Weak fluorescence detection system based on photodiode

Abstract

The utility model relates to a weak fluorescence detection system based on a photodiode, and the system comprises a controller which is used for outputting a first square wave signal and a second square wave signal; the sine wave circuit converts the first square wave signal into a sine wave signal; the first phase-sensitive detection circuit is used for multiplying the response signal by the first square wave signal to obtain a first output signal; the first low-pass filter is used for performing low-pass filtering on the first output signal; the second phase-sensitive detection circuit multiplies the response signal by a second square wave signal to obtain a second output signal; the second low-pass filter is used for performing low-pass filtering on the second output signal; and the solver is used for carrying out square summation processing on the first output signal and the second output signal. The reference signal is multiplied by the signal to be measured, the signal containing the direct current component is output, and the direct current component is in direct proportion to the signal to be measured. And a direct current quantity proportional to the amplitude of the signal to be measured can be obtained by only retaining the direct current component by using the low-pass filter.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a weak fluorescence detection system based on a photodiode, belonging to the technical field of fluorescence detection. BACKGROUND

[0002] Fluorescence detection technology is an analytical method based on fluorescence phenomenon, which uses the characteristic that certain substances (fluorescent substances) emit light of longer wavelength after absorbing light of specific wavelength. This technology is widely used in biology, chemistry, medicine, environmental science and other fields, and has high sensitivity and specificity for the detection and quantification of trace substances.

[0003] The existing portable fluorescence detection equipment usually uses constant current mode to drive light-emitting diodes to provide excitation light for the sample, and obtains the fluorescence signal by turning on the light-emitting diodes.

[0004] This method requires strict light shielding, and the fluctuation of environmental light will affect the detection result. At the same time, the dark current of the photodiode affects the accuracy of the result, and the influence of the input offset of the transimpedance amplifier matched with the photodiode is not easy to remove. CONTENT OF THE INVENTION

[0005] In order to overcome the above problems, the present disclosure provides a weak fluorescence detection system based on a photodiode.

[0006] The technical solution of the present disclosure is as follows:

[0007] A weak fluorescence detection system based on a photodiode, comprising a controller for outputting a first square wave signal and a second square wave signal, the first square wave signal and the second square wave signal being same frequency and same source, and having a phase difference of 90°;

[0008] A sine wave circuit converts the first square wave signal into a sine wave signal having the same phase, amplitude and period as the first square wave signal;

[0009] An LED excitation light source controlled by the sine wave signal emits an excitation signal;

[0010] An optical assembly excites the fluorescent reagent to be measured by the excitation signal and receives a response signal of the fluorescent reagent;

[0011] A first phase-sensitive detection circuit includes a first multiplier that multiplies the response signal and the first square wave signal to obtain a first output signal; and

[0012] A first low-pass filter performs low-pass filtering on the first output signal;

[0013] A second phase-sensitive detection circuit includes a second multiplier that multiplies the response signal and the second square wave signal to obtain a second output signal; and

[0014] a second low pass filter, configured to low pass filter the second output signal;

[0015] a solver, configured to square sum process the first output signal and the second output signal.

[0016] Further, the solver comprises a third multiplier, configured to multiply the first output signal and the first output signal to obtain a third output signal; and

[0017] a fourth multiplier, configured to multiply the second output signal and the second output signal to obtain a fourth output signal; and

[0018] an adder, configured to add the third output signal and the fourth output signal.

[0019] Further, the sine wave circuit comprises a reference clock, a direct digital frequency synthesizer, a digital-to-analog converter and a voltage-to-current conversion module;

[0020] The direct digital frequency synthesizer converts the first square wave signal into a sine wave digital signal;

[0021] The digital-to-analog converter converts the sine wave digital signal into a sine wave analog signal;

[0022] The voltage-to-current conversion module controls the LED excitation light source according to the sine wave analog signal.

[0023] Further, a PD photoelectric sensor is further included for collecting a response signal received by the optical assembly.

[0024] Further, a transimpedance amplifier and a signal amplifier are further included for amplifying the response signal.

[0025] Further, the controller comprises a square wave outputter for outputting the first square wave signal; and

[0026] a phase shifter for phase shifting the first square wave signal by 90° to obtain the second square wave signal.

[0027] Further, a first analog-to-digital converter and a second analog-to-digital converter are further included;

[0028] The first analog-to-digital converter converts the first output signal into a digital signal;

[0029] The second analog-to-digital converter converts the second output signal into a digital signal.

