Endoscope light source apparatus

1. An endoscope light source apparatus comprising:

a first solid-state light source that is configured to emit a first light beam that includes a first wavelength band;

a second solid-state light source that is configured to emit a second light beam that includes a second wavelength band in which a wavelength thereof is longer than in the first wavelength band;

a third solid-state light source that is configured to emit a third light beam that includes a third wavelength band differing from the first and second wavelength bands and that generates white light by being combined with at least one of the first and second light beams;

an optical member that is configured to combine the first light beam and the second light beam with the third light beam to generate a combined light;

an optical filter that is configured to be provided so as to be insertable into and retractable from an optical path of the combined light, and that selectively allows the light in the first, second, and third wavelength bands to pass therethrough; and

a controller that is configured to control turning on and off of the first, second, and third solid-state light sources, and insertion and retraction of the optical filter,

wherein:

in a white-light illumination mode, the controller causes the optical filter to be retracted from the optical path, and turns on the first, second, and third solid-state light sources,

in a first excitation-light illumination mode, the controller causes the optical filter to be inserted into the optical path, turns on the first and second solid-state light sources, and turns on the third solid-state light source so that an intensity of the third light beam becomes lower than intensities of the first light beam and the second light beam, and

in a second excitation-light illumination mode, the controller causes the optical filter to be inserted into the optical path, turns on the first solid-state light source, turns off the second solid-state light source, and turns on the third solid-state light source so that the intensity of the third light beam becomes lower than the intensity of the first light beam.

2. The endoscope light source apparatus according to claim 1 , wherein the optical member comprises:

a first optical member that is configured to combine the first light beam and the second light beam, and

a second optical member that is configured to combine the combined light of the first and second light beams generated by the first optical member with the third light beam.

3. The endoscope light source apparatus according to claim 1 , wherein:

the first wavelength band is from 390 nm to 440 nm, and

the second wavelength band is from 440 nm to 470 nm.

4. The endoscope light source apparatus according to claim 2 , wherein:

the first optical member has a first dichroic mirror surface that allows one of the first light beam and the second light beam to pass therethrough and reflects the other,

the first dichroic mirror surface possesses a first cut-off wavelength at which a transmittance on a transmission-optical-path side thereof becomes 50% and the first light beam and the second light beam overlap with each other, and

an intensity of the combined light of the first and second light beams at the first cut-off wavelength is equal to or greater than 10% of a maximum intensity thereof.

5. The endoscope light source apparatus according to claim 2 , wherein:

the second optical member has a second dichroic mirror surface that allows one of the combined light of the first and second light beams and the third light beam to pass therethrough and reflects the other,

the second dichroic mirror surface possesses a second cut-off wavelength at which a transmittance on a transmission-optical-path side thereof becomes 50% and the combined light of the first and second light beams and the third light beam overlap with each other, and

an intensity of the combined light of the first, second, and third light beams at the second cut-off wavelength is equal to or greater than 10% of a maximum intensity thereof.

6. The endoscope light source apparatus according to claim 2 , wherein:

the first optical member has a first dichroic mirror surface that allows light in the first wavelength band to pass therethrough and reflects light in the second wavelength band, and

the first light beam and the first dichroic mirror surface possess optical characteristics that satisfy conditional expression (1) below:

( I 1/ I 1 max)× T 1≤0.01  (1),

where:

I 1 max is a maximum intensity of the first light beam in the first wavelength band,

I 1 is an intensity of the first light beam at a wavelength 10 nm or more away from the first wavelength band on a long-wavelength side thereof, and

T 1 is a transmittance (%) of the first dichroic mirror surface at a wavelength 10 nm or more away from the first wavelength band on a long-wavelength side thereof.

7. The endoscope light source apparatus according to claim 1 , wherein:

the second light beam and the optical filter possess optical characteristics that satisfy conditional expression (2) below:

( I 2/ I 2 max)× T 2≤0.01  (2),

where:

I 2 max is a maximum intensity of the second light beam in the second wavelength band,

I 2 is an intensity of the second light beam at a wavelength 10 nm or more away from the second wavelength band on a long-wavelength side thereof, and

T 2 is a transmittance (%) of the optical filter at a wavelength 10 nm or more away from the second wavelength band on a long-wavelength side thereof.