Three-dimensional imaging device based on line-laser-induced chlorophyll fluorescence, and method

Abstract

A three-dimensional imaging device based on line-laser-induced chlorophyll fluorescence, and a method. A line-shaped laser light source device (7) emits line laser light, the line laser light is refracted by a triangular prism (2) and irradiates a leaf to be measured, a CMOS camera (1) captures an image at the same time, and as a stepping motor (3) drives the triangular prism (2) to rotate, scanning of the leaf to be measured is completed; an embedded computer (5) performs multi-threaded processing on the image to form three-dimensional point cloud data comprising fluorescence kinetic parameters. Rapid measurement of real-time fluorescence parameters is achieved by means of the line laser light and the long exposure of the CMOS camera (1), and the embedded computer (5) performs multi-threaded processing on the image to obtain the real-time fluorescence parameters. Using line laser scanning to synchronously perform chlorophyll fluorescence detection and three-dimensional point cloud generation alleviates the problems of high cost and large size of area excitation light sources. Moreover, by means of the line laser scanning in light of the long exposure of the camera, large-area chlorophyll fluorescence-based rapid imaging can also be achieved, achieving the purpose of real-time detection.

Description

Three-dimensional imaging device and method for linear laser-induced chlorophyll fluorescence TECHNICAL FIELD

[0001] The present application belongs to the field of photoelectric detection and image processing, and particularly relates to a three-dimensional imaging device and method for linear laser-induced chlorophyll fluorescence. BACKGROUND

[0002] Chlorophyll fluorescence is a non-invasive detection method used to assess early indicators of photosynthesis in plants. Changes in chlorophyll fluorescence occur earlier than changes in chlorophyll content and plant structure. Therefore, it is widely used for photosynthesis detection and to study the growth conditions of plants under different stress conditions. Laser-induced chlorophyll fluorescence imaging methods do not require direct contact or harm to plants, and information is obtained by exciting the fluorescence signal emitted by chlorophyll. This non-invasive feature allows the method to monitor the physiological state of plants in real time and continuously without causing damage to the plants.

[0003] The existing three-dimensional chlorophyll fluorescence imaging device has the following disadvantages: devices using a single-point laser as an excitation light source require multiple point excitations for each leaf, which results in a measurement period of several hours, making it impossible for the device to monitor the chlorophyll fluorescence of the plant canopy in real time; devices using LED area light sources can cover a larger measurement area, but the large size of the lamp panel limits the portability and flexibility of the system. In addition, existing three-dimensional chlorophyll fluorescence detection methods use binocular camera principles to achieve registration between chlorophyll fluorescence images and point clouds, and the accuracy is affected by the relative position of the cameras and the accuracy of the calibration, so the practicability of the system is not strong.

[0004] SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a three-dimensional imaging device and method for linear laser-induced chlorophyll fluorescence.

[0006] The present application achieves the above technical purpose through the following technical means.

[0007] A three-dimensional imaging device for linear laser-induced chlorophyll fluorescence, comprising a CMOS camera, a three-prism, a stepper motor, an embedded computer, a long-wave pass filter, a linear laser light source device, a motorized slide rail, a measurement platform, and a load-bearing frame.

[0008] The load-bearing frame is vertically installed on the measurement platform, the CMOS camera, the stepper motor, and the motorized slide rail are all installed on the horizontal section of the load-bearing frame, and the lens of the CMOS camera is directly opposite the measurement platform; the three-prism is clamped on the rotating shaft of the stepper motor; the linear laser light source device is fixed on the object platform of the motorized slide rail; and the long-wave pass filter is fixed on the lens of the CMOS camera.

[0009] The embedded computer communicates with the step motor, the CMOS camera and the electric slide rail.

[0010] The technical scheme further includes a display screen, which is connected with the embedded computer and used for switching the working mode of the three-dimensional imaging device.

[0011] The three-dimensional imaging method of linear laser-induced chlorophyll fluorescence is a method for obtaining complete fluorescence kinetic parameters and forming three-dimensional point cloud data with fluorescence kinetic parameters.

[0012] Further,

[0013] When a plant below 50 cm is photographed: the linear laser light source device and the triangular prism are located on the same horizontal line, and the emission point of the linear laser light source device is arranged opposite to the triangular prism; the step motor starts from a starting angle and rotates at a step angle of 0.2° each time and stops after each rotation; the linear laser light source device emits linear laser with a line width of 5 mm according to the pulse amplitude modulation measurement principle to irradiate the measured leaf placed on the measurement platform; the embedded computer combines the measurement light, the saturated pulse light and the actinic light into a measurement cycle by using the PWM pulse width modulation technology; in the measurement cycle, the CMOS camera completes multiple imaging and transmits the images to the embedded computer; after one imaging is completed, the step motor continues to rotate at a step angle of 0.2° and continues to image until it rotates to a terminal angle; the embedded computer performs multi-thread processing on the received images, extracts the chlorophyll fluorescence lines in the multiple images and splices them into a complete chlorophyll fluorescence image of the leaf, calculates the fluorescence kinetic parameters, synthesizes a pseudo-color image according to the fluorescence kinetic parameters; meanwhile, three-dimensional point clouds are extracted according to the offset of the laser line pixel points, the pseudo-color image is mapped to the three-dimensional point clouds, and three-dimensional point cloud data with fluorescence kinetic parameters are formed.

