Miniature optical gas sensor

Abstract

The invention discloses a miniature optical gas sensor which comprises a shell, a miniature gas chamber, an oxygen detection unit, a carbon dioxide detection unit and a control processing unit, and the shell is provided with a gas inlet unit and a gas outlet unit; the micro air chamber is arranged in the shell and is communicated with the air inlet unit and the air outlet unit; the oxygen detection unit emits a first light beam to the micro gas chamber and generates a first detection signal to be received by the first detector; the carbon dioxide detection unit emits a second light beam to the micro gas chamber and generates a second detection signal to be received by the second detector; according to the invention, the oxygen detection unit based on the TDLAS principle and the carbon dioxide detection unit based on the non-dispersive infrared principle or the TDLAS principle are miniaturized and integrated, so that the two detection units can share one miniature air chamber cavity, the detection precision of respiratory gas is ensured, and millisecond-level quick response is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular to a micro optical gas sensor. Background Art

[0002] Oxygen consumption measurement is an important indicator for accurately evaluating human cardiopulmonary function. The oxygen breathed by the human body is transported to the lungs through the blood circulation to participate in human metabolism, and the carbon dioxide produced is discharged from the body through breathing movements. As a metabolic product of the human body, the concentration of respiratory carbon dioxide has been considered to be the same basic vital signs as body temperature, respiration, pulse, blood pressure, arterial oxygen saturation, etc. It is widely used in anesthesia monitoring, intensive care, and lung function assessment. Therefore, the detection of respiratory oxygen and carbon dioxide is of great significance in medicine.

[0003] In clinical practice, the basic requirements for sensors that measure respiratory gases (such as oxygen and carbon dioxide) are that they are small in size and light in weight, so that the subject does not feel discomfort when measuring in the respiratory tract; secondly, they require a fast response time, that is, when the subject inhales or exhales gas with a certain breathing rhythm, the sensor must have a very short time resolution for the gas, so that the subject's breath-by-breath can be continuously analyzed. At present, most of the oxygen sensors and carbon dioxide sensors suitable for clinical respiratory monitoring applications on the market use sensors with two different principles for detection. For example, oxygen sensors mostly use paramagnetic principle, electrochemical principle, solid electrolyte principle, and tunable laser principle; sensors suitable for detecting respiratory carbon dioxide gas mostly use non-spectral infrared principle. There are generally two ways to install and configure the sensor's pulmonary function test system. One is to set a micro-mixing chamber, carbon dioxide sensor, oxygen sensor and suction pump in series behind the flow sensor at the subject's mouth and nose. After the suction pump draws the exhaled air into the micro-mixing chamber in proportion, the exhaled air is successively detected by the carbon dioxide sensor and the oxygen sensor. This method is suitable for gas analysis devices that do not require high test response speed; the other is to use oxygen sensors and carbon dioxide sensors that can achieve rapid analysis to directly analyze the gas composition of each moment of inhalation and exhalation at the subject's mouth and nose. This has very demanding requirements on the test response speed of the gas sensor. According to the joint statement of the American Thoracic Society (ATS) and the American College of Chest Physicians (ACCP) on cardiopulmonary exercise testing, "TAT Society. ATS / ACCP Statement on Cardiopulmonary Exercise Testing. Am J Respir Crit Care Med Vol 167. pp 211–277, 2003” mentioned that the response time for oxygen and carbon dioxide tests should be in the millisecond level. Currently, most researchers are conducting research on the rapid response of a single component gas. For example, Servomex of the United Kingdom has published a related patent GB2465565B, which uses the paramagnetic principle to achieve rapid response to oxygen. Although the sensor size can be made compact, the response speed cannot reach the millisecond level. On this basis, adding the carbon dioxide component to achieve a compact sensor structure and a device and method for rapid response to both oxygen and carbon dioxide gases at the same time has certain challenges.In the prior art, for example, the respiratory gas analyzer disclosed in Marquette's patent WO2023239283A1 uses a first sensor based on the NDIR infrared principle to measure exhaled carbon dioxide, and a second sensor based on the electrochemical or paramagnetic principle to measure oxygen; and General Electric's patent US20130023782A1 also discloses the use of a luminescence quenching principle sensor to measure oxygen and an NDIR infrared principle sensor to measure CO2. This simple system integration detection of sensors based on two different principles will result in a large overall size, inconvenient installation, poor compatibility between sensors based on different principles, and the failure to solve the problems of rapid response to both oxygen and carbon dioxide gases at the same time. Summary of the invention

[0004] The main purpose of the present invention is to provide a gas sensor which can detect oxygen and carbon dioxide simultaneously and has small volume, high test accuracy and fast response.

[0005] To achieve the above object, the present invention proposes a micro optical gas sensor for measuring oxygen and carbon dioxide in respiratory gas, the micro optical gas sensor comprising: A housing is provided with an air inlet unit and an air outlet unit; A micro air chamber is provided in the shell for the respiratory gas to be measured to flow; the micro air chamber is provided with a first light input end, a second light input end, a first light output end, a second light output end, an air inlet and an air outlet, and the air inlet and the air outlet are respectively connected to the air inlet unit and the air outlet unit of the shell; an oxygen detection unit, arranged in the housing, comprising a first light source and a first detector, wherein the first light source is a semiconductor laser light source, configured to emit a first light beam to a first light input end of the gas chamber, and the first detector is configured to receive a light beam emitted from a first light output end of the gas chamber and generate a first detection signal; a carbon dioxide detection unit, disposed in the housing, comprising a second light source and a second detector, wherein the second light source is a non-dispersive infrared light source or a semiconductor laser light source, and is used to emit a second light beam to a second light input end of the gas chamber, and the second detector is used to receive the light beam emitted from a second light output end of the gas chamber and generate a second detection signal; and A control processing unit is electrically connected to the first light source, the second light source, the first detector, and the second detector, and is used to control the first light source to emit the first light beam and receive and process a first detection signal transmitted from the first detector to obtain an oxygen concentration, and to control the second light source to emit the second light beam and receive and process a second detection signal transmitted from the second detector to obtain a carbon dioxide concentration.

[0006] Furthermore, the volume of the micro air chamber is 0.5ml~3ml.

