| 摘要 |
A photometric system is provided for use as a spectrophotometer system; or for use as a calibration system for accurately calibrating optical attenuators, such as neutral glass filters, interference-type filters, comb filters, screen filters, and the like. The photometric system of the invention includes a time-division optical attenuator which causes the precise fraction of a light beam to be passed through the system. The time-division optical attenuator is adjustable, so that when an optical attenuator to be calibrated, or a sample to be tested, is introduced into the optical path of the system, the light incident thereon can be changed precisely by any ratio of integers which returns the light output of the system to nearly its original reference level. Since the optical time-division attenuator can make changes in light intensity which are theoretically without error, the accuracy of the system depends only upon the accuracy by which the small difference between the output light from the system under test conditions and the output light from the system under reference conditions can be measured.
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