A light source unit for use in an image display apparatus for irradiating scan light to an optical scanning system to generate an image, the light source unit comprising: a plurality of light emitters to emit corresponding lights having different wavelengths; a plurality of coupling lenses respectively disposed for the plurality of light emitters to respectively pass through the lights emitted from the plurality of light emitters ; and a plurality of aperture members respectively disposed for the plurality of coupling lenses , each aperture member having an aperture to reduce the beam waist diameter for a respective light coming from the coupling lenses , and a light path synthesizer to synthesize the lights coming from the plurality of aperture-formed members characterised in that the light source unit further comprises: a condenser lens to condense light coming from the light path synthesizer such that the light flux diameter of the light that passes through the condenser lens is reduced, the longer the wavelength of the emitted light that passes through each aperture member , the greater the size of the aperture of the corresponding aperture member ; and wherein the coupling lens differentiates convergence of the light depending on the wavelength of the lights emitted from the plurality of light emitters , such that a higher degree of convergence is set to a coupling lens used for a light beam having a longer wavelength , so that the beam waist of the light beams passing through the condenser lens is matched. a plurality of light emitters to emit corresponding lights having different wavelengths; a plurality of coupling lenses respectively disposed for the plurality of light emitters to respectively pass through the lights emitted from the plurality of light emitters ; and a plurality of aperture members respectively disposed for the plurality of coupling lenses , each aperture member having an aperture to reduce the beam waist diameter for a respective light coming from the coupling lenses , and a light path synthesizer to synthesize the lights coming from the plurality of aperture-formed members characterised in that the light source unit further comprises: a condenser lens to condense light coming from the light path synthesizer such that the light flux diameter of the light that passes through the condenser lens is reduced, the longer the wavelength of the emitted light that passes through each aperture member , the greater the size of the aperture of the corresponding aperture member ; and wherein the coupling lens differentiates convergence of the light depending on the wavelength of the lights emitted from the plurality of light emitters , such that a higher degree of convergence is set to a coupling lens used for a light beam having a longer wavelength , so that the beam waist of the light beams passing through the condenser lens is matched. a condenser lens to condense light coming from the light path synthesizer such that the light flux diameter of the light that passes through the condenser lens is reduced, the longer the wavelength of the emitted light that passes through each aperture member , the greater the size of the aperture of the corresponding aperture member ; and wherein the coupling lens differentiates convergence of the light depending on the wavelength of the lights emitted from the plurality of light emitters , such that a higher degree of convergence is set to a coupling lens used for a light beam having a longer wavelength , so that the beam waist of the light beams passing through the condenser lens is matched. <EOS>