WO2016068689A1

WO2016068689A1 - A system and method for performing optical interferometry referencing for optical sensor

Info

Publication number: WO2016068689A1
Application number: PCT/MY2015/000091
Authority: WO
Inventors: Bin Hisham MOHD HAFIZULFIKA; Bin Mohd Zain MOHD NORZALIMAN; Bin Abdullah MUHAMMAD SYARGAWI
Original assignee: Mimos Berhad
Priority date: 2014-10-29
Filing date: 2015-11-05
Publication date: 2016-05-06

Abstract

The present invention relates to the sensing instruments and methods for measuring the phase measurement of an analyte more particularly, to a system and method for performing optical interferometry referencing for phase fluometric optical sensor. One of the advantages of the present invention is that the system and method provides optically the phase of the reference excitation signal at the same phase wavefront with the fluorescence excitation signal in the absent of the analyte. The method of the present invention utilizes interferometry technique to achieve a precision phase measurement. In addition, the system of the present invention engages safely the phase of excitation reference signal as the sensing system phase reference. The present invention further provides a considerable reduction of materials with even greater efficiency and economically during operation.

Description

A SYSTEM AND METHOD FOR PERFORMING OPTICAL INTERFEROMETRY

REFERENCING FOR OPTICAL SENSOR FIELD OF THE INVENTION

The present invention relates to the sensing instruments and methods for measuring the phase measurement of an analyte more particularly, to a system and method for performing optical interferometry referencing for phase fluometric optical sensor.

BACKGROUND OF THE INVENTION

To enhance a precision measurement, an optical sensor utilizing phase measurement technique may achieve by using interferometry method. Trace level phase fluometric optical sensor is needed for such precision because of a demand in higher resolution measurement. Optical fluorescence based chemical sensor such as optical dissolved oxygen sensor targeting part per bilion (ppb) or molecular level concentration is often used to measure accurately and quantitatively of many acutely ill hospitalized patients.

Optical fluorescence based chemical sensor uses optical way to measure and to quantify the analyte concentration while the analyte responses directly to chemical indicator (Ismail, N.H et. al 2013). However, some analytes such as dissolved ammonia has no convenient intrinsic optical property such as absorption or luminescence. Therefore, an alternative option is to use a mediated chemical sensor. In the reagent mediated sensing system, a change in the optical response of an intermediate agent which usually an analyte-sensitive dye molecule corresponds to analyte concentration. The analyte concentration is determined by the fluorescence lifetime decayed of luminophore molecules. By definition, the fluorescence lifetime (τ) of luminophore molecules is the time required for the excited molecules to decay to 1/e or 36.8% of the original population N _(o) according to:

whereN_(t) is the number of excited molecules at time f. Principally the excited state lifetime can be measured using either time domain method or frequency domain method. In the frequency domain method, the intensity of the excitation light source is modulated sinusoidally at high frequency. This excitation function can be described by:

where, F_(t) and E₍₀₎ are the intensities at time t and 0, M_(E) is the modulation factor (ratio of the AC and DC parts of the signal) and ω is the angular modulation frequency. Due to the persistence of the excited state, luminophore molecules which are subjected to such an excitation will give rise to a modulated emission at the same frequency but delayed in phase and partially demodulated with respect to the excitation.

The emitted fluorescence signal can be expressed as follows:

where F_(o) is the average fluorescence intensity. This relationship signifies that measurement of the phase delay (φ), forms the basis of one measurement of the lifetime (τ). In particular, one can demonstrate that:

and thus the phase lifetime can be determined by:

The modulation degree of the excitation M_(E) and the emission M _(F) are given by:

The relative modulation (M) of the emission is then:

The relationship between M and τ can be expressed by:

and thus the modulation lifetime can be determined by

Theoretically, based on the equations described above, it is concluded that the phase-shift and relative modulation of the emission are dependence of relative values of the fluorescence lifetime and light modulation frequency. As the light modulation frequency increases, the phase-shift of the emission increases and the relative modulation of the emission decreases. In the case of single fluorescence exponential decay, the phase lifetime τ_(φ) and the modulation lifetime τ_{(M )} are equivalent at all modulation frequency. Thus, the phase angle and relative modulation is used at any frequency in order to determine the fluorescence lifetime of the sensor material.

