Line laser rapid height measurement device and method

Abstract

The invention relates to a line laser fast height measuring device, comprising a power supply, a linear laser, a shift lens, a CCD sensor, a PCB circuit board and an object loading surface. The object loading surface is a fixed flat surface or a smooth surface on an assembly line. An object to be measured is placed on the object loading surface. A linear laser is installed directly above the object loading surface. The linear laser is used to vertically project a laser line downward. The laser line is projected onto the object to be measured and the object loading surface. The shift lens is arranged obliquely upward. The laser line reflected by the object to be measured and the object loading surface is imaged into the obliquely upward shift lens and focused on the CCD sensor. The CCD sensor is electrically connected to the PCB circuit board. The output end of the PCB circuit board is connected to an output network port and an IO port. The PCB circuit board and the linear laser are respectively connected to a power supply through lines. The invention can quickly and reliably measure the height of an object passing on the assembly line, and effectively improves the problems of low measurement accuracy, slow speed, poor reliability, etc. in the prior art.

Description

[Technical field]

[0001] The invention relates to the field of measurement technology, in particular to a linear laser rapid height measurement device and method. [Background Technology]

[0002] In the existing visual height measurement technology, measurement accuracy, measurement speed and measurement stability and reliability have always been the key points for improving the technology. At present, there are mainly the following types of non-contact height measurement technologies: laser height measurement, visual height measurement and triangulation height measurement. Among them, (1) Laser height measurement is a laser ranging technology that measures the time difference between the emission of laser and the reception of laser, and then multiplies it by the speed of light to get the distance. (2) Visual height measurement is to use a camera to take a picture of the object to be measured, and estimate the height or distance of the object through the image formed by the object on the sensor. (3) Triangulation height measurement is to use a line laser to hit the object to be measured, and then use a camera to take a picture, and use the difference between the irradiation angle and the shooting angle to calculate the height of the object to be measured.

[0003] The above height measurement schemes all have certain shortcomings: (1) The accuracy of laser ranging is not high, and it is mainly for measuring points, and it cannot completely measure the overall height of an object at one time. (2) Visual height measurement requires a fixed scene, and has very high requirements for the brightness of the environment, light angle, etc., and the measurement is not accurate. In addition, this technology requires complex software to process, resulting in slow processing speed and slow measurement speed. (3) Triangulation height measurement technology is relatively good. It uses line lasers and cameras to take pictures. It can use the angle difference to better measure the speed of objects, but this angle difference is difficult to reach the linear range, and the error is not small. If the working environment is constantly vibrating, it will greatly affect the measurement accuracy and lack reliability. [Summary of the invention]

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies and provide a linear laser rapid height measuring device, which can quickly and reliably measure the height of objects passing on the assembly line, effectively improving the problems of low measurement accuracy, slow speed, poor reliability and so on in the prior art.

[0005] In order to achieve the above purpose, a linear laser rapid height measurement device is designed, comprising a power supply 1, a linear laser 2, a shift lens 3, a CCD sensor 4, a PCB circuit board 5 and a loading surface 6, wherein the loading surface 6 is a fixed flat surface or a smooth surface on an assembly line, a measured object 7 is placed on the loading surface 6, a linear laser 2 is installed directly above the loading surface 6, the linear laser 2 is used to project a laser line vertically downward, and the laser line is projected onto the measured object 7 and the loading surface 6, the shift lens 3 is arranged obliquely upward, and the laser line reflected by the measured object 7 and the loading surface 6 is imaged into the obliquely upward shift lens 3 and focused on the CCD sensor 4, the CCD sensor 4 is electrically connected to the PCB circuit board 5, the output end of the PCB circuit board 5 is connected to the output network port and the IO port, and the PCB circuit board 5 and the linear laser 2 are respectively connected to the power supply 1 through lines.

[0006] Furthermore, a U-shaped bracket 8 is disposed across the object-carrying surface 6 , and the linear laser 2 is fixed at a middle position above the U-shaped bracket 8 .

