Endoscope system for fluorescent observation

An endoscope system for detecting fluorescences emitted by a plurality of fluorescent labeling materials introduced into living tissue, comprising:

• an illumination system;
• and
• an observation system;
• wherein
• the illumination system generates an excitation light for the fluorescent labeling materials;
• the observation system includes an objective optical system, an excitation light cut-off filter, a wavelength tunable filter and a detector;
• the wavelength tunable filter is formed as an etalon that includes a plurality of transparent substrates arranged so as to form a gap between said transparent substrates, the surfaces of the substrates that face each other across the gap have semi-transparent films, at least two of which have a spectral transmittance and the following conditions are satisfied:
• T1≧80% and
• T2≦35%,
• where
• T1 is the average transmittance in the wavelength region of 400 nm≦λ≦650 nm, and
• T2 is a transmittance in the wavelength band having a lower boundary that is 50 nm shorter than the peak transmittance wavelength of the shortest fluorescence wavelength, and an upper boundary that is 50 nm longer than the peak transmittance wavelength of the longest fluorescence wavelength.

An endoscope for detecting fluorescence emitted by a plurality of fluorescent labeling materials introduced into living tissue, comprising:

• an illumination unit;
• and
• an observation unit;
• wherein
• the illumination unit generates near-infrared illumination light that includes a wavelength band for excitation of the fluorescent labeling materials;
• the observation unit includes an objective optical system, an excitation light blocking filter, a wavelength tunable filter, and a detector;
• the combination of the excitation light blocking filter and the wavelength tunable filter passes light in the visible region, and has a passband in the infrared region which allows the fluorescence emitted from the fluorescent labeling material that is under observation to pass through;
• and
• the spectral transmittance of said combination satisfies the following conditions:
• T3≧60%
• T4≦0.01%
• T5≧65%
• 5 nm≦d5≦35 nm
• where
• T3 is the average transmittance within the visible wavelength range of 400 nm≦λ≦650 nm,
• T4 is the transmittance for the wavelengths within a range 20 nm above and 20 nm below the wavelength range of the excitation light generated by the illumination unit,
• T5 is the transmittance at the peak transmittance wavelength for an infrared passband,
• d5 is the infrared passband's full width as measured at 50% of the peak transmittance, and
• λ is the wavelength of light incident onto the wavelength tunable filter.