US3098118A

US3098118A - Post-deflection tube with xyzxzy sequence

Info

Publication number: US3098118A
Application number: US40678A
Authority: US
Inventors: Raibourn Paul
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-07-05
Filing date: 1960-07-05
Publication date: 1963-07-16
Anticipated expiration: 1980-07-16

Description

July 16, =1963- I P.- RAIBQURN 3.098. 8

POVST-DEFLECTION TUBE wrra xYzxzY-sEQUmw Filed July 5, 1960 y Y 3 Sheets-Sheet 1 FIG. 2 FIG.6 F|G.7

INVENTOR PAUL RAI BOURN BY 2M Wit AM If ATT RNEYS July 116,1 1963 FIG. 5

P. RAKBOURN 'POST-DEFLECTION TUBE WITH XYZXZY SEQUENCE Filed July 5, 1960 3 Sheets-Sheet =3 GRRG lNVENTOR PAUL RAIBOURN ATTORN 8 a means 3,098,118 POST=DEFLECTION TUBE WITH XYZXZY SEQUENCE Paul Raibourn, Southport, Conn. Filed July 5, 1960, Ser. No. 405678. 9 Claims.. (Cl. 178-5.4)

This invention relates to the reception and display of color television signals of the color sub-carrier type,'such as signals according to the NTSC standards, and more particularly to a cathode ray tube and associated recciver for display of such signals. The cathode ray tube of the invention is of the post-deflection focusing type having a fluorescent screen on which are laid down stripsof material fluorescent n. electron impact in. three primary colors. Color selection is achieved by means of a switching grid, the tube being generally of the typedescribed in United States Patent No. 2,692,532. The invention provides a novel arrangement and disposition of the fluorescent strips on the screen in relation to each other and in relation to the conductors of' the switching grid, with resulting improvement in color balance, brightness, resolution, and reduction in the power required at the switching grid for colorselcction.

The invention will now be described in detail with reference to the accompanying drawings in which FIG. 1 is a diagrammatic view. of a cathode ray tube according to the invention;

FIG. 2 is a fragmentary view of the fluorescent screen of the tube of FIG. 1, showing at an enlarged scale the arrangement of color strips on the screen of a tube according to one embodiment of the invention and the relation thereof to the conductors of the switching grid in that tube;

FIG. 3 is a block diagram of a television receiver suitable for operation of the tube of FIGS. 1 and 2;

FIG. 4 is a vector diagram useful in explaining the invention;

FIG. 5 is a set of waveforms useful in explaining the invention;

FIGS. 6 and 7 are two figures similar to FIG. 2 but illustrating other embodiments of the cathode ray tube of the invention.

The cathode ray tube o'f FlG. 1 comprises an electron gun generally indicated at 2, disposed in the neck portion of an envelope 4. The gun develops a focused electron beam directed at a target area generally indicatcd at 6 and the beam is adapted to be scanned over the target area by means of scanning voltages of the usual type applied to crossed deflection coils 8 and 10. The scanning pattern may be that customarily employed for both black and white and color television signals, comprising two interlaced fields of lines.

The target area 6 includes a large number of side-byside strips 7 of material fluorescent on electron impact in three primary colors, typically red, blue and green, the strips being laiddown in a. cyclically repeating order. For brevity, the strips will hereinafter be referred to as red, green and blue strips to identify the color of the light which they produce upon electron impact. In FIG. 1 the three colors are identified as X, Y and Z, and the cyclical order of strips is seen to be XYZXZY.

For any set of three additive primaries, the invention comprchends the three, different arrangements of the screen or target 6 in which those-colorscan be allocations to the-positions X, Y and Z in the cycle. For'red, green and blue primaries, these arrangements are set forth in the accompanying table: I

R R B B o o B G R o R B o B o R B R R n- B n o o o n o R B a B o R o R B It will be observed. upon a comparison of the table with FIG.1, that while there are apparently six permutations, there are in substance only three, the members of the pairs in the table differing only in a displacement by one of the intervals between adjacent grid conductors 1.4 and 16. For red, blue and green primaries, the presently preferred embodiment for television signal reception comprises the. strip sequence RGBRBG with-the red strips under the grid conductors presently to be mentioned. I

The tube includes between the. gun and the target area,

nearer the latter, a deflection grid generally indicatedv at 12.. This grid includes two sets of interlaced mutually insulated

conductors

14 and 16, which extend generally parallel to the strips and to the target area surface. Switching voltages may be applied between the two sets of grid conductors at

electrodes

18 and 20, one of which connects with all conductors 14 and the other with all conductors 16. In FIG. 1 only a few of. the

grid conductors

14 and 16 are shown. In the tube as manufactured there may be of the order of 800 such conductors, 400 in each set. The spacing on centers of adjacent conductors may be of the order of 0.025 inch.

