A scanning test strip quantitative detection system and method based on phase-locked amplification

Abstract

The invention discloses a scanning test strip quantitative detection system based on phase-locked amplification, comprising a laser emitting unit, a light beam scanning unit, an analog signal generator unit, a signal acquisition unit and a signal processing unit; the laser emitting unit comprises a connected laser diode and a driving circuit, the light beam scanning unit comprises a light beam deflection module and a scanning cylindrical lens; the signal acquisition unit comprises a collecting lens and a photodetector; the signal processing unit comprises a current-voltage conversion circuit, a high-pass filter, a phase-locked amplifier and an analog signal acquisition device connected in sequence; the laser diode outputs laser light to the light beam deflection module of the light beam scanning unit, the light beam scanning unit is connected to the analog signal generator unit, and the analog signal generator unit and the signal acquisition unit are both connected to the signal processing unit; the test strip to be detected is placed below the light beam scanning unit.

Description

Technical Field

[0001] The present invention relates to the field of optical detection technology, and in particular to a scanning test strip quantitative detection system based on phase-locked amplification. Background Art

[0002] Lateral flow immunoassay is a new type of immunoassay technology that combines chromatography and immunoassay. It has the advantages of being fast, simple, highly sensitive, highly specific, highly accurate, and not dependent on large equipment. It is now widely used in medical diagnosis, food safety testing, environmental monitoring, and other fields. The principle is to fix the capture antigen or capture antibody on a specific area of ​​the nitrocellulose membrane as the test line and quality control line. After the sample is added, it will move forward due to capillary action. When passing through the binding pad, the analyte in the sample solution will combine with the colored marker and continue to move forward. When flowing through the test line, the antibody / antigen fixed on the test line specifically binds, and as the concentration of the test solution increases, a color reaction of varying degrees is presented at the test line. Qualitative or even semi-quantitative detection can be achieved in a short time by naked eye observation. However, this visual inspection method has many defects, such as: (1) it is seriously interfered by light and is prone to visual fatigue, leading to misjudgment; (2) it is difficult to visually inspect when the concentration of the analyte is close to the critical range; (3) it is impossible to achieve quantitative detection; (4) the detection limit is high, making it difficult to meet higher detection requirements.

[0003] Test strip readers have higher detection accuracy than visual inspection and can achieve quantitative detection. Currently, test strip readers are mainly divided into three categories: fixed point, photographic, and scanning. Fixed point readers are designed in conjunction with test strips. The light source and detector are fixed according to the detection position of the test strips. There is no motion module and the overall performance is poor. Photographic readers use image sensors such as CMOS / CCD to take pictures of images and then perform data analysis. They have the characteristics of simple structure, fast speed, and strong compatibility. However, due to the performance of image sensors, it is difficult to achieve further breakthroughs in its key technical indicators.

[0004] As a traditional technical solution, the scanning reader has the characteristics of good reliability, high sensitivity and high efficiency, and is widely used. Its technical principle is to use a light beam to scan the test strip, collect the scattered light intensity signal at different positions of the test strip, and establish a mathematical relationship between light intensity and concentration. The main structure includes a light source module, a scanning module, a signal acquisition module and a signal processing module. In the part of the light beam scanning test strip, most of the methods used are to fix the light source and use the motion module to drive the test strip to move and realize scanning. The defect of this method is that due to the rough surface of the test strip and the shot noise of the light source itself, when the concentration of the analyte is close to the critical value, the signal obtained by the signal acquisition module is extremely weak, and the effective signal is submerged in the background noise, so that the detection limit of the instrument cannot meet various detection standards. For example, quantitative detection of microorganisms in food is an important technical means to judge and measure food quality, but the current instrument detection limit still does not meet the national limit standard. Therefore, before conducting microbial detection, it must be cultured and proliferated, and the whole process is time-consuming and labor-intensive. Therefore, how to reduce the detection limit of the scanning reader has become an urgent problem to be solved, which has important application value. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a scanning test strip quantitative detection system based on phase-locked amplification, which is suitable for all quantitative detections based on color reaction test strips. The system uses a sinusoidal voltage waveform to control the scanning module to quickly change the deflection direction of the scanning laser beam. When the laser beam passes over the detection line of the test strip, the signal after photoelectric conversion will present a periodic waveform, and its amplitude and frequency are respectively determined by the concentration of the substance to be detected and the frequency of the scanning waveform. By connecting the photoelectric signal and the reference signal to the input and reference terminals of the phase-locked amplifier respectively, weak signals submerged in background noise can be effectively extracted. Compared with the prior art, this system is expected to significantly reduce the detection limit of the substance to be detected.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A scanning test strip quantitative detection system based on phase-locked amplification includes a laser emission unit, a light beam scanning unit, an analog signal generator unit, a signal acquisition unit and a signal processing unit;

