Furthermore the photogrammetric calibration procedure and the used calibration models will be discussed.
The general grating equation for reflective gratings is written. Besides the fundamental mode of operation of this so-called reflection grating photogrammetry, the properties of a suitable reference structure will be presented in this contribution. A diffraction grating can be a reflection grating or a transmission grating, however. Both systems allow the unambiguous measurement of reflecting free-form surfaces and may, by the use of multiple wavelength and photogrammetric stitching techniques, be extended to the measurement of rather complex geometries. While the first of these approaches works with an active triangulation process based on one camera and a pseudo three-dimensional reference structure, the second one utilises a stereo-photogrammetric camera system in conjunction with a merely two-dimensional reference structure. These techniques are based on the observation of the mirror image of a grid-like reference structure and apply principles that are well-known from measurement systems for non-reflecting surfaces, such as photogrammetry and structured illumination, to the evaluation of specular surfaces. They measured the total reflectivity of a group of weak-FBGs based on the end-face.
The main components are two identical resonant cavities symmetrically configured about the normal of the transmission grating, a /2 plate, and a polarization coupler. proposed a measurement method based on the end-face referenced reflection. An opal such as that shown in Figure 4.15 acts like a reflection grating with rows separated by about (displaystyle 8m. As not only the intensified use of aspheric optics but also the increasing quality standards for technical surfaces call for an enhanced measurement range, the authors have developed two related techniques for the direct three-dimensional measurement of specular reflecting surfaces. 1 is a schematic of the diode laser source. What is the spacing between structures in a feather that acts as a reflection grating, giving that they produce a first-order maximum for 525-nm light at a (displaystyle 30.0°) angle 49. While for non-reflecting surfaces a variety of optical techniques is available that allow the flexible geometric measurement of free-form surfaces, established approaches for the testing of specular surfaces are limited to basic geometries or slight deviations from an assumed reference geometry.
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