GH-type LCD protective glasses and cover structure frame

Abstract

The protective glasses (1) and / or sunglasses according to the invention comprise a frame (2) adapted to support a lens assembly (6) comprising a structured lens (8) made of a plastic material and at least one LC film (9) with GH liquid crystals, arranged inside the structured lens (8) and controlled by an electronic board (5) powered by an energy source. The glasses (1) are characterized in that the structured lens (8) has a free end (11) that extends beyond the contour of the LC film (9), at which the lens assembly (6) is fixed to the frame (2). Furthermore, there is a free space (111) between the frame (2) and the LC film (9). The frame (2) is provided with a vertically protruding rib (21) that covers the free end (11) and the free space (111). Advantageously, the rib (21) not only limits deformation of the lens assembly, but also prevents light from penetrating around the LC film, which would impair comfortable vision.

Description

[Technical field]

[0001] The object of the invention is protective eyewear for the practice of sports activities or for use in transport. [Background technology]

[0002] When practicing sports, it is often necessary to use glasses to protect the eyes from wind, particles, excessive light, etc.

[0003] The same requirement applies when using open modes of transport, including traditional and electric bicycles, scooters or skateboards.

[0004] Glasses currently available on the market offer a great deal of protection for a user's eyes from wind and particles.

[0005] With regard to light protection, there are many types of filters that reduce the amount of light that reaches the user's eyes, each of which is suitable for certain light conditions. For example, current European legislation separates optical filters into five categories and describes, for each category, under what conditions these filters are suitable to protect the user's eyes while ensuring optimal vision. Summary of the Invention [Problem to be solved by the invention]

[0006] However, during sports and when using transport, ambient light conditions can change significantly and rapidly - just consider entering a road tunnel for example - so not only is the use of a single lens not optimal for this type of activity, but changing lens types in response to changing ambient light conditions is also not possible.

[0007] To address this issue, photochromic lenses have been developed that use a chemical reaction to make the lens less transparent as a result of exposure to light, but photochromic lenses are particularly slow to increase their transmittance, taking several minutes to achieve the full transition.

[0008] Furthermore, the use of chemical reactions to reduce the transparency of the filters results in poor control of the activation curve of the lenses and poor control of the filter transmission as a function of the amount of incident light. For example, this type of lens often partially darkens in situations where the light level is less than optimal, which may even exacerbate the situation. This second aspect is exacerbated by the high sensitivity of the filters to ultraviolet light. In fact, ultraviolet light is often present in sufficient amounts even under conditions of insufficient light, resulting in the photochromic lenses darkening rather than darkening even under conditions of insufficient light.

[0009] As if this were not enough, all of these aspects are further exacerbated in the presence of low temperatures, with photochromic lenses always prone to becoming partially blind.

[0010] Electrochromic lenses are also known, typically using polymers whose optical properties change when a magnetic field is applied. Although these lenses are faster than photochromic lenses, they are still fairly slow. Furthermore, the large power required to achieve the state change limits the maximum number of possible changes, and this type of lens only works to automatically adapt to ambient light if a bulky battery is present.

[0011] Finally, lenses using a layer of liquid crystals are known and are the only ones that can react quickly to changes in the ambient light. However, this type of lens is still practically not used in products for general use, due to a number of persistent problems, including low maximum brightness of the filter, the presence of unwanted polarized light, interference with other transparent elements, and undesirable reactions to mechanical stress. For these reasons, this lens is actually used in the field of protective equipment for welding, where TN (Twisted Nematic) planar liquid crystal LC screens are widely used. However, this screen is not suitable for protection from sunlight under normal conditions, since in practice it is too dark in the maximum transmittance state and has a very narrow field of view.

[0012] Device application technology using GH (guest-host) liquid crystals is also known. This type of liquid crystal does not use a polarizing filter and can achieve a transparency of over 50%, which may make it more suitable for use in sun protection devices under normal conditions. However, this type of lens also has its own set of problems, so that devices manufactured in this way are not currently on the market. The problems associated with this technology are listed below.

[0013] (1) The GH liquid crystal layer is subject to mechanical stress, which causes strong changes in the local transparency level of the LC film. Due to the structure of sunglasses, the mechanical stress on the lenses is too large to use GH type LC films.

