Patent Application
20240418969
This application relates generally to the field of high-magnification photography and imaging techniques. More specifically, this application relates to systems and methods that exploit reflectors and/or polarizers, including polarizing beamsplitters, for use in high-magnification cameras or imaging devices. The application also relates to imaging devices or cameras built into cell phones, smartphones, tablets, laptops, drones, or any other mobile devices.
Digital cameras are widely used in mobile devices, for example in smartphones. Camera performance is a major differentiator for consumers and is a driver for market share. Hence mobile device makers and suppliers strive to improve camera performance.
One key aspect of mobile device camera performance is high-magnification (or high-zoom) photography. Typically, cameras or imaging devices that achieve high-magnification photography have long and large lens assemblies (e.g. zoom lenses in DSLR cameras). But mobile devices are thin and compact and cannot contain long lens assemblies. This has traditionally limited their magnification and zoom capabilities.
Accordingly, there is always a need for improved imaging systems and methods.
This application discloses systems and methods for improving the performance of high-magnification, low volume (e.g., thin) cameras or imaging systems. In particular, this application discloses using polarizing beamsplitters, waveplates, and reflectors or mirrors, to increase the path of light in the camera, which enables longer focal lengths and hence higher magnifications, but without a substantial loss of light. This enables, for example, high-magnification small-volume camera photography/videography in low-light conditions. It is useful both for long-distance smartphone photography/videography, and also for near-in ‘macro’ photography/videography (which means taking high-magnification photos or videos of small but nearby objects, such as an ant on a leaf). This application also discloses enabling multiple focal lengths in one camera, for example, to cover a larger range of focal lengths for improved zooming on objects that move towards and away from the camera.
One aspect provides methods and systems for improving the performance of high-magnification small-volume (e.g. thin) cameras or imaging systems, which include polarizations and internal reflections as part of their operation. Such small but powerful magnification cameras are advantageous for smartphones, tablets, drones, and for other mobile devices, or for use in small confined spaces such as in unobtrusive locations in self-driving vehicles. Having internal reflections inside a small camera or imaging system enables a longer path of light, and hence allows use of longer focal lengths, which in turn enables higher magnification. In particular, this application discloses the use of reflectors, beam-splitters, polarizers, and related elements to improve performance, including for enabling operation in low-light conditions.
Also described are methods to enable a single camera to operate at two light paths and two focal lengths simultaneously. This is enabled by splitting the light path into two, where each path is of a different length before it reaches an imaging sensor and therefore two focal lengths (two magnifications) can be supported at the same time within a single small camera or imaging device.
Another aspect includes an imaging or optical system for capturing an image having a lens or substrate having a focal length, a polarizing beamsplitter adjacent to the lens or substrate, a wave plate downstream of the reflective polarizing beamsplitter, a first reflector distal or downstream of the wave plate, a second reflector that is arranged at an angle between 20 and 170 to the first optical path, and a sensor to form the image. The substrate, wave plate, and reflector can be arranged in a first optical path, and the first reflective polarizer can be arranged in a first optical path between the lens and the first reflector. The sensor can be arranged in the first optical path or a second optical path. The polarizing beamsplitter can be on the intersection of the first and second optical path of the second reflector. The light entering the lens of the image is polarized by and transmits through the reflective polarizing beamsplitter, passes through the wave plate, hits the reflector, returns through the wave plate, along the first optical path; and the light then is reflected by the polarizing beamsplitter to along the second optical path, and forms the image on the sensor and the light forms the image on the sensor.
Another aspect can include the waveplate being a quarter-wave plate or rotator or plate.
Another aspect can include one or more additional lenses or substrates having a focal length and the lenses or substrates having spherical or aspherical curved surfaces.
Another aspect includes using cornering prisms or turning reflectors.
Another aspect includes the wave plate being composed of two or more elements.
Another aspect includes the first reflector or the second reflector that is curved, with spherical or aspherical curvature mirror.
Another aspect includes the focal length of the system matched to the round-trip length of the light path.