[0007] Furthermore, the shift lens 3 , the CCD sensor 4 and the PCB circuit board 5 are assembled into a closed camera, and the camera is installed at the same height as the linear laser 2 but at a different horizontal position.

[0008] The present invention also provides a measuring method of a linear laser rapid height measuring device, comprising the following steps: firstly, a linear laser beam is vertically irradiated onto a measured object 7 and a loading surface 6 by a linear laser 2, and the reflected laser line is imaged onto a CCD sensor 4 after passing through a shift lens 3, and objects of different heights leave projections on different rows of the CCD sensor 4 after passing through the measuring line position, and the position of the projected row has a certain projection relationship with the height of the measured object 7, and the height of the measured object 7 can be measured by calibrating the measurement coefficient with an object of known height; when multiple measured objects 7 pass through the measuring line at the same time, they are projected onto different columns on the CCD sensor 4, and multiple measured objects can be measured at the same time.

[0009] Furthermore, the PCB circuit board 5 has an ARM processor and an FPGA chip built in. When the PCB circuit board 5 collects image information on the CCD sensor 4, it is transmitted to the FPGA chip, and then the median line is extracted from the input image data stream; then the ARM processor controls the exposure and takes pictures, and reads the median line data, and finally the number of the measured objects 7 is identified through the ARM processor and the height of the measured objects 7 is calculated according to the cross ratio theorem.

[0010] Furthermore, the steps for the image data stream to enter the FPGA chip to extract the median line are as follows: first, the Gaussian curve template data is preset, and then the input image data stream is geometrically transformed, and the difference convolution between the real-time curve on the image and the Gaussian distribution curve is calculated, and the single-row minimum value is searched and the coordinates are recorded, so as to calculate the coordinate position of the center line of the laser projection.

[0011] Compared with the prior art, the present invention can realize rapid height measurement of multiple objects at the same time, especially on a high-speed assembly line, and can quickly detect the number, width and height of passing objects. The measurement results are accurate and fast, which solves the problems of narrow detection range of sensors on the market, inaccurate height measurement, single function, and detection speed that cannot keep up with the running speed on the assembly line. It realizes a laser height measurement function that integrates detection, measurement, identification and calculation, and is worthy of popularization and application. [Drawings]

[0012] Figure 1 It is a principle block diagram of the present invention;

[0013] Figure 2 It is a schematic diagram of the structure of the present invention;

[0014] Figure 3 It is the imaging principle diagram of the present invention;

[0015] Figure 4 yes Figure 3 The height calculation formula of the cross ratio theorem;

[0016] Figure 5 is a height measurement flow chart of the present invention;

[0017] Figure 6 It is a flow chart of the calculation of the center coordinates of the laser line of the present invention;

[0018] In the figure: 1, power supply 2, linear laser 3, tilt-shift lens 4, CCD sensor 5, PCB circuit board 6, loading surface 7, object to be measured 8, U-shaped bracket. [Specific implementation method]

[0019] The present invention is further described below in conjunction with the accompanying drawings:

[0020] As shown in the accompanying drawings, the present invention provides a linear laser rapid height measurement device, comprising a power supply 1, a linear laser 2, a shift lens 3, a CCD sensor 4, a PCB circuit board 5 and a loading surface 6, the loading surface 6 is a fixed flat surface or a smooth surface on an assembly line, a measured object 7 is placed on the loading surface 6, a linear laser 2 is installed directly above the loading surface 6, the linear laser 2 is used to project a laser line vertically downward, the laser line is projected onto the measured object 7 and the loading surface 6, the shift lens 3 is arranged obliquely upward, the laser line reflected by the measured object 7 and the loading surface 6 is imaged into the obliquely upward shift lens 3, and is focused on the CCD sensor 4, the CCD sensor 4 is electrically connected to the PCB circuit board 5, the output end of the PCB circuit board 5 is connected to the output network port and the IO port, the PCB circuit board 5 and the linear laser 2 are respectively connected to the power supply 1 through lines. Among them, a U-shaped bracket 8 is across the loading surface 6, and the linear laser 2 is fixed at the middle position above the U-shaped bracket 8; the shift lens 3, the CCD sensor 4 and the PCB circuit board 5 are assembled into a closed camera, and the camera is installed at the same height as the linear laser 2 but at a different horizontal position.

