Tracking moving targets behind a scattering medium via speckle correlation

Abstract

Tracking moving targets behind a scattering medium is a challenge, and it has many important applications in various fields. Owing to the multiple scattering, instead of the object image, only a random speckle pattern can be received on the camera when light is passing through highly scattering layers. Significantly, an important feature of a speckle pattern has been found, and it showed the target information can be derived from the speckle correlation. In this work, inspired by the notions used in computer vision and deformation detection, by specific simulations and experiments, we demonstrate a simple object tracking method, in which by using the speckle correlation, the movement of a hidden object can be tracked in the lateral direction and axial direction. In addition, the rotation state of the moving target can also be recognized by utilizing the autocorrelation of a speckle. This work will be beneficial for biomedical applications in the fields of quantitative analysis of the working mechanisms of a micro-object and the acquisition of dynamical information of the micro-object motion.

Imaging and Tracking Through Scattering Medium With Low Bit Depth Speckle

“…It means that some applications, only require auto-correlations of the speckles or cross-correlations between different speckles without reconstructing the object's images, compressing the speckles with low bit depth can hardly affect the results. The movement of a hidden object can be tracked in the lateral direction and axial direction by using the speckles' correlation [25]. This method does not require the reconstruction of the object's image, it only need the cross-correlation between different speckles to track the moving object.…”

“…4a and b. The distance from the center position to the maximum point is proportional to the moving distance of the object [25]. The binary Figs.…”

“…It indicates that the speckle compressed with bit depth does not have an effect in this experiment. When the object moves along the vertical axis direction, the methods of recovering the track by using the binarized speckle can be analogized to the methods of paper [25]. Since the cross-correlation images are almost indistinguishable calculated from the raw speckles and the binarized speckles, the binarized speckles can still be used to recover the track with a high accuracy.…”

“…Ref. [24] has developed a method to obtain intensity transmission matrices of diffusers via spatial-correlation, which is a flexible access to PSF s. In addition, tracking of moving object can be achieved by speckles [25], [26].…”

Direct Object Recognition Without Line-Of-Sight Using Optical Coherence

“…This aspect allows our method to overcome some of the critical practical limitations of the related imaging methods. The proposed method requires hardware (mostly consumer-grade electronics) that is far less expensive than that required for the TOF-based NLOS imaging [16,24,25,26,27,33,37,39,40], and the method is more robust than the memoryeffect based imaging techniques that have a limited field-ofview [11,21]. Moreover, a recent publication [31] also uses only ordinal digital cameras but would require very specific scene setup (an accidental occlusion) to obtain better performance.…”