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A Variable Three-Step Sector Rotating Filter

Volume 17, Number 2 (March 1963) Page 54-55

Kennedy, R.M.; Paolini, A.


Many spectrographic procedures require the use of filters in the optical path, some calling for two transmittance steps and others for three. The filtering of the transmitted light has normally been accomplished with the use of calibrated metallized quartz or, in some instances, with fixed aperture sector wheels. Laboratories that handle a considerable variety of materials for analysis would, out of necessity, need an assortment of these filtering devices. With this in mind, a variable three-step rotating sector has been devised. It permits the recording of 100% and any two combinations of 50% of the transmitted light (i.e., 100% /0 to 50% /0 to 50%), with step three less than step two. The filtering arrangement in inexpensive and relatively easy to construct. It consists of three discs mounted on a shaft, which is rotated through the transmitted light at the appropriate position on the optical bench. The shaft can be mounted on a motor used for step sector rotation or on a conventional laboratory stirrer.