In order to get a good, sharp image, you not only need a good camera, but also the right lens for the camera. Right from the beginning the sheer unlimited selection of possible lenses is apparent. For digital compact cameras there is usually a permanently installed lens; for reflex cameras you can work with exchangeable lenses in order to get the best possible image in many different situations. The individual lenses vary not only in their resolution, angle width, and size, but also in their construction. This is also a “problem” with machine vision cameras and the lenses that are appropriate for them. Which lens is the correct choice for which conditions will be explained in the following article.
What Types of Lenses are There?
Before we explain what to look for when selecting a lens, you should first consider the various types of lenses available. In general there are entocentric or telecentric lenses, as well as wide-angle and fish-eye lenses. Additionally, there are also special lenses for near infrared.
Here, however, we will concentrate exclusively on entocentric lenses as they are primarily found in machine vision applications. Normal entocentric lenses have a fixed–angle aperture for the lenses as well as for the sensor. The aperture angle is similar to the human eye. Far distant objects appear smaller and closer objects appear larger. The most commonly available entocentric lens is found in the human eye.