Measurement device, measurement method, and program

Abstract

A measuring device, measuring method, and procedure are provided to measure the spectrum of pulsed light with higher precision. The measuring device (10) includes: a spectrometer (11) that extracts specific wavelength components from incident light; a photodetector (13) that outputs a signal corresponding to the intensity of the extracted wavelength components; and a processor (16) wherein the processor (16) acquires a first signal and a second signal for each of a plurality of wavelength intervals that divide the wavelength range of the object to be measured, and outputs the difference between the second signal and the first signal as the spectrum of the corresponding wavelength interval, wherein the first signal is output from the photodetector in a light-shielded state, and the second signal is output from the photodetector in an unshielded state corresponding to the intensity of the incident light.

Description

[0001] Cross-referencing of related applications

[0002] This application claims priority to Japanese Patent Application No. 2025-004322 filed on January 10, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a measuring device, measuring method, and procedure. Background Technology

[0004] An optical spectrum analyzer (OSA) is a device that measures the wavelength spectrum of incident light within a certain wavelength range. Patent Document 1 describes an optical spectrum analyzer for measuring the spectrum of incident light after it has been chopped by a chopper.

[0005] Patent Document 1: Japanese Utility Model Application Publication No. 7-23258

[0006] Pulsed light is light that is output intermittently with a predetermined repetition period. Previous designs had room for improvement in the accuracy of pulsed light spectrum measurement. Summary of the Invention

[0007] The purpose of this invention is to enable the measurement of the spectrum of pulsed light with higher precision.

[0008] Several embodiments involve a measuring device, which is (1) a measuring device comprising: a spectrometer that extracts a specific wavelength component from incident light; a photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and a processor, wherein the processor acquires a first signal and a second signal for each of a plurality of wavelength intervals that divide the wavelength range of the measuring object, and outputs the difference between the second signal and the first signal as the spectrum of the corresponding wavelength interval, wherein the first signal is output from the photodetector in a light-shielded state, and the second signal is output from the photodetector in an unshielded state corresponding to the intensity of the incident light.

[0009] As described above, the measuring device divides the wavelength range of the object to be measured into multiple wavelength intervals. For each wavelength interval, the incident light is measured in both shaded and unshaded states, and the difference between the measured signals is output as the spectrum of the wavelength interval. Therefore, according to the measuring device, the influence of drift in the measured values ​​caused by dark current can be suppressed, and the spectrum of pulsed light can be measured with higher accuracy.

[0010] In one embodiment, (2) in the measuring apparatus of (1), the length of each of the plurality of wavelength intervals may be determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

[0011] As mentioned above, the length of each wavelength range is determined by the magnitude of the variation in the measured value caused by the dark current of the photodetector. Therefore, the influence of the drift in the measured value caused by the dark current can be effectively reduced according to the measuring device.

[0012] In one embodiment, (3) in the measuring device of (1) or (2), the processor can divide the wavelength range of the measuring object by using a set interval received from the operator via the operating unit as the wavelength range.

[0013] As described above, the measuring device divides the wavelength range of the object to be measured from the interval set by the operator as the wavelength interval. Therefore, the operator can measure the spectrum by setting the desired wavelength interval according to the characteristics of the photodetector.

[0014] In one embodiment, (4) in any of (1) to (3) of the measuring apparatus, the processor can receive the setting of the time averaging interval from the operator via the operation unit, and for each of the plurality of wavelength intervals, obtain a signal obtained by averaging the signal output from the photodetector in the light-shielded state in units of the time averaging interval as the first signal, and obtain a signal obtained by averaging the signal output from the photodetector in the light-unshielded state in units of the time averaging interval as the second signal.

[0015] As described above, the measuring device receives the time averaging interval setting from the operator and obtains the spectrum for each wavelength interval based on the signal averaged in units of the time averaging interval. Therefore, the operator can measure the spectrum at the desired sampling rate.

[0016] In one embodiment, (5) in any of the measuring apparatuses of (1) to (4), the processor can, for each of the plurality of wavelength ranges, obtain the second signal output from the photodetector in an unshielded state after obtaining the first signal output from the photodetector in a light-shielded state.

[0017] As described above, the measuring device performs measurements in the unshielded state after conducting measurements in the shaded state. Therefore, it is possible to suppress as much as possible the drift caused by dark current that accompanies the temperature rise of the photodetector due to light entering the photodetector.

[0018] In one embodiment, (6) in any of (1) to (5) of the measuring device, the measuring device may further include an optical chopper capable of blocking light incident on the photodetector, wherein the processor acquires, for each of the plurality of wavelength ranges, a signal output from the photodetector in the state of being blocked by the optical chopper as the first signal, and acquires, in the state of not being blocked by the optical chopper, a signal output from the photodetector as the second signal.

[0019] As described above, the measuring device can easily switch between a light-shielding state and a light-unshielding state via an optical chopper.

