Surface Quality Inspection Research Articles

SENSOR PLANNING FOR CARS HEADLAMPS INSPECTION USING EXPERT KNOWLEDGE

This paper presents a vision-sensor-planning application for quality inspection of lens surfaces of car lighting systems. Using the CAD information, expert knowledge of the inspected parts and the camera model, the system automatically synthesizes optimal camera views. The optimal camera views are achieved by a hierarchical genetic algorithm. Results demonstrate the effectiveness of the vision-sensor-planning system.

A glossmeter for inspection of surface quality of low gloss nano-carbon surfaces

The nano-carbon films consisting of nanometrically thin graphite crystallites were produced by chemical vapor deposition method. The nano-graphite crystallites standing perpendicular to substrate surface form mesoporous film with very low gloss. Originally developed glossmeter techniques were applied for inspection of the nano-graphite films to evaluate their homogeneity and level of gloss. In the paper we describe technical details related to the glossmeter techniques and experimental results obtained for the nano-graphite films.

Quality inspection of metal surfaces by diffractive optical element-based glossmeter

Abstract Planar, convex and concave metal surfaces were produced by utilizing finishing processes that are exploited in the production of tools for plastics injection molding. A novel glossmeter, the so-called diffractive optical element-based glossmeter (DOG), was used for the inspection of the gloss of the surfaces. The Society of the Plastics Industry (SPI) A1 standard, which has the lowest surface roughness of such standards, served as a reference for the success of the finishing process. The results show that by using DOG we can gain local microscopic and macroscopic information on the gloss and its variation. The DOG is sufficiently sensitive to detect small gloss variation as well as the texture of the surface, e.g. anisotropy in surface marks. Some of the surfaces in this study have a higher surface quality than the A1 surface.

Colour tonality inspection using eigenspace features

In industrial quality inspection of colour texture surfaces, such as ceramic tiles or fabrics, it is important to maintain a consistent colour shade or tonality during production. We present a multidimensional histogram method using a novelty detection scheme to inspect the surfaces. The image noise, introduced by the imaging system, is found mainly to affect the chromatic channels. For colour tonality inspection, the difference between images is very subtle and comparison in the noise dominated chromatic channels is error prone. We perform vector-ordered colour smoothing and extract a localised feature vector at each pixel. The resulting histogram represents an encapsulation of local and global information. Principal component analysis (PCA) is performed on this multidimensional feature space of an automatically selected reference image to obtain reliable colour shade features, which results in a reference eigenspace. Then unseen product images are projected onto this eigenspace and compared for tonality defect detection using histogram comparison. The proposed method is compared and evaluated on a data set with groundtruth.

Comparative analysis of vision systems for electroplating surface quality inspection

In industrial practice, a human operator establishes the surface quality of an electroplated deposit through a subjective visual inspection, and this tends to be the immediate indicator of a quality defect. Electroplating in connector manufacture is a continuous process yet the quality inspection is an offline, operator-dependent process. The goal of this research was to automate the inspection of surface quality through the application of inline vision systems. Three vision system types were evaluated: a high-speed greyscale system, a standard colour system and a high-speed colour system. The efficacy of each approach was evaluated using attribute repeatability and reproducibility analysis (ARR); other factors considered were throughput, ease of operation and cost. The results proved that the high-speed colour system achieved the highest resolution reliability output for defect identification. Using key factor analysis and designed experiments, the optimum factor conditions were established for the high-speed colour system. To determine the practical implications such as false-positive and -negative results, the work was applied to a high-volume connector manufacturer. The overall benefit of such an implementation is an improvement in the defect rate and a reduction in risk priority number on the failure, modes and effects analysis of the process.

Surface quality inspection of PbWO4 crystals by grazing incidence X-ray diffraction

High-quality scintillating crystals are required for applications in radiographic systems and high-energy physics detectors to achieve the specified optical properties. In order to study the state of the single crystals surface we propose the use of the grazing incidence X-ray diffraction (GID) technique. This technique allows performing a depth profiling of the sample by changing the incidence angle of the X-ray beam with respect to the sample surface. In this work, two samples of a large PbWO4 (PWO) single crystal exhibiting different surface roughness values have been studied. Results have shown that GID is a suitable technique for surface quality inspection.

Optical profilometer with a standalone scanning sensor head

The use of compact disc (CD) pickups as distance sensors in optical profilometry is a well-established practice. The novelty of our device is the use of the built-in objective lens-tracking actuator of the pickup to perform a 1-D beam scanning of the sample. The profilometer prototype presented in this paper is made up of a standalone sensor-actuator optical head that can be easily positioned on samples of complex shapes with every orientation and can be operated by a remote control system. When 2-D scanning is unnecessary or even impossible, as for surface quality inspection of bulky mechanical pieces, a device that uses a CD pickup as both the sensor and the actuator is cheaper, faster, lighter, more compact, and more versatile than standard object-scanning setups that use xy translation stages. A lateral scan range of 800 μm and a vertical scan range of 160 μm are achieved.

On all-optical laser cleaning and inspection of contaminated concave metal surfaces

A technique for all-optical laser cleaning and surface quality monitoring of concave metal surfaces is suggested. Contaminated pharmaceutical punches from a tablet compression machine were cleaned using high-energy laser pulses. Image information obtained from a diffractive-optical-element-based sensor was used in inspection of the surface quality change of the concave punches due to laser cleaning. Alternative method for mechanical cleaning of punches is introduced, which is based on simultaneous laser cleaning and surface quality inspection of the punches.

Diffractive optical element based sensor for surface quality inspection of concave punches

Optical surface quality of concave shaped punches was investigated with a diffractive optical element based sensor. Image information of the present sensor was studied for the purpose of surface roughness and reflectance inspection. The robust sensor is proposed for off-line optical inspection of concave punches.

Crystal Surface Quality Inspection Using Computer-Generated Hologram and Digital Image Processing

Crystal Surface Quality Inspection Using Computer-Generated Hologram and Digital Image Processing

On-line fault detection and pattern recognition on moving webs

The paper discusses the development of requirements for electro-optical inspection systems for automatic inspection of surface quality and detection of defects in moving webs. Some examples of early and recent applications are quoted and reference made to the economic justification. The operating principles, technical features and performance capabilities of some of the various automatic inspection equipments currently available are briefly described as examples to indicate the present state of the technology and to give some indication of the future course of developments.

On-Line Fault Detection and Pattern Recognition on Moving Webs

The paper discusses the development of requirements for electro-optical inspection systems for automatic inspection of surface quality and detection of defects in moving webs. Some examples of early and recent applications are quoted and reference made to the economic justification. The operating principles, technical features and performance capabilities of some of the various automatic inspection equipments currently available are briefly described as examples to indicate the present state of the technology and to give some indication of the future course of developments.

Stylus Tracer Resolution and Surface Damage as Determined by Scanning Electron Microscopy

Stylus type instruments that employ needle tracers for examination of surfaces by means of translating the stylus over the surface and recording the undulations which occur during that traverse are analyzed by means of scanning electron microscopy. The scanning electron microscope (SEM) has superior resolution capabilities and can directly record the interactions of stylus with surface. The true levels of resolution of this instrument are measured and discussed in terms of finite size of the stylus, damage produced in the specimens due to stylus plowing, and stylus skipping and nonparallel tracking. The fundamental difference between magnification and resolution is examined in terms of tracer devices. Needle or stylus tracer devices are found to be dynamic microhardness testors which produce outputs which must be carefully judged as to their meaning and reliability in terms of faithfully recording the topographical nature of surfaces. The potential future of the SEM as a true nondestructive surface quality inspection tool is emphasized.