Patent Publication Number: US-2021168305-A1

Title: Lens

Description:
This present invention relates to an infrared transmitting lens, in particular, but not exclusively, to an infrared transmitting lens for use in a housing containing an apparatus that is subjected to infrared inspection. The present invention further relates to a method of manufacturing an infrared transmitting lens. 
     It is generally known to monitor engineering equipment, particularly electrical components, to maintain their performance and to identify and diagnose potential problems at an early stage. Typically, to carry out such monitoring, the equipment would be shut down and then accessed by an engineer or a mechanic who would restart the equipment and carrying out the required analysis on the equipment. A problem associated with this process is the likelihood of leading to prolonged periods of downtime, as well as health and safety risks on the personnel involved. It is known to instead use infrared cameras to monitor equipment. Another way of preventing prolonged periods of downtime and prevented health and safety risks is the use of a transparent window mounted to a frame or a port, through which components may be viewed. Such windows or ports must be provided with panes, or lenses, that are manufactured from materials which permit the transmission of electromagnetic radiation (ER) in the infrared (IR) wavelength range. This allows the contents within the equipment to be viewed through the windows or ports. 
     Typically, two kinds of infrared transparent lenses are used. The more common type is the use of a lens having a crystalline material. Crystalline (or crystal) lenses provide a good capability of visual and thermal inspection. However, these lenses have high costs associated with them. Costs are further driven up according to their capability of allowing infrared radiation to pass through them. That is, if a clear view through the lens is desired, a high quality is required, which often leads to high costs for materials and manufacture. Another drawback is the limited resistance to impact or adverse conditions in which they are subjected. Crystalline lenses are easy damaged or contaminated by dust or grease, which affects the accuracy of infrared measurements. Therefore, frequent monitoring or maintenance is required. Yet another drawback is the difficulty of manufacturing and processing associated with the use of crystalline. The difficulty of manufacturing and the nature of crystalline also results in limited shapes and sizes possible for crystalline infrared transmitting lenses made of crystalline. For example, it is difficult to make any other shape of crystalline lens other than a planar circle. Crystalline lenses tend not to be suitable for bending, or manufacturing into complex shapes. 
     Another type of transparent lens used, for infrared transmitting lenses, is one made from a polymer, or comprises a polymer. Polymeric lenses are typically manufactured from infrared transmitting polymer. Polymeric lenses are a cheaper alternative to the crystalline lens and can be made in shapes and sizes that crystalline lenses cannot be. Also, polymeric lenses typically must be thinner than crystalline in order to transmit infrared through the polymer sufficiently within the infrared spectrum. Typically, polymer lenses are in the range of about 0.2 millimetres to about 0.45 millimetres (mm) for infrared to be transmitted through the infrared transmitting material. As polymer infrared transmitting lenses must be thin, among other reasons, the polymeric infrared lenses typically lack mechanical strength, resistant to temperature and so also commonly suffer from penetrating damage. 
     It is an object of the invention to alleviate or mitigate at least one or more of the aforementioned problems. Particularly, it is desirable to provide an infrared transmitting lens having an improved capability of thermal inspection. It is also desirable to provide an infrared transmitting lens having a reduced cost of manufacture and having an increased resistance to contamination. It is further desirable to provide an infrared transmitting lens that is structurally strong, resistant to impact and hence having an improved resistance to being damaged. It is further desired to provide an infrared transmitting lens that is structurally strong but offer a greater choice of shapes and sizes possible of the lens over the prior art infrared transmitting lenses. 
     The present invention provides an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to an infrared inspection, the infrared transmitting lens comprising:
         a grille, the grille comprising a network of bars with an array of apertures between the bars, the grille providing mechanical protection to the infrared transmitting lens;   infrared transmitting material, positioned on both sides of the grille.       

     The present invention also provides an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to an infrared inspection, the infrared transmitting lens comprising: a grille, the grille comprising a network of bars with an array of apertures between the bars; the grille further comprising infrared transmitting material, on two sides of the grille. 
     The grille may be generally planar comprising two sides. The grille may provide mechanical protection to the infrared transmitting material. The infrared transmitting material may enable infrared inspection through the array of apertures of the grille and through the infrared transmitting material. The grille may be generally planar having two sides, and an edge. The infrared transmitting material enabling infrared inspection through the array of apertures of the grille and through the infrared transmitting material. 
     The infrared transmitting material enabling infrared inspection through the array of apertures of the grille and through the infrared transmitting material. In some embodiments the infrared transmitting material may cover the apertures of the grille. In some embodiments the infrared transmitting material may cover the apertures of the grille on one side of the grille. In some embodiments the infrared transmitting material may cover the apertures of the grille of both sides of the grille. 
     An infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, the infrared transmitting lens comprising:
         a grille, the grille comprising a network of bars with an array of apertures between the network of bars; the grille further comprising infrared transmitting material, configured, at least partially, between the network of bars of the grille and at least partially filling the array of apertures between the network of bars of the grille.       

     In specific embodiments, when combined with other features, the grille further comprises infrared transmitting material, on one side of the grille. 
     In specific embodiments the infrared transmitting lens is provided with a grille comprising a network of bars having an array of apertures through which infrared inspection can be carried out. The presence of a grille further improves the strength and impact resistance of the lens, reducing the risks of the lens being damaged. Thus, there may be provided a lens which is capable of providing infrared thermal inspection, and which is structurally strong, resistant to impact and hence has resistance to damage. Thus, there may be provided a lens which is capable of allowing infrared transmitting therethrough the lens, and which is structurally strong, resistant to impact and hence has resistance to damage. In specific embodiments the infrared transmitting material is capable of allowing visual inspection, through the infrared transmitting material. 
     In some embodiments, the infrared transmitting material is at least partially positioned between the network of bars, at least partially filling the array of apertures between the network of bars of the grille. In some embodiments the grille comprises infrared transmitting material between the bars of the grille. In specific embodiments the apertures of the array of apertures of the grille are filled with infrared transmitting material. In specific embodiments the apertures of the array of apertures of the grille are sufficiently filled with infrared material that the infrared transmitting lens is fluid tight. In specific embodiments the grille further comprises infrared transmitting material. In specific embodiments the grille further comprises infrared transmitting material between the bars of the grille. In embodiments wherein the grille comprises infrared transmitting material, at least to some degree, between the network of bars and at least partially filling the array of apertures, infrared can be transmitted through the array of apertures of the grille, and through the infrared transmitting material. 
     In specific embodiments, the array of apertures of the grille are equal in size and shape, and arranged in a regular array. 
     In specific embodiments, the apertures of the grille are square, or circular; or rectangular; or triangular; or polygonal; or hexagonal; or any combination of square, circular, rectangular, triangular, polygonal or hexagonal. 
     In some embodiments, the array of apertures of the grille are arranged in a tessellation. In some embodiments the total area of a side of a grille, including bars and apertures is 0.129 metres square or less. For example, in specific embodiments the total area of a side of the grille, including bars and apertures is 0.5 metres square. 
     In specific embodiments, the infrared transmitting lens is planar. This is particularly advantageous since the infrared transmitting lens can be easily mounted within an aperture of the housing, placing the lens flush within the housing aperture. In specific embodiments the infrared lens is smooth on at least one surface. In specific embodiments the infrared transmitting material may be planar. In specific embodiments the infrared material may be flat. In specific embodiments the infrared material is flat on both sides. In specific embodiments the infrared material is flat on one side. In specific embodiments the infrared transmitting material is smooth on at least one side 
     In other embodiments, the infrared transmitting lens may instead be non-planar. In some embodiments, the infrared transmitting lens may be flat, or smooth, on one side and have protrusions on the other side. In specific embodiments the infrared transmitting material may be flat, or smooth, on one side and have protrusions on the other side. Aptly the protrusions may correspond to the apertures or spacing between the bars of the grille such that the infrared transmitting material fits between the bars of the grille. In embodiments wherein two infrared transmitting materials comprising protrusions on one side are used on either side of the grille, such that the protrusions face together, the protrusions may fit into the apertures, or spacing, between the bars of the grille. In specific embodiments with protrusions that correspond to the apertures, or spacing, between the bars of the grille, there may be corresponding indentations on the infrared material on the opposite side of the protrusions. Having corresponding protrusions and indentations enable the overall diameter of the infrared transmitting material to be less. This may be especially important when two infrared transmitting material sheets are used on either side of the grille. 