[0020] Several embodiments involve a measurement method (7) a measurement method of a measurement device, the measurement device comprising: a spectrometer that extracts a specific wavelength component from incident light; a photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and a processor, wherein the measurement method includes the following processing: the processor acquires a first signal and a second signal for each of a plurality of wavelength intervals that divide the wavelength range of the measurement object, and outputs the difference between the second signal and the first signal as the spectrum of the corresponding wavelength interval, wherein the first signal is output from the photodetector in a light-shielded state, and the second signal is output from the photodetector in an unshielded state corresponding to the intensity of the incident light.

[0021] As described above, the measurement method divides the wavelength range of the object to be measured into multiple wavelength intervals. For each wavelength interval, the incident light is measured under both shaded and unshaded conditions, and the difference between the measured signals is output as the spectrum of the wavelength interval. Therefore, according to the measurement method, the influence of drift in the measured values ​​caused by dark current can be suppressed, and the spectrum of pulsed light can be measured with higher accuracy.

[0022] In one embodiment, (8) in the measurement method of (7), the length of each of the plurality of wavelength intervals may be determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

[0023] As mentioned above, the length of each wavelength range is determined by the magnitude of the variation in the measured value caused by the dark current of the photodetector. Therefore, according to the measurement method, the influence of the drift in the measured value caused by the dark current can be effectively reduced.

[0024] In one embodiment, (9) in the measurement method of (7) or (8), the processor can divide the wavelength range of the measurement object by using a set interval received from the operator via the operation unit as the wavelength range.

[0025] As described above, the measurement method divides the wavelength range of the object to be measured from the interval set by the operator as the wavelength interval. Therefore, the operator can measure the spectrum by setting the desired wavelength interval according to the characteristics of the photodetector.

[0026] In one embodiment, (10) in any of (7) to (9) of the measurement method, the processor may receive the setting of the time averaging interval from the operator via the operation unit, and for each of the plurality of wavelength intervals, obtain a signal obtained by averaging the signal output from the photodetector in the light-shielded state in units of the time averaging interval as the first signal, and obtain a signal obtained by averaging the signal output from the photodetector in the unshielded state in units of the time averaging interval as the second signal.

[0027] As described above, the measurement method involves setting a time averaging interval for the operator, and then averaging the signal over that time interval to obtain the spectrum for each wavelength range. Therefore, the operator can measure the spectrum at the desired sampling rate.

[0028] In one embodiment, (11) in any of (7) to (10) of the measurement method, the processor may, for each of the plurality of wavelength ranges, obtain the second signal output from the photodetector in an unshielded state after obtaining the first signal output from the photodetector in a shading state.

[0029] As described above, the measurement method performs measurements under the light-shielded state followed by measurements under the unshielded state. Therefore, it is possible to suppress as much as possible the drift caused by dark current that accompanies the temperature rise of the photodetector due to light entering the photodetector.

[0030] In one embodiment, (12) in any of (7) to (11) of the measurement method, the measuring device may further include an optical chopper capable of blocking light incident on the photodetector, wherein the processor acquires, for each of the plurality of wavelength ranges, a signal output from the photodetector in the state of being blocked by the optical chopper as the first signal, and acquires, in the state of not being blocked by the optical chopper, a signal output from the photodetector as the second signal.

[0031] As described above, the measurement method allows for easy switching between shading and non-shading states using an optical chopper.

[0032] Several implementations involve a procedure (13) for controlling a measuring device having: a spectrometer that extracts a specific wavelength component from incident light; a photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and a processor that controls the measuring device to perform the following steps: for each of a plurality of wavelength intervals that divide the wavelength range of the measuring object, acquiring a first signal and a second signal, and outputting the difference between the second signal and the first signal as the spectrum of the corresponding wavelength interval, wherein the first signal is output from the photodetector in a light-shielded state, and the second signal is output from the photodetector in an unshielded state corresponding to the intensity of the incident light.

[0033] As described above, the program divides the wavelength range of the object to be measured into multiple wavelength intervals. For each wavelength interval, the incident light is measured under both shaded and unshaded conditions, and the difference between the measured signals is output as the spectrum of the wavelength interval. Therefore, according to the program, the influence of drift in the measured values ​​caused by dark current can be suppressed, and the spectrum of pulsed light can be measured with higher accuracy.

[0034] In one embodiment, (14) in the procedure of (13), the length of each of the plurality of wavelength intervals may be determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

[0035] As mentioned above, the length of each wavelength range is determined by the magnitude of the variation in the measured value caused by the dark current of the photodetector. Therefore, according to the procedure, the effect of the drift in the measured value caused by the dark current can be effectively reduced.

[0036] In one embodiment, (15) in the procedure of (13) or (14), the wavelength range of the object to be measured can be divided by using the interval that was received from the operator via the operating unit as the wavelength interval.

[0037] As described above, the program divides the wavelength range of the object to be measured from the interval set by the operator. Therefore, the operator can set the desired wavelength range and measure the spectrum according to the characteristics of the photodetector.

[0038] In one embodiment, (16) in any of (13) to (15) may be that the operator receives the setting of the time averaging interval from the operator via the operation unit, and for each of the plurality of wavelength intervals, obtains a signal obtained by averaging the signal output from the photodetector in the light-shielding state in units of the time averaging interval as the first signal, and obtains a signal obtained by averaging the signal output from the photodetector in the unshielded state in units of the time averaging interval as the second signal.

