Spectrophotometer

Abstract

One form of the spectrophotometer of the present invention comprises: a spectrum measuring section (11, 12) for repeatedly measuring a spectrum of a predetermined wavelength range for a light to be measured, which is laser light; a peak counting section (21, 22) for detecting a peak from the spectrum and counting the number of detected peaks each time the spectrum is obtained by the spectrum measuring section; and a display processing section (24) for displaying the numerical value of the peak counting result obtained by the peak counting section on a screen of the display section in real time. According to the spectrophotometer of the form, the adjustment of a multi-mode laser oscillator can be performed efficiently and accurately.

Description

Technical Field

[0001] The present invention relates to a spectrophotometric device, and in particular to a spectrophotometric device suitable for analyzing laser light. Background Art

[0002] In recent years, lasers have been widely used in various fields such as optical communications, printing, medical treatment, and mechanical processing in addition to precision optical machines, and their scope of application has continued to expand. In the research, development, or adjustment of the manufacturing process, or quality evaluation and management of laser devices, the monitoring of the emission spectrum of laser light is essential, so a spectroscopic measurement device called an optical spectrum analyzer is widely used. An optical spectrum analyzer is a device that measures and displays the light intensity distribution (optical spectrum) of the measured light input by an optical fiber, etc., and can confirm the peak wavelength or peak width, or light intensity, etc. on the spectrum.

[0003] Conventional optical spectrum analyzers are designed to analyze or evaluate not only laser devices but also various optical devices. Therefore, although they are suitable for detailed analysis, they tend to have poor real-time performance. In contrast, as a spectroscopic measurement device that places more emphasis on real-time performance, there is a device called a multi-channel spectrometer, which can simultaneously measure the light intensity of a specified wavelength range for the measured light input to the device (see non-patent document 1, etc.). This type of spectroscopic measurement device is mainly used to measure the spectrum caused by luminescence, absorption, reflection, etc. in approximately real time. In addition, a multi-channel spectrometer has been developed that can cope with the monitoring of laser light with a narrow peak wavelength width by improving the wavelength resolution.

[0004] [Prior art literature]

[0005] [Non-patent literature]

[0006] Non-Patent Document 1: “PMA-12 Multi-Channel Spectrum Spectrometer Series”, [online], [retrieved on February 3, 2020], Hamamatsu Photonics Co., Ltd., Internet <URL: https: / / www.hamamatsu.com / resources / pdf / sys / SDSS0008J_PMA12.pdf>

[0007] Non-Patent Document 2: Ishida Yuzo, “Generation of Ultrashort Pulse Light”, Optics, Vol. 30, No. 6, 2001, ([online], [retrieved on February 3, 2020], Internet <URL: https: / / annex.jsap.or.jp / photonics / kogaku / public / 30-06-kougi.pdf>) Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] Such a high wavelength resolution multi-channel spectrometer can roughly display the optical spectrum (hereinafter referred to as "spectrum") of the input laser light to the user in real time, which is useful, for example, in the case of adjusting the laser device. However, it is usually not easy to properly adjust or evaluate the laser device while viewing the spectrum displayed in real time, and in order to perform such adjustments, evaluations, etc., more effective information is required.

[0010] The present invention is made to solve such problems, and a main object of the present invention is to provide a spectroscopic measurement device that can efficiently and reliably adjust or evaluate a laser device or the like.

[0011] [Technical means to solve the problem]

[0012] One aspect of the spectrophotometer of the present invention, which is designed to solve the above-mentioned problems, includes:

[0013] a spectrum measuring unit that repeatedly measures a spectrum in a predetermined wavelength range for the light to be measured, which is the laser light;

[0014] a peak counting unit that detects peaks from the spectrum and counts the number of detected peaks each time a spectrum is obtained by the spectrum measuring unit, so as to obtain the number of detected peaks corresponding to the longitudinal mode number; and

[0015] The display processing unit displays the numerical value of the peak counting result obtained by the peak counting unit on the screen of the display unit in real time.

