Annularly-distributed multi-reflector laser triangulation distance measuring sensor

Abstract

The utility model discloses a novel annularly-distributed multi-reflector laser triangulation distance measuring sensor, which adopts a plurality of plane reflectors which are annularly or conically distributed. Light spots formed by irradiating laser to the surface of a measured target enter the lens after being reflected by the plurality of plane reflectors, are imaged on the image surface of the camera after passing through the lens, and form a series of annularly distributed image spots. And the diameter of the circular ring corresponds to the measured distance of the target, so that laser ranging can be realized. When the laser directivity is changed, the position of the circular ring is also changed, but the diameter of the circular ring is not changed, so that the influence of the laser directivity change can be thoroughly overcome in principle. According to the method, the laser directivity problem can be thoroughly solved, the distance measurement precision is remarkably improved, the cost of the multiple plane reflectors is far lower than that of an annular reflector, the precision is determined by a support and is easy to guarantee, and the method has wider practicability and universality.

Description

TECHNICAL FIELD

[0001] The utility model relates to a distance measuring sensor. Specifically, it is a laser triangulation distance measuring sensor which can overcome the change of laser directivity and has multiple annular distribution plane mirrors. BACKGROUND

[0002] There are generally four principles of laser ranging methods: laser time of flight (ToF), laser phase difference, laser triangulation and laser confocal. The time of flight method uses the time of flight of laser pulses to measure the distance of an object, which is only suitable for long-distance measurement and has low accuracy in short-distance measurement. The phase difference method uses the phase difference of continuous laser waves to measure the distance of an object, which is suitable for terminal distance measurement but still has low accuracy. The laser triangulation method is based on the principle of laser triangulation distance measurement and has high accuracy and large range, thus becoming the preferred method for short-distance high-precision measurement. The laser confocal method uses the principle of laser dispersion to measure the distance of an object, which has extremely high absolute accuracy but extremely small range, thus being obviously limited in application.

[0003] For a laser triangulation distance measuring sensor, the laser beam is its working medium and the distance measuring reference. When the directivity of the laser beam changes, it will cause the change of the imaging position of the measuring spot, thus causing measurement errors. Especially in the case of using a semiconductor laser, the directivity has both jitter and drift, which simultaneously affect the repeatability and stability of the distance measuring mutual inductor.

[0004] Some scholars have extended the classical laser triangulation distance measuring structure and established two symmetrical structures to measure the object from two directions. This scheme can weaken the influence of the change of the directivity of the laser beam, but cannot completely eliminate it. Especially when two different photoelectric devices are used, the compensation effect will be greatly reduced. At the same time, this symmetrical structure system is complex, expensive and difficult to implement, thus being difficult to popularize and apply.

[0005] The applicant has also proposed a laser triangulation distance measuring sensor with an annular mirror, which reflects the laser spot on the surface of the measured target in a 360° annular manner through the annular mirror, forms an imaging annulus on the image plane of the camera through the lens, and has a corresponding relationship between the diameter of the imaging annulus and the measured distance of the target, so that laser ranging can be realized. When the directivity of the laser changes, the position of the imaging annulus also changes, but the diameter of the imaging annulus does not change, thus completely overcoming the influence of the change of the directivity of the laser in principle and significantly improving the ranging accuracy. However, the annular mirror is difficult to manufacture, has high cost, high assembly precision requirement, is difficult to implement, has low precision, has low cost performance, and thus limits the practical application of the technical scheme. SUMMARY

[0006] The utility model discloses to the defect and insufficient of the prior art laser triangulation sensor to the laser directivity change, propose a kind of annular distribution multi-mirror laser triangulation sensor, adopt multiple plane mirrors to form annular or conical distribution.The light spot formed by laser irradiation to the measured target surface, after being reflected by multiple annular distribution plane mirrors, enter lens, form a series of circular image spots in the form of circular ring distribution on the image plane of camera by imaging through lens.This series of image spot center constitutes the circular ring diameter and the measured distance of target corresponding relationship, so that laser triangulation can be realized.When laser directivity changes, the position of the circular ring also changes, but the diameter of the circular ring does not change, so that the influence of laser directivity change can be completely overcome in principle.The method not only can completely solve the problem of laser directivity, significantly improve the ranging accuracy, and the cost of multiple plane mirrors is far lower than that of annular mirror, and the installation precision is determined by support, which is easy to ensure.The overall structure of the sensor is axisymmetric, and has wider practicability and universality.

