阅读说明：本技术 用于显示三维图像的装置 (Apparatus for displaying three-dimensional image ) 是由 X·罗滕伯格 K·洛德威克斯 于 2019-03-04 设计创作，主要内容包括：一种用于显示三维图像的装置,包括：光场生成单元(110),该光场生成单元(110)被配置成用于接收入射光束(112)并生成三维光场；以及图像显影介质(120),该图像显影介质(120)被布置成接收由该光场生成单元(110)生成的该三维光场,其中该图像显影介质(120)包括在其中悬浮有气泡或颗粒的流体,其中该气泡或颗粒具有在40-500nm范围内的大小。(An apparatus for displaying a three-dimensional image, comprising: a light field generation unit (110), the light field generation unit (110) being configured for receiving an incident light beam (112) and generating a three-dimensional light field; and an image development medium (120), the image development medium (120) being arranged to receive the three-dimensional light field generated by the light field generation unit (110), wherein the image development medium (120) comprises a fluid in which gas bubbles or particles are suspended, wherein the gas bubbles or particles have a size in the range of 40-500 nm.)

1. An apparatus for displaying a three-dimensional image, the apparatus (100) comprising:

a light field generation unit (110), the light field generation unit (110) being configured for receiving an incident light beam (112) and generating a three-dimensional light field; and

an image development medium (120), the image development medium (120) being arranged to receive the three-dimensional light field generated by the light field generation unit (110), wherein the image development medium (120) comprises a fluid in which gas bubbles or particles are suspended, wherein the gas bubbles or particles have a size in the range of 40-500 nm.

2. The device of claim 1, wherein the gas bubbles or particles have a size in the range of 40-200 nm.

3. The device of claim 1, wherein the gas bubbles or particles have a size in the range of 50-150 nm.

4. The device of any one of the preceding claims, wherein the fluid is an aqueous liquid.

5. The device of any one of the preceding claims, wherein the bubbles are filled with air or another gas comprising oxygen, nitrogen or carbon dioxide.

6. The apparatus of any one of the preceding claims, wherein the size of the bubbles or particles in the fluid and the concentration of bubbles or particles are selected to provide an optical attenuation constant in the range of 10-200dB/m for the optical wavelength of the optical beam.

7. The device according to any of the preceding claims, wherein the size of the bubbles or particles and the concentration of bubbles or particles in the fluid are selected for providing an average distance below 200 μ ι η between two adjacent bubbles or particles in the fluid.

8. A device according to any preceding claim, wherein the concentration of bubbles in the fluid is greater than 2 x 10¹⁴Air bubble/m³。

9. The apparatus of any of the preceding claims, further comprising a container (130) in which the image development medium (120) is disposed, wherein at least a portion of a wall (132) of the container (130) is transparent for outputting light scattered by bubbles or particles in the fluid.

10. The apparatus of claim 9, further comprising at least one channel (104; 106), the at least one channel (104; 106) being connected to the container (130) for transporting the image development medium (120) into the container (130) and transporting the image development medium (120) out of the container (130).

11. The apparatus according to any of the claims 9 to 10, wherein the image development medium (120) is arranged in the container (130) such that the container (130) has an increasing concentration of bubbles or particles in the propagation direction of the light of the generated light field.

12. The apparatus of any of the preceding claims, further comprising at least one calibration sensor (160), the calibration sensor (160) configurable to receive light transmitted through the image development medium (120) to detect an intensity of the received light as a measure of attenuation of a light beam propagating through the image development medium (120).

13. The apparatus of any of the preceding claims, further comprising an optical system (118), the optical system (118) being configured to transfer the light field generated by the light field generating unit (110) into the image development medium (120).

14. The apparatus of any of the preceding claims, further comprising a controller unit (150), the controller unit (150) being configured to control the light field generation unit (110) to control a distribution of light in the three-dimensional light field output by the light field generation unit (110).

