Patent GB-490270-A (GB)
Title: Improvements in stereophotogrammetric plotting apparatus
IPC: G01C11/00
Filed: 1937-10-18
Abstract: 490,270. Stereogrammetric apparatus. ZEISS, C., [Firm of]. Oct. 18, 1937, No. 28250. Convention date, Oct. 28, 1936. [Class 97 (i)] Relates to photogrammetric plotting-apparatus, of the kind described in Specification 183,124, [Class 97 (i)], comprising two chambers, each containing a photographic plate and an objective, two mirrors mounted by cardan joints on a carrier universally displaceable with respect to the chambers in such a way that the centre of rotation and the interior axis of rotation of each mirror lie in the reflecting surface, each of the mirrors bearing a mark at the said centre of rotation, and a cardan mounted objective near each chamber objective having one element which can be so adjusted that each point of the plate is sharply imaged at the mark. According to the invention two further mirrors are provided in association with each chamber, one mirror being mounted on the chamber support and the other on the said carrier in such a way that the centre of rotation and the interior axis of rotation of each of these two mirrors lie in the reflecting surface, and that the centres of rotation of the two mirrors, the centre of rotation of the lens system, and the centre of rotation of the mark-bearing mirror lie at the corners of a parallelogram in all positions of the said mirror carrier relatively to the chambers. The Figs. show only one of the two plate-carrying chambers, with its associated optical members and adjustment means. An arm 2 secured to the base 1 supports a shaft 3 on which is rotatably mounted an arm 4, carrying a member 8 which is rotatable in the arm 4 about an axis Y-Y at right-angles to the axis X-X of the shaft 3. A carrier 12 containing the photographic plate 13 and objective 14 is mounted in the member 8 so as to be rotatable about the axis of the objective which passes through the point of intersection I of the axes X-X, Y-Y. A plate 17 is rotatably mounted, by means of a shaft 19 the axis of which coincides with Y-Y, in an arm 18 rotatably mounted on the shaft 3, so that the centre of rotation of the plate is the point I. This plate carries an objective comprising a fixed convergent lens 20 and a divergent lens 23 mounted on a slide 21 from which a pin 24 extends into a groove in a drum 25 which carries a bevel wheel 26 rotated by a bevel wheel 27 on a shaft 28 carrying a pinion 29 gearing with a rack 30 which is displaceable within the plate 17 in a direction parallel to the axis of the lenses 20, 23. The gear ratios are such as to produce such movement of the lens 23 that a point of the plate 13 is always imaged at a point II on the axis of the lenses 20, 23. The base 1 carries a system of slides 31, 33, 35 permitting universal displacement of a carrier 36 on which is mounted so as to be rotatable about an axis Z-Z parallel to X-X a bushing 37 to which housings 38, 39 are secured. A mirror 42 is mounted in the housing 38 by pins 40, 40<1> so as to be rotatable about an axis U-U, at right-angles to Z-Z, lying in the reflecting surface of the mirror which bears a mark 43 at the point of intersection II of the axes Z-Z, U-U. A fork 44 loosely mounted on the pins 40, 40<1> is rigidly connected to the rack 30 and is so geared to the mirror 42 that the mirror rotates in the same sense as the fork through half the angle. The housing 39 contains a mirror 51 mounted on pins 49, 50 and rotated at the same speed as the mirror 42 by gearing 52, 53, 54, the mirrors 42, 51 being at rightangles to each other. Lenses 61, 62 are mounted in the housings 38, 39, the principal focus of the system 61, 62 being at the point II. A housing 56 mounted in an arm 55 is fixed to the arm 18 so as to rotate with the latter about the axis X-X. This housing carries a mirror 57, rotatable about an axis W-W lying in its reflecting surface parallel to Y-Y, and connected to the shaft 19 by gearing 58, 59 so as to rotate at half the speed of the shaft. The mirror 57 is at right-angles to the mirror 42. The distance between the points I, IV is equal to the distance between the points II, III so that these four points lie at the corners of a parallelogram for all positions of the carrier 36 relatively to the plate carrier 12. In any position of the carrier, a ray emanating from a point on the plate 13 and coinciding with the axis of the lens system 20, 23, is incident on the mirror 42 at the point II, is reflected so as to be incident on the mirror 51 at the point III, is again reflected so as to be incident on the mirror 57 at the point IV and is finally reflected in the direction of the prolongation of the line joining the points I, IV.