CA1200631A - Control for differential colour contrast enhancement on a crt screen - Google Patents
Control for differential colour contrast enhancement on a crt screenInfo
- Publication number
- CA1200631A CA1200631A CA000399369A CA399369A CA1200631A CA 1200631 A CA1200631 A CA 1200631A CA 000399369 A CA000399369 A CA 000399369A CA 399369 A CA399369 A CA 399369A CA 1200631 A CA1200631 A CA 1200631A
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- CA
- Canada
- Prior art keywords
- colours
- characters
- symbols
- representation
- colour
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
Abstract
ABSTRACT OF THE INVENTION
Control arrangements for the multi-colour representa-tion of characters or symbols on a screen of a display unit, by means of which, in addition to the characters or symbols, multi-colour graphic patterns and/or multi-colour television pictures can be represented, and in order to increase the legibility of the representation, those characters or symbols which are repre-sented in comparatively dark colours on a dark background are brightened relative to the comparatively light colours. In the event of the representation of graphic patterns and television pictures, the brightness of the comparatively dark colours is unchanged. The arrangement is provided in particular for the representation of characters and symbols for screen text (Interactive-Videotext) or Videotext (Broadcast Videotex).
Control arrangements for the multi-colour representa-tion of characters or symbols on a screen of a display unit, by means of which, in addition to the characters or symbols, multi-colour graphic patterns and/or multi-colour television pictures can be represented, and in order to increase the legibility of the representation, those characters or symbols which are repre-sented in comparatively dark colours on a dark background are brightened relative to the comparatively light colours. In the event of the representation of graphic patterns and television pictures, the brightness of the comparatively dark colours is unchanged. The arrangement is provided in particular for the representation of characters and symbols for screen text (Interactive-Videotext) or Videotext (Broadcast Videotex).
Description
06~1 The inVention xelates t~ a control a~rangement fo~ the representation o~ a visual displa~ on ~ display unit screen by means of which a display can be represented in different colours~
and by means of whi~h not only characters, but also multi-coloured graphic patterns ~nd/or multi-colour television images can be represented.
In recent telecnm~lln;c~tions services such as screen text ~Interactive-Videotexj and Video-text (Broadcast ~i~eotex~ it is possible to represent both characters and graphic patterns in addition to normal television pictures, using a television display device. In this context the term "characters" is to be understood as embracing all alphanumerical characters, special symbols and linear graphic sym~ols, whereas graphic patterns are to be understood as relatively coarse graphic representations.
In the representation of characters and graphic patterns, the screen ~ontent, which ls referred to as a page, is divided into a number of arrays, for ~mpl e into 960 character arrays arranged in 24 rows each comprising 40 character arrays. In the case of the representation of alphAnllmerical characters, one chaxacter is represented in each character array. In this case the character array consis~s of 8xlO or 8x12 image points by means o~ which the individual characters are represented. The same arra~gement can be used to represent fine graphic symbols, which can extend over one array or over several character arrays. In the case of the representation of graphic patterns, each array is split into 2x3 graphic elements and the graphic patterns can be constructed from the possible combinations of light and dark graphic elements.
and by means of whi~h not only characters, but also multi-coloured graphic patterns ~nd/or multi-colour television images can be represented.
In recent telecnm~lln;c~tions services such as screen text ~Interactive-Videotexj and Video-text (Broadcast ~i~eotex~ it is possible to represent both characters and graphic patterns in addition to normal television pictures, using a television display device. In this context the term "characters" is to be understood as embracing all alphanumerical characters, special symbols and linear graphic sym~ols, whereas graphic patterns are to be understood as relatively coarse graphic representations.
In the representation of characters and graphic patterns, the screen ~ontent, which ls referred to as a page, is divided into a number of arrays, for ~mpl e into 960 character arrays arranged in 24 rows each comprising 40 character arrays. In the case of the representation of alphAnllmerical characters, one chaxacter is represented in each character array. In this case the character array consis~s of 8xlO or 8x12 image points by means o~ which the individual characters are represented. The same arra~gement can be used to represent fine graphic symbols, which can extend over one array or over several character arrays. In the case of the representation of graphic patterns, each array is split into 2x3 graphic elements and the graphic patterns can be constructed from the possible combinations of light and dark graphic elements.
-2-`~
The representation of the characters and graphic patterns can take place in the conventional basic colours used in television - red, green and blue, and their complementary colours which are yellow, cyan and magenta, and also in white and black. These colours can also be selected as background colours for a displayed representation.
When characters are represented in relatively dark colours9 such as for example red or blue on a dark background, it has been established that on ac~
count of the relatively low light intensity and a simultaneously low spectral sensitivity of the eye, the characters are difficult to read and recognise in L0 the case o~ red and blue. ~lowever, coarse graphic patterns represented in red or blue are easy to recognise.
From the German OS ~7 40 329 (Eikenberg, et al~ laid open March 18, 1978) and the European OS 0 00~ 197 (~art, et al, published Sept. 19, 1979) it is already known to change the brightness of the colours iE videotex pages are to be represented instead of television pictures on the screen of a television device. The adjustment of the brightness of the colours in the representation o~ the vldeotex pages relative to the brightness of the colours in the represent-atlon of a television picture is carried out by one single operation and appliesboth to the representation of the characters and oE the graphic patterns. ~low-ever this method of setting the brightness oE the co:Lours lnvolves tlle danger that, :Ln the case o~ the representation of graphic patterns, the relatively `llUht colours such as white, yellow and cyan will be brightened too much re-lntlve tn the relat:Lvely dark colours such as red and blue, or, in the case of the representation of characters, the relatively dark colours such as red and blue will be brightened too little.
The representation of the characters and graphic patterns can take place in the conventional basic colours used in television - red, green and blue, and their complementary colours which are yellow, cyan and magenta, and also in white and black. These colours can also be selected as background colours for a displayed representation.
