WO2025251341A1 - 一种线激光诱导叶绿素荧光的三维成像装置及方法 - Google Patents

一种线激光诱导叶绿素荧光的三维成像装置及方法

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Publication number
WO2025251341A1
WO2025251341A1 PCT/CN2024/099533 CN2024099533W WO2025251341A1 WO 2025251341 A1 WO2025251341 A1 WO 2025251341A1 CN 2024099533 W CN2024099533 W CN 2024099533W WO 2025251341 A1 WO2025251341 A1 WO 2025251341A1
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Prior art keywords
fluorescence
image
line
point cloud
laser
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English (en)
French (fr)
Inventor
王纪章
袁萌
付益辉
王涛
周静
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Jiangsu University
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Jiangsu University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/645—Specially adapted constructive features of fluorimeters
    • G01N21/6456—Spatial resolved fluorescence measurements; Imaging

Definitions

  • This invention belongs to the field of photoelectric detection and image processing, and specifically relates to a three-dimensional imaging device and method for line laser-induced chlorophyll fluorescence.
  • Chlorophyll fluorescence is a non-invasive detection method used to assess early indicators of plant photosynthesis. Changes in chlorophyll fluorescence appear earlier than changes in chlorophyll content and plant structure. Therefore, it is widely used for photosynthesis detection and studying plant growth under different stress conditions. Laser-induced chlorophyll fluorescence imaging does not require direct contact with or damage to the plant; it acquires information by exciting the fluorescence signal emitted by chlorophyll. This non-invasive nature allows for real-time, continuous monitoring of plant physiological states without harming the plant.
  • Existing 3D chlorophyll fluorescence imaging devices have several shortcomings: devices using single-point lasers as excitation sources require excitation at multiple points on each leaf, which can lead to a measurement cycle of several hours, making it impossible to monitor chlorophyll fluorescence in the plant canopy in real time; devices using LED surface light sources, while able to cover a large measurement area, have large lamp panels, limiting the system's portability and flexibility. Furthermore, existing 3D chlorophyll fluorescence detection methods all employ binocular cameras to register chlorophyll fluorescence images with point clouds, and their accuracy is affected by the relative position of the cameras and the accuracy of calibration, thus limiting the system's practicality.
  • this invention provides a three-dimensional imaging device and method for line laser-induced chlorophyll fluorescence.
  • the present invention achieves the above-mentioned technical objectives through the following technical means.
  • a three-dimensional imaging device for line laser-induced chlorophyll fluorescence includes a CMOS camera, a prism, a stepper motor, an embedded computer, a long-pass filter, a linear laser source device, an electric slide rail, a measurement platform, and a support frame.
  • the load-bearing frame is vertically mounted on the measuring platform.
  • the CMOS camera, stepper motor, and electric slide rail are all mounted on the horizontal section of the load-bearing frame, with the lens of the CMOS camera facing the measuring platform.
  • the prism is clipped onto the rotating shaft of the stepper motor.
  • the linear laser light source device is fixed on the loading platform of the electric slide rail.
  • the long-pass filter is fixed on the lens of the CMOS camera.
  • the embedded computer communicates with the stepper motor, CMOS camera, and electric slide rail.
  • the above technical solution also includes a display screen, which is connected to an embedded computer and used to switch the working mode of the three-dimensional imaging device.
  • a three-dimensional imaging method for line laser-induced chlorophyll fluorescence wherein the three-dimensional imaging device operates by acquiring complete fluorescence dynamic parameters and forming three-dimensional point cloud data with fluorescence dynamic parameters.
  • the linear laser light source device and the prism are on the same horizontal line, and the emission point of the linear laser light source device is directly opposite the prism; the stepper motor starts from the initial angle and rotates in 0.2° increments, stopping after each rotation; the linear laser light source device emits a 5mm line laser based on the pulse amplitude modulation measurement principle to illuminate the leaf to be measured placed on the measurement platform; the embedded computer uses PWM pulse width modulation technology to combine the measurement light, saturation pulse light, and photochemical light into a measurement cycle; within this measurement cycle, the CMOS camera... Multiple images are captured and transmitted to an embedded computer. After one image is completed, the stepper motor continues to rotate in 0.2° increments to continue imaging until the termination angle is reached.
  • the embedded computer performs multi-threaded processing on the received images, extracts chlorophyll fluorescence lines from multiple images, and stitches them together to form a complete leaf chlorophyll fluorescence image. It calculates the fluorescence dynamics parameters and synthesizes a pseudo-color image based on the fluorescence dynamics parameters. Simultaneously, it extracts a three-dimensional point cloud based on the offset of the laser line pixels and maps the pseudo-color image onto the three-dimensional point cloud to form three-dimensional point cloud data with fluorescence dynamics parameters.
  • the horizontally positioned linear laser light source is adjusted to form an angle ⁇ with the vertical line.
  • PWM pulse amplitude modulation
  • the linear laser light source emits a 5mm line laser beam to illuminate the leaf placed on the measurement platform.
  • the embedded computer uses PWM technology to combine the measurement light, saturation pulse light, and photochemical light into a single measurement cycle.
  • the CMOS camera captures multiple images and transmits them to the embedded computer. After imaging, the electric slide rail slides 5mm towards the CMOS camera to continue measurement until the entire measurement platform is scanned.
  • the embedded computer performs multi-threaded processing on the received images, extracting chlorophyll fluorescence lines from multiple images and stitching them together to form a complete chlorophyll fluorescence image of the leaf. Its fluorescence dynamics parameters are calculated, and a pseudo-color image is synthesized based on these parameters. Simultaneously, a three-dimensional point cloud is extracted based on the offset of the laser line pixels. The pseudo-color image is then mapped onto the three-dimensional point cloud to form three-dimensional point cloud data with fluorescence dynamics parameters.
  • the method for stitching together a complete leaf chlorophyll fluorescence image specifically involves: performing threshold segmentation on each image, extracting chlorophyll fluorescence segments, traversing all images, and placing all extracted chlorophyll fluorescence segments on a canvas to obtain a complete leaf chlorophyll fluorescence image.
  • a three-dimensional imaging method for line laser-induced chlorophyll fluorescence wherein the three-dimensional imaging device operates by rapidly measuring real-time fluorescence parameters to form three-dimensional point cloud data with real-time fluorescence parameters.
  • the stepper motor's rotation range is limited to a vertically downward 45° range.
  • the CMOS camera exposure time is set to 10 seconds
  • the stepper motor's rotation time from -22.5° to 22.5° is set to 10 seconds
  • the linear laser light source is set to operate at maximum power.
  • the CMOS camera is simultaneously triggered to capture an image
  • the linear laser light source is activated to emit a laser, completing the scanning and long-exposure imaging of the blade placed on the measurement platform within 10 seconds.
  • the CMOS ...
