For example, color could be used to detect debris in a process line of fruits or vegetables. There are numerous industrial color sorters based on this principle. Color can also be detected by utilizing a black and white sensor with bandpass filters for specific portions of the visible spectrum. A vector color signal is generally formed from the response of red, green, and blue sensors in the camera. Lenses and filters are an important element for the image sensor.
Filters control the spectral characteristics of the illumination sensed by the camera.
For many applications, optical filters are important for processing the image before it strikes the photosensitive digital array. Most applications require some knowledge of the geometrical relationship between the image sensor and the scene. Spatial calibration permits the measurement of characteristics of the scene from the image. Intensity or color calibration is used to characterize the response of individual pixels. After the signal is sensed at the camera, it is transmitted to an image digitizer to form a array of numbers representing the picture.