DE2318071C3 - Circuit arrangement for correcting image errors in the case of highly saturated colors in a color television receiver - Google Patents

Description

^ r ^P ASL ^n,? i, Y \ ^ ^{color differentiation amplified and the} Gitterelektrocien 2Oi, 21b. 22b the

the on-screen erne strong color picture tube IO fed

lT SE ™ ** ^zur DieColourbildröhrelOeSugtd three electric beams

des Farbdifferenzs.gnals 20c, 21c, 22c, which refer to the the blue, green and red

ΪΪη Γΐ S5 ^en2er - ⁵ P ^ Phor points fall. These shine a blue one

which also emits the color difference - green and a red light, whereby by additive

^ate r! Ä ™ IRM a ■ λ ^ color mixing is generated, the color television picture!.

Embodiments of the invention are the subject matter of the The quality of the color image reproduction will vary

Underdevelopment affects _the most important of the _factors

J) UiCh the jJrfincmng W ₁ d achieves that fuzzy> o factors affect the demodulation properties of the color

which are in a highly saturated color of a demodulation block 30, d. i.e., the demodula

^Md f? ΙΛ? ⁶¹¹⁰⁵ ^ y ". In addition, axes of motion and the reinforcements of the demodulation

color errors are reduced. _{lators R} _ _Y ^ _G _y _{and 5} _ _{r as well as the} types of color

, ^ Ά -? k ^{nUn if- n} v ^We _T ^en A " ⁸ ® ** ¹ *" »*« of the red, green and blue phosphors (three primary

the invention described in more detail. In the drawings a ₅ colors) and the reference white of the color picture tube 10.

^lst JT? ^e , · «ι ι u. ^ MJ · In the NTSC standard, the colors are of the three

Fig. 1 is a block diagram of a normal color fera- primary colors and the reference white defined as follows: visual receivers,

2 shows a graphic representation of the color type red pnmar χ = 0.67, y = 0.33

the NTSC primary colors, the current primary colors _i0 £ ^{rün p!} [ ^imär * ⁼ °> ²¹ ' V = °' ⁷¹

and the chromaticity error, blue primary χ = 0.14, y = 0.08

F i g. 3 is a color diagram showing the chromaticity errors USfT "*? - £ 7 ^{0>31> y =} ° ^l316

shows caused by a color rendering system (white point »C«),

that the chromaticity errors according to FIG. 2 where χ and y are the coordinates of the 1931-CIE- (x, >>) -

_{a5 are} chromaticity diagram.

Fig. 4 shows an enlarged illustration of FIG. 3, These values are for an accurate colorimetric

Fig. 5 a graphical representation of the luminous display is necessary because the transmitted NTSC

Density components, which are carried along by the chrominance signal, are matched to the corresponding chrominance signals,

are used as a function of the normalized color. For the explanation of the theory it is assumed

amplitude, _{30 because} ß _the gain of the video amplifier 2

F i g. 6 is another graph of the one and that the reference white is obtained,

Luminance components of the color signal when the three electrode cathodes 20a, 21a and 22a

7 shows a block diagram of an embodiment with the same luminance signals with the same

a device according to the invention for improving amplitudes are operated and if the grating

the picture quality of a color television picture, ₃₅ electrodes 20b, 21b and 226 no color difference

F i g. 8 is a circuit diagram for an embodiment signals are supplied. Then instructs the NTSC

of the invention, demodulator the demodulators listed below

F i g. 9 shows a graphical representation of the axis of input lation and degrees of gain, so a

Output relationship in the circuit after the accurate colorimetric rendering is done when the

Fig. 8, 40 NTSC primary colors along with the reference white

F i g. 10 a circuit diagram for a different version of point »C« can be used,

form of invention,

F i g. 11 is a graph of the input-axis gain

Output relationship in the circuit according to the

Figures 10, 45

F i g. 12 a circuit diagram for another another Embodiment of the invention,

F i g. 13 is a circuit diagram for a further alternative embodiment of the invention and

F i g. 14 a circuit diagram for yet another 50

Embodiment of the invention. punching greatly improved and its brightness increased

The invention will now be described in detail, with the result that the types of color changed,

ben. The F i g. 1 shows a block diagram of a, The F i. G. 2 shows the types of color more modern

conventional color television receiver for the emp- phosphors compared with those of the NTSC-

catching NTSC television signals. _5S primary colors according to the 1960 CIE diagram for

