The Fisheye lens is a special variety of bug eye lenses, as its visual angle could reach or go beyond the typical human visible range. The image from the fisheye lens is vastly different from the actual world, because the visual view is well-regulated but the effective image from Fisheye lens is beyond the scope. The Fisheye lens is a telephoto lens with relatively large aperture, wide field angle and longer back working distance, the field angle can reach or even exceed 180 degrees. This is why it is able to put a hemispheric, or even beyond hemispheric, field of view on a limited image plane. Since its imaging leads to a significant barrel shaped distortion, and the diaphragm spherical aberration and coma are huge, the imaging theory and auto optimization of the Fisheye lens is totally different from the regular optical lens.
Although the Fisheye lens is not developed as an anti-telephoto wide angle lens, it’s similar structurally to a wide angle telephoto lens, and so is the design method. The major difference between them is that the big barrel distortion of Fisheye lens is inherent; however it’s not one kind of aberration. To reach larger barrel distortions, an almost hemispheric lens with greater negative power needs to be used. For the Fisheye lens, while keeping in mind that the aberration correction is not only on the axle, the outer axle is also important. In addition, the Fisheye lens field angle is 180 degrees. Signifying that while it can satisfy the ideal correction for the whole field aberration, the aperture illumination for the whole image needs to be guaranteed.
We have researched the imaging features of Fisheye lenses, and achieved light path trace and auto-optimization. We not only set the traditional optimization standard, but also introduced Compound Optimization ideas as a supplement, using the release aberration to solve optimization problems. Through the use of Fisheye lenses for optical tracing, we change the reference plan for light entering the lens, thereby confirming its source. We also use the aberrations and the lens aperture within the field of view to calculate the relationship between the aberration and the diaphragm. This is useful for determining the starting position of light sources. Shanghai Optics can optimize the entire process of designing and producing these fantastic lenses, which can help you achieve the highest image quality.
The following is a wide spectrum Fisheye lens design, with a focal length of 14mm, F2.8, and a field of view reaching 180 ° covering the visible-infrared band. The dome extends 180 ° diagonally from the field of view onto a target surface. By controlling the F-θ distortion to less than 3% or even lower, we have made the system able to accurately obtain target orientation information of the desired image. The image quality within the final field of view is improved greatly, when using a 90% field of view and a spot size radius of less than one pixel, and at Nyquist frequencies of 631p/mm in an MTF field greater than 0.3. The field of illumination at the edge of the viewing field is centered by more than 50%.
Fisheye lenses are applied to scientific research, military and civilian applications. The team at Shanghai Optics has excellent design capabilities which can supply quick and high quality complete designs for our customers.