MULTIPLE VIEW DISPLAY

TECHNICAL FIELD

The present invention relates to a multiple view display.

Such displays may be used, for example, when two or moredifferent peopleneedto see two ormore different images on the same display screen. The viewing angle difference ispreferablyquitelarge (around60degrees) betweenviewers.

Such displays may also be used as three-dimensional

(3D) displays, especially autostereoscopic displays. Such displays may be used in 3D mobile handsets, 3D games, 3D computer monitors, 3D laptop displays, 3D workstations and 3D professional imaging (e.g. for medical, design or architectural usage) . In some 3D displays, it is necessary to increase the eye separation distance for a particular viewing distance or decrease the viewing distance for a particular eye separation. Both of these cases require a wider separation angle.

BACKGROUND ART

In normal vision, the two human eyes perceive views oftheworldfromdifferentperspectives duetotheirseparate location within the head. These two perspectives are then used by the brain to assess the distance to various objects inascene. Inordertobuildadisplaywhichwilleffectively display a three dimensional image, it is necessary to

re-createthissituationandsupplyaso-called"stereoscopic pair" of images, one to each eye of the observer.

Three-dimensional displays are classified into two types depending on the method used to supply the different views to the eyes. Stereoscopic displays typically display both of the images over a wide viewing area. However, each of theviews is encoded, for instance bycolour, polarisation state or time of display, so that a filter system of glasses worn by the observer can separate the views and will only let each eye see the view that is intended for it.

Autostereoscopic displays require no viewing aids to be worn by the observer but the two views are only visible from defined regions of space. The region of space in which an image is visible across the whole of the display active areaistermeda"viewingregion" . Iftheobserveris situated such that one of their eyes is in one viewing region and the other eye is in the viewing region for the other image of the pair, then a correct set of views will be seen and a three-dimensional image will be perceived.

For flat panel autostereoscopic displays, the formation of the viewing regions is typically due to a combination of the pixel structure of the display unit and an optical element, generiσally termed a parallax optic. An example of such an optic is a parallax barrier. This elementisascreenwithverticaltransmissiveslitsseparated byopaqueregions. This screencanbesetinfrontofaspatial light modulator (SLM) with a two-dimensional array of pixel apertures as shown in Figure 1.

The display comprises a transmissive spatial light

modulator in the form of a liquid crystal device (LCD) comprising an active matrix thin film transistor (TFT) substrate 1, a counter substrate 2, apixel (picture element) plane 3 formed by a liquid crystal layer, polarisers 4 and viewing angle enhancement films 5. The SLM is illuminated by abacklight (not shown) with illumination in the direction indicatedbyan arrow 6. The display is of the front parallax barrier type and comprises a parallax barrier having a substrate 7, an aperture array 8 and an anti-reflection (AR) coating 9.

The SLM is arranged such that columns of pixels are provided extending vertically for normal viewing with the columns having a horizontal pitch p. The parallax barrier provides an array 8 of apertures or slits with the slits being parallel to each other and extending parallel to the pixel columns. The slits have a width 2w and a horizontal pitch b and are spaced from the pixel plane 3 by a separation s.

The display has an intended viewing distance r _o with left and right viewing windows 10 and 11 at the widest parts oftheviewingregionsdefiningawindowplane12. Theviewing windows 10 and 11 have a pitch e which is generally made substantially equal to the typical or average human eye separation. The centre of each primary viewing window 10, 11 subtends a half angle a to the display normal.

The pitch b of the slits in the parallax barrier is chosen to be close to an integer multiple of the pixel pitch pof the SLM so that groups of columns of pixels are associated with a specific slit of theparallaxbarrier. Figure 1 shows an SLM in which two pixel columns are associated with each

slit of the parallax barrier.

The windows 10 and 11 are formed by the cooperation of each slit of the parallax barrier 7-9 with the pixels associated with it. However, adjacent pixels may cooperate with each slit to formadditionalviewingwindows (not shown) which are located on either side of the windows 10 and 11 in the windows plane 12. The windows 10 and 11 are referred to as primaryviewing windows whereas any additional windows are referred to as secondary viewing windows.

