What do you know about industrial photogrammetry for large part inspection?

introductory

In recent years, the manufacturing industry towards the direction of high-quality rapid development, rapid development towards the direction of digitalisation, rapid development towards the direction of flexible automation, in order to meet the appearance of beautiful and simple and structural high-performance goals, the product shape of industrial products is becoming more and more varied, more and more complex structural design, the use of integrated moulding manufacturing process accounted for a continuous increase in the proportion of these trends on the workpiece geometric dimensions of the detection accuracy put forward more and more These trends put forward more and more requirements on the inspection accuracy of workpiece geometry, the shape and position of the workpiece inspection accuracy, efficiency requirements, especially in the face of large and medium-sized workpiece inspection, due to the inconvenience of the parts to move, the complexity of the measurement environment on-site, the existence of multi-dimensional measurement of the efficiency requirements, all of which put forward a new challenge to the traditional contact dimensional measurement equipment, the use of non-contact optical three-dimensional scanning measuring instrument for high-efficiency full-size measurement of the demand is also gradually increasing. The demand for non-contact optical 3D scanning measuring instruments for efficient full-size measurements is also gradually increasing.

Industrial photogrammetry is one of the more popular non-contact large-scale scene measurement technology, its technology development is relatively mature, with a wide range of application areas. This issue of the “small fine eagle microclassroom”, will lead you to understand the development of industrial photogrammetry technology, the use of this aspect of the classification, the current situation of the product and the direction of the application.

PART 1

Definition and classification of photogrammetry

The technique of using a camera or combination of cameras to measure the shape, size, and spatial position of a subject is called photogrammetry, which began in the mid-19th century with the invention of the camera and the discovery of stereoscopic vision. Simply put, this technique uses photography as a tool and measurement as a goal, extracting information from a two-dimensional image to construct a three-dimensional model.

Schematic diagram of photogrammetric techniques

Photogrammetry technology within the broad scope, according to the use of division, can be divided into: topographic photogrammetry, and non-topographic photogrammetry; if the camera and the object to be photographed according to the distance between the distance to be differentiated, can be divided into: aerospace photogrammetry, as well as aerial photogrammetry, plus ground photogrammetry, followed by close-up photogrammetry, the last is the microphotogrammetry, etc., which has a wide range of applications in the field of land resource It has a wide range of applications in the field of land resources survey, urban planning, forestry, agriculture, seismic survey, resources and environment monitoring, marine development, national defence, construction, industry, cultural relics, biomedical fields and so on.

Schematic diagram of the application of photogrammetric techniques

PART 2

Development and application of industrial photogrammetry

Industrial Measurement is a discipline for designing, modelling, measuring, prototyping, simulation and emulation of products in all aspects of industrial production, testing and research,quality controlAs well as the state of motion, go to provide measurement technology to support the discipline, its measurement content is mainly based on the size, position, shape and other geometric quantities of the product as the main body.

For small and medium-sized in the size of less than 1m range of workpieces, the traditional industrial measuring equipment mainly with the help of coordinate measuring machine, joint arm measuring machine, three-dimensional scanner and other measuring equipment for testing, basically able to reach the product testing and reverse design of the required accuracy requirements. For the size of larger than 1m of large workpieces, laser tracker, latitude and longitude instruments and other optical instruments in the measurement of accuracy to meet the requirements of the use of these optical instruments, but these optical instruments exist in the measurement of the situation is slow, the detection process is cumbersome and complex, in the detection process of manpower consumption is relatively large, and so on such a number of pain points.

Schematic diagram of conventional industrial measuring equipment

Gradually, photogrammetry technology has been applied to the field of industrial measurement as a way to solve these problems, and when combined with industrial measurement technology for product dimensional quality inspection and process control, a niche research area has been formed, which is industrial photogrammetry.

