Laminated fluorescent sensor

Abstract

A laminated fluorescent sensor includes a sealable sensor housing and an optical sensing system embedded inside the sensor housing. The optical sensing system includes a light source (7), a short wave pass filter (8), an air chamber (10), a sensing unit, a long wave pass filter set (12) and an optical signal collecting unit from top to bottom all of which are coaxially set. The optical signal collecting unit is connected with a signal processing system (14); the sensor housing has air inlets (2, 201) and an air pumping port (3), the air inlets (2, 201) are communicated with the air chamber (10) through an air intake passage, the air chamber (10) is communicated with the air pumping port (3) through an air pumping passage. The laminated fluorescent sensor is compact and easy to be arrayed for simultaneously detecting two or more detected objects, has a high signal-to-noise ratio, is applicable in quick detection of micro-trace chemicals including but not limited to explosives and narcotics, provides great detection effects, has distinctly distinguishable signal responses to objects not being detected and to objects being detected, and provides stable and accurate detection.

Claims

1. A laminated fluorescent sensor, comprising: a sealable sensor housing and an optical sensing system embedded inside the sensor housing, wherein: the optical sensing system comprises a light source (7), a short wave pass filter (8), an air chamber (10), a sensing unit, a long wave pass filter set (12), and an optical signal collecting unit from top to bottom all of which are coaxially set; the optical signal collecting unit is connected with the signal processing system (14); the sensor housing has an air inlet and an air pumping port (3), the air inlet is communicated with the air chamber (10) through an air intake passage, the air chamber (10) is communicated with the air pumping port (3) through an air pumping passage.

2. The laminated fluorescent sensor, as recited in claim 1, wherein: the light source (7) is a straw-hat-shaped LED (light emitting diode) lamp, a bullet-shaped LED lamp or a patch-type LED lamp; a divergence angle of the light source (7) is in a range of 7 to 30 degrees.

3. The laminated fluorescent sensor, as recited in claim 2, wherein: the sensor housing comprises an upper housing (1) and a lower housing (101), wherein the upper housing (1) is embedded inside the lower housing (101), the sensor housing has a threaded hole (4) for communicating the upper housing (1) with the lower housing (101), a screw is installed within the threaded hole (4); the light source (7) is fixed to a light source holder (6), the light source holder (6) and the short wave pass filter (8) are embedded inside the upper housing (1); the sensing unit, the long wave pass filter set (12) and the optical signal collecting unit are embedded inside the lower housing (101), the signal processing system (14) and a bottom of the lower housing (101) are sealed.

4. The laminated fluorescent sensor, as recited in claim 1, wherein: the optical signal collecting unit is a PIN-type photodiode (13).

5. The laminated fluorescent sensor, as recited in claim 1, wherein: a transmittance of the short wave pass filter (8) is larger than 30%, an OD (optical density) thereof is in a range of 4 to 6.

6. The laminated fluorescent sensor, as recited in claim 1, wherein: the long wave pass filter set (12) comprises a narrow band filter and a long wave pass filter, or the long wave pass filter set (12) comprises multiple misaligned narrow band filters, a thickness of the long wave pass filter set (12) is in a range of 2 to 5 mm.

7. The laminated fluorescent sensor, as recited in claim 1, wherein: an angle between an outlet of the air intake passage and the sensing unit is in a range of 10 to 50 degrees, an angle between an inlet of the air pumping passage and the sensing unit is in a range of 10 to 50 degrees, or the outlet of the air intake passage and the inlet of the air pumping passage are provided 0.2 to 1 mm above a tangential direction of an edge of the sensing unit.

8. The laminated fluorescent sensor, as recited in claim 1, wherein: when there are multiple optical sensing systems, the multiple optical sensing systems are embedded inside the sensor housing in parallel, the air inlet and the air pumping port (3) are respectively provided at two sides of the air chamber (10).

9. The laminated fluorescent sensor, as recited in claim 1, wherein: the air pumping port (3) is connected with a micro vacuum pump (5), a transparent optical window (9) is provided between the short wave pass filter (8) and the air chamber (10).