     In specific embodiments the infrared transmitting lens may be curved. In specific embodiments the infrared transmitting material is curved. For example, the infrared transmitting lens may have a curved arrangement or a bent shape. The infrared transmitting lens may also be shaped to correspond to the surface of the housing of the apparatus for infrared inspection. In the embodiments where the infrared transmitting lens is a curve, or a bent shape, infrared radiation may still be able to pass through the infrared transmitting lens. 
     Likewise for the transmitting infrared material, in specific embodiments the infrared material may be a curved arrangement or bent shape. The infrared transmitting material, in specific embodiments, may be configured in a curve. In specific embodiments the infrared transmitting material is semi-spherical. In specific embodiment the infrared transmitting material is round in shape. 
     In specific embodiments the grille may comprise a similar shape to the infrared transmitting material. 
     In specific embodiments, the grille comprises metal. In some specific embodiments the grille comprises aluminium or stainless steel, or both aluminium and stainless steel. The grille may comprise, for example, a different metal, such as titanium or copper; or a different material, for example, plastic; or metal coated with plastic; or any combination thereof. In some embodiments the grille may comprise plastic, for example KEVLAR, a Trade Name for a particular synthetic material or plastic. In specific embodiments the grille comprises glass reinforce plastic. In some embodiments the grille comprises carbon fibre. 
     In specific embodiments, the bars are plastic or metal or a combination of metal and plastic. The bars of the grille may comprise metal with a coating of plastic. The bars of the grille may comprise metal with a coating of infrared transmitting material. Aptly the grille has mechanical strength. Aptly the bars have mechanical strength. Aptly the grille, the bars, or both the grille and bars, provide mechanical strength to the lens, the lens structure or both. 
     In some embodiments the grille comprises a width from one side of the bars to the other, in the range of 0.2 millimetres to 3 millimetres. In some embodiments, the grille is in the range of 1 millimetre to 2.5 millimetres wide from one side of the bars to the other side of the bars. In specific embodiments, the grille is in the range of 1.3 millimetres to 2.1 millimetres wide from one side of the grille to the other side of the grille. In specific embodiments the grille is in the range of 1.3 millimetres to 2.06 millimetres wide, from one side of the bars to the other side of the bars. Thus, there is provided a grille which has a low weight, and which has a low cost of manufacture. 
     In some embodiments, the grille is 1.3 millimetres wide from one side of the bars to the other side of the bars. In specific embodiments the grille is 1.5 millimetres wide from one side of the bars to the other side of the bars. In specific embodiments the grille is 2.03 millimetres wide from one side of the grille to the other side of the grille. 
     In some embodiments the bars are the same width as the grille, from one side of the grille to the other side of the grille, in the upright normal use orientation of the grille. However, the width between the bars may be the same or different as the width of the grille. Ideally the greater area of space between the bars, or in other words the greater area of the apertures, or spacing, between the network of bars, the better vision through the grille. However, the greater area of apertures between the network of bars may mean less mechanical strength. Thus, there needs to be a balance of bars and the area of apertures of the grille. Other factors need to be considered in the balance of strength and vision as the mechanical strength of the bars also influences this balance. For example, a bar with high mechanical strength, for example, stainless steel, may allow thinner bars between the apertures of the grille. 
     In some embodiments the area of apertures of the grille is 60 to 85 percent of the total side area of the grille. Thus, with a side area of the grille comprising 80 percent apertures means only 20 percent of the side area of the grille is bars blocking the view. The advantage of having only one grille is that the two grilles do not need to be lined up or else the percentage of the viewing area will be decreased even further from the percentage of bars from one grille. In alternative embodiments the area of the apertures of the grille of the total side area of the grille may be in the range 70 to 80 percent. In specific embodiments, the area of the apertures of the grille of the total side area of the grille may be in the range of 75 to 90 percent. 
     The planar area of an aperture of the grille, on a side of the grille, in some embodiments may be in the range of 10 to 50 millimetres square in area. In specific embodiments the planar area of an apertures of the grille, on a side of the grille may be in the range of 25 to 35 millimetres square. 
     In specific embodiments the infrared transmitting material comprises a polymer. Alternatively, or additionally, the infrared transmitting material may comprise glass or crystalline. The advantage of an infrared transmitting material comprising polymer is that it has ease of manufacture and less cost. Also, polymer has the advantage that it is able to bend without breaking, more so than crystalline and glass. Using polymers as the infrared transmitting material of the present invention, advantageously are also able to withstand compression. Polymers suitable for use in the invention may, for example, comprise polyethylene, high molecular weight polyethylene (HMWPE), high density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, sulphur-based polymers or polymethyl methacrylate, or any combination thereof. Infrared transmitting polymers by the trademark PolyIR, are also suitable infrared transmitting polymers, for use in the present invention. 
     Aptly the infrared transmitting material enables infrared radiation in the wavelength range of about 0.5 micrometres to about 1 millimetre to transmit through the infrared transmitting material and thus through the infrared transmitting lens. In specific embodiments the infrared transmitting material enables infrared radiation in the wavelength range of 0.4 micrometres to 15 micrometres to transmit through the infrared transmitting material and thus through the infrared transmitting lens. In specific embodiments the infrared transmitting material enables infrared radiation in the wavelength range of 0.5 micrometres to 14 micrometres to transmit through the infrared transmitting material and thus through the infrared transmitting lens. In specific embodiments the infrared transmitting material enables infrared radiation in the wavelength range of 0.5 micrometres to 3 micrometres to transmit through the infrared transmitting material and thus through the infrared transmitting lens. In specific embodiments the infrared transmitting material enables infrared radiation in the wavelength range of 3 micrometres to 5 micrometres to transmit through the infrared transmitting material and thus through the infrared transmitting lens. In specific embodiments the infrared transmitting material enables infrared radiation in the wavelength range of 8 micrometres to 14 micrometres to transmit through the infrared transmitting material and thus through the infrared transmitting lens. 
     In some preferred embodiments, the infrared transmitting material is in the range of 0.2 millimetres to 0.45 millimetres wide from one side to the other. By providing an infrared transmitting material in the range of 0.2 millimetres to 0.45 millimetres, the lens has a low weight, and a reduced cost of manufacture. Further, by having an infrared transmitting material that is thin, the transmissivity of the material is improved. These benefits can be provided without forfeiting structurally rigidity and strength, which is provided by the grille. 
     In some embodiments, the infrared transmitting material is in the range of 0.1 millimetres to 0.3 millimetres wide from one side to the other. 
     In specific embodiments, the infrared transmitting material is in the range of 0.15 millimetres to 0.25 millimetres wide from one side to the other. 
     In some embodiments, the infrared transmitting material in total width is 0.5 millimetres or less. For example, the infrared transmitting material on each side of the grille may be the same width, such that each side has a total width of 0.25 millimetres or less. In other embodiments, the infrared transmitting material on each side of the grille may have a different width, but the total width is 0.5 millimetres or less. For example, the infrared transmitting material on one side of the grille may be 0.2 millimetres or less, and the infrared transmitting material on the other side of the grille may be 0.3 millimetres or less. 
     In some embodiments, the infrared transmitting material in total width is 0.4 millimetres or less. For example, the infrared transmitting material on each side of the grille may be the same width, such that each side has a total width of 0.2 millimetres or less. In other embodiments, the infrared transmitting material on each side of the grille may have a different width, but the total width is 0.4 millimetres or less. For example, the infrared transmitting material on one side of the grille may be 0.1 millimetres or less, and the infrared transmitting material on the other side of the grille may be 0.3 millimetres or less. 
     In specific embodiments when two infrared transmitting materials are used these may be pushed together. When pushed together at least some areas of the infrared transmitting material may appear as one infrared transmitting material. Ideally when two infrared transmitting materials are together the total width is less than 0.5 millimetres. 
