Optical spectrum measurement device and optical spectrum measurement method

Abstract

Provided are an optical spectrum measurement device and an optical spectrum measurement method whereby the optical spectrum of light to be measured can be stably measured at high speed and low cost using a small number of optical components. The present invention comprises: an optical branching element (optical fiber coupler (14)) that branches a light guide path (optical fiber cable (12)) for light (L) to be measured into a first branch optical path (first branch optical fiber cable (F1)) and a second branch optical path (second branch optical fiber cable (F2)); a first emission end (F1a) that is provided at the distal end of the first branch optical path and emits light to be measured; a second emission end (F2a) that is provided at the distal end of the second branch optical path and emits light to be measured; a light receiving sensor (line sensor (18)) that receives, for each pixel (18a), the light to be measured emitted from the first emission end and the light to be measured emitted from the second emission end, and outputs an interference signal (Q1); and an optical spectrum calculation unit (28) that calculates an optical spectrum (40) on the basis of the interference signal.

Description

Optical spectrum measuring device and optical spectrum measuring method

[0001] The present invention relates to an optical spectrum measuring device and an optical spectrum measuring method for measuring the optical spectrum of a target light.

[0002] Spectrometers (optical spectrum measuring devices, optical spectrum analyzers) that measure the optical spectrum (optical intensity at each wavelength) of light to be measured are used for evaluating the wavelength characteristics of light sources, evaluating the wavelength dependence of the reflectance or transmittance of optical components, quality evaluation in optical fiber communications, and molecular structure evaluation using Fourier transform infrared spectroscopy. Known spectrometers include dispersive spectroscopy monochromators, dispersive spectroscopy polychromators, Fourier spectroscopy spectrometers, and optical heterodyne spectrometers (see Non-Patent Literature 1).

[0003] A monochromator comprises a diffraction grating, a mechanism for rotating the diffraction grating, and a single photodiode. The rotation mechanism allows for the selection of the wavelength of light incident on the photodiode by rotating the diffraction grating (see Non-Patent Literature 2). A polychromator comprises a fixed diffraction grating and a linear image sensor that detects the light to be measured, dispersed by the diffraction grating, at each wavelength (see Non-Patent Literature 2).

[0004] A Fourier spectroscopy spectrometer comprises a semi-transparent mirror (optical splitter / merger element), a fixed mirror, a movable mirror, a moving mechanism, and a detector (see Non-Patent Literature 1). The semi-transparent mirror splits the light to be measured into measurement light directed towards the fixed mirror and reference light directed towards the movable mirror, and emits interference light from the measurement light reflected by the fixed mirror and the measurement light reflected by the movable mirror toward the detector. The moving mechanism moves the movable mirror along the optical path of the light to be measured. The detector receives the interference light and outputs an interference signal. The Fourier spectroscopy spectrometer then calculates the optical spectrum of the light to be measured by applying Fourier transform processing to the interference signal output from the detector.

[0005] A photoheterodyne spectrometer works by combining the light to be measured with local light (wavelength-swept light) of a known wavelength (frequency), then using an optical sensor to convert the beat signal obtained from the frequency difference between the two lights into an electrical signal, and finally processing this electrical signal to measure the optical spectrum.

[0006] "Fundamentals and Overview of Optical Spectrum Analyzers (Part 1)," [online], [Accessed December 25, 2024], Internet <https: / / www.techeyesonline.com / article / tech-column / detail / Reference-OpticalSpectrumAnalyzer-01 / ?page=2> "Structure and Basic Specifications of Optical Spectrum Analyzers," [online], [Accessed December 25, 2024], Internet <https: / / edn.itmedia.co.jp / edn / articles / 2206 / 23 / news009_2.html>

[0007] By the way, monochromators have the problem of slow measurement speed because they require the rotation of the diffraction grating. Also, monochromators have the problem of lacking stability because they have a large number of optical elements. Polychromators also have the same problem of lacking stability as monochromators because they have a large number of optical elements.

