Laser triangulation distance measuring device

Abstract

The utility model discloses a laser triangulation distance measuring device. The device comprises a laser emission light path module, a combined prism, a receiving lens group and a photoelectric detector which are arranged on the same side of a side to be measured, the receiving lens group is positioned between the combined prism and the photoelectric detector; the combined prism is formed by combining a quasi-orthorhombic prism and an auxiliary prism, the quasi-orthorhombic prism is a prism with a parallelogram-shaped cross section ABCE, the auxiliary prism is a prism with a triangle-shaped cross section BCE, and the quasi-orthorhombic prism and the auxiliary prism are overlapped or coplanar on an AE plane, so that a plane BC of the auxiliary prism is parallel to a plane BC of the quasi-orthorhombic prism; the positions of the output light beam of the laser emission light path module, the receiving lens group and the photoelectric detector need to meet the Sammer condition, namely, the output light beam of the laser emission light path module, the main surface of the receiving lens group and the photosensitive surface of the photoelectric detector intersect at one point. According to the utility model, the problem that the measurement result is influenced by laser angle temperature drift when a high-temperature object is measured by a traditional laser triangulation method can be solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of laser ranging, and particularly relates to a laser triangulation ranging device. Background Technique

[0002] The significance of ranging technology lies in providing an accurate, reliable and efficient means to obtain the distance and position of an object, providing important support and guarantee for scientific research and applications in various fields. Its application in the field of industrial measurement is of great significance for the development of industrial automation. Laser triangulation is an important ranging method, which has the advantages of non-contact, high sampling rate, high resolution and flexible deployment. It is widely used for ranging in the range of 10mm to 1000mm in the fields of industrial measurement, machine vision, etc. In some applications, it is also combined with the scanning of the object to be measured to realize three-dimensional contour and morphology detection. At present, there are a large number of commercial products using laser triangulation ranging on the market, such as the product series of Keyence Corporation in Japan, LK-G400 / G405 / G500 / G505, etc.

[0003] The accuracy of high-precision measurement equipment is often affected by its working environment. For high-precision optoelectronic measurement devices, the relative positions and relative angles between the optoelectronic components in the measurement device change slightly with the use environment. For example, for a laser composed of multiple components, the angle of the output laser beam has a temperature drift. Even in a relatively small working temperature range of 10~30°C, the typical value of its temperature drift can reach 0.01~10mrad. The drift caused by such environmental factors is the main reason for the decrease in the accuracy of optoelectronic measurement devices.

[0004] Although laser triangulation has good resolution, the accuracy of its test results depends on the relative position stability between the components of the test equipment. After high-precision calibration under good stability conditions, it can be ensured that the corrected test results have good accuracy. In order to pursue better accuracy, in laser triangulation measurement, a complex error compensation model is generally used to compensate for the influence of environmental parameters such as environmental temperature, environmental humidity, and atmospheric pressure on the measurement results; in addition, in order to ensure the relative position stability between the components of the test equipment, such equipment often needs to be preheated for a period of time after being powered on to reach a stable state before starting to measure.

[0005] However, with the development trend of Industry 4.0, all walks of life have put forward the demand for industrial detection automation. Some industry application scenarios have harsh, complex or unstable environments due to the particularity of their applications, and some scenarios do not allow the test equipment to have a preheating stage. In such application scenarios, the application of laser triangulation measurement equipment is difficult to obtain test results with good accuracy. For example: in the fields of steel metallurgy / casting, aluminum electrolysis, there is a high temperature environment due to the influence of heat transfer and thermal radiation. In some chemical fields, there is also a high humidity environment. In these application scenarios, the test equipment not only faces harsh environmental parameters (such as high temperature), but also faces the problem of uneven distribution of environmental parameters in the spatial range of the measurement equipment (such as temperature field). The error compensation model of the measurement equipment often cannot compensate for extreme environmental parameters, let alone the complex spatial distribution of environmental parameters. In addition, the hardware of the test equipment itself cannot reach a steady state in its harsh environment, especially when high real-time requirements are put forward for the industrial detection automation link to meet production efficiency. This kind of special application environment limits the application of various types of detection equipment and hinders the promotion and application of its industrial detection automation. Utility Model Content

[0006] In view of the problem of decreased measurement accuracy in harsh environments faced by laser triangulation ranging technology, the utility model proposes a laser triangulation ranging device, which passively compensates for the temperature drift of the relative positions and relative angles between the photoelectric elements that constitute the measuring device, thereby improving the measurement stability of the laser triangulation ranging in harsh environments, so that the proposed laser triangulation ranging has better environmental adaptability, so as to meet the measurement needs in industrial detection automation in some special application environments.