[0008] The laser emitting unit includes a connected laser diode and a driving circuit, the beam scanning unit includes a beam deflection module and a scanning cylindrical lens; the signal acquisition unit includes a collecting lens and a photodetector; the signal processing unit includes a current-voltage conversion circuit, a high-pass filter, a phase-locked amplifier and an analog signal acquisition device connected in sequence;

[0009] The laser diode outputs laser light to the beam deflection module of the beam scanning unit, the beam scanning unit is connected to the analog signal generator unit, and the analog signal generator unit and the signal acquisition unit are both connected to the signal processing unit; the test paper strip to be tested is placed under the beam scanning unit;

[0010] The output wavelength of the laser diode corresponds to the maximum absorption wavelength at the detection line of the test paper strip to be detected. When the laser is focused on the detection line of the test paper strip to be detected, it is absorbed by the substance to be detected gathered on the detection line, causing a change in the intensity of the scattered laser on the surface of the test paper strip to be detected, and the change value is proportional to the concentration of the substance to be detected;

[0011] The beam deflection module is located at the rear focal plane of the scanning cylindrical lens, and can change the angle of the laser beam under the action of the analog signal; the scanning cylindrical lens, on the one hand, focuses the laser beam parallel to the detection line in a linear shape on the surface of the test paper strip to be detected, and on the other hand, converts the angular movement of the laser beam caused by the beam deflection module into a linear movement of the linear focusing spot on the surface of the test paper strip to be detected, while ensuring that the detection line is located in the middle position of the movement path of the linear focusing spot;

[0012] The analog signal generator unit can generate a sinusoidal signal a and a sinusoidal signal b, wherein the frequency of the sinusoidal signal b is twice the frequency of the sinusoidal signal a; the sinusoidal signal a is used to control the beam deflection module, so that the linear laser beam scanned and focused by the beam scanning unit can cross the detection line of the test paper strip to be detected back and forth, thereby causing periodic changes in the intensity of the scattered laser light; the sinusoidal signal b is used as a reference signal of the phase-locked amplifier, and the amplitude and phase can be adjusted;

[0013] The collecting lens refocuses the laser light scattered on the test paper strip to be detected onto the photodetector; the photodetector converts the collected periodically changing scattered light intensity signal into a periodically changing photocurrent signal;

[0014] The current-voltage conversion circuit converts the periodic photocurrent signal generated by the photodetector into a periodic photovoltage signal and inputs it to the high-pass filter; the cut-off frequency of the high-pass filter is lower than the scanning frequency of the light beam scanning unit, and the DC component in the periodic photovoltage signal is filtered out; the AC signal output by the high-pass filter is connected to the signal input end of the phase-locked amplifier; the phase-locked amplifier amplifies the AC signal and converts it into a DC signal output, and the output DC signal voltage value is proportional to the amplitude of the AC signal, that is, proportional to the concentration of the substance to be detected; the analog signal acquisition device is used to collect the DC voltage output by the phase-locked amplifier, and convert the DC voltage into the concentration of the substance to be detected after calibration.

