Reduced Sensitivity to Beam Position & Spatial Uniformity

Many detectors have varying sensitivity across their photosensitive area due to shadowing from bond wires, or small variations in electrical resistivity with position. By positioning a detector some distance behind an optical disk diffuser such that the angle from A to B is small, sensitivity beam to position, shape, and angular distribution is greatly reduced. Detector sensitivity to beam position and spatial position is reduced even further as distance from diffuser to detector is increased. The tradeoff is that the signal attenuation increases, reducing signal to noise ratio.

Close to Ideal Lambertian Angular Distribution

Optical disk diffusers feature a thin diffusing glass coating bonded to a clear glass substrate, resulting in roughly uniform spectral performance from 400 to 2000nm. Light propagating through flashed opal glass diffusers is typically scattered multiple times, effectively randomizing the final output direction isotropically across a full 4π steradians within the glass medium. Outside the medium output is nearly Lambertian, meaning light intensity varies with cosine of angle away from the surface normal. The biggest drawback of Optical Disk Diffusers is signal attenuation. As light is scattered in all directions, both forward and backward, only a small percentage of the incident power arrives at the final detector, which has a limited size and acceptance angle.

Improve Source Uniformity for Microscope Illumination

To improve the uniformity of a high intensity light source, such as an Oriel Continuous Wave Light Source), place one or more of these diffusers at the output aperture of the lamp housing. For high power sources above 200 W, a liquid filter or dichroic hot mirror should be placed in front of the diffuser to protect the flashed opal from potentially damaging heating.