DE2748149A1 - TV set with flat screen - has electrodes running on both sides of layer, on which pulses propagate and when they meet layer properties are changed - Google Patents

Abstract

The screen has a layer between two transparent plates, connected to several electrodes. Its optical properties are changed by application of an electric field. The electrode (73, 74) run along the picture screen lines, and are supplied with pulses (11, 12), which separately do not change the optical properties of the layer (72) but these properties are changed when two pulses propagating along different electrodes meet at a picture point. The pattern of propagation of pulses is such as to produce a normal TV scan. The TV picture may be produced by a very thin assembly.

Description

Flat screen TV

The invention relates to a television set with flat screen, in which the screen has a layer of liquid crystal between two transparent panels which is in communication with electrodes.

Efforts have been made for a long time on television sets without a picture tube get along because the picture tube is a sensitive part, the large dimensions and also requires high voltages and causes large heat losses. Instead of The picture tube can be used with a flat screen that has a layer of one Contains material whose optical properties are obtained by applying an electrical Field can be changed. This is the case with display devices, for example known to use liquid crystals which have birefringent properties and change the polarization direction of incident light. These liquid crystals are located in a gap between two glass plates, each with one on the outside Polarization layer are coated. The polarization layers have different ones Axes of polarization so that the entire plate without the action of an electrical Field does not let light through. On the other hand, it is connected to electrodes that are attached to the liquid crystal layer are connected, a voltage is applied, then the orientations change the molecular axes of the liquid crystal and the direction of polarization of the incident Light is changed. If you place a light source behind the entire plate, So you can adjust the amount of light shining through by modulating the amount applied to the electrodes applied voltage can be changed. The application of this principle on TV screens in which a large number of pixels in an image plane has not yet been realized with the desired success.

The object of the invention is to provide a flat screen television to create, in which in a simple manner a distribution of the image pulses on the different parts of the screen.

To solve this problem, the invention provides that the Electrodes run linearly along the lines of the screen and each with pulses that are individually insufficient to the optical properties of the Change layer, and that the pulses are such that the local Meeting of two impulses on different electrodes at one pixel of the screen the optical properties of the layer at this pixel accordingly the total amplitude of the coincident pulses can be changed.

Such a flat screen does not have the disadvantages listed above the picture tube. He gets by with relatively low voltages. The tensions of the individual impulses at each of the electrodes are not sufficient to generate a pixel to change the appearance of the screen. Only when both impulses meet, an image point is generated at the points where they meet, its brightness depends on the total amplitude of the summed pulses. Because the impulses only meet for a short period of time, the screen should expediently have a wear photoluminescent coating that lets the pixel shine longer than that The overlapping of the impulses that meet each other continues.

In an advantageous development of the invention it is provided that along Each line of the screen has two electrodes that are attached to one end of the first Electrode first pulses with a first pulse frequency are applied, the amplitudes of which are modulated according to the image signals that to the opposite end second pulses with a second pulse frequency are applied to the second electrode, and that the two pulse frequencies differ slightly from one another, such that a first pulse and a second pulse as a result of the transit time delays meet at different points on the screen line.

If the first and the second pulse are exactly at the same time to both If the ends of a screen line are pending, they meet in the middle of the line. If the second impulse is sent e.g. from the right end of the line before the If the first impulse is sent from the left end of the line, both impulses hit in the left half of the line. This can be done by appropriate determination of the phase difference between the first and the second pulse is the point of the The meeting of both impulses can be changed on the screen. Because these changes must occur continuously, the first pulses have a fixed frequency and the second pulses also have a fixed frequency. Both pulse frequencies differ only slightly from each other. The second pulse frequency is preferred slightly smaller than the first pulse frequency.

The ones needed to change the optical properties of the layer Potentials are preferably obtained by applying the pulses to the two electrodes opposite Have polarities. This way they add up when the impulses meet the electrical voltages. Because the time span the mutual overlap of two impulses is only very brief the pulse intervals not from zero voltages, but from a bias voltage. on in this way the electrically changeable layer becomes a bias potential from which the switchover takes place more quickly with incoming impulses.

In the case of smaller screens, the electrodes of all lines of the screen can be used be connected in series. The first pulses are for example at the top left corner of the screen while the second pulses fed to the other End of the electrode lead, which is located at the lower right corner of the screen. The first and second pulses are sent to different ones Electrode leads laid.

In the following, an embodiment of the invention is referred to explained in more detail on the figures.

Fig. 1 shows schematically the path of the first pulses and the second Pulses on a relatively small screen with the electrode pairs all together Lines are connected in series, Fig. 2 shows schematically the meeting of two Pulses at a pixel, Fig. 3 shows a schematic block diagram of the invention Television set, Fig. 4 illustrates the time relationships between the first and the second pulses in the generation of successive pixels, and FIG. 5 schematically shows the division of a screen into several areas to avoid multiple overlaps of a second pulse with first pulses.

