CN106018363A - Wavelength correction control system for dye laser - Google Patents

Abstract

The wavelength correction control system for a dye laser provided by the invention includes a dye laser, a sample pool, a signal detection unit, and a signal processing unit. The dye laser is output after frequency doubling by β-phase partial barium borate crystal, and the output laser after frequency doubling is split by the beam splitter and enters the sample pool through the entrance window; Eliminate interference, focus the fluorescent signal excited by the laser, collect the fluorescent signal through a photomultiplier tube, and monitor the laser energy signal with a photodiode. The signal acquisition card in the signal processing unit receives the signals collected by the photomultiplier tube and photodiode, and transmits them to the computer. The computer controls the parameters of the grating of the dye laser and the β-phase barium metaborate crystal through USB to adjust the laser output wavelength. The wavelength correction control system of the invention can realize the precise positioning of the wavelength of the dye laser on the excitation line of the substance to be measured, and the positioning accuracy is as high as 0.1pm.

Description

A Wavelength Correction Control System for Dye Laser

technical field

The invention relates to the technical field of atmospheric trace gas monitoring with relatively strong selective absorption and relatively narrow absorption line width in environmental monitoring. In particular, it relates to a wavelength correction control system for dye lasers.

Background technique

With the rapid development of the economy, environmental problems are becoming more and more serious, especially the problem of air pollution is getting more and more attention. The composition and concentration of polluting gases in the atmosphere are the primary concern in the control of air pollution. However, there are still many problems in the monitoring of trace gases with relatively strong activity and relatively low concentration in the atmosphere. Especially when laser-induced fluorescence technology is used to detect the concentration of the analyte, the laser excites the analyte to produce fluorescence, and the concentration of the analyte is obtained by detecting the intensity of the fluorescence; the most important thing in this method is to ensure that the laser wavelength and the vibration of the analyte The transitional absorption line produces resonance absorption, and the absorption coefficient is kept at the maximum position, so that the concentration of the analyte can be measured more accurately. Generally, better dye lasers have a temperature drift of 2pm/°C. When the absorption line width of the analyte is relatively narrow, in order to ensure the accuracy of the monitoring results, the long-term stability of the dye laser wavelength is a problem that must be solved. However, the stability of the laser wavelength itself is often not up to the stability required for monitoring. Therefore, how to improve the wavelength stability of the dye laser is an urgent problem for those skilled in the art.

Contents of the invention

The purpose of the present invention is to provide a wavelength correction control system for dye lasers, the control system can improve the stability of the wavelength of the dye laser, make the laser wavelength emitted by the dye laser stable for a long time, and then improve the concentration of trace gases in the atmosphere. monitoring accuracy.

To achieve the above object, the present invention provides a wavelength correction control system for dye lasers, including:

A sample cell, the sample cell includes an air inlet at the top of the sample cell, a vacuum port at the bottom of the sample cell, an incident window and an exit window symmetrically arranged on both sides of the sample cell, vertically arranged At the signal collection port on the other side of the sample pool, the vacuum pumping port is connected to a vacuum pump, and a pressure gauge is provided at the vacuum pumping port;

A dye laser is used to emit laser light. The emitting end of the dye laser is connected with a β-phase barium metaborate crystal, and a beam splitter is arranged between the β-phase barium metaborate crystal and the incident window. The beam splitter for splitting the laser light passing through the β-phase barium metaborate crystal;

A signal detection unit, the signal detection unit includes a fluorescence collection lens connected to the signal collection port, a photomultiplier tube connected to the fluorescence collection lens, and a photodiode arranged in the exit direction of the exit window; The laser light emitted by the dye laser is frequency-multiplied by the β-phase barium metaborate crystal, then split by the beam splitter, and the split laser light enters the sample cell through the incident window, and the materials in the sample cell pass through the Laser excitation to emit fluorescence, the photomultiplier tube collects signals through the signal collection port, and the photodiode collects signals emitted from the exit window;

A signal processing unit, the signal processing unit includes a signal acquisition card, a delay generator and a computer; the signal acquisition card is connected with the photomultiplier tube and the photodiode respectively, for receiving the photomultiplier tube and the photodiode The signal collected by the photodiode, the delay generator is respectively connected with the dye laser and the signal acquisition card for triggering the dye laser and the photodiode; the computer is connected to the signal Between the acquisition card and the dye laser, used for processing the signal passing through the signal acquisition card.

