Patent GB-869290-A (GB)
Title: Optical device for a correct adjustment and reading of the slidable displacement of a carriage in a machine
Inventor: RANTSCH KURT
IPC: G01B11/00
Filed: 1959-03-11
Abstract: 869,290. Optical gauging-apparatus. HENSOLDT & SOHNE OPTISCHE WERKE A.G., M. March 11, 1959, No. 8339/59. Addition to 869,289. Class 106 (2). [Also in Groups XX and XXII] The apparatus of the parent Specification is modified to compensate for tilt of the carriage due to inaccuracies in two guideways which extend in orthogonal directions. In the drilling machine of Fig. 1, the table 500 carrying the workpiece 504 is slidable in the direction 506 in a guideway 500<SP>1</SP> which is itself slidable in an orthogonal direction in a guideway 50011 in a base frame 505. Carried on the table 500 is a horizontal measuring grid 502 the graduation of which below the drilling point K on the workpiece 504 is projected by a lens 510 and a Porro system of the second kind 508... 512 through a semi-transparent layer 513 on to a horizontal mirror 501. which is also carried by the worktable 500 and re-directs the light on to the semi-transparent layer 513 and thence to a lens 516 which focuses an image of the graduation on a reticle 517, where it may be observed through lens 507. By making the optical path length from the measuring scale 502 to the lens 510 equal to the focal length of this lens and by making the distance between the measuring scale and the point K equal to twice this focal length, the mirror 501 will compensate for small tilts due to inaccuracies in the guideways 500<SP>1</SP> and 500<SP>11</SP>. In an alternative form, Fig. 4, the measuring scale is provided on the horizontal mirror surface 540 and light from the scale after reflection at 543, 544 is projected by lens 541 and semi-reflecting mirror 545 on to the mirror 540 and re-directed thereby through the semi-reflector and a lens 547 whereby an image is formed on the reticle 548. Instead of the two lenses 541 and 547 of Fig. 4, a single lens 582 may be provided as shown in Fig. 8, between a semi-reflecting surface 581 and a reflecting prism 583, which directs the light from the lens on to the mirror surface 580 carrying the scale 5801 and redirects the light from this mirror through the lens 582 so that an image of the graduation is formed on the reticle 584. In the arrangement of Fig. 10, a variable magnification is obtained by the provision, between the projecting lens 603 and the tilt compensating mirror 605, of a rotatable mounting containing telescopes 604 1  ... 604 4  of different powers, which telescopes may be selectively positioned in the light path. In this embodiment also, light from the measuring scale 602 first passes through a Pechan prism 600. In apparatus where it is desired to form superposed images of two scale carrying surfaces 610, 611, Fig. 11, an image of each scale is projected by systems 612, 614, 615 and 613, 616, 617 respectively on to a Pechan prism 618 which directs the two images on to a reticle, this prism being pendulously suspended as from a Cardan joint to compensate for small tilts. In place of the lenses 612, 613 and associated reflectors, there may be disposed, between the pendulous prism and each surface, a telephoto objective; and this objective may, if desired, be accommodated in the same Cardan mounting as the prism, as indicated in Fig. 13 for the prism 670 and telephoto objectives 652, 653. In the form shown in Fig. 15, two scale carrying surfaces 696, 697 face away from each other and light rays from each scale are combined by a prism 707 and 708, tilt compensation being effected in each light path by a lens 690 or 691 pendulously mounted between a fixed pair of lenses. In the form shown in Fig. 16, such a pendulous lens 715 provides tilt compensation in a radial drilling machine in which an image of a graduation S on a scale 710 is projected on to a scale-reading reticle 717. Alternatively, the scale 710 may be transparent and an image of a reticle projected thereon through the optical system including the tilt compensating lens, and this image may be observed by the human eye, a microscope, or a photo-electric cell. As shown in Fig. 19, light is projected from a lamp 759 on to the measuring scale 751 and thence through the central transparent part of a reflector 754 and an aperture 755 in a lens 756 on to the tilt compensating mirror 750 which re-directs the light through the lens 756, and after reflection at the mirror 754 on to a lens 757, whereby an image of the graduation is formed on the reticle 758. The reticle may, as shown in Fig. 22, comprise orthogonal scale lines 872, 873 and be movable in orthogonal directions by micrometer screws 876, 877 so that these scale lines may be enclosed between the double lines 880, 881 of the image of the measuring scale. Alternatively, the light from the projecting lens may be divided at 891, Fig. 23, into two beams respectively directed on to reticles 895, 896 which are movable in directions at right-angles by micrometer screws, each reticle having a scale line which extends orthogonally to the direction of the scale line in the other reticle. Fig. 26 shows an arrangement in which the light rays from the measuring scale 502 are projected by a lens 516 and divided by a semi-reflector 900 so that an image is formed in each of two reticles 901<SP>1</SP> and 9021. This arrangement also includes racks 907, 909 which rotate counting wheels 903, 904 and an image of the appropriate counting wheel is projected into the window of the associated scale reader containing a reticle.