[0008] Fourier spectroscopy spectrometers have the problem of slow measurement speed because they require the movement of a moving mirror. Optical heterodyne spectrometers have the problem of high manufacturing costs because they require the use of expensive wavelength-swept light sources. Furthermore, wavelength-swept light sources require a drive mechanism to drive elements that vary the wavelength of the local light, and this drive mechanism has the problem of having a short lifespan.

[0009] This invention has been made in view of these circumstances, and aims to provide an optical spectrum measuring device and an optical spectrum measuring method that can stably, inexpensively, and rapidly measure the optical spectrum of a target light using a small number of optical components.

[0010] A light spectrum measuring device for achieving the object of the present invention comprises: a light guide path for guiding light to be measured; an optical branching element for branching the light guide path into a first branched optical path and a second branched optical path; a first output end provided at the tip of the first branched optical path for emitting light to be measured; a second output end provided at the tip of the second branched optical path for emitting light to be measured; a light receiving sensor having a plurality of pixels, which receives light to be measured emitted from the first output end and light to be measured emitted from the second output end for each pixel, and outputs an interference signal representing the magnitude of the brightness value for each pixel; and a light spectrum calculation unit which calculates the light spectrum of the light to be measured based on the interference signal output from the light receiving sensor.

[0011] This optical spectrum measuring device allows for the measurement of the optical spectrum of the target light with fewer optical components, without the need for displacement mechanisms for optical components or expensive light sources.

[0012] In another aspect of the present invention, the optical spectrum measuring device includes a correspondence information acquisition unit that acquires correspondence information for each pixel, relating the difference in optical path length between the light to be measured incident from a first output end and the light to be measured incident from a second output end to the same pixel. The optical spectrum calculation unit performs the following processes: when the interference signal output from the light receiving sensor is the first interference signal, it outputs a second interference signal representing the magnitude of the brightness value for each optical path length difference based on the first interference signal and the correspondence information acquired by the correspondence information acquisition unit; it performs a Fourier transform on the second interference signal; and it calculates the optical spectrum based on the result of the Fourier transform. This makes it possible to calculate the optical spectrum of the light to be measured based on the interference signal output from the light receiving sensor as the first interference signal.

[0013] In another aspect of the present invention, the optical spectrum measuring device is configured such that the first output end and the second output end are located at the same position in the direction normal to the light-receiving surface of the light-receiving sensor. This allows for easy calculation of the optical path length difference for each pixel.

[0014] In another aspect of the present invention, the optical spectrum measuring device is a line sensor, and the first output end and the second output end are spaced apart in the longitudinal direction of the line sensor. This makes it possible to calculate the optical spectrum of the light to be measured based on the interference signal output from the line sensor.

[0015] In another aspect of the present invention, an optical element is provided between a first output end, a second output end, and a light receiving sensor, and the optical element collimates the light to be measured incident from the first output end to the light receiving sensor and the light to be measured incident from the second output end to the light receiving sensor. This improves the utilization efficiency of the light to be measured emitted from the first output end and the second output end.

[0016] A method for measuring an optical spectrum to achieve the objectives of the present invention comprises: an optical branching step of branching the light to be measured into a first branched optical path and a second branched optical path; an emission step of emitting the light to be measured from a first emission end provided at the tip of the first branched optical path and a second emission end provided at the tip of the second branched optical path; a light receiving step of receiving the light to be measured emitted from the first emission end and the light to be measured emitted from the second emission end pixel by pixel using a light receiving sensor having a plurality of pixels, and outputting an interference signal representing the magnitude of the brightness value for each pixel; and an optical spectrum calculation step of calculating the optical spectrum of the light to be measured based on the interference signal output from the light receiving sensor.

[0017] This invention enables stable, low-cost, and high-speed measurement of the optical spectrum of a target light source using fewer optical components.

