Holographic Beam Homogenizer
Summary:
With the help of BMDO SBIR funding, Physical Optics Corporation (POC) has developed a holographic-based beam homogenizer that diffuses and directs light. Marketed under the trade name of Light Shaping Diffuser® (LSD®), this technology is used in many applications, including machine vision, depth finders, and miniature displays. POC has sold homogenizers to such companies as Kulick & Soffa and Kopin Corporation.
Technology Description:
The holographic beam homogenizer is a thin sheet of material that diffuses light. Placed between a light source and a display, surface, or screen, the homogenizer eliminates “hot spots” (bright concentrations of light) and dark areas, improves transmission efficiency, and redirects light.
Through a patented holographic process, a surface relief hologram of randomized lenslets, replicated from a holographically recorded master, is copied onto a polycarbonate surface. (Holography is a method of producing and storing three-dimensional images by recording the interference pattern created when an object is illuminated with a laser beam. The crests and troughs of a light reflected from the object cancels or adds to those of a “reference beam,” producing a pattern that can be recorded on a light-sensitive surface.) The replicated hologram spreads light evenly on the display or screen, eliminating the “hot spots” and dark areas that typically plague unfiltered light sources such as LEDs or lasers.
Due to their polycarbonate material and microsculpted surface structures, homogenizers are more efficient at transmitting light than regular ground-glass diffusers. Homogenizers transmit 85 to 92 percent of the light they receive, while glass diffusers only have a 50 to 60 percent efficiency. A higher efficiency means less power is needed to illuminate a given area. A higher efficiency also means a higher brightness is possible, making homogenizer-enhanced displays suitable for high ambient light conditions.
POC’s homogenizers can be customized to direct light into a limited solid angle, either circular or elliptical. This beam-shaping 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.
POC recently received a patient (US Patent Number #5,534,386) for this method of laser-recording interference patterns of microsculpted surface structures onto photosensitive mediums. Homogenizers are non-wavelength dependent and will work in either white, monochromatic, coherent, or incoherent light.
MDA Origins:
POC developed several holographic components under BMDO SBIR Phase II contracts for holographic integrated planar interconnects for use in strategic defense electronic systems. One of these components was the holographic beam homogenizer
Spinoff Applications:
Homogenizers can be used in a wide array of products. Because homogenizers save energy and work well in high ambient light, they can benefit battery-powered handheld microelectronic devices that have liquid crystal displays or LED’s. Homogenizers can be used in applications where the exact placement of light is mission critical, such as machine vision, barcode scanners, optical sensors, CD reflectors, spectroscopy and endoscopy devices. And they would work well for any applications that would benefit by a more evenly spread source of light—flashlight and microscope illumination, automotive lighting, lighted signs and projection screens, for example.
Commercialization:
Holographic beam homogenizers are marketed by POC under the trade name Light Shaping Diffusers (LSDs). Individual LSDs cost between $80 and $145 each, depending on the size and type of filter. In addition, POC is scaling up production to meet the high-volume screen applications, bringing the price per unit down to as little as $12 per LSD when ordered in bulk. To help in that process, NIST awarded POC an Advanced Technology Program award in 1993.
Some applications of the LSD include:
•Machine vision: Kulick & 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 to easily locate reference points on the die pad during semiconductor manufacture.
•Projection screens: POC developed two LSD products for the display screen area: the front-projection Lights-On Reflection Screen (LORS™) and the rear-projection DDS™ (Digital Display Screen).
•Aircraft inspection flashlights: When placed in flashlights, LSDs greatly improve beam quality. POC markets the LSDs for aircraft inspection flashlights. Through visual examination, the trained eye can detect glint or shadows that could indicate problems. Contrast is essential to see subtle effects that signal corrosion. Covering a flashlight, the diffusers provide even illumination and transmits more than 90 percent of the light to the target, eliminating glare, “hot spots,” and dark spots. The beam is shaped to fit the viewing area. Inspectors can then focus on the aircraft surface and not the flashlight beam.
•Displays: POCs LSDs are used in many unusual display applications. Techsonic Industries manufactures a depth finder that helps anglers “see” underwater to find fish, grass, brush, and drop-offs in streams. The 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 LED designs.
LSD’s are used by Kopin Corporation for its CyberDisplay, a low-power 0.24 inch liquid crystal display. This display has a 320x240 pixel resolution, which produces a far greater level of detail than do present small screens. In 1997, Motorola signed an agreement with Kopin to incorporate CyberDisplay into VirtuoVue™, a product line of display components that can be incorporated into telephones, pagers, portable global positioning systems and other consumer electronic devices. Kopin provides the display panel, Motorola the integrated circuits. The two companies have also partnered with Gemplus, a worldwide provider of smart cards, to develop components for smart card personal viewing systems. FujiFilm Microdevices, one of the world’s largest providers of electronics to digital camera manufacturers, will also use CyberDisplay for digital camera chipsets, allowing camera owners to enjoy high resolution, small-form color displays.
Light Shaping Diffusers also can produce high-contrast, high-brightness screens for movie screens, flat panel displays, and high definition television. For these applications, LSDs can be fabricated as metal-back reflectors, molded lenses, or thin sheets. By reducing light scatter, these devices would increase brightness in light displays enough to see projection screens, laptop displays, and movie screens in full daylight.
These products, along with two other products developed as a result of other BMDO SBIR projects, have generated commercial sales exceeding $2 million. In addition, these contracts have helped attract venture capital funding of $2.6 million and establish banking credit and equipment leasing lines in excess of $2 million.
Company Profile:
Formed in 1985, POC focuses on developing new photonic technologies. In 1998, POC generated $14.4 million from both government contracts and sales from commercial components and systems. Located in Torrance, California (south of Los Angeles), POC has 55,000 feet of facilities for both research and product manufacturing.
Contact Information:
Rick Shie
Physical Optics Corporation
20600 Gramercy Place Bldg 100
Torrance CA 90501-1821
Tel:310-320-3088
Fax:310-320-8067
email: rshie@aol.com
web: http://www.poc.com/
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