CN110440760B - Preparation method of high-precision photogrammetry target - Google Patents

Abstract

The invention relates to the technical field of photogrammetry, in particular to a preparation method of a high-precision photogrammetry target, which comprises the following steps: processing at least two supporting planes on a sphere to obtain a body of a measuring target; processing at least two reflecting units, wherein the reflecting units comprise reflecting mirrors and identification marks arranged on the reflecting mirrors, and mounting the reflecting units on a supporting plane. The measuring target manufactured by the method has a strong light return reflection effect, the identification mark is used as a background, and the contrast is obvious, so that the manufactured measuring target can obtain a mark image with high contrast under the condition of low-intensity exposure, and the method is suitable for the field of high-precision photogrammetry. During photogrammetry, when a camera images at different stations, photogrammetry targets can be accurately measured in a larger range, the circle centers of any two reflecting units are obtained, and the position of the circle center of the body in space can be obtained according to the position relation between the circle centers and the body center of the body.

Description

A kind of preparation method of high precision photogrammetry target

technical field

The invention relates to the technical field of photogrammetry, in particular to a method for preparing a high-precision photogrammetry target.

Background technique

Photogrammetry is a commonly used technology in the field of technology. There are many aspects that affect the accuracy of digital industrial photogrammetry, such as the acquisition and recognition of high-precision mark center images, high-precision camera calibration algorithms and calibration devices, design and implementation of high-precision marks, beam method Unified adjustment, etc., among which high-precision photogrammetry marks are a key technology that affects their accuracy.

At present, the photogrammetry targets used at home and abroad can be divided into flat type and three-dimensional type. The preparation method of flat type photogrammetry marks mainly includes pasting retroreflective films, such as the method of pasting SCOTCHLITE film with 3M adhesive. The obtained target has low precision and cannot be used in high-precision fields. The three-dimensional target is prepared by sticking and coating glass beads on the outside of the ceramic ball, but the spherical target is very sensitive to external lighting, and the contrast between the edge of the mark and the background is not obvious, etc., it is difficult to achieve high precision. .

SUMMARY OF THE INVENTION

In order to solve the technical problem of low accuracy of photogrammetry targets in the prior art, the present application provides a method for preparing a high-precision photogrammetry target, the purpose of which is to prepare a measurement target suitable for high-precision photogrammetry.

A method for preparing a high-precision photogrammetry target, comprising:

At least two supporting planes are processed on a sphere to obtain the body of the measurement target; the supporting planes and the center of the sphere have a definite spatial positional relationship;

processing at least two reflection units; the reflection units include a reflection mirror and an identification mark arranged on the reflection mirror;

The reflection units are correspondingly installed on the support planes, and one reflection unit is installed on each of the support planes.

Wherein, the reflection unit further includes a plurality of glass beads;

Processing the reflective unit includes:

Silver plating is performed on one side of the glass sheet to form a reflection enhancement film;

A plurality of glass microbeads are fixed on the reflection enhancement film to form a reflection layer, and the mirror is made; the refractive index of the glass microbeads is Nd≥1.93;

A metal film with color is processed around the reflective layer as the identification mark.

Wherein, the supporting planes are circular, two adjacent supporting planes are perpendicular to each other, and the distances from the centers of all supporting planes to the centers of the spheres are the same.

Wherein, the glass sheet is a trapezoidal cylinder, including a bottom surface and a top surface, and the radius of the top surface is smaller than the radius of the bottom surface;

The reflection enhancement film is circular and is located on the top surface of the glass sheet;

The identification mark is a black annular metal film, and the diameter of the outer circle of the identification mark is equal to the diameter of the top surface of the glass sheet.

Wherein, after processing at least two supporting planes on a sphere, the method further includes: uniformly processing a plurality of glue injection holes around the supporting planes.

The corresponding installation of the reflection unit on the support plane includes: aligning the center of the glass sheet with the center of the support plane and then injecting glue into the glue injection hole, and the glass sheet is injected with the glue through the glue. Bonded to the support plane.

Wherein, fixing a plurality of glass beads on the reflection enhancement film to form a reflection layer includes:

A layer of transparent resin glue is uniformly coated on the surface of the reflection enhancement film, and a plurality of glass microbeads are coated on the resin glue to form a reflection layer;

Wherein, the thickness of the resin glue is smaller than the thickness of the glass microbeads.

