High-magnification photography using polarizing beam splitters, wave plates, and reflectors

Abstract

Described herein are systems and methods for enabling small, high magnification cameras to operate in low light (e.g., nighttime) conditions. These camera systems can include the use of polarizing beam splitters, wave plates, and reflectors to allow for long paths of light within the camera. Also described are methods that allow a single camera to operate simultaneously with two optical paths and two focal lengths. Two focal lengths (two magnifications) can be supported within a single camera or imaging device.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 267,100, filed January 24, 2022, which is incorporated by reference in its entirety.

[0002] FIELD OF THEINVENTION This application generally relates to the field of high magnification photography and imaging technology. More specifically, this application relates to a system and method that utilizes a reflector and / or polarizer, including a polarizing beam splitter, for use in a high magnification camera or imaging device. This application also relates to an imaging device or camera built into a cell phone, smartphone, tablet, laptop, or any other mobile device. [Background technology]

[0003] Digital cameras are widely used in mobile devices, e.g., in smartphones. Camera performance is a key differentiator for consumers and a driver of market share. Thus, manufacturers and suppliers of mobile devices strive to improve camera performance.

[0004] One important aspect of the camera performance of a mobile device 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). However, mobile devices are thin and compact and cannot accommodate long lens assemblies. This has traditionally limited their magnification and zoom capabilities.

[0005] Thus, there is a continuing need for improved imaging systems. Summary of the Invention

[0006] 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 the use of polarizing beam splitters, wave plates, and reflectors or mirrors to increase the light path in the camera, which allows for longer focal lengths and therefore higher magnification without substantial loss of light. This enables, for example, high magnification, low volume camera photography / videography in low light conditions. This is useful for both long range smartphone photography / videography and close range "macro" photography / videography (meaning taking high magnification photos or videos of small but nearby objects, such as ants on a leaf). This application also discloses enabling multiple focal lengths in one camera to cover a wider range of focal lengths, for example, for improved zooming on objects moving towards and away from the camera.

[0007] One aspect provides methods and systems for improving the performance of high magnification small volume (e.g., thin) cameras or imaging systems that include polarization and internal reflection as part of their operation. Such small but powerful magnification cameras are advantageous for smartphones, tablets, drones, and other mobile devices, or for use in small limited spaces such as inconspicuous locations in autonomous vehicles. Having internal reflections in a small camera or imaging system allows for a longer path of light, thus allowing the use of longer focal lengths, which in turn allows for higher magnification. In particular, the present application discloses the use of reflectors, beam splitters, polarizers, and related elements to improve performance, including allowing operation in low light conditions.

[0008] Also described is a method that allows a single camera to operate with two optical paths and two focal lengths simultaneously. This is made possible by splitting the optical path into two, each path being a different length before reaching the imaging sensor, and thus two focal lengths (two magnifications) can be supported simultaneously within a single miniature camera or imaging device.

[0009] Another aspect includes an imaging and optical system for capturing an image having a lens or substrate having a focal length, a polarizing beam splitter adjacent to the lens or substrate, a wave plate downstream of the reflective polarizing beam splitter, a first reflector distal or downstream of the wave plate, a second reflector disposed at an angle of 20-170° relative to the first optical path, and a sensor for forming an image. The substrate, wave plate, and reflector can be disposed in the first optical path, and a first reflective polarizer can be disposed in the first optical path between the lens and the first reflector. The sensor can be disposed in the first optical path or the second optical path. The polarizing beam splitter can be on the intersection of the first and second optical paths at the second reflector. Light entering the image lens is polarized by the reflective polarizing beam splitter, transmits through the reflective polarizing beam splitter, passes through the wave plate, hits the reflector, travels back through the wave plate along a first optical path, and then the light is reflected by the polarizing beam splitter to travel along a second optical path and forms an image on the sensor, and the light forms an image on the sensor.

[0010] Another aspect may include a waveplate that is a quarter waveplate or a rotator or plate.

[0011] Alternative embodiments may include one or more additional lenses or substrates having a focal length, and lenses or substrates having spherical or aspherical curved surfaces.

[0012] Another embodiment involves using a cornering prism or a turning reflector.

[0013] Another embodiment includes a waveplate that is composed of two or more elements.

[0014] Another embodiment includes a curved first reflector or second reflector having a spherical or aspherical curvature mirror.

[0015] Another aspect involves the focal length of the system being matched to the round trip length of the optical path.

[0016] Another embodiment includes one or more of a lens or substrate, a polarizing beam splitter, a wave plate, or a reflective surface or mirror that can be mechanically moved, thereby being used to change the overall focal length of the imaging system.

[0017] Another aspect includes integration into a smartphone, cell phone, tablet, laptop, drone, or other mobile device.

[0018] Another embodiment includes a system having a second imaging sensor on a second optical path on the opposite side of the polarizing beam splitter from the first imaging sensor.

[0019] Another aspect includes a focal length of an image formed on the first sensor that is different from a focal length of an image formed on the second sensor.

[0020] Another embodiment includes an imaging sensor disposed at an angle between 20 and 160 degrees relative to the first optical path.

[0021] Another aspect involves taking high magnification photographs or videos.

[0022] Another aspect involves taking photos or videos in low light conditions.

[0023] Another aspect includes doing both far (tele) and close (macro) with a single imaging system, which can be made possible by moving optical elements in the system to allow for larger changes in focal length.

[0024] Another aspect includes a method that includes polarizing light to a first linear polarization, transmitting that polarization through a polarizing beam splitter, a wave plate, and a reflector to return to the beam splitter with a linear polarization substantially orthogonal to the transmitted linear polarization and converted by the beam splitter to a sensor to form an image, thereby allowing for a longer optical path and therefore higher magnification within a compact imaging system and also allowing operation in low light conditions.

[0025] Another embodiment involves creating a composite image from images at two different focal distances, thereby providing the user with an image that is in focus at two different distances simultaneously.

[0026] Another aspect involves selecting which parts of which images are in focus by the autofocus hardware.

[0027] Another aspect includes the hardware being PDAF (phase detection autofocus) sensing.

[0028] Another aspect involves selecting which parts of which images are in focus by software.

[0029] Another aspect involves a composite image being formed by selecting which parts of which images are in focus through hardware and software.

[0030] Other embodiments include a second reflector disposed at an angle of 20-90° to the first optical path, or at an angle of 55-90° to the first optical path.

[0031] Another embodiment includes a wave plate disposed between the polarizer and the first reflector.

[0032] Another embodiment includes a system that includes a second lens, a third mirror, and / or a waveplate that is an optical film.

[0033] Another aspect includes a camera having the systems disclosed herein or incorporating the methods disclosed herein.

