Papers by Keyword: Optical Measurement

Abstract: The traditional contact devices measure material's surface roughness by scratching its surface, which may cause surface damage and sampling error. In order to avoid these troubles, an optical measurement system is used in this paper. Considering the anisotropic and inhomogeneous surface structure of C_f/SiC composite, a multi-scale measure system must be established. Fiber bundle is the first scale to be studied, whose appropriate measurement parameters are studied here. When sampling area is 150μm×150μm and sampling step is from 0.1μm to 0.5μm, the values of 3D surface parameters Sa, Sq, Ssk and Sku are steady and their relative changes are small. 2D surface roughness Ra is adopted to select the proper sampling length. The results show that as long as the sampling length is more than 112μm, the mean value of 2D surface roughness Ra are relatively stable. The critical sampling length is about 1/7 of the standard minimum sampling length in ISO 468-1982. According to the results obtained, the research provides a useful guideline for determination on the appropriate sampling conditions of C_f/SiC composite fiber bundle surface measurement.

Abstract: The article presents the research of use of modern 3D measurement contact-less methods for quality inspection in automotive industry production. Experience with measuring parts and functional assemblies of complex shape and advantages of the optical methods of digitization are shown on a practical example of analysis of dimensional stability of car decorative strip plastic mouldings. The goal is to demonstrate that the modern methods of dimensional analysis of 3D products can significantly participate in optimization of the manufacturing process and ensuring higher quality of the products. Contact-less 3D systems, so called 3D scanners, were used for the measuring purposes. With their help, the tested sample were digitized in high resolution, and he obtained models of real parts underwent a thorough inspection of precision of shape and dimensions. The attention was directed primarily at the problematic spots – deviation of the strip ends when compared to the nominal CAD model. The analysis was performed using various alignment to the CAD model, thus contributing to finding context with respect to mounting points on the vehicle rails. Concurrently, an influence of galvanic plating on the accuracy of the product was studied.

Abstract: Digital image correlation (DIC) became indispensable when monitoring and analyzing adevelopment of displacement or strain fields. The method is capable of capturing strain localization, itis not limited to a relative measurement of discrete points as conventional methods and appears to bemore accurate than measurements by means of extensometers or strain-gauges that often suffer fromimperfect attachment to the measured surface. As open source DIC tools appear, the method becomesfeasible and the development is supported by the growing computational power of modern computers.The presented paper introduces open source 2D DIC tools and simple rules to follow when employingthe method. The presented case study on behavior of fiber reinforced high-performance concretedemonstrates a computational feasibility, accuracy and sensitivity of the method for a relatively lowfinancial cost.

Abstract: The measurement of erythrocyte size was studied by using diffraction technique base on laser. The light from a diode laser was observed with 650 nm and 532 nm of light wavelength through erythrocyte on the slide. The result found that the ring was appeared on the screen alternate with brightness and dark. The first brightness radius was measured on the screen (Y) and the distance of the position of the slide erythrocytes to screen (X) was observed then calculated the diameter of an erythrocyte (d) in microns (μm). The above number were calculated the volume of erythrocyte and compared with automatically complete blood count (CBC) machine by the mean corpuscular volume (MCV) with femtolitre (fl) values​ in the range 60-100 femtolitre. In conclusion, this study showed that the sizes of erythrocyte by laser diffraction technique are similar with the automated blood count. Therefore, it can be applied to measure erythrocyte size.

Abstract: Optical interferometry methods are widely used for measuring microdisplacement with nanometer accuracy. However, most commercially available optical interferometry systems are large and expensive for manufacturing applications. In this study, we report the development of a low-cost portable optical interferometry microscope for factory use. The light source was a tungsten–halogen white lamp with an optical filter. The microscope has an objective lens with a numerical aperture of 0.3, a magnifying power of 10, and field depth of 3.056 μm. Interference images were collected with an NTSC CCD-video camera. The resolution of the interference image is 320 × 240 pixels and stored in BMP format. To obtain phase shifted interferometry images, a piezoelectric actuator was used to monitor the table movement along the optical axis. The total cost of all system parts is approximately 7000 to 8000 US dollars. To evaluate the basic performance of the developed interferometry microscope, we measured a steel ball, the penetration mark of a Rockwell scale hardness indenter, and a gauge block surface with a bump. The developed interferometry microscope can measure continuous and gently sloping surfaces. The processing time is approximately 10–20 s.

