With the help of three BMDO SBIR
Phase II contracts related to holography, Physical Optics Corporation (POC;
Torrance, CA) has become a leader in holographic technology and its application
to photonic systems. POC has developed and commercialized a family
of holographic components called Light Shaping Diffusers™ (LSDs) that control
light scatter into a limited solid angle, which can be either circular
or elliptical in shape. One important function of LSDs is to eliminate
"hot spots" from light sources by homogenizing the illumination, which
is important in Raman and fluorescent imaging. Beam-shaping, in turn, enables
excellent matching between the light source and an area to be illuminated,
such as the slit of a spectrometer, a cuvette, a detector array, a chromatography
plate, or a document. As a result, LSDs could be used in spectroscopy,
endoscopy, robotic vision, document reading, and light-emitting diode (LED)
How It Works
LSDs are surface-relief holograms that can be mass-produced inexpensively. An LSD is like a refractive negative lens in that it bends light, but its surface acts as various-sized, randomly distributed microlenses to produce the desired refraction angle.
LSDs shape light in two ways. First, they homogenize the light beam, eliminating variations in brightness caused by the structure of the light source. Second, they control light energy distribution along both the horizontal and vertical axes to match the light source with the area requiring illumination. An LSD produces a diffusion effect based on refraction rather than scattering, allowing more than 90 percent of the light striking the LSD to be transmitted to the target. The inherently antireflective nature of the holographic microstructure results in the high transmission efficiency.
POC’s LSDs are used in many unusual display applications, such as the Humminbird® Jimmy Houston Pro Flasher™ depth finder (shown above). Techsonic Industries manufactures the depth finder that helps anglers "see" underwater to find fish, grass, brush, and drop-offs in a stream or lake. An LSD provides uniform illumination on the device’s display, which uses a spinning disk to present a visual representation of the water depth. Adding the LSD to the depth finder results in a brighter and easier-to-read high-resolution display than previous light-emitting diode designs.
In addition to display applications,
POC’s LSDs have appeared in machine vision and aircraft inspection. Kulicke
& Soffa Industries, a producer of semiconductor manufacturing equipment,
incorporated an LSD assembly in the machine vision system of a wire bonder.
Improving brightness and light uniformity, the LSD helps the bonder locate
reference points on the die pad during semiconductor manufacture. In aircraft
inspection, POC’s LSDs offer a simple, low-cost improvement adaptable to
most commercial flashlights. Providing even illumination with more than
90 percent of the light transmitted to the subject, this technology improves
inspection efficiency and accuracy.