Patent ID: 8730601

Claim:
A set of filters comprising an illumination light filter and an observation light filter; wherein a transmission characteristic of the illumination light filter is a sum of a first partial characteristic and a second partial characteristic; wherein a transmission characteristic of the observation light filter comprises at least one third partial characteristic; wherein the first partial characteristic has, at wavelengths below a threshold wavelength, at least one wavelength range in which the transmission has values greater than a first value; wherein the second partial characteristic has, at wavelengths above the threshold wavelength, at least one second wavelength range in which the transmission has values less than a second value and greater than a third value, wherein the transmission of the illumination light filter has, between the first wavelength range and the second wavelength range, values less than a fourth value; wherein the third partial characteristic has, at wavelengths above the threshold wavelength, at least one third wavelength range in which the transmission has values greater than the first value; and wherein the fourth value is less than the third value, the third value is less than the second value and the second value is less than the first value, wherein: ∫ S ⁢ T L ⁡ ( r → ) · T O ⁡ ( r → ) · r → · ⁢ ⅆ r ∫ S ⁢ T L ⁡ ( r → ) · T O ⁡ ( r → ) · ⁢ ⅆ r = R → ⁢ ⁢ and ⁢ ⁢  W → - R →  ≤ 0.15 ; wherein {right arrow over (r)} is a coordinate in the CIE xy chromaticity diagram of the CIE 1931 XYZ color space, S is a line called the spectral locus line of the CIE xy chromaticity diagram of the CIE 1931 XYZ color space, and {right arrow over (W)} is the white point in the CIE xy chromaticity diagram of the CIE 1931 XYZ color space.