CN116184360A - Laser triangle distance measuring sensor - Google Patents

Abstract

The invention discloses a laser triangular ranging sensor, which comprises a laser light source, a transmitting lens group, a receiving lens group and a photoelectric device, wherein the transmitting lens group and a measured target are positioned on a transmitting light path of the laser light source; a wedge-shaped mirror is arranged on an optical path between the receiving mirror group and the photoelectric device, and can reflect reflected light transmitted through the receiving mirror group to the photoelectric device. The wedge-shaped mirror arranged behind the receiving mirror group is used for reflecting the reflected light of the measured object to the photoelectric device for imaging, and the optical path difference generated at the two measuring ends of the laser triangular ranging sensor is compensated by the wedge-shaped mirror due to the fact that the wedge-shaped mirror is provided with the thick end and the thin end, so that better imaging quality can be obtained.

Description

Laser triangle distance measuring sensor

Technical Field

The invention relates to the technical field of optical measurement, in particular to a laser triangular ranging sensor.

Background

The displacement sensor based on the laser triangulation ranging principle has the excellent characteristics of non-contact, high precision, wide range, high reliability, no harsh requirement on a measured target and the like. The imaging light spot of the light spot has a certain size on the photosensitive device, and the central position of the imaging light spot needs to be found through software algorithms such as a binary method, a gray level centroid method and the like. However, the methods are all carried out on the basis of supposing that the energy of imaging light spots is in Gaussian distribution, in the traditional laser triangulation ranging sensor, the diffuse reflection light of different distance targets has different signal intensities corresponding to the imaging light spots on a photosensitive surface, and the corresponding light spots have different sizes and shapes, so that the calculated light spot centers are changed, and the measurement accuracy is affected.

This effect is particularly severe at both ends of the range of the laser triangulation sensor. This is because the optical system of a conventional laser delta displacement sensor adopts a constant focusing form, and laser spots are reflected from different object plane positions into a focusing lens group. Because of the lens imaging rule, the point closer to the lens has larger magnification, the point farther from the lens has smaller magnification, the corresponding measured object has small moving distance at the near end and large moving distance at the far end, thus affecting the imaging quality, namely the resolution still has the problem of non-uniformity in the range.

Disclosure of Invention

The invention discloses a laser triangular ranging sensor for improving measurement accuracy, which reduces the influence of optical path difference imaging quality brought by two ends of a measuring range.

In order to solve the problems, the invention adopts the following technical scheme: the laser triangular ranging sensor comprises a laser light source, a transmitting lens group, a receiving lens group and a photoelectric device, wherein the transmitting lens group and the measured object are positioned on a transmitting light path of the laser light source, the receiving lens group is positioned on a reflecting light path of laser reflected by the measured object, a wedge-shaped lens is arranged on a light path between the receiving lens group and the photoelectric device, and the wedge-shaped lens can reflect light transmitted by the receiving lens group to the photoelectric device; the wedge-shaped mirror is a perspective mirror and comprises a transmission surface facing the receiving mirror group and a reflection surface facing away from the receiving mirror group; the transmission surface is obliquely arranged relative to the light emergent surface of the receiving mirror group and the light incident surface of the photoelectric device, the thick end of the wedge-shaped mirror is far away from the receiving mirror group, and the thin end of the wedge-shaped mirror is close to the receiving mirror group.

Further, the transmittance of the transmission surface is greater than 99.5%, and the reflectance of the reflection surface is greater than 95%.

Further, the thickness of the mirror body between the transmission surface and the reflection surface is uniformly increased or decreased along the same direction.

Further, a focusing lens is arranged on the light path between the wedge-shaped lens and the photoelectric device.

Further, the focusing lens is obliquely arranged relative to the light path.

Further, a bandpass filter is arranged on the light path of the receiving lens group at one side close to the measured object.

Further, a diaphragm is arranged on the light path between the receiving mirror group and the wedge-shaped mirror.

Further, the photoelectric device is a linear array CCD.

Further, a correction mirror is arranged on a light path between the receiving mirror group and the wedge-shaped mirror or a light path between the wedge-shaped mirror and the photoelectric device.

