Light homogenizing element

A light homogenizing element includes a light incident surface and at least one diffusion surface, including: a first substrate, a carrier layer, a piezoelectric film, a driving electrode, a light-transmitting layer, and multiple light diffusion microstructures. The first substrate includes a first surface and a second surface opposite to each other. The carrier layer is located on the first surface of the first substrate and includes a light passing region penetrating the carrier layer, and includes a protruding structure enclosing the light passing region. The light-transmitting layer is provided overlapping on the protruding structure, and the surface of the light-transmitting layer covering the light passing region is the light incident surface. The multiple light diffusion microstructures are provided on the at least one diffusion surface, and projections of the multiple light diffusion microstructures on the light-transmitting layer are located in the light passing region.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of China application serial no. 202110318884.5, filed on Mar. 25, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

1. Technical Field

The disclosure is related to an optical element, and in particular to a light homogenizing element.

2. Description of Related Art

Although displays using lasers as the light source may have better color performance (such as having wide color gamut), the speckle of lasers can cause images to appear grainy or with local brightness unevenness, resulting in poor viewing experience for users. In order to suppress the speckle caused by the laser light source due to interference phenomenon caused by high coherence, angular diversity, polarization diversity, and wavelength diversity are the most common techniques used.

For example, solutions using the technique of wavelength diversity require multiple light sources or broadband light sources tend to increase the volume and weight of the overall mechanism, and can even reduce the performance of color gamut. On the other hand, solutions using the technique of angular diversity require movable diffusers so as to uniformize the brightness distribution of the laser light source, which can cause excessive amounts of vibration in the entire mechanism and lead to a reduction in the stability of the light path. Furthermore, none of the above solutions are applicable to wearable displays. Therefore, how to solve the speckle problem of laser light sources while ensuring the miniaturization is one of the research and development priorities of the manufacturers concerned.

SUMMARY

The disclosure provides a light homogenizing element having the advantages of small volume and low vibration.

Other purposes and advantages of the disclosure may be further understood from the technology features disclosed in the disclosure.

In order to achieve one or all of the above-mentioned purposes or other purposes, a light homogenizing element is proposed in an embodiment of disclosure. The light homogenizing element includes a light incident surface and at least one diffusion surface. The light homogenizing element includes a first substrate, a carrier layer, a piezoelectric film, a driving electrode, a light-transmitting layer, and multiple light diffusion microstructures. The first substrate includes a first surface and a second surface opposite to each other. The first substrate includes a first cavity, where the first cavity penetrates from the first surface to the second surface. The carrier layer is located on the first surface of the first substrate and includes a light passing region penetrating the carrier layer, the carrier layer includes a protruding structure, and the protruding structure encloses the light passing region. The piezoelectric film is located on the carrier layer. The driving electrode is located on the carrier layer and drives the piezoelectric film, where the driving electrode applies driving voltage to the piezoelectric film, such that the piezoelectric film is stretched and deformed, pulling the protruding structure to bend and deform. The light-transmitting layer is overlapped and provided on the protruding structure, and a surface of the light-transmitting layer covering the light passing region is the light incident surface. The multiple light diffusion microstructures are provided on the at least one diffusion surface, and projections of the multiple light diffusion microstructures on the light-transmitting layer are located in the light passing region.

Base on the above, the embodiments of the disclosure have at least one of the following advantages or effects. In the embodiment of disclosure, by controlling the voltage difference between the two driving electrodes to change with time, the surface shape of the light incident surface may be quickly switched in time sequence, such that the deflection direction of the light path of the light beam passing through the light homogenizing element may change along with time. In this way, when the light homogenizing element is configured in an optical device with a laser light source, it may cause the speckle of the laser light source to change in time sequence, and can effectively reduce the speckle contrast value, which helps to improve the uniformity of the brightness distribution of the light beam. In addition, with the time-dependent deformation of the light incident surface and by configuring the light diffusion microstructure, after the light beam incident on the light homogenizing element and transmitted in the optical liquid passes through the light diffusion microstructure, the diversity of the deflection angle can be further increased, and the uniformity of the brightness distribution of the light beam after passing through the light homogenizing element can be further improved.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

FIG.1Ais a schematic diagram of a partial cross-sectional diagram of a light homogenizing element according to an embodiment of the disclosure.FIG.1Bis a schematic diagram of a top diagram of a light homogenizing element ofFIG.1A.FIG.2is a schematic diagram of a partial cross-sectional diagram of a light homogenizing element ofFIG.1Abeing deformed by applying driving voltage. Please refer toFIG.1A. A light homogenizing element100of the embodiment includes a first substrate110, a piezoelectric film120, a carrier layer140, a driving electrode150, a light-transmitting layer160, and multiple light diffusion microstructures190. It should be noted that in order to highlight the important technology features of disclosure, the diagrams only represent schematic diagrams, and are not drawn to scale. In the embodiment, the material of the first substrate110may be silicon, for example, but the disclosure is not limited thereto. In the embodiment, the piezoelectric film120is a light-transmitting material, such as a piezoelectric film of a single crystal material, but the disclosure is not limited thereto. In other embodiments, the piezoelectric film120may be non-light-transmitting material. The material of the light-transmitting layer160may include, for example, an organic molecular material, a high molecular material, or a transparent material of glass (silicon oxide), but the disclosure is not limited thereto.