When characters are represented in relatively dark colours9 such as for example red or blue on a dark background, it has been established that on ac~
count of the relatively low light intensity and a simultaneously low spectral sensitivity of the eye, the characters are difficult to read and recognise in L0 the case o~ red and blue. ~lowever, coarse graphic patterns represented in red or blue are easy to recognise.
From the German OS ~7 40 329 (Eikenberg, et al~ laid open March 18, 1978) and the European OS 0 00~ 197 (~art, et al, published Sept. 19, 1979) it is already known to change the brightness of the colours iE videotex pages are to be represented instead of television pictures on the screen of a television device. The adjustment of the brightness of the colours in the representation o~ the vldeotex pages relative to the brightness of the colours in the represent-atlon of a television picture is carried out by one single operation and appliesboth to the representation of the characters and oE the graphic patterns. ~low-ever this method of setting the brightness oE the co:Lours lnvolves tlle danger that, :Ln the case o~ the representation of graphic patterns, the relatively `llUht colours such as white, yellow and cyan will be brightened too much re-lntlve tn the relat:Lvely dark colours such as red and blue, or, in the case of the representation of characters, the relatively dark colours such as red and blue will be brightened too little.
-3-1~0~
This applies ln particular when both characters and graphic patterns are represented on one videotex page and relatively dark characters are represented in the vicinity of large, light areas.
Therefore one object of the present invention is to provide an arrangement which results in a particularly good legibility of characters of different colours on a display unit screen.
The invention consists in a control arrangement for the representation of a display on a display unit screen, using dif~erent colours and providing for characters, multi-colour graph-ic patterns and/or multi-colour television pictures, in which a control unit is provided to automatically brighten the represent-ation of characters in relatively dark colours relative to the comparatively light colours which can be represented and in which ~or representation of characters or symbols in the comparatively dark colours the control unit supplies the display unit with control signals by means of which these colours are brightened.
The proposed arrangement has the advantage that it necessitates only a low outlay in circuitry and can be readily incorporated into existing display units. I'he observer is present-~d with an a~reeable image on the screen. In comparision to an :inc~ease in the overall brightness, the arrangement has the ~dvanta~e that ~lickering o~ the relatively light colours is avoided and that the colours do not change in the representation of graphic patterns or television pictures. Furthermore, in the case of the representation of characters, the colour tone is maintained as the colours are merely brightened. Mi~ed colours are not changed and therefore the colour contrast is likewise retained.
The arrangement involves a particularly low circuitry outlay if, in the case of the representation of characters in the relatively dark colours, the control unit supplies the display unit with control signals by which these colours are brightened.
-4a-1~,.0~31 In particular it is ad~ntageous for the contxol signals to increase the brightness of xepresented charactex~ by the addition of ~orresponding components of the basic colours.
Another possibility of relative b~ightening of the comparatively dark colours consi~ts in that, in the repxesentation of characters in the relatively dark colours, the control unit increases the overall brightness of the representation on the screen and produces si~nal5 ~7hich reduce the brightn~ess of the represented relatively light colours.
If a decoder unit is provided which supplies the display unit with colour signals assigned to the characters which are to be represented, and which contains an image store which stores data words assigned to the characters and the associated colours, an advantageous embodiment of the arrangement is a~hieved in that the control unit contains a converter which converts first code words asslgned to the relatively daxk colours into second code woxds which are assigned to the corresponding brightened colours.
In particular it is advantageous for the converter to precedq the ~mage store in which the second code words can ~e stored in placc of the first code words. Another possibility consists in that the converter is arranged between the image store and an ima~ repetition store. The image repetition stoxe need not contain the content o one entire page. For example it can be sufficient for the image repetition store to store the content o only one line.
A high degree of legibility o~ the chaxacters can a~so be achieved in that the display unit represents characters with an increased image frequency and that chara~ters in the relatively dark colours are represented more frequently than characters in the relati~el~ ht c~lou~s,~ or in th~t the contxol unit supplies the, display unit ~th signals which periodically temporarily block the brightness signals in tha case of the representation of characters in relatively light colours.
Especially in the case of the use o a flat screen on which representation takes place using a plurality of light points, it is'advantageous for the con~rol unit to generate signals which trigger representation involving more light points~o~ the display unit in the event of the representation of characters' in the io relatively dark colours than in the case of the representation of characters in the relatively light colours.
The control arrangement is advantageously used whenever in particular the basic colours blue and red are provided as relatively dark colours and in particular the colours white, yellow and cyan are provided as relatively light colours.
As the brightness of characters having the basic colours blue and red also differ, it is advantageous for the control unit to produce slgnals by means of which the basic colour blue is b~ightened more than the basic colour red in comparison to the 20 r~latively light colours.
It proves particularly expedient to employ the arrangement when alphanumexical characters and/or linear graphic symbols are providQd b~ way of characters.
The use of the arrangement is advantageous not only for the representation of videotex pages which contain exclusively characters or mixed representations of characters and graphic patterns, but the use of the arrangement also proves expedient for the relative brightening of the comparatively dark colours when characters are'to be gated into a television picture.
~ particularl~ ~d~antageous representation of the characters on the screen is achieved i~ the xelati~e bri~htening of the comparatively dark colours takes place only in cases where thexe is a dar~ background colour to the characters.
The invention will now be described with reference to the drawingsr in which:-Figure 1 schematically illustrates an extract from an exemplary videotex page;
Fi~ure 2 is a bloc~ schematic circuit diagram illustrating IO a irst exemplary embodiment of a control arrangement constructed in accordance with the inventlon;
Figure 3 is a block schematic circuit diagram illustrating a second exemplary embodiment of a control arrangement; and Figure 4 is a blocX schematic circuit diagram illustrating a third exemplary embodiment of a control arrangement.