Another aspect includes the one or more of the lens or substrate, polarizing beamsplitter, wave plate, or reflecting surface or mirror being can be moved mechanically, whereby this is used to change the overall focal length of the imaging system.
Another aspect includes integration into a smartphone, cell phone, tablet, laptop, drone, or other mobile device.
Another aspect includes a system having a second imaging sensor, on the second light path on the other side of the polarizing beamsplitter from the first imaging sensor.
Another aspect includes the focal length for the image formed on the first sensor being different than the focal length for the image formed on the second sensor.
Another aspect includes the imaging sensor arranged at an angle between 20 and 160 degrees to the first optical path.
Another aspect includes taking high-magnification photographs or videos.
Another aspect includes taking photographs or videos in low-light conditions.
Another aspect includes taking both long-distance (tele) and near-in (macro) by the single imaging system. This can be enabled by moving optical elements in the system to change the focal length by a larger amount.
Another aspect includes a method including polarizing light into a first linear polarization, transmitting that polarization through a polarizing beamsplitter, a wave plate, and a reflector so that it returns to the beamsplitter with a linear polarization substantially orthogonal to the transmission linear polarization, and so is diverted by the beamsplitter to a sensor to form an image; whereby this enables a longer light path and hence higher magnification inside a small imaging system, and also allows operation in low light conditions.
Another aspect includes creating a composite image from images at two different focal lengths, whereby the user is provided with an image where two different distances are simultaneously in focus.
Another aspect includes selecting which portion of which image is in focus by autofocus hardware.
Another aspect includes the hardware is PDAF (phase detection autofocus) sensing.
Another aspect includes selecting which portion of which image is in focus by software.
Another aspect includes the composite image being formed by selecting which portion of which image is in focus by hardware and software.
Another aspect includes the second reflector arranged at an angle between 20 and 90 to the first optical path or at an angle between 55 and 90 to the first optical path.
Another aspect includes the wave plate arranged between the polarizer and the first reflector.
Another aspect includes a system including a second lens, a third mirror and/or wave plate is an optical film.
Another aspect includes a camera having the system disclosed herein or incorporating methods disclosed herein.
Another aspect includes a method of taking high-magnification imaging by receiving light from a scene through a substrate, wherein the substrate focuses the light, polarizing the light into a first linear polarization, rotating the light; diverting the light and rotating the polarization of the reflected light (a second time) so that the combination of the two polarizations rotates the polarization of the light to substantially orthogonal to the input polarization;
This application will now be described more fully with reference to the accompanying drawings in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein.
This application discloses compact, small-volume cameras or imaging systems that make use of lenses, beam-splitters, reflectors, waveplate retarders, and/or light polarizing elements, and by doing so enables both high-magnification and low-light operation in a single camera. A key aspect herein is specific and innovative arrangements of one or more polarizing beam-splitters, wave-plates, reflectors, lenses and sensors. The arrangements ensure polarization orientations along the path of the light that set how the light progresses through the camera. They enable both a long path of light in a small volume (which permits a long focal length and hence high-magnification) and they ensure a substantial portion of the light entering the camera reaches the sensor to form an image (thus enabling camera operation at low light, e.g. at night time). The resulting embodiments enable small cameras or imaging systems that can achieve both high-magnification and low-light operation in a small volume. Such cameras or imaging systems can be advantageous for use in smartphones, tablets, drones, or other mobile devices.
In current smartphone camera modules, typically there is one camera (e.g. the telephoto camera) that is responsible for high-magnification photography or videography; and another camera (e.g. the normal or wide-angle camera) that is responsible for low-light (e.g. night-time) operation. Specific embodiments include methods and systems for a single camera that could take both high-magnification and low-light photographs or videos, and could do so both for long-range telephoto operation and for macro (closer in) photography/videography. Such embodiments can reduce the camera count, size and/or cost of camera modules and also allow the same or higher performance. Specific methods and systems also enable operation at two focal lengths at the same time, which can provide improved zooming on objects that move towards and away from the camera.
