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

[0001] ACOUSTO-OPTICAL SYSTEM

[0002] The current application relates to an acousto-optical system, comprising at least one acousto-optical element, the at least one acousto-optical element comprising a cover having a first surface and a second surface, a support, and a means, wherein the cover is orientated with the first surface directed towards the support; a part of the first surface is attached to the support; a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile; and 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,

[0003] An optical element is known from e.g. WO 2021 / 032752 Al and WO 2018 / 228671 Al. This document discloses optical devices of specific interest. The working principle is that when a cover is provided that has some desired optical behaviour, e.g. reflecting light, transmitting only some light, etc. the interaction of incident light can be changed by changing the cover contour profile. To facilitate the cover changing shape to facilitate changing the optical behaviour of the optical device, the cover is made relatively thin, in terms of WO 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 of similar devices. Control of scattering, reflection and / or interference behaviour can be used to turn a pixel on or off and / or vary its colour. This way, images can be generated and / or manipulated.

[0004] Several principles of operation are available with such optical devices. A first operational principle is shown in figures 1A - 1C, which correspond to figures 9 - 11 of WO 2021 / 032752 Al. These figures show respectively an optical device with a flat cover, a convex cover, and a concave cover. Light incident on the flat cover (fig. 1A) is reflected as if hitting a smooth and straight surface, i.e. parallel incident rays remain parallel after reflection. As such, specular reflection takes place at the cover. In the convex and concave positions of the cover, parallel incident rays are no longer parallel after reflection, thus causing diffuse reflection. By changing the shape of the cover, it is thus possible to alternate between specular and diffuse reflection. To suit this first operational principle, the cover is sufficiently reflective towards the incident light. In this example, the light is incident on the second surface, which may also be called the outside of the optical device.

[0005] Figures 2A - 2C, which correspond to figures 12 - 14 of WO 2021 / 032752 Al, show a second operational principle. Reference is first made to the substrate which spans the support on an opposite side of the cover, in order to define a cavity between the cover and the substrate. The substrate is partly reflective and partly transmissive. The cover is relatively reflecting. Light incident on the substrate is thus partly transmitted and partly reflected. The transmitted light reflects on the first surface of the cover, i.e. coming from the inside, and is transmitted back through the substrate, where it interferes with the light reflected by the substrate. Depending on the wavelength of the 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 of the optical device can be changed.

[0006] Figures 5 and 6 show even other ways of using the changing cover contour profile. In the case of figure 5, an optical element is shown with a substrate 106 that is relatively reflective. The cover 101 in this case is relatively absorbing. Nevertheless, of an incoming light beam 601, at least some light may be transmitted towards the substrate 106 as transmitted light beam 603. This reflects back via the substrate 106 as reflected light 604. Due to interference of the transmitted light beam 603 and the reflected light 604, a pattern of nodes and antinodes is present. The cover 101 can then be moved, e.g. by changing its cover contour profile 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 or more intensity by controlling the cover. This principle is called interferometric absorption.

[0007] Figure 6 shows the principle of interferometric reflection, similar to fig. 2, but with light 601 incident the cover. In this case, light is partially transmitted through the cover 101, and reflected at the substrate 604, which for that purpose is reflective. The cover 101 reflects some light 605, but also transmits some light 603. After reflecting 604 from the substrate 106, light passing through the cover 101 again interferes with the reflected light 605. By controlling the position or cover contour profile of the cover 101, control is possible of wavelengths of light that do or do not interfere constructively.

[0008] In both cases, light transmitted through the cover may actually be refracted. However, since the figures show a specific example of light incident normal to the cover, the wording transmitting was used. The invention can however be applied, depending on the use-case, to nonnormal light also. These principles have been described only briefly herein, as the operational principles involved are in themselves known, and have been applied e.g. in WO 2018 / 228671 Al (see figures 1 and 2).

[0009] These principles thus show that by varying the reflectance and / or transmittance and / or absorbance of the cover and the substrate, and the direction at which 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 contour profile changes.

[0010] Despite the advantages described for the optical element of WO 2021 / 032752 Al, a desire remains to make it more versatile. It is an object of the invention to meet this desire. The object is achieved by an acousto-optical system according to the preamble, wherein it further comprises a controller configured to control the means of the 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. Said movement of the cover at such a frequency will produce a soundwave, and in turn sound. Altering the frequency in turn can allow finetuning 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.