Optionally, the sample cell also includes airflow axes, laser axes, and detection axes that are perpendicular to each other and intersect at one point, the airflow axis is an axial passage connecting the air inlet and the vacuum port, The laser axis is an axial path connecting the incident window and the exit window, and the detection axis is an axial path in the extending direction of the signal collection port.

Optionally, the photocathode of the photomultiplier tube is arranged at the focal plane of the fluorescence collecting lens.

Optionally, the entrance window and the exit window are provided with windows coated with an anti-reflection film, and the symmetry axes of the two windows, the entrance window and the exit window form a Brewster angle.

Optionally, the photomultiplier tube is used to collect fluorescence signals generated in the sample cell, and the photodiode is used to collect laser energy signals passing through the sample cell.

Optionally, the signal acquisition card adopts a dual-channel high-speed acquisition card, one channel is used to collect the signal collected by the photomultiplier tube, and the other channel is used to collect the signal collected by the photodiode.

Optionally, the computer utilizes the trapezoidal rule to integrally process the signal collected by the signal collection card.

Another object of the present invention is to provide a wavelength correction control method for a dye laser, using the wavelength correction control system for a dye laser to perform wavelength correction control. The control method includes:

Set the laser emitted by the dye laser to output at a position 4-8pm greater than the absorption line of the sample substance;

Call the wavelength scanning function to scan the wavelength of the output laser;

Obtain the fluorescence signal collected by the photomultiplier tube, and obtain the laser energy signal collected by the photodiode;

Integrate and process the fluorescent signal using the trapezoidal rule to obtain a normalized fluorescent signal;

Comparing the normalized fluorescent signals to obtain the strongest value I of the fluorescent signal;

Scan the wavelength of the output laser again to obtain the fluorescence signal intensity;

Comparing the intensity of the fluorescent signal with the strongest value I of the fluorescent signal to obtain a comparison result;

When the comparison result shows that: when the fluorescence signal intensity is 0.95I, the laser output position of the re-scan output laser is the position of the excitation line of the analyte;

Judging whether the fluorescence signal intensity is less than the threshold 0.9I, and obtaining the judgment result;

When the judgment result indicates that the fluorescence signal intensity is less than the threshold value of 0.9I, the wavelength of the output laser is re-scanned to obtain the position of the excitation line of the analyte.

Optionally, when the judgment result indicates that the fluorescence signal intensity is greater than the threshold 0.9I, re-judgment whether the fluorescence signal intensity is less than the threshold 0.9I, and obtain the judgment result until the fluorescence signal intensity is less than the threshold 0.9I.

Optionally, the scanning of the wavelength of the output laser is performed every specific time.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: The wavelength correction control system for dye laser provided by the present invention includes a dye laser, a sample cell, a signal detection unit, and a signal processing unit. The dye laser is frequency-multiplied by β-phase metaborate crystals (β-BaB2O4 crystals, BBO crystals) and then output. After frequency-multiplied, the output laser beams are split by the beam splitter and enter the sample cell through the entrance window; the signal detection unit includes The fluorescence collection lens of the narrowband filter filters out the interference and focuses the fluorescence signal excited by the laser. The fluorescence signal is collected through the photomultiplier tube, and the photodiode monitors the laser energy signal. The signal acquisition card in the signal processing unit receives the signals collected by the photomultiplier tube and photodiode, and transmits them to the computer. The computer controls the parameters of the grating of the dye laser and the β-phase barium metaborate crystal through USB to adjust the laser output wavelength. The wavelength correction control system for dye laser provided by the present invention can realize the precise positioning of the wavelength of the dye laser on the excitation line of the substance to be measured, and the positioning accuracy is as high as 0.1pm; the present invention adopts computer automatic control without manual operation, and realizes Intelligent wavelength correction; using the absorption line of the substance to be measured as a reference, it is highly targeted. For the measurement of different trace substances, it only needs to adjust the sample in the sample cell, which has the ability to be transplanted.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is a schematic structural diagram of a wavelength correction control system for a dye laser provided by an embodiment of the present invention;

Fig. 2 is a flowchart of a wavelength correction control method for a dye laser provided by an embodiment of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a wavelength correction control system for a dye laser, comprising:

