1 1 5 55~ 3 02 The presen-t invention relates to teletext and display 03 equipmen-t for general surfaces, comprised of wire sheaths and 0~ display apparatus, such as cathode ray tubes, receiving the 05 signals transmit-ted by the graphics tablets.
06 One known technique or direct writing on a screen i5 07 -that of the light pen. I-t is based on the use of a cathode ray 08 tube and thus cannot be used for ma-trix type flat screens (liquid 09 crystals, plasmas, electro-luminescent powders, etc.). The light pen technique is based on the synchronous detection by a 11 photodiode of the electron beam sweeping -the cathode tube. By 12 construction, the system allows the acquisition of only one 13 position of the light pen every half picture, which impedes the 14 detection of rapid small movements and thus requires a very low writing speed. For example, the system cannot be used to acquire 16 the fine details of a signature.
17 Graphics tablets with wire sheets are known. A wire 18 graphics tablet includes a non-conducting plate having two sheets 19 of wires, the wires being perpendicularly oriented and all insulated from one another. Ithe wires in one sheet are 21 sequentially energized by an electric current, -then the wires in 22 the next shee-t, and so on. A type of pen or ball point pen 23 enables one to write or draw on a sheet of paper covering the 24 non-conducting plate. The light pen is senstive to the electric field created by the currents passing in the wires and yields an 26 output signal from which the coordinates of -the tip of the pen 27 are determined. The signal thus recovered is used to display for 28 example on a cathode ray tube the writing or the drawing executed 29 on the graphics tablet. The tablet may thus be used to ac~uire in real time a drawing or script, to numerate the signal and to 31 transfer the information to a visualizing apparatus displaying 32 the writing or drawing on a screen, ~or e~ample the screen oE a 33 cathode ray tube.
34 The greatest inconvenience of this teletext system is that the writing surface is separate from the display or 36 visualizing surface.
37 More or less transparent conducting gratings mounted on 38 flexible transparencies are also known which are applied on 39 display screens which display predetermined drawings. These :~ 15~5~3 02 gratings are associa-ted with means which allow the selection of 03 one crossover point among the crossover points oE the grating in 04 order to control -the controllable component in the display 05 drawing under the selected crossover point. Gratings of this 06 type are described in the Luxemberg Patent 65,252, U.S. ~atents 07 3,758,718 and 4,066,855, and also in the publication of K. Crook 08 entitled "CRT TOUCH ~ANELS P~OVIDE MAXIMU~ FLEXIBILITY IN
09 COMPUTER INTERACTION" and published in the technical journal CO~TROL ENGINEERING, Vol. 23, No. 7, pages 33 and 34, ~uly 1976 11 or also in the publication of J.P. ~ennady entitled "COMPUTER
12 INTERFACE DEVICE" published in the IBM TECHNICAL DISCLOSURE
13 BULLETIN, Vol. 22, No. 8B, pages 3542 and 35~3, January, 1980.
14 In practice, these gratings are not graphics tablets as they allow only the selection of one crossover point, while a graphics 16 tablet must allow real time drawing with a display apparatus.
17 One object of the present invention consists of 18 providing a teletext and disp~ay apparatus for general surfaces 19 including a graphics tablet with transparent wires and not necessarily flat in order to match the writing surface with the 21 surface of a cathode ray tube receiving the signals transmitted 22 by the tablet.
23 Some experiments have indicated that coupling exists 24 between the display tube and the pen of the tablet. To remedy this inconvenience, which renders drawing useless, it is 26 suEficient, in the present state of the art to separate the 27 screen and the pen by about 1 metre. We must note that with 28 crossover point selection gratings, we do not have this type of 29 intarference.
Another object of the present invention consists of 31 providing means permitting the superposition of a transparent 32 graphics tablet onto the screeen of a cathode ray tuba.