[0014] (2) To alleviate the above-mentioned mechanical stresses, a possible solution is to apply the LC film to a structural lens, so that the LC film is relatively independent of the deformation of the lens. However, this configuration causes annoying light infiltration from the periphery of the LC film, which reduces the optical quality.

[0015] (3) The most common lenses for manufacturing safety glasses are obtained by injection molding. This technique has considerable advantages, but when applied to eyeglass lenses, it creates internal tensions inside the lens, which, in combination with the GH LC film, produce an annoying "rainbow" effect. A possible solution to this problem would be to use thermoformed lenses. However, this type of lens has a significantly inferior optical quality and precision. Moreover, this technique does not allow the formation of optically "correct" lenses.

[0016] (4) All dynamic lenses sold to date lack adequate control of the activation curve, or function between ambient lighting level and the drop in visible light transmission. Without such precise control of the activation curve, it is virtually impossible to have a device that is truly effective in maintaining an optimal light level as perceived by a user over a wide range of ambient light levels. This problem has yet to be solved.

[0017] The object of the invention is to obtain spectacles which are indeed able to provide optimum light protection not only under the most common light conditions but also against sudden changes in these conditions whilst always ensuring comfortable and effective vision. [Means for solving the problem]

[0018] This object is achieved by a pair of glasses according to claim 1, a lens assembly according to claim 10 and a method for controlling the level of transparency of a lens assembly according to claim 11. Further advantageous embodiments of the invention are disclosed in the dependent claims. Effect of the Invention

[0019] The characteristics and advantages of the spectacles according to the invention will become apparent from the following description, given by way of non-limiting example and in accordance with the accompanying drawings, in which: [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view of protective goggles according to one embodiment of the present invention; [Diagram 2] Exploded view of the safety glasses shown in Figure 1 [Diagram 3] Exploded view of the lens assembly of the safety glasses in Figure 1 [Figure 4] Cross-section of the protective goggles in Figure 1 [Diagram 5] A detailed diagram of Figure 4 [Figure 6] FIG. 1 shows the relationship between ambient light and perceived light for a conventional static lens with a 30% VLT (visible light transmission). [Figure 7] Diagram showing the relationship between ambient light and perceived light using photochromic lenses [Figure 8] FIG. 1 is a diagram showing the relationship between ambient light and the VLT (visible light transmission) of a lens in an exemplary embodiment of the present invention. [Figure 9] FIG. 1 illustrates the relationship between ambient light and perceived light in an exemplary embodiment of the present invention. [Figure 10] FIG. 2 shows a detail of a longitudinal section of protective goggles according to the invention in a further embodiment. [Figure 11] FIG. 2 shows a detail of a longitudinal section of protective eyewear according to the invention in yet another embodiment. [Figure 12] FIG. 2 is a schematic diagram showing the operation of a sensitivity cone applied to glasses according to the present invention during use; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] With reference to the attached figures, the number 1 is used to generically designate protective eyewear according to the invention for the practice of sports activities or for use on motorized vehicles. In particular, the protective eyewear 1 is also sunglasses.

[0022] The eyeglasses 1 comprise a frame 2 adapted to support a lens assembly 6. As shown in FIG.

[0023] As shown in FIG. 6, the lens assembly 6 includes a structural lens 8 and at least one liquid crystal film 9 (hereinafter referred to as LC film) controlled by an electronic board 5 .

[0024] Preferably, the frame 2 is made of a polymer matrix composite material, such as nylon, polycarbonate, epoxy resin, or polyester, and preferably, the frame 2 is made of a polymer matrix composite material, and includes reinforcements, such as glass or carbon fibers, glass microspheres, or graphene.

[0025] In alternative embodiments, the frame 2 is formed from a light metal material such as an aluminum alloy, titanium, or magnesium.

[0026] Depending on the material chosen, the frame 2 is obtained by injection moulding, or alternatively by forging, die casting or metal moulding.

[0027] Advantageously, the materials listed above allow the frame 2 to be sufficiently rigid to avoid deformation of the lens assembly 6 during use, which deformation would be transmitted to the LC film 9 and thereby impair its optical uniformity.

[0028] Preferably, the glasses 1 comprise a pair of temples 3 which are hinged to the frame and which can be folded back onto each other to reduce the size of the glasses when not in use.