[0039] As described above, the program receives the time averaging interval setting from the operator and obtains the spectrum for each wavelength interval based on the signal averaged in units of the time averaging interval. Therefore, the operator can measure the spectrum at the desired sampling rate.

[0040] In one embodiment, (17) in any of (13) to (16) may be that, for each of the plurality of wavelength ranges, after obtaining the first signal output from the photodetector in the light-shielded state, the second signal output from the photodetector in the unshielded state is obtained.

[0041] As described above, the program performs measurements under the shaded state followed by measurements under the unshaded state. Therefore, it is possible to suppress as much as possible the drift caused by dark current that accompanies the temperature rise of the photodetector due to light entering the photodetector.

[0042] In one embodiment, (18) in any of (13) to (17) may be that the measuring device further includes an optical chopper capable of blocking light incident on the photodetector, and the processor acquires, for each of the plurality of wavelength ranges, a signal output from the photodetector in the state of being blocked by the optical chopper as the first signal, and acquires a signal output from the photodetector in the state of not being blocked by the optical chopper as the second signal.

[0043] As mentioned above, the program can easily switch between the light-shielding and non-light-shielding states using an optical chopper.

[0044] The effects of the invention

[0045] According to one embodiment of the present invention, the spectrum of pulsed light can be measured with higher precision. Attached Figure Description

[0046] Figure 1 This is a block diagram illustrating a structural example of a measuring device according to one embodiment.

[0047] Figure 2 It is a schematic representation Figure 1 A diagram illustrating the structure of a beam splitter.

[0048] Figure 3 This is a flowchart illustrating an example of the operation of a measuring device according to one embodiment.

[0049] Figure 4 This is a schematic diagram illustrating an example of the operation of a measuring device according to one embodiment.

[0050] Figure 5 This is a schematic diagram illustrating an example of the operation of a measuring device according to one embodiment.

[0051] Figure 6 This is a graph showing an example of the measurement results of the pulsed light spectrum for each measurement method. Detailed Implementation

[0052] <Implementation Method>

[0053] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, parts having the same structure or function are labeled with the same reference numerals. In the description of this embodiment, repeated descriptions of the same parts are sometimes omitted or simplified as appropriate.

[0054] Figure 1 This is a block diagram illustrating a structural example of a measuring device 10 according to one embodiment. The measuring device 10 measures the intensity distribution, i.e., the spectrum, of incident light at each wavelength. The measuring device 10 can be provided as an OSA (Optical System Amplifier). In this embodiment, the measuring device 10 measures the spectrum of pulsed light output from a pulsed laser. The measuring device 10 includes a beam splitter 11, an optical chopper 12, a photodetector 13, an amplifier 14, an A / D (Analog-to-Digital) converter 15, a processor 16, a memory 17, a display unit 18, and an operation unit 19.

[0055] Beam splitter 11 extracts the desired frequency components from the incident light. Beam splitter 11 is, for example, a monochromator described later. Figure 2 It can be constructed using a single device, but it can also be implemented by any device that functions as a beam splitter.

[0056] The optical chopper 12 modulates the incident light through a rotating light-shielding plate and a slit. The optical chopper 12 can either place the light-shielding plate in the optical path to block the incident light, or place the slit in the optical path to allow the incident light to pass through. By controlling the rotation speed of the optical chopper 12, the measuring device 10 can arbitrarily change the period at which the incident light reaches the photodetector 13.

[0057] The photodetector 13 outputs an electrical signal based on the intensity of the incident light. The photodetector 13 is implemented using a photoelectric conversion element such as a photodiode. The photodetector 13 is an element capable of detecting light of the wavelength of the object being measured.

[0058] For reference Figure 2 As will be described later, in this embodiment, the optical chopper 12 and the photodetector 13 are disposed within the beam splitter 11, but this structure is not limited to this. For example, the optical chopper 12 can be disposed at any position on the optical path until the incident light reaches the photodetector 13. Alternatively, the optical chopper 12 can also be disposed at the front end of the beam splitter 11.

[0059] Amplifier 14 amplifies the electrical signal output from photodetector 13 to a specified range. Amplifier 14 then outputs the amplified electrical signal to A / D converter 15.

[0060] The A / D converter 15 converts the analog electrical signal amplified by the amplifier 14 into a digital signal. The A / D converter 15 then outputs the converted digital electrical signal to the processor 16.

[0061] The processor 16 is configured to include one or more processors or dedicated circuits. In this embodiment, the processor 16 is a general-purpose processor or a dedicated processor specialized for specific processing, but is not limited to these. The dedicated circuit may include, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The processor 16 is communicatively connected to each structural component constituting the measuring device 10 and controls the overall operation of the measuring device 10.

[0062] Furthermore, in this embodiment, the processor 16 controls a series of processes for obtaining the spectrum of the incident light based on the measured values ​​after measuring the incident light using the beam splitter 11, the optical chopper 12, and the photodetector 13, but is not limited to this structure. For example, the processor 16 can be used as a processor or a dedicated circuit that is not built into the measuring device 10 to control the processing of obtaining the spectrum of the incident light based on the measured values.