[0014] In the process of shooting plants in the range of 50cm-100cm: adjust the horizontal one-laser light source device to the angle of θ with the vertical line, the one-laser light source device emits line laser with a line width of 5mm according to the principle of pulse amplitude modulation measurement, irradiate the measured leaf placed on the measurement platform, the embedded computer combines the measurement light, the saturated pulse light and the actinic light into a measurement cycle by using the PWM pulse width modulation technology, in this measurement cycle, the CMOS camera completes multiple imaging and transmits to the embedded computer; after imaging, the electric slide rail slides 5mm to the direction of the CMOS camera, continues to measure until the whole measurement platform is scanned; the embedded computer processes the received images by multi-threading, extracts the chlorophyll fluorescence lines in the multiple images and splices them into a complete chlorophyll fluorescence image of the leaf, calculates the fluorescence kinetic parameters, synthesizes the pseudo-color image according to the fluorescence kinetic parameters; at the same time, extract the three-dimensional point cloud according to the offset of the laser line pixel points, map the pseudo-color image to the three-dimensional point cloud to form three-dimensional point cloud data with fluorescence kinetic parameters.

[0015] Further, the method of splicing a complete chlorophyll fluorescence image of a leaf is specifically: threshold segmentation is performed on each image to extract chlorophyll fluorescence lines, all extracted chlorophyll fluorescence lines are placed on the canvas by traversing all images, and a complete chlorophyll fluorescence image of a leaf is obtained.

[0016] A three-dimensional imaging method of line laser-induced chlorophyll fluorescence, the working mode of the three-dimensional imaging device is to quickly measure real-time fluorescence parameters to form three-dimensional point cloud data with real-time fluorescence parameters.

[0017] Further, the rotation range of the stepper motor is limited within 45° downward vertically, the exposure time of the CMOS camera is set to 10s, the time for the stepper motor to rotate from-22.5° to 22.5° is set to 10s, and the one-laser light source device is set to work at the maximum power; when the stepper motor starts to rotate, the CMOS camera is triggered to shoot and the one-laser light source device is started to emit laser at the same time, and the scanning and long-exposure imaging of the measured leaf placed on the measurement platform are completed within 10s; then the CMOS camera is set to video acquisition mode, and the stepper motor rotates from 22.5° to-22.5° again to complete the acquisition of three-dimensional original information images.

[0018] The embedded computer processes the received images by multi-threading, calculates real-time fluorescence parameters according to the long-exposure images, synthesizes a pseudo-color image according to the real-time fluorescence parameters; at the same time, extracts three-dimensional point cloud according to the offset of the laser line pixel points, and finally maps the pseudo-color image to the three-dimensional point cloud to form three-dimensional point cloud data with real-time fluorescence parameters.

[0019] Further, by changing the duty cycle of the PWM wave output by the embedded computer, a linear laser light source device is driven to respectively emit measuring light, saturating pulse light and actinic light; the laser excitation sequence is set as follows: measuring light, saturating pulse light, measuring light, actinic light, measuring light, 9 times of continuous saturating pulse light, measuring light, and the CMOS camera is triggered to take a picture at the same time when the measuring light is emitted.

[0020] Further, the calculation of the fluorescence kinetic parameter / real-time fluorescence parameter is specifically: performing multiplication operation on the chlorophyll fluorescence image of a complete leaf to obtain a fluorescence region mask image; accumulating the pixel matrix of the mask image to obtain the total number of leaf region pixel values num; performing segmentation operation on the chlorophyll fluorescence image to be calculated and the fluorescence region mask image to obtain a segmented fluorescence image; adding the pixel matrix of the segmented fluorescence image to obtain the total sum of leaf region pixel values Data; and substituting the total number of leaf region pixel values num and the total sum of leaf region pixel values Data into the formula , to obtain the chlorophyll fluorescence parameter value corresponding to the chlorophyll fluorescence image of a complete leaf, i.e. the fluorescence kinetic parameter; the chlorophyll fluorescence image to be calculated includes the chlorophyll fluorescence image of a complete leaf under measuring light, the chlorophyll fluorescence image of a complete leaf under saturating pulse light and the chlorophyll fluorescence image of a complete leaf under actinic light taken by the CMOS camera.

