1. Field of the Invention
The present invention relates to an endoscope system.
2. Description of the Related Art
For example, JP-A-2000-342533 discloses an endoscope system including an endoscope which has an imaging element emitting illumination light from a front end of an endoscope insertion unit and capturing an image of an observation area, and a control device which supplies the illumination light to the endoscope while being connected to the endoscope, and performs a calculation process on an imaging signal from the imaging element. In addition, recently, a technology of using a combination of a fluorescent body and laser light as the illumination light of the endoscope has been put to practical use. In the case of the endoscope system using the illumination light formed by the fluorescent body and the laser light, the fluorescent body is disposed in the front end of the endoscope insertion unit, and the laser light is supplied to the fluorescent body via a thin optical fiber cable, which is an advantage in that the endoscope insertion unit is thin.
In such an endoscope system, in order to accurately examine an affected portion, a chromaticity adjustment process is performed by correcting the chromaticity of a captured image to be the correct chromaticity on the basis of a predetermined chromaticity correcting table. However, there is an individual difference in the optical characteristics of each endoscope and the optical characteristics of a control device to which the endoscope is connected. For this reason, even when the uniform correction of the image signal output from the endoscope is attempted by the control device, it is difficult to perform the correction with correct chromaticity at all times. Particularly, in the case of the illumination device obtained by combining the fluorescent body with the laser light source, since the tone of the final observation image is determined by the delicate relationship of the difference in the light emission characteristics caused by the individual difference of the fluorescent body or the difference in the light emission wavelength caused by the individual difference of the illumination light source, when the endoscope connected to the control device is exchanged with another one, the tone of the captured image may be different for each endoscope.
FIG. 12 shows a distribution of a variation in the illumination light of the endoscope caused by the individual differences of chromaticities (X, Y) of the light sources. When the laser light source is used, since the laser light emitting element has a variation in the light emission wavelength of about ±5 nm, a variation in the chromaticity caused by the individual differences of the light sources (for example, excitation light sources of 440 nm and 445 nm) is about 0.02 in the chromaticities X and Y. When a variation in the characteristics of the illumination light is small, the variation can be adjusted by a white balance function provided in a control device. However, when a variation caused by the individual differences is large, and is out of an adjustable range, the correct tone cannot be realized even when the white balance adjustment is performed. For this reason, the chromaticity of the illumination light determines the color quality of the observation image.