[0063] The memory 17 stores any information used to measure the operation of the measuring device 10. The memory 17 may include, for example, any storage module such as SSD (Solid State Drive), ROM (Read-Only Memory), and RAM (Random Access Memory).

[0064] The display unit 18 includes one or more output interfaces that output information to and notify the operator. The display unit 18 may be, for example, a liquid crystal panel display or an organic EL (Electro Luminescence) display.

[0065] The operation unit 19 includes one or more input interfaces that accept input operations from the operator and obtain input information based on the operator's operation. For example, the operation unit 19 may be a physical button, a capacitive button, or a touch screen integrated with the display of the display unit 18, but is not limited to these. At least one of the display unit 18 and the operation unit 19 may be integrated with the measuring device 10 or may be provided separately.

[0066] The function of the measuring device 10 can be implemented by the processor included in the processor 1 executing the computer program (program) according to this embodiment. That is, the function of the measuring device 10 can be implemented by software. The computer program enables the computer to perform the processing of the steps included in the operation of the measuring device 10, thereby enabling the computer to perform the function corresponding to each step. In other words, the computer program is a program for enabling the computer to function as the measuring device 10 according to this embodiment.

[0067] Figure 2 It is a schematic representation Figure 1 A diagram illustrating the structure of beam splitter 11. Figure 2 This illustrates an example of a beam splitter 11 configured as a monochromator. The beam splitter 11 includes a collimating mirror 112, a diffraction grating 113, a focusing mirror 114, an exit slit 115, an optical chopper 12, and a photodetector 13. Figure 2 In the example, the incident light enters the beam splitter 11 via the optical fiber 111.

[0068] Collimating lens 112 and focusing lens 114 are parabolic mirrors.

[0069] The diffraction grating (grating) 113 is constructed by cutting very fine grooves into a mirror. The diffraction grating 113 is an optical element that extracts light of a specific wavelength from light mixed with various wavelengths. If light of various wavelengths is incident on the diffraction grating 113, diffraction occurs at a predetermined angle according to each wavelength. Therefore, the wavelength can be determined based on the diffraction angle from the diffraction grating 113.

[0070] The optical chopper 12 switches between blocking and transmission (non-blocking) according to the control of the processor 16. The exit slit 115 adjusts the wavelength resolution and light intensity of the beam splitter 11. The photodetector 13 performs photoelectric conversion on the incident light and outputs an electrical signal corresponding to the intensity of the incident light.

[0071] In beam splitter 11, light incident from fiber 111 is collimated into parallel rays by collimating lens 112 and guided to diffraction grating 113. The light diffracted by diffraction grating 113 passes through focusing lens 114, forming a spectrum along the dispersion direction centered on exit slit 115. Therefore, only wavelengths of light converging at exit slit 115 are detected by photodetector 13. The wavelength of the detected light, i.e., the center wavelength of the optical bandpass filter, can be changed by rotating diffraction grating 113. Therefore, beam splitter 11 can determine the spectrum of the incident light by obtaining the relationship between the angle (tilt) of diffraction grating 113 corresponding to the wavelength of the incident light and the intensity of the light detected by photodetector 13.

[0072] exist Figure 2 In this example, an optical chopper 12 is provided in the optical path between the focusing lens 114 and the exit slit 115. The optical chopper 12 switches between blocking or transmitting the incident light based on the control of the processor 16.

[0073] It is generally known that photoelectric conversion devices such as photodiodes output a current called dark current even when no light is incident on them. Therefore, as will be discussed later, a phenomenon called drift sometimes occurs, where the measured value gradually changes over time. This makes it difficult to detect light waves with high sensitivity in the wavelength range where the incident light intensity is low. Figure 6 (Curve 52).

[0074] Regarding this, it is known that an optical chopper is used to measure the electrical signal output from the photoelectric conversion element in both the shaded and unshaded states, and the difference between the two is obtained, thereby suppressing the drift caused by dark current. However, when the incident light of the object being measured is a pulsed light that is intermittently output with a specified repetition period, if the repetition period of the pulsed light is not synchronized with the period of switching between shaded and unshaded states, the change in light intensity cannot be accurately captured. As a result, periodic errors are sometimes mixed into the obtained spectral data, making it difficult to measure the spectrum of the incident light with high precision. Figure 6 (Curve 53).

[0075] Therefore, the measuring apparatus 10 according to this embodiment divides the entire wavelength range of the object to be measured into wavelength ranges corresponding to periods that are longer than the repetition period of the pulsed light and have a sufficiently small effect from the drift of the photodetector 13 (see reference). Figure 4 The measuring device 10 measures the spectrum in both shaded and unshaded states for each wavelength range. The measured value in the unshaded state is subtracted from the measured value in the shaded state to obtain spectral data that has suppressed the influence of dark current. The measuring device 10 combines this spectral data for each wavelength range to obtain spectral data for the entire wavelength range.

