WO2019133101A2

WO2019133101A2 - Lidar systems and optical beam steering devices having neutrally buoyant reflectors therein

Info

Publication number: WO2019133101A2
Application number: PCT/US2018/057531
Authority: WO
Inventors: Andrew Carl Miner; Jonathan King Mapel
Original assignee: Mirada Technologies Inc.
Priority date: 2017-10-26
Filing date: 2018-10-25
Publication date: 2019-07-04
Also published as: WO2019133101A3

Abstract

A light-based detection and ranging (LiDAR) system may include a sealed container having a transparent window in a sidewall thereof. The sealed container may include a polygonal reflector therein, at a location adjacent the transparent window. An optically transparent fluid having a refractive index greater than 1.3, may be provided which surrounds the polygonal reflector within the container and extends between the polygonal reflector and the transparent window. The polygonal reflector and the optically transparent fluid may be configured to be neutrally buoyant relative to each other within the sealed container.

Description

LIDAR SYSTEMS AND OPTICAL BEAM STEERING DEVICES HAVING NEUTRALLY BUOYANT REFLECTORS THEREIN

Reference to Priority Applications

[0001] This application claims priority to U.S. Application Serial No.

15/897,977, filed February 15, 2018, and U.S. Provisional Application Serial No. 62/577,329, filed October 26, 2017, the disclosures of which are hereby incorporated herein by reference.

Field of the Invention

[0002] The invention relates to directing beams of light in specific directions using movable reflective surfaces, and in a robust, reliable manner.

Background of the Invention

[0003] Directing beams of light in specific directions has many applications, and many technologies exist that can accomplish this task. Light, also known as radiation, may be composed of a broad distribution of wavelengths (broad band), such as white light, or may be a very narrow band of wavelengths, such as produced from a typical laser (narrow band). The wavelengths that compose light may be in the visible range, detectable by our eyes, or outside the visible range. Light just beyond the visible range on the long wavelength side of the spectrum is known as infra-red radiation. Light just beyond the visible range on the short wavelength side of the spectrum is known as ultra- violet.

[0004] Beams of light may be directed by various means, but directing light by means of a reflecting, movable surface, or mirror, is the most relevant to the present invention. A technology that can provide a reflective surface, and move that reflective surface in a controlled, high speed manner can find application in uses such as microscopy, projection displays, laser sensors, Light Detection and Ranging (LiDAR) and similar. Should these technologies be enabled in a manner that makes them immune from distortion or damage due to external vibrations, accelerations, and gravitational orientations, the technologies become useful in a broader range of harsh conditions. [0005] There are a number of actuation technologies know in the prior art, when coupled to reflective mirrors provide controlled beam steering. For example, there are a variety of methods for actuation that utilize

electromagnetic effects. One method of directing light in a controlled manner at high speeds uses an electromagnetic device known as a galvanometer. This technology uses permanent magnets and/or ferromagnetic materials with electrical coils. Electrical current driven through the device initiates motion that can be controlled in a closed loop or an open loop manner. This actuation technology coupled to a mirror can provide a high speed

mechanism to control and direct light.

[0006] It has been observed that galvanometer-based technologies consume significant electrical power under operation, making them

incompatible for applications where electrical power is constrained. The electrical power consumption is largely a function of the mass of the mirror being moved, and the fact that significant energy is expended to accelerate the mirror to a position, then decelerate the mirror to stop at the desired position. The back and forth oscillatory nature of the devices is not as energetically favorable with respect to a technology that continuously rotates.

It has been further observed that the mechanical complexity of the

construction of galvanometer-based technologies limits the ability to miniaturize this technology to achieve low cost.

[0007] Light can also be directed in a controlled manner using mirror systems driven by voice coil actuators/motors (VCAs). Voice coil motors are typically relatively simple electrical devices, which are similar to a

galvanometer, and sometimes also called a solenoid. Electrical energy applied to the windings drives a core linearly, driven by magnetic repulsion. Voice coil motors coupled to the edges of a mirror can be actuated in a controlled manner to tile the mirror and effectively direct light.

[0008] It has been observed that voice coil mirror systems consume significant amounts of electrical power, and given that they have multiple parts including fine electrical windings, they are difficult to miniaturize at low cost. The electrical power consumption is largely a function of the mass of the mirror being moved, and the fact that significant energy is expended to accelerate the mirror to a position, then decelerate the mirror to stop at the desired position. The back and forth oscillatory nature of the devices is not as energetically favorable with respect to a technology that continuously rotates.

[0009] Another technology that uses reflective surfaces for directing light in a controlled manner is electrostatic actuation. This technology uses that fact that when voltage is applied across two surfaces at close proximity, positive and negative charges collect on the respective surface, and an attractive force is generated. This actuation effect can be applied in a beam steering technology by using the force generated, and the resulting motion of attractive surfaces to change the angle of a mirror.

[0010] It has been observed that electrostatic actuation results in small movements, which in turn, even when mechanically amplified into larger angles, results in modest angles of motion in the mirror.

