A light apparatus of an optical mouse with an aperture stop and the light
projection method thereof are described. The light apparatus has at least
one image-forming lens and an aperture stop. The image-forming lens
defines an interior area and an external area. The aperture stop has a
pupil. The aperture stop shelters the external area of the image-forming
lens. The pupil of the aperture stop corresponds to the interior area.
The present light apparatus will not produce a light halo on the image
detection unit of the optical mouse when the light source of the optical
mouse projects a light that passes through the image-forming lens of the
light apparatus. Therefore, the image detection unit clearly detects the
image of the image detection surface.