  • the camera is in video acquisition mode, and the stepper motor rotates from 22.5° to -22.5° to complete the acquisition of the original three-dimensional information image;
  • the embedded computer performs multi-threaded processing on the received image, calculates real-time fluorescence parameters based on the long-exposure image, and synthesizes a pseudo-color image based on the real-time fluorescence parameters. At the same time, it extracts a three-dimensional point cloud based on the offset of the laser line pixels, and finally maps the pseudo-color image onto the three-dimensional point cloud to form three-dimensional point cloud data with real-time fluorescence parameters.
  • the linear laser light source device is driven to emit measurement light, saturation pulse light, and photochemical light respectively.
  • the laser excitation sequence is set as follows: measurement light, saturation pulse light, measurement light, photochemical light, measurement light, 9 consecutive saturation pulse lights, measurement light.
  • the CMOS camera is triggered to capture images.
  • the calculation of the fluorescence kinetic parameters/real-time fluorescence parameters specifically involves: multiplying a complete leaf chlorophyll fluorescence image to obtain a fluorescence region mask; summing the pixel matrices of the mask to obtain the total number of pixel values in the leaf region, num; segmenting the chlorophyll fluorescence image to be calculated with the fluorescence region mask to obtain a segmented fluorescence image; summing the pixel matrices of the segmented fluorescence images to obtain the sum of the leaf region image values, Data; and substituting the total number of pixel values in the leaf region, num, and the sum of the leaf region image values, Data, into the formula.
  • the chlorophyll fluorescence parameter value corresponding to a complete leaf fluorescence image is calculated, which is the fluorescence kinetic parameter.
  • the chlorophyll fluorescence image to be calculated includes a complete leaf chlorophyll fluorescence image under measurement light captured by a CMOS camera, a complete leaf chlorophyll fluorescence image under saturated pulse light, and a complete leaf chlorophyll fluorescence image under photochemical light.
  • the extraction of the three-dimensional point cloud specifically involves: extracting the chlorophyll fluorescence images under all saturated pulsed light when the laser line illuminates each position of the leaf under test, and arranging them into an image sequence consistent with the scanning direction of the laser line; analyzing each image in the image sequence, extracting the center line of the laser line in the image, transforming the pixel coordinates of the extracted center line in each image to a reference coordinate system, solving for 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, retrieving the point cloud depth information, and then adding the horizontal and vertical coordinate values to the offset of the laser line pixels in the next image to obtain the true reference coordinates of the point cloud; after traversing the image sequence, a complete point cloud is obtained.
  • the present invention adopts the pulse amplitude modulation (PAM) measurement principle when measuring fluorescence dynamic parameters and the long exposure imaging principle when rapidly measuring real-time fluorescence parameters. Excitation is completed using the existing linear laser light source device without the need for additional light source, which reduces the complexity of the light source system and improves the imaging speed.
  • PAM pulse amplitude modulation
  • the present invention uses a linear laser light source, which has a larger area for exciting fluorescence than a point laser.
  • the complete fluorescence dynamic parameters can be measured within half an hour, and the real-time fluorescence of chlorophyll can be measured within 30 seconds.
  • the excitation light source part of the device of the present invention only includes a linear laser light source device, a stepper motor and a prism.
  • the components fit together very well, greatly compressing the space of the device and making the whole device easy to carry and operate.
  • Figure 1 is a three-dimensional structural schematic diagram of the line laser-induced chlorophyll fluorescence three-dimensional imaging device of the present invention
  • Figure 2 is a schematic diagram of the line laser-induced chlorophyll fluorescence three-dimensional imaging device of the present invention operating in the linewidth compensation mode;
  • Figure 3 shows the system flow of the line laser-induced chlorophyll fluorescence three-dimensional imaging device of the present invention
  • Figure 4 is a flowchart of the calculation of the kinetic/real-time fluorescence parameters described in this invention.
  • FIG. 5 is a flowchart of the three-dimensional point cloud extraction process described in this invention.
  • CMOS camera 2. Prism, 3. Stepper motor, 4. Display screen, 5. Embedded computer, 6. Long-pass filter, 7. Linear laser light source device, 8. Electric slide rail, 9. Power supply, 10. Measurement platform, 11. Support frame.
  • this invention provides a three-dimensional imaging device for line laser-induced chlorophyll fluorescence, including a CMOS camera 1, a prism 2, a stepper motor 3, a display screen 4, an embedded computer 5, a long-pass filter 6, a linear laser source device 7, an electric slide rail 8, a power supply 9, a measurement platform 10, and a support frame 11.
  • the wavelength of the long-pass filter 6 must be greater than 520 nm.
  • the measurement platform 10 is placed flat on a table, and the support frame 11 is installed perpendicular to the measurement platform 10.
  • the CMOS camera 1, stepper motor 3, and electric slide rail 8 are also included.
  • the back of the prism 2 has a slot, which is locked onto the rotating shaft of the stepper motor 3 and rotates with the rotating shaft of the stepper motor 3;
  • the linear laser light source device 7 is fixed on the loading platform of the electric slide rail 8;
  • the embedded computer 5 and the power supply 9 are fixed on the support frame 11;
  • the display screen 4 is fixed above the support frame 11;
  • light-absorbing black velvet is pasted on the measuring platform 10 to make the blades more prominent during fluorescence imaging;
  • the long-pass filter 6 is fixed on the lens of the CMOS camera 1 and is set directly opposite the measuring platform 10.
  • the CMOS camera 1 is a cooled monochrome CMOS camera with an imaging resolution of up to 20 megapixels. It can capture more image details; its dark current is as low as 0.001e-/pixel/s, supports long exposures, and can significantly reduce hotspot noise in dark environments.
  • the stepper motor 3 has a shaft diameter of 5mm, and its servo closed-loop and spring brake design allows for better control of the refraction angle of the prism 2.
  • the low noise of the stepper motor 3 results in less vibration, keeping the entire device relatively still, and allowing the CMOS camera 1 to capture more stable images.
  • By using a stepper motor driver more precise angle rotation control of the stepper motor can be achieved, improving the overall accuracy of the system.
  • the prism 2 has a side length of 5cm, and both the incident and exit surfaces are coated with a single layer of MgF2 antireflective film.
  • a slot is provided on the back for connecting the rotating shaft of the stepper motor 3.
  • the embedded computer 5 uses a motherboard equipped with an RK3568 main control chip and hardware modules such as an HPD322 stepper motor driver.
  • the motherboard runs a Linux-based operating system, enabling comprehensive control and feedback of the stepper motor 3, CMOS camera 1, electric slide rail 8, and display screen 4.
  • the linear laser source device 7 is an adjustable power laser that uses a blue light wavelength of 462nm.
  • the light spot is a linear uniform line, the thickness of which is adjustable.
  • the emitted laser has a line width of 1mm-5mm at one meter.
  • the display screen 4 is a 7-inch HDMI display screen, which is connected to the RK3568 main control chip through an HDMI cable. It deploys a GUI interface to display chlorophyll fluorescence images and has control lines for the operation of the laser-induced chlorophyll fluorescence three-dimensional imaging device.