[0011] Piezoelectric effects also can be coupled to a mirror for beam steering. Certain materials expand when subject to high voltages, in a process known as the piezoelectric effect. It has been observed that mirror systems driven by piezoelectric effects, similar to electrostatic actuators, deliver multiple angles of motion in the mirrors.

[0012] Electrothermal actuation can be used to drive controlled angular deflection in mirrors. This class of device takes advantage of the fact that most materials expand in length when heated. By careful design, electrical power can be dissipated selectively in electrothermal actuators to produce bending or linear extension. This motion can then be coupled with mirrors to deliver a beam steering effect.

[0013] It has been observed that electrothermal actuators are relatively slow, and do not produce high speed precision motion relative to other technologies. Additionally, they typically consume significant electrical power in order to generate the high temperatures in regions of the actuators. In order to produce high temperatures and the associated thermal expansion more efficiently, some such product package the actuators in vacuum or low thermal conductivity gasses, adding to the cost of the product.

[0014] The aforementioned actuation technologies that allow for the controlled steering of light can be realized using several different

manufacturing technologies. These technologies can be manufactured by traditional means, including machining, electrical winding, and hand assembly. Additionally, these beam steering technologies can be realized using semiconductor-like fabrication technologies, known as Micro-Electro- Mechanical Systems (MEMS).

[0015] As these devices are miniaturized, typically the actuation speeds that can be realized increase, due to the reduction in the amount of mass in motion. It has been observed that traditional manufacturing methods such as used in galvanometers and voice coil technologies do not scale down to small sized cost effectively. MEMS manufacturing technology has the capability of forming high precision mechanical structures at sub-millimeter scales, but it has been observed that the beam steering devices manufactured using MEMS fabrication, even when produced on large silicon wafer, do not achieve sufficiently low cost in high production volume. This is generally due to the complexity of each manufacturing step, the number of manufacturing steps, and the complex equipment typically required.

[0016] Another technology that is effective in directing beams of light in a controlled manner is known as a polygonal scanner, in which a polygon with reflective outer surfaces is rotated. Incident light reflecting of the rotating polygon’s perimeter is scanned in three-dimensional (3D) space based on the speed of the polygons, number of outer sides, and the angle of each mirror side. This approach is energetically favorable with respect to the oscillatory technologies where a mirror is accelerated and decelerated back and forth, but lacks the ability for the mirror to maintain a fixed position if required.

Polygonal scanner mirrors are typically mounted on a shaft on bearings, and is rotated using an electromagnetic motor. Polygonal scanners may be configured as a rotating plane with one or two sides that are reflective, or may be a multi-sided polygon with several hundred of reflective faces on the perimeter. Typical mirrors found in these devices have three to eight sides. The mirrors rotate on bearings that may be based on ball bearings or air bearing technology. Polygonal mirrors have found broad application in markets such as bar code readers, 3-D imaging, light detection and ranging (LiDAR), laser printing, and light shows for entertainment purposes.

Polygonal mirrors are typically formed in lightweight metals such as

aluminum, but some applications use copper for low speed stability. For low cost application the polygonal mirrors are formed with plastics. The outer reflective surfaces are formed with the economic and optical needs of the application in mind, and typically include aluminum, gold, silver, or nickel.

[0017] It has been observed that polygonal mirror scanners that use ball bearing based bearing systems can be susceptible to dust and moisture from the environment and under continuous operation, and typically have a lifetime for reliable operation that is under two years. Ball bearing based bearing systems are more robust under mechanical forces and vibration than alternative air bearings, but also can be damaged due to external forces, gravitational changes, and vibrations. It has also been observed that polygonal mirror scanners that use air bearings have long lifetimes when used in stationary, low vibrational environments, but are highly susceptible to shock and vibration that can result in catastrophic failure. Polygonal air bearings keep the high speed rotating shaft and mirror separate from the fixed mounting and motor surfaces by creating a high speed layer of air in a designed gap. This air can be actively pumped into the bearing gap, or naturally entrained into the air bearing gap by the rotation of the device.

When subjected to significant acceleration, the suspended moving mass can bridge that gap, colliding with the fixed surfaces and initiate an imbalance in the high speed rotation, leading to catastrophic failure.

Summary of the Invention

[0018] Light-based detection and ranging (LiDAR) systems according to some embodiments of the invention may include an optical beam steering device containing primary and secondary reflectors therein. In some of these embodiments of the invention, the primary and secondary reflectors are collectively configured to support reflection of incoming light from at least one reflective surface on the primary reflector to at least one reflective surface on the secondary reflector as the primary reflector moves relative to the secondary reflector. In addition, the primary and secondary reflectors may be configured as first and second polygonal reflectors, respectively, and may be collectively configured to support the sweeping of reflected light from a first reflective surface on the primary polygonal reflector to a first reflective surface on the secondary polygonal reflector as the first polygonal reflector rotates relative to the second polygonal reflector. The primary and secondary polygonal reflectors may also be configured to rotate about respective first and second axes, which are orthogonal to each other.

