DE2038561A1 - Image transmission system - Google Patents

Description

7045-70 / Kö / s
RCA 60,946
Convention Date:
August 7, I969

RCA Corporation, New York, N.Y., V.St.A. Image transmission system

The invention relates to an image transmission system, in particular one in which the receiver side is in a novel manner Liquid crystal cells can be used for imaging. The system is particularly suitable for use in conjunction with a conventional television system for transmitting and receiving of multiplexed signals that are demodulated and separated in the receiver can be represented.

A television communication system is known at which the message information originating, for example, from a vidicon camera multiplexed in the form of sequences of line scan signals with the synchronizing signals of a conventional television signal and the multiplexed composite signal is transmitted to a receiver where the line scan signal sequences of the message information demodulated and imaged on a cathode ray tube. Such a system is true for many purposes but it has the disadvantage that one usually needs two cathode ray tubes: one for television reception and another for news information reception, so that the receiving device has correspondingly large dimensions and cannot be made easily portable. Another disadvantage arises emerges from the fact that when the one shown on the cathode ray tube Message information is to be copied onto light-sensitive paper, one must use a paper whose spectral

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sensitivity of the spectral emission characteristics of the phosphors the cathode ray tube is adapted.

In contrast, according to the invention, an image transmission system is provided a device for generating the light values v.m parts nines Image embodying electrical signal sequences characterized by a receiver with an arrangement of liquid crystal cells Le; n, to which the electrical signal sequences are fed sequentially, such that by controlling the light reflection and light transmission Properties of the liquid crystal cells reproduced the image parts on the arrangement of the liquid crystal cells sequentially will.

In one embodiment of the system according to the invention electrical signal sequences of message information with conventional TV signals are multiplexed into a composite video signal. The electrical signal sequences are demodulated, and the message information is shown on the receiver's liquid crystal cell array. The recipient is with a facility for copying the message information onto a photosensitive Record carrier equipped.

The system according to the invention, in the case of the pictorial representation the message information is an array of liquid crystal cells is used, offers a number of advantages over the known, with multiple cathode ray tubes working systems: the receiver can have smaller dimensions and a correspondingly lower weight; its power consumption is less; it is insensitive to magnetic stray fields and can therefore be made more easily as a portable device; he has a geometrical linearity, whereby facilitate assembly and adjustment or alignment; it can provide more light for the reproduction of the information presented deliver; and it offers better spectral matching of the light to light-sensitive recording media for copying purposes.

In the drawing show:

Figure 1 shows the block diagram of an embodiment of the

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BATH ORIGINAL

1 i ndungsjcreme AnI ape j;

Fi pur 2 a series of signal curves on common time phases, win they occur in the system according to FIG. 1;

Fi fmr. 3 and 4 fragmentary sectional views of liquid (χ .eitskri stall zellenan irdnunpen for use in the system according to I i f.iir 1; urd

S the schematic representation of an embodiment a copy nrichtuiifi for the system according to the invention.

The system according to the invention is exemplified below explained as / uliohtfrsystem in connection with a conventional television system.

The system 10 shown in Figure 1 consists of a "Send"; toil 12 and an Emofangteil 14 »which are each contained in the corresponding dashed rectangle. Plant 10 is in In this exemplary case set up in such a way that the message format i inen ν> n an original image 16 to an arrangement 18 of liquids 18a ... 18n, which are arranged in a straight line in the receiving part 14, for display and recording purposes be transmitted.

The transmitting part 12 contains a multiplexer 20 for multiplexing conventional video signals (television video signals) Video synchronization signals and signals from a Vidieonkauera (TV camera) 22. The vidicon camera 22 scans the original image ic, shown here as a card with grief η 12. "" on it, with a deflection frequency determined by a deflection generator 24 from left to right and from top to bottom.

The signal profiles A ... H shown in FIG. 2 are related to one another insofar as they have the same time base. The signal curve A gives the synchronizing signalgeraisch, consisting from the horizontal and vertical synchronization pulses, a common television signal again. This Synchronisiersignalgeeisch A is fed to the deflection generator 24, which generates the horizontal and vertical saw tooth oscillations according to the signal curves B and C.

