Multi-ring mask, light irradiation device, optical microscope, and photoacoustic microscope

A multi-ring mask for spatially intensity-modulating input light in a beam cross-section and outputting modulated light, the multi-ring mask comprising:

• a plurality of ring-shaped light-shielding areas provided around a center position;
• a transmitting area provided between two adjacent light-shielding areas out of the plurality of light-shielding areas;
• an innermost transmitting area provided inside an innermost light-shielding area out of the plurality of light-shielding areas;
• and an outermost transmitting area provided outside an outermost light-shielding area out of the plurality of light-shielding areas, wherein
• the innermost transmitting area includes the center position of the multi-ring mask, and has a circle shape or an ellipse shape,
• a radial width of each of the two adjacent light-shielding areas out of the plurality of light-shielding areas is larger than a radial width of the transmitting area provided between the two light-shielding areas, and
• a pattern of the multi-ring mask is switched when an intensity distribution of the input light is changed by changing a magnification for the input light or a wavelength of the input light.