JP7559441B2 - Spectroscopic equipment - Google Patents

Description

The present invention relates to a spectroscopic measurement device.

Lasers are widely used in a variety of fields, including precision optical equipment, optical communications, printing, medicine, and machining, and the scope of their use has been expanding in recent years. Monitoring the emission spectrum of laser light is essential during research and development of laser devices, adjustments in the manufacturing process, and quality evaluation and management, and a type of 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 through an optical fiber or the like, and makes it possible to confirm the peak wavelength, peak width, and light intensity on the spectrum.

General optical spectrum analyzers are intended to analyze and evaluate not only laser devices but also various optical devices, so although they are suitable for detailed analysis, they tend to be inferior in real-time performance. In contrast, a device called a multichannel spectroscope is known as a spectroscopic measurement device that places more importance on real-time performance and is capable of simultaneously measuring the light intensity over a specified wavelength range for the light to be measured input to the device (see Non-Patent Document 1, etc.). Such spectroscopic measurement devices are mainly used to measure spectra such as emission, absorption, and reflection in near real time. In addition, multichannel spectroscopes have been developed that have improved wavelength resolution to enable monitoring of laser light with a narrow peak wavelength width.

"PMA-12 Multichannel Spectrometer Series", [online], [Retrieved February 3, 2020], Hamamatsu Photonics K.K., Internet <URL: https://www.hamamatsu.com/resources/pdf/sys/SDSS0008J_PMA12.pdf>

A high wavelength resolution multichannel spectrometer as described above can present the optical spectrum of input laser light to the user in almost real time, which is useful, for example, when adjusting a laser device. However, in devices such as DDLs (direct diode lasers) used in laser processing machines, multicolor lasers used for image projection, and laser modules used in measuring instruments, it is necessary to evaluate whether the output of laser light is stable, but such information cannot be obtained from the spectrum displayed in real time.

The present invention was made to solve these problems, and its purpose is to provide a spectroscopic measurement device that can obtain information that is difficult to grasp from a spectrum.

In order to solve the above problems, one aspect of the spectroscopic measurement device according to the present invention is to
a diffraction grating for dispersing the wavelength of the measured light, which is a laser beam;
a detection unit having a plurality of light receiving elements for simultaneously detecting light that has been wavelength-dispersed by the diffraction grating;
a spectrum creating unit that repeatedly creates a spectrum of the laser light based on output signals of the plurality of light receiving elements;
a light intensity calculation unit that calculates a light intensity by adding up output signals from the plurality of light receiving elements each time a spectrum is created by the spectrum creation unit;
a graph creation unit that creates a trend graph showing the time course of the light intensity calculated by the light intensity calculation unit;
The apparatus further comprises a display processing section which displays in real time on the same screen of a display section the spectrum obtained by the spectrum creating section and the trend graph created by the graph creating section.

In the spectroscopic measurement device of the above aspect, the measured light, which is laser light incident on the device, is wavelength-dispersed by a diffraction grating and then reaches each light-receiving element of the detection section. Each light-receiving element outputs a signal according to the intensity of the light incident thereon. Since light of different wavelengths within the wavelength range of the measured light reaches each of the light-receiving elements of the detection section, the spectrum of the measured light can be obtained from the output signals of the multiple light-receiving elements.

However, the diffraction efficiency of the diffraction grating used in the spectroscopic measurement device of the above embodiment differs depending on the wavelength. In addition, semiconductor detectors such as CMOS sensors and CCD sensors are generally used as the detection unit, but it is known that semiconductor detectors have different sensitivity characteristics depending on the wavelength. Therefore, depending on the light receiving element, the output signal may not reflect the intensity of the incident light. In contrast, in the case of light with a narrow wavelength range such as laser light, the diffraction efficiency of the diffraction grating and the influence of the wavelength on the sensitivity characteristics of the light receiving element are small, so there is an almost constant correlation between the intensity of the light input to the light receiving element and the output signal. The inventor of the present application focused on these points and came up with the idea of using data for acquiring a spectrum in real time to calculate the intensity of the light to be measured.

