Laser wavelength measuring method and laser wavelength measuring device

Abstract

To provide a laser wavelength measurement method and a laser wavelength measurement device having high versatility, with which it is possible to measure the wavelength of laser light irrespective of the wavelength band of the laser light being measured.SOLUTION: The laser wavelength measurement method executes: a base phase difference measurement step in which a base laser light is separated into a base measurement light and a base reference light and a phase difference between a first base interference light to a first reflection surface 51 and a second base interference light to a second reflection surface 52 is measured as a base phase difference; a target phase difference measurement step in which a target laser light is separated into a target measurement light and a target reference light, and a phase difference between a first target interference light to the first reflection surface 51 and a second target interference light to the second reflection surface 52 is measured as a target phase difference; and a wavelength calculation step in which the wavelength of the target laser light is calculated on the basis of the base phase difference, the target phase difference and the wavelength of the base laser light.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laser wavelength measurement method and a laser wavelength measurement device for measuring the wavelength of laser light output from a laser device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, measuring devices that measure the wavelength and frequency of laser light are known (see, for example, Patent Documents 1 and 2). The device described in Patent Document 1 uses a reference laser light with a stabilized emission frequency, causes interference between the laser light to be measured and the reference laser light, and measures the beat frequency to calculate the relative frequency deviation of the laser light to be measured with respect to the reference laser light.

[0003] The device described in Patent Document 2 uses an optical frequency comb that outputs light in multiple longitudinal modes at a specified frequency interval and a specified offset frequency, and causes the light from the optical frequency comb to interfere with the laser light to be measured, measuring the beat frequency and determining whether the laser light to be measured is stabilized within the desired frequency range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-274482 A [Patent Document 2] JP2015-5601 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0005] However, when using a reference laser light as in Patent Document 1, the beat frequency that can be measured by interfering the reference laser light with the laser light to be measured is limited to frequencies in the microwave region. Therefore, the laser device that outputs the laser light to be measured is limited to one that uses the same principle as the laser device of the reference laser light or one that uses the same laser medium. In other words, the laser frequency measurement device described in Patent Document 1 is a dedicated device for measuring a specific laser frequency.

[0006] In contrast, as described in Patent Document 2, a laser frequency measurement device using an optical frequency comb uses laser light with a wide band and regularly spaced longitudinal modes, so that it is possible to measure the laser frequency over a wider range. However, when using an optical frequency comb, it is necessary to determine the order of the longitudinal mode, so the uncertainty in the frequency of the laser light to be measured must be sufficiently smaller than the frequency interval of the longitudinal modes of the optical frequency comb. Therefore, a laser frequency measurement device using an optical frequency comb as described in Patent Document 2 can only be used for frequency measurement of high-performance laser light with extremely high accuracy. In addition, an optical frequency comb is a very large-scale and expensive device, and is difficult to operate. As described above, conventional measuring devices for measuring the wavelength and frequency of laser light have the problem that the types of laser light that can be measured are limited. There is a demand for a versatile laser frequency measuring device that can accurately measure the wavelength of laser light regardless of the frequency band (wavelength band).

[0007] An object of the present invention is to provide a highly versatile laser wavelength measurement method and laser wavelength measurement device that are capable of measuring the wavelength of laser light regardless of the wavelength band of the laser light to be measured. [Means for solving the problem]

[0008] A laser wavelength measurement method according to a first aspect of the present invention includes a reference phase difference measurement step of separating a reference laser light having a known wavelength into a reference measurement light and a reference reference light by a light separating unit, reflecting the reference measurement light at a first reflecting surface and a second reflecting surface that is a predetermined first distance away from the first reflecting surface, and measuring a phase difference between a first reference interference light obtained by interfering the reference measurement light and the reference reference light reflected at the first reflecting surface and a second reference interference light obtained by interfering the reference measurement light and the reference reference light reflected at the second reflecting surface as a reference phase difference; a target phase difference measurement step in which the target measurement light and the target reference light are separated by the light separation unit, the target measurement light is reflected by the first reflecting surface and the second reflecting surface, and the phase difference between first target interference light caused by interference between the target measurement light and the target reference light reflected by the first reflecting surface, and second target interference light caused by interference between the target measurement light and the target reference light reflected by the second reflecting surface is measured as a target phase difference; and a wavelength calculation step in which the wavelength of the target laser light is calculated based on the reference phase difference, the target phase difference, and the wavelength of the reference laser light.

[0009] In this aspect, the wavelength of the measurement target is calculated based on the reference phase difference measured in the reference phase difference measuring step, the target phase difference measured in the target phase difference measuring step, and the wavelength of the reference laser light. That is, the first distance can be represented by the phase difference between the interference light (first interference light) of the measurement light and the reference light reflected on the first reflecting surface and the interference light (second interference light) of the measurement light and the reference light reflected on the second reflecting surface, the wave number (integer part) of the laser light relative to the first distance, and the wavelength of the laser light. That is, the first distance can be represented by the reference phase difference when the reference laser light is used, the wave number (reference integer part) of the reference laser light included in the first distance, and the wavelength of the reference laser light, and can also be represented by the target phase difference when the target laser light is used, the wave number (target integer part) of the target laser light included in the first distance, and the wavelength of the target laser light. In other words, the wavelength of the target laser light can be calculated by the wavelength of the reference laser light, the reference phase difference, the target phase difference, the reference integer part, and the target integer part. In this case, since there is no need to detect the beat frequency between the reference laser light and the target laser light, the laser wavelengths of the two may be different. In other words, the reference laser device that emits the reference laser light and the target laser device that emits the target laser light do not need to use the same principle or the same laser medium, and the wavelength bands of the emitted laser light may be different. In addition, there is no need to use a large-scale device such as an optical frequency comb, which simplifies the configuration and reduces costs. That is, in the laser wavelength measurement method of this aspect, the wavelength of the laser light can be properly measured regardless of the wavelength band or accuracy of the laser light to be measured, and without using a large-scale device.

[0010] In the laser wavelength measurement method of this aspect, it is preferable that the reference measurement light and the object measurement light are irradiated as parallel light beams having a predetermined beam diameter onto a measurement structure having the first reflecting surface and the second reflecting surface, the reference phase difference measurement step captures an interference fringe image of the reference measurement light and the reference reference light reflected by the measurement structure, and measures the reference phase difference by analyzing an interference fringe between a first region corresponding to the first reflecting surface and a second region corresponding to the second reflecting surface in the interference fringe image, and the object phase difference measurement step captures an interference fringe image of the object measurement light and the object reference light reflected by the measurement structure, and measures the object phase difference by analyzing an interference fringe between a first region corresponding to the first reflecting surface and a second region corresponding to the second reflecting surface in the interference fringe image.

[0011] In other words, in this embodiment, a reference measurement light or an object measurement light is irradiated onto a measurement structure having a step in which a first reflecting surface and a second reflecting surface are separated by a first distance, and an interference fringe image formed by interference light between the reflected light and the reference light is captured. This makes it possible to shorten the measurement time compared to the case where the first reference interference light, the second reference interference light, the first object interference light, and the second object interference light are measured separately.