[0007] Furthermore, the second light source is a non-dispersive infrared light source; the first light input end and the first light output end are located at two ends of the micro air chamber in the length direction thereof, so that the first light beam emitted by the first light source enters the micro air chamber through the first light input end and is received by the first detector through the first output end; The second light input end and the second light output end are located at relative positions of the micro air chamber in the width direction thereof, so that the second light beam emitted by the second light source enters the micro air chamber through the second input end and is received by the second detector through the second output end.

[0008] Furthermore, the micro air chamber includes a first concave reflector and a second concave reflector arranged at both ends in the length direction thereof; the first light input end is arranged on the first concave reflector, and the first light output end is arranged on the second concave reflector, so that the first light beam incident from the first light input end is reflected multiple times by the first concave reflector and the second concave reflector and then emitted through the first light output end.

[0009] Furthermore, the micro air chamber also includes two limiting plug-ins respectively arranged on the first concave reflector and the second concave reflector to reduce the redundant volume in the micro air chamber; there is a gap between the two limiting plug-ins for the detection light path of the carbon dioxide detection unit to pass through.

[0010] Furthermore, the air inlet unit and the air outlet unit are spaced apart along the length direction of the micro air chamber, and are arranged on both sides of the micro air chamber in its width direction, so that after the respiratory gas to be tested enters the micro air chamber through the air inlet unit, it flows along the tangent direction of the inner wall curved surface of the micro air chamber and finally flows out from the air outlet unit.

[0011] Further, the second light source is a semiconductor laser light source; the first light input end and the second light input end are located at a first end of the micro air chamber in the length direction, and the first light output end and the second light output end are located at a second end of the micro air chamber in the length direction; or, the second light source is a semiconductor laser light source, the first light input end and the second light output end are located at a first end of the micro air chamber in the length direction, and the second light input end and the first light output end are located at a second end of the micro air chamber in the length direction.

[0012] Furthermore, the inner diameter of the micro air chamber is 2-6 mm.

[0013] Furthermore, the micro optical gas sensor further comprises a first semi-transparent and semi-reflective mirror and a second semi-transparent and semi-reflective mirror arranged at both ends of the micro gas chamber in the length direction, so that the light emitted by the first light source passes through the first semi-transparent and semi-reflective mirror and enters the micro gas chamber through the first light input end, is emitted through the first output end and passes through the second semi-transparent and semi-reflective mirror and is received by the first detector, thereby forming a detection optical path of the oxygen detection unit; The light emitted by the second light source is reflected by the first semi-transparent and semi-reflective mirror, enters the micro gas chamber through the second light input end, is emitted through the second output end, and then is reflected by the second semi-transparent and semi-reflective mirror to be received by the second detector, thereby forming a detection light path of the carbon dioxide detection unit.

[0014] Furthermore, a collimating lens is disposed at the first light source and the second light source respectively; and a focusing lens is disposed at the first detector and the second detector respectively.

[0015] Furthermore, the micro optical gas sensor also includes a first packaging structure and a second packaging structure located at both ends of the micro gas chamber, the first packaging structure includes one of the first light source and the first detector, and one of the second light source and the second detector, and the second packaging structure includes the first light source and the other of the first detector, and the second light source and the other of the second detector.

[0016] Further, the first light input end, the second light input end and the first packaging structure are located at a first end of the air chamber, and the first packaging structure includes the first light source and the second light source; The first light output end and the second light output end are located at a second end of the air chamber, and the second packaging structure includes the first detector and the second detector.

[0017] Further, the first packaging structure also includes a first tube seat, a first tube cap, a first carrier, a first NTC element, a first TEC element, a second carrier, a second NTC element, a second TEC element, a first baffle, a first lens, and a second lens, the first tube cap is provided on the first tube seat, the first carrier and the second carrier are provided side by side on the first tube seat, the first baffle is provided between the first carrier and the second carrier, the first light source is provided on the first carrier, the second light source is provided on the second carrier, the first and second NTC elements are provided on the first carrier and the second carrier, respectively, the first and second TEC elements are connected to the first carrier and the second carrier, respectively, the first tube cap has a first through hole corresponding to the first light source, and has a second through hole corresponding to the second light source, the first lens is provided in the first through hole, and the second lens is provided in the second through hole; The second packaging structure also includes a second tube seat, a second tube cap, a first pad, a second pad, a second baffle, a third lens and a fourth lens. The second tube cap is arranged on the second tube seat. The first pad and the second pad are arranged side by side on the second tube seat. The second baffle is arranged between the first pad and the second pad. The first detector is arranged on the first pad, and the second detector is arranged on the second pad. The second tube cap has a third through hole corresponding to the first detector and a fourth through hole corresponding to the second detector. The third lens is arranged in the third through hole, and the fourth lens is arranged in the fourth through hole.

[0018] Further, the first light input end, the second light output end and the first packaging structure are located at the first end of the air chamber, and the first packaging structure includes the first light source and the second detector; The first light output end, the second light input end and the second packaging structure are located at a second end of the air chamber, and the second packaging structure includes the second light source and the first detector.

[0019] Further, the first packaging structure also includes a third tube base, a third tube cap, a third carrier, a third NTC element, a third TEC element, a third cushion block, a third baffle, a fifth lens and a sixth lens, the third tube cap is arranged on the third tube base, the third NTC element is arranged on the third carrier, the third TEC element is connected to the third carrier, the third tube base is provided with the third carrier and the third cushion block side by side, the third baffle is arranged between the third carrier and the third cushion block, the first light source is arranged on the third carrier, the second detector is arranged on the third cushion block, the third tube cap has a fifth through hole corresponding to the first light source, and has a sixth through hole corresponding to the second detector, the fifth lens is arranged in the fifth through hole, and the sixth lens is arranged in the sixth through hole; The second packaging structure also includes a fourth tube seat, a fourth tube cap, a fourth carrier, a fourth NTC element, a fourth TEC element, a fourth pad, a fourth baffle, a seventh lens and an eighth lens. The fourth tube cap is arranged on the fourth tube seat, the fourth NTC element is arranged on the third carrier, the fourth TEC element is connected to the fourth carrier, the fourth carrier and the fourth pad are arranged side by side on the fourth tube seat, the fourth baffle is arranged between the fourth carrier and the fourth pad, the second light source is arranged on the fourth carrier, the first detector is arranged on the fourth pad, the fourth tube cap has a seventh through hole corresponding to the second light source, and has an eighth through hole corresponding to the first detector, the seventh lens is arranged in the seventh through hole, and the eighth lens is arranged in the eighth through hole.

