GB2431035A - Image display array - Google Patents

Abstract

An image display comprises a number of picture elements or pixels 1, 9 arranged in one or more layers behind at least one opaque screen 4, means 3, 8 for raising and lowering the picture elements such that they may be brought into view or hidden behind the screen, and means for holding selected picture elements in the raised position. The raising and lowering means may comprise mechanical means including one or more rigid members. The raising and lowering means may alternatively comprise pneumatic or hydraulic means. The means for holding selected picture elements in the visible position may comprise electromagnetic solenoids.

Description

1 2431035 Pixel Array Image Display This invention relates to a device for

displaying text and graphical images using an array of picture elements (pixels).

There are a number of technologies already in existence for displaying text and graphics in a pixel array form.

One such technology uses an array of either square or round Light Emitting Diodes (LEDs) which are illuminated in accordance with a pattern stored in an electronic memory device.

Such displays are commonplace and used to indicate such things as products and services, special offers, bus route information etc. Unfortunately this type of display technology suffers from two main drawbacks.

Firstly, the display consumes electricity to produce the visual output, even when the information isn't changing. This problem is greatly exacerbated if the display needs to be visible outdoors, potentially in direct sunlight.

Secondly, although multi-coloured LED arrays are available they tend to be quite expensive thereby restricting most applications to a single colour.

An alternative technology exists in the form of the flip-dot' display. This type of technology uses an array of electromagnets to cause coloured discs of material to pivot about an axis of rotation.

The discs are normally coated with a high visibility reflective material on one side and a matt black finish on the other. The array of magnets and the supporting frame are also typically finished in matt black.

The text and graphical information is produced by selectively energising certain electromagnets which cause the associated discs to rotate so that their high-visibility sides are presented to the viewer. The viewing area around the remaining de-energised electromagnets appears black to the viewer.

As with the LED alternative, the flip-dot' technology also suffers from two distinct drawbacks.

Firstly, the display is restricted to two colours only, typically a bright yellow

presented against a black background.

Secondly, the mechanical reliability of the entire array can become a problem.

The force experienced by each coloured disc as a result of the nearby electromagnetic field changes quite dramatically as each disc rotates into position. The electromagnets need to be sufficiently sized as to be able to cause each disc to pull-in' reliably without exerting excessive force once they have rotated into position.

As few as one or two stuck' or orphan' pixels are typically visible and detract considerably from the overall display.

To overcome these problems, the present invention proposes a display means whereby a number of picture forming elements are arranged in one or more layers behind one or more opaque screens, a means is provided whereby several picture forming elements can be simultaneously raised and lowered in such a way that they can be brought into view or hidden behind the screening arrangement and a means is provided whereby individual picture forming elements can be selectively held in the raised visible position.

The advantages of such an arrangement are that a pixel array display can be constructed which can be multi-coloured, is easily visible in direct sunlight, which can be updated relatively quickly and which consumes energy only when the display content is being modified.

Preferably the picture forming elements will be raised and lowered using rigid members although such movement could be produced by an alternative means e.g. using pressurised air.

Preferably the image forming elements will be selectively held in the raised visible position by solenoid actuated locking pins.

This invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a single picture element or pixel'.

Figure 2 shows several picture elements arranged on a lifting member Figure 3 depicts a horizontal section through part of a display showing three picture elements sandwiched between two corrugated walls.

Figure 4 demonstrates how picture elements are raised into view.

Figure 5 depicts the location of locking pin indents on a single picture element Figure 6 is a horizontal section through part of a display illustrating a solenoid driven locking arrangement.

Figure 7 demonstrates the solenoid activation sequence required to raise three picture elements and hold two of them in the raised visible position.

Figure 8 demonstrates how a two-dimensional array of picture forming elements is constructed.

Figure 9 shows how the stepped nature of a two dimensional array can be rotated to form a flat display.

Figure 10 demonstrates the arrangement required for a three-colour display Figure 11 shows the locking pin arrangement for a three-colour display.

Figure 12 shows the pixel carrier cut-outs' required for the three-colour locking pin arrangement.

Figure 13 demonstrates how air pressure could be used to raise picture forming elements.

Figure 14 illustrates an overview of a pneumatically controlled display.

Figure 15 demonstrates how a single solenoid could be used to control three picture forming elements.

Figure 16 shows the pixel carrier cut-outs' required for the single solenoid arrangement.

