Image edge enhancement with two cascaded acousto-optic cells with contrapropagating sound

Abstract

Basic real-time programmable image-processing operations are accomplished by use of acousto-optic ͑AO͒ cells. Instead of frequency-plane filters, the AO cells are placed directly behind the object. The onedimensional edge-enhancement results with one AO cell can be improved by use of two AO cells that are placed in tandem with contrapropagating sound. The dominant second-derivative operation obtained from the transfer function of the undiffracted order works like a one-dimensional Laplacian operator that enables improved edge enhancement.

Theoretical Study of Optical Field Distribution of TeO2 Modulator Diffraction

“…The form of (2) allows introducing the transfer function of the plane wave propagated through the cell [9,10]. This function can be defined as: .............................…”

Notch spatial filtering with an acousto-optic modulator

“…8 and 9, and the physical explanation for the nature of the variation as a function of spatial frequency is given in Ref. 9. The undiffracted order shows a high-pass spatial frequency response, whereas the diffracted order shows low-pass characteristics.…”

“…4 -6 The use of AOM's for image processing has recently been explored. [7][8][9] The novel feature of the technique is that lensless 2-D optical image processing can be achieved. In fact, the 2-D optical image interacts with the sound fields in the AOM's.…”

“…Indeed, the spatial transfer function for an AO modulator working in the Bragg regime that shows the spatial-frequency selectivity of both the diffracted and the undiffracted orders has recently been derived and studied. [7][8][9][10][11] In short, under certain conditions, the undiffracted order has the characteristics of spatial high-pass filtering, while the transfer function for the diffracted order shows low-pass characteristics. To develop more and diversified spatial-filtering operations, techniques to compute spatial transfer functions under a variety of physical situations-such as different nominal angles of optical incidence, the utilization of different diffracted orders at the output, etc.-are needed.…”

Edge-enhanced imaging with polyvinyl alcohol /acrylamide photopolymer gratings

“…2 We can see that the exponential factor is linear in p, thus giving rise to a shift in the propagation of the incident plane waves. This term represents the shift produced by refraction in a plane-parallel plate.…”