US3349172A

US3349172A - Electronic type composing apparatus utilizing a plurality of different type faces

Info

Publication number: US3349172A
Application number: US300007A
Authority: US
Inventors: Mauchel Derek John
Original assignee: Communications Patents Ltd
Current assignee: Communications Patents Ltd
Priority date: 1962-08-09
Filing date: 1963-08-05
Publication date: 1967-10-24
Anticipated expiration: 1984-10-24
Also published as: DE1249687B; GB965613A

Description

Oct. 24, 1967 D. J. MAUCHEL 3,349,172

ELECTRONIC TYPE COMPOSING APPARATUS UTILIZING A PLURALITY OF DIFFERENT TYPE FACES 3 Sheets-Sheet 1 Filed Aug. 5, 1963 8983mm HA1 .0

ll i

mohv mm 51.22

Oct. 24, 1967 D. J. MAUCHEL 3,349,172

ELECTRONIC TYPE COMPOSING APPARATUS UTILIZING A PLURALITY 0F DIFFERENT TYPE FACES 3 Sheets-Sheet 2 Filed Au 5, 1965 06L 24, 1967 n uc g 3,349,172

ELECTRONIC TYPE COMPOSING APPARATUS UTILIZING A PLURALITY OF DIFFERENT TYPE FACES Filed Aug. 5, 1963 3 Sheets-Sheet 5 A05 O\ i EQR E 2 wk R R I W wi s 8 Eu zwwnfig E $23K 8 v wdmikma m m 6m 3 Q E m3. HQEQQ m. Q 3 i5 28 ma R WK QEQEEQ E M23 (G United States Patent 3,349,172 ELECTRONIG TYPE COMPOSING APPARA- TUS UTILIZING A PLURALITY 0F DIF- FERENT TYPE FACES Derek John Mauchel, Her-sham, Sussex, England, assignor to Communications Patents Limited Filed Aug. 5, 1963, Ser. No. 300,007 Claims priority, application Great Britain, Aug. 9, 1962, 30,582/62 Claims. (Cl. 178-613) This invention relates to photographic type composing apparatus and more particularly to type compising apparatus wherein images of selected characters formed on the screen of a cathode ray tube are projected by optical means onto the surface of a photo-sensitive member.

It is known to employ electronic circuit arrangements involving a cathode ray tube for the generation of images corresponding to alphabetical or numerical characters. In such arrangements, the character images are generated by one of a number of different methods, for example, by raster scanning and beam modulation, by writing with the beam or by beam shaping.

In the raster scanning method, the intensity of the elec tronic beam of a cathode ray tube is controlled during the sweep period of each line of the raster. An image of satisfactory quality is provided by this method, but the circuits needed for translating the input command signals into beam control signals become complex when each character is required to have many different forms, corresponding to different type faces.

In the writing method, the desired shape is obtained by a combination of intensification and deflection of the electron beam. The shapes of the characters are such that they may be identified without difficulty, but it is not possible to provide characters having forms corresponding to the various type faces used in type composing machines.

In the beam shaping method, cathode ray tubes are used which differ in several respects from normal forms of display tube. The tubes transmit, not a scanning beam of varying intensity, but a direct electron image.

In one form of tube having a shaped beam, a character matrix is focused onto photo-emissive cathode, so that electrons are emitted from the cathode as a true image of the complete matrix. Characters are selected from the matrix by a first deflection system and are positioned into the desired format on the fluorescent screen by a second deflection system.

High composing speeds are obtainable with this form of tube, but the image on the screen is not defined with sufficient accuracy to provide the well-formed characters needed for high quality printing requirements.

In another form of tube having a shaped beam, a character matrix is provided by a series of stencil-like openings on a plate within the tube and the beam is shaped to the proper configuration by the stencil openings. The characters are again selected from the matrix by a first deflection system and are positioned on the tube screen by a second deflection system. This form of tube is capable of providing wellformed images at high printing speeds. but is expensive. Also, the number of characters available is limited to the number provided by the single matrix and is insufiicient to meet the requirements of high quality' printing.

