Periscope

Abstract

A periscope includes first 1 and second 2 sections. The second section moves relative to the first section, between first and second positions. The first section includes first 3 and second 6 aperture

Description

FIELD This present disclosure relates to a periscope. BACKGROUND Periscopes are used in a number of applications, for example to provide the occupants of a vehicle, such as an armoured vehicle, with a view of an outside environment. In addition to the optical view from the periscope, such vehicles are often also equipped with cameras that may provide digitally enhanced views of the outside environment, for example night vision or thermal imaging. Alternatively, or in addition, other information may be presented on screens, for example speed or position of the vehicle or sensors indicating a condition of the outside environment. It is desirable to provide a periscope in which the user can switch efficiently between viewing an external optical view and an electronically generated display without changing the user’s viewing position. It is also desirable that when switching to viewing the display and back again, the view is comfortable for the user and that eye strain is reduced. It is also desirable to maintain a compact design to allow retrofitting into existing vehicles without affecting the comfort, ease of entry / exit or ease of movement of the user. In some applications, it is also desirable that the periscope system does not reveal the position of the vehicle by transmission of ambient light from the interior of the vehicle to the outside world. Similarly, light from the outside world may wash out other displays desirably observed within the vehicle under low internal lighting conditions and so in some circumstances it is also desirable that the external light can be blocked. SUMMARY In accordance with the present invention there is provided a periscope comprising: a first section comprising: a first aperture, a second aperture, and a first deflector arranged to receive light from the first aperture and deflect said light to pass through the second aperture; and a second section comprising: a second deflector; a display rigidly coupled to the second deflector. The second section is moveable relative to the first section between a first position and a second position. In the first position, the second deflector is positioned to deflect light received from the second aperture toward a viewing position, and in the second position, the display is visible from the viewing position. Thus, the second section of the periscope moves between two positions to selectively direct an image from the upper section or an image from the display to one and the same viewing position. This provides a simple and compact periscope design which has a fixed viewing position and yet allows the user to switch between views. In other words, without movement of the head, the user's view can be switched between a view through the periscope and an electronically generated view from a display, such as a night vision or a thermal image, by a simple movement of the second section of the periscope. Optionally, whether the second section is in the first position or the second position, the position of the display relative to the second deflector remains unchanged. In this way, the number of moving parts may be reduced while ensuring reliable positioning of the second deflector and display in the first and second positions, respectively, and also ensuring a compact design of the periscope and ease of switching between a periscope view and a display view. Optionally, the second section includes at least one optical component arranged to form a virtual image of the display when the display is viewed from the viewing position, wherein the virtual image is positioned behind the display relative to the viewing position. The image of the display may be positioned relative to the viewing position to such an extent as to reduce strain on the viewer’s eyes by allowing the user’s eyes to relax when viewing the display. This can allow the periscope to have a compact overall design while eye strain from reading the display from the viewing position is reduced compared with other designs. Eye strain is reduced due to the virtual image of the display being positioned behind the display and therefore at a more comfortable distance from the viewing position. In other designs, the user must shift focus when switching between the view through the optical window (nearly always a far-field view) and the view of the display (a near-field view). By creating a virtual image of the display behind the display, the extent to which the user must shift focus between views is reduced and thus eye strain is yet further reduced. The at least one component may be provided in duplicate Le. as a biocular arrangement. The second section may be arranged for translational movement between the first and second positions of use. However, such an arrangement is likely to increase the size of the periscope and therefore reduce compactness. To address this problem, the second section can be arranged to pivot between the first position and second position. That is, the second section is preferably pivotable between the first position and the second position about a pivot axis. The pivot axis may be located at an edge of the second section and / or an edge of the first section. The second section may be pivotable through an angle of between 30-90 degrees, typically through an angle of between 30-60 degrees. Preferably, through an angle of 40-50 degrees. When the second section is in the first position, the plane of the second deflector is typically arranged at an angle of around 45 degrees relative to a (e.g., horizontal) viewing path from the viewing position to the second deflector. However, in display mode, the plane of the second deflector is ideally angled at approximately 0 degrees (i.e., is parallel) to the viewing path so that there is minimal obstruction of the display due to the second deflector and at the same time a head-on view of the display is possible. Therefore, the plane of the display is arranged substantially perpendicular to the plane of the second deflector. As such, the display faces in a direction which is substantially perpendicular to the direction in which the second deflector faces. That is, a normal of the second deflector lies parallel to the plane of the display and a normal of the display lies parallel to the plane of the second deflector. Put another way, the normal of the display and the normal of the second deflector are substantially perpendicular and lie in a plane which includes the viewing position. An optimal viewing position for the display can be said to be within the volume subtended by a virtual projection of the display out of the plane of the display. For example, if the display is rectangular, the volume subtended by a projection of the display out of the plane will be a cuboid. The second deflector is positioned outside of such a volume such that when the second section is in the second position, from the perspective of the viewing position the second deflector is positioned above the display. When the second deflector is so positioned, the user adopting the viewing position can view the display head on without the second deflector obstructing the view. This can also provide optimal range of movement of the second section, balancing the need to be able to move the second section efficiently between the first and second positions and the need for the second section to be movable to accommodate a user entering and exiting (or moving within) a space in which the periscope is located. This above-described positional relationship between the display and the second deflector can maximise the view of the display when the second section is in the second position, while minimising the angle through which the second section must be rotated to bring the second deflector into the optimum position for viewing in the periscope mode. Due to the perpendicular arrangement between the second deflector and display, the second section need only be rotated through 45 degrees to move from the first position to the second position. This relatively short rotational movement allows more rapid switching between the first and second positions and provides a more compact design. In the second position, the second deflector preferably forms a light-tight seal to close the second aperture. The light-tight seal may be formed by a resilient member, such as an elastomer sealing ring, provided between a periphery of the second aperture and the second deflector. This arrangement ensures that, in the second position, light from the display or other ambient light from the environment immediately surrounding the viewing position does not escape through the periscope to the external environment, thus reducing the risk that the position of the periscope is revealed to an observer or sensor in the external environment. The second section may be biased into the first position of use by a spring mechanism. This is advantageous in providing positive positioning of the second deflector and reducing the sensitivity of the reflector to vibration, for example when the periscope is mounted in a vehicle. The periscope comprises an adjustment mechanism for adjusting the angle of the second deflector relative to the second section when the second section is in the first position. The adjustment mechanism allows the user to adjust the viewing position to accommodate variations in height, seating position and eye position of the viewer. Alternatively, the periscope is arranged such that the first position and second position of the second section can be adjusted to accommodate a different viewing position. When the second section is in the second position, the optical path (along the optical axis) between the display and the viewing position is substantially straight. This simplified design provides a more compact periscope because it eliminates the need for turning optics for folding the optical path between the display and the viewing position, which can lead to a bulkier design and thus reduced space around the periscope for the user. The at least one optical component may comprise a plurality of optical components comprising lenses or lens groups or diffractive surfaces between the display port and the third aperture. The at least one optical component comprises at least one optical component arranged to form an image of the display behind the display relative to the viewing position. This optical component is of positive optical power, and may include a converging lens or equivalent diffraction pattern. The plurality of optical components may additionally comprise additional optical components. For example, the optical components may comprise a lens or lens group configured to reduce distortion (e.g., Petzval field curvature) in the image of the electronic display when the display is observed from the viewing position. For example, a field flattener such as a (piano) concave lens may be provided proximate to the display, in order to provide a representatively flat image of the display when observed from the viewing position. Alternatively, a diffractive surface may be provided between the display and the viewing position to provide the same reduction in distortion. Alternatively, or in addition, the optical components may comprise a lens or lens group positioned between the display and the viewing position and configured to reduce a first aberration introduced by one or more of the other optical components in the plurality of optical components. The first aberration may include radial distortion (e.g., chromatic aberration). The lens or lens group may include, for example, an achromatic doublet or achromatic triplet. Alternatively, a diffractive surface or surfaces are provided between the display and the viewing position to correct the first aberration. Alternatively, or in addition, the optical components may comprise a lens or lens group positioned between the display and the viewing position and configured to reduce a second aberration introduced by one or more of the other optical components in the plurality of optical components. The second aberration may include spherical aberration or astigmatism and the lens or group of lenses may comprise an aspherical lens or a combination of concave and convex lenses. Alternatively, a diffractive surface may be provided between the display and the viewing position to correct for the second aberration. The above-described optical components may be provided in any order between the display and the viewing position. The order of the optical components is a matter of design implementation and the skilled person will understand that various combinations of the above-described optical components are possible in various orders while meeting the functional requirements of placing the image plane of the display behind the actual position of the display. The display is removably attached to the second section, for example in the form of a detachable cassette. In this way, the electronic components of the periscope can be simply and quickly replaced in the event of malfunction. When moving from the second position to the first position, the periscope may be adapted such that the display is turned on when the second section is in the second position and turned off when the second section is in the first position. The periscope may be adapted such that the display is turned on only when the second section is in the second position so that the display is turned off both when the second section is in the first position and when the second section moves between the first position and the second position. Turning off the display prevents light from the display from being reflected from the user or other surfaces in the environment around the periscope when the second section is in the first position and when the display is not being used. This can be realised when a switch or other component for turning on or off the display is arranged to have a state which is dependent on the position of the second section relative to the first section. The second section is removably attached to the first section of the periscope. In this way, the second section can be quickly and easily removed for servicing and maintenance and / or to allow the user to more easily enter or exit the internal environment in which the periscope is located. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 a shows a cross-sectional view of a periscope in a first mode according to an embodiment; Figure 1 b shows an isometric view of the periscope in the first mode; Figure 2a shows a cross-sectional view of the periscope shown in Figures 1a and 1b in a second mode according to an embodiment; Figure 2b is an isometric view of the periscope in the second mode; and Figure 3 is a cross-sectional view of the periscope of Figure 2a showing the position of a virtual image of the display created by optics positioned in front of the display. OVERVIEW The following overview is provided to aid understanding of the periscopes described herein and is not to be construed as necessarily limiting the present disclosure or the claimed subject matter. It is known for periscopes to allow a user to see out of the periscope and, without the user changing head position, to alternately view a display instead of the view from the periscope. Previous designs are either bulky or provide sub-optimal views of the display, causing eye strain in the user. The present disclosure provides a design which is both compact and user friendly. A conventional periscope includes a first horizontally-facing aperture for capturing a view of an external environment, a first deflector for changing the direction of the path of the incoming light from horizontal to vertical and a second aperture which faces vertically for allowing the light to travel onwards to a second deflector, which redirects the light horizontally to the viewing position taken up by the user. In this way, the user can look in the direction in which the first aperture faces but is not level with the first aperture and therefore can be in a more protected position. In the present disclosure, the periscope is split into two sections: a first (upper) section, which includes the first aperture, first deflector and second aperture and a separate second (lower) section which includes the second deflector. The second section also includes a display mounted below the second deflector. The display and second section face at right angles to each other. The second section can rotate between two positions. In a first position, the second deflector is angled as it would be in the conventional periscope at around 45 degrees to the horizontal, therefore allowing the user to view through the periscope to the outside. The second section can also rotate through around 45 degrees to a second position. In the second position, the second deflector lies horizontal and closes the second aperture so that the user can no longer see through the periscope. Instead, in the second position, the display is brought into the line of site for the user allowing the user to view the display. Therefore, in the first position, the periscope can be said to operate in ‘periscope mode’, allowing a user adopting the viewing position to view the image collected through the first aperture. In the second position, the periscope can be said to operate in 'display mode’, allowing a user adopting the same viewing position to view the display. In the presently described periscope design, to avoid eyestrain, there is at least one optical component housed in the second section between the user’s eye and the display. The at least one optical component moves the apparent position of the display behind the actual position of the display, making it seem further away from the user’s perspective. This reduces eye strain, both when viewing the display and when switching back and forth between the periscope view and the view of the display. Put another way, the first section collects light at a first aperture from an environment, for example an external environment such as the environment outside of a vehicle and redirects the light toward and through a second aperture. The optical path of the collected light is deflected by a first deflector in the first section toward the second aperture. Preferably, the optical path is deflected at approximately right angles by the first deflector, but as the skilled person will appreciate, other angles are also possible depending on the configuration of the periscope. The second section includes a second deflector, a display and at least one optical component arranged to form an image (e.g., virtual image) of the display. The second section is moveable between a first and second position relative to the first section. The display and at least one optical component may be positioned beneath the second deflector and such that light from the display does not irradiate the second deflector or the second aperture regardless of the position of the second section. More particularly, in the first position, the second deflector is positioned such that it deflects light from the second aperture of the first section toward a viewing position. Preferably, the optical path of the light from the second aperture is deflected at approximately right angles to its original path by the second deflector. However, as the skilled person will appreciate, other angles are also possible depending on the configuration of the periscope. In the first position, the first deflector and second deflector work together redirect the light entering the first aperture toward the viewing position. In this way, a user taking up the viewing position can see an image of e.g., the external environment even though the user is not positioned to look directly through the first aperture. In the second position, the display and at least one optical component are positioned such that an image of the display formed by the at least one optical apparatus is viewable from the viewing position. Due to the at least one optical component, the image plane of the (e.g., virtual) image is formed behind the display relative to the viewing position when the display is viewed from the viewing position. In the second position, the at least one optical component allows the user to view an image of the display formed behind the actual position of the display. In this way, a user taking up the viewing position sees the display at a greater distance than the actual distance between the display and the viewing position. The at least one optical component and its placement between the display and the viewing position thus provides the advantage that the display can be placed closer to the viewing position without increasing user eye strain. Furthermore, the positioning of the at least one optical component and display relative to the second deflector such that light from the display does not irradiate the second deflector ensures that direct light from the display does not escape the first aperture. Therefore, the position of the periscope is not given away. Furthermore, the manoeuvrability of the second section in its entirety relative to the first section allows flexibility of user movement within the internal space of, for example, a vehicle housing the periscope, for example to allow a user to enter or exit the internal space or move more freely within it. Therefore, the periscope design provides a more compact periscope design with a more user-friendly switchable view between display and periscope modes. DETAILED DESCRIPTION Figure 1a is a cross-sectional view of a periscope according to an embodiment of the invention. The periscope comprises a first section 1 and a second section 2. Figure 1 b shows an isometric view of the periscope of Figure 1a. The first section 1 includes a prism 1a included in a first section housing 1b, a first aperture 3, a first deflector 4 and a second aperture 6. The first aperture 3 comprises a first planar surface of the prism 1a. The first deflector 4 is a second planar surface of the prism 1a which is oblique to the plane of the first aperture 3. The second aperture 6 is a third planar surface of the prism 1a arranged in a plane perpendicular to the plane of the first aperture 3 and oblique to the plane of the second planar surface. The first deflector 4 receives light entering the first aperture 3 and deflects it toward the second aperture 6. Although the example in Figure 1a includes a prism 1a, a prism is not essential. As the skilled person would understand, other forms of the first aperture 3, second aperture 6 and first deflector 4 are possible. For example, the first aperture 3 and / or second aperture 6 may take the form of a transparent window or even an open space with no physical component present therein. Although the first deflector 4 is shown as a prism surface in Figures 1a and 1b, the skilled person appreciates that the first deflector 4 may take other forms, for example a mirror coupled to the inside of the first section housing 1 b or even a reflective internal surface of the first section housing 1 b. Alternatively, the first deflector 4 may operate by refraction, rather than reflection, to redirect the light toward the second aperture 6. For example, the first deflector 4 may include a pair or series of static Risley prisms instead of a reflective surface. Returning to Figure 1a, the second section 2 includes a second section housing 2a, a second deflector 5, a display 7, at least one optical component 8, an actuator 14 and a third aperture 12. The second section housing 2a is a cuboid frame with a first and second opposing open faces. The first open face is arranged to receive a cartridge comprising the display 7. The second open face provides the third aperture 12. The second deflector 5 is coupled to, or is otherwise a part of, an outside surface of the second section housing 2a that extends between the two opposing open ends. The second deflector 5 is a reflective surface (such as a mirror) which, in the first position of the second section 2, is arranged to re-direct the light from the second aperture 6 toward the viewing position VP. Although the second deflector 5 is shown as a reflective surface, the second deflector 5 may take other forms, such as a pair or series of static Risley prisms arranged to deflect light from the second aperture 6 toward the viewing position VP by refraction rather than reflection. However, it is advantageous if the second deflector is a flat reflective surface since this can provide a more compact design. The display 7 is part of a cassette module (not shown) which is removably mounted to the second section housing 2a for easy replacement. This can ensure that the principal electronic components of the periscope can simply be replaced in the event of a malfunction. The connection between the cassette module and the second section housing 2a may include asymmetrically arranged mating formations, such as pegs and sockets, to ensure that the cassette module and hence the display 7 is in the correct orientation and position relative to the second section 2. The cassette module includes display driving circuitry, a controller and / or other electronics essential for the functioning of the display 7. The display 7 is any display type (e.g., LED, LCD or OLED) capable of outputting an image. The cassette module may be arranged to receive a feed from an external camera or sensor (not shown) arranged to capture an image or other data from a vehicle and / or its environment. The display 7 is configured to show electronically generated digital images, such as night vision images, from, for example, an outside environment of the vehicle in which the periscope is mounted. Other electronically generated images may be displayed, for example including information regarding the movement or geographical position of a vehicle in which the periscope is mounted. Figures 2a and 2b respectively show cross-sectional and isometric views of the periscope of Figures 1a and 1b. Besides the position of the second section 2, all other structural features of Figure 2a are identical to those shown in Figure 1a and vice versa. Figures 1a and 1b show the periscope in a first mode in which the second section 2 is in a first position relative to the first section 1, whereas Figures 2a and 2b show the periscope in a second mode in which the second section 2 is in a second position relative to the first section 1. In the first position as shown in Figures 1a and 1 b, light from the first section 1 of the periscope is reflected by the second deflector 5 towards the viewing position VP. In the second position, the second deflector 5 no longer reflects light toward the viewing position and blocks light passing through the second aperture 6 from the first section 1 of the periscope. In the second position as shown in Figures 2a and 2b, a light-tight seal may be formed around the second aperture so that no light can enter the second aperture 6 to be deflected out of the first aperture 3. A sealing ring (not shown) is provided at the base of the first section 1 around the second aperture 6 to engage the second deflector 5 (or the second section 2 around the second deflector 5) and form the seal when the second section 2 is in the second position. The second section 2 further comprises at least one optical component for affecting the path of light from the display 7 to the viewing position VP when the second section 2 is in the second position. When the