Optics: measuring and testing – Range or remote distance finding – With photodetection
Patent
1988-10-07
1991-01-29
Arnold, Bruce Y.
Optics: measuring and testing
Range or remote distance finding
With photodetection
350319, 350255, 350636, 356251, 358250, G02B 2700, G02B 700
Patent
active
049881663
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to sighting arrangements, more particularly, to an arrangement for sighting or aiming optical equipment such as a primary light source in which a point of light is directed against a mirror which reflects it through a focusable lens to a partially reflective panel through which an operator can see the target to be sighted and on which he can also see the point of light and, by manipulation of the equipment, he can properly align the target and the point of light so that the primary light source, when used, is directed at the target.
FIELD OF THE INVENTION
An example of lighting equipment which requires particular attention to sighting or aiming is a theatrical follow spot. This is the type of lantern which will be used to project light onto a relatively small area (for example, the face of an actor or performer) from some considerable distance. Follow spots, for example, are used for "show throw" applications operating at a range of, say, up to 30 m, or "long throw" applications operating at a range of, say, 30 to 100 m or even more. The operator of a follow spot is often called upon to illuminate a target point such as an actor's face in an otherwise unlit or partially lit auditorium. That involves lining up on the target point before activating the spotlight. Various attempts have been made to enable a follow spot operator to do this with greater or lesser degrees of success. For example, sighting points located on the barrel of the spotlight have been used, as have telescopic sights. These, however, suffer the disadvantage of inconvenience and discomfort in use, and also prevent the operator from seeing what else may be going on around him while he has his eye in the sighting position. Other arrangements which have been tried include the use of a beam leaked from the lamp of the spotlight, the leaked beam being focussed, e.g. onto the ceiling above the operator. The operator sights or aims at the spotlight by aligning the leaked beam on a mark or element of the ceiling. That has the disadvantage of requiring each aiming point individually to be determined in advance, thus failing to provide for onstage variations, last minute changes or whatever.
In the absence of a sighting device, operators of follow spots on occasion indulge in a practice known as "shadowing" which entails flashing the light onto the auditorium as briefly as possible to aim the beam in the hope that the audience will not notice the flash.
The present invention seeks to provide, among other things, an arrangement whereby a spotlight may be aimed through sighting means, which means in their relationship with the spotlight avoid or at least minimize the various disadvantages of the known prior arrangements or techniques.
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention there is provided a spotlight sight comprising a partly reflective panel through which an operator may view a target area, imaging means arranged to produce a virtual image of a light source, as seen in the panel, at or near the target area, adjustable focussing means arranged to enable the visual image to be located at a selected distance from the panel, corresponding to the distance of the target area, the said selected distance being variable between substantially infinity and a closer distance, and the panel being adjustable to effect adjustment of the horizontal and vertical position of the virtual image as seen in the panel.
By ensuring that the image of the light source appears at the required throw, parallax error may be substantially eliminated between the virtual image of the light source and the target, so that the position of the eye of the operator is not critical to sighting. Indeed the arrangements can be set up such that the operator may confirm that his sighting is accurate by moving his head from side to side or up and down. The removal of the parallax error will result in the light source image at the target appearing to move together with the movement of the operators head. The sight may include
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Arnold Bruce Y.
Ben Loha
Samuelson Group plc
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