[0016] [Effects of the Invention]

[0017] As is well known, lasers are roughly divided into single-mode lasers and multi-mode lasers. Single-mode lasers have high light focusing properties, and the cross-sectional shape of the beam is circular, so they are suitable for fine printing or medical, micro-processing and other purposes. On the other hand, multi-mode lasers have poor light focusing properties compared to single-mode lasers, but it is easy to increase the output and is suitable for mechanical processing such as cutting and welding. Since the longitudinal mode number of single-mode lasers is 1, only one peak appears in the spectrum. Therefore, it is relatively easy for the user to adjust the laser device in a single-mode oscillation manner while confirming the spectrum on the display screen.

[0018] On the other hand, in the case of a multimode laser, multiple peaks appear in the spectrum. Multimode lasers particularly require high output and short pulses, but when operating in a mode-locked state, the pulse width or light intensity of the multimode laser depends on the number of longitudinal modes (refer to non-patent document 2, etc.). Therefore, in the adjustment of a laser device that generates a multimode laser, it is important to control the number of longitudinal modes. Moreover, for a multimode laser, it is sometimes important to evaluate cache coherency or the width of the lower hem of a spectral waveform, and such an evaluation also requires grasping the number of peaks on the spectrum. However, it is quite difficult for a user to read the number of peaks from a spectrum displayed in real time. The inventors of the present invention focused on the above aspects and thought of allowing users to intuitively grasp the number of peaks observed in a spectrum obtained in real time.

[0019] That is, when the spectrophotometric measuring device of the form of the present invention is given laser light as the light to be measured, the number of peaks observed on the latest spectrum is displayed as a numerical value on the screen of the display unit every time the spectrum is updated. Therefore, according to the spectrophotometric measuring device of the form of the present invention, the user can confirm the longitudinal mode number of the laser light to be measured in real time on the screen of the display unit. Therefore, for example, in the case where the user adjusts a multi-mode laser device, the adjustment can be performed in such a way that the longitudinal mode number becomes the required number, or the longitudinal mode number can be confirmed and whether the adjustment is appropriate can be immediately determined. As a result, the adjustment efficiency of the laser device and the like is improved and its accuracy is also improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing the configuration of the main parts of a spectroscopic measurement device according to one embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the optical path structure of the multi-channel spectrometer of the spectrometric measurement device according to this embodiment.

[0022] Figure 3 It is a diagram showing an example of a display screen of the spectrophotometer according to the present embodiment.

[0023] Figure 4 (A) Figure 4 (B) is an explanatory diagram of the peak counting process of the spectrophotometer according to the present embodiment.

[0024] [Explanation of Symbols]

[0025] 1: Multi-channel splitter

[0026] 2: Data Processing Department

[0027] 3: Control Department

[0028] 4: Operation Department

[0029] 5: Display unit

[0030] 6: Measurement result display window

[0031] 10: Optical input connector

[0032] 11: Spectroscopic unit

[0033] 12: Inspection Department

[0034] 20: Data storage department

[0035] 21: Spectrum Production Department

[0036] 22: Peak counting unit

[0037] 23: Trend chart production department

[0038] 24: Display processing unit

[0039] 60: Spectrum display bar

[0040] 61: Peak number display column

[0041] 62: Check box

[0042] 63: Trend chart display bar

[0043] 110: Entrance slit

[0044] 111: The first concave mirror

[0045] 112: Diffraction grating

[0046] 113: Second concave mirror

[0047] 114: Rotating part

[0048] C: Intersection

[0049] D0~D8: Light intensity

[0050] Q: Threshold

[0051] S: Strength value DETAILED DESCRIPTION

[0052] Hereinafter, one embodiment of the spectrophotometer according to the present invention will be described with reference to the drawings.

[0053] [Structure of Spectrophotometer of the Present Embodiment]

[0054] Figure 1 This is a diagram showing the configuration of the main parts of the spectrophotometer according to this embodiment.

