For vision measurement at high temperature, pixel error from light refraction by high temperature is a problem that cannot be neglected. The refractive index distribution is nonlinear around the high-temperature component, leading to the light deflection. In this paper, the influence of measurement parameters on the deflection of imaging light and the accuracy after binocular reconstruction are systematically analyzed. The heat transfer theory is used to simulate the air temperature distribution near the measured component, and the corresponding refractive index distribution of air is obtained according to the refractive index formula. Then, the imaging measurement model of the nonlinear refractive index air medium for the high-temperature component is established to obtain the light deflection error. The binocular vision system reconstruction theory is applied to evaluate the measurement error between the theoretical reconstruction point and the object point. The influences of error sources, such as the temperature, optical wavelength, and camera parameters, are investigated systematically. It is found that temperature and base distance are the largest error sources on the final measurement error when the measured distance is fixed.

Coded mark point, as an important part of automatic matching, is widely used in stereo vision and photogrammetry. An encoding scheme named the Initial Dot encoding scheme, has been designed based on the programme of concentric rings, and which is able to solve restrictions on the number of codes and promote the stability of decoding. The designed coding pattern includes three functional points: locating point, start point and coded point. The maximum coding number of the Initial Dot scheme can reach 262,144 when the number of code bits is 18. The recognition experiments show that the Initial Dot encoding scheme can achieve 100% recognition rate at a 75 degree angle, which is very difficult for other coding schemes. By comparing experiments with the Schneider encoding scheme for a large flexible panel, the recognition rate of the proposed scheme is 99%, which is higher than the recognition rate of 90% of the Schneider scheme. The experimental results indicate that the Initial Dot encoding scheme can be successfully applied on flexible solar panels under a 1000 mm × 500 mm field of view.

Phase-shift profilometry (PSP) holds great promise for high-precision 3D shape measurements. However, in the case of measuring moving objects, as PSP requires multiple images to calculate the phase, the movement of the object causes artifacts in the measurement, which in turn has a significant impact on the accuracy of the 3D surface measurement. Therefore, we propose a method to reduce motion artifacts using feature information in the image and simulate it using the six-step term shift method as a case study. The simulation results show that the phase of the object is greatly affected when the object is in motion and that the phase shift due to motion can be effectively reduced using this method. Finally, artifact optimization was carried out by way of specific copper tube vibration experiments at a measurement frequency of 320 Hz. The experimental results prove that the method is well implemented.

Vibration measurements are essential for studying the dynamic properties of structures, as they can better capture the global characteristics of the structure. This paper proposes a three-dimensional measurement method based on projected structured light to address the challenge of measuring the vibration information of engine pipes during operation. By using the data obtained from this method and applying the time domain analysis method for modal analysis, the modal parameters of the engine under operating conditions can be obtained. The feasibility of this method is demonstrated by comparing it with different measurement methods, and it provides an effective solution for modal identification of engines under operating conditions.

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