[0034] Another aspect includes a method of performing high magnification imaging by receiving light from a scene through a substrate, the method including: focusing the light, polarizing the light to a first linear polarization, rotating the light, inverting the light and rotating the polarization of the reflected (second time) light such that the combination of the two polarizations rotates the polarization of the light substantially orthogonal to the input polarization. [Brief description of the drawings]

[0035] [Figure 1] 1 illustrates an exemplary embodiment having lenses, polarizing beam splitters, quarter wave plates, mirrors, and sensors that enable high magnification and low light photography in a camera or imaging system. [Diagram 2] 2 illustrates the exemplary embodiment of FIG. 1 integrated into a smartphone. [Diagram 3] 13 shows another embodiment having a turning mirror or cornering prism integrated into a smartphone. [Figure 4] Another embodiment having lenses, polarizing beam splitters, quarter wave plates, mirrors, and sensors that enable high magnification and low light photography in a phone camera or imaging system. [Diagram 5] 5 shows the embodiment of FIG. 4 integrated into a smartphone. [Figure 6] 1 shows another embodiment that allows for two optical paths and two focal lengths in one camera or imaging system. [Figure 7] 1 shows another embodiment that allows for two optical paths and two focal lengths in one camera or imaging system. [Figure 8] 3 shows another embodiment having two mirrors. [Figure 9] 1 shows another alternative embodiment related to FIG. 1 that allows for two optical paths and two focal lengths in one camera or imaging system. [Figure 10] 10 shows the embodiment of FIG. 9 with the addition of cornering mirrors, integrated into a smartphone. [Figure 11]With respect to the disclosed embodiments, the advantages of optical element movement as related to changing focus are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present application will now be described more fully with reference to the accompanying drawings showing preferred embodiments of the invention, however, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0037] The present application discloses a compact, small volume camera or imaging system that utilizes lenses, beam splitters, reflectors, waveplate retarders, and / or optical polarizing elements, thereby enabling both high magnification and low light operation in a single camera. A key aspect here is the specific and innovative arrangement of one or more polarizing beam splitters, waveplates, reflectors, lenses, and sensors. The arrangement ensures a polarization orientation along the path of the light that sets how the light advances through the camera. They allow both a long path of light within a small volume (enabling a long focal length and therefore high magnification), and they ensure that a significant portion of the light that enters the camera reaches the sensor to form an image (thus enabling camera operation in low light, e.g., at night). The resulting embodiment enables a miniature camera or imaging system that can achieve both high magnification and low light operation in a small volume. Such a camera or imaging system may be advantageous for use in a smartphone, tablet, drone, or other mobile device.

[0038] In current smartphone camera modules, there is typically one camera (e.g., a telephoto camera) responsible for high magnification photography or videography and another camera (e.g., a normal or wide-angle camera) responsible for low light (e.g., night) operation. Particular embodiments include methods and systems for a single camera that can perform both high magnification and low light photography or videography, and can do so for both long-range telephoto operation and macro (closer) photography / videography. Such embodiments can reduce the number of cameras, size, and / or cost of the camera module, while allowing the same or higher performance. Particular methods and systems also allow operation at two focal lengths simultaneously, which can provide improved zooming for objects moving toward and away from the camera.

[0039] High Magnification and Low Light Camera Operation with Polarizing Beamsplitters, Waveplates, and Mirrors The exemplary system enables polarized round-trip light reflection to enable a small volume camera to perform high magnification photography / videography and also enables low light operation. These aspects are achieved by utilizing reflection and polarization to enable a long light path (enabling a long focal length and therefore high magnification) while substantially preventing light loss and thus ensuring that a large amount of light reaches the sensor as is necessary for low light operation. Thus, this type of novel system is suitable for use in mobile devices, e.g., smartphones, to achieve both high magnification (high zoom) and low light operation. It can enable, for example, photography and videography of distant scenes / objects at night, as well as macro photography / videography in low light. Macro photography refers to high magnification images of nearby but small objects, such as ants on a leaf.

[0040] 1 shows an exemplary system consisting of a lens or substrate (201), a polarizing beam splitter (202), a wave plate or quarter wave plate (203), a reflector or mirror (204), and an imaging sensor (401). Since 203 is a quarter wave plate, its phase retardation is selected to be 90 degrees for a selected (visible) wavelength of light. The quarter wave plate converts linearly polarized light to circularly polarized light and vice versa. The quarter wave plate can be oriented such that its optical axis is oriented at an angle of substantially plus or minus 45 degrees with respect to the pass (transmission) polarization orientation of the beam splitter.

[0041] The lenses, beam splitters, wave plates (e.g., quarter wave plates), and mirrors are aligned substantially along the axial axis of the camera (along with the incoming light 101), and the sensor (401) is aligned substantially off-axis at the exit port of the beam splitter (202). This arrangement of elements helps ensure a polarization orientation along the light path that sets how the light progresses through the camera. It allows both a long light path of light in a small volume (which can allow for a long focal length and therefore high magnification), and it ensures that a significant portion of the light entering the camera reaches the sensor to form an image (thus allowing camera operation in low light, e.g., at night). The generated polarization and the resulting light path within the camera are now disclosed in detail.

[0042] Incident light (101) from an object or scene is typically unpolarized and is therefore labeled "U" for unpolarized light in FIG. 1. This light enters and exits (102) a lens (201) to a polarizing beam splitter (202) that, for example, transmits only horizontally polarized light (labeled "H"). The transmitted light (103) then enters a quarter-wave plate (203) and emerges circularly polarized (104), for example, right-handed circularly polarized (depending on the chosen naming convention, therefore labeled "RC" at 104). The light then reflects (105) from a reflector or mirror (204) where it now has left-handed circular polarization (hence labeled "LC" at 105), following the same convention. It then passes through the quarter-wave plate (203) a second time. After the quarter-wave plate, the light emerges linearly polarized, but now with a vertical linear polarization (hence the labeling of "V" at 106) (106). Thus, due to the action of the quarter-wave plate (QWP), the linear polarization of the returning light is 90 degrees different (vertically polarized) at 106 compared to the entrance light at 103 (horizontally polarized). The light then again hits the polarizing beam splitter (202), but this time its polarization has been rotated 90 degrees (by the action of the quarter-wave plate (203)) and is oriented perpendicular to the transmission polarization orientation of the polarizing beam splitter (202), so it is reflected (107) instead of transmitted. After reflecting off the beam splitter, the light (107) reaches the sensor (401) to form an image.

[0043] In alternative embodiments, the single lens can be replaced with a lens group, or additional lenses can be added in front of or between the other elements. The image formed on the sensor (401) is in focus if the distance traveled by the light matches the focal length of the lens (or lenses). The path traveled by the light can be matched with the focal length of the camera lens(es).

[0044] In another embodiment, lenses can be added before or between the elements shown in Figure 1. In particular, lenses can be added before or after the beam splitting polarizer (202). Such lenses can have spherical or aspherical curved surfaces.

[0045] Lenses that can be added after the beam splitting 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), see for example FIG. 6 and lens 221, each lens at this intermediate location acts to bend or focus the light twice. Thus, each such lens can have a stronger effect than it would otherwise. Thus, fewer lenses can be used to achieve the same benefit of image focusing or reduced image aberrations. This is disclosed as an advantage of the current embodiment, both this embodiment and other embodiments herein.

[0046] The mirror or mirror surface (e.g., 204 in FIG. 1) can be curved, either spherically or aspherically. This can act as another light bending or focusing element. By curving the mirror, fewer other non-flat elements (e.g., fewer lenses) may be required.