  • the first operation mode is to acquire complete fluorescence dynamic parameters and form three-dimensional point cloud data with fluorescence dynamic parameters; the second operation mode is to quickly measure real-time fluorescence parameters and form three-dimensional point cloud data with real-time fluorescence parameters.
  • the power supply 9 is a 220V to 12V/24V power supply.
  • the 12V is used to power the CMOS camera 1 and the embedded computer 5, and the 24V is used to power the linear laser light source device 7.
  • a three-dimensional imaging device for line laser-induced chlorophyll fluorescence was constructed.
  • the vertical distance between the measurement platform 10 and the CMOS camera 1 was set to 1 meter.
  • a checkerboard calibration plate was placed on the measurement platform 10, and the linear laser source device 7 was turned on to emit a line laser.
  • the prism 2 was manually rotated to illuminate the checkerboard calibration plate with the line laser.
  • the embedded computer 5 the internal and external parameters of the CMOS camera 1 were calculated using Zhang Zhengyou's planar template calibration method; the relative positional relationship between the measurement platform coordinate system and the CMOS camera coordinate system was calculated; and the equation of the light plane was calculated using the least squares method through two checkerboard calibration plates in different poses and the laser lines illuminating them.
  • 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 set directly opposite the triangular prism 2.
  • the embedded computer 5 sequentially controls the stepper motor 3 to rotate, the linear laser source device 7 to emit a laser beam, and the CMOS camera 1 to capture an image.
  • the rotation range of the stepper motor 3 is limited to a vertical downward 45°.
  • the starting angle is set to -22.5° and the ending angle is 22.5°; starting from the starting angle, it rotates in 0.2° increments, stopping after each rotation;
  • the linear laser light source device 7 emits a 5mm line laser based on the pulse amplitude modulation (PAM) measurement principle to illuminate the blade under test;
  • the embedded computer 5 uses PWM pulse width modulation technology to combine the measurement light, saturation pulse light and photochemical light into a measurement cycle; within this measurement cycle, the CMOS camera 1 completes multiple images and transmits them to the embedded computer 5; after the imaging is completed, the stepper motor 3 continues to rotate in 0.2° increments to continue imaging until it rotates to 22.5° and then stops.
  • PAM pulse amplitude modulation
  • the line laser based on the pulse amplitude modulation (PAM) measurement principle, is controlled by an embedded computer 5 which outputs a PWM wave to regulate the intensity and pulse frequency of the emitted line laser from a linear laser source device 7.
  • PWM pulse amplitude modulation
  • the PWM wave period is set to 800ms, and the duty cycles for the measurement light, saturation pulse light, and photochemical light are set to 0.1%, 95%, and 20%, respectively, corresponding to illumination times of 0.8ms, 760ms, and 160ms.
  • the laser excitation sequence is set as follows: measurement light, saturation pulse light, measurement light, photochemical light, measurement light, nine consecutive saturation pulses, measurement light.
  • the CMOS camera 1 is triggered to capture images during the emission of the measurement light.
  • the embedded computer 5 performs multi-threaded processing on the received images, extracts chlorophyll fluorescence lines from multiple images and stitches them together to form a complete leaf chlorophyll fluorescence image, calculates its fluorescence dynamics parameters, and synthesizes a pseudo-color image based on the fluorescence dynamics parameters; at the same time, it extracts a three-dimensional point cloud based on the offset of the laser line pixels, maps the pseudo-color image onto the three-dimensional point cloud, and forms three-dimensional point cloud data with fluorescence dynamics parameters.
  • the method for stitching together a complete leaf chlorophyll fluorescence image is as follows: based on image processing algorithms, each image is thresholded and segmented to extract chlorophyll fluorescence segments. All images are traversed, and all extracted chlorophyll fluorescence segments are placed on a canvas to obtain a complete leaf chlorophyll fluorescence image.
  • the calculation of the fluorescence dynamics parameters is specifically as follows: Based on an image processing algorithm, a chlorophyll fluorescence image of a complete leaf is multiplied to obtain a fluorescence region mask; the pixel matrix of the mask is accumulated to obtain the total number of pixel values in the leaf region, num; the chlorophyll fluorescence image to be calculated is segmented with the fluorescence region mask to obtain a segmented fluorescence image; the pixel matrix of the segmented fluorescence image is added to obtain the sum of the pixel values in the leaf region, Data; the total number of pixel values in the leaf region, num, and the sum of the pixel values in the leaf region, Data, are substituted into the formula.
  • the chlorophyll fluorescence parameter values i.e., fluorescence kinetic parameters, are calculated to obtain the chlorophyll fluorescence image corresponding to a complete leaf. The specific process is shown in Figure 4.
  • the chlorophyll fluorescence images to be calculated include chlorophyll fluorescence images of an intact leaf under measurement light captured by CMOS camera 1, chlorophyll fluorescence images of an intact leaf under saturated pulse light, and chlorophyll fluorescence images of an intact leaf under photochemical light.
  • the fluorescence kinetic parameters include minimum fluorescence F ⁇ sub>0 ⁇ /sub> under dark adaptation, maximum fluorescence F ⁇ sub> m ⁇ /sub> under dark adaptation, variable fluorescence F ⁇ sub> v ⁇ /sub> , initial photoelectric conversion efficiency of PSII F ⁇ sub>v ⁇ /sub>/F ⁇ sub> m ⁇ /sub>, steady-state fluorescence F after light adaptation, maximum fluorescence F ⁇ sub>m ⁇ /sub> ' after light adaptation, and actual photosynthetic efficiency Y(II) of PSII.
  • the following fluorescence kinetic parameters are those under dark adaptation: When calculating F ⁇ sub>0 ⁇ /sub> , a chlorophyll fluorescence image of a complete leaf under measurement light is selected, and the specific value is obtained according to the calculation steps of fluorescence kinetic parameters; when calculating F ⁇ sub> m ⁇ /sub>, a chlorophyll fluorescence image of a complete leaf under saturated pulsed light is selected, and the specific value is obtained according to the calculation steps of fluorescence kinetic parameters; when calculating F ⁇ sub> v ⁇ /sub> , the formula is F ⁇ sub> m ⁇ /sub> - F ⁇ sub> 0 ⁇ /sub>; when calculating F ⁇ sub>v ⁇ /sub>/F ⁇ sub> m ⁇ /sub> , the formula is (F ⁇ sub> m ⁇ /sub> - F ⁇ sub> 0 ⁇ /sub> )/F ⁇ sub>m ⁇ /sub> .
  • the following fluorescence kinetic parameters are those under light adaptation: When calculating F, a chlorophyll fluorescence image of a complete leaf under photochemical light is selected, and the specific value is obtained according to the calculation steps of fluorescence kinetic parameters; when calculating Fm ', a chlorophyll fluorescence image of a complete leaf under saturated pulsed light after photochemical light is selected, and the specific value is obtained according to the calculation steps of fluorescence kinetic parameters; when calculating Y(II), the formula is ( Fm' -F)/ Fm '.
