Glass bottle for gas concentration detection and concentration detection method and system thereof

Abstract

The present invention discloses a glass bottle for gas concentration detection and a concentration detection method and system thereof. The glass bottle encapsulates a gas to be detected and includes an incident light path, a cylindrical reflection channel, and an exit light path. The incident light path is located at the upper edge of the cylindrical reflection channel, the cylindrical reflection channel is located in the middle part of the glass bottle, and the exit light path is located at the lower edge of the cylindrical reflection channel and directly below the incident light path. The method uses a laser to shoot the laser obliquely downward from the incident light path into the glass bottle, and after multiple reflections through the cylindrical reflection channel, it is emitted from the exit light path. The present invention overcomes the problem of extremely short gas absorption optical path under direct laser transmission through a glass medicine bottle by a total reflection coating on the outer wall of the glass bottle, greatly improves the absorption optical path of trace gases in the glass bottle, and bypasses the bottle body diameter direction that causes optical interference, suppresses optical wave interference to a large extent, and thus greatly improves the accuracy of gas concentration detection in the bottle.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas concentration detection, and specifically relates to a glass bottle for gas concentration detection which is designed by optimizing the internal reflection light path surrounded by a cylindrical surface of a sealed glass bottle, and a concentration detection method and system thereof. Background Art

[0002] There are often a lot of interferences in the actual production process in an open environment. For example, the variability of temperature and humidity in various complex industrial production environments, the uncertain exposure at the detection site, and noise interference such as mechanical vibration all pose huge challenges to the detection accuracy of trace gas concentrations in packaged glass medicine bottles. In order to achieve high-precision detection of trace gas concentrations in packaged glass medicine bottles, the current general technology mostly adopts methods such as shortening the distance that the laser is exposed to the air outside the bottle, filling a certain inert gas (such as nitrogen) in the entire detection background to isolate the air, or continuously purging a certain gas outside the laser absorption spectrum to reduce the contact between the laser and the air outside the bottle to be detected. The above methods are very demanding on the production environment.

[0003] The limited absorption path in the sterile preparation packaged medicine bottle is the main obstacle that restricts the TDLAS technology from realizing high-sensitivity gas detection. At present, the companies at the forefront of technology, such as the American Lighthouse, German BOSCH and Italian Brevetti, all create a closed environment for detection. The actual absorption path of the laser in the glass bottle is the diameter length of the glass bottle. This extremely short absorption length will inevitably limit the accuracy and stability of laser detection. In the conventional method of open environment detection, since the trace gas concentration detection embodiment process in the glass bottle is carried out in an open environment, that is, the total optical path from the laser emitted by the laser to the laser received by the detector, the optical path exposed in the open environment is much larger than the effective light absorption path in the bottle, which leads to the frequent errors in the method of directly transmitting the glass bottle to detect the trace gas concentration in the bottle in an open environment. Therefore, it is urgent to consider the present invention to study the geometric characteristics of the glass medicine bottle and solve the technical bottleneck of the limited absorption path in the packaged medicine bottle, so as to improve the accuracy and stability of laser detection. Summary of the invention

[0004] The purpose of the present invention is to solve the technical bottleneck of limited absorption optical path in packaged medicine bottles, and propose a new method for optimizing the design of cylindrical surround internal reflection optical path, which effectively increases the absorption optical path of laser in glass bottles, thereby improving the accuracy and stability of laser detection.

[0005] On the one hand, the present invention provides a glass bottle for gas concentration detection, wherein the gas to be measured is encapsulated in the glass bottle, and a layer of laser anti-reflection film is coated on the outer wall of the glass bottle, and the glass bottle and the laser anti-reflection film form a cylindrical reflection channel;

[0006] The upper and lower edges of the cylindrical reflection channel are respectively provided with an incident light path opening and an outgoing light path opening, and the incident light path opening and the outgoing light path opening are on the same vertical line;

[0007] The incident light path port is used for incident laser light to enter, and the laser light emitted from the exit light path port is collected and used to calculate the concentration of the gas in the glass bottle.

