To assess the quality of printed solder joints in the jet printing of printed circuit boards, a calibrated camera is used to reconstruct the solder volume via photogrammetry as a specific task of computer vision. This requires a procedure for calibration and orientation determination due to restrictions within the image acquisition process. We herein consider a novel application area called an ultra-close range normal case photogrammetry, where a camera acquires small objects at small operating distances and fields of depth. Because the camera cannot rotate or translate in the z-direction, we propose and evaluate four calibration procedures in terms of their capability in a normal case calibration within the ultra-close range. To set up an optimal calibration pipeline, a three-dimensional (3D) calibration field is used for single and multi-image calibrations. To enhance the accuracy and to simplify the assignment of 3D coordinates to the detected markers, we propose a geometry-based estimation of the lens model to undistort the image points. Close-range applications utilize spacer rings and extension tubes to enlarge the magnification and reduce the operating distance. We also examine the influence of these extensions on the intrinsics of the camera and the reconstruction result. Additionally, we demonstrate the dependence of the accuracy on the lens model in terms of radial and tangential distortions and the number of distortion coefficients regarding the reprojection error repro. Finally, we provide recommendations for a lens configuration for ultra-close range normal case calibrations and measurements, based on the calibration and reconstruction results, which are evaluated by the 2D reprojection error repro and the 3D reconstruction error recon obtained from a second independent calibration field.

ABSTRACT:Printed Circuit Boards (PCB) play an important role in the manufacturing of electronic devices. To ensure a correct function of the PCBs a certain amount of solder paste is needed during the placement of components. The aim of the current research is to develop an real-time, closed-loop solution for the analysis of the printing process where solder is printed onto PCBs. Close range photogrammetry allows for determination of the solder volume and a subsequent correction if necessary. Photogrammetry is an image based method for three dimensional reconstruction from two dimensional image data of an object. A precise camera calibration is indispensable for an accurate reconstruction. In our certain application it is not possible to use calibration methods with two dimensional calibration targets. Therefore a special calibration target was developed and manufactured, which allows for single image camera calibration.

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The main aim of the work is to assess physical parameters of forest woodchips and their impact on the prices achieved by the supplier in transactions with a power plant. During fragmentation of logging residue, high content of green matter and contaminants negatively impacts the quality parameters that serve as basis for settlements. The analysis concerns data on the main parameters -water content, fuel value, sulphur and ash content -from 252 days of deliveries of forest chips to a power plant. The deliveries were realised from forested areas on an average about 340 km from the plant. Average water content and the resultant fuel value of forest chips was within 27-47% and 8.7-12.9 GJ×Mg −1 (appropriately), respectively. They depend on the month in which they are delivered to the power plant. The threshold values for the above-mentioned parameters are set by the plant at a real level and the suppliers have no problems with meeting them. The parameter that is most frequently exceeded is ash content (11.5% of cases). The settlement system does not differentiate on the basis of the transport distance but gives possibility to lower the settlement price when the quality parameters are not met but provides no reward for deliveries with parameters better than the average ones. On the basis of results obtained, it was calculated that average annual settlement price is lower than the contract price by about 0.20 PLN×GJ −1 , which in case of the analysed company may translate into an average daily loss of about 700 PLN.

ABSTRACT:Printed Circuit Boards (PCB) play an important role in the manufacturing of electronic devices. To ensure a correct function of the PCBs a certain amount of solder paste is needed during the placement of components. The aim of the current research is to develop an real-time, closed-loop solution for the analysis of the printing process where solder is printed onto PCBs. Close range photogrammetry allows for determination of the solder volume and a subsequent correction if necessary. Photogrammetry is an image based method for three dimensional reconstruction from two dimensional image data of an object. A precise camera calibration is indispensable for an accurate reconstruction. In our certain application it is not possible to use calibration methods with two dimensional calibration targets. Therefore a special calibration target was developed and manufactured, which allows for single image camera calibration.