A phase-type SPR sensing system without phase modulation structure and its application

Abstract

The present invention discloses a phase-type SPR sensing system and application without phase modulation structure. The phase-type SPR sensing system comprises an incident angle adjustment device, an SPR sensing module, a beam splitter, a polarizer, an imaging lens, and a CCD; the beam expansion light excites the SPR sensing module to produce an SPR phenomenon, and the outgoing light carries phase information, which is decomposed into three paths through two beam splitters. After the three light paths pass through the polarizer and the imaging lens respectively, the CCD detects the p-polarized light, the s-polarized light and its 45° polarization interference light intensity. The angle adjustment device adjusts the incident angle to the SPR angle that minimizes the p-light intensity according to the outgoing p-light intensity, and then extracts the phase information according to the light intensity detected by the three CCDs. The present invention adopts an incident angle adjustment device to improve the angular resolution of the phase-type SPR sensor, and at the same time, based on the polarization interference method, respectively detects two polarized lights and their polarization interference light intensities to extract the phase information, and has the characteristics of simple structure, stability, high cost and low cost.

Description

Technical Field

[0001] The invention belongs to the field of optical sensing and relates to a phase-type SPR sensing system without a phase modulation structure. Background Art

[0002] Phase-type SPR sensors use the surface plasmon resonance (SPR) phenomenon to sensitively respond to the refractive index of dielectrics, and perform highly sensitive sensing of the refractive index. The high frequency of light cannot be detected directly, and traditional phase-type SPR sensors extract the phase of reflected light by introducing complex optical paths or phase modulators. It is precisely because the traditional phase-type SPR sensors have high optical path complexity for extracting phase information or low stability of the introduced phase modulator that traditional phase-type SPR sensors have been difficult to industrialize so far. Therefore, simplifying the optical path of the phase-type SPR sensor is a difficulty that needs to be overcome in its industrialization. In addition, the angular resolution of traditional phase-type SPR sensors is low, and the incident angle cannot be accurately adjusted to the SPR resonance angle, which affects the resolution of the system. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention proposes a phase-type SPR sensing system and application without a phase modulation structure, which does not require the introduction of a phase modulation structure and a complex optical path, and at the same time designs an angle adjustment device to improve the angular resolution of the system to improve the system resolution. In addition, the system uses a defined ratio phase instead of a phase to sense the refractive index, which can achieve a resolution of the same order of magnitude.

[0004] The invention discloses a phase-type SPR sensing system without a phase modulation structure, comprising an incident angle adjustment device, an SPR sensing module, a beam splitter, a polarizing plate, an imaging lens and a CCD.

[0005] The beam expansion light excites the SPR sensor module to produce the SPR phenomenon. The outgoing light carries phase information and is decomposed into three paths through two beam splitters. The three light paths pass through the polarizer and the imaging lens respectively, and then the CCD detects the p-polarized light, s-polarized light and its 45° polarized interference light intensity. The angle adjustment device adjusts the incident angle to the SPR angle that minimizes the p-light intensity according to the outgoing p-light intensity, and then extracts the phase information according to the light intensity detected by the three CCDs.

[0006] In a further specific implementation, the SPR sensor module includes an SPR sensor chip and an isosceles right-angle prism.

[0007] In a further specific implementation, the angle adjustment device includes two right-angle prisms and a rotating table, wherein one right-angle prism is coupled with an SPR sensor chip to form an SPR sensor module, and the two right-angle prisms are combined into a parallelogram structure; the central axis of the sensor chip is located at the rotation center of the rotating table.

[0008] In a further specific implementation, the outgoing light path is decomposed into three paths by two beam splitters. The three light paths use three sets of identical imaging lenses and CCDs to image the SPR sensor chip. A polarizer is placed between the imaging lens and the CCD. By controlling the angles of the three polarizers, the three light paths are respectively a light path for detecting p light, a light path for detecting s light, and a light path for detecting the polarization interference intensity.

[0009] In a further specific implementation, the angle adjustment device adjusts the incident angle by the magnitude of the p-light intensity detected in the outgoing light path until the p-light intensity reaches a minimum value;

[0010] The three light paths of the outgoing light path detect the p light, s light and their 45° polarized interference light intensity respectively, and calculate the reflectivity k respectively. p , k s and k i , the calculation formula of the ratio phase ψ is defined as:

[0011]

[0012] Within a certain range, the ratio phase ψ is a monotonic function of the refractive index, and the interval in which ψ is a monotonic function of the refractive index can be obtained by calibrating or simulating the sensing system using a material with a known refractive index.

