GB2239340A

GB2239340A - Illuminating a hologram

Info

Publication number: GB2239340A
Application number: GB8926165A
Authority: GB
Inventors: Christopher Eyles; Solomon Heskel Balas
Original assignee: THIRD DIMENSION Ltd
Current assignee: THIRD DIMENSION Ltd
Priority date: 1989-11-20
Filing date: 1989-11-20
Publication date: 1991-06-26
Also published as: GB8926165D0

Abstract

A method of illuminating a hologram for display, comprising holding a substantially linear light source 5 spaced from the surface plane of the hologram, which is supported by frame 3, and allowing the light from the light source to fall directly upon the hologram, to illuminate the same for viewing. Apparatus for carrying out the method is also described. The light source may be an incandescent light bulb having an elongate filament extending parallel to and spaced apart from the plane of the hologram. The filament may be a straight wire, a tight helical coil or a coiled coil. An elongate slit or collimator may be positioned between the light source and the hologram. <IMAGE>

Description

A METHOD OF ILLUMINATING A HOLOGRAM AND DISPLAY APPARATUS INCORPORATING SAID METHOD DESCRIPTION The present invention relates to a method of illuminating a hologram for viewing and to display apparatus for carrying out said method.

A holographic image does not appear to be sharp when viewed, unless the hologram carrying the image is correctly and uniformily illuminated. For optimum sharpness, a hologram should be illuminated, or replayed using a laser light source. If a hologram is replayed with a less expensive "white" light source, such as an incandescent lamp, the image may appear blurred.

When replaying a hologram with a "white" light source, the degree of blurring may be minimised by arranging the light source to approximate as closely as possible to a point source. Thus, satisfactory results have been achieved by using a small filament incandescent light bulb, spaced some distance away from the hologram. However such arrangements are very bulky and often impractical in many viewing situations. Arrangements in which the light follows a folded path from the bulb to the hologram have been proposed in order to reduce the bulk of hologram display devices and, thus, display devices for holding and illuminating holograms have included mirrors or other ray bending means interposed between a light source or light sources and the displayed hologram. However, all such display devices are still bulky, complex and costly to manufacture.

An object of the present invention is to provide a simple method of illuminating a hologram for display without causing undue blurring of the image and a simple low cost display device, which does not involve the complexities, bulk or expense of known display devices.

According to the present invention there is provided a method of illuminating a hologram for display, comprising holding a substantially linear light source spaced from the surface plane of the hologram and allowing the light from the light source to fall directly upon the hologram, to illuminate the same for viewing. Preferrably, the light source extends substantially parallel to the surface plane of the hologram. Nore preferably, the hologram is a reflection hologram and the light source is located on the viewed side of the hologram.

In a second apsect, the present invention provides apparatus for carrying out the method of the invention comprising, means for holding the hologram and light source with the light source spaced from the surface plane of the hologram, in such a way that light from the light source can fall directly upon the hologram, to illuminate the same for viewing.

Preferrably the light source extends substantially parallel to the surface plane of the hologram and is located on the viewed side of the hologram.

By employing a linear light source which, surprisingly, can be located close to the hologram without causing significant image blurring, mirrors or other ray bending means need not be employed between the light source and the displayed hologram.

Thus, the method and apparatus of the present invention are both simple and the latter is compact and may be constructed at a much lower cost than previous apparatus.

Preferrably, the light source is an incandescent light bulb having an elongate filament extending parallel to and spaced apart from the plane of the hologram.

In a preferred embodiment the filament is a substantially straight wire, although in an alternative embodiment, the filament may be a tight helical coil or coiled coil. Preferably the bulb envelope is clear glass. Optionally, shading means are placed about the light source, to prevent light from being radiated therefrom in directions away from the hologram or towards a person viewing the hologram.

In an alternative embodiment, the light source includes means defining an elongate slit or a collimator, arranged between an elongate luminous body and the hologram, so as to provide the substantially linear light source. Preferrably, the elongate luminous body is shrouded such that light cannot escape therefrom other than via the collimator or slit.

In a most preferred embodiment, the light source is a low voltage incandescent lamp or light bulb having a substantially straight wire filiment. Preferably the hologram for display has a substantially flat surface plane.