[0029] Assembly of the temples 3 to the frame preferably does not require the use of through pins: in fact, each temple 3 is attached to the frame 2 by interlocking with a temple seat 31 on the frame 2, which is defined between a pair of hemispherical opposing projections or concavities 32, so that even if the temple 3 is forced to rotate beyond its end of travel it will not break, but will simply disintegrate from the frame 2.

[0030] As shown in Figure 2, the temples 3 have an ergonomic shape, characterized by a substantially S-shaped or wave-shaped curvature that follows the curvature of the user's head at the distal ends of the temples, but is attached to the frame away from the user's head near the hinge point. Advantageously, this wave-like shape increases the contact surface with the user's head, improving comfort and retention. It also allows the glasses to be worn comfortably under helmets, headgear, hats, bands, etc.

[0031] Preferably, the temples 3 are made of a material with a modulus of elasticity that is less than half that of the material selected for the frame 2. Advantageously, with this configuration, the deformations of the spectacles 1 necessary for positioning them on the user's face act mainly on the temples 3, thereby avoiding excessive deformations of the frame 2. In this way, the deformations and stresses acting on the structural lenses 8, and thus also on the LC film 9, are reduced.

[0032] Preferably, the frame 2 is interlockingly assembled and includes a rubber nosepiece 7 which facilitates holding the spectacles 1 on the user's nose.

[0033] The frame 2 is provided with a seat or recess 4 in which at least one energy source, for example a solar cell 51 or the entire electronic board 5 including the solar cell 51 is housed.

[0034] Advantageously, the recess 4 is located in the front upper central portion of the frame 2, as shown in FIG. 2, so as not to obstruct the user's field of vision.

[0035] In one embodiment, the recess 4 only houses the energy source, e.g. a solar cell 51, and the electronic board 5 is located in a separate seat, e.g. on the side of the frame 2, or inside the temple 3, or in another location best suited for the particular application.

[0036] Preferably, the solar cell 51 simultaneously functions as a sensor and as an energy source for operating the LC film 9. Advantageously, this configuration makes it possible to avoid the use of batteries, reducing costs and increasing the reliability of the glasses 1.

[0037] In one embodiment, the solar cell 51 is flexible and / or conforms to the curvature of the structural lens 8 .

[0038] The electronic board 5 is waterproof and protected by a coating, potting or other form of waterproof protection treatment.

[0039] As mentioned above, frame 2 surrounds a lens assembly 6 which includes a structural lens 8, preferably formed from a plastic material, such as polycarbonate.

[0040] Preferably, the structural lens 8 protects the electronic board 5 at the front, which is protected at the rear by the wall of the recess 4 located in the frame 2. Advantageously, this arrangement mechanically and chemically protects the electronic board 5. Also, except for the absorption of the structural lens 8, the light reaching the solar cell 51 is filtered in the same way as the light reaching the user's eyes is filtered. In this way, the input signal of the electronic board 5 is correctly adjusted to the user's perception. For example, the input signal of the electronic board 5 is not affected by UV rays, as it should actually be, since UV rays are already blocked by the structural lens 8.

[0041] The structural lens 8 is preferably manufactured by injection molding. In other exemplary embodiments, the structural lens is manufactured by thermoforming, stereolithography, or other additive manufacturing techniques.

[0042] In one exemplary embodiment, the structured lens 8 is treated to have a mirror finish, an anti-reflective finish, an anti-scratch finish, a hydrophobic finish, or an oil-repellent finish, or other finish suitable for a particular application.

[0043] In one exemplary embodiment, the structured lens 8 also includes a multi-layer, opaque mirror finish. In a variation of such an embodiment, the mirror finish characteristics are different in different regions of the structured lens 8.

[0044] In the lens assembly 6, the LC film 9 is disposed internally with respect to the structural lens 8. Preferably, the LC film 9 is laminated to the inner surface of the structural lens 8, preferably by an optical adhesive (optical blue).

[0045] Preferably, the LC film 9 is a GH liquid crystal film. In this type of LC film, dichroic pigments are dispersed in a matrix of liquid crystals, where a magnetic field dictates the orientation of the liquid crystals, which in turn dictates the orientation of the pigments. Typically, in the "active" state, the crystals adopt a helical structure and the pigments are arranged in a plane parallel to the surface of the film, whereas in the "inactive" state, the crystals and pigments are arranged perpendicular to the surface of the film.

