Machine vision is a far-reaching and varied application that requires compact and robust optical systems and lenses that offer good contrast, telecentricity, and high resolution.
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Resolve Optics Ltd has many years experience in producing compact zoom and fixed focus lenses for vision applications such as precise component placement, parts recognition, and the placement, automated alignment, and automated inspection of manufactured components.
The variety of machine vision lenses and optical systems is considerable due to the wide range of sensor formats and the different resolution versions of cameras.
One of the most frequent mistakes in designing a vision system is that the scientist or engineer will often choose a sensor and a camera before selecting a lens. This could result in a situation where an optimized lens is not available for the application.
It is important to consider that all machine vision systems need an image of adequate quality to be produced for the necessary measurements to be taken. The choice of lens or lens combination is a key determinant of the quality of the image.
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The lens selection can additionally affect other factors such as the reproducibility and reliability of the downstream analysis, achievable speed, and measurement accuracy of the vision system.
How to Select a Machine Vision Lens
A recommended selection process for a machine vision lens should include the identification of the optical requirements of the application and reaching a consensus on the main specifications that will achieve this.
These optical parameters should include the resolution (or size of the smallest part or detail to observe or detect), the field of view, working distance, and the depth and range of field (the height of the objects being observed).
Once these four main specifications are agreed and set, choosing an optimized camera and lens is made simple.
There is a specific relationship between the most appropriate lens and the sensor employed in the camera. When the sensor size is known, it is possible to choose an optimised lens that will illuminate the entire area of the sensor without vignetting and shading.
The lens selected also must be able to resolve the pixel size of the sensor. A more detailed machine vision analysis will be achieved if the optical resolution of the lens is high.
Standard resolution lenses (MTF 70 to 90 lp/mm producing low vignetting and distortion) are the most frequently used type of lens for machine vision sensors with a resolution of less than 1 megapixel.
High-resolution lenses (MTF> 120 lp/mm and very low distortion) provide optimized imaging performance in comparison to standard lenses and are especially well suited to cameras containing a small pixel size.
This article provided an overview of the several factors to consider when looking to produce an optimized inspection solution utilizing machine vision.
Contact Resolve Optics now to review any application and to discover more about the refined manufacturing solutions and optical design that the company can provide for use in applications involving machine vision.
This information has been sourced, reviewed and adapted from materials provided by Resolve Optics Ltd.
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