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Tech Papers

Choosing a Lens for Your Machine Vision Application

Lore Technology

Things to consider when choosing a lens…

Selecting a lens is equally important as your camera selection, since it is central to image quality. So, finding the perfect lens for your application is key. Let’s get started on 3 easy steps to narrowing down your search results, and keep in mind, your camera specifications will determine your lens options.

Step 1

Find your camera specifications. What is the sensor size, and what are the resolution capabilities?

For example, the camera below, DFK 33UX264 made by The Imaging Source, has a 2/3” sensor with a resolution of 5 Megapixels.

The Imaging Source DFK 33UX264

  • 2/3 inch Sony CMOS Pregius sensor (IMX264LQR)

  • 2,448×2,048 (5 MP), up to 38 fps

  • Global shutter

  • Trigger and I/O inputs

  • Manufactured by The Imaging Source

Ideally, you would want to match this with a 2/3” lens capable of 5-megapixel resolution, such as the Computar MPW2 series lens.

Side note here, you can go larger with your lens format, but not smaller!

Step 2 

Now that you have narrowed down some standard requirements you need to pick a focal length, and this will be dependent on your field of view. Security and surveillance applications often use vari-focal lenses, which are lenses with adjustable focal lengths. But almost all surveillance cameras come with pre-installed lenses, so at the time of purchase, you will want to specify the field of view so that the camera’s lens matches with your needs.

Industrial cameras do not come with attached lenses. The most popular format for industrial applications is the fixed focal length, commonly available in 6mm, 8mm, 12mm, 16mm, 25mm, 35mm and 50mm. To determine the best fit for you, you will need your working distance, the angle of view and the field of view (see image below for clarification). Once these fields are calculated, you are given the best estimate for the required focal length.

 

focal length diagram for picking a lens blog post.png

Step 3

Now that you have the exact lens requirements, you can pick your lens! This is the difficult part because there are so many different industrial vision lens manufactures with excellent product of similar specifications. You may want to ask your sales representative which one they suggest for your application, or request to demo a few options to find the perfect fit.

Here is a calculator from View-Z for what sort of lens you can use.

 

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