SCANNING SYSTEM WITH A STARING DETECTOR

FIELD OF THE INVENTION

This invention relates to scanning systems for enabling scanning of a broad field of regard.

BACKGROUND OF THE INVENTION

Problems solved by, and advantages of, staring scanning systems are described, for example, in US Patent No. 5,663,825. This patent discloses a scanning system comprising two rotating scanning elements and a fixed sensor. One scanning element is a focal optical assembly that rotates continuously and smoothly to provide azimuth and/or elevation scan. Thus, the line of sight of the assembly rotates during the scan, and so does an image provided thereby. To stabilize this image relative to the sensor, the other scanning element is used which is in the form of a fast scanning mirror spaced from the optical system at a distance kept constant throughout the scan, and which is rotated in the direction opposite to that of the optical system. This mirror holds the line of sight re-directing it to the detector, thereby 'de-scanning' the image and, consequently, enabling the sensor to integrate it and to form a sufficient image signal.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a novel scanning system for scanning a field of regard (FOR) by dividing it into a plurality of fields of view (FOVs) having different spatial orientations, said system further having a reference plane perpendicular with respect to a reference axis of the system and comprising: a fixed optical system having a line of sight in optical communication with said axis; a plurality of discrete reflective surfaces each having different orientations relative to said reference plane and facing in one of a

corresponding plurality of directions of sight to define said FOVs; each reflective surface having an operative state when its FOV is in optical communication with said optical system and a corresponding inoperative state, and being radially spaced from said reference axis at least in the inoperative state; a switching mechanism for switching between said reflective surfaces to successively bring them into their operative state while maintaining substantially unchanged their said orientation and said spatial orientation of the FOV. The switching mechanism may be adapted to successively bring each flat mirror onto said central axis by its movement in a direction parallel or perpendicular to the plane of the mirror. Alternatively, each of said flat mirrors may be fixed, being spaced from said reference axis, and the switching mechanism may comprise a folding member movable to successively establish a folded optical path between each flat reflective surface and said optical system. Such movement provided by the switching mechanism is continuous in the described embodiments, that is, while the optical folding member is moving with respect to the reference axis while optical system is scanning each FOV The folding member may also comprise a member reflecting light in a direction parallel to that of the incident light. The optical folding member is capable of reflecting light in the direction parallel to that of the incident light. Such folding member may, for example, comprise a central mirror disposed on the central axis and a lateral mirror spaced from the central axis and having a fixed orientation relative to the central mirror.

Alternatively, the folding member may be either a retroreflector such as a corner cube, or a reflector, such as a rhomboid prism or periscope, for example. The folding member may also have additional mirrors, lenses or other optical elements.

The switching may be performed by rotating the folding member about the central axis to successively bring the lateral mirror into optical alignment with the flat mirrors or reflective facets, thereby putting them in their operative state. The switching mechanism is adapted to successively bring each reflective surface onto

said central axis, optionally continuously, by its movement in a direction parallel and/or perpendicular to a plane of the reflective surface.

In the present description and claims, the term "optical alignment" means such mutual disposition of two reflective surfaces that at least a part of light reflected by one of the surfaces is admitted by the other.

In the above cases, it is preferable that the reflective surfaces (such as for example flat mirrors) constitute facets of a polygonal member, which is movable in the former case and fixed in the latter case. By virtue of this design, the switching between two adjacent facets may be performed, in both the above cases, by the movement of only one member of the system, which may simplify the system and make it compact. In the former case, this member is the polygonal member and in the latter case it is the folding member.

In other embodiments, the system further comprises a generally unidirectional polygonal member having a same number of reflective facets as a number of said facets of panoramic polygonal member, wherein said reflective facets of said unidirectional polygonal member have axially diverging directions of sight.

In another embodiment, the panoramic polygonal member comprises a first group and a second group of said facets, and further comprising a generally unidirectional polygonal member having a first number of reflective facets as a number of said first group of facets of said panoramic polygonal member, wherein said reflective facets of said unidirectional polygonal member have axially diverging directions of sight, and wherein said generally unidirectional polygonal member further comprises a second number of optically transparent windows as a number of said second group of facets of said panoramic polygonal member. The windows may have corresponding directions of sight to define other corresponding said FOVs; said windows each having an operative state when its FOV is in optical communication with said optical system and a corresponding inoperative state, and being radially spaced from said reference axis at least in the inoperative state; and wherein said switching mechanism is configured for switching between said

reflective surfaces and also said transparent windows to successively bring them into their operative state while maintaining substantially unchanged their said orientation and said spatial orientation of the corresponding FOV.

In another embodiment, the panoramic polygonal member further comprises at least one optically transparent window having a corresponding directions of sight to define another said FOVs; said at least one window having an operative state when its FOV is in optical communication with said optical system and a corresponding inoperative state, and being radially spaced from said reference axis at least in the inoperative state; and wherein said switching mechanism is configured for switching between said reflective surfaces and also said transparent window to successively bring them into their operative state while maintaining substantially unchanged their said orientation and said spatial orientation of the corresponding FOV. The window may comprise an aperture, such as a slit, hole, and so on, or may comprise a optically transparent material that is suitable for the wavelengths being detected by the optical system, for example glass or Perspex for wavelengths in the visible spectrum. Window materials that are optically transmissive for infra red wavelengths may include germanium, silicone, sapphire and so on.

The scanning system is advantageously accommodated in a housing. The housing may be substantially static, and may comprise a plurality of optically transparent windows, each said window aligned with a different said FOV.

Alternatively, the housing may comprise a fixed base and a dynamic or rotatable component mounted for rotation about said reference axis on said base. The rotatable component comprises at least one window — for example one or two windows - each window being alternately alignable with each said FOV as the component is rotated, and may be fixed to the rotatable component at an appropriate position such that the window traces a trajectory, when the component is rotated, passing in registry with each of, or at least some of, the FOVs. Rotation of said rotatable component is synchronized with rotation of said folding member about the reference axis to successively bring the lateral mirror into optical

alignment with each reflective surface and one of said at least one window, thereby putting said reflective surface in its operative state.

The housing window(s) may comprise any suitable light transmissive material that is suitable for the wavelengths being detected by the optical system, for example glass or Perspex for wavelengths in the visible spectrum; germanium, silicone, sapphire and so on for infra red wavelengths; and so on.

