Parallel interval rapid detection method and device

Abstract

The application discloses a parallel interval rapid detection method, and belongs to the technical field of non-contact detection. The method comprises the following steps: placing a measured object on a reference surface, irradiating at least one laser on the measured object, and forming an included angle with the surface of the measured object; horizontally moving the measured object, and obtaining the offset of the laser and the light-dark change amount of the laser before and after the movement of the measured object; and obtaining the height fluctuation of the surface of the measured object according to the offset of the laser, the included angle and the light-dark relationship of the laser. The device using the method comprises a measuring platform, a line scanning camera and a laser emitter. The line scanning camera is used to obtain the light-dark image of the light strip to obtain the depth information of the measured object, the center line of the light strip does not need to be extracted, the surface morphology three-dimensional features of the measured object are efficiently reconstructed, and the surface of the measured object is detected at high speed and high precision.

Description

Technical Field

[0001] This invention belongs to the technical field of non-contact detection, and specifically relates to a method and apparatus for rapid detection of parallel spacing. Background Technology

[0002] The invention patent with application number 201710615803.1 discloses a machine vision system for measuring the position and geometric dimensions of holes and slots. The system uses line laser and line scanning camera to detect the position and dimensions of holes and slots in the horizontal direction on a flat object. The system can only detect the geometric dimensions of holes and slots on a plane and cannot or has difficulty detecting minute undulations.

[0003] In order to obtain the depth information of the object being measured using the traditional laser triangulation method, an area array camera must be used, and the center line of the light stripe must be extracted. Due to the complexity of the surface material, surface properties, and uneven reflection of the object being measured, the accuracy and speed are not high. Summary of the Invention

[0004] In view of this, in order to solve the above-mentioned problems of the prior art, the purpose of the present invention is to provide a method and device for rapid detection of parallel spacing, which can efficiently reconstruct the three-dimensional features of the surface morphology of the object under test, and detect the minute undulations of the object surface at high speed and high precision.

[0005] The technical solution adopted in this invention is as follows:

[0006] In a first aspect, the present invention provides a method for rapid detection of parallel spacing, comprising the following steps:

[0007] Place the object to be measured on a reference surface, and irradiate the object with at least one laser beam at an angle to the surface of the object.

[0008] The test object is moved horizontally to obtain the laser offset and the change in laser brightness before and after the object is moved.

[0009] The height undulation of the surface of the object being measured is obtained based on the laser's offset, angle, and brightness.

[0010] In a further technical solution, the object under test is moved horizontally, and the offset of the laser and the change in the brightness of the laser before and after the object is moved are obtained, including:

[0011] A line scan camera is set up to record the laser's offset and brightness changes frame by frame.

[0012] In a further technical solution, there are two lasers, denoted as laser a and laser b;

[0013] Laser a and laser b are parallel;

[0014] Based on the intensity changes of laser a and laser b irradiating the surface of the object being tested, it can be determined whether the surface of the object is flat, raised, or concave.

[0015] In a further technical solution, let the parallel distance between laser a and laser b be S; the parallel distance S is half the width of laser a or half the width of laser b.

[0016] In a further technical solution, laser a and laser b have different wavelengths, and the line scan camera uses an RGB three-channel color camera.

[0017] In a further technical solution, a laser is used to illuminate a pure white background sample for testing, and the relationship between a change in brightness and position is recorded and denoted as a calibration function.

[0018] In a second aspect, the present invention also provides a rapid parallel spacing detection device using the method of the first aspect, comprising:

[0019] A measurement platform is used to place the object being measured and to move the object.

[0020] A line scan camera is positioned above the measurement platform; the lens of the line scan camera is perpendicular to the measurement platform.

[0021] A laser emitter, at least one, is positioned above the measuring platform; the laser emitter emits a laser beam and forms an angle with the object being measured placed on the measuring platform.

[0022] In a further technical solution, there are two laser emitters; the two laser emitters are arranged in parallel, and the laser wavelengths emitted by the two laser emitters are different.

[0023] In a further technical solution, the line scan camera uses an RGB three-channel color camera.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention uses a line scan camera to acquire the light and dark images of light stripes to obtain the depth information of the object under test. It eliminates the need to extract the center line of the light stripes, efficiently reconstructing the three-dimensional features of the surface morphology of the object under test; and it can detect minute undulations on the surface of the object at high speed and with high precision. Attached Figure Description

[0026] Figure 1 This is a system architecture diagram of the present invention;

[0027] Figure 2 This is a laser cross-sectional intensity distribution diagram of the present invention;

[0028] Figure 3 This is a schematic diagram of the laser optical path of the present invention. Figure 1 ;

[0029] Figure 4 This is a schematic diagram of the laser optical path of the present invention. Figure 2 ;

[0030] Figure 5 This is a schematic diagram of the structure of the present invention.

