ACOUSTO-OPTICAL SYSTEM

Abstract

The invention relates to an acousto-optical system, comprising at least one acousto-optical element, the at least one acousto-optical element comprising a cover, a support, and means. The means is arranged to move the cover from a first cover contour profile to a further cover contour profile which is different from the first cover contour profile. The acousto-optical system further comprises a controller configured to control the means of the at least one acousto-optical element at a frequency of at least 20 Hz, optionally at maximally 25 000 Hz. The invention also relates to an acousto-optical transducer system.

Description

The current application relates to an , comprising at least one acousto-optical element, the at least one acousto-optical element comprising a cover having a rst surface and a second surface, a support, and ameans, wherein the cover is orientated with the rst surface directed towards the support, a part ofthe rst surface is attached to the support, a spatial arrangement ofthe cover as seen in a cross section ofthe cover denes a cover contour prole, and the means is arranged to move the cover from a rst cover contour prole to a further cover contour prole which is different from the rst cover contour prole, An optical element is known from e.g.WO 2021 / 032752 Al andWO 2018 / 228671 Al. This document discloses optical devices ofspecic interest. The working principle is thatwhen a cover is provided that has some desired optical behaviour, e.g. reecting light, transmitting only some light, etc. the interaction ofincident light can be changed by changing the cover contour prole. To facilitate the cover changing shape to facilitate changing the optical behaviour ofthe optical device, the cover is made relatively thin, in terms ofWO 2021 / 032752 Al 2-dimensional. As an example, a single graphene layer cover is presented, with a coating on top to obtain desirable optical behaviour. Since the optical device is very small, they can be used to act like a pixel in a larger collection ofsimilar devices. Control of scattering, reection and / or interference behaviour can be used to turn a pixel on or offand / or vary its colour. This way, images can be generated and / or manipulated. Several principles ofoperation are available with such optical devices.A rst operational principle is shown in gures lA 1C, which correspond to gures 9 11 ofWO 2021 / 032752 Al. These gures show respectively an optical device with a at cover, a convex cover, and a concave cover. Light incident on the at cover (g. lA) is reected as ifhitting a smooth and straight surface, i.e. parallel incident rays remain parallel after reection. As such, specular reection takes place at the cover. In the convex and concave positions ofthe cover, parallel incident rays are no longer parallel after reection, thus causing diffuse reection. By changing the shape ofthe cover, it is thus possible to alternate between specular and diffuse reection. To suit this rst operational principle, the cover is sufciently reective towards the incident light. In this example, the light is incident on the second surface, whichmay also be called the outside ofthe optical device. Figures ZA 2C, which correspond to gures 12 14ofWO 2021 / 032752 Al, show a second operational principle. Reference is rst made to the substrate which spans the support on an opposite side ofthe cover, in order to dene a cavity between the cover and the substrate. The substrate is partly reective and partly transmissive. The cover is relatively reecting. Light incident on the substrate is thus partly transmitted and partly reected. The transmitted light reects on the rst surface ofthe cover, i.e. coming from the inside, and is transmitted back through the substrate, where it interferes with the light reected by the substrate. Depending on the wavelength ofthe light and the distance between the cover and the substrate, the interaction can be constructive or destructive. Since that distance changes when the cover changes shape, the interferometric characteristics ofthe optical device can be changed. Figures 5 and 6 show even otherways ofusing the changing cover contour prole. In the case ofgure 5, an optical element is shown with a substrate 106 that is relatively reective. The cover 101 in this case is relatively absorbing. Nevertheless, ofan incoming lightbeam 601, at least some lightmay be transmitted towards the substrate 106 as transmitted lightbeam 603. This reects back via the substrate 106 as reected light 604. Due to interference ofthe transmitted lightbeam 603 and the reected light 604, a pattern ofnodes and antinodes is present. The cover 101 can then be moved, e.g. by changing its cover contour prole or its position with respect to the support, to place the cover at an antinode for absorbing the light, or at a node for not or absorbing less the light. Accordingly, the exiting light 605 can be present in less ormore intensity by controlling the cover. This principle is called interferometric absorption. Figure 6 shows the principle ofinterferometric reection, similar to g. 2, but with light 601 incident the cover. In this case, light is partially transmitted through the cover 101, and reected at the substrate 604, which for that purpose is reective. The cover 101 reects some light 605, but also transmits some light 603. After reecting 604 from the substrate 106, light passing through the cover 101 again interferes with the reected light 605. By controlling the position or cover contourprole ofthe cover 101, control is possible ofwavelengths oflight that do or do not interfere constructively. In both cases, light transmitted through the covermay actually be refracted. However, since the gures show a specic example oflight incident normal to the cover, the wording transmitting was used. The invention can however be applied, depending on the use-case, to non- normal light also. These principles have been described only briey herein, as the operational principles involved are in themselves known, and have been applied e.g. inWO 2018 / 228671 A1 (see gures 1 and 2). These principles thus show thatby varying the reectance and / or transmittance and / or absorbance ofthe cover and the substrate, and the direction atwhich light is incident (from outside or inside the optical device), it is possible to cause the cover to create a certain interaction with the light, optionally in cooperation with the substrate. The interaction changes when the cover shape changes, i.e. when the cover contourprole changes. Despite the advantages described for the optical element ofWO 2021 / 032752 A1, a desire remains to make itmore versatile. It is an object ofthe invention to meet this desire. The object is achieved by an according to the preamble, wherein it further comprises a controller congured to control the means ofthe at optical element at a frequency of at least 20 Hz, optionally at maximally 25 000 Hz. In turn, the cover will also move at said frequency. Saidmovement ofthe cover at such a frequency will produce a soundwave, and in turn sound. Altering the frequency in turn can allow netuning the sound into a certain pitch. This way, the optical element can simultaneously be used as a speaker element, thus it is an acousto- optical element. The