Wherein, the diameter of the sphere is 38.1±0.003mm, the symmetry of the center of the sphere is 0.004mm, and the positional accuracy of the center of the sphere is ±0.003mm;

The diameter of the support plane is 27.85mm, the flatness of the support plane is 0.003mm, and the roughness is 0.025μm;

After processing at least two supporting planes on a sphere, the method further includes: grinding and polishing the supporting planes, so that the shape and position accuracy of the supporting planes is 0.004 mm and the smoothness is 0.025 μm.

Wherein, the thickness of the glass sheet is 3±0.002mm, the diameter of the top surface is 24mm, and the diameter of the bottom surface is 25mm;

The thickness of the identification mark is 0.005mm, the diameter of the inner circle is 20mm, and the roundness accuracy of the inner circle is ±0.02mm.

Wherein, the sphere is made of 2Cr13 or 3Cr13, and the glass sheet is made of K9 material;

The particle size (ie diameter) of the glass microbeads is 50±5 microns.

Wherein, five support planes are processed on the sphere, the distances between the centers of the five support planes and the center of the sphere are all equal, and the centers of every two adjacent support planes are the same as the center of the sphere. The connecting lines between them are perpendicular to each other; each supporting plane is respectively provided with one of the reflecting units.

According to the preparation method of the high-precision photogrammetry target of the above-mentioned embodiment, by processing at least two supporting planes on a sphere, and then processing at least two reflecting units, the reflecting units are correspondingly installed on the supporting planes, wherein the reflecting units are It includes a reflector and an identification mark set on the reflector, wherein the reflector has a strong retroreflection effect, and the identification mark is used as a background with obvious contrast, so that the measurement target can be made in the case of low-intensity exposure. Obtain high-contrast logo images suitable for high-precision photogrammetry.

Description of drawings

1 is a flow chart of a method for preparing a measurement target according to an embodiment of the present application;

2 is a flowchart of a method for preparing a reflection unit according to an embodiment of the present application;

3 is a schematic structural diagram of a measurement target according to an embodiment of the present application;

4 is a schematic cross-sectional view of a reflection unit according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a working state of a reflection unit according to an embodiment of the present application.

Detailed ways

The present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments have used associated similar element numbers. In the following embodiments, many details are described so that the present application can be better understood. However, those skilled in the art will readily recognize that some of the features may be omitted under different circumstances, or may be replaced by other elements, materials, and methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid the core part of the present application from being overwhelmed by excessive description, and for those skilled in the art, these are described in detail. The relevant operations are not necessary, and they can fully understand the relevant operations according to the descriptions in the specification and general technical knowledge in the field.

Additionally, the features, acts, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can also be exchanged or adjusted in order in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary order unless otherwise stated, a certain order must be followed.

This embodiment provides a method for preparing a high-precision photogrammetry target. Compared with the existing direction, there are mainly improvements in the following two points:

(1) Select a sphere and process five circular support plane support bodies on it, the centers of the five support planes and the body center of the sphere have a certain positional relationship, and a reflection unit is provided on each support plane, It is used to reflect the light beam emitted by the measuring device, so that when the photogrammetry camera is imaging at different stations, the photogrammetry target can be accurately measured in a large range, even in a 360-degree range, and the reflection of any two reflection units can be obtained. The center of the circle, according to the positional relationship between the center of the circle and the center of the body, the position of the center of the body in space can be obtained. At the same time, in this embodiment, in order to facilitate the calculation of the body center position of the main body during the photogrammetry process, the five supporting planes set in this embodiment, every adjacent two are perpendicular to each other, that is, the center of each adjacent two supporting planes The lines connecting with the body center of the body are perpendicular to each other and have the same distance.

(2) The structure of the reflection unit is improved. Specifically, the reflection unit of this embodiment includes a reflection mirror and an identification mark arranged on the reflection mirror. The reflection mirror has a strong retroreflection effect, and the identification mark is used as a background. The obvious contrast enables the manufactured measurement target to obtain a high-contrast sign image under the condition of low-intensity exposure, which is suitable for the field of high-precision photogrammetry.

Example 1:

Referring to FIG. 1 , this embodiment provides a method for preparing a high-precision photogrammetry target. The prepared measurement target includes a body and five reflection units arranged on the body. The preparation method includes:

Step 101: Process at least two supporting planes on a sphere to obtain a body. Specifically, in this embodiment, five supporting planes are machined on the sphere by the method of finishing, and there is a confirmed spatial positional relationship between the supporting plane and the body center of the sphere. In this embodiment, the supporting plane is a circle. Obtain the positions of the circle centers of the two support planes, and then obtain the position of the body center according to the positional relationship between the circle centers of the two support planes and the body center.

