit. 5 is incident. The wavefront detector 5 measures the wavefront of the incident second reference light beam 103 (step ST3).

  The wavefront detection unit 5 performs Zernike coefficient expansion of the wavefront of the second reference light beam 103 measured in step ST3, and acquires the wavefront inclination (step ST4). The wavefront detection unit 5 converts the wavefront inclination acquired in step ST4 into a relative angle between the laser module 20 and the wavefront sensor (step ST5).

The processing from step ST1 to step ST5 will be described with reference to the schematic diagram of FIG.
In FIG. 4, the first beam splitting unit 1 is attached to the substrate of the laser module 20 at a preset angle. In Figure 4, the relative angle between the laser module 20 and the wavefront sensor is shown an example where theta _B. In this case, when the wavefront detection unit 5 of the wavefront sensor measures the wavefront of the second reference light beam 103 in step ST3 and performs Zernike coefficient expansion of the wavefront measured in step ST4, the wavefront slope 2θ is the lowest order component. _B is acquired. Wavefront detection unit 5, as step ST5, performs conversion processing for the acquired wavefront slope 2 [Theta] _B 1/2, to obtain a relative angle theta _B.

Next, processing in which the wavefront sensor detects the wavefront of the light beam to be measured relative to the laser module 20 is shown in steps ST6 to ST11.
The wavefront sensor extinguishes the light source 2 and causes the laser light source 21 of the laser module 20 to emit light (step ST6). The wavefront irradiated from the laser light source 21 passes through the collimator lens 22 of the laser module 20 and becomes the measured light beam 101. The measured light beam 101 passes through the first light beam splitting unit 1 and the second light beam splitting unit 8, is enlarged or reduced by the optical system 7, passes through the beam splitter 4, and enters the wavefront detection unit 5 (step). ST7).

  The wavefront detector 5 measures the wavefront of the light beam 101 to be measured incident at step ST7 (step ST8), performs Zernike coefficient expansion of the measured wavefront, and acquires the wavefront inclination (step ST9). Further, the wavefront detection unit 5 subtracts the relative angle between the laser module 20 converted in step ST5 and the wavefront sensor from the wavefront inclination acquired in step ST9, and the wavefront inclination based on the arrangement angle of the laser module 20, that is, the laser module 20 The wavefront inclination of the light beam to be measured relative to is acquired (step ST10). The wavefront detection unit 5 detects the wavefront of the measured light beam 101 with reference to the arrangement angle of the laser module 20 from the wavefront inclination acquired in step ST10 (step ST11), and ends the process.

The processing from step ST6 to step ST11 will be described with reference to the schematic diagram of FIG.
In step ST9, the Zernike coefficient expansion performed on the wavefront of the measurement beam 101, as the lowest order component includes a wavefront slope theta _L. Wavefront detection unit 5, the relative angle theta _B of the laser module 20 and the wavefront sensor obtained in step ST5 from wavefront slope theta _L is subtracted in step ST10, wavefront slope .delta..theta relative to the placement angle of the laser module 20 (.delta..theta = θ _L −θ _B ) is acquired.

  As described above, the first beam splitting unit 1 is disposed at a preset angle with respect to the substrate of the laser module 20. For example, when the reflecting surface of the first light beam splitting unit 1 is arranged so as to be perpendicular to the target light beam angle, the adjustment target value of the collimator lens 22 of the laser module 20 is the wavefront slope δθ = 0.

  In the description with reference to FIG. 3 and FIG. 4 described above, the wavefront inclination is described as only one direction. However, the actual wavefront inclination is two directions, and the x direction is obtained when the optical axis is the Z direction. Wavefront slope δθx and y-direction wavefront slope δθy are obtained.

  As described above, the first light beam splitting unit 1 has a function of transmitting at least a part of the measured light beam 101 and reflecting at least a part of the first reference light beam 102. Therefore, the first light beam splitting unit 1 can be configured by any combination of, for example, a beam splitter, a narrow band filter, a mirror, and an optical path eccentric mechanism.

