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
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/3406—Control of illumination source
  • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
  • G09G3/3607—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133621—Illuminating devices providing coloured light
  • G02F1/133622—Colour sequential illumination
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
  • G09G2310/0235—Field-sequential colour display
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
  • G09G2310/024—Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/06—Details of flat display driving waveforms
  • G09G2310/061—Details of flat display driving waveforms for resetting or blanking
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/2007—Display of intermediate tones
  • G09G3/2018—Display of intermediate tones by time modulation using two or more time intervals
  • G09G3/2022—Display of intermediate tones by time modulation using two or more time intervals using sub-frames
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
  • G09G3/3611—Control of matrices with row and column drivers
  • G09G3/3622—Control of matrices with row and column drivers using a passive matrix
  • G09G3/3629—Control of matrices with row and column drivers using a passive matrix using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Definitions

• This invention relates to a display device comprising a matrix of pixels arranged in rows and columns, each pixel being selectively settable into a more light transmissive condition and a less light transmissive condition, means for addressing the pixels using a row by row addressing scheme, and an illumination system. It relates particularly to display devices (known as colour sequential displays) in which a given pixel is illuminated with different colour light at different times to form an image having a plurality of colours.
• a number of display devices which use a technique known as colour sequential lighting to produce multicolour displays from intrinsically monochrome non-emissive displays such as liquid crystal displays.
• One such device is disclosed in EP-A-0 261 896. This particular device suffers from the disadvantage that the display can only be illuminated when it is not being updated. As most displays take a significant period of time to update (known as the frame time) the final image is usually only illuminated for a small fraction of the frame time, resulting in a display having a low brightness.
• a colour sequential display which can be illuminated during updating is disclosed in EP-A-0 478 186. Although this display mitigates the above problem, the display device must still be in the non-light transmissive state for an average of 50% of the time, which still results in a display having a less than optimum brightness.
• an illumination system for a display as claimed in claims 12 to 16.
• the present invention enables more efficient illumination of the matrix than with conventional colour sequential displays in which all rows are illuminated with the same colour at the same time or in the same frame time, as it provides the 2 ability to illuminate spaced rows with different colours during a single frame time.
• Figure 1 shows an oblique view of a display device according to the present invention.
• Figure 2 shows the light output from the display device of Figure 1 at successive times.
• FIG. 1 shows an oblique view of a display device according to the present invention.
• the display device comprising a matrix (11) of pixels arranged in rows and columns, each pixel (10) being selectively settable into a more light transmissive condition and a less light transmissive condition, means (12) for addressing the pixels using a row by row addressing scheme, and an illumination system comprising an array (13) of elongate elements (4, 5, 6) which provide light to the matrix in response to electrical impulses, the elements being arranged side by side to give a striped appearance and to face the matrix, adjacent elements providing light having a different one of a plurality of given colours, and means (7) for providing electrical impulses to the elements in a predetermined sequence which is synchronised with the row by row addressing scheme.
• the pixels comprise an electro-optic material, such as for example a layer of a ferroelectric liquid crystal sandwiched between substantially transparent row and column electrodes which are orthogonal to one another and which overlap to define the pixels.
• the array (13) of the illumination system comprises a striped backlight, the elements of the array including an electroluminescent material, such as for example a light emitting polymer.
• Each stripe or element of the array provides one of a plurality of different given colours, in the present embodiment either green light (elements identified by the reference numeral 4), red light (5), or blue light (6), in response 3 to respective electrical signals from the circuit arrangement (7) comprising the backlight drive means.
• a conventional sequential display is disclosed in International Patent Application No. WO 9633483 (Cambridge Display Technology Limited). Each pixel in the pixel array is sequentially addressed and, as a result, only one colour (for example either red, green or blue) may be displayed at a time. This is less efficient than the display disclosed in the present invention, where more than one colour may be displayed simultaneously.
• the array of electroluminescent elements is formed into a substantially planar structure which is arranged to face the matrix of settable pixels in use.
• An optional diffuser (8) is provided in the path of light from the array (13) to the matrix (11). The presence of this diffuser reduces the striped appearance of the display in use.
• the diffuser may, for example, comprise a ground glass screen.