Figure 2 of the accompanying drawings shows the angularzonesoflightcreatedfromanSLMandparallaxbarrier where the parallax barrier has a pitch b of an exact integer multiple of the pixel column pitch p. In this case, the angular zones coming from different locations across the display panel surface intermix and a pure zone of view for image 1 or image 2 does not exist. In order to address this, the pitch b of the parallax optic is reduced slightly so that the angular zones converge at the window plane 12 in frontofthedisplay. This change intheparallaxopticpitch is termed "viewpoint correction" and is shown in Figure 3 of the accompanying drawings. The viewing regions created in this way are roughly kite shaped.

Foracolourdisplay, eachpixelisgenerallyprovided withafilterassociatedwithoneofthethreeprimarycolours. By controlling groups of three pixels each with a different colour filter, substantially all visible colours may be produced. In an autostereoscopic display, each of the stereoscopic image "channels" must contain sufficient of the colour filters for a balanced colour output.

Anotherknowntypeof directional displayis the rear parallax barrier display as shown in Figure 4 of the accompanying drawings. In this case, the parallax barrier 7, 8 is placed behind the SLM 1 to 5 i.e. between the SLM and the backlight. This arrangement has the advantage that the barrier is kept behind the SLM away frompossible damage.

Lenticular screens are used to direct interlaced images to multiple directions, which can be designed to give a 3D image or give multiple images in multiple directions. Practical lenses tend to suffer from scatter and poor anti-reflection performance so that the surface is very visible inbothambient andbacklit environments. Therefore, the image quality of lenticular screens can be poor and the system suffers from similar problems as parallax barriers such as the need for close proximity to the image pixels. An array of prism structures may be used in a similar way.

Holographic methods of image splitting also exist but they suffer from viewing angle problems, pseudoscopic zones and a lack of easy control of the images.

Micropolariserdisplaysuse apolariseddirectional light source and patterned high precision micropolariser elements aligned with the LCD pixels. Such a display offers the potential for high window image quality as well as 2D/3D function in a compact package. The dominant requirement is the incorporation into the LCD of micropolariser elements to avoid parallax issues.

Figure 5 illustrates three known types of dual view displays referredto as Pl, P2 andP3. Eachof these displays is of the front parallax barrier type but could equally well

be of the rear parallax barrier type or could be embodied using different types of parallax optics. The Pl display comprises an LCD 20a comprising columns of pixels displaying the two views as interlaced vertical strips with left and right strips being displayed by interlaced single columns of pixels. Figure 5 illustrates the displays as being autostereoscopic 3D displays withaviewerbeing illustrated at 30. A column 21a of pixels displays a strip of the right eye image whereas a column 22a displays a strip of the left eye image. The adjacent columns 23a and 24a display left eye and right image strips, and so on across the LCD 20a. A parallax barrier 25a is disposed in front of the LCD 20a and controls which pixel columns are visible to which eye of the viewer 30 in the usual way.

The P2 display differs from the Pl display in that pairs of adjacent pixel columns display a strip of one of the views. For example, the pair of adjacent pixel columns 21b and 23b and the pair of adjacent pixel columns 26b and 27b display respective strips of the right eye view whereas the pair of pixel columns 22b and 24b and the pair of pixel columns 28b and 29b display respective strips of the left eye view. The barrier 25b provides wider slits of larger pitch spaced further from the LCD 20b than the barrier 25a for the Pl display. Thus, each eye of the observer 30 can see two columns of pixels through each slit of the barrier 25b.

The P3 display differs from the Pl and P2 displays in that each eye of the viewer 30 sees three columns of pixels through each slit of the parallax barrier 25c and each strip of each of the two views displayed by the LCD 2Oc is displayed bythree adjacent columns ofpixels. Thus, thepixel columns

21c, 23c, 28c and the pixel columns 27c, 31σ, 32c display two strips of the left eye view whereas the pixel columns 22c, 24c, 26c and the pixel columns 29σ, 33c, 34c display two strips of the right eye view.

In general, displays can be classified as being of Pn type where, in each primary viewing window, n columns ofpixels areviewableandeachstripof eachviewis displayed by n adjacent columns of pixels. Pn displays where n is greater than one have advantages over Pl displays in that higher resolution LCD panels or larger separation between thebarrier slit plane andthepixelplane can be usedwithout changing the viewing distance of display at which viewpoint correctionisprovided, i.e. thewindowplane. However, such displays have disadvantages in that the barrier structure may be more visible to the viewer and colour defects as described hereinafter may be produced.

