Optical system for detecting pesticide residues on vegetable leaves

Abstract

The utility model discloses an optical system for detecting pesticide residues on vegetable leaves, which comprises a laser light path and a fluorescent light path, and the laser light path is formed between laser output by a laser source of a pesticide detection system and a to-be-detected leaf. A fluorescence light path is formed between the fluorescence emitted by the to-be-detected leaf and a photoelectric sensor of a photoelectric conversion circuit of the pesticide detection system, and a focusing lens, a band-pass light filter with the full width at half maximum of 40nm and the central wavelength of 500nm and a reflecting cover are sequentially arranged along the fluorescence light path. Due to different characteristic emission fluorescence reactions of different substances, compared with the prior art, the optical system outputs the characteristic emission fluorescence of the pesticide and is an optical signal capable of accurately reflecting pesticide information, and the pesticide detection system disclosed by the utility model is used for detecting the pesticide by utilizing the characteristic emission fluorescence effect of the substances, so that the pesticide detection efficiency is greatly improved. The concentration of the pesticide can be accurately detected, the sensitivity is relatively high, and the detection result is relatively accurate.

Description

Technical Field

[0001] The utility model relates to the detection field, in particular to an optical system for detecting pesticide residues in vegetable leaves. Background Art

[0002] Although pesticides play an important role in preventing crops from pests and diseases, excessive and misuse of pesticides may also have negative impacts on human health and the environment. Therefore, the detection of pesticide residues in agricultural products has become an important means to ensure food safety and environmental protection.

[0003] There are three methods for accurate detection of pesticide residues in the laboratory: gas chromatography, liquid chromatography, and gas chromatography-mass spectrometry. Although these methods have high accuracy, they also have obvious problems such as expensive equipment, cumbersome operation, difficulty in carrying, and inability to conduct rapid and non-destructive detection.

[0004] Chinese utility model patent ZL202122456439.3 discloses a rapid detection device for pesticide residues on vegetable leaves, which includes a cubic detection frame, a pull-out loading platform is provided on one side of the bottom of the detection frame, the pull-out end of the loading platform is flush with the side wall of the detection frame, the loading end of the loading platform extends into the center of the bottom of the detection frame, and a loading area is provided on the upper part of the loading platform; a frustum-shaped light collecting cover is provided above the loading area, the upper and lower ends of the light collecting cover are open, a signal processing system is provided on the upper part of the light collecting cover, a display screen is provided on the upper part of the signal processing system, and a CCD sensor is provided on the lower part; a focusing lens is provided at the lower end of the light collecting cover, and a filter is provided on the inner side of the focusing lens; LED lights are provided on both sides of the lower part of the light collecting cover, and the LED lights are electrically connected to the power supply and the signal processing system respectively. When the detection device is working, the light of the LED lamp is irradiated on the vegetable leaves, and the reflected light on the vegetable leaves is directly read by the CCD sensor, and the optical signal is converted into an electrical signal, and then the electrical signal is transmitted to the single-chip microcomputer for processing, and the single-chip microcomputer transmits the processed data to the display screen for display. This vegetable leaf pesticide residue rapid detection device basically solves the obvious problems of the traditional detection method, such as expensive equipment, cumbersome operation, not easy to carry, and inability to detect rapidly without loss. However, since its CCD sensor reads the reflected light on the vegetable leaves in a way of directly reading image information, thereby obtaining the pesticide information corresponding to the reflected light, and the surface of the vegetable leaves is usually not a smooth surface, the reflected light signal on the vegetable leaves is uneven and very weak, and it is not easy to be read by the CCD sensor. Therefore, there is a large error in the information read by the CCD sensor, and the detection accuracy is poor. Utility Model Content

[0005] The utility model aims to provide an optical system for detecting pesticide residues in vegetable leaves, which can output an optical signal that accurately reflects pesticide information, so that the detection error of the pesticide detection system is small.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] The optical system for detecting pesticide residues in vegetable leaves comprises a laser light path and a fluorescent light path. The laser light path is formed between the laser output from the laser source of the pesticide detection system and the leaves to be detected, and the fluorescent light path is formed between the fluorescence emitted from the leaves to be detected and the photoelectric sensor of the photoelectric conversion circuit of the pesticide detection system. A focusing lens, a bandpass filter with a half-width at half maximum of 40nm and a central wavelength of 500nm, and a reflective cover are sequentially arranged along the fluorescent light path.

[0008] An attenuation plate is arranged on the laser light path.

[0009] The reflective cover has a large end and a small end, the opening of the large end faces the bandpass filter, and the opening of the small end faces the photoelectric sensor of the photoelectric conversion circuit.

[0010] The irradiation angle of the laser source is 45°.

[0011] After adopting the above scheme, the optical system for detecting pesticide residues in vegetable leaves of the utility model, when working, excites the leaves to be tested to emit fluorescence through the laser generated by the pesticide detection system, and then interferes through the bandpass filter to only allow the characteristic emission fluorescence of the pesticide to pass, and then receives the characteristic emission fluorescence of the pesticide through the photoelectric conversion circuit of the pesticide detection system and converts the optical signal into an electrical signal, and then detects and analyzes it through the corresponding circuit of the pesticide detection system to obtain the detection result of whether the pesticide content on the leaves to be tested exceeds the standard. Fluorescence is a type of light in radiation transition, which is the radiation energy released when a substance transitions from an excited state to a ground state. Since the characteristic emission fluorescence reactions of different substances are different, compared with the prior art, the optical system of the utility model outputs the characteristic emission fluorescence of the pesticide, which is an optical signal that can accurately reflect the information of the pesticide. The pesticide detection system of the utility model uses the characteristic emission fluorescence of the substance to detect the pesticide, and can accurately detect the concentration of the pesticide, with high sensitivity and more accurate detection results.

[0012] Furthermore, in the utility model, an attenuation plate is arranged between the laser source and the blade to be measured to reduce the optical power of the laser so as to avoid damage to the blade to be measured caused by the laser beam.

[0013] Furthermore, in the present invention, the irradiation angle of the laser source is set to 45° to obtain fluorescence with maximum intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The system block diagram of the acetamiprid residue detection system for vegetable leaves adopting the utility model;

[0015] Figure 2 It is a schematic diagram of the optical path of the utility model;

[0016] Figure 3 The circuit schematic diagram of the avalanche photodiode bias circuit in the acetamiprid residue detection system for vegetable leaves adopting the utility model;

[0017] Figure 4 It is a circuit principle diagram of the photoelectric conversion and amplification circuit in the acetamiprid residue detection system for vegetable leaves of the utility model;

[0018] Figure 5 The present invention is a circuit schematic diagram of a constant current source driving circuit in a vegetable leaf acetamiprid residue detection system using the utility model. DETAILED DESCRIPTION

[0019] Laser elemental analysis mainly uses laser induced plasma technology to perform elemental analysis of materials. The high pulse energy generated by the laser is irradiated onto the material to be tested through a focusing lens. When the energy absorbed by the surface of the material is greater than a certain threshold, its surface is rapidly vaporized and ionized. The ionized particles diffuse outward, while the unionized particles continue to absorb energy. This state of coexistence of ions and electrons induced by the laser is laser induced plasma. Plasma can release light radiation containing material structural information. The composition of the material can be accurately obtained by analyzing this light radiation spectrum. At the same time, different components will emit light of different wavelengths after being excited by light. By collecting the weak signals excited, it is possible to distinguish what components a substance has, and indicators such as the intensity of light emitted at different concentrations are different. This feature also provides basic theoretical support for the application of photoelectric technology in pesticide content detection.

[0020] The pesticide detection system of the utility model is used to detect the pesticide acetamiprid on vegetable leaves as an example. The applicant detects the pesticide acetamiprid and, through consulting the literature, finds that the excitation wavelength of acetamiprid is 355nm and the optimal emission wavelength of characteristic emission fluorescence is 500nm. The utility model is designed based on this data.

