WO2009087403A1

WO2009087403A1 - Panoramic optical assembly

Info

Publication number: WO2009087403A1
Application number: PCT/GB2009/000072
Authority: WO
Inventors: Leo Atreides
Original assignee: Panascopics Ltd
Priority date: 2008-01-11
Filing date: 2009-01-12
Publication date: 2009-07-16
Also published as: GB2456334A; GB2456334B; GB0800522D0

Abstract

An optical assembly for use in obtaining panoramic images is disclosed. The optical assembly comprises a- mirror (4), a housing (2) and a spacer (6). The mirror (4), housing (2) and spacer 6 may be releasably connected in a first configuration for obtaining panoramic images through the housing (2) and also in a second, different configuration in which the mirror (4) is stored and protected within the housing (2).

Description

PANORAMIC OPTICAL ASSEMBLY

The present invention relates to an optical assembly for use in obtaining panoramic images . More specifically, the invention relates to an optical assembly which comprises a mirror for reflecting an annular image onto an optical device, preferably onto a camera .

Conventional cameras obtain images from a relatively narrow field of view. It is known to obtain a panoramic image by taking several consecutive images in a circle about the observer. The edges of the consecutive images are then matched so as to create 'a continuous 360° image about the observer. Another known technique for obtaining panoramic images is to mount a dome-shaped mirror in front of a camera. The domed surface of the mirror enables, the camera to capture an annular image representing a 360° view around the circumference of the mirror. This annular image may then be transformed into a linear panoramic image by using conventional techniques so as to obtain a panoramic image of the type obtained using the first conventional technique described above. It is desired to provide an improved optical assembly for use in obtaining panoramic images.

From a first aspect, the present invention provides an optical assembly as claimed in claim 1.

The optical assembly of the present invention is configured so as to be able to be arranged in two different configurations. In a first configuration, the housing member acts as a stand and is used to mount the mirror so that an annular image can be reflected through the housing and preferably onto an optical device for capturing the image. The annular image obtained by the optical device is then preferably used to obtain a linear image of a panoramic view about the circumference of the mirror. When the assembly is no longer desired to be used for obtaining panoramic images then it may be arranged in a second, different configuration wherein the mirror is housed within the housing. As such, the present invention provides a collapsible optical assembly which, when not used for obtaining images, may be stored in a compact configuration and in which the mirror is protected to some extent by the housing.

The mirror of the present invention has a reflective surface, which when viewed by an observer or an optical device displays an annular image that is representative of ^sa panoramic view (i.e. a 360° view) around the mirror. According to the preferred embodiments, the mirror is rotationally symmetrical about a central axis extending through its reflective surface. Preferably, the mirror is configured such that when it is viewed along this central axis an annular image representing a panoramic view in directions perpendicular to the axis can be seen.

The mirror of the preferred embodiments is curved. For example, the mirror may have a hemi-spherical surface or any other dome-shaped surface. Less preferably, the mirror may not have a dome-shaped surface, but may instead have a tapered surface. For example, the mirror may be a frustro-conical mirror. Other embodiments are contemplated wherein part of the mirror is dome-shaped and part of the mirror is non- dome-shaped, e.g. the mirror may be part dome-shaped and part frustro-conical . It will be appreciated that the shape, size and curvature of the mirror are not particularly limited provided that when viewed from one axis a panoramic image can. be obtained.

In the preferred embodiments, the mirror is formed by coating a substrate with a _#reflective material. The reflective material may be a paint and/or a metallic coating. Alternatively, the substrate may not be coated and the substrate itself may be reflective. For example, the substrate may be a reflective metal or plastic. According to the preferred embodiments, the mirror is a hollow shell. However, in less preferred embodiments the mirror may be a solid element.

As described above, the housing of the present invention serves two separate functions in the two different configurations. In a first assembly configuration the housing severs as a stand for supporting the mirror in a po.sition for obtaining annular images .