In the extract from a videotex page represented in Figure 1, typical characters AZ, symbols GZ and a graphic pattern GM have been represented~ The alphanumeric characters AZ and graphic symbol ( ' GZ are composed of fine lines, and both are arran~ed, together with the graphic pattern GM, in an assembly of character arrays ZF, the boundaries of which have been shown ~or purposes o~
explanation, but are not normally visible on the display screen.
Fo~ the representation of characters or symbols, each character array ZF in this example is divided into an invisible grid comprising 8x12 image points BP. The characters AZ are represented on the screen by virtue of the differing degress of brightness of the image points BP. The graphic symbols GZ can be represented ln a similar manner to the alphanumeric characters AZ, but one symbol can extend over a plurality of character arrays ZF. The -7~
characters AZ and s~bols GZ can be repre~ented in the three basic colQu~s ~ ~ed~ ~een ~ bluel ~he ~ixed c~lour~ Qf yellow;
cyan or magenta, and in black or ~hite~ but within an~ one character array ZF the colour cannot change. Any of the basic colours, mixed colours or black and white can be used as a background colour.
In the case of the representation of the graphic patterns GM, the chaxacter arrays ZF are divided into 2x3 gr?phic elements GE. The graphic patterns GM are then represented in character arrays ZF with different combinations of the graphic elements GE.
The~graphic elements GE and the background colour can be represented in any basic colour, mixed colour, or black or white.
If the representation of the characters AZ and s~mbols GZ on the screen takes place in relatively dark colours such as red or blue, then particularly if there is a dark background there is a danger that the characters AZ or s~mbols GZ will be dificult to read. This will be particularly so when, as illustrated in Figure 1, a graphic pattern GM in a relatively light colour such as white, yellow or cyan extends very close to characters AZ or ~0 s~mbols GZ in blue or red, for example.
Furthermore, it has been ascertained that in the case of the pure representation of characters these are difficult to read whe~ part of the videotex page is occupied by characters in a relatively light colour and a further offset part of the 2S page is filled with a relatively dark colour.
In the first embodiment of control arrangement, illustrated in Figure 2, a control unit SE is axranged between an image control unit BST and a display unit AE provided with a screen ~not shown~. The ima~e control unit ssT is o~ known design, and contains s~itch~o~er units ~ia.~hlch coloux si~nals emanating from a television receiver or f~om a videotex decoder are selectively switched through t~ the display unit AE. Switch-over units of this kind are generally known, and are described,for example, in the magazine "Wireless World", May 1976, pages 64-68.
The colour signals R, G and B assigned to the basic colours ,~ red, green and blue are supplied to the display unit AE via delay ele.ments V. The colour signals R, G and B are also supplied to the'control unit SE. In the case of the representation of television pictures on the display unit AE! the colour signals consist of analogue-signals whose instantaneous values deter~;ne the colou.rs to be represented and the brightness thereo. In the case of the representation of characters, symbols and graphic patterns, the colour signals consist of binary signals which assume the binary values "0" or Illn. In the case of the representation of the colour red, for example, only the colour ( signal R possesses the binary value "1"'. Similarly in the case o the representation of the colours blue or green, onl~ the colour signal B or G respectively possesses the hinary value "1".
The colour black is represented when all the colour signals have the binaxy value "0", and for representation of the colour white all the colour signals possess the binary value "1". The mixed colours o yellow, cyan and magenta are represented when two of the colour signals R and G, G and B, or R and B, respectively each possess the binary value "1".
When the videotex decoder establishes that a videotex page is to be represented, the corresponding colour signals R, _9_ G and B are ~ed to the display unit AE. In the case of the representation o~ the gra~hic pattexns G~ ~nd the Xepresentation of the background colours~ the colour signals ase ~ed in known manner to the display unit AE. In the case o~ the representation of alphanumeric characters AZ or graphic symbols GZ, the image control unit BST produces corresponding signals SAZ or SGZ
respectively. When one of these signals occurs, an OR-gate Gl in the control unit SE emits a signal Sl to two AND- gates, Ul and U2. If the characters are to be represented in~blue, the ' 10 colour signal B has the binary value "1" whereas the colour signals R and G have the binary values "0". In this case the AND-gate Ul emits a signal S2 via a switching stage SSl to cause an analogue OR-gate G2 to feed a signal S3 to ~he display unit AE.
This signal S3 serves as a brightness signal, and is used to cause the blue characters or symbols to be brightened in relation to the relatively light colours such as white, yellow or cyan The brightening can be effected in known manner in that, in the display unit AE, small constituents of the basic colours, red and green, are produced by corresponding additional colour signals.
It is also possible to supply the s~gnal S3 to the grid of a pictur~ tube in the form of a cathode ray tube in order to increase ~he bxightness. In the case of representation o characters or s~mbols in redr then in a slm; 1 ar manner to that used ~or xapresentation of charactexs or symbols in blue, these are brightened by a signal S4 produced by means of the AND-gate U2.
The switching stages SSl and SS2 can be used tQ change the amplitude of the signals S2 and of the signals S4 respectivelyr and consequently adjust the signals S3 so that the basic colours red and blue can be brightened to differing extents. Here it is 63~
particulaxly advant~geou~ the colour blue t~ be brightened more than the colour ~ed The delay ~lements ~ are provided to compensa~e for the additional transit times which occur in the AND-gates Ul and U2 r the switching stages SSl and SS2, and the OR-gate G2~ so that the signals S3 are presented simultaneously to the correspondins colour signals.
The control unit SE provides that, in the event of the representation of cha~acters in the relatively dark~colours of red and blue, these can be brightened relative to the comparatively li~ht colours in a simple manner.
