Optical axis adjustment method and device

Abstract

To provide an optical axis adjustment method and device capable of easily achieving high-precision speedy optical axis adjustment.SOLUTION: An optical axis adjustment device comprises a deflector 102 which deflects a light beam, an image sensor 101 which images an imaged surface P including a predetermined figure W indicating a predetermined light reception position through the deflector 102, and a processor 103 which controls the deflection direction of the deflector 102 based upon the captured acquired image, wherein the predetermined light reception position in the acquired image is detected from the predetermined figure W included in the acquired image, and the deflection direction of the deflector 102 is so adjusted that the predetermined light reception position meets a reference position r showing a main optical axis AXP before the deflection of the light beam in the acquired image.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an optical axis adjustment method and apparatus for aligning the optical axis of an optical beam with a light receiving position.

Background Art

[0002] When transmitting information spatially using light, it is necessary that the emitted light from the transmitting side is accurately irradiated onto the light receiving part of the receiving side. For this purpose, many techniques for aligning the optical axes between a transmitter and a receiver have been proposed so far.

[0003] For example, according to Patent Document 1, the optical axis is roughly aligned using infrared light with a wide directivity, and then the optical axis is precisely adjusted using infrared light with a narrow directivity. These optical axis adjustments are performed so that the light receiving level becomes equal to or higher than a predetermined intensity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it is not easy to accurately adjust the optical axis based on the change in the light receiving level. In Patent Document 1, a two-stage optical axis adjustment for changing the directivity of the transmitted light is required, and it is not possible to easily achieve high-precision and rapid optical axis adjustment.

[0006] Therefore, an object of the present invention is to provide an optical axis adjustment method and apparatus that can easily achieve high-precision and rapid optical axis adjustment.

Means for Solving the Problems

[0007] An optical axis adjustment device according to an aspect of the present invention is an optical axis adjustment device for irradiating an optical beam to a predetermined light-receiving position, including a deflector that deflects the optical beam, an imaging unit that images an imaging surface including a predetermined figure indicating the predetermined light-receiving position through the deflector, and a processing unit that controls a deflection direction of the deflector based on an acquired image captured by the imaging unit. The processing unit detects the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and adjusts the deflection direction of the deflector so that the predetermined light-receiving position on the acquired image coincides with a reference position indicating a principal optical axis before deflection of the optical beam. An optical axis adjustment method according to an aspect of the present invention is an optical axis adjustment method in an optical axis adjustment device for irradiating an optical beam to a predetermined light-receiving position. The optical axis adjustment device includes a deflector that deflects the optical beam, an imaging unit that images an imaging surface including a predetermined figure indicating the predetermined light-receiving position through the deflector, and a processing unit that controls a deflection direction of the deflector based on an acquired image captured by the imaging unit. The processing unit detects the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and adjusts the deflection direction of the deflector so that the predetermined light-receiving position on the acquired image coincides with a reference position indicating a principal optical axis before deflection of the optical beam. A program according to an aspect of the present invention is a program that causes a computer to function as an optical axis adjustment device for irradiating an optical beam to a predetermined light-receiving position. The optical axis adjustment device includes a deflector that deflects the optical beam, an imaging surface including a predetermined figure indicating the predetermined light-receiving position, and an imaging unit that images the imaging surface through the deflector. The computer realizes a function of detecting the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and a function of adjusting the deflection direction of the deflector so that the predetermined light-receiving position on the acquired image coincides with a reference position indicating a principal optical axis before deflection of the optical beam.

Advantages of the Invention

[0008] According to the present invention, highly accurate and rapid optical axis adjustment can be easily achieved.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] <Overview of the Embodiment> According to an embodiment of the present invention, a light-receiving position to which a light beam is to be irradiated is indicated by a predetermined figure, and the predetermined figure is imaged. The light-receiving position is detected from the captured image, and the deflection direction of the light beam is adjusted so that the light-receiving position coincides with a reference position indicating the optical axis of the light beam. As a result, it is not necessary to monitor the received light amount on the receiving side, and the optical axis can be adjusted on the transmitting side based on the imaged figure, achieving highly accurate and rapid optical axis adjustment.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the components described in the following embodiments and examples are merely illustrative, and are not intended to limit the technical scope of the present invention thereto.

[0012] 1. First Embodiment 1.1) Configuration As illustrated in FIG. 1, an optical axis adjustment device 10 according to a first embodiment of the present invention includes an imaging unit including an image sensor 101, an imaging optical system S, and a mirror member M1, and a main optical axis AX of a transmitted light beam P a deflector 102 capable of deflecting, and a processor 103 that performs deflection adjustment of the deflector 102 based on the imaging data of the image sensor 101.

[0013] The image sensor 101 is a two-dimensional sensor, and a light-receiving region is arranged on the imaging plane of the imaging optical system S. Light from the object plane P is reflected by the mirror member M through the deflector 102 and forms an image on the image sensor 101 through the imaging optical system S. As the deflector 102, a mechanically driven type, an acousto-optic type, or an electro-optic type deflector capable of deflecting a light beam in a desired direction can be used. For example, a galvanometer scanner can be adopted. The processor 103 is a processing unit capable of implementing deflection control by a program, and a CPU (Central Processing Unit) or the like can be used.

