Mathias Schellhorn

Nearfield sensing and actuation for multispectral imaging systems

The sharpness of edge transition is one of the major requirements in optical sensing especially in the field of image processing. Therefore a lot of algorithms were assessed in the field of digital photography. In the field of industrial image processing especially multispectral imaging different focus positions are needed to get an optimal focus position for every sampling channel. Therefore a control loop was developed which uses an inductive sensor to measure the actual position of an image sensor. With this information a voice coil were activated to actuate the sensor into the optimal position. For a correct operation a resolution of less than fifty microns have to be reached. The paper presents the construction as well as the electronic and sensor actor design. First evaluations demonstrating a proof of concept and will also discussed in the paper.

Field programmable gate array based hardware implementation of a gradient filter for edge detection in colour images with subpixel precision

Within the field of industrial image processing the use of colour cameras becomes ever more common. Increasingly the established black and white cameras are replaced by economical single-chip colour cameras with Bayer pattern. The use of the additional colour information is particularly important for recognition or inspection. Become interesting however also for the geometric metrology, if measuring tasks can be solved more robust or more exactly. However only few suitable algorithms are available, in order to detect edges with the necessary precision. All attempts require however additional computation expenditure. On the basis of a new filter for edge detection in colour images with subpixel precision, the implementation on a pre-processing hardware platform is presented. Hardware implemented filters offer the advantage that they can be used easily with existing measuring software, since after the filtering a single channel image is present, which unites the information of all colour channels. Advanced field programmable gate arrays represent an ideal platform for the parallel processing of multiple channels. The effective implementation presupposes however a high programming expenditure. On the example of the colour filter implementation, arising problems are analyzed and the chosen solution method is presented.

Fully automated measuring setup for tactile coordinate measuring machine for three dimensional measurement of freeform eyeglass frames

Coordinate measuring machines are high precession all-rounder in three dimensional measuring. Therefore the versatility of parameters and expandability of additionally hardware is very comprehensive. Consequently you need much expert knowledge of the user and mostly a lot of advanced information about the measuring object. In this paper a coordinate measuring machine and a specialized measuring machine are compared at the example of the measuring of eyeglass frames. For this case of three dimensional measuring challenges the main focus is divided into metrological and economical aspects. At first there is shown a fully automated method for tactile measuring of this abstract form. At second there is shown a comparison of the metrological characteristics of a coordinate measuring machine and a tracer for eyeglass frames. The result is in favour to the coordinate measuring machine. It was not surprising in these aspects. At last there is shown a comparison of the machine in front of the economical aspects.

Programmable system on chip implementation of a principal component analysis for preprocessing of multispectral image data acquired with filter wheel cameras

The acceleration of the acquisition of spectral images and their processing is important for the acceptance of these measurement methods in quality assurance and inspection. A frequently used preprocessing step is the Principal Component Analysis (PCA). It is used in variations, for example, for segmentation, spectral decomposition or data compression. The presented implementation calculates the PCA for the 12 spectral image channels of a filter wheel camera parallel to image acquisition. This includes the determination of the covariance matrix, the calculation of the main components and the transformation of the data. The parallel processing during the sequential imaging acquisition is performed on a System-on-a-programmable-chip (SoPC) Xilinx Zynq-7000 directly within the camera. The algorithm is partitioned into hard and software components and implemented in the field programmable gate array (FPGA) fabric as well as the ARM processor core firmware of the SoPC. In order to ensure the steps of the image acquisition chain in addition to the calculation, the system was implemented as an asymmetric multiprocessing system (AMP) with individual processors. For additional acceleration under static conditions (e.g. continuous testing in the manufacturing process), the feature vector can be stored as a calibration value. The calculation is reduced to the transformation of the data.

Integration of an autonomous optical sensor system in the machining area of milling centers

The integration of quality control in manufacturing process contains this paper and discusses the possibilities for integrated quality control in CNC milling machines without clamping off a workpiece. For these concepts non-contact measurements with image processing sensors have significant benefits for data acquisition in rapidity and a high grade of flexibility. New effective measurement strategies can be developed in effect of the quality controlling in the machining area. These includes classical geometric measurement applications from optical 2D but also options for 3D measurement tasks like determining roughness or other typical image processing applications. This paper presents the challenges for the implementation of an optical sensor system in the machining area of milling centers. Primarily a suitable location in the machining area must be found and an associated strategy has to be developed. The integrated optical image sensor system should be protect against impurity and does not derogate in his functionality. For the full integration as a quality control loop, the results must feed into the machine control. Thus a further interface between measurement program and a machine control is necessary. Another major field of research exists in the optical components. Especially the illumination, image sensor and lens are selected and adaptable for the measurement tasks after the considerations of the above-mentioned basic requirements. The presented research provides a suitable solution to make the CNC manufacture more efficient. Quality controls of the work piece can be executed within the CNC process and potential post processing can be performed simultaneously.

High speed embedded imaging architectures for multi-channel imaging

Multichannel imaging is a key technology for new application fields. Therefore a new parallel image processing architecture was designed. The new platform allows fast processing speed and solves problems in multispectral-imaging and high-precision-imaging systems.