[0046] Preferably, the LC film 9 has a visible light transmission (VLT) of at least 60% in its most transparent state and a maximum of 25% in its most opaque state. For example, the LC film may have a VLT of about 15% in its most opaque state and a VLT of about 65% in its most transparent state.

[0047] Preferably, the contour of the LC film 9 is contained within the contour of the structured lens 8, as shown in Figures 4 and 5. The portion of the contour of the structured lens 8 not occupied by the contour of the LC film 9 defines a free end 11 that attaches the structured lens 8 to the frame 2. Additionally, a space or gap 111 is provided such that the frame 2 is not in direct contact with the LC film 9.

[0048] Preferably, as shown in Fig. 5, the frame 2 has a substantially L-shaped cross section, which means that the frame 2 has an internal vertical rib 21 covering the free end 11 and the gap 111. Advantageously, this configuration prevents light from penetrating around the LC film 9, which would impair comfortable viewing. Furthermore, the frame rib 21 can reduce deformation of the lens assembly 6.

[0049] The LC film 9 is controlled by an electronic board 5 which is preferably connected by a flexible printed circuit board (FPC) 91 .

[0050] The safety glasses 1 are equipped with an electronic board 5 that controls the activation of the LC film 9 as a function of the ambient light level according to a non-linear activation curve. The activation curve dictates that the LC film 9 remains substantially at maximum transparency until a certain light threshold 131 is reached, after which the LC film 9 begins to become less transparent as the ambient light increases.

[0051] As shown in Figure 3, a depolarizing layer 10 is preferably laminated between the structured lens 8 and the LC film 9. The depolarizing effect of the depolarizing layer 10 is preferably obtained by a birefringent film characterized by a wave phase shift between the two optical axes of more than 1500 nm.

[0052] Figures 6, 7 and 9 are graphs showing the relationship between ambient light (in lux) and perceived lighting (in lux) depending on the lenses used in the glasses. The graphs also show: A horizontal line indicating the optimum lighting level (7500 lux) for practising sports activities The grey area indicates the optimum range for the analyzed lens.

[0053] Figure 6 shows the relationship between ambient light and perceived light when using a conventional lens with a VLT (visible light transmission) of 30%. It should be noted that in this case the lens is suitable for certain light conditions (very small grey area of ​​the graph) and therefore has a limited range of optimal use.

[0054] Figure 7 shows the relationship between ambient light and perceived light when using a typical photochromic lens. The aim of a photochromic lens is to maintain adequate transparency in all conditions, but in reality the activation curve of the pigments is not well controlled. For example, the transparency of the filter usually starts to decrease long before the optimal light level is reached. In fact, photochromic lenses, like conventional lenses, have a limited range of optimal use (highlighted by the grey area on the graph).

[0055] FIG. 8 illustrates the relationship between ambient light and the visible light transmission level (VLT=visible light transmittance) of the lens assembly 6 according to the present invention, where the electronic board 5 controls the LC film 9 to keep it in its deactivated state (maximum visible light transmittance) within the low lighting range, indicated by reference numeral 13 in FIG. 8.

[0056] The amplitude of range 13 is defined above by a threshold level indicated at 131 in FIG.

[0057] In one exemplary embodiment, the threshold level 131 is fixed and calculated by dividing the optimal perceived light level, set at 7500 lux for the practice of sports activities or use for transportation, by the maximum visible light transmittance, i.e. maximum transparency, of the lens assembly 6 with a tolerance of 25%.

[0058] The threshold level 131 corresponds to an ambient light level below which the light level perceived by a user through the lens assembly 6 at maximum visible light transmittance is less than optimal, and therefore it is appropriate for the LC film 9 to remain fully deactivated and therefore in its maximum transparency state.

[0059] When the ambient light level rises above the threshold level 131, the electronic board 5 controls, according to a particular control function, by decreasing the visible light transmittance, and therefore the transparency of the LC film 9, as the ambient light level increases until a minimum transparency level of the LC film 9, i.e. a minimum visible light transmittance, is reached.

[0060] Within the low light range 13, the value of the visible light transmittance VLT level of the LC film 9 is determined by a control function defined as follows: VLT=7500Lux / (t·la) where "t" is the visible light transmittance of the structured lens 8 and "la" is the ambient light level in lux.