[0020] The technical solution of the present invention designs a miniature optical gas sensor to simultaneously detect oxygen and carbon dioxide, the main components of medical respiratory gas. The oxygen detection unit based on the TDLAS principle and the carbon dioxide detection unit based on the non-dispersive infrared principle or the TDLAS principle are miniaturized and integrated so that the two detection units can share a miniature gas chamber cavity, thereby ensuring the detection accuracy of respiratory gas and being able to achieve a rapid response to the two component gases of oxygen and carbon dioxide, meeting the millisecond-level response required by medical standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 A cross-sectional view of a first embodiment of a gas sensor provided by the present invention; Figure 2 for Figure 1 Schematic diagram of some structures of gas sensors; Figure 3 This is a simulation diagram of the flow field of the gas to be tested in the micro gas chamber in the first embodiment; Figure 4 It is a structural schematic diagram of another embodiment of the first embodiment; Figure 5 A schematic structural diagram of a second embodiment of a gas sensor provided by the present invention; Figure 6 A schematic structural diagram of a third embodiment of a gas sensor provided by the present invention; Figure 7 A schematic structural diagram of a fourth embodiment of a gas sensor provided by the present invention; Figure 8 for Figure 6 A schematic structural diagram of the first sealing structure in FIG. Fig. 9 for Figure 6 A schematic structural diagram of a second sealing structure in FIG. Fig.10 for Figure 7 A schematic structural diagram of the first sealing structure in FIG. Fig.11 for Figure 7 Schematic diagram of the structure of the second sealing structure.

[0023] Description of Figure Numbers: 100. Micro optical gas sensor; 1. Shell, 11. Air inlet, 12. Air outlet; 2. micro air chamber, 21. first concave reflector, 22. second concave reflector, 23. limiting plug-in, 231. root, 232. head; 3. oxygen detection unit, 31. first light source, 32. first detector; 4. a carbon dioxide detection unit, 41. a second light source, 42. a second detector; 5. Spotlight cover; 6. Semi-transparent and semi-reflective mirror; 7a, a first tube base, 7b, a first tube cap, 7c, a first carrier plate, 7d, a second carrier plate, 7e, a first baffle plate, 7f, a first lens, 7g, a second lens, 7h, a first NTC element, 7i, a second NTC element, 7j, a first TEC element, 7k, a second TEC element; 8a, a second tube base, 8b, a second tube cap, 8c, a first cushion block, 8d, a second cushion block, 8e, a second baffle, 8f, a third lens, 8g, a fourth lens; 9a, a third tube holder, 9b, a third tube cap, 9c, a third carrier board, 9d, a third cushion block, 9e, a third baffle, 9f, a fifth lens, 9g, a sixth lens, 9h, a third NTC element, 9i, a third TEC element; 10a, a fourth tube seat, 10b, a fourth tube cap, 10c, a fourth carrier board, 10d, a fourth spacer, 10e, a fourth baffle, 10f, a seventh lens, 10g, an eighth lens, 10h, a fourth NTC element, and 10i, a fourth TEC element.

[0024] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0026] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] Existing oxygen sensors and carbon dioxide sensors suitable for clinical respiratory monitoring applications mostly use sensors based on two different principles for separate detection. For example, oxygen sensors mostly use the paramagnetic principle, electrochemical principle, solid electrolyte principle, and tunable laser principle; sensors suitable for detecting respiratory carbon dioxide gas mostly use the non-spectral infrared principle. There are generally two ways to install and configure the sensor's lung function test system. One is to set a micro-mixing chamber, a carbon dioxide sensor, an oxygen sensor, and an air pump in series behind the flow sensor at the subject's mouth and nose. After the air pump proportionally draws the exhaled air into the micro-mixing chamber, the exhaled air is successively detected by the carbon dioxide sensor and the oxygen sensor. This method is suitable for gas analysis devices that do not require high test response speed. The other is to use oxygen sensors and carbon dioxide sensors that can perform rapid analysis to directly analyze the gas composition at every moment of inhalation and exhalation at the subject's mouth and nose, which has very demanding requirements on the test response speed of the gas sensor. Currently, researchers are mostly conducting research on the rapid response of single-component gases. However, it is very difficult to add the carbon dioxide component on this basis to achieve a compact sensor structure and rapid dual-gas response. Moreover, simple system integration and testing of two sensors based on different principles will result in a bulky overall volume, inconvenient installation, and poor compatibility between sensors based on different principles. It is very challenging to achieve simultaneous rapid response of both oxygen and carbon dioxide gases in the same gas sensor.

[0029] In view of this, the present invention provides a micro optical gas sensor 100 for measuring oxygen and carbon dioxide. The micro optical gas sensor 100 includes a shell 1, a micro gas chamber 2, an oxygen detection unit 3, a carbon dioxide detection unit 4 and a control processing unit. The shell 1 is provided with an air inlet unit and an air outlet unit; the micro gas chamber 2 is arranged in the shell 1, and is connected to the air inlet unit and the air outlet 12 through an air inlet 11 and an air outlet 12; the oxygen detection unit 3 is arranged in the shell 1, and includes a first light source 31 and a first detector 32. The first light source 31 is a semiconductor laser light source, which is used to emit a first light beam to a first light input end of the micro gas chamber 2, and the first detector 32 is used to receive a light beam emitted from a first light output end of the micro gas chamber 2 and generate a first detection signal; The carbon detection unit 4 is arranged in the shell 1, including a second light source 41 and a second detector 42, the second light source 41 is a non-dispersive infrared light source or a semiconductor laser light source, and is used to emit a second light beam to the second light input end of the micro gas chamber 2, and the second detector 42 is used to receive the light beam emitted from the second light output end of the micro gas chamber 2 and generate a second detection signal; the control processing unit is electrically connected to the first light source 31, the second light source 41, the first detector 32, and the second detector 42, and is used to control the first light source 31 to emit the first light beam and receive and process the first detection signal transmitted from the first detector 32 to obtain the oxygen concentration, and control the second light source 41 to emit the second light beam and receive and process the second detection signal transmitted from the second detector 42 to obtain the carbon dioxide concentration.

