International Business Machines Corporation

Discovision Associates

Raymond J Wilfinger

Howard N Leighton

Christian A Jacquart

James F Dubil

Rene J Glaise

Albert R Basilico

Michael M Siverling

Michael J Burke

Vladimir Riso

Alain M Falcoz

Reflected light from the record in a optical disk player is directed at a string of photo sensitive diodes. Two adjacent diodes of this string of diodes receive light from a selected portion of the track on the disk. The outputs of these two adjacent diodes are summed together to generate the output signal for the optical disk player. The outputs of the two diodes are also subtracted from one another to generate a differential signal for tracking purposes. The magnitude of this differential signal is a measure of the relative magnitudes of the signals on the two adjacent diodes and therefore is one indication of how much of the light from the selected portion of the track reaches each of the diodes. When this differential output becomes larger than a preselected value, decode circuitry responds by changing the combination of adjacent diodes in the string to generate the video output signal and the difference signals.

Solid state electro-optical track follower array

This specification describes a charge-transfer device transversal filter chip in which an input signal is fed in parallel into a number of channels the outputs of which are summed together to provide the desired transversal filter transfer function. Each channel contains an analog shift register, a signal splitter and a polarity selector. The shift registers are of unequal length to provide a different delay thru each channel. The signal splitter provides a plurality of signal paths thru each channel while the polarity selector determines whether a given path in a given channel is added or subtracted in the summation to determine the gain of the given channel in the summation.

Universal transversal filter chip

Analog voltage levels derived from optically scanning a document or from magnetically scanning a magnetic record, depend upon the variable amplitude of a background signal. The analog voltage levels are processed by a bucket brigade circuit to set a threshold from which a binary decision may be made as to the presence of a black or white indicium in optical recognition or a one (1) or zero (0) bit in magnetic reading.

Analog signal manipulation using charge transfer techniques

A charge transfer device capacitive ratio voltage multiplication circuit has been devised which solves the problem of cumulative DC bias offset by adding a DC signal compensation branch to prevent the accumulation of DC offset potential. The circuit can be expanded to form a weighted sum of multiple inputs which does not incur any corresponding DC bias offset, by making the sum of the characteristic capacitances of each of the multiple inputs equal to the characteristic capacitance of the output portion of the charge transfer device circuit. The circuit allows arithmetic operations to be performed on input signals solely in the charge domain without the necessity of converting charge to voltage to charge, thereby avoiding losses, distortions, offsets and a reduction in dynamic range which would otherwise result.

Bucket brigade circuit for signal scaling

The underlying concept of the invention disclosed is the use of charge partitioning for providing a precision weighted tap in a bucket brigade circuit. At the drain node of a charge conducting element in a bucket brigade device, the signal path is split in half with a first half going to the source of a first FET and the second half going to the source of a second FET. The first and second FET devices have their associated overlap capacitances, transconductances and threshold voltages matched by virtue of their close proximity to one another on the semiconductor substrate so as to have matched charge transfer characteristics. The amplitude of the charge stored on the capacitor at the node is therefore divided into two parts, with one portion being transferred by the first FET device and the remaining portion being transferred by the second FET device. This simple circuit accomplishes a precise charge division for the charge entered into the bucket brigade circuit. Successive cells in the bucket brigade device can have their drain nodes connected to matched pairs of first and second FET devices to successively divide the charge stored therein by one-half so that a sequence of decrements in the charge transferred along the bucket brigade chain may be made in multiples of one-half. By selectively gating the outputs of each of the respective tapped branches from the bucket brigade device at a summing node, values of from zero to unity in fractional unit intervals can be generated as an analog output. A digital to analog converter may be formed by inputting a serialized digital word into the input of the bucket brigade device whose successive cells have attached thereto respective pairs of FET charge partitioning devices. The outputs of all branches are summed so that a resultant charge, which is the sum of the charges output by the charge partitioning transistors, will appear at the output as the analog value for the binary serial word input to the bucket brigade device.

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Lagrangeville, NY, United States of America

Raymond J Wilfinger