[0076] As described above, the measuring apparatus 10 of this embodiment compensates for the influence of dark current by subtracting the spectrum measured under the shaded state from the spectrum measured under the unshaded state, thereby enabling highly sensitive spectral measurement even in wavelength ranges with weak signal intensity. Furthermore, by performing measurements for each wavelength range, the measuring apparatus 10 can shorten the measurement time and suppress the influence of drift on the measured spectral data, which is caused by dark current generated during the measurement process.

[0077] Reference Figures 3 to 5 An example of the operation of the measuring device 10 will be explained. Figure 3 This is a flowchart illustrating an example of the operation of a measuring device 10 according to one embodiment. Figure 4 and Figure 5 This is a schematic diagram illustrating an example of the operation of the measuring device 10 according to one embodiment. (Refer to...) Figures 3 to 5 The operation of the measuring device 10 described herein can be equivalent to one of the measuring methods of the measuring device 10. Figure 3 The actions of each step can be performed based on the control of the processor 16 of the measuring device 10.

[0078] exist Figure 3 In step S1, the processor 16 receives the setting of the time average interval from the operator.

[0079] As described above, the measuring device 10 divides the entire measuring range into short wavelength interval units and performs measurements (see reference). Figure 4 Therefore, the measuring device 10 receives from the operator the setting of the time averaging interval corresponding to the repetition period of the pulse light as the incident light.

[0080] The time averaging interval is the interval used to calculate the measured value of one measurement point. For each time averaging interval, the measuring device 10 calculates the average light intensity measured by the photodetector 13 under the shaded state and the average light intensity measured by the photodetector 13 under the unshaded state. For each time averaging interval, the measuring device 10 obtains the measured light intensity value that suppresses the influence of dark current by subtracting the average light intensity measured under the shaded state from the average light intensity measured under the unshaded state. In other words, the time averaging interval corresponds to the sampling interval of the light intensity.

[0081] The operator sets the time averaging interval to a value (msec) that is longer than the repetition period of the pulsed light. By setting the time averaging interval to a value sufficiently large than the repetition period of the pulsed light (e.g., more than 5 times the repetition period), the ON / OFF ratio of the pulsed light can be ensured to be approximately the same in both shaded and unshaded states. However, if the value of the time averaging interval is too large, the sampling interval becomes larger, and the effect of drift caused by dark current in the photodetector 13 becomes non-negligible. Therefore, the operator sets an appropriate value for the time averaging interval based on the characteristics of the photodetector 13, the required measurement accuracy, etc.

[0082] In step S2, the processor 16 calculates the size of the wavelength interval based on the time averaging interval received in step S1.

[0083] Specifically, the processor 16 calculates the wavelength range (number of measurement points) using the following (Equation 1).

[0084] (Equation 1)

[0085] Wavelength range (number of measurement points) = allowable drift time (msec) / time averaging range (msec)

[0086] Here, the drift tolerance time is the time between measurements in the shaded and unshaded states within a segmented interval. Based on the characteristics of the photodetector 13 and temperature, the drift tolerance time is preset in the memory 17 to allow for the neglect of drift caused by dark current in the photodetector 13. For example, with a drift tolerance time of 1000 ms and a time averaging interval of 10 ms, the wavelength interval comprises 100 measurement points.

[0087] The processor 16 divides the entire range of wavelengths of the object to be measured into n wavelength intervals. Figure 4 This represents a wavelength range divided into n wavelength intervals. Figure 4 In the diagram, the horizontal axis represents the wavelength. The vertical axis represents the intensity of the electrical signal output from the photodetector 13 due to the incident light. In steps S3 to S6, the processor 16 obtains spectrum data that suppresses the influence of dark current for n wavelength ranges by measuring under both shading and unshading conditions.

[0088] The following is for Sometimes the k-th wavelength interval is referred to as "wavelength interval k". Figure 4 In this context, "Measurement of k (Obscuring)" refers to the measurement of the spectrum of wavelength range k under obscuring conditions. "Measurement of k (Unobscuring)" refers to the measurement of the spectrum of wavelength range k under unobscuring conditions. The time required to measure one wavelength range under both obscuring and unobscuring conditions is equivalent to the drift tolerance time.

[0089] Figure 5 This indicates the relationship between the passage of time and the wavelength of the incident light at the measured intensity. Figure 5 In the diagram, the horizontal axis represents time, and the vertical axis represents the wavelength of the incident light. Curve 61 represents the measurement of the intensity of the incident light from wavelength λ1 to λ2 from time t1 to time t2 under the condition of being shielded from light. Curve 62 represents the measurement of the intensity of the incident light from wavelength λ1 to λ2 from time t2 to time t3 under the condition of being unshielded from light. Curve 63 represents the measurement of the intensity of the incident light from wavelength λ2 to λ3 from time t3 to time t4 under the condition of being shielded from light. Curve 64 represents the measurement of the intensity of the incident light from wavelength λ2 to λ3 from time t4 to time t5 under the condition of being unshielded from light.