[0030] In the first embodiment of the technical solution of the present invention, as Figure 1 As shown, the oxygen detection unit 3 adopts the TDLAS principle to detect the oxygen concentration, the first light source 31 adopts a TDLAS laser light source, and the wavelength of the tunable oxygen absorption light emitted is 763nm; the carbon dioxide detection unit 4 adopts the non-dispersive infrared principle to detect the carbon dioxide concentration, the second light source 41 adopts a non-dispersive infrared light source, and the second detector 42 adopts a single measurement channel or a dual-channel setting including a reference channel, wherein the filter wavelength of carbon dioxide is 4.26μm, thereby realizing the simultaneous detection of oxygen and carbon dioxide.

[0031] It should be noted that the air inlet unit adopts the form of an air inlet tube to introduce the gas to be tested into the micro air chamber 2 through the air inlet 11, one end of which is connected to the gas warehouse, and the other end is connected to the micro air chamber 2. The air outlet unit adopts the form of an air outlet tube to discharge the gas in the micro air chamber 2 to the outside through the air outlet 12, one end of which is connected to the gas warehouse, and the other end is connected to the micro air chamber 2.

[0032] The volume of the micro air chamber 2 is 0.5ml~3ml. It should be noted that the volume of the micro air chamber 2 in this embodiment is 0.56ml. The oxygen detection unit 3 and the carbon dioxide detection unit 4 share the same micro air chamber 2 for detection.

[0033] Specifically, in the present invention, the first light input end, the second light input end, the first light output end, and the second light output end of the micro air chamber 2 are not limited in their locations, wherein the first light input end and the first light output end may be located at both ends of the micro air chamber 2 in its length direction, and the second light input end and the second light output end are located at relative positions of the micro air chamber in its width direction. Figure 2 As shown, the micro air chamber 2 specifically includes a first concave reflector 21 and a second concave reflector 22 arranged at both ends in the length direction thereof, the distance between the two reflector lenses is 15 mm, and the radius of curvature is also the same, about 12 mm; the first light input end is arranged on the first concave reflector 21, and the first light output end is arranged on the second concave reflector 22, so that the first light beam incident from the first light input end is reflected multiple times by the first concave reflector 21 and the second concave reflector 22 and then emitted through the first light output end, forming a detection light path of the oxygen detection unit 3, and ensuring the detection light path under a limited chamber volume; the second light input end and the second light output end are located at relative positions of the micro air chamber 2 in the width direction thereof, so that the second light beam incident from the second light input end is emitted through the second light output end, forming a detection light path of the carbon dioxide detection unit 4.

[0034] Thus, in this embodiment, an oxygen detection unit 3 with a long optical path is arranged in the length direction of the micro gas chamber 2, and a carbon dioxide detection unit 4 with a short optical path is arranged in the width direction. The two detection units share one micro gas chamber, which ensures the detection accuracy of the two-component gas while achieving rapid response, and the overall sensor volume is more compact.

[0035] In this embodiment, in order to improve the response speed of the gas, the effective utilization rate of the micro gas chamber can be improved by further reducing the redundant volume of the gas chamber. Therefore, the effective flow volume of the gas to be tested in the micro gas chamber will be less than 0.5 ml. Specifically, two limiting plug-ins 23 are arranged on the two concave reflectors of the micro gas chamber 2, one of the two limiting plug-ins 23 is arranged on the first concave reflector 21, and the other is arranged on the second concave reflector 222, which are used to reduce the redundant volume in the micro gas chamber 2, and there is a gap between the two limiting plug-ins 23 for the detection light path of the carbon dioxide detection unit 4 to pass through.

[0036] Thus, by setting two limiting plugs 23 in the micro gas chamber 2, the flow range of the gas to be measured entering the cavity 21 is limited, and both the oxygen measuring beam and the carbon dioxide measuring beam can fully interact with the gas to be measured, thereby shortening the response time.

[0037] It should be noted that the shape of the limiting plug 23 is not limited. For details, please refer to Figure 2 In the first embodiment of the present invention, each of the limiting plugs 23 has a root 231 and a head 232, the root 231 is disposed at the end of the cavity 21 and penetrates a reflector, the head 232 is close to the middle of the cavity 21, and each of the limiting plugs 23 is tapered from the root 231 to the head 232. More specifically, the limiting plug 23 is truncated.

[0038] For further information, see Figure 1 In the first embodiment of the present invention, the air inlet 11 and the air outlet 12 of the micro air chamber 2 are arranged at intervals along the length direction of the micro air chamber 2, and are arranged on both sides of the micro air chamber 2 in the width direction thereof, so that the respiratory gas to be measured flowing from the air inlet unit into the micro air chamber 2 flows along the tangent direction of the inner wall curved surface of the micro air chamber 2 and finally flows out from the air outlet unit, as shown in FIG. Figure 3 The flow field simulation diagram of the gas to be tested in the micro gas chamber of this embodiment is shown, so that the gas to be tested can spirally move forward in the cavity 21, so that the gas to be tested not only flows without obstruction, but also can quickly and without dead zones to fill the entire cavity 21, further improving the response time.

[0039] In the first embodiment of the present invention, the micro optical gas sensor 100 also includes a first mounting seat and a second mounting seat provided on the shell 1, one of the first concave reflector 21 and the second concave reflector 22 and the first light source 31 are installed on the first mounting seat, the other of the first concave reflector 221 and the second concave reflector 222 and the first detector 32 are installed on the second mounting seat, and the limiting plug-in 23 is installed on the first mounting seat and / or the second mounting seat.

[0040] It should be noted that, in the present invention, the connection method between each reflector and its corresponding mounting seat is not limited, and it can be bonding, or clamping, etc.