[0031] The attached diagram is labeled as follows:

[0032] 1-Measuring platform; 2-Line scan camera; 3-Laser emitter. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] Example 1

[0036] like Figure 1 As shown, a method for rapid detection of parallel spacing includes the following steps:

[0037] 101: Place the object to be measured on the reference surface, and irradiate the object with a laser beam at an angle to the surface of the object;

[0038] It should be noted that the laser is emitted by a laser emitter, which emits a laser beam that gradually dims from the center outwards onto the object being measured.

[0039] 102: Move the object under test horizontally to obtain the offset of the laser and the change in the brightness of the laser before and after the object is moved;

[0040] It should be noted that a line scan camera is installed above the object being measured. The laser emitter emits laser light at a certain angle. After the laser light encounters the surface of the object being measured, it will be reflected back. The reflected light is detected by the line scan camera. If the light bends, the offset L of the laser light is obtained.

[0041] It should also be noted that the intensity distribution of the laser cross-section is highest at the center and decreases monotonically and symmetrically towards both sides, as shown in the reference. Figure 2Establish a rectangular coordinate system, with the X-axis representing the width of the laser beam cross-section and the Y-axis representing the laser intensity; let the width be W, the maximum intensity value be A, and the origin of the coordinate axes be located at the center of the laser beam cross-section; let the intensity distribution function of the laser cross-section be I(x), and here we assume this curve... The fitting function is f(x), and the specific form of f(x) is determined by the laser beam itself. Then, I(x) has the following functional expression:

[0042]

[0043] 103: The height undulation of the surface of the object being measured is obtained based on the laser's offset, angle, and the relationship between the laser's brightness and darkness.

[0044] It should be noted that, as Figure 3 As shown, the functional relationship between the laser offset L and the vertical undulation distance H of the measured object is as follows:

[0045] H=L·tanα

[0046] In the formula, α is the angle between the laser and the surface of the object being measured.

[0047] In actual measurement, the length L must be less than 1 / 2 of the laser width. The maximum fluctuation that this method can measure satisfies the following function:

[0048]

[0049] That is, the measurement range is proportional to the laser width and also proportional to the included angle α.

[0050] In this embodiment, the method further includes the step of: irradiating a pure white background sample with a laser to perform a test, recording the relationship between a change in brightness and position, and recording it as a calibration function.

[0051] It should be noted that the above description only calculates for a single cross-section of the laser line, and only the undulation characteristics in the direction parallel to the movement of the object being tested are obtained. While this method can obtain three-dimensional information of the entire plane from a complete laser beam, inconsistencies can occur during laser manufacturing, resulting in different intensity distribution functions at different cross-sections. Therefore, a pure white plane background is used for testing, and the three-dimensional intensity distribution function of the entire test width (perpendicular to the direction of movement) is recorded. That is, in a standard Cartesian coordinate system, the XY plane represents the horizontal position distribution of the laser beam, and the Z-axis represents the laser intensity.

[0052] Calibration further eliminates structural systematic errors and improves the system's measurement accuracy. Based on the above functional relationship analysis, factors affecting system accuracy include, but are not limited to: the laser mounting angle, the linearity of the line-scan camera's photosensitive element, the flatness of the moving platform and its movement accuracy, as well as reducing ambient light interference.

[0053] Example 2

[0054] The parallel spacing rapid detection method described in Example 1 can only detect that the surface of the object being measured has undulations, but cannot determine whether the laser deflection is caused by the protrusion or depression of the surface of the object being measured. Therefore, this example improves upon Example 1 and proposes a parallel spacing rapid detection method, which uses two lasers to irradiate the object being measured in parallel.

[0055] Let the two lasers be laser a and laser b. Based on the intensity changes of laser a and laser b on the surface of the object being tested, determine whether the surface of the object being tested is flat, raised, or concave.

[0056] In this embodiment, laser a is moved away from the line scan camera, and laser b is moved closer to the line scan camera, such as... Figure 4 As shown, at the initial position, laser a is detected to be at its highest intensity, while laser b is at zero intensity. When the surface of the object being measured has protrusions or depressions, if the intensity of laser a decreases while the intensity of laser b increases, it indicates that the surface of the object being measured is protruding; if the intensity of laser a decreases while the intensity of laser b remains zero, it indicates that the surface of the object being measured is depressed.