[0061] The graph in Figure 9 shows the relationship between ambient light and the light perceived by a user wearing protective eyewear 1 according to the present invention. As can be seen from the large grey areas on the graph, protective eyewear 1 provides optimal perceived light over a wide range of ambient brightness. Thus, protective eyewear 1 according to the present invention is not suited to a specific lighting situation, but rather provides optimal visibility over a fairly wide range of lighting conditions.

[0062] Moreover, in an exemplary embodiment, the threshold level 131 is variable as a function of the average ambient light level over a particular time interval, for example, 30 seconds to 5 minutes. Advantageously, the safety glasses 1 are able to eliminate changes in perceived light due to sudden changes in ambient light levels by taking advantage of the ability of the human eye to slowly adapt to changes in ambient light.

[0063] In a further exemplary embodiment shown in Figures 10-12, the circuit board 5 receives as input the ambient light level of a predefined region of the user's field of view, e.g. a sensitivity cone 15. Preferably, the sensitivity cone 15 has an opening angle α between 90 degrees and 10 degrees and is directed towards the front / bottom of the user, as shown in Figure 12.

[0064] The safety glasses 1 are equipped with a device for controlling the opening angle α of the sensitivity cone 15 .

[0065] In the example of FIG. 10, the device for controlling the opening of the sensitivity cone 15 is defined by slats 14 arranged inside the recess 4 and in front of the solar cell 51 .

[0066] In the example of FIG. 11, the device for controlling the opening of the sensitivity cone 15 is defined by a visor 17 which projects forward from the frame 2 and above the recess 4 in which the solar cell 51 is housed.

[0067] In a further embodiment, the opening of the sensitivity cone 15 is defined by a lens or mirror to achieve similar results.

[0068] In another exemplary embodiment, the protective glasses 1 comprise a sensor arranged inside the recess 4, next to the solar cell 51. In this way, by suitable adaptation of the electronic board 5, a definition of the opening of the sensitivity cone can be obtained without cumbersome physical devices such as slats 14 or visors 17. In this example, the electronic board 5 uses the solar cell 51 as the only energy source and the sensor determines the value of the ambient light to be compensated.

[0069] Advantageously, by detection at the sensitivity cone 15, the lens assembly 6 is sensitive to portions of the ground and objects that the user will soon encounter on his way. In this way, it is possible to obtain safety glasses 1 whose correction is substantially predictable in the most common situations of use.

[0070] FIG. 12 shows the case where the protective glasses 1 are used by a cyclist preparing to go through a tunnel. In this situation, a large part of the sensitivity cone 15 is occupied by a poorly lit area (indicated by the number 16). In this situation, the input signal of the electronic board 5 is reduced and the lens assembly 6, or rather the LC film 9, becomes more transparent, even though the cyclist is still illuminated by the sun. Advantageously, the cyclist can therefore optimally see the ground in the poorly lit area 16, even if the light level changes suddenly, and can avoid or react to obstacles or dangers such as holes, stopped cars, rocks, etc., even before reaching that area.

[0071] In one embodiment of the present invention, the opening angle α of the sensitivity cone 15 is fixed and related to the typical speed of the particular activity for which the protective eyewear 1 is designed. Indeed, the higher the typical movement speed of a user, the more desirable a sensitivity cone with a smaller opening is. Advantageously, this configuration allows the user to focus their attention on a reaching object in a time comparable to their reaction time.

[0072] In a further embodiment of the invention, the opening angle α of the sensitivity cone 15 is variable and is constantly adjusted during use in response to an input signal received from, for example, a GPS sensor, an acceleration sensor system or a speed sensor, such as a system based on an optical sensor, for example based on speckle.

[0073] In a further embodiment of the invention, the device for determining the opening of the sensitivity cone 15 allows the user to exchange, for example, the slats 14, so that the protective eyewear 1 can be adapted to a more specific application.

[0074] It is understood that those skilled in the art can make modifications to the above-mentioned device to meet the accompanying needs, all of which fall within the scope of protection defined by the following claims.

