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Study of the method for focal length determination in digital cameras

Hlotov Volodymyr, Hunina Alla

Geomatics, Landmanagement and Landscape

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2019

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no. 4

145--154

EN

The authors analysed the methods for determining the focal length in digital cameras (DC) and proposed a method, the implementation of which is to survey the correct triangular metal prism from the left and right points of the basis. Next, on the stereo pair of digital images obtained from the surveying, the corresponding coordinates of the points on the near and far edges of the prism are measured, and the focal length of the non-metric DC is determined. To test the method, the focal length of the Sony ILCE-7R and Canon EOS 450D cameras was determined. In order to establish the precision parameters of the method, the following parameters were taken into account: determining the accuracy of measurment on the basis of surveying, the accuracy of measuring the heights, the accuracy of calculation of the longitudinal parallax, the accuracy of calculating the difference between the parallaxes.

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Method for determining the focal length in a digital non-metric camera

Hlotov V., Hunina A., Yurkiv M.

Geomatics, Landmanagement and Landscape

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2017

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no. 3

71--81

EN

The authors analysed the methods for determining the focal length in digital cameras (DC) and proposed a method, according to which the control-measuring grid (CMG) is located vertically at a distance from the DC and a photograph of the CMG is made, then the latter (the CMG) is moved along the optical axis of the digital camera to the distance, which is fixed with a micrometre screw and, repeatedly, a series of photographs of the CMG is taken. After that, on the received digital images, the coordinates are measured on the corresponding intersections of the CMG, and subsequently, the focal length for the DC is determined. The a priori estimation of accuracy of determining the focal length for the DC by the proposed method is calculated. For approbation of the method, the focal length in the following cameras was determined: Canon EOS 350D, Canon EOS 450D, Canon EOS 5D.

3

Simple method for manufacturing and optical characterization of tapered optical fibres

Zakrzewski A., Pięta A., Patela S.

Opto-Electronics Review

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2016

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Vol. 24, No. 4

216--222

EN

Photonic devices often use light delivered by a single-mode telecommunication fibre. However, as the diameter of the core of the optical fibre is of 10 microns, and the transverse dimensions of the photonic waveguides are usually micrometer or less, there is an issue of incompatibility. The problem may be solved by application of tapered optical fibres. For efficient light coupling, the taper should be prepared so as to create a beam of long focal lengt hand small spot diameter in the focus. The article describes the design, fabrication and characterization of tapered optical fibres prepared with a fibre-optic fusion splicer. We modelled the tapers with FDTD method, for estimation of the influence of the tapered length and angle on the spot diameter and the focal length of an outgoing beam. We fabricated tapers from a standard single mode fibre by the Ericsson 995 PM fibre-optic fusion splicer. We planned the splicing technology so as to get the needed features of the beam. We planned a multistep fusion process, with optimized fusion current and fusion time. The experimental measurements of best tapered optical fibres were carried out by the knife-edge method.