The optical system preferably comprises an imaging optics and a detector, such as a staring array detector, or a projection screen, for imaging each FOV in its original space orientation. The optical system is adapted for imaging each FOV in any suitable electromagnetic wavelength received therefrom, including, but not limited to, ultraviolet wavelengths, wavelengths in the human visible spectrum, infra red wavelengths, and so on.

It should be appreciated that, since the switching arrangement of the present invention does not change the space orientation of the FOVs of the facets in their operative states, the image of each FOV formed by the imaging optics on the detector or the projection screen, will always be stable, i.e. unsmeared. Due to this, the scanning process may be continuous and, therefore, fast. Also, it is possible to obtain high resolution and sharp images for each FOV, so long as the rotational speed of the folding mirror is such that each facet is in optical communication with the folding mirror, and thus with the optical system, for a time that is the same or greater than the time required for the optical system to register the image.

The facets of the polygonal member and the lateral mirror of the folding member may be equidistant from the central axis or rather may be disposed at different distances therefrom. In the former case, the facets are preferably designed to reflect light incident thereon from their substantially radial directions of sight, in substantially axial direction, and the lateral mirror is designed to admit substantially axially incident light and to reflect it in substantially radial direction. In the latter case, the reflective facets may be located closer to or further from the central axis

than the lateral mirror and, consequently, reflect light towards the lateral mirror along an optical path defining an angle with the central axis.

The system of the present invention may be used for both panoramic scanning and also for scanning fields of regard in a certain direction, thus increasing the resolution of an image obtained thereby. For this purpose, in addition to the panoramic polygonal member, the system may be provided with a generally unidirectional polygonal member having the same number of reflecting sides as the panoramic polygonal member. Such unidirectional member should preferably be so disposed in the system as to enable each of its reflective sides to admit incident light from a direction defining a sharp acute angle with said central axis, and to reflect this light in a substantially radial direction to its associated reflective facet of the panoramic polygonal mirror.

The invention is also directed to a scanning system for scanning a field of regard (FOR) by dividing it into a plurality of fields of view (FOVs), said system having a reference axis and a reference plane perpendicular thereto and comprising:

- an optical system fixedly mounted so as to have its line of sight in optical communication with said axis;

- a panoramic polygonal member having a plurality of reflective facets each radially spaced from said reference axis and facing in different directions of sight one from another to define said FOVs,

- a folding member comprising a central mirror disposed on the reference axis and a lateral mirror spaced from said reference axis, said folding member being capable of switching between said facets by successively bringing said lateral mirror into optical alignment with said facets, and thereby establishing a folded optical path between each facet and the optical system to put each facet into its operative state in which its FOV is viewed by the optical system.

The panoramic polygonal member, the folding member and, optionally, the unidirectional polygonal member constitute a scanning unit, which is also subject of the present invention.

The invention thus also relates to a scanning system for scanning a field of regard (FOR) by dividing it into a plurality of fields of view (FOVs) having different spatial orientations, said system having a reference axis and comprising:

- _. a fixed optical system having a line of sight in optical communication with said axis; an optical folding arrangement for folding light incident on a first reflecting surface arrangement thereof at a location displaced from said reference axis to a reference direction generally parallel and close to said reference axis; a switching mechanism for changing the location, particularly the angular location, of said first reflecting surface arrangement with respect to said reference axis, while enabling said optical folding arrangement to reflect incident light on said first reflecting surface arrangement towards said reference direction, such that in each said location said first reflecting surface arrangement is in optical communication with one of a corresponding plurality of directions of sight to define said FOVs. The optical folding arrangement may comprise a system of reflecting surface in periscope or corner cube configuration, having a second reflecting surface arrangement intersecting the reference axis, and the switching mechanism may be adapted for changing the location of said first reflecting surface arrangement by rotating said optical folding arrangement such that the first reflecting surface arrangement revolves around the reference axis. A plurality of flat mirrors or flat mirror arrangements may be provided to select, control, or fix the specific FOV in optical communication with the first reflective surface arrangement at a corresponding location of said first mirror arrangement around the axis, that is, as the first reflective surface arrangement revolves around the axis. The first and

second reflective surface arrangements may be flat or planar mirrors or internally reflective surfaces, for example

Thus, the invention provides a scanning system with a staring array detector, for scanning a broad field of regard, enabling a detector having a small field of view to be used. In such scanning system, the field of view is effectively temporarily held in a certain direction to permit the detector enough exposure time to obtain an unsmeared image of a corresponding portion of the field of regard.

Without being limited to theory, the scanning system of the invention may be considered to operate as follows. Assuming a simplified embodiment having a single planar mirror, and a folding member having a first mirror and a second mirror parallel to the first mirror (for example having a structure similar to a periscope or corner cube/rooftop arrangement, as described in detail herein), light from a distant scene along a particular FOV is reflected from the planar mirror to the first mirror, and thence to the second mirror, to be then reflected therefrom in a direction substantially parallel to that of the light incident on the first mirror, but displaced therefrom by a distance correlated with the spacing between the first and second mirrors.

If the first mirror is moved in a direction generally perpendicular to that of the optical path through the folding member, so as to scan the surface of the planar mirror from left to right or vice versa while maintaining optical communication between the scene and the first mirror, then the image of the scene as seen from the perspective of the second mirror will remain substantially unchanged. This is so, since, if the scene is at a relatively large distance from the planar mirror, incident rays from any point in the scene are substantially parallel when arriving at any part of the planar mirror. Accordingly, as viewed by the second mirror, there is substantially no change in the image received thereat from the first mirror, as this traverses the length of the planar mirror from left to right or vice versa.

If the second mirror is now constrained to remain in substantially the same location while the first mirror scans the planar mirror, for example by rotating the folding member about an axis passing through the second mirror, then, when

viewing the second mirror along this axis, even as the first mirror is moved with respect to the planar mirror, the image of the scene will remain substantially unchanged until the first mirror is out of optical communication with the planar mirror. Accordingly, a staring detector in optical communication with the second mirror along the rotational axis will have an unsmeared and substantially static view of the FOV of the planar mirror as this is scanned by the first mirror during rotation of the folding member about the axis. By having a number of separate planar mirrors, and/or separate specific arrangements of planar mirrors, and/or windows each having its own FOV, and each arranged such as to be in optical communication with the first mirror during a part of the first mirror's rotation about the aforesaid axis, the view as seen by the staring detector will remain unsmeared and substantially static with each planar mirror (and/or mirror arrangement and/or window) in turn, eventually switching to a different FOV as the first mirror of the folding member moves out of optical communication with one planar mirror and into optical communication with another planar mirror (and/or mirror arrangement and/or window).

