Television system having aperture correction

Abstract

In a color television camera system of the type having camera tubes for the production of red, green and blue color signals, contour signals derived from only one of the color signals are added to all of the color signals.

Description

The invention will be described more fully by way of example with reference to the following embodiments.

FIG. 1 shows a first embodiment of a color television system according to the invention and

FIG. 2 shows a second embodiment.

Referring to FIG. 1, the camera tubes 1, 2 and 3 produce the color signals green G, red R and blue B respectively. These color signals are obtained by projecting, in a manner not shown in FIG. 1, the particular color component of the image to be transmitted onto each target plate of the camera tubes 1, 2 and 3, these three target plates being simultaneously scanned by the respective electron beams. The camera tubes 1, 2 and 3 supply the color signals, G, R and B to conductors 4, 5 and 6 respectively. In connection with the aforesaid choice of the color signal G for deriving the contour signal, the conductor 4 applies the color signal G to the means 7 for deriving the contour signal. This contour signal is supplied by means 7 to the conductor 8, whereas the conductor 9 conveys the green color signal G. Then the contour signal of the green signal G is applied through the conductor 8 and the color signals G, R and B are applied through the conductors 9, 5 and 6 respectively to summation devices 10, 11 and 12 and are added therein. From the output of each summation device 10, 11 and 12 there can be derived the aperture-corrected color signals G.sup.x, R.sup.x and B.sup.x. It will be obvious that this diagram may include further elements such as amplifiers, non-linear parts, filters and, if desired, delay lines and so on. When gamma correction is applied to the color television system, very good results are obtained on the display screen by deriving the contour signal from a non-gamma-corrected color signal and adding it subsequently to the gamma-corrected color signal.

The elements shown in FIGS. 1 and 2 are designated by the same reference numerals. The color signals G, R and B are applied through the conductors 9, 5 and 6 respectively to a matrix network 13, in which the brightness signal Y is composed. The contour signal derived by the means 7 from the green color signal G is added through the conductor 8 in the summation device 14 to the brightness signal Y. At the output of the summation device 14 appears the aperture-corrected brightness signal Y.sup.x.

The means 7 for deriving the contour signal are shown in detail in FIG. 2. By means of storage tubes an integral aperture correction may be obtained in the line direction and in the direction at right angles thereto. If delay lines with separate aperture correction of the vertical and horizontal directions are used, a diagram as shown with the contour signal deriving means 7 in FIG. 2 is employed. The contour signal in the vertical direction is provided by a means 15, while a means 16 is used to generate a contour signal in the horizontal direction so that through the summation device 17 the total contour signal is applied to the conductor 8 and hence, to the luminance signal by adder 14.

In detail, the vertical contour signal generator comprises delay lines 20 and 21 each having a delay of about one line period, i.e., 64 microseconds. The undelayed and twice delayed signals are added together by adder 22 and the resultant sum subtracted in subtractor 23 from the once delayed signal. The result is a vertical contour correction signal that is delayed by about 100 nanoseconds in delay line 24, and then applied to one input of adder 17.

Similarly, the once delayed signal from vertical generator 15 is twice delayed by about 100 nanoseconds each time by delay lines 26 and 27 in horizontal contour signal generator 16. The undelayed and twice delayed signals are added in adder 28 and then subtracted from the once delayed signal in subtractor 29. The resultant horizontal contour correction signal is then applied to adder 17, the output of which is said total contour signal. A delayed green signal is applied through conductor 9 to said matrix 13.

It will be obvious that aperture correction may also be used in one direction within the scope of the invention.

The color signals G through the conductor 9 will have a time delay, because of delay lines 20 and 26 with respect to the color signals R and B through the conductors 5 and 6. By means of a delay line in each of the conductors 5 and 6 the short difference in time in the horizontal direction and the time difference, for example, one line period, in the vertical direction may be eliminated, since this delay becomes manifest on the display screen in a shift of the green field with respect to the red and blue fields. By using interlacing in composing the picture on the display screen, this shift at right angles to the horizontal direction is distinctly visible. The shift of the fields may be obviated in a simple manner by shifting the scan of the target plate by the electron beam in the green camera tube 1 with respect to the scans in the red and blue camera tubes 2 and 3 respectively. With interlacing this means that in the vertical direction, the electron beam of the green camera tube 1, scans the line (n+2) at the instant when in the red and blue camera tubes 2 and 3 in the line n is scanned. Moreover, the delay in the horizontal direction can be corrected by a similar small shift in the horizontal direction over at least one image point.

As stated above, the contour signal is derived from the green color signal only by ay of example, since this signal provides the greatest contribution to the brightness signal. The principle of the invention with its advantages may be applied, thought with less effective results, when the contour signal is derived from the red or the blue color signal.

Claims

1. A color television system comprising means for producing potential images corresponding to each of three color components of an optical image and converting said potential images into color component signals, means to derive a delayed signal from one of said color component signals by comparing the color component signal with itself at substantially adjacent points of the potential image to thereby obtain a contour signal associated with said color component signal, and means for adding said delayed signal to all of said color component signals to sharpen transitions therein.

2. A color television system as claimed in claim 1 wherein said three color signals comprise red, blue, and green signals respectively and the delayed signal is derived from the green color signal.

3. A color television system as claimed in claim 1 wherein an output signal comprises separate color signals and the delayed signal is added to the individual color signals.

4. A color television system as claimed in claim 1 wherein said adding means adds said color signals to form an output signal and the delayed signal is added to the output signal comprising the sum of the color signals.

5. A color television system as claimed in claim 1 wherein said means for deriving a delayed signal comprises means for deriving both a horizontal and a vertical aperture correction signal.

6. A device as claimed in claim 5 wherein said delay means further comprises means for obviating said delay including means for shifting the scan of the signal source from which the delay signal is derived with respect to the scan of the remaining signal sources..Iadd. 7. A color television system comprising means for producing potential images corresponding to each of three color components of an optical image and converting said potential images into color component signals, means to derive delayed horizontal and vertical signals from only one of said color component signals by comparing said one color component signal with itself at substantially adjacent points of the potential image to thereby obtain a contour signal associated with only said one component signal, and means for adding said contour signal to an output signal which included all of said color component signals to sharpen image transitions therein.

.Iaddend..Iadd. 8. A color television system as claimed in claim 7 wherein said three color signals comprise red, blue and green signals respectively, and the contour signal is derived from the green color signal only..Iaddend..Iadd. 9. A color television system as claimed in claim 7 wherein said output signal comprises separate color signals and the contour signal is added to each of the individual color signals..Iaddend..Iadd. 10. A color television system as claimed in claim 7 wherein said output signal is a composite signal formed by adding said color signals in predetermined portions and said contour signal is added to said composite signal..Iaddend..Iadd. 11. A color television system as claimed in claim 7 wherein said delay means further comprises means for obviating said delay including means for shifting the scan of the signal source from which the delay signal is derived with respect to the scan of remaining signal sources..Iaddend.