[0012] In the laser wavelength measurement method of this aspect, it is preferable that the reference phase difference measurement step calculates the reference phase difference based on an amount of shift of the interference fringes of the second region relative to the interference fringes of the first region, relative to an interval between the interference fringes of the first region or the second region, and the target phase difference measurement step calculates the target phase difference based on an amount of shift of the interference fringes of the second region relative to the interference fringes of the first region, relative to an interval between the interference fringes of the first region or the second region.

[0013] As in the above embodiment, when the first reflecting surface and the second reflecting surface are planes perpendicular to the optical path axis of the reference measurement light (object measurement light), the intervals of the interference fringes are the same interval (first interval) in the first region or the second region. In this case, the amount of positional deviation between the interference fringes in the first region and the interference fringes in the second region relative to the first interval is the phase difference. In other words, the reference phase difference can be easily calculated based on the interference fringes in the first region and the second region of the interference fringe image captured when the reference laser light is used, and the object phase difference can be easily calculated based on the interference fringes in the first region and the second region of the interference fringe image captured when the object laser light is used.

[0014] In the laser wavelength measurement method of this aspect, an optical path separation unit is provided that separates the reference laser light and the object laser light into a first optical path toward the first reflecting surface and a second optical path toward the second reflecting surface, and the reference phase difference measurement step measures, as the reference phase difference, a phase difference between an interference light of the reference measurement light and the reference reference light guided to the first reflecting surface along the first optical path and an interference light of the reference measurement light and the reference reference light guided to the second reflecting surface along the second optical path, and the object phase difference measurement step may measure, as the object phase difference, a phase difference between an interference light of the object measurement light and the object reference light guided to the first reflecting surface along the first optical path and an interference light of the object measurement light and the object reference light guided to the second reflecting surface along the second optical path.

[0015] In this embodiment, in addition to the method of obtaining an interference fringe image by imaging a structure having a first reflecting surface and a second reflecting surface as described above, the optical path of the laser light may be separated, and a reference measurement light or an object measurement light may be irradiated to a predetermined measurement point on the first reflecting surface and a predetermined measurement point on the second reflecting surface. Even in this case, as in the above embodiment, in the reference phase difference measurement step, the interference light between the reference measurement light and the reference reference light guided to the first reflecting surface, and the interference light between the reference measurement light and the reference reference light guided to the second reflecting surface can be simultaneously observed. Similarly, in the object phase difference measurement step, the interference light between the object measurement light and the object reference light guided to the first reflecting surface, and the interference light between the object measurement light and the object reference light guided to the second reflecting surface can be simultaneously observed.

[0016] A laser wavelength measurement method of a second aspect of the present invention includes the steps of: reflecting a reference laser light having a known wavelength at a first reflecting surface and a second reflecting surface a predetermined first distance away from the first reflecting surface, and measuring the light intensity of reference interference light caused by interference between the reference laser light reflected at the first reflecting surface and the reference laser light reflected at the second reflecting surface; reflecting a target laser light whose wavelength is to be measured at the first reflecting surface and the second reflecting surface, and measuring the light intensity of target interference light caused by interference between the target laser light reflected at the first reflecting surface and the target laser light reflected at the second reflecting surface; and calculating the wavelength of the target laser light based on the wavelength of the reference laser light, the light intensity of the reference interference light, and the light intensity of the target interference light.

[0017] In this aspect, the first distance between the first and second reflecting surfaces can be calculated by measuring the reference interference light obtained by interfering the reference laser light reflected by the first reflecting surface and the reference laser light reflected by the second reflecting surface in the reference interference measurement step. Therefore, if the object interference light obtained by interfering the object laser light reflected by the first reflecting surface and the object laser light reflected by the second reflecting surface is measured in the object interference measurement step, the wavelength of the object laser light can be calculated based on the first distance calculated based on the reference interference light, the light intensity of the object interference light, and the wavelength of the reference laser light, as in the first aspect. Even in this case, the reference laser device that emits the reference laser light and the object laser device that emits the object laser light do not need to use the same principle or the same laser medium, and the wavelength bands of the emitted laser light may be different. In addition, there is no need to use a large-scale device such as an optical frequency comb, and the configuration can be simplified and the cost can be reduced. In other words, the wavelength of the laser light can be measured regardless of the wavelength band or accuracy of the laser light to be measured.

[0018] In the laser wavelength measurement method of this aspect, the reference interference measurement step measures a change in light intensity of the reference interference light when the first distance is changed by a second distance, the target interference measurement step measures a change in light intensity of the target interference light when the first distance is changed by the second distance, and the calculation step calculates the wavelength of the target laser light based on the wavelength of the reference laser light, the change in light intensity of the reference interference light, and the change in light intensity of the target interference light.

[0019] That is, in this embodiment, in the reference interference measurement step, the first distance is changed by the second distance to measure the change in light intensity of the reference interference light, i.e., the amount of phase shift, using the phase shift method. Similarly, in the target interference measurement step, the phase shift method is used to measure the change in light intensity of the target interference light, i.e., the amount of phase shift. Even when using phase analysis using such a phase shift method, the wavelength of the target laser light can be measured with high accuracy, as in the above embodiment.

[0020] A laser wavelength measurement device according to a third aspect of the present invention includes a reference laser device that emits a reference laser light having a known wavelength, a target laser device that emits a target laser light having a wavelength to be measured, a light separation unit that separates the reference laser light into a reference measurement light and a reference reference light and separates the target laser light into the target measurement light and the target reference light, a first reflecting surface that reflects a portion of the reference measurement light and a portion of the target measurement light, a second reflecting surface that reflects the remainder of the reference measurement light and the remainder of the target measurement light and is positioned a first distance away from the first reflecting surface, and a first reflecting surface that causes interference between the portion of the reference measurement light reflected by the first reflecting surface and the reference reference light. The optical fiber includes a measurement unit that measures each of a reference interference light, a first object interference light obtained by interfering a portion of the object measurement light reflected by the first reflecting surface and the object reference light, a second reference interference light obtained by interfering a portion of the reference measurement light reflected by the second reflecting surface and the reference reference light, and a second object interference light obtained by interfering a remainder of the object measurement light reflected by the second reflecting surface and the object reference light, and a calculation unit that calculates the wavelength of the object laser light based on a reference phase difference which is the phase difference between the first reference interference light and the second reference interference light, a target phase difference which is the phase difference between the first object interference light and the second object interference light, and the wavelength of the reference laser light.

[0021] In such a laser wavelength measurement device, the wavelength of the target laser light can be measured using the same laser wavelength measurement method as in the first aspect described above. Therefore, similar to the first aspect, the wavelength of the laser light can be measured with a simple configuration regardless of the wavelength band or accuracy of the laser light to be measured.

[0022] A fourth aspect of the laser wavelength measurement device according to the present invention includes a reference laser device that emits a reference laser light having a known wavelength; a target laser device that emits a target laser light whose wavelength is to be measured; a first reflecting surface that reflects a portion of the reference laser light and a portion of the target laser light; a second reflecting surface that reflects the remainder of the reference laser light and the remainder of the target laser light and is positioned a first distance away from the first reflecting surface; a measurement unit that measures reference interference light caused by interference between the reference laser light reflected at the first reflecting surface and the reference laser light reflected at the second reflecting surface, and target interference light caused by interference between the target laser light reflected at the first reflecting surface and the target laser light reflected at the second reflecting surface; and a calculation unit that calculates the wavelength of the target laser light based on the wavelength of the reference laser light, the light intensity of the reference interference light, and the light intensity of the target interference light.

