A laser triangulation ranging sensor with an annular reflection structure

Abstract

The present invention provides a laser triangulation ranging sensor with an annular reflection structure, which performs 360° annular reflection on the laser spot on the surface of the measured target through an annular reflector, and forms an image on the image plane of the camera after passing through the lens, and forms a circular ring. The diameter of the imaging circular ring corresponds to the measured distance of the target, thereby realizing laser ranging. When the laser directivity changes, the position of the imaging circular ring also changes accordingly, but the diameter of the imaging circular ring does not change, thereby completely overcoming the influence of the change in laser directivity in principle. This method can not only completely solve the problem of laser directivity, but also significantly improve the ranging accuracy. The ranging sensor can adopt a general industrial-grade lens and camera, which is low-cost and easy to implement. The overall structure of the sensor is axisymmetric, and has wider practicality and versatility.

Description

Technical Field

[0001] The present invention relates to a distance measuring sensor, in particular to a laser triangulation distance measuring sensor with an annular reflection structure capable of overcoming the change of laser directivity. Background Art

[0002] There are generally four principles for laser ranging methods: laser time of flight (ToF), laser phase difference, laser triangulation and laser confocal method. The time of flight method uses the flight time of the laser pulse to measure the target distance. It is only suitable for long-distance measurement and has low accuracy when measuring close distances. The phase difference method uses the continuous fluctuation phase difference of the laser to measure the target distance. It is suitable for terminal distance measurement, but the accuracy is still very low. The laser triangulation method is a method based on the principle of laser triangulation to measure the target distance. It has excellent characteristics such as high accuracy and large range, making it the preferred method for short-distance high-precision ranging. The laser confocal method uses the principle of laser dispersion to measure the target distance. It is characterized by extremely high absolute accuracy, but the range is also extremely small, and its application is obviously limited.

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

[0004] Some scholars have expanded the classic laser triangulation ranging structure and established two symmetrical structures on the left and right to measure the object to be measured from two directions. This solution can weaken the influence of the change in the directivity of the laser beam, but it cannot completely eliminate it. In particular, when two different optoelectronic devices are used on the left and right, the compensation effect will be greatly reduced. At the same time, this symmetrical structure system is complex, expensive, difficult to implement, and difficult to promote and apply. Summary of the invention

[0005] The present invention aims at the serious defect that the existing laser triangulation ranging sensor is sensitive to the change of laser directivity, and proposes a method of an annular reflection structure, which adopts an annular reflector to reflect the laser spot on the surface of the measured target in a 360° annular manner, and then forms an image on the image plane of the camera through the lens to form a circular ring. The diameter of the imaging circular ring corresponds to the measured distance of the target, thereby realizing laser ranging. When the laser directivity changes, the position of the imaging circular ring also changes, but the diameter of the imaging circular ring does not change, thereby completely overcoming the influence of the change of laser directivity in principle. This method can not only completely solve the problem of laser directivity, but also significantly improve the ranging accuracy. The sensor can be constructed using a general industrial-grade lens and camera, which is low-cost and easy to implement. The overall structure of the sensor is axisymmetric, and has wider practicality and versatility.

[0006] The present invention is achieved through the following technical solutions:

[0007] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the sensor includes several parts such as a camera, a lens, a laser, a focusing mirror, a reflector, and a filter, among which:

[0008] The camera is an industrial-grade area array camera, located at the top of the sensor, responsible for converting light signals into image signals;

[0009] The lens is an industrial-grade lens, which is installed on the camera and is responsible for imaging the light signal reflected by the reflector onto the image plane of the camera;

[0010] The laser is an industrial-grade semiconductor laser, located at the lower end of the lens, with the optical axis of the laser coaxial with the optical axis of the lens and a certain distance between them, used to generate a laser beam and project it to the focusing lens;

[0011] The focusing lens is a focusing collimating lens group, whose optical axis is coaxial with the laser and the lens optical axis, and is responsible for focusing the divergent laser beam generated by the laser, projecting it onto the surface of the target to be measured and forming a laser spot, and at the same time has a certain collimation function;

[0012] The reflector is an annular reflector, whose optical axis is coaxial with the optical axes of the focusing mirror, the laser and the lens, and whose inner cylindrical surface has high reflectivity, and can reflect the laser spot from 360° direction and project it to the lens;

[0013] The filter is a narrow-band filter, the central wavelength of which is consistent with the central wavelength of the laser, and can filter out interference from ambient light of other wavelengths.

[0014] The working process of the ring-shaped reflection structure laser triangulation distance sensor of the present invention is as follows: the divergent laser beam emitted by the laser is converged by the focusing mirror to form a focused laser beam, which is projected onto the surface of the measured target and forms a measuring light spot. The measuring light spot enters the lens after being reflected by the ring-shaped reflector, and is imaged on the image plane of the lens through the lens to form an imaging ring. When the distance of the measured target changes, the diameter of the imaging ring also changes accordingly, thereby achieving distance measurement.

