High accuracy machine vision applications are dependent on the production of reproducible, high quality images, whether for inspection or measurement purposes. This means that the images must have sufficient resolution and proper definition of the areas of interest for the inspection or measurement to take place. Each element of a machine vision system has an important role to play in the overall outcome, but the optical system is a critical component since it forms the image of the object on the camera sensor. The construction of a lens system (lens radii, distances between lenses) as well as the distance between the lens and the sensor has an impact on the image.
Once the field of view for the application has been determined, resolution and image quality are the most important selection criteria. Most lenses used in machine vision applications are fixed focus endocentric lenses which provide the same perspective as the human eye. In a perfect lens, all rays of light from a single point on an object plane will be focused to a single point on the image plane. However, all lenses suffer from imperfections that influence the resolution and quality of the image produced by the lens. These include: