How Telecentric Lenses Improve Measurement Accuracy in Optical Metrology

Introduction

In high-precision industries such as aerospace, automotive, and medical device manufacturing, even the smallest dimensional error can lead to costly defects. Telecentric lenses for precision measurement play a critical role in optical metrology, ensuring accurate, reliable, and repeatable measurements. These specialized lenses eliminate perspective distortion, maintaining consistent measurement accuracy regardless of an object’s position within the field of view.

This blog explores how telecentric lenses work, why they are essential in optical metrology, and how they enhance the performance of profile projectors, video measuring systems, and vision inspection machines.

What is a Telecentric Lens?

A telecentric lens is a specialized optical lens designed to maintain a constant magnification regardless of the object’s distance from the lens. Unlike conventional lenses, which introduce perspective errors, telecentric lenses ensure that objects appear the same size across different depths, improving measurement accuracy.

There are three types of telecentric lenses:

Object-Space Telecentric Lenses – Most common in metrology; eliminate perspective distortion.

Image-Space Telecentric Lenses – Ensure uniform magnification on the sensor side, reducing optical errors.

Double Telecentric Lenses – Combine two object and image centricity for the highest accuracy.

Why Use Telecentric Lenses in Optical Metrology?

  1. Eliminates Perspective Errors

Conventional lenses cause parallax errors, meaning objects closer to the lens appear larger than those further away. In contrast, telecentric lenses project images with parallel light rays, eliminating size variations and ensuring consistent measurements.

Use Case: In optical profile projectors, telecentric lenses ensure that small parts like gears, screws, and electronic components are measured accurately, without distortion.

  1. Improves Edge Detection for Automated Vision Systems

In machine vision systems, edge detection is critical for dimensional inspection and defect detection. Telecentric lenses enhance edge contrast, making it easier for image processing algorithms to identify features with sub-pixel accuracy.

Use Case: In bottle and cap inspection systems, telecentric lenses help detect deformations, warping, and missing components with high precision.

  1. Reduces Measurement Variability

Since telecentric lenses provide a uniform image regardless of object depth, they reduce measurement uncertainty and increase repeatability. This makes them ideal for quality control applications in industries that require tight tolerances.

Use Case: In quick measuring machines, telecentric lenses enable rapid, accurate measurement of complex parts without the requiring precise object positioning.

  1. Enhances Optical Metrology in Non-Contact Inspection

Many industries require non-contact inspection to measure delicate or flexible materials that could deform under contact-based methods. Telecentric lenses allow optical systems to capture high-accuracy measurements without physical interaction.

Use Case: Telecentric lenses help measure thin-walled parts and seals without distortion in plastic and rubber component manufacturing.

Applications of Telecentric Lenses in Metrology and Vision Inspection

  • Optical Profile Projectors – When measuring tiny mechanical parts, plastic components, and dies and molds, it guarantees distortion-free magnification.
  • Video Measuring Systems – Provides high-accuracy 2D and 3D measurements for electronics, medical devices, and automotive components.
  • Machine Vision Inspection – Enhances precision in bottle, cap, and label inspection by eliminating size variations due to object movement.
  • CNC Vision Measuring Machines – Improves accuracy in automated metrology systems, reducing errors in complex part measurements.
  •  Automated Optical Inspection (AOI) Systems – Helps electronics manufacturers inspect PCBs with better edge contrast and dimensional accuracy.

Choosing the Right Telecentric Lens for Your Application

When selecting a telecentric lens, consider the following:

  • Field of View (FOV) – Ensure the lens can capture the entire part or feature being measured.
  • Telecentricity Error – A high-quality telecentric lens should have an error below 0.1% for precise results.
  • Depth of Field (DOF) – Choose a lens with sufficient DOF to maintain focus across different object heights.
  • Resolution – High-resolution lenses provide better image clarity for sub-micron level measurements.

Conclusion

In optical metrology, telecentric lenses are revolutionary because they remove perspective distortion, enhance edge detection, and guarantee precise, repeatable measurements. Whether used in optical profile projectors, video measuring systems, or automated vision inspection, these lenses help manufacturers maintain high-quality standards and reduce defects.

At Optomech, we integrate high-performance telecentric lenses into our precision measurement and inspection systems to deliver best-in-class accuracy for various industries.

📞 Get in touch with us today to learn how telecentric technology can improve your quality control processes!