Optical system for pesticide detection

Abstract

The utility model belongs to the field of detection, and relates to an optical system for pesticide detection, 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 leaf to be detected. A fluorescent light path is formed between the fluorescent light emitted by the to-be-detected leaf and a photoelectric sensor of a photoelectric conversion circuit of the pesticide detection system, and a band-pass optical filter with the central wavelength of 500nm, a focusing lens and a Fresnel lens are sequentially arranged along the fluorescent light path; the Fresnel lens is adopted as a main body of the optical focusing system, useless wavelengths of a fluorescent light path are filtered out by adopting the band-pass optical filter with the central wavelength of 500nm, the wavelengths are prevented from influencing the detection precision, the filtered fluorescent light path is focused for the first time through the focusing lens, and then the Fresnel lens is adopted for focusing for the second time, so that the detection precision is improved. The light is concentrated through twice focusing, so that the detection sensitivity and accuracy of weak signals are improved.

Description

Technical Field

[0001] The utility model relates to the field of detection, and particularly relates to an optical system for pesticide detection. Background Art

[0002] Chinese invention patent CN202410414825.1 discloses a method and a detection system for detecting acetamiprid residues on vegetable leaves. A laser is applied to a to-be-detected leaf to excite the to-be-detected leaf to emit fluorescence. This fluorescence is focused and then interfered by a band-pass filter, and then received by a photoelectric conversion circuit to convert the optical signal into an electrical signal. Then, this electrical signal is amplified by an amplifier circuit and the detection signal is output to a control unit. The control unit analyzes this detection signal to obtain the acetamiprid content, and then compares it with the preset acetamiprid content threshold in this control unit to obtain the detection result of whether the acetamiprid content on the to-be-detected leaf exceeds the standard. The present invention uses a laser to excite the to-be-detected leaf to emit fluorescence, and then interferes through a band-pass filter, only allowing the characteristic emission fluorescence of acetamiprid to pass through, and uses the characteristic emission fluorescence effect of substances to detect acetamiprid, which can accurately detect the concentration of acetamiprid, has higher sensitivity, and the detection result is also relatively accurate.

[0003] After the fluorescence emitted by the leaf in the above-mentioned invention patent is focused by a focusing lens, the optical signal is directly input into the photoelectric conversion circuit through a reflection cover under the interference of the band-pass filter. When detecting the pesticide residues on the surface of vegetable leaves, neither the reflection structure nor the general transmission structure can effectively collect and focus the scattered optical signals to the sensor, thus affecting the detection accuracy. Summary of the Invention

[0004] The purpose of the present invention is to provide an optical system for pesticide detection that improves the detection accuracy.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solution:

[0006] An optical system for pesticide detection includes a laser light path and a fluorescence light path. The laser light path is formed between the laser output by the laser source of the pesticide detection system and the to-be-detected leaf, and the fluorescence light path is formed between the fluorescence emitted by the to-be-detected leaf and the photoelectric sensor of the photoelectric conversion circuit of the pesticide detection system. A band-pass filter with a central wavelength of 500nm, a focusing lens, and a Fresnel lens are sequentially arranged along the fluorescence light path.

[0007] Preferably, the band-pass filter, the focusing lens, the Fresnel lens, and the sensing surface of the photoelectric sensor are hermetically encapsulated in a black box, and one end of the black box corresponding to the installation position of the band-pass filter has an open end for the fluorescence light path to enter the black box.

[0008] Preferably, two oppositely arranged parabolic reflecting films are provided at the open end of the black box.

[0009] Preferably, the parabolic reflecting film extends 8 mm from the open end of the black box in a direction away from the open end, and the foci of the two parabolic reflecting films fall on the band-pass filter.

[0010] Preferably, the distance between the Fresnel lens and the sensing surface of the photoelectric sensor is 10 mm.

[0011] Preferably, the focal length of the Fresnel lens is 10 mm.

[0012] Preferably, an attenuation sheet is provided on the laser optical path.

[0013] Preferably, the laser source outputs light emitted by an LD laser with a central wavelength of 355 nm.

[0014] Preferably, the vertical distance between the laser light source and the blade is 1.414 cm.

