There is a variety of well developed methods to measure diffusely reflecting free-form surfaces. For instance fringe projection based systems are commonly used for the contactless optical measurement of such surfaces. The calibration procedures used in these systems are well understood and state of the art [10, 4]. However, contactless measurement of specular free-form surfaces requires new measurement techniques along with the corresponding calibration methods. In this paper a multi-sensor approach for measuring specular free-form surfaces using stereo based phase measuring deflectometry (PMD) combined with a fringe projection sensor unit will be presented. With the stereo enhancement over classical PMD techniques it is possible to measure the shape of the specular free-form surface and not only the slope of the surface. However, the major challenge is the necessary calibration. We present a new calibration method to obtain the orientation information of the deflectome try screen and the measurement cameras needed to calculate the shape of the object from the observed phase values. To solve this task we combined the calibration/ measurement principles of fringe projection and phase measuring deflectometry into a single measurement cycle. The developed calibration algorithm will be described in detail along with an analysis of the calibration accuracy using simulated data

A new multi resolution self calibrating optical 3D measurement system using fringe projection technique named "kolibri FLEX multi" will be presented. It can be utilised to acquire the all around shape of small to medium objects, simultaneously. The basic measurement principle is the phasogrammetric approach /1,2,3/ in combination with the method of virtual landmarks for the merging of the 3D single views. The system consists in minimum of two fringe projection sensors. The sensors are mounted on a rotation stage illuminating the object from different directions. The measurement fields of the sensors can be chosen different, here as an example 40mm and 180mm in diameter. In the measurement the object can be scanned at the same time with these two resolutions. Using the method of virtual landmarks both point clouds are calculated within the same world coordinate system resulting in a common 3D-point cloud. The final point cloud includes the overview of the object with low point density (wide field) and a region with high point density (focussed view) at the same time. The advantage of the new method is the possibility to measure with different resolutions at the same object region without any mechanical changes in the system or data post processing. Typical parameters of the system are: the measurement time is 2min for 12 images and the measurement accuracy is below 3&mgr;m up to 10 &mgr;m. The flexibility makes the measurement system useful for a wide range of applications such as quality control, rapid prototyping, design and CAD/CAM which will be shown in the paper

Bi-directional OLED based microdisplays offer interesting possibilities for new applications. Light emission and detection is included in one chip by using OLED-on-CMOS-technology. Such device has been primary made for optocouplers or photoelectric barriers, but it offers interesting possibilities for other application fields, e.g. multimedia and metrology. A new optical concept of a 3-D metrology sensor based on bi-directional OLED microdisplay will be presented.

Expanding demands on manufacturing technology increase the requirements on necessary non-contact metrology. Several optical metrology systems are based on separated imaging (e.g. camera unit) and image generating units (e.g. projection unit). This fact limits the geometrical miniaturization of the system. We present a compact, highly integrated 3-D metrology system based on the fringe projection principle using a bi-directional OLED microdisplay. The microdisplay combines light emitting pixels based on OLED technology (projection unit) and light detecting pixels based on photo diode technology (camera unit) on one single device, realized by the OLED-on-CMOS-technology. This technology provides the opportunity for a further miniaturization of optical metrology systems. The 3-D metrology system is based on fringe projection onto the surface of the measurement object. The fringes will appear deformed when observed from a dierent angle (triangulation angle). From the deformation of the fringes the 3-D coordinates of all visible points can be calculated and thus the object shape can be determined. For the application of an 3-D Sensor and due an internal display eect, separate lenses for projection and imaging are necessary. The system principle and several optical system congurations are discussed. Due to the application of the bi-directional OLED microdisplay the fringe generating elements and the detectors will be combined into one single device. Based on this integrated device an ultra-compact and solid system concept for 3-D surface metrology is practicable

Complex optical free-form surfaces are very common optical components for the use in modern illumination and lighting systems. In this paper we describe the use of high accurate fringe projection for the measurement of optical free-form surfaces with a resolution in the sub-µm-range. To achieve the required high accuracy the method of uniform measurement scale in fringe projection, proposed by the authors some years ago, is used 1. The basic idea is the exclusive use of phase values for the 3D-data calculation. Because of that, the accuracy of such a measurement set-up is mainly restricted by the lens distortion of the projection system. In order to compensate this we introduce a new method for a 3D-correction of the distortion of the projection lens taking into account spatial dependent distortion parameters. The distortion of the projection lens is determined by a measurement of reference planes which will be used to calculate a 3D-correction matrix. This matrix covers the whole measurement volume (lateral and vertical) and contains the determined distortion of the projection system. As a result the accuracy of the correction improved the absolute accuracy by a factor of four. Furthermore, the data quality is enhanced by a further factor of two using a wavelet filtering for noise reduction. The realized measurement set-up has a measurement field of up to 180 mm in diameter. It will be shown that the measurement of optical free form surfaces with medium range accuracy will be possible where we have reached a limit of 0.5 µm RMS error in a measuring field of 70 mm diameter