Traditional industrial photogrammetry products, is first placed on the surface of the object and around the code points and marking points, and then the use of high-resolution cameras, from different angles and positions on the object shooting, so as to get a certain number of photos, and then the photographs taken into the software to automatically calculate the spatial location of the code points and marking points of the information, these files can be imported into the three-dimensional data acquisition software, and on top of it to obtain the complete three-dimensional dimensional data. These files can then be imported into the 3D data acquisition software to obtain the complete 3D dimensional data.

Photogrammetry into the digital age, is driven by the development of computer technology, as this, today's rapid development of computer vision, instrumentation, sensors, robotics, artificial intelligence and other technologies, but also to the development of industrial photogrammetry technology has injected new vitality.

In recent years, innovative solutions have continued to emerge, especially the combination of high-precision 3D scanning and industrial photogrammetry, which, with its accurate, comprehensive and efficient 3D data acquisition capabilities, has been embedded in the development and design of large-format products for industrial manufacturing, in quality control, insmart manufacturingThe key links, such as direct application requirements and user pain points, so that the detection efficiency has been improved, but also improve the accuracy, for many industries to improve product quality and production automation transformation to give strong support.

PART 3

Why is photogrammetry needed for 3D scanning?

Three-dimensional scanning is a three-dimensional stereo vision optical measurement technology, which integrates optical, mechanical, electrical and algorithmic technologies, and its use is mainly for the spatial structure of the object, the appearance of the dimensions of the colour texture to carry out the data acquisition work, in order to get the spatial coordinate set of the object surface, that is, the point cloud information, colour information, etc., which, like industrial photogrammetry technology, is to transform the physical three-dimensional information of real environment into a digital 3D model with precise dimensional information that can be directly processed by the computer. It has the same purpose as industrial photogrammetry, which is to transform the physical three-dimensional information in the real environment into a digital 3D model with accurate dimensional information that can be directly processed by the computer.

Schematic diagram of multi-line laser 3D scanning technology

Marker points, features or textures are used to stitch 3D data. When stitching, a certain amount of error exists. Although algorithms can be used to optimise it, the accuracy error will continue to accumulate as the number of tessellations increases when data is collected from large objects (several metres - tens of metres).

High-precision 3D scanning can be combined with industrial photogrammetry technology to reduce the cumulative error, the industrial photogrammetry technology in 3D scanning is also known as global photogrammetry, with the help of high-precision handheld 3D scanner can be efficiently obtained with the marking point of the measured part of the dense point cloud information, and then use photogrammetry equipment, by taking pictures of the ruler around the part and the marking point of the surface of the part from a variety of angles, so that the software can form a high-precision marking point and coding point frame with the previous acquisition of the marking point and coding point frame. The photogrammetric equipment is then used to photograph the markers arranged around the part and the markers on the surface of the part from many different angles, so that a high-precision framework of markers and coding points can be formed in the software, and this high-precision framework of markers and coding points can be used in conjunction with the dense point cloud information of the measured part with markers obtained in the previous section, with the aim of controlling the global accuracy of 3D scanning of large-size objects.

Application Schematic

PART 4

Comparison of differences in different product solutions

01

Traditional programme: stand-alone industrial photogrammetric system

System Components

Specialised cameras: Cameras play a major role in photogrammetric systems for image acquisition.

Measurement Scale: The main function of the scale is to control the overall dimensions of the collected data.

Coding points, which consist of a central point and a ring around it, each with its own number, are analysed with the aid of image analysis by the measurement software to determine the coordinates, normal direction and number of the coded point on the object to be measured.

There is a type of point, known as a marker, which helps the system to match and locate points, thus increasing the accuracy of the scan and the precision of the reconstruction.

Measurement software that can be used to analyse images and the associated reference points, and can calculate the 3D coordinates of each reference point.

High-performance portable computers

System Advantages

The non-contact measuring method is used for larger ranges of several metres up to several tens of metres, which is particularly suitable for measuring the external dimensions of large or very large workpieces.

High precision, the use of high-resolution cameras, the use of high-precision measuring scales, the setting of magnetic coding points, but also equipped with advanced software algorithms, in order to ensure the level of global dimensional measurement accuracy.