It is an object of the present invention to provide electronic type compising apparatus capable of high-speed operation and of providing character forms of high quality, using cathode ray tubes of normal design.

It is a further object of the present invention to provide electronic type composing apparatus capable of providing a Wide variety of character forms.

Accordingly one aspect of the present invention pro vides type composing apparatus for the representation of selected characters by cathode ray tube apparatus comprising a first cathode ray tube having deflection means for scanning selected areas of a Screen of the tube, a plurality of character matrices each having a plurality of characters, a plurality of lenses for focusing an image of a selected area of the screen of the said cathode ray tube onto a character of each of the character matrices, light-responsive means for providing electric signals corresponding to the illuminated character of each matrix, means for selecting the electric signal from a single matrix, and a second cathode ray tube having deflection means for reproducing from the selected electric signal an image corresponding to the selected character of the selected matrix. Preferably, the particular character selected by the deflection means of the first cathode ray tube and the particular matrix selected by the matrix selection means are determined by coded electric signals fed to the apparatus.

According to another aspect of the present invention, in apparatus as described in the preceding paragraph, the deflection means of the second cathode ray tube includes correction means whereby variations in the position of the scanned areas on the screen of the first cathode ray tube, dueto instabilities in the deflecting means of the fi st cathode ray tube, are offset by movements in the position of the character image reproduced by the second cathode ray tube.

In order that the invention may readily be carried into effect, an embodiment thereof will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a simplified schematic diagram of an apparatus for producing high quality images of selected characters suitable for projection by optical means onto a photo-sensitive member;

FIG. 2 is a schematic diagram of a circuit arrangement for generating voltages by which the characters and the letter faces are selected; and

FIG. 3 is a schematic diagram of the deflection system of the apparatus of FIG. 1, in Which means is incorpoated to overcome the instabilities in the character selection system, so as to provide automatic registration of the selected characters.

In the apparatus to be described, it is assumed that the text of the matter to be printed has been prepared, using a keyboard machine of conventional type and that a record, for example a perforated tape, has been produced of thep repared text, which includes letter face, letter size, length of line, line spacing and line justification information. Further, it is assumed that the perforated tape is fed to a pneumatic or photo-electric sensing device to detect the presence or absence of perforations in the tape. The sensing device produces signals, of digital form, for controlling the character-generating apparatus of the invention and signals for controlling mechanism by which photo-sensitive material is moved so as to produce lines and columns of type. The mechanism controlling the movement of the photo-sensitive material does not form a part of the present invention and is not described.

Referring to FIG. 1, alpha/numeric symbols corresponding to six alphabets, e.g. three letter faces, upper and lower case, and contours corresponding to punctuation marks, etc., are represented as transparent areas on a group of seven matrices. One of the matrices is repre sented by reference 10. The matrices are of disc form and are mounted in a common plane on a support 11, in a manner to occupy an area of the support bounded by a circle of approximately minimum diameter. The matrices are demountable, to permit of interchange of type faces.

Characters of the matrices are illuminated by light received from the screen of a first cathode ray tube 12, by way of a group of seven object lenses, one of which is indicated by reference 13. The object lenses are mounted in a common plane on a support 14, each lens with its optical axis normal to the screen of the tube 12.

Each matrix contains a total of 37 characters uniformly spaced and disposed in an arrangement 5 x 5 characters square with three additional characters in a row along each side of the square. Each character is contained within an area 0.2 inch square. Thus, the 37 characters form a pattern which occupies substantially the whole area of a disc 1% inches in diameter. The matrices are provided with angular locating means, so that the vertical and horizontal parts of the characters of the. various matrices are in alignment when the matrices are mounted on the support 11.

The tube 12 has a fluorescent screen 12', approximately 5 inches in diameter. The focal length of each lens of the lens group is two inches and the distances between the support 14 and the screen 12' and between the support 14 and the support 11 are approximately eight inches and 2.66 inches respectively, so that the whole of, the screen of the tube 12 is imaged onto the surface of the seven matrices simultaneously.

