Light source device, image projection apparatus, and head-up display apparatus

A head-up display apparatus comprising:

• a light source device;
• and
• an image projection device,
• wherein the light source device comprises:
• a light emitting device that emits a light beam capable of being modulated;
• and
• a scanning device that deflects the light beam in a first direction and a second direction intersecting the first direction,
• wherein the image projection device comprises an image output device that uses the light beam as a light source to output an image,
• wherein the light beam has a light quantity varying region in which a light quantity decreases outward from a center of the light beam in at least one of the first direction or the second direction,
• wherein the scanning device overlaps the light quantity varying regions of a plurality of the light beams with each other with respect to a scanning direction along directions in which the light quantities of the light beams decrease, and
• wherein, in the light beam, assuming the light quantity at a center in at least one of the directions of the light beam as a reference value, a distance from the center to a position where the light quantity is halved from the reference value is equal to a distance from the position where the light quantity is halved from the reference value to a position where the light quantity becomes equal to zero, and, with respect to the position where the light quantity is halved from that of the center, a degree of increase in the light quantity toward the center of the light beam has a symmetric relation with a degree of decrease in the light quantity toward the position where the light quantity becomes equal to zero.