second section 2 is in the first position, the at least one optical component directs the light from the display 7 (if the display is switched on) elsewhere (i.e., in a direction other than towards the viewing position VP). When the second section 2 is in the second position, the second deflector 5 no longer redirects light from the second aperture 6 toward the viewing position VP. Instead, a normal of the display 7 is angled toward the viewing position VP so that a user adopting the viewing position VP can view the display 7 through the third aperture 12 and the at least one optical component. The at least one optical component is shown in the drawings as an optical train comprising a first, second, third and fourth optical components 8, 9,10 and 11. The first optical component 8 is a plano-concave lens provided proximate the display 7. The first optical component 8 is arranged to flatten the image when viewed by the user from the viewing position VP. A second optical component 9 comprising an achromatic doublet is provided after the first optical component 8 in the optical train. The function of the second optical component 9 is to correct the image for chromatic aberrations. The third optical component 10 is provided after the second optical component 9 in the optical train. The third optical component 10 is an aspheric doublet arranged to correct for spherical aberration. The fourth optical component 11 is provided after the third optical component 10 in the optical train. In this case, the fourth optical component 11 is a meniscus lens, which forms the final (virtual) image 20 of the display 7 visible to a user taking up the viewing position VP. Figure 3 shows the position of a virtual image 20 of the display when the display 7 is viewed through the optical train. The periscope in Figure 3 is identical to that of Figures 1a, 1b, 2a and 2b and therefore a description of the periscope will be omitted. In Figure 3, the (virtual) image 20 of the display 7 formed by the optical train (from the perspective of the viewing position VP) is positioned behind the display 7, preferably at around arm's length for a user taking up the viewing position VP. The position of the virtual image 20 (i.e., the position of the image plane of the display 7) behind the display 7 reduces eye strain for the user viewing the display 7 from the viewing position VP. The geometric rays in Figure 3 are provided only for illustrative purposes. The skilled person understands how to implement an appropriate optical design so that the image 20 of the display is positioned behind the display 7 to provide the reduction in eye strain for the user. Furthermore, the optical train is not limited to that shown in Figure 3 and other arrangements are possible provided they meet the requirement that the image 20 of the display is positioned behind the display as described herein. The display 7 may be activated by a microswitch or other micro-actuator when the second section 2 is moved to the second position and deactivated when the second section 2 is moved back to the first position. The actuator 14 is arranged to allow the user to move the second section 2 between the first and second positions. The actuator 14 can be a manual actuator (e.g., a lever) or an automatic actuator (button, switch etc.) which operates a motor, hydraulic system or any other automatic system, module or component arranged to drive movement of the second section 2 relative to the first section 1. It will be seen from the Figures that in rotating from the first position to the second position, the display 7 is always positioned on the non-light-deflecting side of the second deflector 5 and faces in a direction which is substantially parallel with the plane of the second deflector 5. The optical axis of the optical train is therefore also parallel with (and positioned behind) the plane of the second deflector 5. Put another way, the display 7 faces in a direction perpendicular to a normal of a deflective surface of the second deflector 5 and the optical axis of the optical train is perpendicular to the normal of the deflective surface. In this way, the second deflector 5 prevents light emitted from the display 7 escaping through the first aperture 3 via the second aperture 6. This has advantages in some applications, particularly at night, where there is a risk that any light escaping through the first aperture 3 could give away the position of the periscope and hence the user and / or vehicle housing the periscope. The second section 2 is arranged to pivot about an axis A to as to move between the first position and second position. The axis A is substantially perpendicular to the optical axis of the optical train and the main optical axis of the first section 1. The pivoting of the whole of the second section 2 in this way works synergistically with the relative arrangement of the components of the second section 2 as described herein to provide a compact design which allows ease of switching between the pericope view (when the second section 2 is in the first position) and the display view (when the second section 2 is in the second position). As shown by the comparison of Figures 1a and 2a (or of Figures 1b and 2b), the second section 2 rotates through approximately 45 degrees between the first position and the second position. Because the second section 2 is not required to rotate further, the clearance required for the second section 2 is minimal, which allows the periscope to be relatively short in the vertical direction (parallel to the optical axis of the first section 1) and of minimal depth in the horizontal direction (the general direction from the second deflector 5 to the viewing position VP). The embodiments provide a compact design that allows the user's view to be switched between an electronically generated image, such as night vision, and a purely optical image, while reducing eye strain on the user and maintaining a compact overall design. Throughout the description and claims of this specification, the words "comprise" and "include" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) may be combined in any combination, except combinations where at least some of such features are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A periscope comprising:a first section comprising:a first aperture,a second aperture, anda first deflector arranged to receive light from the first aperture and deflect said light to pass through the second aperture; anda second section comprising:a second deflector;a display rigidly coupled to the second deflector;wherein the second section is moveable relative to the first section between a first position and a second position;wherein, in the first position, the second deflector is positioned to deflect light received from the second aperture toward a viewing position, andin the second position, the display is visible from the viewing position.

