Optical films with microstructures can achieve uniform illuminance on the target and glare control with no registration to LEDs. An engineered optical film design with microstructures on both sides is demonstrated. A spacing ratio of 1.64 is obtained compared to 1.28 with just LEDs while there is less light at higher angles for better glare ratings.
Dispersive imaging has been shown to be an effective technique to optically control aliasing in mosaic pattern color sensors. It can be adapted to all of the currently used color filter array patterns and sensor layouts. Depending on the sensor, residual uncompensated errors remain after the optical image is recorded. Results will be demonstrated for several sensor/filter combinations. These will be used to support the conclusion that pixels that are optimum for dispersive filtering produce smaller residual errors. Pixel geometries, color filter array patterns and spectral sensitivities could be produced to minimize these errors. The design of these sensors are discussed in this paper. Optimum solutions are proposed and analyzed. These proposed solutions are compared to imaging systems currently in use.
Dispersive filtering has been shown to be an effective means to prevent color aliasing in digital images from sensors supplied with a mosaic filter pattern. Sensors with mosaic color filters typically measure only a portion of the color information for each pixel. To record full color information requires the information from several laterally displaced pixels. Dispersive filtering introduces a similar lateral displacement in the optical image. When sensed with the corresponding laterally displaced pixels, a color registered data set is produced. Limitations of available optical materials, and color sensors restrict the exact registration to an approximation. This paper quantifies the residual errors of dispersively registered images for two current mosaic sensor types.
Color aliasing, in its most visible and objectionable form, colored moire, persists as a drawback to digital imaging of periodic objects, particularly fabrics. Sensors with mosaic color filters typically measure only 1/3 of the color information for each pixel. With an optical modification, a single subject point can be measured by laterally displaced red, green, and blue pixels. This is done by a shift of the color planes laterally using a dispersive optical element. The element creates an optical effect similar to chromatic aberration but uniform in magnitude and direction over the image. Light from a subject point passes through the optical system but is not focused to a point in the image plane. Instead the red component is focused to a different point than the green and blue components and all are arranged in a line. This element, or filter, causes one subject point to be measured by three sensor pixels, one red, one green and one blue. This in fact may result in an image having more useful information: fewer pixels of color-registered, error free data, rather than a larger number of pixels with color errors.
Many viewing devices have been produced using spinning or oscillating optical elements to artificially enlarge the exit pupils of a stereomicroscope. Further advances have seen the utilization of liquid crystal diffusers so that such devices could operate without moving components. However, the implementations reported thus far have been complex and bulky. The optical system design for a simplified viewing technique is presented in this paper. A standard objective, providing the greater portion of image magnification, is used with an eyepiece which is of a liquid crystal, expanded pupil design. Current limitations in liquid crystal technology prevent eyepiece magnifications greater than 5 X. Therefore, wider fields and higher magnifications are required of the objective lens. Effects of the expansion influence resolution and brightness. Resolution is only minimally reduced as is shown in the experimental results. Brightness reduction can be held to nearly the theoretical limit, but is unavoidable in any system where the exit pupil diameter is increased beyond the eye pupil diameter. As with previous instruments, the advantage of large pupils is the relaxation of eye position constraints. This provides automatic accommodation for interocular variation among users and allows head motion over several centimeters while viewing.