DE1280915B - Process for suppressing the remanent magnetization of the shields or other components of television tubes of a color television camera and arrangement for carrying out the process - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

H04n

German KL: 21 al -34/11

Number: 1280915

File number: P 12 80 915.3-31 (C 37771)

Filing date: December 24, 1965

Opening day: October 24, 1968

The invention relates to a method for suppressing the remanent magnetization of the shields and / or other ferromagnetic components of television pickup tubes of a color television camera using a periodically changing removable magnetic field and an arrangement for carrying out this process.

With modern television tubes for black and white or color television, the focusing of the Electron beam achieved by means of a magnetic field, which is usually fed by a direct current Coil is generated. The deflection coils around the pickup tube are common provided with shields, which are intended to allow coupling of the coils with one another to avoid. All coils are further surrounded by another shield, which is a double one Purpose pursued, namely on the one hand to prevent disruptive scattering to the outside and on the other hand to protect the scanning tube from external magnetic and electronic interference. Although only magnetic materials are used for such shields to avoid interference that show almost no remanence, nevertheless often a slight, changeable one occurs Residual magnetization. This hardly affects cameras for black and white television, is however, extremely disadvantageous in color television cameras because of the optical and electronic images several scanning tubes are superimposed. The variable residual magnetization of certain components of the Deflection devices lead to errors in the superimposition of those corresponding to the primary colors of a color television camera Images, which forces you to make adjustments every time the camera is started up.

From US Pat. No. 2,962,621 a color television set is known in which a demagnetization is made by various shields, etc. of the color television receiver. Included an alternating current with decreasing amplitude is sent to a special degaussing coil created. This degaussing coil is independent of the receiver's usual deflection coils is, is combined with capacitors and a switch in such a way that at the moment of switching on the supply of the receiver in the resonant circuit formed in this way a sequence of rapidly damped Vibration occurs. With this type of demagnetization, however, it is not possible to use the The camera's TV recording tubes are provided with a method for suppressing the remanent Magnetization of the shields or other components of television pick-up tubes Color television camera and arrangement for carrying out the method

Applicant:

Compagnie Frangaise Thomson Houston-Hotchkiss Brandt, Paris

Representative:

Dipl.-Ing. Dipl. Oec. publ. D. Lewinsky, Patent attorney, 8000 Munich 21, Gotthardstr. 81

Named as inventor:
Jacques Donnay, Paris

Claimed priority:

France 8 January 1965 (1236)

Superimpose video signal very precisely. Furthermore, this known degaussing circuit arrangement for color television cameras that have multiple scanning tubes and yet not too large may be, significant disadvantage to having a large space through the use of additional Need special coils, resonant circuits and switches.

The invention is based on the object of creating a method of the type mentioned at the beginning, through which the previously occurring deficiencies of the image overlay in a color television camera without change the coils assigned to the scanning tubes can be eliminated automatically.

This is achieved according to the invention in that at least at the start of commissioning the Camera before or simultaneously with feeding the from zero to a nominal value in the focus coils increasing current generating the focusing field, decreasing from a maximum value to zero Alternating current is fed into the focusing coils.

According to a preferred arrangement for performing this method are in the feed circuit of Focusing coils in a manner known per se

809 628/1335

Claims (1)