FIG. 5 is a diagram illustrating a configuration example of the first light beam splitting unit 1 of the wavefront sensor according to the first embodiment of the present invention, in which a beam splitter is applied to the first light beam splitting unit 1. Yes.
When a beam splitter is used as the first beam splitting unit 1, when the beam splitter reflects a part of the beam to be measured 101 toward the laser light source 21 of the laser module 20, the laser light emitted by the laser light source 21 changes. Or the problem of causing a failure of the laser light source 21 occurs. Therefore, for example, as shown in FIG. 5, a beam splitter 1a and a mirror 1b are combined to form a first light beam splitting unit 1. The beam splitter 1a transmits a part of the measured light beam 101 to the wavefront sensor side and reflects a part of the measured light beam 101 to the mirror 1b side. The mirror 1b reflects the incident measurement light beam 101, and reflects the measurement light beam 101 reflected by the beam splitter 1a to the wavefront sensor side.

  Note that a polarization beam splitter may be applied to the beam splitter 1a to change the polarization of the measured light beam 101 and the polarization of the first reference light beam 102.

  When a narrow band filter is applied to the first beam splitting unit 1, the wavelength λ1 of the measured beam 101 and the wavelength λ2 of the first reference beam 102 are different wavelengths (λ1 ≠ λ2), and the wavelength λ1 is measured. The light beam 101 is transmitted, and the first reference light beam 102 having the wavelength λ2 is reflected. In this case, it is desirable to apply a band transmission filter or a band reflection filter having a half width of about 1 to 20 nm as the narrow band filter. In this case, the chromatic aberration of the optical system can be ignored.

FIG. 6 is a diagram illustrating a configuration example of the first light beam splitting unit 1 of the wavefront sensor according to the first embodiment of the present invention, where a mirror and an optical path eccentricity mechanism are applied to the first light beam splitting unit 1. Is shown.
The optical path decentering mechanism 1d performs a process of switching the optical path between when measuring the measured light beam 101 and when measuring the first reference light beam 102. When measuring the light beam 101 to be measured, the optical path is advanced to the wavefront sensor side. When measuring the first reference light beam 102, the optical path is advanced to the mirror 1c side. The first reference light beam 102 is reflected by the mirror 1c to become a second reference light beam 103 (not shown), and enters the wavefront sensor via the optical path decentering mechanism 1d.

Next, the position adjustment unit 22a that adjusts the position of the collimator lens 22 of the laser module 20 from the wavefront inclination acquired by the wavefront detection unit 5 will be described. The position adjustment unit 22a may be included in a wavefront sensor or an external device. The position adjustment unit 22a includes a position correction amount calculation unit 22b and a position correction unit 22c.
In the following description, it is assumed that the reflection surface of the first light beam splitting unit 1 is perpendicular to the target light beam angle.
The position correction amount calculation unit 22b calculates the position correction amount of the collimator lens 22 in the direction perpendicular to the optical axis of the laser light source 21 based on the wavefront inclination δθx and the wavefront inclination δθy, which are the lowest-order components of the wavefront of the measured light beam 101. The calculation is performed based on the following equations (1) and (2).
Δx = −f × δθx (1)
Δy = −f × δθy (2)

式（１）から式（３）において、ｆはコリメータレンズ２２の焦点距離である。また、式（３）におけるωはビーム半径、Ｚ_４はデフォーカスのＺｅｒｎｉｋｅ係数Ｚである。式（３）に示したように、レーザ光源２１の光軸方向のコリメータレンズ２２の位置補正量は、波面の曲率とビーム半径から算出される。 In addition, the position correction amount calculation unit 22b calculates the position correction amount of the collimator lens 22 in the optical axis direction of the laser light source 21 based on the following equation (3).

In Expressions (1) to (3), f is the focal length of the collimator lens 22. In Equation (3), ω is a beam radius, and Z ₄ is a defocus Zernike coefficient Z. As shown in Expression (3), the position correction amount of the collimator lens 22 in the optical axis direction of the laser light source 21 is calculated from the curvature of the wavefront and the beam radius.

  The position correction unit 22c is based on the position correction amounts Δx and Δy in the direction perpendicular to the optical axis of the laser light source 21 and the position correction amount Δz in the optical axis direction of the laser light source 21 calculated by the position correction amount calculation unit 22b. The lens 22 is adjusted in the x and y directions perpendicular to the optical axis of the laser light source 21 and the z direction that is the optical axis direction of the laser light source 21.

