GB2167879A - Viewing device - Google Patents

Abstract

This invention relates to viewing device and to pictures bearing designs for viewing through such devices. Thus as illustrated in Fig. 2 a viewing device can comprise a sheet of rigid transparent plastics 16 which has a central portion 17 on which subsequently parallel elongate lines 18 are printed with clear varnish. The central portion 17 is supported by winged portions 20 to hold the portion 17 at a fixed distance above the surface on which the device 15 rests. If the device 15 is placed over a picture 10, such as is shown in Fig. 1, the animation of the ruled parts of the picture form a Moiré pattern, giving an impression of movement when the eyes are moved, the picture being viewed from above through the device 15. <IMAGE>

Description

SPECIFICATION Viewing device This invention relates to viewing devices and to pictures bearing designs for viewing through such devices.

It has been known for some time that diagrams, for use on overhead projectors and slide projectors, can be animated by forming a grid pattern of light and dark lines on portion of the diagram and moving a plate having a similar pattern relative to the first pattern.

Whilst this system is successful with many types of back-lit presentations it is not satisfactory for use on opaque printed pictures or diagrams, particularly because the heavy printed pattern tends to obscure the picture, diagram or the like and because having to constantly move the sheet is cumbersome for a viewer.

From one aspect the invention consists in a viewing device for creating and viewing moiré fringes in association with a printed design defining alternate light and dark parallel or substantially parallel elongate areas, comprising an effectively transparent surface having a pattern of parallel elongate areas of alternatingly higher and lower light transmission characteristics, and support means for spacing the surface from the picture or the like such that moire' fringes can be observed on the design when it is viewed through the pattern, and the viewer can cause movement of those fringes by moving his eyes in a direction having a component which is at right angles to the areas on the pattern.

As will be explained in more detail below, it is believed that the moire fringes are created in this arrangement, even if the pitch of the pattern and design are identical, because the "shadow" of each area of the pattern on the picture is displaced when viewed from any normal reading distance, because the light incident on the viewer's eye is converging. This displacement effectively creates a change in pitch of the pattern and hence fringes become visible. The alteration in pitch is dependent on the separation of the picture and the surface and also on the position of the eye relative to the surface. Thus as the surface is lifted the fringe density per unit length increases. The fringe density also increases the nearer the eye is to the screen. Thus the larger the pitch differences created by the effective displacement of the pattern areas the greater the fringe density.

It will be appreciated that if the fringe density is too large the fringes become effectively invisible, whereas if it is too low the fringes are very broad and ill-defined. It has been found that when the viewer's eye is placed between 25 and 35 cm, the surface and the sheet are conveniently separated by between 2 and 3 cm when there are of the order of 20 elongate areas or lines per centimetre in the pattern and in the design. However, acceptable results can be achieved with the surface placed between 0.5 and 6.5 cm from the design.

It is to be understood that the elongate areas are normally in the form of lines, which may be straight or curved, but they are not necessarily continuous and could be made up of a series of dots or squares. Further the areas may be constituted by optical discontinuities such as edges or by transparent coloured areas.

The support means may define an air gap between the pattern and design or alternatively it may consist of an optically transmissive body interposed between the surface and the design. In that case the figures set out above should be adjusted in accordance with the refractive index of the body.

The support means may comprise at least a pair of spaced upright members, such as walls and the members may be integral with the surface. In any of these cases the viewing device may be erectable from the flat and/or collapsible into a generally flat storage position.

The pattern may be printed in clear varnish or the like or it may be machined or moulded.

The surface may be a surface of a sheet of plastics material and the support means may also be formed of plastics material or alternatively card or some other foldable material.

From another aspect the invention consists in a viewing device for creating and viewing moire' fringes in association with a printed grid pattern, comprising a transparent sheet and a grid pattern of parallel or substantially parallel elongate areas of reduced optical transmission formed, machined, or printed thereon.

In this latter case the areas may be printed in clear or coloured varnish.

From a further aspect the invention consists in a viewing device for creating and viewing moire' fringes in association with a printed grid design, comprising a transparent surface having a grid pattern and means for supporting the surface above the printed grid design.

From another aspect the invention may consist in a device for creating moire' fringes in association with a printed grid design, having transparent grid lines or formations formed thereon.

From a still further aspect the invention may consist in a device for creating moire fringes in association with a printed grid design, including a grid pattern and means for spacing the grid pattern from the design in use.

In this latter case the grid may be spaced by more that ten times its thickness or by the width of more than five grid lines of the pattern. The spacing may be more than 0.5 cm.