Figure 17 illustrates an overview of a four-colour, single-solenoid, pneumatically controlled display.

A display of the type provided by this invention is made up of picture elements (pixels) which are typically constructed from reflective material of an appropriate colour. Figure 1 depicts a single pixel (1) attached to a pixel carrier (2).

Figure 2 demonstrates three pixels (1) and associated carriers (2) arranged in a row above a lifting member (3). The lifting member (3) is used to simultaneously raise and lower the pixel carriers (2) and hence the pixels (1).

To prevent the pixel carriers from falling off the lifting member sheets of material are placed on either side to form walls. Grooves are shaped into the walls which align with similar groves formed in the pixel carriers to prevent lateral movement of the pixels along the length of the lifting member.

This can be seen in figure 3 which is a cross section through a row of three pixels. Note the grooves formed in the walls (4) and matching grooves formed in the pixel carriers (2). The pixels themselves (1) are thinner than the pixel carriers (2) and therefore are unaffected by the grooved walls.

Figure 4 shows a frontal view of the three pixels illustrated in figure 3. In the upper diagram a lifting member (3) is raised to lift the pixel carriers (2) and hence the pixels (1) up from behind a wall section (4).

The centre illustration of figure 4 depicts a point where the lifting member is approximately half way along its vertical travel and the individual pixels are emerging from behind the front wall (4).

The lower illustration of figure 4 depicts the point whereby the lifting member has reached the extent of its vertical travel and the associated pixels are all fully exposed.

The diagrams so far have illustrated a means of simultaneously moving a row of pixels up and down using a lifting member travelling within a pair of guiding walls. However, to produce a useful display a means is required whereby some pixels are selectively kept in the raised (visible) position when the lifting member is subsequently lowered.

A simple way to achieve this is shown in figures 5 and 6. In figure 5, a pixel (1) is attached to a pixel carrier (2) which has locating holes (5) drilled into it.

Figure 6 depicts a cross section of part of a display which illustrates a locating pin (7) being driven into a locating hole (5) using a solenoid (6).

By arranging a solenoid operated locking pin behind every pixel it is possible to lock each pixel in either the raised or lowered state.

An example of the sequence of events required to operate such a display is shown in figure 7 In the initial condition, as shown in figure 7 (a), all three pixels are in the lowered state and all three locking pins are in the locked state.

To operate the display the locking pins are first withdrawn as shown in figure 7(b). Then, the lifting member is raised to bring all three pixels into view as shown in figure 7 (c). (Note throughout figure 7 a solid dot has been placed within the cross section of a pixel to indicate when it is in the raised state).

Next, selected locking pins are driven into the locked position as shown in figure 7 (d). The lifting member is then lowered as shown in figure 7 (e). Note that in figure 7 (e) the leftmost and rightmost pixel have remained in the raised state as signified by the solid dot, due to the action of the locking pins, whereas the centre pixel has been allowed to return to the lowered state.

The remaining locking pins are then driven into the pixels in the lowered state to hold them in place as shown in figure 7 (f).

For the sake of clarity only a single row of pixels has been considered so far.

However, to make a useful display a two-dimensional array of pixels is required. Figure 8 shows such an array made up of three rows of four pixels (1) mounted on pixel carriers (2) actuated by lifting members (3) running between support walls (4).

Note that in figure 8 the lifting members (3) have been shown as separate unconnected entities for the sake of clarity. However, in a practical display the lifting members would all be mechanically linked and a means would be provided to cause all the lifting members to raise and lower simultaneously e.g. a geared drive arrangement powered by an electric motor As each subsequent row is positioned behind and above the preceding row the display takes on a stair-case' appearance However, providing the ratio of the pixel height (i.e. vertical step size) is at least four times that of the thickness of each stage of the display, the slope of the stair-case' will be no more than fifteen degrees.

Figure 9 (a) illustrates a cross-section of the stair-case' effect. For most circumstances the slight sloping effect should not be a problem but for those cases where it is the entire display can be contra-rotated as shown in figure 9 (b).

So far only a two colour display has been considered i.e. whereby pixels (1) of one colour are selectively viewed against a background colour formed on the walls (4). However, the type of display provided by this invention is not limited to two colour operation.

Figure 10 illustrates the arrangement required for a three-colour display. The diagram is very similar to that of figure 8 except that a row of alternatively coloured pixels (9) has been placed in front of each row of the original pixels (1).