[0007] The above purpose is achieved through the following technical solutions:

[0008] The utility model firstly provides a laser triangulation distance measuring device, comprising a laser emission optical path module, a combined prism, a receiving lens group, and a photoelectric detector which are arranged on the same side of a surface to be measured; the receiving lens group is located between the combined prism and the photoelectric detector; the combined prism is composed of a rhombus-like prism and an auxiliary prism, the rhombus-like prism is a prism with a cross section of a parallelogram ABCE, the auxiliary prism is a prism with a cross section of a triangle BCE, the two overlap or coplanar on an AE plane so that a surface BC of the auxiliary prism is parallel to a surface BC of the rhombus-like prism; the positions of the output light beam of the laser emission optical path module, the receiving lens group, and the photoelectric detector need to meet the Sham condition: that is, the output light beam of the laser emission optical path module, the main surface of the receiving lens group, and the photosensitive surface of the photoelectric detector intersect at one point.

[0009] Furthermore, the laser emission optical path module is formed by connecting a point light source and an emission lens group.

[0010] Further, the point light source laser light source is coupled to the end face of the fiber output end after being coupled to the optical fiber, or the laser light source passes through a small-diameter diaphragm or a pinhole.

[0011] Further, between the combined prism and the surface to be measured, a weak optical power lens group I and / or a weak optical power lens group II are / is provided, wherein the weak optical power lens group I is located on the optical path between the surface to be measured and the AD surface of the combined prism, and the weak optical power lens group II is located on the optical path between the surface to be measured and the BC surface of the combined prism, so that the optical paths between the surface to be measured passing through the weak optical power lens group I to the AD surface of the combined prism and between the surface to be measured passing through the weak optical power lens group II to the BC surface of the combined prism simultaneously satisfy the Scheimpflug condition.

[0012] Further, a laser filter is provided between the combined prism and the receiving lens group, or a laser filter is provided between the receiving lens group and the photodetector.

[0013] Further, the combined prism is a combination of a reflector and a semi-transparent semi-reflective mirror, and the reflector and the semi-transparent semi-reflective mirror are arranged in parallel.

[0014] The beneficial effects of the present utility model compared with the prior art are:

[0015] The present utility model provides a measuring device and method for laser triangulation ranging based on a prism dual optical path, which performs passive compensation for the temperature drift of the relative positions and relative angles between the various optoelectronic components constituting the measuring device. Simulation analysis shows that: the test results of this method have good distance resolution, and its ranging accuracy is not affected by the temperature drift of the beam emission angle of the laser emission optical path module; the ranging accuracy is less sensitive to the position and angle of the combined prism; the ranging accuracy is less sensitive to the position and angle of the receiving lens group; the ranging accuracy is less sensitive to the position and angle of the photodetector. In a harsh temperature environment, even if there is a relatively severe local temperature non-uniform temperature field, resulting in the drift of the beam emission angle of the laser emission optical path module, resulting in displacements and angular drifts of the laser emission optical path module, combined prism, receiving lens group, photodetector, etc., the detection results of this laser triangulation ranging device can still maintain good accuracy. In view of the problem of the decline in measurement accuracy in the laser triangulation ranging technology under harsh environments, the present utility model provides a measuring device and method for laser triangulation ranging based on a prism dual optical path, which performs passive compensation for the temperature drift of the relative positions and relative angles between the various optoelectronic components constituting the measuring device, improves the measurement stability of the laser triangulation ranging in the face of harsh environments, enables the proposed laser triangulation ranging to have better environmental adaptability, so as to meet the measurement requirements in the industrial detection automation of some special application environments. The present utility model improves the measurement accuracy in harsh environments, enables the measuring device to have higher stability, and can be adapted to a variety of special harsh environments, such as special application scenarios like iron and steel smelting, iron and steel casting, aluminum electrolysis, chemical industry, etc.; the present utility model has good distance resolution, and its ranging resolution is comparable to that of the traditional laser triangulation ranging technology; the present utility model can simplify its error compensation model and calibration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of the laser triangulation ranging device described in Embodiment 1 of the present utility model;

[0017] Figure 2 It is a schematic structural diagram of the combined prism of the present utility model;

[0018] Figure 3 It is a schematic principle diagram of the ranging solution of the laser triangulation ranging device of the present utility model;

[0019] Figure 4 It is a schematic structural diagram of the laser triangulation ranging device described in Embodiment 2 of the present utility model;

[0020] Figure 5 It is a schematic structural diagram of the laser triangulation ranging device described in Embodiment 3 of the present utility model;

[0021] Figure 6 It is a schematic structural diagram of the laser triangulation ranging device described in Embodiment 4 of the present utility model;

[0022] Figure 7 It is a schematic structural diagram of the laser triangulation ranging device described in Embodiment 5 of the present utility model;

[0023] Explanation of reference numerals in the drawings: 1. Laser emission optical path module; 101. Point light source; 102. Emission lens group; 2. Combined prism; 201. Quasi-rhombic prism; 202. Auxiliary prism; 203. Reflecting mirror; 204. Half-transmissive and half-reflective mirror; 3. Receiving lens group; 301. Weak optical power lens group I; 302. Weak optical power lens group II; 4. Photoelectric detector; 5. Measured surface; 6. Laser filter. Specific implementation manners

[0024] The present utility model will be further clarified below in conjunction with the drawings and specific implementation manners. It should be understood that the following specific implementation manners are only used to illustrate the present utility model and not to limit the scope of the present utility model.

