Light irradiation device and light irradiation method irradiating converged light with an object

A light irradiation device for irradiating converged light with an object, the device comprising:

• a light source configured to output a light;
• a phase-modulating spatial light modulator configured to input the light outputted from the light source and to display a hologram modulating a phase of the light at each of a plurality of pixels arranged two-dimensionally, the phase-modulating spatial light modulator further configured to output the phase-modulated light;
• a converging optical system disposed downstream of the spatial light modulator;
• and
• a controller configured to cause the spatial light modulator to display a hologram such that the light outputted from the spatial light modulator is converged at a plurality of converging positions by the converging optical system,
• wherein the controller causes the spatial light modulator to display a first hologram and performs a feedback of the first hologram so as to modify the first hologram, and
• wherein the modifying of the first hologram is performed by measuring intensity of the light converged at each of the converging positions, producing a second hologram by reproducing the first hologram using Iterative Fourier Transformation on the basis of the intensity at any reference point of each of the converging positions, and displaying the second hologram on the spatial light modulator.