The detector 1 derives a uniform chrominance from an IF signal (i-f).

a composite video signal. From this the F i g. 2 also shows the reproduced chrominance signal a luminance signal is cut off, in shifts of different colors when in place Video amplifier 2 amplified and the cathodes 20a, ^ er NTSC primary colors modern luminous substance 21a, 22a of the color picture tube 10 is supplied. 60 zen can be used. From FIG. 2 can be seen

The composite video signal becomes one that the modern phosphorus substances are very large

modulated color signal separated from the bandpass cause chromatic aberration.

limited amplifier 3 amplified and the synchronous These errors and deviations can be small

detectors 4, 5, 6 supplied. Be held in the synchronous detector if the said demodulator

ren 4, 5,6 the modulated color signal is demodulated 65 block 30 according to the theory of N. W. Parker different

and color difference signals (R-Y), (G- Y) and (B-Y) are set up, which in the document with the

singled out. These color difference signals are titled »An Analysis of the Necessary Decoder Correc-

of the relevant color difference amplifiers 7, 8, 9 for Color Receiver Operation with Non-standard

R-Y 90 ° 1.1474 G-Y 236 ° 0.7062 B-Y 0 ° 2.0458

R-Y 82 ° 2.0494 G-Y 246 ° 0.7461 B-Y 2 ° 2.4347

5 6

Receiver Primaries «is no longer used in IEEE Transactions on Broadcast. For the color reproduction "is therefore and Television Receivers, April 1966, is explained. an e _c of 1.5 to 2.14 (Q - 103 °) is not required, the required demodulation axes and the values which are only very detrimental to the modern phosphor strength levels for modern phosphors, as stated later below. This demodulator is said to be described as 5
"Modern phosphor demodulator" are called. In the NTSC system, if the y-value is the color image

tube, which represents its non-linearity, equals one,

Axis gain, the color signal has no luminance component

nents on. This becomes more constant as the "principle

ίο luminance «. Since, however, with the operating conditions the y-value of the picture tube is 2 to 3, the color signal contains a certain amount of luminance components, namely a larger proportion in the modern phosphor system than in the NTSC-Die F i g. 3 shows a comparison of the reproduced 15 systems.

Types of colors in two color rendering systems, whereby in FIG. 5 are the luminance components

the so-called »modern phosphor system«, which are contained in both systems in the color signal near phosphor substances and a modern phosphor on the red part (ie Θ =: - 100 °). After the phordemodulator, with the other, with "NTSC system" F i g. 5 is the ordinate normalized by the luminous system denoting the NTSC primary colors and an ao density component used over the luminance channel NTSC demodulator. is reproduced. In the NTSC system will be

In comparison with FIG. 2, the chromatic aberrations are essential to the luminance components contained in the color signal reduced. for accurate colorimetric reproduction

The F i g. 4 shows an enlarged illustration in the, however, required. The difference in luminance red district of the UCS diagram (uniform coloring components in the modern phosphorus system in art). The comparison to the NTSC system therefore consists of the

The parameters e _c , Q ₀ in FIG. 4, luminance deviations are defined as follows for the one shown: Color. The greater e _c , the greater the luminance

Deviations will occur in the NTSC composite video signal Em , as shown in FIG. 5 can be seen in terms of equation 30. The luminance errors are extraordinary

lich large in the range of 2.14 ^ e _c > 1.5. This

Em = Ey + Ec sin (2 π fet + Q ₀ ) , (1) large errors in the red color can do that again

given red appear much brighter than that

being original red and being viewed by a viewer

Ey the luminance signal, ^{35 perceived as a} preference for the red color.

Ec is the amplitude of the color carrier. In addition, the subjective sharpness is reduced

Qc is the phase angle of the color carrier and ^{the images with red} color, since the broadband

fc the frequency of the color subcarrier is luminance channel reproduced luminance a

details are covered by the large luminous

Equation (1) can also be written as 40 density components, which are over the narrowband color: channel are transmitted. With a conventional

Color television receivers will therefore improve the quality of the image containing an E _M = Ey [I + e _c sin (2π fet + & c)], (2) highly saturated red in the

Playback extremely badly affected.

where e _c = E _c / E _{u is} the so-called normalized am- 45 Apart from this, the greatest defects are the amplitude of the color carrier. The saturation and that caused by the unnecessary part of 2.14 ^ e _c = l 5 hue of the reproduced colors become essentially, that is, a noise disturbance that is determined by e _c or from 6> «in the case of highly saturated colors. Red occurs and is referred to as "color noise disturbance"

That can be modulated corresponding to the red color.