     In specific embodiments the infrared transmitting material may be attached to the grille by adhesive. The adhesive may, for example, be applied to a portion of the side, or sides, of the grille. On a side where adhesive has been applied, the infrared material may be positioned making contact with at least some adhesive, such that the infrared material is held in position. In specific embodiments adhesive applied to both sides of the grille and infrared material is positioned to both sides of the grille. The infrared material may be held in position on both sides of the grille by adhesive. Adhesive does not need to be applied to the complete side or sides of the grille. Ideally a sufficient amount of adhesive will be applied to a side or sides of the grille to enable holding of the infrared material in position. 
     In some embodiments the infrared transmitting material may be attached to the grille by adhesive-tape. In specific embodiments the infrared transmitting material may be attached to the grille by double-sided adhesive-tape. The adhesive-tape, or double-sided adhesive-tape may, for example, be applied to a portion of the side, or a portion of both sides, of the grille. Ideally when adhesive-tape, that only has adhesive on one side of the adhesive tape, is used, the adhesive-tape may be folded over such that adhesive can contact both the grille and the infrared material. Using adhesive tape, or double-sided adhesive-tape has the advantage that adhesive is less likely to run off the bars of the grille and block the gaps between the bars of the grille. 
     In embodiments where adhesive-tape or double-sided adhesive-tape has been applied to, a portion of one side, or a portion of both sides of the grille, the infrared material may be positioned making contact with at least some adhesive, such that the infrared material is held in position. In specific embodiments adhesive-tape, or double-sided adhesive-tape is applied to a portion of both sides of the grille and infrared material is positioned to both sides of the grille. The infrared material may be held in position on both sides of the grille by adhesive-tape, or double-sided adhesive-tape. Adhesive-tape, or double-sided adhesive-tape, does not need to be applied to the complete side or sides of the grille. Likewise the adhesive-tape, or double-sided adhesive-tape, need not be in contact with the entire side of the infrared transmitting material. Ideally a sufficient amount of adhesive-tape, or double-sided-adhesive tape, will be applied to a side or sides of the grille to enable holding of the infrared material in position. In specific embodiments when adhesive-tape, or double-side adhesive-tape is used to secure the infrared materials and grille together, the grille is between two infrared transmitting materials. 
     In some embodiments the corresponding array of apertures of the double-sided adhesive-tape is an exact, or almost exact match to the array of apertures of the grille. In other embodiments the corresponding array of apertures of the adhesive tape are not an exact match. Using a greater amount of double-sided adhesive-tape may give a greater hold. However, applying double-side adhesive-tape to the bars of the grille only and not partially covering any apertures may be difficult. Therefore in some embodiments double-sided adhesive-tape may be used only sufficiently in amount to hold the infrared transmitting material to the grille and that there is sufficient apertures, or part of the apertures, not blocked to enable infrared transmitting inspection through the grille. The double-sided adhesive-tape may, for example in some embodiments, be used only on the outer periphery of the grille in order not to block the array of apertures or at least not block a significant portion of the apertures. 
     Positioning of the adhesive-tape, or double-sided adhesive-tape, to a portion of the side of the grille may be assisted by using a jig that may accurately apply the adhesive-tape, or double-sided adhesive-tape, to the bars of the grille and not block or fill the apertures of the grille, between the bars of the grille, and thus still enable infrared transmission through the grille when adhesive-tape, or double-sided adhesive tape, is used to secure the infrared transmitting material in position. Advantageously using a jig may enable accurate positioning of the adhesive-tape, or double-sided adhesive-tape. A jig may be used to cut the required apertures in the adhesive tape, or double-sided adhesive-tape. 
     In specific embodiments the infrared transmitting lens is circular in shape. In other embodiments the infrared transmitting lens may have a different shape, for example, a square, a triangle, an ellipse, a rectangle, square or an oval. 
     By providing an infrared transmitting lens comprising a grille, wherein the grille comprises infrared transmitting between the network of bars of the grille, the infrared transmitting material has an improved integration with the protective grille. This increases the structural rigidity and strength of the infrared transmitting lens, enabling the manufacture of a thin lens still able to obtain high mechanical strength. 
     The present invention provides a method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the steps of:
         providing a grille, wherein the grille comprises a network of bars with an array of apertures between the network of bars;   providing an infrared transmitting material to a first side of the grille;   providing an infrared transmitting material to a second side of the grille.       

     Also, the present invention further provides a method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the steps of:
         providing a grille, wherein the grille comprises a network of bars with an array of apertures between the network of bars;   providing an infrared transmitting material to a first side of the grille; and   compressing the grille and infrared transmitting material together such that the infrared transmitting material, at least partially, fills the array of apertures between the network of bars of the grille.       

     In specific embodiments the method of manufacturing an infrared transmitting material further comprises the step of applying folded-over adhesive tape, or double-sided adhesive-tape, to a portion of the network of bars of the grille on both sides of the grille before positioning or providing infrared transmitting materials to both sides of the grille. 
     In some embodiments there is provided an infrared transmitting material that is adhered to the grille by compression. In some embodiments the infrared transmitting material adheres to the grille by compression. The compressive force applied aligns the infrared transmitting material with the array of apertures of the grille and may at least partially, fills the array of apertures with the infrared transmitting material. Infrared may pass through the infrared transmitting material and through the array of apertures during an infrared inspection. 
     In specific embodiments, the method of manufacturing an infrared transmitting lens further comprises the step of: providing a second infrared transmitting material to a second side of the grille. In further embodiments the method of manufacturing an infrared transmitting lens further comprises the step of compressing the second infrared transmitting material into the grille on the second side of the grille. Both sides of the grille may be provided with an infrared transmitting material. Advantageously, with infrared transmitting material on both sides of the grille allows protection to both sides of the grille, for example, from corrosion. Having an infrared transmitting material, for example, a polymer compressed from both sides of the grille may enable the space between the network of bars of the grille to be filled more evenly than if the infrared transmitting material was only compressed from one side. When the infrared transmitting material, for example, when comprising polymer, surrounds, or partially surrounds, the grille, the infrared transmitting material protects the grille from degradation, for example corrosion. 
     Also, the present invention provides a method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the step of: extruding an infrared transmitting material around a grille to provide an infrared transmitting lens. 
     In specific embodiments, the method of manufacturing an infrared transmitting lens comprises the steps of: 
     As used herein, the term “aperture” is used to describe any slit, hole, slot, cavity, recess or opening. For example, an aperture may be a through-hole extending through a material from one side to the other. In other embodiments, the aperture may instead be a recess, or space, extending a depth into the surface on one side of a material. An aperture of the grille may be the area between the network of bars, which is not the bars of the grille, but which may be filled with another element, for example, a polymer. 
     As used herein, the term “array” is used to describe a structural arrangement. For example, an array of apertures is used to describe an arrangement of apertures of the grille. The term array includes, but not limited to, a plurality of apertures in a pattern. 
     As used herein, the term “double-sided adhesive-tape” is used to describe a tape that has adhesive on both sides of the tape. 
     As used herein, the term “grille” is used to describe a network of bars with apertures or spacing between the network of bars. The grille may often be generally planar but not limited to planar structures. The grille may be curved. The grille need not be flat. The term “faces of the grille” means the “sides of the grille” referring to the larger two sides of the grille. The outer peripheral portion being the edge of the grille. 
     As used herein, the term “infrared inspection” or “infrared imaging” is used to describe a condition monitoring process involving the detection of electromagnetic radiation in the infrared wavelength range. 
     As used herein, the term “infrared transmitting material” is used to describe a material that is capable of allowing infrared radiation to pass therethrough. The infrared transmitting material may be glass, crystalline material or a polymer, for example. 
     As used herein, the term “planar” is used to describe an element having a length that is substantially greater than its thickness. Generally having two sides or faces. 
     As used herein, the term “providing” includes the meaning of positioning. 
     As used herein, the term “bars” is used to describe the strands, of the grille, that is capable of providing structural strength or rigidity, or both strength and rigidity, to the grille. The bars may comprise any coating that is suitable for preventing corrosion, for example plastic. Typically, the bars comprise metal. The bars may be wire. The bars may be round across the width of the bar. The bars may be rod like in shape. 
