Technical Parameters of Telecentric Lens
Technical Parameters
1) High Image Resolution
The image resolution is typically measured in terms of the CTF (contrast transfer function) that quantifies the spatial frequency contrast of the image sensor in lp/mm (coil per mm). Most machine vision integrators often only collect a large number of inexpensive low-pixel, low-resolution lenses, and only generate blurred images. With the AFT telecentric lens, high resolution images can be generated even with small pixel image sensors (eg 5.5 megapixels, 2/3").
2) Near Zero Distortion
The distortion coefficient is the percentage difference between the physical size and the imaging size of the image sensor. Ordinary machine lenses usually have distortions greater than 1-2%, which can seriously affect the accuracy of the measurement. In contrast, the telecentric lens is strictly controlled to less than 0.1% through strict manufacturing and quality inspection.
3) No Perspective Error
When performing precision linear measurements in metrology applications, it is often necessary to observe from the standard front side of the object (not including the side at all). In addition, many mechanical parts cannot be placed accurately, and the measurement time interval is constantly changing. Software engineers need images that accurately reflect the real thing. The telecentric lens perfectly solves the above confusion: because the entrance pupil can be located at infinity, it only receives the main ray of the parallel optical axis when imaging.
4) Telecentric design and super wide depth of field
The dual telecentric lens not only enhances the natural depth of field with aperture and magnification, but also has an unparalleled optical effect of non-telecentric lenses: the image is unchanged when moving objects within a certain object distance range, that is, the magnification is unchanged.
Application Scenario
1) When it is necessary to detect objects with thickness (thickness > 1/10 FOV diameter);
2) When it is necessary to detect objects that are not in the same plane;
3) When it is not clear what the distance from the object to the lens is;
4) When it is necessary to detect an object with an aperture and a three-dimensional shape;
5) When low distortion is required and the brightness of the image effect is almost identical;
6) When the defect is only illuminated in parallel in the same direction, it can be detected.
How to Choose
1) Object size ------ shooting range.
2) Image size ------ The target size of the CCD used.
3) Working distance ------ the distance from the front surface of the object lens to the subject.
4) Resolution --------- CCD pixel size used.
5) Depth of field ------------ The lens can be a clear image range. The larger the image/object magnification, the smaller the depth of field.
6) Interface ------------ camera interface, mostly C, T and other interfaces.
Depending on the usage (object size and resolution required), select the object size lens and CCD or CMOS camera with the appropriate object size, and obtain the image size to calculate the magnification. Then select the appropriate image lens according to the product list. . During the selection process, attention should also be paid to the influence of the depth of field indicator, because the larger the image/object magnification is, the smaller the depth of field is. In order to obtain a suitable depth of field, it may be necessary to reselect the lens.