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, specific embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 illustrates the three-dimensional space around a scanning point P on a reference axis Z, which may include scenes of interest for the scanning system of the invention;

Fig. 2(a) is a schematic illustration of the optical setup of a scanning system in accordance with a first embodiment of the present invention accommodated in a static housing; Fig. 2(b) is a schematic illustration of the embodiment of Fig. 2(a) accommodated in a dynamic housing.

Fig. 3 is a schematic illustration of the optical setup of a scanning system in accordance with a variation of the embodiment of Figs. 2(a) or 2(b);

Figs. 4(a) and 4(b) are, respectively, isometric and plan views of a panoramic polygonal member used in the scanning system illustrated in Figs. 2(a) or 2(b);

Figs. 5(a), 5(b) and 5(c) illustrate the effect on the direction of FOV by changing the orientation of a corresponding facet of the embodiment of Figs. 2(a) or 2(b);

Fig. 6 is a schematic illustration of the optical setup of a scanning system in accordance with a second embodiment of the present invention;

Figs. 7(a) and 7(b) are, respectively, isometric and plan views of a panoramic polygonal member used in the scanning system illustrated in Fig. 6;

Figs. 8(a) and 8(b) are, respectively, isometric and plan views of a unidirectional polygonal member used in the scanning system illustrated in Fig. 6; Fig. 9 is a schematic illustration of the optical setup of a scanning system in accordance with a variation of the embodiment of Fig. 6;

Fig. 10 is a schematic plan view of a scanning unit used in the scanning system of Fig. 6, and comprising the polygonal members shown in Figs. 7(a) and 7(b) and 8(a) and 8(b); Fig. 11 is a schematic illustration of the optical setup of a scanning system in accordance with another variation of the embodiment of Fig. 6;

Fig. 12 is an optical scheme illustrating the scanning system illustrated in Fig. 6, in operation.

Figs. 13(a) and 13(b) are schematic illustrations of the optical setup of a scanning system in accordance with a third embodiment of the present invention;

Figs. 14(a) and 14(b) are, respectively, isometric and plan views of a panoramic polygonal member used in the scanning system illustrated in Figs. 13(a) and 13(b);

Figs. 15(a) and 15(b) are, respectively, isometric and plan views of a unidirectional polygonal member used in the scanning system illustrated in Figs. 13(a) and 13(b);

Fig. 16 is a schematic plan view of a scanning unit used in the scanning system of Figs. 13(a) and 13(b), and comprising the polygonal members shown in Figs. 7(a) and 7(b) and 8(a) and 8(b);

Figs. 17(a) and 17(b) are a schematic illustration of the optical setup of a scanning system in accordance with a variation of the embodiment of Figs. 13(a) and 13(b); Figs. 18(a) and 18(b) are schematic illustrations of the optical setup of a scanning system in accordance with a fourth embodiment of the present invention;

Figs. 19(a) and 19(b) are, respectively, isometric and plan views of a panoramic polygonal member used in the scanning system illustrated in Figs. 18(a) and 18(b); and Fig. 20 is a schematic illustration of a variation of the optical setup of the scanning system of Figs. 18(a) and 18(b).

DETAILED DESCRIPTION OF EMBODIMENTS

The three-dimensional space around a reference point P on a reference axis Z, which may include scenes of interest for the scanning system of the invention, is illustrated in Fig. 1. Point P is not necessarily a real point, but may be a convenient virtual reference point where one or a number of scanning directions may intersect the reference axis Z. A field of view (FOV) has a space orientation, which may be conveniently expressed with respect to point P in terms of a first angle β with respect to axis Z ₅ and a second polar angle θ defined on any suitable reference plane XY orthogonal to axis Z. For example, in this figure, the FOV marked as FOVi has a space orientation (θi, βi), while the FOV marked as FOV _A has a space orientation (θ ₂ , β ₂ ). In practice, each field of view also has an angular width in both the β and θ directions, which depends on the optical nature of an imaging means or an observer at point P.

These fields of views are illustrated in Fig. 1 as being along planes which are parallel to and intersect the axis Z. Additionally, however, it may be possible to modify the field of view to include an angular component (not shown) with respect to a particular XY plane at a particular point Q thereon displaced from the reference axis Z.

In general, a field of regard (FOR) may be considered as a continuous or discrete plurality of FOVs, each at the same or at a different angle β, and within a particular range of polar angles δθ. While this range δθ may in some embodiments be fully panoramic, i.e., a full 360°, in other embodiments the range δθ may be any other partially panoramic range, for example including but not limited to a range

δθ of 45°, 60°, 90°, 120°, 135°, 180°, 240°, 270°, and so on. Further, it is also possible for the FOR to include more than partially panoramic range, for example, one partial panoramic range at θ = 0° to θ = 90°, and a second panoramic range from θ = 180° to θ = 270°, and so on, and wherein in each panoramic range there are one or more FOVs.

The FOVs according to the invention, for a given FOR, do not all necessarily converge on the same point P.

In a first embodiment of the present invention, a scanning system is provided for scanning a field of regard (FOR) in a plurality of directions θ in up to a 360° panoramic view around axis Z. In this embodiment, each FOV, or for convenience say the center of a FOV, may subtend at P an angle β, which is substantially greater than 0° and less than 180°, for example, β= 30°, or 45°, or 90° or 135°. A schematic illustration of a scanning system 1 according to the first embodiment of the present invention is shown in Fig. 2(a). The scanning system 1 is designed for panoramic scanning with the 360° field of regard (FOR) around the axis Z by dividing it into a plurality of field of views (FOVs). The scanning system 1 has a central axis associated therewith that is co-axial or coincident with reference

axis Z and a reference plane XY (not shown) perpendicular to axis Z. The scanning system 1 comprises a scanning unit, generally designated as 10, and a stationary optical system 12. The optical system 12 is fixedly mounted to any desired structure so that the line of sight or optical axis 23 of the optical system 12 coincides with the central axis Z.

