阅读说明：本技术 具有增强视野的单中心多尺度(mms)相机 (Single center multi-scale (MMS) camera with enhanced field of view ) 是由 庞武斌 戴维·琼斯·布雷迪 于 2019-02-15 设计创作，主要内容包括：本发明揭示有利地展现增强视野FoV的各种布置的单中心多尺度成像系统及相机。此类系统的说明性实例包含从圆环区域有利地捕获大约500兆像素的图像的360°环形FoV MMS透镜。另外,通过改变微型相机成像通道配置,揭示一种范围有利地可从15mm到40mm的提供具有大不相同的成像放大倍率的场景覆盖的多焦点设计。最终,额外说明性配置组合多个MMS系统使得覆盖了4π空间中的任意立体角。(Single center multi-scale imaging systems and cameras that advantageously exhibit various arrangements of enhanced field of view FoV are disclosed. An illustrative example of such a system includes a 360 ° annular FoV MMS lens that advantageously captures an image of approximately 500 megapixels from an annular region. Additionally, by varying the miniature camera imaging channel configuration, a multi-focal design is disclosed that advantageously can range from 15mm to 40mm providing scene coverage with widely differing imaging magnifications. Finally, additional illustrative configurations combine multiple MMS systems to cover an arbitrary solid angle in 4 pi space.)

1. A single-center multi-scale optical system MMS, comprising:

a galileo MMS lens configuration produced by a distorted icosahedral geodesic method, said configuration comprising a plurality of individual cameras positioned to produce a top hemispherical arrangement of a circular field of view FoV.

2. A single-center multi-scale optical system MMS, comprising:

a galileo MMS lens configuration including a plurality of imaging channels, each of the plurality of imaging channels exhibiting an overlap of a portion of an adjacent imaging channel, each of the individual channels exhibiting a different focal length from one another.

3. A single-center multi-scale optical system MMS, comprising:

at least three MMS lens configurations positioned in a back-to-back arrangement along a common plane such that a 360 degree horizontal field of view along that plane is created.

4. The single-center multi-scale optical system of claim 3, wherein:

each of the individual MMS lenses exhibits a horizontal field of view FoV greater than 120 degrees.

5. A single-center multi-scale optical system MMS, comprising:

at least three MMS lens configurations arranged vertically along a common central axis, each individual one of the MMS lens configurations being configured to provide a portion of a 360 horizontal field of view.

Technical Field

The present invention relates generally to optics and digital imaging, and more particularly to an imaging system including large pixel counts of a single-center multi-scale camera with an enhanced field of view.

Background

As those skilled in the art will readily appreciate, digital imaging systems, methods and structures are employed in an increasing number of applications and have become an integral part of every industry that is envisioned-the manufacture, creation, storage, analysis and dissemination of images.

In view of this importance, improved systems, methods, and structures for digital imaging-and in particular-systems, methods, and structures that facilitate the development of large pixel count imaging (gigapixels) -would represent a welcome addition to the art.

Disclosure of Invention

In accordance with aspects of the present invention, improvements in systems, methods, and structures related to single-center multi-scale imaging systems and cameras with enhanced field of view compared to the prior art are made in the art.

In sharp contrast to the prior art, the arrangement of a single-center multi-scale imaging system and camera according to the present invention illustratively provides a 360 ° annular FoV MMS lens that advantageously captures an image of about 500 megapixels from an annular region. Additionally, by changing the miniature camera imaging channel configuration, a multi-focal design is disclosed that can advantageously range from 15mm to 40mm, providing scene coverage with widely differing imaging magnifications. Finally, additional illustrative configurations combine multiple MMS systems such that an arbitrary solid angle in 4 pi space is covered.

This summary is provided to briefly identify some aspects of the present invention that are further described below in the detailed description. This summary is not intended to identify key or essential features of the invention or to limit the scope of any claims.

The term "aspect" should be read as "at least one aspect". The aspects described above and other aspects of the present invention are illustrated by way of example and not limited in the accompanying figures.