In an additional aspect the invention consists in a device for creating moire' fringes in association with a printed grid design, wherein the fringes can be made to move by parallax movement of viewer looking through the device.

From a further aspect the invention consists in a viewing device for viewing a picture, diagram or the like at least part of which incorporates a pattern defining alternate light and dark parallel or substantially parallel elongate areas, comprising a transparent sheet having a pattern of parallel elongate areas of alternate light transmission characteristics and support means for spacing the sheet from the picture or the like, such that when the patterned part of the picture, or the like, is generally parallel with and is viewed through the pattern of the sheet, the viewer can cause apparent movement of the pattern on the picture or the like by moving his eyes in direction having a component which is at right angles to the areas on the pattern.

The invention also consists in a picture, diagram or the like having a portion formed with a design of parallel or substantially parallel light or dark elongate areas and this picture, diagram or the like may form part of a book.

The design may extend across the visual features of the picture or the line and may overlap with areas of varying tone or colour and/or different colours or tones may carry different angles or ptiches or the pattern areas.

The invention also includes apparatus for generating mobile moire' fringes comprising a printed sheet carrying a pattern or patterns having generally parallel closely spaced lines or stripes and a carrier which affords or supports a further pattern or patterns of approximately parallel spaced lines or stripes at a distance above the printed sheet, the print of the carrier above the sheet and the pitches or intervals of the patterns on the carrier and the sheet being such that when viewed from above the carrier at a distance between 25 cm to 50 cm moiré fringe patterns are visible and when the eye is moved in a direction parallel to the plane of the sheet and transverse to the direction of the lines of the carrier parallax is observed and the moiré fringe patterns appear to shift.

In a preferred embodiment at least parts of the carrier or the upper printed pattern are open or transparent to allow both parts to be observed simultaneously from above. The pitch of the lines on the carrier may be approximately equal to or greater than that of the lines on the printed sheet or a multiple of the pitch of the lines on the sheet.

The invention additionally includes a kit comprising a picture, diagram or the like, as defined above in combination with a viewing device as defined above. In this case the viewing device may be packaged with the picture in the flat.

In another aspect the invention consists in a display including a printed sheet or slide bearing a pattern of parallel closely spaced lines or stripes and an effectively transparent screen through which the pattern may be viewed affording or supporting a further pattern of approximately parallel spaced lines or stripes of higher or lower light transmission characteristics such that moire' fringes can be observed on the first pattern.

In a preferred embodiment the screen may be movable, for example, it may be formed as a belt and the first pattern may lie within the belt. Conveniently the belt may be motor driven. The display may also include a casing containing a window for viewing the first pattern.

Accordingly the invention also consists in a display as defined above formed as a single unit, wherein a screen is supported by a pair of walls connected to the printed sheet or slide. Preferably the walls are hinged or otherwise connected so that the screen can be moved relative to the sheet in one direction generally parallel to the sheet to provide apparent movement of the fringes. Additionally or alternatively the walls may be hinged or otherwise connected so that the display can be folded flat. If the walls allow movement of the screen it is preferred that the screen can be rocked backwards and forwards.

The invention further consists in a display as defined above including a body erected from a cardboard net, the body having a window at which the screen can be mounted, a surface for supporting a printed sheet and a pair of walls for spacing the screen from the sheet, the walls being interconnected with the rest of the body by hinge score lines or the like.

The invention may also include a display comprising a device as defined above and a picture on slide bearing a printed grid pattern.

Although the invention has been defined above it is to be understood that it also consists in any inventive combination of the features set out above or in the following description. One object of the invention has been defined, but the invention is not limited to devices fulfilling this object.

The invention may be performed in various ways and a specific embodiment will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a picture in which a part is formed with a grid pattern; Figure 2 shows an erected viewing device; Figure 3 illustrates an alternative viewing device; Figure 4 illustrates another embodiment of a viewing device; Figure 5 is an optical diagram relating to the invention; Figure 6 is a cross-section of a point-of-sale display incorporating the invention; Figure 7 is a section through a hand operated display; Figure 8 is a plan view of a display suitable for use as a greeting card; and Figure 9 is an end view of the display of Fig. 8.

An action picture 10 is shown in Fig. 1 and it can be seen that the rocket exhaust 11 is formed with a design 12 of substantially parallel alternate light and dark lines 13. Certain sections of the design 12, such as 14, are orientated at a slightly different angle to provide apparent movement in a slightly different direction.

It is well known that if a transparent sheet bearing a similar pattern, of slightly different pitch, is moved relative to the design 12 moving moiré fringes will be observed, their direction of movement being determined, inter alia, by the relative orientation of the local pattern lines.