15. The apparatus of any of the preceding claims, further comprising at least one light source (140), the light source (140) being configured to generate the light beam (112) incident on the light field generating unit (110).

Technical Field

The present inventive concept relates to an apparatus for displaying a three-dimensional image. In particular, the inventive concept relates to an apparatus for forming an image based on a projected three-dimensional light field.

Background

The three-dimensional display may be implemented in many different ways. In some implementations, the three-dimensional display may include a distribution of light sources. This means that complex hardware may be required in order to control the sources used to form the three-dimensional display.

However, in another implementation, the holographic image may be formed by three-dimensional control of the light field. Thus, the projection of the light field may form a three-dimensional space. Then, in order to create an image that can be seen by an observer, the three-dimensional light field may need to propagate through a medium that will scatter light. The scattering points form the starting points of the light, so that the scattering points can form a visible image based on the three-dimensional light field.

In US 2010/0321478, volumetric three-dimensional graphics or computer displays are disclosed that allow independent observers to observe static or moving objects from multiple angles with natural depth cues and better image quality. The display utilizes a motion screen formed from an array of microparticles, wherein multiple images are optically projected onto each flight screen as it passes through the image volume, thereby minimizing microparticle mass flow, since only one screen is required per image volume to render several or more necessary slices per volume frame.

However, controlling the medium used for generating the three-dimensional image is relatively complicated, and therefore it is desirable to facilitate control of the medium so as to enable a practically feasible three-dimensional display.

SUMMARY

It is an object of the inventive concept to provide a three-dimensional display which may be practically feasible and which does not require constant and careful control of the medium used for generating the three-dimensional image.

This and other objects of the invention are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims.

According to a first aspect, there is provided an apparatus for displaying a three-dimensional image, the apparatus comprising: a light field generation unit configured to receive an incident light beam and generate a three-dimensional light field; and an image development medium arranged to receive the three-dimensional light field generated by the light field generation unit, wherein the image development medium comprises a fluid having gas bubbles or particles suspended therein, wherein the gas bubbles or particles have a size in the range of 40-500 nm.

The image development medium receiving the three-dimensional field is configured to scatter incident light. Thus, each scattering point may form a starting point for light, such that a viewer may be able to see a three-dimensional image formed by the scattering of light of the three-dimensional light field. The three-dimensional light field may control the intensity of light scattered from each portion of the image development medium to control the three-dimensional image formed, while the image development medium may ensure that a viewable three-dimensional image is formed.

Having the desired distribution of bubbles or particles in the image development medium ensures that the image development medium properly forms a viewable three-dimensional image based on the received three-dimensional light field.

By virtue of the selection of the size of the bubbles or particles according to the inventive concept, the bubbles or particles can exhibit neutral buoyancy. This means that the net effect of bubble or particle movement in the image development medium will be negligible or close to zero. Thus, the distribution of bubbles or particles within the image development medium may remain constant or nearly constant over time.

It will be appreciated that the bubbles or particles may have a negative surface charge, which will help (for sufficiently high concentrations) to have a uniform bubble or particle distribution that remains stable in the medium for a long period of time due to repulsive coulomb forces between bubbles or particles having the same charge. This effect will result in a fairly constant distribution of bubbles or particles in the fluid and a very uniform average distance between bubbles or particles, thereby promoting uniformity of the scattering effect in the image development medium 120.

Thus, one insight of the present invention is that by selecting the size of the bubbles or particles to be in the range of 40-500nm, a stable distribution of bubbles or particles in the image developing medium allows long term stability of the image developing medium. Therefore, the image development medium can be used for a long time to form a three-dimensional image or a three-dimensional image sequence such as a three-dimensional video.

