Virtual image distance (VID) is a key parameter in augmented reality (AR) or virtual reality (VR) systems and has a great influence on product performance and user experience. Therefore, it is very necessary to measure the VID accurately and efficiently. In this paper, we develop a VID measurement system which needs no mechanical scanning in the measurement process. The VID can be measured in a short period of time based on one single image generated by the AR/VR system. An image-telecentric lens is designed which is used to capture the virtual image. A diaphragm with two pinholes is placed at the entrance pupil plane of the imaging lens. When the imaging lens is not focused on the virtual image, the captured image contains two copies of the virtual image with a certain interval which is proportional to the VID in units of diopters. By calculating the interval, we can obtain the VID. A simulation is performed in LightTools to verify the effectiveness of the measurement system, and the result indicates that the measurement error is 5 mm when the virtual image is at 3 m.
Laser cleaning has become a widely used cleaning technology in recent years. Currently, researchers are mainly engaged in the studies of laser cleaning process parameters. However, when the casing of oil tanks, wind turbines, and electronic equipment are cleaned, the high temperature generated by thermal deposition in the substrates will accelerate the aging of oil, reduce the performance of lubricants, and cause the damage of semiconductor devices. These will indirectly lead to mechanical or electronic failures of the devices and systems. To avoid these adverse effects, it is significant to investigate the temperature distribution of the substrate during the laser cleaning process. In this paper, the results of the temperature distribution measurement of the substrates covered with the rust, cooking oil, industrial lubricants and industrial primer has been presented.
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