Color signal that is generated by a conventional color generator, assuming the noise component e "(f) sin generator, has the value 2.14 [2 π fc t -f Q (r)] for e _c , the color signal e _e sin (2 π and for 6> _c the value 103 °. From Fig. 4, fet + 0 _C ) is added, where e _n (i) are the moments to see that the pure red (i.e. the saturated red), amplitude of the noise and 0 (r) of the instantaneous color of the NTSC primary red, the phase angle of the noise is The noise composite NTSC system at e _c = 2.14 and Q _c = 100 ° (== 103 °) 55 nent can be described as follows:
reproduced. With the modern phosphorus system

on the other hand it becomes pure red with the chromaticity of e "sin \ 2nfct + Q (t)]

modern red phosphorus with relatively small- _{= e <s} j _n η π fc t + QA 4- e cos (2 η fc t a- ö ϊ

rem e _c of 1.5 reproduced, and in the larger e _c «a ^« each 1 + w _c ) + e _v cos {2nfct + 6> _e ),

District from 1.5 to 2.14 there is no change to the 60. (3)

Color type with the red color. Is at Q _c the value ^where

of e _c greater than 2.14, then according to the NTSC-Sy- ~ 1 _ ~ _ -57,

stem no color are emitted whose saturation is ^{C <} ~ ^e "~ ^e "'

is greater than the NTSC primary color red. is.

The transmitted NTSC signal contains color composite ₅ The first printout on the right side of the

elements of 2.14 * _Ct > ₌ 0 at 0 = 103 °. In equation (3), the in-phase noise component represents

modern phosphor system will represent the emitted component of the emitted color signal while

signal of 2.14 £ e _c > 1.5 for the color rendering, the second expression shows the phase-deviating noise

7 8

component represents. The synchronous detectors 4, 5 The invention is based on the above

and 6 is therefore supplied with the following voltage: Determinations.

The F i g. 7 is a block diagram for an output

{e _c + ei) sin (2 nfc t + & _c ) implementation of the invention and leaves the general

+ e _g cos (2nfet + 0 _C ). (4) ^{Recognize 5} thoughts on which the invention is based.

The said modulated color signal is the syn-

If one denotes the relationship between the chrondetektor 4 fed to the input terminal 4a,

normalized amplitude e _c and the in Fig. 5 The synchronous detector 4 synchronously demodulates the mo-

reproduced luminance-component-modulated color signal and generated at the output terminal

ten with F (e _C) 0 _c ). the called color difference signal, which is the non-linear

Color channel a noise component Y _n reproduced acting treatment device 15 is supplied,

according to the equation: in which the amplitude of the unnecessary part of the color difference signal is reduced. The signal detector

id) 14 has two input connections 14a, 146, where

—— [y (cc, 0c)] y % ^e i 15 the input terminal 14 a the color difference signal

" ^e " J ^tc ~ ^ec from a signal source such as the synchronous

r Q ι detector 4 is supplied, while the other

+ <- - [Y (e _c , Θ, + 90 °) H Xe, (5) input terminal 146 outputs the luminance signal

\ " ^ee JCc = O of a signal source such as the one mentioned above

ao video amplifier 2 is fed.

as a result of the smaller amplitudes of ei and e _v im The signal detector picks up the special part of the

Compared to e _c . Color difference signal out of the described

The F i g. 5 shows the relationship Y (e _c , Θ _ο ) when causing image deterioration. That from detector 14

Oe = 100 °, while FIG. 6 the relationship generated output signal will operate nonlinearly-

Y (e _c , 190 °) shows the phase angle of 90 ° against as the treatment device 15, in which the

the phase angle according to FIG. 5 is offset. After the amplitude of the color difference signal is decreased,

6, the next expression can be written. The output from the processing device 15 is

are as an equation: amplified by the color difference amplifier 7 and to

{. Color picture tube 10 passed, the now images with strong

-—- [Y (e _c , 190 °)] i = 0. 3o of improved quality.