[0008] The present invention studies the geometric characteristics of glass medicine bottles, focuses on the parallel transparent cylindrical part below the bottleneck of the glass medicine bottle, explores the geometric law of the impact of the incident angle on the multiple reflections and refractions of the laser in the bottle, analyzes the optical conditions for exciting multi-beam interference in the bottle, utilizes the laser wave characteristics by reverse thinking, establishes a mathematical model of the impact of the gas absorption light path in the glass bottle on key optical factors such as the laser incident point, exit point, number of internal reflections, and surround mode, conducts research on the laser particle characteristic enhancement method for optimizing the gas absorption light path in the bottle and suppressing multi-beam interference, greatly increases the absorption light path of the laser in the packaged glass bottle, thereby achieving the effect of relatively weakening the influence of the open environment on the accuracy of detecting the gas concentration in the glass bottle.

[0009] Optionally, the effective absorption optical path length of the laser in the cylindrical reflection channel is:

[0010]

[0011] Wherein, L is the effective absorption optical path length of the laser in the cylindrical reflection channel, M is the number of effective absorption optical path segments of the laser in the glass bottle, l1 is the projection length of an effective absorption optical path on the XY plane, and h1 is the descending height of an effective absorption optical path; wherein, the distance that the laser passes through the gas in the bottle on the inner wall of the glass and contacts the inner wall of the glass bottle again is respectively regarded as an effective absorption optical path.

[0012] Optionally, the calculation formula for the number of effective absorption optical path segments M of the laser in the glass bottle is as follows:

[0013]

[0014] Where H is the height of the laser anti-reflection film coating on the outer glass bottle, m represents the refractive index of the laser from air to the bottle wall, r1 represents the radius of the outer wall of the glass bottle, r2 represents the radius of the inner wall of the glass bottle, α1 is the angle between the projection of the laser incident angle on the XZ plane and the X-axis, and n is the side length of the projection shape of the effective optical path of the laser in the bottle on the XY plane, which is a regular n-gon.

[0015] Optionally, the calculation formulas for the projection length l1 of a section of effective absorption optical path on the XY plane and the descending height h1 of a section of effective absorption optical path are as follows:

[0016]

[0017]

[0018] Among them, r1 represents the radius of the outer wall of the glass bottle, r2 represents the radius of the inner wall of the glass bottle, α2 represents the angle between the projection of the incident angle on the XY plane and the X-axis, α1 represents the angle between the projection of the laser incident angle on the XZ plane and the X-axis, and n represents the side length of the projection shape of the effective optical path of the laser in the bottle on the XY plane, which is a regular n-gon.

[0019] Optionally, the equivalent relationship between n and α2 is as follows:

[0020]

[0021] Where m represents the refractive index of the laser from air to the bottle wall.

[0022] Optionally, the glass bottle is a glass medicine bottle.

[0023] In another aspect, the present invention provides a method for detecting gas concentration, comprising the following steps:

[0024] S1: The laser control module emits laser light from the laser incident light path port to the glass bottle to be inspected at a predetermined angle;

[0025] Wherein, the glass bottle to be inspected is the glass bottle mentioned above, and the incident laser is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path;

[0026] S2: The laser detector receives the laser transmitted from the laser exit light path, and obtains the gas concentration in the glass bottle according to the optical path of the laser in the glass bottle and the second harmonic current signal converted from the photoelectric signal received by the photoelectric detector.

[0027] Optionally, the concentration of the gas is given by:

[0028]

[0029] In the formula, i 2fmax is the peak value of the second harmonic current signal, which is obtained by converting the laser into a current signal after the laser detector acquires the laser and performing orthogonal demodulation with the double frequency of the high-frequency signal of the signal generator; L is the effective absorption optical path length of the laser in the cylindrical reflection channel, S is the second harmonic term coefficient, and N is the concentration of the gas.

