Answers to eight major questions about the application of telecentric lenses

Eight Common Questions About Telecentric Lens Applications

Telecentric lenses are a high-end type of machine vision lens designed to eliminate discrepancies in magnification caused by varying distances between the object under observation (or the CCD chip) and the lens. They are categorized into three types: object-side telecentric lenses, image-side telecentric lenses, and double-sided telecentric lenses.

Due to their unique technical advantages, telecentric lenses are currently in high demand for high-precision inspections in fields like mechanical parts measurement, plastic components measurement, glass products, pharmaceutical parts, and electronic components. Today, the China Machine Vision Mall addresses eight common questions regarding telecentric lenses.

1. What are the advantages of telecentric lenses? Telecentric lenses are designed to use the telecentric principle, offering low distortion and no perspective error, making them ideal for industrial measurement applications. This is why they tend to be more expensive than standard CCTV lenses. Additionally, telecentric lenses come in coaxial designs, offering various working distances and magnification options.

2. Why are low-magnification telecentric lenses more expensive? To reduce distortion and allow parallel light to enter, telecentric lenses must be designed larger than the object being imaged, leading to higher material costs for larger lens elements. This is why low-magnification telecentric lenses tend to be pricier.

3. When using coaxial lighting with a coaxial lens, why is the center brighter while the edges are darker? How can this be corrected? The projected light from coaxial lenses tends to concentrate in the central 5-6 mm, resulting in darker edges, especially with low-magnification coaxial lenses. To address this, ring lights can be added to supplement edge illumination.

4. Can telecentric lenses be used with 2x extenders for CCTV? It is possible but not recommended due to decreased image quality and the need for stronger illumination. This setup can lead to significant quality loss.

5. What does lens resolution represent in telecentric lens specifications? Resolution indicates the lens's ability to resolve the smallest edges of an object. If a lens's resolution is below a certain point, details cannot be discerned, requiring a lens with higher resolution, such as high-magnification microscope objectives.

6. Why is the depth of field with telecentric lenses limited? When designing telecentric lenses, parameters like depth of field, magnification, aperture, and working distance are balanced to achieve optimal performance. The fixed depth of field is a trade-off for other parameters. Increasing the depth of field might compromise other performance aspects, reducing lens quality.

7. What type of lens is needed to see 1μm objects? To view objects smaller than 1μm, high-magnification microscope objectives are required. However, these have very short working distances (around 7 mm) and very shallow depths of field.

8. What is the magnification with telecentric lenses? Telecentric lens magnification varies depending on the specific lens design, working distance, and intended application. The specified magnification generally represents the ratio between the image size and the actual object size.