CONTROL FOR COLOR TELEVISION Filed Jan. 3, 1946 3. Sheets-Sheet l

[Pages:6]Dec. 13, 1949

Filed Jan. 3, 1946

C. E. HUFFMAN

CONTROL FOR COLOR TELEVISION

2,490,812

3. Sheets-Sheet l

S R RSR

-

\

4.44 ATIORNEY

Dec. 13, 1949

Filed Jan. 3, 1946

C. E. HUFFMAN CONTROL, FOR COLOR TELEVISION

2,490,812

3. Sheets-Sheet 2

Dec. 13, 1949

Filed Jan. 3, 1946

C. E. HUFFMAN CONTROL FOR COLOR TELEVISION

2 490,812

3. Sheets-Sheet 3

NVENTOR

4%44 &

BY

ATTORNE W

Patented Dec. 13, 1949

2490,812

UNITED STATES PATENT OFFICE

290,812

CONTROLFOR COLOR TELEVISION

Charles E. Buffman, Upper Montclair, N.J., as signor to Allen B. Du Mont Laboratories, ne,

Passade, N. J., a corporation of Delaware

Application January 3, 1946, Serial No. 638,800

4. Claims. (C. 178-54)

v

This invention relates to a device for obtain ing signals for use in color television to control the scanning path so as to confine it within a predetermined pattern.

In carrying out the invention, light from the image or screen is used in producing signals which cause the scanning spot to follow its intended path in the pattern so that the colors at the re ceiver correspond to those that are being picked

2 In the latter instance a set of photo-sens tive elements are used to develop a signal at the end of each horizontal line, which when ap

plied to the deflection system of the television tube or other image reproducing means as de Scribed in my application, Serial No. 638,799, fled of even date herewith, corrects for deviation from the proper scanning paths.

The photo-sensitive elements are illustrated

up at the transmitter.

0 as cells and will be referred to herein as cells, al

It is known that color television pictures can though photo tubes, barrier layer cells or other

be obtained without the use of moving color fil Suitable light responsive elements may be used.

ters by use of a screen in which each picture Load impedances or resistors may be placed in

line is divided into primary color lines and group both the anode and cathode leads of the photo ing these lines side by side in regular order and s sensitive elements or a single impedance or re

then scanning the individual color lines separ sistance may be placed in the cathode or anode

rately either in field groups of common color circuit and a phase-inverting stage used to

lines or by scanning lines of different colors obtain polarity reversed from that directly ob

in Sequence.

tained from the load impedance. Only one cell

A screen of this sort can be made by coating a per color is required although a pair of cells

surface with fluorescent material which emits white light or light including the desired pri

mary colors uniformly over its entire area and

having closely adjacent thereto on the viewed

may be used for each color when the full output

from each cell is desired without the use of a phase-inverting stage.

The invention may be understood from the de

side, a stationary filter element divided into nar Scription in connection with the accompanying

row adjacent strips colored in the primary Colors. drawings in which:

Or a screen of this character which is more Fig. 1 is a diagram showing an illustrative em

efficient can be made up of three different fluo bodiment of the device;

rescent materials which are themselves arranged Fig. la is a diagram showing a modification

in narrow adjoining strips, in groups contain 30 of a portion of Fig. 1;

ing a narrow line of each of the three different Fig. 2 is a view of that portion of a scree

color emitting phosphors. A screen of this sort which is used as the control area;

is described in my application, Serial No. 623,053, Fig. 3 is a front view of that portion of the

filed October 18, 1945, now abandoned.

Screen on an enlarged scale and partly broken

With a screen having the desired characteris 35 away; tics as indicated above, there is the problem of Fig. 4 is a perspective view of a striated screen

insuring that the Scanning spot traverses the having lines of material which emit light of dif

proper color line and is not displaced therefrom ferent colors, with photocells in front of the

by voltage fluctuations, or by some other dis Screen;

turbance.

40 Fig. 5 is a similar view of a homogeneous fluo

With the present invention signals are ob int Screen with a striated color filter in front tained by means of photosensitive elements which of it:

may be used to control the path of the scanning Fig. 6 is a similar view showing the image of

of a television image. These signals may be used the screen shown in Fig. 4 projected upon an

as the deflecting means or they may be used to 45 auxiliary Screen with photocells disposed before

supplement other deflecting means. The scan the cathode-ray tube.

ning spot is promptly returned to its proper path Fig. 7 is the same as Fig. 3 except that the

after any deviation therefrom. These signals photocells are disposed in front of the auxiliary

are obtained from photoSensitive elements that Scree.

are illuminated by the image or a projection Fig. 8 - the same as Fig. 6 except that the

thereof.

cathode-ray tube screen is made up of homo

The entire scanned area may be used to pro geneous color emitting screen material with a

vide these signals or a small portion of the end striated color filter in front of it.

of each Scanning line may be used for a con Fig. 9 is the same as Fig. 8 except that the

trol area separate from the picture image.

