Research On Theory And Method Of High-resolution Deformation Detection For Wet Surface Of Biomaterials Under Unstructured Environment

With continuous development and progress of modern engineering and medical rehabilitation technology,multifunctional bionic joint design,material selection and other fields have achieved fruitful scientific research results,and have been widely promoted and applied in modern rehabilitation medicine.However,there are still many technical obstacles in improving the level of prosthesis fitting,life cycle and other aspects of joint replacement patients.One of very important aspect is how to fully and adequately understand the three-dimensional deformation distribution of the biological interface between a harder implant and softer human bone.Understanding the three-dimensional deformation distribution of the contact interface has great value and significance for the accurate estimation of its potential stress mismatch and the prevention of loosening,misalignment,interface infection,and osteonecrosis.Currently,although the deformation distributions can be evaluated and simulated by computer-aided design(CAD)and finite element analysis(FEA),the validity of the model requires correct boundary conditions,geometric parameters,and material properties that are not possible for anisotropic human skeletal materials.In addition,due to the influence of unstructured test environments during wet surface testing,such as wetting of biological materials and their surface interfaces,fluctuations of water molecular films due to humidity,and dynamic interference in the testing process,there is still no ideal measurement method or instrument to realize the deformation detection requirements of wet surface materials.Digital speckle pattern interferometry(DSPI)technology is one deformation measurement method based on optical interferometry principle,which has advantages of global coverage,high accuracy,non-contact,and strong environmental adaptability,and is widely used in deformation measurement of various engineering materials.However,when it comes to wet surface detection of biomaterials,the current DSPI technique is still unable to achieve three-dimensional deformation measurement of biomaterials on wet surfaces due to a series of problems such as serious speckle de-correlation,lack of dynamic environmental scattering image quality evaluation methods,and insufficient dynamic detection capability.Therefore,this article starts from the research of DSPI measurement theory,and improves the applicability of DSPI technology in wet surface material deformation measurement through the innovation of DSPI detection related theories and methods,so as to realize the three-dimensional deformation distribution detection of wet surface biological materials.The main work and results of this paper are as follows:1)In order to solve the problem of poor imaging quality which is caused by speckle de-correlation of wet surface biomaterials,the corresponding control and evaluation methods for speckle de-correlation are proposedFor the phenomenon de-correlation of speckles of biomaterials on wet surfaces in non-structural environments,the mechanism of de-correlation on physiological environments and biological wet surfaces is analyzed in detail,and two effective methods of speckle de-correlation control are proposed:(1)Based on the analysis of the speckle de-correlation mechanism caused by the process of wet surface biomaterial de-wetting and the fluctuation of water molecules,a PBS solution media environment imaging method is proposed to avoid the de-wetting process by the liquid environment,so that the liquid molecules on the wet surface remain stable in macro probability;and based on the concept of rotational inertia,an effective evaluation method for the level of scattering stability is proposed,and the quantitative evaluation and experimental verification of the scattering de-correlation level of liquid environmental imaging are carried out;(2)on the basis of the theoretical analysis of the speckle size constraint,a new method is further proposed to realize the control of speckle de-correlation through the speckle size control from the speckle characteristics.And the proposed quantitative evaluation method of the speckle stability is adopted to verify the effect of the proposed speckle size constraint method on the control of speckle de-correlation.2)Since the traditional speckle image quality evaluation index is single and difficult to apply to the quality evaluation of dynamic environmental speckle pattern,a comprehensive evaluation method is studied and proposed in this paper.Based on the traditional speckle pattern evaluation method,a comprehensive evaluation method that integrates multiple factors such as speckle pattern stability,resolution,and contrast is proposed based on the speckle de-correlation characteristics of wet surface biomaterials.The method adopts the average contrast ratio,average speckle pixel ratio,speckle grayscale distribution inhomogeneity and grayscale mean variance as the characterization indexes to comprehensively evaluate the dynamic scattered image quality,and overcomes the limitation that traditional evaluation methods cannot take into account the speckle stability factor.In addition,the effectiveness of the proposed comprehensive evaluation method is verified through comparative experiments.3)Based on characteristics of random disturbances and noise in the physiological environment,a speckle image disturbance avoidance sampling algorithm and an improved VMD filtering method are proposed.In the process of DSPI detection,there are various random perturbations and noise in the physiological environment during the detection process of DSPI.So two research works were carried out on the random disturbance avoidance algorithm and phase map filtering;on the one hand,in order to avoid the influence of random perturbations and other factors on the speckle image in the dynamic environment,a random perturbation avoidance sampling algorithm is proposed based on the statistical characteristics of the grayscale residual distribution of speckle images in the adjacent time domain.On the other hand,based on the VMD filtering technology,the key technology is studied and a modal quantity decision algorithm and a modal selection validity evaluation method are proposed to effectively improve the filtering effect of phase maps.4)In order to improve the 3D deformation dynamic detection capability,a DSPI3 D deformation synchronization measurement method is proposed.The current three-dimensional deformation measurement method cannot meet the dynamic measurement requirements of unstructured environment well.In this paper,a three-dimensional deformation synchronization measurement method for dynamic environment detection is proposed by combining the spatial carrier digital speckle pattern interferometry(SC-DSPI)technology and spatial carrier digital shear speckle pattern interferometry(SC-DSSPI)technology.The proposed 3D deformation simultaneous method not only has a better dynamic measurement capability,but also solves the problem that traditional DSSPI technique cannot accurately measure the deformation due to the lack of accurate integration boundary.5)In order to verify the proposed theory and method,a 3D deformation measurement system was constructed,and the off-plane displacement experiment,in-plane displacement experiment,and 3D deformation measurement experiment were conducted respectivelyAccording to the methods proposed in this paper,such as speckle de-correlation control,dynamic speckle image quality evaluation,perturbation avoidance,phase map filtering,and dynamic environment 3D deformation detection,the system optical path was designed,the hardware and software systems of the measurement system were constructed,the overall construction of the 3D deformation measurement system was completed,and the 3D deformation detection system was intermodulated and tested,which realized the 3D deformation synchronization and real-time online detection.Secondly,based on the 3D deformation detection system,a series of experiments on the effectiveness of the speckle speckle de-correlation control method,off-plane and in-plane displacement measurement,and 3D deformation measurement were carried out respectively,which proved the effectiveness of the theory and method proposed in this paper.Eventually,umder the unstructured environment,clear and accurate phase information is obtained,and deformation distribution measurement with off-plane displacement sensitivity in range of 20-30 nm and measurement accuracy in range of100 nm is achieved.In this paper,the method and theory of high-precision deformation measurement of DSPI on wet surfaces under non-structural environments are investigated,which provides new ideas and methods for high-precision deformation measurements of biological materials on wet surfaces under non-structural physiological environments.The results of the study are important for the acquisition of bio-mechanical properties of the interface between bone and implant,especially for the assessment of the results of implant fitting,material selection and design of patient implants.