Active matrix organic light emitting diode (AMOLED) technology is one candidate to become a low power alternative
in some applications to the currently dominant, active matrix liquid crystal display (AMLCD), technology.
Furthermore, fabrication of the AMOLED on stainless steel (SS) foil rather than the traditional glass substrate, while
presenting a set of severe technical challenges, opens up the potential for displays that are both lighter and less
breakable. Also, transition to an SS foil substrate may enable rollable displays - large when used but small for stowage
within gear already worn or carried or installed. Research has been initiated on AMOLED/SS technology and the first
320 x 240 color pixel 4-in. demonstration device has been evaluated in the AFRL Display Test and Evaluation
Laboratory. Results of this evaluation are reported along with a research roadmap.
A low-power, yet sunlight readable, display is needed for dismounted applications where the user must carry the power source. Such a display could potentially replace paper checklists and maps with electronic counterparts. A reflective active matrix electrophoretic ink display (AMEPID) was evaluated as a candidate technology for such applications. This display technology uses ambient illumination, rather than competing with it, and requires power only when rewriting the display. The device was tested for viewability under a variety of lighting conditions. Readability of displayed text, as compared to standard print on white paper, was evaluated in an indoor office environment and in outdoor lighting conditions. Viewability of the display with night vision goggles (NVGs) was evaluated under simulated full moon, starlight, and overcast illumination conditions. Objective measurements of luminance, contrast ratio and reflectance were conducted under corresponding irradiance conditions and viewing angles using state-of-the-art photometric and radiometric measurement equipment. In addition to visible spectrum measurements, infrared (IR) reflectance and contrast were measured for the extended spectrum of 720-1700 nm. Results are discussed in terms of performance criteria for military displays, which are often much more demanding than for civil applications.
Night Vision Goggles (NVGs) are being used increasingly by the military and law enforcement agencies for night operations. One critical issue in assessing the utility of an NVG is its resolving power or capability to make fine detail distinguishable. The resolution of Night Vision Goggles is typically assessed by measuring the visual acuity of an operator looking through the goggles. These methods can be time consuming. Further, inconsistencies associated with visual observations and judgement add to the variance associated with these measurements. NVG Modulation Transfer Function (MTF) was explored as a possible means of characterizing NVG image quality independent of a human observer. MTF maps the potential contrast output of the NVGs as a function of spatial frequency. The results of this MTF measurement were compared with a commonly used method of visual acuity assessment.
Digital displays will play a critical role in providing a common battlespace picture whether in the aircraft cockpit, command and control facility or carried by ground troops. Advanced display technologies will be key to providing our warfighters with needed information. The purpose of the Display Characterization Facility at Wright-Patterson AFB is to provide quantitative performance data on current and upcoming display technologies and evaluate these technologies for specific Air Force applications. This requires an understanding not only of the specific display technology and its capabilities and limitations but also the capabilities and limitations of the human visual system, the tasks to be performed and characteristics of the environment which may affect the operator-display interaction. To this end, the Display Characterization Laboratory conducts both display hardware measurements and assessments of human performance using the displays under expected environmental conditions. Common display measurements are described along with their implications for operator visual performance.
Holographically formed polymer dispersed liquid crystal (HPDLC) materials meet the requirements for a video rate reflective display. In order to produce a saturated color from a Bragg reflector, the number of index changing layers becomes critical. The fabrication process affects the number of layers forming the reflector, and, as a result, the bandwidth and optical characteristics, including reflection intensity, direction, and spread, of the reflector. The cell thickness and the liquid crystal mixture affect the voltage at which the cell operates and the speed at which the liquid crystal material can switch from the reflective to non-reflective state. The cell designer is forced to work with all of these design parameters simultaneously. This research continues previous work evaluating reflective HPDLC display samples including a method to measure temporal response and refine color reflection characterization.