For simplicity of drawing the tube face bearing the target 6 has. been shown flat in FIG. 1. It may be curved, and the switching grid may be adjusted in shape accordingly. Similarly, the thickness of the phosphor strips has been greatly exaggerated in order to illustrate their variouscolors.

The target area is overlaid on the side thereof adjacent the switching grid with a thin electron-permeable layer 22 by means of which a post-deflection focusing voltage may be applied between the target area and the mean potential of the switching grid.

Thus an accelerating voltage of the order of 5 kv. may be applied between the second anode 9 of the electron gun and the switching grid 12, for example to the midpoint of a resistor connected between

conductors

18 and 20, and a post-deflection voltage of the order of 15 kv. may be applied between the grid 12 and the conducting layer 22 on the screen 6. This post deflection voltage serves to constitute the grid wires, together with the conducting layer 22, into a multiplicity of conveying cylindrical electron lenses, one between each pair of adjacent grid' wires and the screen so that the electron beam undergoes a supplementary focusing in passing from the location of the grid to the screen;

The switching voltage applied to the

grid conductors

14 and 16 serves to impose on the electron beam a supplementary deflection which directs the electron beam at appropriate times to strips on the targetareavv ofthe proper color. The strips are of such width that ii1-the dimension Patented J uly'16, 1963 than the linear dimension of a picture element.

in traversal of a distance less The strip width is accordingly of sub-elemental magnitude. The picture elements on the screen are selected in succession by the line and field scanning voltages applied to the deflection coils 8 and 10. Within each elemental area as so selected the sub-elemental area of appropriate coloris selected by the switching voltage.

In cathode ray tubes of color television reception having a switching grid of the type hereinabove described it has been customary heretofore to dispose electron optically behind adjacent grid conductors strips of two colors alternately with a strip of the third color centered between the two conductors of each pair of adjacent conductors. In such a tube therefore there are as many strips of this last color as there are conductors in the switching grid and half as many strips of each of the other two colors. Accordingly, the resolution has been twice as high in the color of the centered strips.

Specifically, it has been customary to make the centered strip a green strip in order to maximize the brightness of the reproduced picture by reason of the fact that with (reference to the primaries of the NTSC signals) the green, red and blue primaries contribute brightness to standard white in the proportions 0.59, 0.3 and 0.11, and by reason of the fact that the green largely carries the resolution for the eye. Such a strip configuration is illustrated in FIG. 3 of Patent No. 2,745,035.

In accordance with the invention, the phosphor strips are arranged in a repeating cycle containing-six strips. This cycle spans the pitch of two

adjacent conductors

14 and 16 in the switching grid 12, and within this cycle the first and fourth strips are of one color, the second and sixth are of a second color, and the third and fifth are of a third color. The strips are so disposed that the first and fourth strips are electron-optically disposed behind adjacent conductors of the switching grid.

Thus in FIG. 1 the three colors are identified X, Y and Z, these being the primary colors employed in the additive system of color television whose signals the tube is to display. It will be observed that behind each of the grid conductors is a strip of color X and that the strip cycle is XYZXZY.

In FIG. 1 and in FIG. 2, 6 and 7 the effects of parallax have been ignored; these figures may be considered on the assumption, made for convenience of representation in the drawings only, that the cathode ray beam reaches the switching grid oriented normally to the plane defined by the grid conductors.

With red, green and blue primaries in the system of color television signals to be displayed therefore, the inyention comprises three embodiments with respect to the order of the phosphor strips. These embodiments have the strip cycles or sequences RGBRBG, GBRGRB and BRGBGR and are illustrated in FIGS. 2, 6 and 7 respectively.