[0025] Embodiment 1:

[0026] As Figure 1 shown, a laser triangulation ranging device in this embodiment includes a laser emission optical path module 1, a combined prism 2, a receiving lens group 3, and a photoelectric detector 4 disposed on the same side of the measured surface 5; the receiving lens group 3 is located between the combined prism 2 and the photoelectric detector 4; as Figure 2 shown, in this embodiment, the combined prism 2 is composed of a quasi-rhombic prism 201 and an auxiliary prism 202. The quasi-rhombic prism 201 is a prism with a cross-section of a parallelogram ABCE, and the auxiliary prism 202 is a prism with a cross-section of a triangle BCE. The two overlap or are coplanar on the AE surface such that the surface BC of the auxiliary prism is parallel to the surface BC of the quasi-rhombic prism; the positions of the output beam of the laser emission optical path module 1, the receiving lens group 3, and the photoelectric detector 4 need to satisfy the Scheimpflug condition: that is, the output beam of the laser emission optical path module 1, the principal plane of the receiving lens group 3, and the photosensitive surface of the photoelectric detector 4 intersect at one point.

[0027] A method for measuring distance using the laser triangulation ranging device of this embodiment. In this method, a laser beam is emitted through the laser emission optical path module 1 and made to irradiate on the surface to be measured 5, forming a small-sized light spot one on the surface to be measured 5; the diffuse reflection light of the light spot one on the surface to be measured 5 passes through the combined prism 2 via two different optical paths. One optical path is to be refracted successively through the AB surface, reflected by the AD surface, reflected by the BC surface, and refracted by the CD surface of the combined prism 2, and the other optical path is to be refracted successively through the AE surface, transmitted through the BC surface, and refracted by the CD surface of the combined prism 2; then it passes through the receiving lens group 3 and is imaged on the photosensitive surface of the photodetector 4, forming two light spots, namely light spot two and light spot three; the center positions of these two light spots are obtained through the photodetector 4, and the distance between the surface to be measured 5 and the test device is calculated based on the positions of light spot two and light spot three.

[0028] Specifically, as Figure 3 shown, the calculation of the distance between the surface to be measured and the test device has the following basic solution algorithm:

[0029] (1) Taking the optical axis of the receiving lens group 2 as the y-axis and its principal plane as the x-axis, a coordinate system x - o - y is established; the measurement reference plane (such as the front surface of its outer shape) of this laser triangulation ranging device for measuring distance forms an angle of α with the x-axis of the coordinate system x - o - y, and the intersection coordinate with the y-axis is (0, y0), α both and y0 are design parameters of this detection device;

[0030] (2) According to the distance and relative angle between the photodetector 4 and the receiving lens group 3, the coordinate values (x1, y1) and (x2, y2) of the centers of light spot two and light spot three in the x - o - y coordinate system are respectively obtained by converting from the light spot positions on the photodetector 4;

[0031] (3) Using the ray tracing algorithm in optics, reverse tracing is performed for optical path one and optical path two, that is, starting from the two points (x1, y1) and (x2, y2) respectively, two rays are traced, passing through the receiving lens group 3 and the combined prism 2 in sequence; when passing through the combined prism 2: for optical path one, it passes through the CD surface refraction, BC surface reflection, AD surface reflection, and AB surface refraction in sequence, and for optical path two, it passes through the CD surface refraction and AE surface refraction in sequence; after tracing, the straight line equations of optical path one and optical path two are respectively obtained;

[0032] (4) The intersection point of the two straight lines obtained in step (3) is denoted as (xc, yc), then based on the reference plane where the y0 point described in step (1) is located, the distance between the surface to be measured and this reference plane is d = (yc - y0) * cos( α ).

[0033] Embodiment 2:

[0034] As Figure 4 shown, the difference between this embodiment and Embodiment 1 is that the laser emission optical path module is formed by connecting a point light source 101 and an emission lens group 102. In this embodiment, the point light source laser light source is coupled to the end face of the fiber output end after being coupled into the optical fiber, or the laser light source passes through a small-diameter diaphragm or a pinhole. Between the point light source 101 and the emission lens group 102, a structural member with a low coefficient of thermal expansion is preferably used for connection to minimize the stability of the light output angle of the laser emission optical path module 1.