[0047] 1, the size of the system (size and spacing of the disclosed components) may be such that the entire system can fit within the thickness of a smartphone or other mobile device, for example, within a mobile or cell phone, tablet, laptop, or within a small drone. Thus, with respect to the enablements disclosed herein, a central feature of these enablements is that they enable high magnification and low light photography for cameras that may be included in smartphones, tablets, laptops, small drones, or other mobile devices.

[0048] In the next internal reflection path illustrated in FIG. 1, segments 105 and 106 re-traverse the distance already covered by paths 103 and 104. The resulting optical path can therefore traverse a distance that can be longer than the thickness of the camera. This distance can be up to almost twice the thickness of the camera, depending on the arrangement and thickness of the polarizing beam splitter and mirror. This embodiment allows the use of longer camera focal lengths in a smaller space, for example for use inside a smartphone.

[0049] FIG. 2 shows an exemplary type of camera or imaging system that can be used inside a smartphone, tablet, laptop, or other mobile device. This is the exemplary system of FIG. 1, but now shown in more detail as its elements can be oriented inside a smartphone. It consists of a lens or focusing substrate (201), adjacent to it a polarizing beam splitter (202), adjacent to it a wave plate (203), adjacent to it a mirror or reflector (204), all arranged along a first optical path, and an imaging sensor (401) arranged along a second optical path. In the exemplary embodiment of FIG. 2, the lens (201), wave plate (203), and mirror (204) are arranged along a first optical path along the incoming light (along 101, along the Z axis), which means that 201, 203, 204 are oriented perpendicular to this first optical path (in FIG. 2 they are in the XY plane). The imaging sensor (401) is positioned along the second optical path along which the light reaches the sensor (along 107, i.e. along the X-axis), meaning that 401 is oriented perpendicular to this second optical path (in FIG. 2 it is in the YZ plane). The polarizing beam splitter (202) is oriented such that its ports are aligned with both the first and second optical paths, specifically meaning that two ports of the polarizing beam splitter (allowing light 102 to enter and light 103 to exit) are along the first optical axis or path (their faces are in the XY plane of FIG. 2), and the third port of the polarizing beam splitter (allowing light 107 to exit the beam splitter) is along the second axis or path (its face is in the YZ plane of FIG. 2). Although in the illustration and example of FIG. 2 the two optical axes or paths are shown as being perpendicular to each other and precisely aligned along the fundamental axes of the smartphone (precisely along Z and X respectively), the inventors disclose that the invention remains operable even when these paths or axes are not aligned at right angles, or are not aligned along the fundamental axes X, Y, Z of the smartphone, and are disclosed to do so.

[0050] As seen in FIG. 2, an exemplary system can be used in a smartphone to orient the optical axis of a camera (along 101) through the thickness of the smartphone. This arrangement can allow up to doubling the available optical path length (and therefore focal length) across the thickness of the phone. FIG. 2 illustrates such a case, where the optical axis of the camera (along the incoming optical path 101) can be aligned along the thinnest part of the phone (along the Z axis of FIG. 2). The sensor 401 can be conveniently aligned in the YZ plane (as shown), or in the XZ plane, however, the inventors disclose that other sensor orientations are possible (e.g., not in the YZ or XZ plane, but angled relative to them if desired, and then the beam splitter angle should be suitably modified from substantially 45 degrees).

[0051] FIG. 2 shows the orientation, scale and size of the camera embodiment that can be integrated inside an exemplary smartphone. More specifically, the embodiment illustrated in FIG. 2 is also composed of a lens (201), a polarizing beam splitter (202), a quarter-wave plate (203), a mirror (204), and an imaging sensor (401). Incoming, typically unpolarized light (101) enters the lens (201), exits the lens (102), and reaches the polarizing beam splitter (202), which transmits, for example, only horizontally polarized light through the polarizing beam splitter (103, labeled "H"). This transmitted light (103) then enters the quarter-wave plate (QWP) (203) and exits circularly polarized light (104), for example, right-handed circularly polarized light (according to the chosen naming convention choice, hence labeled "RC" at 104). The light then reflects (105) from the mirror (204), where it now has left-handed circular polarization according to the same rule (hence labelled "LC" at 105), and passes through the QWP (203) a second time. After the quarter-wave plate, the light emerges (106) linearly polarised, but now with vertical linear polarization (hence labelled "V" at 106). Thus, due to the action of the QWP, the linear polarization of the returning light is 90 degrees different (vertically polarised) at 106 compared to the entrance light at 103 (horizontally polarised). Thus, when the light again hits the polarising beam splitter (202), this time its polarization has been rotated 90 degrees (by the action of the quarter-wave plate (203)) and is oriented perpendicular to the transmission direction polarization of the polarising beam splitter, so it is reflected (107) instead of being transmitted. After reflecting off the beam splitter, the light (107) reaches the sensor (401) and forms an image.

[0052] The embodiment illustrated in FIG. 2 is a compact, cube-like camera design that can enable similar or better types of magnification than are currently only available in larger volume rectangular (one long axis) periscope camera designs. This embodiment can do so without substantial loss of light, thus enabling its use for low light (e.g., nighttime) operation. With the addition of optical element movements and extra lenses, also disclosed herein, this type of camera design can also further enable both macro and telephoto high magnification low light operation in a single camera. The ability to achieve these advances and features is a desirable high value use case for smartphone applications, as it can potentially reduce camera size and reduce the number of cameras required within a camera module by rolling two camera functions (high magnification and low light) into a single smaller camera.

[0053] Enabling high magnification low light camera operation in a smartphone size and form factor, which is a central aspect and enablement of the present invention. In FIG. 2, there is free space shown between components, e.g., free space in the -X direction between the polarizing beam splitter (202) and the sensor (401). However, this is done primarily for clarity of illustration so that the reader can easily see all components of the embodiment. The inventors note that free space may be included or components may be as close together as desired or permitted by manufacturing or other considerations, and doing so may be anticipated and disclosed.

[0054] The second way in which the present invention can be used is in combination with a periscope shape. The present invention illustrated in FIG. 1 can further include a cornering mirror or prism in front of or after the lens 201, as illustrated in FIG. 3 for the case where the cornering mirror is in front of the lens 201. In this embodiment, the aperture 701 can also be replaced with a lens or lenses, if desired. Such a design, in which the embodiment of FIG. 1 is used in a "periscope" configuration, has advantages over existing smartphone periscope camera designs. In existing periscope designs, the focusing path length available for light is equal to or less than the length of the major axis of the camera (along the Y axis of FIG. 3). This sets the available focal length, and therefore the maximum magnification, of a conventional smartphone periscope camera. In the embodiment shown in FIG. 3, due to polarization (at 202) and polarization rotation (at 203) and reflection (at 204), up to nearly twice the length of the major axis of the camera is available for light travel, and therefore for focusing and magnification.

