PHOTOELECTRIC CURRENT MAGNETIC FIELD SENSOR

PURPOSE:To obtain a small-sized photoelectric current magnetic field sensor of high sensitivity, by providing a reflecting means such as a prism, etc. at the end of a magneto-optical element opposite to the light source side and a single optical element like a polarizing beam splitter which doubles a polarizer and a photodetector at the light source side respectively. CONSTITUTION:A polarizing beam splitter 3b is provided at the output side of an optical fiber 2 to which the light of a light source 1 is made incident. A prism 8a is set at the edge part of a lead glass 4 serving as an magneto-optical element so as to hold the polarizing state of the incident light. In addition, a 45 deg. circumpolarizer 9 is set at the position where the light reflected by the prism 8a is delivered from the glass 4. The light emitted from the circumpolarizer 9 is modulated for its light intensity by the splitter 3b and then led to a photodetector 7. Thus the linear polarized surface is turned by a light Faraday effect when a magnetic field H is applied to the glass 4 and then reflected by the prism 8a to be turned again. The splitter 3b performs the functions of a polarizer and a photodetector. As a result, a small-sized and highly sensitive magnetic field sensor is obtained. A 1/2 wavelength plate can be used in place of the circumpolarizer 9.