| 摘要 |
749,858. Photometric apparatus. OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AERONAUTIQUES, O.N.E.R.A. Sept. 22, 1953 [Sept. 24, 1952], No. 26148/53. Class 97 (1). Apparatus for selectively absorbing certain wavelengths in a beam of radiation, particularly for use in measuring the quantities of certain substances in mixtures of fluids, comprises a layer of a substance capable of absorbing the said wavelengths and having a thickness which varies along a closed curve of the surface thereof, means being provided for causing the beam to travel continuously along the said curve whereby the thickness of absorbing substance through which it is passed is periodically varied. As shown, the absorbing substance 4 is carried in a bridge-shaped space between two transparent plates 1, 2, mounted in a ring 3 for rotation about an axis 00. Beams of light I, II from a source 8 are focused on the substance 4 by mirrors 9 and 10 and respectively pass to a cell 11 containing the fluid to be analysed, and a standard cell 10, whence they are reflected by mirrors 12, 13 to sensitive devices 14 and 15 such as thermoelements, photo-sensitive elements, or masses of gas, the change of state of which serves to measure a radiation. An indicator 17 fed by an amplifier 16 gives a measure of the amount of substance to be measured in the cell 20. The absorbing substance may be discontinuous. A wedge-shaped compensating absorbing layer 18 may be provided, rotatable with the layer 18, and a further compensating filter 20 may be added. |
