Endoscope

1. An endoscope comprising:

an insertion portion to be inserted into a subject;

an operation portion provided at a proximal end of the insertion portion, the operation portion including operation means;

a first light source section provided inside the operation portion, the first light source section being configured to generate first light with which the subject is irradiated;

a light guiding section including an entrance portion provided on a proximal end side of the insertion portion and an emitting portion provided in a distal end portion of the insertion portion, the light guiding section being configured to attenuate light in a narrow wavelength band which is within a range of wavelength band of the first light entering the entrance portion and which is narrower than the wavelength band of the first light, and to emit the light from the emitting portion;

a second light source section provided at the distal end portion of the insertion portion, the second light source being configured to generate the light in the narrow wavelength band within the range of wavelength band of the first light, the light being attenuated by the light guiding section, as second light; and

an optical element provided at the distal end portion of the insertion portion, the optical element combining light emitted from the emitting portion of the light guiding section and the second light and emitting the resulting light from an illuminating window provided at the distal end portion.

2. The endoscope according to claim 1 ,

wherein the first light source section includes a white color light-emitting diode that substantially generates white color light covering a visible wavelength band, as the first light;

wherein the wavelength band in which attenuation occurs when the first light is guided by the light guiding section includes a blue color narrow band; and

wherein the second light source section includes a blue color light-emitting diode that generates light in the blue color narrow band, as the second light.

3. The endoscope according to claim 2 , wherein the first light source section further includes a green color light-emitting diode that generates green color narrow band light, and the endoscope further includes a light amount adjusting section configured to adjust a light amount ratio between an amount of the blue color narrow band light emitted via the optical element and an amount of the green color narrow band light from the green color light-emitting diode, the green color narrow band light being emitted via the optical element.

4. The endoscope according to claim 2 , wherein the optical element selectively combines light in a wavelength band other than the wavelength band in which attenuation occurs when the first light is guided by the light guiding section in the light emitted from the emitting portion of the light guiding section, with the second light.

5. The endoscope according to claim 4 , further comprising an imaging mode selecting section configured to make a selection of one of a first light imaging mode in which first light imaging using illumination with the first light is performed and a second light imaging mode in which second light imaging using illumination with the second light is performed, and a control section configured to control light emission operations of the first light source section and the second light source section based on the selection made by the imaging mode selecting section.

6. The endoscope according to claim 5 , wherein the control section, upon selection of the first light imaging mode, performs control so as to make the first light source section and the second light source section emit light simultaneously, and upon selection of the second light imaging mode, performs control so as to make the first light source section not emit light and selectively make only the second light source section emit light.

7. The endoscope according to claim 6 , further comprising a first light/second light imaging mode selecting section configured to make a selection of a first light/second light imaging mode in which first light illumination with the first light and second light illumination with the second light are alternately provided to acquire a first light image using the first light illumination and a second light image using the second light illumination,

wherein based on the selection made by the first light/second light imaging mode selecting section, the control section controls light emission operations of the first light source section and the second light source section.

8. The endoscope according to claim 7 , wherein in a first light illumination period in which the first light illumination is provided, the control section performs control so as to make the first light source section and the second light source section emit light simultaneously, and in a second light illumination period in which the second light illumination is provided, the control section performs control so as to make the first light source section not emit light and selectively make only the second light source section emit light.

9. The endoscope according to claim 8 , wherein in the second light illumination period, the control section controls a light emission operation of the blue color light-emitting diode included in the second light source section so that a light emission amount is increased relative to that in the first light illumination period.

10. The endoscope according to claim 8 , further comprising an image pickup device disposed in a distal end portion of the insertion portion, the image pickup device picking up an image of an object under the first light illumination and the second light illumination,

wherein the control section controls a signal processing circuit provided in an outside apparatus to which the endoscope is connected, the signal processing circuit performing signal processing for the image pickup device, to:

generate the first light image from a signal picked up by the image pickup device in the first light illumination; and

generate the second light image from a signal picked up by the image pickup device in the second light illumination.

11. The endoscope according to claim 10 , wherein the control section further controls the signal processing circuit to generate a composite image in which the first light image and the second light image are simultaneously displayed adjacent to each other.

12. The endoscope according to claim 9 , further comprising a period setting section configured to set a value of each of a period of the first light illumination and a period of the second light illumination, which are alternately provided.

13. The endoscope according to claim 4 ,

wherein the first light source section includes:

the white color light-emitting diode;

a green color light-emitting diode that generates green color narrow band light;

a second optical element including a first entrance face and a second entrance face that white color light from the white color light-emitting diode and green color narrow band light from the green color light-emitting diode enter, respectively,

the second optical element selectively allowing light other than light having a wavelength band of the green color narrow band light in the white color light entering from the first entrance face to enter the entrance portion of the light guiding section, and

the second optical element selectively allowing light having a wavelength band of the green color narrow band light in the green color narrow band light entering from the second entrance face to enter the entrance portion of the light guiding section.

14. The endoscope according to claim 2 , further comprising a light source fixing portion configured to fix the first light source section and the entrance portion of the light guiding section in contact with each other.

15. The endoscope according to claim 2 , further comprising a timing control section configured to perform timing control so that when light irradiation by the first light source section and light irradiation by the second light source section are switched from one to another, the first light source section and the second light source section are lighted simultaneously for a predetermined period.

16. The endoscope according to claim 2 , wherein a polarizer is disposed between the second light source section and the optical element.

17. The endoscope according to claim 1 , wherein the second light includes light for producing the first light as a result of the light being combined with light emitted from the emitting portion of the light guiding section by the optical element.

18. The endoscope according to claim 1 , further comprising:

a cable extending from the operation portion; and

a power supply wire inserted in the cable, wherein the first light source section receives a supply of drive power for making the first light source section emit light, from a power supply circuit disposed outside the endoscope via the power supply wire.

19. The endoscope according to claim 1 , wherein the operation portion is integrally formed at the proximal end of the insertion portion, and includes a bending operation knob for bending and operating a bending portion provided in the insertion portion, as the operation means.

20. The endoscope according to claim 1 , wherein the optical element comprises a dichroic prism that selectively reflects the second light entered from the second light source section and selectively transmits light in a broadband wavelength other than a wavelength band of the second light in the first light entered from the first light source section.

21. The endoscope according to claim 1 , wherein

the first light source section comprises a white color light emitting diode that emits white color light including light in red, green, and blue wavelength bands in the operation portion, and

the light guiding section comprises a light guide that transmits the white color light.

22. The endoscope according to claim 1 , wherein the first light source section generates light including a visible wavelength band as the first light, and the light guiding section attenuates light in a wavelength band which is within the visible wavelength band and narrower than the visible wavelength band of the first light.