[0019] According to additional embodiments of the invention, the optical beam steering device within a LiDAR system may include an optically transparent container having the primary and secondary reflectors therein, which are at least partially surrounded within the optically transparent container by an optically transparent fluid. In some of these embodiments of the invention, the primary and secondary reflectors are surrounded on all sides thereof by the optically transparent fluid. In addition, the primary and secondary reflectors and the optically transparent fluid may be collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

[0020] According to further embodiments of the invention, an optical beam steering device is provided that includes a multi-lobed polygonal reflector and a drive mechanism, which surrounds at least a portion of the multi-lobed polygonal reflector. In some of these embodiments, the multi-lobed polygonal reflector may include first and second polygonal reflectors and a magnet extending therebetween, and the drive mechanism may be an electromagnetic drive mechanism (e.g., ring-shaped electro-magnet) that surrounds the magnet. An optically transparent container may also be provided, which contains the multi-lobed polygonal reflector and the drive mechanism. The multi-lobed polygonal reflector and the drive mechanism may be surrounded within the optically transparent container by an optically transparent fluid. Moreover, the multi-lobed polygonal reflector and the optically transparent fluid may be collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

[0021] According to further embodiments of the invention, an optical beam steering device is provided, which includes a polygonal reflector and an electro-magnetic drive mechanism extending at least partially through the polygonal-reflector. In some of these embodiments, the polygonal reflector has an annular-shaped opening extending therethrough, and the electro magnetic drive mechanism is aligned to a geometric center of the annularshaped opening. In other embodiments of the invention, an optically transparent container is provided to contain the polygonal reflector and an optically transparent fluid, which surrounds the polygonal reflector. The polygonal reflector and the optically transparent fluid are also configured to be neutrally buoyant relative to each other within the optically transparent container.

[0022] According to further embodiments of the invention, an optical beam steering device is provided, which includes a polygonal reflector having a magnet extending at least partially therethrough. The polygonal reflector can also have a cavity therein, and the magnet can extend at least partially through the cavity. An optically transparent container may also be provided to contain the polygonal reflector along with an optically transparent fluid that surrounds the polygonal reflector. In some of these embodiments of the invention, the polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container. In addition, to facilitate the efficient movement of the polygonal reflector within the optically transparent fluid, the polygonal reflector may be encased within an optically transparent solid material having a smooth outer surface.

[0023] In still further embodiments of the invention, an optical beam steering device may be provided, which includes an optically transparent container having a polygonal reflector therein, which is surrounded on all sides thereof by an optically transparent fluid. Preferably, the polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container. In some of these embodiments of the invention, the optically transparent container may include a fluid inlet port and a fluid outlet port, which are selectively enabled to support rotation of the polygonal reflector within the optically transparent fluid. In other embodiments of the invention, a plurality of light sources may be provided, which are configured to optically drive rotation of the polygonal reflector within the optically transparent container when enabled to direct light towards the polygonal reflector. The polygonal reflector may also be configured to be self-centering within the optically transparent container when rotating within the optically transparent fluid, and may even be annular shaped with a centrally-located opening therein through which the optically transparent fluid can pass. [0024] According to additional embodiments of the invention, an optical beam steering device is provided, which includes an annular-shaped reflector having a polygonal-shaped inner surface therein that faces a center of the annular-shaped reflector. This annular-shaped reflector may be surrounded by an optically transparent fluid within an optically transparent container. The annular-shaped reflector and the optically transparent fluid may be neutrally buoyant relative to each other within the optically transparent container.

[0025] In still further embodiments of the invention, an optical beam steering device is provided, which includes a multi-lobed polygonal reflector. This multi-lobed polygonal reflector can include a first polygonal reflector having a first number of sides mounted to a second polygonal reflector having a second number of sides unequal to the first number of sides. In some embodiments, the first and second polygonal reflectors may be disc-shaped and have planar top and bottom surfaces. In addition, a bottom planar surface of the first polygonal reflector may be in contact with a top planar surface of the second polygonal reflector. An optically transparent container may also be provided, which contains the multi-lobed polygonal reflector and an optically transparent fluid therein. Preferably, the multi-lobed polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

[0026] According to still further embodiments of the invention, a light-based detection and ranging (LiDAR) system may be provided, which includes a sealed container having at least one transparent window in a sidewall thereof. The sealed container may include a polygonal reflector therein, at a location adjacent a first of the at least one transparent window. An optically

transparent fluid having a refractive index greater than 1.3 may be provided which surrounds the polygonal reflector within the container and extends between the polygonal reflector and the first of the at least one transparent window. The polygonal reflector and the optically transparent fluid may be configured to be neutrally buoyant relative to each other within the sealed container. In some additional embodiments of the invention, the optically transparent fluid may include a pocket of gas therein, which is sufficiently large to buffer changes in pressure within the optically transparent fluid over an operating temperature range of the LiDAR system. In alternative embodiments, optically transparent fluid may include an elastic subcontainer therein, which is at least partially filled with a pocket of gas. In still further embodiments, the sealed container may include an asymmetric cavity within the optically transparent fluid, and the polygonal reflector may be disposed within the asymmetric cavity.