     As used herein, the term “tessellation” is used to describe a patterned arrangement of features, typically but not limited to being on a surface of a material. For example, a tessellation maybe a repeat of a particular shape on a surface. 
     As used herein, the term “width” or “thickness” is used to describe the distance between two points, for example, two sides or faces. For example, the grille having a width of 0.5 millimetres indicates a distance of 0.5 millimetres between the two sides of the grille. The term width may also be used to describe the width, thickness or diameter of the bars, from one side of the grille to the other side of the grille. 
     Certain terminology is used in the following description for convenience only and is not limiting. The words ‘right’, ‘left’, ‘lower’, ‘upper’, ‘front’, ‘rear’, ‘upward’, ‘down’ and ‘downward’ designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted. The words ‘inner’, ‘inwardly’ and ‘outer’, ‘outwardly’ refer to directions toward and away from, respectively, a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description. 
     Further, as used herein, the terms ‘connected’, ‘attached’, ‘coupled’, ‘mounted’ are intended to include direct connections between two members without any other members interposed therebetween, as well as, indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import. 
     Further, unless otherwise specified, the use of ordinal adjectives, such as, “first”, “second”, “third” etc. merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner. 
     EXAMPLES 
     Ex1 
     An infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to an infrared inspection, the infrared transmitting lens comprising:
         a grille, the grille comprising a network of bars with an array of apertures between the bars, the grille providing mechanical protection to the infrared transmitting lens;   infrared transmitting material, positioned on both sides of the grille.       

     Ex2 
     An infrared transmitting lens according to example Ex1, wherein the grille further comprises infrared transmitting material between the network of bars of the grille, such that the infrared transmitting material, at least partially, fills the array of apertures between the network of bars of the grille. 
     Ex3 
     An infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to an infrared inspection, the infrared transmitting lens comprising: a grille, the grille comprising a network of bars with an array of apertures between the bars, the grille further comprising infrared transmitting material between the bars of the grille, such that the infrared transmitting material, at least partially fills, the array of apertures between the bars of the grille. 
     Ex4 
     An infrared transmitting lens according to example Ex3, wherein further comprises, infrared transmitting material on one side of the grille. 
     Ex5 
     An infrared transmitting lens according to anyone of examples Ex1, Ex2 or Ex3, wherein the array of apertures of the grille are equal in size and shape, and arranged in a regular array. 
     Ex6 
     An infrared transmitting lens according to anyone of example Ex1 to Ex5, wherein the apertures of the grille are square, or circular; or rectangular; or triangular; or polygonal; or hexagonal; or any combination of square, circular, rectangular, triangular, polygonal or hexagonal. 
     Ex7 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex6, wherein the array of apertures of the grille are arranged in a tessellation. 
     Ex8 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex7, wherein the infrared transmitting lens is planar. 
     Ex9 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex8, wherein the infrared transmitting material comprises a polymer. 
     Ex10 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex9 wherein the grille comprises: plastic, or metal, or a combination of metal and plastic. 
     Ex11 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex10, wherein the grille is in the range of 0.2 millimetres to 3 millimetres wide from one side of the grille to the other side of the grille at a portion of the network of bars. 
     Ex12 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex11, wherein the infrared transmitting material, is in the range of 0.15 millimetres to 0.45 millimetres wide, in total, from one side to the other. 
     Ex13 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex12, wherein the infrared transmitting material in total width is 0.4 millimetres. 
     Ex14 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex13, wherein the infrared transmitting material is nonplanar. 
     Ex15 
     An infrared transmitting lens according to anyone of examples Ex1 to Ex14, wherein the infrared transmitting material forms a seal across the infrared transmitting lens, or the grille, such that the seal is impermeable to fluids. 
     Ex16 
     An infrared transmitting lens according to anyone of wherein the infrared transmitting material comprises protrusions. 
     Ex17 
     An infrared transmitting lens according to example Ex1, wherein further comprises double-sided adhesive-tape on, a portion, of both sides of the grille, the double-sided adhesive-tape is between the grille and the infrared transmitting material. 
     Ex18 
     A method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the steps of:
         providing a grille, wherein the grille comprises a network of bars with an array of apertures between the network of bars;   providing an infrared transmitting material to a first side of the grille; and   compressing the grille and infrared transmitting material together such that at least a portion of the infrared transmitting material is positioned in the array of apertures between the network of bars of the grille.       

     Ex19 
     A method of manufacturing an infrared transmitting lens according to example Ex18, wherein the method further comprises the step of: providing a second infrared transmitting material to a second side of the grille, before the compressing step. 
     Ex20 
     A method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the step of:
         providing a grille, wherein the grille comprises a network of bars with an array of apertures between the network of bars; and,   extruding an infrared transmitting material to the grille, such that at least a portion of the extruded infrared transmitting material is positioned between the network of bars of the grille.       

     Ex21 
     A method of manufacturing an infrared transmitting lens for mounting in an aperture of a housing containing an apparatus to be subjected to infrared inspection, comprising the steps of:
         providing a grille, wherein the grille comprises a network of bars with an array of apertures between the network of bars;   providing an infrared transmitting material to a first side of the grille; and,   providing an infrared transmitting material to a second side of the grille.       

     Ex 22 
     A method of manufacturing an infrared transmitting lens according to example Ex21, further comprising the step of: applying double-sided adhesive-tape to, a portion of the bars of the grille, on both sides of the grille, before; providing an infrared transmitting material to a first side of the grille and providing an infrared transmitting material to a second side of the grille. 
    
    
     
       Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a grille suitable for use in the present invention; 
         FIG. 2  is a perspective view of an infrared transmitting material suitable for use in the present invention; 
         FIG. 3  is a perspective view of an infrared transmitting lens according to an embodiment of the invention; 
         FIG. 4  is a schematic view of an infrared lens of the invention; 
         FIG. 5  is a front view of the infrared lens assembly in  FIG. 4 ; 
         FIG. 6  illustrates an exploded view of an infrared lens assembly; 
         FIG. 7  is a schematic section view of an infrared lens according to an embodiment of the invention; 
         FIG. 8  is a schematic section view of an infrared lens according to another embodiment; 
         FIG. 9  shows a schematic view of an infrared transmitting lens according to an embodiment; 
         FIG. 10  shows a schematic view of an infrared transmitting lens according to another embodiment; 
         FIG. 11  shows a schematic view of an infrared transmitting lens according to a further embodiment; and 
         FIG. 12  shows a schematic view of an infrared transmitting lens according to a yet further embodiment. 
         FIG. 13  shows an exploded view of an infrared transmitting lens according to a further embodiment. 
     
    
    
     Like reference numerals are used to depict like features throughout. 
       FIG. 1  shows a grille  10 . The grille  10  is generally planar and has a front side  12  and a rear side  16 . The grille  10  also has a peripheral edge portion  14  defined between the front side  12  and the rear side  16 . The grille  10  has a substantially circular shape in this embodiment. But in other embodiments, the grille  10  may take the form of another shape, such as, for example, a square, a rectangle, an ellipse or an oval. The grille  10  comprises a network of bars  18 . In this particular embodiment, the grille  10  comprises aluminium, but it should be appreciated that the grille  10  may instead comprise different materials such as, for example, stainless steel, titanium, copper, plastic, a metal coated with plastic, or a plastic coated with a metal. The network of bars  18 , which in this case is aluminium, has an array of apertures  20 . The apertures  20  in this embodiment have a hexagonal shape extending through both the front side  12  and the rear side  16 . That is, the apertures  20  extend through the thickness of the grille  10 . The apertures  20  have a regular hexagonal shape. In this embodiment the edges of the hexagon have an equal length. In other embodiments however, the apertures  20  may have other shapes, for example but not limited to, a circular shape, a rectangular shape, a square shape, a triangular shape, a polygonal shape, or any combination of these shapes. It should further be appreciated that the array of apertures  20  may be arranged in a tessellation, and that the array of apertures  20  may extend to cover a larger area of the grille  10 , or may extend across a smaller area of the grille  10 . For example, the array of apertures  20  may extend to cover almost the entirety of the grille  10 , or substantially the entirety of the grille  10 . That is, the array of apertures  20  may extend towards and meet the outer periphery of the grille  10 . 