The sample cell 1, the sample cell 1 includes an air inlet 11 located at the top of the sample cell 1, a vacuum port 12 located at the bottom of the sample cell 1, and an incident window 13 and an exit window 14 symmetrically arranged on both sides of the sample cell 1, vertically The signal collection port 15 located on the other side of the sample cell 1 is connected to a vacuum pump (not shown in the figure) at the vacuum port 12 , and a pressure gauge 16 is provided at the vacuum port 12 . The sample cell 1 in this embodiment is a 140*100*90mm aviation aluminum cavity, and the inner and outer shells need to be anodized and blackened to reduce stray light and improve the detection accuracy of fluorescence signals and laser energy signals. . The windows of the entrance window 13 and the exit window 14 are sealed with quartz windows coated with an anti-reflection film. The symmetry axes of the two windows and the entrance window 13 and the exit window 14 form a Brewster angle, which is to reduce the reflected light . The sample cell also includes an air flow axis, a laser axis and a detection axis that are perpendicular to each other and intersect at one point. The axial passage of the window 14, the detection axis is the axial passage of the signal collection port 15 extending direction. The design of the three axes perpendicular to each other can reduce the interference of laser stray light, facilitate the excitation and detection of fluorescence, and improve the detection accuracy. The upper part of the airflow axis is ventilated by the air inlet 11, and the lower part is connected to the vacuum pump by the vacuum port 12, and the air pressure in the sample pool is monitored through the membrane vacuum pressure gauge 16. The air pressure of the system remains consistent.

The dye laser 2 is used to emit laser light. The emitting end of the dye laser 2 is connected with a β-phase barium metaborate crystal 3, and a beam splitter 4 is arranged between the β-phase barium metaborate crystal 3 (BBO crystal) and the incident window 13 to split The beam mirror 4 is used to split the laser beam passing through the β-phase barium metaborate crystal 3; in this embodiment, the dye laser 2 is a dye laser pumped by a YAG laser, and its wavelength varies with temperature to 2pm/°C. The wavelength adjustment accuracy after frequency doubling is 0.1pm. A specific beam splitter 4 splits about 8% of the laser light entering the sample cell 1 . According to the needs of the positional relationship between the dye laser 2 and the sample pool 1, the laser beam split by the beam splitter 4 can also be turned into the sample pool 1 by a turning mirror (not shown in the figure), so as to facilitate the sample pool 1 and the placement of the dye laser 2.

Signal detection unit 5, signal detection unit 5 comprises the fluorescence collection lens 51 that is connected to signal acquisition port 15, the photomultiplier tube 52 that is connected with fluorescence collection lens 51, is located at the photodiode 53 on exit window 14 exit direction; Dye laser 2. After the emitted laser is doubled in frequency by the β-phase metaborate crystal, it is split by the beam splitter 4, and the split laser enters the sample pool 1 through the incident window 13, and the substances in the sample pool 1 are excited by the laser to emit For fluorescence, the photomultiplier tube 52 collects signals through the signal collection port 15 , and the photodiode 53 collects signals emitted from the exit window 14 .

Signal processing unit 6, signal processing unit 6 comprises signal acquisition card 61, delay generator 62 and computer 63; Signal acquisition card 61 is connected with photomultiplier tube 52 and photodiode 53 respectively, is used to receive photomultiplier tube 52 and photoelectricity For the signal collected by the diode 53, the delay generator 62 is connected with the dye laser 2 and the signal acquisition card 61 respectively to trigger the dye laser 2 and the photodiode 53; the computer 63 is connected between the signal acquisition card 61 and the dye laser 2, It is used to process the signal passing through the signal acquisition card 61 and control the dye laser 2 to emit laser with a certain wavelength.

The dye laser 2 in this embodiment is output after being frequency-multiplied by a β-phase barium metaborate crystal 3 (β-BaB2O4 crystal, BBO crystal). Enter the sample pool 1; the signal detection unit 5 contains a fluorescence collection lens 51 with a narrow-band filter to filter out interference and focus the fluorescence signal excited by the laser, and collect the fluorescence signal through the photomultiplier tube 52, and the photodiode 53 monitors the laser energy signal . In the signal processing unit 6, the signal acquisition card 61 receives the signal collected by the photomultiplier tube 52 and the photodiode 53, and sends it to the computer 63, and the computer 63 controls the parameters of the grating of the dye laser 1 and the β-phase barium metaborate crystal 3 through USB, so as to Adjust the laser output wavelength. The wavelength correction control system for dye laser provided by the present invention can realize the precise positioning of the wavelength of the dye laser on the excitation line of the substance to be measured, and the positioning accuracy is as high as 0.1pm; the present invention adopts computer automatic control without manual operation, and realizes Intelligent wavelength correction; using the absorption line of the substance to be measured as a reference, it is highly targeted. For the measurement of different trace substances, it only needs to adjust the sample in the sample cell, which has the ability to be transplanted.