[0021] Further, the extraction of the three-dimensional point cloud is specifically: extracting all the chlorophyll fluorescence images under saturating pulse light when the laser line is irradiated on each position of the leaf to be measured, and arranging the picture sequence in the same direction as the laser line scanning direction; analyzing each picture in the picture sequence, extracting the center line of the laser line in the picture, converting the pixel coordinates of the center line extracted in each picture to the reference coordinate system, solving the horizontal and vertical coordinate values in the reference coordinate system, inputting the horizontal and vertical coordinate values into the light plane equation in the reference coordinate system, and inverting the point cloud depth information; adding the horizontal and vertical coordinate values and the offset of the laser line pixel points in the next picture to obtain the real reference coordinates of the point cloud; and after traversing the picture sequence, the complete point cloud is obtained.

[0022] The beneficial effects of the present application are:

[0023] (1) After the chlorophyll fluorescence image is taken in the present application, the fluorescence kinetic parameter / real-time fluorescence parameter is calculated, and the pseudo-color image is synthesized according to the fluorescence kinetic parameter / real-time fluorescence parameter; at the same time, the three-dimensional point cloud is extracted according to the offset of the laser line pixel points, the pseudo-color image is mapped to the three-dimensional point cloud, and the three-dimensional point cloud data with fluorescence kinetic parameter / real-time fluorescence parameter is formed; compared with the traditional chlorophyll fluorescence imaging, the three-dimensional point cloud data with fluorescence kinetic parameter / real-time fluorescence parameter is more conducive to the analysis of the growth of the leaf.

[0024] (2) In the present application, since the position of the CMOS camera and the leaf to be measured does not change when the chlorophyll fluorescence image is photographed and the point cloud is extracted, the coordinate points of the imaging information are also fixed, and there is no need to align them through matrix transformation, so that the chlorophyll fluorescence information fusion is very accurate.

[0025] (3) The present application adopts pulse amplitude modulation (PAM) measurement principle when measuring fluorescence kinetic parameters, adopts long exposure imaging principle when measuring real-time fluorescence parameters, and uses the existing linear laser light source device to complete excitation, without additional light source, which reduces the complexity of the light source system and improves the imaging speed.

[0026] (4) The present application adopts linear laser light source, and the area of the excited fluorescence is larger than that of the point laser, so that the measurement of complete fluorescence kinetic parameters can be completed within half an hour, and the measurement of real-time chlorophyll fluorescence can be completed within 30s.

[0027] (5) The excitation light source part of the device of the present application only contains a linear laser light source device, a stepping motor and a prism, the fit between the components is high, and the space of the device is greatly compressed, so that the whole device is convenient to carry and operate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 is a schematic diagram of the three-dimensional structure of the linear laser-induced chlorophyll fluorescence imaging device according to the present application;

[0029] Fig. 2 is a schematic diagram of the linear laser-induced chlorophyll fluorescence imaging device according to the present application working in the compensation linewidth mode;

[0030] Fig. 3 is a system flowchart of the linear laser-induced chlorophyll fluorescence imaging device according to the present application;

[0031] Fig. 4 is a flowchart of the calculation of kinetic parameters and real-time fluorescence parameters according to the present application;

[0032] Fig. 5 is a flowchart of the extraction of three-dimensional point cloud according to the present application;

[0033] In the figure, 1 is a CMOS camera, 2 is a prism, 3 is a stepping motor, 4 is a display screen, 5 is an embedded computer, 6 is a long-wave pass filter, 7 is a linear laser light source device, 8 is an electric slide rail, 9 is a power supply, 10 is a measurement platform, and 11 is a load-bearing frame. DETAILED DESCRIPTION

[0034] The present application will be further described below in combination with the drawings and specific embodiments, but the protection scope of the present application is not limited thereto.

[0035] As shown in Figure 1, the present application provides a kind of linear laser-induced chlorophyll fluorescence three-dimensional imaging device, including CMOS camera 1, three prism 2, stepper motor 3, display screen 4, embedded computer 5, long wave pass filter 6, linear laser light source device 7, electric slide 8, power 9, measurement platform 10 and bearing frame 11, the wavelength of long wave pass filter 6 needs to be greater than 520nm;Measurement platform 10 is laid on desktop, bearing frame 11 is mutually perpendicular with measurement platform 10 installation;CMOS camera 1, stepper motor 3, electric slide 8 are all installed in the horizontal section of bearing frame 11;Three prism 2 back is provided with clamping groove, is clamped in the rotating shaft of stepper motor 3, and is rotated with the rotating shaft of stepper motor 3;Linear laser light source device 7 is fixed on the object platform of electric slide 8;Embedded computer 5 and power 9 are fixed on bearing frame 11;Display screen 4 is fixed above bearing frame 11;Paste light-absorbing black velvet on measurement platform 10, so that the blade is more prominent when fluorescence imaging;Long wave pass filter 6 is fixed on the lens of CMOS camera 1, and is arranged opposite measurement platform 10.