[0018] Reference numeral 1A denotes a top view of the optical spectrum measuring device of the first embodiment as seen from the Z direction, and reference numeral 1B denotes a side view of the optical spectrum measuring device of the first embodiment as seen from the Y direction. This is an external perspective view of the optical spectrum measuring device of the first embodiment. This figure shows an example of an interference signal output from a line sensor. This is a functional block diagram of the arithmetic unit of the first embodiment. This figure shows an example of a method for calculating the optical path length difference for each pixel of the line sensor. This is a graph of correspondence information. This is an explanatory diagram for explaining the resampling of the interference signal by the resampling unit. This figure shows an example of an optical spectrum calculated through Fourier transform processing by the Fourier transform unit and absolute value calculation processing by the absolute value calculation unit. This is a flowchart showing the flow of optical spectrum measurement processing of the target light by the optical spectrum measuring device of the first embodiment. Reference numeral XA denotes a top view of the optical spectrum measuring device of the second embodiment as seen from the Z direction, and reference numeral XB denotes a side view of the optical spectrum measuring device of the second embodiment as seen from the Y direction.

[0019] [First Embodiment] In Figure 1, reference numeral 1A denotes a top view of the optical spectrum measuring device 10 of the first embodiment as seen from the Z direction, and reference numeral 1B denotes a side view of the optical spectrum measuring device 10 of the first embodiment as seen from the Y direction. Figure 2 is an external perspective view of the optical spectrum measuring device 10 of the first embodiment. In the figures, among the mutually orthogonal XYZ directions, the XY directions are parallel to the horizontal direction, and the Z direction is parallel to the vertical direction.

[0020] As shown in Figures 1 and 2, the optical spectrum measuring device 10 is an interferometer that measures the optical spectrum 40 of the light source L to be measured. This optical spectrum measuring device 10 includes an optical fiber cable 12, an optical fiber coupler 14, a first branch optical fiber cable F1, a second branch optical fiber cable F2, an output end holder 15, a cylindrical lens 16, a line sensor 18, and a computing device 20. Note that the output end holder 15 is not shown in Figure 1, and the optical fiber cable 12, optical fiber coupler 14, and computing device 20 are not shown in Figure 2.

[0021] The optical fiber cable 12 corresponds to the optical guide path of the present invention. One end of the optical fiber cable 12 is the incident end into which the light to be measured L is incident, and the other end of the optical fiber cable 12 is connected to the optical fiber coupler 14. This optical fiber cable 12 guides the light to be measured L to the optical fiber coupler 14.

[0022] The optical fiber coupler 14 corresponds to the optical branching element of the present invention, and branches the optical fiber cable 12 (optical guide path) into a first branch optical fiber cable F1 and a second branch optical fiber cable F2. As a result, the light to be measured L is optically branched at the optical fiber coupler 14 and travels through the first branch optical fiber cable F1 and the second branch optical fiber cable F2, respectively.

[0023] The first branched optical fiber cable F1 corresponds to the first branched optical path of the present invention, and the second branched optical fiber cable F2 corresponds to the second branched optical path of the present invention. The tip of the first branched optical fiber cable F1 is provided with a first output end F1a, and the tip of the second branched optical fiber cable F2 is provided with a second output end F2a. The first output end F1a and the second output end F2a each emit the light L to be measured.

[0024] The output end holding section 15 comprises a support plate 15a and a pressing plate 15b. The support plate 15a supports the ends (first output end F1a and second output end F2a) of the first branch optical fiber cable F1 and the second branch optical fiber cable F2. The pressing plate 15b clamps and fixes the ends of the first branch optical fiber cable F1 and the second branch optical fiber cable F2 between itself and the support plate 15a.

[0025] The first emission end F1a and the second emission end F2a are positioned by the emission end holding portion 15 at an interval in the Y direction parallel to the longitudinal direction of the line sensor 18 (described later), and are positioned at the same position (including substantially the same position) in the X direction parallel to the normal direction of the light-receiving surface of the line sensor 18. In other words, the first emission end F1a and the second emission end F2a are positioned by the emission end holding portion 15 within the same virtual plane parallel to the light-receiving surface of the line sensor 18.

[0026] The cylindrical lens 16 (a rod lens may also be used) converts the interference light of the light to be measured L emitted from the first output end F1a and the light to be measured L emitted from the second output end F2a into so-called sheet light having a constant width in the longitudinal direction (Y direction) of the line sensor 18, and then causes it to be incident on the line sensor 18.