The rows of alternatively coloured pixels (9) are raised and lowered using a set of alternate lifting members (8).

The display operates in a similar manner to the two-colour version already described except that a lifting and selective locking' cycle is performed for one set of pixels (1) using the lifting members (3) then a second cycle is performed for the alternate pixels (9) using the alternate lifting members (8).

A separate set of solenoid driven locking pins is required for the alternate coloured pixels as shown in figure 11. However, the locking pins (7) which operate on the alternate pixel carriers (2) towards the front of the display must pass through the original pixel carriers (2).

Figure 12 illustrates the cut-out (10) required on the carriers of the rear pixels (1) so that the locking pin used to control the carriers of the front pixels (9) can pass through.

An alternative way of raising pixel carriers which does not require rigid lifting members is depicted in figure 13. Here thin inner walls (12) have been fixed in between the outer walls in such a way as to form a chamber around the pixel carrier (2).

Note: the inner walls (12) have upper and lower protrusions which serve to limit the travel of the pixel carrier (2).

The pixel (1)is raised by injecting compressed air into the space (11) beneath the pixel carrier (2) i.e. the pixel carrier and surrounding chamber combine to produce a pneumatic actuator.

An overview of a display system using such pneumatically operated pixels is shown in figure 14. A compressor (16) builds up air pressure in a receiver (15). The air pressure is released into the pixel array (13) under the control of a solenoid operated valve (14).

Using such an arrangement it is possible to construct a display in which the pixels move very quickly. The air pressure provides the vertical movement of the pixels which are then selectively held by the solenoid operated locking pins before the air pressure is released.

Since an update cycle could typically take less than a quarter of a second to complete and be required e.g. every five seconds, the receiver (15) allows a comparatively small compressor (16) to be used.

Since each pixel is independently moved using pneumatic pressure it is possible to use a single locking pin arrangement for each pixel site of a multi- colour display. An example of this is shown in figure 15.

Here a single locking pin (7) is controlled using a solenoid (6) and passes through three walls (4) and two alternate pixel carriers (2). The locking pin (7) has three fins (17) attached to it which interlock with the three pixel carriers (2).

Figure 16 shows the cut-out (10) required in each pixel carrier (2) to allow the locking pin (7) to pass through irrespective of the vertical position of the pixel carrier (2).

Since only one locking pin is used per pixel site each set of coloured pixels must be lifted independently. This requires separate pneumatic control valves for each set of coloured pixels.

Figure 17 illustrates a four-colour display arrangement which uses a single solenoid per pixel site and a three-way pneumatic control valve (18).

Consider a locking pin arrangement such as that of figure 15 used in a four- colour display system such as that of figure 17. The different coloured pixel layers would each be lifted independent of each other using the multi-way pneumatic control valve (18).

If a pixel were required to be changed to a particular colour the corresponding locking pin would be withdrawn immediately prior to the opening of the appropriate pneumatic valve. This would enable all of the pixels at that site to fall to the lower position.

Then, when the pneumatic valve for the selected colour was opened it would cause the desired coloured pixel to rise. After a short delay the locking pin would be re-inserted to hold the correctly coloured pixel in place prior to the air pressure being released.

The locking pin would then remain in the locked position when the valves for the other colours were opened. This would prevent the other coloured pixels from rising.

Note: it is not possible to use a single-solenoid approach for a multicolour display that uses rigid lifting members as the approach requires that certain pixels be locked in the lower position which would prevent the lifting members from moving. It is possible to use the approach in a pneumatically or hydraulically operated display since individual pixels can remain locked in the lower position without affecting the movement of neighbouring pixels.

Claims (1)

1. Claims 1: A display means whereby a number of picture forming elements are

   arranged in one or more layers behind one or more opaque screens, a means is provided whereby several picture forming elements can be simultaneously raised and lowered in such a way that they can be brought into view or hidden behind the screening arrangement and a means is provided whereby individual picture forming elements can be selectively held in the raised visible position 2: A display means according to claim 1 whereby the picture forming elements are raised and lowered by a mechanical means comprising of one or more rigid members.

   3. A display means according to claim I whereby the picture forming elements are raised and lowered by a pneumatic means.

   4 A display means according to claim I whereby the picture forming elements are raised and lowered by a hydraulic means.

   5: A display means according to claims 1, 2, 3 and 4 whereby the individual picture forming elements are selectively held in the visible position using electromagnetic solenoids.