[0036] The CMOS camera 1 uses a refrigeration type black and white CMOS camera, which has a high imaging resolution of 20 million pixels and can obtain more image details. Its dark current is as low as 0.001 e- / pixel / s, supports long exposure, and can significantly reduce the hot spot noise problem in dark environment.

[0037] The shaft diameter of the stepper motor 3 is 5 mm, and the servo closed loop and spring brake design can better control the refraction angle of the three prism 2. The low noise of the stepper motor 3 brings smaller vibration, so that the whole device is in a relatively static state, and more stable images can be obtained when the CMOS camera 1 shoots. By matching the stepper motor driver, more accurate angle rotation control of the stepper motor can be realized, and the overall precision of the system is improved.

[0038] The side length of the three prism 2 is 5 cm, and the incident surface and the exit surface are coated with a single layer of MgF2 antireflection film. The back is provided with a clamping groove for connecting the rotating shaft of the stepper motor 3.

[0039] The embedded computer 5 uses a mainboard with RK3568 main control chip, and is equipped with HPD322 stepper motor driver and other hardware modules. The mainboard runs a Linux-based operating system, which realizes comprehensive control and feedback of the stepper motor 3, CMOS camera 1, electric slide 8 and display screen 4.

[0040] The linear laser light source device 7 is an adjustable power laser, which uses blue light with a wavelength of 462 nm, and the spot is a linear uniform line. The thickness of the linear uniform line can be adjusted, and the emitted laser has a line width of 1-5 mm at one meter.

[0041] The display screen 4 adopts a 7-inch HDMI display screen, is connected with the RK3568 main control chip through an HDMI line, deploys a GUI interface, is used for displaying a chlorophyll fluorescence image, and is provided with a control line laser-induced chlorophyll fluorescence three-dimensional imaging device working mode. The working mode one is to obtain complete fluorescence kinetic parameters, and form three-dimensional point cloud data with the fluorescence kinetic parameters. The working mode two is to quickly measure real-time fluorescence parameters, and form three-dimensional point cloud data with the real-time fluorescence parameters.

[0042] The power supply 9 is a 220V to 12V / 24V power supply, 12V is used for power supply of the CMOS camera 1 and the embedded computer 5, and 24V is used for power supply of the linear laser light source device 7.

[0043] The linear laser-induced chlorophyll fluorescence three-dimensional imaging device shown in FIG. 1 is built, and the distance between the measurement platform 10 and the CMOS camera 1 in the vertical direction is set to 1 meter. The chessboard calibration plate is placed on the measurement platform 10, the linear laser light source device 7 is turned on, the linear laser light is emitted, the three-prism 2 is manually rotated, and the linear laser light is irradiated on the chessboard calibration plate. In the embedded computer 5: the internal parameters and the external parameters of the CMOS camera 1 are solved by using the Zhang Zhengyou plane template calibration method; the relative position relationship between the measurement platform coordinate system and the CMOS camera coordinate system is calculated; and the light plane equation is calculated by using the least square method through two different poses of the chessboard calibration plate and the laser lines irradiated thereon.

[0044] Embodiment 1

[0045] In this embodiment, the linear laser light source device 7 and the three-prism 2 are located on the same horizontal line, and the emission point of the linear laser light source device 7 is directly opposite the three-prism 2.

[0046] After the measured leaf is placed on the measurement platform 10, the embedded computer 5 controls the step motor 3 to rotate, the linear laser light source device 7 to emit linear laser light, and the CMOS camera 1 to shoot in sequence. The rotation range of the step motor 3 is limited within 45° downward vertically, that is, taking the vertical line as the reference, the left side is negative and the right side is positive, the starting angle is set to -22.5°, and the terminal angle is set to 22.5°; starting from the starting angle, the step motor 3 is rotated at a step angle of 0.2°, and stops after each rotation; the linear laser light source device 7 emits linear laser light with a line width of 5mm according to the pulse amplitude modulation (PAM) measurement principle, irradiates the measured leaf, and the embedded computer 5 combines the measurement light, the saturation pulse light and the actinic light into a measurement period by using the PWM pulse width modulation technology. In the measurement period, the CMOS camera 1 completes multiple imaging and transmits to the embedded computer 5; after imaging, the step motor 3 continues to rotate at a step angle of 0.2°, continues to image, and stops until the rotation angle reaches 22.5°.

