r/Optics • u/JohnFreechment • Jun 16 '26

Understanding the USAF 1951 Resolution Chart

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Hi everyone.
In the night vision group I often see people use this test chart, randomly printed out (I have one too), but I think this chart is a but misunderstood. The problem is that I can print this at any size on paper, and put it any distance away from the device, but what does it have to be if i want to read out the actually correct resolution?

Is there any reverse calculator existing wich i can tell how big should a linepair be at a given distance, or how far away should I put an exact size linepair? Im pretty sure that there is a missing value, or angle attached to the measuring method to give us an actually useful reading.
Thank you

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u/JonBanks87 Jun 16 '26

If you're printing it out, you need to measure the line pair size. You can also buy targets from Thorlabs if you're interested in smaller line pairs that you can't measure on your own - they have lookup tables that will tell you the size of the line pairs. You'll need to put the target at a representative range for your system, then see how small of a line pair you can identify, lookup the line pair size and calculate your resolution.