[0023] In such a laser wavelength measurement device, the wavelength of the target laser light can be measured using the same laser wavelength measurement method as in the second aspect described above. Therefore, similar to the second aspect, the wavelength of the laser light can be measured with a simple configuration regardless of the wavelength band or accuracy of the laser light to be measured. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing a laser wavelength measurement device according to a first embodiment. [Diagram 2] 4 is a flowchart showing a laser wavelength measurement method according to the first embodiment. [Diagram 3] FIG. 4 is a diagram showing an example of an interference fringe image captured in the first embodiment. [Figure 4] FIG. 11 is a schematic diagram showing a laser wavelength measurement device according to a second embodiment. [Diagram 5] FIG. 11 is a schematic diagram showing a laser wavelength measurement device according to a third embodiment. [Figure 6] 10 is a flowchart showing a laser wavelength measurement method according to a third embodiment. [Figure 7] FIG. 13 is a schematic diagram showing a laser wavelength measurement device according to a modified example of the third embodiment. [Figure 8]FIG. 13 is a schematic diagram showing a laser wavelength measurement device according to a fourth embodiment. [Figure 9] 13 is a flowchart showing a laser wavelength measuring method according to a fourth embodiment. [Figure 10] FIG. 13 is a schematic diagram showing a laser wavelength measurement device according to a fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] [First embodiment] Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a laser wavelength measurement device 1 of the present embodiment. [Schematic configuration of laser wavelength measuring device 1] As shown in FIG. 1, the laser wavelength measurement device 1 of this embodiment includes a laser arrangement section 10, a collimator lens 20, a beam splitter 30, a reference body 40, a measurement structure 50, an imaging lens 60, an imaging camera 70, and a control section 80. The laser arrangement section 10 is a section for arranging either a target laser device 11 that outputs laser light (target laser light) whose wavelength is to be measured, or a reference laser device 12 that outputs laser light (reference laser light) whose wavelength is known. In this embodiment, the laser device arranged in the laser arrangement section 10 is switched between the target laser device 11 and the reference laser device 12. Thereby, interference fringes when the target laser light and the reference laser light are respectively used are observed, and the wavelength of the target laser light is calculated.

[0026] The collimating lens 20 transmits the laser light output from the laser device arranged in the laser arrangement section 10 as parallel light to the beam splitter 30. For example, in this embodiment, the laser light output from the target laser device 11 and the reference laser device 12 arranged in the laser arrangement section 10 is emitted with an expanded beam diameter, and the collimating lens 20 is arranged at a position where the beam diameter of the laser light becomes a predetermined diameter. Note that a lens that expands the laser light output from the target laser device 11 and the reference laser device 12 to a predetermined beam diameter may be arranged between the laser arrangement section 10 and the collimating lens 20.

[0027] The beam splitter 30 corresponds to the light separation unit of the present invention, and separates the laser light output from the laser device arranged in the laser arrangement unit 10 and collimated by the collimator lens 20 into a reference light and a measurement light. For example, in this embodiment, a half mirror is used as the beam splitter 30, and reflects a part of the laser light incident from the collimator lens 20 side, i.e., the reference light, toward the reference body 40, and transmits the remainder toward the measurement structure 50. In addition, the beam splitter 30 transmits the laser light reflected by the reference body 40 toward the imaging lens 60 and the imaging camera 70, and reflects the measurement light reflected by the measurement structure 50 toward the imaging lens 60 and the imaging camera 70. The reference body 40 has a reference surface that is perpendicular to the optical path of the reference light reflected by the beam splitter 30. As a result, the reference light reflected by the reference surface is reflected along the same optical path as the reference light traveling from the beam splitter 30 toward the reference body.

[0028] The measurement structure 50 includes a first reflecting surface 51 and a second reflecting surface 52 that are perpendicular to the optical path of the measurement light transmitted through the beam splitter 30. The first reflecting surface 51 and the second reflecting surface 52 are spaced apart by a first distance L along the optical path of the measurement light. For example, in this embodiment, the measurement structure 50 includes a base 50A and a protruding portion 50B that protrudes from the base 50A toward the beam splitter 30, and the surface of the base 50A facing the beam splitter 30 constitutes the first reflecting surface 51, and the surface of the protruding portion 50B facing the beam splitter 30 constitutes the second reflecting surface 52. As a result, the measurement light reflected by the first reflecting surface 51 and the second reflecting surface 52 is reflected along the same optical path as the measurement light traveling from the beam splitter 30 toward the measurement structure 50.

[0029] In this embodiment, the measurement structure 50 is provided with the protruding portion 50B at approximately the center of the pedestal portion 50A, but is not limited thereto. For example, the position of the protruding portion 50B relative to the pedestal portion 50A is not particularly limited, and it is sufficient that the first reflection surface 51 of the pedestal portion 50A and the second reflection surface 52 of the protruding portion 50B are included within the irradiation range of the measurement light. Therefore, for example, the protruding portion 50B may be configured to protrude from the outer periphery of the pedestal portion 50A. In addition, the measurement structure 50 may be configured to have, for example, a rectangular parallelepiped block shape, and a recess may be provided in a part (for example, the center) of the surface facing the beam splitter 30. In this case, the bottom surface of the recess becomes the first reflection surface 51, and the surface facing the rectangular parallelepiped beam splitter 30 becomes the second reflection surface 52.

[0030] The imaging lens 60 forms an image on the imaging camera 70 of the interference light of the reference light reflected by the reference body 40 and transmitted through the beam splitter 30 and the measurement light reflected by the measurement structure 50 and then reflected by the beam splitter 30 . The imaging camera 70 captures the interference light and outputs an interference fringe image (captured image) to the control unit 80.

[0031] The control unit 80 controls the laser wavelength measurement device 1. For example, the control unit 80 controls the laser devices (target laser device 11 and reference laser device 12) arranged in the laser arrangement unit 10, the imaging camera 70, etc. The control unit 80 also functions as a calculation unit of the present invention, and calculates the wavelength of the target laser light based on the interference fringe image obtained by the imaging camera 70. The control unit 80 includes a storage unit 81 for storing various data such as an interference fringe image captured by the imaging camera 70 and various programs, and a processor 82 for carrying out various calculation processes. The processor 82 reads and executes the program recorded in the storage unit 81 to function as an analysis unit 821 that analyzes the interference light and a wavelength calculation unit 822 that calculates the wavelength of the target laser light. A detailed description of each functional configuration will be given later.

[0032] [Laser wavelength measurement method] Next, a laser wavelength measurement method in the above-described laser wavelength measurement device 1 will be described. FIG. 2 is a flowchart showing the laser wavelength measuring method of the present embodiment. In the laser wavelength measurement device 1 of this embodiment, when measuring the wavelength of a target laser light, first, an interference fringe measurement using a reference laser light (hereinafter, referred to as a reference interference fringe measurement) is carried out. That is, a measurer places the reference laser device 12 in the laser placement section 10 of the laser wavelength measurement device 1 (step S1). Then, when the measurer performs an input operation on the operation unit (not shown) to the control unit 80 to perform a reference interference fringe measurement, the control unit 80 causes the reference laser device 12 to emit reference laser light and the imaging camera 70 to capture an interference fringe image (reference interference fringe image) (step S2).