[0011] Controller as used herein, is defined as a device that is configured 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.

[0012] At this point it is noted that according to the invention, the cover also has optical properties that allow modulation of light 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, if only acoustic behaviour is desired. Optical properties of the system derive from the optical properties of the cover. There may be varying optical properties suitable for optical modulation, such as varying ratios of transmittance and reflectance or ratios of absorbance and reflectance, 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 of light depending on an input that reflects a desired optical behaviour. This is therefore easily distinguished from a purely acoustic system which may produce some sort of visible response too, but which is not used to modulate light.

[0013] It is noted that any movement of the cover will alter the light output, but keeping the amplitude of the movement sufficiently small and / or the frequency of the movement sufficiently fast, the human eye may not be able to notice the change. Therefore, a good image quality can be retained even when 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.

[0014] The control frequency for sounds can be limited to 25 000 Hz, as humans generally are unable to observe sounds of this 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 if the controller is configured to, for each of the 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 controller may cause the means to operate in such a way as to achieve said movement, for instance by providing input signals to the means that are a combination or superposition of input signals that independently would correspond to the desired acoustic or optical behaviour respectively.

[0015] It is for instance possible, if the means accept an electrical input, to provide both a direct current DC signal in accordance with optical behaviour, and an alternating current AC signal in accordance with acoustic behaviour. As long as the movement of the cover due to the AC signal is sufficiently small, the optical behaviour will remain largely unaffected. The DC signal would act as an offset to the AC signal.

[0016] As an alternative, it is also possible to control the acoustic behaviour and the optical behaviour using separate AC signals. It is for instance possible, if the means accept an electrical input, to provide both an AC signal in accordance with optical behaviour, and an AC signal in accordance with acoustic behaviour. As long as the frequency of the cover due to the AC signal corresponding to the desired optical behaviour is sufficiently fast, the optical behaviour could remain largely unaffected by the AC signal corresponding to the acoustic behaviour.

[0017] The AC signal for optical behavior could act as a modulating signal to the AC signal for the acoustic behaviour which would act as a carrier signal, hence the carrier signal being transformed into modulated envelope.

[0018] In one embodiment of the invention, the means of each of the at least one acousto-optical elements comprises a first means and a further means, and the controller is configured to firstly control the first means in accordance with the desired optical behaviour and secondly control the further means in accordance with the desired acoustic behaviour. Accordingly, the means and further means may be chosen so as to operate at desired but different frequencies. Having the two means separate allows larger freedom of design, and therefore facilitates construction.

[0019] It remains however possible in principle to have a single controller controlling the first means and the further means, to achieve control of the optical and acoustic behaviour. Similar effects can be achieved even if only the first means are present. It is thus possible to achieve similar effects when the single controller is configured to control a single means, when such a means allows to obtain the desired optical behavior and the desired optical behavior by controlling the means with superimposed and / or combined and / or alternated signals. There is thus an advantage to be gained if a single controller is used to control both acoustic and optical behaviour.

[0020] Multiple controllers could be used on the other hand if different principles are used by the first and further means, or if many acousto-optical elements are present so as to reduce latency times.

[0021] It is advantageous if the 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 of elements can be used to create complex visual and / or auditory behaviours.

[0022] It may further be advantageous, if acoustic behaviour and optical behaviour of the acousto- optical elements are respectively controlled within predefined but separate frequency bandwidths. Typically, the bandwidth chosen for optical behaviour would be outside the 20 - 25k Hz range.

[0023] 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 first surface and a second surface, a support, and a sensing means, wherein the cover is orientated with the first surface directed towards the support, a part of the first surface is attached to the support, a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile and the sensing means is arranged to output a signal in correspondence with the shape or a change in shape of the cover. Optionally, this embodiment of the acousto-optical transducer system can also comprise the means of claim 1, in addition to the sensing means. These optional means can be arranged to perform any functionality of the means as described throughout this document, i.e. 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. Of course the acousto-optical transducer system can comprise the other features described in relation to the acousto-optical system hereabove (e.g. that of claims 1 - 11).

[0024] 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 a transceiver system.