55 cells are disposed before the auxiliary screen

2,490,812

3 shown in Fig. 8 and the image is projected upon an auxiliary screen with a color filter close to a cathode-ray tube screen, with photocells dis

posed before the filter. Fig. 10 is a perspective view showing a cathode

ray tube having a homogeneous screen with its image projected upon an auxiliary Screen which

has a striated color filter incorporated in it with

4.

The voltages at Ti-T (Fig. 1) as shown in Fig.11

are as follows:

T is negative signal when red light is emitted by

Screen 5.

T2 is negative signal when blue light is emitted by Screen 5.

T3 is negative signal when green light is emitted

photocells disposed before said auxiliary screen. by Screen 5.

.

Fig. 11 is a schematic view showing several paths of a scanning spot through a control area

0.

T4 is positive signal

Screen 5.

when

red

light

is

emitted

by

and the signals generated thereby.

T5 is positive signal when blue light is emitted by

In the drawings corresponding parts are pro Screen 5.

vided with the same reference characters. Ref erence characters are provided with Subscripts

T6 is positive signal when green light is emitted

by Screen 5.

which identify the respective figures in which they As shown in Fig. 1, three photo-sensitive ele

OCC.

In the drawings reference character indicates

ments 8, 9 and 20 are used in a three color sys tem. Element f8 is sensitive substantially to red

a television receiver using a cathode-ray tube of light only, element 9 is sensitive to blue light only

a television receiver having the usual vertical deflection means 2 and the horizontal deflection means 3. These deflecting means may be either coils or plates.

20

and element 20 to green light only. It is well

understood however that photoelements that are

not inherently color selective may be used in co operation with color filters for the same pur

In this embodiment of the invention the image p0Se.

is indicated as being on the Screen 4 of fluorescent These photoelements may be shielded and

material which is applied to or aSSociated with the tube . This screen in a three color system may consist of groups of red, blue and green colored lines R., B and G. In the control area, 5

hooded to exclude extraneous light and electrical disturbances. When desired they may be lo cated to one side of the screen area 5 and light may be directed to them by a mirror or optical

at one side of the Screen 4 red, blue and green 30 System, so located and of Such a size as not to

fluorescent lines R', B' and G' are provided which are continuation of the picture portion of the

obstruct view of the picture area of the screen 4.

As the Scanning of a complete frame or field

Screen 4.

The portions following phototubes of 6, 7 and 8, or phototubes 6a, 7a and 8a, represented by

block fo, indicate equipment described in detail in my application, Serial No. 638,799, filed of even

3 5

of the screen 4 progresses a series of short bright

parallel lines is produced in the control area S.

Light from this area falls on the photoelements 8, 9 and 20. When the beam is being deflected at the proper rate, the short lines are all of one

date herewith.

color, namely, that of the field being scanned at

As stated in the above mentioned application, the integrating circuit shown therein is adapted 4.

the moment, and because of the nature of these

photoelements or because of the selective filters

to deliver signals to the cathode-ray tube deflec before these photoelements, only the photoele

tion system in which the intelligence derived from

part of a line in a control area is extended to affect

Substantially an entire line or more. In this way a small part of a line is used to

correctly locate the whole line. The control area

ment adapted to that color is excited.

However, when Some disturbance causes the

Scanning spot to depart from its proper trace it

5 Scans a line of another color thus producing a Signal which returns the spot to its proper posi

at the end of the line may be modulated to max- . imum or a definite light intensity regardless of picture content of that line and provides for

tion. The way this is done is indicated in Fig. 11. In this figure reference characters G, R and B indicate green, red and blue lines in the control

maintenance of the line in proper relation whether the picture contains any component of the color being scanned or not.