[0041] For details, please refer to Figure 1 In the first embodiment of the present invention, a focusing cover 5 is provided on the light emitting side of the second light source 41 so that the second light beam emitted by the divergent non-spectral infrared light source can reach the second detector 42 as much as possible.

[0042] Specifically, in the first embodiment of the present invention, the micro optical gas sensor 100 also includes a heating component, and the heating component includes a heater and a thermal insulation component (such as thermal insulation cotton). The heater is arranged on the shell 1 and is electrically connected to the control processing unit, and the thermal insulation component is wrapped around the outer periphery of the shell 1; in this way, heating is performed by the heater, and the temperature of the first concave reflector 21, the second concave reflector 22 and the inner wall of the micro gas chamber 2 is quickly increased by the thermal insulation component to prevent condensation of the reflector and the inner wall of the gas chamber, thereby ensuring the normal operation of the micro optical gas sensor 100 and ensuring detection stability and accuracy.

[0043] In the present invention, optical noise is a negative factor affecting the detection accuracy of the TDLAS principle sensor, and a major source of optical noise is generated by multiple reflections of the detection light on the reflector. Therefore, in another embodiment of the present invention, Figure 4 As shown, the oxygen detection unit 3 adopts a counter-radiation optical path structure, so that the micro gas chamber 2 is longer than the micro gas chamber 2 of the first embodiment of the present invention in length, and is designed to be smaller in width. After the first light source 31 enters the micro gas chamber 2 through the first input end, it is directly output through the first output end at the other end and is received by the first detector 41. In this way, although the overall volume of the sensor will increase to a certain extent, the gas response speed can still be guaranteed, and the optical noise detected by the sensor can also be reduced.

[0044] In the second embodiment of the present invention, the carbon dioxide detection unit originally using the non-spectral infrared principle is replaced with a carbon dioxide detection unit using the TDLAS principle. Specifically, Figure 5As shown, the second light source 41 is a semiconductor laser light source. When detecting carbon dioxide, its light absorption wavelength is 1573nm. Since both gas components are detected using the TDLAS principle, and the laser beam diameter can be manufactured and adjusted to be very fine, correspondingly, the inner cavity of the micro gas chamber can be manufactured to be very fine to reduce the volume of the gas chamber. The inner cavity diameter can be 2~6mm. In this embodiment, the inner cavity diameter is 2.5mm and the volume is 0.5ml. In the present embodiment, the first light input end and the second light input end are located at the first end of the micro gas chamber 2 in the length direction, the first light output end and the second light output end are located at the second end of the micro gas chamber 2 in the length direction, and two semi-transparent and semi-reflective mirrors 6 are further provided at both ends of the micro gas chamber 2 in the length direction, so that the light emitted by the first light source 31 passes through the first semi-transparent and semi-reflective mirror and enters the micro gas chamber 2 through the first light input end, and is emitted through the first output end and then passes through the second semi-transparent and semi-reflective mirror and is received by the first detector 32, thereby forming a detection optical path of the oxygen detection unit, and the light emitted by the second light source 41 passes through the first semi-transparent and semi-reflective mirror and then enters the micro gas chamber 2 through the second light input end and enters the micro gas chamber 2 through the second output end. After being emitted from the output end, it is reflected by the second semi-transparent and semi-reflective mirror and then received by the second detector 42, forming a detection optical path of the carbon dioxide detection unit; a collimating lens is also provided at the first light source 31 and the second light source 41, respectively, and a focusing lens is provided at the first detector and the second detector, respectively, so that the first light beam emitted by the first light source 31 and the second light beam emitted by the second light source 41 are collimated into very thin light beams through the collimating lenses respectively. Since the light beams are very thin, they can pass through the micro gas chamber 2; by setting the focusing lens, the light incident on the first detector 32 and the second detector 42 is focused, so that more light beams are received, so that the micro optical sensor 100 can realize accurate detection of oxygen and carbon dioxide at the same time.

[0045] It should be noted that the two semi-transparent and semi-reflective mirrors 6 can allow the light with a wavelength of 763 nm emitted by the first light source 31 to pass normally through the two semi-transparent and semi-reflective mirrors 6 through coating, while reflecting the light with a wavelength of 1573 nm emitted by the second light source 41 .

[0046] In order to further improve the compactness of the overall sensor and obtain a more integrated micro optical gas sensor, it also includes a first packaging structure and a second packaging structure located at both ends of the micro gas chamber, the first packaging structure includes one of the first light source 31 and the first detector 32, and one of the second light source 41 and the second detector 42, the second packaging structure includes the other of the first light source 31 and the first detector 32, and the other of the second light source 41 and the second detector 42.

[0047] In this way, packaging can be performed according to actual needs, specifically including the following four packaging situations: 1. The first packaging structure includes the first light source 31 and the second light source 41, and the second packaging structure includes the first detector 32 and the second detector 42; 2. The first packaging structure includes the first light source 31 and the second detector 42, and the second packaging structure includes the first detector 32 and the second light source 41; 3. The first packaging structure includes the first detector 32 and the second light source 41, and the second packaging structure includes the first light source 31 and the second detector 42; 4. The first packaging structure includes the first detector 32 and the second detector 42, and the second packaging structure includes the first light source 31 and the second light source 41.

[0048] More specifically, in the third embodiment of the present invention, the oxygen detection unit 3 and the carbon dioxide detection unit 4 are integrated, the first light source 31 and the second light source 41 are integrated into a first packaging structure, and the first detector 32 and the second detector 42 are integrated into a second packaging structure accordingly. Specifically, Figure 6 As shown, the inner cavity of the micro air chamber has a diameter of 3.5 mm and a volume of 1 ml, the first light input end, the second light input end and the first packaging structure are located at the first end of the micro air chamber 2; the first light output end, the second light output end and the second packaging structure are located at the second end of the micro air chamber 2. In this way, the first packaging structure can emit the first light beam and the second light beam at the same time, that is, emit the absorption light of oxygen and carbon dioxide at the same time, and the second packaging structure can receive the first light beam and the second light beam at the same time, that is, receive the absorption light signals of oxygen and carbon dioxide at the same time.