Specifically, as shown inFIG.1A, in the embodiment, the first substrate110has a first surface111and a second surface112opposite to each other, and the first substrate110has a first cavity113. For example, the first cavity113is located in the center of the first substrate110, where the first cavity113penetrates through the first surface111and the second surface112. In addition, in the embodiment, the light homogenizing element100further includes a second substrate170. The second substrate170is located on the second surface112of the first substrate110, where the second substrate170includes at least one second cavity171. For example, as shown inFIGS.1A and1B, in the embodiment, at least one second cavity171includes multiple cylindrical cavities CH, where at least one second cavity171communicates with the first cavity113of the first substrate110, but the disclosure is not limited thereto. In other embodiments, the second cavity171may be a cavity of triangular column, quadrangular column or other shapes; the disclosure is not particularly limited thereto.

Furthermore, as shown inFIG.1A, in the embodiment, the light homogenizing element100further includes an optical liquid130. The optical liquid130is configured to fill the first cavity113, and the optical liquid130also fills the at least one second cavity171. In the embodiment, the light homogenizing element100further includes an elasticity film180; the second substrate170is located between the elasticity film180and the second surface112of the first substrate110; and the elasticity film180covers the second substrate170and at least one second cavity171, so as to seal the optical liquid130. On the other hand, the light-transmitting layer160is located on the first surface111of the first substrate110, and the optical liquid130filling the first cavity113and the second cavity171directly contacts the light-transmitting layer160and the elasticity film180. In the embodiment, the material of the optical liquid130may be a transparent material that may be known to those having ordinary skill in the art, which will not be repeated herein. The material of the second substrate170may be, for example, glass, and the material of the elasticity film180may be, for example, Parylene or Polydimethylsiloxane (PDMS), but the disclosure is not limited thereto.

On the other hand, as shown inFIG.1A, in the embodiment, the carrier layer140is located on the first surface111of the first substrate110. More specifically, as shown inFIG.1A, in the embodiment, the carrier layer140includes a first insulation layer IL1, a second insulation layer IL2, and a wafer layer WF. The second insulation layer IL2and the first insulation layer IL1are provided overlapped. A wafer layer WF is located between the first insulation layer IL1and the second insulation layer IL2. For example, in the embodiment, the material of the wafer layer WF may be silicon, and the material of the first insulation layer IL1and the second insulation layer IL2may be silicon oxide, for example. Thus, the carrier layer140can be easily manufactured using the process technology of silicon-on-insulator (SOI), and may be integrated with the existing process technology.

As shown inFIG.1AandFIG.1B, in the embodiment, the carrier layer140includes a light passing region CA that penetrates the carrier layer140. Furthermore, the carrier layer140encloses a protruding structure PS, and the protruding structure PS encloses the light passing region CA. The protruding structure PS extends from the first surface111of the first substrate110to a center of the light passing region CA in a radial direction R of the light passing region CA. That is, the carrier layer140completely covers the first surface111of the first substrate110and extends to the center of the light passing region CA, and the extended part is the protruding structure PS. In other words, a projection area of the light passing region CA in the elasticity film180is smaller than a projection area of the first cavity113in the elasticity film180. Specifically, in the embodiment, the protruding structure PS of the carrier layer140is made up of the wafer layer WF and the first insulation layer IL1(that is, a boundary of the second insulation layer IL2is the same as a boundary of the first substrate110), but the disclosure is not limited thereto. In other embodiments, the carrier layer140may be a single-layer structure. The carrier layer140may extend to the center of the light passing region CA to form the protruding structure PS. The carrier layer140may be, for example, an insulation layer or a semiconductor layer.