[0014] In FIG. 1, the principal optical axis AX P is the central axis of the light beam incident from a laser light source (not shown) to the deflector 102, and the reference optical axis AX REF is the principal optical axis AX P and is an optical axis orthogonal thereto. The mirror member M1 is, for example, a dichroic mirror. In the present embodiment, the center of the mirror member M1 is on the intersection of the principal optical axis AX P and the reference optical axis AX REF , and the semi-reflecting surface is arranged to be inclined clockwise by 45° with respect to the reference optical axis AX REF . The mirror member M1 transmits a light beam having a predetermined wavelength λ1 and reflects light having other wavelengths λ2 (here, the reflected light L R of the imaging surface P) in the direction of the reference optical axis AX REF .

[0015] The mirror member M1 and the deflector 102 are arranged such that these optical axes coincide with the principal optical axis AX P . The mirror member M1, the imaging optical system S, and the image sensor 101 are arranged such that these optical axes coincide with the reference optical axis AX REF . Here, the position of the reference optical axis AX REF on the light-receiving surface of the image sensor 101 indicates the position of the principal optical axis AX P . In other words, in the captured image acquired by the image sensor 101, the position of the reference optical axis AX REF can be treated as the position of the principal optical axis AX P .

[0016] The light L R having the wavelength λ2 from the imaging surface P enters the mirror member M1 through the deflector 102. The light L R reflected by the mirror member M1 forms an image on the light-receiving surface of the image sensor 101 through the imaging optical system S. Therefore, an image of the imaging surface P is formed on the light-receiving surface of the image sensor 101, and the captured data is output to the processor 103. That is, the image sensor 101 captures the imaging surface P through the deflector 102 and the imaging optical system S.

[0017] On the imaging surface P, a predetermined figure W that can geometrically identify the light-receiving window TA, which is the irradiation target of the light beam, is displayed. As a display method, it is desirable to print the predetermined figure W with a reflective material (retroreflective material), but a plurality of light-emitting elements may be arranged in the shape of the predetermined figure W. In FIG. 1, for the sake of distinguishing from other figures, the predetermined figure W is shown as a triangle for convenience. The predetermined figure W may be any shape that can identify the light-receiving window TA. However, a shape that facilitates figure extraction is desirable. For example, it is desirable to use simple lines such as a shape that surrounds or indicates the light-receiving window TA with only straight lines, a shape that crosses two straight lines, a circular shape, etc. Note that FIG. 1 shows a state where the virtual irradiation position IR of the light beam does not coincide with the light-receiving window TA on the imaging surface P without the deflection adjustment by the deflector 102.

[0018] As will be described later, it is desirable that the imaging surface P be illuminated by illumination light of wavelength λ2. As an illumination method, an illumination light source of wavelength λ2 may be arranged near the imaging surface P, or an illumination light beam may be irradiated onto the imaging surface P along the principal optical axis AX P Further, it is desirable that the image sensor 101 have relatively high sensitivity only to light of wavelength λ2.

[0019] As illustrated in FIG. 2, the processor 103 can realize an optical axis adjustment function including a figure extraction unit 110, a feature point position detection unit 111, and a deflector control unit 112 by executing a program stored in the program memory 104. The figure extraction unit 110 performs image conversion processing on the image data acquired by the imaging unit to extract the predetermined figure W. For example, elements having a linear shape or a circular shape can be easily detected by Hough transformation.

[0020] The feature point position detection unit 111 detects the feature point position indicating the light-receiving window TA from the extracted predetermined figure W. The deflector control unit 112 controls the deflector 102 so as to eliminate the difference between the given reference position r and the feature point position indicating the light-receiving window TA. As already described, the reference position r in the captured image indicates the position of the principal optical axis AX P This reference position r indicates the position of the principal optical axis AX Pand the reference optical axis AX REF can be determined in advance by positioning the mirror member M1, the imaging optical system S, and the image sensor 101 with respect to REF .

[0021] 1.2) Operation Hereinafter, with reference to FIGS. 3 to 5, an optical axis adjustment method executed by the processor 103 will be described.

[0022] Referring to FIG. 3, the processor 103 determines whether it is the image analysis timing (operation 201). If it is the image analysis timing (YES in operation 201), the processor 103 inputs imaging data from the image sensor 101 and acquires an image of the object plane P (operation 202). The acquired image includes an image of a predetermined figure W on the object plane P.

[0023] The processor 103 extracts the shape of the predetermined figure W from the acquired image of the object plane P by, for example, the Hough transform, and geometrically detects the feature point position w from the extracted figure (operation 203). FIG. 4 shows an example of the extraction of the figure W and the detection of the feature point position w from the figure W. If the acquired image is developed on the XY plane, the reference optical axis AX P corresponding to the principal optical axis AX REF has a reference position r at predetermined coordinates (Xr, Yr), and it is assumed that the detected feature point position w has coordinates (Xw, Yw).

[0024] Subsequently, the processor 103 determines whether the coordinates (Xw, Yw) of the detected feature point position w match the coordinates (Xr, Yr) of the reference position r (operation 204). Here, "match" means a state where the difference between the feature point position w and the reference position r is smaller than a predetermined threshold value. This predetermined threshold value is set within a range where the light beam sufficiently irradiates the light receiving window TA and there is no problem in the operation on the system.

[0025] If the feature point position w and the reference position r do not match (NO in operation 204), the processor 103 adjusts the deflection direction of the deflector 102 to eliminate the difference between the coordinates (Xw, Yw) of the feature point position w and the coordinates (Xr, Yr) of the reference position r (operation 205). The above operations 202 to 205 are repeated for each image analysis timing, but are not executed when it is not the image analysis timing (NO in operation 201). Also, when the coordinates of the feature point position w and the coordinates of the reference position r match (YES in operation 204), operation 205 (deflection adjustment) is not executed.