  • the method for synthesizing pseudo-color images specifically involves: based on an image processing algorithm, setting the fluorescence dynamics parameter range to 0–1, and converting the fluorescence dynamics parameter into an RGB pseudo-color image of 0–255.
  • the extraction of the 3D point cloud is specifically as follows: Based on image processing algorithms, chlorophyll fluorescence images under all saturated pulse light when the laser line illuminates each position of the leaf under test are extracted and arranged into an image sequence consistent with the scanning direction of the laser line; each image in the image sequence is analyzed to extract the center line of the laser line in the image; the laser line illuminates the surface of the leaf under test and deforms due to the modulation of its surface height, so the pixel coordinates of the center line extracted in each image are transformed into a reference coordinate system, and the x and y coordinates in the reference coordinate system are solved.
  • the x and y coordinates are input into the light plane equation in the reference coordinate system to retrieve the point cloud depth information.
  • the x and y coordinates are added to the offset of the laser line pixels in the next image to obtain the true reference coordinates of the point cloud; after traversing the image sequence, the complete point cloud is obtained. See Figure 5.
  • the method for mapping the pseudo-color image to the three-dimensional point cloud is as follows: Based on the image processing algorithm, since the same CMOS camera 1 is used for image acquisition and the field of view is consistent, when extracting the three-dimensional point cloud, the number of points in the point cloud is set to be consistent with the resolution of the captured image. This allows the color of the pseudo-color image pixels to be assigned to the corresponding point cloud, thus completing the mapping between the pseudo-color image and the three-dimensional point cloud.
  • Example 1 Because the laser beam refraction method in Example 1, which uses a stepper motor 3 to rotate a prism 2 to refract the laser, is only suitable for relatively short plants (below 50cm), when photographing taller plants (50cm-100cm), the width of the laser beam illuminating the plant leaves changes due to the change in rotation angle, which is detrimental to the synthesis of a complete leaf chlorophyll fluorescence image. Therefore, this embodiment uses an electric slide rail 8 to move the linear laser light source device 7 to compensate for the change in the width of the laser beam illuminating the plant leaves caused by the change in rotation angle.
  • the working process of the device is as follows: the horizontally positioned linear laser source device 7 is adjusted to form an angle ⁇ with the vertical line, where ⁇ ranges from -10° to 0°, and in this embodiment, -10° is preferred (see Figure 2).
  • the embedded computer 5 sequentially emits a line laser from the linear laser source device 7 and takes a picture with the CMOS camera 1.
  • the linear laser source device 7 emits a line laser with a line width of 5mm based on the pulse amplitude modulation (PAM) measurement principle, which is used to measure the blade to be tested.
  • PAM pulse amplitude modulation
  • the blade is illuminated, and the embedded computer 5 uses PWM pulse width modulation technology to combine the measurement light, saturation pulse light and photochemical light into a measurement cycle.
  • the CMOS camera 1 completes multiple images and transmits them to the embedded computer 5.
  • the electric slide rail 8 slides 5mm to the left (closer to the CMOS camera 1) to continue the measurement until the entire measurement platform 10 is scanned.
  • the embedded computer 5 processes the image in the same way as in Example 1.
  • Example 1 and Example 2 are descriptions of working mode one.
  • This embodiment describes working mode two.
  • CMOS camera 1 can transform a line light source into a surface light source. While scanning the entire leaf with a laser line, it can also physically transform the chlorophyll fluorescence excited by a single laser line into an image of the chlorophyll fluorescence of the entire leaf.
  • the embedded computer 5 simultaneously controls the stepper motor 3 to rotate, the linear laser source device 7 to emit a line laser, and the CMOS camera 1 to capture an image.
  • the rotation range of the stepper motor 3 is limited to a vertical downward 45° range.
  • the exposure time of the CMOS camera 1 is set to 10 seconds, the time for the stepper motor 3 to rotate from -22.5° to 22.5° is set to 10 seconds, and the linear laser source device 7 is set to operate at maximum power.
  • the stepper motor 3 starts to rotate, the CMOS camera 1 is triggered to capture an image, and the linear laser source device 7 is activated to emit a laser, completing the scanning and long-exposure imaging of the blade to be tested within 10 seconds. Subsequently, the CMOS camera 1 is set to video acquisition mode, and the stepper motor 3 rotates from 22.5° to -22.5° to complete the acquisition of the three-dimensional original image, which is then sent to the embedded computer 5.
  • the embedded computer 5 performs multi-threaded processing on the received image, calculates real-time fluorescence parameters based on the long-exposure image (chlorophyll fluorescence image of the entire leaf), and synthesizes a pseudo-color image based on the real-time fluorescence parameters. Simultaneously, it extracts a three-dimensional point cloud based on the offset of the laser line pixels, and finally maps the pseudo-color image onto the three-dimensional point cloud to form three-dimensional point cloud data with real-time fluorescence parameters.
  • the specific processes of pseudo-color image synthesis, three-dimensional point cloud extraction, and mapping the pseudo-color image onto the three-dimensional point cloud are the same as in Example 1.
  • the calculation of the real-time fluorescence parameters is the same as that of the fluorescence kinetic parameters. However, when calculating the real-time fluorescence Ft , it is not necessary to perform dark adaptation on the leaf under test.
  • the parameter Ft can be obtained by calculating the long-exposure image according to the image algorithm flow in Figure 4.
  • the parameter Fm can be obtained by calculating the long-exposure image according to the image algorithm flow in Figure 4.

