We introduce the concept of saddle lenses for the generation of uniform illumination with high efficiency. The design principles and experimental verification of beam shapers incorporating saddle lenses are discussed and demonstrated.
In the past few years the microdisplay-based projection television market has been quickly spreading over what used to be the domain of CRT technology. The demand for larger display sizes and improved image quality, together with more accessible pricing is aggressively driving the transition to microdisplays.
The screen is the component of the projection system that directly conveys the visual information to the user, responsible for distributing the luminous energy from the light engine. However, the projection screen is far from a simple diffuser and today's performance requirements for display systems require sophisticated screens to meet the resolution, transmission efficiency, and contrast required by visual displays.
Lightguide devices are commonly used in a large number of applications such as light-delivery systems, illumination, and displays. The general approach is to outcouple light from the lightguide without concern for its propagation properties within the guiding material. We introduce the concept of a lightguide with controlled numerical-aperture as it propagates within the guiding substrate and demonstrate the advantages with this approach, compared to other methods commonly used. We also demonstrate the application of our lightguide technology for general illumination with controlled light distribution and high efficiency.
Unless coupled with some collimating optics, LED sources generally scatter with wide-angle Lambertian intensity profiles. The luminous output of such sources is not amenable to control and redistribution in an efficient manner. In this work we present the design and manufacturing of structures that are able to collect virtually all light from Lambertian LED sources and direct it towards diffusers engineered to illuminate specific regions of space in a controlled fashion. The resulting "engineered luminaire" is thus capable of highly efficient light control and can be applied to a wide variety of illumination situations such as general and architectural lighting.
We demonstrate the application of deterministic microlens diffusers to generate Lambertian scatter in transmission with high efficiency. Two identical surface diffuser elements are used in tandem to spread light with constant radiance. Design methods are discussed and experimental demonstration is presented.
We propose and demonstrate the use of Engineered Diffusers for control and distribution of LED light for general lighting applications. These diffusers are based on refractive microstructures and enable the efficient use of energy by controlling light propagation and directing it to specific regions of space. The microstructures are generally microlens-based arrays with each microlens elements individually designed to meet the desired scatter properties. In addition to light control, Engineered Diffusers can be used for RGB mixing to produce white light with variable color temperature, depending on the RGB content of the source. A single Engineered Diffuser component can be used for efficient color mixing and illumination control. We also discuss the fabrication of Engineered Diffusers by means of a single-point laserwriting method with capability to manufacture the deep refractive structures needed for LED beam shaping.
We propose the use of structured microlens arrays to achieve beam shaping, diffusion, and homogenization. Practical results are presented that elucidate the capabilities of structured microlens arrays to perform complex beam shaping tasks, both intensity control and spatial energy distribution, with high efficiency (mostly limited by surface losses) and without the presence of image artifacts. In addition, the refractive nature of the array naturally yields broadband operation with no zero order. The concept of a structured microlens array incorporates both deterministic and random components so that each microlens is individually designed to perform at least some portion of the beam-shaping task. At the same time, the design process ensures that any statistically significant ensemble of microlenses represents a random process described by select probability density functions. As a result, the structured microlens array incorporates the ability of deterministic diffusers to attain optimal scatter properties and the desirable robustness and homogenizing capabilities of random diffusers. These attributes make structured microlens arrays suitable for a wide variety of applications, from excimer laser beam shaping to display screens. We have designed and fabricated structured microlens arrays using a laser writing system that exposes low-contrast photoresist to a modulated beam on a point-by-point basis to produce a continuous surface-relief profile. The method allows the fabrication of arbitrary surface-relief profiles and depths greater than 100 microns. Experimental results include small-angle (less than 1 degree) and large-angle (up to 180-degree span) diffusion, beam shaping into singly- and multiply-connected domains, flat and controlled intensity profiles.
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