In Fig. 1, a flat screen 10 is schematically according to the invention shown. On this screen there are pairs of electrode lines along the lines of the image 11 relocated.

In Fig. 1, the electrode conductor pairs are each with only a single one Line indicated that marks the relevant line. Lines 11 run from left to right and the right end of each line is with the (left) beginning connected to the line below. This means that the electrode pairs of Lines are connected in series in a corresponding manner.

A first pulse I1, which is applied to an input line 12, that is connected to the beginning of the first line runs through all lines 11 each from left to right and finally arrives at line 13, which connected to the left end of the bottom line.

It should be noted again that the lines 12, 13, as well like the rows labeled 11, each consisting of a pair of continuous electrodes exist, so that in reality there are two parallel conductors. The impulses I1 and the pulses I2 are placed on different conductors.

To generate the first pixel at the top left of On the screen, the pulse I2 runs through all the image lines from right to left and from the bottom up. Only when it has reached the top line of the picture, the first pulse I1 is generated on line 12, so that both pulses 11 and I2 on meet the desired pixel. The two impulses have different ones Polarities so that their voltages add up. The total voltage depends on the amplitude of the relevant pulse I1. These amplitudes vary accordingly the signal voltage of the image signal. This will make the differences in brightness achieved. In contrast, the amplitudes of the pulses I2 are constant.

In Fig. 3 is a block diagram of a television receiver according to Invention shown. The television signal arrives from the antenna 15 in the receiving section 16 where it is amplified. This then takes place in the amplifier and demodulator 17 demodulation. In the step 18, the image signals are changed from the audio signals separated. The sound signals are fed to the loudspeaker 19, while the image signals be passed to a gate circuit 20. The line synchronization signals are derived from the Circuit 18 led out and via a line 21 to the pulse generators 22 and 23 given.

The pulse generator 22 generates the pulses I1 with a pulse repetition frequency f1, while the pulse generator 23 generates the pulses I2 with a frequency f2. The frequencies f1 and f2 differ only slightly from each other, as follows will be explained. The pulses I1 are fed to an analog gate circuit 20, which is controlled thereby and the image signals while the impulses are pending I1 lets through to the screen. To this A pulse sampling is carried out of the image content.

The repetition frequency of the image pulses I1 depends on the size of the screen away. As an example, assume that a screen has a width of 834 mm and a Height of 625 mm. This corresponds to a common screen format.

The screen has 625 lines and the required number of luminous dots amount to 834.

With the usual television signals, the scanning time for one line is 52.5 ps, plus 11.5 ps for the line return. In 52.5 Zs there are 834 image pulses necessary. This means that an image pulse is always generated after 62.949 ns got to. Taking into account the fact that the pulses travel at the speed of light move forward, the length distance between two image pulses is 19075.727 mm.

The current pulse is required to run a line 834 mm long 2.7522 ns.

Should the two opposing pulses I1 and I2 be spaced apart of 1 mm from the beginning of the line, when the impulses meet, the from The pulse emitted at the beginning of the line runs through a period of 0.0033 ns and the Pulse 12 emitted from the end of the line has passed a period of 2.7489 ns. This applies to the line length of 834 mm mentioned above.

If the meeting point of the two pulses is 2 mm from the beginning of the line, then the first pulse I1 (image pulse) requires 0.0066 ns and the second pulse I2 2.7456 ns to get to this point. Postpone these times themselves for every 1 mm distance on the line by 0.0033 ns.

These relationships are shown for one image line in FIG. The abscissa values characterize the distance between the pixel and the line spacing and the time is plotted on the ordinate. The times of the Applying the pulses I1 to the line 12 (Fig. 1) and the times on the right edge of the application of the pulses I2 on line 13 is recorded.

A first pulse 30, which is sent from the beginning of the line at time 0 reaches the end of the line after 2.7522 ns.

Assume that a second pulse is 41 after 60.2043 ns after the time 0 is sent from the end of the line and that a first pulse 31 after a time of 62.9499 ns, i.e. later than pulse 41, from the beginning of the line is sent. Both pulses 31 and 41 hit at a point in time of 62.9532 ns (based on time 0) at a point 51 on each other, which are a distance 1 mm from the beginning of the line. The remaining values for the pulse generation at the beginning of the line and at the end of the line for generating the pixels 52, 53 and 54, which are each from one another have a distance of 1 mm are shown in FIG. 4.

In the selected embodiment, the first pulses have I1 intervals of 62.9499 ns each, resulting in a pulse repetition frequency f1 of 15.885648 MHz corresponds. The pulses I2, on the other hand, are spaced apart from one another in time of 60.2043 ns, which corresponds to a frequency 2 of 15.883983 MHz.