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Abstract

一种线激光诱导叶绿素荧光的三维成像装置及方法，一字型激光光源装置(7)发射线激光，经过三棱镜(2)的折射照射在待测叶片上，同时CMOS相机(1)拍摄图像，随着步进电机(3)带动三棱镜(2)的转动，扫描完待测叶片；由嵌入式计算机(5)对图像进行多线程处理，形成带有荧光动力学参数的三维点云数据；通过线激光与和CMOS相机(1)长曝光实现实时荧光参数快速测量，由嵌入式计算机(5)对图像进行多线程处理，得出实时荧光参数。利用线激光扫描同步进行叶绿素荧光的探测与三维点云的生成，降低了面激发光源的高成本和大体积的问题，同时，通过线激光扫描结合相机的长曝光，还可以实现大范围叶绿素荧光的快速成像，达到实时性探测的目地。

Description

一种线激光诱导叶绿素荧光的三维成像装置及方法 技术领域
本发明属于光电检测和图像处理领域，具体涉及一种线激光诱导叶绿素荧光的三维成像装置及方法。
背景技术
叶绿素荧光是一种非侵入性的探测方法，用于评估植物光合作用的早期指标。与叶绿素含量和植物结构变化相比，叶绿素荧光的变化更早出现。因此，它被广泛应用于光合作用检测以及研究不同胁迫状态下植物的生长状况。激光诱导叶绿素荧光成像方法不需要直接接触或伤害植物，通过激发叶绿素发出的荧光信号来获取信息。这种非侵入性的特点使得该方法能够在实时、连续的条件下监测植物的生理状态，而不会对植物造成损害。
现有叶绿素荧光三维成像装置的不足之处有：使用单点激光作为激发光源的设备需要对每片叶子激发多个点位，这导致整个测量周期可能需要数小时，使得装置无法实时监测植株冠层的叶绿素荧光；采用LED面光源的装置，虽然能够覆盖较大的测量面积，但其灯板体积较大，限制了系统的便携性和灵活性。此外，现有的三维叶绿素荧光探测方法均采用双目相机原理来实现叶绿素荧光图像与点云之间的配准，其精度受到相机的相对位置以及标定的准确性影响，因此系统的实用性不强。
发明内容
针对现有技术中存在不足，本发明提供了一种线激光诱导叶绿素荧光的三维成像装置及方法。
本发明是通过以下技术手段实现上述技术目的的。
一种线激光诱导叶绿素荧光的三维成像装置，包括CMOS相机、三棱镜、步进电机、嵌入式计算机、长波通滤光片、一字型激光光源装置、电动滑轨、测量平台和承重架；
所述承重架垂直安装在测量平台上，所述CMOS相机、步进电机和电动滑轨均安装在承重架的水平段，且CMOS相机的镜头正对测量平台设置；所述三棱镜卡接在步进电机的转动轴上；所述一字型激光光源装置固定在电动滑轨的载物平台上；所述长波通滤光片固定在CMOS相机的镜头上；
所述嵌入式计算机与步进电机、CMOS相机、电动滑轨进行通信。
上述技术方案中，还包括显示屏，所述显示屏与嵌入式计算机连接，用于切换所述三维成像装置的工作模式。
一种线激光诱导叶绿素荧光的三维成像方法，所述三维成像装置的工作模式是获取完整的荧光动力学参数，形成带有荧光动力学参数的三维点云数据。
进一步地：
在拍摄低于50cm的植物时：一字型激光光源装置与三棱镜位于同一水平线，且一字型激光光源装置的发射点正对三棱镜设置；所述步进电机从起始角度开始，按照0.2°的步进角度转动，每转动一次便停止；一字型激光光源装置依据脉冲振幅调制测量原理发射线宽为5mm的线激光，对放置在测量平台上的待测叶片进行照射，嵌入式计算机利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS相机完成多张成像，并传输至嵌入式计算机；一次成像完成后，步进电机继续按照0.2°的步进角度转动，继续成像，直至转动至终止角度；所述嵌入式计算机对接收的图像进行多线程处理，对多张图像中的叶绿素荧光线段进行提取并拼接成一张完整叶片的叶绿素荧光图像，计算其荧光动力学参数，依据荧光动力学参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数的三维点云数据；
在拍摄50cm-100cm范围的植物时：将水平设置的一字型激光光源装置调节至与竖直线的夹角成θ，一字型激光光源装置依据脉冲振幅调制测量原理发射线宽为5mm的线激光，对放置在测量平台上的待测叶片进行照射，嵌入式计算机利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS相机完成多张成像，并传输至嵌入式计算机；成像完成后，电动滑轨向CMOS相机方向滑动5mm，继续测量，直至扫描完整个测量平台；所述嵌入式计算机对接收的图像进行多线程处理，对多张图像中的叶绿素荧光线段进行提取并拼接成一张完整叶片的叶绿素荧光图像，计算其荧光动力学参数，依据荧光动力学参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数的三维点云数据。
进一步地，所述拼接成一张完整叶片的叶绿素荧光图像的方法具体为：对每张图像进行阈值分割，提取出叶绿素荧光线段，遍历所有图像，将所有提取出的叶绿素荧光线段放置在画布上，便获得一张完整叶片的叶绿素荧光图像。
一种线激光诱导叶绿素荧光的三维成像方法，所述三维成像装置的工作模式是快速测量实时荧光参数，形成带有实时荧光参数的三维点云数据。
进一步地，步进电机的转动范围限定在垂直向下45°范围之内，设定CMOS相机曝光时间为10s，设定步进电机从-22.5°转到22.5°的时间为10s，设定一字型激光光源装置工作在最大功率；当步进电机开始旋转时，同时触发CMOS相机拍摄并启动一字型激光光源装置发射激光，在10s内完成对放置在测量平台上的待测叶片的扫描与长曝光成像；随后设定CMOS 相机为视频采集模式，步进电机再从22.5°转到-22.5°，完成三维原始信息图像的采集；
嵌入式计算机对接收的图像进行多线程处理，依据长曝光图像计算实时荧光参数，依据实时荧光参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，最后将伪彩色图像映射至三维点云，形成带有实时荧光参数的三维点云数据。
更进一步地，通过改变嵌入式计算机输出的PWM波的占空比，驱动一字型激光光源装置分别实现测量光、饱和脉冲光和光化光的发射；激光激发序列设定如下：测量光、饱和脉冲光、测量光、光化光、测量光、9次连续的饱和脉冲光、测量光，在发射测量光时，同时触发CMOS相机拍摄。
更进一步地，所述荧光动力学参数/实时荧光参数的计算具体为：将一张完整叶片的叶绿素荧光图像进行乘法运算，得到荧光区域掩模图；将掩模图像素矩阵累加，得到叶片区域像素值总数num；将待计算的叶绿素荧光图像与荧光区域掩模图进行分割运算，得到分割后的荧光图；将分割后的荧光图像素矩阵相加，得到叶片区域像数值总和Data；将叶片区域像素值总数num与叶片区域像数值总和Data代入公式计算，得到一张完整叶片的叶绿素荧光图像对应的叶绿素荧光参数值，即荧光动力学参数；所述待计算的叶绿素荧光图像包括CMOS相机拍摄的测量光下完整叶片的叶绿素荧光图像、饱和脉冲光下完整叶片的叶绿素荧光图像和光化光下完整叶片的叶绿素荧光图像。