[0030] The present disclosure has the following beneficial effects:

[0031] The present disclosure multiplies the reference signal with the to-be-measured sinusoidal signal containing a wide-band noise, and the multiplier outputs a 2nd harmonic sinusoidal wave containing a DC component (2nd harmonic relative to the reference signal). The DC component of the 2nd harmonic sinusoidal wave is proportional to the to-be-measured sinusoidal signal and is related to the phase difference of the reference signal. Using a low-pass filter to retain only the DC component, a DC quantity proportional to the amplitude of the to-be-measured sinusoidal signal can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The architecture diagram of the embodiment of the present disclosure.

[0033] The reference signs in the drawings are as follows:

[0034] 1, first triangular fixed plate; 2, second triangular fixed plate; 3, first mounting rod; 4, second mounting rod; 5, clamping block; 6, baffle; 7, clamping pin; 8, pull rod; 9, fixed groove; 10, pull head; 11, spring; 12, mounting hole group; 13, extension rod; 14, fixed sheet; 15, fixed screw rod; 16, mounting gasket; 17, fixed hole; 18, accommodating cavity. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below in combination with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without any inventive effort fall within the scope of protection of the present disclosure.

[0036] Unless otherwise defined, technical terms or scientific terms used in the present disclosure should be understood as having the common meaning in the field of the present disclosure to those having ordinary skill in the art. The terms "first", "second" and similar terms used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, without excluding other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right" and the like only represent relative positional relationships, which can change accordingly when the absolute positions of the described objects change. In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits the detailed description of some known functions and known components.

[0037] The present disclosure will be described in detail below in combination with the drawings and specific embodiments.

[0038] A weak fluorescence detection system based on a photodiode, comprising a controller for outputting a first square wave signal and a second square wave signal, the first square wave signal and the second square wave signal being same frequency and same source, and having a phase difference of 90°;

[0039] A sine wave circuit for converting the first square wave signal into a sine wave signal having the same phase, amplitude and period as the first square wave signal;

[0040] An LED excitation light source controlled by the sine wave signal and emitting an excitation signal;

[0041] An optical assembly for exciting a fluorescent reagent to be measured by the excitation signal and receiving a response signal of the fluorescent reagent;

[0042] A first phase-sensitive detection circuit comprising a first multiplier for multiplying the response signal and the first square wave signal to obtain a first output signal; and

[0043] A first low-pass filter for low-pass filtering the first output signal;

[0044] A second phase-sensitive detection circuit comprising a second multiplier for multiplying the response signal and the second square wave signal to obtain a second output signal; and

[0045] A second low-pass filter for low-pass filtering the second output signal;

[0046] A solver for square-sum processing the first output signal and the second output signal.

[0047] In an embodiment of the utility model, the solver comprises a third multiplier for multiplying the first output signal and the first output signal to obtain a third output signal; and

[0048] A fourth multiplier for multiplying the second output signal and the second output signal to obtain a fourth output signal; and

[0049] An adder for adding the third output signal and the fourth output signal.

[0050] In an embodiment of the utility model, the sine wave circuit comprises a reference clock, a direct digital frequency synthesizer, a digital-to-analog converter and a voltage-current conversion module;

[0051] The direct digital frequency synthesizer converts the first square wave signal into a sine wave digital signal;

[0052] The digital-to-analog converter converts the sine wave digital signal into a sine wave analog signal;

[0053] The voltage current conversion module controls the LED excitation light source according to the sine wave analog signal.

[0054] The reference clock is used to ensure that the DDS output sine wave frequency is stable, and the same reference clock is used for the square wave and the sine wave to ensure that the phase difference between them is stable.

[0055] In an embodiment of the utility model, still include PD photoelectric sensor, be used to gather the response signal that the optical assembly receives.

[0056] In an embodiment of the utility model, still include transimpedance amplifier and signal amplifier, be used for the response signal amplification.

[0057] In an embodiment of the utility model, the controller includes a square wave output device for outputting the first square wave signal; and

[0058] The phase shifter is used to phase shift the first square wave signal by 90° to obtain the second square wave signal.

[0059] In an embodiment of the utility model, still include first analog-digital converter and second analog-digital converter;

[0060] The first analog-digital converter converts the first output signal into a digital signal;

[0061] The second analog-digital converter converts the second output signal into a digital signal.