de _c 'Jc = O The F i g. 8 shows the circuit diagram of an embodiment

form of the invention. The boxes in the drawing

Equation (5) can therefore be converted as follows to that in FIG. 7 with the same

write: add reference symbols. The ones with interrupted

t i \ 35 line bordered circuit exercises the function of

Y _n = \ [y (e _e . 100 °)] l xci. (6) Signal detector 14 and the non-linear acting

[de _c each _f = e _c treatment facility 15 from. That from Synchion-λ j ^ .- i. / "TNI.!. joj-r> ι. From equation (6) it can be seen that the noise is _{fed to the input} terminal 55 and from the transtorung F _n proportional to the gradient _{+0 sistor} 50 _{ν6Γ8ΐ & Γ} ^ _The amplified color difference signal r, $ Ι occurs at the load resistor 51. The diode 52, the \ - - [Y ( ^e c, 100 °) H forms a known clipper circuit, is i ^c J between the collector electrode 56 of the transistor 50 and the connection point between the cons-the steeper the gradient of the curve F in Fig. 5 45 stands 53, 54 switched, as shown. The resistance, the greater the noise interference, which is reproduced via the levels 53, 54 causing a division of the voltage E _cc , color channel. whereby at said connection point an equal-out of FIG. 5 the conclusion can be drawn, voltage V ₀ , is. Is the voltage of the color that the color noise interference with a modern difference signal at connection point 56 is low! Phosphor system is always greater than in the NTSC-5 ° as the voltage F _n so flows through the diode 52 keil system, and strong color noise changes with current, the normal gain of the transistor causes the modern phosphor system if 50 is maintained. Exceeds the Verbin at a fairly highly saturated red color (that is, e _t! Greater ground point 56 voltage applied to the color difference than 1.5) is emitted. signals the voltage V _a , the diode 52 will conduct. The above explanations therefore suggest that the degree of gain of the Tran is reduced to the part of the color difference transistor 50 that is not required, since the load resistance 5 is derived from the transmitted signal NTSC signal in one of the resistors 53, 54 is bridged to remove the color television receiver, which is equipped with the result that a certain part of the color modern phosphor system is equipped to produce a differential signal of a fairly large amplitude the lack of annoying color noise interference, the 60 has, cut off, whereby the image quality is improved by subjective reduction in sharpness and large. The level of the voltage V _a can be corrected by means of luminance errors. the value of the resistor 54 to the appropriate value, although so far only those for the red color have been set. The degree of amplification, de emerging difficulties were dealt with, as determined by the conductive state of the diode 52, the above remarks apply equally, can also be determined by suitable dimensioning of the wide dimensions for the colors blue and natural. Adjust stands 53, 54 for this purpose. In order to achieve the most favorable simplification of the description, however, it is preferred that the degree of amplification is limited to the color red. about 5 to 6 dB reduced and the threshold)

9 10

value of K “measured a little higher than absolutely necessary. Voltage characteristics of the diodes 108 and 117 in-These relationships are shown in FIG. 9 shown. other are the same. The resistors 109, 118 are used. FIG. 10 shows the circuit diagram for another embodiment of the invention for protecting the diodes 108, 117 and the transistors 5 streams. Capacitors 110 and 119 represent what FIG. 11 is shown. Explanations of the working coupling capacitors. The transistors 111, like this circuit, are not necessary 114 and the resistors 112, 113, 115 form, since both circuits according to FIGS. 8 together a differential amplifier, which operates a differential 10 in a similar way. In the circuit voltage generated, which at the collector electrode according to FIG. 10, two clipper circuits io of the transistor 111 lying voltage (K ₈ -F ₁ ) are used, of which the one circuit from the is proportional.

