Device of reproduction for television colors.

PATENT AS AFRICAN AND MALAGASY

INDUSTRIAL PROPERTY

yaoundê (Cameroon) International Patent Classification : 04 № 02775 hr

O A>M-I-P

THE REQUEST 15 To 19 March 1968 hr 25 min

the O.A.M.P. 1. (N° G.P. 53.223) by the company said:

N V Phillips' GLOEILAMPENFABRIEK, residing to the Netherlands.

DELIVERED THE 15 DECEMBER 1970

' OFFICIAL BALLOT N° PUBLISHES AT 5 of 1970

PRIORITY : Patent application deposited the Netherlands under 6.704.218 mth 22 march 1967 on behalf of the applicant.

Playback device for color television.

X

A reproduction device for color television, having a cathode ray tube with reproduction screen, and two sets of deflection coils whose first, at least, has two half-coils

5 substantially symmetrical, mounted on the neck of the cathode ray tybe, these sets of deflection coils causing, using currents of deviation, the deviation in two substantially orthogonal directions, of at least one electron beam generated in the cathode ray tube.

The reproduction devices such as these may be equipped with cathode ray tubes (hereinafter referred to as a "pipe") of various types; for example it may either be a tube indexes, a shadow pipe or tube chromatron. The differences between these types bear mainly on construction details, on the reproduction screen or in close proximity thereto, and on the number of electron beams required.

An imaging screen of a tube for color TV is provided with phosphors is illuminating in different colors under the influence of an incident electron beam, these phosphors being applied as parallel strips in the tube index and the tube chromatron and as points in the shadow pipe. The tube modern index, operates with an electron beam, the shadow pipe, in uses three, whereas the tube operates either with a chromatron, either with three electron beams.

To obtain, on an imaging screen with phosphor strips, a picture having a luminance and color purity which is sufficient, it is necessary that the spot of an electron beam covers as much as possible the band, without overflowing.

Therefore, in the case of stripes, as in the tube indexes, spot is given the form of an ellipse whose major axis is positioned in the direction of the strip. To obtain a good color containing in a shadow pipe or chromatron, require that the spots of the three beams IC ' coincide throughout the scanning of the screen.

The following problems arise for the different types of tubes:

The major axis of the elliptical spot, in the tube index, depending on the degree of deflection of the beam under the simultaneous action of the two sets of deflection coils. This comes from requirements that govern the embodiment sets of deflection coils and which operate to keep the minor axis of the ellipse as short as possible. Thus, in the corners of the screen reproduction, the spot lies partially beside the belt to scan, and can even go up to cover an adjacent strip is illuminating in another color, which seriously affects the quality of the color rendering.

The shadow pipe and the chromatron, which operate with three electron beams each passing through one of the vertices of an equilateral triangle, are provided with a complicated dynamic radial convergence device electromagnetically-acting. For each electron beam (three) and for each deflection direction (two) should be provided, for this purpose, a current ramp and a current parabolic correction, determined, which requires twelve control members. There have been attempts to drastically reduce the number of. the actuators of the radial dynamic convergence device. This result could be obtained by using sets of deflection coils anastigmatiques, that permit the use of currents or voltages of convergence substantially identical for the three beams. In this manner, the convergence is ensured along axes of deflection, reproduction on the screen;

however, there is still shifts in the corners, since these sites, the three electron beams do not converge. A solution as simple, for the dynamic convergence will be very interesting to the shadow pipe 110 of^I , but it leads of too gross color in the corners of the screen, it is absolutely not applicable to devices known playback. Defects of this kind occur in the shadow pipe and in the chromatron, using three electron beams located in a plane perpendicular to the reproduction screen and sets of deflection coils astigmatic, these tubes do not require any dynamic convergence device.

The purpose of the invention is to obtain, using simple means, in reproducing devices for color television, comprising a tube, for example, index type, type chromatron or type shadow mask, a spot where desired suitable, throughout the scan reproduction by the single electron beam or by the three electron beams (without, in the case of OH the latter pass each by one of the vertices of an equilateral, predicting a convergence device complicated).

