eo_logo
  • Country/Region
  • cart   
 
Telecentric Lens Size Control
Edmund Optics Inc.

Telecentric Lens Size Control

This is Section 4.3 of the Imaging Resource Guide

The field of view (FOV) of any telecentric lens is limited by the front optic diameter; the larger the required FOV, the larger the front optic diameter. Telecentric lenses can grow quite large and heavy with small magnifications, as such magnifications require large front optics; this can be prohibitive in some setups where weight or size is a concern. The f/# of a lens also plays into the size of the lens, particularly at large magnifications where the front optics also grow with the speed of the lens. Figure 1 shows two different 4X telecentric lenses of different f/#s. The lens at the top of Figure 1 shows a system that runs at f/6, and the lens at the bottom runs at a much slower f/16.

Two 4X Telecentric Lenses operating at f/6 and f/16
Figure 1: Two 4X telecentric lenses, operating at f/6 (top) and f/16 (bottom), showing how f/# can partially dictate element size for telecentric lenses.

If a particularly large FOV is required, fixed focal length lenses can be augmented with additional optics in order to produce a pseudo-telecentric lens for large FOV. Figure 2 shows a 25mm fixed focal length lens that has been augmented with a Fresnel lens to make a telecentric lens that has an 8” FOV. This type of augmentation always has lower image quality than a specifically designed telecentric lens, but can be useful where cost-sensitive, large FOV applications require telecentricity. This approach allows for minimal flexibility with regards to working distance, as well as substantial chromatic aberrations due to the use of a Fresnel lens.

Fixed Focal Length Lens augmented with a Fresnel Lens, making it Pseudo-Telecentric
Figure 2: A fixed focal length lens augmented with a Fresnel lens, making it pseudo-telecentric.
Featured Resources
 Application Note
 Application Note
Was this content useful to you?

With over 800 Imaging Lenses and 40 pages of in depth Technical Content, make Edmund Optics Your Partner in Imaging Optics.

Large format, compact, in-line, focus adjustment, or iris adjustment options available for your machine vision or inspection application.

Free training videos with imaging and illumination tips and tricks.

Edmund Optics can not only help you learn how to specify the right imaging optics, but can also provide you with multiple resources and products to surpass your imaging needs.

Need help finding the right product? Have questions on your application? Contact us to discuss your technical questions with our expert engineering staff.

×