Smartphone Projector Calculator

This calculator relies on the fundamental thin-lens equation from geometrical optics: 1/f = 1/d_o + 1/d_i, where 'f' represents the focal length of the magnifying lens, 'd_o' is the object distance (the distance from your phone screen to the lens), and 'd_i' is the image distance (the distance from the lens to the projected wall or screen). Additionally, magnification (M) is calculated as the absolute value of the image distance divided by the object distance (M = |d_i| / d_o). By knowing your lens's focal length and your phone's screen dimensions, the tool computes the resulting projection size in inches, centimeters, feet, and meters.

Imagine you are building a DIY projector using a convex lens with a focal length (f) of 15 centimeters (0.15 meters), and you place your smartphone screen at an object distance (d_o) of 16 centimeters. First, using the lens formula, 1/15 = 1/16 + 1/d_i, we find that the image distance (d_i) equals 240 centimeters (2.4 meters). Next, we compute the magnification: M = 240 / 16 = 15. If your smartphone screen measures 6 inches diagonally, multiplying this by the magnification factor yields a projected image diagonal of 90 inches (or 7.5 feet) on your dark wall.

To achieve the sharpest and brightest projected image, always maximize your smartphone's display brightness to 100% and remove any screen protectors that might scatter light. Keep in mind that projected images will appear upside down due to optical refraction through a single convex lens, so you will need to rotate your phone screen orientation accordingly. Finally, use a completely dark room for the best contrast and visibility.