[0025] The sensing means of the acousto-optical transducer system may be connected to a controller, configured to receive from the sensing means an input. The controller may be configured for recording, converting, or output a signal that correlates with the received input. In case the sensing means are used to control movement of the cover as was described above, the controller may be configured to control the sensing means.

[0026] If the acousto-optical transducer system is to sense sound, the controller may be configured to receive and process a signal having a frequency of at 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.

[0027] For other applications however, it can be advantageous if the acousto-optical system 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 of use to incorporate thousands or even millions of elements in a single system. Together, the acousto-optical elements can then act as a complete speaker, by finetuning the pitches of individual or groups of elements to create the desired sounds on demand. Aside from changing pitches, using a large multitude of acousto-optical elements can change other parameters of the sound, such as the timbre, texture, tone, loudness or envelope. Of course since the elements also exhibit desirable optical behaviour, they can be controlled as e.g. pixels of a display, to collectively generate an image.

[0028] One exemplary embodiment of the acousto-optical system 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 a module attached to the screen, or an altogether separate speaker. The acousto-optical system takes up less space than a separated display / speaker combination, which can increase the practicality and versatility of displays.

[0029] The optical part of the acousto-optical element described herein can be of any suitable type, and provide optical behaviour based on any number of suitable principles.

[0030] As an example, the optical device can operate by reflecting light using the cover. For that purpose, it is possible the cover has a relatively large reflectance as compared to its transmittance. As an example, the value of transmittance divided by reflectance would be not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0031] The transmittance, reflectance and absorbance defined herein may be measured at a wavelength I which varies from 10 nm to 3000 pm. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10 nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700 nm to 2000 nm, most preferably from 850 nm to 1550 nm. In another aspect, more preferably from 30 000 nm to 3 000 000 nm.

[0032] Of course, absorption may 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 reflectance. As an example, the value of reflectance divided by absorbance would be not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0033] The absorbance and reflectance defined above may be measured at a wavelength X which varies from 10 nm to 3000 pm. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10 nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700 nm to 2000 nm, most preferably from 850 nm to 1550 nm. In another aspect, more preferably from 30 000 nm to 3 000 000 nm.

[0034] The acousto-optical element may be configured for reflecting light incident on the second surface. In that case, the transmittance and reflectance may be measured for light incident the second surface.

[0035] Alternatively, the acousto-optical element may be configured for reflecting light incident on the first surface, in that case, the transmittance and reflectance may be measured for light incident the first surface.

[0036] Besides using the cover for reflection only or mainly, it is also possible to employ reflective interference, taking place mainly between a reflected light beam at the substrate (or cover) and a refracted light beam through the substrate (or the cover) that the cover (or substrate) reflects, or absorbing interference, taking place mainly between a reflected light bean with the incident light beam at the substrate (or cover) and its absorption at the cover (or substrate). An acousto-optical element configured for this purpose is called an interferometric acousto-optical device. The absorbance of the cover may accordingly also be relevant, as explained above.

[0037] The interference may take place for light incident the second surface, or for light incident the first surface. In the latter case, a substrate is needed below the cover, as is described further below. The substrate is configured for transmitting a part of the light and reflecting a part of the light. The transmitted light is then reflected on the cover, and transmitted back out through the surface. The egressing light interferes (constructively or destructively) with the directly reflected light. Depending on the position of the cover with respect to the substrate, it is possible to change the interference-based behaviour of the acousto-optical element.

[0038] Depending on the desired optical behaviour, it is of course possible to use a cover with different ratios of reflectance, transmittance and absorbance, optionally in combination with e.g. a reflective, transmissive or absorbing substrate, the terms reflective, transmissive or absorbing being defined using the same ranges for these respective quantities, and / or the same ratio’s between them as is defined for the cover. In general, the optical properties for the substrate are chosen complimentary to the optical properties of the cover. The invention is not limited to any such combination. Of course, the substrate need not be square or rectangular. The substrate’s shape in general is not important, it is even possible for a single substrate to span multiple acousto-optical elements. More relevant may be the shape defined within the support, as this defines the shape of the 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 invention may however be applied to acousto-optical elements of all shapes. This is true for all embodiments described herein, whether they do or do not have a substrate.

[0039] It is noted that for some shapes of acousto-optical elements, the substrate is rigid and planar, while for others it is possible for it to be flexible and / or curved. In such cases, the spacer and cover are adapted to the substrate, in such a way that the second surface of the cover is approximately parallel to the substrate.

