Frequently asked questions about machine vision telecentric lenses

1. What are the advantages of telecentric lenses?

Telecentric lenses can effectively solve the above-mentioned problems of ordinary lenses, and there are no interpretation errors of this nature, so they can be used in high-precision measurement, metrology, etc. Telecentric lenses are high-end machine vision lenses that usually have superior image quality and are particularly suitable for dimensional measurement applications. 

2. Why do low-magnification telecentric lenses cost more? 

Because telecentric lenses are designed to reduce distortion and allow parallel light to enter, the lens design must be larger than the subject. Therefore, low-magnification lenses usually have large diameters and require higher lens material costs, so the price is higher. 

3. When the coaxial light lens uses coaxial light, the middle brightness is brighter and the whole side is dark. What is the reason? How to remedy this? 

Because the projected light of the coaxial light lens is concentrated at about 5~6mm in the center, if the viewing range is larger, the light near the edge will be darker. This is a common phenomenon with low-magnification coaxial light lenses. An external ring light source can be added to make up for insufficient light. 

4. Can the telecentric lens be used with a 2x lens for CCTV? 

Yes, but the image quality deteriorates and the required light intensity is stronger, so it is not recommended. 

5. In the specifications of telecentric lenses, what does the lens resolution (resolving power) mean? 

The definition of lens resolution is the ability of the lens to see clearly the edges of the smallest objects. If it is lower than this resolution, it will not be able to see clearly. You must find another lens with higher resolution, such as a high-power microscope objective. 

6. Why can’t the depth of field of a telecentric lens be very long? 

When designing a telecentric lens, parameters such as depth of field, magnification, aperture, and working distance are taken into consideration to obtain the optimal point. Therefore, the depth of field is a fixed value. If the depth of field is to be increased at the expense of other parameters, the quality of the lens will be affected. 

7. What kind of lens can be used if you want to see an object of 1μm? 

To see objects smaller than 1 μm, a high-power microscope objective must be used, but the working distance becomes very small (about 7 mm) and the depth of field becomes very shallow. 

8. How many times is the image magnified by a telecentric lens? 

The actual magnification of the image is equal to the optical magnification of the lens × the magnification of the monitor. The magnification of the monitor is the diagonal of the monitor divided by the diagonal of the CCD Sensor (a 1/3″ CCD Sensor projected onto a 14-inch Monitor is 59.3 times).