  As described above, according to the first embodiment, the angle of the reference light beam 104 or the position of the fiber end 3c is adjusted so as to maximize the coupling efficiency to the single mode fiber 3b, and is coaxial with the adjusted reference light beam 104. The first reference light beam 102 is adjusted so as to be in the reverse direction, the relative angle between the laser module 20 and the wavefront sensor is obtained from the wavefront inclination of the second reference light beam 103, and obtained from the wavefront inclination of the light beam to be measured. Since the wavefront inclination is obtained by subtracting the relative angle, the wavefront of the light beam to be measured can be obtained with the arrangement angle of the laser module 20 as a reference. Thereby, the focus shift and the optical axis shift of the laser module 20 can be accurately measured.

  In the first embodiment described above, the wavefront sensor is configured to emit and extinguish the laser light source 21 of the laser module 20 and emit and extinguish the light source 2. 1, the wavefront sensor includes a control unit (not shown), and the control unit refers to the detection result of the wavefront detection unit 5 and outputs a control signal for controlling light emission and quenching to the laser light source 21 or the light source 2 of the laser module 20. To do. The control unit may function as a configuration of the external device. Further, instead of the control unit of the wavefront sensor, the user may manually switch light emission or extinction by operating a switch (not shown) connected to the laser light source 21 or the light source 2 of the laser module 20.

  In the first embodiment described above, the attachment surface to which the first light beam splitting unit 1 is attached may be a surface that is perpendicular to the lower surface of the substrate of the laser module 20, for example. Further, a mounting surface may be provided on the manufacturing apparatus of the laser module 20. Furthermore, when a narrow band filter is provided as a configuration of the laser module 20, the narrow band filter can be used as the first light beam splitting unit 1 in the manufacturing process.

Embodiment 2. FIG.
In the second embodiment, a configuration is described in which the wavefront of the light beam to be measured can be acquired with reference to the arrangement angle of the laser module 20 even when the relative angle between the laser module 20 and the wavefront sensor is large. The second embodiment shows a configuration applicable when the second reference light beam 103 reflected by the first light beam splitting unit 1 can be incident on the aperture of a lens constituting the optical system.
FIG. 7 is a diagram showing a configuration of a wavefront sensor according to Embodiment 2 of the present invention.
In the following description, the same or corresponding parts as those of the wavefront sensor according to the first embodiment are denoted by the same reference numerals as those used in the first embodiment, and the description thereof is omitted or simplified.

As shown in FIG. 7, the wavefront sensor according to the second embodiment is provided with an optical system 7 a between the first light beam splitting unit 1 and the wavefront detection unit 5 instead of the optical system 7 shown in FIG. 1. It is composed. The optical system 7 a has a pupil plane at the arrangement position of the first light beam splitting unit 1 and the arrangement position of the wavefront detection unit 5.
For example, as shown in FIG. 7, the optical system 7a can be configured by a Kepler-type beam expander including two convex lenses. In the case of FIG. 7, when the focal length of the convex lens 7b on the laser module 20 side is f1, and the focal length of the convex lens 7c on the wavefront detection unit 5 side is f2, the distance between the first light beam splitting unit 1 and the convex lens 7b is f1. The distance between the convex lens 7b and the convex lens 7c is set to f1 + f2, and the distance between the convex lens 7c and the microlens array (not shown) of the wavefront detection unit 5 is set to f2. With the above-described setting, the arrangement positions of the microlens arrays of the first light beam splitting unit 1 and the wavefront detection unit 5 coincide with the pupil plane of the optical system 7a.

Next, processing in which the wavefront sensor acquires the relative angle between the laser module 20 and the wavefront detection unit 5 will be described with reference to the flowchart of FIG. 3 described in the first embodiment.
In step ST2, the first reference light beam 102 irradiated from the collimator 3 passes through the optical axis of the optical system 7a and is irradiated to the first light beam splitting unit 1. Since the first reference beam 102 is reflected at the center of the pupil plane of the first beam splitting unit 1, the reflected second reference beam 103 is the pupil plane of the microlens array on the wavefront detection unit 5 side. The center of the light is irradiated. That is, the light is irradiated near the optical axis of the wavefront detector 5. The wavefront of the irradiated second reference light beam 103 is measured in step ST3. Thereafter, the processing of step ST4 and step ST5 is performed, and the relative angle between the laser module 20 and the wavefront sensor is acquired.