Diode 52 and the resistors 53, 54 consists with the at the collector electrode of the transistor 111 a threshold value level K ₀ , while the other lying voltage can therefore be expressed by the following circuit from a diode 60 and the resistors equation:
61, 62 with the threshold level Vb . With 15

the circuit according to FIG. 10 is a smoothing "(K. - K) = -λ fc _e log ^ ~ ^Er '

and effective reduction of the reinforcement level ⁶ Ey '

reached and prevented by a sudden

Reduction of the gain by the circuit where λ is a constant that determines the gain according to FIG. 8 shows the reproduced image deterioration ao of the differential amplifier. The tension tert. «(K ₂ - * Ί) is fed to transistor 120. On

In the circuits according to FIGS. 8 and 10, a bias voltage Va no luminance signal for controlling the amplitude, which represents the threshold voltage and is used to reduce the color difference signal, is applied to the resistors 121, 122. How to put emitter electrode of transistor 120. The from the F i g. 4 and 5 it can be seen that the down- As transistor 120 is a pnp transistor; the amplitude will be set if the normalized base voltage, which consists of the signal α (Kj-K ₁ ) and the sized amplitude e _c - E _c / E _v instead of the non-equal voltage as the base bias, normalized amplitude E. _e than the threshold voltage V ₀ ', it is exceeding the certain threshold lenwert lower. In order to theoretically achieve a more accurate transistor 120 conducting and amplifying the input work, e _c must signal out instead of E _e. The base bias of transistor 120 can be grasped. is canceled when transistor 120 becomes active,

Fig. 12 shows the circuit diagram for a further when the absolute value of A (Kg-K ₁ ) the different embodiment of the invention which exceeds the correct threshold value. If this absonormalized amplitude e _{e is} tapped. It will be equally important
pointed out that the normalized subcarrier amplitude e _c 35

by the normalized color difference signal, such as (Äs— Ey) I «fc ₀ log [(Er- Ey) / Ey] ,

Ey can be replaced because E _c corresponds to the value {Er — Ey)

corresponds, where (Er-Ey) the (R- Y> color difference- so the transistor 120 demodulates that part of the signal and Ey the luminance signal

Synchronous detector 4 generates the (R- y) -color difference- 40 log [(Er-Ey) IEy],

signal that the transistor 102 and the

Resistor 103 is supplied to the existing circuit part which is greater than the specific threshold value, will. Desirably, this threshold value is intended to

The transistor 104 amplifies the color difference signal, special normalized amplitude e _c of approximately that in the conventional manner over the color 45 correspond to 1.5 for example,
differential amplifier 7 is supplied to the color picture tube. If the transistor 120 has a high gain, the said color difference signal is above the degree and if the transistor is conducted via the threshold input terminal 14a to the transistor 107, the value K "'is operated, the transistor is caused by the diode 108 a current propor- immediately conductive and thus saturated,
tional to the color difference signal (Er-Ey) flows. 50 is connected to the collector electrode of transistor 120

Between the current flowing through the diode / therefore a positive voltage K _0n . Otherwise lie! and the voltage K across the diode, there is zero voltage at the collector of the transistor. Diode 124 is reverse biased when the

Collector voltage of transistor 120 has the value NuI K == fc ₀ l ° g J + ^ i »55, so that transistor 104 does not affect

will. With a collector _voltage of K 0n, di <

where fc ₀ ^un <i ^ i are constants. The diode 124 is conductive and, as a result of the parallel, the voltage is applied: connection of the load resistors 105 and 123 dei

Gain of transistor 104 down. Öii K ₁ = fc ₀ log (Er-Ey) + Ic ₁ . 60 Desired reduction in the amplitude of the color

differential signal is therefore achieved at [(Er-Ey) IEy]

Furthermore, via the input connection 14 ft dem, ie when e _c exceeds the particular value.
Transistor 116 is supplied with the luminance signal Ey. The in the F i g. 12 is the circuit shown

The voltage at diode 117 is rather complicated; Figure 13 shows the block

65 circuit diagram of a further different embodiment K ₂ = fco log Ey + Ic ₁ . of the invention, which is somewhat simplified.

As is easy to see, the value of voi becomes. In this case, it is assumed that the greater the current- [(Er-Ey) JEy] , the larger (Er-Ey) and j

little Ey becomes, and vice versa. Instead of [(Er-Ey) IEy] , the value [{ Er-Ey) -Ey] can therefore be used to demodulate the signal part which controls the non-linearly acting treatment circuit. The circuit shown in FIG. 13 is based on this principle. The in the F i g. 13 outlined circuit parts correspond to those in FIG. 12 with the same reference numerals provided circuit parts, so that their operation need no longer be described.

