The invention relates to an endoscope system, and more particularly, to an endoscope system which includes a solid-state camera mounted within the distal end of an endoscope to produce a video signal which is fed to a television monitor for allowing medical treatment with laser radiation while the monitor is being observed.
An endoscope system including a solid-state camera, comprising by CCD or MOS elements, and mounted within the distal end of an endoscope is described in a number of publications, including U.S. Pat. No. 4,261,344. As can be appreciated the distal end of an endoscope is very space limited which imposes restrictions on the choices of solid-state cameras which can be used. A higher image sensitivity is achieved with larger picture elements upon which light impinges while a higher resolution is achieved by providing more picture elements of wind space. Such requirements must be met with a minimized overall size. In respects of the sensitivity and resolution, these requirements are best met by a solid-state camera which utilizes charge transfer elements such as a CCD. The size of the solid-state camera can be minimized with a line transfer type camera (which will be hereafter referred to as LT type). However, in an LT type solid-state camera an area upon which light impinges is used in common with an area from which a transfer is made. Accordingly, a charge from the light impinging area may be superimposed upon a video signal during a transfer operation, disadvantageously causing a smearing or distortion. To overcome this difficulty, a pulsed light source may be used in an endoscope so that it illuminates the CCD elements during a selected interval while light is intercepted from CCD elements during a transfer operation.
On the other hand, another endoscope arrangement (which may be referred to as a laser-scope) has also been developed which provides not only the ability to observe, but also the capability of medical treatment, by introducing a laser probe into the interior of the endoscope, for example, into the forceps channel thereof, so that laser radiation may be radiated from the distal end thereof toward an object being treated. In such arrangement, it is readily apparent that during the time that medical treatment with laser radiation with the endoscope, the solid-state camera may respond to the radiation if not otherwise blocked so that the smearing phenomenon can be experienced.
As is known, an infrared rejection filter is normally disposed in front of the solid-state camera in order to prevent infrared noise from being input to the camera. However, in medical laser treatment, a YAG laser which produces infrared radiation is used for purposes of treatment, and simultaneously, a He-Ne laser or the like which produces radiation in the visible portion of the spectrum is used to provide guide light for safety purpose since the output radiation from the YAG laser is invisible. Hence, it will be seen that the mere provision of the infrared rejection filter disposed in front of the solid-state camera mounted within the distal end of the endoscope is inadequate for preventing the smearing effect when a CCD camera of LT type is employed.