The electrodes of the tube 12 are supplied with current from direct current sources S1, S2, and S3, to produce a focused spot on the screen of the tube. The spot is deflected by currents fed to

deflection coils

15 and 16 from vertical and

horizontal deflection amplifiers

17 and 18 respectively.

The

amplifiers

17 and 18 are fed with sawtooth waveforms from terminals 17 and 18' respectively, connected to, the outputs of frame and line waveform generators, which are not shown.

Feedback is provided to-the inputs of the amplifiers by resistors 15' and 16' connected in series with

deflection coils

15 and 16 respectively. A rectangular raster of uniform brilliance is produced on the screen 12. The

size of the raster is such that the area on the surface of each of the matrices, approximately 0.2 inch square, corresponding to the area occupied by a character, is scanned by the projected image of the spot. Voltages fed to X and

Y deflection plates

19 and 20 respectively, position the centre of the raster so that a selected character on the matrices is illuminated by the raster. The positioning voltages are formed in

selector units

21 and 22, having output terminals 21' and 22' respectively, from informa- 7 tion derived from the perforated tape record. The initial position of the raster is determined by voltages fed to X and

Y deflection plates

19 and 20 respectively, from the wipers of potentiometer controls 19" and 20". The

units

21 and 22 are described later in the specification.

The light transmitted by the matrices is collected by condenser lenses of a group of seven lens/photo-multiplier units. These units, one of which is indicated by reference 23, are mounted in a common plane, on a support 24, with the optical axis of each unit normal to and passing through the centre of one of the matrices. In each unit, light from an illuminated character is focused at a distance approximately five inches from the lens centre onto the photo-cathode of the photo-multiplier. The aperture of the condenser lens is made as large as possible, approximately 1% inches, in order that as much light as possible may be collected.

Electric signals generated in the photo-multiplier units by the light variations produced during the scanning of a character are passed, via gates 26 to 32, to the input of a video amplifier 33. A gate is operated to pass the signal output of. the photo-multiplier with which it is associated, corresponding to the type face it is desired to reproduce, only if a control voltage having a predetermined voltage level is fed to it.

The signals controlling the gates are derived from the tape record in a type face selector unit 34 and are fed to the gates via a DC. amplifier 25. Unit 34 is described in detail later in the specification.

The output signal of the amplifier 33 is fed to terminal 33', connected to a cathode of a second cathode ray tube 35, to modulate the beam intensity of the tube. The electrodes of the tube 35 are supplied with current from directcurrent sources S4, S5 and S6 to produce a focused. spot on the screen of the tube. Deflection coils 36 and 37 are fed with currents from

deflection amplifiers

38 and 39, respectively.

Feedback is provided to the input. of the amplifiers by

resistors

36 and 37 connected in series with deflection coils 36 and 37, respectively. The amplifiers are fed with sawtooth waveforms from terminals 17' and 18', so that the scanning rasters of the

tubes

12 and 35 are in synchronism. .Thus, an image is produced on the screen of the tube 35 corresponding to the character selected by the positioning signals derived from

units

21 and 22, the form of which is in turn determined by the signal derived from the type face selector unit 34.

The interpositioning of a lens between the tube 12 and each matrix enables the scanning raster to be imaged onto a character with a reduction in spot size of 3:1. The limitations in resolution present in normal. flying spot scanners, due to finite spot size and parallax produced by the finite, thickness of the glass face of the scanning tube, are thereby reduced. The use of a plurality of lenses and a plurality of matrices enables a large selection of characters to be provided in a single apparatus and, by disposing the characters of the matrices in a pattern to allow minimum spacing between the centre of the matrices, loss of resolution due to off-axis defocusing of the scanning spot is minimised. The image transmission systern provided by the photo-multiplier/cathode ray tube combinationprovides a magnified final image without the corresponding loss of brilliance which occurs in an all optical system.