[0055] like Figure 1 As shown, the device includes a multi-channel spectrometer 1, a data processing unit 2, a control unit 3, an operation unit 4 and a display unit 5. The multi-channel spectrometer 1 includes: a light input connector 10 connected to an optical fiber for inputting the measured light; a spectrometer 11 for wavelength dispersion of the input measured light; and a multi-channel detection unit 12 for detecting the wavelength dispersed light. The data processing unit 2 includes a data storage unit 20, a spectrum production unit 21, a peak counting unit 22, a trend graph production unit 23 and a display processing unit 24 as functional blocks.

[0056] The data processing unit 2 and the control unit 3 use a computer including a central processing unit (CPU) and the like as hardware resources, and realize their respective functions by executing software installed in the computer.

[0057] Figure 2 for Figure 1 Schematic optical path structure diagram of the multi-channel splitter 1.

[0058] Figure 2 In the embodiment, the spectroscopic unit 11 is a Czerny-Turner type spectrometer, which includes an incident slit 110, a first concave mirror 111, a diffraction grating 112, a second concave mirror 113, and a rotating unit 114. The diffraction grating 112 is freely rotated within a specified angle range by the rotating unit 114 including a motor, etc. The detection unit 12 is a linear sensor, and a plurality of light receiving elements are arranged in a wavelength dispersion direction in a manner that can simultaneously detect light within a specified wavelength range. As the detection unit 12, for example, a charge coupled device (CCD) linear sensor or the like can be used.

[0059] [Measurement Operation of Spectrophotometer of the Present Embodiment]

[0060] Reference Figure 1 and Figure 2 Next, a general measurement operation of the multi-channel spectrometer 1 of the spectroscopic measurement device of the present embodiment will be briefly described.

[0061] When measuring the measured light (multimode laser light, etc.), the optical fiber for inputting the measured light is connected to the light input connector 10. The user inputs the prescribed parameters for the measurement by performing prescribed operations in the operation unit 4. Specifically, the user selects one from a plurality of options prepared in advance for each parameter such as the wavelength range (or its central wavelength) to be measured, the exposure time, and the peak detection condition (threshold value, etc., which will be described later).

[0062] First, the control unit 3 controls the rotating unit 114 to set the diffraction surface of the diffraction grating 112 to a predetermined initial angle relative to the first concave mirror 111. The initial angle at this time corresponds to the wavelength range that is one of the parameters selected in advance. When the measurement is started, the measured light is introduced into the device through the optical fiber, and the measured light is introduced into the spectroscopic unit 11 through the incident slit 110.

[0063] In the spectrometer 11, the light to be measured is first irradiated on the first concave mirror 111, and is reflected by the first concave mirror 111 and travels to the diffraction surface of the diffraction grating 112. The light to be measured at this time is approximately parallel light. The light to be measured irradiated on the diffraction surface of the diffraction grating 112 is wavelength dispersed and sent to the second concave mirror 113. The wavelength dispersed light irradiated on the second concave mirror 113 is converged and reflected respectively, and reaches each light receiving element of the detection unit 12. Light of different wavelengths within the specified wavelength range λ1~λ2 reaches each light receiving element of the detection unit 12. Each light receiving element outputs a detection signal corresponding to the intensity of the incident light.

[0064] The detection signal is equivalent to the spectrum of light in the wavelength range of λ1 to λ2. In the data processing unit 2, the data storage unit 20 digitizes the detection signal obtained by each light receiving element of the detection unit 12 and temporarily stores it. At this time, in the detection unit 12, the light receiving signal is accumulated (i.e., integrated) with the exposure time previously selected as one of the parameters to generate a detection signal. Therefore, in the case where the intensity of the incident light is weak, a high-intensity detection signal can be obtained by extending the exposure time. In the case where the light to be measured is a single laser light, the spectrum can usually be fully covered by the one wavelength range.

