GB874120A - Improvements in or relating to focimeters - Google Patents

Abstract

874,120. Lens testing apparatus. CLARKE Ltd., CLEMENT, and ROLLASON, W. A. Jan. 22, 1958 [Jan. 22, 1957], No. 2337/57. Class 97(1) A focimeter, includes in combination a support for the spectacle lens under test, a clamping device which can be moved into position to hold the spectacle lens on the lens support, optical means for measuring the focal power of the lens and also the astigmatic angle of the lens with respect to a fixed axis at right angles to the main optical axis of the focimeter, a marking device whereby marks can be made on the surface of the lens under test whilst held on the support to indicate two axes at right angles thereon, one of such axes representing the fixed axis with respect to which the astigmatic angle has been measured whilst the two axes together define the point in which the surface of the lens is intersected by the main optical axis of the focimeter, and means whereby the marking device can be moved to effect its marking, such means including two axially movable parallel rods which also act to control the clamping device for the spectacle lens, one such rod which carries the marking device and acts as an operating rod therefor also acting as a guide rod for the movement of the clamping device, and the other rod which carries the clamping device and acts as an operating rod therefor also acting as a guide rod for the movement of the marking device. The focimeter is preferably as described in Specification 874,119 and the marking device may as shown be accommodated in its retracted position in a well W below a platform V on which the lens to be tested is supported by an adjustable table (not shown) and spring fingers H. The marking device comprises a base member X which is secured to an axially slidable rod X<SP>1</SP>, and is guided by another axially movable rod X2 parallel to rod X<SP>1</SP>. Pivoted at Z to the base member is a marker frame Z which moves under spring loading to the vertical position defined by a stop X6 when the rod X<SP>1</SP> is pulled to the right. When in this vertical position, five spring urged marking plungers Z5, arranged in the form of a cross, extend parallel to the focimeter optical axis, so that, by moving the rod X<SP>1</SP> further to the right marks can be made on the test lens surface. On releasing the rod X<SP>1</SP> a spring (not shown) moves it to the left and the marker frame is retracted to its Fig. 7 position, a plate Z3 closing well W and the marking plungers engaging an inking pad Z6. The spring fingers H are mounted on a base Y which is guided by a rod X <SP>1</SP> and secured to the rod X2 so that by pulling the latter to the right the fingers can grip a test lens.