Improvement of image inverters contrast transfer performance

Image inverter is a special type of fiberoptic plate, which can directly invert an image by 180° to an image intensifier. The device is making the night vision goggle more compact by integrating the image transfer and image invert function into a phosphor substrate. But due to the image inverter′s special structure, the numerical aperture and luminous flux decrease gradually with the increase of the radial distance from torsion axle centre. Compared with the fiberoptic plate, the image inverter has lower contrast transfer function and lower transmissivity. By improving the glass system to reduce the ion diffusion and interpermeation which may occur to the corecladding interface, the actual numerical aperture of the fiber image inverters can be improved. By means of adjusting EMA absorption, not only the needs of image intensifiers can be reached for the transmissivity of fiber image inverter screens, but also the stray light escaping from the optical fiber can be absorbed to the full extent to improve the contrast. With the selection for a reasonable corecladding ratio, the cladding thickness reduction caused by torsion stretch can be remedied and also the cladding thickness can be increased further more to restrain the light to escape from fibers. The result shows that the innovation mentioned above can improve the contrast transfer characteristics of fiber image inverters.