Study On Micro Stereo Matching And Non-Contact Nondestructive Rapid 3D Photogrammetry

With feed-back vision the binocular micro stereovision system based on stereo lightmicroscope (SLM) makes it possible to achieve 2D/3D high accuracy auto-positioning, 3Dinformation extraction, 3D shape reconstruction and 3D measurement. Therefore, it isextensively used in micromanipulation, micro assembly, micro robot navigation andbioengineering, etc.Based on optical theory and digital image processing, the micro stereo imaging principleof SLM is studied and a novel micro stereo vision system theory is founded to achievemicrofluidic chips detection task. The core parts of the theory are comprised of NURBS basedtwice stereo perspective micro stereo matching algorithm, SLM based micro stereovisionbirefringence variable refractive index correction algorithm and neighborhood critical microstereo occlusion correction algorithm. This improves three key problems including accuracy, speed and stability in micro stereovision measurement.Considering the weak nonlinear perspective projection coupling phenomenon of theweak disparity model of micro stereo vision, a stereo matching algorithm based on NURBS isdeveloped which helps to cope with the false matches due to distortion of the perspectiveprojection, reduces the search range from 60 pixcels to 10 pixcels as well as improves thestability and robustness of the measurement system.As the micro channels on microfluidic chip are covered with a plastic plate, dioptricimaging will happen on both the top and the bottom surface of the plastic plate. In addition, the complexity of micro stereovision system based on SLM makes measurement accuracymuch lower. Therefore, the correlation between optical paths of SLM is derived and microstereovision double refraction variable refractive index correction algorithm based on SLM isimplemented. It quantizes influence of cover plate and optical paths on the refractivecoefficient, and realizes rapid nondestructive non-contact 3D precision measurement ofhyaloid and closed chamber.Neighborhood critical micro stereo occlusion correction algorithm can realize occlusiondetection, occlusion correction and correction verification in real 3D space. This methoddraws essential character of occlusion and weak nonlinear character of the weak disparitymicro stereovision model, adopts occlusion critical points in variable neighborhood toposition, matches the gray feature points forward and reverse local areas determined by edges and verifies orthogonality of 3D space occlusion critical points to excavate depth informationwhich is transformed from 2D image space to 3D object space. Moreover, the depthinformation of occluded part can also be recovered successfully. Relaxed iterative method canincrease stability of this algorithm and improve matching and measurement accuracy.Based on those algorithms mentioned above, a micro-stereo measurement system isdeveloped, which realizes synchronization observation in larger field of view, real time stereodisplay, rapid nondestructive non-contact 3D measurment and real time detection formicrofluidic chips.The measurement range of the system is 31.43～3.49mm in parallel direction and2.66～0.068mm in vertical direction on the magnification of 0.7～9.0. The measurementexperiments show the measurement system has expanded uncertainty 3.4μm in paralleldirection and 5.2μm in vertical direction on the magnification of 9.0.This system makes up for such shortcomings of SEM and AFM as small field of view, lower speed, lossy measurement and higher cost, etc. In a word, the difficulties of accuratepositioning and 3D measuerment in micro assembly and micro manipulation are solved. Theresearch lays a strong foundation for SLM micro stereovision's future development.