[0021] By adopting the method for detecting acetamiprid residues in vegetable leaves of the utility model, a laser with a wavelength of 355nm is applied to the leaves to be tested through a laser source to excite the leaves to be tested to emit fluorescence. After being focused, the fluorescence is interfered by a bandpass filter with a half-width at half maximum of 40nm and a central wavelength of 500nm. Then, the photoelectric conversion circuit receives the interfered fluorescence (characteristic emission fluorescence of acetamiprid) and converts the optical signal into an electrical signal. Then, the amplification circuit amplifies the electrical signal and outputs a detection signal to a control unit. The control unit analyzes the detection signal to obtain the acetamiprid content, and then compares the signal with the acetamiprid content threshold preset in the control unit to obtain a detection result of whether the acetamiprid content on the leaves to be tested exceeds the standard.

[0022] Furthermore, an attenuation plate is arranged between the laser source and the blade to be measured to reduce the optical power of the laser so as to avoid damage to the blade to be measured caused by the laser beam.

[0023] Furthermore, a reflective cover is arranged between the bandpass filter and the photoelectric sensor of the photoelectric conversion circuit to further converge the fluorescent signal through multiple reflections.

[0024] Furthermore, the irradiation angle of the laser source is 45° to obtain fluorescence with maximum intensity.

[0025] The vegetable leaf acetamiprid residue detection system of the utility model is used, such as Figure 1-5 As shown, it includes a circuit part and an optical path part;

[0026] The circuit part includes a control unit, a laser generating circuit, and a photoelectric conversion and amplification circuit. The laser generating circuit includes a constant current source driving circuit and a laser source. The input end of the constant current source driving circuit is connected to the PWM signal output end of the control unit. The output end of the constant current source driving circuit is connected to the laser source. When working, the constant current source driving circuit is controlled by the PWM signal output by the control unit, and the laser source is driven by the constant current source driving circuit to generate a laser with a wavelength of 355nm. The photoelectric conversion and amplification circuit includes a photoelectric conversion circuit and an amplification circuit. The output end of the photoelectric conversion circuit is connected to the input end of the amplification circuit. The output end of the amplification circuit is connected to the detection signal input end of the control unit. The control unit is preset with a acetamiprid content threshold for comparison with the detection result.

[0027] The optical path part includes a laser optical path and a fluorescent optical path. The laser optical path is formed between the laser output by the laser source and the blade to be measured, and the fluorescent optical path is formed between the fluorescence emitted by the blade to be measured and the photoelectric sensor of the photoelectric conversion circuit. A focusing lens, a bandpass filter with a half-width at half maximum of 40nm and a center wavelength of 500nm, and a reflective cover are arranged in sequence along the fluorescent optical path.

[0028] Furthermore, the control unit adopts a single-chip microcomputer MSP430F5529. As an ultra-low power microcontroller under TI, the single-chip microcomputer MSP430F5529 has the characteristics of high performance, low power consumption, rich peripherals and easy development, and has received widespread attention and application. With the rapid development of the Internet of Things, portable devices and other fields, its potential in signal detection has also been developed.

[0029] Furthermore, the photoelectric sensor of the photoelectric conversion circuit adopts an avalanche photodiode (APD), and the bias end of the avalanche photodiode is connected to a bias circuit to compensate for the gain drift of the avalanche photodiode caused by long continuous use or temperature increase due to aging, so as to adjust the output voltage of the power supply to achieve normal working requirements.

[0030] The utility model provides an optical system for detecting pesticide residues in vegetable leaves. Figure 1-2 As shown, it includes a laser light path and a fluorescent light path. The laser light path is formed between the laser output by the laser source and the blade to be measured, and the fluorescent light path is formed between the fluorescence emitted by the blade to be measured and the photoelectric sensor of the photoelectric conversion circuit. A focusing lens, a bandpass filter with a half-height full width of 40nm and a central wavelength of 500nm, and a reflective cover are sequentially arranged along the fluorescent light path.

[0031] Furthermore, in the utility model, an attenuation plate is arranged between the laser source and the blade to be measured to reduce the optical power of the laser so as to avoid damage to the blade to be measured caused by the laser beam.

[0032] Furthermore, in the present invention, the irradiation angle of the laser source is set to 45° to obtain fluorescence with maximum intensity.