Brief Description of the Drawings

[0027] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate various embodiments of the invention and, together with the description, serve to explain the principles of the invention:

[0028] Figure 1 A is a top sectional view of a Neutrally Buoyant Polygonal Scanner (NBPS) according to an embodiment of the invention;

[0029] Figure 1 B is a side sectional view of the NBPS of Figure 1 A;

[0030] Figure 2A is a top sectional view of an NBPS according to an embodiment of the invention;

[0031] Figure 2B is a side sectional view of the NBPS of Figure 2A;

[0032] Figure 3A is a top sectional view of a polygonal reflector according to an embodiment of the invention;

[0033] Figure 3B is a side sectional view of the polygonal reflector of Figure 3A;

[0034] Figure 4 is a side sectional view of an NBPS according to an embodiment of the invention;

[0035] Figure 5 is a perspective view of a conventional polygonal scanner;

[0036] Figure 6 is a perspective view of a conventional polygonal scanner having canted faces;

[0037] Figure 7A is a side view of a dual-polygon scanner system, according to an embodiment of the invention;

[0038] Figure 7B is a top view of the dual-polygon scanner system of Figure 7A;

[0039] Figure 8 is a side view of a hybrid linear-polygon scanner system, according to an embodiment of the invention;

[0040] Figure 9A is a perspective view of a dual-lobed polygon scanner, according to an embodiment of the invention; [0041] Figure 9B is a top view of a dual-lobed polygonal scanner system, according to an embodiment of the invention;

[0042] Figure 9C is a three-dimensional perspective view of a dual-lobed polygonal scanner system, which utilizes the dual-lobed polygon scanner of Figure 9A;

[0043] Figure 10A is a top view of an internal drive polygon system, according to an embodiment of the invention;

[0044] Figure 10B is a three-dimensional perspective view of the internal drive polygon system of Figure 10A;

[0045] Figure 1 1A is a side view of a split polygon rotor, according to an embodiment of the invention;

[0046] Figure 1 1 B is a three-dimensional perspective view of the split polygon rotor of Figure 1 1A;

[0047] Figure 12A is a three-dimensional perspective view of a neutrally buoyant polygon system, according to an embodiment of the present invention;

[0048] Figure 12B is a cross sectional perspective view of an embodiment of the neutrally buoyant polygon system of Figure 12A;

[0049] Figure 13A is a top view of a magnetic neutrally-buoyant polygonal scanner (NBPS), according to an embodiment of the present invention;

[0050] Figure 13B is a three-dimensional perspective view of the magnetic NBPS of Figure 13A;

[0051] Figure 13C is a cross sectional perspective view of the magnetic NBPS of Figure 13B;

[0052] Figure 14A is a top view of a low drag NBPS, according to an embodiment of the present invention;

[0053] Figure 14B is a side view of the low drag NBPS of Figure 14A;

[0054] Figure 14C is a three-dimensional perspective view of the low drag NBPS of Figures 14A-14B;

[0055] Figure 15 illustrates a fluid driven NBPS, according to an embodiment of the present invention;

[0056] Figure 16 illustrates an optically driven NBPS, according to an embodiment of the present invention; [0057] Figure 17A is a top view schematic of a circulation stabilized NBPS, according to an embodiment of the present invention;

[0058] Figure 17B is a cross-sectional view the circulation stabilized NBPS of Figure 17A;

[0059] Figure 18 is a top view of a polygon light steering system, according to an embodiment of the present invention;

[0060] Figures 19A-D are schematic illustrations of view segmentation;

[0061] Figures 20A-B are schematic illustrations of view segmentation;

[0062] Figure 21 is a schematic illustration of view segmentation;

[0063] Figures 22A-B are schematic illustrations of view segmentation;

[0064] Figure 23 is a three-dimensional perspective view of an inverted polygon scanner system, according to an embodiment of the present invention;

[0065] Figure 24A is a side view of a polygon mirror configured for dual faceted send and receive signals, according to an embodiment of the present invention;

[0066] Figure 24B is a top view of a polygon mirror configured for dual faceted send and receive signals, according to an embodiment of the present invention;

[0067] Figure 25 is a side view of a polygon mirror configured for dual faceted send and receive signals, according to an embodiment of the present invention;

[0068] Figure 26A is a side view of a polygon mirror configured to support a temporally actuated field of view, according to an embodiment of the present invention;

[0069] Figure 26B is a top view of an embodiment of the polygon mirror of Figure 26A;

[0070] Figure 26C is a three-dimensional perspective view of the polygon mirror of Figure 26B;

[0071] Figure 27A is a side view of a polygon mirror configured to support a temporally actuated field of view, in one state of operation;

[0072] Figure 27B is a side view of a polygon mirror configured to support a temporally actuated field of view, in a second state of operation; [0073] Figure 27C is a top-down schematic illustration of a temporally actuated field of view;

[0074] Figure 28 is a schematic illustration of control signals and timing for a scanning system with a temporally actuated field of view;