[0007] The utility model is realized through the following technical schemes:

[0008] The utility model discloses a special annular distribution multi-mirror laser triangulation sensor, the sensor includes camera, lens, laser, focusing mirror, optical filter, mirror, support, shell, socket several parts, wherein:

[0009] The camera is industrial grade area array camera, located in the uppermost end inside the sensor, fixed on the shell, responsible for the reflection signal of laser light spot into image digital signal;

[0010] The lens is industrial grade lens, directly installed on the camera, responsible for the light spot signal reflected by mirror imaging on the image plane of camera;

[0011] The laser is industrial grade semiconductor laser, located at the lower end of lens a distance, installed at the center position of support, so that the optical axis of laser and the optical axis of lens are coaxial, for generating laser beam, and projecting to focusing mirror;

[0012] The focusing mirror is focusing collimating mirror group, also installed at the center position of support, the front end of laser, and the optical axis is coaxial with laser and lens, focusing mirror and laser keep a distance, responsible for focusing the divergent laser beam generated by laser, project to the measured target surface and form laser light spot, while having certain collimating function;

[0013] The optical filter is narrowband optical filter, and the center wavelength is consistent with the center wavelength of laser, and can filter out the interference of other wavelength ambient light;

[0014] The mirror is a plane mirror, and a plurality of mirrors are closely arranged on the support and symmetrically distributed around the optical axis of the lens in a ring shape or a conical shape, so that the laser spot can be reflected from all directions and projected to the lens.

[0015] The support is directly fixed in the shell and is used for positioning the laser, the focusing mirror and the plurality of mirrors, so that the laser, the focusing mirror and all the mirrors are coaxial, and the support has a hollow structure, so that the reflected light beam can pass through the support and enter the lens.

[0016] The shell is made of metal material and is used for fixing all the components and parts in the shell and mounting, positioning and fixing the whole sensor.

[0017] The socket is a general industrial socket arranged on the sealing cover and used for power supply and data transmission.

[0018] The working process of the annularly distributed multi-mirror laser triangulation sensor is as follows: the divergent laser beam emitted by the laser is converged into a focused laser beam by the focusing mirror, is projected to the measured target surface and forms a measurement spot, the measurement spot is reflected by the plurality of plane mirrors arranged in a ring shape, enters the lens, and is imaged on the image plane of the camera through the lens, so that a series of image spots distributed in a ring shape are formed. When the distance of the measured target changes, the diameter of the ring formed by the centers of the image spots also changes accordingly, so that the distance can be measured. When the laser directivity changes, the center position of the ring formed by the centers of the image spots also changes accordingly, but the diameter of the ring does not change, so that the influence of the laser directivity drift can be overcome.

[0019] The annularly distributed multi-mirror laser triangulation sensor is characterized in that the support is of an integral axisymmetric structure and is hollow, and is used for fixing the laser and the focusing mirror, so that the optical axes of the laser and the focusing mirror are coaxial with the optical axis of the lens; and the base is of a spoke hollow structure, so that the reflected light of the mirrors can pass through the support and enter the lens.

[0020] The annularly distributed multi-mirror laser triangulation sensor is characterized in that the cross section of the support is of an equilateral polygonal structure and is used for fixing the plurality of plane mirrors and forming the ring distribution; and the axial cross section of the support is rectangular or trapezoidal, and is determined according to different ranges and accuracies.

[0021] The annularly distributed multi-mirror laser triangulation sensor is characterized in that the symmetry error of the polygonal structure of the cross section of the support should be high enough, and is generally not lower than 1 / 5 of the distance measuring accuracy, so as to meet the requirement of the distance measuring accuracy.

[0022] The speciality of the annular distribution multi-mirror laser triangulation ranging sensor is that the mirror is a high reflectivity plane mirror, and the reflectivity is preferably not less than 90%; the mirrors are multiple, and the number of the mirrors is same as the number of the sides of the cross section polygon of the support.

[0023] The speciality of the annular distribution multi-mirror laser triangulation ranging sensor is that the distance between the annular distribution multi-mirror and the lens should be greater than the nearest measuring distance.

[0024] The speciality of the annular distribution multi-mirror laser triangulation ranging sensor is that the length of the annular distribution multi-mirror should meet the requirement of the farthest measuring distance, and should be greater than half of the difference between the farthest distance and the nearest distance.

[0025] The speciality of the annular distribution multi-mirror laser triangulation ranging sensor is that the shell is made of metal material, so that the overall stability and reliability of the sensor are ensured.

[0026] The speciality of the annular distribution multi-mirror laser triangulation ranging sensor is that the shell is of an integrated structure, is hollow, is used for fixing all the devices, and ensures the positional accuracy and stability of all the devices, and reduces the overall weight of the sensor.

