| 摘要 |
730,794. Light projectors. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 10, 1953 [Sept. 11, 1952], No. 22856/52. Classes 75 (2) and 75 (4). [Also in Groups XXXV and XL (a)] A system for producing a beam of light having an angle of divergence in one plane not greater than 2 degrees comprises a compact source electric arc discharge lamp 1 having its arc path located substantially at the focal centre of a parabolic reflector 4, the spacing of the electrodes being not more than 9 mm., while the pressure of a xenon gas filling is approximately 2 atmospheres at 15‹ C. and the voltage drop in the discharge path is less than 25 volts, and the arc path being substantially linear in a direction normal to the plane in which the limited angle of divergence of the beam is required, and a spherical mirror 5 located coaxially with the parabolic reflector with its centre of curvature coincident with the arc path and in front of the lamp so as to obstruct the direct rays of light from the lamp and reflect them on to the parabolic reflector. The beam may spread up to 15 degrees in the horizontal plane. A casing 7 and front glass 6 is provided. The xenon lamp may have a rating of 2¢ kw., the parabolic reflector 4 may have a focal length of 8.5 inches and the spherical mirror 5 may have a diameter of 24 inches to produce a beam spread in the vertical plane of 1.5 degrees. Specifications 545,388, [Group XL], and 640,156, [Group XL (a)], are referred to.
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