[0030] Optionally, the gas is a trace gas, and the trace gas is oxygen. In a third aspect, the present invention provides a detection system based on the gas concentration detection method, comprising: a laser control module, a laser source, a glass bottle, a laser detector, a signal generator, and a data processor;

[0031] Wherein, the laser control module is connected to the laser source and is used to control the laser source to emit laser toward the incident light path of the glass bottle;

[0032] The laser is incident through the incident light path opening on the glass bottle, and is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path opening;

[0033] The laser detector is arranged at a position corresponding to the exit light path on the glass bottle, and is used to collect the laser emitted from the exit light path and convert it into a current signal;

[0034] The signal generator is connected to the laser detector and is used to perform orthogonal demodulation on the current signal and the double frequency of the high-frequency signal to extract the second harmonic signal;

[0035] The data processor is used to calculate the concentration of the gas to be detected in the glass bottle by using the second harmonic signal and the effective absorption optical path length of the laser in the cylindrical reflection channel.

[0036] Beneficial Effects

[0037] The glass bottle described in the present invention is coated with a layer of laser anti-reflection film on the outer wall of the glass bottle body, so that the laser enters the glass bottle from the incident light path at a predetermined oblique downward incident angle, and the total reflection coating on the outer wall of the glass bottle reflects the laser in the bottle multiple times, thereby obtaining a longer absorption light path of a certain gas in the bottle, thereby overcoming the problem of extremely short gas absorption light path under the direct transmission of laser in the glass medicine bottle in the prior art; in a further preferred embodiment, the laser bypasses the bottle body diameter direction that causes optical interference, thereby maximally suppressing wave interference, thereby greatly improving the accuracy and stability of gas concentration detection in the bottle. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the principle of the present invention;

[0039] Figure 2 (a) and (b) are schematic sketches of a light trace in a bottle projected into a regular triangle-like structure on the XZ and XY planes provided by an embodiment of the present invention;

[0040] Figure 3 (a) and (b) are schematic sketches of another embodiment of the present invention, in which the projection of the light trace in the bottle on the XZ and XY planes is a regular quadrilateral-like structure;

[0041] Figure 4 It is the second harmonic current detected by the detector after the laser directly passes through the glass bottle, where the oxygen concentration in the standard bottle is 5%;

[0042] Figure 5It is an embodiment of the present invention. After the laser passes through the cylindrical reflection channel of the present invention, the detector detects the second harmonic current, wherein the light trace in the bottle is a regular triangle, two reflection cycles, and the oxygen concentration of the standard bottle is 5%;

[0043] Figure 6 It is another embodiment of the present invention. After the laser passes through the cylindrical reflection channel of the present invention, the detector detects the second harmonic current, wherein the light trace in the bottle is a regular quadrilateral, there are two reflection cycles, and the oxygen concentration of the standard bottle is 5%. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the conventional method of open environment detection, since the trace gas concentration detection embodiment process in the glass bottle 30 is carried out in an open environment, the sum of the distance from the laser to the incident light path 301 of the glass bottle plus the distance from the exit light path 303 of the glass bottle to the laser detector is much larger than the diameter of the glass bottle to be tested, that is, in the total optical path from the laser emitted by the laser to the laser received by the detector, the optical path exposed to the open environment is much larger than the effective light absorption path in the bottle. This leads to frequent errors in the method of directly transmitting the glass bottle to detect the trace gas concentration in the bottle in an open environment, that is, when detecting the same glass medicine bottle, the second harmonics obtained by the first and second detections have a large amplitude fluctuation, such as Figure 4 As shown, the signal of the laser directly transmitting the glass medicine bottle, the peak value of the amplitude jitter of the demodulated current second harmonic is basically between the interval 5 and 6, and the valley value is basically between 10 and 11. The range thresholds of the four second harmonic fluctuations in the figure occupy a large proportion of the entire peak value. Among them, the difference between the valley value 9 of the first second harmonic and the valley value 8 of the second second harmonic accounts for one-third of the peak-to-valley value of the second second harmonic, and the difference between the valley value 9 and the valley value 7 of the third second harmonic is even greater. As a whole, this leads to a large change in the calculation of oxygen content in the same bottle at different times when the peak value is used for concentration inversion, so there is a poor detection accuracy.