In addition, for image development media comprising bubbles suspended in a fluid, bubbles in the size range of 40-500nm can ensure long-term stability of the bubbles. It will be appreciated that larger size bubbles in the millimeter range may rise quickly to the surface of the media and then collapse upon reaching the surface, while larger size bubbles in the micrometer range tend to decrease in size and disappear in the fluid. Thus, by selecting the size of the bubbles to be in the range of 40-500nm, it can be ensured that the bubbles have long-term stability without decreasing or increasing in size, so as to remain as bubbles suspended in the fluid.

Bubbles or particles suspended in a fluid may cause light scattering based on Tyndall scattering and/or Rayleigh scattering, both of which provide a light scattering mechanism based on the wavelength of light versus the size of the bubbles/particles. Rayleigh scattering may occur for bubble/particle sizes much smaller than the wavelength of light, while Tyndall scattering may occur for bubble/particle sizes less than or about equal to the wavelength of light.

Utilizing Rayleigh scattering and/or Tyndall scattering may allow for the formation of image development media having bubbles or particles disposed in a fluid at an appropriate concentration so as to provide a sufficiently strong intensity of the scattered light in order to make the formed three-dimensional image clearly visible without too high an attenuation of the light propagating through the image development media, thereby enabling the light to reach all portions of the image development media to form an image from a large volume of image development media.

The selection of the concentration of bubbles or particles in the image development medium may be based on ensuring that each portion of the image development medium that forms the smallest discernable detail (voxel) of the three-dimensional image has a uniform scattering effect based on the inclusion of a plurality of bubbles or particles. Further, the selection of the concentration of bubbles or particles may be based on ensuring that the attenuation of light propagating through the image development medium is not too high. Due to the selection of the size of the bubbles or particles according to the concepts of the present invention, it is also possible to ensure that an appropriate concentration of bubbles or particles can be used within the image developing medium.

The use of bubbles or particles having a size of at least 40nm may be advantageous, since in practice it may be difficult to generate bubbles or particles of smaller size while having bubbles or particles of uniform size. Thus, the size of the bubbles or particles may facilitate that a reliable generation of the size of the bubbles or particles may be provided.

The use of bubbles or particles having a size of no more than 500nm may be advantageous because the spacing between two scattering points may not be too large, and thus a uniform scattering effect with high resolution may be provided, resulting in a high quality three-dimensional image.

The bubbles or particles may be generally spherical. Especially for bubbles with a size in the range of 40-500nm, the bubbles may generally form a shape with the largest surface area, which means that the bubbles may be spherical. The size of the spherical bubbles or particles is understood to correspond to the diameter of the spheres. Thus, according to one implementation, the bubbles or particles have a diameter in the range of 40-500 nm.

However, it should be understood that the bubbles or particles need not be precisely spherical. The size of the bubbles or particles may then be understood as the largest cross-sectional dimension of the bubbles or particles.

The equivalent spherical diameter of the irregularly shaped bubbles or particles can be the diameter of a sphere of equal volume as the irregularly shaped bubbles or particles. The size of the bubbles or particles may then be understood as the equivalent spherical diameter of the irregularly shaped bubbles or particles.

Furthermore, it should be understood that while the inventive concept may provide a distribution of bubbles or particles that remains constant or nearly constant over time in the image development medium, it is not necessarily uniform throughout the distribution of the image development medium. As will be described in further detail below, the size of the bubbles or particles may be different between different portions of the image development medium, and the concentration of the bubbles or particles may also be different between different portions of the image development medium.

As used herein, the term "light field generating unit" should be construed as any unit that can form a three-dimensional distribution of light based on an incident light beam. The light field generating unit may be configured to reflect the incident light beam or transmit the incident light beam.

The light field generating unit may comprise a plurality of crystal lattices, wherein each crystal lattice may be configured to interact with a portion of the incident light beam so as to provide an interaction with a portion of the incident light beam. In combination, the interaction between portions of an incident light beam and multiple crystal lattices may form a three-dimensional light field. The lattice may be controllable such that the interaction with the light may be altered, which may enable the distribution of the three-dimensional light field, and thus the three-dimensional image to be displayed, to be dynamically controlled. However, it will be appreciated that a plurality of crystal lattices may provide static interaction with an incident light beam such that the apparatus will be adapted for displaying a particular static three-dimensional image.

