WO2020076235A1

WO2020076235A1 - Assembly and method for switching direction of camera view

Info

Publication number: WO2020076235A1
Application number: PCT/SG2019/050477
Authority: WO
Inventors: Mark Breese
Original assignee: National University Of Singapore
Priority date: 2018-10-09
Filing date: 2019-09-20
Publication date: 2020-04-16

Abstract

An assembly and method for switching direction of camera view. The assembly comprises an illumination source for emitting light; and a beam splitter element configured to be disposed on a camera; wherein the beam splitter element is configured such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera; and wherein the illumination source is configured for switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or for switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states, and such that substantially only one of the first and second beams is directed towards the entry lens in each of the first and second illumination states and each of the first and second polarization states.

Description

ASSEMBLY AND METHOD FOR SWITCHING DIRECTION OF CAMERA VIEW

FIELD OF INVENTION

The present invention relates broadly to an assembly and a method for switching direction of camera view, in particular utilising control of illumination.

BACKGROUND

Any mention and/or discussion of prior art throughout the specification should not be considered, in any way, as an admission that this prior art is well known or forms part of common general knowledge in the field.

In many optical applications such as for endoscopes and borescopes, and all other classes of these devices such as fiberscopes, which operate in a naturally dark environment such as inside a human body or inside a confined cavity, having a varying camera view can be desirable.

While there are several existing methods available to increase the total viewing angular range of e.g. endoscopes and borescopes, they are typically not suitable for a flexible device in a confined space. Furthermore, existing methods typically involve additional mechanical complexity and significant extra cost.

Examples of existing methods to change the direction of view (DOV) of an endoscope include.

1. Different inserts

Use of different rotatable mirror tube and objective sleeves with an off-axis DOV on the end. While such inserts work well, they require changing of components and thus added use complexity. Also, such inserts typically only work for a rigid, straight geometry.

2. Actuated Head

Another existing approach to view different DOV is to use an actuated endoscope head. Actuation allows the tip to be tilted in different directions.

The disadvantage of this approach includes that it relies on a large enough cavity to accommodate such transverse motion.

3. Variable DOV using a tilting prism

Another existing approach to implement selectable DOVs is to fit a rigid endoscope with a tilting prism. For example, a fixed field of view (FOV) of 45° can be tilted over a range of DOV of 95°, giving a total viewing angular range of 140°. On a rotating the head, a total viewing angular range of 140° can be achieved over the full azimuthal range. The disadvantage of this approach is that it only works for a rigid geometry and also necessitates extra mechanical complexity and so cost.

Embodiments of the present invention seek to address at least one of the above problems.

SUMMARY

In accordance with a first aspect of the present invention, there is provided an assembly for switching direction of camera view comprising: an illumination source for emitting light; and a beam splitter element configured to be disposed on a camera; wherein the beam splitter element is configured such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera; and wherein the illumination source is configured for switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or for switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states, and such that substantially only one of the first and second beams is directed towards the entry lens in each of the first and second illumination states and each of the first and second polarization states.

In accordance with a second aspect of the present invention, there is provided a method of switching direction of camera view comprising the steps of providing an illumination source for emitting light; providing a beam splitter element on a camera such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera; switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states; and directing substantially only one of the first and second beams towards the entry lens in each of the first and second illumination states and/or each of the first and second polarization states.

In accordance with a third aspect of the present invention, there is provided a camera device comprising the assembly of the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

Figure 1 shows schematic diagrams illustrating different DOV of viewing devices. Figures 2(a)-(c) show schematic diagrams illustrating different DOV for a fixed FOV of 60°.

Figure 3(a) shows a schematic diagram illustrating CBS splitting a beam of light into two separate beams.

Figure 3(b) shows a schematic diagram illustrating a cube beam splitter (CBS) combining two beams into a single beam.

Figures 4(a)-(c) show schematic diagrams illustrating a CBS on camera entrance aperture with strong ambient lighting with different light shield arrangements over top entrance face and, side entrance face.

Figure 5(a) shows a photograph of a plan view of an endoscope camera aperture surrounded by 6 LEDs.

Figures 5(b)-(d) shows photographs of a plan view and different sides view, respectively, of a CBS located on an endoscope aperture, according to an example embodiment.

Figure 6 shows a photograph of an endoscope and CBS assembly according to a simulated example embodiment.

Figures 7(a)-(d) shows photographs recorded from the endoscope of figure 6 in different operation modes, according to a simulated example embodiment.

Figure 8 shows a schematic diagram illustrating standard operating mode of an endoscope.

Figures 9(a)-(d) show schematic diagrams illustrating the operating modes of an endoscope according to an example embodiment.