Drawings

A more complete understanding of the present invention may be obtained by reference to the accompanying drawings, in which:

FIG. 1 shows a schematic diagram illustrating hexagonal close-packing for localizing FoV output, according to an aspect of the present invention;

FIG. 2 shows an illustrative close packing of 492 circles on a spherical surface using a distorted icosahedron geodesic method, in accordance with aspects of the present invention;

FIG. 3 shows an illustrative diagram of the obscuration that occurs when two miniature cameras are positioned in the optical path of each other, according to an aspect of the present invention;

fig. 4(a) and 4(B) show the calculation of the maximum packing angle cFov, according to an aspect of the present invention, where: FIG. 4(A) illustrates the optical path of one channel in the MMS lens; and FIG. 4(B) illustrates the maximum bank angle given the specified design parameters;

fig. 5(a), 5(B) and 5(C) show schematic diagrams of an illustrative MMS optical imaging system with an annular FoV in accordance with the present invention, wherein: FIG. 5(A) shows an MMS camera on a pole of a FoV with an annular region, while FIG. 5(B) shows 165 circles stacked on a band on the top hemisphere with a polar angle ranging from 43 ° to 76 °, while FIG. 5(C) shows an illustrative layout of an MMS lens design;

fig. 6(a) and 6(B) show illustrative imaging performance of a 360-ring shaped MMS lens, wherein: FIG. 6(A) shows an illustrative layout of one channel of a 360-ring Fov MMS lens design, while FIG. 6(B) shows an illustrative MTF curve according to an aspect of the invention;

fig. 7(a), 7(B), and 7(C) show schematic diagrams of illustrative multifocal systems in which: FIG. 7(A) illustrates monitoring traffic from one end along a street, while FIG. 7(B) shows an illustrative plurality of imaging channels employing optics, and FIG. 7(B) shows an optical layout of a multi-focus system according to aspects of the present invention;

fig. 8(a), 8(B) and 8(C) show graphs of MTF curves for each channel in a multifocal MMS lens design, according to aspects of the present invention, in which: FIG. 8(A) MTF of FoV on axis; FIG. 8(B) shows the MTF of 0.707FoV, and FIG. 8(C) shows the MTF of the edge FoV;

fig. 9(a) and 9(B) show an illustrative method of a 360 ° horizontal FoV optic, according to an aspect of the present invention, including: fig. 9(a) shows an illustrative layout including three back-to-back MMS lenses, and fig. 9(B) shows an illustrative interleaving strategy with stacked MMS lenses;

FIG. 10 shows an illustrative miniature camera and optical window of a 360 ° horizontal FOV imager in accordance with aspects of the present invention;

fig. 11(a) and 11(B) show illustrative tetrahedral configurations of a full spherical MMS lens in accordance with aspects of the present invention, wherein: FIG. 11(A) shows an illustrative spatial division with four MMS lenses, each covering a quarter of a full sphere; and FIG. 11(B) illustratively shows a close-packed miniature camera on one of the four segments;

fig. 12 shows an illustrative layout diagram of a full-spherical MMS lens in accordance with aspects of the present invention.

Detailed Description

The following merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. More particularly, while numerous specific details are set forth, it will be understood that embodiments of the invention may be practiced without these specific details, and in other instances, well-known circuits, structures and techniques have not been shown in order not to obscure the understanding of the present invention.

Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

Thus, for example, it should be appreciated by those skilled in the art that the diagrams herein represent conceptual views of illustrative structures embodying the principles of the invention.

Additionally, those skilled in the art will appreciate that particular methods according to the disclosure can represent various processes which may be substantially represented in computer readable media and so controlled and/or controlled by a computer or processor, whether or not such computer or processor is explicitly shown.

In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example: a) a combination of circuit elements that performs that function; or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicant thus regards any means that can provide those functionalities as equivalent as those shown herein. Finally, and unless explicitly specified otherwise herein, the drawings are not to scale.

With some additional background, we first note that the demand for billion pixel-level cameras and imaging systems has steadily grown in view of their well-established utilization in a variety of applications including broadcast media, imaging, virtual reality, flight control, transportation management, security and environmental monitoring, and the like. Despite this tremendous demand, the utilization of such gigapixel systems is reduced due in part to the cost and system complexity of such systems and the recognized computational and communication challenges of gigapixel image management.

In view of these shortcomings, the art has generated tremendous enthusiasm for single-center multi-scale (MMS) imaging systems and cameras, which can advantageously reduce the cost and complexity of billion pixel imaging systems due to several design and technological breakthroughs. Notably, and as should be readily appreciated by those skilled in the art, MMS imaging systems and cameras advantageously achieve both high angular resolution and a wide field of view (FOV) in a gigapixel-level system. In contrast to gigapixel astronomical telescopes and lithography lenses, MMS imaging systems and cameras according to the present invention can be advantageously manufactured and assembled using commercially available off-the-shelf components and methods, which can only be implemented in a precisely controllable laboratory environment with specially developed tools and materials.