[0027] The utility model provides a kind of processing method based on the above-mentioned annular distribution multi-mirror laser triangulation ranging sensor, specifically as follows:

[0028] (1) open laser, produce a laser to be measured target surface, and form a laser spot, the spot is reflected after multiple plane mirrors and enters lens, and multiple image spots are formed on camera imaging surface;

[0029] (2) the image of a camera is collected and sent into computer processing;

[0030] (3) each image spot is processed respectively, and the corresponding centroid point and its coordinate are extracted;

[0031] (4) multiple image spot centroid coordinates are used for circle fitting, and the center coordinates and radius are obtained;

[0032] (5) the corresponding measured target distance value is calculated using the saved calibration curve data. DRAWINGS

[0033] Figure 1 It is the sensor composition schematic view of the utility model;

[0034] Figure 2 It is the support structure schematic view of the utility model;

[0035] Figure 3 is the shell structure schematic diagram of the utility model;

[0036] Figure 4 is the data local processing principle schematic diagram of the utility model.

[0037] In the figure, 1-camera, 2-lens, 3-laser, 4-focusing mirror, 5-filter, 6-reflector, 7-bracket, 8-housing, 9-socket, 10-measured target. DETAILED DESCRIPTION

[0038] The embodiment of the utility model is described in detail below in combination with the drawings, and the embodiment is implemented on the premise of the technical scheme of the utility model, and detailed implementation mode and specific operation process are given, but the protection scope of the utility model is not limited to the following embodiment.

[0039] The speciality of the annular distribution multi-reflector laser triangulation ranging sensor of the utility model is that the sensor includes camera 1, lens 2, laser 3, focusing mirror 4, filter 5, reflector 6, bracket 7, housing 8, socket 9, as shown in Figure 1 , wherein:

[0040] Camera 1 is an industrial-grade area array camera, located at the uppermost end inside the sensor, fixed on the housing 9, responsible for converting laser spot signal into image digital signal;

[0041] The lens 2 is an industrial-grade lens, directly installed on the camera 1, responsible for imaging the laser signal reflected by the reflector 6 onto the image plane of the camera 1;

[0042] The laser 3 is an industrial-grade semiconductor laser, installed at the center position of the bracket 7, so that the optical axis of the laser 3 is coaxial with the optical axis of the lens 2, used for generating laser beam and projecting to the focusing mirror 4;

[0043] The focusing mirror 4 is a focusing collimating mirror group, also installed at the center position of the bracket 7 and the front end of the laser 3, and its optical axis is coaxial with the optical axes of the laser 3 and the lens 2, the focusing mirror 4 maintains a distance from the laser 3, responsible for focusing the divergent laser beam generated by the laser 3, projecting to the surface of the measured target 10 and forming a laser spot, and at the same time having a certain collimation function;

[0044] The filter 5 is a narrow-band filter, and the center wavelength is consistent with the center wavelength of the laser 3, which can filter out the interference of other wavelength ambient light;

[0045] The reflector 6 is a plane reflector, and there are multiple reflectors, such as eight plane reflectors 6. The reflector 6 is close to the support 7 and is arranged in a ring or cone shape with the optical axis of the lens 2 as the axis of symmetry. It can reflect the laser spot from all directions of 360° and project it onto the lens 2.

[0046] The bracket 7 is directly fixed inside the housing 8 and is used to simultaneously position the laser 3, the focusing lens 4 and multiple reflectors 6, ensuring that the laser 3, the focusing lens 4 and all reflectors 6 are coaxial. It also has a hollow structure so that the reflected beam can pass through and enter the lens 2.

[0047] The outer shell 8 is made of metal, which serves to fix all internal components and parts, and also to install, position and fix the entire sensor.

[0048] The socket 9 is a general-purpose industrial-grade socket, mounted on a sealed cover, used for power supply and data transmission.

[0049] The working process of the annularly distributed multi-reflector laser triangulation rangefinder sensor of this invention is as follows: The divergent laser beam emitted by the laser 3 is converged by the focusing lens 4 to form a focused laser beam. After passing through the filter 5, it is projected onto the surface of the target 10 and forms a measurement spot. This measurement spot is reflected by multiple annularly distributed planar reflectors 6 and enters the lens 2. The image is formed on the image plane of the camera 1 by the lens 2, forming a series of annularly distributed image spots. When the distance to the target 10 changes, the diameter of the annulus formed at the center of these image spots also changes accordingly, thereby achieving distance measurement. When the laser directionality changes, the center position of the annulus formed at the center of these image spots also changes accordingly, but the diameter of the annulus does not change, thus overcoming the influence of laser directionality drift.

