Patent ID: 7746560

Claim:
An illumination optical system comprising: a solid-state lighting element that generates light having a spectral profile with peak intensities at multiple wavelengths such that the light output by said solid-state lighting element is perceived by an observer as being white in color; and a wavelength distribution conversion element having a spectral transmittance profile that includes specified wavelength regions within which the transmittance is nearly constant with increasing wavelength so as to form a step of nearly even intensity, and having specified wavelength regions within which the transmittance changes with increasing wavelength so as to form a transition region; wherein, by the combined effect of said solid-state lighting element and said wavelength distribution conversion element, the wavelength distribution of the light generated by the illumination optical system more closely resembles the wavelength distribution of daylight than the light generated by the solid-state lighting element; and the number of specified wavelength regions where the wavelength distribution conversion element has a transmittance that is lower than the transmittance in said specified wavelength regions that include a peak intensity equals the number of peak intensities generated by the solid-state lighting element.