What is a telecentric lens?
Main features of telecentric lenses
- If it is within the depth of focus, there is no expansion or contraction of the image. → Measurement error can be reduced when measuring dimensions.
- Less distortion of the image due to parallax
- When used in combination with coaxial illumination, there is less unevenness in the brightness of the object.
The types are roughly divided into two-sided telecentric lenses and one-sided telecentric lenses.
We also handle telecentric lenses on both sides and one side.
The features of each are as follows.
Double-sided telecentric lens
The feature is that the size of the subject is not changed regardless of the distance between the camera sensor side and the subject side. In other words, you can change only the distance between the lens and the subject without changing the magnification by changing the distance on the camera sensor side using a close-up ring or the like. However, since the diameter of the lens is physically larger than the projected range, the size of the lens increases as the magnification decreases, and the price also increases. It is used in precision measuring devices and projectors.
One-sided telecentric lens
This lens has a telecentric lens structure only on the subject side. Unlike the telecentric lens on both sides, when the distance on the camera sensor side changes, the size of the subject changes as with the non-telecentric lens. Compared to double-sided telecentric lenses, the lenses are smaller and cheaper. If it is not necessary to change the magnification like a macro zoom lens for dimensional measurement, it may be used as a replacement with a fixed magnification.
(In addition to the subject-side telecentric lens that we handle, there is also an image-side telecentric lens that has a telecentric lens structure only on the camera sensor side. This is a work using a normal camera . It is rarely used for shooting.)
Summary
The main features of telecentric lenses are
- If it is within the depth of focus, there is no expansion or contraction of the image, so the measurement error can be reduced when measuring the dimensions.
- Less distortion of the image due to parallax
- When used in combination with coaxial illumination, there is less unevenness in the brightness of the object. And so on.
Double-sided telecentric lenses used in precision measuring devices and projectors. There is a one-sided telecentric lens that has a telecentric lens structure only on the subject side, and the two-sided telecentric lens is large and expensive, and the one-sided telecentric lens is small and relatively inexpensive.
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