[0050] The unique feature of this novel ring-distributed multi-reflector laser triangulation rangefinder sensor lies in the fact that the bracket 7 adopts an integrated axisymmetric structure, such as... Figure 2 As shown, the interior is hollow, used to fix the laser 3 and the focusing lens 4, ensuring that the optical axes of the laser 3 and the focusing lens 4 are coaxial with the optical axis of the lens 2; the base has a spoke-shaped hollow structure, ensuring that the reflected light from the reflector 6 can pass through the bracket 7 and enter the lens 2.

[0051] The unique feature of this circularly distributed multi-reflector laser triangulation rangefinder sensor lies in the fact that the cross-section of the support 7 is an equilateral polygonal structure, used to fix multiple planar reflectors 6 in a circular distribution; the axial section of the support 7 is rectangular or trapezoidal, depending on the different ranges and accuracies; for example... Figure 2 The bracket 7 shown has an equilateral octagonal cross-section, which can be used to install eight plane mirrors with a trapezoidal axial cross-section.

[0052] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the symmetry error of the polygonal structure of the support 7 should be high enough, generally not less than 1 / 5 of the ranging accuracy, so as to meet the ranging accuracy requirement.

[0053] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the mirror 6 is a high-reflectivity plane mirror, generally not less than 90%, for example, an aluminum-coated mirror; the mirror 6 has multiple pieces, and the number thereof is the same as the number of sides of the polygonal cross section of the support 7; for example Figure 2 The support shown in FIG. 8 is an octagon, and eight plane mirrors can be fixed.

[0054] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the distance between the annularly distributed multi-mirror 6 and the lens 2 should be greater than the nearest measurement distance; for example, for the nearest measurement distance of the lens 2 being 100 mm, the distance between the mirror 6 and the lens 2 should be greater than 110 mm.

[0055] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the length of the annularly distributed multi-mirror 2 should meet the requirement of the farthest measurement distance, and should be greater than half of the difference between the farthest distance and the nearest distance; for example, for the nearest measurement distance of the lens 2 being 100 mm, the range being 50 mm, and the farthest measurement distance being 150 mm, the length of the mirror 6 should be greater than 75 mm.

[0056] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the shell 8 is made of metal material, for example, aluminum alloy, stainless steel, etc., which ensures the overall stability and reliability of the sensor.

[0057] The special feature of the annularly distributed multi-mirror laser triangulation sensor is that the shell 8 adopts an integrated structure and is hollow inside, for fixing all the devices, which ensures the positional accuracy and stability of all the devices and reduces the overall weight of the sensor.

[0058] The utility model provides a kind of processing method based on the annularly distributed multi-mirror laser triangulation sensor described above, specifically as follows:

[0059] (1) turn on the laser 3, generate a laser to the surface of the measured target 10, and form a laser spot, which enters the lens 2 after being reflected by multiple plane mirrors 6, and forms multiple image spots on the imaging surface of the camera 1; as shown in FIG. 1, there are eight annularly distributed image spots; Figure 4

[0060] ​(2) Collect a camera image, sent into the computer processing, such as shown in Figure 4

[0061] (3) Process each spot respectively, and extract the corresponding centroid point and its coordinates; as shown in Figure 4 Eight spots can obtain eight centroid points and their coordinates P1(x1, y1), P2(x2, y2), …, P8(x8, y8);

[0062] (4) Use multiple spot centroid coordinates P1(x1, y1), P2(x2, y2), …, P8(x8, y8) to fit a circle, obtain the center point Pc and its coordinates Pc(xc, yc) and radius R;

[0063] (5) Use the saved calibration curve data f(x) to calculate the corresponding measured target distance value, that is, D=f(R).

[0064] Compared with the prior art, the annularly distributed multi-mirror laser triangulation sensor has the beneficial effects that:

[0065] (1) The annularly distributed multi-mirror laser triangulation sensor of the utility model, through multiple annularly distributed plane mirrors, reflects laser spots to form a series of annularly distributed spots, and uses the diameter of the annulus to measure the distance of the measured target, and the measurement accuracy is much higher than the single-point imaging point distance measurement accuracy, and the improvement amplitude will be several orders of magnitude;

[0066] (2) The annularly distributed multi-mirror laser triangulation sensor of the utility model, through multiple annularly distributed plane mirrors, reflects laser spots to form a series of annularly distributed spots, when the laser directivity changes, the position of the annulus also changes, but the diameter of the annulus does not change, so the influence of the laser directivity change can be completely overcome in principle;

