Illumination optical system that uses a solid-state lighting element which generates white light, and an optical device equipped therewith

1. 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.

2. 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;

said wavelength distribution conversion element satisfies the following conditions:

480 nm≦λ1≦520 nm

580 nm≦λ2≦620 nm

where

λ1 is a wavelength at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from a first step of nearly even transmittance with increasing wavelength to a second step of nearly even transmittance with increasing wavelength; and

λ2 is a wavelength, longer than wavelength λ1, at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from said second step to a third step of nearly even transmittance with increasing wavelength;

said wavelength distribution conversion element being formed of:

a first filter having a spectral transmittance profile that,

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength, and

within a specified wavelength region having wavelengths longer than λ1, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is greater than the transmittance within the specified wavelength region having wavelengths shorter than λ1;

a second filter having a spectral transmittance profile that,

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength,

within a specified wavelength region having wavelengths longer than λ1 but shorter than λ2, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is less than the transmittance within the specified wavelength region having wavelengths shorter than λ1, and

within a specified wavelength region having wavelengths longer than λ2, has a transmittance that is nearly unchanging with increasing wavelength, but the transmittance is greater than the transmittance within the specified region having wavelengths longer than λ1 and shorter than λ2.

3. A microscope that has an illumination optical system as set forth in claim 2 .

4. An apparatus as set forth in claim 3 , wherein said microscope is provided with stereo viewing optics so that a 3-D image may be viewed.

5. An electronic endoscope that has an illumination optical system as set forth in claim 2 .

6. 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;

said wavelength distribution conversion element satisfies the following conditions:

480 nm≦λ1≦520 nm

580 nm≦λ2≦620 nm

where

λ1 is a wavelength at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from a first step of nearly even transmittance with increasing wavelength to a second step of nearly even transmittance with increasing wavelength; and

λ2 is a wavelength, longer than wavelength λ1, at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from said second step to a third step of nearly even transmittance with increasing wavelength;

the transmittance of said wavelength distribution conversion element, within a specified wavelength region having wavelengths shorter than λ1, is less than the transmittance of said wavelength distribution conversion element in a specified wavelength region having wavelengths longer than λ2; and

the transmittance of said wavelength distribution conversion element, in a specified wavelength region having wavelengths longer than λ1 and shorter than λ2, is less than the transmittance of said wavelength distribution conversion element in a specified wavelength region having wavelengths shorter than λ1; and

said wavelength distribution conversion element being formed of:

a first filter having a spectral transmittance profile that,

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength, and

within a specified wavelength region having wavelengths longer than λ1, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is greater than the transmittance within the specified wavelength region having wavelengths shorter than λ1;

a second filter having a spectral transmittance profile that,

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength,

within a specified wavelength region having wavelengths longer than λ1 but shorter than λ2, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is less than the transmittance within the specified wavelength region having wavelengths shorter than λ1, and

within a specified wavelength region having wavelengths longer than λ2, has a transmittance that is nearly unchanging with increasing wavelength, but the transmittance is greater than the transmittance within the specified region having wavelengths longer than λ1 and shorter than λ2.

7. 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;

said wavelength distribution conversion element satisfies the following conditions:

480 nm≦λ1≦520 nm

580 nm≦λ2≦620 nm

where

λ1 is a wavelength at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from a first step of nearly even transmittance with increasing wavelength to a second step of nearly even transmittance with increasing wavelength; and

λ2 is a wavelength, longer than wavelength λ1, at which the spectral transmittance profile of said wavelength distribution conversion element is changing with increasing wavelength from said second step to a third step of nearly even transmittance with increasing wavelength;

said wavelength distribution conversion element has a transmittance, within a specified wavelength region having wavelengths longer than wavelength λ1 and shorter than wavelength λ2, that is higher than the transmittance of said wavelength distribution conversion element within a specified wavelength region having wavelengths shorter than λ1; and

said wavelength distribution conversion element has a transmittance, within a specified wavelength region having wavelengths longer than λ1 and shorter than λ2, that is lower than the transmittance of said wavelength distribution conversion element within a specified wavelength region having wavelengths longer than λ2;

said wavelength distribution conversion element being formed of:

a first filter having a spectral transmittance profile that,

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength, and

within a specified wavelength region having wavelengths longer than λ1, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is greater than the transmittance within the specified wavelength region having wavelengths shorter than λ1;

a second filter having a spectral transmittance profile that

within a specified wavelength region having wavelengths shorter than λ1, has a transmittance that is nearly unchanging with increasing wavelength,

within a specified wavelength region having wavelengths longer than λ1 but shorter than λ2, has a transmittance that is nearly unchanging with increasing wavelength but the transmittance is less than the transmittance within the specified wavelength region having wavelengths shorter than λ1, and

within a specified wavelength region having wavelengths longer than λ2, has a transmittance that is nearly unchanging with increasing wavelength, but the transmittance is greater than the transmittance within the specified region having wavelengths longer than λ1 and shorter than λ2.