Optical concentrator of a new type making it possible to obtain a maximum energy on the sensitive element of a radiation receiver, a method for determining the optimal characteristics of concentrators of this type, and devices for use

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-angle of 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: pSP1/SP 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 tan also being connected by the relationship: wherein # denotes the minimum efficiency required relatively to the maximum possible nSP2/SP 2 defined by -. The front system 9 may be a sinSP2/SP# 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 pSP1/SP must be equal to or less than # wherein: n 1 , sin # 1 and also 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.