As shown inFIG.1A, the piezoelectric film120is located on the carrier layer140, where the piezoelectric film120is provided on the first insulation layer IL1, and the light-transmitting layer160is located on the piezoelectric film120. However, the disclosure is not limited thereto. In other embodiments, the light-transmitting layer160may also be provided between the piezoelectric film120and the carrier layer140, or the piezoelectric film120and the light-transmitting layer160may be formed by other stacking methods. The piezoelectric film120has an opening region OA, and a boundary of the opening region OA is the same as a boundary of the light passing region CA, but the disclosure is not limited thereto. In other embodiments, a projection area of the opening region OA of the piezoelectric film120in the elasticity film180may be greater than or equal to a projection area of the light passing region CA in the elasticity film180. As shown inFIG.1A, in the embodiment, the light-transmitting layer160is provided overlapping on the piezoelectric film120and the protruding structure PS of the carrier layer140, and the light-transmitting layer160covers the light passing region CA.

More specifically, referring to bothFIG.1AandFIG.1B, in the embodiment, a projection range of the light-transmitting layer160on the elasticity film180completely covers a projection range of the light passing region CA on the elasticity film180. The projection region of the light passing region CA on the elasticity film180overlaps the projection region of the first cavity113on the elasticity film180. Furthermore, as shown inFIG.1B, in the embodiment, the projection region of the first cavity113on the elasticity film180at least partially overlaps the projection region of at least one second cavity171on the elasticity film180. In particular, a projection range of the second cavity171on the elasticity film180does not overlap a projection range of the light passing region CA on the elasticity film180. In this way, it can be ensured that the disposition of the second cavity171will not affect the optical performance of the light passing through the light passing region CA.

Next, proceeding to refer toFIG.1AandFIG.1B, in the embodiment, the driving electrode150is located on the carrier layer140and is configured to drive the piezoelectric film120. For example, as shown inFIG.1A, in the embodiment, the piezoelectric film120is sandwiched by the corresponding driving electrode150respectively. The driving electrode150includes a driving electrode151and a driving electrode152, where the driving electrode151, the piezoelectric film120, and the driving electrode152are sequentially stacked on the carrier layer140from bottom to top. In more detail, as shown inFIG.1A, in the embodiment, the piezoelectric film120includes an exterior surface120aand an inner surface120bopposite to each other. The exterior surface120afaces the light-transmitting layer160, and the inner surface120bfaces the carrier layer140. The driving electrode151is located between the carrier layer140and the inner surface120bof the piezoelectric film120. The driving electrode152is located between the exterior surface120aof the piezoelectric film120and the light-transmitting layer160. For example, the materials of the driving electrode151and the driving electrode152may be platinum and gold, respectively. Moreover, as shown inFIG.1B, the shape of the driving electrode150may be a ring, and the driving electrode150surrounds the light passing region CA.

In this way, when the driving electrode150applies a driving voltage to the piezoelectric film120, the piezoelectric film120is deformed by compression or stretching (for example, the piezoelectric film120is compressed or stretched in the direction parallel to the first substrate110) by an electric field, pulling the protruding structure PS to bend and deform (for example, the protruding structure PS bends or stretches in a direction parallel to a normal line of the first substrate110) and driving the light-transmitting layer160into deformation, so as to achieve the purpose of optical zooming. In the embodiment, the piezoelectric film120is deformed by the electric field, such that both the protruding structure PS of the carrier layer140and the light-transmitting layer160are deformed by force. Moreover, because the protruding structure PS of the carrier layer140has a higher elasticity coefficient, the structural strength of the light-transmitting layer160with a smaller elasticity coefficient can be enhanced. As a result, as the electric field changes, the light-transmitting layer160may be bent away from the first cavity113or towards the first cavity113to form a convex spherical or a concave spherical surface deformation so as to achieve the purpose of zooming.

On the other hand, in the embodiment, the elasticity coefficient of the elasticity film180is smaller than the elasticity coefficient of the light-transmitting layer160. Thus, by disposing the elasticity film180having the relatively small elasticity coefficient, volume change of the light homogenizing element when the light-transmitting layer160is deformed can be moderated, such that the light-transmitting layer160located in the light passing region CA can still maintain an approximate spherical shape when a driving voltage is applied to the piezoelectric film120, thereby effectively maintaining the optical quality of the light homogenizing element100.

For example, in the embodiment, the lengths and widths of the first substrate110, the light-transmitting layer160, the second substrate170, and the elasticity film180are all approximately 3-13 mm, and the thicknesses of the first substrate110, the light-transmitting layer160, the second substrate170, and the elasticity film180are approximately 10 micrometer, 25 micrometer, 300 micrometer, and 10 micrometer, respectively. The diameter of the first cavity113is approximately 4 mm, and the diameter of the second cavity171is approximately 1.8 mm. It should be noted that the numerical range here is for illustrative purposes only, and is not used to limit the disclosure.