Disposition and dimensioning of the strips on the screen with reference to the switching grid conductors and the spacing of the latter to compensate for curvature of the target area, if any, for parallax between the grid and screen and for variation in deflection sensitivity of the cathode ray beam over the target area may be made in accordance with the disclosures of Patents 2,745,033 and 2,745,035.

In FIG. 1, and hence in each of FIGS. 2, 6 and 7, there are three phosphor strips for each grid wire, and each such triad contains one strip of each color. Consequently, in all colors there are as many-strips as there are wires in the switching grid, The spacing of the strips disposed behind the grid wires is uniform, whereas the spacing of adjacent strips of each of the other two colors is an alternating one, alternating between a separation of one strip and a separation of three strips.

' In each of the embodiments of FIGS. 2, 6 and 7 there fore the resolution of the tube is unequal as between the color will be encountered three embodiments. In addition, in each embodiment inequality of the dwell times of the cathode ray beam on the three phosphors leads to certain differences in brightness among the three embodiments. These will be discussed after a further description of a preferred embodiment illustrated in FIG. 2, and of its operation.

FIG. 2 shows a plan view of a portion of the target 6 of FIG. 1, adjacent

switching grid conductors

14 and 16 being shown in front of adjacent red strips. sequence is RGBRBG, it being noted that proceeding from any grid conductor is opposite directions the sequence of colors is the same. The four strips on which the cathode ray beam may be focused within the color cell limited by

adjacent conductors

14 and 16 are identified at 15, 17, 19 and 21, and in the embodiment of FIG. 2 these are red, green, blue and red respectively.

The switching voltage employed in the tube of FIG. 1 may advantageously be a sinusoidal one at color subcarrier frequency. On FIG. 2 there has been drawn a circle 24 representing the locus of a vector rotating at uniform velocity. The displacements of the head of this vector from an axis 26 correspond to the displacements, produced by the sinusoidal switching voltage applied to grid 12, of the cylindrical line focus of the cathode ray beam over that portion of the target between the

conductor

14 and 16 between which the circle is shown. The axis 26 lies along the division between adjacent blue and

green strips

17 and 19.

In accordance with the invention the amplitude of the switching voltage is adjusted, with reference to the stiffness of the electron beam which depends upon the accelerating voltages applied to it, so that this locus provides dwell times within each of the

red strips

15 and 21 of approximately one-quarter of a sub-carrier cycle. The corresponding dwell times on the green strip 17 amount to a total of one-quarter of a cycle made up of two passages having a duration of 45 each, and similarly for the blue strip.

The cathode ray beam thus spends twice as much time on strips of the color which lie behind the grid wires as it does on strips of either of the other two colors, but an important feature of the tube of the invention is the fact that the showing of the color switching cycle among the three colors may be varied by adjustment of the amplitude of the switching voltage. In accordance with the invention the phosphors employed are approximately balanced as to their light output (in brightness units) for excitation by a cathode ray beam of constant intensity so that the tube of the invention develops white light when the cathode ray beam is unmodulated. Here again however color balance to produce white light can be achieved by adjustment of switching voltage amplitude despite departures in tube manufacture from such balance among the phosphors.

The invention is however not limited to dwell times on the strips behind the wires of twice the dwell times on the other strips. These dwell times depend, among other things, on the relative width of the strips, which need not be uniform (for some decoding methods this is advantageous), and on the spot size, by which is meant the size of the fluoromcent spot produced by the electron beam.

FIG. 3 is a block diagram of a receiver suitable for operation of the tube of FIGS. 1 and 2. This receiver develops for application to a control electrode of the cathode ray tube, for example either its cathode 3 or its first control grid 5, a voltage which is the sum of an E -E term at the second harmonic of the color subcarrier and a E E term at the third harmonic of the color sub-carrier. These signals occupy the band of chrominance frequencies, roughly from 2 to 4 mc. or from 3 to 4 mc. for NTSC signals. In addition the luminance signal over the zero to 4 mc. range is applied to another The strip control electrodeof'thewathode ray'tube having opposite 'polarity effect, so as to effect an additive combination of the signals applied to the two control electrodes.