[0040] In this case, the cover is preferably reflective, for instance as expressed in the ratio above. The substrate is not as reflective, for example having a ratio of transmittance divided by reflectance of more 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 of the substrate facing away from cover.

[0041] The opposite direction is also possible, where the cover transmits and reflects light, and the substrate reflects the transmitted light. In this case, the cover would be relatively transmissive, for example having a ratio of transmittance divided by reflectance of more 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 reflective for light incident a surface of the substrate facing the cover. The reflectance could be defined by a ratio of transmittance divided by reflectance of not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0042] Unless stated otherwise, transmittance and reflectance are measured for light normal to the surface of the cover.

[0043] In case a cover is used that is relatively reflective, a value of absorbance divided by reflectance of the cover can be less than 0.5, preferably not more than 0.25, more preferably not more than 0. 1, most preferably not more than 0.01, for light incident the first and / or second surface, depending on the desired optical behaviour.

[0044] It is noted that in all cases, the position and shape of the cover influences how the optical device interacts with incident light. Other operational principles which rely on the change of the cover position and shape can however also be applied, and the current invention is thus not limited to either reflective 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 of claim 1, this can be realized by defining the spatial arrangement of the 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 of the cover with respect to the support. As such, depending on the use, changing the position of the cover (without changing its shape) or changing the shape of the cover, thereby changing partially its position, could be used interchangeably.

[0045] The cover may comprise a 2-dimensional portion. The 2-dimensional portion may be an extreme membrane. For the purpose of the invention in general however, it is sufficient if the 2- dimensional portion is sufficiently thin to be deformed and / or moved 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. Instead, it is possible to provide the desired optical properties using additional material, such as an additional layer or an amorphous portion of the cover, which could be or could comprise a metal or an additive. In that regard, reference is made to WO 2021 / 032752 Al which explains multiple configurations of the cover. The skilled person is readily able to vary e.g. the thickness and material of the additional material to arrive at desired optical properties for the cover. In that regard, it is noted the 2-dimensional portion may function as a carrier, whereas the additional material provides desired optical properties.

[0046] The 2-dimensional portion may be as defined in embodiment [39a] of WO 2021 / 032752 Al. Accordingly, the 2-dimensional portion may be one or more of the following: a. One or more 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 or more selected from the group consisting of: graphene, one or more graphitic layers and graphyne; preferably graphene. The preferred BN 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 or more transition metal chalcogenides, each being a transition metal chalcogenide not listed in a.; c. One or more oxides, each being an oxide of a species listed in a. or b.; d. One or more atomic intercalated variants, each being an atomic intercalated variant of a species listed in a. or b.; e. One or more physically, chemically, mechanically and / or electromagnetically functionalised derivatives, each being a chemically functionalised derivative of a 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 of a voltage.

[0047] In one aspect of this 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..

[0048] Specifically, the 2-dimensional portion may 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 of this embodiment, the 2-dimensional portion comprises graphene, preferably is graphene. In one aspect of this embodiment, the 2-dimensional portion comprises boron nitride, preferably is boron nitride.

[0049] As mentioned earlier, the thickness of the 2-dimensional portion is relatively small. For instance, 1 mm or less, preferably 10 pm or less, more preferably 1000 nm or less, more preferably 100 nm or less, more preferably 50 nm or less. In one aspect of this embodiment, more preferably 10 nm or less, more preferably 5 nm or less, most preferably 1 nm or less.

[0050] A minimum thickness may be defined as 25 pm or more, preferably 69 pm or more, more preferably 100 pm or more. In one aspect of this embodiment, the thickness is 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, more preferably still 10 nm or more. In another aspect of this embodiment, the thickness is 15 nm or more, preferably 20 nm or more, more preferably 30 nm or more.

[0051] Accordingly, the 2-dimensional portion may be relatively light per unit area, such as 24 kg / m2or less, preferably 2.4- 101kg / m2or less, more preferably 2.4- 102kg / m2or less, more preferably 2.4- 103kg / m2or less, most preferably 1.2- 103kg / m2or less. A lower limit on the same weight per unit area is 1.7- 109kg / m2or more, preferably 3.4-108kg / m2or more, more preferably 1.8 • 107kg / m2or more . In one aspect of this embodiment, the mean density is 5 • 107kg / m2or more, preferably 1.5- 106kg / m2or more, more preferably 5.4-106kg / m2or more, more preferably 5.7- 105kg / m2or more.

