An on-line optical resonator cavity mirror reflectivity automatic measuring device

Abstract

The application discloses an online optical resonant cavity mirror reflectivity automatic measuring device, which comprises a light source module, an optical resonant cavity module, an air path module, a detection and collection module and a control and driving module. A computer controls standard gas in the air path module to enter the optical resonant cavity. The emergent light is split by a fiber beam splitter, and the detection optical fibers are connected to a spectrometer and a filter wheel respectively. The computer controls a stepping motor to rotate through a driving device, and then controls the filter wheel to rotate so that a band-pass filter selects light of a specific wave band to pass. The passed light is converted into an electric signal through a photomultiplier. The computer obtains the electric signal through an acquisition card and determines the spectrum intensity of the passed wave band in combination with the position of the band-pass filter on the filter wheel. According to the Rayleigh scattering cross section and the absorption cross section of the standard gas under different wavelengths, the Rayleigh scattering extinction coefficient and the absorption coefficient of the standard gas are calculated, so that the automatic measurement of the optical resonant cavity mirror reflectivity is completed. The detection efficiency is improved, the complicated process of changing an optical path for calibrating the mirror reflectivity before experiments is avoided, and the workload of people is reduced.

Description

Technical Field

[0001] This invention relates to the field of optical lens testing technology, and in particular to an online automatic measurement device for the reflectivity of an optical resonant cavity mirror. Background Technology

[0002] Cavity-enhanced absorption spectroscopy is a highly sensitive detection technique commonly used for the detection of various gases. To deduce the concentration of the gas being measured from its absorption spectrum, the reflectivity of the cavity mirrors as a function of wavelength must first be known; that is, the reflectivity of the mirrors needs to be calibrated before measurement. This method makes the detection process for atmospheric gases complex and inefficient. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an online automatic optical resonant cavity mirror reflectivity measurement device, which solves the problems of low gas detection efficiency and high complexity in existing technologies.

[0004] This invention provides an online automatic optical resonant cavity mirror reflectivity measurement device, comprising: a light source module for providing a measurement light beam; an optical resonant cavity module for providing high reflectivity to ensure continuous reflection of light within the cavity, thereby increasing the optical path; a gas path module for providing the test gas and a standard gas to the optical resonant cavity module; a detection and acquisition module, comprising a spectrometer connected to a detection fiber optic cable split by an optical fiber beam splitter, and a filter wheel, a photomultiplier tube, and a data acquisition card connected to a detection fiber optic cable; and a control and drive module, comprising a control device, a drive device, a stepper motor, and a computer.

[0005] Preferably, an online automatic optical resonant cavity mirror reflectivity measurement device is characterized in that the optical resonant cavity module includes a cavity, a lens, a filter, and an aperture; the cavity has a first lens and an incident aperture at the incident end of the measurement beam, and a second lens and an exit aperture at the exit end of the measurement beam; the cavity has an air inlet, an air outlet, and a pressure gauge circumferentially arranged, and the pressure gauge is used to monitor the pressure inside the cavity;

[0006] Preferably, an online automatic optical resonant cavity mirror reflectivity measuring device is characterized in that the optical resonant cavity body is circumferentially connected to the air inlet and the air outlet, a dryer and a filter are provided outside the air inlet, and an air pump is connected to the air outlet for discharging gas from the cavity.

[0007] Preferably, an online automatic measurement device for the reflectivity of an optical resonant cavity mirror is characterized in that a spectrometer in the detection and acquisition module collects information and is connected to a computer;

[0008] Preferably, an online automatic optical resonant cavity mirror reflectivity measurement device is characterized in that the computer is connected to a control device and a drive device respectively; the control device is connected to flow valve one, flow valve two and flow valve three, and is used to control the gas in the first gas path, the second gas path and the third gas path to enter the cavity through the air inlet; the drive device is connected to a stepper motor; the stepper motor is connected to a filter wheel; the filter wheel is connected to a data acquisition card via a photomultiplier tube; and the data acquisition card is connected to the computer.

[0009] Preferably, an online automatic optical resonant cavity mirror reflectivity measurement device is characterized in that the filter wheel has different bandpass filters, and the bandpass filters can select light of a specific wavelength band to pass through.

[0010] This invention uses a computer-controlled gas path module to guide a standard gas into an optical resonant cavity. The emitted light is split by a fiber optic beam splitter, and the probe fibers are connected to a spectrometer and a filter wheel, respectively. The computer controls a stepper motor to rotate, which in turn rotates the filter wheel to different bandpass filters to select specific wavelengths of light for passage. The passed light is converted into an electrical signal by a photomultiplier tube. The computer obtains the electrical signal through a data acquisition card and combines it with the position of the bandpass filter on the filter wheel to determine the spectral intensity of the passed wavelength. Based on the Rayleigh scattering cross section of the standard gas at different wavelengths, the Rayleigh scattering extinction coefficient of the standard gas is calculated to automatically calibrate the reflectivity of the optical resonant cavity mirror. This improves detection efficiency, avoids the complicated process of changing the optical path before calibrating the mirror reflectivity, and reduces the workload. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of an online automatic optical resonant cavity mirror reflectivity measurement device provided in an embodiment of the present invention;

