Abstract
This application note aims to find out which machine vision lens is best for applications carried out in a limited workspace environment by capturing images of QR codes with three different lenses.
Problem Statement
Finding the right lens for applications is challenging, especially when one has many requirements or constraints. For example, one might have limited space in their working environment, or need to produce an image with a wide FOV (Field of View).
To find a solution, the SODA VISION tech team created an experiment comparing three different lenses, Basler M13B02118IR, Computar M0828-MPW3, and Theia SL183M. Combining them with a Basler camera, these setups will allow us to see which lens will be able to detect QR codes within the shortest working distance and have a large FOV at the same time.
Figure 1: Basler M13B02118IR Set Up
Figure 2: Basler M13B02118IR with 100mm working distance
Figure 3: Computar M0828-MPW3 Set Up
Figure 4: Computar M0828-MPW3 with 460mm working distance
Figure 5: Theia SL183M Set Up
Figure 6: Theia SL183M with 100mm working distance
| Basler M13B02118IR | Computar M0828-MPW3 | Theia SL183M | |
| Field of View (FOV) | Same | Same | Same |
| Length from Object to Image | Excellent (125mm) | Poor (510mm) | Excellent (162.5mm) |
| Distortion | High | Low | Low |
| Center to Edge Sharpness | Average | Excellent | Good |
| Smallest Size of QR that can be Read | Average (Cannot be read) | Excellent (Minimum 2 pixels) | Good (Minimum 4 pixels) |
Table 1: Lens Comparison Table between Basler M13B02118IR, Computar M0828-MPW3 and Theia SL183M
Solution
The Theia SL183M lens is the best alternative when comparing the distance from the object to the image. When combined with a Basler camera, the Theia SL183M lens is able to provide an ultra-wide FOV without any distortions in a short object to image distance. Although it does not have the best center to edge sharpness, it is still able to detect information with 4 pixels, and provide a relatively precise image from a short distance of 162.5mm.
Findings
From this experiment, there is no doubt that the Computar lens comes first, followed by the Theia lens, and lastly, the Basler lens when we rank the lenses. The Computar M0828-MPW3 is the best lens for applications, as it has the best center to edge sharpness, a low distortion rate, and only needs a minimum of 2 pixels to detect information. However, it would need to be at least 460mm away from the object to be able to capture an image.
Therefore, if you have a small workspace, consider using the Theia SL183M lens in your applications for a clear yet wide FOV image capture.