[0021] The measuring method of the line laser rapid height measuring device comprises the following steps: firstly, a line laser beam is vertically irradiated on the measured object 7 and the object loading surface 6 by a line laser 2, and the reflected laser line is imaged on the CCD sensor 4 after passing through the shift lens 3, and objects of different heights leave projections on different rows of the CCD sensor 4 after passing through the measuring line position, and the position of the projected row is in a certain projection relationship with the height of the measured object 7, and the height of the measured object 7 can be measured by calibrating the measuring coefficient with an object of known height; when multiple measured objects 7 pass through the measuring line at the same time, they are projected onto different columns on the CCD sensor 4, and multiple measured objects can be measured at the same time.

[0022] In the present invention, the PCB circuit board 5 is built with an ARM processor and an FPGA chip. When the PCB circuit board 5 collects the image information on the CCD sensor 4, it is transmitted to the FPGA chip, and then the median line is extracted from the input image data stream; then the ARM processor controls the exposure and takes pictures, and reads the median line data, and finally the number of the measured objects 7 is identified by the ARM processor, and the height of the measured objects 7 is calculated according to the cross ratio theorem. Among them, the steps of extracting the median line when the image data stream enters the FPGA chip are: firstly, the Gaussian curve template data is preset, and then the input image data stream is geometrically transformed, and the coordinate position of the laser projection center line can be obtained by finding the difference convolution between the real-time curve on the image and the Gaussian distribution curve, searching for the minimum value of a single row and recording the coordinates.

[0023] The device of the present invention includes a power supply, a loading surface, a linear laser, a shift lens, a CCD sensor, a PCB circuit board and an output port; the loading surface can be a fixed flat surface or a smooth surface on an assembly line, which is mainly used to place the object to be measured; the linear laser is installed directly above the loading surface, and is mainly used to illuminate a thin and bright straight line, which is projected onto the object to be measured and the loading surface; the shift lens, the CCD sensor and the PCB circuit board are assembled into a closed camera, and the camera is installed at the same height as the linear laser but at a different horizontal position, so that the emission angle of the linear laser and the imaging angle form a certain difference angle, which is convenient for establishing a focal plane on the CCD sensor. The device of the present invention is used for measuring the height of multiple objects on an assembly line, in a wide range, quickly and reliably, and can effectively improve the problems of low measurement accuracy, slow speed and poor reliability in the prior art.

[0024] The working process of the present invention includes an imaging process and a data processing process. Figure 3 As shown, a linear laser is first shone vertically on the surface to be measured, and then the image is formed on the CCD sensor after passing through the tilt-shift lens. Objects of different heights will leave projections on different rows of the CCD sensor after passing through the measuring line position, and the position of the projected row has a certain projection relationship with the height of the object to be measured. By calibrating the measurement coefficient with an object of known height, the height of the object to be measured can be measured; when multiple objects pass through the measuring line at the same time, they will be projected onto different columns on different CCD sensors, thereby realizing the simultaneous measurement of multiple objects and the measurement of the width of the objects. In order to make objects of different heights clearly imaged in the camera, the angle between the tilt-shift lens and the CCD sensor can be changed, and the principle of the tilt-shift lens can be used to achieve a completely clear imaging effect. The projection of the imaging object on the CCD sensor follows the invariance of the cross ratio of projective geometry (as shown in the attached figure). Figure 4 ), and use the cross ratio invariance to calculate the height of the object being measured. The data processing process is shown in the attached figure. Figure 5 and attached Figure 6 As shown, after the image information on the CCD sensor is collected, it is transmitted to the FPGA, and then the input image data stream is processed at S230; first, the value is preset at S231, and then the input data is transformed at S233, and the best matching effect is achieved by finding the minimum value on the image at S234, so as to find the coordinate position of the center line of the laser projection; then the ARM software controls the camera to perform S220, and the ARM end reads the calculation result of S230, and then the ARM software calculates and recognizes the number, position and height of the objects according to S130.

