GB802584A - Photo-electric polarimeter - Google Patents

Abstract

802,584. Photo-electric polarimeters. ZEISSSTIFTUNG, C., [trading as ZEISS, C. [Firm of]]. Jan. 23, 1956 [Jan. 26, 1955], No. 2115/56. Class 40 (3). [Also in Group XX] A photo-electric polarimeter (Fig. 1) includes a monochromatically-filtered light source 1, a rotatable polarizer 2 producing plane-polarized light of variable azimuth measured on a divided circle 3, the object 4 under examination, a polarizing element 5 to divide the beam into two perpendicularly polarized beams with or without a phase angle, a magneto-optically active substance 6 to produce flicker by changing the azimuths of the planes of polarization, an analyser 7 and a lens 8 to focus the beams together on to the photo-electric cell 9. An alternating magnetic field is produced by coil 10 fed with A.C. from source 14. Polarizer 2 can be rotated by hand or by a phase-dependent motor 15 fed from A.C. source 14 and amplified photocell current. A further development of the apparatus (Fig. 2) has a fixed polarizer 2 with a compensating magneto-optically active substance 11 upon which acts a measurably variable magnetic field produced by D.C. in coil 17 (11 and 17 may alternatively be between the object 4 and the polarizing element 5). Indicator 12 can be calibrated directly in degrees of optical rotation. Automatic compensation occurs in substance 11 if the amplified photo-cell current and the A.C. current inducing the magnetic field in the substance 6 produce via a phasedependent rectifier 16 a D.C. current measured by instrument 12 and supplied to coil 17. This compensation can be made to act very quickly by using high-frequency A.C. in coil 10. Accuracy is further increased (see Fig. 3, not shown) if the constant D.C. from a source is controlled via precision decade resistances by a motor supplied with the amplified photo-cell current and which actuates the resistances successively by an automatic coupling device. The resistances can be calibrated directly in degrees of optical rotation or in percentage concentrations. A numbered drum can be coupled to the resistances, or a printing device may be used to record the result.