Figure 6 illustrates a P2 type of display in which aconventionalvertically stripedcolour filter (orvertical strips of colour pixels) is used. Thus, the colour filter comprises a repeating pattern of vertical red (R), green

(G), and blue (B) strips (or intrinsically coloured pixels are arranged in this way) . The effect of this for one view is illustrated at 35. In particular, the order of colours seen in that view is not the RGBRGB...pattern of the underlying colour pixels but, instead, is RGGBBRRG....

Thus, the viewer may perceive red, green and blue strips on a scale which is four times larger than the pitch of the pixel columns.

Figure 7 illustrates a P3 type of display, again

havingpixelcoloursarrangedas repeatingRGBcolumns. When viewed from the middle of a viewing window, there are no undesirable colour artefacts and the red, green and blue pixel colours are visible in the correct ratios through each slit of the barrier 25.

Figure 8 illustrates what happens when adjacent groups of pixels for left and right images display different image data. In particular, by way of example, each set of three pixel columns such as 36 for the left eye image is shown displaying white whereas the pixel columns such as 37 displaying the right eye image are shown as being black. When the display is viewed from the centre of each viewing window as illustrated at 38, there are no undesirable visual artefacts.

Figure 8 illustrates at 39 the effect of a viewer moving to the left as comparedwith the situation illustrated at 38. This is equivalent to a relativemovement to the right of the barrier 25. The effect of this is that each red column of pixels of the left eyeviewbecomes increasinglyobscured. Although the redpixels of the right eye viewbecome visible, because they are black, the effect is that there is a colour shift towards cyan in the left eye view as perceived by the viewer. Thus, colour artefacts which are dependent on the imagebeingdisplayedareperceivedbytheviewerwhenviewing the display from other than the optimal position.

GB2399653 discloses anon-periodicparallaxbarrier structure in which groups of evenly spaced slits are themselves evenly spaced apart with a different horizontal pitch. Vertically striped colour filtering is also disclosed.

WO02091348 discloses a single view or two-dimensional (2D) display having a non-standard pattern of pixel colouring.

DE19822342 discloses a multiple view display of the P3type. Inordertoallowforlateralmovementofanobserver without shifting a parallax barrier structure relative to a pixel structure, columns of pixels additional to those viewable through each slit when the display is viewed correctly are switched.

Schmidt et at, "Multi-Viewpoint Autostereoscopic Displays from 4D-Vision", Proc. SPIE, vol. 4660, pp 212-221 (2002) and Son et at, "Moire Pattern Reduction in Full-Parallax Autostereoscopic Imaging Systems Using Two CrossedLenticular Plates as a Viewing Zone Forming Optics" , Proceedings of the tenth International Display Work- shop-Fukuoka 2003, paper 3D2-2 disclose so-called staggered parallax barriers inwhich the slits are arranged at an acute angle to the column direction of the display structure. Such arrangements are disclosed for reducing Moire patterning in displays of the Pl type.

EP 1427223 and EP 0829743 discloses Pl displays with repeating groups of RGB columns.

EP 1401216, EPO 0860 728, US 2002/0001128 and EP 0 847 208 discloses viewer position indications in Pl displays.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention, there is provided a multiple view display comprising: a parallax optic comprising a plurality of parallax elements spaced apart at a single first pitch; and a spatial light modulator comprising a plurality of columns of pixels arranged with a second pitch providing viewpoint correction for creating n primary viewing windows for viewing n views, where n is an integer greater than one, with w columns of pixels being viewablethrougheachparallaxelementineachviewingwindow, where w is an integer greater than one, the pixels of each columnbeingofasamecolour, the columnsbeingofxdifferent colours, where x is an integer greater than two, and being arrangedas asequenceofcolours comprisingrepeatinggroups of a same sub-sequence, characterised in that each group comprises y subgroups of z columns, where y is an integer greater than one and z is an integer greater than or equal to x, each subgroup containing columns of all x colours, the smallest repetition pitch of the sequence being equal to y.z columns.

The modulator may include a striped colour filter arrangement whose stripes are aligned with the columns.