[0015] By adopting the foregoing design scheme, the beneficial effects of the present invention are as follows: The present invention uses a Fresnel lens as the main body of the optical focusing system, and uses a band-pass filter with a central wavelength of 500 nm to filter out the useless wavelengths in the fluorescence optical path (including the characteristic wavelength light of chlorophyll, stray light such as excitation light, etc.), avoiding the influence of these wavelengths on the detection accuracy. Then, the filtered fluorescence optical path is first focused by a focusing lens, and then a Fresnel lens is used for the second focusing. The two-time focusing makes the light concentrated, which helps to improve the detection sensitivity and accuracy of weak signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the frame structure of the pesticide detection system of the present utility model;

[0017] Figure 2 is the structural schematic diagram of the optical system of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Using the optical system of the present utility model, the object to be detected is exemplified by the pesticide acetamiprid on vegetable leaves. The applicant detected the pesticide acetamiprid. By referring to the literature, the excitation wavelength of acetamiprid is 355 nm, and the best emission wavelength of the characteristic emission fluorescence is 500 nm. The present utility model is designed based on this data.

[0020] As Figure 1 - Figure 2 shown, an optical system for pesticide detection includes a laser light path and a fluorescence light path. A laser light path is formed between the laser output by the laser source of the pesticide detection system and the leaf to be measured. In this embodiment, since the acetamiprid pesticide has the best absorption characteristics under the irradiation of 355-nm laser, an LD laser with a central wavelength of 355 nm is used to emit light as the laser source. An attenuation sheet is provided on the laser light path to reduce the power of the laser and avoid damaging the leaf to be measured by the laser light beam.

[0021] A fluorescence light path is formed between the fluorescence emitted by the leaf to be measured and the photoelectric sensor of the photoelectric conversion circuit of the pesticide detection system. A band-pass filter with a central wavelength of 500 nm, a focusing lens, and a Fresnel lens are sequentially arranged along the fluorescence light path. By confirming the optimal excitation wavelength and emission wavelength, it helps to reduce the influence of the self-biological activity on the leaf surface on the detection result and improve the detection accuracy.

[0022] In this embodiment, the signal light after passing through the optical system is converted from a weak optical signal to an electrical signal by the photoelectric conversion circuit, and then the signal is transmitted into the logarithmic amplifier circuit for processing, converting the transmitted different light intensities into voltage waveforms, thereby realizing the visual detection of the pesticide residue concentration.

[0023] In this embodiment, the Fresnel lens is used as the main body of the optical system mainly because the Fresnel lens has the following characteristics:

[0024] 1. The Fresnel lens has a high light transmittance: Since the convex lens on the surface of the Fresnel lens can effectively focus and concentrate light, the light transmittance is high, which means that the light passing through the Fresnel lens will be better focused and transmitted, thereby enhancing the brightness and clarity of the weak signal.

[0025] 2. The Fresnel lens has a high light collection efficiency: The design of the Fresnel lens can effectively collect the light in the surrounding environment, so that the weak signal is not easily missed or interfered, which can improve the detection sensitivity and accuracy of the signal.

[0026] 3. The Fresnel lens has good anti-interference ability: The structural design of the Fresnel lens can effectively suppress the interference of background light, making the weak signal easier to be detected and analyzed, which is very important for detecting weak signals in a complex environment.

[0027] Therefore, the Fresnel lens can become an effective tool suitable for weak signal detection, improving the detection sensitivity and accuracy of weak signals, and thus being better applied to the field of weak signal detection.

[0028] In this embodiment, the band-pass filter, the focusing lens, the Fresnel lens and the light-receiving surface of the photoelectric sensor are hermetically packaged in a black box. Here, the light-receiving surface of the photoelectric sensor refers to the side of the photoelectric sensor used to receive optical signals. One end of the black box corresponding to the installation position of the band-pass filter has an open end for the fluorescence light path to enter the black box. At the open end of the black box, there are two oppositely arranged parabolic reflecting films, and each parabolic reflecting film protrudes away from the outer side of the black box; the parabolic reflecting film extends 8 mm from the open end of the black box in the direction away from the open end, and the foci of the two parabolic reflecting films fall on the band-pass filter, so that the reflecting surfaces of the two parabolic reflecting films completely cover the part to be measured of the leaf to be measured, that is, the fluorescence light path emitted by the part to be measured of the leaf to be measured is completely within the space enclosed by the two parabolic reflecting films; the black box here is a conventional black box. By packaging the optical system in the black box, it can effectively avoid the influence of stray light on the correctness and accuracy of detection, and the parabolic reflecting film is set to play the role of concentrating fluorescence.

[0029] In this embodiment, the distance between the Fresnel lens and the light-receiving surface of the photoelectric sensor is 10 mm, and the focal length of the Fresnel lens is 10 mm; due to the irregular and non-smooth surface structure characteristics of the leaf to be measured, the fluorescence signal has great scattering loss, and it is difficult to capture such weak projection signals. Therefore, after preliminary focusing with a focusing lens, the Fresnel lens is used for light concentration. By using the characteristics of the Fresnel lens having good anti-interference ability and being able to effectively suppress background light interference, the detection sensitivity and accuracy of the fluorescence signal are improved.

