Patent GB-1266971-A (GB)
IPC: G02B21/08
Filed: 1969-04-14
Abstract: 1,266,971. Illuminating devices. RESEARCH CORP. April 14, 1969 [April 16, 1968], No.18994/69. Heading G2J.  An optical system comprises means for focusing a slit shaped beam of radiation 21a successively on to each of a plurality of adjacent strips 22 each located in a selected plane 23 of an object whereby a desired area of the plane can be exposed to radiation, and means either for directing a slit-shaped beam of radiation 24b, which beam emanates from the illuminated strip and is used in the formation of an image 15 of the strip, away from the strip along an optical path which coincides with the optical path of the illuminating radiation to an beyond the illuminated strip only in the said strip, or for directing a slit-shaped beam of radiation which passes through a strip adjacent the illuminated strip and in the selected plane, which is used in the formation of an image of said adjacent strip, and which emanates from a region, of the object providing an illuminated background for the image, away from the strip along an optical path which coincides with the optical path of the illuminating radiation to and beyond the illuminated strip only in the said region. In a microscope the slit-shape beam is formed by illuminating a slit 14 in a diaphragm 12. The beam is then directed to an edge 16a of a mirror 16 from which it is reflected to focusing lens 20. The successive strips 22 are illuminated by synchronously scanning the diaphragm 12, mirror edge 16a and image slit 15 in diaphragm 13 about an axis which is coplanar with the optical axes of the radiation incident upon and reflected from mirror 16. The axis of rotation may pass through or near the optical centre of lens 20, or through or near the optical centre of a real image formed by lens 20. Preferably the slits 14, 15 are contained in a plane common to edge 16a. The synchronous scanning may be effected by mounting the slits and mirror assembly between the jars of an electromagnet, Fig.3 (not shown). This embodiment gives "Focal-Plane-Specific illumination". Where the incident and reflected beam intersect below the focal plane "sub-focal plane specific" illumination is provided. If lens 20 gives rise to chromatic dispersion, or if this is deliberately introduced, then rays of different wavelength may be used to illuminate different strips of different depths of the object. The microscope may be used to measure depths in objects, or in production of iso-elevation contour maps. In an alternative embodiment the scanning system incorporates a pair of parallel mirrors linked to the slits and mirror assembly but interposed between the light source and the mirror 16, see Fig.6 (not shown). In a telescope system, Fig. 8, the reflecting mirror 65 lies outside the angle subtended by the slit diaphragms 61, 62. Laser beam A is reflected by mirror 69 through slit 63 and thence via mirror edge 65 and reflectors 70, 71 to the narrow strip of an object or field under view. The image is focused on slit 64 where it is viewed by eye-piece 76. Improved scanning may be achieved in the telescope of Fig.8 by passing the illuminating radiation, and that reflected from the slit-shaped strip of the object or field, to a disc diaphragm having an even number of spaced slits so arranged that at no time is there more than one slit in the field of view. The diaphragm is rotated. In a further embodiment the illuminating radiation may be emitted from each of a plurality of sources arranged to form a panel each beam being focused on a selected strip in the selected plane. The sources are synchronous activated, e.g. by electrically activable strip-shaped light gating means.