| 摘要 |
<p>A night sight provided with an image intensifier may have an externally mounted graticule for aiming. It is known to provide a graticule illumination system for a graticule injected onto the phosphor screen of the intensifier which renders the graticule visible in a color, red for example, which is distinctive from the phosphor color, usually green. The phosphor brightness varies considerably with changes in scene illumination and hitherto it has been found essential to vary the graticule brightness accordingly to maintain graticule visibility without obscuring target details with graticule glare. A graticule in accordance with the invention comprises a light diffusing pattern (13) on one surface of a transparent plate, said surface being effectively in contact with the phosphor screen (11). The graticule is illuminated (19,20) at a predetermined brightness above the screen brightness obtained when the intensifier is used to observe a scene illuminated by overcast starlight but below that of the screen brightness obtained when the intensifier is used to observe a scene illuminated by moonlight. The graticule pattern appears in red when observing very low brightness scenes but appears as a black pattern when observing relatively high brightness scenes.</p> |