In the block diagram of FIG. 3 there is shown at 30 a color television receiver which may be conventional and which performs all the customary functions of a television receiver up to that of the second detector. At the output of thereceiver 30 there is shown a diode 31 which functions as a second detector. This second detector delivers to an amplifier 32 the complete video signal including luminance and chrorninance, synchronizing signals for line and field scanning, and also the color synchronizing signal. In the NTSC signal this burst signal comprises a few cycles at color subcarrier frequency and fixed phase relative to the color sub-carrier used in developing the chrominance at the transmitter, superimposed on the horizontal blanking pulses.

From the detector 31 this total video signal is sent broadly through two channels. Amplifier 32 with a frequency selecting network 34 in its output serves to select the chrominance component in the .34 mc. range. while the to 3 me. luminance component is developed acrossa frequency nonselective circuit iliustratively shown as a resistor 36. The circuit for deriving from the video output of receiver suitably timed line and field scanthing voltages for application to the deflection coils 8 and 12 of tube 4 have been omitted from FIG. 3, since it may be entirely conventional. Similarly, the sound separating and amplifying circuits have been omitted, and there have also been omitted the circuits for developing accelerating voltages for the cathode ray tube, which may likewise be conventional.

The chrominance, after passage through a further amplifier 38, is delivered through a further frequency select- The circuit 42 includes a multi-grid beam defiection tube 48 having a cathode 50, a first-control grid 52, twin screen grids 54 and 56, two

beam deflection electrodes

58 and 60, and two

anodes

62 and 64. The chrominance from the circuit 40 is applied to the first-control grid 52, and the

beam deflection electrodes

58 and 60 ared'riven in push-pull from a transformer 66 which is fed at twice color sub-carrier fresuency from the regenerator 44 For brevity only, this second harmonic will be referred to as 7.2 mc. inview of the location of the color sub- .carrier at 3.58 mc. in the NTSC signals. The invention however is not restricted to operation with these frequencies, nor to operation with the NTSC signals.

The phase of the 'signalapplied to transformer 66 is locked to the reconstituted subcarrier' fundamental in regenerator 44 and can be adjusted with reference thereto by means of a phase control 68.

By means of the 7.2 mc. voltage applied to the

deflection electrodes

58 and 60 in tube 48, current is caused to flow to the two anodes .62 and 64 at intervals of one-' quarter of the color sub-carrier fundamental cycle.

The phasing of the signal applied to transformer is adjusted so that conduction occurs at anode62 at times centered about the E -E and -(E --E phases of the chrominance signal as applied to tube 48. Conduction accordingly occurs at anode 64 at times centered about the (E E and (E E phases of that chrominance. These phases are indicated on the vector diagram of FIG. 4 wherein the vectors .63E

.455 and 5913 identify with respect to the burst the phases of the color subcarrier cycle at which the chrominame is proportional to the red, blue and green primaries respectively.

The E E axis is orthogonal to the E axisand ing network 40 to an axis-selecting circuit shown within a hence to the n M aXiS- dash-line box 42. In addition it is delivered to a subcarrier regenerator 44 which has the function of generating under control of the burst a continuous oscillation at color sub-carrier frequency and fixed phase with reference to that of the burst. The color sub-carrier regenerator 44 also includes components from which the second, third and fourth harmonics of the color sub-carrier are developed. A color sub-carrier regenerator circuit is disclosed in the article entitled Compatible Color TV Returning then to FIG. 3, it is seen that a second harmonic signal applied in opposite phases to the two halves of the axis selection tube 48 will effect a sampling of the chrominance at 90 intervals of the color subcarrier cycle,

i.e., along two orthogonal axes, and these may by proper phasing of the 7.2 me. be made the E -E and E --E axes of FIG. 4.

This is illustrated in FIG. 5 wherein waveform A represents the color sub-carrier, i.e., a voltage of color Receiver at pages 98 to 104 of Electronics for February sub-carrier frequency having its maximum at the burst 1953. The harmonic generators may comprise frequency multiplying circuits of conventional type and hence are not desribed in detail.

An additional function of the regenerator 44 is to prophase. Waveform B represents an arbitrarily assumed chrominance signal, such as might exist for example in the representation of a fiat field of uniform color. The R- M), R- M) B e) and n o ivde switching voltage for the cathode ray tube. This P s at which this chrominanceis sampled are noted on voltage takes the form of a sinusoidal voltage of color in view of the fact that the dwell time of the cathode ray beam on red phosphor strips is twice as long as its dwell time on either of the blue and green phosphor strips.