In other words, in the spectroscopic measurement device of the above aspect of the present invention, when laser light is given as the light to be measured, each time the spectrum is updated, the light intensity of the light to be measured is calculated from the data from which the spectrum was obtained, and a trend graph showing the progress over time is displayed on the same screen of the display unit together with the spectrum. Therefore, the user can check the intensity of the laser light to be measured in real time on the screen of the display unit.

1 is a configuration diagram of a main part of a spectroscopic measurement device according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing the optical path configuration of a multichannel spectroscope in the spectroscopic measurement device of the present embodiment. FIG. 4 is a diagram showing an example of a display screen in the spectroscopic measurement device of the present embodiment.

Below, one embodiment of the spectroscopic measurement device according to the present invention will be described with reference to the attached drawings.

[Configuration of the spectroscopic measurement device of this embodiment]
FIG. 1 is a configuration diagram of a main part of a spectroscopic measuring device according to the present embodiment.
1, the present apparatus includes a multichannel spectrometer 1, a data processing unit 2, a control unit 3, an operation unit 4, and a display unit 5. The multichannel spectrometer 1 includes an optical input connector 10 to which an optical fiber for inputting the light under measurement is connected, a spectroscopic unit 11 for dispersing the wavelength of the input light under measurement, and a multichannel detection unit 12 for detecting the wavelength-dispersed light. The data processing unit 2 includes, as functional blocks, a data storage unit 20, a spectrum creation unit 21, a light intensity calculation unit 22, a trend graph creation unit 23, and a display processing unit 24.

The data processing unit 2 and the control unit 3 can use a computer consisting of a CPU or the like as a hardware resource, and realize their respective functions according to software installed on the computer.

FIG. 2 is a schematic diagram of the optical path configuration in the multichannel spectrometer 1 in FIG.
The spectroscopic unit 11 is a Czerny- Turner type spectrometer, and includes an entrance 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 can be rotated within a predetermined angle range by the rotating unit 114, which includes a motor or the like. The detection unit 12 is a linear sensor in which a large number of light receiving elements are arranged in the wavelength dispersion direction so that light in a predetermined wavelength range can be detected all at once. A CMOS linear sensor, a CCD linear sensor, or the like can be used.

[Measurement Operation of the Spectroscopic Measurement Apparatus of the Present Embodiment]
A normal measurement operation in the multichannel spectrometer 1 of the spectroscopic measurement device of this embodiment will be briefly described with reference to Fig. 2. When measuring light to be measured (such as multimode laser light), an optical fiber for inputting the light to be measured is connected to the optical input connector 10.
The user inputs predetermined parameters for measurement by performing a predetermined operation on the operation unit 4. Specifically, the user selects parameters such as the central wavelength of the wavelength range to be measured and the exposure time from a plurality of options prepared in advance.

The control unit 3 controls the rotating unit 114 so that the diffracting surface of the diffraction grating 112 is at a predetermined initial angle with respect to the first concave mirror 111. The initial angle at this time corresponds to the central wavelength of the initially selected wavelength range. When measurement is started and the light to be measured is introduced into the device through the optical fiber, the light to be measured is introduced into the spectroscopic unit 11 through the entrance slit 110.

In the spectroscopic section 11, the light to be measured first hits the first concave mirror 111, where it is reflected and travels towards the diffracting surface of the diffraction grating 112. At this time, the light to be measured is almost parallel. The light to be measured that hits the diffracting surface of the diffraction grating 112 is dispersed in wavelength and sent to the second concave mirror 113. The wavelength-dispersed light that hits the second concave mirror 113 is reflected while being converged, and reaches each light receiving element of the detection section 12. Light of different wavelengths within the predetermined wavelength range λ1 to λ2 reaches each light receiving element of the detection section 12. Each light receiving element outputs a detection signal according to the intensity of the incident light.

This detection signal corresponds to the spectrum of light in the wavelength range λ1 to λ2. In the data processing unit 2, the data storage unit 20 digitizes the detection signals obtained by each light receiving element of the detection unit 12 and temporarily stores the values (intensity value or count value). At this time, the detection unit 12 accumulates (i.e. integrates) the received light signals for the exposure time initially selected to generate a detection signal. Therefore, if the intensity of the incident light is weak, a detection signal of high intensity (or large count value) can be obtained by extending the exposure time. When the light to be measured is a single laser beam, this single wavelength range is usually sufficient to cover the optical spectrum.