       FIG. 2  illustrates an infrared transmitting lens  100 . In this embodiment the infrared transmitting lens has an infrared transmitting material  130  on one side of a grille  110 . In the  FIG. 2  the infrared transmitting material  130  is largely blocking a view of the grille  110 . For convenience the apertures  120  of the grille  110  are shown by dashed lines. The infrared transmitting lens  100  comprises a grille  110  and an infrared transmitting material  130 . The grille  110  is substantially the same as the grille  10  in  FIG. 1  and therefore will not be described again in detail. In this embodiment the infrared transmitting material  130  is on the front side  112  of the grille  110  and lies parallel and flush against it. The infrared transmitting material  130  in this embodiment is at least partially compressed into the grille  110 . In this embodiment, the infrared transmitting material  130  comprises a polymer  138 . An infrared transmitting material  130  comprises polymer  138  is particularly preferred because it has a relatively lost cost. Additionally, polymer material is easy to mould, compress and/or deform, which is beneficial, as will be discussed. Particularly in this embodiment, the infrared transmitting material  130  comprises polyethylene. However, in other embodiments other polymers may be used, for example, high molecular weight polyethylene (HMWPE), high density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, sulphur-based polymers or polymethyl methacrylate. In this  FIG. 2  embodiment the infrared transmitting material is positioned on one side of the grille and at least partially within the apertures of the grille. 
     In this embodiment, the infrared transmitting material  130  is relatively thin in width. More specifically, the infrared transmitting material  130  in this embodiment has a width of 0.2 millimetres. This is particularly important since the infrared transmitting material  130  is to enable transmitted infrared radiation to pass through the infrared transmitting material  130 . The infrared transmitting material  130  enables infrared radiation in the wavelength range of about 0.5 micrometres to about 14 um to pass through. In specific embodiments the infrared the infrared transmitting material  130  has a front side  132  and a rear side  136 , and a peripheral edge portion  134  defined in between the front side  132  and the rear side  136 . When infrared radiation (not shown) passes through the hexagonal apertures  120  of the grille, the infrared radiation extends towards and transmits through the infrared transmitting material  130 . In other embodiments the infrared transmitting material  130  may comprise a different material, and the infrared transmitting material  130  may have a different width from the front side  132  to the rear side  136  of the infrared transmitting material  130  so long as its width and the properties of the infrared transmitting material  130  allow infrared radiation to pass therethrough. In some embodiments, the infrared transmitting material  130  comprises protrusions (not shown) that correspond to the hexagonal apertures  120  of the grille  110  such that infrared can transmit through the hexagonal apertures  120  and through the protrusions of the infrared transmitting material  130 . 
       FIG. 3  illustrates an embodiment of an infrared transmitting lens  200 . The infrared transmitting lens  200  comprises a grille  210  and a first infrared transmitting material  230 . The grille  210  is substantially the same as the grille  10  in  FIG. 1  and thus will not be described again in detail. Likewise, the first infrared transmitting material  230  is substantially the same as the infrared transmitting material  130  in  FIG. 2  and thus will not be described again in detail. The infrared transmitting lens  200  further comprises a second infrared transmitting material  240  on the rear side (not shown) of the grille  210  and lies parallel and flush against the grille. 
     In the  FIG. 3  embodiment, the second infrared transmitting material  240  comprises a polymer. In other embodiments, the second infrared transmitting material  240  may comprise glass or crystalline, for example. The advantage that both infrared transmitting materials  230 ,  240  are polymer or comprise polymer, include ease of manufacture and lower costs. Suitable polymers include, but not limited to, for example, high molecular weight polyethylene (HMWPE), high density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, sulphur-based polymers or polymethyl methacrylate. In this particular embodiment, both the first infrared transmitting material  230  and the second infrared transmitting material  240  are comprises polypropylene, however it should be appreciated that the materials of the first infrared transmitting material  230  and the second infrared transmitting material  240  may be different polymers, and in other examples, the first infrared transmitting material  230  and the second infrared transmitting material  240  may be different materials altogether, such as, for example, a polymer and a glass. 
     In this embodiment, the second infrared transmitting material  230  also has a relatively thin width. More specifically, the second infrared transmitting material  240  in this embodiment has a width, or thickness, of 0.2 millimetres. Likewise, the first infrared transmitting material  230  also has a width, or thickness, of 0.2 millimetres. Thus, the overall total width of the first infrared transmitting material  230  combined with the second infrared transmitting material  240  has a width of 0.4 millimetres. The grille  210  in this embodiment has a width, from front side of the grille (not shown) to the rear side, of 0.5 millimetres. The material of the first  230  and second  240  infrared transmitting materials and the width of same, allow infrared radiation to pass therethrough. That is, when infrared radiation (not shown) passes through either one of the first  230  and second  240  infrared transmitting materials, the infrared radiation passes through the hexagonal apertures  220  (for convenience shown as dashed lines) of the grille  210  and extends towards and transmits through the other one of the first  230  and second  240  infrared transmitting materials. In some embodiments each of the infrared transmitting materials  230 ,  240  may comprise a number of different materials, and each of the infrared transmitting materials  230 ,  240  may have a different width, so long as its width and the properties of the infrared transmitting material  230 ,  240  allow infrared radiation to pass therethrough. 
     When the infrared transmitting lens  200  is assembled together, the first infrared transmitting material  230  and the second infrared transmitting material  240  are compressed inwards towards the grille  210 , in this embodiment. In some alternative embodiments the first and second infrared transmitting materials are not compressed. In this embodiment a compressive force is applied onto the front side  232 , of the first infrared transmitting material  230  in a direction towards the grille  210 . A compressive force is also applied on the rear side  246  of the second infrared transmitting material  240  compressing towards the grille  210 . The first infrared transmitting material  230  in this embodiment is a polymer. When a compressive force is applied onto the front side  232  of the first infrared transmitting material  230 , a portion of the first infrared transmitting material  230  is positioned between the network of bars. Thus, in this embodiment the grille comprises infrared transmitting material between the bars of the grille. In this specific  FIG. 3  embodiment there is an air gap in the apertures, after compressing the first and second infrared transmitting material together. In this specific  FIG. 3  embodiment the infrared transmitting material at least partially fills the apertures of the grille. In some alternative embodiments, the first transmitting material  230  deforms and fills the array of apertures  220 . Likewise, in some embodiments, when a compressive force is applied onto the rear side  246  of the second infrared transmitting material  240 , a portion of the second infrared transmitting material  240  is positioned between the network of bars. In some embodiments, the second transmitting material  240  deforms and fills the array of apertures  220 . In some embodiments it is the infrared transmitting material from either one side or both sides that may at least partially fill the apertures. In embodiments when the apertures of the grilles are partially filled there may be an air gap. In embodiments where the apertures of the grille are filled there may be little to no air gap. The filling of the array of apertures in this way will be described in more detail later with reference to  FIG. 7 . 
     The present invention covers embodiments where the grille has infrared transmitting material positioned on both sides of the grille. This embodiment may look similar to that of  FIG. 3  shown. In some embodiments where there is infrared transmitting material on both sides of the grille, there need not be necessarily any compression of the infrared transmitting material. In embodiments where there is no compression the infrared material may comprise, for example, polymer, crystalline or glass or any combination thereof. In embodiments where the infrared transmitting material is positioned to a side of the grille the infrared transmitting material may comprise, for example, polymer, crystalline or glass, or any combination thereof. 
     By combining different materials for the infrared transmitting materials used may lead to many different final compositions of the infrared transmitting lens. For example, an infrared transmitting material comprising crystalline may be used on one side of the grille and an infrared transmitting material comprising polymer on the other side of the lens. In this embodiment the apertures of the grille may comprise air. In this specific embodiment with different transmitting material on different sides of the grille may optionally further comprise a compression step such that the infrared transmitting material comprising polymer may be also positioned between the bars on the grille, at least partially filling the apertures of the grille. 