With this. make-up for the voltage E the E E axis is approximately collinear with the E axis in FIG.

4, neglecting the difference in amplitudes between the 65 .63E .59E and .45E vectors of that figure and neglecting the departures of their phases from a symmetrical 120 positioning. On the same assumptions, the E --E axis is orthogonal to the E -E axis, and it is so shown in FIG. 4.

The axis selection circuit 42 samples the chrominance output from circuit 40 along two axes at 90 to each other within the color sub-carrier cycle. For the cathode ray tube of FIG. 2, these axes are the E E and E -E waveform B, and waveforms C and D respectively represent the resulting A.C. voltages on

anodes

62 and 64. While waveforms A through D have a common time scale so that the relative phases of those waveforms are 5 indicated in the figure, no attempt has been made..to

show these waveforms in their correct relative amplitudes. The voltages C and D are seen to be of fixed phase with respect to the waveform A, irrespective of the phase or amplitude of the chrominance waveform B, but to be subject to changes in amplitude and polarity (i.e., 180 phase relation) with changes in the chrominance waveform B. The voltages of waveforms C and D, together with a suitable M (or Y) monochrome component, contain the information necessary to operate the tube of FIGS. 1 and 2. The E -E and E -E signals are however shifted in frequency to the second and third harmonics of the color sub-carrier before application to the cathode ray tube. Specifically, a band-pass filter 69 delivers to a modulator 70 E -E voltage appearing on 7 anode 62 in the 3 to 4 me. range. This modulator also receives, from regenerator 44, the third harmonic of the color sub-carrier through a phase control circuit 71. In the output of modulator 70 a frequency selective'circuit 74 selects the difference between the inputs to the moduaxes, which are shown in the vector diagram of FIG. 4. 75 later, over a frequency range of from 6.7 to 7.7 mc., and

this E -E voltage at the second harmonic of color subcarrier frequency is passedthrough an amplifier 76 before being applied to an adding network 78.

In similar fashion a network 80 selects within the 3 to 4 me. range the BI -E voltage on anode 64 of tube 48 and delivers them to a modulator 82, where they are mixed with the fourth harmonic of the color sub-carrier supplied from regenerator 44 through a phase control 84. A circuit 86 in the output of modulator 82 selects the difference between the two modulator inputs over a frequency range of from about 10.2 to 112 me.

carrier is passed through an amplifier 88, having an adjustable gain, before application to the adder 78. This addermay be of conventional type, and the sum signal is applied to the first control grid 5 of the cathode ray tube 4.

To. the cathode of tube 4 then is applied the NTSC luminance signal E derived from detector 31, or alternatively a modified monochrome signal A converter circuit for developing this E signal from Ey is described at various places in the literature, including US. Patent No. 2,814,778.

The propriety of these frequency shifts of the E -E and E -E voltages and the operation of the receiver of FIG. 3 therewith can be explained in a qualitative manner by consideration of FIG. 2 and of waveforms E, F and G of FIG. 5. From FIG. 2, it is apparent that red information is to be presented twice per switching cycle at 180 intervals thereof. It is also apparent that the separation, on centers, of adjacent green or blue areas along the cyclical cathode ray beam spot path 24 is alternatively 135 and 225 of the fundamental, and that the separation of adjacent blue and green areas is alternately 45 and 180.

In FIG. 5 waveform E represents as a function of time the switching voltage applied to the grid 12 of the cathode ray tube, and the red, green and blue phosphor areas to which this voltage carries the focal point of the cathode ray beam in its cyclical excursion have been sketched in. Waveform F shows, in full lines, the shape of the output of modulator 70 assuming the scanning of a fiat red field at the transmitter-assuming the voltage E -E to be along the positive E direction in FIG. 4. Waveform F shows in dotted lines the output of modulator 70 assuming the scanning of a flat blue or green field at the transmitter. The dotted waveform F is of half the amplitude of the full line waveform F because for E =0 and E =0, E E =.5R whereas for E =O, E =1 and EG=0, and E321, ER EM= EM=.,ZSEB,

Waveform G of FIG. 5, shows, in full lines, the third harmonic voltage Eg-E at the output of modulator 82 assuming the transmitter to be scanning a flat blue field, and it shows at the dotted line G the third harmonic voltage E -E assuming the transmitter to be scanning a fiat green field.