Step 102: Process at least two reflection units. Wherein, the reflecting unit includes a reflecting mirror and an identification mark arranged on the reflecting mirror. The reflecting mirror has a strong retroreflection effect, and the identification mark is used as a background to have obvious contrast, so that the measurement target can be exposed at low intensity. A high-contrast sign image can be obtained in the case of , and high-precision photogrammetry can be realized based on the sign image.

Step 103 : correspondingly install the reflection units on the support planes of the body, and only one reflection unit is installed on one of the support planes. For example, the reflective unit is fixed on the support plane by glue bonding or other fixing methods.

Specifically, the reflective unit in this embodiment further includes a plurality of glass beads, as shown in FIG. 2 , and the method for processing the reflective unit includes:

Step 1021 : perform silver plating on the surface of a glass sheet to form a reflection enhancement film. In this embodiment, the method of vacuum silver plating is used to coat a layer of reflection enhancement film on one side of the glass sheet. Since the reflection effect of silver is good, this embodiment uses the method of vacuum coating to coat the glass sheet with silver to form a reflection Strengthen the film to obtain a silver-coated optical glass sheet.

Step 1022: Fixing a plurality of glass microbeads on the reflection enhancement film to form a reflection layer to make a reflector; wherein, the glass microbeads are made of glass microbeads with a high refractive index using retroreflective materials, and the glass microbeads have a refractive index. Nd≥1.93.

Step 1023: Process a layer of colored metal film around the reflective layer as an identification mark. In this embodiment, the wire cutting method is used to process a black metal ring around the refracting layer, and the black metal ring is used as the background. During the image acquisition process, the black metal ring and the reflector have obvious contrast, so that the A high-contrast sign image can be obtained under the condition of low-intensity exposure of the measurement target, and high-precision photogrammetry can be realized based on the high-contrast sign image.

Wherein, after the supporting plane is processed on the sphere, it also includes: uniformly processing 8 plastic injection holes around the supporting plane, and when installing the reflection unit, align the center of the glass sheet with the center of the supporting plane, so that the center of the glass sheet (that is, The center of the reflection enhancement film) and the body center of the sphere have an installation accuracy of ±0.003mm, and then inject epoxy glue into the glue injection hole, and bond the glass sheet to the support plane through the epoxy glue.

Wherein, fixing a plurality of glass microbeads on the reflection enhancement film to form a refraction layer includes: first, uniformly coating a layer of transparent resin glue on the surface of the reflection enhancement film, and coating a plurality of glass microbeads on the resin glue to form a refraction layer The particle size (ie diameter) of the screened glass microbeads is 50±5 microns, and the thickness of the coated resin glue should be smaller than that of the glass microbeads.

The glass sheet in this embodiment is a trapezoidal cylinder, which includes a bottom surface and a top surface, the radius of the top surface is smaller than the radius of the bottom surface, and the bottom surface is fixed on the body by epoxy glue. The reflection enhancement film on the glass sheet is also circular, the identification mark is a black circular metal film, and the diameter of the outer circle of the identification mark is equal to the diameter of the top surface of the glass sheet. Specifically, the sphere of this embodiment is made of 2Cr13 or 3Cr13, and the glass sheet is made of K9 material. In order to ensure the interchangeability of measurement, the spherical diameter of the main body 1 is consistent with the spherical diameter of the 1.5-inch mirror of the laser tracker. The diameter of the body is 38.1±0.003mm, the symmetry of the center of the sphere is 0.004mm, and the positional accuracy of the center of the sphere is ±0.003mm; five supporting planes are machined on the sphere by milling, and the diameter of the supporting plane is 27.85mm , the flatness of the support plane is 0.003mm, and the roughness is 0.025μm. Every two adjacent support planes are perpendicular to each other, the perpendicularity is 0.004mm, and the distance from the center of each support plane to the body center of the sphere is equal.

Wherein, after machining the support plane on a sphere, the support plane is also ground and polished, so that the shape and position accuracy of the support plane is 0.004mm and the smoothness is 0.025μm.

In this embodiment, the glass sheet is a trapezoidal cylindrical shape, made of K9 material, its thickness is 3±0.002mm, its top surface diameter is 24mm, and its bottom surface diameter is 25mm; the identification mark in this embodiment is a black metal ring , its thickness is 0.005mm, the diameter of the inner circle is 20mm, the diameter of the outer circle is 24mm, and the circularity accuracy of the inner circle is ±0.02mm, and the identification mark is bonded to the glass beads with high refractive index to form a diameter of It is a 24mm retroreflective circle, and a retroreflective silver-coated glass sheet with a mask is prepared as a reflective unit.

