Contents
Source: Wikipedia
Understanding Telecentric Lenses in Optical Systems
Introduction to Telecentricity
Telecentric lenses are commonly used in optical instruments like telescopes and laser scanners. These lenses have an orthographic perspective, where the principal rays are horizontal and the entrance and exit pupil is at infinity. Telecentricity is achieved by using an optical aperture, such as a diaphragm, to ensure that only specific rays contribute to the image formation.
Object-Space Telecentric Lenses
In object-space telecentric lenses, a diaphragm is placed in the back focal plane of the lens to achieve telecentricity. This setup ensures that only rays coming from approximately horizontal directions contribute to the image formation. Object-space telecentric lenses are commonly used in machine vision and measuring telescopes for accurate image processing and size measurements.
Image-Space Telecentric Lenses
Image-space telecentric lenses use an aperture in the front focal plane to create a telecentric setup. This design ensures that light rays are nearly horizontal after passing through the lens, leading to consistent image quality regardless of the sensor position. Image-space telecentric lenses are used in digital cameras and laser scanners for precise imaging and scanning applications.
Bi-Telecentric Systems
Bi-telecentric systems achieve telecentricity in both object and image space by using afocal optical systems. These systems are ideal for applications requiring orthographic perspective and normal light incidence on the sensor. Bi-telecentric imaging systems are used in various fields where precise and consistent imaging is crucial.
Telecentric Zoom Lenses
Telecentric zoom lenses offer adjustable focal lengths and magnifications while maintaining telecentricity. The zoom mechanism in these lenses must keep the stop in the focal plane to ensure consistent image quality. Telecentric zoom lenses provide flexibility in adjusting the field of view and magnification in optical systems.
Applications and Limitations
Telecentric lenses find applications in machine vision, microscopy, laser scanning, and other fields where precise imaging is essential. However, these lenses have limitations, such as restricted depth of field and field of view, making them unsuitable for certain applications requiring large depth of field or wide field of view.
In conclusion, telecentric lenses play a crucial role in various optical systems by providing consistent and accurate imaging capabilities. Understanding the principles and applications of telecentric lenses can help in optimizing optical setups for different requirements in fields ranging from machine vision to laser scanning.
Source: Sill Optics GmbH
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