更进一步地，所述三维点云的提取具体为：将激光线照射在待测叶片每个位置时所有饱和脉冲光下的叶绿素荧光图像提取出来，并排列与激光线扫描方向一致成的图片序列；分析图片序列中的每一张图片，提取出画面中激光线的中心线，将每一张图片中提取到中心线的像素坐标转化到基准坐标系下，求解出基准坐标系下的横纵坐标值，将所述横纵坐标值输入至基准坐标系下的光平面方程，反演出点云深度信息，再将所述横纵坐标值与下一张图片中激光线像素点的偏移进行相加，得到点云真实的基准坐标；遍历完图片序列，获得完整点云。
本发明的有益效果为：
(1)本发明中完成叶绿素荧光图像的拍摄后，计算其荧光动力学参数/实时荧光参数，依据荧光动力学参数/实时荧光参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数/实时荧光参数的三维点云数据；相比于传统的叶绿素荧光成像，带有荧光动力学参数/实时荧光参数的三维点云数据更有利于对叶片的生长情况进行分析。
(2)本发明中，由于拍摄叶绿素荧光图像和提取点云时，CMOS相机与待测叶片的位置未发生改变，因此成像信息的坐标点也是固定的，无需经过矩阵变换将其对齐，因此叶绿素 荧光信息融合非常精确。
(3)本发明在测量荧光动力学参数时采用脉冲振幅调制(PAM)测量原理，在快速测量实时荧光参数时采用长曝光成像原理，利用现有的一字型线激光光源装置完成激发，无需额外增加光源，降低了光源系统的复杂性，又提高了成像速度。
(4)本发明采用一字型激光光源，激发荧光的面积相较于点激光更大，半小时之内即可完成完整荧光动力学参数的测量、30s之内可以完成叶绿素实时荧光的测量。
(5)本发明装置的激发光源部分仅仅包含一字型线激光光源装置、步进电机和三棱镜，部件之间贴合度高，极大程度压缩了装置的空间，使得整个装置方便携带和操作。
附图说明
图1为本发明所述线激光诱导叶绿素荧光三维成像装置的立体结构示意图；
图2为本发明所述线激光诱导叶绿素荧光三维成像装置工作在补偿线宽模式下的示意图；
图3为本发明所述线激光诱导叶绿素荧光三维成像装置的系统流程；
图4为本发明所述动力学/实时荧光参数的计算流程图；
图5为本发明所述三维点云提取流程图；
图中，1、CMOS相机，2、三棱镜，3、步进电机，4、显示屏，5、嵌入式计算机，6、长波通滤光片，7、一字型激光光源装置，8、电动滑轨，9、电源，10、测量平台，11、承重架。
具体实施方式
下面结合附图以及具体实施例对本发明作进一步的说明，但本发明的保护范围并不限于此。
如图1所示，本发明提供一种线激光诱导叶绿素荧光的三维成像装置，包括CMOS相机1、三棱镜2、步进电机3、显示屏4、嵌入式计算机5、长波通滤光片6、一字型激光光源装置7、电动滑轨8、电源9、测量平台10和承重架11，长波通滤光片6的波长需大于520nm；测量平台10平放于桌面，承重架11与测量平台10相互垂直安装；CMOS相机1、步进电机3、电动滑轨8均安装在承重架11的水平段；三棱镜2背面开设有卡槽，卡在步进电机3的转动轴上，跟随步进电机3的转动轴转动；一字型激光光源装置7固定在电动滑轨8的载物平台上；嵌入式计算机5与电源9固定在承重架11上；显示屏4固定在承重架11上方；测量平台10上粘贴吸光黑绒布，使得荧光成像时叶片更加突出；长波通滤光片6固定在CMOS相机1的镜头上，正对测量平台10设置。
所述CMOS相机1采用制冷型黑白CMOS相机，该相机成像分辨率高达2000万像素， 可以获得更多图像细节；其暗电流低至0.001e-/pixel/s，支持长曝光，能显著降低暗环境下的热点噪声问题。
所述步进电机3的轴径为5mm，其伺服闭环与弹簧刹车设计可以更好得控制三棱镜2的折射角度。步进电机3的低噪音带来更小的震动，使整个装置处于相对静止状态，CMOS相机1拍摄时获得更加稳定的图像。通过搭配步进电机驱动器，可以实现步进电机更精确的角度转动控制，提升系统整体精度。
所述三棱镜2的边长均为5cm，入射面和出射面镀单层MgF2增透膜。背面开设有卡槽，用于连接所述步进电机3的转动轴。
所述嵌入式计算机5采用搭载RK3568主控芯片的主板，并搭载HPD322步进电机驱动器等硬件模组。该主板运行基于Linux的操作系统，实现对步进电机3、CMOS相机1、电动滑轨8和显示屏4的全面控制和反馈。
所述一字型激光光源装置7为可调节功率激光器，使用波长为462nm的蓝光波长，光斑为一字型均匀线，其中一字型均匀线粗细可调节，发射的激光在一米处线宽范围在1mm-5mm之间。
所述显示屏4采用7寸HDMI显示屏，通过一根HDMI线与RK3568主控芯片相连，部署GUI界面，用来显示叶绿素荧光图像并设有控制线激光诱导叶绿素荧光的三维成像装置的工作模式，工作模式一是获取完整的荧光动力学参数，形成带有荧光动力学参数的三维点云数据；工作模式二是快速测量实时荧光参数，形成带有实时荧光参数的三维点云数据。
所述电源9为220V转12V/24V电源，12V用于CMOS相机1和嵌入式计算机5的供电，24V用于给一字型激光光源装置7供电。
搭建如图1所示的线激光诱导叶绿素荧光的三维成像装置，设定测量平台10与CMOS相机1在竖直方向上的距离为1米。在测量平台10上放置棋盘格标定板，打开一字型激光光源装置7，发射线激光，手动转动三棱镜2，使线激光照射在棋盘格标定板上。在嵌入式计算机5中：利用张正友平面模板标定法解算出CMOS相机1的内部参数和外部参数；计算出测量平台坐标系与CMOS相机坐标系之间的相对位置关系；通过两个不同位姿的棋盘格标定板及照射在其上的激光线条，使用最小二乘法计算出光平面方程。
实施例1
本实施例中，一字型激光光源装置7与三棱镜2位于同一水平线，且一字型激光光源装置7的发射点正对三棱镜2设置。
将待测叶片放置于测量平台10上后，嵌入式计算机5依次控制步进电机3转动、一字型激光光源装置7发射线激光、CMOS相机1拍摄。步进电机3的转动范围限定在垂直向下45° 范围之内，即以竖直线为基准，其左侧为负、右侧为正，设定起始角度为-22.5°、终止角度为22.5°；从起始角度开始，按照0.2°的步进角度转动，每转动一次便停止；一字型激光光源装置7依据脉冲振幅调制(PAM)测量原理发射线宽为5mm的线激光，对待测叶片进行照射，嵌入式计算机5利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS相机1完成多张成像，并传输至嵌入式计算机5；成像完成后，步进电机3继续按照0.2°的步进角度转动，继续成像，直至转动至22.5°，停止。
