Introduce any telecentric lens field are restricted by the front-end optical diameter;
The required field, the greater the telecentric lens front optical diameter is larger.
Telecentric lens may development of large size, high weight, but the telecentric lens magnification of smaller, because the larger magnification for the front end of the optical element;
In some of the installation, pay attention to weight or size may ban the use of this kind of lens.
Lens f / # may also affect the lens size, especially when large magnification, in this case, the front end of optical element with lens speed development.
Telecentric lens at the top of the figure 1 shows the running system, under the f / 6 at the bottom of the telecentric lens with the aperture of the much slower speed (
Two in the f / 6 (
At the top)
And f / 16 (
At the bottom)
Work under the 4 x telecentric lens, to prove how the f / # can part telecentric lens element size.
If you need a special large field of view, you can use additional optical element to enhance the fixed focal length lens, in order to generate pseudo telecentric lens with large field of view.
Figure 2 shows a 25 mm fixed focal length lens, the enhanced image quality is always lower than designer telecentric lens, but may be in focus on cost and need far heart degrees are useful in large field of application.
This method can implement the minimum flexibility, related to the working distance of different field need different telecentric lens.