[0052] Various operational principles for the means are available, and have been identified 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, which may be identical, may be applied on the opposite side of the cover, e.g. in a mirrored position with respect to the previously mentioned means, so that collectively control can be exerted in both or more directions.

[0053] While above an acousto-optical element has been described that has means configured 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 of the cover changing from the first cover contour profile to the further cover contour profile.

[0054] 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. If a predetermined and externally applied electrical charge is applied to the cover, the electrodes could be used to measure deformation of the cover by capacitive means, for instance as a result of incoming radiation or pressure. An electrode or other type of sensing means would be necessary to measure the changing electric field as the charged cover moves. Hence the acousto-optical elements can also be usable as light-detecting devices such as a camera sensor.

[0055] 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 of the elements, rendering the elements to be usable as sound-detecting devices such as a microphone sensor.

[0056] Continuing along the same idea, it is also possible the sensing means is used only, or additionally, to register sound. If only sound is concerned, the acousto-optical elements would merely be acoustical elements, but may otherwise be unchanged.

[0057] 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.

[0058] In one embodiment of the invention, the means of each of the at least one acousto-optical elements comprise a singular means, whereas in another embodiment the means of each of the at least one acousto-optical elements comprise a first means and a further means, wherein the controller is configured to

[0059] - control the first means in accordance with the desired optical behaviour; and

[0060] - control the further means in accordance with the desired acoustic behaviour.

[0061] Having a single controller control both the optical and the acoustic behaviour may simplify the system. Of course it is still possible to have separate controllers, especially if the means and the further means have different operational principles.

[0062] In either case, it can be of significant advantage if the controller is arranged to individually control at least some or all of the at least one acousto-optical elements. This can remove the need for multiple controllers, and can thus reduce the complexity of the tot acousto-optical system. Furthermore, it could lead to reduced latency times and thus a more responsive optical system to have all acousto-optical elements be controlled by a single controller, or in cases of larger numbers of acousto-optical elements have several groups of elements be controlled by several controllers.

[0063] A possible setup for the controller can be to arrange it to control the elements via the means by supplying an input signal. In such a setup, colours could for example be set by application of a DC voltage, whereas sound can be produced by the application of an AC voltage. Or, a DC voltage could be applied as an offset for the frequency of the sound, whereas the AC voltage is used to actually produce the soundwaves around the offset. The AC and DC 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 of inputs and / or outputs can be supplied either parallelly, or in series.

[0064] As a further example, it is possible to apply an AC signal, so that the cover is sensitive to light of a certain wavelength. A sensing means could be used to measure at the same time a DC signal, which could be representative of an intensity of incident light of the certain wavelength. In such a case there is a combination of a means (for moving the cover) and a sensing means, although in general it is principally possible if these two are embodied as the same component.

[0065] Of course, 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 of a low or zero frequency signal with a relatively high frequency signal in order to achieve similar effects.

[0066] It is possible for the controller to be arranged in such a way as to control acoustical properties using a first frequency bandwidth and optical properties using a second frequency bandwidth, wherein the first frequency bandwidth is different than the second frequency bandwidth.

[0067] For simplified control, it may be of advantage 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 for the acoustic interval and the optical interval to have the same duration, however, this does not always need to be the case, and specific use cases may actually require longer acoustical intervals compared to the optical intervals or vice versa.

[0068] 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 first surface and a second surface, b. a support, and c. a sensing means; wherein the cover is orientated with the first surface directed towards the support, a part of the first surface is attached to the support and a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile. The sensing means is arranged to generate a signal in correspondence with the shape or a change in shape of the cover.

[0069] While an acousto-optical system could exist with just one acousto-optical element, in practice it is likely that a system will comprise larger numbers of elements, 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 larger number of elements can together provide a higher resolution image in regards to the optical part of the elements, or more complex timbres with regards to the acoustic part of the elements.

[0070] In such a way, it can be that the acousto-optical system is a display with integrated speaker functionality. On the other hand, if a sensing means is present in the system, the acousto-optical system could be a camera with integrated microphone functionality. This camera can for example be a hyperspectral camera. Of course, combinations are also possible, i.e. a display with microphone, and a camera with a speaker.