[0026] Note that after the processor 103 adjusts the deflection direction of the deflector 102 to eliminate the difference between the feature point position w and the reference position r, it may re-execute operations 202 to 204 to check whether the difference between the feature point position w and the reference position r has been sufficiently reduced. If the difference exceeds a predetermined threshold, the deflection adjustment can be repeated by operation 205.

[0027] Also, the image analysis timing in operation 201 can be set according to the optical system to which the optical axis adjustment device according to the present embodiment is applied. For example, in an optical communication system using quantum light, accurate alignment of the communication optical beam is required between the transmission side and the reception side. Also, when the amount of light incident on the reception side fluctuates due to the vibration of the communication device, the optical axis can be adjusted at a timing close to real time by shortening the interval of the image analysis timing.

[0028] In FIGS. 4 and 5, when the coordinates (Xw, Yw) of the detected feature point position w and the coordinates (Xr, Yr) of the reference position r do not match, the irradiation position r of the light beam along the current principal optical axis AX P is deviated from the position w of the light receiving window TA which is the irradiation target.

[0029] Therefore, the processor 103 calculates the difference between the coordinates (Xw, Yw) of the feature point position w and the coordinates (Xr, Yr) of the reference position r, and determines the direction and angle θ of the deflection of the deflector 102 to eliminate the difference. As illustrated in FIG. 5, the processor 103 controls the deflector 102 to adjust the principal optical axis AX Pis deflected by an angle θ, and the virtual irradiation position IR of the light beam on the main optical axis AX after deflection PD is assumed to coincide with the light receiving window TA of the irradiation target. In this case, in the imaging image IMG on the image sensor 101, the center of the predetermined figure W overlaps with the reference position r. Therefore, in this state, as shown in FIG. 4, the coordinates (Xr, Yr) of the reference position r and the coordinates (Xw, Yw) of the detected feature point position w match on the XY plane of the acquired image. The deflector 102 is controlled so that the feature point position w and the reference position r match on the acquired image, and the optical axis adjustment is executed.

[0030] 1.3) Effect As described above, according to the first embodiment of the present invention, the light receiving position TA to which the light beam is to be irradiated can be specified by the predetermined figure W, and the image sensor 101 images the predetermined figure W through the deflector 102, the mirror member M1, and the imaging optical system S. The light receiving position TA is detected from the image thus obtained based on the predetermined figure W. The deflection direction of the deflector 102 is adjusted so that the light receiving position TA matches the reference position r on the acquired image. As a result, it becomes possible to adjust the optical axis based on the imaging figure on the transmission side of the light beam. Therefore, it is not necessary to monitor the received light amount on the reception side, and highly accurate and rapid optical axis adjustment is achieved on the transmission side.

[0031] 2. Second Embodiment In the above-described first embodiment, the reference position r corresponding to the reference optical axis AX REF was determined in advance on the acquired image, but the present invention is not limited to this. As described below, it can be detected by the same procedure as the predetermined figure W using a figure capable of specifying the reference position r. Hereinafter, mainly the configurations and functions different from those of the first embodiment will be described, and the same reference numerals will be given to the same components as those in the first embodiment, and the description thereof will be omitted.

[0032] 2.1) Configuration As illustrated in FIG. 6, the optical axis adjustment device 10A according to the second embodiment of the present invention includes an imaging unit composed of an image sensor 101, an optical system S1, an optical system S2, and a mirror member M2. Further, the optical axis adjustment device 10A includes a deflector 102 capable of deflecting the principal optical axis AX of a signal light beam that is a laser beam, and a processor 103A that performs deflection adjustment of the deflector 102 based on the imaging data of the image sensor 101. P

[0033] The principal optical axis AX P is as described in the first embodiment, and the reference optical axis AX REF is an optical axis orthogonal to the principal optical axis AX. P The center of the mirror member M2 is on the intersection of the principal optical axis AX P and the reference optical axis AX, REF and the half-reflecting surface is disposed at an inclination of 45° clockwise with respect to the reference optical axis AX. REF The mirror member M2 has an optical property of transmitting a light beam having a predetermined wavelength λ1 and semi-transmitting and semi-reflecting light having other wavelengths λ2 (here, the reflected light L REF 1 of the reference surface P R and the reflected light L R 2 of the surface to be imaged P).

[0034] The mirror member M2 and the deflector 102 are arranged such that these optical axes coincide with the principal optical axis AX. P The mirror member M2, the optical systems S1, S2, and the image sensor 101 are arranged such that these optical axes coincide with the reference optical axis AX. REF Note that, similar to the first embodiment, in the captured image acquired by the image sensor 101, the position of the reference optical axis AX REF can be treated as the position of the principal optical axis AX. P

[0035] The reflected light L R 1 is from the reference surface P REF to the reference optical axis AX REF ​The reflected light L is incident on the mirror member M2 along the line r, passes through the optical system S2, and forms an image on the image sensor 101. R 2 is the main optical axis AX from the image plane P P The light is incident on the mirror member M2 along the reference optical axis AX REF The light is reflected in the direction of the reference plane P on the light receiving surface of the image sensor 101 through the optical system S2. REF The image sensor 101 captures an image of the reference plane P through the optical systems S1 and S2, and outputs the captured image data to the processor 103A. REF and then images the imaged surface P through the deflector 102 and the optical system S2.

