The camera head consists of an objective lens, a prism assembly and three sensors for acquiring the primary colors of the image. Some camera heads also include an optical zoom for adjusting the image size (magnification). Optical zoom is advantageous because it has no negative effect on the image resolution. In addition, some of the image processing might be performed right in the camera head. Because of better image performance, three-chip cameras were generally accepted as the industry standard for endoscopic surgery about 10 years ago. The primary advantage is that color reproduction is more natural.

As with standard definition endoscopy systems, most HD Camera Heads acquire image data from the telescope. Image quality, however, will depend on the camera acquisition standard that has been applied to a given HD system.

The difference between SD and HD video formats is best visualized by comparing the horizontal and vertical resolution. Typical SD formats offer a 4:3 aspect ratio, 640 by 480 horizontal and vertical lines. The HD format offers a 16:9 aspect ratio, 1280 by 720 horizontal and vertical lines. The 1080 HD standard also offers a 16:9 aspect ratio, but 1920 by 1080 horizontal and vertical lines—seven times the SD resolution at 480 lines.

Temporal resolution is the number of captured images expressed as frames per second (fps). The 720p standard represents progressive scanning—capturing the entire frame as one image 60 times per second. The 1080i standard represents interlaced scanning—capturing two fields of half images with alternating lines that are then combined to create each complete frame.

For HD endoscopy, 1080p60 (1080p at 60fps) is the highest standard available for acquiring and displaying images, and offers a superior viewing experience for surgeons. Because progressive scanning offers twice the temporal resolution when compared with interlaced scanning, it is well suited for fast moving objects and capturing still images, creating a quasi-3D image. Anatomical structures become visible that were hidden in the flatter SD image.

Like most other optical systems, video camera lenses create circular images. Nevertheless, movies, shows and sports events are viewed on a broadcast HDTV set with a wide-screen 16:9 aspect ratio. This is accomplished by over framing the image so that the wide-screen sensor is totally covered by the circular optical image (see image on “Peripheral Vision”). The same is true for laparoscopic surgery where surgeons watch a monitor screen completely filled by the surgical image. The adjacent image (“peripheral vision”) does show the situation for two different aspect ratios. Wide-screen image acquisition increases the horizontal field of view (panoramic image) and decreases the vertical field of view. With laparoscopic instruments primarily entering the field of view laterally, a wide-screen 16:9 aspect ratio seems advantageous. Pulling back the telescope slightly can compensate for the loss in vertical field of view. Another positive effect is that a telescope positioned further from the site of surgical interaction catches less debris and smoke on the front window, improving image quality.