• the display device of figure 1 is operated in the following way. To begin with, no elements of the illumination system are on (i.e. no elements are providing light to the matrix). Data is written onto the matrix one row at a time, starting with the top row. This means that electrical data pulses are provided by the pixel drive means (12) on the column electrodes of the matrix, whilst an electrical addressing pulse is provided on the top row electrode. It is important that the electro-optic material comprising the matrix is able to respond to provide optically distinguishable conditions in pixels being addressed with different data within a few line times. An element at the top of the array comprising the illumination system is then switched on to provide light to the matrix. The colour of this element corresponds to the colour information represented by the data that has been written onto the top row of the matrix. The row second to top of the matrix is then written with information corresponding to the same colour as that of the first row. The addressing is then repeated on the next adjacent row of the matrix with information corresponding to the same colour.
• next row to be addressed is closer to the next element of the illumination system having the same colour as that of the first element, then this next element is switched on in addition to the first, and the process is repeated for subsequent 4 rows until the whole matrix has been addressed and is being illuminated by all the elements of the array having a given colour.
• top row or rows of the matrix are blanked into the less light transmissive condition, and the top element of the backlight array is turned off.
• several rows of the matrix will be blanked and a plurality of elements of the backlight array having the same colour will be switched off before new data corresponding to different colour information is written to the top row of the matrix. This is done so as to prevent or minimise the light from elements having one colour to diffuse or leak into other elements in the array providing different colours.
• area 20 is being illuminated with green light from elements 4, the area 21 is not being illuminated at that point, area 22 is blanked such that the pixels are in the less light transmissive condition, and area 23 is being illuminated with red light from elements 6.
• the brightest and most efficient display is produced when the blanked area (22) is kept as small as possible compatible with the minimisation of light leakage mentioned above.
• the size of the blanked area must be sufficiently large for the rows to have sufficiently blanked and the electro-optic material to have had sufficient time to recover before new data is written. This may be expressed as a time, which for the Hoechst AEG 4851 material used in the embodiment described above is of the order of 400 ⁇ s.
• the actual width of the blanked area (22) will depend on the precise design of the illumination system. It may be possible for either the un-illuminated part of the backlight array (21), or the blanked area (22) of the matrix where the pixels are in the less light transmissive state to be of almost zero height. The important feature is for there to be some substantially dark area between parts of the matrix being illuminated simultaneously with light having different colours (i.e. areas 20 and 23).
• the above display device can provide an advantage over prior art display devices because the length of time a given part of the display is dark can be made small relative to the frame time, so that the display appears to be much brighter than conventional displays.
• each element of the backlight array is constructed and arranged to illuminate at least N rows of the display, 6 as there will be N-l elements having different colours between nearest neighbour elements having the same colour.
• the matrix is constructed such that it is capable of having one row blanked whilst another is being written at the same time, in order to keep the rate at which data needs to be written to a minimum.
• a ferroelectric liquid crystal layer is an example of an electro-optic material which is capable of being operated in this way.
• the blanking and writing may be done in turn.
• the display device described above may advantageously be used with alternative addressing schemes, such as the time weighted grey scale addressing schemes disclosed in EP-A-0 261 901 and EP-A-0319291, which are hereby incorporated into this application by reference.
• Figure 3 shows an example of an addressing sequence according to a 3 bit binary weighted scheme for a 7 row display which achieves 8 grey levels and which is described more fully in EP-A-0 261 901.
• Each horizontal line in this Figure corresponds to a row in the display.
• Each square in the horizontal direction represents the time taken to address a single row.
• the numbers 1, 2, and 3 in each row in the central area show the binary significance of the of the data which is being written (1 denoting the least significant bit and 3 the most significant bit).
• the position of these numbers in the vertical direction show which row is being addressed , whilst the horizontal position of these numbers shows the time period in which the addressing is taking place.
• the dark vertical lines show at what time each frame ends for each row.
• the display device of the present invention has a much higher percentage of time when the pixels output useful light, resulting in a significant brightness advantage over the prior art scheme, especially when many grey levels are employed.
• the array of elements comprising the illumination system comprised an electroluminescent material such as for example a light emitting polymer
• other materials such as light emitting organic or inorganic materials may be used as an alternative.
• the elements do not have to be electroluminescent providing that they are capable of emitting light (or reflecting or scattering light) in response to an electrical impulse.
• the elements may comprise an electrochromic material or a polym ⁇ r dispersed liquid crystal modulator, together with an appropriate light source.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Control Of Indicators Other Than Cathode Ray Tubes (AREA)
• Liquid Crystal Display Device Control (AREA)
• Liquid Crystal (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Applications Claiming Priority (3)

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• 1998
  • 1998-03-27 GB GB9806593A patent/GB2335776A/en not_active Withdrawn
• 1999
  • 1999-03-25 EP EP99913442A patent/EP1066619A1/de not_active Withdrawn
  • 1999-03-25 JP JP2000541656A patent/JP2002510073A/ja active Pending
  • 1999-03-25 KR KR1020007010735A patent/KR20010034715A/ko not_active Application Discontinuation
  • 1999-03-25 WO PCT/GB1999/000934 patent/WO1999050817A1/en not_active Application Discontinuation
  • 1999-04-01 TW TW088105196A patent/TW452752B/zh not_active IP Right Cessation

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