We note that the architecture of the illustrative MMS system generally resembles that of a telescope. More particularly, a single-layer single-center spherical objective is shared by several miniature cameras, where each miniature camera covers a portion of the overall FOV-denoted miniature camera FOV (mfov). We further note that refractive telescopes can be classified as Keplerian (Keplerian) systems with internal image surfaces and Galilean (Galilean) systems with secondary optics positioned in front of the objective focal plane. However, while MMS systems can be designed according to either of these two classifications, and galileo systems enable smaller physical dimensions, prior art MMS imaging systems and cameras all employ keplerian designs because such architectures more readily accommodate the overlap between adjacent miniature camera FOVs and because they are easier to construct.

As will be understood and appreciated by those skilled in the art, the field of view (FoV) and instantaneous field of view (iFoV) are two basic measures of camera performance. Conventionally, FoV describes the angular range of a cone around the optical axis observed by a camera. As is known, fish-eye lenses have long been used to achieve wide field-of-view imaging. For example, Ricoh Theta and Samsung Gear 360 capture a 360 ° × 180 ° image. Despite this impressive FoV, distortions and aberrations in the fish-eye system severely limit the iFoV. For at least this reason, systems that capture a wide field of view by computationally stitching images obtained using time scanning or camera arrays have become increasingly popular. Note that higher resolution full solid angle imaging has been implemented in camera arrays like Facebook Surround 360.

Several platforms have recently been developed that generalize 360-camera designs to include more diverse parallel camera architectures. While camera arrays can be designed to cover any FoV and iFoV, the cost of such systems increases non-linearly as iFoV decreases. One basic problem is that as iFoV decreases, the entrance aperture must increase. Those skilled in the art will readily appreciate that the lens cost increases non-linearly with the entrance aperture size, and this cost will still increase further if the FoV per microlens is reduced as is conventionally required by scaling-since the number of microlenses required to fill a given field of view must also increase as the iFoV decreases.

In sharp contrast, multi-scale designs have been shown in which parallel miniature camera arrays share a common objective lens to allow for wide FoV over a wide range of aperture scales. Single-center multi-scale (MMS) designs using spherical objectives mounted on spherical shells and miniature cameras are particularly effective in this regard.

Although the applicant's previous work has focused primarily on multi-scale designs of lens systems with conventional conical FoV, the present invention describes a novel MMS design suitable for wide-angle applications typically associated with fisheye lenses and annular camera arrays.

In this regard, we note that focus control presents a significant challenge for conventional wide field-of-view imaging systems. More specifically, even though a fish-eye lens may be reasonably focused on a scene in one configuration, such lens design for focus adjustment is extremely challenging. Also, although we do not explicitly discuss focus adjustment in this invention, we note that the ability to independently and locally control the focus state in each miniature camera of an MMS system is a particular advantage of such MMS systems. Nevertheless, we recognize the importance of the work related to the focus control strategies and note that these strategies can be implemented in the systems disclosed herein. We now show how the spherical geometry of the MMS system allows various novel field of view alignments, according to aspects of the present invention.

By way of illustrative example, we note that security cameras are typically mounted on a ceiling or pole that overlooks the field of view of the target. In addition to such installations, modern systems typically incorporate a mechanical horizontal tilt-zoom assembly that allows the camera to scan a wide field of view at high resolution.

Alternatively, such a security camera system may combine a wide-angle point-to-point camera with a long-focus narrow-field-of-view pan camera. In operation, when an event of interest is recorded by a wide-angle camera, a long focal length narrow field-of-view pan camera will be oriented into the event and capture high resolution details.

However, as should be readily appreciated by those skilled in the art, there are at least three disadvantages with such camera system configurations. First, only one region of the full field of view is captured at high resolution. Second, response time and mechanical movement speed may be limited to keep up with rapidly changing events-especially when multiple events occur simultaneously. Third, the mechanical components may make the overall system unreliable and plague high maintenance costs.