The number x of colours may be equal to three. The three colours may be primary colours. The primary colours may be red, green and blue.

The number z of columns of each subgroup maybe equal to x.

The number w of columns viewable in each window may be equal to two. The number y of subgroups in each group may be equal to three. Each sub-sequence may be red, green,

blue, green, blue, red, blue, red, green.

The number w of columns viewable in each window may be equal to three. The number y of subgroups in each group may be equal to six. Each sub-sequence may be red, green, blue, red, green, blue, green, blue, red, green, blue, red, blue, red, green, blue, red, green.

According to a second aspect of the invention, there is provided a multiple view display comprising: a parallax optic comprising a plurality of parallax elements; and a spatial light modulator comprising a plurality of pixels arranged as rows and columns cooperating with the parallax optictocreatenprimaryviewpoint-correctedviewingwindows for viewing n views, where n is an integer greater than one, with a respective single column of pixels being viewable through each parallax element in each viewing window, the pixels being arranged as composite colour groups for displaying respective colour image elements, each group comprising z pixels of x different colours disposed adjacent each other in the same column, where x is an integer greater than two and z is an integer greater than or equal to x, the pixels of each colour for each view being disposed so as to be substantially evenly spaced horizontally and substantially evenly spaced vertically, characterised in that the order in the column direction of the colours of the pixels of each group is different from the order in the columndirectionof the colours of thepixels of eachadjacent group in the same rows.

The pixels of each colour may be disposed so as to be substantially evenly spaced horizontally and sub¬ stantially evenly spaced vertically on the modulator.

The pixels may be arranged in the row direction as repeating sets of z pixels of the x different colours with each row being offset in the row direction relative to each adjacent row by a number of pixels greater than zero and less than z. The offsets between adjacent rows may have the same magnitudes. The offsets between adjacent rows may have the same directions.

The number x of different colours may be three. The three colours may be primary colours. The primary colours may be red, green and blue.

The number z of pixels in each group may be equal to x.

According to a third aspect of the invention, there is provided a multiple view display comprising: a parallax optic comprising a plurality of parallax elements; and a spatial light modulator comprising a plurality of pixels arranged as rows and columns cooperating with the parallax optictocreatenprimaryviewpoint-correctedviewingwindows for viewing n views, where n is an integer greater than one, withwpixels in eachrowbeingviewable through eachparallax element in eachviewing window, where w is an integer greater than one, characterised in that the rows are arranged as groups and the parallax elements are arranged as rows, each ofwhich is alignedwith arespective group of rows of pixels, the pixels comprising sets of pixels of different colours arranged such that the sequence of pixel colours viewable in each viewing window through each parallax element of each row of parallax elements is different from the sequence of pixel colours viewable through the or each nearest parallax

element in the or each adjacent row of parallax elements.

The parallax elements may be aligned in the row direction. The parallax elements may be continuous in the column direction. The pixels may be arranged as repeating colour sequences in the row direction and the rows of pixels of each adjacent pair of groups may be offset with respect to each other in the row direction by at least one pixel pitch and by less than the smallest repetition pitch of the repeating colour sequence.

The pixels of each colourmaybe arranged as columns. The parallax elements of each adjacent pair of rows may be offset with respect to each other in the row direction.

The offsets may be of the same magnitude.

The offsets may be in the same direction.

The groups of rows of pixels or the rows of parallax elements may be arranged as sets with offsets of the sets being in the same direction and with the offsets of adjacent pairs of sets being in opposite directions.

Each group of rows may comprise a single row.

Each group of rows may comprise a plurality of rows. Each group of rows may comprise n rows, the display may be rotatable between a portrait orientation and a landscape orientation, and the parallax elements may be arranged to provide two dimensional parallax. The offset may differ from twice the pitch of the columns to provide viewpoint correction. The pixels of each rowmaybe arranged as groups

of n.w pixels separated from each other by the pitch of the columns.

The number w may be equal to two and the different sequences of pixel colours may comprise different com¬ binations.

The number w may be equal to three and the different sequences of pixel colours may comprise different per- mutations.

The parallax optic may be a parallax barrier.

The spatial light modulator may be a light-attenuating modulator. The modulator may be transmissive. Themodulatormaybe a liquid crystal device.