invention relates to a system comprising at least one such an acousto-optical element. Controller as used herein, is dened as a device that is congured for affecting the means such that the means perform a certain desired behaviour. In general, the controller will provide any type of signal for said purpose as an input to the means. When the means are for instance an electrode, the controller can be a signal generator that applies a desired voltage, said voltage being an input, to the means. At this point it is noted that according to the invention, the cover also has optical properties that allow modulation oflight in order to provide a desirable optical output. It is however possible to use a similar system with similar elements which do not have such optical properties, ifonly acoustic behaviour is desired. Optical properties ofthe system derive from the optical properties of the cover. There may be varying optical properties suitable for optical modulation, such as varying ratios oftransmittance and reectance or ratios ofabsorbance and reectance, as will be explained below. The skilled person is however readily able to distinguish between an optical and a non- optical system, based on the fact that an optical system allows modulation oflight depending on an input that reects a desired optical behaviour. This is therefore easily distinguished from a purely acoustic system whichmay produce some sort ofvisible response too, butwhich is not used to modulate light. It is noted that anymovement ofthe cover will alter the light output, but keeping the amplitude ofthe movement sufciently small and / orthe frequency ofthe movement sufciently fast, the human eyemay not be able to notice the change. Therefore, agood image quality can be retained evenwhen using the optical element as a speaker element at the same time. This is especially true at higher frequencies, such as for example above 500 Hz. The control frequency for sounds can be limited to 25 000 Hz, as humans generally are unable to observe sounds ofthis frequency or higher. Therefore, limiting the frequency can allow for the system to be less complicated, and thus less expensive, as no ability to move at ultrasound frequencies is required. However, for some applications the ultrasound frequency range can be preferred or even required. In such cases, it can be advantageous to not impose an upper limit, or have it set at a higher frequency, such as 100 kHz or 200 kHz. It can be especially advantageous ifthe controller is congured to, for each ofthe at least one acousto-optical elements control the means so as move the cover in accordance with a desired optical behaviour and to superimpose on and / or combining with the resulting movement, a movement in accordance with a desired acoustic behaviour. The resulting movement is one that has both, the desired optical and the desired acoustic behaviour. The controllermay cause the means to operate in such away as to achieve said movement, for instance by providing input signals to the means that are a combination or superposition ofinput signals that independently would correspond to the desired acoustic or optical behaviour respectively. It is for instance possible, ifthe means accept an electrical input, to provide both a direct currentDC signal in accordance with optical behaviour, and an alternating currentAC signal in accordance with acoustic behaviour. As long as the movement ofthe cover due to theAC signal is sufciently small, the optical behaviour will remain largely unaffected. TheDC signal would act as an offset to theAC signal. As an alternative, it is also possible to control the acoustic behaviour and the optical behaviour using separateAC signals. It is for instance possible, ifthe means accept an electrical input, to provide both anAC signal in accordance with optical behaviour, and anAC signal in accordance with acoustic behaviour. As long as the frequency ofthe cover due to theAC signal corresponding to the desired optical behaviour is sufciently fast, the optical behaviour could remain largely unaffected by theAC signal corresponding to the acoustic behaviour. TheAC signal for optical behavior could act as a modulating signal to theAC signal for the acoustic behaviourwhich would act as a carrier signal, hence the carrier signal being transformed into modulated envelope. In one embodiment ofthe invention, the means ofeach ofthe at least one acousto-optical elements comprises a rst means and a further means, and the controller is congured to rstly control the rst means in accordance with the desired optical behaviour and secondly control the furthermeans in accordance with the desired acoustic behaviour. Accordingly, the means and furthermeans may be chosen so as to operate at desired but different frequencies. Having the two means separate allows larger freedom ofdesign, and therefore facilitates construction. It remains however possible in principle to have a single controller controlling the rst means and the furthermeans, to achieve control ofthe optical and acoustic behaviour. Similar effects can be achieved even ifonly the rst means are present. It is thus possible to achieve similar effects when the single controller is congured to control a single means, when such a means allows to obtain the desired optical behavior and the desired optical behaviorby controlling the means with superimposed and / or combined and / or alternated signals. There is thus an advantage to be gained ifa single controller is used to control both acoustic and optical behaviour. Multiple controllers could be used on the otherhand ifdifferent principles are used by the rst and furthermeans, or ifmany acousto-optical elements are present so as to reduce latency times. It is advantageous ifthe controller is arranged to individually control at least some or all of the at least one acousto-optical elements. When the elements are controlled individually, a collective ofelements can be used to create complex visual and / or auditory behaviours. Itmay furtherbe advantageous, ifacoustic behaviour and optical behaviour ofthe acousto- optical elements are respectively controlled within predened but separate frequency bandwidths. Typically, the bandwidth chosen for optical behaviourwould be outside the 20 25kHz range. The invention also relates to an acousto-optical transducer system, comprising at least one optical element, the at least one acousto-optical element comprising a cover having a rst surface and a second surface, a support, and a sensing means, wherein the cover is orientated with the rst surface directed towards the support, a part ofthe rst surface is attached to the support, a spatial arrangement ofthe cover as seen in a cross section ofthe cover denes a cover contour prole and the sensing means is arranged to output a signal in correspondence with the shape or a change in shape ofthe cover. Optionally, this embodiment ofthe acousto-optical transducer system can also comprise the means ofclaim 1, in addition to the sensing means. These optional means can be arranged to perform any functionality ofthe means as described throughout this document, i.e. to move the cover from a rst cover contourprole to a further cover contour prole which is different from the rst cover contour prole. Ofcourse the