' This relative brightening of the comparatively dark colours can be effected in that the display unit A~ is desi~ned for a higher picture frequency and in that the characters AZ and symbols GZ of relatively light colours are represented at a lower picture frequency than the characters AZ and GZ of relatively dark colours. In this case the signal S3 sets a higher picture ~requency so that then the relativel~ dark colours appear brighter.
If the screen is one component of a plurality of light points, and for example is a flat screen, the relative brightening o~ the comparativel~ dark colours can be efected in that the comparatively light colours are represented with a smaller number o~ light points whereas the signal S3 provides that correspondingly morQ.light points are used to represent characters or symbols in the comparatively dark colouxs.
In the alternative control arrangement illustrated in Figuxe 3, the relative brightening of the comparatively dark colours is achieved in representation of videotex pages by increasing the overall brightness, and in the case of the Q~
representation o~ graphic patterns~ GM ~r of background colours the com~aratively light colours are selectively darkened~
A videotex decoder in the image control unit BST emits the colour signals R, G and B and the signals SAZ and SGZ to multiple inputs of a control unit SE~ For representation of graphic patterns GM or of background, the signals SAZ and S~Z each have the binary value "0", so that three AND-gates U3 and U5 are released. If the graphic pattern GM or the background colour ~, i9 to be represented in white, yellow or cyan, the AND-gates, U3, U4 or U5, as the case ma~ be, emit a signal S5, S6 or S7 res~ectively, which is fed via a switching stage SS3, S54 or SS5 respectively, and thence via an analogue OR-gate G3 to form a signal S8 that is f~d to the display unit AE, and darkens these colours, so that in this way the relatively dark colours appear brlghter relative to the comparatively light colours. The delay elements V are provided in order to compensate for the delay times resulting from the AND-gates U3 to U5, the switching stages SS3 to SS5 and the OR-gate G3. The switching stages SS3 to SS5 can serve to individually adjust the degree of darkening for each colour. The signal S8 is expediently conducted to the grid of the o~thode ray tube in order to reduce the brightness of the corxeqpondinq colours.
If representation may take place on the display un~t screen at an increased picture frequency, the signal S8 can be used to reduce the picture frequency in the case of repres~ntation of relatively light colours, so that here too the relatively dark colours appear brighter. In the case of representations composed of a plurality of light points on a flat screen, the signal S8 can be used to reduce the number of operated light paints in the case of the representation o~ xelatiYel~ light colours.
~ nother possibility o~ selectively darkening the xelati~elylight colours involves using tlle signal S8 to make ~he corresponding brightness signal intermittent, i.e. to periodically temporarily interrupt the relevant colour signal. This c n be effected by an AND logic-linking element having one input connected to a clock pulse train signal emitted from an oscillator, ~or ~mrle. ~
~, In the further alterna~ive control arrangement represented by the block circuit diagram illustrated in Figure 4, the control un~t SE itself forms part of the image control unit BST. As regards the videotex decoder, only an image store BSP has been shown, which stores-data words assigned to the characters, symbols and graphic patterns which are to be represented. For ~mpl e these data words contain 16 binary characters, of which 8 are assigned to the alphanumeric characters A~ or graphic elements OE
which are to be represented, and of which a further 8 binary characters represent control signals which characterise the colour ( or the nature of the representation or which indicate that it is a matter o~ data words which are assigned to the alphanumeric characters A~ or the graphic elements GE. First code words composed o three ~inary characters in accordance with the colour signals R, G and B are provided for the representation of the colours.
The control unit SE contains an image repetition sto~e BWS
which in this example intermediately stores the content of one row on the screen. With the exception o~ the first code words which are assigned to the colour signals~ all the other binary characters are directly conducted, as signals S9r to the im~ge repetition store BWS. The colou~ si~nals a~e fed to the im~ge repetition store BWS ~ia ~ conve~tex U~l~
The image repetition store BWS contains ~ore storage positions for data words than the image store BST. In place of three binary characters for the first code words, four binary cha~acters for second code wsrds are provided in the data words r so that in addition to the basic colours, the complementary colours thereto and biack and white, still more colours can be stored. For example the colours "bright blue" and "bright red"
are provided by way of further colours. ~hen the videotex decoder emits the signals SAZ or SGZ and characters or symbols are to be represented in red or blue, the corresponding combinations of the binary characters which are.assigned to these bright colours are stored in tne second code words within the image repetition ~tore BWS. The image repetition store BWS is followed by a second converter UM2 which assigns three colour signals, R1, G1 and B1 to these four binary characters. These colour signals differ from the colour signals R, G and B in that, in.the case of the representation o the characters in blue, the colour signals Rl and 20 ~1 al30 possess glven instantaneous values, and that in the repr~sentation of the characters in red, ~he colour signals Gl and ~1 ~lso possess given instantaneous value, in order to brighten the blue and red on the basis of the additive mixing of the colours.
In another possible design of the image control unit the image store BSP is extended to the extent that second code words formed from four binary characters are provided for the coloursO
In this case the image repetition store BWS is not required and the converter UMl i~ connected preceding the Lmage StQre BSP.
~14-The conyeXteX U~2-can also be designed in such m~nner that, as illustrated in ~igures 2 ~nd 3r it ~roduces additional brightness signals corresponding to the signals S3 or S8, in order to operate the grid of the picture tube, or to change the S picture frequency, or vary the number of light points operated on a flat picture tube.
The converter U~l can be designed to forward the colour signals R, G and B unchanged to the Lmage xepetitl~n store BWS
~, for the representation of characters or symbols. This can be the case, for example, when the ~haracters or symbols are represented on ~ light background. For this purpose the converter UMl can contain a store in which the background colour wnich applies to the character array in question is intermediately stored, and the brightPni ng of the relatively dark colours can take place in dependence upon the contents of said store. An inte ~ te store of this type can also be provided in the control arrangements described with reference to Figures 2 or 3, so that also in this case the relative brightening of the relatively dark colours takes place only when these are represented on a dark background.
