How to pick the right Telecentric Lens

Selecting the right telecentric lens involves careful consideration of several key parameters to ensure optimal performance and accuracy in your application.

First, consider the field of view (FoV), which represents the total area viewable by the lens and captured by the camera sensor. Next, the working distance (WD) defines the distance between the lens and the object where the image is sharpest. Additionally, depth of field (DoF) which indicates the maximum range where the object remains acceptably in focus.

Now let’s evaluate the sensor size, this is calculated by multiplying the pixel size by the sensor resolution. Magnification, is the ratio between sensor size and FoV, which determines the level of detail captured. Lastly, resolution, the minimum distance between distinguishable points, is crucial for accurate measurements.

Having a fixed working distance and aperture, telecentric lenses are classified by their magnification and image circle. Choosing the correct telecentric lens is straightforward. This is done by determining the magnification required to fit the image onto the sensor.

For example, if you need to measure the geometrical features of a mechanical part that has a 10 mm diameter circle with 2 mm of uncertainty on the positioning of the sample while using a 2048 x 2048, 5.5 µm sensor, the optimal choice would be a lens that provides the required FoV of 14mm.

Given the camera resolution and pixel size of (2048 x 2048 pix, 5.5 µm), the sensor dimensions are calculated to be 11.26 x 11.26 mm.

In this example, the Opto Engineering telecentric lens offers a magnification of 1.000X with an image circle of 11 mm. While this lens provides a close match to the required FoV, mechanical vignetting limits the actual FoV to an 11 mm diameter circle.

Alternatively, the Opto Engineering TC2MHRP016-C lens, with a magnification of 0.767X and an image circle of 16.0 mm, offers a FoV of 14.68 x 14.68 mm, providing a very close match.

As you can clearly see in many applications, accurate measurements and excellent performance can be ensured by choosing the appropriate telecentric lens.