WO2015142161A1

WO2015142161A1 - Device for measuring fluorescent components in chemical substance and method thereof

Info

Publication number: WO2015142161A1
Application number: PCT/MY2015/050012
Authority: WO
Inventors: Suhairi SAHARUDIN
Original assignee: Mimos Berhad
Priority date: 2014-03-19
Filing date: 2015-03-09
Publication date: 2015-09-24

Abstract

The present invention relates to an improved device for measuring fluorescent components emitted by a chemical substance and associated method. The device comprises a laser source (100a), a sensor element (101) and an optical detector (102). The laser source (100a) is configured for emitting an excitation light onto the sensor element (101) through an optical fiber comprising a10 fluorescent material admixed with the chemical substance that fluoresces upon irradiation with the excitation light to thereby generating a fluorescent light which is detected by the optical detector (102). The device further comprises a slit adjusting mechanism adjustable for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity.

Description

DEVICE FOR MEASURING FLUORESCENT COMPONENTS IN CHEMICAL SUBSTANCE AND METHOD THEREOF

FIELD OF THE INVENTION

The present invention relates generally to investigation and analysis of materials to determine chemical or physical properties by the use of optical means. More particularly, the present invention relates to an improved device for measuring fluorescent components emitted by a chemical substance and associated method.

BACKGROUND OF THE INVENTION

Optical fiber is desirable in a variety of applications such as spectroscopy or optical coherence tomography. Other than providing communication opportunities over a distance at the speed of light, such optical fiber also can be used to sense parameters like temperature, strain and pressure within a location which is remote and inaccessible by conventional electrical sensors. An optical fiber allows light to reach destinations that are hundreds of kilometers away through the use of low loss glass materials. Optical fiber sensors are attracting more and more interest thanks to their ability to measure or sense parameters using light as the source. The use of laser in optical fiber sensors has allowed detection of a sensing parameter over the farthest target distance due to strong light intensity of the laser. Other light sources such as light emitting diodes (LED) may also be used due to easy light coupling to optical fiber and relatively low cost for system deployment.

Physical sensors are used in many modern machines to measure and monitor physical phenomena such as temperature, strain and pressure. Chemical and bio-sensors, on the other hand, are often employed in a number of applications where the detection of various vapors may be used to discern useful information, which have enormous opportunities in term of optical fiber sensor application. A chemical sensor, for example, mainly utilizes fluorescence or absorbance based materials that are selected based on the type of parameters to measure. Such capability of chemical sensor opens up doors to many applications in various sectors e.g. water quality monitoring, aquaculture, medical and hazardous gaseous detection.

Fluorescence sensor utilizes a light source that is known as excitation source derived from the need to excite sensing material. The sensing material in turn fluoresces to produce a light containing information about the desirable sensing parameter. Though many prior art describing fluorescence sensors, notable shortcomings of the fluorescence sensor are persisted such as limitation of fluorescence material, photo-bleaching of fluorescence material upon exposure to strong excitation light energy, and weak fluorescence emission received for detection.

A need therefore exists for providing technology allowing for economically exploitation and improvements on the fluorescence sensor that overcomes some of the problems in the prior art. Thus, the present invention seeks to provide an improved device and method for measuring fluorescent components emitted by a chemical substance.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Accordingly, the present invention provides a device for measuring fluorescent components emitted by a chemical substance. The device comprises a laser source, a sensor element and an optical detector. The laser source is configured to emit an excitation light. The sensor element coupled to the laser source through an optical fiber comprises a fluorescent material admixed with the chemical substance that fluoresces upon irradiation with the excitation light to thereby generating a fluorescent light. The optical detector is employed in the device for detecting the fluorescent light. The device of the present invention is characterized by a slit adjusting mechanism. The slit adjusting mechanism including a slit is positioned relative to the optical detector defining a slit opening adjustable for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity.

Preferably, the slit can be formed in or by a plate and comprises a movable portion that moves in direction relative to the plate for sizing the slit opening. The slit adjusting mechanism further comprises a slit driver having an electronic driving circuitry configured to facilitate movement of the movable portion according to a control signal.

In one preferred embodiment, the control signal comprises a driving current that is generated in response to the fluorescent light luminous intensity detected along the optical fiber for complying with a predefined allowable light intensity.

In another preferred embodiment, the control signal is configured to trigger a laser driver coupled to the laser source for maintaining luminous intensity of the excitation light emitted therefrom above a minimal intensity level.