The scanning unit 10 comprises an optical folding member 20 rotatable about the axis Z by a drive (not shown) and a stationary panoramic convex polygonal member, designated 30. The folding member 20 is located optically, and in general may also be located axially, between the optical system 12 and the polygonal member 30. Referring to Fig. 3, an alternative mutual disposition of the folding member (indicated at 20') and the polygonal member 30 is shown, in which while the folding member 20' is located optically between the optical system 12 and the polygonal member 30, nevertheless the axial disposition of the polygonal member 30 is now between the optical system 12 and the folding member 20'. In eitiher case, the optical axis 23 of optical system 12 may alternatively be oriented at any angle with respect to axis Z, and may optionally be offset with respect thereto, and any suitable system of mirrors or other reflectors, or other optical elements, for example, may be used to provide the required optical communication between the folding member 20 (or 20') at the rotational axis Z thereof and the optical system 12.

The folding member 20 may have a rigid construction extending generally parallel to the plane XY and it is designed to admit incident light traveling in a generally axial direction with respect to axis Z and at a location spaced from the central axis Z, and to direct this incident light towards the optical system 12, along the central axis Z as illustrated. For this purpose, the folding member 20 comprises a central mirror 22 disposed on the central axis Z and a lateral mirror 24 spaced radially from the central mirror 22 and having a fixed orientation relative thereto. In the scanning unit shown in Fig. 2(a), the folding member 20 is in the form of a periscope, in which the central mirror 22 and lateral mirror 24 are in facing relationship located on parallel spaced planes. Alternatively, folding member 20

may comprise any other suitable arrangement, for example a retroreflector such as a corner cube 20' shown in Fig. 3, in which the central mirror 22 and lateral mirror 24 are in facing relationship and located on intersecting planes, and in which advantageously one of the two mirrors 22, 24, comprises a pair of roof mirrors, i.e., an assembly of two plane mirrors, typically orthogonal one to the other, and attached to each other along a "roof edge", in traditional roof or V-formation. Alternatively, a porro prism may be used instead of the roof mirror arrangement.

In any case, the central mirror 22 and lateral mirror 24 may each comprise for example silvered or other mirroring surfaces, or alternatively may reflect by means of internal reflection through an optically dense medium, for example. The folding member may also be of any other appropriate design and may have additional mirrors, lenses or other optical elements.

The panoramic convex polygonal mirror or member 30 of Figs. 2 and 3 is shown separately in Figs. 4(a) and 4(b), and comprises six substantially flat or planar reflective surfaces or facets 32, each facing in different generally radial directions A to F (with reference to axis Z), that define respective fields of view FOV _A to FOV _F (shown in Fig. 1) having different space orientation, i.e., each having a different angle θ. The directions of sight A to F of any or all of the reflective facets 32 do not need to be strictly radial, i.e., lie along the XY plane, but may optionally form an angle with the plane XY instead, i.e., having an angle β that is about 90°, or alternatively different from 90°. Furthermore, the plane of each facet 32 is not necessarily perpendicular to a radial direction from any point on axis Z, but alternatively may be set at any inclination with respect to the X-Y plane, as desired. The number of reflective facets 32 does not need to be six, but may be any other appropriate number, greater than six or less than six, for example including, but not limited to 2, 3, 4, 5, 7, 8, 9, 10 or more facets. A faster image acquisition time for the system 12 generally enables a greater number of facets to be employed in the polygonal member 30, and thus allow a greater number of different views in the θ direction to be scanned. Also, The number of mirrors used may be based on

width of the field of view, for example if the width (in the θ direction) is, say, 60°, then for a full 360° field of regard, 6 reflective facets would be needed, while with a narrower width of field of view of 20°, 18 facets would be needed.

Reverting to Fig. 2(a), each reflective facet 32 of the polygonal member 30 is laterally or radially spaced from the central axis Z to generally the same distance as the lateral mirror 24 of the folding member 20. In operation, light along each of these directions A to F and incident on the respective facets 32 may be reflected, in turn, in a direction towards lateral mirror 24, and thus the optical system 12, when the folding member 20 is rotated about axis Z to become optically aligned with the particular facet 32.

Further, each reflective facet 32 is inclined relative to the plane XY by an angle α so as to admit incident light from its direction of sight (designated as A in this figure) and to reflect it in generally axial direction towards the lateral mirror 24 of the folding member 20. The angle α may have the same value for all the facets 32, or alternatively the value of angle α (and thus angle β for the particular angle θ, see Fig. 1) may vary from facet 32 to facet 32.

Angle α is in general geometrically related to the corresponding angle β of the FOV of the facet 32, when the field of view intersects the axis Z. However, it should be noted that the facets 32 may have any orientation to the X-Y plane (which is orthogonal to the Z-axis), as already indicated, so long as light may eventually be reflected to the folding member 20 and thus to the optical system 12. Thus, considering an imaginary line N (Figs. 5(a) to 5(c)) perpendicular to the plane of the facet at an incident point Q, this imaginary line N may comprise an angular component inclined along a plane parallel to and intersecting axis Z, and/or an angular component inclined along a plane parallel to the X-Y plane. In such cases where the line N is inclined with respect to both such planes, the field of view viewed by the folding member may not necessarily be aligned with a point P on axis Z.

As illustrated in Figs. 5(a) to 5(c), for cases where the imaginary line N lies along a plane parallel to and intersecting axis Z, different values for angle α define different directions of the FOVA- Thus for a given geometry of system 10, appropriately choosing the angle α for each of the facets 32 can determine the FOV in terms of angle β and angle θ corresponding to the facet. For example, if the system 10 is to be mounted on a ceiling of a room of certain floor dimensions, and it is desired to view a FOR around the room (δθ = 360°) from the floor to a height of x meters from the floor (for example, angle β = 45°, and field of view width 20°x20°), the angle α for the facets 32 must be greater than for a similar situation in which the room has a lower ceiling (and therefore angle β has to be greater than 45°).

In the illustrated embodiment, the angle of each facet 32 is fixed. In other variations of this embodiment, though, a suitable mechanism may be provided for actively changing the angle α of one or more facets 32 as desired, to enable the direction of the field of view, in particular the corresponding angle β, to be further controlled.

Reverting to Fig. 2(a), the scanning system 1 is accommodated in a suitable static housing 29, which can protect the system from mechanical damage, ingress of moisture, dirt, particles, and so on. In the embodiment illustrated, the housing 29 is a substantially static component, and comprises a plurality of optically transparent planar windows 28, made from a suitable transparent material, for example glass, Perspex, and so on. The windows 28 are arranged in generally radial directions on the housing 29 such that each window 28 is substantially perpendicular to the light path from a particular field of view towards a corresponding facet 32. Thus, each facet is in constant optical communication with its field of view via the corresponding window 28. The size of each window is generally such as to allow unobstructed view of the corresponding FOV. A feature of this housing 29 is that it may be hermetically closed, if desired, and has no

moving parts. On the other hand, a large number of windows may have an important economic cost element associated therewith.