Figure 10(a) shows a schematic diagram illustrating a non-polarizing cube beam splitter (CBS) for use in an example embodiment.

Figure 10(b) shows a schematic diagram illustrating a polarizing CBS for use in an example embodiment.

Figures 11(a) and (b) show schematic diagrams illustrating the operating modes of a camera device according to an example embodiment.

Figures l2(a)-(c) show schematic diagrams illustrating the operating modes of a camera device according to an example embodiment.

Figures 13(a) and (b) show schematic diagrams illustrating the use of a customized CBS geometry in a camera device according to an example embodiment.

Figures 14(a) and (b) show schematic diagrams illustrating the use of another customized CBS geometry in a camera device according to an example embodiment.

Figure 15 shows flow chart illustrating a method of switching direction of camera view, according to an example embodiment. DETAILED DESCRIPTION

Embodiments of the present invention provide a method to electrically switch the direction of view of an optical device such as, but not limited to, an endoscope or borescope camera by 90° using a cube beam splitter placed at the front end (distal end). The advantage of this approach according to example embodiments is that it requires little additional equipment to change the direction of view, relying on simple optical components such as prisms or cube beam splitters and selective illumination direction and polarization state.

Embodiments of the present invention utilize prism arrangements of two (or more) DOV from different prism entrance faces, or from different faces of a cube beam splitter to allow two (or more) views to be recorded on the same camera sensor. Consideration is given according to example embodiments on how to separate the two (or more) DOV so that each can preferably be separately viewed without interference from the other direction. This is achieved according to example embodiments by preferably controlling only the direction and/or polarization of light which is used for illumination along each of the two (or more) DOV.

Embodiments of the present invention are well suited to environments which are naturally dark with little or no ambient light entering either DOV which the camera can view. Under these conditions one can arrange the direction of illuminating devices such as light emitting diodes (LEDs) or fiber optic cables such that their light only illuminates parallel to one or other of the prism entrance faces. Their light scatters and reflects off the surface of interest which is either straight-ahead (DOV = 0°), or orthogonal to this (e.g. DOV = 90°), into the prism face along this direction so that only one DOV is viewed at any one time. On changing the direction of illumination to that corresponding to the other prism DOV then a view is recorded of this other view. Another method according to example embodiments described here is to change the polarization state of the illuminating light between S- to P-polarized, with each prism entrance face being chosen to be more sensitive to one of these polarization states than the other.

The advantage of this approach according to example embodiments includes that it requires little additional equipment to change the DOV, preferably relying on simple optical components such as prisms or cube beam splitters and selective illumination direction and polarization.

The field of application of embodiments of the present invention includes, but is not limited to, for endoscopes and borescopes, and all other classes of these devices such as fiberscopes, which operate in a naturally dark environment such as inside a human body or inside a confined cavity. Such devices according to example embodiments are described herein along their main fields of application.

General Review of Endoscopes and Borescopes

Borescopes are primarily used for visual inspection of areas which are not accessible to other tools to check for cracks, coating defects, voids, burrs, corrosion, and other critical problem indicators in turbines, automotive components, and pumps. Endoscopes are normally used to view internal passageways inside human bodies.

Borescopes are produced in many forms but they typically comprise a hollow tube, a light source, an eyepiece and some form of relaying an image from the end of the scope to the eyepiece (often optical lenses or a video camera). For a rigid design, the image is typically conveyed from the distal end along a rigid tube using relay lenses to an eyepiece outside the cavity. Lighting is typically provided through fibre optic cables from an external light source. A prism at the distal end can e.g. provide a DOV of around 45°.

Rigid borescopes give higher quality images, they are easier to use and are less expensive than flexible versions of similar quality. However, flexible versions allow viewing inside cavities of a geometry such that a rigid version cannot access.

While there are small differences between endoscopes and borescopes, here we refer to endoscopes as encompassing the whole field of such viewing devices, including borescopes and fiberscopes.

For an example of a flexible endoscope module where the camera and focusing lens are very small, reference is made to https://www.made-in-china.com/showroom/szcaige/product- detailuNFnAFrEOfcX/China-Newest-l-OMP-HD-Mini-3-9mm-USB-Endoscope-Module-for- DIY-Inspection-Camera-4-LED.html. The external diameter is 3.9 mm. For an example of an unencapsulated module where the LEDs surrounding the camera lens are illustrated, reference is made to https://www.aliexpress.com/item/Inspection-Cainera-Module-XR-IC2M45- Endoscope-Camera-Module-With-Fiill-Accessories-To-DIY-Tube-Snake- Endoscope/32255710984.html.