[0065] On the other hand, when the measured light is a light obtained by combining a plurality of laser lights having different central wavelengths, the multi-channel spectrometer 1 repeatedly obtains detection signals for different wavelength ranges. That is, after obtaining the detection signal of the specified wavelength range while temporarily fixing the position (angle) of the diffraction grating 112, the control unit 3 controls the rotating unit 114 to change the angle of the diffraction surface of the diffraction grating 112 relative to the measured light coming from the first concave mirror 111 by a specified angle. As a result, the wavelength range of the wavelength dispersed light sent from the diffraction grating 112 to the second concave mirror 113 changes. Therefore, in each light receiving element of the detection unit 12, a detection signal for light in a wavelength range (for example, λ2 to λ3) different from the wavelength range λ1 to λ2 is obtained.

[0066] In this way, while the diffraction grating 112 is rotated at a predetermined angle, the detection signal of the predetermined wavelength range is repeatedly obtained by the detection unit 12. Thus, the data storage unit 20 can collect the following data, which represents the spectrum of the light of the wavelength range selected as one of the parameters. When the collection of the data of the predetermined wavelength range is completed, the control unit 3 returns the diffraction grating 112 to the initial position and repeats the measurement. Thus, the data representing the spectrum of the predetermined wavelength range is repeatedly obtained at a predetermined time interval.

[0067] [Display Processing of Spectrophotometer of the Present Embodiment]

[0068] Next, a display processing operation performed by the data processing unit 2 based on the data obtained as described above will be described. Figure 3 It is a diagram showing an example of a display screen of the display unit 5 .

[0069] After obtaining the data of the spectrum of the entire specified wavelength range, the spectrum production unit 21 produces a spectrum (luminescence spectrum) based on the data. Next, the peak counting unit 22 detects peaks according to a specified algorithm for the produced spectrum, and then counts the number of detected peaks. Various algorithms can be considered as the algorithm for peak detection, for example, the following method can be adopted.

[0070] Figure 4 (A) Figure 4 (B) is an explanatory diagram of an example of peak detection processing.

[0071] like Figure 4 As shown in (A), the data representing the light intensity on the wavelength axis are set to D0, D1, D2, D3, ... These data are respectively digitized detection signals obtained by one light receiving element of the detection unit 12. Here, D0 is the data of the shortest wavelength in the set wavelength range.

[0072] The parameters used for peak detection are the number of continuously changing data points P and the threshold Q used to distinguish the intensity of peaks and noise. Figure 4 (A) Figure 4 In the example of (B), P=3.

[0073] Currently, if Figure 4 As shown in (A), study the intensity values ​​of three (i.e., P) consecutive data in one direction along the wavelength axis (in this case, the right direction (increasing wavelength direction), but it can also be the left direction (decreasing wavelength direction)), and find the first three data sets whose intensity values ​​increase in sequence. Figure 4 In the example of (B), D0, D1, and D2 are the three data groups. From here, the intensity values ​​of the data are further studied in the direction of increasing wavelength to find the last three data groups whose intensity values ​​decrease in sequence. Figure 4 In the example of (B), D6, D7, and D8 are the three data groups. In this case, the range from the first data in the first three data groups to the third data in the last three data groups, that is, the range of D0 to D8 is a candidate for one peak.

[0074] Then, in Figure 4 On a graph such as that shown in (B) of FIG. 1 , the intensity values ​​of the first data D0 in the first three consecutive data groups and the last data D8 in the last three consecutive data groups are connected by a straight line. Next, the intersection point C of this line and the vertical line passing through the data D4 representing the maximum intensity among the peak candidates is used as the base point (zero point) of the intensity, and the intensity value S of the data D4 is calculated. If this intensity value S exceeds the threshold value Q, the peak candidate is identified as a formal peak.

[0075] In the set wavelength range as a whole, from the data corresponding to the smallest wavelength to the data corresponding to the longest wavelength, peak detection is performed as described above, the total number of peaks recognized as formal peaks is obtained, and the processing is terminated. Through this processing, the number of peaks observed in the set wavelength range as a whole can be obtained.

[0076] The display processing unit 24 creates Figure 3 The measurement result display window 6 shown in FIG. 1 is displayed on the screen of the display unit 5 via the control unit 3. Figure 3 As shown, in the measurement result display window 6, a spectrum display column 60, a peak number display column 61, a trend graph display column 63, etc. are arranged, and a check box 62 for displaying ON / OFF is arranged on the left of the peak number display column 61.

