Selecting the correct lens for optimum image quality for your application is where Multipix Imaging can help. Lenses can have considerably different characteristics that will impact the final image as well as the suitability for the environment they are being used in.
It may be a very short working distance or very high vibrations that need to be considered, not just the more obvious characteristics of format size and mount-type.
You can use a simple formula to select the lens focal length to provide the correct field of view (coverage). This is a good starting point before moving onto the other considerations
Choose an optical resolution or MTF that ensures crisps edges. Multipix have MTF charts for many of the lenses offered and can explain how this information is used to select lenses.
The optical format is the maximum sensor size the lens has been made to image, for example a 1/2? lens is not suitable for a 2/3? sensor. Selection is important to avoid image clipping or shading at the edges (vignetting).
Example of Vingetting
Example with no Vignetting
The set-up and the construction of a lens will determine the depth of field, ie. the range of distance from the lens that is in focus. DoF can be used to advantage in many applications.
Occurs when a lens is not able to focus all colours (wavelengths) to a single point. There are way to minimise and avoid this artefact arising in the image.
Avoiding perspective distortion is very desirable as it can cause incorrect results from the image processing algorithms. Telecentric lenses offer a solution but it is important to understand when and how to use them.
Read more on our Imaging Guide in Part 7: Machine Vision Lighting