2. The periscope according to claim 1, wherein, in the first position and the second position, the plane of the display is arranged perpendicular to the plane of the second deflector3. The periscope according to claim 1 or 2, wherein a normal of the display and a normal of the second deflector are in a plane in which the viewing position is located.

4. The periscope according to claim 1, 2 or 3, wherein, in the second position, the second deflector blocks the second aperture.

5. The periscope according to any preceding claim, further comprising an actuator arranged to turn on the display when the second section is in the second position.

6. The periscope according to claim 5, wherein the actuator is arranged to turn off the display when the second section is moved away from the second position.

7. The periscope according to any preceding claim, wherein the second section includes at least one optical component arranged to form a virtual image of the display when the display is viewed from the viewing position, wherein the virtual image is positioned behind the display relative to the viewing position.

8. The periscope according to claim 7, wherein, in the second position, a normal of the display forms a straight line from the display to the viewing position and lies along the principal axis of the at least one optical component.

9. The periscope according to claim 7 or 8, wherein the at least one optical component comprises an optical component arranged to form a virtual image of the display behind the display relative to the viewing position.

10. The periscope according to claim 7, 8 or 9, wherein the at least one optical component comprises an optical component arranged to correct distortion in the virtual image of the display.

11. The periscope according to any of claims 7-10, wherein the at least one optical component comprises an optical component arranged to correct a first aberration in the virtual image of the display.

12. The periscope according to any of claims 7-11, wherein the at least one optical component comprises an optical component arranged to correct a second aberration in the virtual image of the display, wherein the second aberration is different from the first aberration.

13. The periscope according to any preceding claim, wherein periscope comprises an actuator arranged to move the second section between the first position and the second position.

14. The periscope according to any preceding claim, wherein the second section is arranged to pivot between the first position and second position.

15. The periscope according to any preceding claim, wherein the second section is hingedly connected to the first section.

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