According to one embodiment, the gas bubbles or particles have a size in the range of 40-200 nm.

The use of bubbles or particles having a size of no more than 200nm may be advantageous because, for example, when air bubbles in water are used, the relative scattering cross-section may be relatively low, so that the scattering loss through the image development medium is also relatively low. This means that light can propagate through the image development medium, thereby enabling light to reach all portions of the image development medium to form an image from a large amount of image development medium. In addition, since the interval between two scattering points may not be too large, a uniform scattering effect with high resolution may be provided so as to form a high-quality three-dimensional image.

According to one embodiment, the gas bubbles or particles have a size in the range of 50-150 nm.

The use of bubbles or particles having a size of not more than 150nm more advantageously ensures that scattering loss by the image developing medium is low and the interval between two scattering points is small, so that a uniform scattering effect with high resolution can be provided.

The use of bubbles or particles having a size of at least 50nm may be advantageous as it may further facilitate that reliable generation of bubbles or particles of this size may be provided.

According to one embodiment, the fluid is an aqueous liquid. This means that non-hazardous liquids can be used, simplifying handling of the image development medium. This may be particularly advantageous because the image development medium removed from the device may be easily disposed of (e.g., when the image development medium is replaced).

The refractive index difference between the aqueous liquid and the substantially transparent gas may provide a suitable level of scattering such that the image development medium may allow a suitable intensity of light to be scattered to view the image while allowing the light to propagate through the image development medium to enable the light to reach all portions of the image development medium to form an image from a volume of image development medium.

It will be appreciated that the correspondence in refractive index between the aqueous liquid and the particles may be provided by selecting a suitable plastics material (e.g. polystyrene material) for forming the particles. However, contrary to the refractive index relationship between the aqueous liquid and the transparent gas, the refractive index of the polystyrene particles may be greater than that of the aqueous liquid.

According to one embodiment, the bubbles are filled with air or another gas comprising oxygen, nitrogen and/or carbon dioxide. This also means that the substances used in the bubbles are not hazardous, which thereby simplifies handling of the image development medium and generation of bubbles.

According to one embodiment, the size of the bubbles or particles and the concentration of bubbles or particles in the fluid are selected to provide an optical attenuation constant in the range of 10-200dB/m for the optical wavelength of the optical beam.

The selection of the size of the bubbles or particles can control the scattering effect of the bubbles or particles, since the scattering cross-section depends on the size of the bubbles or particles.

The selection of the concentration of bubbles or particles also controls optical attenuation in the image development medium because the number of scattering points per volume unit of the image development medium changes.

The optical attenuation constant of the image development medium may define the amount of light that propagates completely through the volume of the image development medium. The light attenuation constant may be selected such that a substantial amount of light is scattered by the image development medium (to have sufficient light intensity when forming a three-dimensional image) while still allowing a substantial amount of light to pass completely through the image development medium (such that the portion of the image development medium furthest from the incident light beam may receive sufficient light intensity to help scatter light having an observable intensity when forming a three-dimensional image). Thus, the scatter attenuation may be set appropriately to allow 10% to 1% of the intensity of the incident beam to propagate through the entire volume of the image development medium. This may allow the image development medium to scatter light of sufficient intensity while allowing the entire volume of the image development medium to receive light of sufficient intensity.

Further, it may be desirable for the volume of the image development medium to be relatively large in order to allow for the formation of relatively large three-dimensional images. For example, one side of a cube of the volume of image development medium may have a size in the range of 0.1-1 m. To have a large volume of image development medium while allowing for adequate light scattering attenuation, it may therefore be desirable to have an optical attenuation constant in the range of 10-200 dB/m.