[0049] Further, Figure 8 and Fig. 9The first packaging structure and the second packaging structure are shown, the first packaging structure also includes a first tube seat 7a, a first tube cap 7b, a first NCT element 7h, a first TEC element 7j, a first carrier 7c, a second carrier 7d, a second NTC element 7i, a second TEC element 7k, a first baffle 7e, a first lens 7f and a second lens 7g, the first tube cap 7b is covered on the first tube seat 7a, the first carrier 7c and the second carrier 7d are arranged side by side on the first tube seat 7a, the first and second NTC elements are respectively arranged on the first carrier 7c and the second carrier 7d through conductive silver glue, the first TEC element 7j and the second TEC element 7k The first tube base 7a is fixedly mounted on the first tube base 7a by high thermal conductive glue, and the first TEC element 7j is connected to the first carrier 7c by high thermal conductive glue, and the second TEC element 7k is connected to the second carrier 7d by high thermal conductive glue, the first baffle 7e is arranged between the first carrier 7c and the second carrier 7d, the first light source 31 is arranged on the first carrier 7c, and the second light source 41 is arranged on the second carrier 7d, the first tube cap 7b is provided with a first through hole corresponding to the first light source 31, and a second through hole corresponding to the second light source 41, the first lens 7f is arranged in the first through hole, and the second lens 7g is arranged in the second through hole. In this way, the first light source 31 and the second light source 41 are separated by the first baffle 7e to prevent interference caused by cross-light. At the same time, by arranging the first lens 7f and the second lens 7g, the first light beam emitted by the first light source 31 and the light beam emitted by the second light source 41 can be collimated to form a very small light beam.

[0050] The second packaging structure further includes a second tube base 8a, a second tube cap 8b, a first cushion block 8c, a second cushion block 8d, a second baffle 8e, a third lens 8f and a fourth lens 8g, wherein the second tube cap 8b is covered on the second tube base 8a, the first cushion block 8c and the second cushion block 8d are arranged side by side on the second tube base 8a, the second baffle 8e is arranged between the first cushion block 8c and the second cushion block 8d, the first detector 32 is arranged on the first cushion block 8c, the second detector 42 is arranged on the second cushion block 8d, the second tube cap 8b is provided with a third through hole corresponding to the first detector 32, and a fourth through hole corresponding to the second detector 42, the third lens 8f is arranged in the third through hole, and the fourth lens 8g is arranged in the fourth through hole. In this way, by providing the second baffle 8e, the first detector 32 and the second detector 42 can be separated to prevent interference caused by crosstalk. At the same time, by providing the third lens 8f and the fourth lens 8g, the light incident on the first detector 32 and the second detector 42 is focused, so that more light beams are received.

[0051] It should be noted that the second lens 7g and the fourth lens 8g are respectively coated so that the second light beam with a wavelength of 1573nm emitted by the second light source 41 can pass through, while the first light beam with a wavelength of 763nm emitted by the first light source 31 cannot pass through, and the first lens 7f and the third lens 8f are respectively coated so that the first light beam with a wavelength of 763nm emitted by the first light source 31 can pass through, while the second light beam with a wavelength of 1573nm emitted by the second light source 41 cannot pass through, thereby preventing possible interference between the two beams of light.

[0052] It should also be noted that the first light source 31 and the second light source 41 are both laser chips, and are fixed on the first carrier 7c and the second carrier 7d in a one-to-one correspondence through eutectic. Similarly, the first detector 32 and the second detector 42 are both detection chips, and are fixed on the first cushion block 8c and the second cushion block 8d in a one-to-one correspondence.

[0053] In the fourth embodiment of the present invention, different from the third embodiment, as Figure 7 As shown, the first light source 31 and the second detector 42 are integrated into a first packaging structure, and the second light source 41 and the first detector 32 are correspondingly integrated into a second packaging structure, so that both ends of the optical path are both transmitting and receiving, and the first light beam can be received while the second light beam is emitted, and the second light beam can be received while the first light beam is emitted, thereby realizing simultaneous and rapid detection of oxygen and carbon dioxide.

[0054] Fig.10Schematic diagram of the first packaging structure, which specifically includes a third tube base 9a, a third tube cap 9b, a third carrier plate 9c, a third NTC element 9h, a third TEC element 9i, a third cushion block 9d, a third baffle plate 9e, a fifth lens 9f and a sixth lens 9g. The third tube cap 9b is covered on the third tube base 9a, the third carrier plate 9c and the third cushion block 9d are arranged side by side on the third tube base 9a, the third baffle plate 9e is arranged between the third carrier plate 9c and the third cushion block 9d, the first light source 31 is arranged on the third carrier plate 9c, and the third NTC element 9h is connected to the third TEC element 9i. The conductive silver glue is arranged on the third carrier 9c, the third NTC element 9h is arranged on the third carrier 9c through the conductive silver glue, the third TEC element 9i is fixedly mounted on the third tube seat 9a through the high thermal conductive glue, and is connected to the third carrier 9c through the high thermal conductive glue, the second detector 42 is arranged on the third cushion block 9d, the third tube cap 9b is provided with a fifth through hole corresponding to the first light source 31, and a sixth through hole corresponding to the second detector 42, the fifth lens 9f is arranged in the fifth through hole, and the sixth lens 9g is arranged in the sixth through hole. In this way, the first light source 31 and the second detector 42 are separated by the third baffle 9e to prevent interference caused by cross-light. At the same time, by providing the fifth lens 9f, the first light beam emitted by the first light source 31 can be collimated to form a very small light beam, and by providing the sixth lens 9g, the light projected in front of the second detector 42 can be focused so that more light beams are received.