To this end, the reproduction device according to the invention is mainly characterized in that, to remove flaws the scan reproduction of the cathode ray tube, which originate from the astigmatism anisotropic sets of deflection coils, a reproduction device is provided with correction means, that send different deflection currents in the half coils of the first set of symmetrical deflection coil, the difference between streams corresponding to a correction current that is dependent upon the product of the instantaneous current value of deflection in the second set of deflection coils and the instantaneous value of the deflection current in the first set of coils.

The invention is based on the idea that the defects inherent in different types of tubes which apparently have different origins, have in fact a common cause, the effect of which, called "astigmatism anisotropic", can be corrected, simply, in the various types of tubes, by the measurement according to the invention. A first group of measures according to the invention is especially characterized in that the first set of deflection coils, is penetrated by a bypass stream which, relative to the current flowing in the second set, has a high frequency;

it is to say that the first set of coils is energized line deflection; the half-coils of the first set are connected to each other and are connected on one side, the other side, to the correction elements, which have an inductive character.

A second group of measures according to the invention is especially characterized in that the first set of deflection coils is energized with current deflection which, with respect to current through the second set, has a low; in other words, the first set of coils is energized deflection frames; the half-coils of the first set of deflection coils are connected together on one side and connected, on the other side, to the correction means, which have a character ohmic.

Another embodiment of a reproducing device according to the invention is characterized in that the reproduction device is provided with a cathode ray tube, in particular a tube-type shadow mask type or chromatron, which operates with three electron beams each passing through one of the vertices of an equilateral triangle, and which is provided with two sets of deflection coils anastigmatiques.

In this embodiment, the device can have the feature that further radial convergence is concurrently applied to three electron beams using a single radial dynamic convergence device, simply, of the electrostatic type. Another possible embodiment is characterized in that the reproduction device is provided with a cathode ray tube, in particular a tube-type shadow mask type or chromatron, operating with three electron beams arranged in a common plane perpendicular to the reproduction screen and provided with two sets of deflection coils astigmatic. Another embodiment is characterized in that the reproduction device is provided with a tube index having two sets of deflection coils astigmatic sec.

The following description, of the accompanying drawings, given by way of non-limiting example, will well understand how

1' can be performed.

The fig. 1 is the block diagram of a reproducing device according to the invention.

Figure 2 illustrates the defect scan to remove, from the fact that it utilizes a reel game which will be described subsequently.

Figure 2, in-, relates to defects that occur in a tube chromatron index or to a single beam.

Figure 2, in b, a shadow pipe or chromatron three beams each passing through to one of the vertices of an equilateral triangle.

Figure 3 illustrates the way in which these defects are removed.

Figure 4 illustrates the residual defects appearing in Figure 2, in b.

Figure 5 represents one embodiment of a portion of a reproducing device according to the invention.

Figure 6 represents a detail of the device

figure 5.

Figure 7 represents another embodiment of a portion of a reproducing device according to the invention.

Figure 8 represents a third embodiment.

Figure 9 represents a fourth embodiment.

Figure 1 schematically depicts a tube (1) having an electron gun (2) that generates an electron beam (3); the latter reaches the screen (4) reproducing point (5). The tube (I) is a tube reproduction for color television; it can both concern a tube indexes, a shadow pipe that a tube chromatron. That's why has not represented construction details close to the screen (4) reproducing or on; it simply requires that the reproduction screen (4) is provided with a phosphor applied as stripes or dots. The function that fill the organs (6), which can be used for acceleration, the concentration of one or more electron beams (3) and/or, in the latter case, for convergence, depends on the type belongs the tube (I). The other elements that provide the tube operation (I), but which are not essential for the explanation of the principle, are not shown in Figure 1.