[0046] In this regard, the present invention provides a glass bottle for gas concentration detection and a concentration detection method and system thereof, which are used to obtain a longer absorption optical path of a gas in the bottle, thereby solving the problem of poor detection accuracy caused by the short absorption optical path. In the following embodiments, glass medicine bottles and trace oxygen are used as examples. In other feasible embodiments, no specific limitation is made to this, and adaptive adjustments can be made according to actual needs. That is, it should be understood that the scheme described in the present invention can be applied to non-trace gases. In this embodiment, trace oxygen often refers to the possibility of leakage in "sterile preparations packaged in medicines", and leakage causes oxygen (trace oxygen) to enter the glass bottle.

[0047] See also Figure 1 FIG. 1 is a stereogram of a cylindrical surround internal reflection form provided in an embodiment of the present invention, see Figure 2 and Figure 3 The figures are the front view and top view of two different cylindrical surround internal reflection embodiments, showing the angle at which the laser enters the glass bottle at the incident light path, the number of effective absorption optical path segments of the laser in the cylindrical reflection channel and the shape of the projection on the XY plane. Figure 1 It only shows that the light trace in the glass bottle is triangular and the number of effective absorption optical path segments is 12. It should be understood that the present invention is not limited to this.

[0048] The embodiment of the present invention provides a glass bottle 30 with cylindrical surround internal reflection, and the glass bottle 30 includes an incident light path opening 301, a cylindrical reflection channel 302, and an outgoing light path opening 303. The incident light path opening 301 and the outgoing light path opening 303 are respectively located at the upper edge and the lower edge of the cylindrical reflection channel 302, and the incident light path opening 301 and the outgoing light path opening 303 are on the same vertical line. The purpose is to make the laser emitter and the laser detector located on the same side. The cylindrical reflection channel 302 is located in the middle of the glass bottle, and the specific position is determined by multiple factors such as the shape and height of the glass bottle, the physical state and height of the drug in the bottle. Without loss of generality, the diameter of a 10ml syringa bottle is 22mm, the height of the bottle is 37mm, and the height of the solid drug at the bottom of the general bottle is 10mm, so the lower boundary of the cylindrical reflection channel is taken as 15mm from the bottom of the bottle, and the upper edge is taken as 35mm from the bottom of the bottle, that is, the height of the cylindrical reflection channel is 20mm.

[0049] The cylindrical reflection channel 302 can be realized by coating a total reflection anti-reflection film on the outer wall of the glass bottle, and its absorption spectrum range is outside the wavelength range of the laser, and the scanning wavelength of the laser covers the absorption spectrum of the trace gas to be detected. In the embodiment of the present invention, the anti-reflection film is not limited to a specific material.

[0050] See also Figure 1As shown, the laser enters the medicine bottle 30 to be tested from the light channel opening 301 at a predetermined angle and obliquely downwards. The laser entering the glass bottle is absorbed by the trace gas within the spectrum range. When the laser touches the glass inner wall of the cylindrical reflection channel, it is refracted and enters the glass bottle wall. When the laser in the bottle wall touches the outer wall coating of the cylindrical reflection channel, total reflection occurs. Finally, the laser reflected in the bottle wall is refracted into the glass bottle. That is, the incident light path 301 is the position where the laser enters the glass bottle. When the laser enters the glass bottle from the air through the incident light path, it will experience refraction from the air to the glass wall and re-refraction from the glass bottle wall to the inside of the glass bottle; the cylindrical reflection channel 302 is used to expand the effective absorption optical path of the laser in the bottle. In the reflection channel, the laser will experience refraction from the inside of the glass bottle to the glass bottle wall, reflection from the glass bottle wall to the coating on the outer wall of the glass bottle, and refraction from the glass bottle wall to the inside of the glass bottle, and so on, spiraling downward repeatedly until the laser reflection times reach a predetermined number, and then it will be emitted from the exit light path 303 below the coating, thereby achieving the purpose of increasing the effective absorption optical path of the laser in the glass bottle to be tested. The exit light path 303 is the specific position where the laser in the bottle is transmitted out of the glass bottle, during which the laser will experience refraction from the inside of the glass bottle to the glass bottle wall and refraction from the glass bottle wall to the air outside the bottle.

