JPS5537938A - Angle converter - Google Patents

Abstract

PURPOSE: To photoelectrically convert the angle by a simple structure by providing the third plate of polarization inputting the angle to be converted to the center rotating shaft and confronting the first and the second plates of polarization respectively, which are arranged by shifting the axes of the polarization by 90° from each other.

CONSTITUTION: The strength of light passing through the third and the first plates of polarization 3, 2 I₂=(I₀/2)cos²θ. In this instance, I is a strength of non-polarization light. The strength of light I₃ passing through the plates 3, 5 is expressed by I₃=(I₀/2)sin²θ, because the axis of polarization of the plate of polarization 3, 5 are displaced by 90°. Accordingly, I₃=(I₀/2)sin²θ. The sum and the difference of I₂, I₃ are I₂-I₃=(I₀/2)cos²θ, I₂+I₃=I₀/2, ane the sum becomes constant without depending on the angle, so that I₂-I₃=(I₂+I₃)cos²θ can be expressed. Accordingly, when taking the difference of the output by controlling the current of the light source 1 so as to have a constant output of the light detector 4, cos²θ, namely the output proportional to the angle θ in which the plate of polarization 3 is rotated can be converted into the electric signal untouched.

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