[0055] Fig.11Schematic diagram of a second packaging structure, the second packaging structure further includes a fourth tube base 10a, a fourth tube cap 10b, a fourth carrier 10c, a fourth NTC element 10h, a fourth TEC element 10i, a fourth cushion block 10d, a fourth baffle 10e, a seventh lens 10f and an eighth lens 10g, the fourth tube cap 10b is covered on the fourth tube base 10a, the fourth carrier 10c and the fourth cushion block 10d are arranged side by side on the fourth tube base 10a, the fourth baffle 10e is arranged between the fourth carrier 10c and the fourth cushion block 10d, the second light source 41 is arranged on the fourth carrier 10c, the fourth NT The C element 10h is arranged on the fourth carrier 10c through conductive silver glue, the fourth NTC element 10h is arranged on the fourth carrier 10c through conductive silver glue, the fourth TEC element 10i is fixedly installed on the fourth tube seat 10a through high thermal conductivity glue, and is connected to the fourth carrier 10c through high thermal conductivity glue, the first detector 32 is arranged on the fourth cushion block 10d, the fourth tube cap 10b is provided with a seventh through hole corresponding to the second light source 41, and an eighth through hole corresponding to the first detector 32, the seventh lens 10f is arranged at the seventh through hole, and the eighth lens 10g is arranged at the eighth through hole. In this way, the second light source 41 and the first detector 32 are separated by the fourth baffle 10e to prevent interference caused by cross-light. At the same time, by providing the seventh lens 10f, the second light beam emitted by the second light source 41 can be collimated to form a very small light beam, and by providing the eighth lens 10g, the light projected in front of the first detector 32 can be focused so that more light beams are received.

[0056] It should be noted that the seventh lens 10f and the sixth lens 9g are respectively coated so that the second light beam with a wavelength of 1573nm emitted by the second light source 41 can pass through, while the first light beam with a wavelength of 763nm emitted by the first light source 31 cannot pass through, and the fifth lens 9f and the eighth lens 10g are respectively coated so that the first light beam with a wavelength of 763nm emitted by the first light source 31 can pass through, while the second light beam with a wavelength of 1573nm emitted by the second light source 41 cannot pass through, thereby preventing possible interference between the two beams of light.

[0057] It should also be noted that the first light source 31 and the second light source 41 are both laser chips, and are fixed on the third carrier 9c and the fourth carrier 10c in a one-to-one correspondence through eutectic. Similarly, the first detector 32 and the second detector 42 are both detection chips, and are fixed on the third cushion block 9d and the fourth cushion block 10d in a one-to-one correspondence.

[0058] In the third and fourth embodiments of the present invention, the micro optical gas sensor 100 also includes a first driving circuit board and a second driving circuit board, the first driving circuit board is electrically connected to the first light source 31, the second light source 41, and the control processing unit, and the second driving circuit board is electrically connected to the first detector 32, the second detector 42, and the control processing unit.

[0059] Embodiment 3 and embodiment 4 of the present invention are both in an integrated packaging form, so that the overall sensor size can be smaller, the optical path is simple and easy to implement, and the cost is low; the oxygen detection unit 3 and the carbon dioxide detection unit 4 both use a basic opposite-shooting method in the micro gas chamber 2 to realize gas detection, without the need for multiple returns, and the response speed is fast.

[0060] The sensors provided by the various embodiments of the present invention were used to conduct a comparative test experiment with the sensors using the traditional Herriot cell. The gases to be tested (oxygen and carbon dioxide) were introduced into the absorption cell at a set flow rate. The original data of the sensor was recorded using a serial port tool, and the response time of the sensor from air to the range point T90 was calculated. The experimental results are shown in Table 1 below: Table 1 Fast response time under different flow rates in various embodiments Unit: ms

[0061] It can be concluded that under the same test conditions, compared with the existing paramagnetic oxygen sensor / TDLAS laser oxygen sensor and non-spectroscopy infrared sensor in series combination for measuring oxygen and carbon dioxide in respiratory gas, at the same flow rate, the response speed of the micro-optical gas sensor 100 provided by each embodiment of the present invention is significantly faster, and it has more advantages as a medical respiratory gas sensor, that is, it can achieve miniaturized design and high-precision measurement while also achieving rapid response, greatly improving practicality.

[0062] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A miniature optical gas sensor for measuring oxygen and carbon dioxide in breath gas, characterized in that: The micro optical gas sensor comprises: A housing is provided with an air inlet unit and an air outlet unit; A micro air chamber is provided in the shell for the respiratory gas to be measured to flow; the micro air chamber is provided with a first light input end, a second light input end, a first light output end, a second light output end, an air inlet and an air outlet, and the air inlet and the air outlet are respectively connected to the air inlet unit and the air outlet unit of the shell; an oxygen detection unit, arranged in the housing, comprising a first light source and a first detector, wherein the first light source is a semiconductor laser light source, configured to emit a first light beam to a first light input end of the gas chamber, and the first detector is configured to receive a light beam emitted from a first light output end of the gas chamber and generate a first detection signal; a carbon dioxide detection unit, disposed in the housing, comprising a second light source and a second detector, wherein the second light source is a non-dispersive infrared light source or a semiconductor laser light source, and is used to emit a second light beam to a second light input end of the gas chamber, and the second detector is used to receive the light beam emitted from a second light output end of the gas chamber and generate a second detection signal; and A control processing unit is electrically connected to the first light source, the second light source, the first detector, and the second detector, and is used to control the first light source to emit the first light beam and receive and process a first detection signal transmitted from the first detector to obtain an oxygen concentration, and to control the second light source to emit the second light beam and receive and process a second detection signal transmitted from the second detector to obtain a carbon dioxide concentration.

2. A micro optical gas sensor as claimed in claim 1, characterized in that: The volume of the micro air chamber is 0.5ml~3ml.

3. A micro optical gas sensor as claimed in claim 1 or 2, characterized in that: The second light source is a non-dispersive infrared light source; the first light input end and the first light output end are located at two ends of the micro air chamber in the length direction thereof, so that the first light beam emitted by the first light source enters the micro air chamber through the first light input end and is received by the first detector through the first output end; The second light input end and the second light output end are located at relative positions of the micro air chamber in the width direction thereof, so that the second light beam emitted by the second light source enters the micro air chamber through the second input end and is received by the second detector through the second output end.

4. A micro optical gas sensor as claimed in claim 3, characterized in that: The micro air chamber includes a first concave reflector and a second concave reflector arranged at both ends in the length direction thereof; the first light input end is arranged on the first concave reflector, and the first light output end is arranged on the second concave reflector, so that the first light beam incident from the first light input end is reflected multiple times by the first concave reflector and the second concave reflector and then emitted through the first light output end.