For a solid red field, waveforms G and G fall to zero amplitude.

It is evident from inspection of waveforms F, F, G and G that with a flat red field the cathode ray tube will be caused by waveform F to conduct on the red portions of the switching cycle of waveform E, and that with a blue field the dotted voltage of waveform F will combine with voltage G to cause the tube to conduct during the blue portions of the switching cycle.

Similarly, with a flat green field, the dotted waveform F and the dotted waveform G will combine to cause conduction during the green portions of the switching cycle.

Looking now at FIG. 2, it may be seen that the second harmonic component FI -E if in the polarity of waveform F as for a uniform red field, for example, will This, E E voltage at the third harmonic of the color subtend to gate on-the cathode ray beam, inta'receiver employing the tube of FIG. 2, atthc phases of the color switching cycle which carry the beam farthest from the axis 26, i.e. to gate it on over the strips of color X, which in the embodiment of FIG. 2 are red. For a fiat or uniform red field, the third harmonic component of waveforms G and G is of zero amplitude, and the tube produces red light only.

If, as is true for a field containing no red, the E E component possesses the polarity of waveform F, it will .tend to gate on the'cathode ray beam at the phases of the color switching cycle which bring the beam (or, more exactly, its point of focus on the target or screen) nearest to the axis 26. Under these circumstances the third harmonic voltage E -E will,- for a uniform green field, be of the polarity of waveform G (and it will of course be of non-zero amplitude), and it will tend to gate on the beam each time the beam passes over the strip 17 and also when the beam passes over strip 21. This last is rendered harmless however by the fact that E E voltage of waveform F is at its negative maximum, thus preventing the development of unwanted red light.

The sum of the second and third harmonic voltages will thus be to gate the beam on twice in the green strip 17, but the effect of the positive peaks of the second harmonic voltage G is to shift the points of maximum beam current downwardly in FIG. 2, toward axis 26, with a resultant tendency to contamination of the reproduced green picture by blue light from strip 19.

This error can be mitigated by the use of an E -E component at the fundamental color sub-carrier frequency and of suitable low amplitude phased to have its maximum positive effect (i.e. in increasing the cathode ray beam current) on the strip 15. While this additional Eg-E component at fundamental frequency will be unable to produce undesired red illumination on strip 15, due to the fact that the second harmonic ES -E voltage is there at its negative minimum, it will, when added to the second harmonic E -E and third harmonic BI -E voltages result in gating on of the beam most strongly at points higher on the strip 17, reducing contamination by blue light from strip 19. This E E fundamental component thus has the phase indicated in FIG. 5 by waveform E but having, for a green field, the polarity opposite to that af waveform E. For a blue field, it will be shifted in phase of the fundamental cycle and have the polarity of waveform E, its operation in that case being evident from a consideration of the foregoing discussion.

Such a fundamental E -E component is illustrated in FIG. 3 as being fed to adder 78 from anode 64 of tube 48, without frequency change, via an amplifier 81. The foregoing qualitative explanation of the operation of the invention has been given with respect to solid color fields only. The operation of the invention is however of course not limited thereto when the transmitter is scanning a fiat field in the color X which is the color of the strips under the grid wires, and waveform F represents the voltage E E when the transmitter is scanning a. field in either of the other two colors Y and Z. Waveform G represents generally the voltage E E delivered to amplifier 88 when the transmitter is scanning a flat field of the color Y, and waveform G represents at the voltage at the same point when the transmitter is scanning a flat field of the color Z.

The tube of the invention has at least three important -advantages over grid switching tube of the prior art.

One of these is the fact that, by adjustment of the amplttude of the switching voltage applied to the grid 12 white balance may be achieved without tampering with the signal or other voltages in the electron gun. In the operation of prior art grid switching tubes, such as those of the general type illustrated in Patent No. 2,745,035 including a strip configuration RGBG with adjacent grid conductors over adjacent red and blue strips, it has often patterns by virtue of beats with neighboring video frequencies in the intelligence. Such acomponent is particularly objectionable in the reproductionot black and white signals because of the absence in the received sig nal of a burst to which the color-switching voltage and hence this 3.58rnc. beam modulation component can bev locked. In the absence of such a burst, this-beam modui lation component cannot be dependably held to an odd multiple of one-half time frequency, as-is required to eifect cancellation thereof in the reproduced picture on successive scannings of the same line in the raster.