However, if there is no relative movement of the two patterns when one is lying on top of the other no movement of the fringes can be discerned however much the viewer moves his eyes.

Surprisingly, it has been discovered that if the sheet is lifted, but held stationary with respect to the picture 10, movement of the viewer's eyes generally at right angles to the grid pattern will produce movement of the fringes and hence in this embodiment the exhaust will appear to flow from rocket and the rotor 12a will rotate. It is through that this effect is due to parallax, but other physical phenomena may be responsible.

In addition it has been determined that width of the fringes decreases as the sheet is lifted from the picture 10. Thus, initially, the fringes are broad and relatively fuzzy and eventually they obtain a spacing of the same order of that of the lines 13 and are no longer visible. As will be explained in more detail below it is believed that the change in spacing arises from an apparent change in the effective pitch of the pattern of the sheet. The same effect occurs when the observer's eye is brought nearer the sheet.

The optimum spacing of the sheet and the picture 10 may vary according to intended use, but it is preferred that it lies within the range 0.5 and 6.5 cm and the range 2 to 3 cm is particularly advantageous for normal book size printing.

A viewing device which meets these criteria is illustrated in Fig. 2 and indicated at 15. The device comprises a sheet of rigid transparent plastics 16 which has a central portion 17 on which substantially parallel elongate lines 18 are printed with clear varnish. A slot 19 is formed on either side of the line pattern portion 17 to enable the device to be erected from the flat, into the erected position illustrated, so that wing portions 20 of the sheet 16 constitutes legs which hold the pattern portion 17 at a fixed distance above the surface on which the device 15 rests. Thus the erected device 15 can be placed over the picture 10 and animation of the exhaust and rotor can be seen by simple movement of the eyes when the picture is viewed from above.

The device 15 should be placed such that its lines 18 are substantially parallel to the lines 13 and the eye movement is preferably orthogonal with respect to those lines. The direction of movement is determined by the direction of eye movement, the relative pitches of the lines 13 and 18 and the relative orientations of those lines.

The use of clear varnish to form the lines 18 greatly enhances the light transmission of the viewing device and the picture is not obscured as it would be with traditional sheets.

The ability to erect the device 15 from a flat blank is important, because it is intended that the device will normally be supplied with a book or looseleaf publication and hence many packaging problems are overcome.

Fig. 3 shows an alternate device 15 in which the main body portion is formed from a cardboard blank, which carries a window of transparent plastics bearing the pattern portion 17. The cardboard blank 21 is provided with fold-lines 22, tabs 23 and slots 24, so that wall 25 can be erected as shown in Fig. 3.

A further embodiment of the device 15 is shown in Fig. 4. In this case the walls 26 are formed separately from the viewing sheet 27 and are engaged in slots 28 in the sheet 27 by means of slotted tabs 29. The walls 26 and sheet 27 are preferably of rigid clear plastics and may be supplied in a single sheet, so that they can be pressed out by the eventual user before they are erected.

It is believed that the fringes result from the optical principles as set out below. However a very similar visual effect can be achieved by placing a semi-circular or similar lens over a line and the lines or their edge portion may each constitute such a lens.

The optical principles involved are best explained with reference to the sketch in Fig. 5.

This is not drawn to scale and for convenience the viewer's eye E is shown very close to the transparent grid 0, while the height of the grid Q above the printed paper P and the intervals between the grid lines are greatly exaggerated.

In Fig. 5, the parallel grid lines on the printed sheet P are indicated at P and the printed clear varnish lines on the grid Q are shown at q. For convenience here the interval or the pitch of the lines q is shown as exactly equal to that of the lines p. The height of eye E above the printed page is shown as H, and the height of the grid Q above the printed page is shown as h.

The use of the "static" grid Q spaced above the printed page has two primary effects.

Firstly, the spacing causes parallax when the eye E moves horizontally. In effect the grid lines q appear to shift horizontally in relation to the printed lines p.

The second effect is an apparent alteration in the pitch of the lines q. As shown in the sketch, lines of sight X from the eye E to the grid lines q on the grid can be projected onto the plane of the printed page P such that the grid lines q appear to be positioned at points W. It can also be seen readily that although the pitch of the actual grid lines q is equal to the pitch of the printed lines p, the apparent pitch of the projected grid lines w is considerably increased. This increase in pitch is approximately equal to the value x where x+p q H H-h In practice the normal height of eye of an observer looking at a printed page is about 40 cm and a convenient spacing h for the grid above the page is about 2.5 cm. Thus the practical observed difference in the pitch of the lines q is quite small though appreciable.

