|Imaging techniques for 3 D Endoscopy
There are lots of image generation types existing to produce stereoscopic images in the endoscopy. They are:
In this technology a dual-channel optical scope is connected to two video cameras and delivers two pictures that are displayed to the viewer on a stereoscopic display. An example to this is the system used in the Intuitive© robot, the DaVinci as shown in Fig 3.2. Da Vinci surgical system has four arms. Three of the arms are for tools. The fourth arm is for an endoscopic camera with two lenses. The surgeon sits at the console and looks through two eye holes at a 3-D image of the procedure. The da Vinci System scales, filters and translates the surgeon's hand movements into more precise micro-movements of the instruments, which operate through small incisions in the body as shown in Fig 3.3.
Fig 3.2: Da Vinci system
The advantage of this technique is that it displays a very bright, high-quality image generated from two 3-chip cameras. The disadvantages are common to many systems that implement similar techniques; the images generated by two scopes and two cameras are different not only in the picture angle, but also in brightness, color, optical distortion and sharpness. This commonly results in user side-effects such as fatigue, headache, dizziness and eye-strain. In addition, using current video and optics technology limits the size to a rather large, cumbersome camerascope complex. Also, producing an angled scope becomes a major technical challenge, especially if the scope is rotatable.
Fig 3.3: The diagram showing the surgeon operating in da Vinci system
This closely related technology, developed and sold by Fujinon,uses dual channel video generated by two video chips that are mounted on the end of the scope. The two images created are digital, and bypass the disadvantages of the optic distortions created by the optic scope. However the problems with separated images still exist and the small distance between the chips enables to create a "weak" 3D effect due to disparity. This, to a certain extent, is what determines the accuracy and intensity of depth perception, and is determined mostly by the distance between the two sources of the image, which corresponds to the distance between our pupils. When the technical barriers allow a small distance, the picture generated has a weak 3D effect.
This technology, used in the Storz 3D scope, relies on the fact that the camera is never absolutely still, and that minor angle changes occur between frames. The streaming video is thus divided by a shutter mechanism into two, slightly different steaming videos and when displayed on a stereoscopic display device a stereoscopic image is created. The advantages of this technology are that it can be generated using a single optic scope and there is no need to replace the whole system except for the camera and image processing unit. However, the small, unpredictable changes that are generated by the cameras instability create an image with low disparity, and the 3D perception is weak. In addition, the shutter mechanism creates a flicker that has user side effects similar to those that accompany dual-channel video.
In this technology, developed by VisionSense, a small start-up company, a microscopic array of lenses is placed in front of a single video chip on the end of the scope, similar to the structure of an insect eye. The lens array creates many small, slightly distorted images. When fed into a powerful image-processing computer, the images are divided into "left" and "right" images using a specialized algorithm, and a streaming stereoscopic video is generated. The advantages of this technology are that the image is generated from a single CCD, thus avoiding the differences between the two eyes, and that it is the first system to truly generate an image that contains volumetric information about the observed space. This ability harbors the potential of creating hybrid images using other information, like pre-operative CT or MR or online imaginf, and manipulating the image in many ways. The disadvantage is currently lower picture intensity and system instability.