Medical endoscopes make use of total internal reflection.They consist of two bundles of optical fibres: one for illumination and one to form an image from light passing through a lens covering the other fibre bundle through which the image can be observed.
The fibre bundle is coherent so all the fibres must end the same relative positions.The fibre is inserted into a body cavity which is illuminated by one of the fibre bundles and the light travels from the lens covering the other through the lens of the other bundle where the image can be observed.
The fibre bundle is coherent so all the fibres must end the same relative positions.The fibre is inserted into a body cavity which is illuminated by one of the fibre bundles and the light travels from the lens covering the other through the lens of the other bundle where the image can be observed.