[0033] The reflector used in the utility model is coated with a high-reflection film, and the diffusely reflected light can be reflected multiple times with low loss. Figure 2 As shown, the reflective cover has a large end and a small end, the opening of the large end faces the focusing lens, and the fluorescent light beam preliminarily focused by the focusing lens enters through the opening of the large end of the reflective cover, and is further converged by multiple reflections in the reflective cover. The opening of the small end of the reflective cover is the focusing point of the fluorescent signal, which is opposite to the avalanche photodiode of the photoelectric conversion circuit. The fluorescent signal excited by the laser is reflected multiple times in the reflective cover and finally enters the sensing surface of the avalanche photodiode.

[0034] As a preferred embodiment, in the present invention, the distance between the laser source and the blade to be measured is 5 cm, and the optimal vertical distance h is 3.46 cm. The photosensitive diameter of the avalanche photodiode used is 1.13 cm. When the distance between the avalanche photodiode and the focusing lens is 11 mm, the emitted fluorescent signal can be collected and converged to the maximum extent.

[0035] The laser source uses LD (laser diode). When working, there is a close relationship between PWM (pulse width modulation) wave and LD (laser diode) power control. PWM wave is a commonly used digital signal modulation technology that controls the average power by adjusting the pulse width of the signal. In laser diodes, PWM signals are usually used to adjust the working state of the laser diode, thereby controlling its output power. By changing the duty cycle of the PWM signal, precise control of the output power of the laser diode can be achieved. When the duty cycle of the PWM signal increases, the working time of the laser diode increases, and the output power also increases accordingly. On the contrary, when the duty cycle of the PWM signal decreases, the working time of the laser diode decreases, and the output power also decreases. Therefore, by adjusting the duty cycle of the PWM signal, precise regulation of the output power of the laser diode can be achieved.

[0036] like Figure 5 As shown, the constant current source drive circuit is mainly composed of two LED bias power supplies MAX1916 (U5, U9). The input ends (pin 1) of the LED bias power supply MAX1916 (U5) and the LED bias power supply MAX1916 (U9) are respectively connected to the PWM signal output end of the control unit, and the three output ends of the LED bias power supply MAX1916 (U5) are respectively connected to the laser source LD3, the laser source LD4 and the laser source LD5; the three output ends of the LED bias power supply MAX1916 (U9) are respectively connected to the laser source LD8, the laser source LD7 and the laser source LD6. The LED bias power supply MAX1916 (U5, U9) can provide a constant current bias power supply. The LED bias power supply MAX1916 uses a single resistor to set the bias current of up to three LEDs, and can also drive the laser light source. When driving the LD, the LED bias current is matched to 0.3% through the current matching MAX1916 unique current matching architecture. The power supply current is as low as 40μA in normal operation and 0.05μA when disabled. Compared with the use of ballast resistors, the bias change synchronized with the voltage change is reduced, the dropout voltage is significantly reduced, and in some applications, the efficiency is significantly improved. The MAX1916 achieves a 200mV output with a 9mA load on each output. For circuits that only require one or two outputs, just leave the output port that is not connected to the output unconnected. The EN terminal is the power input terminal of the MAX1916. When the EN terminal voltage is higher than 2.5V, the device is enabled; when the EN terminal voltage is lower than 2.2V, the device is disabled, that is, there is a flexible threshold range. When the drive current is high, EN provides 40μA current to power the integrated circuit. Drive the EN terminal to put LD3, LD4, LD5 (or LD8, LD7, LD6) and SET into a high impedance state.

[0037] like Figure 4As shown in the figure, the photoelectric conversion and amplification circuit includes two parts: the photoelectric conversion circuit and the isolation amplifier circuit. The photoelectric conversion circuit is mainly composed of an avalanche photodiode, a current mirror ADL5317 (U4) and its peripheral circuits, and a logarithmic amplifier AD8305 (U6), which is used to convert the collected and captured optical signals into electrical signals. The isolation amplifier circuit is mainly composed of an isolation amplifier AMC1300 (U7) and an operational amplifier TLV6001 (U8).