Alternatively, and referring to Fig, 2(b), the system may be accommodated in a dynamic housing 29', which may comprise a fixed base 27 and component 26 or cover that is rotatable about axis Z with respect to the base, but otherwise function as housing 29 of Fig. 2(a) in protecting the system 1 from the external environment, mutatis mutandis. The rotating component 26 may be opaque or translucent, and comprises a single window 28' that is alternately in registry with each facet 32 in turn as the component is rotated about axis Z. The rotation of this component 26 is synchronized with the rotation of the folding member 20, so that the single window 28' is in registry with the particular facet 32 that the folding member 20 is in optical communication with. Optionally, the folding member 20 may be mechanically coupled with component 26. A feature of this embodiment relative to housing 29 is that only a single window is needed, reducing costs and possibly weight, though on the other hand a driving mechanism is required to rotate the component 26.

The first embodiment has been described for an application in which a full panoramic view (δθ = 360°) is provided. Other variations of the embodiment may also be provided in which the angular range in the θ direction may be more limited, for example the angular range δθ may be about 90°, and thus may be suitable for applications in which it is desired to place the scanning system against a corner of a room. In such a variation, the polygon member 30 may be approximately a quarter of that illustrated for the embodiment of Figs. 4(a) and 4(b), and the folding member may alternatively be adapted for oscillating by an angle θ = 0° to θ = 90°, for example. Similarly, the angular range δθ may be about 180°, and thus may be suitable for applications in which it is desired to place the scanning system against a wall of a room. In such a variation, the polygon member 30 may be approximately a half of that illustrated for the embodiment of Figs. 4(a) and 4(b), and the folding

member may still rotate fully around 360°, or alternatively may be adapted for oscillating by an angle θ = 0° to θ = 180°, for example.

A second embodiment of the present invention, illustrated in Fig. 6, comprises features and elements of the first embodiment as described above, mutatis mutandis, with differences as will become clearer herein. According to the second embodiment, a scanning system is provided for scanning a field of regard (FOR) in a plurality of directions at angle θ in up to a 360° panoramic view around axis Z. However, in this embodiment, each FOV, or for convenience say the center of a FOV, may be considered to subtend at a convenient point P an angle β, which is equal or not much greater than 0°, for example, β= 0°, 5°,or 10° or 15°, or up to 30° and is thus particularly applicable for applications in which a focused area of interest substantially close to axis Z is to be scanned.

Thus, the scanning system 101 according to the second embodiment of the present invention is shown in Fig. 6 and comprises: scanning unit 110; stationary optical system 112 having optical axis 123 co-axial with the central axis Z; rotatable optically folding member 120; and a stationary panoramic convex polygonal member 130; similar to the components described with respect to the first embodiment, mutatis mutandis. Additionally, the system 101 according to this embodiment further comprises a second stationary generally unidirectional polygonal member, designated 140, and the scanning system 101 is designed for scanning a field of regard (FOR) in a certain general direction G, substantially along or at small angles β to the axis Z, by dividing the FOR into a plurality of field of views (FOVs). Thus by "generally unidirectional" is meant a plurality of directions that are either parallel or diverging one from another at small angles, typically about 30° or less.

In this embodiment, and referring to Figs. 7(a) and 7(b), the convex polygonal member 130, which by way of illustration comprises six substantially flat or planar reflective surfaces or facets 132, each facing in different generally

radial directions of sight A to F (with reference to axis Z) that define respective fields of view FO V _A to FO V _F respectively (shown in Fig. 1) having different spatial orientations (at least regarding angle θ) one from the other. As with the first embodiment, the facets 132 may have the same or different angular settings α (i.e., provide FOVs with corresponding angle β) with respect to axis Z.

As may be seen in Figs. 8(a) and 8(b), the unidirectional polygonal mirror or member 140 of this embodiment is substantially concave and has the same number of reflective sides or facets 142 as the panoramic polygonal member 130. The reflective facets 142 have directions of sight Gl to G6 all facing generally in the same direction G, and each diverging at the same or a different angle β in accordance with the desired FOR of the system, and defining respective fields of view FOVi to FO Vβ (shown in Fig. 1) that have different spatial orientations (angle θ) circumferentialry around the axis Z. In the illustrated embodiment, and reverting to Fig. 6, each reflective facet 142 is also inclined at the same angle α as the corresponding facing facet 132, and is thus so inclined relative to the plane XY as to reflect light incident from its direction of sight (for example designated as Gl in the figure), at corresponding angle β, along the direction of sight of its associated reflective facet 132 of the panoramic polygonal member 130.

In operation, light along each of these directions Gl to G6 and incident on the respective facets 142 of second polygonal member 140 are reflected towards the facing corresponding facet 132 of the first polygonal member 130, and may subsequently be reflected, in turn, in a direction towards lateral mirror 124, and thus the optical system 112, when the folding member 120 is rotated about axis Z to become optically aligned with the particular pair of facets 132 and 142. The folding member 120 is located optically, and in general also axially, between the optical system 112 and the polygonal members 130 and 140. Referring to Fig. 9, an alternative mutual disposition of the folding member (indicated at 120') and the polygonal members 130 and 140 is shown, in which while the folding member 120' is located optically between the optical system 112 and the polygonal

members 130 and 140, nevertheless the axial disposition of the polygonal members 130 and 140 is now between the optical system 112 and the folding member 120'.

Fig. 10 schematically shows a plan view of the scanning unit 110, when assembled from the panoramic and unidirectional polygonal members, 130 and 140, respectively, and the folding member 120. In the embodiment illustrated in Figs. 6 and 10, the unidirectional polygonal member 140 is generally concave and surrounds the panoramic polygonal member 130. However, this does not necessarily have to be the case, and as for example is shown in Fig. 11, it is possible for the second polygonal member 140' to be generally convex and surrounded by a generally concave first polygonal member 130'.