The number n of windows may be equal to two.

The sets ofpixelsmaybe of three colours. The three colours may be primary colours. The primary colours may be red, green and blue.

It is thus possible to provide an improved multiple view display. Embodiments and examples of such a display may achieve combinations of one or more of the following advantages:

Improved image quality; Reduced colour artefacts in multiple view mode;

Reduced colour artefacts when used in single view mode;

Reduction in colour artefacts dependent on viewer

position .

Pn displays where n is greater than one provide an advantage in that the space in between a pixel plane of the spatial light modulator and a plane containing the parallax elements may be made greater than for Pl displays. Thus, any substrate between the planes can be of larger thickness and this reduces manufacturing problems, for example in handling relatively thin glass. In addition, it makes it possible or easier for the parallax optic, such as a parallax barrier, to be of an active type without requiring the use of thin substrates suchas thin glass. It is thereforeeasier to provide a display which is switchable between multiple view and single view modes. For example, a parallax barrier canbeembodiedbyaliquidcrystaldevicewhichcanbeswitched toasubstantiallyuniformtransmissivemodesoaseffectively to disable the parallax barrier and permit normal viewing of a single image or view throughout a wide viewing region.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic horizontal cross-sectional view of a known multiple view display;

Figures 2 and 3 are diagrammatic plan views il- lustrating the generation of viewing regions and the effect of viewpoint correction;

Figure 4 is a diagrammatic horizontal

cross-sectionalviewof anotherknownmultipleviewdisplay;

Figure 5 is a diagrammatic plan view illustrating different types of known multiple view displays;

Figure 6 illustrates an undesirable colour artefact produced by a known type of P2 display;

Figures 7 and 8 illustrate the generation of an undesirable visual artefact in a known type of P3 display;

Figure 9 is a diagram illustrating a multiple view P2 display constituting an embodiment of the invention;

Figure 10 is a diagram illustrating a multiple view

P3 display constituting an embodiment of the invention;

Figure 11 is adiagramillustratingP2 andP3 displays constituting embodiments of the invention;

Figure 12 illustrates another pixel arrangement for use in an embodiment of the invention;

Figure 13 is a diagram illustrating a known Pl type of displayandaPl type of displayconstitutingan embodiment of the invention;

Figures 14 to 16 illustrate further pixel ar¬ rangements for displays constituting embodiments of the invention;

Figures 17 and 18 illustrate P2 types of displays with staggered barrier slit arrangements constituting

embodiments of the invention;

Figure 19 illustrates a P3 type of display with a staggered barrier slit arrangement constituting an em- bodiment of the invention;

Figure 20 illustrates a display of the type shown in Figure 19 with a zig-zag barrier slit arrangement;

Figure 21 illustrates a display of the type shown in Figure 17 with a zig-zag barrier slit arrangement;

Figure 22 illustrates a P3 type of display having portrait and landscape viewing modes and constituting an embodiment of the invention; and

Figure 23 illustrates another P3 type of display havingportrait andlandscapeviewingmodes andconstituting an embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Like reference numerals refer to like parts throughout the drawings.

Themultipleviewdisplays describedhereinafterare all of the two or dual view type but displays providing more than two views may also be provided. The displays may be used for any suitable application such as autostereoscopic 3D image displayand display to more than one viewer of images which may be independent and unrelated to each other. All of the displays are colour displays made up of red, green andbluepixelswithtriplets ofRGBpixels formingacomposite

colour or "white" group. However, other arrangements are possible, such as composite groups comprising RGGB pixels or RGYB pixels, where Y pixels are white. The displays comprise flat panel liquid crystal devices as the spatial lightmodulatorsandparallaxbarriersastheparallaxoptics. However, other types of spatial light modulators (including light-emitting types) and other types of parallax optics may be used.

The P2 display shown in Figure 9 comprises and LCD

20 and a parallax barrier 25 such that two columns of pixels with associated colour filter stripes are viewable in each viewing region through each slit of the parallax barrier 25. The display differs from known types of display in the horizontal ordering or sequence of red, green andblue filter stripes which extend vertically in the column direction of pixels and each of which is associated with a single pixel column. In particular, the filter sequence (from left to right in Figure 9) comprises a repeating subsequence of RGBGBRBRG filter stripes.

