Improvements in or relating to apparatus for identifying colour

Abstract

Abstract 643,396. Photo-electric colour analysis. THOMASSON, D. W. Jan. 1, 1948, No. 90. [Class 40 (iii)] In a system for determining the colour content of a sample under test the sample is scanned in turn by successive parts of the spectrum, the reflected or transmitted light being used to control the deflection of a cathode-ray indicator in one direction while a time base, synchronized with the scanning, controls it in the other. The illuminating head is shown in Fig. 1. White light from a source L<SP>1</SP> is split into its spectrum components by a prism L<SP>4</SP> and is then reflected from mirrors L<SP>7</SP> and L‹ (hidden by L<SP>7</SP>) through a gate L<SP>10</SP> (Fig. 3), having a number of separately adjustable shutters LG2 to adjust each colour independently and lens L" and L<SP>12</SP> on to the sample. Surrounding the mirrors is a rotating drum L<SP>8</SP> having slits in its periphery so that each part of the spectrum in turn passes to the sample. In the path of the light to the sample S, Fig. 6, is a rotatable standard white disc W which may be coated with magnesium chloride and which has a hole cut in its face to permit of illumination of the sample. Light reflected from the face of the disc or from the sample passes to a photo cell P<SP>2</SP>, the output of which is amplified at P 3, P<SP>4</SP> and applied through a D.C. restorer DO to the Y-plates of cathode-ray tube. A motor M drives the scanning drum L<SP>8</SP> and the disc W through a Geneva stop mechanism G and also controls the time base P6. The speeds of the drum and disc are so arranged that during one progression of the time base from left to right the sample is illuminated by the successive spectral colours, during the second, the standard disc and during the third no light passes from the illuminating head. This gives a graph of the variation of the different colour contents of the sample together with a pair of horizontal lines one representing zero photocell output and the other the output with the standard white in position. An antilogarithmic scale may then be placed on the end of the tube and the height of the " white " line adjusted. by the potentiometer T. In a modification (Fig. 8, not shown), the light from the sample is directed first through the sample to the photo-cell and then through a standard material which may be distilled water by means of a reciprocating prism. It is stated that the photo-cell output may be taken to the amplifier through separate individually adjustable resistors or potentiometer, thereby dispensing with the light gate.

Inventors

No inventors recorded.

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