To determine the phase shift of the fluorescence signal with reference to the modulated excitation signal, a detection system should be carried out for signals with predetermined frequency, which is generally generated by electronics module within the system. There are ways for determining phase of a wavefront either using electronic or analytical technique. Conventionally, the phase measurement is determined electronically such as through zero crossing detection method. Another phase measurement is the use of analytical technique such as through Fourier transform method.

Zero crossing detection is the most direct method for measuring phase difference between excitation signal and fluorescence signal. The time at which each signal crosses the zero- voltage axis is determined, usually by using high-speed comparator as depicted in Figure 1. This produces a trigger pulse in each channel to drive a XOR gate. The output from the XOR gate is a rectangular wave, the duty cycle of which is proportional to the phase difference between the input signals. If this signal is integrated by means of a suitable low pass filter, a DC voltage is produced that is an analogue representation of the phase angle. The weakness of this method in the phase fluometry optical sensing is that the phase referencing of the sensing system is shifted. This is due to the phase of reference signal is different as compared to the phase of fluorescence emission signal without presence of analyte. In this case, the excitation light beam phase used as the reference signal phase. However, the phase wavefront of the reference signal is not represented as the reference phase of the sensing system.

In some phase fluometry optical sensing system, the sensing phase reference uses phase of the fluorescence emission signal with the absence of the analyte. This procedure requires a repetition in each measurement session at different time and place to ensure the precision measurement. This procedure is often complicated and constitutes a possible source of error.

To overcome the above drawbacks, the present invention provides a system and method for performing optical interferometry referencing for phase fluometric optical sensor. The optical double referencing method is further disclosed for phase fluometric optical sensor. The present invention provides optically the phase of the reference excitation signal at the same phase wavefront with the fluorescence excitation signal in the absent of the analyte. The method of the present invention utilizes interferometry technique to achieve a precision phase measurement. In addition, the system of the present invention engages safely the phase of excitation reference signal as the sensing system phase reference. The present invention further provides a considerable reduction of materials with even greater efficiency and economically during operation.

SUMMARY OF THE INVENTION

The present invention provides a system for performing optical interferometry referencing for phase fluometric optical sensor comprising a controller to control a light source to produce a light beam at a predetermined wavelength and analyze a phase of an incoming reference light beam wavefront as a reference phase and a phase of combined fluorescence light beams coming from a sensor in absence of an analyte to compute and optimize the phase of the combined fluorescence light beams wavefront to make a same phase value as the phase of the reference light beam; a first optical dichroic beamsplitter receiving the light beam to split the light beam into two separated light beams, a first separated light beam is guided to the sensor to produce a fluorescence emission light beam and guided back to the first optical dichroic beamsplitter in the same optical path; and a second separated light beam is guided to an interferometric measurement module as a reference light beam; the interferometric measurement module having a second optical dichroic beamsplitter receiving the fluorescence emission light beam which returns to the first optical dichroic beamsplitter and propagates in parallel with the reference light beam in a same optical path and further splitted the fluorescence emission light beam into two separated fluorescence light beams, a first separated fluorescence light beam propagates to a fixed mirror and reflected back to the second optical dichroic beamsplitter and a second separated fluorescence light beam propagates to a moveable mirror and reflected the fluorescence light beam back to the second optical dichroic beamsplitter; the first reflected fluorescence light beam from the fixed mirror and second reflected fluorescence light beam from the moveable mirror are combined and have an interference at the second optical dichroic beamsplitter; the combined reflected fluorescence light beams and the reference light beam are guided to a photo detector wherein the controller sets the combined phase as the sensing phase reference as detected in the photo detector and shift the sensor senses the presence of analytes and the controller further compute and calculate the analyte concentration by determining the relationship between the shifted phase and equations used for different types of analyte. In one of the embodiment of the present invention, the interferometric measurement module is based on Michelson interferometer.