Claims

1. A frame (2) adapted to support a lens assembly (6), At least one lens assembly (6) at least partially surrounded by the frame, the lens assembly (6) having at least one structural lens (8) formed of a plastic material and at least one GH-type liquid crystal LC film (9) disposed inside the structural lens (8) and controlled by an electronic substrate (5) powered by an energy source, Comprising, The structural lens (8) has a free end (11) extending beyond the outer contour of the LC film (9), and the lens assembly (6) is fixed to the frame (2) at the free end (11), There is a free space (111) between the frame (2) and the LC film (9), The frame (2) is provided with a vertical protruding rib (21) covering the free end (11) of the structural lens and the free space (111) of the LC film (9), Protective glasses and / or sunglasses (1).

2. The electronic substrate (5) controls the activation of the LC film (9) having a maximum transparency state as a function of the ambient light level, such that the LC film (9) substantially maintains the maximum transparency state until a light threshold (131) is reached, and then the LC film (9) begins to decrease in transparency as the ambient light increases, The protective glasses and / or sunglasses (1) according to claim 1.

3. The light threshold (131) is calculated by dividing an optimum level of perceived light set at 7500 lux by the maximum visible light transmittance (VLT) level of the lens assembly (6) with a 25% tolerance, The protective glasses and / or sunglasses (1) according to claim 2.

4. The light threshold (131) is variable in relation to the average ambient light measured over a time interval between 30 seconds and 5 minutes, The protective glasses and / or sunglasses (1) according to claim 2.

5. The electronic substrate (5) responds primarily to the ambient light measured within a sensitivity cone (15) directed towards the front and / or lower part of the user's field of view, Such a sensitivity cone (15) has an opening angle (α) between 90 degrees and 10 degrees, The protective glasses and / or sunglasses (1) according to claim 2.

6. The LC film (9) has a maximum visible light transmittance (VLT) of less than 25% in its minimum transparency state and more than 60% in its maximum transparency state. The protective glasses and / or sunglasses (1) according to any one of claims 1 to 5.

7. The power source of the electronic substrate (5) is a solar cell (51). The control device for the opening angle (α) of the sensitivity cone (15) exists in the form of a lamellar structure (14) arranged in front of the solar cell (51) or a visor (17) protruding from the frame (2) in front of and above the solar cell (51). The protective glasses and / or sunglasses (1) according to claim 5.

8. It includes a pair of temples (3) attached to the frame (2) by hinges. The temple (3) is formed of a material having an elastic modulus that is half or less of the elastic modulus of the material forming the frame (2). The protective glasses and / or sunglasses (1) according to any one of claims 1 to 5.

9. The electronic substrate (5) is powered by an energy source. The energy source consists of one or more solar cells (51) and / or The energy source is located behind the structural lens (8) and outside the outer periphery of the LC film (9) and / or The energy source is located outside the outer periphery of the LC film (9) at the upper center of the glasses. The protective glasses and / or sunglasses (1) according to any one of claims 1 to 5.

10. At least one structural lens (8) formed of a plastic material and At least one GH-type liquid crystal LC film (9) arranged inside the structural lens (8) and controlled by an electronic substrate (5) powered by an energy source. Comprising The electronic substrate (5) controls the activation of the LC film (9) having a maximum transparency state as a function of the ambient light level, so that the LC film (9) substantially maintains the maximum transparency state until the light threshold value (131) is reached, and then the LC film (9) begins to decrease in transparency as the ambient light increases. A protective and / or sun lens assembly (6).

11. A method for controlling the transparency level of a protective and / or sun lens assembly (6). The lens assembly (6) includes a structured lens (8) formed of a plastic material, and a GH-type liquid crystal LC film (9) disposed inside the structured lens (8) and controlled by an electronic substrate (5) powered by a solar cell (51). The method comprises controlling, by the electronic substrate (5), activation of the LC film (9) having a state of a maximum visible light transmittance level (maximum VLT level) as a function of the ambient light level, as follows: maintaining the LC film (9) substantially at the maximum VLT level until a light threshold value (131) is reached; when the light threshold value (131) is exceeded, reducing the VLT level as the ambient light increases; A method. **Claim 12** The light threshold value (131) is fixed and calculated by dividing an optimum level of perceived light set at 7500 lux by the maximum visible light transmittance (VLT) level of the lens assembly (6) with a tolerance of 25%, or The light threshold value (131) is variable in relation to the average ambient light measured over a time interval between 30 seconds and 5 minutes. The method according to claim 11.

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