[0047] The principle of pulse amplitude modulation (PAM) measurement of linear laser, the PWM wave output by the embedded computer 5 controls the emission of linear laser light intensity and pulse frequency of the linear laser light source device 7. By changing the duty cycle of the PWM wave to drive the linear laser light source device 7 to realize the emission of measuring light, saturated pulse light and actinic light respectively. The PWM wave period is set to 800ms, and the duty cycles of measuring light, saturated pulse light and actinic light are set to 0.1%, 95% and 20% respectively, and the corresponding irradiation time is 0.8ms, 760ms and 160ms. The laser excitation sequence is set as follows: measuring light, saturated pulse light, measuring light, actinic light, measuring light, 9 times of continuous saturated pulse light, measuring light, and the CMOS camera 1 is triggered to shoot at the same time when the measuring light is emitted.

[0048] The embedded computer 5 performs multi-thread processing on the received images, extracts chlorophyll fluorescence lines in multiple images and splices them into a complete chlorophyll fluorescence image of a leaf, calculates the fluorescence kinetic parameters, synthesizes a pseudo-color image according to the fluorescence kinetic parameters, extracts a three-dimensional point cloud according to the offset of the laser line pixel points, maps the pseudo-color image to the three-dimensional point cloud, and forms a three-dimensional point cloud data with fluorescence kinetic parameters.

[0049] The method of splicing into a complete chlorophyll fluorescence image of a leaf is specifically: based on an image processing algorithm, threshold segmentation is performed on each image to extract chlorophyll fluorescence lines, all extracted chlorophyll fluorescence lines are placed on the canvas by traversing all images, and a complete chlorophyll fluorescence image of a leaf is obtained.

[0050] The calculation of the fluorescence kinetic parameters is specifically: based on an image processing algorithm, a complete chlorophyll fluorescence image of a leaf is subjected to multiplication operation to obtain a fluorescence region mask image; the pixel matrix of the mask image is accumulated to obtain the total number of leaf region pixel values num; the chlorophyll fluorescence image to be calculated is segmented with the fluorescence region mask image to obtain a segmented fluorescence image; the pixel matrix of the segmented fluorescence image is added to obtain the total sum of leaf region pixel values Data; and the total number of leaf region pixel values num and the total sum of leaf region pixel values Data are substituted into the formula to calculate the chlorophyll fluorescence parameter value corresponding to a complete chlorophyll fluorescence image of a leaf, i.e. the fluorescence kinetic parameter. The specific process is shown in FIG. 4.

[0051] The chlorophyll fluorescence image to be calculated includes a complete chlorophyll fluorescence image of a leaf under measuring light, a complete chlorophyll fluorescence image of a leaf under saturated pulse light and a complete chlorophyll fluorescence image of a leaf under actinic light shot by the CMOS camera 1.

[0052] The fluorescence kinetic parameters include minimum fluorescence F0 under dark adaptation, maximum fluorescence Fm under dark adaptation, maximum fluorescence Fm under saturated pulse light, minimum fluorescence F0 under saturated pulse light, maximum fluorescence Fm under actinic light, minimum fluorescence F0 under actinic light, and the like.m Variable fluorescence F v PSII primary light energy conversion efficiency F v / F m Post-light adaptation steady-state fluorescence F, post-light adaptation maximum fluorescence F m PSII actual photosynthetic efficiency Y(II).

[0053] The following fluorescence kinetic parameters are parameters under dark adaptation: when calculating F0, select the chlorophyll fluorescence image of the complete leaf under the measuring light, and obtain the specific value according to the calculation steps of the fluorescence kinetic parameters; when calculating F m , select the chlorophyll fluorescence image of the complete leaf under the saturating pulse light, and obtain the specific value according to the calculation steps of the fluorescence kinetic parameters; when calculating F v , the formula is F m -F0; when calculating F v / F m , the formula is (F m -F0) / F m .

[0054] The following fluorescence kinetic parameters are parameters under light adaptation: when calculating F, select the chlorophyll fluorescence image of the complete leaf under the actinic light, and obtain the specific value according to the calculation steps of the fluorescence kinetic parameters; when calculating F m ', select the chlorophyll fluorescence image of the complete leaf under the saturating pulse light after the actinic light, and obtain the specific value according to the calculation steps of the fluorescence kinetic parameters; when calculating Y(II), the formula is (F m '-F) / F m '.

[0055] The method for synthesizing the pseudo-color image is specifically: based on an image processing algorithm, setting the fluorescence kinetic parameter range to 0-1, and converting the fluorescence kinetic parameter into a 0-255 RGB pseudo-color image.