[0036] As shown in FIG. REF The main optical axis AX of the light beam is P The reference optical axis AX corresponds to REF A reference figure R that can geometrically identify the reference position of is displayed. As a display method, it is preferable to print the reference figure R with a reflective material (retroreflective material), but multiple light-emitting elements may be arranged in the shape of the reference figure R. As in the first embodiment, a predetermined figure W that can geometrically identify the light-receiving window TA that is the irradiation target of the light beam is displayed on the imaged surface P. However, it is preferable that the reference figure R and the predetermined figure W have shapes that allow each figure to be extracted even if the reference position and the light-receiving window TA overlap. Specific examples will be described later.

[0037] In FIG. 7, the reference figure R is shown as a circle for convenience in order to distinguish it from the given figure W. The reference figure R is aligned with the main optical axis AX P The reference optical axis AX corresponds to REF It is sufficient if the shape can specify the position r of the reference figure R. As described above, it is desirable to be able to extract the respective shapes even if the reference figure R and the predetermined figure W overlap. For example, if the reference figure R is a circle, it is desirable for the predetermined figure W to have a shape that surrounds the reference figure R and is composed only of straight lines that can indicate the light receiving window TA.

[0038] As will be described later, the reference plane P REFAnd the object image plane P is preferably illuminated by illumination light of wavelength λ2. As an illumination method, the reference plane P REF and an illumination light source of wavelength λ2 may be arranged in the vicinity of each of the object image plane P. Also, the principal axis AX P An illumination light beam along the reference plane P through the mirror member M2 REF And the object image plane P may be irradiated respectively. Also, it is desirable that the image sensor 101 has a relatively high sensitivity only to light of wavelength λ2.

[0039] Also, as shown in FIG. 7, the optical systems S1 and S2 constitute one imaging optical system focused on the reference plane P REF And an image of the reference plane P is formed on the light receiving surface of the image sensor 101. Also, the optical system S2 constitutes one imaging optical system focused on the object image plane P, and an image of the object image plane P is formed on the light receiving surface of the image sensor 101. REF As illustrated in FIG. 8, the processor 103A can realize an optical axis adjustment function including a graphic extraction unit 110A, a feature point position detection unit 111A, and a deflector control unit 112A by executing a program stored in the program memory 104A. The graphic extraction unit 110A performs image conversion processing on the image data acquired by the imaging unit and extracts a reference graphic R and a predetermined graphic W. For example, elements having a linear shape or a circular shape can be easily detected by Hough transform.

[0040] The feature point position detection unit 111A detects a reference position r from the extracted reference graphic R, and detects a feature point position w indicating the light receiving window TA from the extracted predetermined graphic W. The deflector control unit 112A controls the deflector 102 so as to eliminate the difference between the detected reference position r and the feature point position w.

[0041]

[0042] 2.2) Operation Hereinafter, with reference to FIG. 9 and appropriately referring to FIGS. 4 and 5, an optical axis adjustment method executed by the processor 103A will be described.

[0043] 9, the processor 103A judges whether it is time to analyze an image (operation 201). If it is time to analyze an image (YES in operation 201), the processor 103A inputs the captured image data from the image sensor 101 and calculates the reference plane P REF An image of the imaged surface P is acquired (operation 202). The acquired image includes a reference surface P REF The image includes an image of a reference figure R and a predetermined figure W on the imaged surface P.

[0044] The processor 103A converts the reference plane P REF The shape of the reference figure R is extracted from the acquired image of the object plane P, and the shape of the predetermined figure W is extracted from the acquired image of the object plane P, and the reference position r and the feature point position w are geometrically detected from the extracted reference figure R and the predetermined figure W, respectively (operation 203). As shown in Fig. 4, if the acquired image is expanded on the XY plane, the detected reference position r will be the coordinates (Xr, Yr), and the feature point position w will be the coordinates (Xw, Yw).

[0045] Next, the processor 103A judges whether the coordinates (Xw, Yw) of the feature point position w match the coordinates (Xr, Yr) of the reference position r (operation 204). If they do not match (NO in operation 204), the processor 103A adjusts the deflection direction of the deflector 102 so as to eliminate the difference between the coordinates (Xw, Yw) of the feature point position w and the coordinates (Xr, Yr) of the reference position r (operation 205).

[0046] The deflection adjustment of the deflector 102 is as described in FIG. 5. The processor 103A controls the deflector 102 to eliminate the difference between the feature point position w and the reference position r, and adjusts the main optical axis AX P is deflected by an angle θ. This causes the main optical axis AX after deflection to PD In this way, the virtual irradiation position IR of the light beam can be made to coincide with the light receiving window TA of the irradiation target. In this manner, the optical axis adjustment is performed.

[0047] The above operations 202 to 205 are repeated for each image analysis timing, but are not executed when it is not the image analysis timing (NO in operation 201). Also, when the feature point position w and the reference position r match (YES in operation 204), operation 205 (deviation adjustment) is not executed. Here, the definition of "match" is as described in the first embodiment.

[0048] Note that after the processor 103A adjusts the deflection direction of the deflector 102 so as to eliminate the difference between the feature point position w and the reference position r, operations 202 to 204 may be re-executed to confirm whether the difference between the feature point position w and the reference position r has been sufficiently reduced. When the difference exceeds a predetermined threshold, the deviation adjustment can be repeated by operation 205.

[0049] Also, the image analysis timing in operation 201 can be set according to the optical system to which the optical axis adjustment device according to this embodiment is applied. For example, in an optical communication system using quantum light, accurate alignment of the communication optical beam is required between the transmission side and the reception side. Also, when the amount of light incident on the reception side fluctuates due to the vibration of the communication device, it becomes possible to perform optical axis adjustment at a timing close to real time by making the interval of the image analysis timing shorter.