Exemplary systems enable polarized round-trip light reflections, to allow a small-volume camera to conduct high-magnification photography/videography, and that also enable low-light operation. These aspects are achieved by exploiting reflections and polarizations to both enable a long path of light (which enables a long focal length and hence high-magnification), and also to substantially prevent loss of light, and thus to make sure a large amount of light reaches the sensor as is needed for low-light operation. This type of novel system is therefore suitable for use in mobile devices, e.g. in smartphones, to achieve both high-magnification (high zoom) and enable low-light operation. It could, for example, enable photography and videography of far scenes/objects at night, and macro-photography/videography in low light. Macro photography refers to high-magnification images of nearby but small objects, such as an ant on a leaf.
The lens, beamsplitter, wave plate (e.g., quarter-wave plate), and mirrors are aligned substantially along the axial axis of the camera (along the incoming light 101); and the sensor (401) is aligned substantially off-axis at an exit port of the beamsplitter (202). This arrangement of the elements helps ensure polarization orientations along the path of the light that set how the light progresses through the camera. It enables both a long path of light in a small volume (which can permit a long focal length and hence high-magnification) and it ensures a substantial portion of the light entering the camera reaches the sensor to form an image (thus enabling camera operation at low light, e.g. at night time). The created polarization and resulting path of the light in the camera are now disclosed in detail.
Incoming light (101) from an object or scene is typically not polarized, and so is labeled ‘U’ for unpolarized light in
In another embodiment, a single lens can be replaced by a lens group, or additional lenses can be added before or between the other elements. If the distance the light has traveled is matched to the focal length of the lens (or lenses), then the image formed on sensor (401) will be in focus. The path the light has traveled can be matched with the focal length of the camera lens or lenses.
In another embodiment, lenses can be added before or in between the elements shown in
Lenses that can be added after the beamsplitting polarizer (202) and before the mirror (204) can have a double effect. Since light can pass through any such lens twice, once for the forward light path (103, 104) and again for the return light path (105, 106), e.g. see also
The mirror or mirrored surfaces (e.g. 204 in
For the exemplary embodiment illustrated in
In the following internally reflecting path illustrated in
As can be seen in
The embodiment illustrated in
To enable high-magnification low-light camera operation in a smartphone size and form factor, that is a central aspect and enablement of the current invention. In
A second way the invention can be used is in combination with a periscope geometry. The invention illustrated in
In the current exemplary embodiment of
Hence for essentially the same camera volume as a conventional periscope camera, the available focal length and hence magnification is about twice as great. By exploiting a reflector and polarizing beamsplitter and quarter-wave plate, as herein disclosed, this 2× magnification benefit over a conventional periscope design is achieved without a substantial loss of light. The end result is a compact camera that improves magnification but is still appropriate for low-light operation. Such a camera or imaging system is of high value for smartphone use.
There is free space shown between the components, e.g. a free space in the −X direction between the polarizing beamsplitter (202) and the sensor (401) in
Sensor 401 can be placed further out in the −X direction if desired, and this can be used to even further increase the available path the light will travel, and hence the available focal length for magnification. However, moving sensor 401 in −X provides less benefit than moving mirror 204 in the +Y direction, since the latter distance is traversed twice (as noted above) and therefore provides a greater increase in magnification per camera volume increase. If a designer wishes to increase magnification further in our embodiment, at the cost of increasing camera size, the 204 mirror +Y displacement choice will provide more magnification increase for a given camera size increase than a 401 sensor −X displacement, though both are disclosed as viable options.
The sensor (401), beamsplitter (202), wave plate (203), and mirror (204) are aligned substantially along the axial axis of the camera (along 103, 104); and the entry lens (201) and incoming light (101) are aligned substantially off-axis at an entry port of the beamsplitter (202). This specific arrangement of the elements, as shown in
As noted earlier, incoming light (101) from the object or scene is typically not polarized, and so is labeled ‘U’ for unpolarized light in
These changes enable a periscope-like orientation of the camera, as shown in
More specifically, the embodiment of
The size of the system (the size and spacing of the components disclosed) can be such that the whole system can fit inside a smartphone or other mobile device, e.g. inside a mobile or cell phone, a tablet, a laptop, or inside a small drone.
