Although solid-state lighting (SSL) products are often intended to have product lifetimes of 15 years or more, the rapid change in technology has created a need for accelerated life tests (ALTs) that can be performed in the span of several months. A critical element of interpreting results from any systems-level ALT is understanding of the impact of the test environment on each component. Because of its ubiquity in electronics, the use of temperature-humidity environments as potential ALTs for SSL luminaires was investigated. Results from testing of populations of three commercial 6” downlights in environments of 85°C and 85% relative humidity (RH) and 75°C and 75% RH are reported. These test environments were found to accelerate lumen depreciation of the entire luminaire optical system, including LEDs, lenses, and reflectors. The effects of aging were found to depend strongly on both the optical materials that were used and the design of the luminaire; this shows that the lumen maintenance behavior of SSL luminaires must be addressed at the optical systems level. Temperature-Humidity ALTs can be a useful test in understand lumainaire depreciation provided that proper consideration is given to the different aging rates of various materials. Since the impact of the temperature-humidity environment varies among components of the optical system, uniform aging of all system components in a single test is difficult to achieve.
An electrostatic MEMS actuator is described for use as an analog micromirror device (AMD) for high performance, broadband, hardware-in-the-loop (HWIL) scene generation. Current state-of-the-art technology is based on resistively heated pixel arrays. As these arrays drive to the higher scene temperatures required by missile defense scenarios, the power required to drive the large format resistive arrays will ultimately become prohibitive. Existing digital micromirrors (DMD) are, in principle, capable of generating the required scene irradiances, but suffer from limited dynamic range, resolution and flicker effects. An AMD would be free of these limitations, and so represents a viable alternative for high performance UV/VIS/IR scene generation. An electrostatic flexible film actuator technology, developed for use as "artificial eyelid" shutters for focal plane sensors to protect against damaging radiation, is suitable as an AMD for analog control of projection irradiance. In shutter applications, the artificial eyelid actuator contained radius of curvature as low as 25um and operated at high voltage (>200V). Recent testing suggests that these devices are capable of analog operation as reflective microcantilever mirrors appropriate for scene projector systems. In this case, the device would possess larger radius and operate at lower voltages (20-50V). Additionally, frame rates have been measured at greater than 5kHz for continuous operation. The paper will describe the artificial eyelid technology, preliminary measurements of analog test pixels, and design aspects related to application for scene projection systems. We believe this technology will enable AMD projectors with at least 5122 spatial resolution, non-temporally-modulated output, and pixel response times of <1.25ms.
A large seamless display that could be set up rapidly, operated effectively, and moved quickly would be a great value to the military. Such a display system would be even more beneficial if it consisted entirely of easily available, commercial, off-the-shelf components, not dependent on a single supplier. We have designed a seamlessly tiled projection system to meet these needs. The system consists entirely of easily available, commercial, off-the-shelf equipment. We created software that records the location of projected images as detected by a digital camera, computes the movements necessary to align the images, and drives the projection lenses to align the seamlessly tiled display. We developed a method for rapid mechanical mounting of the projectors and camera. We chose commercial folding stands and a mirror-based alignment method that accelerated the mechanical setup. In field trials, our prototype was operational within one-half hour of opening the shipping cases.
We have developed a mechanical, optical and digital system based only on commercially available equipment to allow a seamlessly tiled projection display system to be set up and aligned very rapidly. Using a digital camera and motorized projectors, our prototype system can be unpacked, aligned, and put into use within a half-hour. To minimize the number of projectors for a given pixel count, we do not overlap the projected fields and we do not move the images by digital displacement within the projected field. We use motorized lens mounts to displace the images to proper positions for tiling, a method that does not induce keystone distortion. The movement is under control of a digital camera using an image-processing system, making it unnecessary for an operator to control the movement of the lenses.