The circuits of the

units

21, 22 and 34 are similar. The circuit of 21 is shown in FIG. 2. A three-element sensing device, not shown inthe drawing, detects the presence or absence of holes in the perforated tape record and provides a 3-bit digital signal to input terminals 40, 41 and 42 of

electronic gates

43, 44 and 45, respectively. Connected to the

gates

43, 44 and 5 are

resistor pairs

46, 46, 47, 47' and 48, 48', respectively. Each gate provides, from a DC. source 49, a substantially constant voltage across the resistor pair with which it is associated, whenever a hole is detected by the element of the sensing device connected to its input terminal. Summing

resistors

50, 51 and 52 are connected to the junctions of resistor pairs 46, 46', 47, 47 and 48, 48' respectively and to an output terminal 21'. The values of the resistor pairs 46, 46, 47, 47 and 48, 48 are chosen so that. the voltages occurring at their

junctions

53, 54 and 55 respectively have a 122:4 relationship. Thus a 3-bit binary coded signal fed to input terminals 40, 41, 42, produces a DC. signal at output terminal 21 which may have any one voltage level of a series of seven uniformly distributed voltage levels. The DC. signal is fed to deflection plate X of tube 12, FIG. 1, and the preset voltage from potentiometer 19" is fed to deflection plate X The value and polarity of the preset voltage and the values of the seven voltage levels are such that the mean position of the spot of the tube 12 may have any one of seven equi-spaced positions along the whole horizontal diameter of the tube.

Unit 22 is similar to unit 21 and also produces from a 3-bit binary coded signal fed to its input terminal, a DC. signal having one of seven voltage levels. This signal is fed via terminal 22, FIG. 1, to the Y deflection plate of the tube 12 and the preset voltage is fed from potentiometer 20" to the Y deflection plate of the tube. The values of the voltages are such that the spot of the tube may have any one of seven equi-spaced positions along the whole vertical diameter of the tube.

Thus a total of 7 X 7=49 positions are available using 3-bit binary coded signals fed to the input terminals of

units

21 and 22. In the present arrangement, 37 of the 49 positions are used, so that the usable positions lie within an area having an outline approximating to a circle. Unit 34 is also similar to unit 21 and produces, from a 3-bit binary coded signal, fed to its input terminals, a DC. signal having one of seven voltage levels. This signal is fed from output terminal 34 to the input amplifier 25. The amplifier output is fed to the control input of gates 26 to 32, FIG. 1. Each gate is adjusted to operate at a predetermined voltage corresponding to one of the seven voltage levels provided by the unit 34.

In the arrangement of FIG. 1, it is necessary for the deflection voltages of the character selector systems to have a high order of stability if accurate registration of the characters, reproduced on the screen of the tube 35, is to be achieved. The stability requirements of the system may be reduced if an automatic registration system is used. Such a system is incorporated in the deflection system described with reference to FIG. 3. In this system, each rectangular area of a matrix occupied by a character is provided with a transparent dot, so as to generate, in the video signal, a reference pulse at the instant the scanning pulse passes the dot. The dot is positioned so that the reference pulse is the first element of the video signal corresponding to a character. The pulse and a timing waveform co-operate in a manner to produce two correction voltages. The correction voltages and the scanning voltages of the tube 35 are combined in a sense to offset the inaccuracies introduced by errors in the positioning voltages of the scanning cathode ray tube 12.-

Reference is now made to FIG. 3, in which parts of the apparatus described with reference to FIG. 1 are shown bearing the same reference numbers as in FIG. 1. Frame and

line waveform generators

60 and 61, respectively, have their outputs connected respectively to input terminals 17' and 18' of

amplifiers

17 and 18, FIG. 1, and to input summing resistors of

amplifiers

38 and 39. As already described,

amplifiers

38 and 39 supply deflection coils 36 and 37 with currents to generate the scanning raster of the tube 35.

The amplifier 38 has summing

resistors

62, 63 and 64 connected to its input. Resistor 62 is fed from generator 60 with the frame deflection waveform, resistor- 63 is fed with a correction signal and resistor 64 is fed with the feedback signal generated across resistor 36'.