Thus, the size of the bubbles or particles in the fluid and the concentration of the bubbles or particles may be selected to ensure that the optical attenuation constant is set in the range of 10-200 dB/m.

According to one embodiment, the size of the bubbles or particles and the concentration of bubbles or particles in the fluid are selected for providing an average distance below 200 μm between two adjacent bubbles or particles in the fluid.

As mentioned above, the size of the bubbles or particles and the concentration of the bubbles or particles may be selected to control the light attenuation constant of the image development medium and to ensure that the light attenuation constant is suitable for a volume of suitable size that allows the image development medium to be used in forming a three-dimensional image.

However, the concentration of bubbles or particles may also need to be selected to take into account that there should be a sufficient number of bubbles or particles within the smallest discernable lattice of the image-developing medium so that each voxel will provide reliable light scattering. Thus, for each voxel, the image visualization medium should include multiple scattering points (i.e., bubbles or particles) so that light of sufficient intensity will be reliably scattered from each voxel.

The size of the voxels may be set by the desired resolution of the apparatus. However, for large size displays (e.g., image development media having dimensions of 1 × 1 × 1 m), high quality images may typically require the sides of the cubic voxels to have a size of 1 mm. Thus, it may be desirable that a plurality of scatter points may fit into voxels with 1mm sides. It will also be appreciated that smaller sides of the cubic voxels may be required for smaller size displays (e.g., image development media having dimensions of 0.1 × 0.1 × 0.1 m). For example, the sides of a cubic voxel may have a size of 100 μm. Thus, it may be desirable that a plurality of scattering points may fit in a voxel with a side of 100 μm, such that the concentration of scattering points increases relative to the large size display example described above. However, since the total volume of the image development medium is small, the light attenuation constant, which increases due to the increased concentration of scattering points, may not cause problems when the three-dimensional light field propagates through the entire volume of the image development medium.

Thus, to obtain suitable resolution in forming three-dimensional images, in some embodiments, the image development medium may be selected to have an average distance of less than 200 μm between adjacent bubbles or particles in the image development medium. In other embodiments, the image development medium may be selected such that adjacent bubbles or particles in the image development medium have an average distance of less than 30 μm between them.

According to an embodiment, the concentration of bubbles in the fluid is greater than 2 x 10¹⁴Air bubble/m³. In fluids, especially in aqueous liquids, such concentrations of bubbles can provide an antimicrobial function in the image developing medium. This may mean that bacterial growth does not occur or is significantly reduced in the image development medium, which may be particularly usefulAdvantageously, because the image development medium can be retained in the device for long term use. Therefore, the risk of bacteria being present in the image developing medium is low, which can simplify the handling of the image developing medium when it is replaced in the apparatus.

According to an embodiment, the device further comprises a container in which the image development medium is arranged, wherein at least a part of the wall of the container is transparent for outputting light scattered by bubbles or particles in the fluid.

The container may provide a well-defined space in which the image development medium may be disposed. Thus, the image development medium may be held within the container to form a volume for generating a three-dimensional image.

The container may advantageously comprise transparent walls in order to allow light to be transmitted through the container walls and to the viewer. A portion of the container wall may be transparent to allow viewing of the three-dimensional image formed in the image development medium from a particular direction. However, the entire wall of the container may be transparent so as to allow the three-dimensional image to be viewed from all directions.

According to an embodiment, the container may be arranged relative to the light field generating unit so as to receive light into the image developing medium. For example, the container may be formed on a common substrate in which the light field generating unit is formed, e.g. arranged above the light field generating unit, for receiving light through a bottom surface of the container.

The apparatus may include one or more optical components (such as one or more lenses) between the light field generating unit and the container for controlling the distribution of the three-dimensional light field in the image developing medium within the container. Such optical components may form part of the container wall for directing light into the image developing medium.

According to an embodiment, the device further comprises at least one channel connected to the container for transporting the image development medium into and out of the container.