Another important advantage of the invention is that, in particular in the embodiment illustrated in FIG. 2 in which the red phosphor strips are disposed under the grid conductors, a great increase in brightness results from the increased dwell time of the cathode ray beam on the red and from the consequent reduced necessity to dilute the more efiicient blue and green phosphor materials employed in the other strips.

Still another important advantage of the tube of the invention is that it possesses the same number of phos- 1-0 red "electron optically centered behind adjacentof said conductors.

5. A cathode ray tube comprising an electron gun, a target having thereon a multiplicity of substantially parallel phosphor strips luminescent on electron impact in three a primary colors X, Y and Z additive to produce white light, and a multiplicity of linear conductors mounted phor strips in each of the three primary colors, making the resolution in the three colors more nearly equal.

I claim:

l. A cathode ray tube comprising an electron gun, a target area having a multiplicity of strips of material disposed thereon fluorescent in a plurality of primary colors X, Y, Z, and a grid of interlaced mutually insulated conductors arranged between the gun and target area, said strips being laid down in a repeating cycle according to the sequence XYZXZY, with said strips extending substantially parallel to said conductors and with adjacent of the strips fluorescent in the color X electron optically centered behind adjacent of said conductors.

2. A cathode ray tube comprising an electron gun, a target having thereon a multiplicity of substantially parallel phosphor strips luminescent on electron impact in three primary colors X, Y and Z additive to produce white light, and a multiplicity of linear conductors mounted between said target and electron gun, said conductors extending substantially parallel to said strips, alternate of said conductors being connected together and adjacent of said conductors being mutually insulated, said strips being laid down in a cyclical order XYZXZY with adjacent strips of the color X electron optically disposed behind adjacent of said conductors.

3. A cathode ray tube comprising an electron gun, a target having thereon a multiplicity of substantially parallel phosphor strips luminescent on electron impact in three primary colors X, Y and Z additive to produce white light, a multiplicity of linear conductors mounted between said .target and electron gun, said conductors extending subposed thereon fluorescent in a plurality of primary colors red, blue and green, and a grid of interlaced mutually insulated conductors arranged between the gun andtarget area, said strips being laid down in a repeating cycle according to the sequence red, green, blue, red, blue, green; with said'strips extending substantially parallel to said conductors and with adjacent of the strips fluorescent in between said target and electron gun, said conductors extending substantially parallel to said strips, alternate of said conductors being connected together and adjacent .of said conductors being mutually insulated, said strips being laid down in a cyclical order XYZXZY with adjacent strips of the color X electron optically disposed behind adjacent of said conductors, the strips of the color X being less eflicient than strips of the colors Y and Z in producing light from the energy of cathode rays incident thereon.

6. A cathode ray tube comprising an electron gun, a target area having a multiplicity of strips of material disposed thereon fluorescent in a plurality of primary colors X, Y, Z, and a grid of interlaced mutually insulated conductors arranged between the gun and target area, said strips being laid down in a repeating cycle according to the sequence XYZXZY, with said strips extending substantially parallel to said conductors and with adjacent of the strips fluorescent in the color X electron optically centered behind adjacent of said conductors, said strips fluorescent in the color X being less efiicient than strips of the colors Y and Z in producing light from the energy of cathode rays incident thereon and being wider than said conductors whereby a beam of cathode rays gen-.

erated in said gun may impact said strips of the color X from either side of the conductors behind which they are centered.

7. A television receiver for the display of color television signals of the color sub-carrier type employing three primary colors X, Y and Z additive to produce white, said receiver including in a cathode ray tube two electron beam intensity controlling electrodes, a switching grid of two sets of interlaced mutually insulated conductors and a multiplicity of phosphor strips laid down on a target in the cyclical order XYZXZY with adjacent strips of the color X aligned with adjacent of said conductors, said receiver further comprising means to develop luminance and chrominance signals in separate channels, means to take a first sample of the chrominance signal at opposite phases of the color sub-carrier cycle, one of said phases being the phase allocated to the color X, means to take a second sample of the chromin-ance at two opposite phases one-quarter cycle from said one phase, means to heterodyne said first sample with a voltage at a multiple of said sub-carrier frequency and to select the heterodyne signal at the second harmonic of saidsub-carrier frequency, means to heterodyne said second sample with a voltage at a multiple of said sub-carrier and to select the heterodyne signal at the third harmonic of said sub-carrier frequency, means to apply the sum of said second and third harmonic signals to one of said electrodes, means to apply a signal derived from said luminance signal to the other of said electrodes, and means to apply between said sets of conductors a voltage at sub-carrier frequency of such amplitude that the cathode ray beam in said [tube is directed in the aggregate for substantially one-half the color sub-carrier cycle to strips of the color X and for substantially one-quarter of the sub-carrier cycle to strips of each of the colors Y and Z.