On the other hand, in the embodiment, an outer diameter of the driving electrode150is approximately 2-10 mm, an inner diameter is approximately 0.5-6 mm, a diameter of the light passing region CA is approximately 0.5-6 mm, and a size of the protruding structure PS of the carrier layer140is approximately 0.5-4 mm. In particular, according to the size change of the protruding structure PS, the elasticity coefficient also changes, and the degree of protruding of the light-transmitting layer160will also vary. Thus, when the driving electrode150applies an appropriate driving voltage to the piezoelectric film120, the tensile force causing the piezoelectric film120to deform will keep the protruding structure PS and the light-transmitting layer160to deform within a desired range. Thus, under such configuration, by the strain action of the optical liquid130, the piezoelectric film120, the protruding structure PS of the carrier layer140, and the light-transmitting layer160, the light homogenizing element100may adjust the curve radius of the light-transmitting layer160in the light passing region CA so as to achieve the effect of zooming. The following provides further explanation with reference toFIG.2.

FIG.2is a schematic diagram of a partial cross-sectional diagram of a light homogenizing element100ofFIG.1Aby applying driving voltage. Specifically, as shown inFIG.2, a driving voltage is applied to the piezoelectric film, driving the light-transmitting layer160into deformation. The carrier layer140, the piezoelectric film120, the driving electrode150, and the light-transmitting layer160may together enclose a zoomable cavity; and the zoomable cavity may communicate with the first cavity113. In particular, since the thicknesses of the piezoelectric film120and the driving electrode150may be much smaller than the thickness of the carrier layer140, the region enclosed by the light passing region CA and the light-transmitting layer160may also be directly taken as a zoomable cavity. Furthermore, the range of the first cavity113will change due to the deformation of the carrier layer140, but the zoomable cavity may still communicate the first cavity113.

In the embodiment, when the light-transmitting layer160is deformed, since the first cavity113, the second cavity171, and the zoomable cavity enclose a sealed space, the volume of the optical liquid130filling in the cavity remains constant, the optical liquid130will flow in the first cavity113, the second cavity171, and the zoomable cavity. Since the elasticity coefficient of the elasticity film180is much smaller than the elasticity coefficient of the light-transmitting layer160, volume change of the light homogenizing element when the light-transmitting layer160deforms can be adjusted. At this time, the elasticity film180covering the second cavity171and the second substrate170at this time will also be deformed, such that the optical liquid130may flow smoothly without causing unwanted deformation. In other words, without providing the elasticity film180, unwanted deformation degree of the light-transmitting layer160may occur. With the disposition of the elasticity film180, the shape of the light-transmitting layer160can be deformed to within the expected degree and the optical quality of the light homogenizing element100can be maintained. Thus, by disposing the elasticity film180having relatively small elasticity coefficient, the light-transmitting layer160located in the light passing region CA can still maintain an approximate spherical shape when a driving voltage is applied, thereby effectively maintaining the optical quality of the light homogenizing element100.

In the embodiment, the cross-sectional profile of the deformed light-transmitting layer160is a convex curve from the first surface111of the first substrate110, and the curvature of the curve may be controlled by the voltage difference applied by the driving electrode151and the driving electrode152. In other words, the surface shape of the light incident surface (i.e. the surface of the light-transmitting layer160) of the light homogenizing element100may be changed by the voltage difference between the two driving electrodes. For example, in the disclosure, the driving voltage ranges between 0 and 50 volts, but the disclosure is not limited thereto.

Furthermore, in the embodiment of disclosure, when controlling the voltage difference between the two driving electrodes to change with time, the surface shape of the light incident surface may be quickly switched in time sequence, such that the deflection direction of the light path of the light beam passing through the light-transmitting layer160of the light homogenizing element may change along with time. In this way, when the light homogenizing element is configured in an optical device with a laser light source, it may cause the speckle of the light source to change in time sequence, and can effectively reduce the speckle contrast value, which helps to improve the uniformity of the brightness distribution of the light beam.

It is worth mentioning that the light homogenizing element100of the embodiment drives the light incident surface into deformation by the piezoelectric effect, with a response rate of more than tens of kilohertz (kHz), and may adopt micro mechanical system (MEMS) for manufacturing. In other words, the light homogenizing element100of the embodiment has the advantages of fast response, silent movement, and microformability. Although the embodiment adjust the surface shape of the light incident surface of the light homogenizing element100with the principle of piezoelectricity, but the disclosure is not limited thereto. In other embodiment, the light homogenizing element may adjust the surface shape of the light incident surface by using electromagnetic coil or electroactive polymer.