[0033] The analysis unit 821 then analyzes the captured reference interference fringe image to obtain a first reference interference light obtained by interfering between the reference measurement light and the reference reference light reflected by the first reflecting surface 51 of the measurement structure 50 and a second reference interference light obtained by interfering between the reference measurement light and the reference reference light reflected by the second reflecting surface 52 of the measurement structure 50 (reference phase difference Δφ ref ) is calculated (step S3: reference phase difference measurement step).

[0034] Here, a method for calculating the phase difference based on the interference fringes appearing in a first region of the interference fringe image corresponding to the first reflecting surface and the interference fringes appearing in a second region of the interference fringe image corresponding to the second reflecting surface will be described. FIG. 3 is a diagram showing an example of an interference fringe image captured by the imaging camera 70. As shown in FIG. In Figure 3, the region where interference fringes appear due to interference light between the measurement light and reference light reflected by the first reflecting surface 51 is designated as first region Ar1, and the region where interference fringes appear due to interference light between the measurement light and reference light reflected by the second reflecting surface 52 is designated as second region Ar2. 3, when the first reflecting surface 51 and the second reflecting surface 52 are separated by a first distance L, the interference fringes in the first region Ar1 and the interference fringes in the second region Ar2 are observed to be shifted by a shift amount b according to the first distance L. The interval between the interference fringes appearing in the first region Ar1 is the same as the interval between the interference fringes appearing in the second region Ar2, and this interval between the interference fringes is denoted as a. In this case, the phase difference between the interference light between the measurement light and reference light reflected by the first reflecting surface 51 and the interference light between the measurement light and reference light reflected by the second reflecting surface 52 of the measurement structure 50 is expressed by the following equation (1).

[0035]

number

[0036] Therefore, in step S3, the analysis unit 821 calculates the interval a of the interference fringes in either the first region Ar1 or the second region Ar2 in the reference interference fringe image. ref and the deviation amount b of the interference fringes of the second area Ar2 relative to the interference fringes of the first area Ar1 of the reference interference fringe image. ref Analyze and use equation (1) to obtain the reference phase difference Δφ ref Calculate.

[0037] Next, the measurer places the target laser device 11, the wavelength of which is to be measured, in the laser placement unit 10 of the laser wavelength measurement device 1 (step S4). Then, when the measurer performs an input operation on an operation unit (not shown) to the control unit 80 to perform a target interference fringe measurement, the control unit 80 causes the target laser device 11 to emit target laser light and causes the imaging camera 70 to capture an interference fringe image (target interference fringe image) (step S5).

[0038] The analysis unit 821 then analyzes the captured target interference fringe image to obtain the phase difference (target phase difference Δφ meas ) is calculated (step S6: target phase difference calculation step). Target phase difference Δφ meas is the reference phase difference Δφ ref Similarly, the spacing a of the interference fringes in either the first region Ar1 or the second region Ar2 in the target interference fringe image meas and the shift amount b of the interference fringes of the second area Ar2 relative to the interference fringes of the first area Ar1 of the target interference fringe image. meas can be calculated by analyzing and using equation (1).

[0039] Thereafter, the wavelength calculation unit 822 calculates the reference phase difference Δφ ref and the target phase difference Δφ obtained in step S6 meas and the wavelength of the reference laser light, the wavelength of the target laser light is calculated (step S7: wavelength calculation step). In this embodiment, the first distance L between the first reflecting surface 51 and the second reflecting surface 52 is measured in advance within an error range of half the wavelength of the reference laser light and the target laser light, and the value is stored in the storage unit 81. Similarly, the wavelength λ of the reference laser light ref is stored in advance in the storage unit 81. In addition, it is assumed that an approximate value for the wavelength of the target laser light is known in advance, is input to the control unit 80 by the measurer operating the operation unit, and is stored in the storage unit 81. The first distance L is defined as n, the refractive index of air, and λ, the wavelength of the known reference laser light. ref , the wavelength of the target laser light is λ meas In this case, it can be expressed by the following formula (2).

[0040]

number

[0041] In addition, in formula (2), N ref is the integer part (reference integer part) of the interference signal of the reference interference light, and indicates the wave number of the reference laser light included in the first distance L. meas is the integer part (object integer part) of the interference signal of the object interference light, and indicates the wave number of the object laser light included in the first distance L. refis a fractional part of the interference signal of the reference interference light, and is the phase difference between the interference light between the first reference measurement light and the reference light reflected by the first reflecting surface 51, and the interference light between the second reference measurement light and the reference light reflected by the second reflecting surface 52. meas is a fractional part of the interference signal of the object interference light, and is the phase difference between the interference light between the first object measurement light and the object reference light reflected by the first reflecting surface 51, and the object interference light between the second object measurement light and the reference light reflected by the second reflecting surface 52. Therefore, as described above, by measuring the first distance L in advance, the integer part N ref , N meas can be determined. Moreover, the following formula (3) can be derived from the above formula (2).

[0042]

number

[0043] In step S7, the wavelength calculation unit 822 calculates the wavelength λ of the reference laser light corresponding to the wavelength of the reference laser light. ref Based on the first distance L, an appropriate reference integer part N ref The reference integer part N ref may be stored in advance in the storage unit 81. In addition, the wavelength calculation unit 822 calculates an appropriate target integer part N based on the approximate wavelength (provisional wavelength) of the target laser light and the first distance L. meas Determine. Then, the wavelength calculation unit 822 calculates the wavelength λ of the reference laser light. ref , reference integer part N ref , the target integer part N meas , the reference phase difference Δφ obtained in step S3 ref , and the target phase difference Δφ obtained in step S6 meas By substituting into equation (3), the wavelength λ of the target laser light is obtained. meas , and the wavelength λ meas The frequency of the target laser light corresponding to the above is calculated.

[0044] [Effects of this embodiment] The laser wavelength measurement device 1 of this embodiment is configured so that a reference laser device 12 that outputs reference laser light with a known wavelength and a target laser device 11 that outputs target laser light to be measured can be arranged in a laser arrangement section 10. The laser wavelength measurement device 1 also includes a beam splitter 30 that separates the laser light output from the laser device arranged in the laser arrangement section 10 into measurement light and reference light, a first reflecting surface 51 and a second reflecting surface 52 that reflect the measurement light, an imaging camera 70 (measurement section) that measures interference light between the measurement light and the reference light, and a control section 80 (calculation section).

