J. Le Bihan

An immune oriented multi-agent system for biological image processing

Abstract In this article, we present a parallel image processing system based on the concept of reactive agents. Our system lies in the oRis language, which allows to describe finely and simply the agents’ behaviors to detect image features. We also present a method of segmentation using a multi-agent system, and two biological applications made with oRis. The stopping of this multi-agent system is implemented through a technique issued from immunology: the apoptosis.

Use of deformable template for two-dimensional growth ring detection of otoliths by digital image processing:: Application to plaice (Pleuronectes platessa) otoliths

Abstract Today, most computer-assisted age reading software is limited to one-dimensional processing. Automated two-dimensional growth ring detection is closely linked to the ability of image processing algorithms to perceive structure continuity. By using deformable models, based on closed B-splines, it is possible to fit a shape to the image features using maximum or minimum criteria according to the nature of translucent or opaque zones. Otolith edge contours were used as templates that were inflated from the core toward the edge in order to detect the growth zones. Template step sizes were modulated by an a priori growth pattern in order to take into account the decrease in ring size. A reference test image set ( n =102) of plaice otoliths, previously aged by one reader, was processed. For the first age groups, there was a total agreement with reader estimates. Mean agreement with reader estimates for age groups 1–5 averaged 80% but decreased for age groups 6–8. Overall, age was significantly underestimated by an average of −0.89 year.

Growth ring detection on fish otoliths by a graph construction

We present an algorithm for the detection of fish otolith growth rings based on a graph construction method. The identification of growth rings, for age estimation, is routinely achieved in fishery laboratories by human readers. One of the major problem encountered during an automatic image processing is the lack of ring continuity perception. We present an approach to this continuity perception based on the 2D reconstruction of rings from the restoration of the connectivity of nodes detected in polar coordinates. The node connection is based on an a priori knowledge of ring geometry.

Accurate analytical approximation for normalized diode characteristic

An analytical function is proposed as an approximation of the generalized normalized diode equation. This function is simple, has a right asymptotic behaviour and achieves very good accuracy. Copyright

Optical packet synchronization device based on acousto-optic interaction: characterization and performance

An optical packet synchronizer for telecommunication networks at 1.55 µm is presented. The device carries out the phase alignment of packet flows at the input of a switching node. It is based on packets switching by means of an acousto-optic cell towards various optical paths achieved with optical fibres. The characterization of an acousto-optic cell providing four diffraction directions is presented. From this cell we have implemented a synchronizer device with four discrete delays (400 ns delay resolution) and we have experimentally evaluated its performance in terms of configuration time (130 ns), insertion loss (< 18 dB), transparency to data bit rate and cross-talk (< -22 dB).

Acousto‐optic deflector‐based optical packet synchronization

We propose a novel optical packet synchronizer for use in telecommunication networks at a 1.5 μm wavelength. An experimental setup shows the feasibility of the system using an acousto-optic deflector and a single-mode fiber delay line array. The proposed system achieves an optical transparency to the data bit rate, and is suitable for nonregenerative application within an optical network.xa0© 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 209–211, 2000.

Locations and amplitudes of the extrema of the sinx/x function

This paper addresses the calculation of the extrema of the sin x/x function. First the Newton-Raphson method is used, which allows us to obtain the extrema locations very fast through the use of a recursion formula. Then a second approach is proposed, which gives the extrema locations and the extrema amplitudes in the form of series expansions. Simple, accurate algebraic expressions are derived.

Z-Transform based method for coefficient computation and generating function derivation for sinc N FIR filters

SincN FIR filters, constituted of a cascade of N sinc filters, each of length M, are encountered in digital signal processing applications. It is shown that the use of Z-Transform techniques is an efficient method to derive straightforward recurrence relations for fast computation of the impulse response. A simple general expression, valid for all the filter coefficients, can also be obtained. In addition, generating functions for the sincN FIR filters transfer functions are given.

All-optical logic OR gate based on cross gain modulatilon in Semiconductor Optical Amplilfiers

Semiconductor optical amplifiers (SOAs) are very attractive components for optical communication systems. We have already shown that two-cascaded SOAs in a counterpropagating configuration (TC-SOA-CC) based on XGM is interesting for all-optical signal processing (Kim et al., 2000). The contra-directional input signals are injected in SOA. In this configuration, a negative feedback controls the evolution of the SOA gains. The presence of a positive gain variation in SOA can be useful to perform all-optical logic OR gate at the output of SOA.

Evaluation of BER and WDM Crosstalk Penalty at 2.5 Gb/s in an SOA by Holding Beam Injection around Transparency Wavelength

We experimentally demonstrate the influence of a high power continuous wave (CW) injection, as a holding beam (HB), into an SOA around the gain transparency wavelength on the bit error rate (BER) of a signal modulated at 2.5 Gb/s traveling through the amplifier. We show that the injection of an HB power of 19 dBm at 1480 nm inside an SOA, in three regimes (absorption, transparency and gain), can reduce the signal BER, mainly, when working at high input signal powers. As a result for a BER of 10-9, an improvement more than 2.5 dB of input power can be obtained following the HB regime injection. In addition, we use the HB injection in an SOA based multi-channel WDM transmission system to reduce the crosstalk penalty between signals, which is caused by the cross-gain modulation (XGM). Experiment shows that the crosstalk penalty between two signals is suppressed and the SOA induced BER is improved when injecting the HB in the absorption regime. However, this penalty is noticeably reduced by the HB injection in the two other regimes