Notch spatial filtering with an acousto-optic modulator

Abstract

The role of acousto-optic ͑AO͒ modulators in programmable real-time image processing has recently been demonstrated. For fully investigating the image-processing capabilities of the AO modulator, general techniques to derive spatial transfer functions are needed for a variety of physical situations. We develop a technique to determine the spatial transfer functions numerically for various cases of beam incidence on an AO modulator. Normal incidence and incidence at twice the Bragg angle are investigated as examples for which double-sided and single-sided notch spatial filtering, respectively, are achieved. The observed spatial-filtering characteristics are reconciled with simple intuitive physical arguments.

Optical image processing using acousto-optic modulators as programmable volume holograms: a review [Invited]

“…For Δδ = 0.15, i.e., the tilt angle is 0.15ϕ B away from the exact Bragg angle incident, Fig. 17 While single-sided notch filtering has been previously investigated [13] , it was not without a special consideration to the AOM. With the consideration of off-Bragg angle incidence, we simply need to provide a slight tilt to the AOM.…”

“…The tandem arrangement of two AOMs has been investigated for expanding the possibilities of using Bragg diffraction for high frequency modulation of optical beams [11,12] . To develop more and diversified spatial-filtering operations, Banerjee et al also investigated techniques to compute spatial transfer functions under a variety of physical situations [13] . Davis and Nowak performed operations similar to those obtained with both the fractional Hilbert transform and fraction derivative spatial-filtering operations [14] .…”

Edge-enhanced imaging with polyvinyl alcohol /acrylamide photopolymer gratings

“…These Bragg diffraction effects in AOLMs have been described by use of the spatialfrequency transfer function formalism. 4 Next, we show that the classic closed-form expressions from Kogelnik's theory 12 provide a direct way to obtain accurate spatial-frequency transfer functions for holographic gratings. According to Kogelnik's theory, for a volume phase unslanted transmission grating the expressions for the transmitted, R, and the diffracted, S, wave amplitudes after the waves pass through the hologram are…”

Acousto-Optic Transfer Function Control by a Phased-Array Piezoelectric Transducer

“…This is the most common AOTF type, widely available and used in various hyperspectral imaging experiments [11,12]. Several previous applications of AO devices for optical image processing include image edge enhancement in coherent light [13][14][15][16][17][18][19][20] and phase imaging [21][22][23]. Novel designs of optical traps based on LBS by an AOSF have been recently demonstrated by Obydennov et al [24,25].…”