On the other hand, when the light to be measured is light obtained by combining laser beams with different center wavelengths, the acquisition of detection signals for different wavelength ranges is repeated. That is, when a detection signal over a predetermined wavelength range is obtained with the position (angle) of the diffraction grating 112 fixed, the control unit 3 controls the rotating unit 114 to change the angle of the diffraction surface of the diffraction grating 112 with respect to the light to be measured arriving from the first concave mirror 111 by a predetermined angle. This changes the wavelength range of the wavelength-dispersed light sent from the diffraction grating 112 to the second concave mirror 113. Therefore, each light receiving element of the detection unit 12 obtains a detection signal for light in a wavelength range different from the above-mentioned wavelength range λ1 to λ2 (for example, λ3 to λ4. Note that the wavelength λ2 and the wavelength λ3 may be the same or different).

In this way, while rotating the diffraction grating 112 by a predetermined angle, the detection unit 12 repeatedly obtains the detection signal. This allows the data storage unit 20 to collect data representing the spectrum of light across the entire wavelength range initially selected. When the collection of data across the predetermined wavelength range is completed, the light intensity calculation unit 22 obtains the intensity value or count value of the light incident on each light receiving element from the data across that wavelength range, and adds up these values to calculate the light intensity of the light to be measured. At this time, the light intensity calculation unit 22 corrects the data obtained from each light receiving element based on the dark current signal of that light receiving element, and then obtains the light intensity value or count value. The value of the dark current signal of each light receiving element may be stored in advance in the data storage unit 20, or may be measured each time a measurement operation of the light to be measured is performed.

When the light intensity calculation unit 22 has finished calculating the light intensity of the light to be measured, the control unit 3 returns the diffraction grating 112 to its initial position and repeats the above-mentioned measurement. This allows the data on the light spectrum over a predetermined wavelength range and the light intensity value (or count value) to be repeatedly obtained at predetermined time intervals.

[Display Processing in the Spectroscopic Measurement Device of the Present Embodiment]
Next, a display processing operation performed by the data processing unit 2 based on the data obtained as described above will be described. Fig. 3 is a diagram showing an example of a display screen of the display unit 5. In Fig. 3, the light intensity is represented by a count value.
When data on the optical spectrum over a predetermined wavelength range is obtained, the spectrum creation unit 21 creates a spectrum (emission spectrum) based on the data. Next, the display processing unit 24 displays the latest optical spectrum created by the spectrum creation unit 21 in the spectrum display field 60. Every time a new optical spectrum is obtained, the optical spectrum displayed in the spectrum display field 60 is updated. The display processing unit 24 also displays the count value indicating the light intensity calculated by the light intensity calculation unit 22 as a numerical value in the light intensity value display field 61. In the example of Fig. 3, "1,234,567" represents the light intensity. This numerical value is also updated every time a new spectrum is created, that is, in almost real time.

Furthermore, each time an optical spectrum is created, the trend graph creation unit 23 creates a trend graph showing the change over time, with the horizontal axis representing the number of measurements and the vertical axis representing the count. The display processing unit 24 displays this created trend graph in the trend graph display field 63. Therefore, each time a new optical spectrum is obtained, the trend graph is also updated and a new line is added to the graph. The numerical value displayed in the light intensity value display field 61 is the latest light intensity, so past values cannot be seen by looking at this. In contrast, since the trend graph shows the passage of time, the user can check past count values and their changes on the trend graph.

For example, when performing machining using laser light, it is necessary to adjust the laser oscillator so that laser light of a specified light intensity is stably output. In such a case, it is possible to determine whether the operation of the laser oscillator is stable by visually checking the trend graph displayed in the trend graph display area 63.

[Modification]
In the above description, the display modes of the optical spectrum, the optical intensity values, and the trend graphs are not limited to those shown in FIG. 3, and can be changed as appropriate.

