FR2684510A1 - SCANNING DISPLAY APPARATUS. - Google Patents

Abstract

Provided is a scanning display apparatus comprising an input terminal (1) which receives an input video signal, a sampling means operating at a certain sampling rate, a converting means (3). time base where the sampled image signal is written at the indicated sampling rate, and in which it is read at a different rate, which results in compression or expansion of the time base, a display means (7) receiving the compressed or dilated time-based image signal, which is used to display the image using a scanning beam modulated by the compressed or expanded time-based image signal, and a deflection means (5, 6) which generates deflection currents to excite the scanning beam, the deflection means produces a horizontal deflection current (iH) which has a frequency different from the horizontal frequency of the video signal d 'Entrance.

Description

The present invention relates to a scanning display apparatus.

  When an image reproduced from a video signal is displayed on a screen with a format different from that of the image itself, or when the image is displayed after enlargement, part of the initial image may missing on the display screen due to the format difference. To avoid this missing part, a method is known in which the input video signal is subjected to a signal processing, such as image compression or expansion aimed at adapting it to the constants of the deflection system of the device. display, before it is displayed (for example, patents

  Japanese made available to the public under publication numbers 1-221 067, 2-

  92077 and 2-277383), and a method in which the amplitude of the vertical or horizontal deflection system is modified so as to compress or dilate the image (for example Japanese patents made available to the public under the n

  57-206 178, 60-119 181, 62-128 669, 62-128 670 and 62-

  271,579, the latter corresponding to British patent application born 8602644).

  However, with the first method, there is a defect such that the quality of the image deteriorates as a result of the processing of the signals aimed at compressing or dilating the image. This tendency is particularly clear in the case where the number is reduced. scan lines to use to display the image So, for example, there are a total of 525 scan lines and 483 scan lines

  displayed on the screen in the NTSC system for the 4: 3 format.

  When displaying a 16: 9 format image on an NTSC display device after signal processing to compress the image so that it has the same horizontal width as the display device, the number of scanning lines to be used to display the image decreases (see for example the patent 2-92 077 cited above) and passes to only 383 scanning lines As a result, the details and the precision of the image become insufficient, and a zigzag effect may appear in parts forming lines

  obliques for certain signal processing methods.

  With the second method, there is no deterioration of the image quality. However, since the amplitude of the deflection varies at the cost of applying a great power to the deflection system, not only disturbances appear in the linearity of the deflection system and amplifying elements of the deflection system, but there will also be a limitation of certain types of display forms For example, no display is possible in the area where it does not exist display lines, so that this area is lost Thus, when the format is changed by reducing the amplitude or the vertical scanning width so as to compress the vertical width of the image, while the number of lines effective scanning does not vary and remains equal to 483 in the

  display device, there is an area that is not scanned above or below

  below the displayed image, in proportion to the compression of the vertical amplitude In addition, it is annoying that the signal present in the vertical return period, the data signals, or else the automatic adjustment signal

  product superimposed during the vertical return period appear visible-

  ment in the form of a shimmer on the screen, since these signals are unrelated to the image Although we know of means allowing to materially obscure the corresponding part so that we do not see it (see for example the Japanese patent made available to the public under the publication certificate

  62-128 670), such a means is quite expensive.

  In addition, if there is an area on the screen that is not scanned and in which the beam current does not flow at all, a difference between this area and the area in which the current always flows to display the image appears on the screen and gives, over time, a burning or printing phenomenon This phenomenon is a serious problem, in particular in the projection image tube intended for a projector, where an excitation current flows

important.

  We also know well, therefore, how to display information

  image or character mations by means of the overscan lines appearing on the screen when the vertical amplitude has been reduced, or else additional scan lines inserted in the period produced by shortening the vertical return period ( See for example Japanese patents made available to the public under publication numbers 57-206 178 and 60-119 183, and the Japanese utility model published under number 61-37 668) In these cases, the number of scan lines that can be used is small, and there is less freedom to

display forms.