[0090] exist Figure 5 In the diagram, curves 61 and 62 from time t1 to t3 represent measurements within wavelength range k. Curves 63 and 64 from time t3 to t5 represent measurements within wavelength range (k+1). Here, times (t2-t1), (t3-t2), (t4-t3), and (t5-t4) correspond to the allowable drift time, respectively. The measuring device 10, for each wavelength range, for each time-averaged interval set in step S1, obtains the average value of the measured values ​​under both shading and unshading conditions, calculates the difference between the two, and obtains spectral data that suppresses the influence of dark current. As a result, the measured values ​​of the light intensity of the measurement points calculated in step S2 are obtained for each wavelength range.

[0091] The following is in accordance with The following describes an example of the operation of obtaining spectral data in wavelength range k. Processor 16 sets the initial value of k to k=1 and executes the processing below step S3.

[0092] In step S3, the processor 16 acquires the spectral data of wavelength interval k under the light-shielding state. Specifically, the processor 16 rotates the diffraction grating 113 while measuring the intensity of the incident light, based on the drift tolerance time and the wavelength range that should be measured in wavelength interval k. For each time-averaging interval set in step S1, the processor 16 averages the measured values ​​to obtain the spectrum of the incident light intensity measured at intervals of the time-averaging intervals.

[0093] In step S4, the processor 16 acquires the spectral data of wavelength interval k under the unshielded state. Specifically, similar to step S3, the processor 16 rotates the diffraction grating 113 while measuring the intensity of the incident light, based on the drift tolerance time and the wavelength range to be measured in wavelength interval k. The processor 16 averages the measured values ​​for each time averaging interval set in step S1 to obtain the spectrum of the incident light intensity measured at intervals of the time averaging intervals.

[0094] In step S5, the processor 16 subtracts the spectrum data obtained in step S3 from the spectrum data obtained in step S4 under the unshielded state to obtain spectrum data for wavelength range k that has suppressed the influence of dark current. Specifically, the processor 16 subtracts the measured values ​​under the shielded state from the measured values ​​under the unshielded state for each intensity of the incident light measured by averaging in each time averaging interval to obtain the spectrum for wavelength range k.

[0095] In step S6, the processor 16 determines whether measurements have been completed for the entire wavelength range. Specifically, the processor 16 determines whether spectral data suppressing the influence of dark current has been obtained for the entire wavelength range from wavelength range 1 to wavelength range n.

[0096] If the processor 16 has completed the measurement for the entire wavelength range (YES in step S6), it proceeds to step S7; otherwise (NO in step S6), it increments the value of k by 1 and returns to step S3.

[0097] In step S7, the processor 16 connects the spectral data of each wavelength range determined by the processing from steps S3 to S6 to obtain the spectral data of the entire wavelength range.

[0098] In step S8, processor 16 outputs the full-wavelength spectrum data obtained in step S7. Specifically, for example, processor 16 can output the full-wavelength spectrum data to memory 17 for storage. Processor 16 can also output the full-wavelength spectrum data to display unit 18 for display. Processor 16 can also output the full-wavelength spectrum data to storage media such as USB (Universal Serial Bus) memory or other devices. If the processing in step S8 ends, processor 16 will... Figure 3 The processing of the flowchart has ended.

[0099] Figure 6 This is a graph showing an example of the measurement results for the spectrum of pulsed light for each measurement method. Figure 6 In the diagram, the horizontal axis represents wavelength, and the vertical axis represents the intensity of the incident light. Figure 6In the figure, the vertical axis represents the light intensity in decibels and milliwatts (dBm) after logarithmic calculation.

[0100] exist Figure 6 In the diagram, curve 51 represents an example of measuring the spectrum of the same incident light using measuring device 10. Curve 52 represents an example of measuring the spectrum of the same incident light without using optical chopper 12. Curve 53 represents an example of measuring the spectrum of the same incident light with and without light blocking using optical chopper 12 at a period asynchronous to the repetition period of the pulsed light.

[0101] Actual incident light exhibits complex spectral shapes not only in the central frequency band but also in the low and high frequency bands. In contrast, curve 52 has a nearly horizontal shape in the low and high frequency bands. This indicates that, without using the optical chopper 12, the weak light intensity information in the low and high frequency bands is submerged in drift errors caused by dark current and cannot be detected. Although curve 53 has a shape roughly similar to the true spectrum of the incident light, it shows errors in intensity that increase or decrease for a given wavelength. This indicates that periodic errors are introduced into the obtained spectral data because the repetition period of the pulsed light is not synchronized with the switching period between shading and unshading.

[0102] In contrast, the measurement result of the measuring device 10, i.e., curve 51, has a shape that is approximately similar to the true spectrum of the incident light. This is because curve 51 measures the low-intensity components of the low-frequency and high-frequency bands with high sensitivity and does not contain periodic errors like those found in curve 53. Therefore, according to the measuring device 10, measurement spectrum data with higher sensitivity than curve 52 can be generated. Furthermore, according to the measuring device 10, more accurate measurement spectrum data without periodic errors can be generated compared to curve 53. Thus, according to the measuring device 10, the spectrum of pulsed light can be measured with higher precision.