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(Figure 2) generated for the beam deflection of the vidicon camera 22. the Horizontal deflection oscillation B is a sawtooth with a duration of approximately 63.5 microseconds, corresponding to the duration of one horizontal line interval in the synchronization mixture A, and with a repetition frequency of 60 Hz, i.e. the television frame change frequency. This in The original image 16 to be transmitted to the system 10 is therefore scanned by the video camera 22 at a frequency that is determined by the horizontal and vertical deflection saw teeth according to waveforms B or C and is therefore much lower than the sampling frequency of a conventional television camera (the reasons for this will be can still be seen). The horizontal deflection pulse according to signal curve B falls within the vertical blanking interval of the usual television signal and therefore does not interfere with normal television reception.

The output signals of the vidicon camera 22 are sequences of electrical signals (vidicon signals), one per scan line, as shown by the signal curve D in FIG. The vidicon signals (signal curve D) are generated in the multiplexer 20 with conventional video signals, for example from a studio television camera, as well as with the synchronizing signal mixture (signal curve A) multiplexed, so that a composite video signal results. The output of the multiplexer 20 may take the form of the composite video signal have according to the signal curve £ in Figure 2. Specifically, the signal curve E comprises a conventional video signal (television signal) with the additional information according to signal curve D from the vidicon camera 22. The composite video signal (signal curve E) is treated like a normal television signal in the transmitter, i.e. modulated onto a carrier and then transmitted or sent out. The transmission can either be wireless or via a coaxial cable. The transmitted, with the composite video signal (signal course E) modulated carrier is received at the receiving part 14 e.g. by means of an antenna (not shown) and a conventional television receiver 26, where the carrier is demodulated. The resulting composite video signal is sent to a sync signal separation circuit 28, which can be contained in the television receiver 26, as well as the input of an η-stage shift register 30. The shift register 30 has as many stages as there are liquids

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crystal cells (18a ... 18n) are provided in the arrangement 18. The television receiver 26 can be designed in a conventional manner so that it can accommodate the video signal parts of the transmitted video signal table (Signal curve E) reproduces.

The vidicon signal (signal curve D) is separated from the composite video signal (signal curve E) with the help of a clock pulse arrangement with the synchronization separation circuit 28, a key generator 31, a shift pulse gate 32 and a shift pulse generator 34, ie demodulated. The synchronization signal separation circuit 28 receives the composite video signal (signal curve E) from the receiver 26 and delivers a vertical synchronization signal on the output side according to signal curve F (FIG. 2). The vertical synchronizing signal can also be obtained from the synchronizing signal separation circuit of the television receiver 26. The vertical synchronization signal is fed to the gating generator 31, which supplies a gating signal according to signal curve 6 from the output side. This gating signal is a rectangular pulse which has the duration of a horizontal line, ie approximately 63.5 microseconds, and is synchronous with the horizontal deflection pulse (signal curve B) for the vidicon camera.

The shift pulse generator 34 generates a running sequence of shift pulses · The number of shift pulses during each 63.5 microsecond interval is equal to the number of stages in the η-stage shift register 30. By means of the gating signal (Signal- ^ f course 6) from the gating generator 31, the shift pulses H passed through the shift pulse gate 32 into the shift register 30. The shift register 30 is therefore only when the Auftastsignals 6 actuated, while it is inactive in the absence of the Auftastsignals. The input to shift register 30 is the video signal D, i.e. the demodulated composite video signal. The video signal D is therefore only in the shift register 30 during! of Occurrence of the shift pulses H scanned and saved. The duration of one line interval (approximately 63.5 microseconds) is required in each case to complete one line scan of the image 16 corresponding sequence of vidicon signals into the shift register 30

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insert.