The amplifier 39 has summing

resistors

65, 66 and 67 connected to its input. Resistor 65 is fed, from generator 61, with the line deflection waveform, resistor 66 is fed with a correction signal'and resistor 67 is fed with the feedback signal produced across resistor 37'.

The correction signals are produced in a manner which is described later in the specification.

As is stated earlier in the specification, the mechanism of the computing apparatus controlling the movement of the photo-sensitive material to form lines' and columns of text from the successive character images reproduced on the screen of the display cathode ray tube is not described in the specification. For the purpose of explanation, however, it is assumed that a pulse signal, generated by a cam-operated contact 68, associated with the control mechanism of the apparatus, is fed to an input terminal 69 when the photo-sensitive material is suitably positioned for exposure.

The pulse signal from terminal 69 is fed to an input of the frame waveform generator 60 and to the set input of a first bistable unit 70. The generator 60 is a non-repetitive device and is triggered, by a pulse signal applied to its input, to generate a single sawtooth waveform. In a preferred. form of' the apparatus, the period of the waveform is 4 milliseconds.

A pulse, produced by the generator 60 at the commencement of the fly-back period, is fed to a reset input of the first bistable unit 70. The set and reset pulses condition the unit 70, so that a pulse is produced having a length corresponding to a frame waveform period. This pulse is fed to an input of the line waveform generator 61. In the generator 61, a succession of line scanning waveforms is generated only during the period of the input pulse. In a preferred form of the apparatus, the number of these scanning waveforms generated is approximately 200.

Thus, a single scanning raster is generated on the screens of

tubes

12 and 35 simultaneously, whenever a trigger signal is fed to input terminal 69. The video signal fed to terminal 33' modulates the beam intensity of the tube 35, so that a selected character, scanned by the beam of the tube 12, is reproduced on the screen of the tube 35.

In the arrangement so far described, the accuracy of registration of the reproduced characters depends upon the stability of the voltages generated by the

selector units

21 and 22. To offset any drift in the voltage generated by unit 22, a correction voltage is fed to amplifier 38 via a summing resistor 63. This correction voltage is derived by comparing the frame sawtooth voltage with a reference voltage. The compared voltage is fed to a store, which is clamped on receipt of the first element of the video signal produced by the reference dot, to retain the difference voltage which obtains at that instant of time. The reference voltage is set to a value equal to that of the frame scanning voltage at that instant when the position of the image of the scanning spot coincides with that of the reference dot, with no drift present.

The reference voltage is provided by a potentiometer 71 connected to a stable D.C. source of supply, not shown. This voltage and a sawtooth voltage from unit are fed to a comparator 72. The instantaneous difference voltage, of positive or negative polarity according to the relative magnitudes of the two voltages, is fed to a store 73. The store is supplied with clamping and reset pulses derived from an and gate 74 and from the bistable unit 70, respectively.

The store is a capacitor/bridge rectifier arrangement of conventional design. The capacitor is charged, on receipt of the clamping pulse, to the level of the voltage applied to its input and is discharged on receipt of the reset pulse.

The and gate 74 is fed with a pulse from bistable unit 70, one frame period in length, and with a video sigrial from terminal 33' of amplifier 33, FIG. 1. When the first element of the video signal is received, the gate 74 is operated and a clamping pulse is passed to the store 73. If the scanning raster is not accurately positioned with respect to the character being scanned, the reference pulse occurs at a period of time when input voltages to the comparator are not equal. Under these conditions, the difference of error voltage provided by the comparator '72, of positive or negative polarity, is stored in the unit 73.

The error voltage is fed, via an amplifier 82, to input resistor 63 of amplifier 38 in a sense to displace the positionof the scanning raster of tube 35 vertically by an amount to offset any discrepancy in amplitude of the voltage generated by the selector unit 22.

Drift in the voltage generated by selector unit 21 is offset by a correction voltage fed to amplifier 39. This correction voltage is derived from the line sawtooth voltage and from a reference voltage provided by a potentiometer 75, connected to a stable D.C. source of supply, not shown. This voltage and the line sawtooth voltage from unit 61 are fed to a comparator 76. The instantaneous difference voltage produced by the comparator, of positive or negative polarity according to the relative magnitude of the two voltages, is fed to a store 77 when a pulse signal is fed to the comparator via an and gate 78.

