Principle
The new generation videokymographic system includes two charge-coupled device (CCD) image sensors, a color area CCD and a monochromic high speed line-scan CCD. For the kymographic imaging, the high speed line-scan CCD is used to capture a selected line which is usually perpendicular to the glottal axis of vocal folds. The color area CCD sensor is used to obtain the normal two-dimensional image. A beam-splitter is used to optically split the image from the laryngoscope into two paths, one path for the area CCD and the other path for the line-scan CCD. The two CCDs can work simultaneously so that the laryngoscopic image and kymographic image can be obtained at the same time. By means of the beam-splitter, the position of the linear CCD is fixed on the reflective center of the area CCD, i.e. the kymogram taken from the line-scan CCD shows the vibration of the center line on the laryngoscopic image.
The system is divided into two parts, a camera head and a controller unit. The two parts connect each other by a high performance video cable. The camera head only houses the image sensors and the beam-splitter in order to reduce weight and size for easy handling. In the main controller unit, an embedded micro-processor and a frame buffer memory are used, which provides the possibility to output the video images in real time as different video format. The system has two output interfaces, an analog and a digital. On the analog video output, the two images are presented on a standard analog video monitor. The image on the screen is vertically split into two half parts. The left half shows the larynoscopic image and the right one displays the kymogram. The video data also appears on the digital output port, which can be acquired by a digital video frame grabber. A custom-made software can be used to capture, display and store the images. A database system is also included in the software.