Roger Melen

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I am a Stanford PhD Electrical Engineer that has pursued a entrepreneurial career in leading edge semiconductor, networking, computer and systems including military, medical, office equipment and automotive efficiency, communications, entertainment and safety themes,

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Papers by Roger Melen

CCD Image Sensors for A Reading Aid For the Blind

Charge-coupled devices: Technology and applications

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Charge-coupled devices for use in electronically-focused ultrasonic imaging systems

Iee Proceedings F Communications, Radar and Signal Processing, 1980

Pulse-echo ultrasonic imaging techniques make possible the dynamic visualisation and characterisa... more Pulse-echo ultrasonic imaging techniques make possible the dynamic visualisation and characterisation of many soft-tissue structures with no known patient risk; however, the extraction of this information requires an ultrasonic imaging system capable of producing a high-resolution image over a sizeable field of view in real time. This paper describes the development of the cascade charge-coupled device (C3D) designed specifically for electronically-focused ultrasonic imaging systems. The C3D lens described here further enhances the desirability of such systems because the delay-line hardware needed to focus and beam steer a linear array of piezoelectric transducers is reduced to a single l.s.i. device, and because clock-frequency control does not require individual control signals for each transducer channel and therefore greatly limits the amount of external circuitry necessary to support the imaging system. The analysis of the fundamental limits of the C3D approach to ultrasonic imaging includes the effects of the asynchronous transfer of charge between sections operating at different clock frequencies, with emphasis on the impact of this process on the time-delay accuracy of the C3D lens and on the maximum level of sidelobe suppression. The firstgeneration C3D lens has been fabricated and tested in a static water tank. These measurements indicate that the lens produces near-theoretical lateral resolution as predicted by the aperture theory of linear arrays. Based on preliminary results, a second-generation device is proposed whose additional capabilities would include full interpolation of the field of view for a scan-linc-frec image presentation and on-chip apodisation to obtain higher degrees of sidelobe suppression.

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Estimation of linear stroke parameters using iterative total least squares methods

In this paper we present an algorithm to enhance the accuracy of the estimation of the parameters... more In this paper we present an algorithm to enhance the accuracy of the estimation of the parameters of linear stroke segments in a two-dimensional printed character image. The algorithm achieves high accuracy in comparatively less computational time than most traditional methods. It is invariant under rotation and translation and no a priori information about the image is required. The Iterative Total Least Squares (ITLS) method begins at a randomly assigned initial approximation of the line parameters. A rectangular window is centered using the current stroke approximation, and a new line estimate is generated by making a total least squares fit through the pixels contained within the window. This is then repeated until convergence is reached. Adaptive adjustments of the window size and choice of profile can further improve the obtained accuracy. In addition, a `fast' ITLS method has been developed.

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Journey Learning System