       FIG. 4  shows, an infrared transmitting lens, of the present invention, optionally within a window assembly  300 . The embodiment shown in  FIG. 4  is not to be construed as requiring the optional window frame, covers and other window assembly components, these are included for illustrative purposes only. The infrared transmitting lens comprises a grille  310  and infrared transmitting material  330 ,  340  positioned on both sides of the grille  310 , a first infrared transmitting material  330  positioned on one side of the grille  310  and a second infrared transmitting material  340  positioned on the other side of the grille  310 . Thus, this embodiment comprises a grille  310  wherein the grille  310  further comprises infrared transmitting material on two sides of the grille  310 . The infrared transmitting lens, in this embodiment, is a composition of parts. The arrangement of the grille  310 , first infrared transmitting material  330  and second infrared transmitting material  340  is substantially the same as the infrared transmitting lens  200  in  FIG. 3  so will not be described here again in detail. The infrared transmitting lens  300  of the  FIG. 4  embodiment is however shown after compression. The  FIG. 4  embodiment of an infrared transmitting lens  300  is illustrated after the first  330  and second  340  infrared transmitting materials are compressed together by hand towards the grille  310 . In alternative embodiments the compression may be by a machine. The compression used to compress the first  330  and second  340  infrared transmitting material, in this embodiment, is in the range of 5 to 38 Newtons. The infrared transmitting lens  300  in this embodiment is shown, for illustrative purposes, optionally with a window comprising a rim  352 ,  362 , and also optionally an attachment mechanism  364 ,  370 . As the first  330  and second  340  infrared transmitting material is compressed a portion of the infrared transmitting material enters the array of apertures of the grille  310  and therefore at least a portion of the infrared transmitting material is positioned between network of bars of the grille  310 . Thus, in this embodiment the grille  310  comprising bars, further comprises infrared transmitting material between the bars of the grille  310 . The polymer (in this embodiment) of the first  330  and second  340  infrared transmitting materials coats the outer surfaces of the grille  310 , on both sides of the grille  310  in the network of bars of the grille  310 . At the aperture portion of the grille  310  where the first and second infrared transmitting material are compressed together a portion of the first and second infrared transmitting material is at least partially positioned between the network of bars of the grille  310 . In this embodiment the infrared transmitting lens is shown optionally sitting in a window frame that comprises removable protective screens  350 ,  360 , with protrusions  356 ,  366 . The infrared transmitting lens is held in the window frame or ridge  362  and  352  by attachment mechanisms  364 ,  370 . In specific embodiments the removable screens  350 ,  360  would be normally positioned over the infrared transmitting lens but when inspection is required both protective screens  350 ,  360  would be temporarily removed, for example, by sliding these out of view of the infrared transmitting lens. Ideally both protective screens  250 ,  360  are slid out of view, by a mechanism or operation from the outer side of the window thus the container does not have to be opened to remove the protective screens  350 ,  360 . The grille in this embodiment is 0.4 millimetres in width. Both the first and second infrared transmitting materials are 0.2 millimetres in width before compression. However, after compression, as a portion of the first  330  and second  340  infrared transferring material is positioned between the network of bars of the grille  310 , the width of the combined first  330  and second  340  infrared transmitting material is 0.4 millimetres in width. millimetres. Thus, even though the total width of the infrared transmitting material is required to be relatively thin, preferably less than 0.45 millimetres, this arrangement of the  FIG. 4  embodiment enables a grille of a larger width (than the total width of the infrared transmitting material) to be used. Advantageously a wider and stronger grille can be used to give mechanical strength or protection, that still enables a relatively thin (preferably less than 0.45 millimetres) width of infrared transmitting material to be used. 
       FIG. 5  shows a plan view of the infrared transmitting lens of the  FIG. 4  embodiment in use, also showing the optional window rim  452  and optional attachment points  466 ,  456  for the optional protective screens  350 ,  360 . 
       FIG. 6  illustrates an exploded assembly view of window assembly  500  comprising an infrared transmitting lens, also shown in exploded view. The infrared transmitting lens comprises a grille  510  and infrared transmitting material  530 ,  540  on both sides of the grille.  FIG. 6  also shows the optional components that make up the window assembly  500 , the window assembly  500  having a central axis  570 . The  FIG. 6  embodiment window assembly shows optional front and back protective screens  550 ,  560 . Each component is generally planar in shape, having a front side and a rear side. Each component in this embodiment is also substantially circular in shape. The window assembly  500  shows an infrared transmitting lens comprising a grille  510  positioned centrally in the infrared transmitting lens. The grille  510  is formed from a network of bars. In this embodiment, the grille  510  is formed from aluminium. The network of bars (aluminium), has an array of apertures  520 . In this embodiment the apertures  520  have a hexagonal planar shape. The apertures  520  extend through the width of the grille  510 . It should be appreciated that the array of apertures  520  may extend to cover a larger side surface area of the grille  510 , or may extend to cover a smaller side surface area of the grille  510 . For example, the array of apertures  520  may extend to cover substantially the entirety of the grille  510 . That is, the array of apertures  520  may extend towards and meet the outer periphery of the grille  510 . 
     On either side of the grille  510 , there is provided infrared transmitting material  530 ,  540 . Specifically, in this embodiment, a first infrared transmitting material  530  made of a polymer is positioned on a front side of the grille  510 . A second infrared transmitting material  540  also made of a polymer is positioned on a rear side of the grille  510 . In this embodiment the grille  510  comprises infrared transmitting material on two sides of the grille  510 . The infrared transmitting material  530 ,  540  on either side of the grille  510  lies parallel and flush against the grille  510 . The material of the first  530  and second  540  infrared transmitting materials and the width of same, allow infrared radiation to pass therethrough. When infrared radiation (not shown) passes through either one of the first  530  and second  540  infrared transmitting materials, the infrared radiation passes through he hexagonal apertures  520  of the grille  510  and extends towards and transmits through the other one of the first  530  and second  540  infrared transmitting materials. 
     In this embodiment, the infrared transmitting materials  530 ,  540  have a width from one side to the other, of 0.2 millimetres, and they comprise a polymer. However, it should be appreciated that each of the infrared transmitting materials  530 ,  540  may comprise a different material, and each of the infrared transmitting materials  530 ,  540  may have a different width, so long as its width and the properties of the infrared transmitting material  530 ,  540  allow infrared radiation to pass therethrough. 
     For illustrative purposes of showing the lens of the present invention in use, optional covers, and rim and other optional window components are shown. A first movable optional cover  550  is provided on a front side, positioned near to the first infrared transmitting material  530 . The first removable optional cover  550  has a rim  552  positioned around the periphery of the first movable optional cover  550 . The rim  552  is provided with attachment points  556 . 
     Similarly, a second optional cover  560  is provided at the rear side, positioned near the second infrared transmitting material  540 . The second optional cover  560  also has a rim  562  positioned around the periphery of the second cover  560 . The rim  562  also has attachment points  568 . In this embodiment the optional attachment points  568 ,  556  assists to hold the optional cover in place when viewing is not required but enable easy removal of the optional covers from any one side when viewing through the infrared transmitting lens is required. 
     In use, the infrared transmitting lens  530 ,  510 ,  540  can be mounted in an aperture of a housing containing an apparatus to be subjected to infrared inspection. The window assembly  500  can be mounted within a housing. Thus, infrared radiation can be transmitted through the apertures  520  of the grille  510  and through the infrared transmitting materials  530 ,  540  to inspect inside the housing. In this embodiment, the infrared transmitting lens comprising the grille  510  and the first  530  and second  540  transmitting materials can be assembled together by compressing the first infrared transmitting material  530  and the second infrared transmitting material  540  inwards towards the grille  510 . In some embodiments, when a compressive force is applied on the first infrared transmitting material  530 , the first infrared transmitting material  530  deforms and fills the array of apertures  520  of the grille  510 . This is better shown in  FIG. 7 . 