According to the preferred embodiments, the annular image on the mirror can be viewed through the housing. In particular, the first end of the housing comprises a portion through which the annular image on the mirror can be viewed from the second end of the housing. According to the preferred embodiments, the first end of the housing comprises an opening through which the annular image can be viewed. Preferably, this opening is circular, although other shapes are also contemplated herein. In other embodiments the first end of the housing comprises a transparent portion through which the annular image can be viewed. In these embodiments it is preferable that the transparent portion at the first end of the housing is. flat and perpendicular to a central axis through the mirror. It is also contemplated herein that the housing may be formed entirely from transparent material, for example, from a transparent plastic. In the first assembly configuration the mirror is removably mounted to a first end of the housing. The assembly is configured such that the mirror is repeatedly mountable to and demountable from the first end of the housing. In the preferred embodiments the assembly comprises a spacer for removably mounting the mirror in spaced relationship from the first end of the housing. This is particularly advantageous as the spacer may be used to increase the distance between the mirror and the housing such that the focal plane of the mirror is in the desired plane, but without increasing the size of the housing. In less preferred embodiments the first end of the housing and/or the mirror may be configured such that the mirror is directly mountable to the first end of the housing without the use of a spacer. In the preferred embodiments, the spacer is repeatedly connectable to and disconnectable from the first end of the housing and/or the mirror.

Preferably, the spacer comprises a stem for connecting the first end of the housing to the mirror in spaced relationship. The stem is preferably a cylindrical rod, although the stem may have a cross- section which is any shape other than circular. According to the preferred embodiments , one end of the stem can be releasably coupled to the first end of the housing. Preferably, the spacer comprises a stem connector configured to be releasably connectable to the first end of the housing such that in the first assembly configuration the annular image on the mirror can be viewed through the stem connector and from the second end of the housing.

^■In the preferred embodiments the first end of the housing and the stem connector both comprise means for releasably engaging each other. According to one set of embodiments, the first end of the housing comprises at least one projection which extends in a direction away from the main body of the housing and preferably towards the mirror in the first assembly configuration. The stem connector preferably comprises at least one complementary aperture or recess for receiving the at least one projection in use. In a particularly preferred embodiment the at least one projection comprises first and second portions, wherein the first portion extends away from the main body of the housing in a first direction towards the second portion and the second portion extends in a second, different direction to the first portion and to a distal free end. Preferably, the first and second portions are substantially perpendicular to each other. In this embodiment the spacer connector preferably comprises at least one slot through ^'which the at least one projection can extend such that when the slot is moved relative to the projection the stem connector is trapped between the main body of the housing and the second portion of the projection. In the preferred embodiment, the at least one projection and the at least one slot which interlock are curved and preferably have the curvature of part of a circle.

Although one type of connection has been described above, other types of releasable connection are also - S -

contemplated herein. For example, the housing and spacer connector may have a screw threaded, engagement or may clip together with releasable clips .

In the preferred embodiment the stem connector comprises a transparent disk and one end of the stem is connected to the disk. Preferably, the disk is circular and the stem is connected to the disk at the central axis of the disk. In the first assembly configuration, light is reflected from the mirror and into the housing through the disk. The disk may have planar major faces. Alternatively, the disk may act as a lens and one or both major faces of the disk may have convex and/or concave portions. In these embodiments the disk acts to focus or diverge the light passing from the mirror and into the housing so that the annular image is focussed in the desired manner.

Preferably, in the first assembly configuration, the spacer enables the mirror to move towards and away from_. the housing. This enables the focal plane of the mirror to be varied. In the preferred embodiments, wherein the spacer comprises a stem, the mirror preferably has an aperture for receiving the stem. The aperture is preferably along the central axis through the reflective surface of the mirror (i.e. preferably along the axis of symmetry of the mirror) . In these embodiments , the mirror is preferably configured such that the aperture of the mirror can be moved along the stem. The mirror preferably further comprises means to releasably engage the stem so that the mirror can be maintained at different positions along the stem and therefore at different distances from the housing in the first assembly configuration. Preferably, the means for releasably engaging the stem is located adjacent the aperture in the mirror and preferably behind the reflective surface of the mirror. In the preferred embodiment the means for releasably engaging the stem is a clamp or clasp. However, any other means may be used to provide the releasable engagement. For example, the stem and mirror may be configured to have a screw threaded engagement .

As has been described above, in a second assembly configuration the housing of the present invention houses the mirror inside of it. Accordingly, the housing comprises a cavity which is sized and configured to receive and store the mirror. In particularly preferred embodiments, at least part of the .housing cavity is complementary in shape to the mirror.

Therefore, in certain preferred embodiments the cavity comprises a concave dome-shaped surface for receiving a convex dome-shaped mirror. Other cavity shapes are also contemplated herein which are complementary in shape to the other shaped mirrors which have been described above .