Furthermore, as shown inFIGS.1A and2, the light homogenizing element100further includes at least one diffusion surface DS, and part of the optical liquid130is located between the light incident surface (that is, the surface of the light-transmitting layer160) and at least one diffusion surface DS. The multiple the light diffusion microstructures190of the light homogenizing element100are provided on the at least one diffusion surface, and projections of the multiple light diffusion microstructures190on the light-transmitting layer160are located in the light passing region CA, and do not overlap with the second cavity171. In other words, the light diffusion microstructures190are provided on the transmission path of the light beam passing through the light homogenizing element100. More specifically, in the embodiment, at least one diffusion surface DS is part of a surface of the second substrate170that contacts the optical liquid130, a projection of the part of the surface on the light-transmitting layer160is located in the light passing region CA, and the optical liquid130contacts the multiple light diffusion microstructures190. In this way, after the light beam incident from the light-transmitting layer160and transmitted in the optical liquid130passes through the diffusion surface DS where the light diffusion microstructures190are located, the diversity of the deflection angle can be further increased. In other words, with the temporal deformation of the light incident surface and by configuring the light diffusion microstructures190on the diffusion surface DS, the uniformity of the brightness distribution of the light beam passing through the light homogenizing element can be further improved.

In the embodiment, the light diffusion microstructure190is, for example, a periodic structure in the form of microlens, but the disclosure is not limited thereto. In other embodiment, the light diffusion microstructure190may also be a periodic structure in the form of micro prism or micro pyramid, or is embodied by a surface microstructure similar to a diffraction optical element (DOE) or a diffuser with a diffusion particle.

The following will list some other embodiments to explain the disclosure in detail, the same component will be marked with the same sign, and the description of the same technology content of omit, reference can be made to the aforementioned embodiment for omitted parts, and will not be repeated below.

FIG.3is a partial sectional schematic diagram of another light homogenizing element according to an embodiment of the disclosure. Referring toFIG.3, the light homogenizing element300of the embodiment is similar to the light homogenizing element100ofFIG.1, and the differences between the two are as follows. The main difference is: the configuration position of light diffusion microstructures390of the light homogenizing element300is different from the configuration position of the light diffusion microstructures190of the light homogenizing element100. Specifically, the light diffusion microstructures390of the light homogenizing element300are provided on a side of the elasticity film180away from the second substrate170, and the diffusion surface DS faces away from the second substrate170. In other words, the elasticity film180of the embodiment is located between the light diffusion microstructures390and the second substrate170. Moreover, the light homogenizing element300may also selectively include a third substrate DB. The third substrate DB is disposed between the elasticity film180and the light diffusion microstructures390, and the projection on the light-transmitting layer160is located in the light passing region CA.

More specifically, the light diffusion microstructures390are provided on a surface of the third substrate DB away from the elasticity film180(i.e. the diffusion surface DS). In the embodiment, the material of the third substrate DB may include polyimide (PI), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), or polycarbonate (PC), but the disclosure is not limited thereto.

Specifically, as shown inFIG.3, the third substrate DB is only provided in the light passing region CA of the light homogenizing element300, and does not overlap the second cavity171in the direction perpendicular to the light incident surface. In other words, the third substrate DB provided with the light diffusion microstructures390does not contact the part of the elasticity film180covering the second cavity171. However, the disclosure is not limited thereto. In other embodiments, a gap may also be provided between the third substrate DB disposed with the light diffusion microstructures390and the elasticity film180. For example, the diffuser plate may be provided on a fixed mechanism or gel, such that a predetermined pitch from the elasticity film180is maintained.

Similar to the light diffusion microstructures190, the light diffusion microstructures390also overlap the first cavity113in the direction perpendicular to the light incident surface. In other words, the light diffusion microstructures390are provided on the transmission path of the light beam passing through the light homogenizing element300. Therefore, after the light beam incident from the light-transmitting layer160and transmitted in the optical liquid130passes through the diffusion surface DS where the light diffusion microstructures390are located, the diversity of the deflection angle can be further increased. In other words, with the temporal deformation of the light incident surface of the light homogenizing element300and by configuring the light diffusion microstructures390on the diffusion surface DS, the uniformity of the brightness distribution of the light beam passing through the light homogenizing element300can be further improved.

FIGS.4to6are partial sectional schematic diagrams of different light homogenizing elements according to an embodiment of the disclosure. Referring toFIGS.4to6, a light homogenizing element400, a light homogenizing element500, and a light homogenizing element600of the embodiment is similar to the light homogenizing element100, and the difference is as follows. The main difference is: the configuration positions of light diffusion microstructures490, light diffusion microstructures590, and light diffusion microstructures690of the light homogenizing element400are different from the configuration position of the light diffusion microstructures190of the light homogenizing element100.