脉冲振幅调制(PAM)测量原理的线激光，由嵌入式计算机5输出PWM波，控制一字型激光光源装置7发射线激光的光强与脉冲频率。通过改变PWM波的占空比来驱动一字型激光光源装置7分别实现测量光、饱和脉冲光和光化光的发射。设定PWM波周期为800ms，测量光、饱和脉冲光和光化光的占空比分别设为0.1％、95％和20％，对应的照射时间为0.8ms、760ms和160ms。激光激发序列设定如下：测量光、饱和脉冲光、测量光、光化光、测量光、9次连续的饱和脉冲光、测量光，在发射测量光时，同时触发CMOS相机1拍摄。
嵌入式计算机5对接收的图像进行多线程处理，对多张图像中的叶绿素荧光线段进行提取并拼接成一张完整叶片的叶绿素荧光图像，并计算其荧光动力学参数，依据荧光动力学参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数的三维点云数据。
所述拼接成一张完整叶片的叶绿素荧光图像的方法具体为：基于图像处理算法，对每张图像进行阈值分割，提取出叶绿素荧光线段，遍历所有图像，将所有提取出的叶绿素荧光线段放置在画布上，便获得一张完整叶片的叶绿素荧光图像。
所述荧光动力学参数的计算具体为：基于图像处理算法，将一张完整叶片的叶绿素荧光图像进行乘法运算，得到荧光区域掩模图；将掩模图像素矩阵累加，得到叶片区域像素值总数num；将待计算的叶绿素荧光图像与荧光区域掩模图进行分割运算，得到分割后的荧光图；将分割后的荧光图像素矩阵相加，得到叶片区域像数值总和Data；将叶片区域像素值总数num与叶片区域像数值总和Data代入公式计算，得到一张完整叶片的叶绿素荧光图像对应的叶绿素荧光参数值，即荧光动力学参数。具体流程如图4所示。
所述待计算的叶绿素荧光图像包括CMOS相机1拍摄的测量光下完整叶片的叶绿素荧光图像、饱和脉冲光下完整叶片的叶绿素荧光图像和光化光下完整叶片的叶绿素荧光图像。
所述荧光动力学参数包括暗适应下最小荧光F0、暗适应下最大荧光Fm、可变荧光Fv、PSII原初光能转化效率Fv/Fm、光适应后稳态荧光F、光适应后最大荧光Fm'、PSⅡ实际光合效率Y(II)。
下述荧光动力学参数为暗适应下的参数：在计算F0时，选取测量光下一张完整叶片的叶绿素荧光图像，按照荧光动力学参数的计算步骤得到具体数值；在计算Fm时，选取饱和脉冲光下一张完整叶片的叶绿素荧光图像，按照荧光动力学参数的计算步骤得到具体数值；在计算Fv时，公式为Fm-F0；在计算Fv/Fm时，公式为(Fm-F0)/Fm。
下述荧光动力学参数为光适应下的参数：在计算F时，选取光化光下一张完整叶片的叶绿素荧光图像，按照荧光动力学参数的计算步骤得到具体数值；在计算Fm'时，选取光化光之后的饱和脉冲光下一张完整叶片的叶绿素荧光图像，按照荧光动力学参数的计算步骤得到具体数值；在计算Y(II)时，公式为(Fm'-F)/Fm'。
所述合成伪彩色图像的方法具体为：基于图像处理算法，设定荧光动力学参数范围为0～1，将荧光动力学参数转换为0～255的RGB伪彩色图像。
所述三维点云的提取具体为：基于图像处理算法，将激光线照射在待测叶片每个位置时所有饱和脉冲光下的叶绿素荧光图像提取出来，并排列与激光线扫描方向一致成的图片序列；分析图片序列中的每一张图片，提取出画面中激光线的中心线；线激光照射到待测叶片表面，受其表面高度的调制发生形变，因此将每一张图片中提取到中心线的像素坐标转化到基准坐标系下，求解出基准坐标系下的x、y，将x、y输入至基准坐标系下的光平面方程，即可反演出点云深度信息，再将x、y与下一张图片中激光线像素点的偏移进行相加，得到点云真实的基准坐标；遍历完图片序列，即可获得完整点云。参见图5。
所述伪彩色图像映射至三维点云的方法具体为：基于图像处理算法，由于是同一台CMOS相机1进行图像采集，视场大小一致，因此在提取出三维点云时，将点云的数量与拍摄的图片分辨率设置一致，即可将伪彩色图像像素点的颜色赋给与之相对应的点云，完成了伪彩色图像与三维点云的映射。
实施例2
由于实施例1中通过步进电机3带动三棱镜2旋转从而折射线激光的工作方式，仅适用于较为低矮(低于50cm)的植株；在拍摄较高(50cm-100cm)植株时，会因为旋转角的变化而导致照射在植株叶片上的激光线宽度发生变化，不利于一张完整叶片的叶绿素荧光图像的合成。因此，本实施例通过电动滑轨8来带动一字型激光光源装置7进行平移，从而抵消因为旋转角的变化而导致照射在植株叶片上的激光线宽度变化。
本实施例中装置的工作过程为：将水平设置的一字型激光光源装置7调节至与竖直线的夹角成θ，θ的范围-10°-0°，本实施例优选为-10°，参见图2；将待测叶片放置于测量平台10上后，嵌入式计算机5依次一字型激光光源装置7发射线激光、CMOS相机1拍摄。一字型激光光源装置7依据脉冲振幅调制(PAM)测量原理发射线宽为5mm的线激光，对待测 叶片进行照射，嵌入式计算机5利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS相机1完成多张成像，并传输至嵌入式计算机5；成像完成后，电动滑轨8向左(靠近CMOS相机1方向)滑动5mm，继续测量，直至扫描完整个测量平台10。
测量结束后，嵌入式计算机5对图像进行处理的过程与实施例1一致。
实施例1和实施例2均是对工作模式一的描述。
实施例3
本实施例是对工作模式二的描述。
CMOS相机1在长曝光拍摄模式下可以将线光源转变为面光源，在激光线扫描整个叶片的同时，可以将单激光线上所激发出的叶绿素荧光从物理手段转变为整个叶片的叶绿素荧光图像。
如图1所示，将待测叶片放置于测量平台10上后，嵌入式计算机5同时控制步进电机3转动、一字型激光光源装置7发射线激光、CMOS相机1拍摄。步进电机3的转动范围限定在垂直向下45°范围之内，设定CMOS相机1曝光时间为10s，设定步进电机3从-22.5°转到22.5°的时间为10s，设定一字型激光光源装置7工作在最大功率，当步进电机3开始旋转时，同时触发CMOS相机1拍摄并启动一字型激光光源装置7发射激光，在10s内完成对待测叶片的扫描与长曝光成像；随后设定CMOS相机1为视频采集模式，步进电机3再从22.5°转到-22.5°，完成三维原始图像的采集，并发送给嵌入式计算机5。
嵌入式计算机5对接收的图像进行多线程处理，依据长曝光图像(整个叶片的叶绿素荧光图像)计算实时荧光参数，依据实时荧光参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，最后将伪彩色图像映射至三维点云，形成带有实时荧光参数的三维点云数据。具体的伪彩色图像合成、提取三维点云以及将伪彩色图像映射至三维点云的过程均与实施例1相同。
所述实时荧光参数的计算与荧光动力学参数的计算相同，但在计算实时荧光Ft时，无需对待测叶片进行暗适应，将拍摄到的长曝光图像按照图4中的图像算法流程计算，即可获得参数Ft；在计算暗适应状态下最大荧光Fm时，需要对待测叶片进行暗适应，将拍摄到的长曝光图像按照图4中的图像算法流程计算，即可获得参数Fm。