[0013] Beneficial effects of the present invention

[0014] The present invention adopts a method of realizing refractive index sensing by decomposing the outgoing light path to calculate the ratio phase, removing the phase modulator of the traditional phase-type SPR sensor, and achieving the effect of simplifying the light path and data analysis process. At the same time, an angle adjustment device is adopted, and the present invention improves the angular resolution of the phase-type SPR sensor, further improving the stability and resolution of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system diagram of a phase-type SPR sensing system without a phase modulation structure of the present invention.

[0016] Figure 2 This is a simulation result diagram of the application range of a phase-type SPR sensing system without a phase modulation structure of the present invention.

[0017] Figure 3 This is a flow chart of angle adjustment of the angle adjustment device of the present invention.

[0018] Description of reference numerals:

[0019] 1-rotating table, 2-right angle prism, 3-sensor chip, 4-rotating motor controller, 5-first reflector, 6-beam splitter, 7-second reflector, 8-polarizer, 9-imaging lens, 10-CCD, 11-switch, 12-computer. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] Example 1

[0022] In this example, a rotating motor is used as part of the angle adjustment device. Figure 1 As shown, a system diagram of a phase-type SPR sensing system without a phase modulation structure of the present invention includes a rotating table 1, a right-angle prism 2, a sensor chip 3, a rotating table controller 4, a first reflector 5, a beam splitter 6, a second reflector 7, a polarizer 8, an imaging lens 9, a CCD 10, a switch 11, and a computer 12.

[0023] Two right-angle prisms 2 are combined into parallel prisms, and one of the right-angle prisms 2 is coupled with a sensor chip 3. The expanded beam passes through the right-angle prism 2 to excite the SPR phenomenon on the sensor chip 3, and then exits through the other right-angle prism 2, and the exit light is parallel to the incident light. The central axis of the sensor chip 3 is adjusted to coincide with the rotation axis of the rotating table 1, so when the rotating table rotates to change the incident angle, the exit light path does not change with the change of the incident angle. The exit light path is turned by the first reflector 5, and then the light path is divided into three paths by two beam splitters 6, and the second reflector 7 turns one of the split light paths. The polarizer 8 controls the three light paths to detect p light, s light and 45° polarized interference light respectively. Each light path uses the same imaging lens 9 and CCD 10 to obtain image information and exchange information through the switch 11 and the computer 12. The angle adjustment device consists of two right-angle prisms 2 and a rotating table 1. The computer 12 calculates the angle adjustment amount required by the angle adjustment device based on the grayscale obtained by the CCD detection of the p light path, and transmits the information of the required rotation amount of the angle adjustment device to the rotating motor controller 4. The rotating motor controller 4 controls the rotation of the angle adjustment device, and finally makes the incident angle satisfy the minimum reflectivity of the p light, that is, quantitatively judges the incident angle to the SPR angle.

[0024] The sensor chip 3 sets a channel as the calibration channel, which does not have any samples inside, and the channel with samples is the detection channel. The grayscale ratio of the detection channel and the calibration channel obtained in the image information measured by each optical path is the reflectivity obtained by the optical path detection, which are k p , k s and k i The calculation formula for the ratio phase ψ is defined as:

[0025]

[0026] The ratio phase ψ is not a physical quantity, but within a certain range, it is a monotonic function of the refractive index. Therefore, the refractive index can be sensed by the ratio phase ψ instead of the phase. This range and the p-light intensity I emitted from the calibration channel of the sensor chip 3 are p0 ,s light intensity I s0 , 45° polarized interference light intensity I0, specifically and These two indicators affect whether the ratio phase ψ satisfies the condition of being a monotonic function of the refractive index. Figure 2 The range of values ​​of x1 and x2 shown in the figure makes ψ a monotonic function of the refractive index within a certain range. The range obtained by simulation needs to be adjusted to better match the actual range. Before application, the sensor can also be calibrated with a series of materials with known refractive indices and judged from the actual test results whether it is within the actual range.

[0027] Example 2

[0028] The angle adjustment device is composed of two right-angle prisms 2 and a rotating platform 1. This embodiment provides an angle adjustment algorithm such as Figure 3 As shown. It is mainly divided into two parts:

[0029] (1) Determine the rotation direction, set the initial rotation direction and rotation angle. If the p-light reflectivity decreases, the rotation direction is the initial rotation direction; if the p-light reflectivity increases, the rotation direction is opposite to the initial rotation direction.