[0050] 2.3) Effects As described above, according to the second embodiment of the present invention, the reference optical axis AX corresponding to the principal optical axis AX of the optical beam P REF ​Identify the position of [object] with the reference figure R, and identify the light-receiving position TA to which the light beam is to be irradiated with the predetermined figure W. The image sensor 101 images the reference figure R through the optical system S1, the mirror member M2, and the optical system S2, and images the predetermined figure W through the deflector 102, the mirror member M2, and the optical system S2. Based on the reference figure R, detect the reference position r from the thus obtained image, and based on the predetermined figure W, detect the light-receiving position TA. Adjust the deflection direction of the deflector 102 so that the light-receiving position TA coincides with the reference position r on the acquired image. Thereby, it becomes possible to adjust the optical axis based on the imaging figure on the transmission side of the light beam. Therefore, it is not necessary to monitor the received light amount on the reception side, and highly accurate and rapid optical axis adjustment is achieved on the transmission side.

[0051] Furthermore, according to the second embodiment, since the reference surface P is imaged through the optical system S1, the mirror member M2, and the optical system S2 to detect the reference position r, even if the optical axis adjustment device 10A excluding the imaged surface P is displaced in position due to vibration or the like, the position of the overall reference optical axis AX REF can be correctly detected. REF

[0052] 3. Examples In the above-described first and second embodiments, it is desirable to illuminate the imaged surface P or the reference surface P REF and the imaged surface P with illumination light having a wavelength λ2. Hereinafter, the illumination means in the optical axis adjustment device according to the second embodiment described above will be described. However, mainly, the configurations and functions different from those of the second embodiment will be described, and the same reference numerals will be given to the components similar to those of the second embodiment, and the description thereof will be omitted.

[0053] 3.1) First Example As illustrated in FIG. 10, the optical axis adjustment device 10A1 according to the first example has a configuration in which an illumination light generation unit 105 and a dichroic mirror DM1 are added to the configuration of the optical axis adjustment device 10A according to the second embodiment (see FIG. 6).

[0054] The illumination light generation unit 105 includes a laser light source 106 with a wavelength of λ2 and a beam expander 107. The laser light source 106 outputs an optical beam with a wavelength of λ2 to the beam expander 107. The beam expander 107 outputs collimated light with a diameter larger than the input optical beam as an illumination light beam to the dichroic mirror DM1. The optical axis AX of the illumination light generation unit 105 G is the principal optical axis AX P and is orthogonal to it, and the dichroic mirror DM1 is arranged at the intersection point with the principal optical axis AX P .

[0055] The half-reflecting surface of the dichroic mirror DM1 is arranged to be inclined by 45° clockwise with respect to the optical axis AX G . The dichroic mirror DM1 has an optical characteristic of transmitting a signal optical beam with a wavelength of λ1 and reflecting an illumination light beam with a wavelength of λ2 different from λ1.

[0056] The illumination light beam is reflected by the dichroic mirror DM1 and travels in the direction of the principal optical axis AX P and irradiates the imaging surface P through the mirror member M2 and the deflector 102. Also, the illumination light beam is reflected by the mirror member M2 in the direction of the reference optical axis AX REF and irradiates the reference surface P REF through the optical system S1. As described above, it is assumed that a reference pattern R and a predetermined pattern W are printed on the reference surface P REF and the imaging surface P with a retroreflective material respectively.

[0057] The reflected light L REF 1 on the reference surface P R passes through the optical system S1 and the mirror member M2, and forms an image of the reference pattern R on the light receiving surface of the image sensor 101 through the optical system S2. Also, the reflected light L R 2 on the imaging surface P passes through the deflector 102, is reflected by the mirror member M2, and forms an image of the predetermined pattern W on the light receiving surface of the image sensor 101 through the optical system S2. In this way, the imaging data of the reference surface P REF and the imaging surface P are output to the processor 103B, and the processor 103B controls the deflection direction of the deflector 102 to perform the above-described optical axis adjustment.

[0058] Furthermore, the processor 103B can control the timing at which the illumination light generation unit 105 emits an illumination light beam. That is, the laser light source 106 is driven only at the above-described image analysis timing to emit an illumination light beam. Thereby, the reference plane P REF and the imaging plane P are illuminated, and the optical axis adjustment can be performed based on their reflected lights L R 1 and reflected light L R 2. Alternatively, by constantly driving the laser light source 106 to illuminate the reference plane P REF and the imaging plane P, the optical axis correction can be performed in real time, and a more delicate optical axis adjustment becomes possible.

[0059] Note that the illumination light beam from the illumination light generation unit 105 illuminates the imaging plane P in the direction of the main optical axis AX by the dichroic mirror DM1. Therefore, especially when manually adjusting the deflector 102, this illumination light beam can also be used as guide light. P

[0060] As illustrated in FIG. 11, the reference figure R of the reference plane P REF is circular, and the predetermined figure W of the imaging plane P has a shape such that the respective figures can be extracted even when the reference figure R overlaps. Desirably, the predetermined figure W is displayed on the entire surface of the imaging plane P. Specifically, the predetermined figure W is composed of four line segments that radially and evenly extend from the light receiving window TA as the center. As an example, the predetermined figure W is composed of a straight line Px in the x direction and a straight line Py in the y direction that are the same as those divided in the light receiving window TA region. By extracting the straight lines of the predetermined figure W on the image acquired by the image sensor 101, the position of the light receiving window TA between them can be specified. Also, the circular reference figure R can be easily extracted regardless of how it overlaps with the predetermined figure W composed of straight lines.