[0045] The control unit 80 of this embodiment arranges the reference laser device 12 in the laser arrangement unit 10, and calculates a phase difference between a first reference interference light obtained by interfering the reference measurement light and the reference reference light reflected by the first reflecting surface 51 with each other when the reference laser light is separated into the reference measurement light and the reference reference light by the beam splitter 30, and a second reference interference light obtained by interfering the reference measurement light and the reference reference light reflected by the second reflecting surface 52 with each other, as a reference phase difference Δφ ref Then, a reference phase difference measurement step (step S3) is carried out to measure the reference phase difference. In addition, the control unit 80 of this embodiment arranges the object laser device 11 in the laser arrangement unit 10, and when the object laser light is separated into the object measurement light and the object reference light by the beam splitter 30, calculates a phase difference between a first object interference light obtained by interfering the object measurement light and the object reference light reflected by the first reflecting surface 51 and a second object interference light obtained by interfering the object measurement light and the object reference light reflected by the second reflecting surface 52 as an object phase difference Δφ meas Then, a target phase difference measuring step (step S6) is carried out to measure the target phase difference. Then, the control unit 80 calculates the reference phase difference Δφ ref , target phase difference Δφ meas , the integer part N of the interference signal based on the first distance L ref ,N meas , and the wavelength λ of the reference laser light ref Based on this, the wavelength λ of the target laser light meas A wavelength calculation step (step S7) is then carried out to calculate the frequency.

[0046] In the laser wavelength measurement device 1 and the laser wavelength measurement method, the reference phase difference Δφ ref and the target phase difference Δφ measured in the target phase difference measurement step. meas and the wavelength λ of the reference laser light ref Based on this, the wavelength of the measurement object can be calculated. In other words, the first distance L is determined by the reference phase difference Δφ as shown in equation (2). ref , reference integer part N ref , target phase difference Δφ meas , the target integer part N meas , the wavelength λ of the reference laser light ref In this embodiment, the wavelength λ of the target laser is expressed by the formula (3). meas In this case, the reference laser device 12 and the target laser device 11 do not need to use the same principle or the same laser medium, and the wavelength bands of the emitted laser light may be different. In addition, there is no need to use a large-scale device such as an optical frequency comb, which simplifies the configuration and reduces costs.

[0047] In the laser wavelength measurement device 1 of this embodiment, the reference measurement light and the object measurement light are irradiated onto a measurement structure 50 having a first reflecting surface 51 and a second reflecting surface 52 as parallel light beams with a predetermined beam diameter. Then, in the reference phase difference measurement step, the analysis unit 821 of the control unit 80 captures an interference fringe image of the reference measurement light and the reference reference light reflected by the measurement structure 50, and calculates the reference phase difference Δφ by using the formula (1) by analyzing the interference fringes between the first region Ar1 corresponding to the first reflecting surface 51 and the second region Ar2 corresponding to the second reflecting surface 52 in the interference fringe image. ref Similarly, in the object phase difference measuring step, the analysis unit 821 captures an interference fringe image of the object measurement light and the object reference light reflected by the measurement structure 50, and measures the object phase difference Δφ by using the formula (1) by analyzing the interference fringes between the first area Ar1 and the second area Ar2 in the interference fringe image. meas Measure. This makes it possible to shorten the measurement time compared to the case where the first reference interference light, the second reference interference light, the first object interference light, and the second object interference light are measured separately. ref and the target phase difference Δφ meas can be calculated.

[0048] [Second embodiment] Next, a second embodiment will be described. In the first embodiment, the laser light output from the target laser device 11 and the reference laser device 12 is expanded to a predetermined beam diameter as shown in Fig. 1, and then collimated by the collimator lens 20. Therefore, the measurement light irradiated to the measurement structure 50 is irradiated to an irradiation range including the first reflecting surface 51 and the second reflecting surface 52, and an interference fringe image is captured. In contrast, the present embodiment differs from the above embodiment in that measurement points are set on the first reflecting surface 51 and the second reflecting surface 52, respectively, and interference light of the light reflected at the measurement points is observed. In the following description, the same reference numerals will be used to designate components that have already been described, and description thereof will be omitted or simplified.

[0049] FIG. 4 is a schematic diagram showing a laser wavelength measurement device 1A of the present embodiment. As shown in FIG. 4, the laser wavelength measurement device 1A of this embodiment includes a laser arrangement unit 10, an optical path separation unit 20A, a beam splitter 30, a reference body 40, a measurement structure 50, an imaging camera 70, and a control unit 80. In the present embodiment, similarly to the first embodiment, the laser arrangement unit 10 can arrange the target laser device 11 and the reference laser device 12. Here, in the present embodiment, the target laser device 11 and the reference laser device 12 arranged in the laser arrangement unit 10 output laser light as parallel light, and irradiate a predetermined point (first measurement point) on the first reflecting surface 51 and a predetermined point (second measurement point) on the second reflecting surface 52 with the laser light.

[0050] The optical path separation unit 20A is composed of, for example, a beam splitter 21 and a mirror 22. The laser light of the laser device arranged in the laser arrangement unit 10 is separated by the beam splitter 21 into a first optical path toward the first reflecting surface 51 and a second optical path toward the second reflecting surface 52. For example, in this embodiment, the light reflected by the beam splitter 21 and reflected again by the mirror 22 is the light that is directed toward the first reflecting surface 51, and the optical path of this light is the first optical path. On the other hand, the light that has passed through the beam splitter 21 is the light that is directed toward the second reflecting surface 52, and the optical path of this light is the second optical path.

[0051] In the laser wavelength measurement device 1A configured as described above, the image captured by the imaging camera 70 includes the first measurement point on the first reflecting surface 51 and the second measurement point on the second reflecting surface 52, but no interference fringes appear as in the first embodiment. However, the first measurement point in the captured image becomes an interference signal (tone value) corresponding to the light intensity of the interference light between the measurement light reflected at the first measurement point and the reference light, and the first measurement point in the captured image becomes an interference signal (tone value) corresponding to the light intensity of the interference light between the measurement light reflected at the first measurement point and the reference light. Therefore, the analysis unit 821 calculates the reference integer part N ref and the reference phase difference Δφ ref and the target integer part N of the interference signal when the target laser device 11 is used as the laser device. meas and the target phase difference Δφ meas and can be calculated. As a result, the wavelength calculation unit 822 of the control unit 80 calculates the wavelength λ of the target laser light by using the formula (3) in the same manner as in the first embodiment. meas And the frequency of the target laser light can be calculated.

[0052] [Effects of this embodiment] The laser wavelength measurement device 1A of this embodiment is equipped with an optical path separation section 20A that separates the reference laser light and the target laser light output from the reference laser device 12 and the target laser device 11 arranged in the laser arrangement section 10 into a first optical path toward the first reflecting surface 51 and a second optical path toward the second reflecting surface 52. Then, in the reference phase difference measurement step, the analysis unit 821 of the control unit 80 measures a phase difference (reference phase difference) between the interference light of the reference measurement light and the reference reference light guided along the first optical path to the first reflecting surface 51, and the interference light of the reference measurement light and the reference reference light guided along the second optical path to the second reflecting surface 52. Similarly, in the reference phase difference measurement step, the analysis unit 821 measures a phase difference (object phase difference) between the interference light of the object measurement light and the object reference light guided along the first optical path to the first reflecting surface 51, and the interference light of the object measurement light and the object reference light guided along the second optical path to the second reflecting surface 52. Even in this case, the wavelength λ of the target laser light can be calculated by using the above-mentioned formula (3). meas The reference laser device 12 and the target laser device 11 do not need to use the same principle or the same laser medium, and the wavelength bands of the emitted laser light may be different. Therefore, similar to the first embodiment, the wavelength λ of the target laser light can be calculated regardless of the wavelength band or accuracy of the target laser light to be measured. meas This makes it possible to perform highly versatile laser wavelength measurement that can measure the wavelength and frequency of a laser. In addition, there is no need to use a large-scale device such as an optical frequency comb, which simplifies the configuration and reduces costs.