In yet another preferred embodiment, the device further comprises a plurality of transmission channels. The plurality of transmission channels can be coupled to the optical fiber through an optical switch configured for switchably directing the excitation light to the sensor element and the fluorescent light from the sensor element. Essentially, each transmission channel of the plurality of transmission channel comprising a sensor element.

In accordance with another aspect, the present invention provides a method of measuring fluorescent components emitted by a chemical substance. The method comprises the steps of emitting an excitation light; irradiating the excitation light on a fluorescent material admixed with the chemical substance to thereby generating a fluorescent light; and detecting the fluorescent light. The method is characterized by the step of adjusting a slit opening for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity. Preferably, the method includes the step of receiving a control signal comprising a driving current generated in response to the fluorescent light luminous intensity for complying with a predefined allowable light intensity. The method further comprises the step of maintaining luminous intensity of the excitation light above a minimal intensity level.

It is an advantage of the present invention that provides a device which can automatically adjust slit opening of the slit adjusting mechanism positioned in front of the optical detector to control fluorescent light luminous intensity incident on the optical detector while maintaining moderate signal resolution. Hence, the device overcomes the shortcoming of the conventional fluorescence sensors that receive weak fluorescence emission for light detection.

It is another advantage of the present invention that the device can automatically adjust energy or luminous intensity of the excitation light delivered to the sensor element through the use of a control signal fed back to the device. Such the adjustment provided through the device substantially prevents and inhibits photo-bleaching of the fluorescent material when exposed to the strong excitation light. The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: Figure 1 is a schematic diagram showing an architecture of the device according to an embodiment of the present invention ; and Figure 2 is a flow diagram showing the steps performed by a processor for measuring fluorescent components, according to an embodiment of the present invention ;

It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to provide a device for measuring fluorescent components emitted by a chemical substance which overcomes the shortcomings of the conventional fluorescence sensors that receive weak fluorescence emission for light detection, and is prone to photo-bleaching of the fluorescent material when exposed to the strong excitation light.

The device of the present invention comprises a laser source 100a that is coupled to a sensor element 101 through an optical fiber, as shown in Figure 1 . The laser source 100a is configured for emitting an excitation light which is transmitted along the optical fiber towards the sensor element 101. The laser source 100a may include an LED or a laser diode source generally emitting a light. No limitation is imposed herein in this respect. However, it is preferred that only one single laser source 100a is used to generate the excitation light for the device. A laser driver 100b is positioned close to the laser source 100a for controlling luminous intensity of the excitation light emitted therefrom. The term "luminous intensity" used herein may refer to an evaluation of the wavelength- weighted power released by a laser source in a certain direction per unit solid, based on the brightness of the light in a harmonized form of the sensitivity of the human eye. The sensor element 101 comprises a fluorescent material. The fluorescent material can be admixed with the chemical substance or target sample, and is configured to fluoresce upon irradiation with the excitation light. If excitation light is irradiated onto the chemical substance, a fluorescent light containing fluorescent components is emitted from the chemical substance. The fluorescent components may contain information such as measured values of parameters. An optical detector 102 is employed into the device for detecting the fluorescent light emitted by the chemical substance. The optical detector 102 can be selected among the sensors of light or other electromagnetic energy. Preferably, the sensitivity of the optical detector 102 can be selected accordingly.

In this embodiment, the device further comprises a plurality of transmission channels that is coupled to the optical fiber through an optical switch 104. It is preferred that each transmission channel 105 of the plurality of transmission channels comprises a sensor element 101 that is attached therewith for measuring and sensing the chemical substance or target sample. The plurality of transmission channels is switchable from one transmission channel to another transmission channel using the optical switch 104 in accordance with a switching command signal (see dotted line in Figure 1 ). The optical switch 104 directs the excitation light emitted from the laser source 100a to the sensor element 101 through one of the plurality of transmission channels. Similarly, the optical switch 104 directs the fluorescent light emitted by the chemical substance from the sensor element 101 to the optical detector 102 through one of the plurality of transmission channels for detection. For example, if an excitation light is transmitted to the sensor element 101 through a first transmission channel, a corresponding fluorescent light emitted from the chemical substance in response to the excitation light is also routed to the optical detector 102 through the similar transmission channel, i.e. the first transmission channel. To isolate backward propagating fluorescence emission light from forward propagating excitation light, an optical isolator 109 is disposed along the optical fiber between the laser source 100a and the optical switch 104. Preferably, the optical isolator 109 allows transmission of excitation light in only one direction routed towards the sensor element 101 through an optical coupler 108. Other than receiving excitation light, the optical coupler 108 is also configured for dividing a fluorescent light incoming from the sensor element 101 at a predetermined ratio into two optical paths. Preferably, the fluorescent light upon passing the optical coupler 108 is divided into two equal optical paths. The first optical path of fluorescent light is directed to the optical detector 102 for detection and measurement. The second optical path is directed to a data acquisition and control module comprising a media converter 106 and a processor 107.