       FIG. 7  shows an embodiment comprising an infrared transmitting lens  600  comprising a grille  610 , a first infrared transmitting material  630  on one side of the grille  610  and a second infrared transmitting material  640  on the other side of the grille  610 . Thus, this embodiment comprises a grille  610  further comprising infrared transmitting material  630 ,  640  on both sides of the grille  610 . The grille  610  comprises an array of apertures  620 . In this embodiment, the grille comprises steel. In this embodiment the first infrared transmitting material  630  and the second infrared transmitting material  640  both comprise a polymeric material. More specifically, the first infrared transmitting material  630  and the second infrared transmitting material  640  comprise polyethylene. When a compressive force is applied on the outside of the first infrared transmitting material  630  towards the grille  610 , the first infrared transmitting material  630  deforms and fills the array of apertures  620  from the front side. Likewise, when a compressive force is applied on the outside of the second infrared transmitting material  640  towards the grille  610 , the second infrared transmitting material  640  deforms and fills the array of apertures  620  from the rear side. Thus, the apertures  620  are at least partially filled with the deformed polymer infrared transmitting materials  630 , 640 . The embodiment shown in  FIG. 7  is shown already compressed towards both sides of the grille. The apertures  620  are at least partially filled with polymer of the infrared transmitting materials  630  and  640 . In this embodiment the infrared transmitting materials  630 ,  640  cover the grille  610  giving protection to the steel grille from corrosion. Infrared radiation is able to pass through the infrared transmitting materials  630 ,  640  and through the apertures  620  of the grille  610 . In this embodiment the width of the grille  610  is 0.2 millimetres. In this embodiment the width of both the first  630  and second  640 , infrared transmitting materials, after compression are 0.2 millimetres each. The total width of the infrared transmitting lens  600  of the  FIG. 7  embodiment is 0.4 millimetres. In some embodiments, the apertures  620  are completely filled with infrared transmitting material  630 ,  640  from one or both sides of the grille  610 , from the first infrared transmitting material  630  or the second infrared transmitting material  640 , or both the first transmitting material  630  and second infrared transmitting material  640 . Aptly the infrared transmitting material  630  and  640  form a seal. In some embodiments the infrared transmitting material  630 ,  640  form a seal that is fluid tight. Thus, in embodiments with a fluid tight seal, fluids, gas and liquids, cannot pass through the infrared transmitting lens. In other embodiments the infrared transmitting material may form a liquid tight seal and thus gas could pass through. 
     For illustrative purposes only, embodiments of the invention including those of  FIGS. 4, 5, 6, 7 and 8  are shown and explained by embodiments of a lens of the present invention in use with optional window frame and optional covers and optional other window components. Window frame components and covers are optional and not to be limitations to these or other embodiments of the invention. 
     In the  FIG. 8  embodiment, as illustrated in  FIG. 8 , the infrared transmitting lens (the combined, grille  710 , first infrared transmitting material  730 , and the second infrared transmitting material  740 ) may be curved. Window assembly  700  comprises an infrared transmitting lens comprising a grille  710 , and first and second infrared transmitting materials  730 ,  740 . The window assembly  700  of this  FIG. 8  embodiment also shows optional, first and second covers  752 ,  762 . The optional covers  752  and  762  are also curved. In this embodiment, the grille  710  has a curved profile, as does the first infrared transmitting material  730  and second infrared transmitting material  740 . The first  730  and second  740  infrared transmitting materials have substantially the same curvature as the grille  710  so as to engagingly contact with the grille  710 . Advantageously by having the infrared transmitting material  730 ,  740  with the same curvature as the grille  710  aids even distribution of the infrared transmitting material  730 ,  740  into the aperture of the grille  710  or over the grille  710 . As previously described, the first infrared transmitting material  730  or the second transmitting material  740 , or both the first  730  and second  740  infrared transmitting material, in some embodiments, may deform and at least partially fill the array of apertures (not shown) in the grille  710 . The window assembly  700  is further provided with an optional curved first cover  752  and an optional curved second cover  762 . Again, the first optional cover  752  and second optional cover  762  have substantially the same curvature as the grille  710 , and as the first and second transmitting materials  730 ,  740 . This arrangement is particularly advantageous as the curved infrared transmitting lens may be exposed to more potential damage. The curvature of the components within the infrared transmitting lens or window assembly  700  can be modified to correspond to the required curvature wanted for the infrared transmitting lens. Advantageously, in this embodiment, both infrared transmitting materials  730  and  740  comprise a polymeric infrared transmitting material, to allow the curved construction. The grille comprises a metal, in this embodiment. 
       FIG. 9  shows a part cross cut section of an infrared transmitting lens  800  according to an embodiment of the present invention. The infrared transmitting lens  800  comprises a grille  810  formed from a network of bars. The grille  810  comprises a network of bars. In this particular embodiment, grille  810  and the network of bars of the grille  810  comprises stainless steel. The network of bars of the grille has an array of apertures, however for simplicity, only one aperture is shown. The aperture is filled with an infrared transmitting material  830 . In this embodiment, the infrared transmitting material is a polymeric material. More specifically, the infrared transmitting material comprises polyethylene. When infrared radiation (not shown) is directed towards the aperture of the grille  810 , and the infrared transmitting material  830  therein, the infrared radiation transmits through the aperture and the infrared transmitting material  830 . The Infrared transmitting material  830  enables infrared radiation in the wavelength range of about 0.5 micrometres to about 1 millimetre to transmit through the infrared transmitting material  830  and thus through the infrared transmitting lens  800 . In this particular embodiment, the infrared transmitting material  830  has a width, from one side to the other side, of 0.4 millimetres. This is the same in this particular embodiment as the width of the grille at 0.4 millimetres. In other embodiments the infrared transmitting material  830  may have a different width, so long as its width and the properties of the infrared transmitting material  830  allow infrared radiation to pass therethrough. In this  FIG. 9  embodiment there is no infrared transmitting material  830  on the outer surface of the sides of the grille  810  at the network of bars portion of the grille. Advantageously the grille is made of stainless steel and therefore is resistant to corrosion. The infrared transmitting lens of the  FIG. 9  embodiment may be produced by extruding infrared transmitting polymer  830  into the apertures of the grille  810 . 
       FIG. 10  shows an infrared transmitting lens  900  according to another embodiment. The infrared transmitting lens  900  comprises a grille  910  that is substantially the same as the grille  810  in  FIG. 8 , so will not be described again in detail. In this particular embodiment, the infrared transmitting lens comprises an infrared transmitting material  930  on a front side of the grille  910  positioned parallel and flush against the grille  910 . The infrared transmitting material  930  comprises polymer, in this embodiment. To produce the  FIG. 10  embodiment a sheet of infrared transmitting polymer  930  is placed, or positioned, on one side of the grille  910 , and compressed into the grille by hand. A force of compression of approximately twenty newtons is used to compress the sheet of infrared transmitting material into the grille  910 . In some alternative embodiments the compressing process of the infrared transmitting material may be a mechanical process. The infrared transmitting material  930  deforms and partially fills the aperture  920  of the grille  910 . The apertures are filled sufficiently enough to offer protection, and prevent movement of objects through the infrared transmitting lens. In this  FIG. 10  embodiment the sheet of infrared transmitting material is 0.2 millimetres in width before compression. After compression the sheet of infrared transmitting material is has a width of 0.4 millimetres in the apertures  920  portions of the grille and a width of 0.1 millimetres at the network of bars portion of the grille  910 . The grille is 0.5 millimetres in width from one side to the other side, at the network of bars portion of the grille. Infrared radiation is able to travel through the grille at the aperture portions of the grille  910 , through the infrared transmitting material  930 . In this embodiment the infrared transmitting material  930  forms a fluid seal, preventing fluid from passing though the grille  910 . The polymeric infrared transmitting material  930  also protects the grille from degradation for example from corrosion, or harmful chemicals. 
     In a further embodiment similar to that shown in  FIG. 10 , another infrared transmitting material, comprising polymer, similar to the first infrared transmitting material  930  could be positioned on the other side of the grille  910  and compressed together to give infrared transmitting material on both sides of the grille  910 . The second infrared transmitting material (not shown) would be a mirror image of the infrared transmitting material  930  shown in the  FIG. 10 . Ideally the two infrared transmitting materials would join in the apertures of the grille  910 . Again, the infrared transmitting materials form a fluid seal across the grille  910 . 