After the 63.5 microsecond interval, the vidicon signals remain in shift register 30 until another signal sequence, which corresponds to the next line scan of the information, Will be received. This is the FaH after 1/60 of a second, i.e. after about 16 milliseconds. Each line scan, according to the Vidicon signals D, remains in for a period of 16 milliseconds Shift register 30 stored · The output signals of shift register 30 are either positive or negative DC signals. These direct current signals are sent directly to the corresponding liquid crystal cells 18a ··· l8n in the arrangement 18, so that they reflect their light reflection and light transmission properties control in a manner to be described.

The arrangement 18 of the liquid crystal cells l8a ·. · L8n is essentially described in U.S. Patent 3,322,485 (dated 30. 5 · 1967) described type trained ·

FIG. 3 shows a horizontal section of the arrangement 18 of liquid crystal cells 18 · ... 18n. The assembly 18 has two parallel glass plates 40 and 42 which are spaced apart by a spacer 44 of electrically insulating material about 25 microns or less. A separate pair of opposing electrodes is arranged in each of the cells 18a ... 18n. The electrodes, for example the opposing electrodes 46 and 48 in the cell 18a of the arrangement 18, are preferably transparent and can consist of layers of indium oxide or tin oxide on the plates 40 and 42 respectively. The space between the plates 40 and 42 is filled with a liquid crystal mass 50 which, for example, consists of a single organic, thermotropic, nematic compound such as p-anisal-pT-aminophenyl acetate

CCH «),

CHO - < _v , y-CH-N-Cv> • OC (CHj) ₂ CH ₃ or

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CH = N

or from a mixture, for example from equal parts by weight of the three compounds mentioned. The liquid crystal compositions described in US Pat. No. 3,322,485 can also be used. A mass 50 in shape
A mixture of equal parts by weight of the above three compounds has the advantage of a low crystal mesophase transition temperature (25 ° C.) and a wide operating temperature range (25 ° C. to 105 ° C.) in which the mesophase is stable.

The liquid crystal mass 50 is enclosed between the parallel plates 40 and 42 by suitable means, for example the spacer 44 '; however, separate connections for the various electrodes, for example 46 and 48, are led out of the arrangement 18, so that signals (voltages from the n-stage shift register 30) can be applied to the electrodes and the light reflection and light transmission properties of each cell can thereby be controlled. A reflective covering 52, for example made of aluminum or silver, is attached to the outside of the plate 40 so that light is reflected, as will be explained below
will. Alternatively, the electrode 46 can be made of both reflective and conductive material, for example aluminum
produce so that the reflective coating 52 is dispensable. Λ With the arrangement 18 of the liquid crystal cells l8a ... l8n
According to FIG. 3, the pictorial representation takes place by means of reflected light. The light reflection and light transmission properties of the liquid crystal cells result in a temperature range which is determined by the composition of the respective mass 50. The liquid crystal cell assembly is maintained at its operating temperature by any suitable known means.

Figure 4 shows an arrangement 18Ο, which is essentially the arrangement 18 is similar to FIG

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or transmitted light occurs. The effect and considerationjs wise of arrangements of the type of arrangements 18 and 180 made of liquid crystal cells is detailed in the above USA patent described. In short, this mode of operation is as follows: If between the two electrodes (e.g. 46 and 48) a cell has a voltage above a threshold value, i.e. a voltage that has a field between approximately 10 and 10 volts is generated per cm, there is a sudden change in the optical properties of the mass 50 in only that part the mass 50, which is located between the two electrodes and is exposed to the electric field. As a result, a Part of the incident light - which is preferably collimated - scattered and then reflected in the direction perpendicular to the front plate 42, so that this scattered light is observed visually or on a light-sensitive recording medium can be recorded. In the absence of an electric field between the two Electrodes of a cell, the mass 50 remains clear, so only that dark image of the reflective coating 52 is perceived.

In the case of the arrangement 180 according to FIG. 4, the pictorial representation takes place through perception of the light passing through. Will When an electric field is placed between the two electrodes of a cell, as described above, there is a sudden change in the optical properties in that part of the liquid crystal mass 50 which is directly between the two energized electrodes. In the case of the arrangement 180, this change in the optical properties manifests itself as a scattering of the light passing through. A viewer to whom so far the entire The mass 50 area appeared evenly light, now that part looks ale darker. The darker surface area corresponds only to that surface area that is defined by the field between the two conductive electrodes of the excited cell is affected.