5. A micro optical gas sensor as claimed in claim 4, characterized in that: The micro air chamber also includes two limiting plug-ins respectively arranged on the first concave reflector and the second concave reflector to reduce the redundant volume in the micro air chamber; there is a gap between the two limiting plug-ins for the detection light path of the carbon dioxide detection unit to pass through.

6. A micro optical gas sensor according to any one of claims 1 to 5, characterized in that: The air inlet and the air outlet of the micro air chamber are arranged at intervals along the length direction of the micro air chamber, and are arranged on both sides of the micro air chamber in the width direction, so that after the respiratory gas to be measured enters the micro air chamber through the air inlet unit, it flows along the tangent direction of the inner wall curved surface of the micro air chamber and finally flows out from the air outlet unit.

7. A micro optical gas sensor as claimed in claim 1, characterized in that: The second light source is a semiconductor laser light source; the first light input end and the second light input end are located at the first end of the micro air chamber in the length direction, and the first light output end and the second light output end are located at the second end of the micro air chamber in the length direction; or, The second light source is a semiconductor laser light source, the first light input end and the second light output end are located at a first end of the micro air chamber in the length direction, and the second light input end and the first light output end are located at a second end of the micro air chamber in the length direction.

8. A micro optical gas sensor as claimed in claim 7, characterized in that: The inner diameter of the micro air chamber is 2-6 mm.

9. A micro optical gas sensor as claimed in claim 7 or 8, characterized in that: It also includes a first semi-transparent and a second semi-transparent and a semi-reflective mirror disposed at both ends of the micro air chamber in the length direction, so that the light emitted by the first light source passes through the first semi-transparent and a semi-reflective mirror and enters the micro air chamber through the first light input end, is emitted through the first output end and passes through the second semi-transparent and a semi-reflective mirror and is received by the first detector, thereby forming a detection optical path of the oxygen detection unit; The light emitted by the second light source is reflected by the first semi-transparent and semi-reflective mirror, enters the micro gas chamber through the second light input end, is emitted through the second output end, and then is reflected by the second semi-transparent and semi-reflective mirror to be received by the second detector, thereby forming a detection light path of the carbon dioxide detection unit.

10. A micro optical gas sensor as claimed in claim 9, characterized in that: A collimating lens is disposed at the first light source and the second light source respectively; and a focusing lens is disposed at the first detector and the second detector respectively.

11. A micro optical gas sensor according to claim 7 or 8, characterized in that: It also includes a first packaging structure and a second packaging structure located at both ends of the micro air chamber, the first packaging structure includes one of the first light source and the first detector, and one of the second light source and the second detector, and the second packaging structure includes the other of the first light source and the first detector, and the other of the second light source and the second detector.

12. A micro optical gas sensor as claimed in claim 11, characterized in that: The first light input end, the second light input end and the first packaging structure are located at a first end of the air chamber, and the first packaging structure includes the first light source and the second light source; The first light output end and the second light output end are located at a second end of the air chamber, and the second packaging structure includes the first detector and the second detector.

13. The gas sensor according to claim 12, characterized in that The first packaging structure further includes a first tube seat, a first tube cap, a first carrier, a first NTC element, a first TEC element, a second carrier, a second NTC element, a second TEC element, a first baffle, a first lens, and a second lens. The first tube cap is disposed on the first tube seat. The first carrier and the second carrier are arranged side by side on the first tube seat. The first baffle is disposed between the first carrier and the second carrier. The first light source is disposed on the first carrier, and the second light source is disposed on the second carrier. The first and second NTC elements are disposed on the first carrier, respectively. The first and second TEC elements are connected to the first carrier, respectively. The first tube cap has a first through hole corresponding to the first light source and a second through hole corresponding to the second light source. The first lens is disposed in the first through hole, and the second lens is disposed in the second through hole. The second packaging structure also includes a second tube seat, a second tube cap, a first pad, a second pad, a second baffle, a third lens and a fourth lens. The second tube cap is arranged on the second tube seat. The first pad and the second pad are arranged side by side on the second tube seat. The second baffle is arranged between the first pad and the second pad. The first detector is arranged on the first pad, and the second detector is arranged on the second pad. The second tube cap has a third through hole corresponding to the first detector and a fourth through hole corresponding to the second detector. The third lens is arranged in the third through hole, and the fourth lens is arranged in the fourth through hole.

14. The gas sensor according to claim 11, characterized in that The first light input end, the second light output end and the first packaging structure are located at a first end of the air chamber, and the first packaging structure includes the first light source and the second detector; The first light output end, the second light input end and the second packaging structure are located at a second end of the air chamber, and the second packaging structure includes the second light source and the first detector.

15. The gas sensor according to claim 14, characterized in that The first packaging structure further includes a third tube base, a third tube cap, a third carrier, a third NTC element, a third TEC element, a third cushion block, a third baffle, a fifth lens and a sixth lens, wherein the third tube cap is disposed on the third tube base, the third NTC element is disposed on the third carrier, the third TEC element is connected to the third carrier, the third carrier and the third cushion block are arranged side by side on the third tube base, the third baffle is disposed between the third carrier and the third cushion block, the first light source is disposed on the third carrier, the second detector is disposed on the third cushion block, the third tube cap has a fifth through hole corresponding to the first light source, and has a sixth through hole corresponding to the second detector, the fifth lens is disposed in the fifth through hole, and the sixth lens is disposed in the sixth through hole; The second packaging structure also includes a fourth tube seat, a fourth tube cap, a fourth carrier, a fourth NTC element, a fourth TEC element, a fourth pad, a fourth baffle, a seventh lens and an eighth lens. The fourth tube cap is arranged on the fourth tube seat, the fourth NTC element is arranged on the third carrier, the fourth TEC element is connected to the fourth carrier, the fourth carrier and the fourth pad are arranged side by side on the fourth tube seat, the fourth baffle is arranged between the fourth carrier and the fourth pad, the second light source is arranged on the fourth carrier, the first detector is arranged on the fourth pad, the fourth tube cap has a seventh through hole corresponding to the second light source, and has an eighth through hole corresponding to the first detector, the seventh lens is arranged in the seventh through hole, and the eighth lens is arranged in the eighth through hole.

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