This applies ln particular when both characters and graphic patterns are represented on one videotex page and relatively dark characters are represented in the vicinity of large, light areas.
Therefore one object of the present invention is to provide an arrangement which results in a particularly good legibility of characters of different colours on a display unit screen.
The invention consists in a control arrangement for the representation of a display on a display unit screen, using dif~erent colours and providing for characters, multi-colour graph-ic patterns and/or multi-colour television pictures, in which a control unit is provided to automatically brighten the represent-ation of characters in relatively dark colours relative to the comparatively light colours which can be represented and in which ~or representation of characters or symbols in the comparatively dark colours the control unit supplies the display unit with control signals by means of which these colours are brightened.
The proposed arrangement has the advantage that it necessitates only a low outlay in circuitry and can be readily incorporated into existing display units. I'he observer is present-~d with an a~reeable image on the screen. In comparision to an :inc~ease in the overall brightness, the arrangement has the ~dvanta~e that ~lickering o~ the relatively light colours is avoided and that the colours do not change in the representation of graphic patterns or television pictures. Furthermore, in the case of the representation of characters, the colour tone is maintained as the colours are merely brightened. Mi~ed colours are not changed and therefore the colour contrast is likewise retained.
The arrangement involves a particularly low circuitry outlay if, in the case of the representation of characters in the relatively dark colours, the control unit supplies the display unit with control signals by which these colours are brightened.
-4a-1~,.0~31 In particular it is ad~ntageous for the contxol signals to increase the brightness of xepresented charactex~ by the addition of ~orresponding components of the basic colours.
Another possibility of relative b~ightening of the comparatively dark colours consi~ts in that, in the repxesentation of characters in the relatively dark colours, the control unit increases the overall brightness of the representation on the screen and produces si~nal5 ~7hich reduce the brightn~ess of the represented relatively light colours.
If a decoder unit is provided which supplies the display unit with colour signals assigned to the characters which are to be represented, and which contains an image store which stores data words assigned to the characters and the associated colours, an advantageous embodiment of the arrangement is a~hieved in that the control unit contains a converter which converts first code words asslgned to the relatively daxk colours into second code woxds which are assigned to the corresponding brightened colours.
In particular it is advantageous for the converter to precedq the ~mage store in which the second code words can ~e stored in placc of the first code words. Another possibility consists in that the converter is arranged between the image store and an ima~ repetition store. The image repetition stoxe need not contain the content o one entire page. For example it can be sufficient for the image repetition store to store the content o only one line.
A high degree of legibility o~ the chaxacters can a~so be achieved in that the display unit represents characters with an increased image frequency and that chara~ters in the relatively dark colours are represented more frequently than characters in the relati~el~ ht c~lou~s,~ or in th~t the contxol unit supplies the, display unit ~th signals which periodically temporarily block the brightness signals in tha case of the representation of characters in relatively light colours.
Especially in the case of the use o a flat screen on which representation takes place using a plurality of light points, it is'advantageous for the con~rol unit to generate signals which trigger representation involving more light points~o~ the display unit in the event of the representation of characters' in the io relatively dark colours than in the case of the representation of characters in the relatively light colours.
The control arrangement is advantageously used whenever in particular the basic colours blue and red are provided as relatively dark colours and in particular the colours white, yellow and cyan are provided as relatively light colours.
As the brightness of characters having the basic colours blue and red also differ, it is advantageous for the control unit to produce slgnals by means of which the basic colour blue is b~ightened more than the basic colour red in comparison to the 20 r~latively light colours.
It proves particularly expedient to employ the arrangement when alphanumexical characters and/or linear graphic symbols are providQd b~ way of characters.
The use of the arrangement is advantageous not only for the representation of videotex pages which contain exclusively characters or mixed representations of characters and graphic patterns, but the use of the arrangement also proves expedient for the relative brightening of the comparatively dark colours when characters are'to be gated into a television picture.
~ particularl~ ~d~antageous representation of the characters on the screen is achieved i~ the xelati~e bri~htening of the comparatively dark colours takes place only in cases where thexe is a dar~ background colour to the characters.
The invention will now be described with reference to the drawingsr in which:-Figure 1 schematically illustrates an extract from an exemplary videotex page;
Fi~ure 2 is a bloc~ schematic circuit diagram illustrating IO a irst exemplary embodiment of a control arrangement constructed in accordance with the inventlon;
Figure 3 is a block schematic circuit diagram illustrating a second exemplary embodiment of a control arrangement; and Figure 4 is a blocX schematic circuit diagram illustrating a third exemplary embodiment of a control arrangement.
In the extract from a videotex page represented in Figure 1, typical characters AZ, symbols GZ and a graphic pattern GM have been represented~ The alphanumeric characters AZ and graphic symbol ( ' GZ are composed of fine lines, and both are arran~ed, together with the graphic pattern GM, in an assembly of character arrays ZF, the boundaries of which have been shown ~or purposes o~
explanation, but are not normally visible on the display screen.
Fo~ the representation of characters or symbols, each character array ZF in this example is divided into an invisible grid comprising 8x12 image points BP. The characters AZ are represented on the screen by virtue of the differing degress of brightness of the image points BP. The graphic symbols GZ can be represented ln a similar manner to the alphanumeric characters AZ, but one symbol can extend over a plurality of character arrays ZF. The -7~
characters AZ and s~bols GZ can be repre~ented in the three basic colQu~s ~ ~ed~ ~een ~ bluel ~he ~ixed c~lour~ Qf yellow;
cyan or magenta, and in black or ~hite~ but within an~ one character array ZF the colour cannot change. Any of the basic colours, mixed colours or black and white can be used as a background colour.
In the case of the representation of the graphic patterns GM, the chaxacter arrays ZF are divided into 2x3 gr?phic elements GE. The graphic patterns GM are then represented in character arrays ZF with different combinations of the graphic elements GE.