In yet another embodiment of the present invention, the first optical dichroic beamsplitter receiving the light beam guided to split the light beam into two separate light beams depending on a beamsplitter ratio.

In another embodiment of the present invention, the controller produce the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam by moving the moveable mirror perpendicular to the fluorescence light propagation coming from the second dichroic beamsplitter.

In yet another embodiment of the present invention, the moveable mirror has a maximum travel range at half wavelength of the fluorescence light for 2π phase different. A method of performing optical interferometry referencing for phase fluometric optical sensor comprising producing a light beam at a predetermined wavelength by a controller; splitting the light beam into a first separated light beam and a second separated light beam by a first optical dichroic beamsplitter; guiding the first separated light beam to a sensor to produce a fluorescence emission light beam and guided back to the first optical dichroic beamsplitter in the same optical path; guiding a second separated light beam to an interferometric measurement module as a reference light beam; receiving the fluorescence emission light beam which returns to the first optical dichroic beamsplitter by a second optical dichroic beamsplitter of the interferometric measurement module and propagating the fluorescence emission light beam in parallel with the reference light beam in a same optical path; splitting the fluorescence emission light beam into a first separated fluorescence light beam and a second separated fluorescence light beam; propagating the first separated fluorescence light beam to a fixed mirror of the interferometric measurement module and reflecting back to the second optical dichroic beamsplitter of the interferometric measurement module; propagating the second separated fluorescence light beam to a moveable mirror of the interferometric measurement module and reflecting the second separated fluorescence light beam back to the second optical dichroic beamsplitter; combining the first reflected fluorescence light beam from the fixed mirror and second reflected fluorescence light beam from the moveable mirror and have an interference at the second optical dichroic beamsplitter; guiding the combined reflected fluorescence light beams and the reference light beam to a photo detector; setting the combined phase as the sensing phase reference as detected in the photo detector by the controller and shifting the sensor senses the presence of analytes; and computing and calculating the analyte concentration by the controller by determining the relationship between the shifted phase and equations used for different types of analyte.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

Figure 1 illustrates a prior art the phase measurement determined electronically through zero crossing detection method. Figure 2 illustrates a schematic diagram of system of optical double referencing michelson interferometric based optical phase fluorometric sensor in accordance of the present invention. Figure 3 illustrates a moveable mirror used in the system at maximum KI2 wavelength mirror movement to shift 2π degree of the phase of the fluorescence wavefront in accordance of the present invention.

Figure 4 illustrates a flow chart of method for performing optical interferometry referencing for phase fluometric optical sensor in accordance of the present invention.

Figure 5 illustrates an optical dissolved ammonia phase fluometric based sensor experiment conducted for 72 hours without the interferometric measurement module in accordance of the present invention.

Figure 6(a) illustrates a result in graph without the present of the analyte for two different phase measurements in accordance of the present invention.

Figure 6(b) illustrates a result in graph for phase reference which is not constant throughout the experiments in accordance of the present invention.

DETAILED DESCRIPTIONS OF THE INVENTION The present invention will now be described in detail in connection with specific embodiments with reference to the accompanying drawings.

As used herein, analyte means any substance that requires analysis for the purposes of either identification of one or more analytes, or measurement of properties, or quantification of one or more analytes, or the like, or combinations thereof. Analyte may be in any given physical form, and this includes solution, suspension, emulsion, solid, and the like.

The present invention provides a system for performing optical interferometry referencing for phase fluometric optical sensor. The system of the present invention comprises of few major components as illustrated in Figure 2. Among others, a controller (100) to control a light source (200) to produce a light beam (301) at a predetermined wavelength and analyze a phase of an incoming reference light beam wavefront as a reference phase and a phase of combined fluorescence light beams coming from a sensor (400) in absence of an analyte to compute and optimize the phase of the combined fluorescence light beams wavefront to make a same phase value as the phase of the reference light beam.