[0075] Figure 29 is a cross-sectional view of an NBPS with internally integrated light sources and detectors, according to an embodiment of the invention;

[0076] Figure 30A is an illustration of a movable polygon system, according to an embodiment of the present invention;

[0077] Figure 30B is an illustration of the movable polygon system of Figure 30A, when the rotational axis of the polygon is rotated;

[0078] Figure 30C is an illustration of the movable polygon system of Figure 30A, when the rotational axis of the polygon is translated laterally;

[0079] Figure 31 is an NBPS according to an embodiment of the present invention;

[0080] Figure 32 is an NBPS according to an embodiment of the present invention;

[0081] Figure 33 an NBPS according to an embodiment of the present invention;

[0082] Figure 34 an NBPS according to an embodiment of the present invention;

[0083] Figure 35 an NBPS according to an embodiment of the present invention;

[0084] Figure 36 an NBPS according to an embodiment of the present invention;

[0085] Figure 37 an NBPS according to an embodiment of the present invention;

[0086] Figure 38 an NBPS according to an embodiment of the present invention;

[0087] Figure 39 an NBPS according to an embodiment of the present invention;

[0088] Figure 40 an NBPS according to an embodiment of the present invention; Detailed Description of the Invention

[0089] Reference will now be made in detail to embodiment(s) of the present invention. While the invention will be described in conjunction with the embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

[0090] Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be

recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, and components may not have been described in detail as not to unnecessarily obscure aspects of the present invention. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.

[0091] The terms“a” or“an,” as used herein, are defined as one or more than one. The term“another,” as used herein, is defined as at least a second or more. The terms“including” and/or“having”, as used herein, are defined as comprising (i.e., open transition).

[0092] The present invention enables the control of a reflective surface or mirror, enabling the redirection of an incident beam of light. Critically, the controlled scanning of light is enabled in a manner making the system highly resistant to external forces and vibration.

[0093] Figure 1A is a schematic representation of a top sectional view of a Neutrally Buoyant Polygonal Scanner (NBPS) 100 according to an

embodiment of the invention. A polygonal reflector 101 is centrally located, surrounded by a fluid 102. The polygonal reflector 101 and fluid 102 are contained within a rigid solid container 103. Incident light 104 passes through an optically transparent wall of the container 103 and the optically transparent fluid 102, and is reflected by the rotating polygonal reflector 101. Reflected light 105 is emitted from the NBPS 100 at various angles dictated by the rotational position of the polygonal reflector 101 .

[0094] Key to the present invention is the nature of the design and composition of the polygonal reflector 101 and the fluid 102. The solid polygonal reflector 101 is designed to have an average density equivalent to an average density of the fluid 102. Additionally, the solid polygonal reflector

101 is preferably designed to have its center of mass located at its geometric center so that the system of the combined polygonal reflector 101 and fluid

102 is substantially neutrally buoyant. When this neutrally buoyant condition is present, the polygonal reflector 101 does not float, nor does it sink within the surrounding fluid 102 under the influence of gravity. Accordingly, as the orientation of the NBPS 100 with respect to gravity changes, there is little to no relative motion induced between the polygonal reflector 101 and the fluid 102. This condition may be present, for example, when the NBPS 100 is employed in an automobile, in a condition where the automobile’s orientation changes going up or down a hill, the relative position of the polygonal reflector 101 and the fluid 102 is relatively unaffected. More broadly, this condition of neutral buoyancy of the polygonal reflector 101 and fluid 102 and the coincident center of mass and geometric center of the polygonal reflector 101 make the combined system largely immune relative motion and disruption due to external forces and moments 106 applied to the container 103 of the NBPS 100. Under turbulence, road vibration, spinning, or other conditions that a polygonal scanning system may see in various applications, the resulting forces and moments 106 will generally not alter the relative position of the polygonal reflector 101 within the fluid 102. This holds true whether the polygonal reflector 101 is rotating at high speed relative to the container 103 as is the case when the NBPS 100 is in operation, or if the polygonal reflector 101 is stationary with respect to the container 103, as is the case when the NBPS is not in operation. The achievement of neutral buoyancy enables perfect or near perfect immunity to the effects of external forces and moments 106 is one advantageous aspect of at least some embodiments of the invention.

[0095] In an additional embodiment of the present invention, the average density of the polygonal reflector 101 designed to be similar to the density of the fluid 102. In other words, since the density of all materials changes to some degree over a range of expected operating temperatures, the present invention discloses methods of designing the polygonal reflector 101 to have an average density similar to the average density of the fluid 102, over the temperature ranges that the system will typically see under operation in a respective application. For example, when the NBPS 100 is used in an application where the environmental temperature may range from -30 to 80 °C, the polygonal reflector 101 and the fluid 102 may be designed to have the identical average density at the typical operating temperature of 20 °C, and therefore have ideal immunity from external forces and moments 106 at that specific temperature. At lower or higher temperatures, the degree of density change of the respective polygonal reflector 101 and the fluid 102 may be different, but by design, their average densities remain similar over the anticipated range of operating temperature, to thereby provide a relatively high degree of immunity from the effects of externally applied forces and moments 106.