3 4 DC power source and a regulator for changing magnetizations to clear. In this circuit of direct current and a low-frequency, in the focusing coils Fc of the individual Abseiner amplitude controllable alternator probes R ₁ B, V connected to a circuit, the direct current source contains the following circuit elements. A ßung of the AC circuit is bridged by a capacitor 5 DC voltage source S, a DC strength generator. Regulator Ri, for example by the anode resistor - According to further preferred embodiments, the regulator is formed to - change the DC - of a transistor and is biased by the control current and the low-frequency AC circuit Cc , and a low-frequency generator through control circuits controlled, the io quent alternating current generator Ga with variable amplitude from a common control circuit, which is regulated by the regulator Ca , and the individual focussing is. The capacitor C is used to switch the AC coils in series, and to close due to compensating circuit which Regeler Ri bridged for the one resistors or connected in parallel and is practically infinite resistance, each lying in series with a Ausgleichswider- 15 The control circuit Cc is under the influence of. Control circuit P a continuously variable The method and the arrangement according to the polarization signal that controls the controller Ri in such a way below with reference to in the drawing that this explains a circuit shown linearly to its nominal value in more detail. It emits increasing direct current. The amplitude Displays 20 regulator Ca are under the influence of one of the Fig. La is a diagram of a television pick-up tube, the control circuit P outgoing pulse a signal, Fig. Ib is a diagram of a display tube that triggers the low-frequency generator Ga, of which emits an alternating current for three color channels, whose amplitude of Fig. 2a shows a circuit diagram as well as which drops linearly to zero from a maximum value. Fig. 2b and 2c are circuit arrangements of the photo 25 die of the control circuit P in predetermined kissing coils. The impulses emitted in a sequence usually occur at In FIG. 1 a, a television recording tube TA is shown each time the camera is put into operation, the example being used to scan the rotations. Only component is used to reach the control circuit Cc. It then contains the most important parts of a pulse when the low-frequency swine , an electron gun R, a storage electrode m ₃₀ supply of the generator Ga has decayed, whereby and shields surrounding the scanning tube bl. Before the increasing supply of the focusing-In Fig. Ib, the three-color picture tube Π of a coil all remanence magnetizations deleted corresponding color television receiver is shown. will. The demagnetization of the sampling tube, which contains three beam generating systems B ', R' corresponding ferromagnetic parts is thus DA and V that achieves the reproduction of images in blue, red, ₃₅ by that they are the material hysteresis and green determines a Luminescent screen e and grind, with amplitude falling to a zero value, in a grid s to separate the three colors. talking electron beams. The electron- It should be noted that the sequence of the gun R ', which reproduces the red information, can be any steps, in particular it also sends out electron beams whose changes _{40 are} possible, the focusing coils at the same time with those of the electron generator R to apply decreasing alternating current and the increasing direct current of the beam emitted by the associated scanning tube. Next can be one and are synchronized. The corresponding impingement same circuit at the same time the three or four focus points on the disk in the transmission and m sierungsspulen food, which are the three or four Abdem screen when receiving e with α d and loading the camera ₄₅ taströhren correspond. The individual draws. Focusing coils F _{CJ, "Fcb} · ■ ■ possibility in the arrangement of the beam generating systems B ', R' series be connected, with each coil, a drain and V and the Gitterss is in a known manner the same resistance R _2%, R _2B ··· connected in parallel is made in such a way that the beams emitted by the electron gun R ' (Fig. 2 b), or can be connected in parallel, on the channel only to 50 with balancing _resistors R _{3 R} , R sB ... in series with pigments red Encounter luminescence. When: are provided for each coil. Giving rise to the switching elements by the effect of interfering magnetic fields, the α of Fig. 2b and 2c are connected to the circuit points Remanenzbereichen the shield bl of the red and b of the circuit of Fig. 2a in place einabtaströhre, the scanning beam of the electron Zigen coil Fc connected. For the sake of the tone generator R being deflected, it encounters a space requirement and low weight, the position of the storage disk which corresponds to another circuit part P, Cc and Ca of Fig. 2a from the area of the image. The color components of the actual camera separately and in their own of the area b are, however , housed in the area a ', the container, which is assigned to the area α , reproduced, as a result of which no true color reproduction achieved at this point 60 patent claims: will. This phenomenon becomes even more complicated, 1. Procedure for the suppression of the reman if the scanning tubes remanence magnetization th magnetization of the shields and / or have different distribution. other ferromagnetic components of television F i g. Figure 2 shows a simplified block diagram of a pickup tube of a color television camera Circuit according to the invention, the task of which is 65 use of a periodically variable consists in every start-up or after decreasing magnetic field, thereby a predetermined sequence which is characterized in the shielding that at least at the beginning; remanence of the scanning tubes remaining ■ the commissioning of the camera before or at the same time an alternating current that decreases from a maximum value to zero is fed into the focusing coils at the same time as the current, which increases from zero to a nominal value in the focusing coils (Fc) and generates the focusing field. 2. Arrangement for performing the method according to claim 1, characterized in that in the feed circuit of the focusing coils (Fc) in a known manner a direct current source (S) and a controller (Ri) for changing the direct current, a low-frequency, amplitude controllable alternating current generator (Ga) are provided, the direct current source (S ) being bridged by a capacitor (C) to close the alternating current circuit. 3. Arrangement according to claim 2, characterized in that the controller (Ri) for changing the direct current and the low-frequency alternating current generator (Ga) are controlled by control circuits (Cc, Ca) which in turn are acted upon by a common control circuit (P). 4. Arrangement according to one of claims 1 to 3, characterized in that the individual focusing coils (F _CR , F _CB ...) are connected in series and bridged by balancing resistors (R ₂ R, R _{2 B} · · ·) (Fig . 2 B). 5. Arrangement according to one of claims 1 to 3, characterized in that the individual focusing coils (F _CR , F _CB ...) are connected in parallel and each in series with a balancing resistor (R ₃ H, R ₃ B · · ·) lie (Fig. 2c). Considered publications:
U.S. Patent No. 2,962,621. 1 sheet of drawings 809 628/1335 10.68 © Bundesdruckerei Berlin