The measurement target prepared by this embodiment has obvious contrast, so that the formed measurement target can obtain a high-contrast sign image under the condition of low-intensity exposure, which is suitable for the field of high-precision photogrammetry; at the same time, shooting at the same station When shooting, the photogrammetry target can be accurately measured in a wide range, even in a 360-degree range, without rotating the measurement target, which improves the measurement efficiency.

Embodiment 2:

Please refer to FIG. 3 and FIG. 4 , this embodiment provides a measurement target suitable for high-precision photogrammetry, the measurement target is obtained by the method of Embodiment 1, and includes a main body 1 and five reflections arranged on the main body 1 unit, for the convenience of description, the five reflection units are hereinafter referred to as the first reflection unit 10, the second reflection unit 20, the third reflection unit 30, the fourth reflection unit and the fifth reflection unit, wherein the fourth reflection unit and The fifth reflection unit is not shown in the figure due to the relationship of the viewing angle. The five reflection units have the same structure, four of which are arranged along a weft of the main body 1, and the other is arranged at the top. The body 1 of the embodiment is a sphere, the material is stainless steel 3Cr13 or 2Cr13, and the hardness is required to be HRC40. In order to ensure the interchangeability of measurement, the spherical diameter of the main body 1 is consistent with the spherical diameter of the 1.5-inch mirror of the laser tracker. The body 1 is provided with five supporting planes. As shown in FIG. 3 , the supporting plane 11 corresponding to the first reflecting unit 10 is used as an example for illustration. The supporting plane 11 is circular with a diameter of 27.85 mm. Vertical, the verticality is 0.004mm, the flatness of the support plane 11 is 0.003mm, and the roughness is 0.025μm, to ensure that the distance between the center of each support plane 11 and the center of the sphere is accurate to 13mm±0.003mm, and each two adjacent support planes 11 The lines connecting the center of the circle and the center of the sphere are all perpendicular to each other, so that the coordinates of the center of the sphere can be known by the coordinates of the center of the circle of at least three supporting planes.

Among them, in order to improve the retroreflection effect, this embodiment focuses on providing a reflection unit with good retroreflection effect. As shown in FIG. 4 , this embodiment takes the first reflection unit 10 as an example for description, and the first reflection unit 10 includes A reflector and an identification mark 101 arranged on the surface of the reflector, wherein the reflector includes a glass sheet 104, a reflection enhancement film 103 coated on the outer surface of the glass sheet 104, and a reflection layer fixed on the reflection enhancement film 103, the reflection layer is composed of A plurality of glass microbeads 102 with high refractive index are closely arranged on a plane, and the particle size is 50±5 μm, and the refractive index Nd≥1.93. A plurality of glass microbeads 102 are arranged on the outer surface of the reflection enhancement layer 103, and the reflection enhancement layer 103 is a silver-plated layer, which can enhance the reflection effect of back light. The identification mark 101 is a black metal ring, which is obtained by the method of vacuum plating black film, its thickness is 0.005mm, and the inner circularity is required to be ±0.02μm.

Wherein, in order to fix the glass sheet 104 on the corresponding support plane 11, eight tapered glue injection holes 105 are provided on the support plane 11 for injecting glue and then bonding the glass sheet. The glass microbeads 102 in this embodiment are made of materials with strong retroreflection.

Among them, the glass sheet 104 is a trapezoidal truncated thin sheet, its thickness is 3±0.002mm, the top and bottom of the sheet has two circular sections of different sizes, the diameter of the large circle is 25mm, the diameter of the small circle is 24mm, and the surface of the small circle is plated with silver The reflection enhancement layer 103 is formed. In order to facilitate glue injection, the diameter of the large circle of the optical glass sheet 104 is smaller than the diameter of the support plane 11 on the main body 1 , and the material of the optical glass sheet 104 is K9. The diameter of the inner circle of the identification mark 101 is equal to the diameter of the small circle of the glass sheet 104 . The center of the glass sheet 104 , the identification mark 101 and the supporting plane 11 and the spherical center of the body 1 are on a straight line, and the positional accuracy is required to reach ±0.003mm.

As shown in Fig. 5, the incident light emitted by the photographing device is refracted by the glass beads 102 and then reflected by the reflection enhancing layer 103, and then exits along an optical path parallel to the incident light and is received by the photographing device. The light reflection effect is better than that of the existing flat mirror type reflection surface. With the identification mark 101 as the background, the contrast is large, so that the manufactured measurement target can obtain a high-contrast mark image under the condition of low-intensity exposure. in the field of high-precision photogrammetry.