The transistor 130 receives the color difference signal {Er-Ey) from the transistor 102. The transistor 131 is supplied with the luminance signal Ey via the input contact 146. The transistors 130, 131, together with the resistors 132, 133 form a differential amplifier that generates the differential signal

generated at the collector electrode of the transistor, where «is a constant. The pnp transistor 120 becomes conductive when the absolute value « [{Er-Ey) -Ey] exceeds the threshold value determined by the resistors 121, 122, as has already been done in connection with FIG. 12 described. If transistor 120 becomes conductive, diode 124 also becomes conductive. In this case, the load resistor 105 of the transistor 104 is bridged by the resistor 123 and the gain of the transistor 104 is reduced. In this way the desired reduction in amplitude is achieved

Fig. 14 shows a circuit of still another embodiment of the invention. The transistor 171 receives the {R- p color difference signal from the synchronous detector 4. The collector electrode of the transistor 171 is connected to the diode 160 and the resistor 161 through the coupling capacitor 161. Since the value of the resistor 161 is very large, the load resistance of the transistor 171 can be regarded as consisting of the resistor 172 when the diode 160 is non-conductive. If the transistor 156 is non-conductive, the DC voltages at the connection points 164 and 192 are equal to the supply voltage £ _c «. Since the threshold voltage across silicon diode 160 is approximately 0.7 volts, diode 160 is non-conductive when the color difference signal at junction 164 is positive or slightly negative. On the other hand, the diode 160 becomes conductive if the junction point 164 is supplied with a negatively directed color difference signal which exceeds the threshold value. In this case the resistor 172 is bridged by the resistor 190 and the gain of the transistor 171 is reduced. This mode of operation is similar to the mode of operation of the circuit Θ according to FIG. 8. The circuit according to FIG. 14 is shown in FIG. 8 shown as box 14.

The input terminal 146 receives the luminance signal supplied with a sync pulse, which is supposed to be directed negatively. The condenser 151 forms together with the diode 152 a clamping circuit, which the DC voltage component of the luminance signal restored. The luminance signal is fed to transistor 156 via resistors 153, 155 supplied. The resistor 153 separates the clamping circuit from the next stage, so that the Clamping circuit can work precisely. The transistor 156 forms a high gain amplifier with the load resistors 190,192 and with the preload diode 157. The diode 157 forms together with the base-emitter connection of the

Transistor 156 is a threshold element. If the luminance signal applied to the base of transistor 56 exceeds the threshold value of the threshold value element, the transistor 156 is conductive, since the from the Transistor 156 has a high gain. Then the collector voltage reaches at transistor 156 the value of approximately zero volts. The voltage at the anode 192 of the diode 160 then drops, and diode 160 is biased in the opposite sense. This means that the threshold of diode 160 increases so that the diode remains non-conductive even if a negative large color difference signal of the cathode 164 of the diode 160 is supplied. Diode 158 protects the transistor 156 together with the resistance 155 against

ao oversaturation, as is known per se. Exceeds the luminance signal exceeds the certain threshold value, so that the transistor 156 becomes conductive, one can use the Describe the mode of operation of the diode 160 as follows:

Color difference luminance diode 160
signal signal

_v1 . ■. _t .

negauv grou ^

S ¹⁰ ^ locked

locked _small

negative small
or positive

spem

It can be seen from this that the diode 160 only becomes conductive when the color difference signal is negative large amplitude and the luminance signal has a small amplitude. The degradation of the The amplitude of the color difference signal therefore occurs if the reproduced color image is relatively dark (corresponding to a small luminance signal) and is heavily saturated with red. This is a consequence of the fact that the negative ^ directed

Color difference signal at said connection point 164 amplifies the red beam current in the picture tube as a result of the polarity reversal in the color difference amplifier 7. This effect in FIGS. 8 and 10 have been omitted for the sake of simplicity of description. In this way the special part of the _{capital e} becomes e [corresponding to a capital {Er-Ey) JEy

or a large {E — E) —E] effectively and more easily singled out.

As can be seen from the description above is, the device according to the invention causes an effective reduction in color noise, one Elimination of the luminance errors and an improvement in image sharpness, which is the case with highly saturated Colors appear in a conventional color television receiver.

