Lens Stereoscopy

3D viewing is widely used in cinemas today. Technologies such as, Active Shutter, Polarization and Interference filter method are used for 3D projection. In all these methods the basic idea is to provide two different images to each eye like we naturally perceive the world. Then the brain does the rest of the work and combines those images to perceive depth. Although 3D vision is most common in movies at present, in the past it was used in Remote Sensing for military purposes. The instrument used for this purpose is the Stereoscope.

the stereoscope with an image

The Stereoscope consists of two lenses resting on a stand that focus on the two separate images of the stereoscopic image sheet. When looking through the two lenses, each eye sees a slightly different image that is meant for that eye and this results in the perception of depth - the image appears 3 dimensional. This is very useful in analyzing aerial photographs because it allows viewing the ground terrain in 3D.

test image for stereoscopic vision

Shown above is a test image that is used to check stereoscopic vision. The relative heights at which the symbols appear to be seen can be checked against the actual order of heights which are provided overleaf.

Stereoscope with a test image

While in modern remote sensing, stereoscopes have been replaced by more advanced computerized equipment that not only provide 3D views but also help manipulate images in 3D, the stereoscope helps understand the basics of stereoscopic vision. Lens Stereoscopy can also be considered as the foundation of all modern stereoscopic equipment.