[0096] In an embodiment of the present invention, the polygonal reflector 101 may be a composite assembly of various solid materials, detailed in a following figure, and may include plastics, metals, and ceramics. Additionally, in order to match the average density of the fluid 102, the polygonal reflector 101 may contain encapsulated regions of low density gas, such as air or helium, or low density solids such as aerogel. The outer reflective surface of the polygonal reflector 101 is coated with a reflective material dictated by the optical requirements of the application, and may be composed of aluminum, silver, copper, nickel, gold or a dielectric mirror stack containing one or more dielectric materials. The polygonal reflector 101 may have any number of sides, including six as illustrated, but may range from two to several hundred. A polygon with a low number of sides sweeps a reflected beam 105 over a relatively large angle, but may induce chaotic fluid motion in the fluid 102 as the polygonal reflector 101 rotates. A polygon with a high number of sides sweeps a reflected beam 105 over a relatively smaller angle but at a higher temporal frequency, and may result in less chaotic fluid motion in the fluid 102 as the polygonal reflector 101 rotates. In a preferred embodiment of the present invention, the fluid 102 is a liquid. And, in order to provide a wide range of operating temperatures while remaining in the liquid state without freezing or boiling, the liquid may be a Fluorinert liquid such as FC-40 or FC- 43 and polymerized siloxane fluids with organic side chains, oils, and the polydimethylsiloxane family of liquids. Other liquids are contemplated as well and will be recognized by those skilled in the art. The container 103 is composed of a material that is optically transparent at the wavelength of light used in the incident light 104, such as glass or plastic. The specific choice and composition depends on the wavelength for the application.

[0097] Figure 1 B is a side cross-sectional view of the NBPS 100 of Figure 1A. The polygonal reflector 101 is shown centrally in a side view, submerged in a fluid 102, all encapsulated by a container 103 and top/bottom lids 107. The incident beam of light 104 is shown reflected as the reflected light 105.

[0098] In a preferred embodiment of the present invention, the lids 107 are composed of non-ferromagnetic metals such as aluminum (Al). In additional embodiments they are composed of non-ferromagnetic materials such as plastic, nonmagnetic steels, nonmagnetic stainless steel, brass, copper, or ceramics. Optionally, in additional embodiments, the container 103 and lids 107 can be composed of a single continuous common material that is appropriately optically transparent.

[0099] Figure 2A shows a top cross-sectional view of a Neutrally Buoyant Polygonal Scanner (NBPS) 200 according to an embodiment of the invention. Figure 2B shows a side cross-sectional view of the NBPS 200 of Figure 2A.

In both figures, the polygonal reflector 201 has a central hole through it, allowing it to rotate about a central hub of a lid/hub structure 202. A fluid 102 surrounds the polygonal reflector 201 and the gap between the central lid/hub 202, thereby creating, in effect, a fluid bearing.

[00100] As with the NBPS embodiment shown in Figures 1A and 1 B, the polygonal reflector 201 illustrated by Figures 2A and 2B is preferably designed to have an average density identical or nearly identical to that of the fluid 102 at a certain temperature within the operating range. The average densities of the polygonal reflector 201 remains similar to the fluid 102 over the temperature range of operation, so that there is little or no relative motion between the polygonal reflector 201 and the fluid 102 when subject to external forces and moments 106 at a certain temperature and minimal relative motion across the temperature range of operation.

[00101] The polygonal reflector 201 may be composed of the same materials previously described for the polygonal reflector 101 of Figures 1A-1 B. The lid/hub 202 is preferably composed of a non-magnetic material such as certain metals including aluminum, certain stainless steels, and copper. In additional embodiments of the invention, the lid/hub 202 may be composed of plastics. The lid/hub 202 and surrounding container 103 may also be configured a single continuous material that is appropriately optically transparent.

[00102] Figure 3A is a top cross-sectional diagram of an embodiment of the polygonal reflector 101 and Figure 3B is a side sectional view of the polygonal reflector of Figure 3A. A main body 301 is shown, with embedded magnetic materials 302. The polygonal reflector 101 is shown as having six sides, with six embedded magnetic materials 302 therein. A reflective coating 303 covers the outer perimeter of the main body 301 , providing a reflective surface to reflect incident light. A fluid 102 surrounds the polygonal reflector 101.

[00103] This embodiment of the polygonal reflector 101 illustrates the ability to provide the overall function of the NBPS, which is to reflect light at large angles and at high speed, while delivering the reliable function and

advantageous benefits enabled by the present invention, which is neutral buoyancy. To create neutral buoyancy between the polygonal reflector 101 and the surrounding fluid 102, the main body 301 material is typically of lower density than the fluid 102, while the reflective coating 303 (e.g., metal) typically has a higher density. The contribution of the reflective coating 303 to the average density is small, given that it typically is a thin coating with a relatively small volume. However, given the typical nature of magnetic materials, the embedded magnetic materials 302 are of relative high density.