A first optical dichroic beamsplitter (300) is provided to receive the light beam (301) to split the light beam into two separated light beams, a first separated light beam (302) is guided to the sensor to produce a fluorescence emission light beam (303) and guided back to the first optical dichroic beamsplitter (300) in the same optical path; and a second separated light beam (51 1) is guided to an interferometric measurement module (500) as a reference light beam (511). In the preferred embodiment, the first optical dichroic beamsplitter (300) receiving the light beam guided to split the light beam into two separate light beams depending on a beamsplitter ratio.

The interferometric measurement module (500) having a second optical dichroic beamsplitter (501) receiving the fluorescence emission light beam (512) which returns to the first optical dichroic beamsplitter (300) and propagates in parallel with the reference light beam (511) in a same optical path and further splitted the fluorescence emission light beam (512) into two separated fluorescence light beams (513,514). In the preferred embodiment, the interferometric measurement module is based on Michelson interferometer. However, it applies to other types of inteferometer such as Twyman-Green, Mach-Zehndar, Smartt Point-Diffraction and Mirau-Nomarski interference microscope.

The first separated fluorescence light beam (514) propagates to a fixed mirror (502) and reflected back (515) to the second optical dichroic beamsplitter (501) and a second separated fluorescence light beam (513) propagates to a moveable mirror (503) and reflected the fluorescence light beam (516) back to the second optical dichroic beamsplitter

(501) . Subsequently, the first reflected fluorescence light beam (515) from the fixed mirror

(502) and second reflected fluorescence light beam (516) from the moveable mirror (503) are combined (517,518) and have interference at the second optical dichroic beamsplitter (501). The combined reflected fluorescence light beams (517,518) and the reference light beam (519) are guided to a photo detector (504). At this time, the controller (100) sets the combined phase. The sensing phase reference as detected in the photo detector (504) with the sensor shifted to sense the presence of analytes. The controller (100) produces the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam by moving the moveable mirror (503) perpendicular to the fluorescence light propagation coming from the second dichroic beamsplitter (501).

The controller (100) in the controller box synchronize the light source (200), the detector (504) and the moveable mirror (503) in controlling the light source intensity, the detector timing window and the movement of the mirror to make the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam.

The controller (100) further computes and calculates the analyte concentration by determining the relationship between the shifted phase and equations used for different types of analyte.

Figure 3 illustrates a moveable mirror used in the system at maximum λ/2 wavelength mirror movement to shift 2π degree of the phase of the fluorescence wavefront in accordance of the present invention. The moveable mirror has a maximum travel range at half wavelength of the fluorescence light for 2π phase different.

In operation, the method of performing optical interferometry referencing for phase fluometric optical sensor illustrated in Figure 4. The method begins with a single light source (200) to provide a light beam (301 ) which normally at a wavelength that has higher energy level (410). The light beam (301 ) is guided to a dichroic beamsplitter (300) to split the light beam (301 ) into two separate light beams (302,51 1 ) depending on the beamsplitter ratio. One of the separated light beam (302) is guided to the sensor (400) whether via free space or in a single or plurality of waveguide medium. Another separated light beam (51 1 ) is guided to the interferometric measurement module (500) and used as a reference light beam (412). The sensor in the system of the present invention is a fluorescence based opto-chemical sensor. However, the fluorescence emission from the sensor applies to others such a direct fluorescence chemical sensor, evanescence based and surface plasmon resonance (SPR) reactions. The fluorescence emission (303) from the sensor (400) is guided back to the dichroic beamsplitter (300) in the same optical path as the first light beam (302). The fluorescence emission light beam passes through the first dichroic beam splitter (300) and propagate along with the reference light beam (51 1 ) using the same optical path. Both light beams (51 ,512) are guided to the second dichroic beamsplitter (501 ) in the interferometric measurement module (500). The interferometric measurement module (500) is based on Michelson interferometer and comprising the second dichroic beamsplitter (501), a fixed mirror (502), a moveable mirror (503) and a photo detector (504). The second dichroic beamsplitter (501) is an optical selective wavelength beamsplitter which reflects and splits at two different wavelengths. The reference light beam (51 1 ) is reflected to the photo detector (504). The controller (100) then analyzes the phase of the reference light beam wavefront and set as a reference phase. The fluorescence emission light beam (512) further splits into two separated fluorescence light beams (414) (513, 514). One of the separated fluorescence light beam (514) propagates to a fixed mirror (502) and reflects back to the second dichroic beamsplitter (501 ) at fixed optical path length. Another fluorescence light beam (513) propagates to a moveable mirror (503) which also reflected back the fluorescence light beam to the second dichroic beamsplitter (501 ). Both reflected fluorescence light beam (515) from the fixed mirror (502) and the fluorescence light beam (516) from the moveable mirror (503) are combined and to have an interference at the second dichroic beamplitter (501 ). The combined reflected fluorescence light beams (517,518) are guided to the photo detector (504). At this moment, the controller ( 00) analyzes the phase of the combined fluorescence light (517,518) coming from the sensor with the absent of the analyte. The controller (100) optimizes the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam (519) by moving the moveable mirror (503) perpendicular to the fluorescence light propagation coming from the second dichroic beamsplitter(416)(501 ). The moveable mirror (503) has a maximum travel range at half wavelength of the fluorescence light for 2π phase different. The controller (100) sets the combined phase as the sensing system phase reference (418). The phase of combined fluorescence light beams then shifted if the sensor senses the presence of analyte. Finally, the controller (100) computes and calculates the analyte concentration by the relationship between the phase shifted and the equations provided for different type of analyte sensing mechanism such as Stern Volmer equation for dissolved oxygen and Handerson- Hasselbach equation for dissolved ammonia. EXAMPLE