The image pulses 12, the amplitudes of which correspond to the time course of the line signal are modulated at time intervals of 62.9499 ns taking into account their propagation at the speed of light a spatial one Distance of approx. 19 m from each other.

This means that the next following pulse is generated, if the first impulse on the screen has a line length of approx. 19 m (including return line) has gone through. In the case of relatively small screens, the total line length can be the sum of the lengths of all lines must be smaller than the spatial distance between two Pulses, so that one proceeds in principle according to the scheme shown in FIG could, where the pulses Ii at the top left of the screen and the pulses I2 at the bottom can be entered on the right-hand side of the screen. For larger screens, this type of Pulse feed but the disadvantage that in each case several first pulses I1 and several second impulse I2 ran on the screen because the previous impulse was itself is still on the screen while the next pulse is being generated will. In addition to the intended image points, there would therefore always be other unintentional ones Image points arise.

To avoid this, the screen 60 of FIG. 5 is divided into several Divided line areas. In the example shown, there are two line areas available. The total line length of the upper line area 61 is incl.

Line return so long that it is smaller than the spatial distance two consecutive impulses. The same applies to the lower line area 62. The incoming image pulses 11 are fed to a distributor 63, the one Contains line counter. The line counter is activated by the interlace signals on the line 21 controlled. If its counter reading has the number of lines in the first line area 61, it switches the pulses I1, which are first passed on to the upper line 121 have now been transferred to the lower line 122. In this way one achieves that the total line length of the upper field and the total line length of the lower Field is each smaller than the pulse spacing, so that undesired pulse crossings be avoided. If necessary, the screen can be used for even larger screens be divided into even more line areas. The line areas don't have to either necessarily be spatially contiguous blocks in the manner shown. Rather, for example, the odd-numbered lines can belong to the first line area and the even-numbered lines are assigned to the second line area.

In Fig. 2, the structure of a line is shown schematically. Between two glass plates 70, 71 is a liquid crystal layer 72. Along the Glass plates 70, 71 run in the row direction, transparent electrodes 73, 74, which are separated from one another by the liquid crystal layer 72. The electrodes run parallel to each other and face each other. A pair of electrodes 73, 74 forms a line in the representation according to FIG. 1 and is therefore in FIG. 1 shown with just one line.

The image pulses I1 travel on the electrode line 73, e.g. left to right, while the second pulses 12 on the electrode line 74 of wander right to left. At the point where both pulses I1 and I2 meet, the electric field strength in the liquid crystal is so great that the molecular axes to be turned around and the liquid crystal at this point its optical Properties changed. Polarization layers can be applied to the outside of the glass plates 70, 71 to be appropriate.

In addition, there can be a luminescent layer here, which causes an afterglow. The time at which the two pulses I1 and I2 is only very short and would not be perceived by the human eye at all, if there was no afterglow.

Other electrode shapes are shown in FIGS. To Fig. 6 is a crystal plate 75 outside with overlapping electrodes 76, 77 provided. In contrast to FIG. 2, FIG. 6 shows a cross section through the screen , the electrode lines 76 and 77 each forming a row in pairs.

A similar arrangement for a liquid crystal 78 is shown in FIG shown. Two glass plates 79, 80 form a cavity in which a liquid crystal is located 78 is located.

Electrodes 81, 82 are arranged along the plate surfaces, of which Two electrodes face each other in pairs and one screen line form. The electrodes are transparent.

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Claims (5)

Claims flat screen television in which the screen has a layer between two transparent plates, which is connected to electrodes in Connection is and their optical properties are changed by applying an electrical Change the field so that the electrodes do not work (73, 74; 76, 77; 81, 82) run linearly along the screen lines (11) and are each fed with pulses (I1, 12) that are individually insufficient, to change the optical properties of the layer (72, 75, 78), and that the Pulses (I1, I2) are dimensioned in such a way that when two coincide locally The optical pulses are sent to different electrodes at a pixel on the screen Properties of the layer at this pixel corresponding to the total amplitude of the coinciding impulses are changed. 2. Television set according to claim 1, characterized in that along each screen line (11) two electrodes (73, 74; 76, 77; 81, 82) run that at one end of the first electrode first pulses (I1) with a first pulse frequency (f1) are placed, the amplitudes of which are modulated according to the image signals that to the opposite end of the second electrode second pulses (I2) with a second pulse frequency (f2), and that the two pulse frequencies (f1, f2) differ slightly from each other, such that a first pulse (I1) and a second pulse (I2) due to the propagation delays at different Place the screen line meet. 3. Television set according to claim 1 or 2, characterized in that the pulses (I1, I2) on the two electrodes have opposite polarities. 4. Television set according to one of claims 1 to 3, characterized in that that the electrode pairs of several screen lines are connected in series. 5. Television set according to one of the preceding claims, characterized in that that the layer (72, 78) consists of a liquid crystal.