acousto-optical transducer system can comprise the other features described in relation to the hereabove (e.g. that ofclaims 1 ll). In case the means and the sensing means are both present (separately or as a single component), and they are controlled by a single controller or multiple controllers, then the acousto- optical transducer system is a bidirectional transducer system, optionally atransceiver system. The sensing means ofthe acousto-optical transducer system may be connected to a controller, congured to receive from the sensing means an input. The controllermay be congured for recording, converting, or output a signal that correlates with the received input. In case the sensing means are used to control movement ofthe cover as was described above, the controllermay be congured to control the sensing means. Ifthe acousto-optical transducer system is to sense sound, the controllermay be congured to receive and process a signal having a frequency ofat least 20 Hz, optionally at maximally 25 000 Hz. In some applications, only a single acousto-optical element is used. This can for example be an alarm comprising a single element that lights up and / or changes colour or otherwise creates a visual output to attract attention and plays an alarm sound at the same time. For other applications however, it can be advantageous ifthe comprises at least 1 000 such acousto-optical elements, preferably at least 10 000, more preferably at least 100 000, and even more preferably at least 1 000 000 acousto-optical elements. For common use, it can be ofuse to incorporate thousands or even millions ofelements in a single system. Together, the acousto-optical elements can then act as a complete speaker, by netuning the pitches ofindividual orgroups ofelements to create the desired sounds on demand. Aside from changing pitches, using a large multitude ofacousto-optical elements can change other parameters ofthe sound, such as the timbre, texture, tone, loudness or envelope. Ofcourse since the elements also exhibit desirable optical behaviour, they can be controlled as e.g. pixels ofa display, to collectively generate an image. One exemplary embodiment ofthe could be a display with integrated speaker functionality. In conventional displays, a separate device is needed to provide sound accompanying the image provided by the display. This either needs to be amodule attached to the screen, or an altogether separate speaker. The takes up less space than a separated display / speaker combination, which can increase the practicality and versatility of displays. The optical part ofthe acousto-optical element described herein can be ofany suitable type, and provide optical behaviourbased on any number ofsuitable principles. As an example, the optical device can operate by reecting light using the cover. For that purpose, it is possible the cover has a relatively large reectance as compared to its transmittance. As an example, the value oftransmittance divided by reectance would be not more than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably not more than 0.0 1 . The transmittance, reectance and absorbance dened herein may be measured at a wavelength X which varies from 10nm to 3000 um. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700nm to 2000 nm, most preferably from 850nm to 1550 nm. In another aspect, more preferably from 30 000nm to 3 000 000 nm. Ofcourse, absorptionmay also be considered. As an example, the optical device can operate by absorbing light using the cover. For that purpose, it is possible the cover has a relatively large absorbance as compared to its reectance. As an example, the value ofreectance divided by absorbance would be notmore than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably notmore than 0.01. The absorbance and reectance dened above may be measured at awavelength X which varies from 10nm to 3000 um. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700nm to 2000 nm, most preferably from 850nm to 1550 nm. In another aspect, more preferably from 30 000nm to 3 000 000 nm. The acousto-optical elementmay be congured for reecting light incident on the second surface. In that case, the transmittance and reectance may be measured for light incident the second surface. Alternatively, the acousto-optical elementmay be congured for reecting light incident on the rst surface, in that case, the transmittance and reectance may be measured for light incident the rst surface. Besides using the cover for reection only or mainly, it is also possible to employ reective interference, taking place mainly between a reected lightbeam at the substrate (or cover) and a refracted lightbeam through the substrate (or the cover) that the cover (or substrate) reects, or absorbing interference, taking place mainly between a reected light bean with the incident lightbeam at the substrate (or cover) and its absorption at the cover (or substrate). An acousto-optical element congured for this purpose is called an interferometric acousto-optical device. The absorbance ofthe covermay accordingly also be relevant, as explained above. The interference may take place for light incident the second surface, or for light incident the rst surface. In the latter case, a substrate is needed below the cover, as is described further below. The substrate is congured for transmitting a part ofthe light and reecting a part ofthe light. The transmitted light is then reected on the cover, and transmitted back outthrough the surface. The egressing light interferes (constructively or destructively) with the directly reected light. Depending on the position ofthe cover with respect to the substrate, it is possible to change the interference-based behaviour ofthe acousto-optical element. Depending on the desired optical behaviour, it is ofcourse possible to use a cover with different ratios ofreectance, transmittance and absorbance, optionally in combination with e.g. a reective, transmissive or absorbing substrate, the terms reective, transmissive or absorbing being dened using the same ranges for these respective quantities, and / or the same ratios between them as is dened for the cover. In general, the optical properties for the substrate are chosen complimentary to the optical properties ofthe cover. The invention is not limited to any such combination. Ofcourse, the substrate need not be square or rectangular. The substrates shape in general is not important, it is even possible for a single substrate to span multiple acousto-optical elements. More relevantmay be the shape dened within the support, as this denes the shape ofthe acousto-optical element in plan view. It is possible this shape is square or rectangular, to create a pixel-like element, but circular acousto-optical elements are also envisaged. The inventionmay howeverbe applied to acousto-optical elements of all shapes. This is true for all embodiments described herein, whetherthey do or do not have a substrate. It is noted that for some shapes ofacousto-optical elements, the substrate is rigid and planar, while for others it is possible for it to be exible and / or curved. In such cases, the spacer and cover are adapted to the substrate, in such away that the second surface ofthe cover is approximately parallel to the substrate. In this case, the cover is