ECE532 Biomedical Optics © 1998 Steven L. Jacques, Scott A. Prahl Oregon Graduate Institute

Collection by an aperture

An aperture is essentially a hole through which light can pass to reach some detection system.

An aperture to collect a limited solid angle of light.

Consider an aperture with a detector placed behind the aperture. Only the light which enters the aperture but hits the detector will be detected. Hence the aperture has a limiting cone of acceptance.

• The figure shows the cyan cone of light that reaches one edge of the detector.
• The figure shows the magenta cone of light that reaches the other edge of the detector.
• The figure shows the green cone of light that reaches the center of the detector.
• The total cone of acceptance has a half-angle of θ = 35.7°.
• The further the detector is from the aperture, the narrower is the solid angle of collection.