[0071] It is principally possible to have systems arranged as only an acoustic system, or only an optical system, and performing just the function of a camera, display, speaker or microphone. Therefore, the invention also relates to an acoustic system and an optical system separately.

[0072] The invention also relates to a method of operating an acousto-optical system as described in the previous paragraphs. Said method comprising the step of controlling, in an acousto-optical system as described hereabove, controlling the means of the at least one acousto-optical element at a frequency of at least 20 Hz, optionally at maximally 25 000 Hz. In particular, control may include combination of desired 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.

[0073] In particular, the means and / or further means may each, independent from one another, comprise any one or more of:

[0074] - an optical actuator, such as an optical tweezer or photonic circuitry;

[0075] - a means for applying or changing radiation incident on the cover, such as a radiation source.

[0076] - a means for influencing a gas pressure acting on the cover;

[0077] - a speaker or any other sound emitter;

[0078] - a thermal actuator, operating via thermal expansion; and - an electromagnetic and / or superconducting actuator, for instance operating based on tunneling or field emission.

[0079] At this time, it is noted that regardless of the actuation method used, given a sufficiently 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 cophenomena usually pair up. Examples of such pairs, which may be used in the currently described invention as a non-exclusive list of examples, are:

[0080] Thermo-electrical and electro-thermal actuation;

[0081] Thermo-optical and opto-thermal actuation;

[0082] Thermo-magnetic and magneto-thermal actuation; Opto-electrical and electro-optic actuation; and Magneto-optic and opto-magnetic actuation.

[0083] At the same time, quantum and superconducting effects may also play a role. Accordingly, use can be made of such effects if desired.

[0084] It is noted that the substrate may be used to define a cavity below the cover. The index of refraction of said cavity can be of influence on the optical behaviour of the optical element. The index of refraction of the cavity can be influenced by at least partially filling the cavity. To facilitate said filling the cavity may be enclosed by one or more of the support, the cover and the substrate, or may even be sealed entirely. If the cavity is indeed sealed, it can be filled with a substance. Different fillings of the cavity can lead to different refractive indices, and thus a different optical behaviour. The cavity may for this purpose be filled with a gas composition. Aside from a gas or gas mixture, the cavity may also be filled by a liquid (mixture) and / or liquid crystals, or even a solid filling, which may have a greater effect on the refractive index. Another option would be to instill a vacuum inside of the cavity. Definition of, and filling of the cavity may also be done for other reasons than influencing the index of reflection, i.e. to provide absorption, to provide structure rigidity, or other reasons.

[0085] Moreover, the substance filling a cavity can be of influence on other than the optical behaviour of the optical element, including but not limited to the mechanical response of the cover and the electrical influence of the means. A filled cavity can also be used to exert a pressure on the cover, in order to move it using pressure based means.

[0086] 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 of whether or not the characterizing portion of the claims is applied. In this novel way of using the device, a substrate opposite the cover is necessary, so that a cavity is formed between the cover and the substrate. The device is configured to allow entry of electromagnetic radiation, such as (visible) light, into the cavity between the support and the substrate, and to allow egress of the 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 first or second surface), the light now travels substantially parallel to the cover, through the cavity. In this case, the cavity acts like a waveguide. To form a waveguide, the skilled person is able to choose suitable materials for the support, the substrate and the material at the cover’s first surface and optionally for material to fill the cavity with, so that waves are influenced by the cover. This influence could for example result in a change in amplitude, phase or the state of the light. Suitably chosen characteristics, such as optical characteristics, of the cover allow interaction with light passing through the cavity. By changing the contour shape of the cover, or by changing its position, the waveguide formed in the cavity can be altered. The changing influence of the cover on waves passing through can be used to modulate the light.

[0087] The invention will be further elucidated with reference to the attached drawings, in which: Figures 1A, IB and 1C show schematically interaction of light with an optical element known in the state of the art;

[0088] Figures 2A, 2B and 2C show schematically interference interaction of light with an optical element known in the state of the art;

[0089] Figures 3A - 3D show schematically different operations of an acousto-optical element for optical behaviour;

[0090] Figure 4 shows schematically acoustic behaviour of an acousto-optical element;

[0091] Figures 5 and 6 show schematically an optical element for different interferometric effects; and

[0092] Figure 7 shows schematically in perspective view another way of using the optical element.