(3) The electron beam is deflected in two substantially orthogonal directions, by a first and a second set of deflection coils (7) and (8) each consisting of half-coils (7¹ ), (7") and (8¹ ), (8"). Deflection current generators (9) and (10) éventuelleme s provided, in known manner, of output transformers, provide games of deflection coils (7) and (8), deflection currents having an amplitude and a high or low as the impact point (5) of the electron beam (3) moves on the screen (4) reproduction along lines forming a frame. Since in the example embodiment shown in fig. 1, the first set of deflection coils (7) is assumed providing scanning along the lines and that, in television systems known, complaints are generally horizontal, is dénommera, subsequently, that first set of deflection coils (7), "set of horizontal deflection coils"; accordingly, the second set of deflection coils (8) will be referred to as, "set of vertical deflection coils". Emerges from the description that the principle of the invention is also of value by inverting the functions of sets of deflection coils. May be varied, a usual way which will not be described, the brightness of the phosphor, at the point of impact (5), on the reproduction screen, by making the intensity of the electron beam current (3) generated by the electron gun (2), subject to a television signal.

In accordance with the principle of the invention, the reproduction device known, described above, is provided with members (it) which correction based on information provided by the members (12), regarding the instantaneous value and the direction of the deflection current in the set of vertical deflection coils (8), introduce a difference between the currents flowing through the deflection coil halves (7') (7") and horizontal deflection. As is will show during the description of Figure 9, it is also possible to arrange such that members (12) introduce, based on the information provided by the members (it), regarding the instantaneous value and the direction of the deflection current passing through the coil arrangement (7) deflecting, a difference between the currents passing through the half-vertical deflection coils (8') and (8").

For the invention aims can be reached, requires that, in the example envisaged, this difference corresponds to a correction current that is dependent on the product of the instantaneous current value deviation in vertical deflection coil arrangement (8) and the instantaneous value of the deflection current in the set of horizontal deflection coils (7). When, conventionally, deflection currents through the half-coils (7 "), (7 ') or (8") (8') are the same, obtained, seen from the barrel of (1), two magnetic poles of opposite and names with the same intensity, e.g. a north pole n and south pole S. gold, the correction current increases a deflection currents and reduces the other, so that the intensity of one of the poles is increased and that of the other pole reduced. In the example considered, this result can indicate by a north pole and a south pole n + n reinforced weakened s + n or n + s weakened by a north pole and a south pole s + s reinforced. As a result the varying correction current generates a magnetic field substantially quadrupole (the n, n or O, O) variable intensity.

The purpose that a search is made by applying this measure according to the invention eliminate defects of the type illustrated by Figures 2. The reproduction screen (4) is divided by two deflection axes (21), (22) into four quadrants 1 to IV.

The deflection axis (22) is obtained supplies only deflection current that at horizontal deflection coil arrangement (7) and the axis (21) in field by current deflection in the free deflection coils (8). The lines are scanned substantially parallel to the axis of deflection (21), under the control of the horizontal deflection coil arrangement, (7). It spring of Figures 2 that has not been applied correction for the raster distortion manifested as pincushion.

The reproduction screen (4) shown in fig. 2, in-, may in particular be the screen of a tube (I) wherein the electron gun (2) provided with a diaphragm eliipsoidal and the sets of deflection coils (7) and (8), by their design, (5) give spot the shape of an ellipse. The reproduction screen (4) is provided with stripes of phosphor not shown, parallel to the axis of vertical deflection (21), the major axis of the spot (5) ellipsoidal to be directed along the longitudinal axis of the strips. This can be achieved for a portion of the screen (4) reproduction using sets of deflection coils (7) and (8) in ES astigmatiqu ., free of coma. The astigmatism assumes that an electron beam deflected by the sets of coils (7) and (8) does not biodiv ersity RA focus but a focal meridional and a sagittal focal. By the focal length of the meridional cOjncider coil arrangement (7) and the horizontal focal saggitale vertical coils of the game (8) with the screen (4) reproduction, it is achieved that, along the axes of deflection (21), (22), the major axis of the spot (5) in the form of an ellipse is directed vertically, what is shown in Figure 2, has in, by the $>ERT (5') and (5"). However, when the electron beam (3) is deflected simultaneously in a horizontal direction and a vertical direction, the major axis of the spot (5) is rotated (see spotlight 5" ' in the quadrant of I). This rotation occurs in the different quadrants I to IV as shown in Figure 2, has, and increases, in proportion to the deviation angle.