[0055] In the present exemplary embodiment of FIG. 3, light enters the smartphone (ray 100) along the -Z axis through an aperture 701 (which can also be a lens or group of lenses) and is turned substantially 90 degrees by a turning mirror (200) or equivalently a cornering prism. The lens (201) can remain after the turning mirror or cornering prism (as shown in FIG. 3) or can be placed in front of the turning mirror or cornering prism, in or near the aperture 701. The light can then proceed through the embodiment in the same manner as shown and discussed in FIG. 1 and FIG. 2. The difference is that now the axial direction of the camera is oriented along the Y axis of the phone (rather than along the thin Z axis as in FIG. 2). Alternatively, the camera can be oriented so that its long axis is along the X axis of the smartphone. In either case, the light crosses the long axis of the camera twice (from 202 to 204 and then back to 202). This means that the available optical path travel distance, and therefore the available focal length, is from 201 to 204, back to 202, and then up to and around 401 (depending on the size and placement of 202). This is nearly twice as large as would be available with a conventional periscope design.

[0056] Thus, for essentially the same camera volume as a conventional periscope camera, the available focal length, and therefore the magnification, is approximately doubled. By utilizing reflectors and polarizing beam splitters and quarter-wave plates as disclosed herein, this 2x magnification benefit over conventional periscope designs is achieved without substantial loss of light. The end result is a compact camera that improves magnification but is still suitable for low-light operation. Such a camera or imaging system would be of high value for smartphone use.

[0057] There is free space shown between components, for example, free space in the -X direction between the polarizing beam splitter (202) and the sensor (401) in Figure 3. This free space may be maintained, or the components may be moved closer together as desired or permitted by manufacturing or other considerations, and doing so is anticipated and disclosed.

[0058] The sensor 401 can be placed further out in the -X direction if desired, which can be used to further increase the available paths for the light to travel, and therefore the available focal length for magnification. However, moving the sensor 401 in the -X direction offers less benefit than moving the mirror 204 in the +Y direction, since the latter distance is traversed twice (as described above), and therefore offers a greater increase in magnification per camera volume increase. If the designer wishes to further increase magnification at the expense of increasing the camera size in our embodiment, the choice of the 204 mirror +Y displacement offers a greater magnification increase for a given camera size increase than the 401 sensor -X displacement, although both are disclosed as viable options.

[0059] 4 shows an exemplary system consisting of a lens (201), a polarizing beam splitter (202), a quarter wave plate (203), a mirror (204), and an imaging sensor (401). Since this embodiment includes a quarter wave plate, its phase retardation is selected to be 90 degrees for a selected (visible) wavelength of light. The quarter wave plate is oriented such that its optical axis is oriented at an angle of substantially ±45 degrees with respect to the removal (reflection) polarization orientation of the beam splitter.

[0060] The sensor (401), beam splitter (202), wave plate (203), and mirror (204) are aligned substantially along the axial axis of the camera (along 103, 104), and the entrance lens (201) and the incident light (101) are aligned substantially off-axis at the entrance port of the beam splitter (202). As shown in FIG. 4, this particular arrangement of elements ensures a polarization orientation along the light path that sets how the light advances through the camera. It allows both a long light path of light in a small volume (enabling a long focal length and therefore high magnification), and it ensures that a significant portion of the light that enters the camera reaches the sensor to form an image (thus enabling camera operation in low light, e.g., at night). The generated polarization and the resulting light path within the camera are now disclosed in detail.

[0061] As mentioned earlier, incident light (101) from an object or scene is typically unpolarized and is therefore labeled "U" in FIG. 4 for unpolarized light. Unpolarized light contains both horizontal and vertical polarization components. This incident light enters a lens (201), exits a lens (102) and reaches a polarizing beam splitter (202), which transmits, for example, only vertically polarized light through the polarizing beam splitter (153, labeled "V"). This polarizer therefore removes and reflects the horizontally polarized component of the light. This means that the horizontally polarized light is reflected from the beam splitting polarizer at a substantially 90 degree angle (optical path 103, labeled "H"). This horizontally polarized reflected light then enters a quarter wave plate (QWP) (203) and emerges circularly polarized (104), for example right-handed circularly polarized (depending on the chosen choice of naming convention, hence labeled "RC" at 104). The light then reflects (105) from the mirror (204) where it now has left circular polarization (hence labelled "LC" at 105) according to the same rule. It then passes through the QWP (203) a second time. After the quarter wave plate the light emerges (106) linearly polarised, but now with vertical linear polarization (hence labelled "V" at 106). Thus, due to the action of the QWP, the linear polarization of the returning light (106) is now the same as the light polarization that the polariser lets through (90 degrees different from the horizontal polarization that was previously removed). This vertically polarised light (106, labelled "V") therefore now passes through the polarising beam splitter and reaches the sensor (401) to form an image.

[0062] Figure 5 shows an orientation of the camera along the long axis of the smartphone (along axis X or Y in Figure 5) that requires a cornering mirror or turning prism (e.g., does not require element 200 of Figure 3). Comparing Figures 4 and 5 with Figures 1 and 2, the orientation of the entrance lens (201) and the imaging sensor (401) is reversed. In Figure 4, the entrance lens (201) is oriented horizontally and the sensor (401) is oriented vertically, whereas in Figure 1 it was the other way around. Furthermore, the sensor (401) is brought forward (to the left) of the camera in Figures 4 and 5.

[0063] These changes allow for a periscope-like orientation of the camera, as shown in FIG. 5, but without the need for cornering mirrors or turning prisms. This means that the length of the camera can be used more effectively. Now, the entire camera length from 401 to 204 (along the Y axis in FIG. 5) can be used almost twice as effectively with a double pass of light to 202 to 204 and back, i.e., along 103, 104 for the forward light and along 105, 106 for the return light. This is achieved without having an extra turning mirror or cornering prism (e.g., 200 in FIG. 3) that takes up some of the valuable available length. This is an added advantage of the embodiment shown in FIG. 4 and FIG. 5. The embodiment of FIG. 4 can also be oriented along the other long axis of the smartphone (700), along the X axis (instead of along the Y axis as shown in FIG. 5).

[0064] More specifically, the embodiment of FIG. 5 consists of a lens or focusing substrate (201) with a polarizing beam splitter (202) underneath, adjacent to a wave plate (203) on one side, adjacent to a mirror or reflector (204), and adjacent to an imaging sensor (401) on the other side of the polarizing beam splitter. The lens or focusing substrate (201) is positioned along a first optical path along the incoming light (along 101, i.e. along the Z axis in FIG. 5), meaning that 201 is oriented perpendicular to this first optical path (in FIG. 5, it is in the XY plane). The imaging sensor (401), wave plate (203), and mirror (204) are positioned along a second optical path along the light returning to the imaging sensor (along 107, along the Y axis in FIG. 5), meaning that 401, 203, 204 are oriented perpendicular to this second optical path (in FIG. 5, they are in the XZ plane). The polarizing beam splitter (202) is oriented such that its ports are aligned with both the first and second optical paths, specifically meaning that one port of the polarizing beam splitter (allowing light 102 to enter) is along the first optical path or axis (its face is in the XY plane of FIG. 5), and the second and third ports of the polarizing beam splitter (allowing light 103 to exit and light 107 to exit) are along the second optical path or axis (the faces of these ports are in the XZ plane of FIG. 5). Although in the illustration and example of FIG. 5 the two optical axes or paths are shown as being orthogonal to each other and precisely aligned along the cardinal axes of the smartphone (exactly along Y and Z respectively), the inventors disclose and are disclosed to do so that the invention remains operable even when these axes are not aligned at right angles or are not aligned along the cardinal axes X, Y, Z of the smartphone.