[0013] Figure 2 This is a structural diagram of the filter wheel of an online automatic optical resonant cavity mirror reflectivity measurement device provided in an embodiment of the present invention;

[0014] Figure 3 This is a structural block diagram of an online automatic optical resonant cavity mirror reflectivity measurement device provided in an embodiment of the present invention;

[0015] In the diagram: 1. Light source; 2. Filter; 3. Lens I; 4. Entrance aperture; 5. Cavity; 6. Filter; 8. Air pump; 10. Exit aperture; 11. Lens II; 12. Fiber optic splitter; 13. Gas cylinder I; 14. Gas cylinder II; 15. Flow valve I; 16. Flow valve III; 17. Flow valve II; 18. Filter wheel; 19. Spectrometer; 20. Pressure gauge; 21. Dryer; 22. Mass flow meter I; 23. Mass flow meter II; 24. Mass flow meter III. 25 Computer, 26 Stepper Motor, 27 Photomultiplier Tube, 28 Data Acquisition Card, 501 Cavity 1, 502 Cavity 2, 503 Air Inlet, 504 Air Outlet, 1201 Detection Fiber 1, 1202 Detection Fiber 2, 1501 First Air Path, 1502 Atmospheric Inlet, 1601 Third Air Path, 1701 Second Air Path, 2501 Drive Device, 2502 Control Device, 1801 Bandpass Filter. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figure 1 and Figure 3 As shown, Figure 1 This is a schematic diagram of the structure of an online automatic optical resonant cavity mirror reflectivity measurement device provided in this embodiment. Figure 3 This is a structural block diagram of an online automatic optical resonant cavity mirror reflectivity measurement device provided in an embodiment of the present invention, including a light source module, an air path module, an optical resonant cavity module, a detection and acquisition module, a control module, and a filter wheel.

[0018] Specifically, the light source module 1 provides a measurement beam; the optical resonant cavity module provides high reflectivity to ensure continuous reflection of light within the cavity, thereby increasing the optical path; and the gas path module provides measurement gas to the optical resonant cavity module. The gas path module includes a first gas path 1501 for conveying the gas to be measured, a second gas path 1701 for conveying a standard gas, and a third gas path 1601 for conveying the standard gas. The first gas path includes a flow valve 15 and a mass flow meter 22 for monitoring the flow rate of the incoming atmospheric gas. The second gas path 1701 includes a gas cylinder 13 for storing the standard gas. The third gas path 1601 includes a gas cylinder 14 for storing standard gas, a flow valve 16, and a mass flow meter 23 for monitoring the flow rate of standard gas; a detection and acquisition module, which includes a spectrometer 19 connected to a detection fiber 1201 split by an optical fiber splitter 12, a filter wheel 18, a photomultiplier tube 27, and an acquisition card 28 connected by a detection fiber 1202; and a control and drive module, which includes a control device 2502, a drive device 2501, a stepper motor 26, and a computer 25.

[0019] Specifically, during the automatic measurement of the reflectivity of the endoscope, the standard gas stored in the gas cylinder 13 is nitrogen, and the standard gas stored in the gas cylinder 14 is nitrogen dioxide. The control device 2501 of the gas circuit module is driven by the computer 25, which in turn controls the flow valve 27 and the flow valve 36 to deliver the standard gas nitrogen and nitrogen dioxide to the air inlet 503. The flow rates of the nitrogen and nitrogen dioxide standard gases are recorded by the mass flow meter 3 24 and the mass flow meter 2 23, respectively. After passing through the filter 6 and the dryer 21, the gas enters the cavity 5 through the air inlet 503. After being filtered by filter 2, light from light source 1 is focused and coupled into cavity 5 by lens 3. An incident aperture 4 limits the size of the incident beam and suppresses stray light entering the cavity. An exit aperture 10 limits the size of the outgoing beam, which is collected by lens 11. The splitting ratio of fiber optic beam splitter 12 is 1:99. 99% of the light energy of the first outgoing beam is connected to spectrometer 19, and 1% of the light energy of the second outgoing beam is connected to filter wheel 18. Computer 25 controls stepper motor 26 via drive device 2501. Figure 2 As shown, the filter wheel 18 rotates, and then the bandpass filter 1801 selects light of a specific wavelength to pass through. After passing through the photomultiplier tube 27, the information is transmitted to the computer 25 by the acquisition card 28.

[0020] Specifically, the filter wheel 18 selects different wavelengths through the bandpass filter 1801. Based on the Rayleigh scattering cross section of nitrogen at different wavelengths, the expression for calculating the Rayleigh scattering extinction coefficient of nitrogen through the Rayleigh scattering cross section of nitrogen is as follows:

[0021]

[0022] In expression 1-1, The extinction coefficient of nitrogen Rayleigh scattering. The Rayleigh scattering cross section of nitrogen gas. This represents the nitrogen molecule concentration, corresponding to its purity.

