Features and advantages of telecentric zoom lenses

Telecentricity refers to a principle characteristic of lens imaging. Telecentric lenses can be classified into three types: object-side telecentric, image-side telecentric, and dual-sided telecentric. An object-side telecentric lens has its entrance pupil located at infinity on the object side, causing all principal rays entering the lens to be parallel to the lens's optical axis. An image-side telecentric lens has its exit pupil located at infinity on the image side, leading to all principal rays reaching the imaging sensor to be parallel to the lens's optical axis.

Telecentric Zoom Lenses

1. No Parallax in Captured Images:

   • In machine vision applications, most objects being inspected are in three-dimensional space, having both planar and depth characteristics. Non-telecentric lenses introduce parallax effects when capturing 3D objects due to variations in depth dimensions. This impact is inherent to non-telecentric lens imaging and cannot be eliminated.

2. Ultra-Deep Depth of Field:

   • For instance, if a sample has a coiled structure, there will be significant depth variance relative to lens focusing. With traditional lenses, it can be challenging to achieve simultaneous focus on all parts of such an object due to the limited depth of field compared to the outer diameter of the coiled structure. Telecentric lenses, with their larger depth of field, can address this problem.

3. Effectively Avoids Reflection and Glare:

   • In visual inspections, appropriate lighting is critical for proper imaging. In many cases, using standard lighting solutions can result in unwanted light angles and reflections that can distort or degrade the image quality. Telecentric lenses help reduce these unwanted light artifacts and allow for more consistent and reliable imaging.

4. Fixed Optical Magnification:

   • For lenses with an infinite imaging distance, different object distances within the depth of field can lead to variations in magnification, creating a "closer objects appear larger" effect. In precision visual inspections, accurate spatial measurements often require a consistent magnification ratio between the object and image space, which telecentric lenses can provide. This stability in magnification is crucial for accurate size reproduction and measurement in machine vision applications.