Speckle reduction in multimode fiber with a piezoelectric transducer in radial vibration for fiber laser marking and display applications

Abstract

We propose and experimentally demonstrate an effective method to reduce far-field speckle noise in multimode fiber with a short cylindrical piezoelectric transducer (PZT) vibrating in radial direction. In this study, the fiber was coiled as tightly as possible around the mandrel of the PZT and periodic stretching effect was caused by the radial oscillations of the actuator. This technique can be adapted at a high modulation frequency, so the speckle patterns can be timeaveraged. The output of the optical fiber was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded 256 levels in selected area and by calculating the mean value and standard deviation of the intensity, we can measure the speckle contrast and vibration effect in quantitative measurands. It was clearly observed that the characteristics of the speckle pattern in vibration-ON-state were significantly reduced than that of vibration-OFF-state by comparing the proposed measurands as well as direct CCD images. We expect that the proposed speckle reduction technology would find viable applications in realization of fiber laser, laser marking, optical trapping and projection display systems.

Laser speckle suppression by the phase modulation of input beam in a multimode fiber

“…To restrain speckle, exerting disturbance in the process of speckle forming is an effective way to get suppressed speckle. Researchers exert mechanical disturbance on the fiber in the process of speckle forming to superpose speckle [3], [4] .…”

A cost-efficient open source laser engine for microscopy

“…Perturbing the speckle pattern faster than the camera frame rate effectively averages it out. Several approaches have been explored in order to remove speckles from a multimode fiber profile, including rotating optical elements [12,16], oscillating diffusive membranes [14,17] or mechanical agitation [12,[18][19][20].…”

Speckle reduction in laser imaging applications using rotating magneto-optical disk

“…Although speckle is deliberately exploited in some applications, e.g., digital speckle photography [6,7], the presence of speckle tends to mask the image information, and thus its reduction is generally highly desirable [8,9]. As a result, many speckle reduction methods have been proposed to reduce speckle noise without blurring important features in the image, such as edges, corners, or points [10][11][12][13][14][15][16][17][18]. As discussed in [2], such methods are generally based on introducing phase delays into the projected light or reducing the temporal and spatial coherence of the laser source.…”