Volume 2 Issue 4
Authors: Xin Yang; Guohua Cao; Xuezhu Lin; Lijuan Li
Abstract: A CCTV monitor optical system was designed by using Zemax (optical design and analysis software). The effective focal length of the system is 5 mm, the F-number and the full field of view angle is 2.8 and 70° respectively. The image sensor of the lens is 1/2 in CCD, whose pixel size is 6.5 um×6.5 um. To achieve the lens with the feature of compact structure and wide field of view (FOV), an inversed telephoto system is used to be compressed and simplified. Based on the characteristics of CCTV lens, a certain degree of field curvature is allowed to exist to keep a higher resolution. The result shows that only 5 spheric lenses can meet the requirements. The MTF value is above 0.3 within 0.7 FOV at the Nyquist frequency, the MTF values are all above 0.5 at the 1/2 Nyquist frequency. As various components are spherical mirror, the system with simple form and compact structure has the practical application value.
Keywords: CCTV Monitor Lens; Optical Design and Optimization; Wide Field of View
Authors: Andrey V. Ustinov; Sergey G. Volotovsky; Svetlana N. Khonina
Abstract: We theoretically investigated the transverse parameters and the depth of the focal region formed by a lensacon (a tandem of a lens and an axicon). In this case the focal spot size becomes variable and it can be smaller than when optical elements are used separately. The concept of a new phase diffractive optical element (DOE) – fractional axicon – is introduced. It has a fractional dependence on the radial coordinate. Depending on the value of the power the fractional axicon allows to form either a decreasing scale or an increasing scale Bessel beams with a corresponding field depth extension. In the former case the fractional axicon is similar to the lensacon and in the latter case it is similar to the logarithmic axicon but there is no singularity in the centre. Thus, the offered element expands a set of the optical elements forming “light strings” actively used in metrology.
Keywords: Linear Axicon; Lensacon; Fractional Axicon; Focal Spot Size; Field Depth