       FIG. 11  shows an infrared transmitting lens  1000  according to a further embodiment. The infrared transmitting lens  1000  comprises a grille  1010  that is substantially the same as the grille  810  in  FIG. 8  and grille  910  in  FIG. 9 , so will not be described again here in detail. The infrared transmitting lens  1000  further comprises a first infrared transmitting material  1030  positioned parallel and flush against a front side of the grille  1010  and a second infrared transmitting material  1040  positioned parallel and flush against a rear side of the grille  1010 . The  FIG. 11  embodiment is manufactured by placing, or positioning, two identical infrared transmitting sheets  1030 ,  140  comprising polymer on either side of a grille  1010  and compressing the two sheets of infrared transmitting material together into the grille  1010 . The two infrared transmitting materials  1030  and  1040  both comprise polymer. The two infrared transmitting materials  1030  and  1040  are both manufacture as largely planar sheets with protrusions. The protrusions of the sheets of infrared transmitting materials are configured to correspond to the configuration, shape and positioning of the apertures in the grille  1010 , such that the protrusions of the infrared transmitting materials  1030  and  1040  fit into the corresponding apertures of the grille. Further, in this embodiment the infrared transmitting materials  1030  and  1040  may abut, for example, flat, against a side, or opposites sides of the grille, with the protrusions within the apertures of the grille  1010 . Advantageously, no compression is required in this embodiment. Each infrared transmitting material  1030  and  1040  may form a fluid seal. Advantageously such a configuration may give a good seal, and is easy to fit. Further the protrusion configuration of this embodiment is easy to manufacture and store. Similar embodiments may use only one preformed infrared transmitting material with protrusions where the protrusions correspond to the array of apertures of the grille. In some embodiments the preformed sheets of infrared transmitting material with protrusions on one side may be planar and smooth on the opposite side of the preformed sheet of infrared transmitting material. In some alternative embodiments the preformed sheets of infrared transmitting materials with protrusions on one side, may have corresponding indents on the opposite side of the sheet of infrared transmitting material. 
     A force may still be applied to compress this embodiment but it is not necessary to produce a seal or a complete infrared transmitting lens. Both sides of the grille need not be covered by an infrared transmitting material to produce an infrared transmitting lens. The infrared transmitting lens may comprise a sheet of infrared transmitting material wherein the infrared transmitting material comprises a preformed sheet of infrared transmitting material. Further the infrared transmitting material may comprise protrusions. The protrusions of the sheet of infrared transmitting material may correspond to the apertures of the grille. 
     In an alternative embodiment where a compression force is desired, the force used to compress the two sheets of infrared transmitting material  1030 ,  1040  into the grille  1010  may be between 15 and 40 Newtons of force. In this embodiment, the first infrared transmitting material  1030  on a front side of the grille  1010  deforms and partially fills the aperture between the bars of the grille  1010  from the front side. The second infrared transmitting material  1040  on the rear side of the grille  1010  deforms and partially fills the aperture of the grille  1010  from the rear side. In this particular embodiment, the first infrared transmitting material  1030  and the second infrared transmitting material  1040  deform and fill the aperture of the grille  1010  from their respective sides and contact in the middle of the aperture, thus, partially at least, filling the aperture. In other embodiments, the first infrared transmitting material  1030  and the second infrared transmitting material  1040  deform and partially fill the aperture of the grille  1010  from their respective sides and are separate from one another. Thus, the aperture remains partially filled. The width of both the first  1030  and second  1040  infrared transmitting material are equal, at 0.2 millimetres in diameter before compression. After compression the width of the first  1030  and second  1040  infrared transmitting material together, in total, is 0.4 millimetres at the aperture portion of the grille  1010 . The grille  1010  has a width of 0.35 millimetres. In this  FIG. 11  embodiment the infrared transmitting material  1030 ,  1040  coats the grille, thus offering protection against degradation, for example, corrosion. The grille  1010  gives structural protection to the infrared transmitting material and the infrared transmitting lens. 
       FIG. 12  shows an infrared transmitting lens  1100  according to a yet further embodiment. The infrared transmitting lens  1100  comprises a grille  1120  that is substantially the same as the grilles as described in  FIGS. 9, 10 and 11 , so will not be described again here in detail. The infrared transmitting lens  1100  further comprises a first infrared transmitting material  1130  positioned parallel and plush against a front side of the grille  1110  and a second infrared transmitting material  1140  positioned parallel and flush against a rear side of the grille  1110 . The grille  1110  is formed from a network of bars. In this particular embodiment, the grille and bars comprise aluminium, however alternatively in other embodiments the bars may comprise a different material, such titanium or copper, plastic, plastic coated with a metal, or a different metal. The network of bars, which in this embodiment is aluminium, has an array of apertures  1120 , however for simplicity, only one aperture  1120  is shown. In this embodiment, each of the first infrared transmitting material  1130  and the second infrared transmitting material  1140  are not compressed, and thus do not deform to fill the aperture  1120  of the grille  1110 . In some embodiments an air gap may exists in the apertures  1120  of the grille  1110  between the first  1130  and second  1140  infrared transmitting materials. Both, the first  1030  and second  1040  infrared transmitting material is 0.2 millimetres in width. The grille  1110  is 0.5 millimetres in width. The first  1030  and second  1040  infrared transmitting material cover the grille  1110  protecting the grille  1110  from, for example, corrosion. The total width of the infrared transmitting lens of the  FIG. 12  embodiment is 0.7 millimetres. 
       FIG. 13  shows an exploded view of an infrared transmitting lens  500  that, in this particular embodiment, uses double-sided adhesive-tape  555 . An exploded view of  FIG. 13  is shown to assist in understanding the component parts but in use the double-sided adhesive-tape  555  would contact both the grille  510  and the infrared transmitting material  550 ,  560 ; holding the infrared transmitting material  550 ,  560  to the grille  510 . In this embodiment there are two infrared transmitting materials  550 ,  560 , one on each side, or face, of the grille  510 . In this embodiment the grille  510  comprises stainless steel, metal, to give strength and structural rigidity to the infrared transmitting lens  500 . The grille  510  comprises an array of apertures  520  to enable the infrared light to pass through. The grille is 0.2 millimetres in width, from one side, or face, to the other side, or face, of the grille in this example. To each side, or face, of the grille there is a double-sided adhesive tape  555  with an array of apertures  557  that correspond to the array of apertures  520  of the grille  510 . In the embodiment shown here, the corresponding array of apertures  557  of the double-sided adhesive-tape  555  is an exact, or almost exact, match to the array of apertures  520  of the grille  510 . In this embodiment a jig (not shown) could be used to cut the array of apertures  557  of the double-side adhesive-tape  555 . In other embodiments the corresponding array of apertures  557  of the adhesive tape  555  may not an exact match, for example the double-side adhesive tape may be only near the peripheral edge of the sides of the grille  510 . In this  FIG. 13  the central axis  570  is shown by a dashed line, however this dashed line does not exist in the embodiment. 
     Various modifications to the detailed designs are described above are envisaged. For example, previously it is described that the first infrared transmitting material and the second infrared transmitting material are compressed inwards towards the grille. This urges the first transmitting material and the second infrared transmitting material towards the grille and optionally, deforming the infrared transmitting material into the apertures of the grille. In some embodiments the grille may be formed by extrusion. In some embodiments, one or more, of the infrared transmitting material may be extruded around the grille. That is, the grille is produced by feeding a material such as, for example, aluminium, through an extruder along with infrared transmitting material on one or both sides of the grille. This produces an infrared transmitting lens having a grille and infrared transmitting material(s) in one step such that the grille is provided with infrared transmitting material(s) provided within, around or on, or any combination of within, on or around the grille, removing the need for a compression step to attachingly engage the infrared transmitting material with the grille. When the infrared transmitting material, for example, an infrared transmitting material comprising polymer, surrounds, or partially surrounds, the grille, the infrared transmitting material protects the grille from degradation, for example, from corrosion. 
     It will be clear to a person skilled in the art that features described in relation to any of the embodiments described above can be application interchangeably between the different embodiments. The embodiments described above are examples to illustrate various features of the invention. 
     Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Through the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
     Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect embodiment, or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract or drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.