Popular science about telecentric lenses

Telecentric lenses are optical products designed to correct parallax, which is common in traditional industrial lenses. They maintain a constant image magnification within a certain object distance range, making them invaluable for situations where objects being measured are not on the same plane. Because of their unique parallel optical path design, telecentric lenses are widely used in machine vision applications requiring high lens distortion control.

Industrial lenses are critical imaging components in machine vision systems, and they must meet specific requirements to ensure the system functions properly. At the beginning of the 21st century, as machine vision systems became more widely used in precision inspection fields, standard industrial lenses struggled to meet these demands. Telecentric lenses emerged to address this gap and meet precision inspection needs.

Notable Features of Telecentric Lenses:

1. High Resolution: They offer high-resolution imaging capabilities, providing precise and detailed images crucial for inspection and analysis.
2. Ultra-Wide Depth of Field: Telecentric lenses can achieve a broader depth of field than standard lenses, which is beneficial for capturing clear images of objects with varying depths.
3. Ultra-Low Distortion: With a distortion coefficient below 0.1%, these lenses minimize measurement errors, unlike standard industrial lenses, which typically have higher distortion rates.
4. Unique Parallel Light Path Design: This design ensures that the image magnification remains constant across a range of object distances, providing consistent imaging results.

Technical Parameters of Telecentric Lenses:

1. High Image Resolution: Quantified by Contrast Transfer Function (CTF), measured in line pairs per millimeter (lp/mm). Telecentric lenses, even with smaller pixel image sensors (like 5.5 million pixels), can produce high-resolution images.
2. Nearly Zero Distortion: Traditional lenses might have a distortion of over 12%, while telecentric lenses keep it below 0.1%.
3. No Perspective Error: In metrology applications requiring precise linear measurement, telecentric lenses eliminate perspective error by only allowing parallel rays to form the image.
4. Telecentric Design with Ultra-Wide Depth of Field: These lenses maintain a consistent magnification even when the object distance changes within a certain range.

How to Choose a Telecentric Lens?

• Object Size: Determine the field of view required.
• Image Size: The sensor size of the camera (CCD or CMOS) being used.
• Working Distance: The distance from the lens's front surface to the object.
• Resolution: The pixel size of the camera sensor.
• Depth of Field: A larger magnification ratio results in a smaller depth of field, so this factor must be considered.
• Mount Interface: Common interfaces include C-mount and T-mount.

These are some key aspects to consider when selecting a telecentric lens for industrial applications. By understanding these factors, you can choose a telecentric lens that best fits your machine vision and precision inspection needs.