  In this way, when the second reference light beam 103 reflected by the first light beam splitting unit 1 is within the field of view of the convex lenses 7b and 7c of the optical system 7a, the relative angle between the laser module 20 and the wavefront sensor is measured. It can be performed.

  As described above, according to the second embodiment, the optical system 7a having the pupil plane is provided at the arrangement position of the first light beam splitting unit 1 and the microlens array of the wavefront detection unit 5, and the first light beam splitting is performed. Since the second reference light beam 103 reflected by the unit 1 is configured to be irradiated in the vicinity of the optical axis of the wavefront detection unit 5, the second reference light beam 103 reflected by the first light beam splitting unit 1 is optical. If the viewing angle of the convex lenses 7b and 7c constituting the system 7a is within the viewing angle, the wavefront of the light beam to be measured can be obtained based on the arrangement angle of the laser module 20 even when the relative angle between the laser module 20 and the wavefront sensor is large. Can do.

Embodiment 3 FIG.
In the first embodiment and the second embodiment described above, the configuration in which the optical axis reference of the wavefront sensor is determined using the reference light source 6 in the optical axis adjustment performed before the wavefront sensor performs the optical axis measurement process is shown. . On the other hand, the incident angle of the first reference light beam 102 may change or the microlens position of the wavefront detection unit 5 may change with the passage of time after the optical axis adjustment. When these changes occur, an error occurs in the relative angle between the measured laser module 20 and the wavefront sensor. Therefore, it is necessary to periodically adjust the optical axis reference of the wavefront sensor. Therefore, the third embodiment shows a configuration for correcting a change in the incident angle of the first reference light beam 102 that occurs with the passage of time.

FIG. 8 is a diagram showing a configuration of a wavefront sensor according to Embodiment 3 of the present invention.
In the following description, the same or corresponding parts as those of the wavefront sensor according to the first embodiment are denoted by the same reference numerals as those used in the first embodiment, and the description thereof is omitted or simplified.
As shown in FIG. 8, the wavefront sensor according to Embodiment 3 is provided with a retroreflector 10 and an optical path switching mechanism 11 in addition to the wavefront sensor shown in FIG.

  The retroreflector 10 is an optical element that reflects incident light rays in the incident direction, and includes, for example, a lens 10a and a mirror 10b disposed at a position away from the lens 10a by the focal length of the lens 10a. The light beam emitted from the collimator 3 is collected by the lens 10a and reflected by the mirror 10b. The reflected light reflected by the retroreflector 10 is divided by the beam splitter 4, and a part of the light enters the wavefront detector 5. The retroreflector 10 may be configured with a corner cube reflector or a corner cube prism.

  The optical path switching mechanism 11 switches the optical path from the collimator 3 to the retroreflector 10 and the optical path from the collimator 3 to the laser module 20. The optical path switching mechanism 11 is configured by a shutter such as a rotary solenoid. In FIG. 8, when the optical path from the collimator 3 toward the retroreflector 10 is switched, the light beam irradiated by the collimator 3 is divided by the beam splitter 4 and partly incident on the retroreflector 10. Become. On the other hand, when the optical path from the collimator 3 toward the laser module 20 is switched, the light beam irradiated by the collimator 3 is split by the beam splitter 4 and a part thereof enters the first light beam splitting unit 1 installed in the laser module 20. This becomes the first reference beam 102. In the example of FIG. 8, the beam splitter 4 splits the beam irradiated by the collimator. However, the beam is split using different beam splitters, and the first reference beam 102 and the third reference beam 105 are split. You may comprise as follows.

Next, the operation of the wavefront sensor will be described. The optical axis adjustment performed before the optical axis measurement process is the same as in the first and second embodiments, and thus the description thereof is omitted. With reference to the flowchart of FIG. 9, a process for acquiring the wavefront inclination based on the arrangement angle of the laser module 20 of the wavefront sensor of the third embodiment will be described.
FIG. 9 is a flowchart showing the operation of the wavefront sensor according to the third embodiment of the present invention. In the following, the same steps as those of the wavefront sensor according to the first embodiment are denoted by the same reference numerals as those used in FIG. 3, and the description thereof is omitted or simplified.