In the embodiments of Figs. 6 and 11, the panoramic and unidirectional polygonal members 130 and 140 (indicated at 130' and 140' in Fig. 11) are disposed so that the reflecting facets 142 of the unidirectional polygonal member 140 (or 140') are generally parallel to the corresponding reflective facets 132 of the panoramic polygonal member 130 (or 130'). However, as shown in Fig. 9, the reflecting facets 132 and the reflecting facets 142 may be inclined relative to the plane XY or axis Z in different senses and diverge with respect to one another.

With reference to Figs. 6, 9, 11, and also to Fig. 12, in operation of the scanning unit 10, the light incident on a particular reflective facet 142 is redirected thereby to the associated reflective facets 132 and is reflected thereby towards the folding member 120. The folding member 120 is continuously rotated about the axis Z, preferably with a constant rotational speed, to switch between the reflective facets 132. Thereby, these facets are successively brought into their operative position in which their FOVs, and consequently the FOVs of the respective reflective facets 142, are viewed by the optical system 112. During the scanning process, the lateral mirror 124 of the folding member 120 is continuously brought into optical alignment with one after another portion of each reflective facet 132, moving from one reflective facet 132 to another, neighboring reflective facet. During such optical alignment, the lateral mirror 124 admits light from the reflective facet 132 which it is passing by, and reflects this light to the central

mirror 122 which in turn re-directs the light into the optical system 112. With the folding member 120 being rotated continuously, the lateral mirror 124 is continuously brought into the alignment with all the facets 132 in turn, thereby switching successively between the fields of view FOVi to FOV ₆ of the reflective sides 142, and consequently scanning the entire FOR. Since during the scanning process, each reflective facet 132, its corresponding reflective side 142 and the lateral and central mirrors 122 and 124 are in fixed disposition relative to each other, to the detector and to the associated FOV, the FOV is viewed by the optical system in its original space orientation during the entire scanning of this FOV. As with the first embodiment, and reverting to Fig. 6, the scanning system

101 may be similarly accommodated in a suitable static housing 129, mutatis mutandis, wherein the plurality of optically transparent planar windows 128 are arranged in generally axial directions such that each window 128 is substantially perpendicular to the light path from a particular field of view towards a corresponding reflective side 142. Alternatively, and in a similar manner of the first embodiment as illustrated in Fig. 2(b), mutatis mutandis, the system may instead be accommodated in a dynamic housing, which may instead comprise a fixed base a rotating component having a single window that is alternately in registry with each reflective side 142 in turn as the component is rotated about axis Z. With reference to Fig. 12, the optical system 12 may comprise any suitable image acquisition system, for example any suitably designed camera for day or night vision. The optical system 12 may comprise an imaging optics 50 having a relatively small field of view and adapted to operate in collimated light designated as R, and an array detector 52 located in the focal plane of the imaging optics. The field of view of the imaging optics may, for example, be 20°xl6°. Optionally, the system of the present invention may be miniaturized, wherein a front lens 54 of the imaging optics 50 is configured to have a very small entrance pupil and each reflective facet 132, when in its operative position, is located in the vicinity of this entrance pupil. Alternatively, the lateral member 124 of the folding member may be disposed in the vicinity of the entrance pupil. Clearly, the optical system may be

designed to operate in any desired spectral range, and it may, accordingly, comprise such optical elements as filters 56, for example. In any case, it is to be noted that the optical system may take any number of images when aligned with each particular FOV, each image having the same or a different integration time, F number, operative spectral range (for example, visible spectrum, UV, IR ₅ and so on). Further, the optical system may include a variety of filters (for example a UV filter, or an IR filter), each of which may be selectively engaged so as to appropriately filter the light reaching the optical system, and any suitable mechanism may be used for this. Furthermore, when the optical system is operating in a particular spectral range (or example UV or IR), the optical system may be configured for obtaining a plurality of images, while the folding member is still at the same FOV, each image being at a different portion of the spectral range.

A similar arrangement as illustrated in Fig. 12 may be provided for the first embodiment, mutatis mutandis. When the folding member 120 is rotated, one or more image is obtained by the optical system 112 of every field of view FOVi to FOV ₆ for the second embodiment, (or FOV _A to FOV _F . for the first embodiment). Each such image is obtained when the lateral mirror 124 of the folding member 120 is in the optical alignment with at least a portion of each reflective facet 132 for a 'staring' time which corresponds to the integration time of several frames of the detector 52. Also, at least one exposure time is spent when the lateral mirror 124 passes from its alignment with one reflective facet 132 into alignment with another, neighboring facet. Images obtained during each scanning cycle are then combined in a full image. This full image has a resolution much higher than that obtained with the same detector without the division of the FOR into a plurality of the FOVs corresponding to the number of reflective sides in the polygonal members of the scanning unit 110 according to the present invention.

Clearly, the system according to the second embodiment can be modified to operate as the first embodiment by removing the second polygonal member 140.

A third embodiment of present invention, illustrated in Figs. 13(a) to 16, comprises features and elements of the first and second embodiments as described above, mutatis mutandis, with some differences as will become clearer herein. This embodiment essentially enables some features of the first and second embodiments to be combined. Thus, according to the third embodiment, a scanning system is provided for scanning a field of regard (FOR) in a plurality of directions at angle θ in up to a 360° panoramic view around axis Z, and each FOV, or for convenience say the center of a FOV, may subtend at a convenient point P an angle β, which may be either equal or not much greater than 0°, or, instead, substantially greater than 0° but less than 180°, and is thus particularly applicable for applications in which both a panoramic view around the system and also a focused area of interest substantially close to axis Z are to be scanned.

Thus, the scanning system 201 according to the third embodiment of the present invention comprises: scanning unit 210; stationary optical system 212 having optical axis 223 co-axial with the central axis Z; rotatable optically folding member 220; and a stationary panoramic convex polygonal member 230; similar to the components described with respect to the first and second embodiment, mutatis mutandis.

However, and as illustrated in Figs. 14(a) and 14(b), while the convex polygonal member 230 is similar to the convex polygonal member as described for the first and second embodiments, mutatis mutandis, by way of example the polygonal member 230 for the third embodiment comprises twelve facets 232, rather than six, which for convenience are grouped into two groups of facets that are arranged in an alternating manner around the periphery of the member 230, and are further designated as facets 232a and 232b, respectively. In other variations of this embodiment the member 230 may have a greater or lesser number of facets 232, and these may be arranged in any manner in the member 230. Optionally, each of the facets 232a, 232b may be similar or different in either orientation α and/or size/shape, and so on, to one another.