As described above, lighting for an endoscope is typically implemented using either LEDs or fibre optic cables. In conventional operation there is an array of unpolarised illuminating devices placed at the distal end, around the camera, projecting light in the same direction as the camera. Light emitted from the illuminating devices falls on the interior cavity surface and is reflected back from the region-of-interest into the camera.

Direction-of-View (DOV)

Figure 1 shows a schematic drawing illustrating the DOV of the viewing device (camera or eyepiece). The straight-ahead direction has a DOV = 0°, illustrated in numeral 100, and orthogonal to this, the DOV = 90°, illustrated at numeral 102.

A small optical prism placed directly on a camera entrance aperture can be used to change the direction of view (DOV). This allows adjacent cameras to have their direction of view deflected so as to form a wide-angle contiguous field of view.

If the region of interest is straight-ahead then a 0° DOV is most appropriate. For applications such as examining a rifle barrel, a 90° DOV is most appropriate. If the region of interest is very close to the entrance aperture, e.g. engine valves near a spark plug hole, or polyps in certain locations along the colon, a backward-looking, e.g. 120° DOV illustrated at numeral 104, is appropriate.

Field-of-View (FOV)

Another important optical consideration is the field of view (FOV) of the camera. Only when the DOV and FOV are considered together can a proper understanding of the total viewing angular range that can be achieved by rotating the device be attained.

Figures 2(a)-(c) show schematic diagrams where the FOV is fixed at 60° for an endoscope 200. In figure 2 (a) the DOV = 0° so the real and apparent FOV are coincident. When the endoscope 200 is rotated the view does not change so there is no capability to see sideways or to increase the total viewing angular range. In figure 2(b) the endoscope 202 has a DOV = 30° and the total viewing angular range which can be viewed by rotating is increased. One can still just see straight-ahead (at DOV = 0°) which is important for navigation and localization, but one still cannot see orthogonal to this (DOV = 90°). In figure 2(c) the endoscope 204 has a DOV = 50° and now rotation of the endoscope 204 provides an even larger total viewing angular range but now there is a blind spot 206 in the straight-ahead direction, making navigation and localization difficult.

Another option is to have a very large FOV, e.g. 120°, so that for a DOV of 40°, one can see straight-ahead and also orthogonal to this. However, the very large FOV limits the magnification of the viewed area.

For two prisms, placed back-to-back on a camera entrance aperture, the field of view of each can be incident on the same camera sensor, forming an overlapping image. Methods to separate or limit the two views can be provided, e.g. only allowing half the field of view of each direction to fall on the sensor so that it records a split view from two directions, each covering half the original field of view. This same principle can be used with a cube beam splitter (CBS) placed directly on a camera entrance aperture such that two fields of view (FOV) from orthogonal directions are incident on the same sensor. A range of options can be provided to separate or limit the two FOV to form a split view.

In the above described prism geometries a mechanical or electrical shutter in front of each prism entrance face can be used, each of which could be independently opened or closed. Only the DOV corresponding to the prism face with an open shutter is recorded on the camera sensor. The DOV for recording photos can thus easily and rapidly be switched by changing which shutter is opened or closed. Similarly the DOV for recording videos can be changed by rapidly switching which shutter is opened or closed, and if this is done rapidly enough then a composite, wide-angle video may be recorded. Use of such an electrical shutter means that the DOV can be switched with no moving mechanical components.

Embodiments of the present invention can provide a flexible endoscope with increased total viewing angular range in a confined cavity. In an example embodiment, the DOV of an endoscope camera may be changed by 90° using a cube beam splitter placed at the front end of the endoscope (distal end).

An example embodiment of the present invention controls the intensity and/or polarization of light reflected or scattered into the two entrance faces of a cube beam splitter (CBS), in an environment which is naturally dark, i.e. low or zero ambient lighting, such as the interior of a cavity which may be within a physical structure or within a human body. Control of the intensity and/or polarization of light preferably requires no moving parts, unlike existing methods to change the direction of view of an endoscope or borescope.

Cube Beam Splitter for use in example embodiments

A cube beam splitter (CBS) 300 is typically used to separate, advantageously independent of wavelength, a beam of light 302 into two equally intense, beams 304, 306 travelling in orthogonal directions, as shown in figure 3(a). The ratio of the split is chosen during manufacture. There are generally three types of CBS, each having different dependence on the polarization of the incoming light. First consider a non-polarizing CBS (average transmission/ reflection along the respective directions of beams 304, 306 of 50% of S- and P-polarized light).