[0053] [Third embodiment] Next, a third embodiment will be described. In the first and second embodiments, the wavelength λ of the target laser light is calculated by using the interference light between the measurement light and the reference light reflected by the first reflecting surface 51 of the measurement structure 50 and the interference light between the measurement light and the reference light reflected by the second reflecting surface 52, since formula (2) is satisfied for the first distance L between the first reflecting surface 51 and the second reflecting surface 52, formula (3) is used to calculate the wavelength λ of the target laser light. meas and calculates the frequency. In contrast, the third embodiment does not use the measurement structure 50 and measures the wavelength λ of the target laser light. meas This embodiment differs from the above embodiment in that the frequency is calculated.

[0054] FIG. 5 is a schematic diagram showing a laser wavelength measurement device 1B of this embodiment. The laser wavelength measurement device 1B of this embodiment includes a laser arrangement unit 10, a beam splitter 30, a half mirror 40A, a mirror 53, an imaging camera 70, and a control unit 80, as shown in FIG. In this embodiment, similarly to the second embodiment, the target laser device 11 and the reference laser device 12 arranged in the laser arrangement section 10 output laser light as parallel light.

[0055] In this embodiment, of the laser light output from the laser device arranged in the laser arrangement section 10, the laser light that has passed through the beam splitter 30 is incident on the half mirror 40A. The half mirror 40A transmits a portion of the light incident from the beam splitter 30 side and reflects the remainder toward the beam splitter 30. The mirror 53 has a mirror surface perpendicular to the optical path of the laser light, and the light transmitted through the half mirror 40A is totally reflected by the mirror 53. As a result, the light transmitted through the half mirror 40A is reflected by the mirror 53, and then transmitted through the half mirror 40A again to return to the beam splitter 30. In this embodiment, the mirror 53 constitutes the first reflecting surface of the present invention, and the half mirror 40A constitutes the second reflecting surface of the present invention.

[0056] In the laser wavelength measurement device 1B of this embodiment, the imaging camera 70 can capture an image of interference light between light reflected by the mirror 53 as the first reflecting surface and light reflected by the half mirror 40A as the second reflecting surface. In this case, the phase of the interference light is determined by the distance between the half mirror 40A and the mirror 53. That is, in this embodiment, the distance from the half mirror 40A to the mirror 53 is the first distance L, and the first distance L can be expressed by the formula (2) used in the first embodiment.

[0057] FIG. 6 is a flowchart showing a laser wavelength measuring method in this embodiment. In this embodiment, similarly to the first embodiment, in step S1, the reference laser device 12 is arranged in the laser arrangement section 10 and is made to output a reference laser beam. Then, the analysis unit 821 causes the imaging camera 70 to capture an image of interference light (reference interference light) between the reference laser light reflected by the mirror 53 and the reference laser light reflected by the half mirror 40A (step S2A: reference interference measurement step). That is, in step S2A, the imaging camera 70 receives the reference interference light, thereby making it possible to measure the light intensity of the reference interference light.

[0058] Thereafter, in step S4, the measurer places the target laser device 11 in the laser placement unit 10 and causes it to output a target laser light. Then, the analysis unit 821 causes the imaging camera 70 to capture an image of interference light (object interference light) between the object laser light reflected by the mirror 53 and the object laser light reflected by the half mirror 40A (step S5A: object interference measurement step). That is, in step S5A, the imaging camera 70 receives the object interference light, thereby making it possible to measure the light intensity of the object interference light.

[0059] Thereafter, the analysis unit 821 calculates the light intensity of the reference interference light, the light intensity of the target interference light, and the wavelength λ of the reference laser light. ref Based on this, the wavelength λ of the target laser light meas And the frequency is calculated (step S7A; calculation step). In this embodiment, the distance (first distance L) between the half mirror 40A and the mirror 53 is a known fixed value, so the reference integer part N ref and the reference phase difference Δφ ref In addition, if the approximate wavelength of the target laser light is known, the target integer part N of the target interference signal can be obtained based on equation (2). meas and the target phase difference Δφ meas Therefore, in this embodiment as well, the wavelength calculation unit 822 calculates the wavelength λ of the target laser light by using the formula (3). meas And the frequency of the target laser light can be calculated.

[0060] [Effects of this embodiment] In the laser wavelength measurement device 1B of this embodiment, in a reference interference measurement step (step S2A), the light intensity of reference interference light obtained by interfering between the reference laser light reflected by the mirror 53, which is the first reflecting surface, and the reference laser light reflected by the half mirror 40A, which is the second reflecting surface, is measured. Also, in a target interference measurement step (step S5A), the light intensity of target interference light obtained by interfering between the target laser light reflected by the mirror 53 and the target laser light reflected by the half mirror 40A is measured. Then, in a calculation step (step S7A), the wavelength calculation unit 822 calculates the light intensity of the reference interference light, the light intensity of the target interference light, and the wavelength λ of the reference laser light. ref Using the above, the wavelength λ of the target laser light is meas Calculate. Therefore, in this embodiment, as in the first embodiment, it is not necessary to use the same principle or the same laser medium for the reference laser device and the target laser device, and it is possible to perform highly versatile laser wavelength measurement. In addition, it is not necessary to use a large-scale device such as an optical frequency comb, and it is possible to simplify the configuration and reduce costs.

[0061] [Modification of the third embodiment] In the third embodiment described above, the first reflecting surface is mirror 53 and the second reflecting surface is half mirror 40A, but this is not limited to this, and the first reflecting surface and the second reflecting surface may be formed by other optical components arranged on the optical path. FIG. 7 is a schematic diagram of a laser wavelength measurement device 1C in a modified example of the third embodiment, and shows an example in which optical fibers are used instead of the half mirror 40A and the mirror 53. For example, in a laser wavelength measurement device 1C shown in FIG. 7, an optical fiber 90 is used instead of the half mirror 40A and the mirror 53 of the third embodiment. In this case, the end face of the optical fiber 90 corresponds to the first reflecting surface and the second reflecting surface. For example, in the optical fiber 90, an end face 91 onto which the light transmitted through the beam splitter 30 is incident is the second reflecting surface, and an end face 92 on the opposite side of the optical fiber 90 is the first reflecting surface. In this case, a first distance L between the end face 92 which is the first reflecting surface and the end face 91 which is the second reflecting surface corresponds to the length of the optical fiber 90. Therefore, in this embodiment, similarly to the third embodiment, the wavelength λ of the target laser light meas and the frequency can be calculated.

