Abstract
Conventional phase measuring deflectometry (PMD) takes up a large measurement space and is not suitable for compact online measurement, as the liquid crystal display (LCD) has to be placed in parallel with the mirror under test. In this paper, a compact online phase measuring deflectometry (COPMD) with the LCD screen set perpendicular to the mirror under test is presented for surface shape distortion real-time measurement. The configuration of the COPMD in an enclosed laser cavity is proposed, and the principle of the method is theoretically derived by using the vector-form reflection law. Based on the analysis model, the fringe modulation regulation of the LCD is revealed, and the measurement errors caused by misalignments of the components are illustrated. The validity and flexibility of the COPMD method are verified in the experiment by using a single-actuator deformable mirror as the mirror under test and the PMD method as the comparison. The proposed COPMD method remarkably expands the application range of the conventional PMD method, as it could make efficient use of compact space and is applicable for real-time measurement in enclosed laser facilities and assembled laser systems.
Highlights
High-power lasers are widely developed and applied in many applications because of their advantages of good beam quality, high pumping efficiency, and compact structure.Especially in the inertial confinement fusion (ICF) research field, high-power lasers with a single beam of tens thousands of joules are used to ignite thermonuclear fuel to release huge amounts of energy [1]
liquid crystal display (LCD) screen set perpendicular to the mirror under test is presented for the surface shape distortion real-time measurement
The configuration of the compact online phase measuring deflectometry (COPMD) method in an enclosed laser cavity is proposed, and the three-dimensional simulation model in the coordinate system is established to explore the relationship between the LCD screen and the mirror under test
Summary
High-power lasers are widely developed and applied in many applications because of their advantages of good beam quality, high pumping efficiency, and compact structure. As a low-cost, full-field three-dimensional shape measurement technique with a high dynamic range, the phase measuring deflectometry (PMD) method was first introduced in 2004 and improved to be a flexible and effective approach to inspect specular reflecting surfaces [12]. Limited by the wavefront reconstruction principle and algorithm, the screen of the liquid crystal display (LCD) has to be placed in parallel with the surface of the mirror under test, which takes up a large measurement space [12–29] These mentioned methods are primarily constrained in offline tests and not applicable for real-time measurement in the enclosed laser facility. A compact online phase measuring deflectometry (COPMD) with the LCD screen set perpendicular to the mirror under test is proposed for the surface shape distortion measurement.
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