[0065] The size of the system (size and spacing of the disclosed components) can be such that the entire system can fit inside a smartphone or other mobile device, for example inside a mobile or cell phone, tablet, laptop, or inside a small drone. Figure 5 shows how the embodiment of Figure 4 can be integrated into a smartphone (700). Thus, a central feature of this enablement is to enable high magnification and low light photography for a camera that can be integrated into a smartphone, tablet, laptop, small drone, or other mobile device.

[0066] In FIG. 5, the long axis of the camera (from the beam splitter 401 to the mirror 204) is shown along the longest Y axis of the smartphone. However, the camera could equally be oriented along the mid-length X axis of the smartphone if desired. It could also be oriented at an angle in the XY plane, but this would typically not be convenient. In any case, there is freedom to choose the length of the spacing from the sensor 401 to the beam splitter 202 to the mirror 204 as desired. We note that increasing the distance from the sensor 401 to the beam splitter 202 may be less desirable than increasing the distance from the beam splitter 202 to the mirror 204, since the latter distance is traversed twice by the path of the light (once by the forward paths 103, 104 and again by the return paths 105, 106). Thus, for an available or selected camera length, the designer may choose to place the beam splitter 202 and input lens (201) (or camera aperture) further to the left (towards -Y) in FIG. 5, as this allows for a longer total optical path length and therefore a longer focal length and higher magnification for a given camera length.

[0067] Enabling multiple focal lengths in one compact imaging system Disclosed next is an exemplary system that allows operation at multiple focal lengths. In a camera, such as that used in a mobile device, an object may be photographed or videotaped at different distances. For example, a user may take a video of an object approaching or receding, or the user may move toward or away from the object while taking a video or photo. This means that 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 short to long distances. Currently, in mobile devices, lenses or other optical elements may be mechanically moved to change the focus of the camera. However, the range of mechanical movement 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 space occupied by other elements. For example, if a mobile camera is 10 millimeters long to fit inside the thickness of a smartphone, for example, for a non-periscope camera geometry, and a non-moving lens, PCB board, and sensor occupy 6 millimeters of that space, only 4 millimeters are left to perform lens movement to change the focal length. For periscope cameras, the above values ​​are different, but the length of the camera is still limited due to the need to fit many other components into a smartphone, so how much a camera can change focal length in a smartphone or other mobile device may be limited.

[0068] The exemplary systems shown in Figures 6 and 7 are systems that can improve the focusing performance of a camera. The disclosed embodiments allow for two focal lengths in one camera, which can allow for a larger range of focal lengths for, for example, zooming. These exemplary systems include one or more lenses, a polarizing beam splitter (202), a quarter wave plate (QWP, 203), a mirror(s) (e.g., 204) or other elements acting as reflective elements, and a sensor(s) (401, 451). Specifically, for the exemplary systems disclosed in Figures 6 and 7, there are two light paths within one camera, each of which can have a different optical path length and therefore can support different focal lengths. In these exemplary systems, the "15x channel" path has light traveling approximately three times (3x) the distance of the "5x channel." It should be understood that "15x" and "5x" are just two examples. Embodiments may similarly have "Ax" and "Bx" channels, where A is one level of magnification and B is another level of magnification, with the optical path and focal length matched to the selected A and B values. Additionally, while these figures show two separate sensors, the inventors have disclosed and anticipate that it is also possible to use two portions of one sensor.

[0069] Two focal lengths may have advantages compared to only a single focal length. For example, two focal lengths may more easily cover a desired range of focal lengths than the one-by-one focal lengths available in conventional cameras. For example, the optical element(s) may be moved to change a first "5x" focal length from 1x to 10x. Similarly, the optical element(s) may be moved to change a second "15x" focal length from 10x to 20x. Thus, the total range covered is 1x to 20x, which may be substantially greater than the range that can be covered by a conventional camera with moving optical element(s). This may improve the magnification range. It may also allow for improved zooming and an improved ability to keep objects in focus as they move towards and away from the camera.

[0070] Figure 6 shows an exemplary system consisting of at least one lens (labeled 201), a polarizing beam splitter (202), a quarter wave plate (203), a mirror (204), and two imaging sensors (401 and 451). The light path for one channel, e.g., the "15x channel," is the same as shown in Figure 1. The light path for the other channel is the previously unused light path (153) in Figure 1. However, now that light is picked up by an additional sensor (451).

[0071] Figure 7 shows an alternative exemplary system consisting of at least one lens (labeled 201), a polarizing beam splitter (202), a quarter wave plate (203), a mirror (204), and two imaging sensors (401 and 451). Here, the light path for one channel, e.g., the "15x channel," is the same as shown in Figure 4. The light path for the other channel is the previously unused light path (153) in Figure 4. However, now that light is picked up by an additional sensor (451).

[0072] In the embodiment of Figures 6 and 7, lenses can be added along the first channel, along the second channel, or along both channels. Such lenses can be used to set different focal lengths along the two channels to desired values. We note that in the case of lenses that the light traverses twice, these lenses can have a stronger effect because, due to round-trip reflections, they focus the light twice onto the same lens. The first lens can also be replaced by a simple aperture if so desired.

[0073] It should be understood that picking up a previously unused portion of light (153), as shown in Figures 6 and 7, may be done for various embodiments disclosed herein that use a polarizing beam splitter, and it may also be done for variations of those embodiments as anticipated and disclosed herein.

[0074] As mentioned above, the exemplary systems of Figures 6 and 7 can be configured to operate at two different focal lengths, i.e., two different magnifications. Alternatively, the magnification of the two channels can be kept the same, but the focal depth can be different from one channel to the other.

[0075] Next, another advantage of these embodiments is disclosed. Consider a scene with two camera-scene distances of interest. Some examples: A couple may be taking a selfie in front of a historic building, and there is a distance A from the smartphone camera to the couple, and a distance B from the smartphone camera to the building, where B is not equal to A. Or a couple may be taking a photo or video in front of a natural scene, such as a range of mountains behind the couple. 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 examples where there may be effectively two (or more) subject distances from the camera to the scene being photographed or videotaped.

[0076] With a conventional smartphone camera, the user must choose to either focus on the couple or on the historic building, but not both. The embodiments of Figures 6, 7, 9, 10 and their variations allow a solution to this problem. The two channels allow two simultaneous photographs or videos of such a scene, one photograph or video taken via one channel on one sensor (e.g., 401) at one focal length (e.g., aligned to distance A), and another photograph or video taken of the same scene via a second channel on the other sensor (e.g., 451) at a second focal length (e.g., aligned to distance B). Alternatively, both photographs or videos of both channels can be taken with two parts of one sensor, as disclosed above.

[0077] Particular embodiments may provide a composite photograph or video formed from the two channels, where the composite photograph or video is formed such that the scene is presented to the user as being substantially in focus at both distance A and distance B. That is, returning to the single example above, both the couple and the historic building are in focus in the composite image that is displayed or provided to the user.

