Light source device, image projection apparatus, and light source optical system

A light source device comprising:

• multiple light source units each including a light source configured to emit a first color light beam, each of the multiple light source units configured to:
• convert at least part of the first color light beam into a second color light beam emitted from an emitting region;
• and
• emit the second color light beam to form a conjugate image;
• and
• a light combiner configured to combine the conjugate images formed by the multiple light source units to form a combined image, in which the conjugate images partially overlap each other, on a plane at a position of an entrance surface of a light uniformizing element along a central axis of the light uniformizing element,
• wherein a conditional expression below is satisfied:
• 1.3>SC/SI>0.7
• where SC is an area of the combined image in which a light intensity is equal to or greater than 1/e2 of a peak intensity of the conjugate images on the plane at the position of the entrance surface of the light uniformizing element, and SI is an area of the entrance surface of the light uniformizing element.