preferably reective, for instance as expressed in the ratio above. The substrate is not as reective, for example having a ratio oftransmittance divided by reectance ofmore than 0.5, more than 0.75, more than 0.9 or even more than 0.99, or even more than 1, preferably for light incident from a surface ofthe substrate facing away from cover. The opposite direction is also possible, where the cover transmits and reects light, and the substrate reects the transmitted light. In this case, the coverwould be relatively transmissive, for example having a ratio oftransmittance divided by reectance ofmore than 1, for light incident the second surface, so that it is relatively transmissive. Said ratio could for instance be between 1 and 3, such as between 1.5 and 2.5, such as around 2. The absorbance could in this case be relatively high. The substrate would preferably be reective for light incident a surface ofthe substrate facing the cover. The reectance could be dened by a ratio oftransmittance divided by reectance ofnotmore than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably notmore than 0.01. Unless stated otherwise, transmittance and reectance are measured for light normal to the surface ofthe cover. In case a cover is used that is relatively reective, a value ofabsorbance divided by reectance ofthe cover can be less than 0.5, preferably notmore than 0.25, more preferably not more than 0.1, most preferably notmore than 0.01, for light incident the rst and / or second surface, depending on the desired optical behaviour. It is noted that in all cases, the position and shape ofthe cover inuences how the optical device interacts with incident light. Other operational principles which rely on the change ofthe cover position and shape can however also be applied, and the current invention is thus not limited to either reective or interferometric operational principles. In any case, the invention is not limited solely to a cover with a changing shape or a changing cover. In terms ofclaim 1, this can be realized by dening the spatial arrangement ofthe cover with respect to the support. After all, a cover that has not changed in shape but is at a different position with respect to the support, still has a different spatial arrangement as seen in cross section ofthe coverwith respect to the support. As such, depending on the use, changing the position ofthe cover (without changing its shape) or changing the shape ofthe cover, thereby changing partially its position, could be used interchangeably. The covermay comprise a 2-dimensional portion. The 2-dimensional portion may be an extreme membrane. For the purpose ofthe invention in general however, it is sufcient ifthe 2- dimensional portion is sufciently thin to be deformed and / ormoved using the applicable means. In general, it is not necessary, however possible, that the 2-dimensional portion has favourable optical properties in and of itself. lnstead, it is possible to provide the desired optical properties using additional material, such as an additional layer or an amorphous portion ofthe cover, which could be or could comprise a metal or an additive. In that regard, reference is made toWO 2021 / 032752 A1 which explains multiple congurations ofthe cover. The skilled person is readily able to vary e.g. the thickness and material ofthe additional material to arrive at desired optical properties for the cover. In that regard, it is noted the 2-dimensional portionmay function as a carrier, whereas the additional material provides desired optical properties. The 2-dimensional portion may be as dened in embodiment [39a] ofWO 2021 / 032752 A1. Accordingly, the 2-dimensional portion may be one ormore ofthe following: a. One ormore selected from the group consisting of: C, BN, P, MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2, NbS2, NbSe2, NbTe2, TaS2, TaSe2, TaTe2, TiSe2, VSe2, CrS2, CrSe2, B, Ge, Si, Si2BN, Sn, Pb, P, Sb, Bi. The preferred C in this context is one ormore selected from the group consisting of: graphene, one ormore graphitic layers and graphyne, preferably graphene. The preferredBN in this context is h-BN. The preferred P in this context is black phosphorus or phosphorene. The preferred B in this context is borophene. The preferred Ge in this context is germanene. The preferred Si in this context is silicene. The preferred Sn in this context is stanene. The preferred Pb in this context is plumbene. The preferred Sb in this context is antimonene. The preferred Bi in this context is bismuthine, b. One ormore transition metal chalcogenides, each being a transition metal chalcogenide not listed in a., c. One ormore oxides, each being an oxide ofa species listed in a. or b., d. One ormore atomic intercalated variants, each being an atomic intercalated variant ofa species listed in a. or b., e. One ormore physically, chemically, mechanically and / or electromagnetically functionalised derivatives, each being a chemically functionalised derivative ofa species listed in a. or b..A preferred physical functionalisation is perforation or atomic barrage treatment.A preferred mechanical functionalisation is stretching or stressing.A preferred electromagnetic functionalisation is application ofa voltage. In one aspect ofthis embodiment, the 2-dimensional portion is a combination selected from the group consisting of: a., b., c., d., e., a.+b., a.+c., a.+d., a.+e., b.+c., b.+d., b.+e., c.+d., c.+e., d.+e., a.+b.+c., a.+b.+d., a.+b.+e., a.+c.+d., a.+c.+e., a.+d.+e., b.+c.+d., b.+c.+e., b.+d.+e., c.+d.+e., b.+c.+d.+e., a.+c.+d.+e., a.+b.+d.+e., a.+b.+c.+e., a.+b.+c.+d. and a.+b.+c.+d.+e.. Specically, the 2-dimensional portionmay comprise or be graphene or boron nitride or both.A preferred boron nitride is hexagonal boron nitride. Graphene is preferably chemical vapour deposited. Boron nitride is preferably chemical vapour deposited. In one aspect ofthis embodiment, the 2-dimensional portion comprises graphene, preferably is graphene. In one aspect ofthis embodiment, the 2-dimensional portion comprises boron nitride, preferably is boron nitride. As mentioned earlier, the thickness ofthe 2-dimensional portion is relatively small. For instance, 1mm or less, preferably 10 um or less, more preferably 1000nm or less, more preferably 100nm or less, more preferably 50nm or less. In one aspect ofthis embodiment, more preferably 10nm or less, more preferably 5 nm or less, most preferably 1 nm or less. A minimum thickness may be dened as 25 pm or more, preferably 69pm or more, more preferably 100pm ormore. In one aspect ofthis embodiment, the thickness is 1 nm or more, preferably 3 nm or more, more preferably 5 nm ormore, more preferably still 10nm or more. In another aspect ofthis embodiment, the thickness is 15 nm ormore, preferably 20nm or more, more preferably 30nm or more. Accordingly, the 2-dimensional portionmay be relatively light per unit area, such as 24 kg / m2 or less, preferably 2.4-10l kg / m2 or less, more preferably 2.4- 102 kg / m2 or less, more preferably 2.4-103 kg / m2 or less, most preferably 1.2- 103 kg / m2 or less.A lower limit on the same weight per unit area is 1.7- 109 kg / m2 or more, preferably 3.4- 108 kg / m2 ormore, more preferably 1.8- 107 kg / m2 or more. In one aspect ofthis embodiment, the mean density is 5-107 kg / m2 or