The above embodiment is merely one example of the present invention, and it is clear that any modifications, alterations, or additions made within the spirit and scope of the present invention are also encompassed within the scope of the claims of this application.

[Various aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Item 1) One aspect of the spectroscopic measurement device according to the present invention is
a diffraction grating for dispersing the wavelength of the measured light, which is a laser beam;
a detection unit having a plurality of light receiving elements for simultaneously detecting light that has been wavelength-dispersed by the diffraction grating;
a spectrum creating unit that repeatedly creates a spectrum of the laser light based on output signals of the plurality of light receiving elements;
a light intensity calculation unit that calculates a light intensity by adding up output signals from the plurality of light receiving elements each time a spectrum is created by the spectrum creation unit;
a graph creation unit that creates a trend graph showing the time course of the light intensity calculated by the light intensity calculation unit;
The apparatus further comprises a display processing section which displays in real time on the same screen of a display section the spectrum obtained by the spectrum creating section and the trend graph created by the graph creating section.

The spectroscopic measurement device described in paragraph 1 can grasp not only the spectrum of the laser light, which is the light to be measured, but also the change over time in the light intensity of the laser light. Therefore, it is possible to quickly evaluate whether the output of the laser light is stable, for example, in a DDL used in a laser processing machine, a multi-color laser used for image projection, a laser module used in a measuring instrument, etc.

(2) In the spectroscopic measurement device described in 1, the display processing unit can display the numerical value of the light intensity, which is the calculation result of the light intensity calculation unit, on the same screen as the spectrum and the trend graph.

According to the spectroscopic measurement device described in paragraph 2, the light intensity value of the laser light is displayed on the display screen in real time. Therefore, in addition to evaluating whether the light intensity of the laser light is stable, for example, in a DDL used in a laser processing machine, a multi-color laser used for image projection, or a laser module used in a measuring instrument, it is possible to grasp the light intensity as an absolute value.

(3) In the spectroscopic measurement device described in 1 or 2, the light intensity calculation unit can correct the output signal of each of the plurality of light receiving elements based on a dark current signal output from the light receiving element when no light is incident on the light receiving element, and calculate the light intensity from the corrected output signal.

The spectroscopic measurement device described in paragraph 3 can eliminate the influence of the dark current signal of the light receiving element, thereby making it possible to obtain accurate light intensity.

REFERENCE SIGNS LIST 1... Multi-channel spectrometer 10... Optical input connector 11... Spectroscopic section 110... Entrance slit 111... First concave mirror 112... Diffraction grating 113... Second concave mirror 114... Rotating section 12... Detection section 2... Data processing section 20... Data storage section 21... Spectrum creation section 22... Light intensity calculation section 23... Trend graph creation section 24... Display processing section 3... Control section 4... Operation section 5... Display section

Claims (3)

a diffraction grating for dispersing the wavelength of the measured light, which is a laser beam;
a detection unit having a plurality of light receiving elements for simultaneously detecting light that has been wavelength-dispersed by the diffraction grating;
a spectrum creating unit that repeatedly creates a spectrum of the laser light based on output signals of the plurality of light receiving elements at predetermined time intervals ;
a light intensity calculation unit that, each time a spectrum is created by the spectrum creation unit, counts the output signals of the plurality of light receiving elements used to create the spectrum , obtains a count value of each light receiving element, and calculates a light intensity by adding up the count values of the plurality of light receiving elements ;
a graph creating unit that creates a trend graph showing the time course of the light intensity calculated by the light intensity calculation unit every time the spectrum is created by the spectrum creating unit;
a display processing unit that displays the spectrum obtained by the spectrum creation unit and the trend graph created by the graph creation unit on the same screen of a display unit in real time. The spectroscopic measurement device according to claim 1, wherein the display processing unit displays the numerical value of the light intensity calculated by the light intensity calculation unit on the same screen as the spectrum and the trend graph. the light intensity calculation unit corrects an output signal of each of the plurality of light receiving elements based on a dark current signal output from the light receiving element in a state where no light is incident on the light receiving elements, and calculates light intensity from the corrected output signal;
The spectroscopic measurement device according to claim 1 .

Images