A CBS 300 can also be used to combine, advantageously independent of wavelength, beams 308, 310 of light or images entering from orthogonal directions together, as shown in figure 3(b). Consider a CBS 400 placed on the aperture of a small camera 402, such as that of a smartphone, as shown in figure 4(a). In figure 4(b) light 404 entering from the side is reflected into the camera 402, equivalent to beam 310 in the figure 3(b). If no light enters the top surface 406, for example by blocking this direction with a light shield 408, then the only image 407 recorded is from the side face. Conversely, in figure 4(c), only light 410 entering from the top face is recorded, equivalent to beam 308 in the figure 3(b), since a shield 412 placed over the side face allows no light to enter from the other direction. The only image 413 recorded is from the top face. Use of a shield 408, 412 to cover one face is used for such an environment with high ambient lighting, since an image 414 recorded with both prism entrance surfaces exposed is an overlap of two images from the two prism entrance surfaces, as shown in figure 4(a), i.e. the camera records respective images of both DOV in figures 4(b) and (c) simultaneously.

Because the splitting and combining is wavelength independent according to example embodiments, colour images over the entire wavelength range of the illumination source(s) can be recorded for each view.

Cube beam splitter located on endoscope according to example embodiments

Consider the typical dimensions of an endoscope 500, see photograph shown in figure 5(a), with an outer diameter of 7 mm. A 1 mm border where the LEDs e.g. 502 are located leaves an in inner diameter of 5 mm, into which a CBS 504 is placed on top of the camera aperture according to an example embodiment, see photograph in figure 5(b). The CBS 504 is preferably small enough to fit within the inner diameter so as not to obstruct the LEDs e.g. 502. The diagonal length of the CBS 504 is less than the inner diameter of 5 mm in this example embodiment, so the side length of the CBS 504 is less than 5/V2 - 3.5 mm. In figure 5(b) a CBS 504 of 3.2 mm side length is shown according to an example embodiment. Figures 5(c), (d) show respective side views. No holder for the CBS 504 is shown here for clarity.

The geometry in figure 5(b)-(d) is identical to figure 4, with a top entrance face (arrow 506) and a side entrance face (arrow 508). Consider the following endoscope 600 with CBS 602 according to an example embodiment as shown in figure 6.

Figures 7(a)-(d) show photographs recorded from the endoscope 600 under different illumination conditions. In figure 7(b) strong ambient room lighting results in the camera recording the two overlapping DO Vs. To simulate an environment which is naturally dark, such as inside a cavity or inside a body, all rooms lights were switched off. Now, in the absence of any illumination provided along either DOV, the camera records no image, see figure 7(a). To simulate illumination control according to an example embodiment, a torch beam producing unpolarised white light is used to illuminate only in a straight-ahead direction, i.e. DOV = 0°, with the recorded image in figure 7(c), and only in the orthogonal direction, i.e. DOV = 90°, with the recorded image in figure 7(d). Careful choice of illumination direction preferably allows the camera to record only that image along the illuminated direction, according to example embodiments.

Lighting Arrangement according to example embodiments

Embodiments of the present invention utilize the capability to allow light into one or other of the entrance faces of the CBS using different illuminating schemes. Figures 7(a)-(d) described above illustrate how light can be switched from illuminating parallel to one or other of the entrance faces of the CBS. It is preferred that lighting is not used to simultaneously illuminate both faces, as then one is in the same situation as shown in figure 7(b) where the recorded camera image is an overlap between the two separate images viewed through each entrance face.

As to how to arrange such a lighting scheme according to example embodiments, the arrangement of conventional LEDs around an endoscope camera is first considered. Figure 8 shows schematic drawings of different views illustrating conventional operation with four LEDs e.g. 800 arranged at equal spacing around the camera 802, providing illumination perpendicular to the camera 802 entrance face (i.e. parallel to the DOV = 0°). The LEDs e.g. 800 are all connected together on the same electrical circuit.

Figures 9(a)-(d) show the modified endoscope operation according to an example embodiment. In this embodiment, three lights 901-903 remain on one electrical circuit and the remaining one 904 is on a separate circuit so that there are two separate groups of lights 901-903 and 904 which can be independently switched on/off. Over the single light 904, a highly-reflective surface 906 angled at 45° is placed so as to change the direction of illumination by 90°, to make it perpendicular to the CBS side entrance face 908, i.e. parallel to DOV = 90°. According to this example embodiment one preferably has the means of separately illuminating along the DOVs of either entrance face 908, 910. For LEDs as the lights 901-904 according to an example embodiment, the light intensity can be simply controlled, allowing the illuminating intensity to be varied as appropriate.

Specifically, in figure 9(a) all lights 901-904 are off. Assuming a dark environment, the camera 912 records no image from either direction. In figure 9(b) all lights 901-904 are on. The camera 912 records views from straight-ahead (DOV = 0°,“lightning” object) and side direction (DOV = 90°,’’arch” object) simultaneously. In figure 9(c) only the lights 901-903 parallel to straight ahead direction are on. The camera 912 records the view from DOV = 0° only, i.e. an image of “lightning” object. In figure 9(d) only light 904 parallel to the sideways direction is on. The camera 912 records view from DOV = 90°, i.e. an image of the“arch” object.