In sharp contrast, MMS achieves a wide field of view and high resolution in real time. With this architecture, the performance of the parallel small aperture optical device is superior to that of a conventional single aperture lens, thereby significantly improving the information efficiency. In addition, the shared objective of MMS makes the layout more compact compared to the layout of a multi-camera cluster. Since the MMS imaging sensor is mounted on a spherical surface-as long as no significant mutual occlusion occurs-the object can be imaged from any spatial angle by a suitably configured miniature camera.

Those skilled in the art will know and appreciate that there are numerous ways to arrange an array of miniature cameras, and thus also numerous ways to configure a FoV. This flexibility provides tremendous opportunities for different FoV configurations and other camera settings for various application scenarios. In addition to the arrangement flexibility of one MMS lens, more configurations can be realized by using a plurality of MMS lenses as a combination.

As an illustrative example, we have previously described a design for compact wide field-of-view imaging using three MMS systems. In this disclosure, we now disclose and describe enhancements to our design to include compact 360-ring cameras, multi-focal length/extended depth of field systems, and global imaging systems. However, we note that the illustrative design presented herein is intended to serve as a brief illustration of the potential of a system constructed in accordance with the invention-indeed, a system can be constructed that covers any field of view and depth of field.

As should be readily understood by those skilled in the art, conventional cameras capture images in a rectangular format due to the format of the film, electronic sensor, and display device. In most cases, the captured FoV plan is streamed in its entirety for rendering, e.g., the FoV shape/format of any captured image data is determined by the rendering convention employed.

However, with advances in optics, electronics, and computing technology, this tight coupling between image capture and rendering needs to be decoupled to further utilize the image information and further create novel functionality. We note that any image format can be achieved by combining image frames derived from multiple focal planes. In addition, as new image and video rendering technologies are explored and subsequently developed, alternative image navigation methods will be readily available for developing new rendering approaches.

As will be further understood and appreciated by those skilled in the art, MMS lenses extend their FOV by adding small-sized auxiliary lenses. The resulting ultra-high information capacity advantageously allows for countless FoV configuration options and image resolution formats, which provides broad applicability to new and different application scenarios.

As will be known and appreciated by those skilled in the art-in systems that include an MMS architecture, miniature cameras are stacked or otherwise positioned on a spherical surface. Thus, the range and format of the captured FoV is determined by the way the miniature cameras are stacked. Also, while this positioning/packing is a relatively trivial task in the case of 2D planes, close packing on a sphere can be more challenging.

We note that, depending on the extent of the target pile-up region, local pile-up or global pile-up strategies may be preferred. A local pile-up strategy is preferred if the pile-up region comprises only a small portion of a complete sphere on which the miniature camera will be positioned.

Turning now to fig. 1, a schematic diagram illustrating hexagonal close packing for localizing FoV output according to aspects of the present invention is shown. As illustratively shown in this figure, the packed area covers approximately 90 ° × 50 ° FoV, and with hexagonal close packing, the miniature cameras are aligned along the weft. This stacking method produces a near rectangular FoV overlay, similarly producing a conventional image format with a soxhlet defined by:

empirically, aspect ratios less than 0.17 produce less disturbance and uniform packing density, which results in high image quality and reduced lens complexity. Following this rule of thumb, the hexagonal packing strategy can only achieve a latitude angle span of up to 60 °.

We note that previous additional work has implemented a stacking strategy based on a distorted icosahedron geodesic. By iteratively subdividing the regular icosahedron projected onto a sphere, this strategy produces an approximately uniformly distributed circular grid across the earth.

Fig. 2 shows an illustrative close packing of 492 circles on a spherical surface using a distorted icosahedron deionization method (strategy) in accordance with an aspect of the present invention. Even with this extensive global packing approach, the overall extent of the packing region is still limited because the optical paths from different channels may interfere with each other.

FIG. 3 shows an illustrative diagram of the obscuration that occurs when two miniature cameras are positioned in the optical path of each other, according to an aspect of the present invention. As can be seen from fig. 3, when the close-packed region extends to about 180 °, the optical path is disturbed by the sensor located on the opposite side of the sphere (i.e., the spherical lens). Of course, the maximum stack angle also depends on the specifications of the optical system used.

In this regard, we can now estimate the maximum angle cFoV within which the light path remains unobstructed. We note that galileo style MMS lenses exhibit the following parameters: focal length of spherical objective lens is f_oRadius of the objective lens is R, and distance between the diaphragm and the center of the objective lens is d_osThe center of the entrance pupil and the center of the objective lens are lHalf of the FoV angle of each sub-imager is α.

