This section provides an overview for telecentric lenses as well as their applications and principles. Also, please take a look at the list of 8 telecentric lens manufacturers and their company rankings.
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A telecentric lens is a lens with an optical axis that is parallel to the principal ray. By using this lens, it is possible to capture images with no angle of view and no error due to parallax. Even objects with uneven surfaces or depth can be read at a constant magnification, making it suitable for precision processing.
It is also capable of producing images without stereoscopic effect, so that no distortion occurs at the center and edges of the image.
It is used for inspecting minute scratches and detecting dust on objects that easily reflect light, such as glass surfaces.
Telecentric lenses are used in various applications.
An example is the inspection of three-dimensional objects. When a three-dimensional object such as a pin is photographed with a normal lens, the center and the edges of the image will look different from each other. This is because the object is distorted by parallax. However, by using tele lenses, an accurate image can be read without distortion.
They are also used for inspecting dust and scratches. This is because it is easier to find dust and scratches as centric well as to avoid missing them due to parallax. By using telecentric lenses, the reflectance of light can be read as a difference in contrast, enabling the detection of microscopic dust and scratches.
Telecentric lenses are characterized of having a parallel optical axis with the main beam of light, and can be divided into three main types depending on how the lens is used:
The disadvantage of telecentric lenses are that they are likely to be large in diameter; only light rays incident perpendicular to the CCD/CMOS element surface are formed, so the appropriate lens diameter for the system depends on the element dimensions.
If the object to be imaged is small, the lens diameter can be small, but the lens diameter must be large in relation to the size of the object. Therefore, it is difficult to use telecentric lenses in areas where space is limited.
In addition, telecentric lenses are not suitable for systems that use binocular parallax to perform rigid body transformation of the camera (e.g. VR and AR). The reason is that depth information is lost. Since only parallel light is extracted, objects in the background and objects in the foreground are captured as images at the same magnification.
This makes it unsuitable for 3D rigid body transformation.
One point to note here is that telecentric lenses are not, by any means, ideal lenses.
The expression "no error" only means that the conditions are close to ideal because errors caused by the angle of view can be reduced compared to normal lenses. For example, when focusing on distortion, it depends on the lens, so it cannot be generalized, but optical distortion of ±0.5% is common.
Of course, the distortion level is still smaller than that of a normal lens. With normal lenses, distortion levels of ±20% or more being common.
Again, keep in mind that the use of telecentric lenses does not necessarily mean zero distortion. Of course, if an error of ±0.5% does not affect performance, then distortion correction is not necessary and the lens is ideal for the system.
However, if it does affect performance, then software or hardware distortion correction is required, just as with a normal lens.
*Including some distributors, etc.
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Founded in Mumbai, India in 2006, Otto Chemie Pvt. Ltd. is an ISO 9001:2015 & GMP certified chemical manufacturing company and distributor. Otto Chemie serves customers in many industries including agriculture and food processing, pharmaceuticals, oil & gas, cement, as well as educational and R&D industries. Product offerings include antibiotics, amino acids, vitamins, detergents, ionic liquids, materials science compounds, labware, oil, metal & ceramic science compounds and tools, oils, reagents, solvents.
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