The segmentation of surface deformations like scratches or embossed patterns can be decisively supported by using several images taken under different illumination directions. To demonstrate this approach we present two applications-the segmentation of embossed letters and the detection of grains on grinding wheels-together with two illumination devices which aid in the development of such solutions. We address further the problem of (additive) shading and how at may be solved using conventional approaches based on 'real' or estimated reference images and as well as by artificial reference images obtained by a rendering approach using a model of the setup. Finally we give an outlook on the planning of illumination setups.

In this paper we present two algorithms to derive sequences of morphological gray-scale opening/closing operators from gray-scale (anti-) granulometries which transform images containing textures of two previously known classes into images within which segmentation can be done simply by using a threshold.

Methods of signal processing which have been developed and tested for the detection of venous embolism using ultrasound Doppler systems are presented. The detection scheme developed is based on a time-frequency characterization of the Doppler signals obtained with a suitable transducer placed on the cartoid vein. The developed scheme has been implemented and tested for the automatic signaling of an embolism which can occur in the course of a surgical operation.

We propose and illustrate the application of wavelet descriptors for the quantitative description of shapes. Fourier descriptors are known to be useful for describing shapes based on their boundaries. As these basically operate at one given scale or resolution, their application leads to loss of information of salient features of a shape contained at other scales. Due to their inherent multiscale properties wavelet descriptors are potentially suitable for shape discrimination in such situations. The basic techniques of applying wavelet descriptors in practical applications are given.

The application of SAR speckle reduction filters for the purpose of ultrasonic imaging is introduced. A new adaptive filter is proposed which yields a significant improvement of sharpness in edge areas and better smoothing in homogeneous regions. The new filter incorporates high statistical moments which are weighted by their normalized local entropy determined by a moment window around the central pixel. Furthermore, a recursive version, which is algorithmically more efficient, is suggested. The results are illustrated by applying the filter to noise-corrupted artificial edge areas and ultrasonic agar phantoms. As a practical application the diagnosis of immune rejections in transplanted kidneys is demonstrated.>

An adaptive finite impulse response (FIR) algorithm for adjusting the coefficients of an adaptive filter for suppressing periodic disturbances is presented. Due to the fact that the poles of the filter are spaced equidistantly, superior convergence properties and attenuations are obtained. The effectiveness of the adaptive filter is compared with the performance of known algorithms. The algorithm converges for ratios of fundamental frequency to sampling frequency which are much lower than those achievable with other algorithms and the attenuation of the filter to the periodic disturbances is much better.>

In spread-spectrum communication systems, a basic task which has to be performed is the synchronization of the receiver pseudonoise (PN) signal with the pseudonoise signal contained in the input. In this paper, a synchronization system employing a surface acoustic wave tapped delay line (SAW TDL) matched filter for both initial synchronization (acquisition) and tracking is presented. The periodic correlation peaks at the SAW TDL output repeatedly correct the epoch of the local PN signal clock phase and the code generator initial condition to their correct values. As the correlation impulses are distorted and attenuated due to the effects of message modulation, Doppler frequency shifts and unavoidable interferences, a modulation canceller and a differentiating device are employed to improve synchronization performance. Formulas for estimating the performance of a system incorporating these ideas are given. A hardware implementation of the suggested system has been built and tested. Experimental results obtained with the system are presented.

The large time-bandwidth products realizable with the aid of surface acoustic wave (SAW) tapped delay lines facilitate the construction of accurate timing circuits which can be employed e.g. in the p-n signal synchronizing circuit of a spread spectrum system. The performance of such a timing circuit, which employs a 255 chip SAW tapped delay line and a circuit for detecting the maximum of the correlation peak, is investigated theoretically and the theoretical results are checked by experiment. It is found that the input signal level required for the timing circuit with differentiation to achieve a specified timing variance is less than that of a timing circuit without differentiation by about 3 dB. Furthermore, differentiation makes the timing circuit practically immune to changes of the threshold level.

For a non-coherent detection circuit with a broad-band pre-detection filter and narrow-band post-detection-filter, equations are obtained for the probability of detection of a pulsed sinusoidal signal embedded in white noise. The equations can be used to calculate the detection probability directly from envelope form, noise power at the input of the circuit and the impulse response of the postdetection filter. The application of the equations is illustrated with reference to a sliding correlator acquisition circuit for PN-code generators.