2.2. System design
Acquisition and processing of the image is performed with a commercial personal computer and a PCI-bus image frame grabber. The frame grabber board digitizes the camera image and the software processes the digital image on the PC. A near-infrared (NIR) camera (e.g., Hitachi KP-F2A) with significant improvement in NIR wavelength ensitivity is used to avoid the interference from ambient light and improve image contrast that separates the oyster from the background. Unlike regular Charge-Coupled-Device (CCD) cameras, NIR camera is more sensitive to the invisible spectrum. This camera (Hitachi KP-F2A) was chosen because of its unique features such as near-infrared sensitivity, high-speed electronic shutter for acquiring image of fast moving object, progressive scanning for full frame resolution, and flexible gain and offset adjustments. A long-pass interference filter that allows only invisible light to pass was used for this system to get optimal image contrast between the product and the background. A light chamber is designed to create a controlled lighting environment to provide uniform lighting for this application (Lee et al., 2004).