Specifically, as shown inFIG.4, in the embodiment ofFIG.4, at least one diffusion surface DS of the light homogenizing element400is a microstructure surface of an elasticity film480located in the light passing region CA. The microstructure surface faces away from the second substrate170; that is, the diffusion surface DS faces away from the second substrate170. More specifically, the multiple light diffusion microstructures490and the elasticity film480of the embodiment are integrally formed, and the diffusion surface DS may be formed by the multiple light diffusion microstructures490.

On the other hand, as shown inFIG.5, in the embodiment ofFIG.5, the multiple light diffusion microstructures590of the light homogenizing element500are located between the second substrate170and an elasticity film580. The at least one diffusion surface DS is part of a surface of the second substrate170that contacts the elasticity film580. The elasticity film580directly covers the multiple light diffusion microstructures590.

As shown inFIG.6, in the embodiment ofFIG.6, some of the multiple light diffusion microstructures690are located on one side of the second substrate170, and the other of the multiple light diffusion microstructures690are located on the other side of the second substrate170, and are disposed corresponding to the some of the multiple light diffusion microstructures690. In other words, the light homogenizing element600has two diffusion surfaces. For example, the multiple light diffusion microstructures690of the light homogenizing element600includes multiple first light diffusion microstructures691and multiple second light diffusion microstructures692. The first light diffusion microstructures691and the second light diffusion microstructures692are provided on a first diffusion surface DS1and a second diffusion surface DS2, respectively. The first diffusion surface DS1is part of a surface of the second substrate170contacting the optical liquid130, and the second diffusion surface DS2is part of a surface of the second substrate170contacting the elasticity film580.

In this way, in the embodiments of theFIGS.4to6, after the light beam incident from the light-transmitting layer160and transmitted in the optical liquid130passes through the light diffusion microstructures490, the light diffusion microstructures590, and the light diffusion microstructures690, the diversity of the deflection angle can be further increased. In other words, with the temporal deformation of the light incident surface and by configuring the light diffusion microstructures490, the light diffusion microstructures590, and the light diffusion microstructures690, the uniformity of the brightness distribution of the light beam after passing through the light homogenizing element400, light homogenizing element500, and light homogenizing element600can be effectively improved.

FIG.7Ais a schematic diagram of another light homogenizing element according to an embodiment of the disclosure.FIG.7Bis a partial sectional schematic diagram of a light homogenizing element ofFIG.7A. Referring toFIGS.7A and7B, a light homogenizing element700of the embodiment is similar to the light homogenizing element100ofFIG.1, and the differences between the two are as follows. The main differences are the configuration of the driving electrode and the driving method. Specifically, as shown inFIGS.7A and7B, in the embodiment, the driving electrode750includes multiple arc-shaped electrodes750a,750b,750c,750d,and the arc-shaped electrodes750a,750b,750c,750dare arranged on a circular region CR. The circular region CR surrounds the light passing region CA, and the arc-shaped electrodes750a,750b,750c,and750dare provided on the exterior surface120aof the piezoelectric film120by surrounding the first cavity113, and are separated from each other. The arc-shaped electrode750a(the arc-shaped electrode750b,the arc-shaped electrode750c,or the arc-shaped electrode750d) further includes a driving electrode751a(a driving electrode751b,a driving electrode751c,a driving electrode751d) and a driving electrode752a(a driving electrode752b,a driving electrode752cor a driving electrode752d). The driving electrode751a(the driving electrode751b,the driving electrode751c,or the driving electrode751d), the piezoelectric film120, the driving electrode752a(the driving electrode752b,the driving electrode752cor the driving electrode752d) are sequentially stacked on the carrier layer140from bottom to top. Moreover, in the embodiment, the polarity direction of the driving voltage applied by any of the arc-shaped electrodes750a,750b,750c,and750dis opposite to the polarity direction of the driving voltage applied by an adjacent arc-shaped electrode. For example, the polarity direction of the driving voltage applied by the arc-shaped electrode750ais opposite to the polarity direction of the driving voltage applied by the arc-shaped electrode750b.For example, with the time-sharing driving of the driving electrodes, the piezoelectric film120of the embodiment may cause the surface of the light-transmitting layer160to form a planar inclination on the first surface111of the first substrate110, and the planar inclination angle may change along with time. In the embodiment, an angle θ between the light incident surface and the first surface111of the first substrate110(i.e. the inclination angle) may range between 0.5 degrees to 20 degrees, but the disclosure is not limited thereto.

In this way, by quickly switching the inclination angle of the light incident surface in time sequence, the deflection direction of the light path of the light beam coming from the light source (such as laser light source) after passing through the light-transmitting layer160of the light homogenizing element700can also change along with time. Also as a result, with the change of the speckle of the laser light source in time sequence, the speckle contrast can be effectively reduced, which helps to improve the uniformity of the brightness distribution of the light beam.