[0078] If this region of the scene corresponds to a location occupied by a couple, then this first region of the scene is substantially in focus on a first channel terminating at a first sensor (401), with its focal length matched to distance A by appropriately moving optical elements along that first channel. However, this same region is out of focus on a second channel terminating at a second sensor (451), but with its focal length matched to distance B by appropriately moving optical elements along that channel. Thus, in the composite photograph shown to the user, an image of this region should be taken from the first sensor and not the second sensor.

[0079] Conversely, if this region of the scene corresponds to a location occupied by a historic building, this region will be substantially in focus in the second channel and not in the first channel, and therefore in the composite image shown to the user, the image of this region should be obtained from the second sensor and not the first sensor.

[0080] Selecting which region from which channel or sensor to display can be accomplished by using any of the available sensor hardware, or by software running on the embodiments of Figures 6, 7, 9, 10, or variations thereof, or a combination of the two. Regarding hardware: We disclose that sensors, including smartphone camera sensors, can include a PDAF (phase detection autofocus) sensing component. PDAF looks at light coming from the same region of the scene but entering the image sensor from different directions (e.g. converging on the location from the left or right side of the lens, or from the top versus the bottom). If the light is in phase from such different directions, that region of the scene is in focus. We disclose that PDAF can be used to identify whether the subregion in question is more in focus on the first or second sensor. Other autofocus hardware solutions commonly used in phones can also be used. Based on this, a more focused version of each subregion can be selected, and these can be combined into one composite image. The resulting composite image can therefore substantially focus on both the couple and the historic building, a result that is not currently possible with conventional smartphone cameras.

[0081] Which sub-regions from which sensors to display to form the dual focus composite image can also be determined by software. Comparing the image contrast for each sub-region across both sensors is one measure. For example, the contrast between edges within that region can be used as a selection criterion. Another measure is to use low-pass spatial filtering. If a small region is out of focus on the sensor, applying a low-pass (smoothing) spatial filter will not change the image much since that part of the image is already blurred. We disclose that for each sub-region, we subtract a low-pass version of the image from itself. For regions where the image and its low-pass version are substantially different, that part of the image is more in focus. Thus, this software method (low-pass filtering and subtraction) can be used to identify whether a region of the scene is more in focus on the first or second channel or sensor. Once that identification is 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 determine whether a small region is more in focus on the first or second channel or sensor, and are anticipated and disclosed.

[0082] When a composite image is formed, the difference in magnification across the two channels is accounted for. Specifically, if a pattern of in-focus areas is present on a first sensor, it forms a partial (patchworked) first image, and a complementary set of in-focus areas is present on a second sensor, it forms a partial (patchworked) second image. It is understood that when these two images are combined into one composite image, one or both of them are scaled (enlarged or reduced) to account for the difference in magnification channel 1 vs. channel 2. They can also be centered relative to each other if needed.

[0083] It is further understood that the above is an approximate description. There may be some parts of the scene that are not at either distance A or B, for example there may be a tree further behind the historic house at a distance C from the camera that is not equal to either A or B. The scene area corresponding to this tree may be displayed with the highest alignment available. Similarly, the house may not be exactly at distance B, nor may all of the couple be exactly at distance A. Again, for each small area, the version that is the best focus from the two channels or sensors may be presented to the user. When interpolating between the two channels, one or many parts of the composite image may be a combination of images from both channels. Furthermore, distances A and B are themselves ranges, such ranges corresponding to the focal depth of each channel of the camera. Thus, in the above, the couple is substantially in focus from a certain distance from Amin to Amax, and the historic house is in focus from Bmin to Bmax.

[0084] In Figures 6, 7, 9, 10 and their variations, two focusing ranges are available. This dual focusing can be used to provide composite photographs and videos in which both distance ranges are substantially in focus in each composite image. Doing so is disclosed and is not available in conventional cameras and forms a valuable benefit of the present invention.

[0085] Sometimes a user may wish to have a portion of a scene, e.g. a central subject of a scene, in focus and the rest of the scene out of focus (blurred) in order to draw visual attention to the subject of the scene. This is commonly referred to as the bokeh effect when taking a photo or video. By being able to independently focus the two channels at different focal lengths, the present invention can also be used to more easily achieve such a bokeh effect. It can do so by selecting one of the two channels to be more out of focus, by creating a composite image in which parts of the scene are intentionally selected to be out of focus, and / or by a combination of both methods.

[0086] Figures 6, 7, 9, and 10 show embodiments that can enable more accurate separation of a target object from its background. For example, if the background is distracting, e.g., essentially camouflaged to the object of interest, then if the scene can be separated into two focused elements, one for the object and one for the background, a composite photograph can be generated in which the target object is clearly shown and the background is shown, less shown, or hidden as desired.

[0087] Additional Disclosed Aspects for the Embodiments Herein, the inventors have disclosed additional aspects and features of the invention. The features disclosed herein are anticipated for one, more than one, or all of the above embodiments. An important aspect here is the specific and innovative arrangement of one or more polarizing beam splitters, wave plates, reflectors, lenses, and sensors. The disclosed arrangement sets the polarization orientation along the path of the light, which selects how the light advances through the embodiment. The choices disclosed herein allow both a long path of light in a small volume (enabling a long focal length and therefore high magnification), and they ensure that a substantial portion of the light entering the camera embodiment reaches the sensor to form an image (thus enabling camera operation in low light, e.g., at night). The resulting embodiment enables a compact camera or imaging system that can achieve both high magnification and low light operation.

[0088] For example, optical elements can be added to further improve performance: for example, to reduce imaging aberrations, one or more lenses or focusing substrates can be added to the spherical or aspheric curved surfaces, before, between, or after the polarizers and rotators.

[0089] It is also possible to add an additional turning mirror or cornering prism, for example just before or just after the first lens, so that the optical path is turned substantially 90 degrees. This can allow the imaging system to operate along the length (rather than the width) of the mobile device, thereby increasing the available length for the optical path.

[0090] FIG. 8 shows the embodiment of FIG. 1, but with the addition of a turning mirror (205). This mirror allows the sensor to be rotated to a substantially 90 degree orientation compared to FIG. 1. If desired, it is also possible to further increase the optical path lens, but the inventors note, as before, that this increase may be less advantageous than increasing the distance from the beam splitter 202 to the mirror 204, since the distance is traversed twice by the light (103, 104 and 105, 106), thus allowing a larger increase in the total optical path length for a given increase in the volume of the camera. The inventors also disclose that the turning mirror may be oriented differently, so that the sensor (401) can be in the plane of the page of FIG. 8, rather than being oriented vertically.

[0091] Figures 9 and 10 illustrate that turning mirrors can be added to both channels of the embodiment of Figure 6, or the designer can choose to add a turning mirror to one channel but not the other. Now, Figure 10 shows how the variant of Figure 9 has the correct size and scale to be included in a smartphone. Compared to Figure 6, the variants of Figures 9, 10 allow both sensors (401 and 405) to be rotated substantially 90 degrees. Alternatively, only one of them can be rotated substantially 90 degrees if so desired.