Additionally, the system 201 according to this embodiment further comprises a modified second stationary partially panoramic and partially unidirectional polygonal member, designated 240. The scanning system 201 is accordingly designed for scanning a field of regard (FOR) that is partially in a certain general direction G, substantially along or at small angles to the axis Z, and partially in a plurality of directions in up to a 360° panoramic view around axis Z, by dividing it into two pluralities of field of views (FOVs), thus affording a relatively broader three-dimensional FOR. As may be seen in Figs. 15(a) and 15(b), the unidirectional polygonal mirror or member 240 of this embodiment is substantially concave and has the same number of reflective sides or facets 242 corresponding to number of facets 232b of one group of facets 232 of the panoramic polygonal member 230. Furthermore, the polygonal member 240 further comprises a plurality of optically transparent windows 241, which may comprise slits as illustrated in the figures, or alternatively apertures, or alternatively may comprise transparent facets made from an optically transparent medium. The polygonal member 240 comprises the same number of windows 241 as the number of facets 232a of the member 230, and are arranged in the illustrated embodiment in an alternating manner with respect to the reflective facets 242 around the periphery of the member 240. Thus, when the polygonal members 230, 240 are axially mounted with respect to one another (Fig. 16) for enabling the system 201 to operate, the windows 241 are in opposed relationship to and in optical communication with the facets 230a, while the facets 242 are in opposed relationship to and in optical communication with facets 230b. Each of the six facets 232a, and six facets 232b, face in different generally radial directions A to F, and G ₁ to G ₆ , respectively (at least regarding the corresponding angle θ with reference to axis Z). As will become clearer herein, one set of directions A to F define respective fields of view FOVA to FO V _F (shown in Fig. 1) having different space orientations. As with the first embodiment, the directions of sight A to F of any or all of the reflective facets 232a do not need to

be strictly radial, i.e., lie along the XY plane, but may optionally form an angle with the plane XY instead, i.e., may have a corresponding angle β different from 90°. As the windows 241 are in the line of sight of directions A to F, being optically transparent they allow the facets 232a to operate in the same manner as the facets 30 of the first embodiment, mutatis mutandis. As illustrated in Fig. 13(b), in operation, light along each of these directions A to F and incident on the respective facets 232b may be reflected, in turn, in a direction towards lateral mirror 224, and thus the optical system 212, when the folding member 220 is rotated about axis Z to become optically aligned with the particular facet 232b. As with the second embodiment, the reflective facets 242 have directions of sight Gl to G6 all facing generally in the same direction G, and each diverging at the same or a different angle β in accordance with the desired FOR of the system, and defining respective fields of view FO Y ₁ to FOV ₆ that have different spatial orientations circumferentially around the axis Z. In the illustrated embodiment, and reverting to Figs. 14(a), 14(b), each reflective facet 242 is also inclined at the same angle α as the corresponding facing facet 232b, and is thus so inclined relative to the plane XY as to reflect light incident from its direction of sight (designated as Gl), at the same corresponding angle β, along the direction of sight of its associated reflective facet 232 of the panoramic polygonal member 230. However, the angle α (and therefore the corresponding angle β) may vary between the facets.

Thus, light along each of these directions Gl to G6 and incident on the respective facets 242 of second polygonal member 240 may be reflected towards the facing corresponding facet 232b of the first polygonal member 230, and may subsequently be reflected, in turn, in a direction towards lateral mirror 224, and thus the optical system 212, when the folding member 220 is rotated about axis Z to become optically aligned with the particular pair of facet 232b and 242.

Thus, the system according to this embodiment is configured such that in operation, as the folding member 220 is rotated about axis Z, it alternately becomes optically aligned with a pair of facets 232b and 242, providing an image to the optical system of one or another of the field of views FOV ₁ to FOV ₆ , or with a

window 241 and facet 232b, providing an image to the optical system of one or another of the field of views FO V _A to FOV _F , as illustrated in Figs. 13(a) and 13(b), respectively.

A variation of this embodiment is illustrated in Figs 17(a), 17(b) similar to the embodiment illustrated in Fig. 3 and Fig 9, mutatis mutandis, in which the reflecting facets 232a, 232b, and the reflecting facets 242 and windows 241, may be inclined relative to the plane XY or axis Z in different senses and diverge with respect to one another, and in which a different configuration for the folding member 220' is provided. Reverting to Figs. 13(a) and 13(b), the scanning system 201 may be accommodated in a suitable dynamic housing 229', similar to that described for the first and second embodiments, mutatis mutandis, but with some differences with ' respect thereto. Thus, while the housing 229' also comprises a fixed base 227 and rotatable component 226, there are two windows 228a and 228b, which are typically at the same radial position with respect to axis Z, but face in different directions. The window 228a is situated on the component 226 such that it is alternately in registry with each facet 232 in turn as the component is rotated about axis Z, being substantially perpendicular to the light path from a particular field of view towards the corresponding facet 232. On the other hand, window 228b is situated on the component 226 such that it is alternately in registry with each reflective facet 242 in turn as the component is rotated about axis Z, being substantially perpendicular to the light path from a particular field of view towards the corresponding reflective facet 242.

The rotation of this component 226 is synchronized with the rotation of the folding member 220, so that each window 228a, 228b is alternately in registry with the particular facet 232 or reflective facet 242 that the folding member 220 is in optical communication with.

Alternatively, the system 201 may be accommodated in a static housing (not shown) similar to that described for the first and second embodiments, mutatis mutandis, with the main difference that such a housing now comprises two sets of

windows, one set of windows permanently aligned with facets 232, and the second set aligned with reflective facets 242.

A fourth embodiment of present invention, illustrated in Figs. 18(a) to 19(b), comprises features and elements of the first, second and third embodiment as described above, mutatis mutandis, with some differences as will become clearer herein. This embodiment also provides similar features to those provided by the third embodiment but in a simpler form.

Thus, according to the fourth embodiment, a scanning system is also provided for scanning a field of regard (FOR) in a plurality of directions at angle θ in up to a 360° panoramic view around axis Z, and each FOV, or for convenience say the center of a FOV, may subtend at a convenient point P an angle β, which may be either equal or not much greater than 0°, or instead substantially greater than 0° but less than 180°, and is thus also particularly applicable for applications in which both a panoramic view around the system and also a focused area of interest substantially close to axis Z are to be scanned.

