GB785796A - Apparatus for examining the capacity of human beings to discriminate between light of different intensity and of different colour - Google Patents

Abstract

785,796. Colour and intensity descrimination testing apparatus. NEDERLANDSE ORGANISATIE VOOR TOEGEPASTNATUURWETENSCHAPPELIJK ONDERZOEK TEN BEHOEVE VAN DE RIJKSVERDEDIGING. April 1, 1955 [April 3, 1954], No. 9580/55. Class 97(1) In apparatus for testing the ability of human beings to discriminate between test areas and a background surface of different luminosity intensity or colour, the test areas consist of groups of holes in a partition wall separating two compartments which can be illuminated by light of variable intensity and colour. Preferably, the holes of the test areas differ in size from one test area to another but not in relative spacing, and are viewed at such a distance through the front opening that they cannot be seen separately. The insides of the compartments are diffusely and non- selectively reflecting and, for a given difference in the intensity or colour in the lighting of the compartments, the number of test areas visible to an observer is a measure of his discriminating ability. The compartments may be rectangular (Fig. 1, not shown) and each of two lamps may illuminate both of them. As shown, spherical compartments 30, 31 are made as nearly as possible the same and, the back of partition wall 32 in the rear compartment 31 is accordingly blackened to correspond with opening 37. The partition wall is slidably mounted between the two spherical compartments and light from one or more of four lamps 40, 41, 42 and 43 (only two of which are shown) is focused on the wall of each sphere as nearly as possible opposite the test areas 33 and the correponding flattened position 36. A third compartment 65 may be provided and illuminated by lamps 66, 67, the surfaces 68 and 69 being blackened and the brightness of the inner surfaces of this compartment being made equal to that of sphere 30. A colour filter 51 and two relatively rotatable plane polarizing filters 52 are provided .for each lamp. The latter may be replaced by an adjustable iris diaphragm on a neutral density wedge or, alternatively, the current 'to the lamps may be variable. A shutter 60 is mounted in housing 45 so that it interrupts the light either from one white lamp 42 or from three coloured lamps 43 and 62, 64 (Fig. 4 not shown). It is possible to obtain colours in the two compartments of the same brightness by observing the flickering on rotating shutter 60 and adjusting this to a minimum. The holes of test areas may be tapered towards the observer and the test areas and the-surrounding area of the partition wall may be provided with uniformly distributed small black areas to increase the relative brightness due to the holes.