Fig. 4(a) and 4(B) show the calculation of the maximum packing angle cFov, where: FIG. 4(A) illustrates the optical path of one channel in the MMS lens; and fig. 4(B) illustrates the maximum bank angle given specified design parameters in accordance with aspects of the present invention.

As depicted in fig. 4(a), the imaging channels are positioned on the edge of the multi-channel MMS system. The line connecting the point of incidence of the marginal ray with the center of the objective serves as the other edge of the multi-channel system. If all channels are bounded by cones contained by these two edges, the system is unobstructed.

The net half diameter of the objective lens can be approximated as:

where f is the total effective focal length.

The free angle cFoV can be determined from the following relationship:

assuming that the main parameters are F20 mm, F/#2.5, F₀＝47.06，R＝21.11mm，d_osAn illustrative design of 27.49mm, α, 5.7, and substituting these parameters into EQN. (2) and EQN. (3), we have a clear FoV angle, i.e., cFoV 77.35 °.

Fig. 4(B) shows this free-stacking lid as the top of a sphere illustrated herein. As we will now describe, this set of design specifications will be used to show an illustrative configuration with a circular FoV.

We note-and as should be readily appreciated by those skilled in the art-cameras with a circular field of view benefit numerous modern applications-such as for security purposes in parks, squares, traffic circles, and entryways/exits where the view of the top and bottom with the content is not critical. 360 ° loop FoV cameras have been developed to improve the perception of context in surveillance, navigation applications, and Virtual Reality (VR) and Augmented Reality (AR) for stereo effects [19 ]. 360 ° photography is also known as panoramic imaging. A common method of performing panoramic imaging is to lay down multiple cameras into a circle. As mentioned previously, this approach typically ends with bulky and expensive hardware. The remainder of this section shows how the MMS architecture handles this issue with excellent flexibility.

Fig. 5(a), 5(B) and 5(C) show schematic diagrams of an illustrative MMS optical imaging system with an annular FoV in accordance with the present invention, wherein: fig. 5(a) shows an MMS camera on a pole of a FoV with a ring-shaped area, while fig. 5(B) shows 165 circles stacked on a band on the top hemisphere with a polar angle ranging from 43 ° to 76 °, while fig. 5(C) shows an illustrative layout of an MMS lens design.

As illustrated in fig. 5(a), consider an arrangement in which the camera is mounted on the top of a pole 4m high from the ground. The viewing angle of the camera (the angle formed by the upright and the dashed line) is 45 when aimed at the inner boundary and 75 when aimed at the outer boundary. By simple calculation, the radius of the inner boundary is 4m, while the radius of the outer boundary is about 14.93 m. The distance between the inner circle and the camera is about 5.67m and the distance between the outer circle and the camera is about 15.45 m.

A square image sensor chip would be ideal for MMS lens design because of its advantages in generating mosaics. The effective focal length f is chosen to be 20mm, which is sufficient to meet the required angular resolution. The aperture size is F/# ═ 2.5, and the FoV for each sub-imager (miniature camera) is 11.4 °.

Since the surveillance area covers a wide area of a hemisphere, the local pile-up approach can result in poor quality in terms of pile-up uniformity. Here we configure the MMS lens by choosing a set of circular grooves that result from the twisted icosahedron geodesic method previously shown in fig. 2. The respective slots with miniature cameras are highlighted in patches in fig. 5(B), and the layout of the corresponding optical design is shown in fig. 5 (C).

Fig. 6(a) and 6(B) show illustrative imaging performance of a 360-ring shaped MMS lens, wherein: fig. 6(a) shows an illustrative layout of one channel of a 360-ring Fov MMS lens design, while fig. 6(B) shows an illustrative MTF curve according to an aspect of the present invention.

With reference to these figures, we note that another optical design now disclosed contains 165 miniature cameras, which cover polar angles from 43 ° to 76 °. Due to the discrete addition of the FoV in steps of 11.4 ° per channel, the covered FoV is not exactly equal to the required FoV.

Fig. 6(a) shows the size of one channel of the optical device. The radius of the spherical lens is 21.11mm and the total trajectory of the optics is 60 mm. The image area of each focal plane is 2.8mm × 2.8mm, and the resolvable pixel pitch, which can be estimated by the MTF curve shown in fig. 6(B), is about 1.67 μm, and thus, the resolution element of each focal plane is about 2.8 megapixels. The total resolution element is about 500 Mpixel.