  When a light beam is emitted from the light source 2 in step ST1, the beam splitter 4 splits the light beam into a first reference light beam 102 directed to the laser module 20 and a third reference light beam 105 directed to the retroreflector 10. (Step ST21). The optical path switching mechanism 11 blocks the first reference light beam 102 toward the laser module 20 and passes the third reference light beam 105 toward the retroreflector 10 (step ST22). The third reference light beam 105 that has passed through the optical path switching mechanism 11 is reflected in the incident direction by the retroreflector 10 and enters the wavefront detector 5 via the beam splitter 4 (step ST23). The wavefront detector 5 measures the wavefront of the third reference light beam 105 incident in step ST23 (step ST24). The wavefront detection unit 5 performs Zernike coefficient expansion of the wavefront measured in step ST24, and acquires the wavefront inclination (step ST25). The retroreflector 10 reflects the third reference light beam 105 toward the incident direction, the optical axis of the third reference light beam 105 toward the wavefront detection unit 5 in the beam splitter 4, and the first light beam splitting by the beam splitter 4. Since the optical axis of the first reference light beam 102 toward the unit 1 is opposite and coaxial, the wavefront inclination acquired in step ST25 is the same as the wavefront inclination of the reference light beam 104 shown in FIG.

  Next, the optical path switching mechanism 11 passes the first reference light beam 102 toward the laser module 20 and blocks the third reference light beam 105 toward the retroreflector 10 (step ST26). The first reference light beam 102 that has passed through the optical path switching mechanism 11 in step ST <b> 26 is reflected by the first light beam splitting unit 1 to become the second reference light beam 103, and the wavefront detection unit 5 uses the second reference light beam 103. The wavefront is measured (step ST3). The wavefront detection unit 5 performs Zernike coefficient expansion of the wavefront measured in step ST3, and acquires the wavefront inclination (step ST4). The wavefront detector 5 subtracts the wavefront inclination of the third reference light beam 105 acquired in step ST25 from the wavefront inclination acquired in step ST4 (step ST27), converts the wavefront inclination after the subtraction, and the laser module 20 The relative angle of the wavefront sensor is acquired (step ST28).

  Next, the wavefront sensor performs a process of acquiring a wavefront based on the arrangement angle of the laser module 20. First, the processing from step ST6 to step ST9 shown in the flowchart of FIG. 3 is performed. The wavefront detection unit 5 subtracts the wavefront inclination of the third reference light beam 105 acquired in step ST25 and the relative angle between the laser module 20 and the wavefront sensor converted in step ST28 from the wavefront inclination acquired in step ST9. The wavefront inclination with respect to the arrangement angle of the module 20 is acquired (step ST29). The wavefront detector 5 detects the wavefront of the measured light beam 101 with reference to the arrangement angle of the laser module 20 from the wavefront inclination acquired in step ST29 (step ST30), and ends the process.

  As described above, according to the third embodiment, the retroreflector 10 that reflects the light beam irradiated from the collimator 3 toward the incident direction, the optical path from the collimator 3 toward the retroreflector 10, and the collimator 3 Since the optical path switching mechanism 11 that switches the optical path toward the laser module 20 is provided, even when an angle change occurs in the first reference light beam 102, the angle change is acquired and acquired by the wavefront sensor. Since the angle change is subtracted from the wavefront inclination of the third reference beam, the angle change of the first reference beam is corrected, and the wavefront can be acquired based on the arrangement angle of the laser module 20. it can. Thereby, an accurate wavefront measurement can be performed.

  In the third embodiment described above, since the change in angle generated in the first reference light beam 102 can be corrected, the optical axis of the first reference light beam 102 and the optical axis of the reference light beam 104 are coaxial and There is no need to adjust to the opposite direction. Therefore, there is no need to provide the angle adjusting means for the reference light beam 104, the angle adjusting means for the beam splitter 4 and the adjusting means for moving the lens 3a in parallel as shown in the first embodiment.

  In the first embodiment described above, the optical axis of the first reference light beam 102 irradiated from the fiber end 3c and the optical axis of the reference light beam 104 incident on the fiber end 3c are coaxial and in opposite directions. The configuration to be adjusted is shown. However, when the retroreflector 10 shown in the above-described third embodiment is used to measure the relative angle difference between the optical axis of the first reference light beam 102 and the optical axis of the reference light beam 104, The optical axis of one reference beam 102 and the optical axis of the reference beam 104 are not necessarily coaxial and in opposite directions.

  In addition to the above, within the scope of the present invention, the present invention can be freely combined with each embodiment, modified any component of each embodiment, or omitted any component in each embodiment. Is possible.