This arrangement according to an example embodiment thus advantageously uses the same basic lighting geometry as for a conventional endoscope, causing minimal changes to the manufacturing process.

For fibre optic illumination a similar arrangement according to another example embodiment of two independent bundles, with a reflective surface over one of them to provide sideways illumination, allows this lighting modality to achieve the same goal of providing independent lighting perpendicular to the CBS entrance faces.

Cube Beam Splitter Holder according to example embodiments

The holder for the CBS according to example embodiments of the present invention, in addition to providing a means to anchor and locate the CBS, preferably also assists in assuring that only one entrance face receives light so that the recorded image contains as little as possible stray light from the other entrance face. In practise, while one may never reduce this to absolutely zero, careful design of the CBS holder for use in example embodiments can reduce it to the point where it preferably does not significantly contribute to the recorded light intensity.

A light shield separating the two adjacent entrance faces of the CBS may be used according to example embodiments. The shield preferably extends sufficiently far so as to provide adequate shielding, but it preferably does not restrict the field of view of either entrance face. One solution according to example embodiments is to provide an angled shield at 45° between the two faces. Another function of the holder according to example embodiments is ensure that no stray light enters any of the three side faces of the CBS which do not form any of the FOV which can be seen by the camera. They can, however, still transmit light into the camera and so degrade the image so that they are preferably adequately shielded. This means that preferably no light can enter from the illuminating LEDs, or from light scattered off any cavity surface, via those faces.

Polarization of illuminating light according to example embodiments

The above described example embodiments considered how to selectively display one of two views entering a CBS from either the top face or the side face by arranging non-polarized illumination to be parallel to one or the other DOV. Hence only the intensity of light falling on each face determines how much will be recorded on the camera sensor. This is the case for an ideal non-polarizing CBS 1000 as shown in figure 10(a) where the amounts of S- and P- polarized light deflected towards the camera face 1001 from the top and the side entrance faces 1002, 1004, respectively, is similar, being about 50% in each case.

For a polarizing CBS 1006, the situation is different, as shown in figure 10(b). Now almost 100% of the S -component entering from the side face 1008 is deflected into the camera face 1010 whereas almost 100% of the P-component continues undeflected. Conversely for light entering from the top face 1012 of the CBS 1006, almost 100% of the S-component is deflected away from camera entrance face 1010 whereas almost 100% of the P-component continues undeflected into the camera entrance face 1010.

There is a third class of CBS, typically just called a standard CBS, which have characteristics between those of unpolarized and polarized CBS, in that the average percentage of light deflected into the camera entrance face from the top and side entrance faces is about 50%, but the components entering the camera face are partially polarized.

Polarization thus offers another method according to example embodiments to selectively choose to view the side or top DOV on the camera sensor, by altering the polarization state of the illuminating light from P- to S-, as shown in figures 11(a) and (b). The standard definition of polarization is assumed here, with P-polarization meaning the direction of oscillations are confined to a plane parallel to the page, and S- polarization meaning the direction of oscillations are confined to a plane orthogonal to the page.

In this example embodiment, illumination elements 1101-1104 are controllable in terms of the polarisation of their emitted light advantageously independent of illumination direction. Specifically, in figure 11(a) all illumination elements 1101-1104 emit P-polarized light. The camera 1106 records only the view from straight-ahead (DOV = 0°, arrow 1105,“lightning” object). In figure 11(b) all illumination element 1101-1103 emit S-polarized light. The camera 1106 records only the view from DOV = 90°, arrow 1108,“arch” object. In this example embodiment, the illumination elements 1101-1104 are preferably arranged such that the sum of the respective fields of illumination e.g. 1112 results in an approximately semi- spherical, here forward and sideways, total field of illumination.

In one embodiment, the illumination elements 1101-1104 use fibre optic cables to illuminate the distal end of the endoscope, using a separate, external light source (not shown). The polarization fed into the fibre optics can be varied simply by rotating a linear polarizer layer placed in front of a random light source, or by rotating an already-polarized light source.

In a different embodiment using LEDs placed around the distal end of an endoscope, linear polarizers of a certain alignment can be placed over the LEDs such that one set of the LEDs emits P-polarized light, and another set of the LEDs emits S-polarized light. Illumination polarization states are changed in such an embodiment by switching between the different sets of LEDs.

