Electromagnetic radiation concentrator

摘要

1,110,821. Aerials. C. JACOBSEN & CIE. 4 May, 1965 [6 May, 1964], No. 18822/65. Heading H4A. [Also in Divisions F4 and G2] An electromagnetic radiation concentrator, particularly for use in the infra-red, comprises a front system 9, Fig. 1, of relative aperture 1 - which forms an image of the source in its N focal plane 10, the maximum inclination # 1 to the axis of the system of rays forming the image 1 being such that sin # 1 #-, and at least one 2N trunco-conical element 11 of internal refractive index n 1 and apex half-angleγof 0À1 radian or less, which converges the beam by internal reflections on its trunco-conical surface, the entry surface 12 of element 11, having the maximum diameter d 1 being disposed in coincidence with image plane 10 and the minimum diameter d x being associated with a sensitive element 14 immersed in a medium 15 of refractive index n 2 wherein: p1 being the maximum number of internal reflections experienced by a ray forming the maximum angle # 1 with the optical axis before entering the element 11 and given by: # 1 being given by: n 1 , n 2 , sin # 1 and tanγalso being connected by the relationship: wherein # denotes the minimum efficiency required relatively to the maximum possible n2 2 defined by -. The front system 9 may be a sin2# 1 lens, concave mirror (16), Fig. 2 (not shown), or solid trunco-conical member 105, Fig. 10 (not shown), with a convex front surface. In the latter case the optical axis 106 may be deflected through 90 degrees by means of a 45 degrees surface 107. The element 11 may be hollow or solid in which case the reflections on its surface are all total internal reflections and p1 must be equal to or less than # wherein: n 1 , sin # 1 andγalso being connected by the relationships: The trunco-conical element 11 may be formed from several materials placed end-to-end, or made from a series (26), Fig. 3 (not shown), of parallel fibres (27). Scanning may be used in association with the device, Fig. 6 (not shown), and an application to centimetre radar, Fig. 5, is described in which the front system is a parabolic mirror 60, the trunco-conical element 61 is of aluminium and the sensitive element 59 is a dipole antenna having an effective diameter of 0À5 cm. Detailed steps are enumerated for designing specific systems.