[0027] The line sensor 18 corresponds to the light-receiving sensor of the present invention, and a plurality of pixels 18a (light-receiving elements) are arranged on its light-receiving surface along the Y direction, which is the longitudinal direction of the line sensor 18. The line sensor 18 receives interference light between the light to be measured L emitted from the first output end F1a and the light to be measured L emitted from the second output end F2a, for each pixel 18a, via the cylindrical lens 16. The line sensor 18 then outputs an interference signal Q1 (corresponding to the first interference signal of the present invention) representing the magnitude of the brightness value of the interference light of the light to be measured L for each pixel 18a (for each pixel number) to the arithmetic unit 20.

[0028] Figure 3 shows an example of the interference signal Q1 output from the line sensor 18. For each pixel 18a of the line sensor 18, the difference in optical path length (hereinafter simply referred to as "optical path length difference") between the light to be measured L incident from the first output end F1a and the light to be measured L incident from the second output end F2a is different for the same pixel 18a. Therefore, as shown in Figure 3, the magnitude of the brightness value of the interference signal Q1 output from each pixel 18a of the line sensor 18 changes.

[0029] Figure 4 is a functional block diagram of the arithmetic unit 20 of the first embodiment. As shown in Figure 4, the arithmetic unit 20 includes an arithmetic circuit composed of various processors and memory, etc. The various processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices [for example, SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays)]. The various functions of the arithmetic unit 20 may be realized by a single processor, or by multiple processors of the same or different types.

[0030] The arithmetic unit 20 functions as a signal acquisition unit 22, a storage unit 24, a corresponding information acquisition unit 26, and an optical spectrum calculation unit 28 by executing a control program (not shown).

[0031] The signal acquisition unit 22 is connected to the line sensor 18 via a communication interface (not shown), and acquires the interference signal Q1 from the line sensor 18 and outputs it to the optical spectrum calculation unit 28 (resampling unit 30).

[0032] In addition to the control program (not shown) described above, the memory unit 24 stores correspondence information 25. The correspondence information 25 is information that associates the optical path length difference, which has been pre-calculated for each pixel 18a (pixel number) of the line sensor 18.

[0033] Figure 5 shows an example of a method for calculating the optical path length difference for each pixel 18a of the line sensor 18. As shown in Figure 5, the origin O is set to the midpoint in the Y direction between the first output end F1a and the second output end F2a, and the distance (interval) between them in the Y direction is set to "L ｆ When set to (mm), the position coordinates of the first exit end F1a are (0, -L ｆ It is expressed as ( / 2) and the position coordinates of the second exit end F2a are (0, L ｆ It is expressed as / 2).

[0034] Also, when the length of the line sensor 18 in the Y direction is "W ｓ (mm)", the number of pixels of the line sensor 18 is "N (pix.)", and the pixel number of the pixel 18a is n (n = 0, 1,..., N - 1), the "Y ｎ " which is the Y-direction position of the arbitrary n-th pixel 18a is represented by the following [Equation 1].

[0035]

[0036] Therefore, when the X-direction distance from the first emission end F1a and the second emission end F2a to the light-receiving surface of the line sensor 18 is "L ｓ (mm)", the position coordinates of the n-th pixel 18a are (L ｓ , Y ｎ - W ｓ / 2). Thus, the distance d １ from the first emission end F1a to the n-th pixel 18a and the distance d ２ from the second emission end F2a to the n-th pixel 18a are represented by the following [Equation 2].

[0037]

[0038] The distance d １ and the distance d ２ represented by the above [Equation 2] are used to calculate the optical path length difference "d" of the n-th pixel 18a as shown in the following [Equation 3].

[0039]

[0040] FIG. 6 is a graph of the correspondence information 25. By calculating the optical path length difference for each pixel 18a of the line sensor 18 using the above [Equation 1] to [Equation 3], the correspondence information 25 as shown in FIG. 6 is obtained and stored in the storage unit 24.

[0041] Returning to FIG. 4, the correspondence information acquisition unit 26 acquires the correspondence information 25 from the storage unit 24 and outputs it to the optical spectrum calculation unit 28 (resampling unit 30). Note that the correspondence information acquisition unit 26 may acquire the correspondence information 25 from an external server instead of acquiring it from the storage unit 24.

