The measurement accuracy of the vision measuring machine will be affected by three situations, which are optical error, mechanical error and human operation error.
The mechanical error mainly occurs in the manufacturing and assembly process of the vision measuring machine. We can effectively reduce this error by improving the assembly quality during production.
The following are precautions to avoid mechanical errors:
1. When installing the guide rail, its base must be sufficiently level, and a dial indicator needs to be used to adjust its level accuracy.
2. When installing the X and Y axis grating rulers, they must also be kept in a completely horizontal state.
3. The worktable must be adjusted for level and verticality, but this is a test of the technician’s assembly ability.
Optical error is the distortion and distortion generated between the optical path and components during imaging, which is mainly closely related to the manufacturing process of the camera. For example, when the incident light passes through each lens, the refraction error and the error of the CCD lattice position are generated, so the optical system has nonlinear geometric distortion, resulting in various types of geometric distortion between the target image point and the theoretical image point.
The following is a brief introduction of several distortions:
1. Radial distortion: It is mainly a problem of the symmetry of the main optical axis of the camera lens, that is, the defects of the CCD and the shape of the lens.
2. Eccentric distortion: The main reason is that the optical axis centers of each lens cannot be strictly collinear, resulting in inconsistent optical centers and geometric centers of the optical system.
3. Thin prism distortion: It is equivalent to adding a thin prism to the optical system, which will not only cause radial deviation, but also tangential deviation. This is due to lens design, manufacturing defects, and machining installation errors.
The last one is human error, which is closely related to the user’s operating habits and mainly occurs on manual machines and semi-automatic machines.
Human error mainly includes the following aspects:
1. Get the error of the measurement element (unsharp and burr edges)
2. The error of Z-axis focal length adjustment (the error of the clearest focus point judgment)
In addition, the accuracy of the vision measuring machine is also closely related to its frequency of use, regular maintenance and use environment. Precision instruments require regular maintenance, keep the machine dry and clean when not in use, and keep away from places with vibration or loud noise when operating it.
Post time: Jun-13-2022