Figure 5 shows the optical dissolved ammonia phase fluometric based sensor experiments conducted for 72 hours without the interferometric measurement module. A bifurcated fiber is used to replace the dichroic mirror in the setup which has the similar function. Although without the present of the analyte, the result shows that two different phase measurements are depicted on Figure 6(a). In addition, the result also indicates the phase reference is not constant throughout the experiment period as shown in Figure 6(b). One of the advantages of the present invention is that the system and method provides optically the phase of the reference excitation signal at the same phase wavefront with the fluorescence excitation signal in the absent of the analyte. The method of the present invention utilizes interferometry technique to achieve a precision phase measurement. In addition, the system of the present invention engages safely the phase of excitation reference signal as the sensing system phase reference. The present invention further provides a considerable reduction of materials with even greater efficiency and economically during operation.

The foregoing embodiment and advantages are merely exemplary and are not to be construed as limiting the present invention. The description of the embodiments of the present invention is intended to be illustrative and not to limit the scope of the claims and many alternatives, modifications and variations will be apparent to those skilled in the art.

REFERENCE

1. Ismail, N.H.; Mohd Zain, M.N.; Witjaksono, G., "Performance of TEOS/Octyl- triethoxylane/triton x-100 on tris(4, 7'-diphenyl-1, 10'-phenanthroline) Ruthenium (II) sol-gel for fluorescence-based optical sensor, " Photonics (ICP), 2013 IEEE 4th International Conference on , vol., no., pp.278,280, 28-30 Oct. 2013. doi:

10.1 109/ICP.2013.6687138.

