Developments in advanced computer integrated manufacturing technology, coupled with the
emphasis on Total Quality Management, are exposing needs for new techniques to integrate all
functions from design through to support of the delivered product. One critical functional area
that must be integrated into design is that embracing the measurement, inspection and test
activities necessary for validation of the delivered product.
This area is being tackled by a collaborative project supported by the UK Government
Department of Trade and Industry. The project is aimed at developing techniques for analysing
validation needs and for planning validation methods. Within the project an experimental
Computer Aided Validation Expert system (CAVE) is being constructed. This operates with a
generalised model of the validation process and helps with all design stages: specification of
product requirements; analysis of the assurance provided by a proposed design and method of
manufacture; development of the inspection and test strategy; and analysis of feedback data. The
kernel of the system is a knowledge base containing knowledge of the manufacturing process
capabilities and of the available inspection and test facilities.
The CAVE system is being integrated into a real life advanced computer integrated
manufacturing facility for demonstration and evaluation.
Image processing systems have found wide application in
industry. For most computer integrated manufacturing faci-
lities it is necessary to adapt these systems thus that they
can automate the interaction with and the integration of CAD
and CAM Systems.
In this paper new approaches will be described that make use
of the coupling of CAD and image processing as well as the
automatic generation of programmes for the machining of
Conditions for the glass transition temperature evaluation of a 1pm thick polymer film on an aluminum substrate
using laser induced surface acoustic waves propagating along the aluminum surface have been investigated.
A basic element of a machine vision system is the corresponding illumination system.
The price or even the feasibility of a machine vision system depends siginuicantly on the quality
of the image and the image itself is directly Influenced by the illumination quality of the object
(intensity, Intensity distribution, size, etc.).
Fiber optic illumination components are very suitable as illumination elements because they are
flexible, robust, they need only few adjusting elements and provide therefore easy means for well
defined and controlled illumination situations.
The very first step in a machine vision project is the image creation process. A good knowledge
of the illumination problems and the properties of illumination components helps to create an
optimal image and this in turn gives the opportunity to keep the image analysis system (hardand
software) as simple as possible.
While the classical way to create a good image is the illumination experiment, there are methods
to do a simulation of fiber optic components and to calculate the influence of design parameters
on the illumination distributions. This helps to predefine illumination parameters before creating
any hardware for illumination.
The paper describes a method of image transferring by a non-co-
herent fiber optic bundle. The idea results from comparision of
image propagation mechanisms in image guides and non-coherent bund-
les. The paper shortly describes, from the image transmission point
of view, both coherent and non-coherent fiber optic bundle and pro-
poses microprocessor based system, performing non-coherent bundle
The principle and the firstresults of a new 3D camera will be presented. This camera is based on a holographic technique
named conoscopic holography. The simplicity of the technique, using only a crystal, waves plates and polarizers, and its
compatibility with CCD sensors make possible the fabrication of low cost and flexible conoscopic vision systems. The
first prototype is an tive rangefmder which will be developed into a profilometer and a 3D camera a resolution of 1 jnn
and a precision of a 2-3 jim have already been obtained. The numerical processing is based on Fourier Transforms, quickly
performed by available dedicied hardware.
A stereoscopic theodolite measuring system is used to determine the three dimensional positioning
accuracy of an industrial robot. The control of the theodolite movement and the robot movement,
the image processing and the coordinate calculations were done by a host computer, which also
processes the measuring data and communicates them by the local computer network. The spatial
positioning accuracy of the robot is measured separately on translational and rotational axes.
This paper describes a method of active light ranging, which in principle
is based on triangulation, but where the range information is deduced from
at least two measurements of the luminance of the object. With this tech-
nique it is possible in a simple manner to obtain range data for each pixel
in a computer vision system. The sources of error inherent in the method are
discussed and a number of examples of photometric range finders and 3-D vision
systems are given.
Features &e extrzted from the angular specrwn of light scattered fnxn the sur(e of machined surfxes
which are then used as inputs to a hrarcha1 neural net. The net is "U1nCd by aselected training set of feures
from surfaces whose quality has already been independently establishet These samplessicrepeatedlypresented to
the sensors and the network makes a deCISIOn about the surface roughness which is then compared to the rrect
answa, and the TOf used to modify the conntion weights. Following this training pcziod, the net is be able to
identify the quality of new surfes presented to IL Indeed, it is able to ck, so even in the presence of noise which
is likely to be caused by poor illumination. Results, using this laser scattering technique, from a set of prepared
sirfaces are dixussed with regard to fusion of different features in der to obtain an adequate measure of surfe
roughness ung the harchkal newal nwor
The pixel-wise classification of CCD colour Images Into previously learned colour classes at video-rate
is a demanding vision task, both with regard to the complicated cluster shapes encountered in natui-
al scenes and to the required computing power for real-time operation. We discuss two classical solutions
based on an algorithmic statistical classifier and on a Neural Network paradigm and propose an
alternative simple and low-cost classifier based on approbriately trained look-up-tables. Two different
learningrules for the supervised training of this LUT classifier are presented for the colour classification
of both synthetic and natural blotechno1ojr scenes. The proposed LUT classifier shows all the
positive features of a (simulated) 3-layer perceptron Neural Network, but performs 60.000 times faster
with simple, commercially available components.