more, preferably 1.5- 106 kg / m2 or more, more preferably 5.4-106 kg / m2 or more, more preferably 5.7- 105 kg / m2 ormore. Various operational principles for the means are available, and have been identied throughout the previous paragraphs. It is noted that some operational principles may allow exerting a force on the cover only in one direction, whereas others the same means can be used to exert forces in opposing or even various directions on the cover. In case the operational principle only allows forces in a single direction, further means, whichmay be identical, may be applied on the opposite side ofthe cover, e.g. in a mirrored position with respect to the previously mentioned means, so that collectively control can be exerted in both ormore directions. While above an acousto-optical element has been described that has means congured to affect the cover, the inverse is also possible and envisaged. Accordingly, the means may alternatively or additionally be arranged to provide an output that is representative ofthe cover changing from the rst cover contour prole to the further cover contour prole. In this manner, the acousto-optical element can be used as a sensor responsive to any phenomenon, not necessarily optical, that changes the cover shape. For instance, incident radiation, pressure, sound waves, an electrical charge, temperature, etc. could all be sensed using suitable means. As an example, an electrode could be used to sense a changing electrical charge, e.g. changing in response to a charged cover moving. Ifapredetermined and externally applied electrical charge is applied to the cover, the electrodes could be used to measure deformation ofthe coverby capacitive means, for instance as a result ofincoming radiation or pressure. An electrode or othertype ofsensing means would be necessary to measure the changing electric eld as the charged cover moves. Hence the acousto-optical elements can also be usable as light-detecting devices such as a camera sensor. In these circumstances, the element described herein need not be described as an acousto- optical element per se. These same principles can thus be applied to the acoustic parts ofthe elements, rendering the elements to be usable as sound-detecting devices such as a microphone sensor. Continuing along the same idea, it is also possible the sensing means is used only, or additionally, to register sound. Ifonly sound is concerned, the acousto-optical elements would merely be acoustical elements, butmay otherwise be unchanged. It is noted that the functionality, given a suitable sensing means, can also be combined. E.g. an acousto-optical component used to render an image can be used to sense sound at the same time, or vice versa. In one embodiment ofthe invention, the means ofeach ofthe at least one acousto-optical elements comprise a singular means, whereas in anotherembodiment the means ofeach ofthe at least one acousto-optical elements comprise a rst means and a furthermeans, wherein the controller is congured to - control the rst means in accordance with the desired optical behaviour, and - control the furthermeans in accordance with the desired acoustic behaviour. Having a single controller control both the optical and the acoustic behaviourmay simplify the system. Ofcourse it is still possible to have separate controllers, especially ifthe means and the furthermeans have different operational principles. In either case, it can be ofsignicant advantage ifthe controller is arranged to individually control at least some or all ofthe at least one acousto-optical elements. This can remove the need for multiple controllers, and can thus reduce the complexity ofthe tot . Furthermore, it could lead to reduced latency times and thus amore responsive optical system to have all acousto-optical elements be controlled by a single controller, or in cases oflargernumbers ofacousto-optical elements have several groups ofelements be controlled by several controllers. A possible setup forthe controller can be to arrange it to control the elements viathe means by supplying an input signal. In such a setup, colours could for example be setby application ofaDC voltage, whereas sound can be produced by the application ofanAC voltage. Or, aDC voltage could be applied as an offset for the frequency ofthe sound, whereas theAC voltage is used to actually produce the soundwaves around the offset. TheAC andDC signals required to achieved desired behaviour could be combined in a single signal provided to the means by the controller. Note that these are just examples and are not exhaustive options. Such different types ofinputs and / or outputs can be supplied either parallelly, or in series. As a further example, it is possible to apply anAC signal, so that the cover is sensitive to light ofa certain wavelength.A sensing means could be used to measure at the same time aDC signal, which could be representative ofan intensity ofincident light ofthe certain wavelength. In such a case there is a combination ofameans (formoving the cover) and a sensing means, although in general it is principally possible ifthese two are embodied as the same component. Ofcourse, when the means are controlled differently, e.g. not via electricity as an output from the controller that is received by the means as an input, it is possible still to use a combination ofa low or zero frequency signal with a relatively high frequency signal in order to achieve similar effects. It is possible for the controller to be arranged in such away as to control acoustical properties using a rst frequency bandwidth and optical properties using a second frequency bandwidth, wherein the rst frequency bandwidth is different than the second frequency bandwidth. For simplied control, itmay be ofadvantage to have the controller control the acoustical properties and the optical properties in an alternating, repeating pattern, i.e. sound-colour-sound- colour. In such a case, the repeating pattern can be divided into duty cycles, wherein each duty cycle comprises one acoustic interval, and one optical interval. It is possible forthe acoustic interval and the optical interval to have the same duration, however, this does not always need to be the case, and specic use cases may actually require longer acoustical intervals compared to the optical intervals or vice versa. The invention also relates to an acousto-optical transducer system, comprising at least one acousto-optical element, the at least one acousto-optical element comprising: a. a cover having a rst surface and a second surface, b. a support, and c. a sensing means, wherein the cover is orientated with the rst surface directed towards the support, a part ofthe rst surface is attached to the support and a spatial arrangement ofthe cover as seen in a cross section ofthe cover denes a cover contour prole. The sensing means is arranged to generate a signal in correspondence with the shape or a change in shape ofthe cover. While an could exist with just one acousto-optical element, in practice it is likely that a system will comprise largernumbers ofelements, such as at least 10 such acousto-optical elements, or at least 100, preferably at least 1.000, even more preferably at least 10.000, even more preferably at least 100.000, and most preferably