We report on a novel kind of accelerating beams that follow parabolic paths in free space. This accelerating peculiar polygon beam (APPB) not only exhibits autofocusing property, but also possesses two types of accelerating intensity maxima, i.e., the cusp and spot structure. We also provide a detailed insight into the theoretical origin and characteristics of this spatially accelerating beam through catastrophe theory. Moreover, experimental results confirm the peculiar features presented in the theoretical findings, and the APPB is further verified to exhibit self-healing property during propagation with either obstructed cusp or spot-like main lobe reconstructing after a certain distance. This accelerating beam with multiple types of main lobes has never been achieved previously, and we anticipate that APPB will facilitate the applications in the areas of biomedical manipulation and optofludics.
With the development of 3D vision technology in the field of consumption, speckle structured light based 3D measurement has been more and more used in various mobile terminals. Temperature compensation is one of the critical problems in speckle structured light. As a result of environmental temperature and self-heating, the operating temperature of speckle structured light module used in consumer field varies greatly. The wide range of temperature change makes it difficult to conduct accurate measurement. Due to the limitation of volume and cost, traditional temperature compensation methods play a very limited role in mobile terminals. This paper introduced the working principle of speckle structured light. Depth tilt caused by temperature changes was reported. A quantitative standard was established to evaluate the effect of temperature. The drift of speckle image was analyzed when the temperature changed. The relationship between speckle drift and depth tilt was studied. A temperature compensation technology based on BP (Back Propagation) neural network technology was proposed. The mapping between the corresponding points at different temperatures was obtained by training the BP neural network. The drift speckle image was corrected using the mapping relationship. Finally, a verification experiment was carried out. The results showed that after temperature compensation the depth tilt angle was suppressed significantly, which verified the effectiveness of the proposed method.
The acousto-optic tunable filter (AOTF)-based spectrometer has been widely used in hyperspectral imaging applications. The sidelobe phenomenon which is the result of sinc2 shape of the spectral response reduces the quality of the spectral data critically. Especially when a laser appears in the scene, the image point of the laser will be present in images of several bands with varying positions and intensity. This paper discussed the sidelobe phenomenon using the phase mismatching theory and proposed a sidelobe model based on the three-surface AOTF model(TSAM) which was a previous related work. This model provided a simplified method to trace laser light in the AOTF imaging system. A verification experiment was demonstrated, in which a dual-channel AOTF imaging system was introduced. The laser pixel coordinate and DN value were extracted from the panchromatic image and were put into the proposed model, which gave the predicted positions and DN values in different bands. The measured values were extracted from the spectral images. Results showed that the predicted values were in g