Illumination – Light source and modifier – Including reflector
Patent
1993-09-02
1994-12-13
Husar, Stephen F.
Illumination
Light source and modifier
Including reflector
3621531, 362277, 362319, 362346, F21V 700
Patent
active
053734297
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an illuminator, especially a runway approach flashlight, for forming a directable, generally rectangular light beam, comprising a light source, such as a xenon lamp, an illuminator body, and a reflector supported to it and comprising a generally cup-like rear reflector fitted behind the light source.
Finish Published Specification 66074, for instance, discloses an illuminator of substantially the above-described type for similar purposes. The runway approach flashlight according to the invention should radiate a flashing light so as to form a beam having the shape of a horizontal rectangle in cross-section. This beam has to be directed at a predetermined angle with respect to the horizontal plane. Within the area of the beam, the effective light intensity values have to be adjustable in compliance with various specifications both as concerns the width of the beam and the maximum/minimum ratio of the intensities. In the above-mentioned known arrangement, the illuminator with its casing has been made tiltable for directing the beam by providing the back portion of the casing with a joint with respect to which the front edge of the casing can be lifted by means of an adjusting screw. This way of adjustment requires that the electronics controlling the illuminator unit should be placed in a housing separate from the illuminator in order that the tiltable structure would not be too heavy and clumsy. On the other hand, the directing of this kind of illuminator, that is, the adjustment of the angle of tilt, has to be checked at least after the illuminator has been installed e.g. on a light support possibly several meters above the surface of the earth. In this known arrangement, the light beam itself is shaped by an elliptical rear reflector and optical means positioned in front of a light source. The light distribution in the illuminator is fixed and cannot be adjusted in compliance with various specifications, but possible changes in the distribution of light have to be made by modifying the structure of the illuminator unit itself.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an illuminator in which the light beam is more easily and more simply adjustable in both shape and direction than in the illuminators known from the prior art. This is achieved by means of an illuminator according to the invention, which is characterized in that the reflector further comprises an ellipsoidal counter reflector fitted in front of the light source, the main axis of the counter reflector being substantially parallel to the shorter side of the light beam.
The arrangement of the invention also provides an illuminator in which the illuminator casing need not be tilted for directing the light beam but the light beam is directed by tilting only the reflector and the light source supported to it.
Two prismatic refraction plates of transparent material are supported preferably to the rear reflector, substantially in the plane of its mouth, in such a way that they cover the mouth of the rear reflector with the exception of a substantially centrally positioned area of uniform width. By means of these prismatic refraction plates, both the dimensions and the intensity distribution of the rectangular light beam emitted by the illuminator can be varied. Preferably, the refraction plates are supported to the rear reflector so as to be adjustable. As to the maximum/minimum ratio of the light beam intensities, it is preferable that light can be guided to the corner areas of the primary beam by means of the refraction plates, whereby the refracting angle of the refraction plates may be about 15.degree. and the directional angle within the range from 2.degree. to 5.degree.. The width of the area of uniform width between the refraction plates also affects substantially the maximum/minimum ratio of the intensities.
Furthermore, it is preferable that the rear reflector be divided into three sections substantially parallel with the longer side of the light beam
REFERENCES:
patent: 4320442 (1982-03-01), McCamy
Husar Stephen F.
Idman Oy
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