Explain the selection methods and calculation formulas of industrial lenses

The selection of industrial lenses is a critical step in designing machine vision systems, as the choice of lens directly affects image quality. Here is an industrial lens selection method and related formulas shared by POMEAS engineers, based on their years of practical experience.

Industrial Lens Selection Method and Formulas

1. Determine Camera Parameters

   • First, identify the type of camera interface, sensor size, and resolution. For example, if the industrial camera is 2/3-inch with a C-mount and a resolution of 5 megapixels, then the required industrial lens must support at least a 2/3-inch sensor, with at least 5 megapixels, or 160 LP/mm in line-pairs resolution.

2. Calculate Focal Length and Field of View

   • Next, determine the required field of view (FOV) and working distance (WD), then use the following formulas to calculate the focal length (f):
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3. Practical Lens Selection

   • Example: If the required field of view is 100x100mm and the working distance is 500mm, then the focal length should be below 50mm. Given these constraints, industrial lenses typically have focal lengths of 12mm, 16mm, 20mm, 25mm, 35mm, 50mm, 75mm, etc. The shorter the focal length, the wider the field of view, hence the larger the viewing area.
   • If the sensor size is 2/3-inch, you could choose a 35mm focal length industrial lens; if it's 1/2-inch, a 25mm focal length industrial lens would be more suitable, or even smaller.

For ease of calculation during the industrial lens selection process, here's a reference table for sensor sizes:

• 1.1-inch: 12mm x 12mm, diagonal 17mm
• 1-inch: 12.7mm x 9.6mm, diagonal 16mm
• 2/3-inch: 8.8mm x 6.6mm, diagonal 11mm
• 1/1.8-inch: 7.2mm x 5.4mm, diagonal 9mm
• 1/2-inch: 6.4mm x 4.8mm, diagonal 8mm
• 1/3-inch: 4.8mm x 3.6mm, diagonal 6mm
• 1/4-inch: 3.2mm x 2.4mm, diagonal 4mm

These are the fundamental guidelines for selecting industrial lenses and the corresponding formulas, which I hope will be helpful to you.