As will be understood by those skilled in the art, for a single focal length camera, the magnification varies for objects of different distances. The farther an object is from the camera, the smaller the magnification. As will be appreciated, this property may lead to difficulties in recognizing objects spread over deep depths of view.

One solution to this problem is to employ a zoom lens. This zoom lens adjusts (zooms) to a long focal length for distant objects and a short focal length for near objects. Another alternative solution employs a camera cluster containing multiple cameras exhibiting different focal lengths, with the camera exhibiting the long focal length being used for distant objects and the camera exhibiting the short focal length being used for closer objects.

Compared to both technologies, the MMS lens architecture provides a more compact, more modular, and less expensive method of performing multi-focus imaging. In an MMS lens architecture, the total effective focal length of any individual channel can be changed by altering the design of its secondary optics. By applying different secondary optics, we can advantageously integrate multiple focal lengths within a single optical system.

Fig. 7(a), 7(B), and 7(C) show schematic diagrams of illustrative multifocal systems in which: fig. 7(a) illustrates monitoring traffic from one end along a street, while fig. 7(B) shows an illustrative plurality of imaging channels employing optics, and fig. 7(B) shows an optical layout of a multi-focus system according to aspects of the invention.

Fig. 7(a) illustratively shows an arrangement of streets supervised extending from one end of the street, where the object plane is a narrow slanted strip, as measured from the camera's perspective, which results in large object distance variations. In this illustrative arrangement, the viewing angle range is from 25 ° to 85 °. To capture the detailed information over the entire band, a multi-focus system is advantageously employed.

Fig. 7(B) shows an illustrative MMS lens covering different street segments with channels of different focal lengths. As the road segment moves away from the camera, the respective channel increases its focal length to achieve more uniform ground sampling.

Those skilled in the art will understand and appreciate that uniform sampling is not possible with limited field-of-view segmentation. However, we can attempt to obtain nominally uniform sampling with a multifocal imager having equal magnification in the axial field of view point of each channel. In this illustrative example, we can mount the camera 10m above the ground with each channel covering a 10 ° area with a 1.5 ° overlap between adjacent channels. With 7 channels, the total range of monitoring is about 110 m. The focal length for each channel and the corresponding object distance for the central field of view are listed in table 1.

Channel #	1	2	3	4	5	6	7
								Visual angle (degree)	30.0	38.5	47.0	55.5	64.0	72.5	81.0
Axial object Range (m)	11.55	12.78	14.66	17.66	22.81	33.26	63.92
								Focal length (mm)	15.00	16.38	18.48	21.71	27.00	36.73	59.39

TABLE 1 axial object Range for each imaging channel for quasi-uniform sampling Rate

With continued reference to this figure-and as shown in table 1-a uniform sampling rate across the street requires a focal range from 15mm to 59.39mm, which requires 4 x zoom capability. Unfortunately, however, our illustrative MMS design only achieves a focal range of 15mm to 40 mm. As a result, the 7 th channel cannot satisfy the quasi-uniform condition. Nevertheless, varying sensor spacing may be employed to compensate for this.

Fig. 7(C) shows an illustrative layout of this lens design and the size of some critical dimensions. The MTF curve for each channel is shown in fig. 8. For a given main objective, there is a best-matched system focal length at which optimal imaging performance can be achieved. However, when the focal length deviates from the optimal match, the performance may be slightly degraded.

Fig. 8(a), 8(B) and 8(C) show graphs of MTF curves for each channel in a multifocal MMS lens design, according to aspects of the present invention, in which: FIG. 8(A) MTF of FoV on axis; FIG. 8(B) shows the MTF exhibiting 0.707FoV, and FIG. 8(C) shows the MTF with edge FoV. As can be seen from these figures, channel 4 exhibits the highest MTF both on-axis and off-axis FoV, while satisfactory performance can be obtained due to the focal length scaling on either side being about 2.7 ×. Available detailed design prescription data is provided in table S2.

As previously discussed, optical path occlusion may prevent any FoV configuration of an MMS camera. Nevertheless, this limitation can be overcome by using multiple MMS cameras in combination. One such example that has been demonstrated is where multiple MMS lenses are co-aimed to stagger the continuous coverage of a wide FoV. Here, we disclose yet another example.