33 According to one characteristic of the invention~ a 34 teletext and display apparatus is provided, as described above, including a graphics tablet with wires energized by alternating 36 currents, whose non-conducting plate is transparent and whose 37 wire sheets are perpendicularly oriented with one another are 38 made up of transparent electrical conductors or of small 39 electrical wires, which makes -them practically invisible, the 02 table being applied onto the screen of the cathode ray tube and 03 associated with means to detect the electric field created by the 04 alternating currents in order to deduce display signals which 05 are, amony other things, transmitted to the said display tube, 06 with, between the screen of the cathode ray tube and the bottom 07 side of the graphics tablet, a transparent non-magnetic 08 conducting coating.
03 In accordance with another characteristic, the electric current energizing the sheets of wires is a high frequency 11 current, for example, of the order of lOM~z.
12 More particularly, the invention is a teletext an~
13 display apparatus comprising a pair of wire sheet units forming 14 an orthogonal array of conductors, display apparatus for supporting the wire sheet units in front of a display un~t and 16 being operated responsive to signals from the array of 17 conductors. Transparent insulating apparatus separates the pair 18 of wire sheet units, whereby the wire sheet units form a graphics 19 tablet in front of the display area. The wires are energized with an alternating current. ~ transparent non-magnetic 21 conductive layer is interposed between the graphics tablet and 22 the display area.
23 The characteristics of the above mentioned invention, 24 as well as others, will become clearer af~er reading the following discription of embodiments, the said description being 26 made with referece to the adjoining figures, among which:
27 Figure 1 is a schematic view of writing and display 28 apparatus according to the invention, 29 Figure 2 is a cross-sectional view of a transparent tablet according to the invention, applied on the screen of a 31 cathode ray tube, 32 Figure 3 is a cross-sectional view of one variation of 33 the tablet of Figure 2, applied on the screen of a cathode ray 34 tube, and Figure 4 is a view of one tablet surrounded by a frame.
36 ln Figure 1, we have shown a cathode ray tube apparatus 37 1 operating as a television receiver, on the screen of which is 1 ~5~73 01 3a 02 applied a transparent graphics tablet 2. The pen 3 associated 03 with the tablet is connected to a transmission clrcuit, itself 04 connected to a reception circuit which energizes the receiver of 05 apparatus 1.
06 It should be noted that, in the condi-tions of the use 07 of the invention, the use of a pen leaving a written trace is not 03 compulsory. A pen, in the original sense of the term is 09 sufficient. This pen may even be a simple metal rod with an insulating sheath and a rounded tip.
11 On the screen of the cathode ray tube, is displayed the 12 drawing executed by the pen 3 on tablet 2. The transmission from 13 the pen to the apparatus being instantaneous~ the operator has 14 the feeling of writing directly on the screen of the tube which '!~
7 155~73 02 is visible through the -table. Thi5 iS why we can simple use, as 03 pen, a metal rod sheathed by an insulator. In other respects, if 0~ the receiver of the apparatus may receive signals coming from 0S other tablets, the opera-tor may participate directly in a 06 conference.
07 On the sect:ion of Figure Z, we have shown a layer 4 08 with, on one side, horizontal conductors 5, and on the other 09 side, vertical conductors, such as 6O The material of layer 4 is transparent, insulating, but allows the passage of magnetic 11 fields. Amongst the materials that could be used to make up 12 layer 4, glass can be noted.
13 The conductors 5 and 6 are conducting strips, of 14 negligible resis-tance and transparent.
To obtain these conducting strips, many -techniques are 16 known, such as, for example:
17 - cathodic vaporization of a transparent conducting 18 layer of a mixture o~ oxides of tin and indium (Indium Tin 19 Oxide-ITO), - the use of the PYROSOL procedure, developed at the 21 Commissariat a L'Energie Atomique, applied to coating wi-th 22 transparent conductors, 23 - a fabrication of transparen-t indium oxide conducting 24 films, according to a process described in the American technical journal "JOURNAL OF VACUUM SCIENCE TECHNOLOGY", Vol. 12, No. 1, 26 January, 1975, 27 - deposits of flouride doped SnO2 on Triplex glass 28 according to a process developed by the Societe Saint-Gobain, 29 - deposits o In2O2 on glass according to a process developed by the Societe Protis.