at least 1.000.000 acousto- optical elements. These largernumber ofelements can together provide a higher resolution image in regards to the optical part ofthe elements, ormore complex timbres with regards to the acoustic part ofthe elements. In such a way, it can be that the is a display with integrated speaker functionality. On the other hand, ifa sensing means is present in the system, the could be a camerawith integrated microphone functionality. This camera can for example be a hyperspectral camera. Ofcourse, combinations are also possible, i.e. a display with microphone, and a camerawith a speaker. It is principally possible to have systems arranged as only an acoustic system, or only an optical system, and performing just the function ofa camera, display, speaker or microphone. Therefore, the invention also relates to an acoustic system and an optical system separately. The invention also relates to amethod ofoperating an as described in the previous paragraphs. Said method comprising the step ofcontrolling, in an as described hereabove, controlling the means ofthe at least one acousto-optical element at a frequency ofat least 20 Hz, optionally at maximally 25 000 Hz. In particular, controlmay include combination ofdesired optical behaviour and desired acoustic behaviour, combined e.g. by modulating inputs / outputs, by superimposing inputs / outputs, by alternating inputs / outputs in the time domain, or otherwise. In particular, the means and / or furthermeans may each, independent from one another, comprise any one ormore of: - an optical actuator, such as an optical tweezer or photonic circuitry, - ameans for applying or changing radiation incident on the cover, such as a radiation source. - ameans for inuencing a gas pressure acting on the cover, - a speaker or any other sound emitter, - a thermal actuator, operating viathermal expansion, and - an electromagnetic and / or superconducting actuator, for instance operating based on tunneling or eld emission. At this time, it is noted that regardless ofthe actuation method used, given a sufciently small system, any one actuation method will often have some corresponding co-phenomenon in another domain as well. As such, at nano-scale, the actuation method and corresponding co- phenomena usually pair up. Examples ofsuch pairs, whichmay be used in the currently described invention as a non-exclusive list ofexamples, are: - Thermo-electrical and electro-thermal actuation, - Thermo-optical and opto-thermal actuation, - Thermo-magnetic and magneto-thermal actuation, - Opto-electrical and electro-optic actuation, and - Magneto-optic and opto-magnetic actuation. At the same time, quantum and superconducting effects may also play a role. Accordingly, use can be made ofsuch effects ifdesired. It is noted that the substrate may be used to dene a cavity below the cover. The index of refraction of said cavity can be ofinuence on the optical behaviour ofthe optical element. The index ofrefraction ofthe cavity can be inuenced by at least partially lling the cavity. To facilitate said lling the cavity may be enclosed by one ormore ofthe support, the cover and the substrate, ormay even be sealed entirely. Ifthe cavity is indeed sealed, it can be lled with a substance. Different llings ofthe cavity can lead to different refractive indices, and thus a different optical behaviour. The cavitymay for this purpose be lled with a gas composition. Aside from agas or gas mixture, the cavity may also be lled by a liquid (mixture) and / or liquid crystals, or even a solid lling, whichmay have a greater effect on the refractive index. Another option would be to instill avacuum inside ofthe cavity. Denition of, and lling ofthe cavitymay also be done for other reasons than inuencing the index ofreection, i.e. to provide absorption, to provide structure rigidity, or other reasons. Moreover, the substance lling a cavity can be ofinuence on other than the optical behaviour ofthe optical element, including but not limited to the mechanical response ofthe cover and the electrical inuence ofthe means.A lled cavity can also be used to exert a pressure on the cover, in order to move it using pressure based means. As a further remark, it is noted that the structure described herein as acousto-optical element can be used in a different and novel way as well, regardless ofwhether or not the characterizing portion ofthe claims is applied. In this novel way ofusing the device, a substrate opposite the cover is necessary, so that a cavity is formed between the cover and the substrate. The device is congured to allow entry ofelectromagnetic radiation, such as (visible) light, into the cavity between the support and the substrate, and to allow egress ofthe same, also between the support and the substrate. In contrast to the principles shown above, in which light interacts by being incident the cover (either from the rst or second surface), the lightnow travels substantially parallel to the cover, through the cavity. In this case, the cavity acts like awaveguide. To form a waveguide, the skilled person is able to choose suitable materials for the support, the substrate and the material at the covers rst surface and optionally for material to ll the cavity with, so that waves are inuenced by the cover. This inuence could for example result in a change in amplitude, phase or the state ofthe light. Suitably chosen characteristics, such as optical characteristics, ofthe cover allow interaction with light passing through the cavity. By changing the contour shape ofthe cover, orby changing its position, the waveguide formed in the cavity can be altered. The changing inuence ofthe cover on waves passing through can be used to modulate the light. The invention will be further elucidated with reference to the attached drawings, in which: Figures 1A, 1B and 1C show schematically interaction oflight with an optical element known in the state ofthe art, Figures 2A, 2B and 2C show schematically interference interaction oflight with an optical elementknown in the state ofthe art, Figures 3A 3D show schematically different operations ofan acousto-optical element for optical behaviour, Figure 4 shows schematically acoustic behaviour ofan acousto-optical element, Figures 5 and 6 show schematically an optical element for different interferometric effects, and Figure 7 shows schematically in perspective view anotherway ofusing the optical element. Figure 1A shows interaction oflight with ofa at cover 101, which is supported by supports 104. The parallel rays 601 and 602 are both deected by the same angle and remain parallel after interaction with the cover 101. This constitutes specular reection. Figure 1B shows interaction oflight with a convex cover. Due to the rounded convex cover contour prole, a rst ray 601 is deected by almost 180° and the second ray 602 is only deected by a small angle. The rays 601 and 602 are no longer parallel after reection at the cover. This constitutes diffuse reection. Figure 1C shows interaction oflight with a concave cover. Due to the rounded concave cover contour prole, a rst ray 601 is deected by an angle less than 90° and the second ray 602 is deected by almost 180°. The rays 601 and 602 are no longer parallel after reection at the cover. This constitutes diffuse