A specific embodiment of the present invention will now be described with reference to the following drawings : - Figure 1 is a side view of a device in accordance with the present invention; Figure 2 is a view on arrow C in Figure 1 and; Figure 3 is a view on arrow A in Figure 1.

The components of the display apparatus 1 illustrated in Figures 1-3 are formed from an opaque plastics resin material, such as polystyrene, polycarbonate, or ABS unless otherwise stated. The apparatus 1 will now be described with reference to all Figures 1-3.

The apparatus 1 comprises a foot member 2, a frame 3 and a lamp holder 4. The foot memeber 2 is arranged to support the frame 3 which, in turn, is arranged to accommodate and support a hologram for display. The lamp holder 4 is carried by the frame 3 and is arranged to hold a lamp 5. The foot member 2 is substantially rectangular in plan (note:the foot member 2 is viewed edge on in all of the figures) and comprises a rectangular plate like portion 6, with a substantially semi-circular cross sectioned ridge portion 7 upstanding along one edge thereof. A channel shaped socket 8 is formed along the length of the ridge portion 7; the opening of the socket 8 being disposed along the crest of the ridge portion 7.

The frame 3 comprises a substantially rectangular rear panel 9, having radiused corners, and a marginal member 10 extending around the periphery of the rear panel 9 and upstanding from a front face 11 thereof.

The marginal member 10 has susbtantially the same thickness as the rear panel 9 and a slot 12 is formed between the front face 11 of the rear panel 9 and the marginal member 10, along one side of the frame 3.

The slot 12 is of greater length than the distance separating the arms of the marginal member 10, that extend along the edges of the frame 3 adjoining the edge of the frame 3 through which the slot 12 is formed. An under cut grove 13 is formed in the inner margin of the marginal member 10, where the latter joins the rear panel 9, as a continuation of the slot 12.

The lamp holder 4 comprises a substantially rectangular cross sectioned arm 14 extending between a lamp accommodating shade 15 and a supporting member 16. The supporting member 16 is substantially cylindrical and is provided with a length-wise extending, rectangular cross sectioned channel 17, extending radially inwardly from the surface of the support member 16. The channel 17 is dimensioned to be frictionally engagable upon the edge of the frame 3, with an edge portion of the rear panel 9 and a similar portion of the marginal member 10 accommodated within the channel 17, as shown in Figure 1. A secondary arm 18 extends away from the support member 16, in such a way that it defines an extension to one of the sides of the channel 17.

The lamp accommodating shade 15 is in the form of an inverted trough, having a substantially U-shaped cross section and comprises two substantially parallel long side walls 19, each of which forms one leg of the U, and two substantially parallel end walls 20. The end walls 20 are orthogonal to the side walls 19 and extend between adjacent ends thereof and the curved portion of the lamp accommodating shade 15, which forms the base of the U and joins the side walls 19.

The lamp 5 comprises a tubular glass envelope 21 extending between metal end caps 22. Each metal end cap 22 comprises a substantially cylindrical portion 23, adjacent to the glass envelope 21, and an outermost conical portion 24. The end caps 22 are hollow and a thin straight wire filament 25 extends between the apices of their conical portions 24 within the end caps 22 and the glass envelope 21.

The assembly of the end caps 22 and the glass envelope 21 are preferably partially evacuated. The location of the lamp 5, within the lamp shade 15, is shown in the figures 1 and 2 in broken lines and is such that the filament 25 is substantially parallel to the side walls 19 of the shade 15 and the channel 17 in the supporting member 16. The lamp 5 is held in place by two conventional spring clip means, one engaging each of the metal end caps 22. The spring clip means are not shown, but are arranged to allow the lamp to be removed for replacement. An electrical conductor is connected to each of the spring clip means and extends from both of said means along the arm 14, to exit, in a flexible plastic sheathed cable 25, from the free end of the secondary arm 18. An electrical pathway is provided through the filament 25 by this arrangement of conducting elements.