The housing preferably at least partially encloses the mirror in the second assembly configuration. In preferred embodiments the housing comprises walls which only partially enclose the mirror.

The housing preferably comprises a wall which may be opened or removed so as to allow the mirror to be inserted into the housing in the second assembly configuration. The housing is preferably configured such that the removable wall is capable of being repeatedly removed and reconnected. Preferably, the removable wall is at the second end of the housing. In this embodiment the main body of the housing preferably comprises at least one projection which releasably inter-locks with at least one channel in the removable end wall. The projection and channel are configured such that the end wall may be pushed onto the main body of the housing (in a direction running from the first to the second end of the housing) and then the end_. wall may be rotated relative to the main body of the housing so as to releasably lock the main body and end wall of the housing together.^' Each of the channels preferably comprises a first portion extending into the removable end wall and partially through the wall to a second portion. The second portion of the channel preferably extends within the end wall in a direction perpendicular to the first portion of the channel. Preferably, each of the projections on the housing which engages a channel comprises a first portion which extends away from the main body of the housing towards a second portion. The second portion preferably extends perpendicular to the first portions and towards a free end. Although an interlocking connection of projections and channels has been described above, any other type of releasable and re-engagable connection may be used, e.g. a screw-threaded connection. In the preferred embodiments, the housing is configured such that in the first assembly configuration an annular image may be reflected from the mirror, through the housing and out of the second end of the housing. This enables an optical device or viewer to receive the annular image through the housing. In the preferred embodiments, the second end of the housing comprises a wall through which the annular image can be - S -

viewed. In the preferred embodiments, the wall comprises an opening through which the image can be viewed. Preferably, the opening is circular, although it may be any other shape. In other embodiments, the wall does not comprise an opening, but at least part of the wall is transparent so as to allow the annular image to be viewed therethrough.

In the preferred embodiments, wherein the end wall comprises an opening, the area of the opening increases in a direction from the first end of the housing to the second end of the housing (when the end wall is connected to the main body of the housing) . Preferably, the area of the opening increases in a stepped fashion. For example, the wall of the opening may comprise a tubular portion of a first diameter and a tubular portion of a second, greater diameter. Alternatively, the wall of the opening may gradually taper outwardly. The configuration of the opening in the removable wall enables it to be mounted to the lens barrel of an optical device. As such, the wall acts as a platform for mounting the optical assembly over the optical device in the first assembly configuration such that the optical device may capture annular images from the mirror . In the embodiments which comprise a spacer for spacing the mirror from the housing in the first assembly configuration, it is preferable that at least part of the spacer may also be housed inside of the housing in the second assembly configuration. According to the embodiments wherein the spacer comprises a stem and a spacer connector, the spacer connector is preferably configured such that it may releasably engage the first end of the housing with the stem projecting inside of the housing in the second assembly configuration. In these embodiments the stem preferably extends through the aperture in the mirror in the second assembly configuration.

Preferably, the stem is fixedly and permanently connected to the spacer connector. In this embodiment, the spacer connector is releasably connectable to the first end of the housing in a first orientation such that the stem is held outside' of the housing in the first assembly configuration. The spacer connector is also releasably connectable to the first end of the housing in a second orientation such that the stem is held inside of the housing in the second assembly configuration.

In an alternative embodiment, the stem is not fixedly and permanently connected to the spacer connector. In this embodiment the stem is releasably clampable within the spacer connector so that it may be slideable with respect to the connector. In ^'this embodiment, when the spacer connector is engaged with the first end of the housing, the stem may be slid through the spacer connector and into the housing in the second assembly configuration. Similarly, the stem may be pulled through the spacer connector and out of the housing in order to mount the mirror in the first assembly configuration.

Preferably, the length of the stem is equal to or shorter than the distance between the first and second ends of "the housing such that the stem can be fully housed within the housing in the second assembly configuration . According to another aspect, the present invention provides an optical assembly as claimed in claim 15.

According to another aspect, the present invention relates to a combination of any one of the optical assemblies described above and an optical device for capturing images .

The optical device referred to herein is preferably a camera and more preferably a digital camera. Although the preferred optical device is a compact camera, the optical assembly may be configured to be mounted onto an SLR lens or lens ring adaptor. Other optical devices such as video recorders are also contemplated herein.