10. The laminated fluorescent sensor, as recited in claim 1, wherein: the sensing unit is a fluorescent sensing film (11), a volume of the air chamber (10) corresponding to the fluorescent sensing film (11) with a diameter of 10 mm is in a range of 50 to 500 mm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a structurally schematic view of a laminated fluorescent sensor provided by the present invention.

[0027] FIG. 2 is a structurally schematic view of a double-laminated fluorescent sensor provided by the present invention.

[0028] FIG. 3(a) is a top view of an air passage unit of the double-laminated fluorescent sensor.

[0029] FIG. 3(b) is a right view of the air passage unit of the double-laminated fluorescent sensor.

[0030] FIG. 4 is a test result chart of detecting several common narcotics by using the laminated fluorescent sensor according to a first embodiment of the present invention.

[0031] FIG. 5 is a result chart of simultaneously detecting several narcotics and explosives by using the double-laminated fluorescent sensor according to a second embodiment of the present invention.

[0032] In the drawings, 1: upper housing; 101: lower housing; 2: first air inlet; 201: second air inlet; 3: air pumping port; 4: threaded hole; 5: micro vacuum pump; 6: light source holder; 7: light source; 8: short wave pass filter; 9: optical window; 10: air chamber; 11: fluorescent sensing film; 12: long wave pass filter set; 13: photodiode; 14: signal processing system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] The present invention will be further described in detail with accompanying drawings as follows. In the present invention, relevant directions are defined based on that the fluorescent sensing film of FIG. 1 is horizontally disposed, and the first air inlet is located at the right side, which is only intended to describe more clearly rather than limiting the present invention, for example, the air inlet may actually be located at any side of the upper housing; according to the condition of the gas to be detected, the sensor provided by the present invention is able to be turned over or inverted, that is to say, the fluorescent sensing film is not necessarily in a horizontal state when in use.

[0034] Related technical terms and other descriptions of the laminated fluorescent sensor provided by the present invention are as follows. The laminated structure of the present invention refers to a special structure wherein an excitation light source, a short wave pass filter, a sensing unit, a long wave pass filter set, and an optical signal collecting unit are coaxially set.

[0035] The signal-to-noise ratio of light intensity refers to the ratio of the relative values of the light intensity of the laminated fluorescent sensor with the sensing film and without the sensing film; the response rate refers to the response time of the sensor to the detected object; The selectivity refers to the distinguishability when the laminated sensor detects the detected object and the non-detected object.

[0036] Referring to FIGS. 1 and 2, a laminated fluorescent sensor provided by the present invention comprises a sealable sensor housing and at least one optical sensing system disposed in the sensor housing, when there are multiple optical sensing systems, the multiple optical sensing systems are disposed in the sensor housing in parallel. The sensor housing comprises an upper housing 1 and a lower housing 101, wherein: the sensor housing has multiple threaded holes 4 for communicating the upper housing 1 with the lower housing 101, screws are respectively installed into the multiple thread holes 4, an engaged structure is disposed between the upper housing 1 and the lower housing 101, the upper housing 1 is fixedly connected with the lower housing 101 through the engaged structure and the screws. The optical sensing system is embedded inside the sensor housing. Through the accurate engaged structure and the screws, airtight environment and optical conditions required by sensing and detecting are formed.

[0037] The optical sensing system comprises a light source 7, a short wave pass filter 8, an optical window 9, an air chamber 10, a fluorescent sensing film 11, a long wave pass filter set 12, a photodiode 13 and a signal processing system 14 connected with the photodiode 13. The sensor housing has an air passage unit, air inlets and an air pumping port 3, wherein the air passage unit comprises an air intake passage and an air pumping passage. The air passage unit of the sensor housing and the air chamber 10 are designed as a seamless connection for reducing a loss of detected substance vapor into the fluorescence sensing film 11. The air intake passage and the air pumping passage are respectively distributed at two sides of the air chamber 10 and communicated with the air chamber 10, the air intake passage is communicated with the air inlets which are funnel-shaped, the air pumping passage is communicated with the air pumping port 3, the air pumping port 3 is communicated with a micro vacuum pump 5.