The~graphic elements GE and the background colour can be represented in any basic colour, mixed colour, or black or white.
If the representation of the characters AZ and s~mbols GZ on the screen takes place in relatively dark colours such as red or blue, then particularly if there is a dark background there is a danger that the characters AZ or s~mbols GZ will be dificult to read. This will be particularly so when, as illustrated in Figure 1, a graphic pattern GM in a relatively light colour such as white, yellow or cyan extends very close to characters AZ or ~0 s~mbols GZ in blue or red, for example.
Furthermore, it has been ascertained that in the case of the pure representation of characters these are difficult to read whe~ part of the videotex page is occupied by characters in a relatively light colour and a further offset part of the 2S page is filled with a relatively dark colour.
In the first embodiment of control arrangement, illustrated in Figure 2, a control unit SE is axranged between an image control unit BST and a display unit AE provided with a screen ~not shown~. The ima~e control unit ssT is o~ known design, and contains s~itch~o~er units ~ia.~hlch coloux si~nals emanating from a television receiver or f~om a videotex decoder are selectively switched through t~ the display unit AE. Switch-over units of this kind are generally known, and are described,for example, in the magazine "Wireless World", May 1976, pages 64-68.
The colour signals R, G and B assigned to the basic colours ,~ red, green and blue are supplied to the display unit AE via delay ele.ments V. The colour signals R, G and B are also supplied to the'control unit SE. In the case of the representation of television pictures on the display unit AE! the colour signals consist of analogue-signals whose instantaneous values deter~;ne the colou.rs to be represented and the brightness thereo. In the case of the representation of characters, symbols and graphic patterns, the colour signals consist of binary signals which assume the binary values "0" or Illn. In the case of the representation of the colour red, for example, only the colour ( signal R possesses the binary value "1"'. Similarly in the case o the representation of the colours blue or green, onl~ the colour signal B or G respectively possesses the hinary value "1".
The colour black is represented when all the colour signals have the binaxy value "0", and for representation of the colour white all the colour signals possess the binary value "1". The mixed colours o yellow, cyan and magenta are represented when two of the colour signals R and G, G and B, or R and B, respectively each possess the binary value "1".
When the videotex decoder establishes that a videotex page is to be represented, the corresponding colour signals R, _9_ G and B are ~ed to the display unit AE. In the case of the representation o~ the gra~hic pattexns G~ ~nd the Xepresentation of the background colours~ the colour signals ase ~ed in known manner to the display unit AE. In the case o~ the representation of alphanumeric characters AZ or graphic symbols GZ, the image control unit BST produces corresponding signals SAZ or SGZ
respectively. When one of these signals occurs, an OR-gate Gl in the control unit SE emits a signal Sl to two AND- gates, Ul and U2. If the characters are to be represented in~blue, the ' 10 colour signal B has the binary value "1" whereas the colour signals R and G have the binary values "0". In this case the AND-gate Ul emits a signal S2 via a switching stage SSl to cause an analogue OR-gate G2 to feed a signal S3 to ~he display unit AE.
This signal S3 serves as a brightness signal, and is used to cause the blue characters or symbols to be brightened in relation to the relatively light colours such as white, yellow or cyan The brightening can be effected in known manner in that, in the display unit AE, small constituents of the basic colours, red and green, are produced by corresponding additional colour signals.
It is also possible to supply the s~gnal S3 to the grid of a pictur~ tube in the form of a cathode ray tube in order to increase ~he bxightness. In the case of representation o characters or s~mbols in redr then in a slm; 1 ar manner to that used ~or xapresentation of charactexs or symbols in blue, these are brightened by a signal S4 produced by means of the AND-gate U2.
The switching stages SSl and SS2 can be used tQ change the amplitude of the signals S2 and of the signals S4 respectivelyr and consequently adjust the signals S3 so that the basic colours red and blue can be brightened to differing extents. Here it is 63~
particulaxly advant~geou~ the colour blue t~ be brightened more than the colour ~ed The delay ~lements ~ are provided to compensa~e for the additional transit times which occur in the AND-gates Ul and U2 r the switching stages SSl and SS2, and the OR-gate G2~ so that the signals S3 are presented simultaneously to the correspondins colour signals.
The control unit SE provides that, in the event of the representation of cha~acters in the relatively dark~colours of red and blue, these can be brightened relative to the comparatively li~ht colours in a simple manner.
' This relative brightening of the comparatively dark colours can be effected in that the display unit A~ is desi~ned for a higher picture frequency and in that the characters AZ and symbols GZ of relatively light colours are represented at a lower picture frequency than the characters AZ and GZ of relatively dark colours. In this case the signal S3 sets a higher picture ~requency so that then the relativel~ dark colours appear brighter.
If the screen is one component of a plurality of light points, and for example is a flat screen, the relative brightening o~ the comparativel~ dark colours can be efected in that the comparatively light colours are represented with a smaller number o~ light points whereas the signal S3 provides that correspondingly morQ.light points are used to represent characters or symbols in the comparatively dark colouxs.
In the alternative control arrangement illustrated in Figuxe 3, the relative brightening of the comparatively dark colours is achieved in representation of videotex pages by increasing the overall brightness, and in the case of the Q~
representation o~ graphic patterns~ GM ~r of background colours the com~aratively light colours are selectively darkened~
A videotex decoder in the image control unit BST emits the colour signals R, G and B and the signals SAZ and SGZ to multiple inputs of a control unit SE~ For representation of graphic patterns GM or of background, the signals SAZ and S~Z each have the binary value "0", so that three AND-gates U3 and U5 are released. If the graphic pattern GM or the background colour ~, i9 to be represented in white, yellow or cyan, the AND-gates, U3, U4 or U5, as the case ma~ be, emit a signal S5, S6 or S7 res~ectively, which is fed via a switching stage SS3, S54 or SS5 respectively, and thence via an analogue OR-gate G3 to form a signal S8 that is f~d to the display unit AE, and darkens these colours, so that in this way the relatively dark colours appear brlghter relative to the comparatively light colours. The delay elements V are provided in order to compensate for the delay times resulting from the AND-gates U3 to U5, the switching stages SS3 to SS5 and the OR-gate G3. The switching stages SS3 to SS5 can serve to individually adjust the degree of darkening for each colour. The signal S8 is expediently conducted to the grid of the o~thode ray tube in order to reduce the brightness of the corxeqpondinq colours.