You need to point the camera at the object to be measured to take a picture, and it is easy to operate without complicated professional operation and settings.

The equipment is convenient, not constrained by the environment, and not limited by the scope of measurement, in complex conditions, also able to carry out the execution of the measurement operation, the adaptability of the application of the strong ability, so on and so forth.

With strong compatibility, the output file is composed of 3D coordinate information of marked and coded points, which can be directly imported into mainstream 3D data acquisition software as the frame points for 3D scanning, which can effectively ensure the accuracy of the 3D scanner when scanning large objects.

system disadvantage

Firstly, the user is asked to surround the large part, then to stand at quite a few different angles, and then, to take spot shots, and lots of multi-angle photos.

-High learning costs and requires operators with extensive experience to ensure stable accuracy;

For photogrammetric systems in conventional programmes, the use of code points is inevitable in order to clarify three-dimensional spatial relationships. However, the process of arranging the code points is cumbersome, and the larger the object, the more code points are required and the longer it takes.

Measurement process

An example of a 3D inspection of a casting is the CCTV photogrammetry system;

02

New solution: built-in industrial photogrammetry system

Programme Advantages

The UE Pro and Trio are two 3D scanning devices with an integrated design and built-in photogrammetric functions, which enable them to be used for multiple purposes. This is also the reason why they can achieve the operating conditions that are not limited by the shape of the object, and efficiently control the global accuracy of 3D data of large-sized workpieces through such characteristics. The UE Pro, with its built-in binocular photogrammetry, and the Trio, with its built-in trinocular photogrammetry, are able to efficiently obtain accurate measurements in photogrammetry mode without the use of coding points, with a volumetric accuracy of up to 0.015 mm + 0.02 mm/m.

Continuous full-angle shooting eliminates the need to select a specific angle for a fixed point shot, making the measurement process simple. Here, even novices can take full-angle photos, thereby ensuring a stable level of accuracy and presenting a highly efficient, stable, and easy-to-use feature.

The data is displayed in real time, and the results are presented as a streaming real-time video with a high degree of visualisation, which can be supplemented in real time for angles not captured, thus further ensuring that the accuracy of all scales is at a level.

Flexibility and ease of operation are the hallmarks of this system, which is highly adaptable to the environment, eliminating the need to move out into the open for photogrammetric measurements of very large workpieces, as well as for heavy workpieces.

CCTF, by virtue of its own ability, independently developed an invention patent technology, which uses high-precision handheld 3D scanner to replace high-resolution SLR camera, and integrated photogrammetric scale, but also do not need to arrange the coding point, which in the powerful algorithms under the auspices of the target frame of the large scene can be quickly locked in the spatial location of the target frame, at the same time, can also be efficiently control the global accuracy of the large-size object 3D scanning, the role of a significant advantage. Its role is significant and has outstanding advantages.

Measurement process

Take the CCTV UE Pro multifunctional laser handheld 3D scanner, plus, photogrammetry, complete 3D data of a helicopter fuselage, as an example.

Product Application Direction

Full-size inspection provides an inspection tool that is objective and precise, capturing the complete three-dimensional data of an object non-destructively and quickly, thus enabling high quality and efficient dimensional quality control, significantly reducing the errors and costs associated with manual operations in traditional measurement methods.

Specifically for product design and development, can provide high-precision 3D model data as a reference basis to help engineers in the production of product prototypes, quickly and accurately completed, in reverse engineering, can also quickly and accurately start to carry out, for the design of the verification process, can also be carried out quickly and accurately, including iterative optimisation process, can be quickly and accurately reached, and ultimately to achieve the purpose of shortening the product design cycle, and thus improve design efficiency and accuracy. The purpose of the product design cycle, and thus improve the design efficiency and accuracy.

Giving accurate working data to CNC machining, additive manufacturing, integrated moulding, robotic system, etc., so as to ensure the accuracy and consistency of the manufacturing process to help intelligent manufacturing, and effectively achieve the double enhancement of production efficiency and yield rate, and then help factories to build automated, intelligent, and flexible manufacturing production lines.