Speckle Reduction by Optimized Multimode Fiber Combined With Dielectric Elastomer Actuator and Lightpipe Homogenizer

Ma, Qianli; Xu, Chanqing; Kitai, Adrian; Stadler, David

doi:10.1109/jdt.2016.2568458

Cited by 16 publications

(7 citation statements)

References 16 publications

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“…Voice coil motors are the simplest type of motor but they produce strong mechanical vibrations in the system. The motion of the dielectric elastomer actuator diffuser was used to reduce speckle contrast in which a diffuser is derived by an electroactive polymer membrane [28]. Speckle reduction in mini projector was reported by vibrating diffuser at 100 Hz frequency [29].…”

Section: Introductionmentioning

confidence: 99%

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Kumar

Gupta

Dubey

et al. 2020

J. Opt.

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We report the design and development of an efficient speckle reduction device for projection imaging. The device is composed of a combination of a rod-shaped waveguide diffuser and a reflective pyramidal cavity. The simulation results reveal that the pyramidal cavity with waveguide diffuser is a highly efficient light guide comparable to the other conventional light guides. Further, the device was developed and tested experimentally on the basis of speckle contrast and image quality for both the microscopic and macroscopic objects. An acrylic rod-shaped waveguide diffuser was developed and mounted at the middle of a pyramidal shaped cavity which was fabricated using 3D printer. Four highly reflecting mirrors were installed to make the cavity reflective. The system is highly effective for the speckle suppression due to the coherence reduction via multiple scattering from the rod-shaped waveguide diffuser and multiple reflections from the pyramidal cavity. In the system, a combined effect of spatial and angular diversity along with intensity averaging leads to an effective speckle free uniform illumination. Reduced speckle contrast using the proposed system was observed up to 2%, which is nearly equivalent to mechanically moving diffuser system. The device is able to reduce speckle contrast significantly without using any moving parts and in addition, it does not consume any electrical energy. The proposed system is compact, low cost, efficient, and very effective for low to high power laser sources in speckle reduction. Experimental results are compared with stationary and rotating diffuser system on the basis of computed speckle contrast and image quality.

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Section: Introductionmentioning

confidence: 99%

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Kumar

Gupta

Dubey

et al. 2020

J. Opt.

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show abstract

“…The second method is to eliminate the degree of temporal coherence of the laser by the inclusion of a vibrating diffuser [7], dynamic deformable mirror [8,9], or electroactive polymers [10]. The third method is spatially varying independent to include dielectric elastomeric actuators (DEA) [11,12], or rely upon moving the screen [13]. The above methods can reduce the speckle contrast value to between 0.03 and 0.05.…”

Section: Introductionmentioning

confidence: 99%

Speckle reduction using deformable mirrors with diffusers in a laser pico-projector

2017

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We propose a design for speckle reduction in a laser pico-projector adopting diffusers and deformable mirrors. This research focuses on speckle noise suppression by changing the angle of divergence of the diffuser. Moreover, the speckle contrast value can be further reduced by the addition of a deformable mirror. The speckle reduction ability obtained using diffusers with different divergence angles is compared. Three types of diffuser designs are compared in the experiments. For Type 1 which uses a circular symmetric diffuser the speckle contrast value can be decreased to 0.0264. For Type 2, the speckle contrast value can be reduced to 0.0267 because of the inclusion of an elliptical distribution diffuser. With Type 3 which includes a combination of the circular distribution diffuser and elliptical distribution diffuser, the speckle contrast value can be reduced to 0.0236. For all three types, the speckle contrast value is lower than 0.05. Under this speckle value, the speckle phenomenon is invisible to the human eye.

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“…Speckle is the main reason for limited application of laser illumination in many technical devices [3][4], especially portable projectors [5][6]. Therefore, various methods have been developed for speckle suppression [6][7][8][9][10][11], among which the method based on diffractive optical element (DOE) is one of the most important and simplest methods for speckle reduction. The method uses active DOE to decrease the spatial coherence of a laser beam by means of changing the intensity and the phase of diffraction orders (referred to as angle diversity).…”

Section: Introductionmentioning

confidence: 99%

Dispersion of speckle suppression efficiency for binary DOE structures: spectral domain and coherent matrix approaches

Lapchuk¹,

Prygun²,

Fu³

et al. 2017

Opt. Express

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We present the first general theoretical description of speckle suppression efficiency based on an active diffractive optical element (DOE). The approach is based on spectral analysis of diffracted beams and a coherent matrix. Analytical formulae are obtained for the dispersion of speckle suppression efficiency using different DOE structures and different DOE activation methods. We show that a one-sided 2D DOE structure has smaller speckle suppression range than a two-sided 1D DOE structure. Both DOE structures have sufficient speckle suppression range to suppress low-order speckles in the entire visible range, but only the two-sided 1D DOE can suppress higher-order speckles. We also show that a linear shift 2D DOE in a laser projector with a large numerical aperture has higher effective speckle suppression efficiency than the method using switching or step-wise shift DOE structures. The generalized theoretical models elucidate the mechanism and practical realization of speckle suppression.

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Speckle Reduction by Optimized Multimode Fiber Combined With Dielectric Elastomer Actuator and Lightpipe Homogenizer

Cited by 16 publications

References 16 publications

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Speckle reduction using deformable mirrors with diffusers in a laser pico-projector

Dispersion of speckle suppression efficiency for binary DOE structures: spectral domain and coherent matrix approaches

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