  DESCRIPTION OF SYMBOLS 1 1st light beam splitting part, 1a, 4 beam splitter, 1b, 1c, 10b mirror, 1d optical path decentering mechanism, 2 light source, 3 collimator, 3a, 10a lens, 3b single mode fiber, 3c fiber end, 5 wavefront detection part , 6 Reference light source, 7, 7a Optical system, 7b, 7c Convex lens, 8 Second beam splitting unit, 9 Power meter, 10 Retroreflector, 11 Optical path switching mechanism, 20 Laser module, 21 Laser light source, 22 Collimator lens 101 measured beam, 102 first reference beam, 103 second reference beam, 104 reference beam, 105 third reference beam.

Claims (6)

A light beam splitting unit that is installed at a preset angle in the optical module that irradiates the light beam to be measured, transmits at least part of the incident light beam, and reflects at least part of the incident light beam;
A reference beam irradiation optical system that irradiates the beam splitting unit with a first reference beam in a direction opposite to the irradiation direction of a reference beam serving as an angle reference of the wavefront sensor;
The wavefront inclination of the second reference light beam obtained by reflecting the first reference light beam irradiated by the reference light beam irradiation optical system by the light beam splitting unit is measured, and the measured wavefront inclination is used to measure the wavefront inclination. A wavefront detector for calculating a relative angle ;
An optical system is provided between the light beam splitting unit and the wavefront detection unit,
A wavefront sensor in which the light beam splitting unit and the wavefront detection unit are arranged on a pupil plane of the optical system .   The wavefront detection unit measures the wavefront inclination of the measured light beam irradiated by the optical module and transmitted through the light beam splitting unit, and calculates a relative angle with the optical module from the measured wavefront inclination of the measured light beam. 2. The wavefront sensor according to claim 1, wherein the wavefront sensor subtracts and detects the wavefront of the light beam to be measured with reference to the installation angle of the optical module.   The reference beam irradiation optical system includes a lens that collects the reference beam and a single mode fiber that combines the reference beam collected by the lens, and the single mode fiber or the reference beam is the reference beam. The wavefront sensor according to claim 1, wherein the wavefront sensor is adjusted based on the light intensity of the light beam. A retroreflector for reflecting the third reference beam irradiated by the reference beam irradiation optical system in the coaxial reverse direction;
The wavefront detection unit measures a wavefront inclination of the third reference light beam reflected by the retroreflector, and determines a relative angle with respect to the optical module and the third reference light beam from the wavefront inclination of the light beam to be measured. The wavefront sensor according to any one of claims 1 to 3, wherein a wavefront of the light beam to be measured is detected by subtracting a wavefront inclination and using an arrangement angle of the optical module as a reference. A reference light beam irradiation optical system of a wavefront sensor for measuring a wavefront of a light beam to be measured irradiated by an optical module irradiates a first reference light beam in a direction opposite to a reference light beam irradiation direction as an angle reference of the wavefront sensor; ,
A light beam splitting unit that is installed on the pupil plane of an optical system at a preset angle in the optical module and transmits at least part of the incident light beam and reflects at least part of the incident light beam, Reflecting the first reference ray;
The wavefront detector of the wavefront sensor installed on the pupil plane of the optical system measures the wavefront inclination of the second reference light beam obtained by reflecting the first reference light beam, and the measured wavefront inclination Calculating a relative angle with respect to the optical module. A reference light beam irradiation optical system of a wavefront sensor for measuring a wavefront of a light beam to be measured irradiated by an optical module irradiates a first reference light beam in a direction opposite to a reference light beam irradiation direction as an angle reference of the wavefront sensor; ,
A light beam splitting unit that is installed on the pupil plane of an optical system at a preset angle in the optical module and transmits at least part of the incident light beam and reflects at least part of the incident light beam, Reflecting the first reference ray;
The wavefront detector of the wavefront sensor installed on the pupil plane of the optical system measures the wavefront inclination of the second reference light beam obtained by reflecting the first reference light beam, and the measured wavefront inclination Detecting the wavefront of the light beam to be measured with reference to the installation angle of the optical module using
A position adjusting unit that calculates a position correction amount of a lens constituting the optical module from the detected wavefront of the light beam to be measured, and adjusts the position of the lens using the calculated position correction amount; Optical module positioning method.

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