The fluorescent light transmitted through the second optical path is routed to the media converter 106. The media converter 106 is configured for performing optical-to-electrical conversion. Preferably, the media converter 106 can include an electro-optical transceiver that is configured to convert an optical signal, i.e. fluorescent light received through an optical signal port into an electrical signal and vice versa. More preferably, the electrical signal carries information regarding level of energy and luminous intensity of the fluorescent light passing through the optical switch 104. To convey the corresponding converted electrical signal, means for electrically conveying electrical signal can be employed at the data acquisition and control module.

Flow diagram showing the steps performed by the processor 107 for measuring fluorescent components is shown in Figure 2 which will be discussed in further detail below.

The processor 107 preferably comprises a computer program comprising instructions which when executed by a computer cause the computer to process the input, i.e. the electrical signal and the fluorescent light according to the flow diagram disclosed herein in Figure 2. Upon selection of sensor element 101 , an excitation light is next transmitted to the same. Optical pulses generated by the laser source 100a along the optical fiber are utilized for measuring optical fiber attenuations by way of using time of flight principle which is alternatively launched into the optical fiber based on a timing signal generated by a timer in the data acquisition and control module. The timer provides synchronization signals between the optical switch 104 and the data acquisition and control module for triggering a control signal (see dotted line in Figure 1 ). Strength of the return pulse subjected to Rayleigh scattering is measured to obtain information regarding the attenuations and optical fiber length values which, in turn is being translated into the amount of energy or luminous intensity required for compensating the shortfalls via the control signal.

The electrical signal corresponding to the fluorescent light converted by the media converter 106 is routed to the processor 107. A control signal based on the electrical signal is generated by the processor 107 in response to the fluorescent light luminous intensity which is detected along the optical fiber through the second optical path for complying with a predefined allowable light intensity or threshold value. The predefined allowable light intensity or the threshold value may include, for example, light attenuation limit value and luminous intensity limit value. To convey the control signal, means for conveying control signal can be employed at the device.

If attenuation of the optical pulses is below a threshold value, the processor 107 produces a control signal including a corresponding driving current which is next transmitted to the laser drive 100b for maintaining luminous intensity of the excitation light emitted therefrom above a minimal intensity level. For example, the control signal comprising an increased driving current is injected into the laser drive 100b to compensate for the shortfall in the energy of luminous intensity of the excitation light. Such adjustment fed back traveling between the data acquisition and control module and the laser drive 100b substantially prevents and inhibits photo-bleaching of the fluorescent material when continuously exposed to the strong excitation light. Distance between a laser source 100a and a sensor element 101 is accounted in determining the energy or luminous intensity of the excitation light. For example, at relatively far distance between laser source and sensor element, the energy or luminous intensity of excitation light is provided stronger than that of shorter distance.

Fluorescent light emitted by the fluorescent material has luminous intensity that constitutes half of energy of excitation light it receives. Hence, to allow adequate or sufficient energy and fluorescent light luminous intensity detected at the optical detector 102, an excitation light having energy or luminous intensity at least twice the emission power (or luminous intensity) of the fluorescent material is required as a foundation in the flow diagram. In addition, this, advantageously, omits the need for recalibration of energy or luminous intensity of the excitation light when accommodating different locations of sensor elements in the device contradicted to prior art. If degree of fluorescent light luminous intensity is below a threshold value, the processor 107 produces a control signal including a corresponding driving current that is next transmitted to a slit adjusting mechanism placed near to the optical detector 102 for sizing a slit 103a. Preferably, the control signal carries information and decision that are determined by way of calculating projected emission power of excitation light received at various distances versus attenuations or optical loss incurred in the optical fiber. For example, the control signal comprising an increased driving current is injected into a slit driver 103b to size up the slit 103a to receiving more and higher energy and fluorescent light luminous intensity illuminated or incident on the optical detector 102 for detection. This particular capability of the device in the present invention, advantageously, overcomes the shortcoming of the conventional fluorescence sensors that receive weak fluorescence emission for light detection.

