What is the difference between telecentric and normal lenses?

Differences Between Telecentric and Normal Lenses

Telecentric lenses and normal lenses are both crucial components in various optical systems, serving a wide range of imaging and measurement applications. However, they are designed with different principles and serve different purposes. Below, we outline the key differences between these two types of lenses.

1. Optical Design and Principal Operation

Normal Lenses: Traditional lenses, or normal lenses, operate on the principle where the angles of the incoming light rays change as they pass through the lens, causing the magnification to change with object distance.
Telecentric Lenses: Telecentric lenses are designed such that the rays of light are parallel to the optical axis in either the object space, image space, or both, ensuring that the magnification of the object is constant regardless of its distance from the lens.

2. Depth of Field

Normal Lenses: Generally have a shallow depth of field, especially at wider apertures, which makes them ideal for applications where selective focus is desired.
Telecentric Lenses: Offer a much larger depth of field, which is beneficial in industrial measurement applications where maintaining focus across the entire object is necessary for accuracy.

3. Magnification Variation

Normal Lenses: Experience magnification variation with the change in object distance. This means objects will appear larger or smaller as they move closer to or further from the lens.
Telecentric Lenses: Provide constant magnification over a range of object distances, making them particularly valuable in precision measurement tasks where maintaining consistent scale is paramount.

4. Applications

Normal Lenses: Are widely used in general photography, videography, and any application where lens versatility and artistic control over depth of field are important.
Telecentric Lenses: Are primarily used in machine vision, metrology, and other industrial applications where accuracy and consistency in imaging and measurements are required.

5. Cost and Complexity

Normal Lenses: Are generally less expensive and simpler in design compared to telecentric lenses.
Telecentric Lenses: Due to their specialized design and the precision required in manufacturing, are typically more expensive and complex.

Conclusion

In summary, the choice between telecentric and normal lenses depends on the specific requirements of the application. Telecentric lenses are unmatched in applications requiring precise measurements and consistent magnification, while normal lenses offer greater flexibility and are more suited for general imaging purposes.