[0038] The sensor housing comprises the upper housing 1 and the lower housing 101, wherein: the light source 7 and the short wave pass filter 8 are installed within the upper housing 1, the upper housing 1 is configured to define the air chamber 10 and the air passage unit, the light source 7 is fixedly installed within the upper housing 1 through a light source holder 6; the fluorescent sensing film 11, the long wave pass filter set 12 and the photodiode 13 are installed within the lower housing 101, the signal processing system 14 and a bottom of the lower housing 101 are sealed; multiple stepped holes are provided within the upper housing 1 and the lower housing 101 for installing components, so that the components are able to be embedded within the upper housing 1 and the lower housing 101.

[0039] An angle between the air intake passage near the fluorescent sensing film 11 and a sensor film substrate, or an angle between the air pumping passage near the fluorescent sensing film 11 and the sensor film substrate is in a range of 10 to 50 degrees. Or, the air intake passage near the fluorescent sensing film 11, and the air pumping passage near the fluorescent sensing film 11 are provided 0.2 to 1 mm above a tangential direction of an edge of the sensing film substrate. The air intake passage and the air pumping passage are unable to face against the fluorescence sensing film 11 to prevent the impact of the airflow from damaging the fluorescence sensing film; and the air intake passage and the air pumping passage are also unable to be close to the fluorescence sensing film 11 to block the flow of the airflow on a surface of the fluorescence sensing film 11. The air inlets and the air pumping port 3, all of which are communicated with an external environment, are able to be designed on any side of the upper housing 1 as needed, which just ensures that the air passage unit allows gas to be detected to pass through the air chamber.

[0040] For example, when there is one optical sensing system, two air inlets are respectively provided at two positions, wherein: a first air inlet 2 is provided at a side wall of the upper housing 1, a second air inlet 201 is provided at a top end of the upper housing 1, the air pumping port 3 is provided at the top end of the upper housing 1, the first and second air inlets and the air pumping port 3 are respectively provided at a left side and a right side of the air chamber 10, referring to FIG. 3(a) and FIG. 3(b); where there are two optical sensing systems, air inlets are provided at a front side of a top portion of the upper housing 1, the air pumping port 3 is provided at a rear side of a bottom portion of the upper housing 1, and all of the air inlets and the air pumping port 3 are provided between the two optical sensing systems.

[0041] The light source 7 acts as an excitation source of the fluorescence sensing film 11 and is embodied as an LED (light emitting diode) lamp which are able to be a straw-hat-shaped LED lamp, a bullet-shaped LED lamp or a patch-type LED lamp. A main emission wavelength range of the light source 7 is matched with an optimal excitation waveband of the fluorescent sensing film 11 as much as possible. A divergence angle of the light source 7 is in a range of 7 to 30 degrees.

[0042] A distance between the short wave pass filter 8 and the light source 7 is within 3 mm, which is based on a principle of not losing the effect of the short wave pass filter 8. The short wave pass filter 8 has a transmittance of more than 30% for excitation light, and has a large cutoff depth to a fluorescent emission band of the fluorescent sensing film 11. Generally, an OD (optical density) of the short wave pass filter 8 is in a range of 4 to 6.

[0043] The optical window 9 is made from a light-transmitting material for preventing the short wave pass filter 8 from being contaminated by the gas to be detected.

[0044] A volume of the air chamber 10 of the sensor is determined by not affecting the fluidity of the gas to be detected on a surface of the fluorescent sensing film 11, not affecting a size of the air passage unit, and a sensitivity of the sensor itself, and the volume of the air chamber 10 corresponding to the fluorescent sensing film 11 with a diameter of 10 mm is in a range of 50 to 500 mm.sup.3.

[0045] There are many optical substrates available for the fluorescent sensing film 11. The main principle is that the optical substrates have no interference to the sensing film or the fluorescent detection band, and are optical media that are able to conduct fluorescence, such as glass. There is no requirement for the smoothness and flatness of the optical substrate. The sensing material is coated or chemically bonded to the optical substrate to form a diaphragm for quick replacement.