In
Disclosed next are exemplary systems that allow operation at multiple focal lengths. In a camera, such as used in a mobile device, an object may be photographed or videographed at different distances. For example, the user may take a video of an object that is approaching or receding, or the user may move towards or away from an object while taking a video or photos. That means it is desirable for the camera to be able to focus on an object or scene at a range of distances, e.g., continuously from a short to a long distance. Currently, in mobile devices, lenses or other optical elements can be mechanically moved to change the focus of a camera. However, the range of mechanical motion of elements (e.g., lenses) in a mobile device is limited by the thickness of the device, or by the length of the camera, and/or by the amount of room taken up by other elements. For example, if a mobile camera is 10 millimeters long, e.g. to fit inside the thickness of a smartphone for a non-periscope camera geometry, and non-moving lenses, PCB board, and sensor take up 6 millimeters of that space, then only 4 millimeters is left in order to execute lens motion to change focal length. For a periscope type camera, the values above would be different, but there would still be a limit on the camera length due to the need to fit many other components into the smartphone. Thus how much cameras can change focal length in a smartphone or other mobile devices can be limited.
Exemplary systems shown in
Two focal lengths can have advantages as compared to just a single focal length. For example, two focal lengths can more easily cover a range of desired focal lengths than the one-at-a-time focal length that is available in conventional cameras. For instance, an optical element or elements may be moved to vary the first “5×” focal length from 1× to 10×. Likewise, an optical element or elements may be moved to vary the second “15×” focal length from 10× to 20×. Thus the range that would be covered in total would be 1× to 20×, which could be substantially greater than what could be covered by a conventional camera with a moving optical element or elements. This would allow an improved range of magnification. It can also allow improved zooming, and an improved ability to keep an object in focus as it moves towards and away from the camera.
For the embodiments of
It is understood that picking up the previously unused portion of the light (153), as shown in
As noted above, the exemplary systems of
Next is disclosed another advantage of these embodiments. Consider a scene that has two camera-to-scene distances of importance. Some examples: a couple may be taking a selfie in front of a historic building and there is the distance A from the smartphone camera to the couple, and the distance B from the smartphone camera to the building, where B is not equal to A. Or the couple could be taking a photo or video in front of a natural scene, such as a range of mountains behind them. Here there is a distance A from the camera to the couple, and a much larger distance B from the camera to the mountains. Or, in a macro photography setting, there may be a butterfly on a leaf and then the rest of the tree behind the butterfly. There are many other instances where there may be substantially two (or more) distances of interest from camera to the scene to be photographed or videographed.
For a conventional smartphone camera, the user has to pick: either the couple is in focus, or the historic building is in focus, but not both. The embodiments of
Specific embodiments can provide a composite photograph or video formed from the two channels, and this composite photo or video would be formed in such a way that the scene would be presented to the user as substantially in focus at both distance A and distance B. Meaning, to return to one example above, both the couple and the historic building would be in focus on the composite images displayed or provided to the user.
If this region of the scene corresponds to a location taken up by the couple, then this first region of the scene will be substantially in focus in the first channel that ends in the first sensor (401), and whose focal length has been matched to distance A by appropriately moving optical elements along that first channel. But this same region will be out of focus on the second channel that ends in the second sensor (451), and whose focal length has been matched to distance B by appropriately moving optical elements along that channel. Thus, in the composite photo shown to the user, the image for this region should be taken from the first and not the second sensor.
If conversely, this region of the scene corresponds to a location taken up by the historic building, then this region will be substantially in focus on the second but not the first channel. Hence in the composite image shown to the user, the image for this region should be taken from the second and not the first sensor.