During the operation of this device in a three color System, signals are produced acroSS load

resistors 2-7 in the following manner. When

50 55

area 5 (Fig. 3) on an enlarged scale. When the spot is tracing only one line, say the red line S,

both a positive and a negative signal R-- and R are produced as shown in Fig. 11 and no pulse is applied to the block ?o as explained in my ap

plication fled herewith.

lines R. emit light the red filter 8 transmits red light to cell 6 causing it to conduct current from battery 9 through resistances 2, and 3 back to the battery. In like manner, blue light from lines B' transmited through filter f causes cell to conduct current from battery 9 through resista ances 4 and 5, and in like manner green light

60

.. When the spot becomes displaced and begins to Scan a green line as shown at 4' as it begins to get off of a red line 5' the signals R'-- and R'- are produced which do not apply a pulse to block 0, but the signal G'- produced by the green line causes the spot to return to its proper trace as explained in said application.

from lines G' transmitted by filter 20 causes cell 8 to conduct current from battery 9 through re sistances 6 and f. The voltage drop developed across these resistors provides signals which are applied to the deflection system of cathode-ray tube through equipment represented by block 0 as described in my application, Serial No. 638,799, filed herewith.

Fig. 11 illustrates several possible conditions

"Of the Scanning Spot and the resulting voltages at the output terminalsT-Ti, Fig. 1, with respect

to ground. The voltage of battery 9 is separated

65 70

Similarly the spot is returned by the signal

B'-- when it begins to scan a blue line B'.

In the modification shown in Fig. 4 the screen is made of striated lines of red, blue and green fluorescent material R4, B4 and G4 from which signals are obtained by phototubes R., B and C for Scanning spot control as described above.

In the modification shown in Fig. 5 a homo geneous fluorescent Screen S5 is provided with a striated color filter F made up of red, blue and

green color strips Rs, Bs and Gs for obtaining the

different color lines.

from these ottput voltages by condensers C-CB. 75 In the modification shown in Fig. 6 the image

2,490,812

to be viewed is projected upon an auxiliary Screen S6 with the photocells located so as to intercept light from the cathode-ray tube Screen.

The modification shown in Fig. 7 is similar to

6

control signals for the beam of said cathode-ray tube, and means to apply said control signals to

s beam deflecting System of said cathode-ray

ube.

Fig. 6 but the cells are located in front of an aux 2. In a Scanning system for use in color tele

iliary screen S7 onto which the image is pro vision, a cathode-ray tube having on the inside

jected.

face thereof groups of parallel lines of screen

The modification shown in Fig. 8 is similar to material in Sequence, each line in a group fluoresc Fig. 6 except that the cathode-ray tube Screen is ing in a color different from those of the other made up of homogeneous color emitting Screen ( lines in Said group, short lines of Screen material material with a striated filter before it and with aligned with Said parallel lines at one end thereof

photocells located so as to intercept light from to provide a signal producing area, the beam of

the striated filter Fs.

Said cathode-ray tube being modulated to a

The modification shown in Fig. 9 is the same definite intensity while traversing said signal pro

as Fig. 8 except that the cells intercept light from ducing area, light filters located in front of said

an auxiliary Screen Sg.

area which pass red, blue and green light, re

In the modification shown in Fig. 10 the light spectively, phototubes located in position to re

from a homogeneous screen S10 is projected by ceive light from the respective filters and produce

lens system PO onto an auxiliary screen AS10 that control signals for the beam of said cathode-ray

is provided with color filters or lines of color sep arating elements through which the light reaches

20

tube, and means comprising a Source of potential and resistors between said source and said photo

the phototubes 6, 7 and 8 and is used for keeping tubes to apply said control signals to the beam

the scanning spot aligned as described above.

deflecting system of said cathode-ray tube.

Figs. 1 to 5 show how this invention can be 3. The system of claim 1 in which adjacent practiced when images are to be viewed directly 5 lines of Said short lines emit light of different on cathode-ray tubes and Figs. 6 to 10 show how colors.

the invention can be practiced when images are 4. The system of claim 1 in which light of dif

to be projected optically upon an auxiliary Screen. ferent Color is emitted from adjacent lines of said

What is claimed is:

short lines directly to Said light filters.

1. In a Scanning system for use in color tele 3) vision, a cathode-ray tube having on the inside

CHARLES E. HUFFMAN.

face thereof groups of parallel lines of Screen ma

REFERENCES CITED

terial in sequence, each line in a group fluorescing in a color different from those of the other lines in said group, short lines of Screen material

3. 5

The following references file of this patent:

are

of

record

in

the

aligned with said parallel lines at one end thereof

UNITED STATES PATENTS

to provide a signal producing area, the beam of said cathode-ray tube being modulated to a

definite intensity while traversing said signal pro

Number

Name

Date

2,415,059 Zworykin ---------- Jan. 28, 1947

ducing area, light filters located in front of said

FOREIGN PATENTS

area which pass red, blue and green light re spectively, phototubes located in position to re ceive light from the respective filters and produce

Number 524,443

Country

Date

Great Britain -------- Aug. 7, 1940

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