[0051] The predetermined incident angle can be decomposed into an angle α2 between the projection on the XY plane and the X axis and an angle α1 between the projection on the XZ plane and the X axis; by controlling the incident angle component α2, the projection of the laser light path in the bottle on the XY plane can be formed into a predetermined required quasi-regular n-gon; at the same time, by controlling the incident angle component α1, the laser can go around a predetermined integer circle in the bottle, and the number of effective optical path segments of the laser in the bottle is an integer multiple of n, so that the laser can be emitted from the predetermined laser exit light path opening 303. For example, by controlling the angle α2, the laser light path in the bottle is a quasi-regular quadrilateral, and by controlling the angle α1, the number of circling cycles is 2, that is, the number of effective optical paths of the laser in the glass bottle is 8, and finally the laser is emitted from the laser exit light path opening. Therefore, according to actual needs and application effects, the angle α1 and the angle α2 are adjusted to meet the application needs.

[0052] Among them, the distance that the laser passes through the incident light path opening 301 from the inner wall of the glass through the gas in the bottle to contact the inner wall of the glass bottle again is the first effective absorption light path; due to the characteristics of the cylindrical reflection channel 302, there will be a second section, a third section..., and the length of each effective absorption light path is the same.

[0053] Theoretical analysis:

[0054] Conventional method In open environment detection, if the direct transmission method is used to detect the concentration of trace gas in the bottle, the light intensity signal I(t) detected by the photoelectric detector is:

[0055] I(t)=I0(t)·exp[-S1(T)N1L1P1g(v)]·exp[-S(T)NLPg(v)] (1)

[0056] In this embodiment, a cylindrical reflection channel is added to the detection glass bottle, and the effective absorption optical path L of the laser with an emission light intensity of I0(t) in the glass bottle is significantly improved compared with the effective absorption optical path of direct transmission. Therefore, the weight of the absorption term exp[-S(T)NLPg(v) of the laser in the bottle in the above formula is increased, and the weight of the absorption term exp[-S1(T)N1L1P1g(v)] of the laser outside the bottle in the total light intensity absorption is relatively reduced; when the effective absorption optical path of the laser in the bottle is made large enough through the cylindrical reflection channel, the absorption term exp[-S1(T)N1L1P1g(v)] of the laser outside the bottle can be ignored, which greatly weakens the interference of external environmental noise, thereby improving the detection accuracy and stability of trace gas concentration in the glass medicine bottle.

[0057] That is, after the laser passes through multiple reflections in the cylindrical reflection channel in the detection bottle, the current signal i(t) after the laser coming out from the exit light path 303 is converted by the photoelectric detector is calculated as follows:

[0058] i(t)=i0(t)exp[-S(T)NLPg(v)] (2)

[0059] Among them, i0(t) is the injection current of the laser, S(T) is the absorption line intensity at temperature T, which is only a function of temperature T, N is the volume concentration of the trace absorption gas in the bottle, L is the effective absorption optical path of the laser in the bottle, P is the static total pressure of the gas, and g(v) is the absorption line linear function.

[0060] Furthermore, the laser is emitted from a predetermined exit light path, and the laser detector obtains the exit laser, converts it into a current signal, and then performs orthogonal demodulation with the double frequency of the high-frequency signal of the signal generator, thereby extracting the second harmonic signal i of the current. 2f (t), which is calculated as follows:

[0061] i 2f (t) = i0(t)NLScos(2wt) (3)

[0062] Where i0(t) is the laser injection current, S is the second harmonic term coefficient, w is the angular frequency of the second harmonic current signal, and t is time.

[0063] Finally, the oxygen concentration information in the glass bottle is inverted according to the peak value of the second harmonic, and the calculation formula is as follows:

[0064]

[0065] Among them, i 2fmax is the peak value of the second harmonic current signal.

[0066] Since there are relatively good existing processing methods for the above-mentioned concentration inversion, it is not the focus of this application and will not be elaborated here.