  The following description, intended to illustrate the invention, aims

  to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: FIGS. 1A and 1B are simplified diagrams showing examples of display forms used in a scanning display device according to the invention; Figure 2 is a simplified block diagram showing an embodiment of a scanning display apparatus according to the invention; Figures 3 A, 3 B, 3 C, 3 D, 3 D ', 3 E and 3 F and Figures 4 A, 4 B, 4 C, 4 D, 4 D', 4 E and 4 F are diagrams time showing the operation of the scanning display apparatus shown in Figure 2; Figure 5 is a simplified block diagram showing another embodiment of the scanning display apparatus according to the invention; and Figures 6 A to 6 L are simplified diagrams showing other examples of display forms which can be displayed in the display apparatus.

  scan shown in Figure 5.

  When displaying an image of 16: 9 format which consists of 525 lines on a display device having a screen of 4: 3 format, as shown for example in Figures l A and 1 B, 525 lines are not enough for scanning the entire screen of the display device According to the invention, the frequency of oscillation of the horizontal oscillating circuit of the display device is adjusted in correspondence with the ratio of the vertical width of the screen of the display device to the vertical width of the image to be displayed, so that, for example, the number of scanning lines increases. In the example presented in FIGS. 1A and 1B, this ratio is 4: 3, so that the horizontal oscillation frequency is fixed at 4/3 times the oscillation frequency used to display a 4: 3 image and therefore 643 effective scanning lines and 700 lines are produced in total Par therefore, the same density of scanning lines is obtained on the whole screen as in the part displaying a 16: 9 format image Figure l A shows the case where the image is placed in the middle of the screen, and figure 1 B shows

  the case where the image is placed on the upper side of the screen.

  We will now explain in relation to FIG. 2 an embodiment of a scanning display device according to the invention. The scanning display device basically comprises a terminal 1 for video signal input, a circuit 2 for synchronization signal separation, a time base conversion circuit 3 which comprises frame memories 3 a and 3 b, or the like, a horizontal oscillation circuit 4, a deflection circuit 5

  horizontal, a vertical deflection circuit 6, and a display tube 7.

  In the case where the image is displayed with the same number of scanning lines as the image initially transmitted, horizontal synchronization signals SH and vertical synchronization SV are extracted from the video signal P supplied to the input terminal 1 of video signal, while the video signal P is supplied to the time base conversion circuit 3, so that a compressed or expanded time base image signal PC is produced The time base conversion circuit 3, which is used to convert the time base of the image signal contained in the video signal P, consists of two frame memories 3 a and 3 b and a control circuit 3 c which controls the frame memories 3 a and 3 b using write and read clock signals and write and read addresses produced as a function of the horizontal synchronization signal SH, the vertical synchronization signal SV, and a signal of horizontal synchronization S'H which is produced independently of in the horizontal oscillation circuit 4 inside the scanning display apparatus, in synchronism with the vertical synchronization signal SV The image signal PC, whose time base has been compressed or expanded by the time base conversion circuit 3 is supplied to the display tube 7, in which the scanning beam is excited in correspondence with the horizontal deflection current i H and the vertical deflection current iv coming respectively from the horizontal deflection circuit 5 and the diversion circuit

  vertical 6 above mentioned, so as to display the image.

  We will hereinafter explain in more detail the time base conversion operation, in relation to FIGS. 3 A to 3 F and 4 A to 4 F, using the example of time base compression a 16: 9 aspect image

  and its display on a 4: 3 screen.

