JPS5619409A - Optical sensing system - Google Patents

Abstract

PURPOSE:To improve the measurement precision of a physical quantity by separating a light wave consisting of two different-wavelength components into two polarized components after its polarization state is varied by a physical quantity to be measured and then by permitting one component to pass through a filter that stops a wave of one wavelength. CONSTITUTION:Output light beams from light sources 21 and 22 of lambda1 and lambda2 in wavelength are mixed in one, which is sent to optical crystal 26, which varies in polarization state with a physical quantity, by way of polarizer 25. Light from optical crystal 26 is separated by polarizing separating element 27 into Pa component 28 and Pb component 29 and Pa has wavelength component lambda1 removed by filter 30. Then, Pa having the wavelength component lambda1 removed and Pb are mixed by light mixer 31, whose output is separated by light branching filter 33 into wavelength compoments lambda1 and lambda2, which are measured by photodetector 34 in terms of light intensity. Here, the component of wavelength lambda1 includes only component Pb and that of lambda2 carries Pa+Pb. In this system, the relation between voltage V of a measured value and the polarized component is shown by expression 1. Therefore, measured value V can be found from the ratio of Pa+Pb to measuring value Pb with high precision.