[0015] The special feature of the ring-shaped reflective structure laser triangulation distance measuring sensor of the present invention is that the ring-shaped reflector can be made of optical materials or metal materials.

[0016] The special feature of the annular reflective structure laser triangulation ranging sensor of the present invention is that the cylindricity error of the inner cylindrical surface of the annular reflector should be high enough, generally not less than 1 / 5 of the ranging accuracy, so as to meet the requirements of ranging accuracy.

[0017] The special feature of the annular reflective structure laser triangulation ranging sensor of the present invention is that the reflectivity of the inner cylindrical surface of the annular reflector should be high enough to meet the camera sensitivity requirement, and is generally not less than 80%.

[0018] The special feature of the ring-shaped reflective structure laser triangulation distance measuring sensor of the present invention is that the distance between the ring-shaped reflector and the lens should meet the requirement of the closest measuring distance and should be slightly larger than the closest measuring distance.

[0019] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the length of the ring-shaped reflector should meet the requirement of the farthest measuring distance and should be greater than half of the difference between the farthest distance and the shortest distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the composition of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention;

[0021] Figure 2 It is a schematic diagram of the optical composition structure of the sensor of the present invention;

[0022] In the figure, 1-camera, 2-lens, 3-laser, 4-focusing mirror, 5-reflecting mirror, 6-filter, 7-target to be measured. DETAILED DESCRIPTION

[0023] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiment.

[0024] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the sensor comprises a camera 1, a lens 2, a laser 3, a focusing lens 4, a reflector 5, a filter 6 and the like. Figure 1 As shown, where:

[0025] The camera 1 is an industrial-grade area array camera, located at the top of the entire sensor, responsible for converting the light signal transmitted by the lens 2 into an image signal; in order to ensure that the volume of the entire sensor is relatively compact, a small-sized industrial-grade camera is preferably used;

[0026] The lens 2 is an industrial-grade lens, which is directly mounted on the camera 1 and is responsible for imaging the light signal reflected by the reflector 5 onto the image plane of the camera 1. In order to ensure that the volume of the entire sensor is relatively compact, a small-sized industrial-grade lens is preferably used;

[0027] The laser 3 is an industrial-grade semiconductor laser, located at the lower end of the lens 2. The optical axis of the laser 4 is coaxial with the optical axis of the lens 2 and is kept at a distance. The laser beam is used to generate a laser beam and project it to the focusing lens 4.

[0028] The focusing lens 4 is a focusing collimating lens group, whose optical axis is coaxial with the optical axis of the laser 3 and the lens 2, and is responsible for focusing the divergent laser beam generated by the laser 3, projecting it onto the surface of the target 7 to form a laser spot, and also has a certain collimation function;

[0029] The reflector 5 is an annular reflector, whose optical axis is coaxial with the optical axes of the focusing mirror 4, the laser 3 and the lens 2, and whose inner cylindrical surface has high reflectivity, and can reflect the laser spot from 360° direction and project it to the lens 2;

[0030] The filter 6 is a narrow-band filter, the central wavelength of which is consistent with the central wavelength of the laser 3, and can filter out interference from ambient light of other wavelengths.

[0031] The working process of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is as follows: the divergent laser beam emitted by the laser 3 is converged by the focusing mirror 4 to form a focused laser beam, which is projected onto the surface of the measured target 7 and forms a measuring light spot, which enters the lens 2 after being reflected by the ring-shaped reflector 5, and is imaged on the image plane of the camera 1 through the lens 2 to form an imaging ring. When the distance of the measured target 7 changes, the diameter of the imaging ring also changes accordingly, thereby achieving ranging.

[0032] The special feature of the annular reflective structure laser triangulation ranging sensor of the present invention is that the annular reflector 5 can be made of optical materials, such as quartz glass, resin, organic glass and the like; it can also be made of metal materials, such as steel, aluminum alloy, brass and the like.

[0033] The special feature of the annular reflection structure laser triangulation ranging sensor of the present invention is that the cylindricity error of the inner cylindrical surface of the annular reflector 5 should be high enough, generally not less than 1 / 5 of the ranging accuracy, so as to meet the ranging accuracy requirement; assuming that the ranging accuracy requirement is ±1um, the cylindricity error of the inner cylindrical surface of the annular reflector 5 should not be less than ±5um.

[0034] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the reflectivity of the inner cylindrical surface of the ring-shaped reflector 5 should be high enough to meet the requirements of camera sensitivity, and is generally not less than 80%.