[0062] [Fourth embodiment] In the third embodiment, the positions of the half mirror 40A and the mirror 53 are fixed, and the first distance L is a fixed value. However, the first distance L may be variable. FIG. 8 is a schematic diagram of a laser wavelength measurement apparatus 1D according to the fourth embodiment. The laser wavelength measurement device 1D of this embodiment includes a laser arrangement unit 10, a beam splitter 30, a half mirror 40A, a mirror 53, an imaging camera 70, and a control unit 80. In this embodiment, the target laser device 11 and the reference laser device 12 are arranged in parallel in the laser arrangement unit 10. With this configuration, it is not necessary to switch the target laser device 11 and the reference laser device 12 when measuring the laser wavelength. In this embodiment, the half mirror 40A is configured to be movable by the actuator 41 along the optical path of the laser light.

[0063] In this embodiment, the analysis unit 821 can perform analysis of the interference light using a phase shift method. In other words, if the phase of the interference light between the light reflected by the half mirror 40A and the light reflected by the mirror 53 changes by dΔφ when the half mirror 40A is moved by a second distance dL, the relationship between dL and dΔφ is expressed by the following equation (4).

[0064]

number

[0065] Therefore, when interference light is measured simultaneously using the reference laser light and the object laser light as in this embodiment, formula (4) can be expressed as the following formula (5).

[0066]

number

[0067] Therefore, the wavelength λ of the target laser light meas can be calculated by the following formula (6).

[0068]

number

[0069] FIG. 9 is a flowchart showing a laser wavelength measuring method in this embodiment. In this embodiment, the control unit 80 controls the object laser device 11 and the reference laser device 12 to emit object laser light and reference laser light (step S11). When an image is captured by the imaging camera 70 (step S12), the captured image includes a target measurement point where interference light (target interference light) between the target laser light reflected by the half mirror 40A and the target laser light reflected by the mirror 53 is received, and a reference measurement point where interference light (reference interference light) between the reference laser light reflected by the half mirror 40A and the reference laser light reflected by the mirror 53 is received. The analysis unit 821 stores in the storage unit 81 an interference signal (tone value) corresponding to the light intensity of the target interference light at the target measurement point and an interference signal (tone value) corresponding to the light intensity of the reference interference light at the reference measurement point (step S13).

[0070] Next, the analysis unit 821 controls the actuator 41 to move the half mirror 40A by the second distance dL (step S14), and causes the imaging camera 70 to capture an image (step S15). Then, the analysis unit 821 subtracts the interference signal at the reference measurement point stored in step S13 from the interference signal at the reference measurement point of the captured image captured in step S15 to obtain the change in light intensity of the reference interference light, that is, the amount of phase shift dΔφ ref is measured (calculated) (step S16: reference interference measurement step). Similarly, the analysis unit 821 subtracts the interference signal at the target measurement point stored in step S13 from the interference signal at the target measurement point in the captured image captured in step S15 to obtain the change in light intensity of the target interference light, that is, the amount of phase shift dΔφ meas is measured (calculated) (step S17: target interference measuring step). Thereafter, the wavelength calculation unit 822 calculates the wavelength λ of the target laser light according to equation (6). meas and further calculate the wavelength λ meas is converted into the frequency of the target laser light (step S18: calculation step). In this embodiment, the configuration in which the half mirror 40A is moved by the actuator 41 has been exemplified, but the mirror 53 may be moved, or both the half mirror 40A and the mirror 53 may be moved.

[0071] [Effects of this embodiment] In the laser wavelength measurement apparatus 1D of this embodiment, in the reference interference measurement step, the change in the light intensity of the reference interference light when the first distance L is changed by the second distance dL, that is, dΔφ ref In the target interference measuring step, the change in the light intensity of the target interference light when the first distance L is changed by the second distance dL, that is, the phase shift amount dΔφ is measured. meas Then, in the calculation step, the wavelength calculation unit 822 calculates the wavelength λ of the target laser light based on the formula (6). meas Calculate. Even when using phase analysis using such a phase shift method, it is possible to perform highly versatile laser wavelength measurement that is not dependent on the wavelength band of the target laser light, as in the above embodiment, and it is possible to simplify the configuration of the laser wavelength measurement device 1D without requiring a large-scale device such as an optical frequency comb. Furthermore, in this embodiment, the wavelength λ of the target laser light can be calculated based on equation (6). meas In this case, the integer part of the interference signal (reference integer part N ref , the target integer part N meas ) is not necessary, and the occurrence of errors due to incorrect determination of the integer part can be suppressed.

[0072] [Variations] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention.

[0073] [Variation 1] For example, in the first embodiment, the beam splitter 30 reflects the reference light toward the reference body 40 and transmits the measurement light toward the measurement structure 50, but the positions of the reference body 40 and the measurement structure 50 may be interchanged. In this case, the beam splitter 30 reflects the measurement light toward the measurement structure 50 and transmits the reference light toward the reference body 40.

[0074] [Variation 2] In the first embodiment, an example in which a half mirror is used as the beam splitter 30 has been described, but the present invention is not limited thereto, and for example, a polarizing beam splitter may be used. In this case, the beam splitter 30 reflects, for example, the S-polarized reference light toward the reference body 40, and transmits the P-polarized measurement light toward the measurement structure 50. In addition, when this configuration is adopted, a λ / 4 plate is disposed between the beam splitter 30 and the reference body 40, and between the beam splitter 30 and the measurement structure 50, and a polarizing plate is provided between the beam splitter 30 and the imaging lens 60.

[0075] [Variation 3] In the second and third embodiments, the laser device arranged in the laser arrangement unit 10 is the reference laser device 12, and after the reference phase difference measurement step or the reference measurement step is performed, the laser device arranged in the laser arrangement unit 10 is changed to the target laser device 11, and the target phase difference measurement step or the target measurement step is performed. In contrast, as in the fourth embodiment, both the target laser device 11 and the reference laser device 12 may be arranged in the laser arrangement unit 10, and the target laser light and the reference laser light may be irradiated simultaneously. For example, in the case of the second embodiment, the first reference measurement point of the reference laser light irradiated to the first reflecting surface 51, the first target measurement point of the target laser light irradiated to the first reflecting surface 51, the second reference measurement point of the reference laser light irradiated to the second reflecting surface 52, and the second target measurement point of the target laser light irradiated to the second reflecting surface 52 are each set to a different measurement point. Thereby, the light intensities of the first reference measurement point, the first target measurement point, the second reference measurement point, and the second target measurement point can be measured from one captured image captured by the imaging camera 70. The same is true in the third embodiment, where the measurement points of the reference laser light reflected by the half mirror 40A and the reference laser light reflected by the mirror 53, and the measurement points of the target laser light reflected by the half mirror 40A and the target laser light reflected by the mirror 53 are different points, so that the light intensities of both can be measured simultaneously from a single captured image.

[0076] [Variation 4] In the first embodiment as well, an example has been shown in which the laser devices arranged in the laser arrangement section 10 are replaced with the reference laser device 12 and the target laser device 11, but the present invention is not limited to this. FIG. 10 is a schematic diagram showing a modification of the first embodiment. A laser wavelength measurement device 1E in FIG. 10 has a target laser device 11, a first collimating lens 23, a reference laser device 12, a second collimating lens 24, and a beam splitter 13 arranged instead of the laser mounting unit 10 and collimating lens 20 in the first embodiment. In this configuration, the beam splitter 13 reflects the object laser light output from the object laser device 11 and collimated by the first collimating lens 23 toward the beam splitter 30. The beam splitter 13 also transmits the reference laser light output from the reference laser device 12 and collimated by the second collimating lens 24 toward the beam splitter 30. In such a configuration, the target laser device 11 is deactivated and the reference laser device 12 is activated, steps S1 to S3 are performed, the target laser device 11 is activated, the reference laser device 12 is deactivated, and steps S4 to S6 are performed.