[0030] (2) The rotation angle is halved successively until the minimum rotation angle of the rotating stage 1 is reached, and the incident angle with the lowest reflectivity of the p-light is found.

[0031] The specific steps are as follows:

[0032] The initial rotation direction set in this embodiment is the positive direction, and the initial rotation angle is θ k =0.5°, the initial step number k=0, the step number after rotation is k=k+1, the grayscale ratio of the detection channel and the calibration channel of the p-light path is its reflectivity R k .

[0033] When determining the direction of rotation, compare the reflectivity R after rotation k and the reflectivity R before rotation k-1 , if R k -R k-1 <0, the rotation direction is the set initial rotation direction; if R k -R k-1 >0, the rotation direction is opposite to the initial rotation direction, which is the negative direction, and rotates to the initial position.

[0034] After determining the rotation direction, the angle is adjusted by gradually halving the rotation angle, i.e. θ k =0.5θ k-1 , when θ k-1 =θ min When (the minimum rotation angle θ of the angle adjustment device is reached min ), θ k =θ k-1 =θ min The direction of each rotation is still determined by comparing the reflectivity R before and after rotation. k-1 and R k When the angle adjustment device rotates to the nth step at the minimum rotation angle, the reflectivity R n >R n-1 , then the incident angle at step n-1 is the SPR angle. Therefore, at step n+1, the angle adjustment device adjusts the incident angle to the state at step n-1, that is, to the SPR angle.

[0035] The present invention decomposes the outgoing light path into three paths to detect the p-light, s-light and their 45° polarized interference light intensity respectively, calculates the ratio phase according to the formula, realizes the sensing of the refractive index, thereby removing the phase modulator and simplifying the optical path of the phase-type SPR sensor. In addition, the present invention adopts an angle adjustment device to improve the angular resolution of the traditional phase-type SPR sensor to improve the resolution of the system. The present invention has the characteristics of simple structure, convenient data extraction method and high angular resolution.

[0036] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention. The protection scope of the present invention is given by the attached claims and any equivalents thereof.

Claims

1. A phase-type SPR sensing system without a phase modulation structure, characterized in that: It includes an incident angle adjustment device, an SPR sensor module, a beam splitter, a polarizer, an imaging lens, and a CCD; The beam expansion light excites the SPR sensor module to produce the SPR phenomenon. The outgoing light carries phase information and is decomposed into three paths by two beam splitters. The three light paths pass through the polarizer and the imaging lens respectively, and then the p-polarized light, s-polarized light and their 45° polarized interference light intensity are detected by the CCD. The incident angle adjustment device adjusts the incident angle to the SPR angle that minimizes the p-light intensity according to the outgoing p-light intensity, and then extracts the phase information according to the light intensity detected by the three CCDs. The SPR sensor module comprises an SPR sensor chip and an isosceles right-angle prism; The incident angle adjustment device comprises two right-angle prisms and a rotating platform, wherein one right-angle prism is coupled with an SPR sensor chip to form an SPR sensor module, and the two right-angle prisms are combined into a parallelogram structure; the central axis of the sensor chip is located at the rotation center of the rotating platform; The sensor chip sets a channel as the calibration channel, which has no sample inside, and the channel with the sample is the detection channel; the grayscale ratio of the detection channel and the calibration channel obtained in the image information measured by each optical path is the reflectivity obtained by the optical path detection, which are k p , k s and k i ; The calculation formula for the ratio phase ψ is defined as:

2. A phase-type SPR sensing system without a phase modulation structure according to claim 1, characterized in that: The outgoing light path is decomposed into three paths by two beam splitters. The three light paths use three sets of identical imaging lenses and CCDs to image the SPR sensor chip. A polarizer is placed between the imaging lens and the CCD. By controlling the angles of the three polarizers, the three light paths are respectively used to detect p-light, s-light, and the polarization interference intensity.

3. An application method of a phase-type SPR sensing system without a phase modulation structure according to claim 1, characterized in that: The incident angle adjustment device adjusts the incident angle according to the intensity of the p-light detected in the outgoing light path until the intensity of the p-light reaches a minimum value; The three light paths of the outgoing light path detect the p light, s light and their 45° polarized interference light intensity respectively, and calculate the reflectivity k respectively. p , k s and k i , the calculation formula of the ratio phase ψ is defined as: The refractive index is sensed by the ratio phase ψ instead of the phase.

4. The application method according to claim 3, characterized in that: By using a material with a known refractive index to calibrate or simulate the sensing system, the interval in which ψ is a monotonic function of the refractive index is obtained.

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