1. Field of the Invention
The present invention relates to an endoscope apparatus configured to use illuminating light of a plurality of wavelength bands to pick up an image.
2. Description of the Related Art
In recent years, endoscopes configured to inspect inside of subjects are widely used in a medical field and the like. Illumination light of narrow bands of a plurality of wavelength bands is used to pick up an image of a traveling state or the like of blood vessels near a surface layer of a biological tissue to perform endoscopy (or diagnosis) in some cases.
To generate an image by picking up an image of blood vessels near a surface layer of a biological tissue, light of a plurality of wavelength bands, such as light with a wavelength of 600 nm easily absorbed by deep blood vessels near the surface layer and light with a wavelength of 630 nm that is reference light not easily absorbed by the deep blood vessels compared to the light of the wavelength of 600 nm, is used to generate an image emphasizing the deep blood vessels.
In generating such an image, it is difficult to acquire a sufficiently bright image when the reference light is from a visible long wavelength to a near infrared region, because a transmittance of a lens and a sensitivity of image pickup are reduced. Furthermore, balance of light of each wavelength needs to be adjusted to appropriately set color balance, but this is not clearly defined so far.
For example, Japanese Patent Application Laid-Open Publication No. 2009-135907 as a first conventional example is disclosed to provide an image pickup device capable of providing a desirable image with fine color components according to a penetration depth of light in an object, the image pickup device including a light emitting section configured to emit light of first to third wavelength regions (650 nm, 450 nm, and 540 nm) and first to third light receiving elements with sensitivity for the first to third wavelength regions, wherein spectral sensitivities of the respective light receiving elements, a spectral reflectance of the object, and a spectral intensity of light emitted to the object by a light emitting portion are multiplied to obtain values, the values are integrated throughout the wavelength regions to calculate relative light receiving intensities of the respective light receiving elements, and the light receiving elements are arranged on the image pickup device so that the number of first light receiving elements:the number of second light receiving elements:the number of third light receiving elements are 2:2:1 because the relative light receiving intensities are 2:1:1 in the first light receiving elements:the second light receiving elements:the third light receiving elements.
Japanese Patent No. 5404968 as a second conventional example is disclosed to provide an endoscope apparatus capable of clearly displaying blood vessels of a deep part of mucosa at an appropriate brightness without performing cumbersome work of administration of a medicine, wherein narrow band light near the wavelength of 600 nm and narrow band light near the wavelength of 630 nm are emitted, each narrow band signal is multiplied by a light adjustment control parameter, and a largest weight 0.6 is provided to a narrow band signal near the wavelength of 600 nm.