In FIG. 1, the vidicone signals (demodulated from the composite video signal according to signal curve E) are from the η-stage shift register 30 of the arrangement 18 of liquid crystal cells l8a ... l8n. Those liquid crystal cells whose electrodes

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a voltage is applied, for example the cells 18a, 18b and 18c, are in a light-scattering state for 16 milliseconds, while e.g. the cell 18d, its electrodes are de-energized are not excited and consequently are not in a light-scattering state. The liquid crystal cells usually do not respond to excitation as quickly as the fluorescent substances in a cathode ray tube when excited by electrons strahlj, however, the interval of 16 milliseconds is long enough to switch the excited liquid crystal cells on and off and to set them ready to receive the information from the next line of the vidicon camera signals.

For copying or recording the information provided by the arrangement 18 of fluids ^ Liquid crystal cells of reflected light for the purpose of reproduction ™ of the original image 16 becomes a photosensitive recording medium 60 (Figure 1) in the direction of arrow 62, i.e. at right angles to the longitudinal extension of the arrangement 18 of the liquid crystal cells emotional. The transport of the recording medium 60 can be carried out by suitable devices with the scanning of the original image 16 must be synchronized. The image of the arrangement 18 is by means of a suitable optics, shown as a simple lens 63, focused on the recording medium 60. As a recording medium 60 one can use either photographic film in conjunction with a suitable camera or an electrophotographic recording material in connection with an electrostatic printing device from that disclosed in U.S. Patent 2,890,968 (dated June 16, 1959) or ^ U.S. Patent 3,168,021 (dated February 2, 1965) use. In an electrostatic printing apparatus, the recording material 60 is first made uniform, for example, by a corona discharge device charged, then imagewise exposed and finally developed with a suitable developer, as in the mentioned USA patents.

FIG. 5 shows a device for exposing the recording! carrier 60 with reflected collimated light when using the Arrangement 18 (Figure 3) of liquid crystal cells. The arrangement 18 is made up of light sources 64 and 66 with the aid of mirrors

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_ ₁₀ _ 2Ü38561

68 and 70 eit collimated light that is at an angle to the perpendicular of the Arrangement l8 is directed, illuminated. The light sources 64 and 66 and the mirrors 68 and 70 are arranged so that the on the array 18 collimated light from the array when none of the cells of the array 18 are excited with signals 18 is not reflected perpendicularly and not through the lens 63. When a cell of the arrangement 18 is loaded with a Excitation signal and corresponding light scattering through the liquid crystal mass between the excited electrodes, light is emitted from the relevant cell onto the image area of the recording medium 60 reflected. If you have the recording medium 60 every I / 60 seconds Moved by a distance corresponding to the width of the cell 18a... 18n, a reproduction can be made on the recording medium 60 of the original image 16 and then develop. When using the I80 arrangement instead of the 18, the recording medium 60 can also be exposed to light passing through the arrangement I80.

The invention can not only, as described above, use in conjunction with a conventional television system. Rather, other electrical signal sequences can also be used generated, transmitted and demodulated. For example, those from an electronic data processing system can be encoded in Form generated and transmitted over a narrowband channel electrical signal sequences after decoding in the receiver fiction_ processed in accordance with. Instead of an optical system working with reflected light, other arrangements, for example an optical system for contact printing of the displayed images on the recording medium by means of pass through to be used by the light.