[0067] Specifically, when the laser is inside the bottle 30 to be tested, the projection of the first effective light absorption path on the XY plane is:

[0068]

[0069] r1 represents the radius of the outer wall of the glass bottle, r2 represents the radius of the inner wall of the glass bottle, and α2 represents the angle between the projection of the incident angle on the XY plane and the X-axis.

[0070] Furthermore, by controlling the component α2 of the laser incident angle, the polygonal shape of the projection of the light trace in the bottle on the XY plane can be determined. The equivalent relationship between the side length of the regular n-gon and α2 is as follows:

[0071]

[0072] Wherein, m represents the refractive index of the laser from air to the bottle wall, and n is the length of the side of the projection shape of the effective optical path of the laser in the bottle on the XY plane. The quasi-regular n-gon is a quasi-regular triangle, a quasi-square, a quasi-regular pentagon, or a quasi-polygon with other values.

[0073] Furthermore, the angle between the laser incident angle and the Z axis determines the number of effective absorption optical path segments of the laser in the cylindrical reflection channel. The height h1 that the laser drops in each effective absorption optical path is calculated as follows:

[0074]

[0075] Where α1 is the angle between the projection of the laser incident angle on the XZ plane and the X axis.

[0076] See also Figure 2 The projection of the light trace on the XY plane, the projection of the light trace AB of the bottle wall on the horizontal axis is approximately equal to the thickness AC of the glass bottle wall. Under this premise, the calculation formula for the vertical distance the light trace descends in the process of passing through the glass bottle wall is:

[0077]

[0078] Where β1 is the angle between the projection of the laser refraction angle on the air-glass bottle wall in the XZ plane and the X-axis.

[0079] The calculation formula for the effective absorption path length M of the laser in the glass bottle is as follows:

[0080]

[0081] Among them, M is also an integer multiple of n, and H is the height of the cylindrical coating.

[0082] Furthermore, the calculation formula for the effective absorption optical path length of the laser in the cylindrical reflection channel is as follows:

[0083]

[0084] In the above formula, L, S, i0(t), i 2fmax It is linearly related to the gas concentration N; the outer radius r1, inner radius r2, refractive index m and coating height H of the detection bottle are all determined.

[0085] The following is a more detailed explanation of the embodiments of the present invention through examples. The glass medicine bottle we currently use has an outer radius r1 = 11 mm, an inner radius r2 = 10 mm, a coating height H = 20 mm, and a refractive index of the glass m = 1.51. Figure 2 Without loss of generality, the projection of the light trace on the XY plane is assumed to be a quasi-equilateral triangle. Through the above calculation formula (6), it can be deduced that the angle α2=28.74° between the laser incident from the incident light path and the XY plane; at the same time, α2 is substituted into the calculation of formula (5) to obtain the side length l1=16.97mm of the quasi-equilateral triangle. It is assumed that two quasi-equilateral triangles can be achieved in the cylindrical reflection channel, that is, the laser has 6 effective absorption light paths in the bottle. Therefore, the angle α1=11.76° between the incident angle and the Z axis can be obtained through formula (9). According to formula (7), the descending height h1=3.06mm of each effective absorption light path in the bottle can be calculated, so the incident angle of the laser controls the total effective absorption light path L=103.46mm of the laser in the bottle. Finally, the concentration of trace gas in the bottle is inverted by processing the light intensity signal after the laser penetrates the glass bottle.

[0086] See also Figure 5 As shown in FIG. 1 , it is a schematic diagram of the second harmonic of four consecutive cycles measured after the laser passes through the cylindrical reflection channel in one embodiment of the present invention, wherein the laser reflection light trace in the bottle is a regular triangle and the operation period is two triangular periods. It can be seen that the peak value fluctuation of the second harmonic in the figure is within the 12th and 13th thresholds, and the valley value fluctuation is within the 14th and 15th thresholds. The amplitude fluctuation variance of the second harmonic after passing through the regular triangle cylinder is much smaller than Figure 4 The fluctuation variance of the second harmonic amplitude of the current after direct laser transmission is Figure 5 The second harmonic amplitude in Figure 4The second harmonic amplitude in the system has a large gradient increase. Since the optical path of the laser in the whole system is the same in an open environment, but the effective absorption optical path of the laser in the bottle is nearly 5 times longer than that of direct transmission, the proportion of the second harmonic fluctuation threshold in the entire second harmonic peak value is greatly reduced, and the demodulated current second harmonic waveform is more regular. Therefore, there is a relatively high accuracy when using the acquired current second harmonic peak value to invert the trace gas concentration in the bottle.

