Within the framework of a French research program, we have developed an optical system dedicated to the measurement
of works of art. The purpose is to record the actual optical characteristics of the objects' surfaces in order to be able to
display the art object on a screen with a high degree of realism. Three types of data are recorded: 3D shape, true colours
and texture.
The 3D shape is obtained using a structured light sensor that gives a dense point cloud. A specific procedure
allows automatic registration of several point clouds without any contact with the surface.
The colours maps are recorded with the structured light sensor's RGB camera and using a built-in lighting
system. Both camera and lighting are calibrated using a well-defined procedure. Merging the colour data with the 3D
data is straightforward because the same camera is used for both tasks.
The texture information is related to the so-called BRDF (Bi-directionnal reflectance distribution function): at
each point on the surface, the reflectance is a function of the direction of observation and the direction of illumination.
To record this complex texture information, several illumination sources are used, as well as an additional moving
camera. Thus, for one 3D point cloud, a complete set of colour pictures is processed to produce texture files that are
directly linked to the 3D points.
The paper details the measurement procedure as well as the associated data processing. Several results are presented.
KEYWORDS: Temperature metrology, Control systems, Black bodies, Machine vision, Inspection, Electronic imaging, Calibration, Lithium, Bromine, Body temperature
Many devices are used to realize non-contact temperature measurements. Whenever the body to be controlled behaves as a black body, all the devices inferring the temperature from the body radiation are accurate and reliable. On the other hand, when the body exhibits a behavior different from the black body, emissivity compensation has to be done. In case of a known emissivity, the mono-wavelength system (spectral system) is mainly used. However, when the body under examination radiates as a gray body a bicolor system is more likely to be used. In our case, we present a real time multispectral imaging system based on two CCD cameras. The system is herein presented, characterized and applications such as vision control system are presented.
In the present case, two CCD, which function transfer are different due to a carefully selected set of filters, acquire data in two different wavelength ranges. This system has the advantage of providing an accurate temperature measurement as well as to display it in real time.
KEYWORDS: Machine vision, Laser processing, Image processing, Control systems, Temperature metrology, Cladding, Process control, Cameras, Signal processing, Image filtering
In many industrial applications, the material surface is, most of the time, the preponderant factor in the life time of a piece. In such cases, it is relevant to be able to improve the superficial properties of the material. To do so, on solution: the laser cladding process, consists in deposing a hardfacing alloy where the constraints are more likely to occur. The process involves the delivery of fine grained alloy powder blown into the melt pool during the laser irradiation. In a coaxial delivery system, the powder spray distribution as well as the grain speed have a tremendous impact on the process efficienty. We herein present different experimental methods enabling to assess the particle speed as well as their distribution within the spray. Our configurations employ a laser sheet illumination of the power spray, a CCD camera and a PC to process the obtained images. In order to study the power distribution versus the nozzle distance, the laser sheet was moved away from the nozzle with low incremental steps such as to establish a profile of the spray. For speed measurements, various configurations were used. Images either manually processed or automatically using algorithms such as Hough, or Fourier Transform.
KEYWORDS: Inspection, 3D modeling, RGB color model, Temperature metrology, Volume rendering, Thermography, Infrared imaging, Cameras, Data acquisition, Infrared cameras
A conceptual system to produce 3D thermal models of tires for tire inspection and defect characterization is proposed. The system uses registered range and thermal information to build highly detailed 3D models using either a volumetric or mech-based approach. To achieve this goal, two narrow bandpass filters are used in conjunction with two IR cameras to obtain the true temperature of the target body. The thermal information is then translated to texture data and mapped as an overlay onto a 3D model. The textures are realizable through the use of three-component texture maps that include rgb values to specify the texture coordinates in the plane. The objective is to generate a movie loop depicting a tire endurance test so that an operator may analyze potential tire defects through texture characteristics that appear as a thermal signature changing dynamically with time.
We herein present a paper dedicated to machine vision systems used in the metallurgy industry for process control. Various systems, aim at performing on-line process control, are presented. The present study is mainly focused on the control of surface treatment processes. Control of processes such as HF welding and laser cladding are shown. Surface temperature being often a crucial point in the process control, monochromatic and dual-wavelengths non-contact temperature methods are introduced.
Wavelet transforms are efficient tools for texture analysis and classification. Separable techniques are classically used but present several drawbacks. First, diagonal coefficients contain poor information. Second, the other coefficients contain useful information only if the texture is oriented in the vertical and horizontal directions. So an approach of texture analysis by non-separable transform is proposed. An improved interscale resolution is allowed by the quincunx scheme and this analysis leads to only one detail image where no particular orientation is favored. New orthogonal isotropic filters for the decomposition are constructed by applying McClellan transform on one dimension B-spline filters. The obtained wavelet function have better isotropic and frequency properties than those previously proposed by Feauveau. Since IIR filters are obtained, an integration in Fourier domain of the whole operations of the transform is proposed. A texture analysis is performed on wavelet details coefficients. Simple parameters are calculated from each scale. Finally, the evolution over scales of the parameters is obtained and this multiscale parameter is used to characterize the different textures. An application of this method is posed with the analysis of human cells. The aim is to distinguish states of evolution. As no information is provided by monoscale classical methods on these images, the proposed process allows to identify several states. In this process a reference curve is constructed for each states calculated from the multiscale variance of known images. When a new image is analyzed, a new evolution curve is calculated and a measure of the distance with the references is done. This technique is more efficient than classical ones as multiscale information is used.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.