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Sven3376

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**Summary:**calculation a projection lens system for a pattern projector

**Summary:**calculation a projection lens system for a pattern projector

Hello,

I want to build a small pattern projector. This projector should project a pattern on a wall, which is 200mm away from the projector. The size of the projected pattern at this distance should be 110 x 110 mm. The dimensions of the projector should be 25 x 25 and max. 50mm long. I have found this page from Edmund optics, where the describe such a system (starts at the middle of the page: Application 3: Building a Projection System) https://www.edmundoptics.com/resources/application-notes/optics/optics-application-examples/

They said, that I need two lenses for the projection lens system and two lenses for the condenser lens system. For the illumination I use a 40W LED with a diameter of 20mm. My magnification M = Image/Object = 110mm/10mm = 11. On this site they calculated the lenses for the projection lens system as follows: F1 = F2 / M (where F2 is the throw distance). So my F1 = 200mm / 11mm =~18mm. So I need two achromatic lenses with a focal length of 18mm. For the condenser system the use this formula: F2 = F1 * M = 18mm * 11mm = 200mm. So I need two PCX lenses with a focal length of 200mm. I´´ am not sure if this calculation is correct. For me, it seems a little bit to easy what EdmundOptics is calculating there? What do the experts say?

best regards,

Sven