Polarizers placed on CBS surfaces according to example embodiments Depending on the type of CBS used and the required mode of selection of how light is changed between its two entrance faces, there is the option of placing suitably-oriented polarizing layers on one or both of the entrance faces according to example embodiments. This can allow a non polarizing CBS to be made sensitive to the polarization state of the illuminating light. While one can use a polarizing CBS for this purpose in other example embodiments as described above, they can have a drawback in that they may not accurately reproduce the correct range of colours entering them. Example embodiments using suitably-oriented polarizing layers on one or both of the entrance faces may help to overcome this limitation.

Polarizer placed on CBS camera entrance surface according to example embodiments

Depending on the type of CBS used and the type of illumination used (angle, polarization) one may place a polarizing layer at the base of the CBS, directly on top of the camera aperture, so that only light of a certain polarization enters the camera, according to example embodiments.

Tilting CBS to change DOV from side entrance face according to example embodiments

For the example embodiments described above it has been described how to change the DOV between the straight-ahead direction (DOV = 0°) and the orthogonal direction (DOV = 90°), and as illustrated in figure 12(a). The change of angle of 90° is determined by the CBS 1200 geometry according to example embodiments. However, there may be occasions where one wants a change of DOV smaller or larger than this, for example a combination of DOV = 0° and DOV = 70° or DOV = 110°. Such occasions may depend on what the FOV of the camera is and where the regions of interest are located. Figure 12(b) shows how the DOV of the side entrance face 1202 may be made less than 90° by tilting the CBS 1200 by -10°. The DOV from the top entrance face 1204 is unchanged since the upper and lower surfaces through which light enters and exits remain parallel, whereas the DOV from the side entrance face 1202 changes according to the CBS 1200 tilt angle since this is determined by the angle of the central inclined surface. Figure 12(c) shows how the DOV of the side entrance face 1202 may be made greater than 90° by tilting the CBS 1200 by +10°. Again the DOV from the top entrance face 1204 is unchanged whereas the DOV from the side entrance face 1202 is now 110°.

Another method of introducing small changes to the DOV of either face according to example embodiments is to place a wedge prism on one or both surfaces. This has the effect of tilting the incoming light by a few degrees, allowing the DOV to be altered by angles e.g. up to 7°. Farger-angle wedge prisms in different embodiments will deflect light through larger angles but at the expense of introducing a noticeable amount of refraction-induced colour distortion into the deflected images.

Customized CBS geometry to change DOV from side entrance face according to example embodiments

The above described example embodiments of tilting a conventional CBS is effective in changing the DOV of the side entrance surface. However, in such embodiments the central rays entering each face are non-perpendicular to the surfaces, causing some refraction which can distort the images and also limits the FOV of the top entrance face. One way of customizing the DOV of the side face without this problem is to customize the CBS geometry so that the top and side entrance faces remain perpendicular to the incoming central rays according to example embodiments. In one example embodiment shown in figure 13(a) and (b), a customized CBS 1300 geometry is used, here applied to a rear camera 1301 of a mobile phone 1303, where the angle of the diagonal surface 1302 of the CBS 1300 is changed, from 45° to 55°. The DOV of the side entrance face 1304 is altered, the DOV of the top entrance face 1306 remains unchanged at 0°.

There are many possible variations on such customized beam splitters according to various embodiments, which can also be customized to deflect light into the side face from angles greater than 90°, in order to view backwards facing regions (compare figure 12(c) described above). Figures 14 (a) and (b) show an example embodiment of such a customized CBS 1400 which is designed with a side view DOV of 110°, here applied to a rear camera 1401 of a mobile phone 1403, in which the angle of the diagonal surface 1402 is changed from 45° to 35°. In both these examples of customized, non-cubic beam splitters in figures 13 and 14, the upper and lower surfaces through which light from the forward direction (DOV = 0°) is viewed are parallel.

Different types of beam splitters such as Plate Beam Splitters according to example embodiments

The above described example embodiments have focused only on one class of beam splitters, namely cube beam splitters. There are other types which would produce a similar effect as described here in various example embodiments, though some specific features may differ. For example, Plate Beam splitters, which have the capability to tailor the reflected/transmitted ratio and may be tilted to different angles to achieve a similar effect as that described for the example embodiments above, whereby the angular separation between the two viewing faces which a camera can view can be altered in different example embodiments.

Capsule Endoscopy according to example embodiments

A capsule endoscope uses a miniature wireless camera with antenna, battery, lenses and lights etc. enclosed in a capsule to take photographs of e.g. the digestive tract. It is useful in situations where a conventional endoscope cannot reach. The capsule endoscopy camera fits inside a small capsule which the patient swallows. As the capsule travels through the digestive tract, the camera takes thousands of pictures that are transmitted to a recorder, e.g. worn on a belt around the waist.