[0042] The optical spectrum calculation unit 28 calculates the optical spectrum 40 of the light target L based on the interference signal Q1 input from the signal acquisition unit 22 and the corresponding information 25 input from the corresponding information acquisition unit 26. This optical spectrum calculation unit 28 functions as a resampling unit 30, a Fourier transform unit 32, an absolute value calculation unit 34, and a correction unit 36.

[0043] Figure 7 is an explanatory diagram illustrating the resampling of the interference signal Q2 by the resampling unit 30. As shown in Figure 7, the resampling unit 30 (also called the signal conversion unit or signal correction unit) resamples (converts and corrects) the interference signal Q1 (see reference numeral 7A) input from the signal acquisition unit 22 and the corresponding information 25 input from the corresponding information acquisition unit 26 to an interference signal Q2 (see reference numeral 7B) that represents the magnitude of the luminance value for each optical path length difference at equal intervals. The interference signal Q2 corresponds to the second interference signal of the present invention. The resampling unit 30 then outputs the interference signal Q2 to the Fourier transform unit 32.

[0044] Figure 8 shows an example of an optical spectrum 40 calculated through a Fourier transform process by the Fourier transform unit 32 and an absolute value calculation process by the absolute value calculation unit 34. As shown in Figure 8 and Figure 4 described above, similar to optical spectrum calculation in known Fourier spectroscopy methods, the Fourier transform unit 32 performs a Fourier transform on the interference signal Q2 input from the resampling unit 30, and the absolute value calculation unit 34 takes the absolute value of the numerical calculation result expressed as a complex number after the Fourier transform, thereby obtaining the optical spectrum 40 of the light target L.

[0045] Furthermore, as is evident from the above equations [Equation 2] to [Equation 3] that show the optical path length difference, the pixel number and optical path length difference shown in Figure 6 are not proportional but nonlinear, and the graph in Figure 6 is not a straight line. For this reason, even if Fourier transform processing is performed on the interference signal Q1 (luminance value) output from the line sensor 18, there will be a nonlinear error in the relationship between wavelength and luminance value (intensity). For this reason, the correction unit 36 ​​corrects (calibrates) the nonlinear error in the optical spectrum 40 using a known correction method (calibration method), such as a method using a gas cell or a method using multiple laser light sources with calibrated wavelengths. The correction unit 36 ​​outputs the corrected optical spectrum 40 to the storage unit 24 and a display unit (not shown).

[0046] [Operation of the First Embodiment] Figure 9 is a flowchart showing the flow of the optical spectrum measurement process of the target light L by the optical spectrum measuring device 10 of the first embodiment of the optical spectrum measurement method of the present invention, which has the above configuration.

[0047] As shown in Figure 9, when the light to be measured L enters the optical fiber cable 12 (step S1), the light to be measured L enters the optical fiber coupler 14 via the optical fiber cable 12 and is optically branched by the optical fiber coupler 14 (step S2, corresponding to the optical branching step of the present invention). As a result, the light to be measured L enters the first branch optical fiber cable F1 and the second branch optical fiber cable F2, respectively, and the light to be measured L is emitted from the first output end F1a and the second output end F2a, respectively (step S3, corresponding to the output step of the present invention).

[0048] Then, the light to be measured L (interference light) is received by each pixel 18a of the line sensor 18 (step S4, corresponding to the light receiving step of the present invention). As a result, the line sensor 18 outputs an interference signal Q1 to the arithmetic unit 20, and the signal acquisition unit 22 of the arithmetic unit 20 acquires this interference signal Q1 and outputs it to the resampling unit 30 (step S5).

[0049] Furthermore, the correspondence information acquisition unit 26 acquires correspondence information 25 from the storage unit 24 and outputs this correspondence information 25 to the resampling unit 30 (step S6). Note that the timing of acquiring the correspondence information 25 is not particularly limited as long as it is before step S7, which will be described later.

