Contributor: Stas Fainer

Some optical systems map infinite parallel lines, to lines on the image plane which meet at a single point, making an illusion that the parallel lines meet "at infinity". This single point is called the vanishing point.

For an optical system comprising an ideal lens with focal length \(f\), located on the \(XY\) plane, such that its optical axis coincides with the \(X\)(horizontal) axis and the lens coincides with the \(Y\) axis, the vanishing point for a line with a slope \(m\), located at \(x<0\), is given by the \((x,y)\) coordinates \((f,m f)\) .