[0015] The present invention also provides a scanning test strip quantitative detection method based on phase-locked amplification, comprising:

[0016] The wavelength of the laser output by the laser diode corresponds to the maximum absorption wavelength at the detection line of the test paper strip to be detected. When the laser is focused on the detection line of the test paper strip to be detected, it is absorbed by the substance to be detected gathered on the detection line, causing the change of the intensity of the scattered laser on the surface of the test paper strip to be detected, and the change value is proportional to the concentration of the substance to be detected;

[0017] The angle of the laser beam output by the laser diode is changed by the beam deflection module; the laser beam is focused linearly on the surface of the test paper strip to be tested in parallel with the detection line by the scanning cylindrical lens. The scanning cylindrical lens can convert the angular movement of the laser beam caused by the beam deflection module into the linear movement of the linear focusing spot on the surface of the test paper strip to be tested, while ensuring that the detection line is located in the middle position of the movement path of the linear focusing spot;

[0018] The analog signal generator unit generates a sinusoidal signal a and a sinusoidal signal b. The sinusoidal signal a is used to control the beam deflection module so that the laser beam can cross the detection line of the test paper strip to be detected back and forth, causing periodic changes in the intensity of the scattered laser light. The sinusoidal signal b is used as a reference signal of the phase-locked amplifier. The frequency of the reference signal is twice that of the sinusoidal signal a, and the amplitude and phase of the reference signal can be adjusted.

[0019] The laser light scattered on the test paper strip to be tested is refocused on the photodetector through the collecting lens; the photodetector converts the collected periodically changing scattered light intensity signal into a periodically changing photocurrent signal;

[0020] The periodic photocurrent signal generated by the photodetector is converted into a periodic photovoltage signal through a current-voltage conversion circuit and input into a high-pass filter; the high-pass filter filters out the DC component in the periodic photovoltage signal and outputs an AC signal to the phase-locked amplifier; the phase-locked amplifier amplifies the AC signal and converts it into a DC signal output, and the DC signal voltage value is proportional to the concentration of the substance to be detected; the analog signal acquisition device collects the DC voltage output by the phase-locked amplifier, and converts the DC voltage into the concentration of the substance to be detected after calibration.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] 1. The present invention utilizes a focused laser beam to periodically scan the detection line of a test strip to generate a periodic absorption signal, and then uses a phase-locked amplification technique to extract weak signals at low concentrations from noise, thereby significantly reducing the detection limit of a scanning test strip reader.

[0023] 2. Utilizing the twice-frequency relationship between the laser scanning period and the absorption signal periodicity, the twice-frequency signal of the laser scanning signal is used as the reference signal of the phase-locked amplifier, effectively avoiding false signals caused by mechanical jitter during the laser scanning process.

[0024] 3. Using a cylindrical lens to focus the scanning laser beam into a linear spot, the use of linear laser scanning detection line can effectively avoid the periodic signal fluctuation caused by the rough surface of the test strip and improve the quantitative accuracy.

[0025] 4. It has a wide range of applications and can be used for all color-reaction-based test strips, including colloidal gold test strips and fluorescent test strips. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the quantitative detection system in the example of the present invention.

[0027] Figure 2 This is a diagram of a periodic voltage signal output by a current-to-voltage conversion circuit.

[0028] Figure 3 This is a graph of the periodic voltage signal after being filtered by a high-pass filter.

[0029] Figure 4 This is a diagram of the DC voltage signal output by the lock-in amplifier.