[0050] Next, the resampling unit 30 resamples the interference signal Q1 input from the signal acquisition unit 22 to interference signal Q2 based on the correspondence information 25, and then outputs this interference signal Q2 to the Fourier transform unit 32 (step S7). Then, the Fourier transform processing of the interference signal Q2 by the Fourier transform unit 32 (step S8) and the absolute value calculation processing of the numerical calculation result after the Fourier transform by the absolute value calculation unit 34 (step S9) are performed in a known manner, thereby calculating the optical spectrum 40 of the light target L. Steps S8 and S9 correspond to the optical spectrum calculation steps of the present invention.

[0051] Then, the correction unit 36 ​​corrects (calibrates) the nonlinear error of the light spectrum 40 using a known method (step S10), and outputs the corrected light spectrum 40 to the storage unit 24 and the display unit (not shown) (step S11). As a result, the measurement result of the light spectrum of the light target L is stored in the storage unit 24 and displayed on the display unit.

[0052] As described above, in the optical spectrum measuring device 10 of the first embodiment, the light to be measured L is split into two and emitted from the first output end F1a and the second output end F2a, respectively, and the interference light of each light to be measured L is received by the line sensor 18, making it possible to measure the optical spectrum of the light to be measured L based on the interference signal Q1 output from the line sensor 18. Since this optical spectrum measuring device 10 does not require a displacement mechanism such as a diffraction grating that is provided in conventional spectrometers, a decrease in the measurement speed of the optical spectrum 40 is prevented, and the number of optical components is also smaller compared to conventional spectrometers, making it more stable than conventional spectrometers. Furthermore, since the optical spectrum measuring device 10 does not require expensive components such as wavelength-swept light sources, manufacturing costs can be reduced. As a result, the optical spectrum measuring device 10 can measure the optical spectrum of the light to be measured L stably, at low cost and at high speed with a small number of optical components.

[0053] [Second Embodiment] In Figure 10, reference numeral XA denotes a top view of the optical spectrum measuring device 10 of the second embodiment as seen from the Z direction, and reference numeral XB denotes a side view of the optical spectrum measuring device 10 of the second embodiment as seen from the Y direction. In the optical spectrum measuring device 10 of the first embodiment, the light to be measured L emitted from the first output end F1a and the second output end F2a is diffuse light, so a portion of the light to be measured L does not enter the light-receiving surface of the line sensor 18 (see reference numeral 1A in Figure 1). Therefore, in the optical spectrum measuring device 10 of the second embodiment, the utilization efficiency of the light to be measured L emitted from the first output end F1a and the second output end F2a (the proportion that enters the light-receiving surface of the line sensor 18) is improved.

[0054] As shown in Figure 10, the optical spectrum measuring device 10 of the second embodiment has basically the same configuration as the optical spectrum measuring device 10 of the first embodiment, except that it is equipped with collimating lenses 50A and 50B (corresponding to the optical elements of the present invention). For this reason, components that are functionally or structurally identical to those of the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0055] The collimating lens 50A is positioned between the first output end F1a and the cylindrical lens 16, and the collimating lens 50B is positioned between the second output end F2a and the cylindrical lens 16. The collimating lens 50A collimates (parallels) the light to be measured L emitted from the first output end F1a, and directs most or all of this light to be measured L onto the light-receiving surface of the line sensor 18 via the cylindrical lens 16. The collimating lens 50B collimates the light to be measured L emitted from the second output end F2a, and directs most or all of this light to be measured L onto the light-receiving surface of the line sensor 18 via the cylindrical lens 16.

[0056] As described above, in the optical spectrum measuring device 10 of the second embodiment, the light to be measured L emitted from the first output end F1a and the second output end F2a is collimated by the collimating lenses 50A and 50B, thereby increasing the proportion of the light to be measured L incident on the light-receiving surface of the line sensor 18 from the first output end F1a and the second output end F2a compared to the first embodiment. As a result, the utilization efficiency of the light to be measured L emitted from the first output end F1a and the second output end F2a is improved.

[0057] In the second embodiment described above, the light to be measured L is collimated by the collimating lenses 50A and 50B, but various known optical elements capable of collimating the light to be measured L may be used instead of the collimating lenses 50A and 50B.

