Patent GB-386321-A (GB)
Title: Improvements in and relating to photographic view finder, distance meter and exposure meter instruments
IPC: G02B23/14
Filed: 1931-07-10
Abstract: 386,321. View-finder, distance-meter, and exposure-meter. GAUTHIER, A., Calmbach, Enz, Wurteniberg, Germany. July 10, 1931, No. 19925. [Class 98 (i).] An exposure-meter and a view-finder, serving also as a distance-meter, are combined in one casing which may be a separate instrument or fitted as a complete unit with the shutter casing In the latter case the shutter and/or the diaphragm may be set synchronously with the operation of the exposure-meter. The distancemeter may comprise a graduated scale of a focusing view-finder with either an adjustable screen or adjustable finder lens; or a range-finder of the split-image type may be used. A common focusing screen may be used for view-finding and exposure-meter purposes. The screen may be used alternately for finding and exposure determining, or different portions used for the two purposes. The exposure meter is of the vanishing mark or extinction type. In one construction, Figs. 1 and 2, the focusing finder comprises a lens 5, mirror 3 and focusing screen 6 adjustable by a ring 7 for giving the range which is indicated on a scale 34, Fig. 4, by an arrow 33 on the screen Alternatively the lens 5 may be fitted in a graduated focusing mount. The exposure-meter comprises an opening 27, Figs. 1, 2 and 5, in the shutter mount which can be varied by a tapering slot or series of apertures 13 synchronously with the setting of the exposure setting ring 12. A cylinder 14 has a triangular slot 16 through which light is reflected by a mirror 15 on to a section 35 of the focusing screen 6. An outer cylinder 17, also having a slot 21, is rotated by a pin and slot connection 18, 19 with the camera lens diaphragm setting means, and is adjusted until the fixed slot 16 in the cylinder 14 is masked by the cylinder 17 so as to render the first graduation 36 of the distance scale 34 invisible. A telescopic cap 8, 9 fitted with a viewing eye-piece 10 is provided for viewing the focusing screen and when collapsed covers the instrument. Various arrangements, Figs. 7, 8, 9, 11 and 12 (not shown), are described in connection with the diaphragm 13 setting and controlling means. The distance-meter may alternatively be of the split-image type having two laterally spaced openings 114, 115, Fig. 22. A fixed mirror 116 behind the opening 114 gives one side of a divided image R, L, Fig. 24. The other half is obtained from the opening 115 by two mirrors 117, 118 and is brought into alignment by angular adjustment of the mirror 117, the distance being obtained by the adjusting disc 119. The associated exposure-meter has arrangements as above described in conjunction with the aperture 27 for extinguishing a mark 112 adjacent the image field. An independent hand instrument, Figs. 13 and 14 comprises a finder lens 55 on a sliding mount 56 and focused by a distance graduated operating ring 59 : a stationary focusing screen 52 : a partitioned tubular compartment 60 coaxial with a triangular opening 64 in a disc 62 on the lens mount 56 : and a graduated ring 63 having a wedge slot 65 which is adjusted until a mark on the focusing screen, seen through the lens 54, disappears. In modified constructions, Figs. 15 and 16 (not shown), the lens 55 and exposure-meter opening are situated in the tubular wall of the instrument and reflectors provided : rotating rings with exposure time, diaphragm stop, and plate speed scales are also provided. Apparatus of this type may also be provided integral with the shutter mount, Figs. 17 and 18 (not shown). In another arrangement, similar to Figs 1 and 2, the focusing screen 99, Fig. 21, is adjusted from a lever 108 moving over a distance scale. The mirror 96, behind the finder lens 98, is angularly movable and the whole of the focusing screen used for the exposure-meter comprising a variable diaphragm 102 and fixed mirror 101.