4 ms·
The benefit of a Fresnel lense is that it only needs to roughly collimate the light, not to focus an image, whereas for a telescope mirror or lense you want as
by codeduck 7y ago
The benefit of a Fresnel lense is that it only needs to roughly collimate the light, not to focus an image, whereas for a telescope mirror or lense you want as much incident light to come to the focal plane at the same focal length.