reection. Figure 2A shows interference interaction with a at cover. Aside from the supports 104, a substrate 106 is also present in this example ofthe state ofthe art, which lies on the bottom ofthe optical element. The support 104, cover 101 and substrate 106 dene a cavity having a depth 205. The substrate 106 is transmissive and absorbing to an extent and the cover 101 is reective, such that an incoming ray 601 undergoes interference which is dependent on the depth 205. Figure 2B shows interference interaction with a convex cover. The cover 101 ofthe optical element ofgure 12 has been deformed into a convex shape (cover contour prole). This was brought aboutby ameans pushing the cover 101 upwards. This increases the depth 205 and the interference behaviour ofincoming light 601 is altered. Figure 2C shows interference interaction with a concave cover. The cover 101 ofthe optical element ofgure 12 has been deformed into a concave shape (cover contour prole). This was brought aboutby the means pushing the cover 101 downwards. This decreases the depth 205 and the interference behaviour ofincoming light 601 is altered. Now rst referring to gures 5 and 6, it is noted that depending on the optical properties of the cover 101 and the substrate 106, different operational principles are also usable for inuencing incident light. Figure 5 for instance, shows an optical element similar to that ofgures 1 and 2, but with a cover 101 that is relatively absorbing, and a substrate 106 that that is relatively reective. As a result, incident light 601 transmitted 602 through the cover 101 interacts with light reected 604 from the substrate to form a pattern ofnodes and antinodes. The cover can be controlled by means (not shown) to be placed at or away from a node or antinode, to accordingly absorb strongly or less strongly light, so that the intensity ofexiting light 605 can be controlled. In gure 6 a cover 101 is present that is both transmissive and reective, and a substrate that is reective. Accordingly, use can be made ofinterferometric reection, similar to gures 2A 2C, however now the optical element is congured for light incident the cover 101. Otherwise, the optical elementmay be identical to that described above. In gures 3A 4, an acousto-optical element 99 is shown, with a support 4, a cover 1, and a substrate 6, as is dened in the claims.A means is also present in the substrate 6 to move the cover 1, but is not shown. In gure 3A, a dashed line represents schematicallymovement ofthe cover in response to the means activating. Accordingly, and as described above, a certain optical behaviour can be expected depending on the height ofthe cover. Figure 3B shows two dashed positions for the cover 1, between which the cover 1 can alternate by suitable operation ofthe means. The resulting optical behaviour is an average ofthe optical behaviours at the two respective positions. This alternating, called grayscale dithering, can be performed ofa relatively low frequency, for instance of< 20 Hz. Figure 3C shows schematically the cover 1 changing positions between positions that cause the acousto-optical device to output different colours. By changing between these positions rapidly, a mixture of colours can be output. This changing, called hue dithering, can be performed at a frequency ofe.g. >20 Hz.A combination is shown in gure 3D, allowing many more colours to be output, for instance at > 500 Hz, and called gamut dithering. It is noted that whilst the acousto-optical element is described herein primarily as a light modulator in order to output light ofdesired characteristics, the opposite is also possible ifthe means are a sensing means or a sensing means is otherwise present. The sensing means is congured to react to the cover, which interacts with impinging light, to create a signal corresponding to the incoming light. Accordingly, the incoming light can be sensed. Figure 4 shows sound waves 20, 21 emitting from and impinging on the cover 1 ofan acousto-optical device as described before. Sound waves 20 can be generated by actuating the cover in a frequency that is audible, e.g. 20 25k Hz. Similarly, sound waves 21 impinging the cover 1 can be registeredwhen the covermoves as a result ofthe sound waves, and a sensing means is present. The sensing means may be the aforementioned means, ormay be separately provided. The functionalities can be combined however, for instance by providing grayscale dithering at an audible frequency. Accordingly, the optical behaviour is not inuenced, butnow an audible signal is also produced by the same element, which therefore thus is an acousto-optical element. Ofcourse this can still be combined with even higher frequency changes, for instance to provide hue orgamut dithering. It is noted herein that the cover is shown to move without changing shape, although in practice the coverwould adjust its cover contour prole to its position. Finally, reference is made to gure 7, which shows a perspective view ofa device, such as an optical element, similar to that described herein. Like before, the device has a substrate 106 and support 104, which in this case are monolithic. The support 104 denes a cavity C that is of longitudinal shape in this example. Cover 101 held by the support 104 spans the cavity C. Materials for the support 104, the substrate 106, the material at the covers rst surface and material with which the cavity C is lled are chosen so that the cavity C acts as a waveguide. Incidentwaves 601, such as light, can therefore pass through from one side to another, and egress as exited light 602. Viameans 107, in this case presented on top ofthe support 104, although not strictly necessary, the cover 101 can be moved, or its cover contour prole changed. As a result, the cover 101 at least locally inuences the light passing through the cavity C in order to modulate it. It is noted thatterms like preferably, generally and typically are not utilized herein to limit the scope ofthe claims or to imply that certain features are critical, essential, or even important to the structure or function ofthe claims. Rather, these terms are merely intended to highlight alternative or additional features thatmay ormay not be utilized in a particular embodiment ofthe present disclosure. Likewise, for the purposes ofdescribing and dening the present disclosure, it is noted that the terms substantially and approximately and their variants are utilized herein to represent the inherent degree ofuncertainty thatmay be attributed to any quantitative comparison, value, measurement or other representation, as well as to represent the degree by which a quantitative representationmay vary without resulting in a change in the basic function ofthe subject matter at issue. Moreover, when certain steps or states are alternated or alternating, it possible though not excluded that further states are present in between, as long as the alternating states are repeated one after another, but not necessarily directly after one another. While certain representative embodiments and details have been shown forpurposes of illustrating the present disclosure, it will be apparent to those skilled in the art that various changes may be made without departing from the scope ofthe disclosure, which is dened in the appended claims.