FIG.8is a partial sectional schematic diagram of another light homogenizing element according to another embodiment of the disclosure. Referring toFIG.8, a light homogenizing element800of the embodiment is similar to the light homogenizing element100ofFIG.1, and the difference the two is as follows. The main difference lies in that the light homogenizing element800further includes multiple optical particles PA. Specifically, as shown inFIG.8, in the embodiment, the optical particles PA are provided dispersed in the optical liquid130, and the refractive index of the optical particles PA is different from the refractive index of the optical liquid130. In this way, after the light beam incident from the light-transmitting layer160and transmitted in the optical liquid130passes through the optical particles PA, the diversity of the deflection angle of the light path can be further increased. In other words, the uniformity of the brightness distribution of the light beam after passing through the light homogenizing element800can be further improved.

FIGS.9to13are partial sectional schematic diagrams of different light homogenizing elements according to an embodiment of the disclosure. Referring toFIG.9, a light homogenizing element900of the embodiment is similar to the light homogenizing element100ofFIG.1A, and the difference the two is as follows. As shown inFIG.9, in the embodiment, the light-transmitting layer960is provided between a piezoelectric film920and a carrier layer940. For example, the light-transmitting layer960may be formed by the first insulation layer IL1ofFIG.1A. Its material is silicon oxide and has light transmittance. The carrier layer940only includes the second insulation layer IL2and the wafer layer WF. Specifically, as shown inFIG.9, in the embodiment, the light-transmitting layer960(first insulation layer IL1) is stacked on the wafer layer WF, and the wafer layer WF is located between the second insulation layer IL2and the light-transmitting layer960.

In this way, the carrier layer940and the light-transmitting layer960may be easily fabricated by the silicon-on-insulator (SOI) process, and may be integrated with existing process technology, but the disclosure is not limited thereto. In other embodiments, the carrier layer940also only includes the second insulation layer IL2and the wafer layer WF, the second insulation layer IL2is located between the first substrate110and the wafer layer WF, and the light-transmitting layer960is located between the wafer layer WF and the piezoelectric film920. The piezoelectric film920covers the light passing region CA, and its material may selectively include high molecular material or glass. Further, as shown inFIG.9, in the embodiment, the piezoelectric film920may selectively cover the light passing region CA.

In this way, in the light homogenizing element900, the predetermined driving voltage may also be applied to the piezoelectric film920, so as to cause the piezoelectric film920to deform by stretching stress, thereby driving the protruding structure PS of the carrier layer940and the light-transmitting layer960into deformation. In the embodiment, the light homogenizing element900also has the structure of the light diffusion microstructure190as does the light homogenizing element100, so the light homogenizing element900also has the advantages described for the light homogenizing element100, which will not be repeated here.

Referring toFIG.10, a light homogenizing element1000of the embodiment is similar to the light homogenizing element100ofFIG.1A, and the difference the two is as follows. As shown inFIG.10, in the embodiment, a carrier layer1040only includes first insulation layer IL1and the wafer layer WF. A light-transmitting layer1060may be formed by second insulation layer IL2ofFIG.1A. It has light transmittance, and the material is silicon oxide. Specifically, as shown inFIG.10, the wafer layer WF is located between the first insulation layer IL1and the light-transmitting layer1060, and the light-transmitting layer1060is located between the first substrate110and the wafer layer WF. In the embodiment, the light homogenizing element100may selectively further include an auxiliary piezoelectric film AP. The auxiliary piezoelectric film AP is provided on the light-transmitting layer1060, and may selectively cover only the light-transmitting region, so as to improve the stability of the light-transmitting layer1060. Moreover, the auxiliary piezoelectric film AP will not be deformed by stretching stress due to the driving voltage. In the embodiment, the light homogenizing element1000also has the structure of the light diffusion microstructure190as does the light homogenizing element100, so the light homogenizing element1000also has the advantages described for the light homogenizing element100, which will not be repeated here.

Referring toFIG.11, a light homogenizing element1100of the embodiment is similar to the light homogenizing element100ofFIG.1A, and the difference the two is as follows. As shown inFIG.11, in the embodiment, a light-transmitting layer1160is the carrier layer inFIG.1A. It is formed by the insulation layer, and the material is silicon oxide or glass. The first substrate110and the light-transmitting layer1160may be silicon glass bond wafer (SOG wafer). In the embodiment, the light-transmitting layer1160of the light homogenizing element1100is equivalent to the protruding structure of the carrier layer ofFIG.1Aextending to the center of the light passing region CA and connected to each other without a through hole penetrating the carrier layer. Specifically, as shown inFIG.11, the light-transmitting layer1160is located between the first substrate110and the piezoelectric film120. In this way, in the light homogenizing element1100of the embodiment, a predetermined driving voltage may also be applied to the piezoelectric film120, so as to cause the piezoelectric film120to deform by stretching stress, thereby driving the light-transmitting layer1160into deformation. In the embodiment, similar to the piezoelectric film of the light homogenizing element100, the piezoelectric film of the light homogenizing element1100is also deformed by stretching stress. Moreover, the light homogenizing element1100also has the structure of the light diffusion microstructure190, as does the light homogenizing element100. Therefore, the light homogenizing element1100also has the advantages described for the light homogenizing element100, and will not be repeated here.

