Real-time measurement of dynamic micro-displacement and direction using light's orbital angular momentum

Abstract

In this Letter, we propose an orbital angular momentum (OAM) sensor to simultaneously measure the dynamic micro-displacement and the direction of a moving object in real time. The micro-displacement of the moving object can be detected by the calculation of the petals' rotation angle caused by the coaxial interference between the measured OAM beam and its reference OAM beam, and the direction (forward or backward) of the moving object can be achieved by the clockwise or anticlockwise of the petals' rotation. We also develop an algorithm to monitor the petals' rotation angle and the rotation direction. The experimental results demonstrate that the proposed sensor can achieve high precision ([Formula: see text]) and a longer measuring range ([Formula: see text]). Additionally, the OAM sensor is sensitive to the topological charge in the OAM mode, the initial distance, and the velocity of the moving object. The sensor can perform the non-contact measurement, so it will be a promising method in micro-vibration sensing, surface unevenness sensing, and microbial movement sensing.

Generation of orbital angular momentum hologram using a modified U-net

“…Orbital angular momentum (OAM) is demonstrated by a helical wavefront beam with exp(ilϕ), [1] where l is a topological charge and ϕ is an azimuthal angle and has been applied as an information carrier in optical communication, [2][3][4][5][6] quantum information, [7][8][9] etc. Recently, holography based on OAM has received growing interest for its large capacity in information encryption, data storage and opto-electronic computing.…”

Refractive index variation rate measurement method based on OAM interferometry and time-frequency analysis

“…S. Yu et al realized a high-precision magnetic field intensity measurement with superposition OAM beams combined with the Faraday effect 7 . J. Zhu et al proposed a method for detecting the dynamic micro-displacement and direction of a moving object by using a petal-like interference pattern 8 . Z. Zhang et al obtained a measurement error rate that is less than 10 nm/s by using a system for detecting tiny velocity based on a rotating petal-like light structure and single-point detector 9 .…”

Dynamic Micro-Vibration Measurement Based on Orbital Angular Momentum

“…Orbital Angular Momentum (OAM), defined mathematically as exp(ilθ) where θ is the azimuthal angle and l is the Topological Charge (TC), has been identified as a distinct physical dimension with applications in various optical technologies. These include holography and optical multiplexed displays, as evidenced in recent studies [13,14], as well as in areas like optical storage [15,16], optical communication [17,18], and optical sensor [19,20], among others.…”

“…In optical sensors, OAM has several advantages. In our previous work [19], an OAM sensor was used to simultaneously measure the dynamic micro-displacement and the direction of a moving object in real-time. Y. Ren and colleagues successfully achieved simultaneous and independent detection of both rotational and linear motion.…”

“…Compared to the OAM-OAM method [19,[21][22][23], our proposed GS-OAM method offers two main advantages. Firstly, the combination of Gaussian and OAM light more readily produces petal-shaped light patterns, and misalignment has a significantly lesser impact on the GS-OAM method than on the OAM-OAM method.…”