[0092] Such an additional turning mirror can be added to other disclosed embodiments if so desired. The turning mirror can also be a cornering prism. Moreover, it can be any element that acts as a reflector. For example, a polarizer that does not pass (reflects) vertically polarized light can also function as a mirror in the examples of FIG. 8, FIG. 9, or FIG. 10. For example, replacing element 205 in FIG. 8, FIG. 9, or FIG. 10 with a polarizer oriented to reflect polarized light back down the light path (107) would make that element act as a reflector and is contemplated in this disclosure. It is also contemplated to orient the added reflective surface so that the light is redirected in other directions, for example, in the + or -Z direction in FIG. 10. Doing so would allow one or both of the sensors (401 and 451) to be oriented in the YX plane of FIG. 10.

[0093] Those skilled in the optical arts will recognize that there may be other modifications and variations possible in light of the above teachings or which may be acquired from practice of the invention. Such modifications as are suitable for the particular use contemplated are anticipated and are covered by this disclosure.

[0094] In some embodiments, a single lens can be replaced with a lens group, or additional lenses can be added before or between the other elements. An aperture, such as aperture 701 in Figures 3 and 10, can also be replaced by a lens or lenses. Or, conversely, the first lens (e.g., lens 201 in the figures) can be replaced by an aperture, with the required lens placed after the aperture.

[0095] It is disclosed that the elements or their surfaces can be curved instead of being flat. Alternatively, curved optical surfaces can be placed in front of or after the disclosed elements. Specifically, the mirrors or mirror surfaces can be curved, either spherical or aspherical. In Figs. 1-11, the reflecting mirrors can be curved. If the quarter wave plate (e.g., 203 in Figs. 1-11) remains a flat element, but it is desired to bend the light coming to or leaving it, a curved optical lens or half lens can be placed in front of 203, after 203, or both. Furthermore, if such components are available, one, some, or all of the polarizers and wave plates can be curved or shaped instead of remaining flat. In general, one, some, or many of the elements can be curved or have curved surfaces, or have curved optical elements in front of or after them.

[0096] Any of the optical elements in the embodiments may be moved, e.g., translated or tilted, over time, or for some element types, their shape may be adapted over time. Such movement or shape change is commonly used to change focus and / or correct video jitter in cameras and imaging systems, and the same can be used in the systems disclosed herein. There are many means 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 movements is disclosed with respect to our embodiments.

[0097] Specific embodiments disclosed can enable more camera performance for the same amount of element movement. For example, consider the embodiment of FIG. 1. If mirror 204 is moved to the right by an amount ΔX, the change in optical path length is twice that amount, 2ΔX. This is shown in more detail in FIG. 11. For a mirror movement ΔX (labeled 4), light from lens (201) to sensor (401) traverses the distance the mirror has been displaced twice. It traverses it in the forward direction (added optical path 114) and again in the return direction (added optical path 115).

[0098] The above double-the-motion benefits are advantageous for small camera applications, including cameras in smartphones and other mobile devices. In such cameras, the amount of space available for element movement is limited. It is therefore highly desirable to extract more optical path change, and therefore more focusing change, from the same amount of element movement. The above advantages have been presented in relation to the embodiment of FIG. 1, but apply equally to other embodiments presented herein.

[0099] For example, as shown in Figures 2, 3, 5, and 10, there is free space shown between components, such as free space in the -X direction between the polarizing beam splitter (202) and the sensor (401) in Figures 2 and 3. However, this is done primarily for clarity of illustration so that the reader can easily see all of the components of the invention. The inventors note that this free space may be retained, or the components may be moved closer together as desired or permitted by manufacturing or other considerations, and doing so is anticipated and disclosed.

[0100] The disclosed embodiments are selected to enable low light operation in addition to high magnification. Low light is achieved by inventively selecting a design that delivers a significant portion of light, e.g., almost all of the light of one type of polarization, to the sensor. The inventors note that delivering a significant amount of light to the sensor allows for a better signal-to-noise ratio. If more light reaches the sensor, the signal from the object or scene is high compared to the dark noise level of the imaging sensor (dark noise is the amount of sensor noise when no light reaches the sensor). By keeping the amount of light reaching the sensor at a high level, the signal-to-noise ratio is increased, which in turn allows the camera to operate well with less light, i.e., at lower light levels.

[0101] Particular embodiments may utilize linear and circular polarizer elements. Such polarizing elements may include, but are not limited to, thin film polarizers, microwire grid polarizers, wave plates, liquid crystal rotators, Fresnel rhombuses, and similar devices. One or more of the polarizers may be tunable polarizers, such as liquid crystal polarizers, whose polarization orientation may be changed by applying a voltage. Polarization rotators, such as quarter-wave rotators, may be implemented through a number of different means and may also be tunable.

[0102] The disclosed polarizing beam splitters referred to in the embodiments can also be polarizing beam splitter cubes, plate polarizing splitters, Glan-Thompson prisms, microgrid polarizers, reflective polarizing films, or any other type of beam splitting polarizer.Similarly, the quarter wave plate can also be a quarter wave rotator or retarder, a Fresnel-Rhomb retarder, a birefringent crystal, a material or component with different refractive indices that achieves retardation of light preferentially along one axis over another, a material or component that dephases one element of light polarization from another, or any other type of wave plate retarder.

[0103] The mirror or reflector may be fabricated from a metal, semiconductor, or dielectric substrate and coated with a reflective metal or multilayer dielectric reflector, or any other type of reflective or mirror component, such as those used in smartphone cameras or other types of cameras or imaging systems.

[0104] The imaging sensor can be a time-integrating sensor, a charge-coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, an avalanche photodiode array, a photomultiplier array, a nanoparticle or nanomaterial-based sensor, a grayscale or color sensor, any type of sensor used in smartphone or mobile device cameras, or any other type of sensor.

[0105] It is understood that the various stated numbers are not exact values ​​and may have variations. For example, a quarter wave plate or quarter wave rotator introduces a phase shift of substantially 90 degrees (pi / 2) of light. However, this amount is not and need not be exactly 90 degrees, both for light optics reasons (light at different angles of incidence, or light of different wavelengths, undergoes different phase shifts) and for engineering or manufacturing reasons (e.g., variations in wave plate thickness due to manufacturing variations) that also introduce variations in phase shift. This disclosure covers such variations away from the "ideal" 90 degree phase shift value, both for unavoidable reasons (as described above) or for intended reasons where a system designer wishes to vary the phase to accommodate system constraints. Other similar cases, such as "90 degrees or 45 degrees" polarization, "5x or 15x" magnification, etc., are covered as well and are understood to be examples or approximations.

[0106] Some numbers are also understood to include their logically opposite sign counterparts. For example, those skilled in the art of optics will recognize that the systems disclosed herein will work equally well if +90 or +45 degrees are replaced by -90 or -45 degrees, as long as the interrelationship of the embodiments between the polarizations remains self-consistent. Similarly, for linear polarization, for left or right circular polarization, or for elliptical polarization, there is a change in sign or the addition of an overall positive or negative phase that does not change the system operation. It is understood that such substitutions are anticipated and are covered by the present disclosure.