For the 360 ° annular FoV lens described previously, we note that the viewing angle ranges from 43 ° to 76 °. However, as illustratively shown in fig. 3, light blockage occurs when the coverage area is near the equator.

Fig. 9(a) and 9(B) show an illustrative method of a 360 ° horizontal FoV optic, according to an aspect of the present invention, including: fig. 9(a) shows an illustrative layout including three back-to-back MMS lenses, and fig. 9(B) shows an illustrative interleaving strategy with stacked MMS lenses.

As shown in fig. 9(a), one solution according to aspects of the invention is characterized by configuring three MMS lenses positioned back-to-back, each covering a FoV greater than 120 °. Collectively, a 360 ° panoramic image in the horizontal direction is captured without occlusion.

Another configuration according to an aspect of the present invention provides a spherical camera in which a free space is left between adjacent optics and sensors to pass light. To achieve this field of view using a multi-scale array, some miniature camera positions are saved for light passage. For continuous FoV coverage we combine together image blocks captured by multiple MMS cameras.

We now turn our attention to fig. 9(B), which schematically shows four MMS lenses, stacked vertically and staggered to fully cover a 360 ° horizontal FoV. In the simplest configuration, all four MMS cameras are identical, but are twisted relative to each other at staggered angular positions. The cone angle of each small circle is here 10 deg., and the number of circles along one orbit of the sphere is 36. While we have indicated that all four cameras are the same, those skilled in the art will know and appreciate that this identity is not necessary.

FIG. 10 shows an illustrative miniature camera and optical window of a 360 ° horizontal FOV imager in accordance with aspects of the present invention. As illustrated in the figures, each miniature camera is directed at a respective transparent tunnel, each transparent tunnel providing a horizontally arranged, pre-rounded view, which advantageously provides a nearly unobstructed optical channel. The detailed lens design data is shown in table S3.

Finally, we now present a final illustrative example, which is an omnidirectional camera that can be viewed with uniform angular resolution in all directions. Previously in the present invention we estimated that the maximum occlusion free angle of the MMS lens is less than 80 deg., which implies that a complete 4 pi spherical FoV coverage requires a minimum of 4 MMS lenses. Each of the four cameras is located at one of the vertices of a regular tetrahedron and covers a solid angle slightly larger than pi steradians. Additional coverage is used for overlap.

11(A) and 11(B) show illustrative tetrahedral configurations of a full spherical MMS lens, according to aspects of the present invention, wherein: FIG. 11(A) shows an illustrative spatial division with four MMS lenses, each covering a quarter of a full sphere; and figure 11(B) illustratively shows a closely packed miniature camera on one of the four segments.

As shown in fig. 11(a), the area projected by one triangular surface of the tetrahedron on its circumscribed sphere determines the minimum coverage area of each MMS lens. As shown in fig. 11(a), the maximum field angle of this triangular spherical block is 125.26 °. As shown in fig. 10(B), we cut stacked patches from the densely stacked spheres using the distorted icosahedron geodesic method.

Fig. 12 shows an illustrative layout diagram of a full-spherical MMS lens in accordance with aspects of the present invention. The configuration shown in the figure is a 4 pi full space camera, delimited by a sphere with a radius of 74 mm. Advantageously, this illustrative imager has the potential to employ the MMS lens design recipe used above in our first example and detailed in table S1 to achieve a uniform angular resolution of 83 μ rad over the entire spatial coverage.

To provide a quantitative perception of all the design examples disclosed herein, we provide table 2, which describes the field of view configuration, angular resolution, information capacity, and physical size of each example. This table helps to verify the effectiveness of the MMS lens architecture in building a high pixel count, multi-function field of view configuration camera with a compact small form factor.

Thus far, those skilled in the art will readily appreciate that, although methods, techniques, and structures according to the present disclosure have been described with respect to particular implementations and/or embodiments, those skilled in the art will recognize that the present disclosure is not so limited. Accordingly, the scope of the invention should be limited only by the attached claims.

Table 2.

Characterization of MMS lens design

TABLE S1 optical prescription data for rectangular, 360 Ring and full spherical FoV MMS lenses

TABLE S2 optical prescription data for multifocal MMS lenses

TABLE S3.360 design data for horizontal FoV MMS lenses