[0103] As described above, the measuring device 10 includes: a spectrometer 11 that extracts specific wavelength components from incident light; a photodetector 13 that outputs a signal corresponding to the intensity of the extracted wavelength components; and a processor 16. For each of a plurality of wavelength intervals that divide the wavelength range of the object to be measured, the measuring device 10 acquires a first signal and a second signal, the first signal being output from the photodetector 13 in a light-shielded state, and the second signal being output from the photodetector 13 in an unshielded state corresponding to the intensity of the incident light. The measuring device 10 outputs the difference between the second signal and the first signal as the spectrum of that wavelength interval.

[0104] As described above, the measuring device 10 divides the wavelength range of the object to be measured into multiple wavelength intervals. For each wavelength interval, the incident light is measured in both the shaded and unshaded states, and the difference between the measured signals is output as the spectrum of the wavelength interval. Therefore, according to the measuring device 10, the influence of the drift of the measured value caused by dark current can be suppressed, and the spectrum of pulsed light can be measured with higher accuracy.

[0105] Furthermore, the length of each of the multiple wavelength ranges can be determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector 13 during the measurement of the spectrum of that wavelength range.

[0106] As described above, the length of each wavelength range is determined according to the magnitude of the variation in the measured value caused by the dark current of the photodetector 13. Therefore, according to the measuring device 10, the influence of the drift in the measured value caused by the dark current can be effectively reduced.

[0107] In addition, the measuring device 10 can use the range set by the operator via the operation unit 19 as the wavelength range to divide the wavelength range of the object to be measured.

[0108] As described above, the measuring device 10 divides the wavelength range of the object to be measured from the interval set by the operator as the wavelength interval. Therefore, the operator can measure the spectrum by setting the desired wavelength interval according to the characteristics of the photodetector 13.

[0109] Additionally, the measuring device 10 can also receive a setting of the time averaging interval from the operator via the operation unit 19. The measuring device 10 can acquire, for each of multiple wavelength intervals, a signal obtained by averaging the signal output from the photodetector 13 in a light-shielded state over a time averaging interval, as a first signal. The measuring device 10 can also acquire, as a second signal, a signal obtained by averaging the signal output from the photodetector 13 in an unshielded state over a time averaging interval.

[0110] As described above, the measuring device 10 receives the setting of the time averaging interval from the operator and obtains the spectrum for each wavelength interval based on the signal averaged in units of the time averaging interval. Therefore, the operator can measure the spectrum at the desired sampling rate.

[0111] In addition, the measuring device 10 can obtain a second signal output from the photodetector 13 in an unshielded state after obtaining a first signal output from the photodetector 13 in a light-shielded state for each of the multiple wavelength ranges.

[0112] As described above, the measuring apparatus 10 performs measurements in the unshielded state after performing measurements in the shaded state. Therefore, it is possible to suppress as much as possible the drift caused by dark current that accompanies the temperature rise of the photodetector due to light entering the photodetector. Furthermore, the measuring apparatus 10 can also perform measurements in the shaded state after performing measurements in the unshielded state.

[0113] Additionally, the measuring device 10 may also include an optical chopper 12, which can block light incident on the photodetector 13. The measuring device 10 can acquire, for each of multiple wavelength ranges, a signal output from the photodetector 13 when the light is blocked by the optical chopper 12, as a first signal, and acquire a signal output from the photodetector 13 when the light is not blocked by the optical chopper 12, as a second signal.

[0114] As described above, the measuring device 10 can easily switch between a light-shielding state and a light-unshielding state via the optical chopper 12.

[0115] As described above, the measuring device 10 cancels out the influence of dark current by subtracting the measuring data under the shaded state from the measuring data under the unshaded state, thereby measuring the spectrum of the incident light with high sensitivity. Furthermore, the measuring device 10 measures the spectrum for each wavelength range, thereby shortening the measurement time and suppressing the influence of drift caused by dark current during the measurement process on the measured spectral data.

[0116] This invention is not limited to the embodiments described above. For example, multiple modules shown in the block diagram can be integrated, or a single module can be divided. Instead of executing the multiple steps shown in the flowchart in a sequential order, they can be executed in parallel or in a different order, depending on the processing capacity of the device executing each step or as needed. Furthermore, modifications can be made without departing from the spirit of this invention.

[0117] Alternatively, the structure and operation of the measuring device 10 can be distributed among multiple computers that can communicate with each other. Alternatively, some or all of the structural elements of the measuring device 10 can be located in other devices such as PCs (Personal Computers).

[0118] Explanation of the label

[0119] 10: Measuring device

[0120] 11: Spectrometer

[0121] 12: Optical Chopper

[0122] 13: Photodetector

[0123] 14: Amplifier

[0124] 15: A / D Converter

[0125] 16: Processor

[0126] 17: Memory

[0127] 18: Display Section

[0128] 19: Operations Department

[0129] 111: Fiber optic

[0130] 112: Collimating lens

[0131] 113: Diffraction grating

[0132] 114: Focusing lens

[0133] 115: Exit slit

[0134] 51-53: Curves

[0135] 61-64: Curves

Claims

1. A measuring device, comprising: A beam splitter extracts specific wavelength components from incident light; A photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and processor, In the measuring device, The processor acquires a first signal and a second signal for each of the multiple wavelength intervals that divide the wavelength range of the measurement object. The difference between the second signal and the first signal is output as the spectrum of the corresponding wavelength interval. The first signal is output from the photodetector when the light is blocked, and the second signal is output from the photodetector in the unblocked state, corresponding to the intensity of the incident light.