[0061] The control of the processor 103B is substantially equivalent to the optical axis adjustment flow illustrated in FIG. 9. That is, the processor 103B, at the image analysis timing, the reference plane P REF ​An imaging image of the object imaging surface P is acquired, and a circular reference figure R and a predetermined figure W composed of four line segments are extracted from the acquired image. As already described below, the reference position r and the feature point position w are geometrically detected from the extracted reference figure R and predetermined figure W, respectively, and the deflector 102 is controlled to eliminate the position difference therebetween, thereby performing optical axis adjustment.

[0062] 3.2) Second Embodiment With reference to FIG. 12, an optical axis adjustment device according to a second embodiment of the present invention will be described. Since the configuration of the second embodiment is basically the same as that of the first embodiment, the same reference numerals are given to the same blocks and detailed description thereof is omitted.

[0063] In FIG. 12, it is assumed that a transmitting communication device 300 and a receiving communication device 400 are optically connected by an optical transmission line 30. However, the optical transmission line 30 in the present embodiment is a free space link that performs optical transmission in the atmosphere without using an optical fiber or the like. Therefore, in order to realize stable free space transmission between the spatially separated communication devices 300 and 400, it is necessary to accurately align the optical axes of the communication devices 300 and 400.

[0064] The communication device 300 has the same configuration as the optical axis adjustment device 10A1 according to the first embodiment illustrated in FIG. 10, except that a light transmitting unit 108 that transmits laser light as a signal light beam having a wavelength λ1 is added. Therefore, the same reference numerals are given and the description thereof is omitted.

[0065] The communication device 400 includes an imaging surface P, a dichroic mirror DM2, and a light receiving unit 401 in the first embodiment. The imaging surface P is as described in the first embodiment (see FIG. 11). The dichroic mirror DM2 has the property of transmitting a signal light beam with a wavelength λ1 and reflecting an illumination light beam with a wavelength λ2. The light receiving unit 401 has a light receiving surface 402 of a photodetector and receives the signal light beam with the wavelength λ1. If the optical axis adjustment between the communication device 300 and the communication device 400 is completed, the signal light beam correctly enters the light receiving surface 402. In this embodiment, the light receiving surface 402 of the light receiving unit 401 and the light receiving window TA of the imaging surface P are provided separately, and the position of the light receiving surface 402 corresponds to the position of the light receiving window TA of the imaging surface P.

[0066] The optical axis adjustment between the communication device 300 and the communication device 400 is as described in the first embodiment. That is, the processor 103B of the communication device 300 acquires the reference surface P REF and the captured image of the imaging surface P at the image analysis timing, and extracts a circular reference figure R and a predetermined figure W composed of four line segments from the acquired image. Hereinafter, the reference position r and the feature point position w are geometrically detected from the extracted reference figure R and the predetermined figure W, respectively, and the deflector 102 is controlled to eliminate the position difference therebetween, thereby performing the optical axis adjustment.

[0067] In this way, by performing the optical axis adjustment between the communication device 300 and the communication device 400, stable spatial transmission becomes possible. The optical axis adjustment device according to this embodiment is suitable for accurate optical axis adjustment between spatially separated communication devices 300 and 400. In particular, accurate optical axis alignment is required in an optical communication system such as a quantum key distribution system (QKD) using a weak signal light of 1 photon or less. Even in such an optical communication system, stable spatial transmission is possible with the optical axis adjustment device according to this embodiment.

[0068] 3.3) Other Embodiments In the above first and second embodiments, the illumination light generation unit 105 emits an illumination light beam with a wavelength λ2, and the dichroic mirror DM1 reflects it in the direction of the main optical axis AX P towards the reference surface P REFand the imaging surface P was illuminated. However, the present invention is not limited to this illumination method. Reference surface P REF and the light with wavelength λ2 from the imaging surface P may be imaged on the image sensor 101. Hereinafter, other embodiments will be described.

[0069] <Third Embodiment> As illustrated in FIG. 13, in the optical axis adjustment device 10A2 according to the third embodiment, instead of the illumination light generation unit 105 and the dichroic mirror DM1 of the optical axis adjustment device 10A1 according to the first embodiment, illumination units IS1 and IS2 are provided. The illumination unit IS1 has a configuration in which a plurality of light emitting diodes (LEDs) with wavelength λ2 are arranged, and the reference surface P REF is irradiated with illumination light with wavelength λ2. Similarly, the illumination unit IS2 has a configuration in which a plurality of LEDs with wavelength λ2 are arranged, and the imaging surface P is irradiated with illumination light with wavelength λ2.

[0070] In this way, the reference surface P REF and the light with wavelength λ2 from the imaging surface P can be imaged on the image sensor 101. Since the other configurations and operations are the same as those of the above-described embodiments and examples, the same reference numerals are given and the description is omitted.

[0071] <Fourth Embodiment> As illustrated in FIG. 14, the optical axis adjustment device 10A3 according to the fourth embodiment does not illuminate the reference surface P REF and the imaging surface P as in the first to third embodiments, but causes both the reference figure R and the predetermined figure W or only the predetermined figure W to emit light by the light emitting element with wavelength λ2.

[0072] In FIG. 14, the reference surface P REFA plurality of light emitting elements (here, LEDs) are arranged in the shape of a reference figure R. Each light emitting element emits light with a wavelength of λ2 and displays the reference figure R as a whole. Also, on the imaging surface P, a plurality of light emitting elements are arranged in the shape of a predetermined figure W. Each light emitting element emits light with a wavelength of λ2 and displays the predetermined figure W as a whole. Note that, instead of arranging a plurality of light emitting elements, a configuration may be adopted in which a light shielding mask having a transmissive portion of the reference figure R or the predetermined figure W is disposed in front of a light source with a single wavelength λ.

