Infrared images are susceptible to Gaussian noise during acquisition and transmission. To meet the quality requirements for infrared image data in image processing, an asymptotic Non-Local Means (NLM) algorithm based on an improved Scharr operator was proposed for denoising infrared images of electrical equipment. Firstly, the RGB infrared images were converted to the Y channel. Secondly, the improved Scharr operator was used to adjust the computation weights of the NLM algorithm, better preserving the edge details of the images. To optimize the denoising effect, a multi-layer pyramid was constructed, and a layer-by-layer denoising fusion method was adopted to obtain the initially denoised images. Finally, for the residual noise in the initially denoised images, asymptotic denoising was employed, adjusting the filter parameters based on the image characteristics for secondary denoising, followed by image reconstruction to obtain the denoised images. Experimental results showed that the proposed algorithm achieved clear and complete denoised images, with Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity (SSIM) improved by 0.78 to 4.95 and 0.01 to 0.08, respectively, compared to other methods. This indicated that the method is effective for high-efficiency denoising of infrared images of electrical equipment.
The phase-shifted sensitivity of an interferometer can be enhanced by increasing the group index. In this paper, we experimentally demonstrate a slow light sensor by placing an active fiber Bragg grating (FBG) in one arm of the Michelson’s interferometer. A 25 KHz AC voltage was applied to a piezoelectric (PZT) set nearby the active FBG. Once the wavelength is varied to near the FBG band edge, the maximum phase-shifted amplitude appears, which is about 1.8 rad and is 4 times greater than that when wavelength is near the center of the reflection band. The active FBG is pumped by a 980 nm laser diode, which can help us to stabilize the system works in the slow light regime to obtain the maximum phase shift. It provides a very simple approach to increase the phase-shifted sensitivity, which is likely to have important applications for strain and acoustic sensors.
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