![]() Thus, each lens must be calibrated to calculate the specific distortion parameter so that an appropriate compensation can be applied. Owing to manufacturing imperfections, the camera parameters that describe the distortion can vary from camera to camera, even among cameras of the same type and model. This process generally makes use of an assumed model for the distortion, and estimation of the parameters of this model usually requires a calibration step. Compensation for radial distortion in fish-eye lenses can be carried out using post-processing of the images taken using the lens. Additionally, the radial distortion introduced by these lenses does not preserve the rectilinearity of an object straight lines in the real world can usually be approximated as circular sections in the distorted image plane. However, in wide-angle and fish-eye lenses, radial distortion can cause severe problems, not only visually but also for further processing in applications such as object detection, object recognition and classification. ![]() For normal and narrow field-of-view (FOV) cameras, the effects of radial distortion can be considered negligible for most applications. Radial lens distortion causes points on the image plane in the wide-angle / fish-eye camera to be displaced in a nonlinear fashion from their ideal position in the rectilinear pin-hole camera model, along a radial axis from the centre of distortion in the image plane. In this paper, we consider only radial distortion. It can be seen that although the fish-eye image shows a far larger portion of the environment, it also introduces severe distortion compared with the standard lens camera, which shows minimal distortion. By far, the most obvious form of distortion is radial distortion, with tangential distortion commonly considered to be negligible. The two primary types of distortion introduced by wide- angle cameras are radial distortion and tangential distortion. ![]() 1 shows the difference between a standard lens camera and a fish-eye lens camera (taken using the same camera at the same physical distance from the line diagram). However, wide-angle lenses inherently introduce distortion into an image, with this distortion becoming particularly evident in fish-eye cameras. These are very desirable in automotive applications, as they can fully display a vehicle’s blind zones to the driver. Lenses with larger fields of view are known as wide-angle lenses, with a fish-eye lens having a field-of-view of up to 180 8 or larger. A standard lens generally has an approximate angular field of view of up to about 55 8, but standard lenses are generally not sufficient to fully cover the entire blind zone. Vehicles’ blind zones can be very large up to 21 m rearward for a large sports utility vehicle and up to 65 m rearward for some large goods vehicles. The sizes of these areas are determined by the size and design of the vehicle and mirrors. The blind zones are the areas around the vehicle that cannot be seen directly by the driver by looking forward or by using any of the vehicle’s standard rear-view mirrors (internal and external) from the normal sitting position. also describe how the consumer demand and legislative requirements can be met by employing wide-angle / fish-eye camera technology on vehicles, with several car manufacturers employing wide- angle cameras on their vehicles. consumer and legislative demand for camera systems that display a vehicle’s blind zones to the driver has been described by Hughes et al.
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