Claims

1. A system for performing optical interferometry referencing for phase fluometric optical sensor comprising

a controller (100) to control a light source (200) to produce a light beam (301) at a predetermined wavelength and analyze a phase of an incoming reference light beam wavefront as a reference phase and a phase of combined fluorescence light beams coming from a sensor (400) in absence of an analyte to compute and optimize the phase of the combined fluorescence light beams wavefront to make a same phase value as the phase of the reference light beam; a first optical dichroic beamsplitter (300) receiving the light beam to split the light beam into two separated light beams, a first separated light beam (302) is guided to the sensor (400) to produce a fluorescence emission light beam (303) and guided back to the first optical dichroic beamsplitter (300) in the same optical path; and a second separated light beam (51 1) is guided to an interferometric measurement module (500) as a reference light beam; the interferometric measurement module (500) having a second optical dichroic beamsplitter (501 ) receiving the fluorescence emission light beam (303) which returns to the first optical dichroic beamsplitter (300) and propagates in parallel with the reference light beam in a same optical path and further splitted the fluorescence emission light beam (303) into two separated fluorescence light beams, a first separated fluorescence light beam (514) propagates to a fixed mirror (502) and reflected back to the second optical dichroic beamsplitter (501 ) and a second separated fluorescence light beam (513) propagates to a moveable mirror (503) and reflected the fluorescence light beam back to the second optical dichroic beamsplitter (501 ); the first reflected fluorescence light beam (5 5) from the fixed mirror (502) and second reflected fluorescence light beam (516) from the moveable mirror (503) are combined and have an interference at the second optical dichroic beamsplitter (501 ); the combined reflected fluorescence light beams (517,518) and the reference light beam (519) are guided to a photo detector wherein the controller (100) sets the combined phase; the sensing phase reference as detected in the photo detector and the sensor (400) shifted to sense the presence of analytes; and the controller (100) further compute and calculate the analyte concentration by determining the relationship between the shifted phase and equations used for different types of analyte.

2. The system as claimed in Claim 1 wherein the interferometric measurement module (500) is based on Michelson interferometer. 3. The system as claimed in Claim 1 wherein the first optical dichroic beamsplitter (300) receiving the light beam guided to split the light beam into two separate light beams depending on a beamsplitter ratio. 4. The system as claimed in Claim 1 wherein the controller (100) produce the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam by moving the moveable mirror (503) perpendicular to the fluorescence light propagation coming from the second dichroic beamsplitter (501).

The system as claimed in Claim 4 wherein the moveable mirror (503) has a maximum 5.

travel range at half wavelength of the fluorescence light for 2π phase different.

A method of performing optical interferometry referencing for phase fluometric optical 6. sensor (400) comprising producing a light beam (301) at a predetermined wavelength by a controller (100); splitting the light beam (301) into a first separated light beam (302) and a second separated light beam by a first optical dichroic beamsplitter (300); guiding the first separated light beam (302) to a sensor (400) to produce a fluorescence emission light beam and guided back to the first optical dichroic beamsplitter (300)in the same optical path;

guiding a second separated light beam (511) to an interferometric measurement module (500) as a reference light beam; receiving the fluorescence emission light beam which returns to the first optical dichroic beamsplitter (300) by a second optical dichroic beamsplitter (501) of the interferometric measurement module (500) and propagating the fluorescence emission light beam (303) in parallel with the reference light beam in a same optical path; splitting the fluorescence emission light beam (303) into a first separated fluorescence light beam and a second separated fluorescence light beam; propagating the first separated fluorescence light beam to a fixed mirror (502) of the interferometric measurement module (500) and reflecting back to the second optical dichroic beamsplitter (501) of the interferometric measurement module (500); propagating the second separated fluorescence light beam to a moveable mirror (503) of the interferometric measurement module (500) and reflecting the second separated fluorescence light beam back to the second optical dichroic beamsplitter (501); combining the first reflected fluorescence light beam from the fixed mirror (502) and second reflected fluorescence light beam from the moveable mirror (503) and have an interference at the second optical dichroic beamsplitter (501); guiding the combined reflected fluorescence light beams and the reference light beam to a photo detector; setting the combined phase as the sensing phase reference as detected in the photo detector by the controller (100) and shifting the sensor (400) senses the presence of analytes; and computing and calculating the analyte concentration by the controller (100) by determining the relationship between the shifted phase and equations used for different types of analyte.

7. The method as claimed in Claim 6 wherein the the interferometric measurement module (500) is based on Michelson interferometer.

8. The method as claimed in Claim 6 wherein the first optical dichroic beamsplitter (300) receiving the light beam guided to split the light beam into two separate light beams depending on a beamsplitter ratio.

9. The method as claimed in Claim 6 wherein the controller (100) produce the phase of the combined fluorescence light wavefront to make a same phase value as the phase of the reference light beam by moving the moveable mirror (503) perpendicular to the fluorescence light propagation coming from the second dichroic beamsplitter (501).

10. The system as claimed in Claim 9 wherein the moveable mirror (503) has a