Bi-telecentric lens principle and application range

Understanding the Principles and Applications of Double Telecentric Lenses

Industrial lenses are critical components in machine vision systems, and telecentric lenses are valued for their unique properties. This guide explores the basics of telecentric lenses, focusing on their principles, application areas, and selection criteria.

Double Telecentric Lens Principles

Issues with Non-Telecentric Lenses Traditional lenses face several challenges:

1. Changing Magnification with Work Distance: As the work distance changes, the image size changes, leading to varying magnification with the same focal length lens. This inconsistency can be problematic in precision measurement applications.
2. Depth of Field Limitations: Standard lenses offer limited depth of field, leading to blurriness when objects are outside this range. Designers address this with focusing rings, but these are inadequate if the object's depth varies significantly.
3. Resolution Limitations: With advancements in imaging sensor technology, traditional lenses can struggle to match the resolution required, with a typical limit of about 10 micrometers.

Double Telecentric Lens as a Solution Double telecentric lenses address these issues by incorporating an aperture at the center of the optical system. This design ensures that the principal rays are parallel to the optical axis, resulting in consistent magnification across varying work distances and providing a larger depth of field. This characteristic ensures that the image's height and magnification remain constant, even with significant changes in work distance.

When to Use Telecentric Lenses?

Based on FALenses Technology's extensive experience, here are scenarios where double telecentric lenses are highly beneficial:

1. Thick Objects with Multiple Planes: When measuring objects with significant depth, like food containers or beverage bottles.
2. Uncertain Object Placement: When the object's placement is inconsistent or at varying angles to the lens.
3. Objects Subject to Vibrations: When work distances fluctuate due to vibrations on a production line.
4. Objects with Apertures or Three-Dimensional Objects: For accurate measurements of 3D objects or those with holes.
5. Low Distortion and Consistent Brightness: When distortion must be minimized and consistent image brightness is required.
6. Defects Only Detectable with Parallel Illumination: When defects require parallel illumination for detection.
7. High Precision Measurement: When required measurement accuracy exceeds conventional lenses, such as a permissible error of 1 micrometer.

Conclusion

Double telecentric lenses offer a robust solution for machine vision applications where precision, consistent magnification, and large depth of field are critical. These lenses are particularly valuable in high-precision measurement tasks and scenarios where traditional lenses fall short due to inherent optical limitations.