[0077] The display processing unit 24 displays the latest spectrum created by the spectrum creating unit 21 in the spectrum display column 60. The spectrum displayed in the spectrum display column 60 is updated every time a new spectrum is acquired. In addition, the display processing unit 24 displays the peak count value obtained by the peak counting unit 22 in the peak number display column 61 as a numerical value. Figure 3 In the example of , "15" is the number of peaks. This value is also updated every time the number of peaks corresponding to a newly acquired spectrum is obtained, that is, it is updated in substantially real time. Moreover, when a check mark is attached to the check box 62 of the display on / off (ON / OFF), the display processing unit 24 superimposes a mark 64 on the spectrum displayed in the spectrum display column 60, and this mark 64 indicates the peak counted as the number of peaks, that is, the peak detected according to the algorithm.

[0078] Figure 3 In the example, the circle mark near the top of each peak is the mark 64. Of course, the mark 64 can be any mark as long as it can easily distinguish visually between those counted as peaks and those not counted, for example, a mark of an appropriate shape such as an arrow mark can be used. Moreover, instead of using a mark, the display color of the peak can be changed to indicate those counted as peaks and those not counted. Alternatively, if the process is to count peaks whose peak intensity is above a certain threshold, instead of using the mark 64 to indicate each peak separately, a horizontal line indicating the threshold used can be overlapped and displayed on the spectrum, so that the peaks exceeding this line are counted.

[0079] Moreover, the trend chart making unit 23 sets the horizontal axis to time (or sampling times) and the vertical axis to the number of peaks whenever the numerical value of the number of peaks corresponding to the spectrum is obtained, and makes a trend chart showing the time change of the number of peaks. The display processing unit 24 displays the produced trend chart in the trend chart display column 63. Therefore, whenever a new spectrum is obtained and the number of peaks is obtained based on this spectrum, the trend chart is also updated and a new line is added to the chart. The numerical value displayed in the number of peaks display column 61 is the latest value, so the user cannot grasp the previous numerical value even if he looks at this numerical value. In contrast, the trend chart has time passing, so the user can confirm the value of the previous number of peaks or the change of the number of peaks in the trend chart.

[0080] For example, in the case where the user adjusts the laser oscillator, if the parameters of the oscillator are changed, the position or number of the longitudinal modes of the laser will change accordingly. Therefore, as the parameters of the laser oscillator change, the spectrum displayed in the spectrum display column 60 changes, and the value displayed in the peak number display column 61 also changes. Moreover, a line corresponding to the new peak number is also added to the trend chart displayed in the trend chart display column 63. Therefore, while watching these displays, the user adjusts the parameters of the laser oscillator in a manner such that the peak number becomes a target value. Moreover, in the case of confirming the stability of the operation of the laser oscillator, the user only needs to confirm whether the peak number changes while watching the display.

[0081] As described above, according to the spectrophotometer of this embodiment, the user can adjust or evaluate the laser device while visually confirming the numerical value of the count result of the number of peaks on the spectrum and the information on the time change of this numerical value displayed on the screen of the display unit 5. Thus, efficient and reliable adjustment or evaluation can be performed.

[0082] [Modifications]

[0083] In the above description, the display form of the spectrum, peak number and trend chart is not limited to Figure 3 , can be changed appropriately.

[0084] Furthermore, the above-described embodiment is merely an example of the present invention, and any appropriate changes, modifications, or additions made within the scope of the gist of the present invention are also included in the claims of the present application.

[0085] [Various forms]

[0086] Those skilled in the art will appreciate that the exemplary embodiments described above are specific examples of the following forms.

[0087] (Item 1) One aspect of the spectrophotometer of the present invention includes:

[0088] a spectrum measuring unit that repeatedly measures a spectrum in a predetermined wavelength range for the light to be measured, which is the laser light;

[0089] a peak counting unit that detects peaks from the spectrum and counts the number of detected peaks each time a spectrum is obtained by the spectrum measuring unit, so as to obtain the number of detected peaks corresponding to the longitudinal mode number; and

[0090] The display processing unit displays the numerical value of the peak counting result obtained by the peak counting unit on the screen of the display unit in real time.