Claims

1. Acoustic-optical system, comprising at least one acoustic-optical element, which comprises at least one acoustic-optical element: a. a covering with a first and a second surface, b. a support, and c. a means, whereby: - the cover is oriented with the first surface facing the support; - a part of the first surface is attached to the support, - a spatial arrangement of the deck considered in a cross-section of the cover defines a cover contour profile, - the device is designed to move the cover from a first cover contour profile to a further cover contour profile that differs from the first cover contour profile, where the acoustic-optical system further comprises: - a control system configured to the means of at least one acoustic-optical element to be controlled at a frequency of at least 20 Hz, optionally at maximum 25,000 Hz.

2. Acoustic-optical system according to the previous conclusion, where the control is configured to, for each of at least one acoustic-optical element: - to control the device to move the cover in accordance with a desired optical behavior, and - to superimpose a movement in accordance with a desired acoustic behavior on and / or combine with the resulting movement.

3. Acoustic-optical system according to the previous conclusion, where the control is configured to, for each of at least one acoustic-optical element, alternately: - to control the device to move the cover in accordance with a desired optical behavior, and - to control the device to move the cover in accordance with a desired acoustic behavior.

4. Acoustic-optical system according to the previous conclusion, where the means of each of the at least one acoustic-optical element comprises a primary means and a further means, where the control is configured to: - to control the first agent in accordance with the desired optical behavior, and - to control the further device in accordance with the desired acoustic behavior.

5. Acoustic-optical system according to one of claims 1 3, where the means of each of which at least one acoustic-optical element is a single means.

6. Acoustic-optical system in accordance with one of the preceding claims, where the control is configured to control the acoustic-optical elements individually.

7. Acoustic-optical system in accordance with one of the preceding claims, where the control is configured to control the acoustic-optical elements by feeding them to the means of a combination of inputs that are continuous, alternating, analog and / or digital outputs and / or by the application of a combination of agents that are continuous, alternating, analogous and / or digital inputs are.

8. Acoustic-optical system in accordance with one of the preceding claims, where the control is configured to control acoustic properties by means of a first frequency bandwidth and optical properties by means of a second frequency bandwidth, where the first frequency bandwidth is different from the second frequency bandwidth.

9. Acoustic-optical system according to one of claims 1 8, where the control designed to control the acoustic and optical properties in a alternating, repeating pattern.

10. Acoustic-optical system according to the previous conclusion, where the repeating pattern comprises operating cycles, where each operating cycle an acoustic interval and an optical includes interval.

11. Acoustic-optical system according to the previous conclusion, where the acoustic interval and the optical interval have the same duration, or where preferably the acoustic interval has a longer duration.

12. Acoustic-optical converter system, comprising at least one acoustic-optical element, which comprises at least one acoustic-optical element: d. a covering with a first and a second surface, e. a support, and f. a detection device, whereby: - the cover is oriented with the first surface facing the support, - a part of the first surface is attached to the support, - a spatial arrangement of the deck considered in a cross-section of the cover defines a cover contour profile, - the detection device is designed to generate a signal in accordance with the shape or a change in shape of the cover.

13. Acoustic-optical system in accordance with one of the preceding claims, comprising at least 1,000 of such acoustic-optical elements, preferably at least 10,000, preferably at least 100,000, and preferably at least 1,000,000 acoustic-optical elements.

14. Acoustic-optical system according to one of claims 1 11, possibly in combination with conclusions 12 13, where the acoustic-optical system a screen with integrated speaker functionality is, or a screen with integrated microphone functionality.

15. Acoustic-optical system according to one of the claims 12 13, possibly in combination with conclusions 1 11, where the acoustic-optical system a camera with integrated microphone functionality is, or a camera with integrated speaker functionality.

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