The reproduction screen (4) shown in fig. 2, in b, is the screen of a tube configured as a shadow pipe, provided with either a single electron gun (2), or (2) three barrels causing three electron beams (3) each passing through one of the vertices of an equilateral triangle. (3) Each electron beam is associated with one of the three fundamental colors, namely red, green or blue and circular spots (5)

on the reproduction screen (4) are respectively indicated by

THE RG B.

(5), (5) and (5). To obtain a picture free of color-shift, must be-as-the s three electron beams (3) reach a shadow mask (not shown) at the same point.

This convergence is marked on the screen (4) reproduction

THE RG B.

by the fact that the spots (5), (5) and (5) coincide. This can in principle be obtained along the axes of deflection (21) and (22) using one hand, sets of deflection coils (7) and anastigmatiques (8) and a single radial dynamic convergence device (and not three as the reproduction devices known). The radial dynamic convergence device may be constituted by members (6) shown in Figure 1, and be of the electrostatic type. Gold, because it is the same device that acts on the three electron beams (3), remains offsets that increase as the distance of the corners of the screen (4), since then,

THE RG B.

(5) the spots, (5) and (5) are not formed by electron beams (3) which reach the shadow mask in a same location. Figure 2 represents, in b, residual defects observed in the quadrants 1 to IV, on the reproduction screen (4), with respect to a frame that would be scanned without these defects occur.

We now describe, with reference to Figures 3 and 4, how the measurement according to the invention, explained facing Figure 1, eliminates, simply, defects at that point different, like those illustrated in Figure 2 in a and in b.

In Figure 3, is partially represented four magnets forming two north poles (31), (32) and two south poles (33), (34) which need not have the same intensity as the north poles (31) and (32). Like poles are placed opposite to each other and form a pair, one of the pairs being disposed practically 90° each other, such that the magnets generate a magnetic quadrupole field.

Has been represented in the quadrupole field, a circle (35) which is assumed to be traced by cathode-ray emerging from the plane of the drawing, some of these rays are indicated by points (36), (37) and (38). In the quadrupole field, the field from the north pole (31) is deflected and applying force availability of three fingers, it is determined that on entering the quadrupole field, the CRT represented by the point (38) is subjected to the action of a force directed along the arrow (39). As it leaves the quadrupole field, the radius (38) located on the circumference (35) has moved in the direction of the arrow (39), so that the ray leaves the quadrupole field point (38'). It has represented the movement (toward (36 ') and (37')) of various points (e.g. (36) and (37)) (35) of the circle formed by the cathode ray entering the quadrupole field. As a result hr after passage in the quadrupolar field the circle (35) has become an ellipse (40).

It is obvious that the degree of deformation of the circle into an ellipse, it is to say the movement of various points depends on the strength of the quadrupole field. The same effect can be obtained in the absence of the poles (33) and (34) because in this case, the north poles (31) and (32) cause an almost quadrupole, and vice versa. Of course, there will be a slight additional deformation of the ellipse (40).

It follows from the foregoing a circumference (35) for passing therethrough a CRT, is transformed by the action of an almost quadrupole, into an ellipse (40) inclined. Accordingly, an electron beam consisting of cathode ray contained in a circle (35), it is to say an electron beam with a circular cross section, ellipsoidal assumes a shape when it passes through a quadrupole field or quasi-quadrupole.

We can also see that an electron beam ellipsoidal section is rotated as it passes through a quadrupole field.

By comparing Figure 3, Figure 2, a-frame, and Figure 1, is comes down to the following findings: an electron beam (3) ellipsoidal section deflected by the deflection coil sets (7) and (8), form, in the quadrant of I, on the reproduction screen (4), a spot eliipsoidal (5" ') shifted rightward.

This rotation is caused by so-called "astigmatism anisotropic" sets of deflection coils (7) and (8), which according to the idea of the present invention, is all the more marked as closer to the corners of the screen (4) since the beam is subjected to the action of a almost quadrupole of increasing intensity. According to the measurement according to the invention, is superimposed on the magnetic field in the horizontal direction for the deflection, a almost quadrupole, which, for the quadrant of I, corresponds to two north poles generated electromagnetically.