Referring toFIG.12, a light homogenizing element1200of the embodiment is similar to the light homogenizing element900ofFIG.9, and the difference the two is as follows. As shown inFIG.12, in the embodiment, the number of a driving electrode1250may be four, namely, a driving electrode1251, a driving electrode1252, a driving electrode1253, and a driving electrode1254. The configuration of the driving electrode1251and the driving electrode1252are similar to the configuration of the driving electrode151and the driving electrode152of the light homogenizing element900(as shown inFIG.9), and will not be repeated here. Furthermore, the driving electrode1253and the driving electrode1254of the light homogenizing element1200are provided in the region surrounded by the driving electrode1251(or the driving electrode1252), and the piezoelectric film120is sandwiched between the driving electrode1253and the driving electrode1254.

For example, when the driving electrode1251, the driving electrode1252, the driving electrode1253, and the driving electrode1254apply different driving voltages to the piezoelectric film120, the piezoelectric film120will bend and deform correspondingly, causing the light beam passing through the piezoelectric film120to deflect. It is worth noting that at this time, a cross-sectional profile of the exterior surface120a(i.e. the light incident surface) of the piezoelectric film120of the light homogenizing element1200is wavy. Accordingly, the diversity of the deflection angle can be further increased after the light beam passes through the piezoelectric film120, resulting in advantages similar to those described for the light homogenizing element100, which will not be repeated here.

Referring toFIG.13, a light homogenizing element1300of the embodiment is similar to the light homogenizing element100ofFIG.1A, and the difference the two is as follows. As shown inFIG.13, in an embodiment of the disclosure, the light homogenizing element1300further includes a diffuser plate1390. The elasticity film180is provided between the diffuser plate1390and the second substrate170, and the elasticity film180corresponding to the at least one second cavity171does not contact the diffuser plate1390. The diffuser plate1390may be fixed to the elasticity film180corresponding to the second substrate170or at least overlap with the part corresponding to the second substrate170through the adhesive layer AD, for example.

In this way, after the light beam incident from the light-transmitting layer160and transmitted in the optical liquid130passes through the light diffusion microstructures190and then passes through the diffuser plate1390to be further diffused, and the diversity of its deflection angles can be further increased. In other words, with the time-dependent deformation of the light incident surface and by configuring the light diffusion microstructures190and the diffuser plate1390, the uniformity of the brightness distribution of the light beam after passing through the light homogenizing element1300can be improved, and the diversity of its deflection angles can be further increased.

The aforementioned light diffusion microstructures390, the light diffusion microstructures490, the light diffusion microstructures590, and the light diffusion microstructures690may also replace the light diffusion microstructures190of the embodiment shown inFIGS.7B to13and be configured in the aforementioned light homogenizing elements700,800,900,1000,1100,1200,1300, such that the light homogenizing elements700,800,900,1000,1100,1200,1300can achieve similar effects and advantages, which will not be repeated here.

In summary, the embodiments of the disclosure have at least one of the following advantages or effects. In the embodiment of disclosure, by controlling the voltage difference between the two driving electrodes to change with time, the surface shape of the light incident surface may be quickly switched in time sequence, such that the deflection direction of the light path of the light beam passing through the light homogenizing element can change along with time. In this way, when the light homogenizing element is configured in an optical device with a laser light source, it may cause the speckle of the laser light source to change in time sequence, and can effectively reduce the speckle contrast value, which helps to improve the uniformity of the brightness distribution of the light beam. In addition, with the time-dependent deformation of the light incident surface and by configuring the light diffusion microstructure, after the light beam incident on the light homogenizing element and transmitted in the optical liquid passes through the light diffusion microstructure, the diversity of the deflection angle can be further increased, and the uniformity of the brightness distribution of the light beam after passing through the light homogenizing element can be further improved.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the disclosure, but the disclosure is not limited thereto. Although the disclosure is described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the technical solutions described in the above-mentioned embodiments can still be modified, and some or all of the technical features may be replaced equivalently; such modifications or replacements do not depart from the scope of the technical solutions described by the embodiments of the disclosure.