Light-Source Optical System, Fiber Light Source, Microscope, and Automotive Headlight

A light-source optical system comprising:

• a laser light source that radiates excitation light;
• a wavelength conversion unit that is irradiated with the excitation light from the laser light source to generate light having a wavelength different from that of the excitation light;
• and
• a light deflection and convergence unit that causes, of the light generated through the wavelength conversion by the wavelength conversion unit, three or more light beams radiated from the wavelength conversion unit in mutually different directions to converge at and re-enter the wavelength conversion unit from the backward direction of another light beam, radiated from the wavelength conversion unit in a direction different from the directions of the three or more light beams, thereby making the three or more light beams overlap the other light beam to form a single light beam in which each of the at least four light beams overlaps the other at least three light beams,
• wherein the wavelength conversion unit has a transmittance not less than 60% with respect to the light generated through the wavelength conversion.