A second bistable unit 79 is set, by the trigger signal applied to terminal 69, to provide a signal to a first input of the and? gate 78, so that the first element of the video signal, fed to a second input of the and gate 78, is passed to the comparator.

A third bistable unit 80 is set, by the first element of 7 the video signal, to provide a signal to one input of an and gate 81. A pulse, produced by the generator 61 at the commencement of the ,fly-back period, is fed to a second input of the and gate 81. A reset signal is passed to the second bistable unit 79 when the two inputs to the and gate 81 are present simultaneously. The bistable unit 80 is reset by the trigger signal supplied to terminal 69.

The difference or error voltage, of positive or negative polarity, is stored in the unit 77. The error voltage is fed, via an amplifier 86 to input resistor 66 of amplifier 39, in a sense to displace the position of the scanning raster of the tube 35 horizontally, thereby to offset any discrepancy in the amplitude of the voltage generated by selector unit 21.

A potentiometer 83,connected to a DC. source of supply not shown, provides a bias voltage to the control grid of tube 35 via a summing resistor 84. This voltage is set to a value to cut off the electron beam during the period when a scanning raster is not being generated, so that an image of the stationary spot is not then formed. The signal provided by the first bistable unit 70 is fed to the control grid via summing resistor 85, to reduce the bias during scanning, so that an image of a character is provided by the video signal fed to terminal 33.

The same signal is fed to the grid voltage supply circuit 53 of tube 12, FIG. 1, so that screen 12' is not damaged in the period when no deflection voltages are being generated.

What we claim is:

1. Type composing apparatus for the representation of selected characters by cathode ray tube apparatus comprising a first cathode ray tube having deflection means for scanning selected areas of a screen of the. tube, a plurality of character matrices each having a plurality of characters, a plurality of lenses for focusing an image of a selected area of the screen of the said cathode ray tube onto a character of each of the character matrices, light-responsive means for providing electric signals corresponding to the illuminated character of each matrix, means for selecting the electric signal from a single matrix, and a second cathode ray tube having deflection means for reproducing from the selected electric signal an image corresponding to the selected character of the selected matrix, the deflection means of the second cathode ray tube including correction means whereby variations in the position of the scanned areas on the screen of the first cathode ray tube, due to instabilities in the deflecting means of the first cathode ray tube, are offset by movements in the position of the character image reproduced by the second cathode ray tube.

2. Type composing apparatus as claimed in claim 1, including a source of electric signals, said electric signals identifying, by the coded form thereof, the particular character to be selected 'by the deflection means of the first cathode ray tube and the particular matrix to be se-.

lected by the matrix selection means, said deflection means and said matrix selection means being controlled according to said coded electric signals.

3. Type composing apparatus as claimed in claim 1, in which said light-responsive means comprise a plurality of lens-photomultiplier units, each focused upon a character matrix, each connected for supplying an output signal to a separate one of a plurality of signal lines each including a switching gate, the electric signal from a selected matrix being derived from one of said plurality of signal lines, by opening a selected switching gate.

4. Type composing apparatus as claimed in claim 1, in which said plurality of character matrices each has similar characters correspondingly positioned thereon, the characters of different matrices corresponding to different type faces.

5. Type composing apparatus as claimed in claim 1,

in which said deflection means for scanning selected areas ofsaid first cathode ray tube comprise X and Y beamdeflection means supplied, respectively, with beam deflection controlled in magnitude by X and Y selector units respectively, each selector unit having three input terminals for a 3-bit binary coded input signal, three gates connected to control the potential. applied to signal summing means each according to the binary coded input signal to one input terminal and an output terminal supplied with an output signal from the signal summing means.