One problem with this approach to recording e.g. the small intestine is that one has no control over the orientation of the capsule. Therefore, fitting them with a small beam splitter, for example a CBS, according to example embodiments, advantageously provides the ability to capture images from two different views which in turn can help to better visualize features towards the front or on the sidewalls that might otherwise be missed. Assembly and method according to example embodiments

In one embodiment, an assembly for switching direction of camera view comprises an illumination source for emitting light; and a beam splitter element configured to be disposed on a camera; wherein the beam splitter element is configured such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera; and wherein the illumination source is configured for switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or for switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states, and such that substantially only one of the first and second beams is directed towards the entry lens in each of the first and second illumination states and each of the first and second polarization states.

The illumination source may comprise a plurality of light emitting elements. The plurality of light emitting elements may be disposed peripherally around the beam splitter element. The illumination source may be configured such that in the first direction state, a first set of one or more of the light emitting elements is emitting light, and such that in the second direction state, a second set of one or more of the light elements is emitting light.

In the first direction state, the illumination direction may be substantially perpendicular to the first face and in the second direction state, the illumination direction may be substantially perpendicular to the second face.

The assembly may further comprise a reflecting element for directing the emitted light in one of the first or second direction states.

The beam splitter element may be non-polarizing.

The beam splitter element may be polarizing.

The assembly may further comprise a polarizing unit configured for filtering the first and/or second beams. The polarizing unit may comprise one or more polarizing elements disposed on respective faces of the beam splitter element.

The beam splitter element may be configured to be tiltable relative to the entry lens.

The beam splitter element may be configured such that one of the first and second light beams is substantially parallel to a forward direction from the entry lens and the other one is at a non zero angle relative to the forward direction.

The beam splitter element may be configured such that one of the first and second light beams is at an angle of substantially equal to or greater than 90 degrees relative to a forward direction from the entry lens.

In one embodiment, a camera device comprising the above assembly according to example embodiments is provided. Figure 15 shows flow chart 1500 illustrating a method of switching direction of camera view, according to an example embodiment. At step 1502, comprising an illumination source for emitting light is provided. At step 1504, a beam splitter element is provided on a camera such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera. At step 1506, an illumination direction of the emitted light is switched, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or at step 1508 a polarization of the emitted light is switched, independent of the illumination direction, between first and second polarization states, and at step 1510 substantially only one of the first and second beams is directed towards the entry lens in each of the first and second illumination states and/or each of the first and second polarization states.

The illumination source may comprise a plurality of light emitting elements. The method may comprise disposing the plurality of light emitting elements peripherally around the beam splitter element. The method may comprise emitting, in the first direction state, light from a first set of one or more of the light emitting elements, and emitting, in the second direction state, light from a second set of one or more of the light elements.

The method may further comprise directing the emitted light in one of the first or second direction states using a reflection element.

The beam splitter element may be non-polarizing.

The beam splitter element may be polarizing.

The method may further comprise filtering the first and/or second beams using a polarizing unit. The polarizing unit may comprise one or more polarizing elements disposed on respective faces of the beam splitter element.

The method may further comprise tilting the beam splitter element relative to the entry lens.

Embodiments of the present invention can have one or more of the following features and associated benefits/advantages:

Industrial applications of example embodiments

There are thus a wealth of commercial applications for embodiments of the present invention this technology, including for both medical endoscopes and industrial borescopes. Embodiments of the present invention offer simplicity and low cost in selecting a different field of view, requiring no actuation of the whole device or rotating prisms and associated mechanical components.

Embodiments of the present invention offer a unique method of switching the field of view in very small diameter endoscopes and borescopes.

Aspects of the systems and methods described herein such as image processing, control of the camera, control of the shutters, control of the filters and/or control of the illumination may be implemented as functionality programmed into any of a variety of circuitry, including programmable logic devices (PLDs), such as field programmable gate arrays (FPGAs), programmable array logic (PAL) devices, electrically programmable logic and memory devices and standard cell-based devices, as well as application specific integrated circuits (ASICs). Some other possibilities for implementing aspects of the system include: microcontrollers with memory (such as electronically erasable programmable read only memory (EEPROM)), embedded microprocessors, firmware, software, etc. Furthermore, aspects of the system may be embodied in microprocessors having software -based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the above device types. Of course the underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS), bipolar technologies like emitter-coupled logic (ECL), polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog and digital, etc.

The above description of illustrated embodiments of the systems and methods is not intended to be exhaustive or to limit the systems and methods to the precise forms disclosed. While specific embodiments of, and examples for, the systems components and methods are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the systems, components and methods, as those skilled in the relevant art will recognize. The teachings of the systems and methods provided herein can be applied to other processing systems and methods, not only for the systems and methods described above.