The two fields are generated by the game of deflection coils (7), because the current passing through the winding (7"), is more intense as that sent in the half-coil (7¹ ). As has been said previously, this leads, for the spot (5" '), in a north pole and a south pole s + n n + n.

In this manner, the electron beam (3) ellipsoidal section is rotated to the left. When considering the defects occurring on the whole screen (4), can be eliminated rotate to the right or to the left, the astigmatism caused by anisotropic, by making the CCW rotation caused by two north poles in the quadrant I and III and the right rotation caused by two south poles in the quadrants II and IV, tributary of both the instantaneous value of the deflection current passing through the coil arrangement (7) horizontal deflection and to that of the current flowing in the vertical deflection coil arrangement (8).

We now examine, with reference to Figure 4, residual defects that occur in the shadow pipe, illustrated by Figure 2, in b. It is assumed (see Figure 1) that the sets of deflection coils (7) and (8) are anastigmatiques and wherein the tube is provided with a single radial dynamic convergence device (6 members), acting in a same measurement on the three electron beams (3).

Figure 4, in b, serve to illustrate residual defects that appear in the quadrant of I (fig. 2, in b).

Without astigmatism anisotropic and for radial convergence is too low, the sets of deflection coils (7) and (8) - deflect the three electron beams such that they reach the screen (4) (41) at respective points, (42) and (43). Because the three electron beams (3) are generated by an electron gun (2) same three diaphragms, so that they pass each through one of the ring members, of an equilateral triangle, or by three electron guns (2), following the same pattern, the spots (41), (42) and (43), which respectively correspond to the electron beams (3), carrying the information relating to the red, green and blue, also lie at the vertices of an equilateral triangle. If the radial convergence correction is applied as appropriate, the three electron beams (3) meet the shadow mask in a same point denoted (44), which corresponds to what is shown in fig. 2, in b, along the axes of deflection (21) and (22).

However, if there is astigmatism anisotropic, and if the convergence correction is applied too low, the points (41), (42) and (43) on the screen (4) reproducing respectively move to the points (41 '), (42') and (43 ') (see turning point 5' " in the quadrant I as shown in Figure 2, a-frame). If applied for the three electron beams (3); along the axes (21) and (22), a uniform radial convergence correction is as effective as possible, the points (41') R.

(42¹ ) and (43¹ ) respectively move to the points (5),

G-B.

(5) and (5), which makes the fçon whose residual defects occur in the quadrants I and III on the reproduction screen (4) shown in fig. 2, in b. The fig. 4, in-, illustrates the residual defects that occur in the quadrants II and IV. By following the same reasoning, it appears that these residual defects can be eliminated as described is facing of Figures 2, in has, and Figure 3, electron beam (3) ellipsoidal.

When the three (3) electronic fiasceaux lie in a common plane substantially perpendicular to the screen (4) reproduction, there is also residual defects, due to the anisotropic astigmatism. H is evident that in this case also, it can eliminate the effects of astigmatism anisotropic using an almost quadrupole.

Figure 5 represents one embodiment of a portion of the reproducing device according to the invention. The components found in the device of Figure 1 bear the same references in Figure 5 and Figures following. The generator (10) deflection current sends, via members (12), at vertical deflection coil arrangement (8), a deflection current I is substantially sawtooth.

(12) The members (as shunt) (51) provide at multiplier belonging to the correction member (it), information

regarding the instantaneous value of the deflection current I and

v relating its direction. The multiplier (51) also receives, via the member (52), information about the instantaneous value and direction of current ^ 2, 1 supplied by the generator (9) deflection current to the set of horizontal deflection coils (7). In this way, the multiplier (51) provides a

correction current I is proportional to the product of currents

C.

i and I deflection. The sign of the correction current I flows V H-C.