Selecting which region to display from which channel or sensor can be achieved by either using available sensor hardware; or by software operating on the embodiments of
Which small region to display from which sensor, to form a doubly in-focus composite image, can also be decided by software. Comparing image contrast for each small region across both sensors is one way. For example, the contrast between edges in that region can be used as the selection criteria. Another way is to use low-pass spatial filtering. If a small region is out-of-focus on a sensor, then applying a low-pass (smoothing) spatial filter will not change the image much, because that part of the image is already blurred. We disclose subtracting the low-passed version of an image from itself, for each small region. For regions where the image and its low-pass version differ substantially, that part of the image is more in focus. Thus this software method (low-pass filtering and subtraction) can be used to discern whether a region of the scene is more in-focus on the first or second channel or sensor. Once that discernment has been made, the more in-focus version of each region can be used to form the composite image for the user. Other software methods known in the art can also be used to decide if a small region is more in focus on the first or second channel or sensor, and are anticipated and disclosed.
When the composite image is formed, the difference in magnification across the two channels will be accounted for. Specifically, if there is a pattern of in-focus regions on the first sensor, forming a partial (patchworked) first image; and there is a complementary set of in-focus regions on the second sensor, forming a partial (patchworked) second image. It is understood that when these two images are combined into one composite image, one or both of them will be scaled (expanded or shrunk) to undo the difference in magnification for channel one versus channel two. They can also be centered on each other if needed.
It is further understood that the above is an approximate description. There may be some parts of the scene that are neither at distance A or B, for example, there may be a tree that is further behind the historic house, at a distance C from the camera that is not equal to either A or B. Scene regions corresponding to this tree can be displayed in the highest focus available. Likewise, the house may not be entirely at exactly distance B, nor all of the couple at exactly distance A. Again, for each small region, the version that is in best focus from the two channels or sensors can be presented to the user. Interpolating between the two channels; one or many portions of the composite images may be a combination of images from both channels. Further, the distances A and B are themselves ranges, such ranges corresponding to the depth of focus of each channel of the camera. So, in the above, the couple would be substantially in-focus from some distance from Amin to Amax, and the historic house would be in-focus from Bmin to Bmax.
In
Sometimes a user may desire that one part of the scene, e.g. the central subject of the scene, be in focus; and that the rest of the scene be out of focus (blurred) in order to draw visual attention to the subject of the scene. This is commonly referred to as a Bokeh effect in taking a photograph or a video. By being able to focus two channels independently, at different focal distances, the current invention can also be used to achieve such a Bokeh effect more readily. It can do so by selecting one of the two channels to be more out of focus; and by creating a composite image where parts of the scene are intentionally selected to be out of focus; and/or by a combination of both methods.
Herein we disclosed additional aspects and features of the invention. The features disclosed herein are anticipated for one, multiple, or for all of the embodiments above. A key aspect herein is specific and innovative arrangements of one or more polarizing beam-splitters, wave-plates, reflectors, lenses and sensors. The disclosed arrangements set polarization orientations along the path of the light and this selects how the light progresses through the embodiments. The selections disclosed herein enable both a long path of light in a small volume (which permits a long focal length and hence high magnification) and they ensure a substantial portion of the light entering the camera embodiments reaches the sensor to form an image (thus enabling camera operation at low light, e.g. at night time). The resulting embodiments enable small cameras or imaging systems that can achieve both high-magnification and low-light operation.
Optical elements can be added, for instance to further improve performance. For example, in order to reduce imaging aberrations, one or multiple lenses or focusing substrates may be added of spherical or aspherical curved surfaces; before, between, or after the polarizers and rotators.
It is also possible to add in additional turning mirrors or cornering prisms, for example immediately before or immediately after a first lens, so that the light path is bent by substantially 90 degrees. This can allow the imaging system to operate along the length (rather than the width) of a mobile device, and thereby can increase the available length for the light path.
Such additional turning mirrors can be added to other disclosed embodiments, if so desired. The turning mirrors can also be cornering prisms. Further, it can be any element that acts as a reflector. For example, a polarizer that does not pass (that reflects) vertically polarized light will also function as a mirror for the examples of
A person familiar with the art of optics will recognize that there may be other modifications and variations that are possible in light of the above teachings, or that may be acquired from practice of the invention. Such modifications as are suited to the particular use contemplated are anticipated, and are covered by this disclosure.