To obtain a moving moiré fringe pattern it is first necessary to establish conditions for static moiré fringes. For this there need to be two super-imposed sets of grid lines of comparable pitch. The moiré fringe patterns are then produced naturally and automatically by the eye either as a result of the vernier effect when two grids of slightly different pitch overlap, or as a result of relative inclination between two sets of grid lines of the same or different pitch.

In the example illustrated in the diagram, the pitch of the two sets of lines p, q as printed is equal, but due to the effect of the height of eye H and the height of the grid h there is an alteration in apparent pitch which provides the conditions for moire' fringes. The necessary conditions can also be obtained if the pitch of the two sets of lines p, q is not exactly equal, provided that when observed from the height H there is a small but noticeable pitch difference. As a generality, if the pitch of the lines q is less than that of the lines p there is a latent risk that when observed from height H the pitch of the two sets of lines may appear to be equal in which case moire fringes will not be observed. The pitch of the lines q should, therefore, be equal to or slightly greater than that of the lines p.

The grid 0 spaced above the printed sheet P thus provides the two essential elements for static animation. Moire fringe patterns are produced and simple movement of the eye E horizontally in the direction W causes apparent shift of the lines q and hence movement of the moire fringes, by parallax.

The same effect can be produced, of course, by holding the eye stationary and moving the grid 0 relative to the printed sheet P.

The principles enunciated above can also be used to provide a point-of-sale or other portable display.

For example in Fig. 6 a display 30 comprises a casing 31, having a window 32, and a support or base 33. Mounted within the casing is a printed sheet 34 bearing an advertising message or information and a clear belt 35 which can be driven by an electric motor 36. The sheet 34 is mounted within the belt 35. Thus it can be viewed through the window 32 and the front portion 36 of the belt 35. The belt 35 is printed with lines 18 and so as the belt moves the line pattern portion of the sheet 34 becomes animated.

Fig. 7 shows a similar arrangement for displaying slides, except here the belt 35 is driven manually by means of knob 37. This construction is particularly suitable for teaching aids and for use by sales representatives.

In Figs. 8 and 9 the display 40 comprises a cardboard body 41, a printed sheet 42 and an effectively transparent screen 43. The screen 43 is mounted in a window 44 in the top 45 of the body or sleeve 41 whilst the printed sheet 42 is attached to the internal surface 46 of the bottom 47 of the body 41. Alternatively the surface 46 may bear the printing and constitute the sheet. The body or sleeve 41 has a pair of side walls 48 which are hinged to the top 45 and bottom 47 by score lines extending along the respective junctions.

Thus the sleeve or body 41 may be formed from a single cardboard net.

The provision of the hinges 49 allows the top 45 to be laterally deflected as indicated in broken line in Fig. 9. This deflection causes relative movement of the screen 43 relative to the sheet 42 and hence movement of the moire fringes formed by the apparent interraction of grid patterns 50 and 51 on the sheet 42 and screen 43 respectively. (For clarity only a part of grid 51 is shown).

It will be appreciated that this deflection can be repeatedly reversed so that there will be apparent movement of, for example, the water in the fountain. Additionally the hinges 49 allow the body or sleeve 41 to be folded flat and hence the display 40 can be readily sent through the post as a greeting card, calendar or the like. In the case of a greeting card an appropriate message would be printed on the external surface of the bottom 47.

Claims (33)

1. A viewing device for creating and viewing moire' fringes in association with a printed design defining alternate light and dark parallel or substantially parallel elongate areas, comprising an effectively transparent surface having a pattern of parallel elongate areas of alternatingly higher and lower light transmission characteristics, and support means for spacing the surface from the design or the like such that moire' fringes can be observed on the design when it is viewed through the pattern, and the viewer can cause movement of those fringes by moving his eyes in a direction having a component which is at right angles to the areas on the pattern.

2. A device as claimed in Claim 1 wherein the support means are erected to support the surface between 0.5 and 6.5 cm from the design.

3. A device as claimed in Claim 2 when support means support the surface between 2 and 3 cm above the design.

4. A device as claimed in any one of Claims 1 to 3 where they are of the order of 20 elongate areas or lines per cm in the pattern and in the design.

5. A device as claimed in any one of the preceding claims wherein the elongate areas are substituted by a series of dots or squares or the like or by optical discontinuities.

6. A device claimed in any one of the preceding claims where the support means defines an air gap between the pattern and the design.

7. A device as claimed in any one of Claims 1 to 5 when the support means is substituted by an optically transmissive body interposed between the surface and the design.