[0056] The extraction of the three-dimensional point cloud is specifically: based on an image processing algorithm, extracting all the chlorophyll fluorescence images under the saturating pulse light when the laser line is irradiated on each position of the to-be-measured leaf, and arranging the picture sequence in the same direction as the laser line scanning direction; analyzing each picture in the picture sequence, and extracting the center line of the laser line in the picture; the line laser is irradiated to the surface of the to-be-measured leaf, and is deformed due to the modulation of the surface height, so that the pixel coordinates of the extracted center line in each picture are converted to the reference coordinate system, and the x and y in the reference coordinate system are solved, and the x and y are input to the light plane equation in the reference coordinate system, so that the point cloud depth information is inversed, and then the x and y and the offset of the laser line pixel point in the next picture are added to obtain the real reference coordinates of the point cloud. Referring to FIG. 5.

[0057] The method of mapping the pseudo-color image to the three-dimensional point cloud is specifically: based on an image processing algorithm, since the same CMOS camera 1 is used for image acquisition and the field of view size is consistent, when the three-dimensional point cloud is extracted, the number of point clouds is set to be consistent with the resolution of the photographed picture, so that the color of the pixel point of the pseudo-color image is assigned to the corresponding point cloud, and the mapping of the pseudo-color image to the three-dimensional point cloud is completed.

[0058] Embodiment 2

[0059] Since the working mode of rotating the three-prism 2 by the stepper motor 3 to refract the linear laser in embodiment 1 is only applicable to relatively low plants (lower than 50 cm); when a relatively high plant (50 cm-100 cm) is photographed, the width of the linear laser irradiated on the plant leaf will change due to the change of the rotation angle, which is not conducive to the synthesis of the chlorophyll fluorescence image of a complete leaf. Therefore, in this embodiment, the linear laser light source device 7 is translated by the electric sliding rail 8 to offset the change of the width of the linear laser irradiated on the plant leaf due to the change of the rotation angle.

[0060] The working process of the device in this embodiment is: adjusting the linear laser light source device 7 arranged horizontally to an angle of θ with the vertical line, the range of θ is-10°-0°, and the preferred value of this embodiment is-10°, as shown in FIG. 2; after the leaf to be measured is placed on the measurement platform 10, the embedded computer 5 sequentially emits linear laser by the linear laser light source device 7 and photographs by the CMOS camera 1. The linear laser light source device 7 emits linear laser with a width of 5 mm according to the pulse amplitude modulation (PAM) measurement principle, and irradiates the leaf to be measured. The embedded computer 5 combines the measurement light, the saturated pulse light and the actinic light into a measurement cycle by using the PWM pulse width modulation technology. In the measurement cycle, the CMOS camera 1 completes multiple imaging and transmits to the embedded computer 5. After imaging, the electric sliding rail 8 slides to the left (towards the CMOS camera 1) by 5 mm, and continues to measure until the entire measurement platform 10 is scanned.

[0061] After the measurement is completed, the embedded computer 5 processes the images in the same way as in embodiment 1.

[0062] Embodiments 1 and 2 are both descriptions of working mode 1.

[0063] Embodiment 3

[0064] This embodiment is a description of working mode 2.

[0065] The CMOS camera 1 can convert the line light source into a surface light source in the long exposure shooting mode, and can convert the chlorophyll fluorescence excited by the single laser line into a chlorophyll fluorescence image of the whole leaf while the laser line scans the whole leaf.

[0066] As shown in FIG. 1, after the to-be-measured leaf is placed on the measurement platform 10, the embedded computer 5 controls the rotation of the stepping motor 3, the emission of the linear laser light source device 7, and the shooting of the CMOS camera 1. The rotation range of the stepping motor 3 is limited within 45° vertically downward, the exposure time of the CMOS camera 1 is set to 10 s, the time for the stepping motor 3 to rotate from -22.5° to 22.5° is set to 10 s, and the linear laser light source device 7 is set to work at the maximum power. When the stepping motor 3 starts to rotate, the shooting of the CMOS camera 1 and the emission of the linear laser light source device 7 are triggered at the same time, and the scanning and long exposure imaging of the to-be-measured leaf are completed within 10 s. Subsequently, the CMOS camera 1 is set to the video acquisition mode, the stepping motor 3 rotates from 22.5° to -22.5°, the acquisition of the three-dimensional original image is completed, and the three-dimensional original image is sent to the embedded computer 5.

[0067] The embedded computer 5 performs multi-thread processing on the received image, calculates the real-time fluorescence parameter according to the long exposure image (the chlorophyll fluorescence image of the whole leaf), and synthesizes the pseudo-color image according to the real-time fluorescence parameter. Meanwhile, the three-dimensional point cloud is extracted according to the offset of the laser line pixel point, and finally the pseudo-color image is mapped to the three-dimensional point cloud to form the three-dimensional point cloud data with the real-time fluorescence parameter. The processes of pseudo-color image synthesis, three-dimensional point cloud extraction, and mapping of the pseudo-color image to the three-dimensional point cloud are the same as those in Embodiment 1.