If representation may take place on the display un~t screen at an increased picture frequency, the signal S8 can be used to reduce the picture frequency in the case of repres~ntation of relatively light colours, so that here too the relatively dark colours appear brighter. In the case of representations composed of a plurality of light points on a flat screen, the signal S8 can be used to reduce the number of operated light paints in the case of the representation o~ xelatiYel~ light colours.
~ nother possibility o~ selectively darkening the xelati~elylight colours involves using tlle signal S8 to make ~he corresponding brightness signal intermittent, i.e. to periodically temporarily interrupt the relevant colour signal. This c n be effected by an AND logic-linking element having one input connected to a clock pulse train signal emitted from an oscillator, ~or ~mrle. ~
~, In the further alterna~ive control arrangement represented by the block circuit diagram illustrated in Figure 4, the control un~t SE itself forms part of the image control unit BST. As regards the videotex decoder, only an image store BSP has been shown, which stores-data words assigned to the characters, symbols and graphic patterns which are to be represented. For ~mpl e these data words contain 16 binary characters, of which 8 are assigned to the alphanumeric characters A~ or graphic elements OE
which are to be represented, and of which a further 8 binary characters represent control signals which characterise the colour ( or the nature of the representation or which indicate that it is a matter o~ data words which are assigned to the alphanumeric characters A~ or the graphic elements GE. First code words composed o three ~inary characters in accordance with the colour signals R, G and B are provided for the representation of the colours.
The control unit SE contains an image repetition sto~e BWS
which in this example intermediately stores the content of one row on the screen. With the exception o~ the first code words which are assigned to the colour signals~ all the other binary characters are directly conducted, as signals S9r to the im~ge repetition store BWS. The colou~ si~nals a~e fed to the im~ge repetition store BWS ~ia ~ conve~tex U~l~
The image repetition store BWS contains ~ore storage positions for data words than the image store BST. In place of three binary characters for the first code words, four binary cha~acters for second code wsrds are provided in the data words r so that in addition to the basic colours, the complementary colours thereto and biack and white, still more colours can be stored. For example the colours "bright blue" and "bright red"
are provided by way of further colours. ~hen the videotex decoder emits the signals SAZ or SGZ and characters or symbols are to be represented in red or blue, the corresponding combinations of the binary characters which are.assigned to these bright colours are stored in tne second code words within the image repetition ~tore BWS. The image repetition store BWS is followed by a second converter UM2 which assigns three colour signals, R1, G1 and B1 to these four binary characters. These colour signals differ from the colour signals R, G and B in that, in.the case of the representation o the characters in blue, the colour signals Rl and 20 ~1 al30 possess glven instantaneous values, and that in the repr~sentation of the characters in red, ~he colour signals Gl and ~1 ~lso possess given instantaneous value, in order to brighten the blue and red on the basis of the additive mixing of the colours.
In another possible design of the image control unit the image store BSP is extended to the extent that second code words formed from four binary characters are provided for the coloursO
In this case the image repetition store BWS is not required and the converter UMl i~ connected preceding the Lmage StQre BSP.
~14-The conyeXteX U~2-can also be designed in such m~nner that, as illustrated in ~igures 2 ~nd 3r it ~roduces additional brightness signals corresponding to the signals S3 or S8, in order to operate the grid of the picture tube, or to change the S picture frequency, or vary the number of light points operated on a flat picture tube.
The converter U~l can be designed to forward the colour signals R, G and B unchanged to the Lmage xepetitl~n store BWS
~, for the representation of characters or symbols. This can be the case, for example, when the ~haracters or symbols are represented on ~ light background. For this purpose the converter UMl can contain a store in which the background colour wnich applies to the character array in question is intermediately stored, and the brightPni ng of the relatively dark colours can take place in dependence upon the contents of said store. An inte ~ te store of this type can also be provided in the control arrangements described with reference to Figures 2 or 3, so that also in this case the relative brightening of the relatively dark colours takes place only when these are represented on a dark background.
Claims (14)
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A control arrangement for the representation of a dis-play on a display unit screen, using different colours and providing for characters, multi-colour graphic patterns and/or multi-colour television pictures, in which a control unit is provided to automatically brighten the representation of characters in relatively dark colours relative to the compara-tively light colours which can be represented and in which for representation of characters or symbols in the comparatively dark colours the control unit supplies the display unit with control signals by means of which these colours are brightened.
2. A control arrangement as claimed in claim 1, in which the control signals increase the brightness of the represented characters or symbols by adding corresponding constituents of the basic colours.
3. A control arrangement as claimed in claim 1, in which representation of characters or symbols in the comparatively dark colours is effected by the control unit increasing the overall brightness of the representation on the screen and producing signals by means of which the brightness of the repre-sented comparatively light colours is reduced.
4. A control arrangement as claimed in claim 3, wherein an image store is provided in an image control unit which precedes the display unit, the control unit containing a converter which converts first code words assigned to the relatively dark colours into second code words which are assigned to the corresponding brightened colours.
5. A control arrangement as claimed in claim 4, in which the converter is arranged prior to the image store in which the second code words can be stored in place of the first code words.