positive to negative and vice versa, depending on the direction of deflection currents I and 1 ^, when changing from one quadrant to another. This change of sign is indispensable because, as has been already shown above, the field corrector quasi quadrupole, acting in the quadrants 1 and III must be different from that the quadrants II and IV. The correction current ^ I-is applied to the primary winding of a transformer (53) (54) having a secondary consisting of two parts (55) or (56). The free end of the winding portion (55) or (56) is connected to that of the half-coil (7') or (7"), respectively. The correction current I-^ generates, in the described manner, in the winding (55), (56), a correction current I in ', so that the deflection current passing through the winding (7') is equal to 1 ^ - the I '_C. and that passed through the half-coil (7") is equal to i + i ' ^. It follows that the set of deflection coils (7) generates a deflection field during normal (induced by 1 ^) and has almost quadrupole (induced by I ' ^), while the intensity of the quadrupole field is dependent upon the product deflection currents of I " and I.

The system according to the invention is very simple:

in e ffet, based on the fact that the coils (7 ') and (7 ") right turning, it is concluded that during scanning of one line in the quadrant (I-) on the reproduction screen (4) (see Figure 2) the coil (7'), viewed from the tube (1), must have a south pole and the coil (7") of TiN north pole. The direction of current flow in the coils (7') and (7") thus corresponds to the direction 1 ^, indicated in Figure 5. In the quadrant of I, they must produce a rotation to the left (spotlight 5 "'), which corresponds to a quadrupole field to two north poles generated by the coils (7') and (7"). This is achieved by weakening the south pole of the coil (7 ') (1 ^ - the I') and reinforcing the north pole of the coil (7") (1 + ^ the I '). In the

(ll) quadrants, the direction of the current I is reversed and therefore can be

hr

indicated by -1 ^. Because I has the same sign in the quadrants (I-)

(ll) and, the I 'also changes direction and becomes - the I'. Therefore, the

c. C.

coil (7') has a north pole and the coil weakened (7") a south pole reinforced, which means that almost quadrupole generated by two south poles. This results in a clockwise rotation in the quadrant (Π). A like reasoning applies for the quadrants (lll) and (rearward Iy).

It is evident that the multiplier (51) can be designed in known manner using, for example, tubes or transistors, Figure 6 represents one embodiment of the multiplier (51), where advantage is taken of the Hall effect, a particularly simple manner. By disposing a plaquelle Hall (61) in a small air gap of an output transformer belonging to the current generator (lG) and providing the vertical deflection current of I, can be utilized directly, the magnetic field flux) ^ * proportional to 1. By supplying the manner shown in Figure 6, to the wafer Hall (6l), a current the O { I is proportional to the horizontal deflection current (4 o { representing a proportionality factor); obtained (62) across (63) and a voltage proportional to the product I currents I and 1 ^. This voltage e is applied, for example, to the amplifier (64), which provides the correction current I as already mentioned. It is clear that the magnetic field for the wafer (61) Hall may also correspond to the deflection current

l-horizontal, while current I is supplied to the wafer

v-hr

(61).

Figure 7 represents one embodiment of a reproducing device according to the invention wherein the correcting members (11) are provided with magnetic transducers. The transducers (71 ') and (71") are designed in the same way, so that out of that the transducer (71'). This transducer (71 ') includes a core (72') of a material having a non-linear hysteresis loop, carrying a plurality of windings wound to the right, these windings which may be formed by several parts. To obtain a bias, the winding (73 ') consisting of two parts, is connected to a DC power source (74') so that a constant flow is generated in the center leg of the core (72'). This flow could also be obtained by means of permanent magnets. Around the center leg of the core (72 ') winding is wound (75'), connected between the current generator (9) horizontal deflection and yoke (7'). Further, the transducer (71 ') is provided with a split winding (76'). (12) The members that provide information about the instantaneous value and the

direction of the dye vertical deflection of I, are connected to enrou -

V.

lead Agency (7, 6') and (76") connected in series.

The windings (76 *) and (76 ") are connected such that the streams generated in the central branch of the cores (72 ') and (72") for a determined value of the vertical deflection current, oppose the premagnetization of £luxes, it is to say that a flow weakened in the center leg of the core (72') corresponds to a stream reinforced in the center leg of the core (72") and vice versa. Because the induction coil windings (75 ') and (75 ") increases as decrease the flow embraced, and vice versa, an increase in the impedance of the enraulement (75') corresponds to a decrease in the impedance of the winding (75") and vice versa.

