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BIRIS 3D Laser Camera

The BIRIS 3D Laser Camera (Figure 1a) is a portable monochrome 3D imaging system developed to work in difficult environments where reliability, robustness, and ease of maintenance are as important as accuracy. NRC has used the BIRIS system to digitize architectural building elements and sculptures in Italy.

Capabilities important for fieldwork include portability and tolerance to sunlight. The camera is controlled by a laptop computer and mounted either on a tripod or on a motorized stage. The dual aperture technique, when combined with advanced signal processing algorithms, allows BIRIS to become very tolerant of ambient light illumination, e.g. sunlight. This is particularly important in field recording of archaeological and architectural applications.

Commercially, NRC has licensed this technology to ShapeGrabber Corporation (http://www.shapegrabber.com).

Principle of operation:
Based on NRC's patented BIRIS dual aperture technology, as illustrated in Figure 1b, the main components of the BIRIS camera are a standard CCD camera, a camera lens, and a mask with two apertures. This mask replaces the iris of the camera lens - hence the name Bi-iris. A laser line, produced by a solid-state laser diode and a cylindrical lens, is projected on the object. A double image of the laser line is measured on the CCD camera at p1 and p2. The separation between the two imaged lines and their relative location on the CCD are proportional to the distance between the object and the camera. Hence, they provide information about the shape and dimensions of the object.

The camera, controlled by a laptop computer, is mounted either on a conventional tripod (Figure 1c) or on a motorized linear translation stage (Figure 1d). The BIRIS camera has a maximum range (camera to object distance) of 2 m and an accuracy of 80 microns (0.08 mm) at a range of 0.3 m and 1.8 mm at 1 m.

Figure 1: The BIRIS 3D Laser Camera
(a) The BIRIS 3D Laser Camera is a compact and portable monochrome imaging system and is ideally suited for field recording applications. (b) Illustration of the optical principle (c) The camera is shown attached to a motorized rotation stage mounted on tripod. The cases for carrying the system and laptop computer controller are in the foreground. (d) The camera mounted on a linear translation stage imaging a section of a Hieroglyphic Stairway at the Peabody Museum (photo courtesy of Innovision 3D Inc.)