GB609960A - An improved protractor for the graphical tracing of rays in an optical system - Google Patents

Abstract

609,960. Protractors. DICKSON, J. H., and RAYNER, W. H. March 26, 1946, No. 9363. [Class 97 (iii)] A protractor for tracing the paths of refracted rays of light comprises a transparent disc 1 or other lamina bearing a datum line 2 representing the normal, a datum point 3 representing the point of incidence, a scale of angles 4, and a sine scale 6 with its zero on the datum line 2 and with a series of lines extending from the graduations in a direction parallel to the line 2, a radial arm 9 bearing a scale of refractive index 11 with its zero at the datum point 3 being provided; the length on the sine scale from zero to the 90 degrees line is equal to the length on the radial arm from the datum point to the mark for unity refractive index. The radial arm 9 may be pivoted at the centre 3 of the disc 1 together with a second arm 8 or may be supplied as an accessory. Preferably, the radial arm 9 carries a cursor 13 with a magnifier 14 and index line 18, further magnifiers being provided at the centre 15 and at the end 16 of the arm 8. Verniers and micrometer or tangent screws may be provided and the disc 1 may be adjustably carried by a parallel motion linkage.