[0030] Figure numerals: 1-laser emitting unit, 2-beam scanning unit, 3-analog signal generator unit, 4-signal acquisition unit, 5-signal processing unit, 11-laser diode, 12-driving circuit, 21-beam deflection module, 22-scanning column lens, 31-analog signal generator, 32-sinusoidal signal a, 33-sinusoidal signal b, 41-collecting lens, 42-photodetector, 51-current-voltage conversion circuit, 52-high-pass filter, 53-phase-locked amplifier, 54-analog signal acquisition device. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] like Figure 1 As shown, this embodiment provides a scanning test strip quantitative detection system based on phase-locked amplification, including a laser emitting unit 1, a beam scanning unit 2, an analog signal generator unit 3, a signal acquisition unit 4 and a signal processing unit 5;

[0033] The laser emitting unit 1 includes a connected laser diode 11 and a driving circuit 12, the beam scanning unit 2 includes a beam deflection module 21 and a scanning cylindrical lens 22; the signal acquisition unit 4 includes a collecting lens 41 and a photodetector 42; the signal processing unit 5 includes a current-voltage conversion circuit 51, a high-pass filter 52, a phase-locked amplifier 53 and an analog signal acquisition device 54 connected in sequence;

[0034] The driving circuit 12 provides drive for the laser diode 11, and the laser diode 11 outputs laser light to the beam deflection module 21 of the beam scanning unit 2. The scanning cylindrical lens 22 is placed directly below the beam deflection module, and the test paper strip to be tested is placed directly below the scanning cylindrical lens 22. The beam deflection module 21 is connected to the analog signal generator unit 3; in this embodiment, the collecting lens 41 and the photodetector 42 are set at a 45° angle to the plane of the test paper strip to be tested, the photodetector 42 is located above the collecting lens 41, and the photodetector 42 is connected to the current-voltage conversion circuit 51; the analog signal generator unit 3 is also connected to the phase-locked amplifier 53.

[0035] The driving circuit 12 is used to drive the laser diode 11 to output a laser with a wavelength corresponding to the maximum absorption wavelength of the test strip to be detected. When the laser is focused on the detection line of the test strip, it is absorbed by the substance to be detected, causing a change in the intensity of the scattered laser on the surface of the test strip, and the change value is proportional to the concentration of the substance to be detected.

[0036] The beam deflection module 21 contains a deflectable reflector and is located at the rear focal plane of the scanning cylindrical lens 22. The angle change of the deflectable reflector is proportional to the amplitude of the driving voltage. The input end of its driving circuit can be connected to an analog signal to control the deflection angle of the reflector so as to quickly deflect the laser beam. The deflection angle of the reflector is proportional to the amplitude of the analog signal. On the one hand, the scanning cylindrical lens 22 focuses the laser beam reflected by the beam deflection module 21 on the surface of the test strip and presents a linear focused light spot parallel to the direction of the detection line. On the other hand, it converts the beam angle movement caused by the beam deflection module 21 into a linear movement of the linear focused light spot on the surface of the test strip, and the movement direction is perpendicular to the detection line.

[0037] The analog signal generator unit 3 includes an analog signal generator 31, which can generate a sinusoidal signal a32 and a sinusoidal signal b33. The sinusoidal signal a32 is used to control the rotation of the reflector in the beam deflection module 21, so that the laser beam focused by the scanning line of the beam scanning unit 2 quickly crosses the detection line of the test strip back and forth, thereby causing a periodic change in the intensity of the scattered laser. The sinusoidal signal b33 is used as a reference signal of the phase-locked amplifier 53, and the frequency is twice that of the sinusoidal signal a32, and the amplitude and phase can be adjusted.

[0038] The collecting lens 41 refocuses the laser light scattered on the test strip onto the photodetector 42. The photodetector 42 converts the collected periodically changing scattered light intensity signal into a periodically changing photocurrent signal.

[0039] The current-voltage conversion circuit 51 converts the periodic photocurrent signal generated by the photodetector 42 into a periodic photovoltage signal and inputs it to the high-pass filter 52. The cut-off frequency of the high-pass filter 52 is lower than the scanning frequency of the light beam scanning unit 2, and its function is to filter out the DC component in the periodic photovoltage signal. The AC signal output by the high-pass filter 52 is connected to the signal input terminal of the phase-locked amplifier 53. The phase-locked amplifier 53 amplifies the AC signal and converts it into a DC signal output. Its voltage value is proportional to the amplitude of the AC signal, that is, proportional to the concentration of the substance to be detected. The analog signal acquisition device 54 is used to collect the DC output voltage of the phase-locked amplifier 53, and convert it into the concentration of the substance to be detected after calibration.