  The video signal P, which is used to display a 16: 9 format image and which is supplied to the video signal input terminal 1, has horizontal periods H and vertical periods V, as shown respectively in FIGS. 3A and 4 A The image to be displayed is made up of effective image parts He included within the horizontal periods H, which are contained in effective image parts Ve of the vertical periods V The effective image parts He of the video signal P are sampled and subjected to an analog / digital conversion according to a predetermined sampling frequency, this is not shown in the drawings The digital image signal is written in the frame memories 3 a and 3 b at the addresses write, with alternation for each frame, in relation to the write clock signal The write clock signal and the write addresses are produced in the control circuit 3 c on the basis of the horizontal synchronization signal SH and the vertical synchronization signal SV extracted in the synchronization signal separation circuit 2 The digital image signal written in the memories 3 a and 3 by is read at the reading addresses, alternately for each frame, in relation to the read clock signal The read clock signal and the read addresses are produced on the basis of a horizontal synchronization signal S'H, which is produced in the

  horizontal oscillation circuit 4 in synchronism with the synchronization signal

  vertical SV, so that it has a frequency equal to 4/3 times the sampling frequency, and on the basis of the vertical synchronization signal SV The read digital image signal is converted into an analog signal, and becomes a image signal Pc consisting of the compressed effective image parts He, included inside the compressed effective image parts Ve, which is obtained by compressing the time base of the effective image parts He and Ve in the ratio 3/4, as shown in FIGS. 3B and 4B, but, in practice, a frame later for example, respectively The image signal Pc is supplied to an image signal input of the tube display 7 Since the reading of the memories is controlled so that the digital image signal is not read during the time when there are no effective image parts He in the horizontal periods, according to the horizontal synchronization signal S'H, the signal

  suppression level is supplied to the display tube 7.

  At the same time, the horizontal deflection circuit 5 produces the horizontal deflection current i H, as shown in FIG. 3 E, on the basis of the horizontal synchronization signal S'H produced in the horizontal oscillation circuit 4, and the vertical deflection circuit 6 produces the vertical deflection current iv which has a waveform showing the trace periods Vt and the return periods Vr, as shown in FIG. 4 E, on the basis of the vertical synchronization signal SV, so that the scanning beam of the display tube 7 is excited by the currents of horizontal deflection i H and of vertical deflection iv Thus, the image of format 16: 9 is displayed according to the form of display represented on FIG. 1 A In this case, if the temporal positioning of the reading of the digital image data in the frame memories 3 a and 3 b is adjusted relative to the vertical synchronization signal SV, as r represented in FIG. 4 C, the image is displayed from the top of the screen, as represented in FIG. 1 B In addition, if one fixes the level of the image signal supplied to the display tube 7 plus high that the suppression level, as represented by the dashed line in FIGS. 3 B, 4 B, 3 C and 4 C during the time when the image signal Pc based on compressed time does not exist, the current of the beam circulates even when the image is not displayed, so that the phenomenon of burning or printing is prevented. For this purpose, the combination of an 8 or 8 ′ level signal generator circuit and a switch 9 or 9 'is optional before or

  after the time base conversion circuit 3, as shown in FIG. 2.

  In this structure, both of the frame memories 3 a and 3 b are used, having a capacity greater than the quantity of image data corresponding to a

  frame, and the level signal coming from circuit 8 is generated alternately

  level signal, and the video signal, coming from the video signal input terminal 1, via the switch 9, at the predetermined time, to the corresponding zone of memories 3 a and 3 b, or alternatively the level signal, coming from the level signal generating circuit 8 ', and the video signal, coming from memories 3 a and 3 b, to the display tube 7 via the switch 9' at the moment

predetermined.

  In the case where a video signal associated with a 4: 3 format image is provided, it is possible to display the 4: 3 format image on the whole screen by compressing the time base of the video signal according to the positioning. represented in FIG. 4 C and by modifying the coefficient of use of the trace periods Vt and of the return periods Vr of the vertical deflection current i'v, as represented in FIG. 4 F, but keeping the same amplitude as that presented in FIG. 4 E. We now pass to FIGS. 5 and 6 A-6 L, in relation to which we will now explain other embodiments of the apparatus

  display device according to the invention In the embodiment explained above

  above, when the 16: 9 aspect image is displayed on the 4: 3 aspect screen, there are one or more image-free areas at the top or bottom of the screen However, since the scanning lines exist on the screen, it is possible to display other information on the zone, such as for example information produced by a signal and / or data generating device integrated into the device. display or of information received from character broadcasting services, namely Teletext services or

  videotex, without overlapping with the image already displayed.