[0093] Figure 1A shows interaction of light with of a flat cover 101, which is supported by supports 104. The parallel rays 601 and 602 are both deflected by the same angle and remain parallel after interaction with the cover 101. This constitutes specular reflection.

[0094] Figure IB shows interaction of light with a convex cover. Due to the rounded convex cover contour profile, a first ray 601 is deflected by almost 180° and the second ray 602 is only deflected by a small angle. The rays 601 and 602 are no longer parallel after reflection at the cover. This constitutes diffuse reflection.

[0095] Figure 1C shows interaction of light with a concave cover. Due to the rounded concave cover contour profile, a first ray 601 is deflected by an angle less than 90° and the second ray 602 is deflected by almost 180°. The rays 601 and 602 are no longer parallel after reflection at the cover. This constitutes diffuse reflection. Figure 2A shows interference interaction with a flat cover. Aside from the supports 104, a substrate 106 is also present in this example of the state of the art, which lies on the bottom of the optical element. The support 104, cover 101 and substrate 106 define a cavity having a depth 205. The substrate 106 is transmissive and absorbing to an extent and the cover 101 is reflective, such that an incoming ray 601 undergoes interference which is dependent on the depth 205.

[0096] Figure 2B shows interference interaction with a convex cover. The cover 101 of the optical element of figure 12 has been deformed into a convex shape (cover contour profile). This was brought about by a means pushing the cover 101 upwards. This increases the depth 205 and the interference behaviour of incoming light 601 is altered.

[0097] Figure 2C shows interference interaction with a concave cover. The cover 101 of the optical element of figure 12 has been deformed into a concave shape (cover contour profile). This was brought about by the means pushing the cover 101 downwards. This decreases the depth 205 and the interference behaviour of incoming light 601 is altered.

[0098] Now first referring to figures 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 influencing incident light. Figure 5 for instance, shows an optical element similar to that of figures 1 and 2, but with a cover 101 that is relatively absorbing, and a substrate 106 that that is relatively reflective. As a result, incident light 601 transmitted 602 through the cover 101 interacts with light reflected 604 from the substrate to form a pattern of nodes 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 of exiting light 605 can be controlled. In figure 6 a cover 101 is present that is both transmissive and reflective, and a substrate that is reflective. Accordingly, use can be made of interferometric reflection, similar to figures 2A - 2C, however now the optical element is configured for light incident the cover 101. Otherwise, the optical element may be identical to that described above.

[0099] In figures 3A - 4, an acousto-optical element 99 is shown, with a support 4, a cover 1, and a substrate 6, as is defined in the claims. A means is also present in the substrate 6 to move the cover 1, but is not shown.

[0100] In figure 3A, a dashed line represents schematically movement of the cover in response to the means activating. Accordingly, and as described above, a certain optical behaviour can be expected depending on the height of the cover.

[0101] Figure 3B shows two dashed positions for the cover 1, between which the cover 1 can alternate by suitable operation of the means. The resulting optical behaviour is an average of the optical behaviours at the two respective positions. This alternating, called grayscale dithering, can be performed of a 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 of e.g. >20 Hz. A combination is shown in figure 3D, allowing many more colours to be output, for instance at > 500 Hz, and called gamut dithering.

[0102] It is noted that whilst the acousto-optical element is described herein primarily as a light modulator in order to output light of desired characteristics, the opposite is also possible if the means are a sensing means or a sensing means is otherwise present. The sensing means is configured 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.

[0103] Figure 4 shows sound waves 20, 21 emitting from and impinging on the cover 1 of an 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 registered when the cover moves as a result of the sound waves, and a sensing means is present. The sensing means may be the aforementioned means, or may be separately provided.

[0104] The functionalities can be combined however, for instance by providing grayscale dithering at an audible frequency. Accordingly, the optical behaviour is not influenced, but now an audible signal is also produced by the same element, which therefore thus is an acousto-optical element. Of course this can still be combined with even higher frequency changes, for instance to provide hue or gamut dithering.

[0105] It is noted herein that the cover is shown to move without changing shape, although in practice the cover would adjust its cover contour profile to its position.