The scanning system 301 according to the fourth embodiment of the present invention thus comprises: scanning unit 310; stationary optical system 312 having optical axis 323 co-axial with the central axis Z; and rotatable optically folding member 320 having mirrors 322, 324; similar to the components described with respect to the first and second embodiment, mutatis mutandis.

Additionally, the system 301 according to this embodiment further comprises a modified stationary partially panoramic and partially unidirectional convex polygonal member, designated 330, and the scanning system 301 is accordingly designed for scanning a field of regard (FOR) that is partially in a certain general direction G, substantially along or at small angles to the axis Z, and partially in a plurality of directions in up to a 360° panoramic view around axis Z, by dividing it into a plurality of field of views (FOVs), thus affording a relatively broader three-dimensional FOR.

As illustrated particularly in Figs. 19(a) and 19(b), the convex polygonal member 330 comprises a plurality of reflective facets 332, similar to the convex polygonal member as described for the first and second embodiments, mutatis mutandis, and by way of example the polygonal member 330 for the third embodiment also comprises six facets 332. Further, though, the polygonal member 330 also comprises a plurality of optically transparent windows 331, which may comprise slits as illustrated in the figures, or alternatively apertures, or alternatively may comprise transparent facets made from an optically transparent medium. The polygonal member 330 may comprise the same number of windows 331 as the number of facets 332, and in the illustrated embodiment the windows 331 are arranged in an alternating manner with respect to the reflective facets 332 around the periphery of the member 330. In other variations of this embodiment the member 330 may have a greater or lesser number of facets 332 than six, and these may be arranged in any manner in the member 330. Optionally, each of the facets 332 may be similar or different in either orientation α and/or size/shape, and so on, to one another. Additionally or alternatively, the member 330 may have a greater or lesser number of windows 331 than six, and these may be arranged in any manner in the member 330. Optionally, each of the windows 331 may be similar or different in either orientation α and/or size/shape, and so on, to one another. Further, the windows 331 and facets 332 may be arranged in any desired manner with respect to one another.

Each of the six facets 332 faces in a different generally radial direction A to F, respectively (at least regarding the corresponding angle θ with reference to axis Z). As will become clearer herein, one set of directions A to F define respective fields of view FOVA to FO V _F (shown in Fig. 1) having different space orientations. As with the first or third embodiments, the directions of sight A to F of any or all of the reflective facets 232a do not need to be strictly radial, i.e., lie along the XY plane, but may optionally form an angle with the plane XY instead, i.e., may have a corresponding angle β different from 90°; moreover, the facets may also be oriented with respect to the XY plane such that an imaginary line orthogonal to each facet

may be inclined at any desired angle with respect to axis Z, as is also the case with the other embodiments described herein, mutatis mutandis. As the facets 332 are in the line of sight of directions A to F, they operate in the same manner as the facets 30 of the first embodiment, mutatis mutandis. As illustrated in Fig. 18(b), in operation, light along each of these directions A to F and incident on the respective facets 332 may be reflected, in turn, in a direction towards lateral mirror 324, and thus the optical system 312, when the folding member 320 is rotated about axis Z to become optically aligned with the particular facet 332.

The windows 331, being optically transparent, have directions of sight Gl to G6 all facing generally in the same direction G, as with the second embodiment, mutatis mutandis. Each such direction of site may be diverging at the same or a different angle β in accordance with the desired FOR of the system, and defining respective fields of view FOVχ to FOV ₆ that have different spatial orientations circumferentially around the axis Z. Thus, light along each of these directions Gl to G6 passes through each corresponding window 331 and is incident on lateral mirror

324, and is thus received by the optical system 312, when the folding member 320 is rotated about axis Z to become optically aligned with the particular window 331.

Thus, the system according to this embodiment is configured such that in operation, as the folding member 320 is rotated about axis Z, it alternately becomes optically aligned with a window 331, providing an image to the optical system of one or another of the field of views FOVi to FOV ₆ , or with a facet 332, providing an image to the optical system of one or another of the field of views FO V _A to FOVp, as illustrated in Figs. 18(b) and 18(a), respectively.

In a variation of this embodiment, the convex polygonal member 330 may be removed, defining a plurality of respective fields of view including FOVi to FOV ₆ that have different spatial orientations circumferentially around the axis Z, along directions Gl to G6, for example.

The scanning system 301 may be accommodated in a suitable dynamic housing 329', similar to that described for the third embodiment, mutatis mutandis, and thus comprises a fixed base 327 and rotatable component 326 having two

windows 328a and 328b. The radial window 328a is situated on the component 326 such that it is alternately in registry with each facet 332 in turn as the component is rotated about axis Z, being substantially perpendicular to the light path from a particular field of view towards the corresponding facet 332. On the other hand, axial window 328b is situated on the component 226 such that it is alternately in registry with each window 331 in turn as the component is rotated about axis Z, being substantially perpendicular to the light path from a particular field of view towards the corresponding window 331. In a similar manner to the third embodiment, mutatis mutandis, the rotation of this component 326 is synchronized with the rotation of the folding member 320, so that each window 328a, 328b is alternately in registry with the particular facet 332 or window 331 that the folding member 320 is in optical communication with.

Alternatively, the system 301 may be accommodated in a static housing (not shown) similar to that described for the third embodiments, mutatis mutandis. Optionally, and illustrated in Fig. 20, a lens 350, or other suitable optical elements, may be mounted to the folding member 320 via bracket or strut 352 and optically aligned with lateral mirror 324 of the folding member 320. Thus, light along directions Gl to G6 first passes through the lens before traversing a window 331 and being incident on the lateral mirror 324, when this is optically aligned with the particular window 331 and the corresponding direction Gl to G6. Accordingly, to enable the strut 352 to rotate through the polygonal member 330, this comprises a through aperture 353 of appropriate diameter. Optionally, filters or other optical elements may also be provided and suitably attached to the lens 350 and/or the strut 352. The lens 350 allows the actual field of view offered by the window 331 to be significantly changed, increased or decreased, according to the type of lens used.

The embodiment illustrated in Fig. 20 may also be accommodated in a static housing or a dynamic housing, similar to that described with respect to the embodiment illustrated in Figs 18(a) and 18(b), mutatis mutandis. Optionally, and in the case of the dynamic housing, the lens 350 may optionally be mounted to the rotating component of the housing, substantially aligned with axial window 328b.

It should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to".

The scanning system and the scanning unit of the present invention have been described above based on specific examples thereof, and their different features may clearly be modified in various manners obvious to a person skilled in the art.