To make efficient practical use of the attractive properties
of standard neural network models it seems reasonable to com
bine a recognition network with appropiate conventional preprocessing.
In this contribution we describe the current research
at IPA concerning such a hybrid approach to acoustic
pattern recognition. The inputs of the recognition network are
feature vectors consisting of local frequency characteristics
extracted from the Wigner representation of the patterns. Simulations
show that the system is capable to recognize individually
learned objects in a scene.
In the manufacturing of continuously formed products such as metal plates and plastic
sheets, on-line monitoring of thickness is important for quality control. Most cases require
noncontact measurements. The most widely used optical technique is "optical triangulation" in
which a lateral effect position-sensing detector is used. However, the technique has a limited
measurement range to resolution ratio making it not suitable for some on-line applications.
In this paper we propose a new approach to measure thickness in which the position of a
scanning laser beam is timed. It eliminates the restriction of measurement range by the
dimension of the detector as in traditional optical triangulation. Also, because small area
silicon photodiodes are used, signal-to-noise ratio is largely enhanced thus improving the
resolution. The probe we built demonstrates a 47 % measurement range-to-standoff distance
ratio and a 2.8x104 measurement range-to-resolution ratio. Also, its performance is not
influenced by large changes in object reflectivity.
We developed pattern inspection techniques for simultaneously measuring both the width and
the thickness of conductive patterns printed on ceramic green sheets.
The measuring optics use a He-Ne laser scanner. Thickness is measured by beam splitting,
and width, by light diffusion. The beam-splitting optics measure the height by determining the
ratio of reflected to transmitted light intensity. By optimizing the arrangement of the optics, we
attain a resolution of 5 im and a height measurement range of [70 pm. Pattern width measurement
is based on the fact that a beam of light diffuses when it strikes the substrate, but does not
diffuse when it strikes the conductive pattern. A spatial ifiter in the focal plane raises the S/N
ratio to four regardless of the state of the conductor surface.
We used these techniques to inspect the conductive patterns on green sheets. Our system inspects
conductor patterns 3-dimensionally at 12 Mplxels per second with a 5 i.m resolution.
The inadequacy of the stuck-at fault model has been well aired and oced1 ,2All studies agree that this model does
not reflect the physical failures of real devices,3 principally because such failures do not exhibit a 1:1 mapping onto the
logic domain.2 ,' Circuit layouts which are based on stick diagrams do however reflect the physical domain in sufficient
detail to enable both structural defects, together with shorts and opens in metallic and non-metallic domains, to be detected
and located. The author has proposed the adoption of a novel method which processes information obtained from a scanfling
laser beam reflected from a surface profile. Scanning may be of a raster nature over the surface, or follow a suitable
path search along layouts. The latter search type has been simulated in PROLOG using breadth-first (BRFS), Euler (ES),
and neighbour-first (NFS) searches. It is suggested that by creating and modifying an acquired-knowledge database
(AKDB), according to defect occurrence, it is also possible to search those regions where defects may be present in order
of decreasing probability. Thus a useful library of the distribution of defect density statistics would be created by virtue of
In this paper the experimental hardware results presented are based upon reflectance measurements obtained by raster scanning
in three different optical modes. In addition results of search simulations and a discussion of the AKDB are included.
Such a topological approach to the testing problem offers a test structure for exploitation which is technology independent,
fast and is adaptable to parallel processing.
The increasing integration of semiconductor circuits requires absolutely defect-free masks. Before their exposure to
an c-beam writer the unstructured masks (blanks) have to be inspected in a clean room environment for particles on
surfaces, pin-holes in the chromium layer and inclusions or scratches in the glass. Based on a HeNe laser scanner and
by comparing relative directions and intensities of the scattered light, the position, size and type of defects were
automatically classified. The criteria for classification will be explained. The smallest detectable defect diameter was
0.3 p.m. For presentation under a TV-microscope each defect could be located within 100 m.
