Calculate distances and focal length for your homemade smartphone projector.
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Calculation Results
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About this calculator
Quick Reference
doDistance from object (phone) to lens
diDistance from lens to image (screen)
fFocal length of the lens
MMagnification (di / do)
Overview
A DIY smartphone projector uses a magnifying lens to project your phone's screen onto a wall. This calculator helps you find the correct distances based on the lens focal length.
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Pro Tips
Focal length (f) is usually printed on the lens or can be found online.
The phone must be placed further away than the focal length (do > f) to create a real image.
The projected image will be inverted (upside down and flipped), so you need to lock your phone's rotation and turn it upside down.
A dark room and a high-brightness setting on your phone are essential.
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Fun Facts
"The image you see on the wall is a 'real image' because the light rays actually converge there."
"If you place the phone closer than the focal length (do < f), you get a 'virtual image' (like a magnifying glass), which cannot be projected onto a screen."
"Projector lenses are often convex (curved outward) to focus the light."
