Research On 3D Shape Measurement Method Of Mirror Object Based On Stripe Reflection

The optical 3D measurement technology based on structured light is widely used in high-speed detection,product development,quality control,reverse engineering and other fields with its advantages of high precision,high efficiency and non-contact.With the rapid development of modern manufacturing,the quality inspection requirements for many precision parts and devices will become higher and higher.Although optical 3D measurement technology is quite mature in the measurement of diffuse reflection objects,it is still a difficult point for class mirror or specular measurement.Therefore,the measurement of specular three-dimensional methods has far-reaching significance.In the traditional specular measurement method,sinusoidal stripes are used as projection stripes,and the quality of the stripes is reduced due to the nonlinear influence of the display.In this paper,the triangular wave stripe is used as the projection stripe,and the sinusoidal stripe is obtained by the defocusing effect of the air system.The CCD camera receives the deformed fringes modulated by the specular object reflection,demodulates and phase-decodes the acquired fringe image to obtain the absolute phase of the specular object.The three-dimensional shape of the specular object is restored by directly establishing a mathematical model between the height and the absolute phase.The research content and work of this paper mainly include the following aspects:1.This paper analyses the principle of triangle wave stripe defocusing,Comparing triangular fringes and standard sinusoidal fringes as the projection stripe CCD camera to be obtained,The triangle wave stripe defocus can filter out the higher harmonics of smaller amplitude and filter out the High-frequency noise that existence of the environment,obtain better stripe quality,and reduced the impact of LCD display nonlinearity on measurement errors.2.This paper analyses and introduces the phase unwrapping algorithm,and introduces the tri-band phase unwrapping method and the tri-band heterodyne phase unwrapping method.In order to extract the higher precision phase value,this paper uses the three-frequency heterodyne combined with the reverse phase error compensation method to unwrap phase,which is effective for restoring the three-dimensional shape of the mirror object.3.According to a new mathematical model principle,a new measurement system isbuilt,and an improved specular object measurement method based on stripe reflection is proposed.This method uses triangular wave stripe instead of sinusoidal fringe projection,through air defocusing system.The defocusing effect obtains a relatively standard sinusoidal fringe image,obtains phase information with higher precision,and then performs CCD camera calibration and system parameter calibration on the system to recover the three-dimensional shape information of the mirror object.4.Through the construction of the measurement system,a concave mirror and a plane mirror measurement experiment were carried out,and the three-dimensional shape of the two mirror objects was restored.The measurement error of the concave mirror is 0.0174 mm,The experimental results show the effectiveness and robustness of the measurement method.