As an optional implementation manner, the photocathode of the photomultiplier tube 52 is arranged at the focal plane of the fluorescence collecting lens 51, so as to improve the accuracy of obtaining fluorescence signals. The photomultiplier tube 52 is used to collect the fluorescent signal generated in the sample cell, and the photodiode 53 is used to collect the laser energy signal after passing through the sample cell. The signal acquisition card 61 adopts a dual-channel high-speed acquisition card, wherein one channel is used to collect the signal collected by the photomultiplier tube 52, and the other channel is used to collect the signal collected by the photodiode 53. The dual-channel high-speed acquisition card is used to separate the two signals. Acquisition ensures no signal interference and high acquisition efficiency.

As an optional embodiment, the computer 63 utilizes the trapezoidal rule integral to process the signal collected by the signal acquisition card 61. Of course, Simpson integral and Bode integral processing methods can also be used. In this embodiment, the trapezoidal rule integral processing method is selected to make the calculation easier , which in turn can reduce the computational burden of the program and improve the efficiency of the system for detecting fluorescence.

In the above embodiments, the dye laser 2 is a high repetition rate pulsed dye laser, and the delay generator 62 triggers the dye laser 2 and the photodiode 53 to ensure that the fluorescence signal and the laser energy signal are captured in time.

In the above embodiments, the airtightness of the control system should be ensured to avoid interference to the system by air trace gases, especially for analytes with relatively strong reactivity.

Another object of the present invention is to provide a wavelength correction control method for a dye laser, using the wavelength correction control system for a dye laser to perform wavelength correction control. The control method includes:

Step 201: Setting the laser emitted by the dye laser to output at a position 4-8pm greater than the absorption line of the sample substance;

Step 202: calling the wavelength scanning function to scan the wavelength of the output laser;

Step 203: Obtain the fluorescent signal collected by the photomultiplier tube, and obtain the laser energy signal collected by the photodiode;

Step 204: using the trapezoidal rule to integrate and process the fluorescent signal to obtain a normalized fluorescent signal;

Step 205: Comparing the normalized fluorescent signals to obtain the strongest value I of the fluorescent signal;

Step 206: scanning the wavelength of the output laser again to obtain the fluorescence signal intensity;

Step 207: Comparing the intensity of the fluorescence signal with the strongest value I of the fluorescence signal to obtain a comparison result;

When the comparison result shows that: when the fluorescence signal intensity is 0.95I (the threshold value 0.95I is different due to the difference in the stability of each system), the laser output position of the scanning output laser is the position of the excitation line of the object to be measured;

Step 208: Judging whether the fluorescence signal intensity is less than the threshold 0.9I (the specific threshold needs to be set according to the specific conditions of the system), and obtaining the judgment result;

When the judgment result indicates that the fluorescence signal intensity is less than the threshold value of 0.9I, the wavelength of the output laser is re-scanned to obtain the position of the excitation line of the analyte.

As an optional implementation, in the above method, when the judgment result indicates that the fluorescence signal intensity is greater than the threshold value 0.9I, re-judgment whether the fluorescence signal intensity is less than the threshold value 0.9I, and obtain the judgment result until the fluorescence signal intensity is less than the threshold value 0.9I .

As an optional implementation, scanning the wavelength of the output laser is carried out once at a specific time. In this embodiment, the specific time is 30 minutes. In this way, the wavelength scanning at a fixed time reduces the concentration fluctuation of high-concentration test samples on wavelength positioning. Influenced by this, the accuracy of the positioning of the excitation line of the object under test is improved.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. the wavelength Correction and Control system for dye laser, it is characterised in that including:

Sample cell, described sample cell includes the air inlet being located at described sample cell top, is located at described sample cell The vacuum orifice of bottom, is symmetrically set in entrance window and the exit window of described sample cell both sides, is vertical at described The signals collecting mouth of sample cell another side, described vacuum orifice connects vacuum pump, and described vacuum orifice Place is provided with piezometer；

