Patent ID: 8432162

Claim:
A magnetic sensor that measures a magnetic field by using an optical pumping method, comprising: a cell that encloses therewithin atoms or ions each having a single electron in the outermost shell thereof and that is arranged inside the magnetic field; a light source that causes pulsed first linearly polarized light to be incident upon the cell; a circularly polarized light generator that converts a portion of second linearly polarized light, which is the first linearly polarized light having passed through the cell, into elliptically or circularly polarized light and causes the portion of second linearly polarized light to be incident upon the cell; and a polarimeter that detects an angle of rotation of a first polarization plane, which is polarization plane of the first linearly polarized light, and an angle of rotation of a second polarization plane, which is a polarization plane of the second linearly polarized light, the circularly polarized light generator causing elliptically polarized light or circularly polarized light, whose light intensity varies periodically, to be incident upon the cell, and when a maximum light intensity of the elliptically polarized light or circularly polarized light incident upon the cell from the circularly polarized light generator is denoted by Imax, a minimum light intensity of the elliptically polarized light or circularly polarized light incident upon the cell from the circularly polarized light generator is denoted by Imin, and a minimum light intensity of the elliptically polarized light or circularly polarized light that causes spin polarization of the atoms or the ions enclosed in the cell when the magnetic field is zero is denoted by IC, the relation between IC, Imax and Imin of Imax>IC>Imin holds true.