The structure of each reflection unit in this embodiment is the same, and the structures of the other reflection units are the same as those of the first reflection unit 10 , which will not be repeated here.

The beneficial effects of the patent of the present invention are: the accuracy of the photogrammetry target is far better than that of the traditional single-sided retroreflective patch target, and it has a strong retroreflective effect. Logo image, especially suitable for the field of high-precision photogrammetry. In addition, the target with multiple light-reflecting surfaces enables the photogrammetry camera to accurately measure the photogrammetry target in a large range, even in a 360-degree range when imaging at different stations, without the need to manually rotate the photogrammetry target. Greatly improved efficiency.

The above specific examples are used to illustrate the present invention, which are only used to help understand the present invention, and are not intended to limit the present invention. For those skilled in the art to which the present invention pertains, according to the idea of the present invention, several simple deductions, modifications or substitutions can also be made.

Claims (8)

1. A method for preparing a high-precision photogrammetric target, characterized by comprising:

processing at least two supporting planes on a sphere to obtain a body of a measuring target; the supporting plane and the sphere center of the sphere have a determined spatial position relationship;

processing at least two reflecting units; the reflecting unit comprises a reflecting mirror and an identification mark arranged on the reflecting mirror;

mounting said reflection units on said support planes, one reflection unit being mounted on one of said support planes;

wherein processing the reflection unit includes:

performing silver plating treatment on one side of the glass sheet to form a reflection enhancement film;

fixing a plurality of glass beads on the reflection enhancement film to form a reflection layer to manufacture the reflector; the refractive index Nd of the glass beads is more than or equal to 1.93;

processing a layer of metal film with colors around the reflecting layer to serve as the identification mark;

the glass sheet is in a trapezoidal cylinder shape and comprises a bottom surface and a top surface, and the radius of the top surface is smaller than that of the bottom surface;

the reflection enhancement film is circular and is positioned on the top surface of the glass sheet;

the identification mark is a black circular metal film, and the diameter of the excircle of the identification mark is equal to that of the top surface of the glass sheet.

2. The method for preparing a measurement target according to claim 1, wherein the support planes are circular, two adjacent support planes are perpendicular to each other, and distances from centers of all the support planes to a center of the sphere are the same.

3. The method for preparing a measurement target according to claim 2, wherein the step of processing at least two support planes on a sphere further comprises: uniformly processing a plurality of glue injection holes on the periphery of the support plane;

the mounting the reflection unit on the support plane includes: and after the circle center of the glass sheet is aligned with the circle center of the supporting plane, injecting glue into the glue injection hole, and bonding the glass sheet on the supporting plane through the glue.

4. The method of claim 3, wherein the fixing a plurality of glass beads on the reflection enhancing film to form a reflection layer comprises:

uniformly coating a layer of transparent resin adhesive on the surface of the reflection enhancement film, and coating a plurality of glass beads on the resin adhesive to form a reflection layer;

wherein, the thickness of the resin adhesive is smaller than that of the glass beads.

5. The method for preparing a measurement target according to claim 1, wherein the diameter of the sphere is 38.1 ± 0.003mm, the symmetry of the sphere center is 0.004mm, and the sphere center position accuracy is ± 0.003 mm;

the diameter of the supporting plane is 27.85mm, the flatness of the supporting plane is 0.003mm, and the roughness is 0.025 mu m;

after processing at least two supporting planes on a sphere, the method further comprises the following steps: and grinding and polishing the support plane to ensure that the form and position precision of the support plane is 0.004mm and the smoothness is 0.025 mu m.

6. The method for producing a measurement target according to claim 4, wherein the glass sheet has a thickness of 3 ± 0.002mm, a diameter of the top surface of 24mm, and a diameter of the bottom surface of 25 mm;

the thickness of the identification mark is 0.005mm, the diameter of the inner circle of the identification mark is 20mm, and the roundness precision of the inner circle is +/-0.02 mm.

7. The method for preparing a measurement target according to claim 4, wherein the sphere is made of 2Cr13 or 3Cr13, and the glass plate is made of K9;

the particle size of the glass beads is 50 +/-5 microns.

8. The method for preparing a measurement target according to claim 5, wherein five support planes are processed on the sphere, distances between centers of the five support planes and a connecting line between the centers of the sphere are equal, and a connecting line between centers of every two adjacent support planes and the center of the sphere are perpendicular to each other; each supporting plane is provided with one reflecting unit.

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