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Claims (12)

Claims 1.) Image transmission system ext a device for generating ν> n light values of electrical signal sequences embodying parts of an image, characterized by a receiver (14), with an arrangement (18) of liquid crystal cells (18a ... 18n) and by a device (26 , 28, 30, 31, 32, 34) for the sequential supply of the signal sequences jan the arrangement of liquid crystal cells (18a ... . 2. image transmission system according to claim 1 thereby characterized that in the receiver a device (to, 63, (.4, 6 t », 68, 70) for copying the reproduced image parts is provided during the control of the liquid crystal cells. 3. Image transmission system according to claim 2, characterized characterized in that the copying device has a light-sensitive recording medium (60) and a device for exposing the same old contains the reproduced image parts. 4. Image transmission system according to one of the preceding claims, in which by scanning an original image at a predetermined frequency per line scan a signal sequence from in " Depending on the light values of the image in the course of the scanning changing signals is generated, thereby characterized in that the signal sequences of the arrangement of liquid crystal cells (18a ... 18n) are supplied in synchronism with the scanning of the original image, such that the lines of the scanned original image at the predetermined frequency can be reproduced sequentially. 5. Image transmission system according to claim 4, characterized characterized in that the recipient is a facility. 009887/1580 for copying the reproduced lines of the scanned original image exhibits during the excitation of the liquid crystal cells. 6. Image transmission system according to claim 5, d a d u r c h characterized in that the copying device one light-sensitive recording medium and a device for sequential exposure of the same with the "individual reproduced Contains lines. 7. image transmission system one of claims 4 to 6, dad ur ch marked that the facility a shift register receiving the signal sequences for supplying the signal sequences to the arrangement of liquid crystal cells (30) with one stage each for each liquid crystal cell and connection to this, as well as one connected to the individual stages Clock pulse generator (28, 31, 32, 34) which causes the signal sequences from the shift register are fed to the liquid crystal cells in synchronism with the scanning of the original image (16) contains, the individual signal sequences the liquid crystal cells energize until the next signal sequence arrives. 8 · Image transmission system according to claim 7, characterized in that the clock pulse generator device one connected to the individual stages of the shift register (30) Shift pulse gate (32), one on the shift pulse gate connected shift pulse generator (34) and a device (28, 31) which, under control by the signal sequences, the shift pulse gate and the shift pulses from the shift pulse generator into the shift register in coincidence with the signal sequences infiltrated in such a way that the Etissigkeitskristallzellen are excited synchronously with the scanning. 9 * image transmission system according to one of claims 4 to 8, characterized in that the liquid 009887/1580 crystal cells are arranged in a straight line next to each other, in such a way that a corresponding scan line of the original image is reproduced with each signal sequence 10. Image transmission system according to one of the preceding claims for transmitting and receiving composed of individual images, video and synchronizing signals containing image information, characterized by a first device (22, 24, 20) for generating message image information embodying line scan video signals and for sequentially multiplexing the same with at least the synchronization signals to composite television signals for transmission; second means (26, 28) for receiving and separating the individual ä NEN line scan video signals in the received Fernsehsignalge raising, wherein the multiplexing and the separation of the line scan video signals is carried out at a frequency of one line scan video signal per message frame per frame of the image information; and means having a liquid crystal cell assembly (Id) which, under the control of the separated line scan video signals, depicts the news image information. 11. Image transmission system according to claim 10, characterized in that the device with the liquid crystal cell arrangement has a number of liquid crystal cells (18a ... 18n) arranged in a straight line, a slide % register (30) with a number of the number of liquid crystal cells corresponding to Stages, each of which is connected to a liquid! keitskristallzelle is connected, a device (28, 31, 32, 34) for the sequential supply of the individual separated line scan video signals to the shift register and a device for supplying the line scan «Videoe: signals from the shift register to the Liquid crystal cell arrangement, j such that this · the line « of the image information reproduced sequentially, contains. 12. Image transmission system after Claim 10 or 11, 4 - 009887/1580 ORlQJNAL INSPECTED 2Ü38561 characterized in that, in addition, a television receiver (26) for receiving the composite television signals and for Representation of the image information is provided. 13. Image transmission system according to one of Claims 10 to 12, characterized by a device for copying the displayed message image information with a photosensitive recording medium (60) of the reference can be moved onto the liquid crystal cell arrangement synchronously with the line-by-line display of the news image information, in such a way} that the entire message picture information is copied « i'CIMAL INSPECTED 009887/1580