[0035] Embodiment 3:

[0036] As Figure 5 shown, the difference between this embodiment and Embodiment 1 is that between the combined prism 2 and the surface to be measured 5, a weak optical power lens group I 301 and / or a weak optical power lens group II 302 are provided, and their optical power is less than one-tenth of that of the receiving lens group 3. Among them, the weak optical power lens group I 301 is located on the optical path between the surface to be measured 5 and the AD surface of the combined prism 2, that is, on optical path I; the weak optical power lens group II 302 is located on the optical path between the surface to be measured 5 and the BC surface of the combined prism 2, that is, on optical path II; by working in combination with the receiving lens group 3, both optical path I and optical path II simultaneously satisfy or nearly satisfy the Scheimpflug condition, so as to obtain better spot quality on the area array detector.

[0037] Embodiment 4:

[0038] As Figure 6 shown, the difference between this embodiment and Embodiment 1 is that a laser filter 6 is provided between the combined prism 2 and the receiving lens group 3, or a laser filter 6 is provided between the receiving lens group 3 and the photodetector 4. The laser filter 6 filters out the wavelength bands other than the light beam emitted by the laser emission optical path module 1, so that the photodetector 4 can obtain a better signal-to-noise ratio.

[0039] Embodiment 5:

[0040] As Figure 7 shown, the difference between this embodiment and Embodiment 1 is that the combined prism 2 adopts a combination of a reflector 203 and a semi-transmissive semi-reflective mirror 204, and the reflector 203 and the semi-transmissive semi-reflective mirror 204 are arranged in parallel. The reflector 203 and the semi-transmissive semi-reflective mirror 204 preferably adopt materials with a low coefficient of thermal expansion, and preferably use structural members with a low coefficient of thermal expansion for connection between the two, so that the relative angular relationship between the two can maintain stability in a harsh environment.

[0041] The above are the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present utility model, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present utility model.

Claims

1. A laser triangulation distance measuring device, characterized in that: The laser triangulation distance measuring device comprises a laser emission optical path module (1), a combined prism (2), a receiving lens group (3), and a photoelectric detector (4) arranged on the same side of a surface to be measured (5); the receiving lens group (3) is located between the combined prism (2) and the photoelectric detector (4); the combined prism (2) is composed of a rhombus-like prism (201) and an auxiliary prism (202); the rhombus-like prism (201) is a prism with a cross section of a parallelogram ABCE; the auxiliary prism (202) is a prism with a cross section of a triangle BCE, and the two overlap or coplanar on the AE plane so that the surface BC of the auxiliary prism (202) is parallel to the surface BC of the rhombus-like prism (201); the positions of the output light beam of the laser emission optical path module (1), the receiving lens group (3) and the photodetector (4) need to satisfy the Sham condition: that is, the output light beam of the laser emission optical path module (1), the main surface of the receiving lens group (3) and the photosensitive surface of the photodetector (4) intersect at one point.

2. The laser triangulation distance measuring device according to claim 1, characterized in that: The laser emission optical path module is formed by connecting a point light source (101) and an emission lens group (102).

3. The laser triangulation distance measuring device according to claim 2, characterized in that: The laser light source of the point light source (101) is coupled to the end face of the optical fiber output end, or the laser light source of the point light source (101) passes through a small diameter aperture or a pinhole.

4. The laser triangulation distance measuring device according to claim 1, characterized in that: A weak light focal power lens group 1 (301) and / or a weak light focal power lens group 2 (302) are provided between the combined prism (2) and the surface to be measured (5), wherein the weak light focal power lens group 1 (301) is located on the optical path between the surface to be measured (5) and the AD surface of the combined prism (2), and the weak light focal power lens group 2 (302) is located on the optical path between the surface to be measured (5) and the BC surface of the combined prism (2), so that the optical path between the surface to be measured (5) through the weak light focal power lens group 1 (301) and the AD surface of the combined prism (2) and the optical path between the surface to be measured (5) through the weak light focal power lens group 2 (302) and the BC surface of the combined prism (2) both satisfy the Sham conditions.

5. The laser triangulation distance measuring device according to claim 1, characterized in that: A laser filter (6) is provided between the combined prism (2) and the receiving lens group (3), or a laser filter (6) is provided between the receiving lens group (3) and the photoelectric detector (4).

6. The laser triangulation distance measuring device according to claim 1, characterized in that: The combined prism (2) adopts a combination of a reflector (203) and a semi-transparent and semi-reflective mirror (204), and the reflector (203) and the semi-transparent and semi-reflective mirror (204) are arranged in parallel.

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