[0038] During operation, the temperature rise of the avalanche photodiode (APD) with continuous operation will produce a large temperature drift, which seriously interferes with the operation of the APD circuit. The current mirror ADL5317 (U4) can control the bias voltage of the APD to maintain a basically constant gain. The APD photocurrent is input from the VAPD pin (pin 8) of the current mirror ADL5317 (U4) and flows out from the IPDM pin (pin 11) of the current mirror ADL5317 (U4). Here, U_bias needs to be introduced from the high-voltage bias voltage so that the APD circuit can work properly. The mirror current of the monitoring current mirror is used to reduce the conversion noise. The monitoring current output by the current mirror ADL5317 (U4) can be directly connected to the translinear logarithmic amplifier AD8305 (U6) to achieve high-precision monitoring of the APD. The current is input from the INPT pin (pin 4) of the logarithmic amplifier AD8305 (U6), and the logarithmic amplification and current signal conversion into a voltage signal are completed. Then, the current is output from the VOUT pin (pin 12) (the maximum output voltage of this pin is 1.2V). The logarithmic amplifier AD8305 has low noise and can also filter noise in the frequency response, so it has excellent noise removal performance.

[0039] The isolation amplifier circuit is composed of the isolation amplifier AMC1300 (U7) and the operational amplifier TLV6001 (U8). After optimization, the input current enters the isolation amplifier AMC1300 (U7) and can be directly connected to a shunt resistor or other low voltage level signal source. The isolated signal will undergo a differential operation in the isolation amplifier AMC1300 (U7) to improve the signal-to-noise ratio. The operational amplifier TLV6001 plays the role of amplification and limiting, limiting its output voltage (to the ADC1 pin of the control unit) to 0-3.3V.

[0040] The bias circuit of the avalanche photodiode uses the boost DC-DC converter MAX5026 (U1) to achieve the purpose of stable operation of the APD. The boost DC-DC converter MAX5026 has a slow internal FET rise, low di / dt and dv / dt noise; easy to filter noise spectrum; high integration; low cost and small size. It provides a high voltage bias voltage of 24.7-71V, and the avalanche photodiode (APD) is in working state. The switching delay is increased, and the high-frequency voltage burrs are smoothed. Therefore, the noise generated by various capacitors is minimized.

[0041] like Figure 3 As shown in the figure, when working, the current flows out from the power supply, flows into the 4th and 5th pins of the boost DC-DC converter MAX5026 (U1), and flows out from the 6th pin to provide a high-voltage output, and then passes through the current pump composed of capacitor C1, diode D1, and diode D2, and finally outputs a stable high voltage from the U_bias terminal. By adjusting the input voltage of U1, the circuit voltage can be adjusted greatly. For example, when the input voltage of U1 changes from 0 to 2.5V, this bias circuit can generate an adjustable output voltage.

[0042] A current mirror is an instrument used to measure current. It can accurately measure current by amplifying, inverting or attenuating the current. In scientific research and engineering, current mirrors are often used to measure weak currents or to precisely control currents.

[0043] The combination of a logarithmic amplifier and a low-noise amplifier has important advantages in many applications. The logarithmic amplifier can convert the input signal to a logarithmic output, while the low-noise amplifier can provide high-quality signal amplification. The combination of the two can bring the following advantages:

[0044] 1. Wide dynamic range: The logarithmic amplifier can convert the input signal into a logarithmic output, while the low-noise amplifier can amplify the signal while maintaining the signal-to-noise ratio, giving the entire system a large dynamic range.

[0045] 2. High precision: This helps to improve the precision of the system and the accuracy of the measurement. The low noise amplifier can maintain the high quality of the signal and provide high-precision amplification.

[0046] 3. High signal-to-noise ratio: The low-noise amplifier can provide a lower noise level, and the logarithmic amplifier can compress the signal. This combination can amplify and process the signal while maintaining a high signal-to-noise ratio.

[0047] 4. Suitable for sensor applications: The combination of logarithmic amplifiers and low-noise amplifiers is very useful in many sensor applications, such as photoelectric sensors, sound sensors, etc., which can provide higher dynamic range and better signal-to-noise ratio, thereby improving the performance and sensitivity of the sensor.