According to another aspect, the present invention relates to a method of obtaining an annular image comprising using any one of the optical assemblies described above.

The development of a platform for mounting an optical assembly to an optical device is novel in its own right. Therefore, from. a further aspect the present invention provides an optical assembly platform comprising a first side having means for releasably connecting the platform to a stand (or housing) of an optical assembly and a second opposite side for mounting against an optical device in use, the platform comprising an opening for mounting the platform on the end of a lens barrel of the optical device, wherein the opening increases in area from the first side of the platform to the second side of the platform.

The platform may have any one or combination of the preferred features of the removable end wall of the optical assembly described above. For example, the platform may comprise at least one channel having a first portion extending into the first side of the platform to a second channel portion, wherein the second channel portion extends perpendicularly to the first channel portion and between the first and second sides of the platform.

Preferably, the circumference of the opening increases in a stepped manner from the first to the second side of the platform. Alternatively, the area of the opening increases in a gradually tapering manner from the first to the second side of the opening.

Another aspect of the present invention is directed to a combination of the above described optical assembly platform and the camera, preferably a digital camera.

Various embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

Fig. 1 shows an optical assembly according to a preferred embodiment of the present invention arranged in a first configuration for use in obtaining panoramic images ;

Fig. 2 shows the preferred optical assembly just prior to being arranged in the first configuration;

Figs. 3A-3B show cross-sectional images of components of the mirror of the preferred optical assembly;

Fig. 4 shows a side-view of the housing of the preferred optical assembly;

Figs. 5A-5B show views of the removable wall of the housing of the preferred optical assembly; Fig. 6 shows the preferred optical assembly just prior to being arranged in a second configuration wherein the mirror is stored within the housing; and Fig. 7 shows the preferred optical assembly arranged in the second configuration.

Fig. 1 shows an optical assembly according to a preferred embodiment of the present invention arranged in a first configuration for use in obtaining panoramic images. The assembly comprises a housing 2, a mirror 4 and a spacer 6 for mounting the mirror 4 to the housing 2 in spaced relationship. The spacer 6 comprises a transparent disk 8 and a stem 10. ' As can be seen from Fig. 1, the mirror 4 is mounted above the first end 2a of the housing 2 by the spacer 6. The first and second ends of the housing 2a, 2b have openings 14 arranged therein. In use, the opening 14 in the second end 2b of the housing 2 is mounted over a camera, or any other type of optical device. As the spacer disk 8 is transparent the camera is, able to capture images reflected from the mirror 4. As the mirror 4 is dome-shaped, the camera captures an annular image which is representative of a 360° panoramic view around the circumference of the mirror 4.

Fig. 2 shows the components of the optical assembly just prior to being arranged in the first assembly configuration shown in Fig. 1.

The mirror 4 is a hollow element housing a dome- shaped reflective surface 4a and a backing cap 4b. Annular orifices 5 are provided in the reflective surface 4a and the backing cap 4b in order to receive and engage the spacer stem 10 in the first assembly configuration . The transparent disk 8 of the spacer 6 is attached to one end of the stem 10 and comprises circumferential slots 16 which engage with projections 18 on the first end 2a of the housing 2 in the first assembly configuration. Apertures 20 are also provided circumferentially spaced from the slots 16 for reasons which will become apparent below. The first end 2a of the housing 2 comprises projections 18 configured to engage with the slots 16 in the transparent disk 8. The projections 18 comprises a first portion 18a which extends upwardly and away from the main body of the housing 2. The projections also comprise a second portion 18b which extends from the first portion 18a towards a free end. The second portion 18b of the projections 18 extends perpendicularly to the first portion 18a. The projections 18 curve around the circumference of the opening 12 in the first end 2a of the housing 2 and have a curvature matching that of the slots 16 in the transparent disk 8. In order to arrange the assembly in the first configuration, as shown in Fig. 1, the projections 18 are inserted into the slots 16 in the transparent disk 8. The disk 8 is then rotated circumferentially relative to the housing 2 such that the disk 8 becomes trapped between the second portions 18b of the projections 18 and the main body of the housing 2. The second end of the housing 2b has a detachable wall 22 comprising channels 24 for releasably engaging projections 26 on the main body of the housing 2. The wall 22 is used for mounting the optical assembly over an optical device in the first assembly configuration and is removable in order to insert the mirror 4 into the housing 2 in the second assembly configuration, which will be discussed further below. Figs. 3A-3B show cross-sectional views through components of the mirror 4. As described above, the reflective surface of the mirror 4a comprises an orifice 5 for receiving the stem 10 of the spacer 6. A clamping means 28 is provided behind the reflective surface 4a for clamping the stem 10 in the first assembly configuration. The clamping means 28 comprises finger elements which are biased towards the axis of the orifice 5 through the mirror 4. This enables the mirror to be releasably engaged at different positions along the stem 10. As shown in Fig. 3B, the backing plate of the mirror 4b has an axial channel 5b therein for receiving a portion of the stem 10. The axial channel 5b in, the backing plate 4b assists in stabilising the mirror 4 in the first assembly configuration. The outer regions of the mirror 4a and backing plate 4b comprise a circumferential tongue 30 and circumferential groove 32 respectively for engaging each other.