[0068] The calculation of the real-time fluorescence parameter is the same as the calculation of the fluorescence kinetic parameter, but when the real-time fluorescence F t is calculated, the to-be-measured leaf does not need to be dark adapted, and the long exposure image is calculated according to the image algorithm process in FIG. 4 to obtain the parameter F t ; when the maximum fluorescence F m in the dark adaptation state is calculated, the to-be-measured leaf needs to be dark adapted, and the long exposure image is calculated according to the image algorithm process in FIG. 4 to obtain the parameter F m .

[0069] The embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any obvious improvement, replacement, or modification made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. A three-dimensional imaging apparatus for linear laser-induced chlorophyll fluorescence, characterized by, The three-dimensional imaging device comprises a CMOS camera (1), a triangular prism (2), a stepping motor (3), an embedded computer (5), a long-wave pass filter (6), a linear laser light source device (7), a motorized slide rail (8), a measuring platform (10) and a load-bearing frame (11); The load-bearing frame (11) is vertically installed on the measuring platform (10), the CMOS camera (1), the stepping motor (3) and the motorized slide rail (8) are all installed on the horizontal section of the load-bearing frame (11), and the lens of the CMOS camera (1) is arranged to face the measuring platform (10); the triangular prism (2) is clamped on the rotating shaft of the stepping motor (3); the linear laser light source device (7) is fixed on the object platform of the motorized slide rail (8); and the long-wave pass filter (6) is fixed on the lens of the CMOS camera (1). The embedded computer (5) communicates with the stepping motor (3), the CMOS camera (1) and the motorized slide rail (8).

2. The apparatus according to claim 1, wherein The three-dimensional imaging device further comprises a display screen (4) connected with the embedded computer (5) and used for switching the working mode of the three-dimensional imaging device.

3. A three-dimensional imaging method based on the three-dimensional imaging device of laser-induced chlorophyll fluorescence according to any one of claims 1-2, characterized in that, The working mode of the three-dimensional imaging device is to obtain complete fluorescence kinetic parameters and form three-dimensional point cloud data with the fluorescence kinetic parameters.

4. The three-dimensional imaging method according to claim 3, characterized in that: when a plant below 50 cm is photographed: the linear laser light source device (7) and the triangular prism (2) are located on the same horizontal line, and the emission point of the linear laser light source device (7) is arranged to face the triangular prism (2); the stepping motor (3) starts from the initial angle and rotates at a step angle of 0.2°, and stops after each rotation; the linear laser light source device (7) emits a line laser with a line width of 5 mm according to the pulse amplitude modulation measurement principle to irradiate the leaf to be measured placed on the measuring platform (10), the embedded computer (5) combines the measurement light, the saturated pulse light and the actinic light into a measurement cycle by using the PWM pulse width modulation technology, and in the measurement cycle, the CMOS camera (1) completes multiple imaging and transmits the images to the embedded computer (5); after one imaging is completed, the stepping motor (3) continues to rotate at a step angle of 0.2° and continues to image until it rotates to the terminal angle; the embedded computer (5) performs multi-thread processing on the received images, extracts the chlorophyll fluorescence lines in the multiple images and splices them into a complete chlorophyll fluorescence image of the leaf, calculates the fluorescence kinetic parameters, synthesizes a pseudo-color image according to the fluorescence kinetic parameters, extracts three-dimensional point clouds according to the offset of the laser line pixel points, maps the pseudo-color image to the three-dimensional point clouds, and forms three-dimensional point cloud data with the fluorescence kinetic parameters. When the plant in the range of 50cm-100cm is photographed: the horizontal one-laser light source device (7) is adjusted to the angle of θ with the vertical line, the one-laser light source device (7) emits line laser with the line width of 5mm according to the principle of pulse amplitude modulation measurement, the leaf to be measured placed on the measuring platform (10) is irradiated, the embedded computer (5) combines the measurement light, the saturated pulse light and the actinic light into a measurement cycle by using the PWM pulse width modulation technology, in the measurement cycle, the CMOS camera (1) completes multiple imaging and transmits to the embedded computer (5); after the imaging is completed, the electric sliding rail (8) slides 5mm to the direction of the CMOS camera (1) and continues to measure until the whole measuring platform (10) is scanned; the embedded computer (5) carries out multi-thread processing on the received images, extracts the chlorophyll fluorescence lines in the multiple images and splices into a complete chlorophyll fluorescence image of the leaf, calculates the fluorescence kinetic parameters, synthesizes the pseudo-color image according to the fluorescence kinetic parameters; at the same time, the three-dimensional point cloud is extracted according to the offset of the laser line pixel points, the pseudo-color image is mapped to the three-dimensional point cloud, and the three-dimensional point cloud data with the fluorescence kinetic parameters is formed. The method for splicing into a complete chlorophyll fluorescence image of the leaf is specifically: threshold segmentation is carried out on each image, the chlorophyll fluorescence lines are extracted, all the extracted chlorophyll fluorescence lines are placed on the canvas, and a complete chlorophyll fluorescence image of the leaf is obtained.