The circuits described above cannot only be used for the {R— y) color difference channel, but also for the (G- Y) and the {B— Y> color difference channels. Although the above description relates to the NTSC system, the invention can, however, be adapted to the PAL and the SECAM systems as well

In addition 9 sheets of drawings

Claims (5)

ι 2 of the picture and an extraordinarily strong preferential claim: a certain color arises. '. The noise interference can be caused by various 1. Circuit arrangement for correcting transmission errors on transmission lines and Image errors in highly saturated colors in a S the receiver in a color television system ver-Farbferasehempfänger, be identified by this. Sometimes the reproduced image is shows that a signal detector (14) with two more saturated than the original image scene, there Inputs for a color difference signal and that on the transmission line fluctuations of the Luminance signal a certain amplitude transmission properties occur. part of the color difference signal picks out, which on io DT-OS 20 15 588 describes an automatic Creates a highly saturated color on the screen, hue and saturation correction for color television a control signal to reduce the receiver, which is able to detect fluctuations in the Derives the amplitude of the color difference signal and compensates for the transmission properties of lines The non-linear working limiter circuit and the saturation of the reproduced color (15), which also keeps the color difference signal 15 constant. This arrangement can consequently is fed. reduce the noise that occurs in an un- 2. Circuit arrangement according to / claim 1, the necessary increase in saturation in the case of power loss, characterized in that the signal detector (14) signals from transmission lines occur. In color television receivers consisting of a first device (108, 111, 114, 117) , however, there are still others, which have a normalized color difference signal and noise interference. by dividing the color difference signal by the US-PS 35 78 903 shows a control circuit, Luminance signal generated, as well as from a second to avoid the picture tube color saturation Establishment (120,121,122) that lets with the establishment that occurs when the load demands on the (108, 111, 114, 117) is connected and those deflection circuits over-radiation, ie overdrive Part of the normalized color difference signal determined, 35 at bright image areas, cause that exceeds a certain threshold. Furthermore, the US-PS 32 42 259 shows an arrangement 3. Circuit arrangement according to claim 1, with the result that the noise behavior of color television characterized in that the signal detector (14) enhances receivers with line phosphor picture tubes leaves a special portion of the luminance signal, and it is the purpose of this arrangement that singles out a certain threshold value 30 effects of noise when receiving exceeds, and generates a control signal that the black and white images and when receiving signals non-linear working limiter circuit (15) to improve one with weak color content, which by has a different threshold value and the amplitude the malfunction of circuit parts - like both Color difference signal, which the other thresholds - for example unnecessary impedance changes - cause exceeds, decreases if no control signal 35 are gentle. This three references concern the improvement difference signal despite approaching the other tion of noise interference, which is not reduced by the anomalous threshold value, if the or incorrect behavior of the transmission line Control signal is supplied. or the recipient. It has, however 4. Circuit arrangement according to claim 1, shown 40 that with highly saturated colors also characterized in that the non-linearly operating noise sources remain when the over-limiter circuit (15) a shunted line and the receiver are working properly, which has the load resistance (51) of a. Color difference amplifier responsive to the television system having a transmission line and Control signal bridged. 45 contains a Farbferoseh receiver and after 5. Circuit arrangement according to claim 1 and 2, prior art works completely error-free, at characterized in that the non-linear, highly saturated colors are nonetheless noise interference tend limiter circuit (15) and the signal occur. These difficulties are not yet detector (14) consist of clipper circuits. been addressed. 50 In recent years, the luminous efficiency of phosphors has been continuously improved, which has led to a change in the types of colors. Accordingly, the receiver's color demodulator had to be redesigned to be more faithful 55 color rendering. This change to the The invention relates to a circuit arrangement for color demodulator which increases the noise interference to correct image defects in highly saturated, highly saturated colors, as detailed below Colors in a color television receiver. is explained. In known television receivers, it is consequently the task of the present inventor to appear saturated color, for example with red or 60 dung, to specify a circuit arrangement that is used in Blue, noise interference, and since this interference in a color television receiver image errors when strong horizontal direction on the screen can correct color saturation, which are large as noise, the image quality will be considerably impaired, even in the best known receivers pregnant. occur and mainly from the color demodulator Besides the noise interference diminishes at 65 being generated. Saturated color the sharpness, and color errors occur. This object is achieved according to the invention on, whereby when looking at the picture the impression is solved that a signal detector with two inputs for a reduced sharpness in the very bright parts a color difference signal and the luminance signal