We propose a novel design of two-dimensional geometrical waveguide combiner, which integrates the vertical pupil expansion area and horizontal pupil expansion area into one planar waveguide. Different from previous solutions, the proposed design allows larger FOV and easier pupil matching with compact structure. The relationship between maximum vertical FOV and slanted angle of partially reflective mirror array, the exit pupil matching method for vertical and horizontal FOV are discussed. Then the optimization process of the waveguide structure to obtain a large FOV and uniform illuminance is showed, and the simulation shows that the method is solid. The FOV of the designed waveguide combiner is 𝑉FOV × 𝐻FOV 33° × 49.5° and diagonal FOV 57.4°, and the thickness of the waveguide is 1.7𝑚𝑚.
With the development of ultra-precision machining technology, parts with microstructures on the surface are playing an increasingly important role in engineering practice. The scanning interference microscope measurement method is widely used in the measurement of microscopic surface topography. This paper proposes a method of interference microscopy combined with subaperture stitching. The first step is to divide and measure the sub-aperture. There is a partial overlap area between the divided adjacent subapertures. The white light interferometer measures each sub-aperture in turn. The second step is edge feature detection. There are highly steep edge features between the bottom of the groove and the surface of the surface microgroove. The stitching algorithm detects edge features by detecting the slope threshold of the sub-aperture. The third step is to correct the abscissa. Project the detected edge feature data onto the OXY plane to generate a 2D data set. The multi-dimensional motion scanning platform inevitably has motion errors in the measurement process, so the edge characteristic curves of adjacent sub-apertures have obvious lateral displacement in the overlapping area. The lateral displacement and angle of the lateral coordinate of each sub-aperture are corrected by the least square method. The fourth step is the height coordinate correction. The stitching algorithm minimizes the height difference between the corresponding points in the overlapping area, and solves it with a linear least squares problem model. We have completed the measurement of the fringe pattern on the computer-generated hologram (CGH) substrate and the complete topography of the long groove on the 10mm hemisphere. After the sub-aperture global iterative stitching algorithm, there is no stitching trace in the simulation result. For the long groove on the hemisphere, we designed a four-dimensional scanning motion platform and a special fixture to ensure that the long groove on the hemisphere rotates around an axis perpendicular to the geodesic line. The center of the white light interference fringe is always at the center of the long slot aperture.
With the development of ultra-precision machining technology, parts with microstructures on the surface are playing an increasingly important role in engineering practice. The scanning interference microscope measurement method is widely used in the measurement of microscopic surface topography. This paper proposes a method of interference microscopy combined with subaperture stitching. The first step is to divide and measure the sub-aperture. There is a partial overlap area between the divided adjacent subapertures. The white light interferometer measures each sub-aperture in turn. The second step is edge feature detection. There are highly steep edge features between the bottom of the groove and the surface of the surface microgroove. The stitching algorithm detects edge features by detecting the slope threshold of the sub-aperture. The third step is to correct the abscissa. Project the detected edge feature data onto the OXY plane to generate a 2D data set. The multi-dimensional motion scanning platform inevitably has motion errors in the measurement process, so the edge characteristic curves of adjacent sub-apertures have obvious lateral displacement in the overlapping area. The lateral displacement and angle of the lateral coordinate of each sub-aperture are corrected by the least square method. The fourth step is the height coordinate correction. The stitching algorithm minimizes the height difference between the corresponding points in the overlapping area, and solves it with a linear least squares problem model. We have completed the measurement of the fringe pattern on the computer-generated hologram (CGH) substrate and the complete topography of the long groove on the 10mm hemisphere. After the sub-aperture global iterative stitching algorithm, there is no stitching trace in the simulation result. For the long groove on the hemisphere, we designed a four-dimensional scanning motion platform and a special fixture to ensure that the long groove on the hemisphere rotates around an axis perpendicular to the geodesic line. The center of the white light interference fringe is always at the center of the long slot aperture.
Optical windows are important for a wind tunnel to enable observation or imaging of the internal flow-field. In order to reduce the interference to the internal flow and not to modulate the input observation ray field as much as possible, the interior and exterior surfaces of the optical window often adopt complex free-form surface design and must be used in pairs. This requires high accuracy of both the surface form and their relative position. In this paper, Trace-Pro optical software is used for the ray tracing analysis of the wind tunnel observation window defined by discrete points on the inner and outer surfaces. The conclusion is that the collimated beam is also the collimated beam after passing through the single observation window, which means the transmitted wave-front can be well resolved by a standard interferometer. The ray data in Trace-Pro is imported into MATLAB to obtain the modulated wave-front error which is contributed by the difference between the inner and outer surfaces of the monolithic optical window. It hence can be used to guide the corrective machining of the window surface. In addition, the influence of different misalignment on the interferometric test of the window is analyzed. Finally, the method is experimentally demonstrated on an optical free-form window. The surface positioning error is reduced with corrective machining based on the measured transmitted wave-front.
In form metrology, multi-probe scanning method based on error separation technique can be used successfully to
eliminate motion error of slideway. Due to high repeatability of flexure hinge, a virtual multiple sensor concept is
presented. The system employs a single probe with the accurate movement of flexure hinge to achieve virtual multiprobe.
This single probe scanning method can realize and extend the function of multiple-probe method. This paper
describes the principle of this new method; Measurement process of method is modeled and the predefined test curve is
reconstructed by the application of simultaneous equation and least-squares methods. It shows that scanning systems
with virtual multiple sensors allow the influence of random and systematic errors to be reduced. We also conducted the
experiment repeatedly to measure the profile of workpiece. It shows that reconstructed curves in each experiment are
nearly superposed.
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