Such an arrangement reduces undesirable colour artefacts in multiple view image displays. However, if such a display is used in a 2D or single viewmodewith the parallax barrier 25 disabled or removed, undesirable colour stripes with a period of nine pixel column may be generated. For example, in such a mode, a region with a relatively high density of blue pixels is illustrated at 40.

Figure 10 illustrates aP3 display in which the pixel colour sequence in the horizontal or row direction differs fromknown displays. In this display, the pixel colours are arranged as a repeating sequence of RGBRGBGBRGBRBRGBRG.

Such an arrangement results in different colour shifts in different columns as a viewer moves laterally in front of thedisplaysothat, at asufficientlylargeviewingdistance, colour shift artefacts with observer movement as described hereinbeforeare reducedandmaybe imperceptible. However, again, when used in a single view mode with the parallax barrier 25 removed or disabled, colour stripe artefacts may be visible (a region of high blue density is shown at 40) .

Figure 11 illustrates alternative P2 andP3 displays in which the pixels are not arranged as columns of single colours. In each of these displays, each row comprises a repeating sequence of RGB pixels. However, the patterns in adjacent rows are staggered or offset in the row direction by one pixel so that the pixels of each colour are aligned diagonally on the LCD 20. In the P2 display, the colours "average"' vertically through the barrier slits so that undesirable colour artefacts are substantially avoided in the multiple view and single view modes. Similarly, in the P3 display, different colour shifts occur in different rows, so that undesirable colour shift artefacts are substantially avoided.

Figure 12 illustrates an alternative pixel colour patternforaP2orP3displaydifferingfromthoseillustrated in Figure 11 in that the rows are staggered or offset in onedirectionforthreerows andthenintheoppositedirection for three rows. Such an arrangement may be used to remove or reduce any undesirable effects caused by the diagonal colour striping in Figure 11, for example in the single view mode.

Adjacentrowsmaybeoffsetbyoneortwopixelpitches

in the case of LCDs having pixels of three different colours. As an alternative, the order of the pixel colours may be changed in each row.

Figure 13 illustrates a Pl display of known type at

41andaPldisplayconstitutinganembodimentoftheinvention at 42. ThePl displayat 42 uses the same colourpixelpattern as the displays shown in Figure 11 so that the pixels of each colour which are viewable in each viewing window are substantially evenly spaced vertically and horizontally, althoughtheverticalandhorizontalpitchesmaybedifferent from each other.

When, for example, P2 and P3 displays are used as autostereosσopic 3D displays, it is possible for abinocular disparitytoarisebetweenpixelsofdifferentcoloursbecause of the colour pixel patterning in relation to the parallax barrier structure. This may result in unexpected stereoscopic features. For example, a red plane and a green plane which are intended to appear at the same distance from the viewer may appear to be separated in depth.

Figures 14 to 16 illustrate colour pixel patterns which may be used in order to reduce variations in binocular disparity between the individual colours. Figures 14 and 15 illustrate patterns for use with displays of the P2 type. Thus, Figure 14 illustrates a pattern in which the colours arearrangedasverticalstripswithahorizontallyrepeating sequence of RGRGBRBRGBGB.

Figure 15 illustrates a pattern based on the same repeating colour sequence but in which adjacent rows are offset by four pixel column widths. The pattern shown in

Figure 16 is the same as that shown in Figure 9.

In the previously described embodiments, each parallax barrier 25 comprises evenly spaced continuous vertical slits. In the embodiments illustrated in Figures 11, 12 and 15, adjacent rows of pixel colours are offset fromeachotherintherowdirection. Thecontinuousvertical slits are equivalent to and may be considered as individual slits for each row, which slits are aligned with each other in the row direction to form the continuous vertical slits in the column direction. However, a similarperformancemay be achieved by having offset rows of slits cooperating with colour pixel patterns where each column of pixels is of the same colour.

Figure 17 illustrates an example of such an ar¬ rangement in which the colour filter stripes are arranged as a repeating sequence of RGB stripes. Each row of pixels cooperates with a row of slits with the slits of adjacent rows being offset approximately by the pixel column pitch (allowingforviewpointcompensation) . Thisarrangementmay be used in a P2 type of display and is effectively equivalent to the P2 display shown in Figure 11.

