1. Field of the Invention
The present invention relates to an endoscope system.
2. Description of the Related Art
As a technology for signal transmission of a captured image between an endoscope and a controller connected to the endoscope, a system employing analog transmission is described in JP-A-60-55923. In this system, a noise elimination device generates positive and negative video signals on the basis of image information of a captured image and these video signals are synchronized with each other and transmitted to the controller, so that degradation in the image quality may be restored by utilizing the symmetry between these video signals. Thus, image information may be transmitted with high noise resistance and without causing a large failure in the image. In the analog transmission, however, image data to be transmitted and an ultimate image obtained at the destination are weighted in a ratio of 1:1 in general, and therefore, the degree of influence is low when disturbance of noise is weak but the degree of influence on a transmitted image is increased as the disturbance of noise is stronger. Therefore, it is necessary to sufficiently improve the noise resistance for improving the transmission performance.
In the transmission of image information, it has been also proposed to digitalize the image information and serially transmit the digitalized information in order to reduce the image quality degradation caused during the transmission (see JP-A-2009-201540 and JP-A-2008-80007). In the serial transmission of a digital signal, however, data differently weighted are transmitted in a time series, and therefore, if a highly weighted bit (namely, an upper bit) is influenced by noise, the influence appears remarkably in a received image. Furthermore, although noise may be eliminated through error correction by adding an error check code to every prescribed data in the serial data transmission, there is a limit to bits that can be corrected for errors, and if a burst error occurs, it cannot be corrected, and hence the image is unavoidably degraded.
Therefore, even when a captured image signal is serially transmitted to the controller from the endoscope for reducing the degradation in the image quality, when noise externally influences during the transmission, the influence of the noise conspicuously appears in a displayed image.