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US 2002/0000952 A1Published application
Method and circuit arrangement for controlling the operating point of a cathode ray tube
AssigneeSiemens Aktiengesellschaft
InventorsKlaus Burkhardt, Uwe Nagel, Erich Schaefer, Hartmut Schulz
Life of this patent
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Abstract
A method and a circuit arrangement for controlling the operating point of a cathode ray tube (30) for use in image technology applications. A video signal (10) is supplied to both the tube (30) and to a cathode ray tube model (20), which the model (20) uses to emulate a beam current. From the emulated beam current and a measured beam current, a characteristic quantity for adjusting the operating point is determined.
Claims9
Method for controlling the operating point of a cathode ray tube, to which a video signal is supplied and which includes a control grid that applies a control voltage from an adjusting unit for adjusting the operating point, comprising:
- a) during a calibration phase using a test image for a set operating point with different brightness and/or contrast values:
- supplying a test video signal to a cathode ray tube model and to the cathode ray tube;
- determining an emulated beam current from the video signal using the cathode ray tube model,
- measuring a beam current of the cathode ray tube, which is proportional to the video signal,
- calculating first characteristic quantities from the measured beam current and the emulated beam current,
- storing said first characteristic quantities calculated from the measured and emulated beam currents in a memory location,
- b) during normal operation, when the cathode ray tube is controlled with picture signals:
- supplying a picture video signal to the cathode ray tube model and to the cathode ray tube;
- determining an operational beam current from the picture video signal using the cathode ray tube model,
- measuring an operational beam current of the cathode ray tube, which is proportional to the picture video signal,
- calculating second characteristic quantities from the measured operational beam current and the operational emulated beam current;
- comparing the second characteristic quantities with the first characteristic quantities stored in the memory, and
- adjusting the control voltage until the second characteristic quantities substantially match the first characteristic quantities stored in the memory during the calibration phase, as a function of said comparison.
10 more elements
A circuit arrangement for controlling the operating point of a cathode ray tube, to which a video signal is supplied and which includes a control grid that applies a control voltage to the cathode ray tube, said circuit arrangement comprising:
- a cathode ray tube model that (a) determines an emulated beam current from a test video signal during a calibration phase using a test image for a set operating point with different brightness and contrast values and that (b) determines an operational emulated beam current from a supplied video signal during normal operation;
- an arithmetic unit that (a) calculates first characteristic quantities during the calibration phase from a measured beam current value and the emulated beam current, which is proportional to the video signal, and that (b) calculates second characteristic quantities during the normal operation from an operating measured beam current and an operating emulated beam current, which is proportional to the video signal;
- a memory for storing the first characteristic quantities,
- a comparator for comparing the second characteristic quantities determined during the normal operation with the first characteristic quantities stored in the memory during the calibration operation, and
- an adjusting unit that adjusts the control voltage until the second characteristic quantities substantially match the first characteristic quantities stored in the memory.
2 more elements
A device, comprising:
- a cathode ray tube;
- a control grid for applying a control voltage to said cathode ray tube;
- a high voltage generator for inducing an anode voltage at a point on said cathode ray tube, which causes a beam current to flow inside said cathode ray tube;
- a first integrator for integrating the beam current over an image cycle;
- a cathode ray tube model for generating an emulated beam current;
- a second integrator for integrating the emulated current over the image cycle;
- an arithmetic unit for determining first and second characteristic quantities in the form of respective quotients of the measured beam current and emulated beam current, wherein the first characteristic quantities are determined during a calibration phase and the second characteristic quantities are determined during normal operation of said cathode ray tube;
- a memory location for storing the first characteristic quantities;
- a comparator for comparing the second characteristic quantities with the first characteristic quantities stored in said memory location;
- and
- an adjustment unit that adjusts the control voltage in said control grid so that the second characteristic quantities substantially match the first characteristic quantities stored in said memory location.
8 more elements
A method for controlling the operating point of a cathode ray tube, comprising:
- supplying a video signal to a cathode ray tube;
- applying a control voltage to an adjustment unit for adjusting the operating point;
- inducing an anode voltage at a point on the cathode ray tube using a high voltage generator, which causes a beam current to flow inside the cathode ray tube;
- integrating the beam current over an image cycle to produce a measured beam current;
- generating an emulated beam current using a cathode ray tube model;
- integrating the emulated beam current over one image cycle;
- calculating first and second characteristic quantities as respective quotients of the integrated measured beam current and the integrated emulated beam current values, wherein the first characteristic quantities are determined during a calibration phase and the second characteristic quantities are determined during normal operation;
- storing the first characteristic quantities in a memory location;
- comparing the second characteristic quantities with the first characteristic quantities stored in the memory location;
- and
- adjusting the control voltage so that the second characteristic quantities substantially match the first characteristic quantities stored in the memory location.
8 more elements
Dependencies are inferred from the claim text.