[0048] When the acetamiprid residue detection system for vegetable leaves of the utility model is used, the control unit sends a PWM signal to the constant current source drive circuit, and the constant current source drive circuit provides a constant current bias power supply to the laser source, which excites the laser source to start working and emits a laser with a wavelength of 355nm. The laser is irradiated at an angle of 45° to the leaf to be measured. In order to avoid damage to the leaf to be measured by the laser beam, an attenuation plate can be set between the laser source and the leaf to be measured to reduce the optical power of the laser. Under the excitation of laser, the leaf to be tested and the acetamiprid remaining on it respectively emit fluorescence of corresponding wavelengths. The fluorescence is initially focused by a focusing lens in front of the leaf to be tested, and then interfered by a bandpass filter with a half-width at half maximum of 40nm and a central wavelength of 500nm, so that only the characteristic emission fluorescence of acetamiprid passes through. The fluorescence passing through the bandpass filter then enters the reflecting cover in front of the bandpass filter, and is further concentrated by multiple reflections in the reflecting cover. The opening at the small end of the reflecting cover is the focusing point of the fluorescence signal, which is opposite to the avalanche photodiode of the photoelectric conversion circuit. The fluorescence signal excited by the laser is reflected multiple times in the reflecting cover and finally enters the sensing surface of the avalanche photodiode. The fluorescence signal is converted into a current signal by an avalanche photodiode and input into the VAPD pin (pin 8) of the current mirror ADL5317 (U4), and flows out from the IPDM pin (pin 11) of the current mirror ADL5317 (U4) to the INPT pin (pin 4) of the logarithmic amplifier AD8305 (U6), completing logarithmic amplification and converting the current signal into a voltage signal, and then output from the VOUT pin (pin 12) of the logarithmic amplifier AD8305 (U6). It is then isolated and amplified by the isolation amplifier AMC1300 (U7) and the operational amplifier TLV6001 (U8), and finally the signal is output to the detection signal input terminal (ADC1) of the single-chip microcomputer MSP430F5529. The single-chip microcomputer MSP430F5529 analyzes the detection signal, and obtains the acetamiprid content according to the calculation method preset in the single-chip microcomputer MSP430F5529. The signal is then compared with the acetamiprid content threshold preset in the single-chip microcomputer MSP430F5529 to obtain the detection result of whether the acetamiprid content on the tested leaf exceeds the standard.

[0049] The calculation method of the detection signal is preset in the single-chip microcomputer MSP430F5529 to obtain the acetamiprid content, and the acetamiprid content threshold is preset in the single-chip microcomputer MSP430F5529, and the measured acetamiprid content is compared with the acetamiprid content threshold. These are all existing functions of the single-chip microcomputer MSP430F5529 and are conventional technical means in this field. Specifically, for example, a preset program can be built into the single-chip microcomputer MSP430F5529 to convert the collected digital quantity into a corresponding voltage value, and then the converted voltage value is substituted into the pre-optimized and fitted voltage-light intensity relationship to obtain the corresponding excitation fluorescence intensity, and then the calculated fluorescence intensity is substituted into the light intensity-acetamiprid content polynomial to obtain the acetamiprid content, and compared with the preset acetamiprid content threshold to obtain the detection result of whether the acetamiprid on the tested leaf exceeds the standard.

[0050] An external display can be connected to the output end of the single-chip microcomputer MSP430F5529, and the user can directly see the test results on the display.

[0051] The product form of the utility model is not limited to the embodiments of this case. Any appropriate changes or modifications made by anyone with similar ideas should be deemed to be within the patent scope of the utility model.

Claims

1. An optical system for detecting pesticide residues in vegetable leaves, characterized by: It includes a laser light path and a fluorescent light path. The laser light path is formed between the laser output by the laser source of the pesticide detection system and the leaf to be tested. The fluorescent light path is formed between the fluorescence emitted by the leaf to be tested and the photoelectric sensor of the photoelectric conversion circuit of the pesticide detection system. A focusing lens, a bandpass filter with a half-height full width of 40nm and a central wavelength of 500nm, and a reflective cover are sequentially arranged along the fluorescent light path.

2. The optical system for detecting pesticide residues in vegetable leaves according to claim 1, characterized in that: An attenuation plate is arranged on the laser light path.

3. The optical system for detecting pesticide residues in vegetable leaves according to claim 1, characterized in that: The reflective cover has a large end and a small end, the opening of the large end faces the bandpass filter, and the opening of the small end faces the photoelectric sensor of the photoelectric conversion circuit.

4. The optical system for detecting pesticide residues in vegetable leaves according to claim 1, characterized in that: The irradiation angle of the laser source is 45°.

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