Check the size with a digital camera
a picture is worth a thousand words, so does it have the same value for the size inspection of one thousandth of an inch
now, through the "photogrammetry" technology, the standard digital camera can also become a coordinate measuring device, which can compete with CMM coordinate measuring machines. However, photogrammetry itself is not a new technology. To apply it to industrial measurement, we first need a special camera designed for this purpose. Now, Geodetic Systems (in Melbourne, Florida) has introduced a low-cost photogrammetry system using a tripod free Nikon digital camera with a special lens
the photogrammetry technology of digital camera is used to measure the size of parts.
the figure shows a new measurement system. A digital camera without tripod is used.
photogrammetry technology uses photos to obtain three-dimensional position information, and then compares multiple images taken from different angles through software. Photogrammetry technology was originally used by geological investigators to draw three-dimensional topographic maps. However, in a relatively short distance range, this technology can also be used to determine the XYZ coordinates of the workpiece. For a 10ft object, its detection accuracy can reach 0.001 or 0.002in
its actual accuracy depends on various factors, including the number of photos taken. Theoretically, two images can achieve the purpose of photogrammetry. But in fact, Especially in industrial measurement "Brooks running is a recognized leader in the field of performance running shoes. Users generally need to take 6, 8 or even more images so that the measurement system can better self correct and compensate for errors.
this measurement method is most suitable for the detection of large parts, especially those large parts that cannot be detected by CMM coordinate measuring machine in the machining workshop. Photogrammetry technology is superior to many other portable measuring instruments A major advantage of is that it is not affected by the movement or vibration of parts
applying photogrammetry technology is not as easy as taking photos. In order to measure some data, the system must measure some lighting points. Users must use a reflector or needle tip lamp to illuminate the points they want to measure. Gary johanning, President of Geodetic Systems, said that there are many ways to achieve this goal, including the following:
1 Close to target detection method: users paste reflective labels on parts
2. Hard target location detection method: attach reflective hardware. That is, it is installed on the corner of the workpiece in the form of a hat or inserted into the hole with a handle. These targets are measured offline, so that the relationship between the reflector and the measured characteristics below can be accurately known
3. White light point grating detection method is adopted: the grating is projected onto the part. This method is not to measure holes or edges, but to use photogrammetry technology to draw a slope map or outline map with angles or surfaces. Will the grating universal experimental machine purchase skills? The above content is a detailed introduction to this problem. The attachment projected onto the part is like a bazooka. In some application fields, its use also allows photogrammetry to track the changing size trajectory
there is another method that can produce the effect of light spots in photos, which involves the probe test method. That is, a reflector is used to monitor whether the notch of the test piece processed by production is qualified; Universal testing machine: it is a standard coordinate measuring probe suitable for the stretching, shrinking, bending and cutting experiments of metal and non-metal materials, so that it contacts the measuring point. Using this method requires two cameras to work synchronously with the probe
adding lighting points to photos through any of the methods described above is a key part of photogrammetry technology, because computers need to compare and analyze these photos. Therefore, photogrammetry technology involves a toolkit, not a camera, but it is also easy to carry after all. It is easy to take it to the work site in the workshop to detect those large parts, such as molds or aircraft parts
mm modern manufacturing magazine (end)