| The scanning mirror is a key component on the hyperspectral imager, which ismainly used for optical transition and motion compensation. The angular errors andposition errors of the scanning mirror have an effect on the image quality of thehyperspectral imager, so the dynamic test of the scanning mirror is very important toimprove to the image quality of the hyperspectral imager. The encoder is often used tomeasure the angular velocity of the scanning mirror, and the contact measurementmethod would produce a certain angle measurement error, so it is important to raise anon-contact method for the scanning mirror measurement. In order to measure thedynamic movement of the scanning mirror in a quite large angular range, the dynamiccontinuous angular measurement with high accuracy must be realized firstly. And thenthe angular velocity of the scanning mirror can be analyzed according to the results ofthe angular measurements. Optical angular measurement methods are used widelyamong all the non-contact angular measurement methods. Most optical anglularmeasurement methods can not satisfy the requirements on the measurement range andaccuracy at the same time. The measurement ranges of most optical methods are onlya few seconds to several minutes, and they can not be applied to the dynamic anglemeasurement of the scanning mirror. The theodolite is widely used in angularmeasurement, but the theodolite can not realize real-time dynamic measurement.A non-contact laser dynamic measurement system for the scanning mirror isproposed in this dissertation according to the project requirements. The variationangle of the scanning mirror can be obtained according to the shifting of the laserfacular on the linear CCD, and then the angular velocity can be calculated. A linelaser, attenuator, array mirrors, linear CCD, image acquisition and computersubsystems are included in the system. A large angle measurement range is divided into five small angle ranges by the array mirrors, and the rotation angle can bemeasured by reusing a linear CCD to ensure the measurement accuracy.Firstly, the working principle and the basic structure are introduced in thedissertation.The mathematical model of the system is established with thehomogeneous coordinate transformation method, which contains the errors ofprocessing and alignment. According to the Monte Carlo method, the errordistribution schemes of the system are performed through the absolute position erroranalysis and relative position error analysis.The results show that the errordistribution schemes based on the relative position error analysis method can greatlyreduce the requirements of the processing and alignment. Finally, the cubicpolynomial fitting method is applied for the measurement. The function about theposition of laser facular and the angular displacement can be calculated based on thecubic polynomial fitting. The angular displacement can be measurement by thetheodolite and the position of laser facular is come from the computer. Compared totraditional angle measurement instruments, the system realizes non-contact dynamicangular measurement in wide measurement range.Each component in the measurement system is selected according to the relevantparameters, and the experimental platform is proposed.Before the experiments, thefactors which have an effect on the measurement accuracy are analyzed. The finalexperimental results show that the rotation angle could be measured within11°. Thesensitivity and accuracy of angle measurement was2.5″and3″. The accuracy ofvelocity measurement is better than±7%.The measurement system is applied in the practical project, and some practicaldesigns are gived based on the prototype and experimental results includingoptomechanical design, electronics design and related alignment design. Themeasurement system can be applied in other occasions, and two examples of theapplication are performed finally in the dissertation. |
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