Abstract: A method for regulating the biasing voltage of column control circuits of an array screen formed of LEDs distributed in lines and columns, the column control circuits being adapted to turning on at least one LED of a line. The method consists of increasing the biasing voltage when the current flowing through at least one activated LED is smaller than a determined luminance current and of decreasing the biasing voltage when the current flowing through each activated LED is equal to the determined luminance current.

Abstract: A method for controlling cells of a plasma screen of array type, formed of cells arranged at the intersections of lines and columns, including the step of sequentially applying to each line an activation potential and, during the activation of a line, applying an activation potential to selected columns, in which, while a line is activated, the selected columns are non-simultaneously activated.

Abstract: A method for displaying an image on an array screen by activation of screen pixels arranged in rows and columns, each pixel of a same row corresponding to a memory point of a same memory row, the memory point being set to an activation state when the corresponding pixel is to be activated, including the steps of identifying, among sets of the memory rows, the row sets for which at least one memory point of a row of the set is at the activation state; and successively selecting the only lines corresponding to the rows of the sets of rows identified for the pixel activation. The present invention also provides a device for displaying an image on an array screen.

Abstract: A method and circuit for displaying an image by activation of pixels of an array screen based on an image stored in digital form in memory point rows of a frame memory, having a stand-by mode that provides, at a frequency proportional to the display frequency, a cyclic succession of offset values; and for each row address of the frame memory, activating pixels of a screen line associated with said address offset by a same offset value based on the read states of the row associated with the address, and/or activating pixels of a screen line associated with the row address based on the read states of the frame memory row associated with the address offset by a same offset value.

Abstract: A method for regulating the biasing voltage of column control circuits of an array screen formed of LEDs distributed in lines and columns, the column control circuits being adapted to turning on at least one LED of a line. The method consists of increasing the biasing voltage when the current flowing through at least one activated LED is smaller than a determined luminance current and of decreasing the biasing voltage when the current flowing through each activated LED is equal to the determined luminance current.

Abstract: The invention concerns a method for controlling a matrix plasma panel cells, consisting of cells (4) arranged at the intersections of lines (6) and columns (8), comprising a step which consists in sequentially applying to each line an activating potential and, during a line activation, in applying an activation potential to selected columns, wherein while a line is being activated, the selected columns are activated non-simultaneously.

Abstract: A driver circuit for driving a plasma display panel comprising a plurality of cells arranged in a matrix of lines and columns; comprising a set of driver output stages connected to line or column electrodes to which a first electrode of cells of a same line or a same column are connected, respectively. The driver circuit includes a detection device for detecting a short circuit between two or more of the outputs of the driver output stages. It allows to test for alignment faults in the flexible cable connecting together the driver module housing incorporating the driver circuit and the electrodes of the plasma display panel.

Abstract: The device comprising a video processing circuit (7) for processing the video data received, a correspondence memory (8) for transcoding these data, a video memory (9) for storing the transcoded data, the video memory being linked to column drivers (10) in order to control the column addressing of the plasma panel on the basis of column control words, a control circuit (11) for the line drivers (12), is characterized in that the control circuit for the line drivers simultaneously selects at least two successive lines during the transmission by the column drivers (10) of at least one of the bits of the column control words relating to one of these lines.

Abstract: The invention relates to a process and device for scanning cells of a matrix-controlled display for the displaying of grey levels of a video signal, the scan being split up into sub-scans relating to each bit of column control words, characterized in that, when the coding of image does not activate the high-order bit, the processing sub-scan relating to this bit is allocated to the displaying of an additional item which corresponds to a bit of lower weight than the smallest weight of the column control word used when the condition is not fulfilled. The applications of the invention relate to matrix-controlled display devices using the principle of temporal modulation for the generation of halftones, especially plasma panels of the a.c. type with memory or d.c. type with memory.

Abstract: A method for testing output connections of at least one driver circuit that drives a plasma display panel. According to the method, at least one output of the driver circuit is switched to a high level for a predetermined time period. The output of the driver circuit is switched to a low level, and the time to discharge the output of the driver circuit with a constant discharge current is measured. It is determined whether a capacitive load is connected to the output of the driver circuit based on the measured time to discharge. In one preferred method, these steps are repeated for each of the outputs of the driver circuit. A driver circuit for driving a plasma display panel is also provided. The driver circuit includes driver output stages, and means for selectively sinking a constant discharge current from the output of at least one of the driver output stages to ground.