6. Type composing apparatus as claimed in claim 1, in which each area of a matrix occupied by a character includes: a point of distinctive optical characteristic, pro-- 7. Type composing apparatus as claimed in claim 6,

in which the deflection meansof the second cathode ray tube include X and Y beam, deflection signal amplifiers each having three summing resistors in its input, the first resistor being fed with a signal from the line and frame waveform generators, respectively, of the deflection means of the first cathode ray tube, the second resistor being fed with a line and frame correction signal respectively and the third resistor being fed with a feedback signal generated in a resistor in the outputof the same signal amplifier.

8. Type composing apparatus as claimed ,in claim 7, in which a character recording operation thereof is initiated by a control pulse, said control pulse being fed to trigger said frame Waveform generator and to set a first bistable unit which is reset by a pulse at the commencement of the fly-back of the frame waveform generator, the set reset conditions of the first bistable unit providing a pulse fed to render the said line waveform generator operative to provide a single raster on the screens of both said first and second cathode ray tubes.

9. Type composing apparatus as claimed in claim 8, in which'the correction signals to the second summing resistors of said X and Y beam deflection signal amplifiers are derived by comparing respectively the line waveform generator signal and the frame waveform generator signal with reference voltages at the instant of generation of said distinctive signal element of the selected electric signal.

10.. Type composing apparatus as claimed in claim .3, in which each switching gate of said plurality of signal lines opens solely upon application thereto of a control signal of predetermined amplitude different for each switching gate and the means for selecting the electric signal from a single matrix includes a selector unit having three input terminals for a 3-bit binary coded input signal, three gates connected to control the potential applied to signal summing means each according to the binary coded input signal to one input terminal and an output terminal supplied with an output signal from the signal summing means, said output signal 'being supplied selectively to control said switching gates.

References Cited UNITED STATES PATENTS 2,624,798 1/1953 Dinga l786.7 2,762,862 9/ 1956 Bliss l786.7 2,830,285 4/1958 Davis 2502l7 2,907,018 9/1959 Haining 1786.8 3,226,706 12/1965 Artzt 340-l46.3

IOHN'W; CALDWELL, Acting Primary Examiner.

DAVID G. REDINBAUGH, Examiner.

J. A. ORSINO, Assistant Examiner,

relationship of,

Claims

1. TYPE COMPOSING APPARATUS FOR THE REPRESENTATION OF SELECTED CHARACTERS BY CATHODE RAY TUBE APPARATUS COMPRISING A FIRST CATHODE RAY TUBE HAVING DEFLECTION MEANS FOR SCANNING SELECTED AREAS OF A SCREEN OF THE TUBE, A PLURALITY OF CHARACTER MATRICES EACH HAVING A PLURALITY OF CHARACTERS, A PLURALITY OF LENSES FOR FOCUSING AN IMAGE OF A SELECTED AREA OF THE SCREEN OF THE SAID CATHODE RAY TUBE ONTO A CHARACTER OF EACH OF THE CHARACTER MATRICES, LIGHT-RESPONSIVE MEANS FOR PROVIDING ELECTRIC SIGNALS CORRESPONDING TO THE ILLUMINATED CHARACTER OF EACH MATRIX, MEANS FOR SELECTING THE ELECTRIC SIGNAL FROM A SINGLE MATRIX, AND A SECOND CATHODE RAY TUBE HAVING DEFLECTION MEANS FOR REPRODUCING FROM THE SELECTED ELECTRIC SIGNAL AN IMAGE CORRESPONDING TO THE SELECTED CHARACTER OF THE SELECTED MATRIX, THE DEFLECTION MEANS OF THE SECOND CATHODE RAY TUBE INCLUDING CORRECTION MEANS WHEREBY VARIATIONS IN THE POSITION OF THE SCANNED AREAS ON THE SCREEN OF THE FIRST CATHODE RAY TUBE, DUE TO INSTABILITIES IN THE DEFLECTING MEANS OF THE FIRST CATHODE RAY TUBE, ARE OFFSET BY MOVEMENTS IN THE POSITION OF THE CHARACTER IMAGE REPRODUCED BY THE SECOND CATHODE RAY TUBE.