| 摘要 |
An optical device for sighting a target to be aimed at in the line of sight of a user, and adapted to be mounted in place of the conventional rear sight, the device, either itself, or via an adaptor, registering with an existing feature on the gun whereby original alignment can be maintained if the device is removed and replaced. The device comprises a thick meniscus optical element (1) of short focal length, e.g. less than 5 cm, formed of transparent plastics material by a replicating process and having a front surface (4) for facing the target and a back surface (3) in which the user views an image of the target. A quaternary LED (2) is used as a source of light directed at and reflected back from the back surface (3) to create a sighting image for the user to align with the image of the target as viewed in the optical element. The back surface (3) is a parabolic aspherical surface of short focal length, and the front surface (4) is an aspherical correcting surface which minimises the aberrations in the image of the target as viewed by the user. The device includes a cover (40) movable from a covering condition - in which it reduces the power consumption of the light source towards zero and thus acts as though effectively switching off illumination from the light source - and an uncovering condition in which it permits the sighting device to be used. For use on a hand gun to be retained in a holster when not being used, the said cover is attached to the holster by a lanyard (41) whereby removal of the gun from its holster by the user removes the cover (40) from the sighting device. |
