As light hits each lens and is transmitted onward, rays cross, resulting in parallax and a trapezoidal image. Unlike other types of distortion which are part of the inherent properties of the lens, keystone distortion is caused by improper alignment in a lens array. Fig.5 shows the F-Thetaĭistortion in a scanning lens with the maximum deflection angle of 29ᵒ. has over 55 years of experience in design and manufacturing low distortion f-theta lenses. F-theta distortion, which describes the relative deviation of the actual image height y from ?∙?, is defined asĪs with other aberrations, F-theta distortion is determined by the optical design of the lens. Because the optical system cannot completely correct all the aberrations, f-Theta lens cannot fully meet the linear relationship. In the F-Theta lens system, the actual image height is designed to satisfy the relation of ?∙?, which is smaller than the ideal image height ?∙? in a conventional camera lens system. The ideal image height of an f-theta lens can be calculated using Equation 4
#Camera lens distortion and instagram software
This type of distortion is called moustache or wave distortion, and requires special attention to wavelength when calibrating software to remove distortion from the final image.į-theta lenses (used in laser scanning systems) are usually designed to produce a certain amount of distortion (barrel distortion) so that the image height is proportional to the field angle of θ. Some lenses that are engineered to exhibit very low levels of distortion may have both positive and negative distortion.
One should also be aware that the level of distortion may change as working distance changes and is dependent on wavelength. Figure 4 shows a simulated image of a wide angle lens with -50% distortion.įor a multi-element lens assembly distortion will usually be positive or negative, but it may not be linear across the image. Figure 3 shows the distortion in a fisheye lens with effective focal length of 3.0mm. A fisheye lens or ultra wide-angle lens produces strong visual distortion. Figure 2 shows images of a rectilinear object with zero distortion and -3% distortion.Īs with other aberrations, a lens with a larger field of view will generally exhibit a larger amount of distortion. Generally distortion in the order of 2 to 3% is acceptable visually. Since distortion affects the image shape, its appearance is very important especially in visual systems. Where y is the actual height in the image plane and y p is the predicated height in the image plane.įor a conventional camera lens, the predicated or ideal image height y p can be calculated using Equation 2.ĭistortion, which describes the deviation of the actual image height y from the idea image height ?∙?, is defined asĭistortion can be positive (pincushion distortion) or alternately negative (barrel distortion), shown in Figure 1.ĭistortion in a simple lens is a third-order aberration which increases with the cube of the field height. The amount of optics distortion typically can be expressed as a percentage of the predicated image height.
Wide angle lenses and zoom lenses also create their own signature type of distortion. In cameras, image creators use an effects library which includes radial distortion, barrel distortion, perspective distortion and pincushion distortion to introduce novelty effects into their images. In laser applications, f-theta lenses are chosen to introduce a certain amount of distortion into an optical system. There are many reasons why a lens distortion effect may be desirable. In some situations, distortion is engineered into a system. Digital fine-tune programs are often used to provide lens correction and eliminate unwanted distortion from a final image. Distortion varies with wavelength, and in situations where a narrow band of light is used it may be computed at the central wavelength. It occurs when information is displaced geometrically, and while it changes the shape of an image will not result in image blur.ĭistortion correction can be done post production in a photo editor, since the amount of distortion a lens introduces can be mathematically quantified at any given point. Lens distortion is a cosmetic-type optical aberration which does not decrease the amount of information in an image.
0 kommentar(er)