  More specifically, when a subtitle or legend is displayed

  on the area, this is not annoying, because there is no overlap with the image.

  To achieve what has been presented above, instead of the general circuit,

  signal level 8 or 8 'of the embodiment of Figure 2, we can provide, as shown in Figure 5, a 10 or 10' image processing circuit The image processing circuit 10 or 10 'can produce characters or image data by itself or else manipulate the video signal supplied from outside the apparatus The image processing circuit 10 or 10 'and, alternatively, the switch 9 or 9' interchange the image signals, and the image signal from the image processing circuit 10 or 10 'is supplied to the display tube 7 after the image data of the main image has been read in the frame memories 3 a and 3 b, as shown in FIG. 4 D To achieve this, both of the frame memories 3 a and 3 b having a capacity greater than the amount of data are used. image corresponding to a frame and the image processing circuit 10 and, or alternatively, the commutat eur 9 so that digital image data from the image processing circuit

  are described in the remaining area of the frame memories 3 a and 3 b, that is to say

  tell the area not related to the main image data, or the image processing circuit 10 'and, or, the switch 9' are controlled so that the image signal coming from the image processing circuit image 10 'is supplied to the display tube 7 after the main image data has been read in

the frame memories 3 a and 3 b.

  Several examples of the above-described scanning display device will be explained below. In the case where an HM 1 main image of 16: 9 format is displayed using 525 scanning lines on a scanning device. display with a 4: 3 screen from the top of the screen, as shown in Figure 6 A, since the lower area of the screen, where the main HM image 1 is not displayed, may be used to display three auxiliary images H 51, H 52 and H 53 in 16: 9 format or four auxiliary images S 51, S 52, S 53 and S 54 in 4: 3 format, as represented by a dashed line, respectively using scanning lines, namely 525/3 lines, the initial data of the auxiliary images is compressed by carrying out an extraction of 1/3 in the horizontal and vertical directions and the compressed images obtained are displayed there. auxiliary images H 51, H 52 and H 53 or S 51, S 52, S 53 and S 54, we have the compressed image data, as shown in FIGS. 3 D, 4 D, 3 D 'and 4 D', in the positions of the respective horizontal and vertical periods corresponding to the area where the auxiliary images are placed on the screen. well-known form of display corresponds to the image-on-image (POP) function and the respective compressed images can be images from sources

  different images or from a single source at different times.

  In the above-mentioned case, since the number of scanning lines used to display the compressed images is in a whole proportion of that of the initial image, it suffices to simply apply a rough treatment,

which is very simple.

  Other variants, represented by the display forms of FIGS. 6 B to 6 F are also possible. Since, to display these forms, the methods indicated above are used, we will omit to provide detailed explanations. FIGS. 6 B to 6 H relate to a display device having the format 4: 3, and FIGS. 6 I to L relate to a display device having the format 16: 9. In FIG. 6B, a main image of 4: 3 format which has been compressed to 9/16 the screen size of the display tube is displayed using 525 lines and seven auxiliary images of format 4 : 3 which have been compressed to 1/16 of the screen size are respectively displayed using 175 lines on the peripheral zone In FIG. 6 C, four images of format 4: 3 which have been compressed to 1 / 4 of the screen size are respectively displayed equally using 525 lines In Figure 6 D, two main images in 4: 3 format which have been compressed to 1/4 the size of the screen are displayed in the middle of the screen evenly using 525 lines and five 4: 3 aspect ratio auxiliary images that have been compressed to 1/16 the screen size, or many others