In use a reflection hologram is inserted into the frame 3, through the slot 12, so as to be held by its peripheral edge in the slot 12 and the undercut groove 13, to be viewable within the marginal member 10. An edge of the frame 3 is then pushed into the channel shaped socket 8 and engaged into the gripping means located therein in the position shown in Figure 1. The support member 16 is then pushed onto the edge of the frame 3 which lies opposite that held in the socket 8. As can be seen in the drawings, the edges of the frame 3 engaged by the channel shaped socket 8 and channel 17 are substantially parallel to one another. The support member 16 is located on the frame 3, so that the secondary arm 18 lies flat against the rear panel 9 of the frame 3, to provide added support to the complete lamp holder 4.The cable 26 is arranged to extend substantially parallel to the rear panel 9, curving away therefrom and into contact with the upper surface of the plate-like portion 6 of the foot member 2. The cable 26 is held in place on the foot member 2 by a clip 27 which protrudes from the plate-like portion 6. The cable 26 is connected to a low voltage power supply, so as to cause the filament 25 of the lamp 5 to glow brightly.

As can be seen clearly in figure 1, rays of light 28 emitted by the filament 25 will fall directly upon a hologram located within the frame 3. The walls 19 and 20 of the shade 15 prevent light from spilling significantly beyond the edges of the hologram. The gripping means, located within the ridge portion 7 of the foot member 2, are arranged to allow the assembly of the frame 3 and lamp holder 4 to be moved and held in any position between that illustrated in heavy lines in figure 1 and that illustrated in broken lines in figure 1. The image presented by a hologram held within the frame 3 is completely visible to an observer located at a position shown at 29 in figure 1, although the observer may move a significant distance from the illustrated position, in order to see around the holographic image, without the image becoming significantly distorted, or partially faint.

The low voltage power supply is preferably a combined mains electric plug, transformer and rectifier means arranged to provide a twelve volt supply.

Optionally, the inside of the lamp accommodating shade 15 is lined with a reflector and the opening defined between the long walls 19 and end walls 20 of the lamp accommodating shade 15, is covered in by means defining an elongate slit or collimator.

Claims

CLAINS

1. A method of illuminating a hologram for display, comprising holding a substantially linear light source spaced from the surface plane of the hologram and allowing the light from the light source to fall directly upon the hologram, to illuminate the same for viewing.

2. A method as claimed in claim 1, wherein the light source extends substantially parallel to the surface plane of the hologram.

3. A method as claimed in either of claims 1 and 2, wherein the hologram is a reflection hologram and the light source is located on the viewed side of the hologram.

4. Apparatus for carrying out a method as claimed in claim 1, comprising means for holding the hologram and light source with the light source spaced from the surface plane of the hologram, in such a way that the light from the light source can fall directly upon the hologram, to illuminate the same for viewing.

5. Apparatus as claimed in claim 4, further comprising a substantially linear light source.

6. Apparatus as claimed in either claim 4 or 5, wherein the light source extends substantially parallel to the surface plane of the hologram and is located on the viewed side of the hologram.

7. Apparatus as claimed in any of claims 4-6, wherein the light source is an incandescent light bulb having an elongate filament, extending parallel to and spaced apart from the plane of the hologram.

8. Apparatus as claimed in any of claim 7, wherein the filament is a substantially straight wire.

9. Apparatus as claimed in any of claims 8, wherein the filament is a tight helical coil or coiled coil.

10. Apparatus as claimed in any of claims 7-9, wherein the bulb envelope is clear glass.

11. Apparatus as claimed in any of claims 4-10, wherein shading means are placed about the light source, to prevent light from being radiated therefrom in directions away from the hologram, or towards a person viewing the hologram.

12. Apparatus as claimed in any of claims 4-6, wherein the light source includes means defining an elongate slit or a collimator, arranged between an elongate luminous body and the hologram, so as to provide the substantially linear light source.

13. Apparatus as claimed in claim 12, wherein the elongate luminous body is shrouded to prevent any substantial escape of light, other than via the collimator or slit.

14. Apparatus as claimed in any of claims 4-13, wherein the light source is a low voltage incandescent lamp or light bulb having a substantially straight wire filament.

15. Apparatus as claimed in any of claims 4-15, wherein the hologram for display has a substantially flat surface plane.

16. A method of illuminating a hologram for display substantially as hereinbefore described with reference to the accompanying drawings.

17. Apparatus for illuminating a hologram for display, substantially as hereinbefore described with reference to the accompanying drawings.