[0073] Reference surface P REF Alternatively, one side of the imaging surface P may be made to emit light. In particular, a configuration in which the imaging surface P is made to emit light with a light emitting element is suitable for a communication system in which communication devices are spatially separated from each other as in the second embodiment because imaging can be performed with stronger light compared to the reflected light L R 2.

[0074] <Deflector> The deflector 102 used in each of the above-described embodiments and examples can be a mechanically driven type, an acousto-optic type, or an electro-optic type. FIG. 15 illustrates a galvanometer scanner as the mechanically driven deflector 102. As is well known, a galvanometer scanner can scan a light beam in the X / Y directions by rotating two reflecting mirrors and can be used as the deflector 102.

[0075] 4. Supplementary Note Some or all of the above-described embodiments and examples can be described as follows in the supplementary note, but are not limited thereto. (Supplementary Note 1) An optical axis adjustment device for irradiating a predetermined light receiving position with a light beam, a deflector that deflects the light beam, an imaging unit that images a captured image surface including a predetermined figure indicating the predetermined light receiving position through the deflector, a processing unit that controls a deflection direction of the deflector based on an acquired image captured by the imaging unit, including wherein the processing unit Detect the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, Adjust the deflection direction of the deflector so that the predetermined light-receiving position on the acquired image coincides with a reference position indicating the principal optical axis before deflection of the light beam on the acquired image, Optical axis adjustment device. (Appendix 2) The optical axis adjustment device according to Appendix 1, wherein the processing unit has preset the reference position at a predetermined position on the acquired image captured by the imaging unit. (Appendix 3) The imaging unit is, An imaging optical system focused on the object surface to be imaged, A two-dimensional sensor provided on the imaging surface of the imaging optical system and outputting imaging data of the object surface to be imaged to the processing unit, The optical axis adjustment device according to Appendix 2, including. (Appendix 4) Further having a mirror member disposed on an intersection point between the principal optical axis and a reference optical axis orthogonal to the principal optical axis between the light source of the light beam and the deflector, The imaging optical system is disposed between the mirror member and the two-dimensional sensor, The mirror member has a property of transmitting the light beam of the first wavelength and reflecting light of a second wavelength different from the first wavelength, and reflects the light of the second wavelength from the object surface to be imaged toward the two-dimensional sensor, The optical axis adjustment device according to Appendix 3. (Appendix 5) The optical axis adjustment device according to any one of Appendices 1-4, further having an illumination light source for illuminating the object surface to be imaged with light of a wavelength different from that of the light beam. (Appendix 6) The optical axis adjustment device according to any one of Appendices 1-4, having a light-emitting element that emits light from the predetermined figure on the object surface to be imaged, and the emission wavelength of the light-emitting element is a wavelength different from that of the light beam. (Appendix 7) Further having a reference surface including a reference figure indicating the reference position, The imaging unit images the reference surface, The processing unit detects the reference position from the reference figure included in the acquired image of the reference plane imaged by the imaging unit. The optical axis adjustment device according to Supplementary Note 1. (Supplementary Note 8) The imaging unit an imaging optical system that focuses on both the imaged surface and the reference surface; a two-dimensional sensor provided on the imaging surface of the imaging optical system, for outputting imaging data of the imaged surface and the reference surface to the processing unit; The optical axis adjustment device according to Supplementary Note 7, including the above. (Supplementary Note 9) The imaging optical system includes a mirror member, a first optical system, and a second optical system. The mirror member is disposed on the intersection of the main optical axis and a reference optical axis orthogonal to the main optical axis between the light source of the light beam and the deflector. The mirror member, the first optical system, the second optical system, the reference surface, and the two-dimensional sensor are disposed on the reference optical axis. The first optical system is disposed between the mirror member and the reference surface, and the second optical system is disposed between the mirror member and the two-dimensional sensor. The mirror member transmits the light beam of the first wavelength, has semi-transmissive and semi-reflective characteristics for incident light of a second wavelength different from the first wavelength, reflects the light of the second wavelength from the imaged surface toward the two-dimensional sensor, and transmits the light of the second wavelength from the reference surface to the two-dimensional sensor. The optical axis adjustment device according to Supplementary Note 8. (Supplementary Note 10) The optical axis adjustment device according to any one of Supplementary Notes 7-9, further having an illumination light source for illuminating the imaged surface and the reference surface with light of a wavelength different from that of the light beam. (Supplementary Note 11) The optical axis adjustment device according to any one of Supplementary Notes 7-9, having a light-emitting element that emits at least the predetermined figure on the imaged surface and the reference figure on the reference surface, and the emission wavelength of the light-emitting element is a wavelength different from that of the light beam. (Supplementary Note 12) An optical communication system in which a first communication device provided with the optical axis adjustment device according to any one of Supplementary Notes 1-4 and 7-9 and a second communication device provided with the imaging surface are optically connected with a space as an optical transmission path. (Supplementary Note 13) The optical communication system according to Supplementary Note 12, having a light emitting element that emits the predetermined figure on the imaging surface, and the emission wavelength of the light emitting element being different from the wavelength of the light beam. (Supplementary Note 14) An optical axis adjustment method in an optical axis adjustment device for irradiating a light beam to a predetermined light receiving position, wherein the optical axis adjustment device includes a deflector that deflects the light beam, an imaging unit that images, through the deflector, an imaging surface including a predetermined figure indicating the predetermined light receiving position, and a processing unit that controls a deflection direction of the deflector based on an acquired image imaged by the imaging unit, the processing unit detects the predetermined light receiving position on the acquired image from the predetermined figure included in the acquired image, and adjusts the deflection direction of the deflector so that the predetermined light receiving position coincides with a reference position indicating a principal optical axis before deflection of the light beam on the acquired image. Optical axis adjustment method. (Supplementary Note 15) The optical axis adjustment method according to Supplementary Note 14, wherein the processing unit presets the reference position at a predetermined position on an acquired image imaged by the imaging unit. (Supplementary Note 16) The optical axis adjustment device further has a reference surface including a reference figure indicating the reference position, and the processing unit detects the reference position from the reference figure included in the acquired image of the reference surface imaged by the imaging unit. The optical axis adjustment method according to Supplementary Note 14. (Supplementary Note 17) A program for causing a computer to function as an optical axis adjustment device for irradiating a light beam to a predetermined light receiving position, wherein the optical axis adjustment device includes a deflector that deflects the light beam, an imaging surface including a predetermined figure indicating the predetermined light receiving position, and an imaging unit that images the imaging surface through the deflector. The computer A function of detecting the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image A function of adjusting the deflection direction of the deflector so that the predetermined light-receiving position coincides with a reference position indicating the principal optical axis before deflection of the light beam on the acquired image A program for realizing the above (Appendix 18) The program according to Appendix 17, wherein the computer preliminarily sets the reference position at a predetermined position on the acquired image captured by the imaging unit (Appendix 19) The optical axis adjustment device further has a reference surface including a reference figure indicating the reference position The computer detects the reference position from the reference figure included in the acquired image of the reference surface captured by the imaging unit The program according to Appendix 17