The technical scheme adopted by the invention can achieve the following beneficial effects:

1. the wedge-shaped mirror arranged behind the receiving mirror group reflects the reflected light of the measured object to the photoelectric device for imaging, and as the wedge-shaped mirror has thick and thin ends and is uniform and excessive between the thick and thin ends, the optical path difference generated at the two measuring ends of the laser triangular ranging sensor is compensated by the wedge-shaped mirror, so that better imaging quality can be obtained;

2. the reflected light generated on the transmission surface and the reflected light reflection path generated on the reflection surface have deviation through the introduced wedge-shaped mirror, so that the stray light generated by the transmission mirror surface can be furthest limited from entering the photoelectric device, and the interference on the test result is reduced;

3. the wedge-shaped mirror in the invention is only used for replacing the position of the plane reflecting mirror in the related technology, and a lens is not additionally arranged, so that the structural variation is not large, and the size of the sensor is not changed due to the addition of a device.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a laser triangulation ranging sensor according to the present invention;

FIG. 2 is a schematic diagram of a conventional laser triangulation ranging sensor;

FIG. 3 is a schematic diagram showing a comparison of focus spot circles on a photosurface before and after modification of a conventional sensor;

FIG. 4 is a graph showing the shape of a focused light spot on a photosensitive surface of a conventional sensor according to different test distances;

FIG. 5 is a graph of the shape of a focused spot on a photosurface of a sensor according to the invention as a function of different test distances;

1-a laser light source; 2-an emission mirror group; 3-a receiving lens group; 4-wedge mirrors; 5-optoelectronic devices; 6-band pass filters; 7-a focus expanding lens; 8 plane mirrors.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples herein, which are within the scope of the invention as defined by the claims, will be within the scope of the invention as defined by the claims.

The terms first, second and the like in the description and in the claims, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged, as appropriate, such that embodiments of the present application may be implemented in sequences other than those illustrated or described herein, and that the objects identified by "first," "second," etc. are generally of a type and not limited to the number of objects, e.g., the first object may be one or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.

The laser triangulation ranging sensor provided in the embodiment of the present application is described in detail below with reference to fig. 1 through a specific embodiment and an application scenario thereof.

The invention relates to a laser triangular ranging sensor, which comprises a laser light source 1, a transmitting lens group 2, a receiving lens group 3 and a photoelectric device 5, wherein the transmitting lens group 2 and a measured object are positioned on a transmitting light path of the laser light source 1, the receiving lens group 3 is positioned on a reflecting light path of laser reflected by the measured object, a wedge-shaped lens 4 is arranged on a light path between the receiving lens group 3 and the photoelectric device 5, and the wedge-shaped lens 4 can reflect light transmitted by the receiving lens group 3 to the photoelectric device 5; the wedge-shaped mirror 4 is a transflector, and the wedge-shaped mirror 4 comprises a transmission surface facing the receiving mirror group 3 and a reflection surface facing away from the receiving mirror group 3; the transmission surface is obliquely arranged relative to the light emergent surface of the receiving lens group 3 and the light incident surface of the photoelectric device 5, the thick end of the wedge-shaped lens 4 is far away from the receiving lens group 3, the thin end of the wedge-shaped lens 4 is close to the receiving lens group 3, the reflected light of a long-distance measured object is close to the thin end of the wedge-shaped lens 4 and the reflected light of a short-distance measured object is close to the thick end of the wedge-shaped lens 4.

The shape of the wedge-shaped mirror 4 can be similar to a wedge used in woodworking technology, the thickness of the wedge-shaped mirror 4 gradually decreases or increases from one end of the mirror body to the other end corresponding to the wedge-shaped mirror 4 to form a non-axisymmetric lens structure, the transmission surface and the reflection surface of the wedge-shaped mirror 4 can be triangular, square, round or other shapes, and preferably, the thickness of the mirror body between the transmission surface and the reflection surface uniformly changes along the same length direction or width direction.

When laser ranging is performed, diffuse reflection light of light spots on a measured object passes through the receiving mirror group 3 and then is reflected by the wedge-shaped mirror 4 to be imaged on the photoelectric device 5. Wherein, most of diffuse reflection light firstly passes through the transmission surface of the wedge-shaped mirror 4 in the process of passing through the wedge-shaped mirror 4, then is reflected on the reflection surface of the wedge-shaped mirror 4, finally is emitted to the photoelectric device 5 through the transmission surface and is imaged through the photoelectric device 5; the transmission surface of the wedge-shaped mirror 4 is both an incident surface and a reflecting surface, i.e. the transmission surface of the wedge-shaped mirror 4 is arranged facing the light outgoing side of the receiving mirror group 3 and the light incoming side of the optoelectronic device 5. The diffuse reflection light of the measured object passes through the wedge-shaped mirror 4 to generate a section of optical path, and the section of optical path corrects the optical path difference at the two ends of the measuring range, so that the resolution in the measuring range is more uniform. The measuring range of the laser triangular distance measuring sensor refers to the testing range between the farthest testing distance and the nearest testing distance between the sensor and the tested object, and the two ends of the measuring range are the far end and the near end. The diffuse reflection light projection position of the measured object at the far end is deviated towards the thin end of the wedge-shaped mirror 4, the diffuse reflection light projection position of the measured object at the near end is deviated towards the thick end of the wedge-shaped mirror 4, the diffuse reflection light is reflected on the reflecting surface of the wedge-shaped mirror 4, and the light passes through two optical paths in the wedge-shaped mirror 4. The optical path difference generated at the two ends of the measuring range is properly adjusted through the wedge-shaped mirror 4, so that the optical path of diffuse reflection light generated at different test distances of a measured object to the photoelectric device 5 is similar, the optical path difference is reduced, and further, the corresponding shape of imaging light spots on the photosensitive surface of the photoelectric device 5 is the same or small, the light spots are distributed in Gaussian, and the measuring precision is improved.