Abstract: Disclosed are a method for the control of an image display screen displaying half-tones and a display device implementing this method. The disclosed method is used to control an image display screen of the type having cells arranged in rows and columns and working either in a state known as an "OFF" state or in a state known as an "ON" state in which they are activated and produce light. The method consists in activating the cells of each row during sub-periods of different duration, with orders of distribution of the sub-periods that are different between two successive rows. This results in a reduction of the amplitude of the variations of a load constituted by the cells in the <<lit>> state of these two consecutive rows. Application inter alia to alternating plasma panels.

Abstract: A method for the control of a display screen whose pixels are cells producing light is used to minimize certain image defects known as excess brightness defects caused by major variations in the number of cells activated. For this purpose, the invention operates on the sub-division of the activation times of the cells during a given cycle time to reduce a time during which cells, selected as a function of their luminance level, are the only ones to be activated. The disclosed method can be applied especially to the control of alternating type plasma panels.

Abstract: A bottom open display case for jacketed cassettes wherein the jacket is retained in the display case which itself is of transparent plastics material. A base is attached to the bottom end of the display case and is slidable laterally from a closed position to an open position where an opening in the base aligns itself with the cassette in the display case allowing the cassette to be removed from the display case. A flexible tab on an end wall of the display case acts as a spring to return the base to its initial closed position where it is out of alignment with the cassette in the display case.

Abstract: A more accurate voltage-to-time and then time-to-voltage conversion is accomplished by tailoring the amplitude versus time characteristics of the pulses generated in the voltage-to-time conversion. One embodiment includes applying a ramped voltage supply to an amplifier coupled between the voltage/time converter and the time/voltage converter. The ramped supply is arranged to condition the amplitude of a portion of respective pulses to include a slope similar to the ramped voltage applied to the time/voltage converter. This tends to effect a more accurate response in the time/voltage converter.

Abstract: Disclosed is a method for the addressing of each column of a matrix type LCD panel consisting in the production of a pulse to control a driver transistor of said column, said pulse having a duration determined by the value of the video signal sample at input, said pulse acting on the conduction state of said transistor to connect said column to a supply terminal where a voltage gradient develops. According to the method two pulse durations, the sum of which is predetermined, are alternated and, in order that a given value of a video signal sample may produce the same optical effect from one period to the next one, differentiated excitation voltages are applied to at least one of the electrodes sandwiching the liquid crystal layer, namely said column and its counter-electrode. Application notably to active matrix LCD panels.

Abstract: The present invention is a video drive apparatus of the two ramp type which includes facility to selectively adjust the brightness and/or the contrast of an image reproduced on a display device. In this apparatus, at least one of the ramp signals is generated digitally by for example a counter. Provision is made to change the counting rate of such counter which effects a change in display contrast. Provision is also made to selectively change the phase of the ramp signal applied to the second stage relative to the start of respective pulses of the PWM signal thereby effecting brightness changes in the reproduced image.

Abstract: An actuation circuit for a liquid crystal display includes a plurality of pixel elements constructed in the form of a matrix of columns and rows and a plurality of column capacitors connected to respective columns of the liquid crystal display that can be charged to store a signal to be displayed. The activation circuit comprises a number of blocks which each comprise a separate group of the columns forming the matrix of pixel elements, a corresponding number of column capacitors, and a plurality of data lines. The individual data lines receive respective signals and are connected to the column capacitors. A switch device is connected to each respective block for successively switching between the number of blocks.

Abstract: A method of and an apparatus for determining sound propagation speed in a medium which is subject to variations in this speed. A measuring tube containing the medium is energized by a loudspeaker (ultraacoustic transducers) with a controllable energizing frequency in resonance with the measuring tube containing a column of the medium to be evaluated. The resonant output frequency is detected and modulated with a low frequency signal and the mean value of the modulated output signal is formed and counted. For a predetermined count, the elapsed time is measured and from this value the propagation velocity is calculated.