2. The measuring device according to claim 1, wherein, The length of each of the plurality of wavelength intervals is determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

3. The measuring device according to claim 1 or 2, wherein, The processor receives a set interval from the operator via the operation unit as the wavelength interval, and divides the wavelength range of the object to be measured.

4. The measuring apparatus according to any one of claims 1 to 3, wherein, The processor receives the setting of the time averaging interval from the operator via the operation unit. For each of the multiple wavelength ranges, the signal obtained by averaging the signal output from the photodetector in the light-shielded state over the time averaging interval is used as the first signal, and the signal obtained by averaging the signal output from the photodetector in the unshielded state over the time averaging interval is used as the second signal.

5. The measuring apparatus according to any one of claims 1 to 4, wherein, For each of the plurality of wavelength ranges, after obtaining the first signal output from the photodetector in a light-shielded state, the processor obtains the second signal output from the photodetector in an unshielded state.

6. The measuring apparatus according to any one of claims 1 to 5, wherein, The measuring device also includes an optical chopper, which can block light incident on the photodetector. For each of the plurality of wavelength ranges, the processor obtains the signal output from the photodetector when the light is blocked by the optical chopper as the first signal, and obtains the signal output from the photodetector when the light is not blocked by the optical chopper as the second signal.

7. A measurement method, which is a measurement method using a measuring device, The measuring device has: A beam splitter extracts specific wavelength components from incident light; A photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and processor, The determination method includes the following processing: The processor acquires a first signal and a second signal for each of the multiple wavelength intervals that divide the wavelength range of the measurement object. The difference between the second signal and the first signal is output as the spectrum of the corresponding wavelength interval. The first signal is output from the photodetector when the light is blocked, and the second signal is output from the photodetector in the unblocked state, corresponding to the intensity of the incident light.

8. The determination method according to claim 7, wherein, The length of each of the plurality of wavelength intervals is determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

9. The determination method according to claim 7 or 8, wherein, The processor receives a set interval from the operator via the operation unit as the wavelength interval, and divides the wavelength range of the object to be measured.

10. The determination method according to any one of claims 7 to 9, wherein, The processor receives the setting of the time averaging interval from the operator via the operation unit. For each of the multiple wavelength ranges, the signal obtained by averaging the signal output from the photodetector in the light-shielded state over the time averaging interval is used as the first signal, and the signal obtained by averaging the signal output from the photodetector in the unshielded state over the time averaging interval is used as the second signal.

11. The determination method according to any one of claims 7 to 10, wherein, For each of the plurality of wavelength ranges, after obtaining the first signal output from the photodetector in a light-shielded state, the processor obtains the second signal output from the photodetector in an unshielded state.

12. The determination method according to any one of claims 7 to 11, wherein, The measuring device also includes an optical chopper, which can block light incident on the photodetector. For each of the plurality of wavelength ranges, the processor obtains the signal output from the photodetector when the light is blocked by the optical chopper as the first signal, and obtains the signal output from the photodetector when the light is not blocked by the optical chopper as the second signal.

13. A program for controlling a measuring device, the measuring device having: A beam splitter extracts specific wavelength components from incident light; A photodetector that outputs a signal corresponding to the intensity of the extracted wavelength component; and processor, The program controls the measuring device to perform the following steps: For each of the multiple wavelength intervals that divide the wavelength range of the measurement object, a first signal and a second signal are obtained. The difference between the second signal and the first signal is output as the spectrum of the corresponding wavelength interval. The first signal is output from the photodetector when the light is blocked, and the second signal is output from the photodetector in the unblocked state, corresponding to the intensity of the incident light.

14. The procedure according to claim 13, wherein, The length of each of the plurality of wavelength intervals is determined based on the magnitude of the variation in the measured value caused by the dark current of the photodetector during the measurement of the spectrum of the corresponding wavelength interval.

15. The procedure according to claim 13 or 14, wherein, The wavelength range of the object to be measured is divided by using the interval set by the operator via the operating unit as the wavelength interval.

16. The procedure according to any one of claims 13 to 15, wherein, The operator receives the setting of the average time interval from the operator via the operating unit. For each of the multiple wavelength ranges, the signal obtained by averaging the signal output from the photodetector in the light-shielded state over the time averaging interval is used as the first signal, and the signal obtained by averaging the signal output from the photodetector in the unshielded state over the time averaging interval is used as the second signal.

17. The procedure according to any one of claims 13 to 16, wherein, For each of the plurality of wavelength ranges, after obtaining the first signal output from the photodetector in the light-shielding state, the second signal output from the photodetector in the unshielded state is obtained.

18. The procedure according to any one of claims 13 to 17, wherein, The measuring device also includes an optical chopper, which can block light incident on the photodetector. For each of the multiple wavelength ranges, the signal output from the photodetector when the light is blocked by the optical chopper is obtained as the first signal, and the signal output from the photodetector when the light is not blocked by the optical chopper is obtained as the second signal.

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