Phase modulation device and laser microscope

A phase modulation device for correcting a wave front aberration generated by an optical system including an objective lens disposed on an optical path of a light flux of light to be emitted from a light source, comprising:

• a first phase modulation element which includes a plurality of first electrodes disposed to impart to the light flux an amount of phase modulation to cancel a phase distribution in accordance with a first ratio of a second aberration component of the wave front aberration to a first aberration component of the wave front aberration, and modulates a phase of the light flux in accordance with a voltage applied to each of the plurality of first electrodes;
• a second phase modulation element which includes a plurality of second electrodes disposed to impart to the light flux an amount of phase modulation to cancel a phase distribution in accordance with a second ratio of the second aberration component of the wave front aberration to the first aberration component of the wave front aberration, the second ratio being smaller than the first ratio, and modulates a phase of the light flux in accordance with a voltage applied to each of the plurality of second electrodes;
• and
• a control circuit which controls voltages applied to the plurality of first electrodes and voltages applied to the plurality of second electrodes in accordance with an optical path length from the objective lens to a light focusing position of the light flux.