Figure 18 illustrates aP2 displayinwhichtheoffset between adjacent rows of slits of the parallax barrier is equaltoapproximatelytwicethepixelcolumnpitch (allowing for viewpoint compensation) .

Figure 19 illustrates a P3 display in which the adjacent rows of slits are offset relative to each other by approximately one pixel column pitch (allowing for viewpoint compensation) .

Displays of the type shown in Figures 17 to 19 have limited vertical freedom of movement of the viewer in order to avoid crosstalk. In particular, if a viewer views the display from above or below the intended horizontal viewing plane, the wrong pixels become visible through the parallax barrier slits. This effect may be reduced by reducing the height of the individual slits (indicated by X in Figure

19) toprovidegreaterverticalviewingfreedomat theexpense of reduced brightness for a given display illumination.

Figures 20 and 21 illustrate modifications of the P3 and P2 displays shown in Figures 19 and 17, respectively, in order to reduce or remove any diagonal "banding" which might be unacceptable. In each of these displays, the parallax barrier slit rows are offset in one direction for three rows and then in the opposite direction for three rows.

Figure 22 illustrates a P3 display which may be used in a portrait viewing mode or a landscape viewing mode or may be switched between these modes. The LCD 20 comprises a vertically striped colour filter with repeating groups of RGB stripes, for example as illustrated in Figure 7. The individual colour pixels are arranged as square-shaped composite colour groups so that the pitch p2 of the rows is approximately three times the pitch pi of the columns with the display oriented in the portrait mode.

Theparallaxbarrier comprises apattern of openings suchas 50 ofsquare shape. Intheportraitmode, theopenings

50 are arranged as rows with a pitch differing from 6pl so as toprovideviewpoint correction. Adjacent rows areoffset with respect to each other by approximately the column pitch

pi and each row of openings 50 cooperates with two rows of pixels.

In Figure 22, pixels of different colours are indicated by different shading and the pixels which display- left and right image pixels are indicated by L and R, respectively.

In the portrait mode, the display of Figure 22 overcomes the colour shifting artefacts described here¬ inbefore in the same way as the display illustrated in Figure 19.

In the landscape mode, the display is effectively rotated through 90 degrees so that the barrier openings 50 are arranged as columns with a pitch of 2p2. In this viewing mode, the right and left eyes of the viewer 30 can see the same areas of pixels of different colours throughout a wide lateralviewingrangewithoutanyundesirablecolourshifting artefacts. ,

The allocation of the LCDpixels to the left andright images changes between the portrait and landscape modes. When the display is of the type which is switchable between thesemodes, a displaycontrollermaybe arrangedto allocate the pixels correctly to the left and right views when the display orientation is changed. This may be actuated automatically or manually.

If the display is not required to be switchable between the portrait and landscape viewing modes, then the display controller may be preset to provide the pixel allocation for the mode of operation of the display.

Figure 23 illustrates only the portrait mode of another P3 display which may be switched between portrait and landscape modes. For the dual view display illustrated in Figure 23, the rows of pixel are arranged in groups of six separated from each other by pixels such as 51 which are switched to their black state. Alternatively, such pixels 51 may be used to display data for one of the views or may be controlled to show a grey level appropriate to both views so as to increase viewer freedom. The rows of openings are staggered in the row direction by an amount which differs fromtwice the column pitch in order to provide viewpoint correction. Similarly, the pixels 51 which are switched to black are staggered in adjacent rows by twice the column pitch. The presence of a "redundant" pixel 51 separating groups of six pixel in each row results in the colour viewable from each primary viewing region through each opening 50 in the middle of the set of three pixels cycling through red, green and blue across the display in the row direction. Staggering of the redundant or black pixels between adjacent pairs of rows results in the colour beingbalancedacross fourrows andprovides relativelysmall colour separation which is less visible to the viewer.

In order to provide a 2D or single view mode of operation, the parallax barrier in all of the embodiments mayberemovedordisabled. Forexample, theparallaxbarrier may comprise a switσhable liquid crystal cell having the appropriate electrode-patterning so as to be switchable between amultipleviewmodewith thebarrier structure being provided and a single view mode with the barrier structure being disabled.