  information of the character type, are respectively displayed above and

  below the main images using 525/2 lines In Figure 6 E, two main images in 4: 3 format which have been compressed to 1/4 of the screen size are displayed on the top side of the screen. screen evenly using 525 lines or 525/2 lines, and several types of information are displayed above and below the main images, respectively, using appropriately distributed number lines In this case, it is not always necessary that the density of the lines used to display the main images be equal to that of the display of the different types of information. In FIG. 6 F, six images of 4: 3 format which have been compressed to 1/9 of the screen size are displayed separately on the top side and the bottom side of the screen using 525 lines or 525/2 lines, and several types of information are displayed between these images using appropriately distributed number lines On the f igure 6 G, a high definition image in 16: 9 format is displayed using 1125/2 or 1125/3 lines In Figure 6 H, a high definition image in 16: 9 format is displayed on the top side of the screen using 1125/2 or 1125/3 lines, and an auxiliary image or more types of information are displayed below In Figures 6 E or 6 F, although the number of scan lines has been reduced in an entire ratio compared to the initial number, the images should be displayed according to this method in the case where the performance of the display apparatus is lower than that of the initial signal as regards the sharpness and the accuracy, even if you use the same number of scanning lines as the signal to display the image This is especially suitable for displaying the high definition signal (HDTV) on a normal display device As above, you can choose the number of scan lines to add to get the best re possible quality on the display device. As previously, in FIG. 6 I, two main images of 4: 3 format are displayed equally in the middle of the screen using 525 or 525/2 lines and several types of information are displayed at above and below the main images using suitably distributed numbers of lines In Figure 6 J, three 4: 3 format images are displayed equally on the top side of the screen using 525 lines and two 16: 9 format images are displayed equally on the bottom side of the screen using 525 lines, while different types of information are displayed on the remaining parts In Figure 6 K, a main image in 4: 3 format is displayed using 1050 lines, or three times 525 lines, and three auxiliary images in 4: 3 format are displayed vertically on the right side of it using 1050/3 lines, while different types of information are displayed on the r parts estantes In Figure 6 L, two main images in 4: 3 format are displayed using

  525 lines and two auxiliary images in 4: 3 format and different types of information

  tions are displayed on the remaining parts using 525 lines.

  Various forms of display, other than those presented above are applicable, if necessary. The display device to be used is not only limited to the display tube, but projection type displays can also be used, for example. example of the direct beam scanning type

or of the projection tube type.

  According to the invention, the quality of the image which is displayed is not deteriorated and the phenomenon of burning or printing produced on a display screen is prevented, so that this technique is suitable for projectors and means analogues The invention can be applied to display apparatuses having any type of format.

  simple, without any interpolation between scan lines.

  Of course, those skilled in the art will be able to imagine, from

  the device whose description has just been given for illustrative purposes only and

  in no way limiting, and various variants and modifications which do not go beyond the scope

of the invention.

Claims (5)

  A streak display apparatus, comprising: means (1) forming a video signal input terminal for receiving an input video signal; sampling means for sampling at least part of the image signal of the input video signal with a certain sampling rate; time base conversion means (3) in which the sampled video signal or digital data corresponding thereto is written using said sampling rate, and in which they are played with a rate different from said sampling rate, so that a compressed or expanded time-based image signal is obtained; display means (7) receiving the compressed or expanded time-based image signal and serving to display one or more images using one or more scanning beams modulated by the image signal to compressed or expanded time base; and deflection means (5, 6) for producing vertical deflection and horizontal deflection currents to excite the one or more scanning beams; characterized in that the deflection means produces a horizontal deflection current (iu-) which has a frequency different from the frequency   horizontal of the input video signal.   2 Apparatus according to claim 1, characterized in that the format of the image to be displayed from the input video signal is different from the format   of the screen of the display means (7).   3 Apparatus according to claim 2, characterized in that the image to be displayed from the input video signal has the ratio 16: 9 and   the display unit screen (7) has a 4: 3 aspect ratio.   4 Apparatus according to claim 3, characterized in that the image to be displayed from the input video signal is formed using 525 scanning lines and the screen of the display means (7) is scanned using 700 scan lines.   Apparatus according to claim 2, characterized in that information other than said image indicated above can be displayed on the remaining area which appears due to the difference between the format of said image il indicated above and that of the screen of the display means and in which the image   above shown is not displayed.