[0023] Furthermore, the bandpass filter 1801 on the filter wheel 18 selects light of a specific wavelength band to pass through. The transmitted light is converted into an electrical signal by the photomultiplier tube 27. The computer 25 uses the information obtained by the acquisition card 28 and combines it with the position of the bandpass filter 1801 on the filter wheel 18 to determine the spectral intensity of the two standard gases, nitrogen and nitrogen dioxide, passing through the wavelength bands, respectively. and

[0024] Light source 1 emits a light beam, which undergoes multiple reflections within cavity 5. Each reflection results in one exit from the output end. By summing these reflections, the intensity of the exiting light can be obtained. Furthermore, by analyzing the changes in the intensity of the exiting light when the gas being measured is present or absent within cavity 5, the absorption coefficient of the gas being measured can be measured. The expression for this coefficient is:

[0025]

[0026] In expression 1-2, α abs (λ) is the total absorption coefficient of the measured gas, σ i (λ) is the absorption cross section of the gas i being measured, N i R(λ) represents the number concentration of the gas molecules being measured, R(λ) represents the reflectivity of the cavity mirror, and α represents the molecular concentration of the gas being measured. Ray I(λ) is the Rayleigh scattering extinction coefficient inside the cavity, I(λ) is the intensity of the emitted light when the cavity contains the gas being measured, and I0(λ) is the intensity of the emitted light when the cavity contains only air or nitrogen.

[0027] Specifically, by making a simple transformation of expression 1-2, we can obtain the expression for calculating the reflectivity of the optical resonant cavity mirror:

[0028]

[0029] In expressions 1-3, R(λ) represents the reflectivity of the laparoscope, and d represents the length of cavity 5. It is the molecular number concentration of nitrogen dioxide standard gas. It is the standard gas absorption cross section of nitrogen dioxide. The extinction coefficient of nitrogen Rayleigh scattering. For nitrogen spectral intensity, The standard gas spectral intensity of nitrogen dioxide is used, and the reflectivity of the lens at different wavelengths can be automatically calibrated using expressions 1-3.

[0030] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An online automatic measurement device for the reflectivity of an optical resonant cavity mirror, characterized in that, include: The system includes a light source module for providing a measurement beam; an optical resonant cavity module comprising a cavity with an inlet and an outlet for continuous reflection of light within the cavity to increase the optical path; a gas path module comprising a first gas path for supplying atmospheric gas, a second gas path for supplying nitrogen standard gas, and a third gas path for supplying nitrogen dioxide standard gas, each gas path being equipped with a flow valve and a mass flow meter, and the second and third gas paths each having a gas cylinder for storing the standard gas; and a detection and acquisition module comprising an optical fiber beam splitter, a spectrometer, a filter wheel, a photomultiplier tube, and a data acquisition card, wherein the optical fiber beam splitter outputs light from the cavity. The optical beam is split, with one path connected to a spectrometer via a probe fiber 1, and the other path connected sequentially to a filter wheel, a photomultiplier tube, and a data acquisition card via a probe fiber 2. The filter wheel has different bandpass filters to select specific wavelengths of light for passage. The control and drive module includes a computer, a control device, a drive device, and a stepper motor. The computer controls the flow valves of each gas path via the control device, and controls the filter wheel to switch bandpass filters via the drive device and the stepper motor. Based on the electrical signal acquired by the data acquisition card and the position of the bandpass filters on the filter wheel, the computer determines the nitrogen spectral intensity at the corresponding wavelength. and the spectral intensity of nitrogen dioxide standard gas The nitrogen Rayleigh scattering extinction coefficient is calculated according to the following formula: The computer calculates the total absorption coefficient of the gas being measured based on the change in light intensity of the emitted light when the gas being measured is present in the cavity, according to the following formula: Transforming the above equation, we obtain the laparoscope reflectivity: in, For the reflectivity of the endoscope, The length of the cavity. The Rayleigh scattering cross section of nitrogen gas. This refers to the number concentration of nitrogen molecules. This refers to the standard gaseous number concentration of nitrogen dioxide. The standard absorption cross section for nitrogen dioxide is given. The intensity of the emitted light when the cavity contains only nitrogen gas. The intensity of the emitted light when the cavity contains the gas being measured.

2. The online automatic optical resonant cavity mirror reflectivity measurement device according to claim 1, characterized in that, The optical resonant cavity module includes a cavity, a lens, a filter, and an aperture; the cavity has a first lens and an incident aperture at the incident end of the measurement beam, and a second lens and an exit aperture at the exit end of the measurement beam; the cavity has an air inlet, an air outlet, and a pressure gauge in its circumferential direction, and the pressure gauge is used to monitor the pressure inside the cavity.

3. The online automatic optical resonant cavity mirror reflectivity measurement device according to claim 2, characterized in that, The optical resonant cavity is circumferentially connected to the air inlet and air outlet. A dryer and a filter are provided outside the air inlet, and an air pump is connected to the air outlet to discharge the gas inside the cavity.

4. The online automatic reflectivity measurement device for an optical resonant cavity mirror according to claim 1, characterized in that, In the detection and acquisition module, the photomultiplier tube collects light intensity information and combines it with the wavelength corresponding to the filter wheel to return spectral information to the computer.

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