In some embodiments, a single lens can be replaced by a lens group, or additional lenses can be added before or between the other elements. An aperture, e.g. aperture 701 in
It is disclosed that elements or their surfaces may be curved, instead of flat. Or curved optical surfaces may be placed before or after disclosed elements. Specifically, mirrors or mirrored surfaces may be curved, either spherically or aspherically. In
Any of the optical elements in the embodiments may be moved over time, e.g. translated or tilted, or for some element types their shape may be adapted over time. Such motion or shape change is commonly used to change focus in cameras and imaging systems, and/or to correct for video jitter, and the same can be used in the systems disclosed herein. There are many ways to affect such motion, including piezo, electrostatic, magnetic, motor actuated rack-and-pinion, MEMS (micro-electro-mechanical system) actuators, or other types of actuation. Including such movement is disclosed for our embodiments.
Specific embodiments disclosed can enable more camera performance for the same amount of element motion. Consider for example the embodiment of
The above double-the-motion benefit is advantageous for small camera applications, including for cameras in smartphones and other mobile devices. In such cameras, the amount of space available for element motion is limited. Thus extracting more change in light path and hence more focusing change, from the same amount of element motion, is highly desirable. The above advantage was presented in the context of the embodiment of
As shown in
The disclosed embodiments have been selected to enable low-light operation, in addition to high-magnification. Low-light has been achieved by inventively selecting designs that deliver a substantial portion of the light to the sensor, e.g. almost all light of one type of polarization. We note that delivering a substantial amount of light to the sensor enables a better signal-to-noise ratio. When there is more light reaching the sensor, the signal from the object or scene is higher compared to the dark noise level of an imaging sensor (dark noise is the amount of sensor noise when there is no light reaching the sensor). By keeping the amount of light reaching the sensor at a high level, signal-to-noise is increased, and this in turn enables the camera to operate successfully with less light, i.e. at lower light levels.
Specific embodiments can make use of linear and circular polarizer elements. Such polarization elements may include but are not limited to: thin film polarizers, micro wire-grid polarizers, wave-plates, liquid crystal rotators, Fresnel rhombs, and similar devices. One or more of the polarizers can be adjustable polarizers, such as liquid crystals polarizers whose polarization orientation may be changed by applying voltages. The polarization rotators, e.g. a quarter-wave rotator, may also be implemented via multiple different means, and may also be adjustable.
The disclosed polarizing beamsplitter referred to in the embodiments can also be: a polarizing beamsplitter cube, a plate polarizing splitter, a Glan-Thompson prism, a micro-grid polarizer, a reflective polarizing film, or any other type of beamsplitting polarizer. Likewise, the quarter-wave plate can also be: a quarter wavelength rotator or retarder, a Fresnel rhomb retarder, a birefringent crystal, a material or component with different refractive indexes that achieves a retardation of light along preferentially one axis over another, a material or component that dephases one element of light polarization from another, or any other type of waveplate retarder.
The mirror or reflector can be manufactured from metal, semiconductor or dielectric substrates and coated with reflective metal or multi-layer dielectric reflectors, or any other type of reflective or mirror component, for example as is used in smartphone cameras or other types of cameras or imaging systems.
The imaging sensor can be a time-integrating sensor, a CCD (charge-coupled device) sensor, a CMOS (complementary metal oxide semiconductor) sensor, avalanche photodiode arrays, photomultiplier arrays, nanoparticle or nano-material based sensors, grayscale or color sensors, any type of sensor used in smartphone or mobile device cameras, or any other type of sensor.