5. The method of three-dimensional imaging according to claim 4, characterized in that, The working mode of the three-dimensional imaging device is to measure the real-time fluorescence parameters quickly and form the three-dimensional point cloud data with the real-time fluorescence parameters.

6. A three-dimensional imaging method based on the three-dimensional imaging device of laser-induced chlorophyll fluorescence according to any one of claims 1 to 2, characterized in that, 7. The three-dimensional imaging method according to claim 6, characterized in that: the rotation range of the stepper motor (3) is limited within the range of 45° downward vertically, the exposure time of the CMOS camera (1) is set to 10s, the time for the stepper motor (3) to rotate from-22.5° to 22.5° is set to 10s, and the one-laser light source device (7) is set to work at the maximum power; when the stepper motor (3) starts to rotate, the CMOS camera (1) is triggered to shoot and the one-laser light source device (7) is started to emit laser at the same time, and the scanning and long-exposure imaging of the leaf to be measured placed on the measuring platform (10) are completed within 10s; then the CMOS camera (1) is set to the video acquisition mode, the stepper motor (3) rotates from 22.5° to-22.5° again, and the acquisition of the three-dimensional original information image is completed; the embedded computer (5) carries out multi-thread processing on the received images, calculates the real-time fluorescence parameters according to the long-exposure image, synthesizes the pseudo-color image according to the real-time fluorescence parameters; at the same time, the three-dimensional point cloud is extracted according to the offset of the laser line pixel points, and finally the pseudo-color image is mapped to the three-dimensional point cloud, and the three-dimensional point cloud data with the real-time fluorescence parameters is formed. ​ 8. The three-dimensional imaging method according to claim 4 or 6, characterized by, The duty cycle of the PWM wave output by the embedded computer (5) is changed to drive the linear laser light source device (7) to emit measuring light, saturating pulse light and actinic light respectively; the laser excitation sequence is set as follows: measuring light, saturating pulse light, measuring light, actinic light, measuring light, 9 times of continuous saturating pulse light, measuring light, and the CMOS camera (1) is triggered to take a picture at the same time when the measuring light is emitted.

9. The method of three-dimensional imaging according to claim 8, characterized in that, The calculation of the fluorescence kinetic parameters / real-time fluorescence parameters is specifically: performing multiplication operation on the chlorophyll fluorescence image of a complete leaf to obtain a fluorescence region mask image; accumulating the pixel matrix of the mask image to obtain the total number of leaf region pixel values num; performing segmentation operation on the chlorophyll fluorescence image to be calculated and the fluorescence region mask image to obtain a segmented fluorescence image; and adding the pixel matrix of the segmented fluorescence image to obtain the total sum of leaf region pixel values Data. The total number of pixel values num in the leaf area and the total sum of pixel values Data are substituted into the formula The chlorophyll fluorescence parameter value corresponding to the chlorophyll fluorescence image of a complete leaf is obtained by calculation, that is, the fluorescence kinetic parameter; the chlorophyll fluorescence images to be calculated include the chlorophyll fluorescence image of a complete leaf under measurement light, the chlorophyll fluorescence image of a complete leaf under saturated pulse light, and the chlorophyll fluorescence image of a complete leaf under actinic light, which are captured by the CMOS camera (1).

10. The three-dimensional imaging method according to claim 4 or 6, characterized by, The extraction of the three-dimensional point cloud is specifically: extracting all the chlorophyll fluorescence images under saturating pulse light when a laser line is irradiated on each position of the leaf to be measured, and arranging the picture sequence in the same direction as the laser line scanning direction; analyzing each picture in the picture sequence, extracting the center line of the laser line in the picture, converting the pixel coordinates of the center line extracted in each picture to the reference coordinate system, solving the horizontal and vertical coordinate values in the reference coordinate system, inputting the horizontal and vertical coordinate values into the light plane equation in the reference coordinate system, and inverting the point cloud depth information; adding the horizontal and vertical coordinate values to the offset of the laser line pixel points in the next picture to obtain the real reference coordinates of the point cloud; and traversing the picture sequence to obtain a complete point cloud.

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