[0067] (3) The annularly distributed multi-mirror laser triangulation sensor of the utility model, through multiple annularly distributed plane mirrors, reflects laser spots to form a series of annularly distributed spots, when the measured target is a step or other local shielding reflection light, individual spots also correspond to the phenomenon of shielding disappearance, but it does not affect the fitting and diameter calculation of the entire annulus, thereby effectively overcoming the reflection light shielding phenomenon; At the same time, no matter which direction appears local shielding, it does not affect the distance measurement function, so the direction dependence problem of the traditional laser triangulation is completely solved;

[0068] ​(4) The annularly distributed multi-mirror laser triangulation sensor of the utility model can be constructed by using general industrial lenses and cameras, low cost is realized, integration is easy, the displacement custom part is an annular mirror, and the cost can be reduced by batch customization, thereby laying a good foundation for popularization and application of the method;

[0069] (5) The annularly reflected structure laser triangulation sensor of the utility model has an overall structure that is axisymmetric, and the lateral dimension is obviously smaller than that of a conventional laser triangulation sensor, thereby having wider applicability and versatility.

[0070] (6) The annularly reflected structure laser triangulation sensor of the utility model uses multiple plane mirrors to replace the annular mirror, is simple to manufacture, has low cost, and thereby has outstanding performance-price ratio and promotional value.

[0071] (7) The annularly reflected structure laser triangulation sensor of the utility model uses a specially made bracket to fix multiple annularly distributed plane mirrors, the number and angle of which are adjustable and controllable, and is flexible and convenient.

[0072] Therefore, the technical scheme of the utility model has very outstanding advantages compared with the conventional laser triangulation sensor.

Claims

1. A ring-distributed multi-mirror laser triangulation sensor, characterized in that: The sensor comprises a camera, a lens, a laser, a focusing mirror, a filter, a mirror, a bracket, a housing, and a socket, wherein: The camera is an industrial-grade area array camera, located at the uppermost end inside the sensor housing, responsible for converting laser spot reflection signals into image signals; The lens is an industrial-grade lens, mounted on the camera, responsible for imaging the laser signals reflected by the mirror onto the image plane of the camera; The laser is an industrial-grade semiconductor laser, located at a distance below the lens, mounted at the center of the bracket, so that the laser optical axis is coaxial with the lens optical axis, used to generate a laser beam and project it onto the focusing mirror; The focusing mirror is a focusing collimating mirror group, with its optical axis coaxial with the laser and lens optical axes, located at the front end of the laser, responsible for focusing the divergent laser beam generated by the laser and projecting it onto the target surface to form a laser spot, while also having a certain collimating function; The filter is a narrow-band filter with a center wavelength consistent with that of the laser, capable of filtering out the interference of other wavelengths of ambient light; The mirror is a flat mirror, with multiple pieces closely arranged on the bracket, symmetrically distributed around the lens optical axis in a ring or cone shape, capable of reflecting the laser spot from all directions and projecting it onto the lens; The bracket is directly fixed inside the housing, used to position the laser, focusing mirror, and multiple mirrors simultaneously, ensuring that the laser, focusing mirror, and all mirrors are coaxial, while also having a hollow structure to allow the reflected light beam to pass through and enter the lens; The housing is made of metal material, which not only fixes all internal components and parts, but also serves as the mounting, positioning, and fixing of the entire sensor; The socket is a general industrial socket, placed on the sealing cover, used for power supply and data transmission.

2. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The bracket adopts an integrated axisymmetric structure, hollow inside, used to fix the laser and focusing mirror, ensuring that the optical axes of the laser and focusing mirror are coaxial with the lens optical axis; the base is a spoke-style hollow structure, ensuring that the reflected light of the ring-shaped mirror can pass through the bracket and enter the lens.

3. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The bracket cross-section is an equilateral polygon structure, used to fix multiple flat mirrors to form a ring-shaped distribution; the bracket cross-section is rectangular or trapezoidal.

4. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The symmetry error of the bracket cross-section polygon structure should be high enough, generally not less than 1 / 5 of the ranging accuracy, in order to meet the ranging accuracy requirements.

5. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The mirror is a high-reflectivity flat mirror, generally not less than 90% for better performance; there are multiple mirrors, with the number equal to the number of sides of the bracket cross-section polygon.

6. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The distance between the flat mirror and the lens should be greater than the nearest measurement distance.

7. The ring-distributed multi-mirror laser triangulation sensor of claim 1, wherein: The length of the flat mirror should meet the requirements of the farthest measurement distance, and should be greater than half the difference between the farthest and nearest distances.

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