所述实施例为本发明的优选的实施方式，但本发明并不限于上述实施方式，在不背离本发明的实质内容的情况下，本领域技术人员能够做出的任何显而易见的改进、替换或变型均属于本发明的保护范围。

Claims (10)

  1. 一种线激光诱导叶绿素荧光的三维成像装置，其特征在于，包括CMOS相机(1)、三棱镜(2)、步进电机(3)、嵌入式计算机(5)、长波通滤光片(6)、一字型激光光源装置(7)、电动滑轨(8)、测量平台(10)和承重架(11)；
    所述承重架(11)垂直安装在测量平台(10)上，所述CMOS相机(1)、步进电机(3)和电动滑轨(8)均安装在承重架(11)的水平段，且CMOS相机(1)的镜头正对测量平台(10)设置；所述三棱镜(2)卡接在步进电机(3)的转动轴上；所述一字型激光光源装置(7)固定在电动滑轨(8)的载物平台上；所述长波通滤光片(6)固定在CMOS相机(1)的镜头上；
    所述嵌入式计算机(5)与步进电机(3)、CMOS相机(1)、电动滑轨(8)进行通信。
  2. 根据权利要求1所述的线激光诱导叶绿素荧光的三维成像装置，其特征在于，还包括显示屏(4)，所述显示屏(4)与嵌入式计算机(5)连接，用于切换所述三维成像装置的工作模式。
  3. 一种基于权利要求1-2任一项所述的线激光诱导叶绿素荧光的三维成像装置的三维成像方法，其特征在于，所述三维成像装置的工作模式是获取完整的荧光动力学参数，形成带有荧光动力学参数的三维点云数据。
  4. 根据权利要求3所述的三维成像方法，其特征在于：
    在拍摄低于50cm的植物时：一字型激光光源装置(7)与三棱镜(2)位于同一水平线，且一字型激光光源装置(7)的发射点正对三棱镜(2)设置；所述步进电机(3)从起始角度开始，按照0.2°的步进角度转动，每转动一次便停止；一字型激光光源装置(7)依据脉冲振幅调制测量原理发射线宽为5mm的线激光，对放置在测量平台(10)上的待测叶片进行照射，嵌入式计算机(5)利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS相机(1)完成多张成像，并传输至嵌入式计算机(5)；一次成像完成后，步进电机(3)继续按照0.2°的步进角度转动，继续成像，直至转动至终止角度；所述嵌入式计算机(5)对接收的图像进行多线程处理，对多张图像中的叶绿素荧光线段进行提取并拼接成一张完整叶片的叶绿素荧光图像，计算其荧光动力学参数，依据荧光动力学参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数的三维点云数据；
    在拍摄50cm-100cm范围的植物时：将水平设置的一字型激光光源装置(7)调节至与竖直线的夹角成θ，一字型激光光源装置(7)依据脉冲振幅调制测量原理发射线宽为5mm的线激光，对放置在测量平台(10)上的待测叶片进行照射，嵌入式计算机(5)利用PWM脉宽调制技术将测量光、饱和脉冲光和光化光组合为一个测量周期，在此测量周期内，CMOS 相机(1)完成多张成像，并传输至嵌入式计算机(5)；成像完成后，电动滑轨(8)向CMOS相机(1)方向滑动5mm，继续测量，直至扫描完整个测量平台(10)；所述嵌入式计算机(5)对接收的图像进行多线程处理，对多张图像中的叶绿素荧光线段进行提取并拼接成一张完整叶片的叶绿素荧光图像，计算其荧光动力学参数，依据荧光动力学参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，将伪彩色图像映射至三维点云，形成带有荧光动力学参数的三维点云数据。
  5. 根据权利要求4所述的三维成像方法，其特征在于，所述拼接成一张完整叶片的叶绿素荧光图像的方法具体为：对每张图像进行阈值分割，提取出叶绿素荧光线段，遍历所有图像，将所有提取出的叶绿素荧光线段放置在画布上，便获得一张完整叶片的叶绿素荧光图像。
  6. 一种基于权利要求1-2任一项所述的线激光诱导叶绿素荧光的三维成像装置的三维成像方法，其特征在于，所述三维成像装置的工作模式是快速测量实时荧光参数，形成带有实时荧光参数的三维点云数据。
  7. 根据权利要求6所述的三维成像方法，其特征在于：
    步进电机(3)的转动范围限定在垂直向下45°范围之内，设定CMOS相机(1)曝光时间为10s，设定步进电机(3)从-22.5°转到22.5°的时间为10s，设定一字型激光光源装置(7)工作在最大功率；当步进电机(3)开始旋转时，同时触发CMOS相机(1)拍摄并启动一字型激光光源装置(7)发射激光，在10s内完成对放置在测量平台(10)上的待测叶片的扫描与长曝光成像；随后设定CMOS相机(1)为视频采集模式，步进电机(3)再从22.5°转到-22.5°，完成三维原始信息图像的采集；
    嵌入式计算机(5)对接收的图像进行多线程处理，依据长曝光图像计算实时荧光参数，依据实时荧光参数合成伪彩色图像；同时，根据激光线像素点的偏移提取出三维点云，最后将伪彩色图像映射至三维点云，形成带有实时荧光参数的三维点云数据。
  8. 根据权利要求4或6所述的三维成像方法，其特征在于，通过改变嵌入式计算机(5)输出的PWM波的占空比，驱动一字型激光光源装置(7)分别实现测量光、饱和脉冲光和光化光的发射；激光激发序列设定如下：测量光、饱和脉冲光、测量光、光化光、测量光、9次连续的饱和脉冲光、测量光，在发射测量光时，同时触发CMOS相机(1)拍摄。
  9. 根据权利要求8所述的三维成像方法，其特征在于，所述荧光动力学参数/实时荧光参数的计算具体为：将一张完整叶片的叶绿素荧光图像进行乘法运算，得到荧光区域掩模图；将掩模图像素矩阵累加，得到叶片区域像素值总数num；将待计算的叶绿素荧光图像与荧光区域掩模图进行分割运算，得到分割后的荧光图；将分割后的荧光图像素矩阵相加，得到叶片区域像数值总和Data；将叶片区域像素值总数num与叶片区域像数值总和Data代入公式 计算，得到一张完整叶片的叶绿素荧光图像对应的叶绿素荧光参数值，即荧光动力学参数；所述待计算的叶绿素荧光图像包括CMOS相机(1)拍摄的测量光下完整叶片的叶绿素荧光图像、饱和脉冲光下完整叶片的叶绿素荧光图像和光化光下完整叶片的叶绿素荧光图像。
  10. 根据权利要求4或6所述的三维成像方法，其特征在于，所述三维点云的提取具体为：将激光线照射在待测叶片每个位置时所有饱和脉冲光下的叶绿素荧光图像提取出来，并排列与激光线扫描方向一致成的图片序列；分析图片序列中的每一张图片，提取出画面中激光线的中心线，将每一张图片中提取到中心线的像素坐标转化到基准坐标系下，求解出基准坐标系下的横纵坐标值，将所述横纵坐标值输入至基准坐标系下的光平面方程，反演出点云深度信息，再将所述横纵坐标值与下一张图片中激光线像素点的偏移进行相加，得到点云真实的基准坐标；遍历完图片序列，获得完整点云。
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