[0040] Figure 2 The figure shows the AC voltage signal output by the current-voltage conversion circuit 51. The trough area of ​​the signal corresponds to the beam scanning unit 2 deflecting and focusing the scanning laser beam on the detection line on the surface of the test strip. The higher the concentration of the substance to be detected, the deeper the trough of the AC voltage signal. The periodicity of the signal comes from the periodic linear motion of the scanning laser beam on the surface of the test strip. When the scanning laser beam crosses the detection line, its frequency is twice that of the sinusoidal signal a32 of the beam deflection module 21, and is the same as the frequency of the sinusoidal signal b33 as the reference signal of the phase-locked amplifier 53.

[0041] Figure 3 The figure shows the periodic photovoltage signal after the DC component is filtered out by the high-pass filter 52.

[0042] Figure 4 The figure shows the DC voltage signal output by the phase-locked amplifier 53. The phase-locked amplifier 53 extracts the component with the same frequency as the sinusoidal signal 33 in the periodic voltage signal, amplifies it and converts it into a DC voltage signal output, and the output voltage value reflects the concentration of the object to be tested. According to the principle of the phase-locked amplifier, the noise of the photodetector and the random fluctuation of the scattered light intensity caused by the rough surface of the test strip are effectively suppressed due to the difference in frequency from the reference signal. Therefore, the present invention can extract the absorption signal of the substance to be tested from the noise and reduce its detection limit.

[0043] Finally, it should be pointed out that the above examples are only used to illustrate the calculation process of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above examples, a person skilled in the art should understand that the calculation process described in the above examples can still be modified, or some parameters can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding calculation method deviate from the spirit and scope of the calculation method of the present invention.

[0044] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A scanning test strip quantitative detection system based on phase-locked amplification, characterized in that: It includes a laser emitting unit, a beam scanning unit, an analog signal generator unit, a signal acquisition unit and a signal processing unit; The laser emitting unit includes a connected laser diode and a driving circuit, the beam scanning unit includes a beam deflection module and a scanning cylindrical lens; the signal acquisition unit includes a collecting lens and a photodetector; the signal processing unit includes a current-voltage conversion circuit, a high-pass filter, a phase-locked amplifier and an analog signal acquisition device connected in sequence; The laser diode outputs laser light to the beam deflection module of the beam scanning unit, the beam scanning unit is connected to the analog signal generator unit, and the analog signal generator unit and the signal acquisition unit are both connected to the signal processing unit; the test paper strip to be tested is placed under the beam scanning unit; The output wavelength of the laser diode corresponds to the maximum absorption wavelength at the detection line of the test paper strip to be detected. When the laser is focused on the detection line of the test paper strip to be detected, it is absorbed by the substance to be detected gathered on the detection line, causing a change in the intensity of the scattered laser on the surface of the test paper strip to be detected, and the change value is proportional to the concentration of the substance to be detected; The beam deflection module is located at the rear focal plane of the scanning cylindrical lens, and can change the angle of the laser beam under the action of the analog signal; the scanning cylindrical lens, on the one hand, focuses the laser beam parallel to the detection line in a linear shape on the surface of the test paper strip to be detected, and on the other hand, converts the angular movement of the laser beam caused by the beam deflection module into a linear movement of the linear focusing spot on the surface of the test paper strip to be detected, while ensuring that the detection line is located in the middle position of the movement path of the linear focusing spot; The analog signal generator unit can generate a sinusoidal signal a and a sinusoidal signal b, wherein the frequency of the sinusoidal signal b is twice the frequency of the sinusoidal signal a; the sinusoidal signal a is used to control the beam deflection module, so that the linear laser beam scanned and focused by the beam scanning unit can cross the detection line of the test paper strip to be detected back and forth, thereby causing periodic changes in the intensity of the scattered laser light; the sinusoidal signal b is used as a reference signal of the phase-locked amplifier, and the amplitude and phase can be adjusted; The collecting lens refocuses the laser light scattered on the test paper strip to be detected onto the photodetector; The photoelectric detector converts the collected periodically changing scattered light intensity signal into a periodically changing photocurrent signal; The current-voltage conversion circuit converts the periodic photocurrent signal generated by the photodetector into a periodic photovoltage signal and inputs it to the high-pass filter; the cut-off frequency of the high-pass filter is lower than the scanning frequency of the light beam scanning unit, and the DC component in the periodic photovoltage signal is filtered out; the AC signal output by the high-pass filter is connected to the signal input end of the phase-locked amplifier; the phase-locked amplifier amplifies the AC signal and converts it into a DC signal output, and the output DC signal voltage value is proportional to the amplitude of the AC signal, that is, proportional to the concentration of the substance to be detected; the analog signal acquisition device is used to collect the DC voltage output by the phase-locked amplifier, and convert the DC voltage into the concentration of the substance to be detected after calibration; the periodicity of the signal comes from the periodic linear motion of the scanning laser beam on the surface of the test strip. When the scanning laser beam crosses the detection line, its frequency is twice the sinusoidal signal a of the beam deflection module, and is the same as the frequency of the sinusoidal signal b serving as the reference signal of the phase-locked amplifier.