31 It is also possible to replace the conducting deposits 32 by wires, for example metallic, with negligible resistance and 33 very fine, for example a few hundredths of a mm. These wires may 34 be either glued to a transparent substrate or immersed in it.
~he small size of these wires makes them almost invîsible, thus 36 the transparency of the wire tablet.
37 It is clear that Erom the moment we know how to lay 38 conductors or glue wires of the layers of the active portion of a 39 wire tablet, we can easily realize these layers on non-fLat 1 1~55~3 02 surfaces.
03 Similarly, the active part of the wire tablet may be 04 realized on a flexible support. In this case, the 05 non-conducting, transparent substrate which is permeable to 06 electromagnetic ~ields must be flexible~ The respective 07 elasticity coefficien-ts of the substrate and the material of the 08 conductive layers must be chosen such that the deformation oE the 09 substrate does not bring about breaks in the conductors.
In the example shown in Figure 2, the electrical ll current passing in conductors 5 and 6 is a high frequency current 12 of the order of 10MHz. In Canadian Patent 1,101,961, issued 13 May 26, 1981, a graphics tablet is described for which the layers 14 are energized by currents having frequencies o-f the order of 10MHz, the searching frequency for the wires of the sheet being 16 of the order of one hundred kilohertz. Notwithstanding the 17 advantages already obtained by using this tablet with a high 18 frequency current, it has been observed that, if we apply such a 19 tablet to the screen 7 of a television which recei.ves the signals collected by the pencil of the tablet, the disturbances mentioned 21 above do not exist anymore, that is, the illuminated spot on the 22 screen follows the position of the pencil on the tablet.
23 On the section of Figure 3, we find layer 4, having its 24 sheets of conductors 5 and 6, placed against -the front lining 7 of the television tube. Between the layer 4 and the surface of 26 lining 7, a very thin layer 8 of non-magnetic material is 27 provided which may be a metal or a metallic oxide conductor 28 similar to the material used for the realization of the 29 conducting bands, the thickness of film 8 being small enough that it appears transparent. The film 8 which makes up a continuous 31 metallic surface is electrically connected to ground. In this 32 variation we can use low fre~uency currents in the sheets o~ the 33 tablet. In fact, the film 8 is a decoupling screen between the 34 current of the tablet and the electron beam of the tube.
In the preceding examples, a layer 4 is provided 36 between the two conducting sheets 5 and 6. However, this layer 37 carries out two functions, that is to be a material support for 38 the sheets and to insulate them, it appears that if enamelled ~ 15;573 02 wires are used the layers may be omitted as support and the face 03 of the television tube may be used to support the wires 0g directly. The wires may be fixed to the tube with transparent 05 glue. The positioning of the wires on the tube can be improved 06 by providing small grooves defining their lateral position. Of 07 course, a conducting layer under the wires, such as, 8, Figure 3, 08 can be provided.
09 In the preceding examples, a cathode ray tube screen can be used as display apparatus. It should be well understood 11 that the transparent graphics wire tablets in accordance with the 12 invention may equally well be applied to other types of display 13 apparatus.
14 It is of course necessary to connect the ends of the lS wires making up the sheets to the current sources to carry out 16 the search of the writing surface, for example as described in 17 the aforenoted Canadlan patent. Thus, we provide around the 18 tablet's writing surface, a frame made of insulating material in 19 which the end of each wire is connected to an electronic switch set in the frame or to a connection terminal carried by the 21 frame. The energizing and control currents being large in 22 number, it is advantageous, in order to reduce the number of 23 connections, to provide an address decoder set directly in the 24 frame near the switches.
Figure g illustrates a tablet provided with a frame 9 26 that surrounds the tube screen. On the table, the wire sheets 27 are set such that the parallax error due to the tube is 28 corrected. The end of each wire is extended on the frame 9 to a 29 switch 10, which in the described example can satisfy 70 connections. To simplify the embodiment, many connectors can be 31 provided, instead of a single one.