The frequency of the current substantially sawtooth^1 is, in the example contemplates, much superior to that of

the current I, so that the instantaneous value of I for

v-V.

a period of one line can be considered constant.

There is between the windings (75') and (75") an impedance difference, which is a function of this constant value, so that the currents of deviation in the half coils (7¹ ) and (7") are different. Accordingly, an almost quadrupole is generated in the tube (10, field whose intensity is a function of the difference between the currents in the coils identical (7¹ ) and (7"), resulting in a difference between the voltage drops across both coils. The value of the difference between the voltage drops depends, for the deviation in the horizontal direction, the instantaneous value of the current deflection sawtooth 1^and is at a maximum for the edge of the screen (4) reproducing and zero for the deflection axis (21) (in effect 1^is then equal to zero). The strength of the quadrupole field proportional to côtte difference between the voltage drops to thereby causes rotation correction sought according to the invention. The directions of currents represented in Figure 7 correspond for the maximum deflection currents substantially sawtooth 1^I at the edge of the screen (4) reproduction in the quadrant of I (see Figure 2). It appears that the flow in the center leg of the core (72") is higher than that in the core (72¹ ), so that the impedance of the winding (75") is lower than that of the winding (75') what corresponds, as has been already described, a quadrupole field to two north poles, which causes a rotation to the left.

With the correction member (11) shown in Figure 7, can also yield a decrease in the raster distortion in east-west direction, as shown in particular in Figure 2, in b. If it sends, in the coils (7 ') and (7") - I-currents 1 ^' ^ ^ + 1 and the I '_C. , as described by facing

of Figure 5, the horizontal deflection field generated by a current run 1^and the quadrupolar field by a current I ' for the edges of the screen (4) reproduction that are parallel

to the deflection axis (21) (fig. 2), the I reaches an amplitude that is constant for the entire screen (4), thus producing the raster distortion known in east-west direction. However, if the returned in the coils (7 ') and (7 "), currents of I - 1 ^" ^ ^ and 1, the I " being a function of (1 ^. I-), the current through the coil (7') may

expressed by I, the I - 1 "- 1 of I" and that passed through the coil (7")

^hr 2^C. 2°

i-i - 1 by "+ I-I-". The current I-i - 1" generates a field of " 2^C 2^H 2^C

the normal deviation while current I are 1" generates a field

+ *^C

quadrupole. The amplitude (- (ΐ ^ - 1 I-" ^) the horizontal deflection current substantially sawtooth, which corresponds to the edges (east-west) in the quadrants (I-) and (ll) of the screen (4), depends on

the instantaneous value of the vertical deflection current of I, V-so

obtained distortion reduction frame east-west.

For the quadrants (lll) and (VI), it is necessary, to simultaneously remove the raster distortion and the effects of astigmatism anisotropic, that the coil (7') is the fuse 1^and the coil (7 ") by the current 1 - I-^" ^. This implies that, for the quadrants (the I) and (II) or (III-) and (VI), the winding (75") or (75') respectively must have an inductance that does not depend on the deflection current I-. This can be achieved using transducers (71') and (71"), by saturating thereof such that the current deviated -

except I-only increases the inductance of the winding a V

(75') or (75") respectively, that to demagnetization.

It is evident that any asymmetry in the setting

the impedance, which acts in the sense described above, will have a similar effect. Such asymmetry occurs often in transducers (71'), (71") that are not pre-magnetized into the substantially linear portion of the hysteresis loop of the core material. In conclusion, it is possible to reduce raster distortion east-west, simply, by choosing the proper degree of bias.