[0107] For example, with reference to Figures 1-11, specific embodiments can operate with the polarizing beam splitter and other components selected such that each horizontally polarized light (labeled "H" in the figures) is replaced by a vertically polarized light ("V") and vice versa. For example, in Figure 1, the polarizing beam splitter 202 can be oriented such that 103 is vertically linearly polarized ("V" instead of "H") and then the return path 106 is horizontally ("H") polarized. It is still possible for the light exiting and returning from the polarizing beam splitter (202) to differ by 90 degrees, and thus the overall path of the light and system operation would remain as shown in Figure 1 (except that every "H" is replaced by a "V" and vice versa). In this sense, changing the orientation of the polarizing beam splitter (202) by 90 degrees would leave the system operable and is anticipated and disclosed.

[0108] Changing the orientation of the polarizing beam splitter (202) by any other angle other than 90 degrees, or any change to any convention for what is chosen to be called horizontal or vertical polarization, would also leave the system operational. Any such change is understood to be the addition of any phase angle, which can be selected as desired (e.g., to align the polarization at the sensor with an axis that is convenient for the design of the system), and is also anticipated and disclosed, as is understood and disclosed for the embodiment of FIG. 1, as well as for other embodiments disclosed in this invention.

[0109] The term "polarizing beam splitter" refers to a polarizing beam splitter that splits incident unpolarized light into two orthogonally polarized beams. Most high performance polarizers are based on birefringent crystals. Unpolarized light is projected internally onto an inclined surface that transmits one polarization and reflects the other.

[0110] The phase-shifted combination of linear polarization states produces what is called a circular polarization state. Circular polarization can be left-handed (rotates counterclockwise as the beam propagates) or right-handed (rotates clockwise). It is disclosed that left and right polarization states are orthogonal and therefore can also be used as polarization states in the disclosed invention, similar to how horizontal and vertical linear polarizations are used. There are also elliptical polarization states that are neither perfectly linear nor perfectly circular, but are combinations. The inventors disclose that elliptical polarization states are also contemplated and can also be used in the present invention. It is known that the Poincaré sphere can be used to represent polarization states, and that any polarization (linear, circular, or elliptical) can be represented on this sphere. The inventors disclose that linear and circular polarizations are just specific special cases, and more generally, the invention disclosed herein can use polarizations that are anywhere on the Poincaré sphere, for example, substantially orthogonal to each other, or polarizations that occupy points that are not directly adjacent on the Poincaré sphere.

[0111] It is further disclosed that there are many known means to actually achieve 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 conventional grinding and polishing, single point diamond turning, molding, 3D printing, or lithographic definition. In addition, lenses or substrates with focal lengths can also be made by holography, diffractive optics, diffraction gratings, two-dimensional and three-dimensional photonic crystals, microstructured metal and dielectric materials, and metalenses using refractive index gradient materials. Polarizers can be made from a variety of materials, such as polymeric materials with oriented polymer chains like Polaroid polarizers, liquid crystal materials, glass, oriented elongated metal nanoparticles embedded in crystals or polymers, Fresnel reflections from dielectric surfaces, birefringent crystal materials, thin films and microscale wire grid materials, or other materials.

[0112] Waveplates or wavelength rotators can be made from a variety of birefringent materials, such as thin films of crystalline materials, oriented polymers, liquid crystal materials, and prism-based rotators, or other materials.

[0113] 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 have been chosen and described to explain the principles of the invention and its practical application, and to enable those skilled in the art to utilize the invention in various embodiments. Modifications are anticipated and covered by the present disclosure as appropriate for the particular use contemplated.

Claims

1. 1. An imaging system for capturing light to form an image, comprising: a polarizing beam splitter; a substrate having a focal length; A wave plate; A reflector and an imaging sensor; 1. An imaging system, wherein the polarizing beam splitter, the wave plate, the substrate having a focal length, and the reflector are arranged along an axis, the substrate being positioned between the polarizing beam splitter and the reflector, and the wave plate being positioned between the polarizing beam splitter and the wave plate.

2. The system of claim 1 , wherein the sensor captures the image with light reaching the sensor.

3. The system of claim 1 , wherein the image is at a focus.

4. The system of claim 1 , wherein the wave plate is a quarter wave plate.

5. The system of claim 1 , wherein the substrate is a lens.

6. The system of claim 1 , wherein the substrate is between the polarizing beam splitter and the wave plate.

7. The system of claim 1 , wherein the substrate is between the wave plate and the reflector.

8. The system of claim 1 , wherein the reflector is a mirror.

9. The system of claim 1 , wherein the path of light reflected by the polarizing beam splitter forms an angle of approximately 90° with the incident light.

10. The system of claim 1 , wherein the sensor is aligned with an axis at an exit port of the polarizing beam splitter.

11. 5. The system of claim 4, wherein the optical axis of the quarter wave plate is rotated 45 degrees relative to the polarization direction of the light reflected by the polarizing beam splitter.

12. 10. The system of claim 1, further comprising a second substrate having a second focal length, the second substrate being aligned substantially off-axis at the entrance port of the polarizing beam splitter.

13. The system of claim 1 , wherein the sensor is aligned off-axis at the exit port of the polarizing beam splitter.

14. 5. The system of claim 4, wherein the optical axis of the quarter wave plate is rotated 45 degrees relative to the polarization direction of light transmitted by the polarizing beam splitter.

15. The method of claim 1 , wherein the photograph or video is taken under low light conditions.

16. 1. A method for performing high magnification imaging, comprising: Receiving light from the scene, reflecting and polarizing the light to a first linear polarization; transmitting the light through a substrate having a focal length; reflecting said light; rotating the polarization of the light to a polarization orthogonal to the first linear polarization, the light being orthogonally polarized light; transmitting the orthogonally polarized light through a sensor to form an image; capturing an image of the scene.

17. The method of claim 16 , wherein the light is reflected off a polarizing beam splitter.

18. The method of claim 16 , wherein a polarizing beam splitter polarizes the light and reflects the light to the sensor.

19. The method of claim 16 , wherein a waveplate rotates the polarization of the light.

20. The method of claim 16 , wherein the focal length of the imaging system is matched to the round-trip optical path length.

21. 17. The method of claim 16, further comprising autofocusing the image using PDAF (phase detection autofocus) sensing.

22. 1. An imaging system that captures light to form an image, comprising: a polarizing beam splitter; a substrate having a focal length; A wave plate; A reflector and an imaging sensor positioned to receive light from the polarizing beam splitter; 1. An imaging system, wherein the polarizing beam splitter, the wave plate, the substrate having a focal length, and a reflector are arranged along an axis, and the wave plate is positioned between the polarizing beam splitter and the reflector.

23. 23. The imaging system of claim 22, wherein light is reflected to propagate in an opposite direction relative to the input optical path.

24. 23. The imaging system of claim 22, wherein light is reflected to propagate in a direction orthogonal to the input optical path.

25. 23. The imaging system of claim 22, wherein a polarizing beam splitter polarizes the light and diverts the reflected light to the sensor.

26. The imaging system of claim 22 , wherein a waveplate rotates the polarization of the light.

Images