[0062] The flowcharts and block diagrams in the drawings illustrate the possible implementation architecture, function and operation of the system, method and computer program product according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram can represent a module, a program segment, or a part of code containing one or more executable instructions for implementing the specified logic function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different order than that noted in the drawings. For example, two blocks represented in succession can actually be executed substantially in parallel, and they can also be executed in reverse order, depending on the function involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0063] The units involved in the embodiments of the present disclosure can be implemented in a software manner or in a hardware manner. In some cases, the name of the unit does not constitute a limitation on the unit itself.

[0064] The functions described above can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Program-specific Integrated Circuits (ASICs), Program-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

[0065] The above description is only preferred embodiments of the present disclosure and a description of the principles of the technology used. It should be understood by those skilled in the art that the scope of the disclosure involved in the present disclosure is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with each other to form a technical solution with similar functions disclosed in the present disclosure (but not limited to).

[0066] In addition, although each operation is described in a specific order, this should not be understood as requiring the operations to be performed in the specific order shown or in a sequential order. In certain circumstances, multitasking and parallel processing can be advantageous. Similarly, although several implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Certain features described in the context of separate embodiments can also be combined in a single embodiment. Conversely, various features described in the context of a single embodiment can also be separated and implemented in multiple embodiments.

[0067] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are merely illustrative of exemplary forms of implementing the claims.

[0068] For the present disclosure, the following points need to be explained:

[0069] (1) The drawings of the embodiments of the present disclosure only involve the structures involved in the embodiments of the present disclosure, and other structures can refer to the general design.

[0070] (2) In the case of no conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0071] The above merely describes the embodiments of the present disclosure, and does not limit the patent scope of the present disclosure, and any equivalent structure or direct or indirect application in other related technical fields made by using the content of the present disclosure and the drawings is also included in the patent protection scope of the present disclosure.

Claims

1. A photodiode-based weak fluorescence detection system, characterized by, The controller is configured to output a first square wave signal and a second square wave signal, the first square wave signal and the second square wave signal being of the same frequency and source, and having a phase difference of 90°; The sine wave circuit is configured to convert the first square wave signal into a sine wave signal having the same phase, amplitude and period as the first square wave signal; The LED excitation light source is controlled by the sine wave signal and emits an excitation signal; The optical assembly is configured to excite a fluorescent reagent to be tested by the excitation signal and receive a response signal of the fluorescent reagent; The first phase-sensitive detection circuit includes a first multiplier configured to multiply the response signal by the first square wave signal to obtain a first output signal; The first low-pass filter is configured to low-pass filter the first output signal; The second phase-sensitive detection circuit includes a second multiplier configured to multiply the response signal by the second square wave signal to obtain a second output signal; The second low-pass filter is configured to low-pass filter the second output signal; The solver is configured to square-sum process the first output signal and the second output signal. The solver includes a third multiplier configured to multiply the first output signal by the first output signal to obtain a third output signal; The fourth multiplier is configured to multiply the second output signal by the second output signal to obtain a fourth output signal; and 2. The photodiode-based weak fluorescence detection system of claim 1, wherein, The adder is configured to add the third output signal and the fourth output signal. The sine wave circuit includes a reference clock, a direct digital frequency synthesizer, a digital-to-analog converter and a voltage-to-current conversion module; The direct digital frequency synthesizer is configured to convert the first square wave signal into a sine wave digital signal; The digital-to-analog converter is configured to convert the sine wave digital signal into a sine wave analog signal; 3. The photodiode-based weak fluorescence detection system of claim 1, wherein, The voltage-to-current conversion module is configured to control the LED excitation light source according to the sine wave analog signal. The PD photoelectric sensor is configured to collect the response signal received by the optical assembly. The transimpedance amplifier and the signal amplifier are configured to amplify the response signal. The controller includes a square wave outputter configured to output the first square wave signal; and 4. The photodiode-based weak fluorescence detection system of claim 1, wherein, The phase shifter is configured to phase shift the first square wave signal by 90° to obtain the second square wave signal.

5. The photodiode-based weak fluorescence detection system of claim 4, wherein, The first analog-to-digital converter and the second analog-to-digital converter are further included; 6. The photodiode-based weak fluorescence detection system of claim 1, wherein, The first analog-to-digital converter is configured to convert the first output signal into a digital signal; The second analog-to-digital converter is configured to convert the second output signal into a digital signal.

7. The photodiode-based weak fluorescence detection system of claim 1, wherein, ​ ​ ​

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