[0077] [Variation 5] In the first embodiment, a reference interference fringe image for a reference laser light is captured in steps S1 to S3 to calculate a reference phase difference, and then a target interference fringe image for a target laser light is captured in steps S4 to S6 to calculate a target phase difference. In contrast, as a laser wavelength measurement method, the processes of steps S1 to S3 may be performed after the processes of steps S4 to S6 are performed. Also, after capturing a reference interference fringe image in steps S1 to S2 and capturing a target interference fringe image in steps S4 to S5, calculation of each phase difference (reference phase difference, target phase difference) in steps S3 and S6 may be performed. [Industrial Applicability]

[0078] The present invention can be used in a measuring device for measuring the wavelength or frequency of a laser beam. [Explanation of symbols]

[0079] 1, 1A, 1B, 1C, 1D, 1E...laser wavelength measuring device, 10...laser arrangement section, 11...target laser device, 12...reference laser device, 20A...optical path separation section, 30...beam splitter (optical separation section), 40...reference body, 40A...half mirror (second reflecting surface), 41...actuator, 50...measurement structure, 51...first reflecting surface, 52...second reflecting surface, 53...mirror (first reflecting surface), 70...imaging camera (measurement section), 80...control section (calculation section), 81...memory section, 82...processor, 90...optical fiber, 91...end surface (first reflecting surface), 92...end surface (second reflecting surface), 821...analysis section, 822...wavelength calculation section, Ar1...first region, Ar2...second region, L...first distance.

Claims

1. a reference phase difference measurement step of separating a reference laser light having a known wavelength into a reference measurement light and a reference reference light by a light separating unit, reflecting the reference measurement light at a first reflecting surface and a second reflecting surface that is a predetermined first distance away from the first reflecting surface, and measuring, as a reference phase difference, a phase difference between a first reference interference light obtained by interfering the reference measurement light and the reference reference light reflected at the first reflecting surface, and a second reference interference light obtained by interfering the reference measurement light and the reference reference light reflected at the second reflecting surface; an object phase difference measuring step of separating an object laser light having a wavelength to be measured into an object measurement light and an object reference light by the light separating unit, reflecting the object measurement light on the first reflecting surface and the second reflecting surface, and measuring a phase difference between a first object interference light obtained by interfering the object measurement light and the object reference light reflected on the first reflecting surface and a second object interference light obtained by interfering the object measurement light and the object reference light reflected on the second reflecting surface as an object phase difference; a wavelength calculation step of calculating a wavelength of the target laser light based on the reference phase difference, the target phase difference, and the wavelength of the reference laser light; Implemented the following: The reference laser light and the object laser light are separated by a light separating unit into a first light path toward the first reflecting surface and a second light path toward the second reflecting surface; the reference phase difference measuring step measures, as the reference phase difference, a phase difference between an interference light of the reference measurement light and the reference reference light guided to the first reflecting surface along the first optical path and an interference light of the reference measurement light and the reference reference light guided to the second reflecting surface along the second optical path; A laser wavelength measurement method, in which the target phase difference measurement step measures, as the target phase difference, the phase difference between the interference light of the target measurement light and the target reference light guided to the first reflecting surface along the first optical path, and the interference light of the target measurement light and the target reference light guided to the second reflecting surface along the second optical path.

2. a reference interference measurement step of reflecting a reference laser light having a known wavelength by a first reflecting surface and a second reflecting surface that is a predetermined first distance away from the first reflecting surface, and measuring the light intensity of reference interference light produced by interference between the reference laser light reflected by the first reflecting surface and the reference laser light reflected by the second reflecting surface; a target interference measuring step of reflecting a target laser light having a wavelength to be measured by the first reflecting surface and the second reflecting surface, and measuring a light intensity of a target interference light caused by interference between the target laser light reflected by the first reflecting surface and the target laser light reflected by the second reflecting surface; a calculation step of calculating a wavelength of the target laser light based on a wavelength of the reference laser light, a light intensity of the reference interference light, and a light intensity of the target interference light; A laser wavelength measurement method comprising the steps of:

3. the reference interference measuring step measures a change in light intensity of the reference interference light when the first distance is changed by a second distance; the object interference measuring step measures a change in light intensity of the object interference light when the first distance is changed by the second distance; The calculation step calculates a wavelength of the target laser light based on a wavelength of the reference laser light, a change in light intensity of the reference interference light, and a change in light intensity of the target interference light.

3. The laser wavelength measuring method according to claim 2.

4. a reference laser device that emits a reference laser beam having a known wavelength; A target laser device that emits a target laser light having a wavelength to be measured; an optical path separation unit that separates the reference laser light and the object laser light into a first optical path and a second optical path; a light separation unit that separates the reference laser light into a reference measurement light and a reference reference light, and separates the object laser light into an object measurement light and an object reference light; a first reflecting surface that reflects the reference measurement light separated by the light separating unit from the reference laser light separated into the first optical path, and the object measurement light separated by the light separating unit from the object laser light separated into the first optical path; a second reflecting surface that reflects the reference measurement light separated by the light separating unit from the reference laser light separated into the second optical path, and the object measurement light separated by the light separating unit from the object laser light separated into the second optical path, and is disposed a first distance away from the first reflecting surface; a measurement unit that measures first reference interference light caused by interference between the reference measurement light and the reference reference light of the first optical path reflected at the first reflecting surface, first object interference light caused by interference between the object measurement light and the object reference light of the first optical path reflected at the first reflecting surface, second reference interference light caused by interference between the reference measurement light and the reference reference light of the second optical path reflected at the second reflecting surface, and second object interference light caused by interference between the object measurement light and the object reference light of the second optical path reflected at the second reflecting surface; a calculation unit that calculates a wavelength of the object laser light based on a reference phase difference that is a phase difference between the first reference interference light and the second reference interference light, a target phase difference that is a phase difference between the first object interference light and the second object interference light, and a wavelength of the reference laser light; A laser wavelength measuring device comprising:

5. a reference laser device that emits a reference laser beam having a known wavelength; A target laser device that emits a target laser light having a wavelength to be measured; a first reflecting surface that reflects a portion of the reference laser light and a portion of the target laser light; a second reflecting surface that reflects the remainder of the reference laser light and the remainder of the object laser light and is disposed a first distance away from the first reflecting surface; a measurement unit that measures a reference interference light obtained by interfering between the reference laser light reflected on the first reflecting surface and the reference laser light reflected on the second reflecting surface, and a target interference light obtained by interfering between the target laser light reflected on the first reflecting surface and the target laser light reflected on the second reflecting surface; a calculation unit that calculates a wavelength of the target laser light based on a wavelength of the reference laser light, a light intensity of the reference interference light, and a light intensity of the target interference light; A laser wavelength measuring device comprising:

Images