Feature

Fast Zoom Fisheye Lens for Electronic Cameras

J. Brian Caldwell

Fisheye lenses are normally designed to cover a full-field angle of 180°, and are scaled so that the 180° image circle either fits entirely within a rectangular image area (circular fisheye) or just covers the entire diagonal of the image area (diagonal fisheye). This month's design, is an unusual zoom fisheye lens that is a circular fisheye at the short focal length position and a diagonal fisheye at the long focal length position. Unlike most zooms, the field angle remains nearly constant during zooming so that the image circle changes size. Figure 2 shows how the image circle progressively fills the rectangular CCD during zooming. The lens is intended for a 1/3" CCD having a diagonal of 6 mm. The system is telecentric throughout the zoom range to match the characteristics of the detector.