[0057] In this embodiment, lasers a and b are parallel and spaced apart by a distance S, which is exactly half the width of laser b, ensuring that the edge of laser b is flush with the center line of laser a. With this configuration, when the object being measured has slight undulations, the presence of detected laser a indicates whether the surface of the object is raised or recessed. Furthermore, ensuring the parallelism of lasers a and b allows for the calculation of the vertical undulation distance H of the object through the intensity change of laser a. The same applies to laser b, which will not be elaborated upon in this embodiment.

[0058] In this embodiment, laser a and laser b have different wavelengths; preferably, laser a is red light and laser b is blue light, and the line scan camera is an RGB three-channel color camera. When a change in laser brightness is detected, it indicates that the current test point has undulations, but it is unclear whether it is a convexity or a concaveness. At this time, the presence or absence of the bright bar of laser b (blue light) is detected to indicate whether the object being tested is convex or concave, thus achieving the effect of determining whether it is a convexity or a concaveness. Its change pattern is the opposite of the brightness change of laser a (red light), that is, when laser a (red light) changes from bright to dark, it indicates that the undulations are gradually increasing, while when laser b (blue light) changes from dark to bright, it indicates that the undulations are gradually increasing.

[0059] Naturally, laser a is not limited to red light, and laser b is not limited to blue light.

[0060] Example 3

[0061] This embodiment discloses a rapid parallel spacing detection device, including a measurement platform, a line scan camera, and at least one laser emitter.

[0062] The measuring platform is used to place the object to be measured and to move the object. The line scan camera is located above the measuring platform with its lens perpendicular to the measuring platform. The laser emitter is located above the measuring platform to emit laser light and forms an angle with the object to be measured placed on the measuring platform.

[0063] Specifically, the measurement platform includes a track and a platform body. The track is a straight line and laid horizontally on a reference surface. The platform body is slidably set on the track. The object to be measured is placed on the platform body, and at the same time, the platform body slides at a uniform speed on the track to realize the movement of the object to be measured.

[0064] In this embodiment, there are two laser emitters, which are arranged in parallel and emit laser wavelengths that are different from each other.

[0065] In this embodiment, the line scan camera is an RGB three-channel color camera.

[0066] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for rapid detection of parallel spacing, characterized in that, The method includes the following steps: Place the object to be tested on a reference surface, and irradiate the object with two lasers at an angle to the surface of the object. The test object is moved horizontally, and the offset of the laser and the change in the brightness of the laser are obtained before and after the test object is moved. The height undulation of the surface of the object being measured is obtained based on the laser's offset, angle, and brightness. The horizontal movement of the test object, and the acquisition of the laser offset and brightness change before and after the movement of the test object, include: A line scan camera is set up, which records the offset and brightness changes of the laser beam frame by frame. The number of lasers is two, denoted as laser a and laser b; Laser a and laser b are parallel; Based on the intensity changes of laser a and laser b irradiating the surface of the object being tested, it is determined whether the surface of the object being tested is flat, raised, or concave. Let S be the parallel distance between laser a and laser b; the parallel distance S is half the width of laser a, and the edge of laser b is flush with the center line of laser a; laser a is away from the line scan camera, and laser b is close to the line scan camera. In the initial position, laser a is detected to be at its highest intensity, and laser b is at zero intensity; when the surface of the object being measured has protrusions or depressions, if the intensity of laser a decreases while the intensity of laser b increases, it indicates that the surface of the object being measured is protruding; if the intensity of laser a decreases while the intensity of laser b remains zero, it indicates that the surface of the object being measured is depressed. This method is based on a rapid parallel spacing detection device, which includes: A measurement platform for placing the object to be measured and for moving the object to be measured; A line scan camera is positioned above the measurement platform; the lens of the line scan camera is perpendicular to the measurement platform. Two laser emitters are positioned above the measuring platform; the laser emitters emit laser light and form an angle with the object being measured placed on the measuring platform.

2. The method for rapid detection of parallel spacing according to claim 1, characterized in that, The lasers a and b have different wavelengths, and the line scan camera uses an RGB three-channel color camera.

3. The method for rapid detection of parallel spacing according to claim 1, characterized in that, It also includes the following steps: The laser was used to illuminate a pure white background sample for testing. The relationship between the change in brightness and the position was recorded and denoted as the calibration function.

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