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.
Many systems utilize the transmission standards developed for television.
However, other systems utilize custom transmission schemes to meet speed or resolution requirements. The varying signal between the synchronizing pulses describes the analog intensities for one line of the image. A digitizer breaks this line up into pixels having a digital representation of intensity. The spatial resolution is the number of pixels used to represent the 2-D image. The image is arranged into a number of rows and columns of cells, typically representing a rectangular portion of the projected scene.