6. A control arrangement as claimed in claim 4, in which the converter is arranged between the image store and an image repetiton store.
7. A control arrangement as claimed in claim 6, in which the display unit represents the characters or symbols with increased picture frequency, and that characters or symbols in the relatively dark colours are represented more frequently than characters or symbols in the relatively light colours.
8. A control arrangement as claimed in claim 6, in which the control unit supplied the display unit with signals by means of which the brightness signals are periodically temporarily blocked in the event of the representation of characters or symbols in relatively light colours.
9. A control arrangement as claimed in claim 8, in which the control unit produces signals which, in the event of the representation of characters or symbols in the relatively dark colours, triggers a representation with more light points on the display unit than in the case of the representation of charac-ters or symbols in relatively light colours.
10. A control arrangement as claimed in claim 9, in which the basic colours blue and red are provided as relatively dark colours and white, yellow and cyan are provided as relatively light colours.
11. A control arrangement as claimed in claim 10, in which the control unit produces signals by means of which the basic colour blue is brightened more than the basic colour red in com-parison to the relatively light colours.
12. A control arrangement as claimed in claim 11, in which alphanumeric characters and/or linear graphic symbols are pro-vided as the characters or symbols.
13. A control arrangement as claimed in claim 12, in which the relative brightening of the comparatively dark colours is effected when characters or symbols are gated into a television picture.
14. A control arrangement as claimed in claim 1 or 13, in which the relative brightening of the comparatively dark colours takes place only in the event of a dark background colour for characters or symbols.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3112249.3 | 1981-03-27 | ||
| DE19813112249 DE3112249C2 (en) | 1981-03-27 | 1981-03-27 | Arrangement for displaying characters on a screen |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1200631A true CA1200631A (en) | 1986-02-11 |
Family
ID=6128524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000399369A Expired CA1200631A (en) | 1981-03-27 | 1982-03-25 | Control for differential colour contrast enhancement on a crt screen |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0062702B1 (en) |
| CA (1) | CA1200631A (en) |
| DE (1) | DE3112249C2 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4931785A (en) * | 1986-06-17 | 1990-06-05 | Ascii Corporation | Display apparatus |
| US5140312A (en) * | 1986-06-17 | 1992-08-18 | Ascii Corporation | Display apparatus |
| US5339094A (en) * | 1987-08-11 | 1994-08-16 | Murrell Nicholas J | VDU line marker |
| US5585822A (en) * | 1991-09-12 | 1996-12-17 | Kabushiki Kaisha Toshiba | Display control apparatus |
| US6031517A (en) * | 1986-12-15 | 2000-02-29 | U.S. Philips Corporation | Multi-color display unit, comprising a control arrangement for color selection |
| US6040818A (en) * | 1989-08-11 | 2000-03-21 | International Business Machines Corporation | Method and apparatus for displaying pixels on a display device |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4965825A (en) | 1981-11-03 | 1990-10-23 | The Personalized Mass Media Corporation | Signal processing apparatus and methods |
| USRE47642E1 (en) | 1981-11-03 | 2019-10-08 | Personalized Media Communications LLC | Signal processing apparatus and methods |
| US7831204B1 (en) | 1981-11-03 | 2010-11-09 | Personalized Media Communications, Llc | Signal processing apparatus and methods |
| DE3910486C2 (en) * | 1989-03-31 | 1996-10-02 | Siemens Ag | Real-time method for displaying color information on black and white monitors |
| DE4029163C1 (en) * | 1990-09-14 | 1992-01-02 | Grundig E.M.V. Elektro-Mechanische Versuchsanstalt Max Grundig Hollaend. Stiftung & Co Kg, 8510 Fuerth, De |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3829613A (en) * | 1972-12-29 | 1974-08-13 | Cit Alcatel | Color intensity control system |
| DE2803746C2 (en) * | 1978-01-28 | 1980-06-26 | Saba Gmbh, 7730 Villingen | Circuit arrangement for displaying characters in different colors on the screen of a display device |
| JPH0153555B2 (en) * | 1978-03-13 | 1989-11-14 | Rca Licensing Corp | |
| DE2829431C3 (en) * | 1978-07-05 | 1981-11-19 | Saba Gmbh, 7730 Villingen-Schwenningen | Circuit arrangement for displaying characters in different colors on the screen of a display device |
| DE2946953C2 (en) * | 1979-11-21 | 1984-08-23 | Loewe Opta Gmbh, 8640 Kronach | Color monitor with a circuit arrangement for fading in colored alphanumeric characters and / or graphic symbols |
-
1981
- 1981-03-27 DE DE19813112249 patent/DE3112249C2/en not_active Expired
- 1981-10-30 EP EP19810109428 patent/EP0062702B1/en not_active Expired
-
1982
- 1982-03-25 CA CA000399369A patent/CA1200631A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4931785A (en) * | 1986-06-17 | 1990-06-05 | Ascii Corporation | Display apparatus |
| US5140312A (en) * | 1986-06-17 | 1992-08-18 | Ascii Corporation | Display apparatus |
| US6031517A (en) * | 1986-12-15 | 2000-02-29 | U.S. Philips Corporation | Multi-color display unit, comprising a control arrangement for color selection |
| US5339094A (en) * | 1987-08-11 | 1994-08-16 | Murrell Nicholas J | VDU line marker |
| US6040818A (en) * | 1989-08-11 | 2000-03-21 | International Business Machines Corporation | Method and apparatus for displaying pixels on a display device |
| US5585822A (en) * | 1991-09-12 | 1996-12-17 | Kabushiki Kaisha Toshiba | Display control apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0062702B1 (en) | 1985-10-09 |
| EP0062702A1 (en) | 1982-10-20 |
| DE3112249A1 (en) | 1982-10-07 |
| DE3112249C2 (en) | 1986-09-18 |
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| MKEX | Expiry |