2. A scanning test strip quantitative detection method based on phase-locked amplification, characterized in that: include: The wavelength of the laser output by the laser diode corresponds to the maximum absorption wavelength at the detection line of the test paper strip to be detected. When the laser is focused on the detection line of the test paper strip to be detected, it is absorbed by the substance to be detected gathered on the detection line, causing the change of the intensity of the scattered laser on the surface of the test paper strip to be detected, and the change value is proportional to the concentration of the substance to be detected; The angle of the laser beam output by the laser diode is changed by the beam deflection module; the laser beam is focused linearly on the surface of the test paper strip to be tested in parallel with the detection line by the scanning cylindrical lens. The scanning cylindrical lens can convert the angular movement of the laser beam caused by the beam deflection module into the linear movement of the linear focusing spot on the surface of the test paper strip to be tested, while ensuring that the detection line is located in the middle position of the movement path of the linear focusing spot; The analog signal generator unit generates a sinusoidal signal a and a sinusoidal signal b. The sinusoidal signal a is used to control the beam deflection module so that the laser beam can cross the detection line of the test paper strip to be detected back and forth, causing periodic changes in the intensity of the scattered laser light. The sinusoidal signal b is used as a reference signal of the phase-locked amplifier. The reference signal frequency is twice that of the sinusoidal signal a, and the amplitude and phase of the reference signal can be adjusted. The laser light scattered from the test paper strip to be inspected is refocused onto the photodetector through a collecting lens; The photodetector converts the collected periodically changing scattered light intensity signal into a periodically changing photocurrent signal; The periodic photocurrent signal generated by the photodetector is converted into a periodic photovoltage signal through a current-voltage conversion circuit and input into a high-pass filter; the high-pass filter filters out the DC component in the periodic photovoltage signal and outputs an AC signal to a phase-locked amplifier; the phase-locked amplifier amplifies the AC signal and converts it into a DC signal output, and the DC signal voltage value is proportional to the concentration of the substance to be detected; the analog signal acquisition device collects the DC voltage output by the phase-locked amplifier, and converts the DC voltage into the concentration of the substance to be detected after calibration; the periodicity of the signal comes from the periodic linear motion of the scanning laser beam on the surface of the test strip. When the scanning laser beam crosses the detection line, its frequency is twice the sinusoidal signal a of the beam deflection module, and is the same as the frequency of the sinusoidal signal b serving as the reference signal of the phase-locked amplifier.

Images