8. A television receiver for the display of color television signals of the color sub-carrier type employing three primary colors X, Y and Z additive to produce white, said receiver including in a cathode ray tube a multiplicity of phosphor strips laid down on a target in the cyclical order XYZXZY and a switching grid adjacent said target with the conductors of said grid electron optically aligned with said strips of color X, said receiver further including means to develop luminance and chrominance signals in separate channels, means to take a first sample of the chrominance signal at opposite phases of the color sub-carrier cycle, one of said phases being the phase allocated to the color X, means to take a second sample of the chrominance at two opposite phases 'onequarter cycle from said one phase, means to heterodyne said first sample with a voltage at a multiple of said subcarrier frequency and to select the heterodyne signal at the second harmonic of the color sub-carrier frequency, means to heterodyne said second sample with a voltage at a multiple of said sub-carrier frequency and to select the heterodyne signal at the third harmonic of said subcarrier frequency, means to apply the sum of said second and third harmonic signals to a first beam intensity controlling electrode in said tube, means to apply to a second beam intensity controlling electrode in'said tube a signal derived from said luminance signal, and means to apply between the conductors of said switching grid a voltage at color sub-carrier frequency.

9. A television receiver for the display of color telev vision signals of the color sub-carrier type employing three primary colors X, Y and Z additive to produce white, said receiver including in a cathode ray tube two electron beam intensity controlling electrodes, a switching grid of two sets of interlaced mutually insulated conductors and a multiplicity of phosphor strips laid down on a target in the cyclical order XYZXZY with adjacent strips of the color X aligned with adjacent of said conductaors,-said receiver further comprising means to develop luminance and chrominance signals in separate channels, means to take a first sample of the chrominance signal at opposite phases of the color sub-carrier cycle, one of said phases being the phase allocated to the color X, means to take a second sample of the chrominance at two opposite phases one-quarter cycle from said one phase, means to heterodyne said first sample with a voltage at a multiple of said sub-carrier frequency and to select the heterodyne signal at the second harmonic of said sub-carrier frequency, means to heterodyne said second sample with a voltage at a multiple of said sub-earrier and to select the heterodyne signal at the third harmonic of said sub-carrier frequency, means to apply the sum of said second and third harmonic signals and of said second sample to one of said electrodes, means to apply a signal derived from said luminance signal to the other of said electrodes, and means to apply between said sets of conductors a voltage at sub-carrier frequency of such amplitude that the cathode ray beam in said tube is directed in the aggregate for substantially one-half the color sub-carrier cycle to strips of the color X and for substantially one-quarter of the sub-carrier cycle to strips of each of the colors Y and Z.

2,755,410 Schlesinger July 17, 1956

Claims

1. A CATHODE RAY TUBE COMPRISING AN ELECTRON GUN, A TARGET AREA HAVING A MULTIPLICITY OF STRIPS OF MATERIAL DISPOSED THEREON FLUORESCENT IN A PLURALITY OF PRIMARY COLORS X,Y,Z, AND A GRID OF INTERLACED MUTUALLY INSULATED CONDUCTORS ARRANGED BETWEEN THE GUN AND TARGET AREA, SAID STRIPS BEIN LAID DOWN IN A REPEATING CYCLE ACCORDING TO THE SEQUENCY XYZXZY, WITH SAID STRIPS EXTENDING SUBSTANTIALLY PARALLEL TO SAID CONDUCTORS AND WITH ADJACENT OF THE STRIPS FLUORESCENT IN THE COLOR X ELECTRON OPTICALLY CENTERED BEHIND ADJACENT OF SAID CONDUCTORS.