Next, referring to fig. 2, in the related art, a plane mirror 8 is disposed at the position of the wedge-shaped mirror 4 in the present invention to reflect the reflected light of the receiving mirror set 3 onto the optoelectronic device 5, and then image on the photosensitive surface of the optoelectronic device 5; however, even in the case of the plane mirror 8, part of the light enters the back surface through the reflecting surface, and is reflected by the back surface to reach the optoelectronic device 5, and then is imaged on the photosensitive surface; because the two surfaces of the plane reflecting mirror 8 are in parallel relation, light reflected by the back surface of the reflecting surface of the plane reflecting mirror 8 becomes stray light, and the stray light reaches the photoelectric device 5 to greatly influence the test result. In addition, the wedge-shaped mirror 4 in the invention is only used for replacing the position of the plane reflecting mirror 8 in the related art, and is not provided with a lens, so that the structural variation is small, the size of the sensor is not changed due to the addition of a device, and the sensor does not need to be subjected to excessive structural design.

In order to improve the measurement accuracy of the sensor, sufficient imaging strength needs to be ensured, the transmittance of the transmission surface of the wedge-shaped mirror 4 is greater than 99.5%, the reflectance of the reflection surface of the wedge-shaped mirror 4 is greater than 95%, and the transmittance of the transmission surface and the reflectance of the reflection surface can be realized through a coating process.

The installation position of the wedge-shaped mirror 4, the angle between the transmission surface and the reflection surface, the working distance of the sensor itself, the distance between the receiving end and the transmitting end, the lens material, the position of the photoelectric device 5 and other influence factors are related, and when the optical design is performed, the factors are comprehensively considered, and the optimal focusing light spot of the linear array CCD is obtained through simulation, so that the installation position of the wedge-shaped mirror 4, the angle between the transmission surface and the reflection surface and the lens material are determined.

Further, a focusing mirror 7 is provided on the optical path between the wedge mirror 4 and the optoelectronic device 5. The focal length of the lens of the focus expanding lens 7 is negative, so that the focusing position is increased, the position of the focusing point on the linear array is increased, and therefore, the total number of pixels of the CCD on the linear array can be utilized as much as possible, and clearer tiny changes can be distinguished, so that the measurement precision is improved.

Further, the focusing lens 7 is disposed obliquely with respect to the optical path. The light is refracted to different degrees by reflecting laser at different positions after passing through the wedge-shaped mirror 4, so that the light deviates from the original position to different degrees, the light can be corrected by the inclination of the inclined focusing expanding mirror 7, and the deviation influence of the asymmetric structure of the wedge-shaped mirror 4 on the light is reduced. In another embodiment of the present invention, a correction mirror is disposed on the optical path between the receiving mirror group 3 and the wedge-shaped mirror 4 or the optical path between the wedge-shaped mirror 4 and the optoelectronic device 5, the correction mirror has a shape similar to the wedge-shaped mirror 4, and the correction mirror is a lens, so that light with different degrees of refraction deviation can be corrected.

Further, a diaphragm is provided on the optical path between the receiving mirror group 3 and the wedge mirror 4. The diaphragm is used for shielding stray light at the periphery of the light beam, so that imaging quality can be improved, light spots are distributed in a Gaussian mode, external environment light can be shielded, and the resistance of the triangular ranging system to the environment light is improved.