Preferably, the slit 103a of the slit adjusting mechanism defines a slit opening that is adjustable for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity. The slit opening can be adjusted to allow more photons incident on the optical detector 102 to thus increase light detection efficiency. More preferably, the control signal is routed to the slit driver 103b which drive the slit opening of the slit 103a positioned relative to the optical detector 102. In this embodiment, the slit 103a is positioned in front of the optical detector 102 just before the fluorescent light entrance.

The slit 103a further comprises a movable portion that moves in a direction relative to the plate when sizing the slit opening. Movement of the movable portion is facilitated by the slit driver 103b which receives a control signal generated by the data acquisition and control module. The slit driver 103b further comprises an electronic driving circuitry that is configured to process the control signal received. The slit 103a may be formed in or by a plate and its slit opening can have any shape such as square, circle and rectangle. In this embodiment, the slit opening is a square having a width and a length. For instance, when sizing up the square slit opening driven by the slit driver 103b, the width or the length or both of them can expand to a desired slit opening size via the movable portion.

The method of measuring fluorescent components will now be described by way of an example.

Example

In operation, the laser source 100a emits an excitation light which travels through the optical fiber to the sensor element 101 . The excitation light is routed through one of the plurality of transmission channels using the optical switch 104. Upon irradiation with the excitation light, the fluorescent material admixed with the chemical substance fluoresces to generate a fluorescent light. Next, the fluorescent light that is incoming from the sensor element 101 travels in a direction opposite to the excitation light and is directing to the optical coupler 108. The optical coupler 108 divides the fluorescent light at a predetermined ratio into two optical paths. The first optical path of fluorescent light is directed to the optical detector 102 for detection and measurement. The second optical path is directed to a data acquisition and control module comprising a media converter 106 and a processor 107. Upon receiving the fluorescent light, the data acquisition and control module generates a control signal accordingly. The control signal is next transmitted to the laser driver 100b for compensating the shortfalls in excitation light and to the slit driver 103b for adjusting the slit 103a through the slit adjusting mechanism for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity.

While this invention has been particularly shown and described with reference to the exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

A device for measuring fluorescent components emitted by a chemical substance, comprising:

a laser source (100a) for emitting an excitation light;

a sensor element (101 ) coupled to the laser source (100a) through an optical fiber comprising a fluorescent material admixed with the chemical substance that fluoresces upon irradiation with the excitation light to thereby generating a fluorescent light; and

an optical detector (102) configured for detecting the fluorescent light; characterized in that,

the device further comprising a slit adjusting mechanism including a slit (103a) positioned relative to the optical detector (102) defining a slit opening adjustable for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity.

A device according to Claim 1 further comprising a plurality of transmission channels coupled to the optical fiber through an optical switch (104) configured for switchably directing the excitation light to and the fluorescent light from the sensor element (101 ).

A device according to Claim 2, wherein each transmission channel (105) of the plurality of transmission channel comprising a sensor element (101 ).

A device according to Claim 1 , wherein the slit (103a) formed by a plate comprising a movable portion that moves in direction relative to the plate for sizing the slit opening.

A device according to Claim 4, wherein the slit adjusting mechanism further comprising a slit driver (103b) having an electronic driving circuitry configured to facilitate movement of the movable portion according to a control signal.

A device according to Claim 5, wherein the control signal including a driving current generated in response to the fluorescent light luminous intensity detected along the optical fiber for complying with a predefined allowable light intensity.

7. A device according to Claim 5, wherein the control signal triggers a laser driver (100b) coupled to the laser source (100a) to maintain luminous intensity of the excitation light emitted therefrom above a minimal intensity level.

8. A method of measuring fluorescent components emitted by a chemical substance, comprising:

emitting an excitation light;

irradiating the excitation light on a fluorescent material admixed with the chemical substance to thereby generating a fluorescent light; and

detecting the fluorescent light;

characterized in that,

the method further comprising the step of adjusting a slit opening for selectively receiving the fluorescent light according to different degrees of fluorescent light luminous intensity.

9. A method according to Claim 8 including receiving a control signal comprising a driving current generated in response to the fluorescent light luminous intensity for complying with a predefined allowable light intensity.

10. A method according to Claim 8 further comprising the step of maintaining luminous intensity of the excitation light above a minimal intensity level.