Television – Monitoring – testing – or measuring – Testing of image reproducer
Reexamination Certificate
1999-09-30
2003-06-24
Lee, Michael H. (Department: 2614)
Television
Monitoring, testing, or measuring
Testing of image reproducer
C348S807000, C348S181000
Reexamination Certificate
active
06583814
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to digital convergence or raster correction on the screen of a television receiver, particularly a projection television, and more particularly to an indicator or cursor for locating a position for manual adjustment of digital convergence.
Raster correction is generally used for the adjustment of parameters such as screen deflection, north-south of, or east-west distortions, pincusion distortions, non-linearity of deflection and other picture geometry faults in the horizontal and vertical directions. A particular field of application is convergence adjustment with a projection television receiver in which three monochromatic pictures are projected onto a screen by three picture tubes, one for each of the three primary colors. It is to be understood that as used herein a television receiver means any type of device having an electronic screen (raster) mode of picture reproduction. The device can be fed with a television broadcast signal or also purely as a monitor controlled by a RGB signal, a CSCC signal or separately with the luminance signal and color sub-carrier of any video signal source.
It is known in the art that a grid pattern of horizontal and vertical white lines is displayed on the screen forming a number of crossing points uniformly distributed over the screen. A certain crossing point of the raster design can be marked with a faded-in cursor and a particular deflection parameter of a selected point of the picture can be evaluated and a correction value for the point can be determined. The cursor fulfills two functions. The first function is the marking of the position of the portion of the picture for which the correction is required. The second function indicates whether or not correction is necessary and the extent of the correction needed.
In the prior art cross-shaped cursors are known. During convergence correction these cursors are set to a crossing point of the lines in such a manner that the cursor becomes coincident with the horizontal and vertical lines. In order that the cursor can be distinguished from the lines of the pattern it is known by JP-A 55 16 3980 to render the brightness of the cursor different from the brightness of the grid pattern. A further approach causes the cursor to become blinking. However all these solutions suffer from considerable drawbacks.
It has become evident that with a cursor with a brightness higher than the grid pattern a lack of definition can occur by defocussing; the cursor can even effloresce whereby the exact adjustment of the convergence is made difficult by the view of the cursor.
In order to avoid the above drawbacks it was proposed in U.S. Pat. No. 5,214,499 to use a cursor having a brightness inferior to the brightness of the grid pattern. This solution ensures that the presentation sharpness for the cursor on the screen is sufficient and that the adjustment of the convergence by view to the cursor can be performed with high accuracy.
In case the adjustment of convergence has to be performed automatically by means of a video camera it should be ensured that the brightness of the cursor and the brightness of the grid pattern differ by a factor of about 2. In connection with the last-mentioned solution it is necessary therefore to present the grid pattern with a very high brightness. This represents a heavy load for the high voltage supply sources for the individual picture tubes to a greater extent than during normal operation of the television device. As the adjustment of convergence is dependent also on the loading of the high voltage source it is impossible to achieve in this manner a convergence adjustment being optimal for normal operation.
When using a blinking cursor the periodic change between ON and OFF of the cursor is felt unpleasant during adjustment of convergence. With an automatic adjustment of convergence by means of a camera the camera has to be synchronized to the blinking of the cursor whereby hardware becomes more complex. A blinking cursor or a cursor with temporarily varying brightness therefore is not suitable for practical purposes.
Furthermore it is possible principally to present the cursor with a color different from the color of the grid pattern which normally is represented in pure white color. With a grid pattern in pure white color a faulty convergence adjustment is noticeable by colored edges which however can be noticed best at a pure-white cursor.
In a digital convergence system convergence values are determined for each display color and applied at an array of points located at intersections of an alignment grid superimposed, for example, on a black background. Alternatively, the background can be gray or shaded. In a manual digital convergence system a user may manually adjust deflection parameters at the grid intersections, in either or both horizontal and vertical scan directions, to superimpose individual colored lines to form a white grid on the black background. These adjustment values are then stored for each grid intersection and subsequently read out to provide a converged display image. During the convergence adjustment process the alignment grid display must be stable and free from transient geometric distortions, for example, resulting from instability of deflection fields forming the scanned raster, or raster size variation due to power supply loading effects causing the cathode ray tube (CRT) ultor or high voltage supply to vary.
In a CRT display, image brightness is directly related to the scanning beam current, where the darkest area represents the smallest current and the brightest area represents the greatest beam current. Thus it may be appreciated that the beam current varies dynamically at video frequency rates. It is well known that a scanned raster size is inversely proportional to the square root of the high voltage or EHT applied to the wall anode of the CRT. Hence, if the high voltage supply exhibits poor voltage regulation with beam current variation, the high voltage value will vary in response to the displayed image brightness, typically dropping with increasing beam current. As a result, the scanned raster size will vary, particularly in the area of any high brightness image content. It may further be appreciated that brightness modulation of the raster size is undesirable not only during normal image display, but also during convergence alignment where brightness modulation results in convergence errors.
SUMMARY OF THE INVENTION
In accordance with inventive arrangements a system for adjustment of convergence is provided enabling an optimal adjustment of convergence and also enabling the automatic implementation of adjustment of convergence. The cursor advantageously is formed by at least one irregularity of the grid pattern.
Automatic systems for picking up pictures require high differences in brightness between the individual objects for ensuring satisfactory operation. Contrary to this, however, irregularities within a pattern having no irregularities otherwise and having a brightness being variable within far limits are very easily noticeable by automatic systems for picking up pictures. Applying this recognition to the convergence correction in a television device yields the advantage that the brightness of the indispensable grid pattern can be adjusted in such a manner that the high voltage source is loaded only in such an extent which is typical for normal operation. In this way one of the important conditions for achieving optimal adjustment of convergence within normal operation mode is fulfilled.
According to one embodiment of the inventive arrangements the irregularity within the grid pattern is formed by an additionally represented element, e.g. by an additional line. The irregularity however can also be formed by omitting a portion of the grid pattern. This can be achieved for example by providing interruptions within one of the lines forming the grid pattern. In case only a single irregularity is provided within the grid pattern the position of the cursor is defined by the position of
George John Barrett
Gleim Günter
Heizmann Fredrich
Runtze Albert
Fried Harvey D.
Kolodka Joseph J.
Lee Michael H.
Thomson Licensing SA
Tripoli Joseph S.
LandOfFree
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