[0058] [Other] In the above embodiments, the light to be measured L emitted from the first output end F1a and the second output end F2a is received by the line sensor 18. However, instead of the line sensor 18, various light receiving sensors having multiple pixels 18a, such as an area sensor in which multiple pixels 18a are arranged in a two-dimensional array, may be used.

[0059] In each of the above embodiments, the positions of the first output end F1a and the second output end F2a in the X direction are aligned. However, if the difference in optical path length of the light target L for each pixel 18a can be calculated or measured, the positions of the first output end F1a and the second output end F2a in the X direction may be misaligned.

[0060] In the embodiments described above, an optical fiber cable 12 is used as an example of an optical guide path, and an optical fiber coupler 14 is used as an example of an optical branching element. However, various known optical guide paths and optical branching elements may be used instead.

[0061] 10...Optical spectrum measuring device, 12...Optical fiber cable, 14...Optical fiber coupler, 15...Output end holding unit, 15a...Support plate, 15b...Pressing plate, 16...Cylindrical lens, 18...Line sensor, 18a...Pixel, 20...Calculation unit, 22...Signal acquisition unit, 24...Storage unit, 25...Corresponding information, 26...Corresponding information acquisition unit, 28...Optical spectrum calculation unit, 30...Resampling unit, 32...Fourier transform unit, 34...Absolute value calculation unit, 36...Correction unit, 40...Optical spectrum, 50A, 50B...Collimating lens, F1...First branch optical fiber cable, F1a...First output end, F2...Second branch optical fiber cable, F2a...Second output end, L...Measurement target light, O...Origin, Q1, Q2...Interference signal, d1, d2...Distance

Claims

1. An optical spectrum measuring device comprising: an optical guide path for guiding light to be measured; an optical branching element for branching the optical guide path into a first branch optical path and a second branch optical path; a first output end provided at the tip of the first branch optical path for emitting the light to be measured; a second output end provided at the tip of the second branch optical path for emitting the light to be measured; a light receiving sensor having a plurality of pixels, which receives the light to be measured emitted from the first output end and the light to be measured emitted from the second output end for each pixel and outputs an interference signal representing the magnitude of the brightness value for each pixel; and an optical spectrum calculation unit which calculates the optical spectrum of the light to be measured based on the interference signal output from the light receiving sensor.

2. The optical spectrum measuring device according to claim 1, comprising: a correspondence information acquisition unit that acquires correspondence information for each pixel relating the optical path length difference between the light to be measured incident from the first exit end and the light to be measured incident from the second exit end to the same pixel, wherein the optical spectrum calculation unit performs the following processes: when the interference signal output from the light receiving sensor is a first interference signal, it outputs a second interference signal representing the magnitude of the luminance value for each optical path length difference based on the first interference signal and the correspondence information acquired by the correspondence information acquisition unit; it performs a Fourier transform process on the second interference signal; and it calculates the optical spectrum based on the result of the Fourier transform process.

3. The optical spectrum measuring device according to claim 1 or 2, wherein the first output end and the second output end are arranged at the same position in the normal direction to the light-receiving surface of the light-receiving sensor.

4. The optical spectrum measuring device according to claim 3, wherein the light receiving sensor is a line sensor, and the first output end and the second output end are spaced apart in the longitudinal direction of the line sensor.

5. The optical spectrum measuring device according to claim 1 or 2, comprising an optical element provided between the first output end and the second output end and the light receiving sensor, and the optical element collimates the light to be measured incident from the first output end to the light receiving sensor and the light to be measured incident from the second output end to the light receiving sensor.

6. An optical spectrum measurement method comprising: an optical branching step of branching the light to be measured into a first branch optical path and a second branch optical path; an emission step of emitting the light to be measured from a first emission end provided at the tip of the first branch optical path and a second emission end provided at the tip of the second branch optical path; a light receiving step of receiving the light to be measured emitted from the first emission end and the light to be measured emitted from the second emission end for each pixel using a light receiving sensor having a plurality of pixels, and outputting an interference signal representing the magnitude of the brightness value for each pixel; and an optical spectrum calculation step of calculating the optical spectrum of the light to be measured based on the interference signal output from the light receiving sensor.

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