Endoscopic Camera Systems and Charged Coupled Device

The current generation of endoscopic cameras employs the charge coupled device chip. The digital image is captured on a charge coupled device using either a digital still or a digital video camera. Photoreceptors, within the charge coupled device , rapidly assess the different light intensities that make up the endoscopic image. The charge coupled device generates pixels by converting unique light intensities within an image into corresponding electronic signals, which are then transmitted to a storage element on the chip (3).

Digital cameras are classified according to the amount of resolution determined by the number of pixels and the number of charge coupled device chips. The average charge coupled device resolution of single-chip camera ranges between 400,000 and 440,000 pixels, whereas three-chip cameras exceed 450,000 pixels. Display resolution of the cameras ranges between 350 to 450 and 700 horizontal lines for single-chip and three-chip cameras, respectively (4).

The development of the three-chip camera that contains three individual charge coupled device chips for the primary colors—red, green, and blue—represented a significant improvement in charge coupled device camera technology (Fig. 2).

In addition to composite super video home systemand component signals, the three-chip cameras also provide an "uncoded" red, green, and blue signal. Color separation is achieved using a prism system overlying the chips (5). This three-chip camera design provides improved color fidelity and enhanced image resolution. Moreover, three-chip cameras produce less "noise" due to the pure red, green, and blue signals (6,7). A digital converter capturing each voltage signal as an image translates the voltage values into discrete numbers, either as 0 or 1. The encoded numbers for each image element or pixel include information on color, light intensity, and contrast. These variables can then be modified using image-processing software within the camera (8).

Theoretically, three-chip cameras produce better quality images than singlechip cameras. Despite the apparent advantages of three-chip cameras, some clinical comparisons have favored one-chip systems. Using normal video monitors, previous studies have implied that the resolution between the two cameras did not alter the visual perception of an image. For endoscopic imaging, digital contrast enhancement is a feature more important than the number of camera chips.

Three-chip cameras appeared to have no advantage over well-designed singlechip systems (1,5,9). However, this apparent limitation may change with the introduction of high-resolution digital monitors and high-definition television, because the amount of image information and the degree of perception are increased with these digital-imaging modalities (10).

FIGURE2 ■ Three charge coupled device system as opposed to one charge couple device. Red, green, and blue sent to three separate charge couple devices by a prism. Abbreviation: CCD, charge coupled device.

FIGURE 1 ■ Schematic representation of analog vs. digital video systems. Abbreviation: CCD, charge coupled device.

FIGURE2 ■ Three charge coupled device system as opposed to one charge couple device. Red, green, and blue sent to three separate charge couple devices by a prism. Abbreviation: CCD, charge coupled device.

The development of the digial video endoscope has been a major advance in the endoscopic systems.

Digital videoendoscopes have fewer interfaces. The digital information is directly transmitted to an image display unit, with minimal image loss, interference, and distortion.

The replacement of smaller caliber laparoscopes with an integrated digital videoendoscope can be expected in the near future.

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