Abstract: Automatic surface defect inspection within mass production of high-precision components is growing in demand and requires better measurement and automated analysis systems. Many manufacturing industries may reject manufactured parts that exhibit even minor defects, because a defect might result in an operational failure at a later stage. Defect quantification (depth, area and volume) is a key element in quality assurance in order to determine the pass or failure criterion of manufactured parts. Existing human visual analysis of surface defects is qualitative and subjective to varying interpretation. Non-contact and three dimensional (3D) analyses should provide a robust and systematic quantitative approach for defect analysis. Various 3D measuring instruments generate point cloud data as an output, although they work on different physical principles. Instrument’s native software processing of point cloud data is often subject to issues of repeatability and may be non-traceable causing significant concern with data confidence.This work reports the development of novel traceable surface defect artefacts produced using the Rockwell hardness test equipment on flat metal plate, and the development of a novel, traceable, repeatable, mathematical solution for automatic defect detection and quantification in 3D. Moreover, in order to build-up the confidence in automatic defect analysis system and generated data, mathematical simulated defect artefacts (soft-artefact) have been created. This is then extended to a surface defect on a piston crown that is measured and quantified using a parallel optical coherence tomography instrument integrated with 6 axis robot. The results show that surface defect quantification using implemented solution is efficient, robust and more repeatable than current alternative approaches.

Abstract: Digital holography can record 3-D image of the object by using one CCD camera. Surface shape can be measured by changing angles of the object-illuminating mirror. But the measured signals are wrapped because of the periodicity of a sinusoidal function, and then phase unwrapping is needed. We have developed a new modified phase unwrapping method and applied it to surface measurement. Unwrapping errors were significantly reduced in comparison to application of the previous method.

Abstract: This paper presents results of a carried out research in the field of scanning precision of contactless optical 3D scanners. Results stated in this paper bring great benefits to practice, since it demonstrates the quality and limits of measuring by means of contactless optical systems in real conditions and therefore its possible use in the field of inspecting the dimensional and shape precision of industrial products.A measurement etalon of various shapes and sizes was designed and manufactured for the purpose of this analysis. The nominal dimensions of the etalon were set by measuring of the coordinate measuring machine and these real values were compared to the model obtained by optical digitisation of Atos II and RevScan. Based on the evaluation of results, scanner measurement precision diagrams were drawn according to the studied aspects, e.g. dependence on the shape of the measured element and its nominal size. Another essential part of the research was determining the ability of 3D scanners to capture detailed parts of the model and assessing the scanning limits for each of the optical systems.

Abstract: The problem of obtaining sound parts by Incremental Sheet Forming is still a relevant issue, despite the numerous efforts spent in improving the toolpath planning of the deforming punch in order to compensate for the dimensional and geometrical part errors related to springback and punch movement. Usually, the toolpath generation strategy takes into account the variation of the toolpath itself for obtaining the desired final part with reduced geometrical errors. In the present paper, a correction algorithm is used to iteratively correct the part geometry on the basis of the measured parts and on the calculation of the error defined as the difference between the actual and the nominal part geometries. In practice, the part geometry is used to generate a first trial toolpath, and the form error distribution of the resulting part is used for modifying the nominal part geometry and, then, generating a new, improved toolpath. This procedure gets iterated until the error distribution becomes less than a specified value, corresponding to the desired part tolerance. The correction algorithm was implemented in software and used with the results of FEM simulations. In particular, with few iterations it was possible to reduce the geometrical error to less than 0.4 mm in the Incremental Sheet Forming process of an Al asymmetric part, with a resulting accuracy good enough for both prototyping and production processes.

Abstract: Currently, the chemical pollution of water detection is mainly based on optical method. However, the optical detector is easily restricted by light and weather conditions. Optical measurement can be set on the target feature point, such as the laser reflection apparatus in laser measurement. This article applied the optical measurement method to research detection of water chemical pollution. Use theoretical and mathematical models of optical measurement method to perform the detection of chemical contamination in water. Optical measurement method is the trend of future development.