Figure 8 represents another embodiment of the device to transducers, described opposite of Figure 7, also for removing astigmatism anisotropic, the raster distortion east-west. The transducer (81), which may include, in the manner shown, two E-shaped cores and an intermediate leg or four core rings, is provided with four windings wound to the right, each consisting of two parts. The coil (82) serves to bias the transducer (81) and is connected, for this purpose, to a DC power source (83). Information about the instantaneous value and the direction of the vertical deflection current I is provided by the tension member (12) to the winding (84). The winding portions (85) and (86) are connected in series between the half-coil (7') and a coil (87) adjustment, which a grip is connected to the current generator (9) horizontal deflection. The winding portions (88) and (89) are connected in series between the half-coil (7") and the other end of the coil (87) adjustment. The setting spool (87) serves to make symmetrical, statically, the two parts of the set of deflection coils (7) connected in parallel.

The transducer device (8l) operates as follows. Assuming that the windings are wound to the right and that currents flow in the direction indicated in Figure 8, the winding portions (85) and (86) embrace a flux that is equal to the difference between the bias flux IP and the flow (P-generated by the vertical deflection current, the winding portions (88) (89) and the sum of the flux kiss ψ and flux ψ . Thus, the astigmatism anisotropic is removed, in the quadrant (I-) of the shield (4) reproduction (fig. 2), using a quadrupole almost field, as described is facing the preceding figures.

The distortion removal in the bezel frame

(I-) is achieved because the winding portions (85) (86) and (88) or

(89) and are connected such that the direction of the streams of £ Ψ - ψ

'B.' V or Y-" ^ + ψ_V. ,, respectively, does not correspond to the direction of the field generated by the horizontal deflection current passing through the winding portion (85) or (89), respectively, but in that of the field generated by current flowing through the winding portion (86) (88) or, respectively, it is known that the action degaussing current, on a bias flux, superior to excitation. For high values of the horizontal deflection current in the winding part (7¹ ) and (7"), it occurs, due to the action degaussing, more emphasis on increase in impedance formed by the winding portions (85) and (86) and an attenuation of the decrease in impedance of the coil portions (88) and (39). It follows that as a result of the described measuring, the total impedance of the set of deflection coils (7) and means for performing correction (it) is relatively greater so as to result in a decrease in the raster distortion.

The same reasoning applies for the other quadrants of the reproduction screen (4).

Figure 9 represents a portion of an exemplary embodiment of a reproducing device according to the invention, wherein the almost quadrupole for eliminating influence of anisotropic astigmatism is generated by the vertical deflection coil arrangement (8). In connection with the character ohmic coil arrangement (8) for the vertical deflection current of I, the symmetry may be adjusted dynamically, deflection between the currents in the coils (8¹ ) and (8") is obtained by the use of resistors controlled. Is shown in Figure 9 the resistors (91) and (92) tributary of a magnetic field. These resistors can be formed using needles of NiSb that function as electrical conductors, in a mass of InSb conducts electricity. Depending on whether the value of the magnetic induction field perpendicular to both the direction of the needle and the direction of the current, which are themselves orthogonal, is higher or lower, the resistors (9l) and (92) have a high-ohmic or low. Resistors of this type are in particular described in the article "Indiumantimonid avec eingebautengerichtet, elektrischgutleitendenEinschltlssen: soild of InSb - NiSb" H. Weiss and M Wilhelm published in "margin for ZeitschriftPhysik", 176, 1963, pages 399 - 408.

Because, as has been said previously, the values of the resistors (91) and (92) must vary in opposite directions, use is made of the magnetic bias. The magnets (93) and (94) which can be designed as permanent magnets or e-to-sintered body magnets, form a block with the closure plates (95) and (96); the block is placed for example, in the gap of the output transformer of the horizontal deflection current generator (9) (not shown). The magnetic pole between the magnet (94) and the resistor (92) is the name the opposite located between the magnet (93) and the resistor (91); the magnetic fields contain through the closure plates (95) and (96). If the pole of the magnet (94) placed close to the resistor (92) is a north pole, the magnetic field represented, flow ^ " horizontal deflection current proportional to the L ^, weakens the field strength (92) and strengthens the field in the resistance (91). Therefore, the value of the resistor (92) decreases the resistance of the resistor (91) increases. Hr as a result different drive currents are transmitted to the spool halves (8') and (8") so that the astigmatism anisotropic is removed, by a rotation in the direction of the field near-quadrupole.