In order to spin the polygonal reflector 101 , the magnetic materials support the function of the reflector as a rotor in an electromagnetic motor, driven by electromagnetic forces from above and below. In an embodiment of the present invention where the rotational motion of the polygonal reflector 101 is generated by an external variable reluctance electric motor, the magnetic materials 302 may be high permeability ferromagnetic material such as iron, mu-metal (e.g., nickel-iron soft alloy) or silicon steel. In an embodiment where the motion of the polygonal reflector 101 is initiated by a brushless DC motor, stepper motor, or similar, the magnetic materials 302 may be composed of permanent magnetic materials with permanent north and south poles. The embedded magnetic materials 302 enable the polygonal mirror to function as the moving rotor of an electromagnetic motor, and the careful design, sizing and volume of the main body 301 , the magnetic materials 302, and the reflective coating 303 allow the average density to match that of the external fluid 102, which gives the system an overall neutral buoyancy and significant immunity to the degrading effects of external forces and moments 106.

[00104] Figure 4 shows a cross sectional view of the NBPS 400. An upper motor assembly 401 is shown in contact with the lid 107. A lower motor assembly 402 is shown in contact with the lid 107. These assemblies, along with the centrally located polygonal reflector/mirror 101 , which serves as a rotor, create what is known is a double stator pancake style electromagnetic motor. The polygonal reflector/mirror 101 , with its embedded magnetic materials responds to time varying magnetic fields generated in the upper motor assembly 401 and lower motor assembly 402, allowing the polygonal reflector/mirror 101 to rotate with respect to the fixed lids 107 and container 103. At the same time, the condition of neutral buoyancy created between the polygonal mirror 101 and the fluid 102 protects the polygonal mirror form damage due to external forces or moments 106.

[00105] According to additional embodiments of the invention, an NBPS may be implemented using drive mechanisms that are adaptations of existing motor technologies, such as homopolar, hysteresis synchronous motors and inductive motor technologies. These two motor technologies can be attractive as drive mechanisms for an NBPS because they can be formed without magnetic materials located on the rotor. As such, the neutrally buoyant mirror system described herein, which serves as the rotor, can be formed without heavy magnetic materials such as steel or ferrite, or permanent magnets.

This allows for the average density to be more easily balanced with the surrounding fluid. This also enables the rotor, which can omit magnetic materials as part of its structure and has no physical shaft connecting it to the stator, to float freely when the motor electrical power is turned off, rather than be attracted to permanent magnets located in the stator structure. Homopolar motors are driven by passing electrical current onto the rotor through slip-ring structures. This current traveling in the rotor experiences Lorentz forces, causing the rotor to rotate. An induction motor is composed of electrically conducting coils, often arranged in a structure known as a“squirrel cage.” As the name suggests, no electrical contact exists between the spinning rotor and the surrounding stator, and the electrical current is induced in the rotor windings in response to current and magnetic fields generated in and from the surrounding stator. An NBPS may also be realized using additional electrical motor configurations that allow a rotor to spin without physical contact to the stator, beyond the aforementioned homopolar and induction motor

configurations.

[00106] Embodiments of the present invention also provide a means of extending the reliability and lifetime of rotating polygon mirror systems, not just by creating an environment of neutral buoyancy, but by creating an environment of near neutral buoyancy, or in other words, of reduced effective mass. Reliability of both electromagnetically driven, free standing polygons as well as rotating polygons mounted on a shaft and motor can be improved by reducing the effective mass of the system. As the effective mass is reduced, the physical response to external forces is reduced, which in turn reduces the stress and torque on shafts and electric motor and shaft bearings. Actually mass can be reduced by a variety of weight saving means, but the present invention teaches the method of reducing the effective mass of the rotating mirror system by enclosing it in an environment of gas or fluid with the same density as, or a closer density to the rotating mass than simply using air. By this means, short of achieving ideal neutral buoyancy, stress and strain can be reduced to an acceptable level to extend product lifetime by near neutral buoyancy and reduced effective mass, by virtue of the fluid environment in which the system is enclosed.

[00107] Prior Art Figure 5 shows a polygonal scanning system 500 that utilizes a polygon 501 having outer surfaces coated with a reflective material appropriate for the chosen wavelength of the incident laser light 104. The rotational movement of the polygon 501 sweeps the reflected beam in a repeated line pattern 502. [00108] Prior Art Figure 6 shows a vertically canted polygonal scanning system 600 that utilizes a vertically canted polygon 601. Each face of the canted polygon 601 may be at a unique angle with respect to vertical, in contrast with a standard polygon 501 having sides that are all at the same angle. The outer surfaces are coated with a reflective material appropriate for the chosen wavelength of the incident laser light 104. The rotational movement of the canted polygon 601 sweeps the reflected beam in a two dimensional repeated pattern 602, where each separate horizontal line of the repeated pattern 602 corresponds to the each canted face of the canted polygon 601.