Through the cooperation of the wedge-shaped mirror 4, the diaphragm, the receiving mirror group 3 and the focus expanding mirror 7, the distortion phenomenon caused by the optical path difference at two ends of the measuring range is greatly reduced when the laser triangular distance measuring sensor is used for measuring distance, light spots are Gaussian distributed on the receiving surface, and the influence of the distance of a target object on measuring accuracy is greatly reduced. Referring to fig. 3, compared with the light spot dispersion circles on the front and rear photosurfaces, the difference of the light spots in the vertical direction before improvement is large, the light spots in all directions after improvement are nearly restrained, and the light spots are round and distributed in gaussian; referring to fig. 4 and 5, the graphs show that in the meridian direction test process, the light spot shape on the photosensitive surface and the distance between the measured object and the sensor change, the solid line is normal distribution along with the test distance in the meridian direction, the broken line is deviation in the sagittal direction, the test condition of the traditional laser triangulation ranging sensor is shown in fig. 4, the test condition of the laser triangulation ranging sensor is shown in fig. 5, and compared with the two graphs, the focus light spot obtained by the test in the invention synchronously changes along with the change of the distance in both directions, so that the focus light spot is in gaussian distribution, the imaging quality is effectively improved, and the light spot distortion phenomenon is reduced.

Further, a bandpass filter 6 is disposed on the optical path of the receiving lens group 3 near the side of the measured object. The band-pass filter 6 can filter stray light of other frequency spectrums, such as natural light, artificial light and the like from the outside, only allows light of a working frequency band to pass, and effectively avoids other stray light from entering the sensor to cause interference to a detection result. Through the cooperation of band-pass filter 6 and wedge mirror 4, in the in-process of carrying out the range finding, reduce the influence to the test result because the stray light that exists outside the sensor and inside, improve the measurement accuracy.

Further, the optoelectronic device 5 in the laser triangulation ranging sensor is a linear array CCD. The CCD is made of a semiconductor material with high sensitivity, can convert light into electric charge, and convert the electric charge into digital signals through an analog-to-digital converter chip, and the digital signals are stored by a flash memory or a built-in hard disk card in the camera after being compressed, so that the data can be easily transmitted to a computer, and the image can be modified according to the needs and imagination by means of the processing means of the computer. CCDs are composed of a number of photosensitive units, typically in megapixels. When the CCD surface is irradiated by light, each photosensitive unit reflects charges on the component, and signals generated by all the photosensitive units are added together to form a complete picture. The linear array CCD consists of a photosensitive area array and a shift register scanning circuit, and has the advantages of high information processing speed, simple peripheral circuit and easy realization of real-time control.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of the present application is not limited to performing the functions in the order shown or discussed, but may also include performing the functions in a substantially simultaneous manner or in an opposite order depending on the functions involved, e.g., the described methods may be performed in an order different from that described, and various steps may also be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention.

Claims (9)

1. The laser triangular distance measuring sensor is characterized in that,

the device comprises a laser light source, a transmitting lens group, a receiving lens group and a photoelectric device, wherein the transmitting lens group and the measured target are positioned on a transmitting light path of the laser light source, and the receiving lens group is positioned on a reflecting light path of laser reflected by the measured target;

a wedge-shaped mirror is arranged on a light path between the receiving mirror group and the photoelectric device, and can reflect the light transmitted through the receiving mirror group to the photoelectric device; the wedge-shaped mirror is a perspective mirror and comprises a transmission surface facing the receiving mirror group and a reflection surface facing away from the receiving mirror group;

the transmission surface is obliquely arranged relative to the light emitting surface of the receiving lens group, the thick end of the wedge-shaped lens is far away from the receiving lens group, and the thin end of the wedge-shaped lens is close to the receiving lens group.

2. The laser triangulation ranging sensor according to claim 1, wherein the transmittance of the transmissive surface is greater than 99.5% and the reflectance of the reflective surface is greater than 95%.

3. The laser triangulation ranging sensor according to claim 1, wherein a mirror thickness between the transmissive surface and the reflective surface increases or decreases uniformly in the same direction.

4. The laser triangulation ranging sensor according to claim 1, characterized in that a focusing mirror is arranged on the optical path between the wedge mirror and the optoelectronic device 5.

5. The laser triangulation ranging sensor as claimed in claim 4, wherein the focusing mirror is disposed obliquely with respect to the optical path.

6. The laser triangulation ranging sensor according to claim 1, wherein a bandpass filter is provided on an optical path of a side of the receiving lens group close to the object to be measured.

7. The laser triangulation ranging sensor according to claim 1, wherein a diaphragm is provided on an optical path between the receiving mirror group and the wedge mirror.

8. The laser triangulation ranging sensor according to claim 1, wherein the optoelectronic device is a linear array CCD.

9. The laser triangulation ranging sensor according to any one of claims 1 to 8, wherein a correction mirror is provided on an optical path between the receiving mirror group and the wedge mirror or an optical path between the wedge mirror and the optoelectronic device.

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