[0025] As attached Figure 2 As shown, the present invention is typically used in an assembly line to detect the height, width and other parameters of the passing objects to see if they meet the standards, thereby providing a control signal for the next stage of the assembly line. If the assembly line speed is accurately controlled, the present invention can also be used for three-dimensional scanning of the object's shape. Figure 2 In the figure, the loading surface 6 is a smooth hard surface, located at the bottom, for mounting the bracket, placing the object to be measured 7, and projecting the laser. A U-shaped bracket 8 is arranged across the loading surface, and a linear laser 2 is fixed in the middle above the U-shaped bracket 8. The linear laser 2 projects the laser line vertically downward, and the reflected laser line is imaged into the tilt-shift lens 3 which is tilted upward, and is focused on the CCD sensor 4. It can be seen that the focused image fully reflects the height and width information of the object to be measured; and then the image is transmitted to the PCB circuit board 5 for processing.

[0026] The present invention is not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A linear laser rapid height measurement device, characterized in that: The device comprises a power supply (1), a linear laser (2), a tilt-shift lens (3), a CCD sensor (4), a PCB circuit board (5) and a loading surface (6); the loading surface (6) is a fixed flat surface or a smooth surface on an assembly line; a measured object (7) is placed on the loading surface (6); a linear laser (2) is installed directly above the loading surface (6); the linear laser (2) is used to project a laser line vertically downward; the laser line is projected onto the measured object (7) and the loading surface (6); the tilt-shift lens (3) is arranged obliquely upward; the laser line reflected by the measured object (7) and the loading surface (6) is imaged into the obliquely upward tilt-shift lens (3) and is focused on the CCD sensor (4); the CCD sensor (4) is electrically connected to the PCB circuit board (5); an output end of the PCB circuit board (5) is connected to an output network port and an IO port; the PCB circuit board (5) and the linear laser (2) are respectively connected to the power supply (1) via lines; Objects of different heights leave projections on different rows of the CCD sensor (4) after passing through the measuring line position, and the positions of the projected rows form a certain projection relationship with the height of the measured object (7). By calibrating the measurement coefficient with an object of known height, the height of the measured object (7) can be measured; The PCB circuit board (5) has an ARM processor and an FPGA chip built therein. When the PCB circuit board (5) collects image information on the CCD sensor (4), it transmits it to the FPGA chip, and then extracts the median line from the input image data stream. Then, the ARM processor controls the exposure and takes pictures, and reads the median line data. Finally, the number of the measured objects (7) is identified through the ARM processor, and the height of the measured objects (7) is calculated according to the cross ratio theorem. The steps for extracting the median line when the image data stream enters the FPGA chip are as follows: first preset the Gaussian curve template data, then perform a geometric transformation on the input image data stream, and by finding the difference convolution between the real-time curve on the image and the Gaussian distribution curve, search for the minimum value of a single row and record the coordinates, the coordinate position of the center line of the laser projection can be obtained.

2. The linear laser rapid height measurement device according to claim 1, characterized in that: A U-shaped bracket (8) is disposed across the top of the object-carrying surface (6), and the linear laser (2) is fixed at a middle position above the U-shaped bracket (8).

3. The linear laser rapid height measurement device according to claim 2, characterized in that: The shift lens (3), the CCD sensor (4) and the PCB circuit board (5) are assembled into a closed camera, and the camera is installed at the same height as the linear laser (2) but at a different horizontal position.

4. The linear laser rapid height measurement device according to claim 1, characterized in that: When a plurality of measured objects (7) pass through the measuring line at the same time, they are projected onto different columns on the CCD sensor (4), so that the plurality of measured objects can be measured simultaneously.

Images