The use of CCD sensors in optical metrology requires synchronous sampling of the image with a good signalnoise
performance. . A system has been developed to digitize optimally the signals from high-resolution CCD
sensors. The data acquisition system is split into two parts -the first is a storage unit for the IBM PC/AT family
of computers with a fast, digital, input-output interface, with 8-bit transmission speed DC-4OMHz and 16 bit
operation DC-2OMHs. The digitization of the analogue signal is performed on separate units, up to 2m from the
computer. Separating the analogue processing from the computer and using a separate power supply not only
reduces the electrical noise from the digital electronics to a minimum but also allows greater flexibility in designing
custom 'front ends' for a wide range of sensors.
The storage card has two 1M byte banks of memory. These are normally used to provide double buffering of
1M pixel images, but can also be used to store 2M byte images without double buffering.
Practical experience, using 8 and 10 bit video front ends, indicates that the geometrical resolution possible
with modern CCD sensors is approaching 1/100 of the pixel period. The digital signal processing required for this
performance does not depend on the CCD camera's PSF and it is insensitive to variations offocus and orientation.
Non contact video inspection systems measuring geometric elements
of workpieces. These measurements should be done with high
accuracy and speed. During the design period of the UMS432 of
Wild Leitz the parameters that could reduce the expected
measuring accuracy and allowed speed were investigated. In this
paper especially the influence of the imaging part and the image
analysis is analysed.
Surface parameterisation using phase measurement of
interferometric fringe patterns is supported by a strong theoretical
basis. However, little work has been published with regard to the
practical implementation of the available methods as tools for
industrial inspection. This paper attempts to justify the choice of
Fourier Fringe Analysis for this purpose and addresses some aspects
of its implementation.
This paper discusses the construction and capabilities of a time-of-flight laser rangefmder system for profiling measurements
on hot surf,es (< 1400C), especially measurement of the thickness profile of the lining of a converter in iron works.
Thebkgmtmdradiation is the main source ofthe noise in the receiverin this kind ofmeasurement. The inherentlylow signalto-
noise ratio, typically 10 - 40,can be improved by the construction, adjustment ofthe parallel optics and optimization of the
gain of the receiver avalanche photodiode. A stability of +1- 5 mm and a resolution of a few mm can be achieved in real
measurement sitoations with a measurement time ofless than 1 second per poinL The non-linearity of the device at the near
end ofthe measurementrange due to the paralleloptics and optical fibres is reduced to 5 mm by modifying the optics and using
a mode mixer. The poor temperature stability, typically about -2 mm/'C, ofa device with different receiver channels for start
and stop pulses can be improved by stabilizing the temperature ofthe electronics, orbeuer still, by using one electrical channel,
in which case the temperature drift is almost zero in the temperature range -10C -+35C.
The feasibility of an opto-electronic inspection system for the sorting and grading
of apples with respect to ripeness and quality is studied. This study comprises a
detailed spectral analysis of the healthy skin as well as a variety of visual
defects. Three different apple species were studied: Cox orange, Golden delicious
and Golden rennet. Spectral wavebands of interest appear to be the chlorophyll peak
around 570nm, the ripeness peak around 64Onrrt and the near infra-red beyond 75Onxn.
Stem and calix of apples pose a separate problem because their spectral reflection
cannot be distinguished from that of most visual defects. A solution for this
problem is given.
An optical/digital approach to the classification of rough surfaces using
Fourier spectrum sampling is described. The sampling of the 2-D Fourier
spectrum is achieved with wedge ring detector which reduces an infinitely
dimensioned spectrum image into a set of 64 measurements. To discriminate
three metal milled samples in this reduced subspace we employ the
Karhunen-Loève transformation. The classification procedure then selects
automatically the best subspace from the K-L feature vectors.
A special application case of multiresolutlon image processing is pointed out.
From the imager's original picture. a set of image copies is derived. Each of these
copies is generated with different demagnification factors along both image coordi-
nates. Simple compact object structures are demagnifled from picture to picture and
appear in a specific reduced image as single pixels. For a real-time application, a
tailored hardware solution was constructed, which involves a special filter design
to minimize accumulation of anti-allasing errors. The application for rough defect
classification during strip material fabrication is discussed. In this case, flaws
of a given length/width ratio can easily be detected by simple, minimum templates.
Image processing has been used to analyze TV -holographic fringe patterns of
deformations and vibrations. The processed pictures give improved detection and
information for the operator of the interferometer. A lower detection limit of about ?./50
for deformation analysis has been achieved, while amplitudes down to V500 and phase
values with an accuracy about 3° have been measured on vibrating objects. Examples of
applications of the techniques are shown.