Fig. 4 shows a side view of the main body of the housing 2. It can be seen from this view that the second portion 18b of each projection 18 comprises a protrusion 18c which extends from the lower surface of the second portion 18b towards the main body of the housing 2. These protrusions 18c engage with the recesses 20 in the transparent disk 8 (shown in Fig. 2) when the disk 8 is screwed onto the first end of the housing 2a. This increases the rotational force that is required to unscrew the disk 8 from the housing 2 and assists in maintaining the assembly in the first configuration.

The main body of the housing 2 also comprises projections 34 for engaging the removable wall 22. The projections 34 have a first portion 34a extending away from the main body of the housing 2 in the direction from the first 2a to the second end 2b of the housing 2. The projections 34 also have a second portion 34b which extends laterally outwards in a direction perpendicular to the first portion 34a.

Figs¹. 5A-5B show views of the removable wall 22 of the housing 2. Fig. 5A shows a perspective view of the end wall 22. It can be seen that the end wall 22 comprises channels 24 for releasably engaging the projections 34 located towards the second end 2a of the main body of the housing 2. The projections 34 and channels 24 are configured such that the end wall 22 may be pushed onto the main body of the housing 2 in a direction running from the first 2a to the second end 2b of the housing and then the end wall 22 may be rotated relative to the main body of the housing 2 so as to releasably lock the main body 2 and end wall 22 of the housing together. Each of the channels 24 comprises a first portion 24a extending into and partially through the wall 22 to a second portion 24b. The second portion of the channel 24b extends perpendicularly to the first portion of the channel 24a.

Fig. 5B shows a cross-sectional view of the removable wall 22. As can be seen from this figure, the opening 14 increases in diameter in a stepped manner in a direction from the first end of the housing 2a towards the second end of the housing 2b (when the wall 22 is attached to the main body of the housing 2) . The increase in diameter forms a ledge 36 which can be used to- mount the optical assembly over an optical device. More specifically, the opening 14 may be mounted over the lens barrel of a camera such that the ledge 36 abuts the end face of the camera barrel .

Fig. 6 shows the arrangement of the components just prior to being arranged in the second assembly configuration, wherein the mirror 4 is stored within the housing 2. As can be seen from this figure, the mirror 4 is arranged between the main body of the housing 2 and the removable wall 22 of the housing. The mirror 4 is orientated with its convex dome-shaped surface 4a directed towards the concave cavity of the housing 2. The spacer 6 is arranged in a second orientation, wherein the stem 10 is directed towards the housing 2. Fig. 7 shows the preferred assembly in the second configuration. As will be appreciated, the housing end wall 22 has been reconnected with the mirror 4 inside of the housing 2. The spacer 6 has been reconnected to the first end of the housing 2a with the stem 10 projecting inside of the housing 2 and through the orifices 5a, 5b in the mirror 4. The slots 16 in the transparent disk 8 and the projections 18 on the first end of the housing 2a are rotationally engaged in a similar manner ,to that described above in relation to the first assembly configuration. It will be appreciated that the second assembly configuration has the advantages that it is significantly more compact and the housing 2 serves to protect the mirror 4.

It will be appreciated that various modifications to the above described embodiment may be made without departing from the scope of the invention, which is defined by the appended claims. For example, the housing may not have a removable wall, but may merely be open at its second end. The mirror may then be. held within the housing in the second assembly configuration by the engagement between the mirror and stem. Embodiments are also contemplated wherein the transparent disk is replaced by a wheel having spokes or replaced by a lens .