Industrial Applicability

[0076] The present invention can be used in an optical system that requires optical axis adjustment and a communication device of an optical communication system

Explanation of Signs

[0077] 10, 10A, 10A1, 10A2, 10A3 Optical axis adjustment device 101 Image sensor (two-dimensional sensor) 102 Deflector 103, 103A, 103B Processor (processing unit) M1 Mirror member S Imaging optical system L R Reflected light P Imaged surface W Predetermined figure TA Light-receiving window w Feature point position P REF Reference surface R Reference figure r Reference position AX P Principal optical axis AX PD Changed principal optical axis AX REF Reference optical axis

Claims

1. An optical axis adjustment device for irradiating a light beam to a predetermined light-receiving position, comprising: a deflector for deflecting the light beam; an imaging unit that images an imaging surface including a predetermined figure indicating the predetermined light-receiving position through the deflector; a processing unit that controls the deflection direction of the deflector based on an acquired image captured by the imaging unit; and the processing unit detects the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and adjusts the deflection direction of the deflector so that the predetermined light-receiving position coincides with a reference position indicating the principal optical axis before deflection of the light beam on the acquired image. Optical axis adjustment device.

2. The optical axis adjustment device according to claim 1, wherein the processing unit pre-sets the reference position at a predetermined position on an acquired image captured by the imaging unit.

3. The optical axis adjustment device according to claim 1 or 2, further comprising an illumination light source for illuminating the imaging surface with light having a wavelength different from that of the light beam.

4. The optical axis adjustment device according to claim 1 or 2, comprising a light-emitting element that emits light from the predetermined figure of the imaging surface, and the emission wavelength of the light-emitting element is a wavelength different from that of the light beam.

5. further comprising a reference surface including a reference figure indicating the reference position, the imaging unit images the reference surface, and the processing unit detects the reference position from the reference figure included in the acquired image of the reference surface captured by the imaging unit. The optical axis adjustment device according to claim 1.

6. The optical axis adjustment device according to claim 5, further comprising an illumination light source for illuminating the imaging surface and the reference surface with light having a wavelength different from that of the light beam.

7. The optical axis adjustment device according to claim 5, comprising a light-emitting element that emits at least the predetermined figure on the imaged surface and the reference figure on the reference surface, and having a light-emitting wavelength of the light-emitting element different from the wavelength of the light beam.

8. An optical communication system in which a first communication device provided with the optical axis adjustment device according to any one of claims 1, 2, and 5 and a second communication device provided with the imaged surface are optically connected with a space as an optical transmission path.

9. An optical axis adjustment method in an optical axis adjustment device for irradiating a light beam to a predetermined light-receiving position, The optical axis adjustment device includes a deflector that deflects the light beam, an imaging unit that images an imaged surface including a predetermined figure indicating the predetermined light-receiving position through the deflector, and a processing unit that controls a deflection direction of the deflector based on an acquired image imaged by the imaging unit. The processing unit, detects the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and adjusts a deflection direction of the deflector so that the predetermined light-receiving position coincides with a reference position indicating a principal optical axis before deflection of the light beam on the acquired image. Optical axis adjustment method.

10. A program for causing a computer to function as an optical axis adjustment device for irradiating a light beam to a predetermined light-receiving position, The optical axis adjustment device includes a deflector that deflects the light beam, an imaged surface including a predetermined figure indicating the predetermined light-receiving position, and an imaging unit that images the imaged surface through the deflector. By the computer, a function of detecting the predetermined light-receiving position on the acquired image from the predetermined figure included in the acquired image, and a function of adjusting a deflection direction of the deflector so that the predetermined light-receiving position coincides with a reference position indicating a principal optical axis before deflection of the light beam on the acquired image. A program for realizing the above.

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