[0087] See also Figure 6 FIG. 1 is another embodiment of the present invention, which is a schematic diagram of the second harmonic of four consecutive cycles measured after the laser passes through the cylindrical reflection channel, wherein the laser reflection light trace in the bottle is a regular quadrilateral and the operation period is two quadrilateral-like periods. It can be seen that the upper boundary of the second harmonic fluctuation is within the 16th and 17th thresholds and the lower boundary is within the 18th and 19th thresholds. Due to the further increase in the effective absorption optical path of the laser, the four consecutively measured second harmonic fluctuations are relatively Figure 4 , Figure 5 The method is more stable, the waveform is more regular, and the peak height is higher, so there is a relatively higher accuracy when inverting the trace gas concentration in the bottle by obtaining the peak value of the second harmonic of the current.

[0088] This shows that the present invention optimizes the cylindrical surround internal reflection light path, constructs a "laser particle characteristic optical amplifier" in a narrow space, and relatively suppresses the amplitude fluctuation of the second harmonic, thereby effectively improving the accuracy of laser detection of trace gas concentration in glass bottles and the stability of the system.

[0089] Based on the above-mentioned glass bottle with optimized optical path, the present invention provides a gas concentration detection method using the glass bottle, comprising the following steps:

[0090] S1: The laser control module emits laser light from the laser incident light path port to the glass bottle to be detected at a predetermined angle, and the scanning wavelength of the laser light covers the absorption spectrum of the gas to be detected;

[0091] Wherein, the glass bottle to be tested is the above-mentioned glass bottle, and the incident laser is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path. Wherein, due to the characteristics of the glass bottle structure, after each reflection, an effective absorption optical path of the gas to be tested of the same length will be added in the glass bottle to be tested;

[0092] S2: The laser detector receives the laser transmitted from the laser exit light path, and obtains the gas concentration in the glass bottle according to the optical path of the laser in the glass bottle and the second harmonic current signal converted from the photoelectric signal received by the photoelectric detector.

[0093] The relevant formulas for optical path design can be found in the corresponding description above and will not be repeated here. Based on the above gas concentration detection method, the present invention provides a gas concentration detection system, including: a laser control module, a laser source, a glass bottle, a laser detector, a signal generator and a data processor;

[0094] The laser control module is connected to the laser source and is used to control the laser source to emit laser toward the incident light path of the glass bottle. The specific laser source is a laser, for example, the central wavelength of the laser is 760nm, and the laser control module is used to control the temperature control and current control of the normal operation of the laser. The current control is a combination signal of a high-frequency sine wave and a low-frequency sawtooth wave carried by the laser drive to emit the laser.

[0095] The laser is incident through the incident light path opening on the glass bottle, and is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path opening;

[0096] The laser detector is arranged at a position corresponding to the exit light path on the glass bottle, and is used to collect the laser emitted from the exit light path and convert it into a current signal;

[0097] The signal generator is connected to the laser detector and is used to perform orthogonal demodulation on the current signal and the double frequency of the high-frequency signal to extract the second harmonic signal;

[0098] The data processor is used to calculate the concentration of the gas to be detected in the glass bottle by using the second harmonic signal and the effective absorption optical path length of the laser in the cylindrical reflection channel. The specific calculation formula can refer to the above formula (4).

[0099] It should be emphasized that the examples described in the present invention are illustrative rather than restrictive, and therefore the present invention is not limited to the examples described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solution of the present invention that do not depart from the purpose and scope of the present invention, whether modified or replaced, also fall within the scope of protection of the present invention.