This facilitates replacement of the image developing medium in the container at regular intervals. Thus, when the quality of the image development medium deteriorates (e.g., the size and/or concentration of air bubbles in the image development medium changes), the image development medium may be transported out of the container through the channel and replaced with a new image development medium having the desired characteristics.

The at least one passage ensures that replacement of the image developing medium can be easily performed without requiring disassembly of the components of the apparatus.

Although the image development medium may be provided with long-term stability, the image development medium still needs to be replaced at regular intervals, such as once per day, once per week, or once per month, in order to maintain the desired characteristic quality of the image development medium.

According to an embodiment, the image development medium is arranged in the container such that there is an increasing concentration of bubbles or particles in the propagation direction of the light field generated in the container.

Since light is scattered while propagating through the image development medium, the intensity of the light is attenuated in the propagation direction of the light. This means that the intensity of light received by the volume of a portion of the image development medium will decrease along the direction of propagation of the light and thus the intensity of scattered light may decrease. The effect of the reduction in scattered light intensity may be at least partially offset by increasing the concentration of bubbles or particles along the propagation of the light. This may allow a three-dimensional image to be formed with relatively uniform light intensity in all portions of the three-dimensional image.

Additionally or alternatively, the image development medium is arranged in the container to have an increasing size of bubbles or particles suspended in the fluid along a propagation direction of light of the light field generated in the container. This may also offset the effect of the decrease in scattered light intensity along the direction of propagation of light in the image development medium, since the scattered light intensity may increase as the size of the bubbles or particles increases.

According to a further embodiment, the image development medium is arranged in the container to have a combination of an increasing concentration of bubbles or particles and an increasing size of bubbles or particles suspended in the fluid in the propagation direction of the light field generated in the container.

The concentration of bubbles or particles and the size of the bubbles or particles may thus be used in combination so as to allow a three-dimensional image to be formed with relatively uniform light intensity in all parts of the three-dimensional image.

In the case where the concentration or size of the bubbles or particles in the developing medium is different, the bubbles or particles may tend to rearrange so that a constant concentration and a random size distribution are obtained after a certain time.

According to an embodiment, the container may comprise a transparent partition wall to separate between different portions of the image development medium having different characteristics (concentration of bubbles or particles and/or size of bubbles or particles). The transparent partition walls may be very thin and formed of a material having the same or at least a similar refractive index as the fluid of the image development medium, so that the propagation of light in the container is minimally affected. Thus, the transparent partition walls can ensure that bubbles or particles of different concentrations and/or sizes are maintained within the image developing medium over a long period of time.

Alternatively or additionally, the container may comprise a plurality of channels allowing introduction of fluids having different characteristics into different parts of the container, such that the image development medium may have different characteristics along the propagation direction of the light, at least for a short time. Multiple channels may be used to introduce a desired concentration of bubbles or particles of a desired size at various portions of the container, either continuously or as needed, to maintain different concentrations and/or sizes of bubbles or particles in different portions of the image developing medium.

According to one embodiment, the apparatus further includes at least one calibration sensor that may be configured to receive light transmitted through the image development medium to detect an intensity of the received light as a measure of attenuation of the light beam propagating through the image development medium.

When the image development medium in the device is replaced, a calibration sensor may be used to determine the attenuation of light by the new image development medium. The results of calibrating the sensor may be used to set the intensity of light to be received by the image development medium.

The calibration sensor may also be used to determine the degradation of the image development medium so that it can detect whether the characteristics of the image development medium have changed (e.g., whether the concentration of bubbles has decreased) so that it can be identified whether the image development medium needs to be replaced.

Where the container comprises a dividing wall for arranging the image development medium in a plurality of compartments, each compartment may be associated with a respective calibration sensor. Thus, the results from the calibration sensor of each compartment may be used as an input for setting the intensity of light to be received by the image development medium and/or controlling the provision of a desired characteristic of each compartment, e.g. providing a required light attenuation of the image development medium in each compartment (so that the image development medium in the compartment may be replaced if an undesired characteristic is identified).

