GB870555A - Improvements in optical goniometers - Google Patents

Abstract

870,555. optical goniometers. NEDERLANDSCHE INSTRUMENTEN COMPAGNIE NEDINSCO N. V. Oct. 8, 1957, No. 31472/57. Class 97(1) A two-circle optical goniometer for the measurement of angles between the faces of a crystal comprises a goniometer head on which a crystal holder is secured by means of apparatus permitting rotation about two mutually perpendicular axes both perpendicular to the axis of the goniometer head, a flat mirror being mounted in a stationary manner with respect to the crystal holder and parallel to one of the two said axes, the mirror providing a reference direction in respect of which a definite orientation of the crystal in the holder may be performed. As shown the crystal is mounted on a pin 10 carried by a slide 8 carried by a member 27 rotatable on a member 28 itself rotatable about a perpendicular axis on a holder 2 rotatable about an axis perpendicular to the other two axes. Rotatable about the same axis as the member 28 is a casing 3 containing a target 17 illuminated by a lamp 30 by way of mirrors 32, 33 and lens 22. An image of the target is framed by a lens 18 at the crystal and when a face of the crystal is suitably oriented light reflected thereby forms an image of the target at the cross wires 20 of a telescopic system 5, 21. The angular positions of the casing 3 and holder 2 at which such coincidence occurs are indicated on scales 25, 12 respectively both seen in an eyepiece 7 by means of the optical systems shown. For certain X-ray measurements a selected direction in the crystal must be placed exactly parallel to the axis of the holder 2. To effect this operation the angles of the faces of the crystal are first measured by means of the rotatable scales 12, 25. From these readings are calculated the settings of the scales 22, 25 which will ensure that the flat mirror 9 secured to the slide 8 shall reflect an image coincident with the cross wires 20 when the required crystal direction is parallel to the rotational axes of the holder 2. The holder 2 and casing 3 are then rotated until these values are set on the scales 12 and 25 and the mirror 9 and pin 10 are adjusted by rotation of the members 27, 28 until the mirror produces such coincidence. In this position therefore the desired crystal axis is parallel to the axis of holder 2 and the entire holder may be removed for insertion in an X-ray apparatus.