It is understood that various stated numbers are not exact values, but can have variations. For instance, a quarter-wave plate or quarter-wave rotator will introduce a substantially 90 degree (pi/2) phase shift of the light. However, the amount will not and need not be exactly 90 degrees, both for reasons of light optics (light at different incidence angles, or at different wavelengths of light will undergo different phase shifts) and for engineering or manufacturing reasons (variations in wave plate thickness e.g. due to manufacturing variations) which will also introduce changes in phase shift. The current disclosure covers such variations away from an “ideal” 90 degree phase shift values, both for unavoidable reasons (such as above) or for intended reasons if the system designer wishes to change the phase to accommodate system constraints. Other similar cases, such as “90 or 45 degree” polarization, “5× or 15×” magnification, etc., are also similarly covered, and are understood to be example or approximate numbers.
Some numbers are also understood to include their logical opposing sign counterpart. For example, a person knowledgeable in the field of optics will recognize that the systems disclosed herein will work equally well if +90 or +45 degrees is replaced by −90 or −45 degrees, so long as the embodiment inter-relation between polarizations is kept self-consistent. Likewise, for linear polarizations, for left or right handed circular polarization, or for elliptical polarization, there are changes in sign or via the addition of an overall positive or negative phase, that will not change system operation. Such replacements are understood to be anticipated, and are covered by the present disclosure.
For example, in relation to
Changing the orientation of the polarizing beamsplitter (202) by any other angle that is not 90 degrees, this is also a change with respect to an arbitrary convention on what is selected to be called horizontal or vertical polarization, and making such a change also would leave the system operational. Any such change is understood to be the addition of an arbitrary phase angle, and can be selected as desired (for example to align polarization at the sensor with an axis that is convenient for design of the system), and is also anticipated and disclosed. It is understood and disclosed for the embodiment of
The term “polarizing beamsplitter” refers to a polarizing beamsplitter that divides incident unpolarized light into two orthogonally polarized beams. Most high-performance polarizers are based on birefringent crystals. Unpolarized light is incident internally on a tilted surface, so as to transmit one polarization and reflect another.
Phase-shifted combinations of linear polarization states will create what is termed circular polarization states. Circular polarization can be left-handed (rotating counter-clockwise as the beam propagates) or right-handed (rotating clockwise). It is disclosed that left-and right-hand polarization states are orthogonal and can therefore also be used as polarization states in the disclosed invention, similar to how horizontal and vertical linear polarization are used. There are also elliptical polarization states that are neither fully linearly nor fully circular, but are a combination. We disclose that elliptical polarization states are also contemplated in the current invention and may also be used. It is known that a Poincare sphere can be used to represent polarization states, and any polarization (linear, circular, or elliptical) can be represented on this sphere. We disclose that linear and circular polarizations are just specific special cases, and that more generally the inventions disclosed herein can use polarizations that are anywhere on the Poincare sphere and that are, for example, substantially orthogonal relative to each other, or that occupy points that are not immediately adjacent on the Poincare sphere.
It is further disclosed that there are many known ways to practically accomplish some of the elements listed as components in the disclosed embodiments. For example, lenses can be made from glass or plastic or other materials. They can be made using traditional grinding and polishing, single point-diamond turning, molded, 3D printed, or lithographically defined. In addition, lenses or substrates having a focal length can also be made through the use of holography, diffractive optics, gratings, two and three-dimensional photonic crystals, meta-lenses that use microstructured metal and dielectric materials as well as gradient index materials. Polarizers can be made from a variety of materials, such as polymer material with oriented polymer chains like Polaroid polarizers, liquid crystal materials, oriented elongated metallic nanoparticles embedded in glass, crystal or polymer, Fresnel reflection from dielectric surfaces, birefringent crystalline materials, thin film and micro-scale wire grid materials, or other materials.
Waveplates or wave rotators can be made from a variety of birefringent materials, such as thin films of crystalline material, oriented polymers, liquid crystal materials, and prism based rotators, or other materials.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. Overall, the embodiments herein were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments. Modifications as are suited to the particular use contemplated are anticipated, and are covered by this disclosure.
This application is a continuation of International Patent Application No. PCT/US2023/061181, filed on Jan. 24, 2023 claims the benefit of U.S. Provisional Patent Application No. 63/267,100, filed Jan. 24, 2022, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63267100 | Jan 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2023/061181 | Jan 2023 | WO |
| Child | 18781114 | US |
