| 摘要 |
1,218,289. Light modulators. THOMSONCSF. 11 April, 1968 [21 April, 1967], No. 17711/68. Heading H4F. An arrangement for providing a visible image of an object emitting infra-red radiation comprises in an enclosure 1 a ferroelectric plate 5, Fig. 1, which is maintained near its Curie temperature and is backed by a mirror 4 and a sheet of infra-red absorbing material 3 on which is deposited a grid 2 of infra-red absorbing material, and variations of the refractive index (or indices, see later) due to a non- homogeneous distribution of temperature across the plate 5 produced when an infra-red image is projected on to sheet 3 (arrow 1R) is converted into a visible image on screen 11 by light from a source 6 and a Schlieren optical system including a mirror bar arrangement 7. The assembly 2-5 may be mounted on a prism Fig. 2 (not shown). In a further embodiment, Fig. 3 (not shown), a ferroelectric plate which is exposed to the infra-red image is disposed between a polarizer and an analyser; a plate which is transparent to infra-red radiation and reflects visible radiation may be used, Fig. 4 (not shown), or the ferroelectric plate may be backed by a mirror layer and an infra-red absorbing layer, a semi-transparent plate being used Fig. 5, (not shown). The ferroelectric material may comprise KH 2 PO 4 or KD 2 PO 4 . An electric field may additionally be applied across the ferroelectric plate in a direction parallel or perpendicular to the ferroelectric axis c, the light beam which renders visible the variations of the difference between the two refractive indices of the ferroelectric material (birefringence) being parallel or perpendicular to axis c, Figs. 6-9 (not shown). |