Claims

1. A glass bottle used for gas concentration detection, characterized in that: The gas to be tested is encapsulated in the glass bottle, and the outer wall of the glass bottle is coated with a layer of laser anti-reflection film, and the glass bottle and the laser anti-reflection film form a cylindrical reflection channel; The upper and lower edges of the cylindrical reflection channel are respectively provided with an incident light path opening and an outgoing light path opening, and the incident light path opening and the outgoing light path opening are on the same vertical line; The incident light path is used for incident laser light to enter, and the incident laser light is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path. The laser light emitted from the exit light path is collected and used to calculate the concentration of the gas in the glass bottle; The effective absorption optical path length of the laser in the cylindrical reflection channel is: Wherein, L is the effective absorption optical path length of the laser in the cylindrical reflection channel, M is the number of effective absorption optical path segments of the laser in the glass bottle, l1 is the projection length of a section of effective absorption optical path on the XY plane, and h1 is the descending height of a section of effective absorption optical path; The distance that the laser passes through the gas in the bottle and contacts the inner wall of the glass bottle again is regarded as an effective absorption optical path; The calculation formula for the effective absorption path length M of the laser in the glass bottle is as follows: Where H is the height of the laser anti-reflection film coating on the outer glass bottle, m represents the refractive index of the laser from air to the bottle wall, r1 represents the radius of the outer wall of the glass bottle, r2 represents the radius of the inner wall of the glass bottle, α1 is the angle between the projection of the laser incident angle on the XZ plane and the X-axis, and n is the side length of the projection shape of the effective optical path of the laser in the bottle on the XY plane, which is a regular n-gon.

2. The glass bottle according to claim 1, characterized in that: The calculation formulas for the projection length l1 of an effective absorption optical path on the XY plane and the descending height h1 of an effective absorption optical path are as follows: Wherein, α2 represents the angle between the projection of the incident angle on the XY plane and the X-axis.

3. The glass bottle according to claim 2, characterized in that: The equivalent relationship between n and α2 is as follows: Where m represents the refractive index of the laser from air to the bottle wall.

4. The glass bottle according to claim 1, characterized in that: The glass bottle is a glass medicine bottle.

5. A gas concentration detection method, characterized in that: The steps include: S1: The laser control module emits laser light from the laser incident light path port to the glass bottle to be inspected at a predetermined angle; Wherein, the glass bottle to be inspected is the glass bottle according to any one of claims 1 to 4, and the incident laser is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path; S2: The laser detector receives the laser transmitted from the laser exit light path, and obtains the gas concentration in the glass bottle according to the optical path of the laser in the glass bottle and the second harmonic current signal converted from the photoelectric signal received by the laser detector.

6. The method according to claim 5, characterized in that: The concentration formula of the gas is as follows: In the formula, i 2fmax is the peak value of the second harmonic current signal, which is obtained by converting the laser into a current signal after the laser detector acquires the laser and performing orthogonal demodulation with the double frequency of the high-frequency signal generated by the demodulation board; L is the effective absorption optical path length of the laser in the cylindrical reflection channel, S is the second harmonic term coefficient, N is the concentration of the gas, and i0(t) is the injection current of the laser.

7. The method according to claim 5, characterized in that: There is no interference from other elements near the gas absorption spectrum.

8. A detection system based on the method of claim 5, characterized in that: include: Laser control module, laser source, glass bottle, laser detector, signal generator and data processor; Wherein, the laser control module is connected to the laser source and is used to control the laser source to emit laser toward the incident light path of the glass bottle; The laser is incident through the incident light path opening on the glass bottle, and is refracted and reflected in a reciprocating spiral downward in the cylindrical reflection channel until it is emitted from the exit light path opening; The laser detector is arranged at a position corresponding to the exit light path on the glass bottle, and is used to collect the laser emitted from the exit light path and convert it into a current signal; The connection between the laser detector and the demodulation board is used to perform orthogonal demodulation on the current signal and the double frequency of the high-frequency signal to extract the second harmonic signal; The signal generator is connected to the laser detector; The data processor is used to calculate the concentration of the gas to be detected in the glass bottle by using the second harmonic signal and the effective absorption optical path length of the laser in the cylindrical reflection channel.

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