[0046] The long wave pass filter set 12 is configured to filter out the excitation light and the stray light such as the double-frequency light and the infrared tail on the sensing film. Generally, the intensity of the excitation light is 3 to 10 orders of magnitude larger than the intensity of the fluorescence, and even larger. If the signal-to-noise ratio of light intensity is improved by a single-type filter, the OD value generally needs to be 6-8, but the increase of the OD value causes the decrease in the transmittance of the fluorescent band, and also increases the thickness of the filter and the manufacturing cost. The long wave pass filter set 12 provided by the present invention is designed according to the wavelength distribution range of the specific excitation light source and the fluorescent emission range of the sensing film. The long wave pass filter set comprises a narrow band filter and a long wave pass filter, or the long wave pass filter set comprises multiple misaligned narrow band filters for improving the signal-to-noise of light intensity of the sensor and saving cost. Moreover, the thickness of the long wave pass filter set 12 is controlled to be in a range of 2 to 5 mm.

[0047] The narrow band LED lamp has a main light emitting band, but there are some stray light near the main light emitting band. Generally, only the short wave pass filter is unable to achieve the filtering effect, so the long wave pass filter set is required to assist the filtering. For a sensing unit with large Stokes displacement, a narrow band filter and a long wave pass filter are used to achieve the filtering effect, such as the excitation light is in a range of 430 nm to 500 nm and the fluorescent emission is in a range of 600 nm to 800 nm, the selected long wave pass filter set comprises a 650 nm narrow band filter and a 350 nm-600 nm cut-off long wave pass filter. According to the experimental verification, the narrow band filter is close to the sensing unit. For a sensing unit with small Stokes displacement and the excitation light in the ultraviolet band, such as between 300 nm and 400 nm, the fluorescent emission waveband is between 380 nm and 470 nm, the misaligned narrow band filters are suggested to be used, wherein the misaligned narrow band filters are a narrow band filter with a bandwidth of 20 nm and a wavelength of 410 nm, and a narrow band filter with a bandwidth of 10 nm and a wavelength of 415 nm. According to experimental verification, a narrow band filter with a short wavelength is required to be close to the sensing unit.

[0048] A gap of 0.2 to 0.6 mm is provided between the long wave pass filter set 12 and the fluorescent sensing film for fixing the filter, and a distance between the long wave pass filter set 12 and the photodiode 13 is in a range of 0 to 1 mm.

[0049] The photodiode 13 is a PIN-type photodiode.

[0050] Under the premise of ensuring the signal-to-noise ratio of light intensity, the response rate and the selectivity, the length, width and height of the laminated fluorescent sensor are controlled to be within 2 cm. Relevant optical components are only the optical source 7, the filters, and the photosensitive member, so that the sensor is simple in structure and easy to install, and is able to be expanded to an arrayed sensor which is able to simultaneously detect multiple types of substances.

[0051] The gas to be detected enters from the inlet of the air intake passage, passes through the air chamber 10, and is discharged from the air pumping port 3. The light emitted from the light source 7 is irradiated onto the fluorescent sensing film 11 by the short wave pass filter 8 to generate fluorescence, and the excitation light and the stray light is filtered out by the long wave pass filter set 12, and then is received by the PIN-type photodiode 13.

[0052] The aperture and thickness of the optical lens mounted inside the sensor housing are the same as the size of the optical lens itself. Components of the optical sensing system are limited in size for limiting the scope of activities, so as to ensure the vibration resistance, impact force and shading conditions required by fluorescence sensing of the optical components.

First Embodiment

[0053] As shown in FIG. 1, a single laminated fluorescent sensor comprises a sensor housing comprising an upper housing 1 and a lower housing 101, and an optical sensing system disposed within the sensor housing. Optical components of the optical sensing system are embedded into an interior of the sensor housing in a specific order, and then the upper housing 1, the lower housing and a signal processing system 14 connected with the lower housing 101 are fixed through threaded holes 4 and screws, so that a complete laminated fluorescent sensor is formed. Light emitted by the light source 7 is diffused by the short wave pass filter 8 and the air chamber 10, and then irradiated onto the fluorescent sensing film 11 to generate fluorescence, and the excitation light and the stray light is filtered out by the long wave pass filter set 12, and then is received by the PIN-type photodiode 13, the photodiode 13 performs photoelectric signal conversion and transmits an electrical signal to the signal processing system 14, the signal processing system 14 monitors the intensity change of the fluorescence emitted from the fluorescent sensing film 11 in real time. When the vapor of the substance to be detected reaches the air chamber 10 via the first air inlet 2 or the second air inlet 201, and reversibly interacts with the fluorescent sensing film 11, the fluorescence intensity emitted by the fluorescent sensing film 11 is enhanced or weakened. The test result is determined by the magnitude of the change in fluorescence intensity.