[0035] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the distance between the ring-shaped reflector 5 and the lens 2 should meet the requirements of the closest measuring distance and should be slightly larger than the closest measuring distance; Figure 2 As shown, assuming that the closest measuring distance is 50 mm, the distance between the annular reflector 5 and the lens 2 should be no less than 50 mm.

[0036] The special feature of the ring-shaped reflective structure laser triangulation ranging sensor of the present invention is that the length of the ring-shaped reflector 5 should meet the requirements of the farthest measuring distance and should be greater than half of the difference between the farthest distance and the shortest distance; Figure 2 As shown, assuming that the closest measuring distance is 50 mm and the farthest measuring distance is 100 mm, the length of the annular reflector 5 should be no less than 25 mm.

[0037] Compared with the prior art, the annular reflection structure laser triangulation ranging sensor of the present invention has the following beneficial effects:

[0038] (1) The ring-shaped reflective structure laser triangulation ranging sensor of the present invention reflects the laser spot through the ring-shaped reflector to form an imaging ring, and uses the diameter of the imaging ring to measure the distance of the measured target. Its measurement accuracy is much higher than the ranging accuracy of a single imaging point, and the improvement is several times higher.

[0039] (2) The ring-shaped reflective structure laser triangulation ranging sensor of the present invention reflects the laser spot through the ring-shaped reflector to form an imaging ring. When the laser directivity changes, the position of the imaging ring also changes, but the diameter of the imaging ring does not change. Therefore, the influence of the change of laser directivity can be completely overcome in principle.

[0040] (3) The ring-shaped reflective structure laser triangulation ranging sensor of the present invention reflects the laser spot through the ring-shaped reflector to form an imaging ring. When the measured target is a step or other part that partially blocks the reflected light, the imaging ring will also be partially missing, but it will not affect the fitting and diameter calculation of the entire imaging ring, thereby effectively overcoming the reflected light blocking phenomenon; at the same time, no matter which direction the local blocking occurs, it will not affect the ranging function, thus completely getting rid of the direction dependence problem of traditional laser triangulation ranging;

[0041] (4) The annular reflective structure laser triangulation ranging sensor of the present invention can be constructed using a general industrial-grade lens and camera, which is low-cost and easy to integrate. The customized displacement part is an annular reflector, which can reduce costs through batch customization, thereby providing a good foundation for the promotion and application of this method.

[0042] (5) The overall structure of the annular reflective structure laser triangulation ranging sensor of the present invention is axially symmetrical, and its lateral size is significantly smaller than that of the traditional laser triangulation ranging sensor, so it has wider applicability and versatility.

[0043] It can be seen that the technical solution of the present invention has very outstanding advantages compared with the traditional laser triangulation ranging sensor.

Claims

1. A laser triangulation ranging sensor with an annular reflection structure, characterized in that: The sensor includes a camera, a lens, a laser, a focusing mirror, a reflector, and a filter, wherein: The camera is an industrial-grade area array camera, located at the top of the sensor, responsible for converting light signals into image signals; The lens is an industrial-grade lens, which is installed on the camera and is responsible for imaging the light signal reflected by the reflector onto the image plane of the camera; The laser is an industrial-grade semiconductor laser, located at the lower end of the lens, with the optical axis of the laser coaxial with the optical axis of the lens and a certain distance between them, used to generate a laser beam and project it to the focusing lens; The focusing lens is a focusing collimating lens group, whose optical axis is coaxial with the laser and the lens optical axis, and is responsible for focusing the divergent laser beam generated by the laser, projecting it onto the surface of the target to be measured and forming a laser spot, and at the same time has a certain collimation function; The reflector is an annular reflector, whose optical axis is coaxial with the optical axes of the focusing mirror, the laser and the lens, and whose inner cylindrical surface has high reflectivity, and can reflect the laser spot from 360° direction and project it to the lens; The filter is a narrow-band filter, the central wavelength of which is consistent with the central wavelength of the laser, and can filter out interference from ambient light of other wavelengths.

2. The laser triangulation ranging sensor according to claim 1, further characterized in that: The annular reflector can be made of optical materials or metal materials.

3. The laser triangulation ranging sensor according to claim 1, further characterized in that: The cylindricality error of the inner cylindrical surface of the annular reflector is high enough and is not less than 1 / 5 of the ranging accuracy.

4. The laser triangulation ranging sensor according to claim 1, further characterized by: The reflectivity of the inner cylindrical surface of the annular reflector is high enough, preferably not less than 80%.

5. The laser triangulation ranging sensor according to claim 1, further characterized by: The distance between the annular reflector and the lens meets the requirement of the closest measuring distance and is greater than the closest measuring distance.

6. The laser triangulation ranging sensor according to claim 1, further characterized by: The length of the annular reflector meets the requirement of the farthest measuring distance and is greater than half of the difference between the farthest distance and the shortest distance.

Images