8. A device as claimed in Claim 6 wherein the support means comprises at least a pair of spaced right angle members.

9. A device as claimed in Claim 8 wherein the upright members are integral with the surface.

10. A device as claimed in any one of Claims 6 8 or 9 wherein the viewing device is erectable from the flat and/or collapsible into a generally flat storage position.

11. A device as claimed in any one of the preceding claims wherein the pattern is printed in clear varnish or the like.

12. A device as claimed in any one of Claims 1 to 10 wherein the pattern is machined or moulded.

13. A device as claimed in any one of the preceding claims wherein the surface has a surface of a sheet of plastics material.

14. A viewing device for creating and viewing moiré fringes in association with a printed grid pattern, comprising a transparent sheet and a grid pattern of parallel or substantially parallel elongate areas of reduced optical transmission formed, machined or printed thereon.

15. A viewing device for creating and viewing moire' fringes in association with a printed grid design, comprising a transparent surface having a grid pattern and means for supporting, the surface above the printed grid design.

16. A device for creating moiré fringes in association with a printed grid design, having transparent grid lines or formations formed thereon.

17. A device for creating moiré fringes in association with printed grid design, including a grid pattern and means for spacing the grid pattern from the design in use.

18. A device as claimed in Claim 17 wherein the screen is spaced by more than ten times its thickness or by the width of more than five grid lines of the pattern.

19. A device for creating moire fringes in association with printed grid design, wherein the fringes can be made to move by parallax movement of a viewer looking through the device.

20. A viewing device for viewing a picture, diagram or the like at least part of which incorporates a pattern defining alternate light and dark parallel or substantially parallel elongate areas, comprising a transparent sheet having a pattern of parallel elongate areas of alternate light transmission characteristics and support means for spacing sheet from the picture or the like such that when the patterned part of the picture, or the like, is generally parallel with and is viewed through the pattern of the sheet, the viewer can cause apparent movement of the pattern on the picture or the like moving his eyes in direction having a component which is at right angles to the area of the pattern.

21. A picture diagram or the like having a portion formed with a design of parallel or substantially parallel light or dark elongate areas.

22. A picture as claimed in Claim 20 wherein the design extends across visual features of the picture or the like.

23. Apparatus for generating mobile moire' fringes comprising a printed sheet carrying a pattern or patterns having generally parallel closely spaced lines or stripes and a carrier generally affords or supports a further pattern or patterns of approximately parallel spaced lines or stripes at a distance above the printed sheet, the print of the carrier above the sheet and the pitches or intervals of the patterns on the carrier and the sheets being such that when the carrier is viewed from above at a distance between 25 and 50 cm moire fringe patterns are visible and when the eye is moved in a direction parallel to the plane of the sheet and transverse to the direction of the lines of the carrier parallax is observed and the moir6 fringe patterns appear to shift.

24. Apparatus as claimed in Claim 23 wherein at least parts of the carrier or the upper printed pattern are open or transparent to allow both parts to be observed simultaneously, from above.

25. A kit comprising a picture, diagram or the like as claimed in Claim 21 in combination with a viewing device as claimed in any one of Claims 1 to 20.

26. A display including a printed sheet or slide bearing a pattern of parallel closely spaced lines or stripes and an effectively tran sparent screen through which the pattern may be viewed affording or supporting a further pattern of approximately parallel spaced lines or stripes of higher or lower light transmission characteristics such that moire fringes can be observed on the first pattern.

27. A display as claimed in Claim 26 formed as a single unit, wherein a screen is supported by a pair of walls connected to the printed sheet or slide.

28. A display as claimed in Claim 27 wherein the walls are hinged or otherwise connected so that the screen can be moved relative to the sheet in one direction generally parallel to the sheet to provide apparent movement of the fringes.

29. A display as claimed in any one Claims 26 to 28, including a body erected from a cardboard net, the body having a window in which the screen can be mounted, a surface for supporting a printed sheet and a pair of walls for spacing the screen from the sheet, the wall being interconnected with the rest of the body by hinge score lines or the like.

30. A viewing device for creating and viewing moire fringes in association with a printed design defining alternate light and dark parallel or substantially parallel elongate areas, subsequently as hereinbefore described with reference to the accompanying drawings.

31. A picture diagram or the like subsequently as hereinbefore described with reference to the accompanying drawings.

32. Apparatus for generating mobile moire fringes subsequently as hereinbefore described with reference to the accompanying drawings.

33. A display subsequntly as hereinbefore described with reference to the accompanying drawings.