[0030] As a preferred method of this embodiment, the vertical distance between the laser light source and the leaf to be measured is 1.414 cm. The calculation method of the vertical distance between the laser light source and the leaf to be measured is as follows: According to the strength of the fluorescence signal, the residue content of acetamiprid pesticide on vegetable leaves can be quantitatively detected. First, it is necessary to ensure that there is a definite corresponding relationship between the fluorescence signal intensity detected each time and the corresponding amount of pesticide, and it is also necessary that the light spot formed by the laser passing through the attenuation sheet can completely cover the leaf. On the one hand, it is convenient for one-time detection and reduces the workload. On the other hand, it reduces the error of accidental factors.

[0031] However, as the area of the laser light spot increases while the light intensity of the laser light source remains unchanged, the illuminance on the vegetable leaf decreases, affecting the occurrence of the fluorescence effect. The illuminance formula of the light source is as follows:

[0032] (1);

[0033] From Substituting into formula (1) gives:

[0034] (2);

[0035] Wherein, is the luminous intensity of the LD laser light source, is the illuminance of the light source, is the straight-line distance from the leaf to be measured to the laser light source, is the vertical distance from the laser light source to the leaf to be measured, is the angle between the light source and the leaf to be measured.

[0036] It can be seen from the above formula that as the vertical distance from the laser light source to the leaf to be measured increases, the illumination intensity of the leaf to be measured decreases, and after passing through the distance , the spot area will expand accordingly. Therefore, the illuminance formula of the light source can be expressed in the following form:

[0037] (3);

[0038] (4);

[0039] Wherein, is the field of view angle of the sensor, with the unit of rad; is the spot area, with the unit of square centimeter .

[0040] Assume that the area of the leaf to be measured is 1 , so the area S of the leaf to be measured that can participate in fluorescence excitation is . At the same time, the field of view angle of the sensor is designed to be 90°, then:

[0041] (5);

[0042] (6);

[0043] It can be seen from formula (5) and formula (6) that the optimal vertical distance between the light source and the leaf to be measured is 1.414 cm, and the detection accuracy is further improved by optimizing the light source irradiation distance.

[0044] In summary, the present invention uses a Fresnel lens as the main body of the optical focusing system, and uses a band-pass filter with a central wavelength of 500 nm to filter out the useless wavelengths in the fluorescence optical path (including stray light such as the characteristic wavelength light of chlorophyll and excitation light), so as to avoid the influence of these wavelengths on the detection accuracy. Then, the filtered fluorescence optical path is first focused by a focusing lens, and then a Fresnel lens is used for the second focusing. Through the two-time focusing, the light is concentrated, which helps to improve the detection sensitivity and accuracy of weak signals.

[0045] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical system for pesticide detection, characterized in that: 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 bandpass filter with a central wavelength of 500nm, a focusing lens, and a Fresnel lens are sequentially arranged along the fluorescent light path.

2. An optical system for pesticide detection as claimed in claim 1, characterized in that: The bandpass filter, the focusing lens, the Fresnel lens and the sensing surface of the photoelectric sensor are sealed and packaged in a black box. The end of the black box corresponding to the installation location of the bandpass filter has an opening end for the fluorescent light path to enter the black box.

3. An optical system for pesticide detection as claimed in claim 2, characterized in that: Two parabolic reflective films arranged opposite to each other are arranged at the opening end of the black box.

4. An optical system for pesticide detection as claimed in claim 3, characterized in that: The parabolic reflective film extends 8 mm from the opening end of the black box in a direction away from the opening end, and the focal points of the two parabolic reflective films fall on the bandpass filter.

5. The optical system for pesticide detection according to claim 1, characterized in that: The distance between the Fresnel lens and the sensing surface of the photoelectric sensor is 10 mm.

6. An optical system for pesticide detection as claimed in claim 1, characterized in that: The focal length of the Fresnel lens is 10 mm.

7. An optical system for pesticide detection as claimed in claim 1, characterized in that: An attenuation plate is arranged on the laser light path.

8. An optical system for pesticide detection as claimed in claim 1, characterized in that: The laser source outputs LD laser emission light with a central wavelength of 355 nm.

9. An optical system for pesticide detection as claimed in claim 1, characterized in that: The vertical distance between the laser source and the blade is 1.414 cm.

Images