Claims

Claims :

1. An optical assembly comprising a mirror and a housing; wherein the assembly is configured such that the mirror is repeatedly mountable to and demountable from a first end of the housing; wherein the assembly is configured such that in a first configuration the mirror may be mounted to the first end of the housing and outside of the housing such that, in use, an annular image representative of a panoramic view around the mirror can be viewed on said mirror from a second, opposite end of the housing; and wherein the housing is configured such that in a second configuration of the assembly the mirror may be housed inside of the housing.

2. An optical assembly as claimed in claim 1, wherein the housing comprises a cavity which is complementary in shape to the shape of the mirror and which is configured so that the mirror may be housed inside of the cavity in the second configuration.

3. An optical assembly as claimed in claim 1 or 2 , wherein said assembly comprises a spacer for removably mounting said mirror in spaced relationship from the first end of said housing in said first configuration.

4. An optical assembly as claimed in claim' 3, wherein said assembly is configured so as to allow the spacing between the mirror and the first end of the housing to be varied in use.

5. An optical assembly as claimed in claim 3 or 4, wherein said spacer comprises a stem having a first end which is releasably engageable with said mirror and a second end for being coupled to the first end of said housing.

6. An optical assembly as claimed in claim 5, wherein said spacer comprises a stem connector arranged at the second end of the stem and wherein said stem connector is configured to be releasably connectable to the first end of said housing such that in said first configuration said annular image can be viewed through said stem connector from said second end of the housing,

7. An optical assembly as claimed in claim 6, wherein said stem connector comprises at least one circumferential slot and said first end of said housing comprises at least one projection configured to inter- lock with said slot in use.

8. An optical assembly as claimed in claim 6 or 7 , wherein said stem connector comprises a transparent disk.

9. An optical assembly as claimed in claim 6, 7 or 8 , wherein said stem connector comprises a lens for focussing or diverging light passing therethrough.

10. An optical assembly as claimed in any of claims 5- 9, wherein the stem has a length which is equal to or shorter than the distance between the first and second ends of the said housing.

11. An optical assembly as claimed in any of claims 5- 10, wherein said mirror comprises an axial orifice for allowing movement of the mirror along the stem and a clamp for releasably clamping the mirror^' in a fixed position on the stem.

12. An optical assembly as claimed in any preceding claim, wherein the second end of said housing comprises a removable wall which may be removed so as to allow the mirror to be inserted into the second end of the housing to arrange the assembly in the second configuration.

13. An optical assembly as claimed in any preceding claim, wherein the second end of the housing' comprises a wall having a transparent portion or an opening for allowing said annular image to be viewed through said housing when the assembly is in the first configuration.

14. An optical assembly as claimed in claim 13, wherein the _.area of the opening in said wall increases in a direction from the first end of the housing to the second end of the housing.

15. An optical assembly comprising a mirror for obtaining a panoramic image and a stand for mounting said mirror above an optical device in a first assembly configuration; wherein said assembly is configured such that said mirror is releasably mountable to and demountable from said stand and such that said mirror may be housed inside of said stand in a second assembly configuration .

16. An optical assembly as claimed in any preceding claim, further comprising an optical device for capturing an image reflected from the mirror.

17. A method of obtaining an annular image representative of a panoramic view comprising using an optical assembly as claimed in any preceding claim.

18. An optical assembly platform comprising a first side having means suitable for releasably connecting the platform to a stand of an optical .assembly and a second opposite side for mounting against an optical device in use, the platform comprising an opening for mounting the platform on the end of a lens barrel of the optical device, wherein the opening increases in area from the first side of the platform to the second side of the platform.

19. An optical assembly platform as claimed in claim 18, wherein the circumference of the opening increases in a stepped manner from the first to the second side of the- platform.

20. An optical assembly platform as claimed in claim 18 or 19, wherein the platform comprises at least one channel having a first portion extending into the first side of the platform to a second channel portion, wherein the second channel portion extends perpendicularly to the first channel portion and between the first and second sides of the platform.

21. A combination of a platform as claimed in claim 18, 19 or 20 and an optical device comprising a lens barrel, wherein the opening in the platform is sized and configured such that the platform is mountable on the lens barrel with the end of the lens barrel received in the opening and such that the end of the barrel abuts the wall of the opening between said first and second sides of said platform.