According to one embodiment, the apparatus further comprises an optical system for transferring the light field generated by the light field generating unit into the image development medium.

The optical system may guide the light from the light field generating unit into the image developing medium. This may mean that the requirements for a specific geometrical relationship between the light field generating unit and the image development medium may be alleviated by guiding the light using an optical system.

Further, the optical system may include one or more components for controlling the light field, such as one or more lenses and/or aperture stops for controlling a three-dimensional light field formed in the image development medium.

According to an embodiment, the apparatus further comprises a controller unit for controlling the light field generation unit to control the distribution of light in the three-dimensional light field output by the light field generation unit.

This means that the light field generation unit can be controlled such that the distribution of light in the three-dimensional light field can be dynamically changed. For example, the light field generating unit may comprise an array of unit cells, wherein the optical properties of each unit cell are individually controllable. Thus, by controlling the optical properties of the unit cell, the distribution of the three-dimensional light field formed by the combined interaction between the incident light and the light-field generating unit can be controlled.

The controller may thus control and change the distribution of light in the three-dimensional light field output by the light field generation unit, and thus form a three-dimensional image by the device. This may be used to allow the device to display a three-dimensional image that is changing, such as allowing the device to display a three-dimensional video.

According to an embodiment, the apparatus further comprises at least one light source configured to generate a light beam incident on the light field generating unit.

This means that the device may comprise all the components for forming a three-dimensional display: the image forming apparatus includes a light source providing a light beam, a light field generating unit for converting the light beam into a distribution of a three-dimensional light field, and an image developing medium for forming a three-dimensional image viewable by an observer. Thus, the apparatus may be packaged with a suitable relationship between the light source and the light field generating unit, such that the apparatus may be easily used. Furthermore, an arrangement comprising a light source may allow a complete system providing a three-dimensional display in a compact manner.

However, it should be understood that the device may be delivered and sold without including a light source. A user wishing to put the device into use may then combine the device with a separately purchasable light source.

The light source may be arranged to form a coherent light beam, such as a laser beam. This may provide for an accurate control of the three-dimensional light field formed by the light field generating unit.

According to a second aspect of the present inventive concept, there is provided an apparatus for displaying a three-dimensional image, the apparatus including: a light field generation unit configured to receive an incident light beam and generate a three-dimensional light field; and a bubble generating device configured to generate bubbles in the image developing medium to form the image developing medium including a fluid of bubbles suspended therein, wherein the bubbles have a size in a range of 40-500 nm.

The effects and features of this second aspect are largely analogous to those described above in connection with the first aspect. The embodiments mentioned in relation to the first aspect are largely compatible with the second aspect.

Therefore, according to the second aspect, the apparatus for displaying a three-dimensional image may include a bubble generation device so that the apparatus can form an image development medium having bubbles of an appropriate size. This means that the device may be capable of generating bubbles of appropriate size so that the image development medium may be generated when the apparatus is to be used, or at regular intervals when replacement of the image development medium may be required.

It should be understood that even though the image development medium may have long term stability, in order to maintain the quality of the generated three-dimensional image, it may be necessary to replace the image development medium at regular intervals, for example, it may be necessary to replace the image development medium once a day, once a week, or once a month depending on the requirements of the quality of the formed three-dimensional image.

By virtue of the apparatus having the bubble generating device, the apparatus does not need to be combined with any advanced or complicated device to replace the image developing medium.

Further, the apparatus may include a container in which the image development medium is to be accommodated, such that the bubble generating device may be configured to generate bubbles in the image development medium that is conveyed into the container. The apparatus may be further configured such that the image development medium in the container contains a three-dimensional light field such that the image development medium may form a three-dimensional image based on the received three-dimensional light field.