An investigation of a NIR camera system for road surface classification has been conducted for several road conditions. The surfaces were illuminated with three wavelengths, 980 nm, 1310 nm and 1550 nm and a halogen lamp, to simulate a real environment application with surrounding light. A measuring scheme to deal with surrounding light has been implemented enabling road condition classification from NIR images in a real environment. The retrieved camera images have been analyzed and an RGB representation of the different surfaces has been created to classify the different road conditions. The investigation shows that it is possible to distinguish between dry, moist, wet, frosty, icy and snowy road surfaces using a NIR camera system in a disturbed environment.

Today, there are a lot of vehicles and tyre testing carried out on lake ice surfaces. Thus, it is important to have knowledge about parameters that affect roadgrip. The thesis within this paper is that the liquid like layer which appears due to increasing temperature can be reduced by manipulating the ice roughness. This in turn should decrease the temperature dependence of the roadgrip in temperatures around 0°C. In order to investigate this, measurements of temperature, surface roughness and hardness and roadgrip were performed on three outdoor ice surfaces using an IR thermometer, an optical sensor with three IR-diodes, a steel ball drop indentation test and an RT3 curve, respectively. Additional ice roughness measurements were also made on two tempered ice surfaces in an ice hall. Results show a clear connection between ice temperature and roadgrip, unfortunately the created ice roughness was too small to influence the change in roadgrip

In order to classify the road condition, dry asphalt and asphalt covered with water, ice and snow a technique using a sensor called Road eye is presented. The Road eye sensor uses three wavelengths and one photo detector to determine the intensities that are reflected from the road surface and is then able to estimate the road condition. By linking the Road eye sensor to a GPS and a Mulle, a miniature wireless Embedded Internet System, the road conditions can be associated with the correct road position, making it possible to use the information in many different applications.

Diffuse reflection from various surfaces have been studied using several different methods in order to draw conclusions about the surfaces. First of all the aim was to perform fast and accurate shape measurements of molded steel objects on-line in a production system. Two measurement methods were used, stereoscopic imaging with projected fringes and dual wavelength digital holography. Information from the CAD model of the object was used to speed up the shape determination, mainly by enhancing the performance of the phase unwrapping. The uncertainty of the shape result was between 3.5 µm and 40 µm depending on the measurement method. The request on conformity between the object and the CAD model varied between 0.1 mm and 1.6 mm. To overcome the influence of speckles in the case of using interference fringes in the stereoscopic imaging an investigation of speckle reduction using a moving aperture was performed. The technique resulted in a decrease in the speckle contrast of about 60%.Secondly, diffuse reflections that come not only from the surface, but also from beneath it were studied. Measurements were done both on ice surfaces with the aim to identify changes in the surface structure and on glass spheres and sand grains with the aim to detect different moist content in granular material. The ice measurements showed an increase in the back reflection and a decrease in the specular reflection when the surface went from being smooth to being rough, a fact that can be useful when considering the roadgrip of icy roads. Depending on the water content in the granular materials the moist measurements when illuminating the surfaces with white light showed differences in the shape of the reflection distribution in the plane of incidence. Given these differences a simple model describing the water content was proposed.All experiments, except the ones on ice, have been performed in the laboratory. The results have been analyzed and compared to simulations, model estimations, and in the case of the shape measurements with the corresponding CAD models, all with relatively good outcome.In this thesis the work is presented in six papers. One about the speckle reduction method, three about the shape measurements and two about the ice surface structure and the moist in granular material, respectively.

Reflection measurements were performed on dry and moistened sand grains and glass spheres, respectively. A simple model for determining the water content is proposed from looking at the reflection distribution in the plane of incidence. The model is a combination of two sheared cosine-functions and consists of only two parameters. One parameter controls whether the reflection is mainly in the forward or backward direction. The former is true when the water content is high and the latter is true when the material is dry. The other parameter gives an idea of the homogeneity of the material.

In order to measure the shape of a large number of identical components in a manufacturing industry we propose a method where digital holography is used to capture an image of the object and then the shape of the object is achieved by using information from the CAD-model. The holographic recording of the object is done using dual wavelengths giving a synthetic wavelength of about 400 μm. This gives a phase map where the phase intervals represent a depth distance on the object of about 0.2 mm. To find the shape of the object the phase map has to be unwrapped. Since the surface contains discontinuities we use information from the CAD-model of the measured object and unwrap the phase iteratively. The result becomes a digital point representation of the measured surface that can either be used just as a description of the object shape or as a way to describe how well the object has been manufactured compared to the CAD-model. The measurement process that is proposed is adapted for on-line purposes; hence it is fast and reliable.

We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

In automotive industry there is an interest of controlling the shape of a large number of identical components on-line in the manufacturing process. We propose a method to do this by capturing a digital hologram of the object and then using information from its computer aided design (CAD) model to calculate the shape and determine the agreement between the manufactured object and the CAD-model. The holographic recording of the object is done using dual wavelengths with a synthetic wavelength of approximately 400 μm. The optical measurement results in a wrapped phase map with the phase values in the interval [−π, π]. Each phase interval represents a depth distance on the object of about 0.2 mm. The phase unwrapping is done iteratively using information from the CADmodel. This implies that it is possible to measure large discontinuities on the surface of the measured object. The method also gives a point-to-point correspondence between the measurement and the CAD-model which is vital for tolerance control.

When measuring a three-dimensional shape with triangulation and projected interference fringes it is of interest to reduce speckle contrast without destroying the coherence of the projected light. A moving aperture is used to suppress the speckles and thereby reduce the phase error in the fringe image. It is shown that the phase error depends linearly on the ratio between the speckle contrast and the modulation of the fringes. In this investigation the spatial carrier method was used to extract the phase, where the phase error also depends on filtering the Fourier spectrum. An analytical expression for the phase error is derived. Both the speckle reduction and the theoretical expressions for the phase error are verified by simulations and experiments. It was concluded that a movement of the aperture by three aperture diameters during exposure of the image reduces the speckle contrast and hence the phase error by 60%. In the experiments, a phase error of 0.2 rad was obtained.

When measuring 3D-shape with triangulation and projected interference fringes it is of interest to reduce the phase error in the fringe pattern. A study has been carried out concerning parameters that will affect the phase error and an analytical expression has been derived. It is concluded that the phase error depends on the speckle contrast, C, and the modulation, M, of the fringes and since the phase in this investigation is determined using the spatial carrier method the phase error also depends on the filtering of the Fourier spectrum. To reduce the phase error this work has been focusing on suppressing the speckle contrast. For this the method with a moving aperture is used; a disk with several apertures is rotated in the aperture plane of the camera lens. To verify the derived expression for the phase error and the method to suppress speckles both numerical simulations and experiments have been performed. In the measurements made it was concluded that after an aperture movement of three aperture diameters the speckle contrast and hence the phase error was reduced by 60 %. A phase error of 0.15 radians was obtained in the experiments, thus approximately 1/40 of a fringe period