[0054] As shown in FIG. 4, the laminated fluorescent sensor is used to detect several common narcotics. A left picture shows a signal-to-noise ratio of light intensity of the laminated fluorescent sensor; the signal-to-noise ratio of the laminated sensor reaches above 30 by coating 10 L fluorescent sensing film with a concentration of 0.05% onto a glass piece with a diameter of 15 mm, that is, the signal-to-noise ratio of the laminated narcotic sensor reaches above 30; a right picture shows that the substance to be detected is collected every 30 seconds, a sampling time is controlled in a range of 1 to 5 seconds, a response time of the sensor is almost synchronized with the sampling time. In FIG. 4, a signal response distinguishability of the laminated sensor is compared when a non-detected object and a detected object is detected, wherein signals are clearly distinguished and positioned stably and accurately.

[0055] The light intensity of the laminated fluorescent sensor on the fluorescent sensing film is only in a range of 5 to 30 W. Compared with 100 W or above (tested on the surface of the sensing film using a Thorlabs model PM100D power meter) which is required by a conventional sensor with a certain angle between the light source and the detection unit, the photobleaching and photodamage of the fluorescent sensing film by the excitation light are greatly reduced.

Second Embodiment

[0056] In practice, it is often necessary to simultaneously detect two or more types of objects to be detected, such as explosives and narcotics. As shown in FIG. 2, a double-laminated fluorescent sensor is illustrated, which comprises an upper housing 1, a lower housing 101 and two optical sensing systems. According to different types of objects to be detected, corresponding fluorescent sensing films 11 and corresponding optical components are selected, the optical components of the optical sensing system are embedded into the exterior of the sensor housing in a specific order, and then the upper housing 1 and the lower housing 101, the lower housing 101 and the signal processing system 14 are fixed through threaded holes 4 and screws, so that a complete double-laminated fluorescent sensor is formed. Light emitted by the light source 7 is diffused by the short wavelength pass filter 8 and the air chamber 10, and then irradiated onto the fluorescent sensing film 11 to generate fluorescence, and then the excitation light and the stray light is filtered out by the long wave pass filter set 12, and then is received by the PIN-type photodiode 13, the signal processing system 14 monitors the intensity change of the fluorescence emitted from the fluorescent sensing film 11 in real time. When the vapor of the substance to be detected is divided into two parts via the first air inlet 2 for respectively entering into the air chambers 10 of the double-laminated fluorescent sensor, and then respectively reversibly interact with the fluorescent sensing films 11, the fluorescence intensity emitted by the fluorescent sensing films 11 is enhanced or weakened. The test result is determined by the magnitude of the change in fluorescence intensity.

[0057] FIG. 5 is a result chart of simultaneously detecting several narcotics and explosives by using the double-laminated fluorescent sensor according to a second embodiment of the present invention. The second embodiment of the present invention is a preliminary development of the first embodiment of the present invention. Although there are respective optical sensing systems, one air inlet and one air pumping port are shared to simultaneously detect or mutually verify two kinds of detected substances, thereby increasing the detecting ability.

[0058] In summary, the expansion direction of the present invention may be that the respective sensing systems are simply distributed in parallel, that is, there are respective optical sensing systems and air chambers, but share the same air inlet and the air pumping port; or may share the same air chamber, the excitation light source and the photodiode to achieve high integration; of course, it is also able to be partially integrated, partially integrated, and finally achieve highly integrated array-stacked sensors, simultaneously or alternately detecting multiple types of substances without interfering with each other.

[0059] Finally, the above description merely shows some of the embodiments of the present invention, and all changes and developments made with reference to the structures and optical sensing systems mentioned in the present invention are the subject of the present invention.