I am trying to write a program using opencv to calculate the distance from a webcam to a one inch white sphere. I feel like this should be pretty easy, but for whatever reason I’m drawing a blank. Thanks for the help ahead of time.
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I am trying to write a program using opencv to calculate the distance from a webcam to a one inch white sphere. I feel like this should be pretty easy, but for whatever reason I’m drawing a blank. Thanks for the help ahead of time.
You can use triangle similarity to calibrate the camera angle and find the distance.
You know your ball’s size:
Dunits (e.g. cm). Place it at a known distanceZ, say 1 meter = 100cm, in front of the camera and measure its apparent width in pixels. Call this widthd.The focal length of the camera
f(which is slightly different from camera to camera) is thenf=d*Z/D.When you see this ball again with this camera, and its apparent width is
d'pixels, then by triangle similarity, you know thatf/d'=Z'/Dand thus:Z'=D*f/d'whereZ'is the ball’s current distance from the camera.