The elements and acts of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the systems and methods in light of the above detailed description.

In general, in the following claims, the terms used should not be construed to limit the systems and methods to the specific embodiments disclosed in the specification and the claims, but should be construed to include all processing systems that operate under the claims. Accordingly, the systems and methods are not limited by the disclosure, but instead the scope of the systems and methods is to be determined entirely by the claims.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "hereunder," "above," "below," and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list.

Claims

1. An assembly for switching direction of camera view comprising:

an illumination source for emitting light; and

a beam splitter element configured to be disposed on a camera;

wherein the beam splitter element is configured such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera; and

wherein the illumination source is configured for switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or for switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states, and such that substantially only one of the first and second beams is directed towards the entry lens in each of the first and second illumination states and each of the first and second polarization states.

2. The assembly of claim 1, wherein the illumination source comprises a plurality of light emitting elements.

3. The assembly of claim 2, wherein the plurality of light emitting elements are disposed peripherally around the beam splitter element.

4. The assembly of claim 3, wherein the illumination source is configured such that in the first direction state, a first set of one or more of the light emitting elements is emitting light, and such that in the second direction state, a second set of one or more of the light elements is emitting light.

5. The assembly of any one of the preceding claims, wherein in the first direction state, the illumination direction is substantially perpendicular to the first face and in the second direction state, the illumination direction is substantially perpendicular to the second face.

6. The assembly of any one of the preceding claims, further comprising a reflecting element for directing the emitted light in one of the first or second direction states.

7. The assembly of any one of the preceding claims, wherein the beam splitter element is non-polarizing.

8. The assembly of any one of claims 1 to 6, wherein the beam splitter element is polarizing.

9. The assembly of any one of the preceding claims, further comprising a polarizing unit configured for filtering the first and/or second beams.

10. The assembly of claim 9, wherein the polarizing unit comprises one or more polarizing elements disposed on respective faces of the beam splitter element.

11. The assembly of any one of the preceding claims, wherein the beam splitter element is configured to be tiltable relative to the entry lens.

12. The assembly of any of the preceding claims, wherein the beam splitter element is configured such that one of the first and second light beams is substantially parallel to a forward direction from the entry lens and the other one is at a non-zero angle relative to the forward direction.

13. The assembly of any of the preceding claims, wherein the beam splitter element is configured such that one of the first and second light beams is at an angle of substantially equal to or greater than 90 degrees relative to a forward direction from the entry lens.

14. A method of switching direction of camera view comprising the steps of:

providing an illumination source for emitting light;

providing a beam splitter element on a camera such that first and second reflected beams of the emitted light incident on first and second faces, respectively, of the beam splitter element are directable towards an entry lens of the camera;

switching an illumination direction of the emitted light, independent of a wavelength and a polarization of the emitted light, between first and second direction states and/or switching a polarization of the emitted light, independent of the illumination direction, between first and second polarization states; and

directing substantially only one of the first and second beams towards the entry lens in each of the first and second illumination states and/or each of the first and second polarization states.

15. The method of claim 14, wherein the illumination source comprises a plurality of light emitting elements.

16. The method of claim 15, comprising disposing the plurality of light emitting elements peripherally around the beam splitter element.

17. The method of claim 16, comprising emitting, in the first direction state, light from a first set of one or more of the light emitting elements, and emitting, in the second direction state, light from a second set of one or more of the light elements.

18. The method of any one of claims 14 to 17, wherein in the first direction state, the illumination direction is substantially perpendicular to the first face and in the second direction state, the illumination direction is substantially perpendicular to the second face.

19. The method of any one of claims 14 to 18, further comprising directing the emitted light in one of the first or second direction states using a reflection element.

20. The method of any one of claims 14 to 19, wherein the beam splitter element is non polarizing.

21. The method of any one of claims 14 to 19, wherein the beam splitter element is polarizing.

22. The method of any one of claims 14 to 21, further comprising filtering the first and/or second beams using a polarizing unit.

23. The method of claim 22, wherein the polarizing unit comprises one or more polarizing elements disposed on respective faces of the beam splitter element.

24. The method of any one of claims 14 to 23, further comprising tilting the beam splitter element relative to the entry lens.

25. The method of any of claims 14 to 24, wherein the beam splitter element is configured such that one of the first and second light beams is substantially parallel to a forward direction from the entry lens and the other one is at a non-zero angle relative to the forward direction.

26. The method of any of claims 14 to 25, wherein the beam splitter element is configured such that one of the first and second light beams is at an angle of substantially equal to or greater than 90 degrees relative to a forward direction from the entry lens.

27. A camera device comprising the assembly of any one of claims 1 to 13.