[0106] Finally, reference is made to figure 7, which shows a perspective view of a 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 defines 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 cover’s first surface and material with which the cavity C is filled are chosen so that the cavity C acts as a waveguide. Incident waves 601, such as light, can therefore pass through from one side to another, and egress as exited light 602. Via means 107, in this case presented on top of the support 104, although not strictly necessary, the cover 101 can be moved, or its cover contour profile changed. As a result, the cover 101 at least locally influences the light passing through the cavity C in order to modulate it.

[0107] It is noted that terms like “preferably”, “generally” and “typically” are not utilized herein to limit the scope of the claims or to imply that certain features are critical, essential, or even important to the structure or function of the claims. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure. Likewise, for the purposes of describing and defining the present disclosure, it is noted that the terms “substantially” and “approximately” and their variants are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement or other representation, as well as to represent the degree by which a quantitative representation may vary without resulting in a change in the basic function of the subject matter at issue.

[0108] 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.

[0109] While certain representative embodiments and details have been shown for purposes 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 of the disclosure, which is defined in the appended claims.

Claims

1. CLAIMS1. Acousto-optical system, comprising at least one acousto-optical element, the at least one acousto-optical element comprising: a. a cover having a first surface and a second surface, b. a support, and c. a means; wherein: the cover is orientated with the first surface directed towards the support; a part of the first surface is attached to the support; a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile; 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, wherein 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.

2. Acousto-optical system according to the previous claim, wherein the controller is configured to, for each of the at least one acousto-optical elements:- control the means so as to move the cover in accordance with a desired optical behaviour; and- superimpose on and / or combining with the resulting movement, a movement in accordance with a desired acoustic behaviour.

3. Acousto-optical system according to the previous claim, wherein the controller is configured to, for each of the at least one acousto-optical elements, altematingly:- control the means so as to move the cover in accordance with a desired optical behaviour; and- control the means so as to move the cover in accordance with a desired acoustic behaviour.

4. Acousto-optical system according to the previous claim, wherein the means of each of the at least one acousto-optical elements comprise a first means and a further means, wherein the controller is configured to:- control the first means in accordance with the desired optical behaviour; and- control the further means in accordance with the desired acoustic behaviour.

5. Acousto-optical system according to any of claims 1 - 3, wherein the means of each of the at least one acousto-optical elements are a single means.

6. Acousto-optical system according to any of the preceding claims, wherein the controller is arranged to individually control acousto-optical elements.

7. Acousto-optical system according to any of the preceding claims, wherein the controller is arranged to control the acousto-optical elements through supplying to the means a combination of inputs that are continuous, alternating, analogue and / or digital outputs and / or through being supplied a combination of means that are continuous, alternating, analogue and / or digital inputs.

8. Acousto-optical system according to any of the preceding claims, wherein the controller is arranged to control acoustical properties using a first frequency bandwidth and optical properties using a second frequency bandwidth, wherein the first frequency bandwidth is different than the second frequency bandwidth.

9. Acousto-optical system according to any of claims 1 - 8, wherein the controller is arranged to control the acoustical properties and the optical properties in an alternating, repeating pattern.

10. Acousto-optical system according to the previous claim, wherein the repeating pattern comprises duty cycles, wherein each duty cycle comprises one acoustic interval, and one optical interval.

11. Acousto-optical system according to the previous claim, wherein the acoustic interval and the optical interval have the same duration, or wherein preferably the acoustic interval is of a longer duration.

12. Acousto-optical transducer system, comprising at least one acousto-optical element, the at least one acousto-optical element comprising: d. a cover having a first surface and a second surface, e. a support, and f. a sensing means; wherein: the cover is orientated with the first surface directed towards the support;a part of the first surface is attached to the support; a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile; the sensing means is arranged to generate a signal in correspondence with the shape or a change in shape of the cover.

13. Acousto-optical system according to any of the preceding claims, comprising 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.

14. Acousto-optical system according to any of claims 1 - 11, possibly in combination with claims 12 - 13, wherein the acousto-optical system is a display with integrated speaker functionality, or a display with integrated microphone functionality.

15. Acousto-optical system according to any of claims 12 - 13, possibly in combination with claims 1 - 11, wherein the acousto-optical system is a camera with integrated microphone functionality, or a camera with integrated speaker functionality.

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