Dye laser, is used for launching laser, and the transmitting terminal of described dye laser connects β phase metaboric acid Crystal of barium, is provided with beam splitter between described β phase barium metaborate crystal and described entrance window, described beam splitter is used In being split through the laser of described β phase barium metaborate crystal；

Acquisition of signal unit, described acquisition of signal unit includes the phosphor collection being connected to described signals collecting mouth Camera lens, the photomultiplier tube being connected with described phosphor collection camera lens, it is located in described exit window exit direction Photodiode；Described dye laser launch laser after described β phase barium metaborate crystal double frequency, Through described beam splitter beam splitting, the laser after beam splitting enters in described sample cell by described entrance window, described sample Material in product pond launches fluorescence through laser excitation, and described photomultiplier tube is adopted by described signals collecting mouth Collection signal, described photodiode gathers the signal of described exit window injection；

Signal processing unit, described signal processing unit includes data acquisition card, delay time generator and computer； Described data acquisition card is connected with described photomultiplier tube and described photodiode respectively, is used for receiving institute State the signal that photomultiplier tube and described photodiode gather, described delay time generator respectively with described dyestuff Laser instrument is connected with described data acquisition card, is used for triggering described dye laser and described photoelectricity two pole Pipe；Described computer is connected between described data acquisition card and described dye laser, is used for processing process The signal of described data acquisition card.

Wavelength Correction and Control system for dye laser the most according to claim 1, its feature Being, described sample cell also includes air stream axle, laser axis and the detection being mutually perpendicular to two-by-two and intersecting at a point Axle, described air stream axle is to connect described air inlet and the axial passageway of described vacuum orifice, and described laser axis is Connecting described entrance window and the axial passageway of described exit window, described detection axis is that described signals collecting mouth extends The axial passageway in direction.

Wavelength Correction and Control system for dye laser the most according to claim 1, its feature Being, the photocathode of described photomultiplier tube is located at the focal plane of described phosphor collection camera lens.

Wavelength Correction and Control system for dye laser the most according to claim 1, its feature Being, described entrance window and described exit window are provided with the window being coated with anti-reflection film, window described in two with described enter The axis of symmetry penetrating window and described exit window is Brewster's angle.

Wavelength Correction and Control system for dye laser the most according to claim 1, its feature Being, described photomultiplier tube is for gathering the fluorescence signal produced in described sample cell, described photoelectricity two pole Pipe is for gathering the laser energy signal after described sample cell.

The most according to claim 1 or 5 for the wavelength Correction and Control system of dye laser, its Being characterised by, described data acquisition card uses dual channel high speed capture card, and one of them passage is used for gathering institute Stating the signal that photomultiplier tube gathers, another passage is for gathering the signal that described photodiode gathers.

7. the wavelength control method for correcting of a dye laser, it is characterised in that utilize such as claim The wavelength Correction and Control system for dye laser described in 1 carries out wavelength Correction and Control, control method bag Include:

The laser setting dye laser transmitting is exporting more than sample material Absorption Line 4-8pm position；

Call length scanning function the wavelength of Output of laser is scanned；

Obtain the fluorescence signal that photomultiplier tube gathers, obtain the laser energy signal that photodiode gathers；

Utilize fluorescence signal described in trapezoidal rule Integral Processing, it is thus achieved that normalized fluorescence signal；

Relatively described normalized fluorescence signal, it is thus achieved that fluorescence signal intensity values I；

Again scan the wavelength of Output of laser, obtain fluorescence signal intensity；

Relatively described fluorescence signal intensity and described fluorescence signal intensity values I, it is thus achieved that comparative result；

When described comparative result represents: when described fluorescence signal intensity is 0.95I, described again scan output The laser outgoing position of laser is determinand excitation line position；

Judge that whether described fluorescence signal intensity is less than threshold value 0.9I, it is thus achieved that judged result；

When described judged result represents: described fluorescence signal intensity is less than threshold value 0.9I, rescan output and swash The wavelength of light, obtains determinand excitation line position.

The wavelength control method for correcting of dye laser the most according to claim 7, it is characterised in that When described judged result represents: described fluorescence signal intensity is more than threshold value 0.9I, rejudge described fluorescence letter Whether number intensity is less than threshold value 0.9I, it is thus achieved that judged result, until described fluorescence signal intensity is less than threshold value 0.9I。

The wavelength control method for correcting of dye laser the most according to claim 7, it is characterised in that The every special time of wavelength of described scanning Output of laser is carried out once.