[0091] According to the spectrometer described in the first item, the number of peaks corresponding to the longitudinal mode number of the laser light is displayed on the display screen in real time. Therefore, when the user adjusts the multi-mode laser oscillator, for example, it can be quickly determined based on the number of peaks whether the adjustment is appropriate, thereby improving the efficiency and accuracy of the adjustment.

[0092] (Item 2) The spectrophotometer according to Item 1 may further include: a graph generator for generating a graph showing a trend of the peak counting result obtained by the peak counting unit over time;

[0093] The display processing unit displays the trend graph and the real-time numerical values ​​of the peak counting results on the same screen.

[0094] According to the spectrophotometer described in the second item, the user can not only easily grasp the number of peaks at the time point, that is, the longitudinal mode of the laser light, from the display, but also grasp the temporal change of the longitudinal mode at a glance. Therefore, for example, by checking the trend graph while adjusting the laser oscillator, the user can grasp the relationship between the adjustment state and the longitudinal mode corresponding thereto, and can quickly adjust the laser oscillator so as to obtain the desired longitudinal mode.

[0095] (Item 3) Moreover, in the spectroscopic measurement device described in Item 2, the display processing unit can display the spectrum obtained by the spectrum measurement unit, the trend chart, and the real-time numerical values ​​of the peak counting results on the same screen, and display the information representing each detected peak reflected by the numerical values ​​on the displayed spectrum.

[0096] According to the spectrophotometer described in the third item, the user can confirm the waveform detected as a peak and the waveform not detected as a peak on the spectrum. Thus, the user can determine whether the peak detection conditions (parameters) at this time are appropriate and change the peak detection conditions as needed.

[0097] (Item 4) Moreover, in the spectroscopic measurement device described in any one of items 1 to 3, the spectrum measurement unit may include: a diffraction grating for wavelength-dispersing the light to be measured; a multi-channel detector for simultaneously detecting the wavelength-dispersed light obtained by the diffraction grating; and a rotating unit for rotating the diffraction grating to change the wavelength range of the wavelength-dispersed light reaching the detector.

[0098] According to the spectrophotometer described in claim 4, the wavelength resolution can be improved and a spectrum in a wide wavelength range can be measured in a short time. Therefore, the spectrophotometer described in claim 4 can also observe peaks with narrow wavelength widths, and the range or types of laser light that can be measured can be expanded.

Claims

1. A spectrophotometric device, comprising: a spectrum measuring unit that repeatedly measures a spectrum in a predetermined wavelength range for the light to be measured, which is the laser light; a peak counting unit that detects peaks from the spectrum and counts the number of detected peaks each time a spectrum is obtained by the spectrum measuring unit, so as to obtain the number of detected peaks corresponding to the longitudinal mode number; as well as The display processing unit displays the numerical value of the peak counting result obtained by the peak counting unit on the screen of the display unit in real time.

2. The spectrophotometer according to claim 1, further comprising: a graph making unit for making a trend graph showing the time passage of the peak counting result obtained by the peak counting unit, The display processing unit displays the trend graph and the real-time numerical values ​​of the peak counting results on the same screen.

3. The spectrophotometer according to claim 2, wherein: The display processing unit displays the spectrum obtained by the spectrum measuring unit, the trend graph, and the real-time numerical values ​​of the peak counting result on the same screen, and displays information indicating each detected peak reflected in the numerical values ​​on the displayed spectrum.

4. The spectrophotometer according to claim 1, wherein: The spectrum measurement unit includes: a diffraction grating for wavelength-dispersing the measured light; a multi-channel detector for simultaneously detecting the wavelength-dispersed light obtained by the diffraction grating; and a rotation unit for rotating the diffraction grating to change the wavelength range of the wavelength-dispersed light reaching the detector.

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