[00109] Figure 7A is a side view of a dual polygon scanner system 700. In this configuration, one or more incident lasers 104 illuminate the side of a primary polygon 701. The rotation of the primary polygon 701 sweeps repeated vertical lines of reflected light 702. This vertical line of reflected light 702 in turn illuminates the side of a secondary polygon 703. The secondary polygon 703 is oriented non-coaxial to the primary polygon 701. As such, the reflected light 702 is reflected in an additional axis by the secondary polygon 703, generating a two dimensional sweep of light 704. In the case where the secondary polygon 703 is orthogonal to the primary polygon 701 , vertical and horizontal scanning of the incident laser light 104 is achieved.

[00110] Figure 7B is a horizontal view of the dual polygon scanner system 700 of Figure 7A. This perspective is provided to better illustrate the coordinated action of the primary polygon 701 and the secondary polygon 703 in generating a two dimensional sweep of light 704.

[00111] The dual polygon system 700 offers an advantage by allowing a greater degree of design freedom for the system over single polygon systems. The dual polygon system 700 allows the angle scanned in the horizontal and the frame rate of the horizontal axis be controlled by geometry and rotational speed of one polygon, whereas the angle scanned and frame rate of the second axis is independently controlled by the geometry and rotational speed of the second polygon.

[00112] In an embodiment of the present invention, the primary polygon 701 and the secondary polygon 703 are placed orthogonal to each other. They may be composed of metals, or polymers with coatings appropriate for the choice of incident laser light 104. The polygons may be traditional polygons driven by traditional means such as electromagnetic motors on shafts, or air bearings. In an additional embodiment of the present invention, one or more of the polygons may be a NBPS. In other embodiments of the present invention, either polygon may have each of its reflective faces at the same angle with respect to the rotational axis as polygon 501, or one or more of the polygons may be a canted polygon 601 , having one or more faces at different angles with respect to the rotational axis. The system may be illuminated with one or more incident light sources 104, arranged in one or more banks or rows.

[00113] Figure 8 is a side view of a hybrid linear-polygon laser scanning system 800. An incident beam 104 illuminates a linear scanning mirror 801, which scans in one axis 802. This motion creates a scanned line pattern 803, which illuminates and is reflected off the polygonal scanner 804. The rotational motion of the polygonal scanner 804 reflects this scanned line pattern 803 to create a two dimensional scanned light pattern 805.

[00114] The embodiment of the invention illustrated by Figure 8 allows for the overall hybrid linear-polygon system 800 to be more compact than alternatives such as the dual polygon system 700 of Figures 7A-7B. This embodiment of Figure 8 offers the advantages of customizing the density or distribution of the two dimensional scanned light pattern 805 by controlling the position of the linear scanning mirror 801 , while the polygonal scanner 804 rotates at relatively constant speed.

[00115] The hybrid linear-polygon laser scanning system 800 can be realized with the incident laser 104 first illuminating the linear scanning mirror 801 , or it may be reversed, where the incident laser 104 first illuminates the polygon scanner 804, and then is linearly scanned. The linear scanning mirror 801 may be a galvanometer, MEMS scanner, voice coil, liquid crystal phase modulator, or a holographic optical beam steering element, for example. Since the linearly scanned mirror 801 provides only one dimension of beam steering, it may only require smaller deviations in overall angle for applications in LiDAR, where one angular dimension, typically vertical, has a shorter field of view requirement than the orthogonal, typically horizontal, angular dimension. The scanning mode may be point to point or resonant. In another embodiment of the present invention, the linear scanning mirror 801 may be a two dimensional scanning mirror, which increases the degree of customization available when illuminating the two dimensional scanned light pattern 805.

[00116] Figure 9A is a three-dimensional view of a dual-lobed polygonal scanner 901. The scanner 901 has polygon structures at the top and bottom that are coated with a reflective coating appropriate for the wavelength of light used in the application. The central region is composed of a permanent magnet or ferromagnetic material to allow it to be driven electromagnetically. Figure 9B is a top view of a dual-lobed polygonal scanner system 900, where the scanner 901 of Figure 9A is encompassed by an electromagnetic drive mechanism 902. The electromagnetic drive mechanism 902 is energized in order to induce controlled rotation of the scanner 901 as well as to stabilize its position. Figure 9C is a three-dimensional perspective view of a dual-lobed polygonal scanner system 900, where the scanner 901 is surrounded by the electromagnetic drive mechanism 902.

[00117] The dual-lobed polygonal scanner system 900 advantageously provides two spatially separated polygon surfaces at the top and bottom, which are useful for separately scanning an outgoing laser beam and directing incoming reflected light, as is needed in a LiDAR system. The

electromagnetic drive mechanism 902 can be centrally located in order to not block optical access to the reflective polygon lobes while providing rotational and positional control. The two polygons (i.e., top and bottom polygons) may have different heights, and each may be independently configured for different optical functions, such as the sending and receiving of optical beams in a LiDAR system.

[00118] In an embodiment of the present invention, the scanner 900 can be a traditional metal or metal coated plastic reflective polygon, or a NBPS, submerged in a fluid that allows it to maintain neutral buoyancy. The symmetric construction is advantageous for operation as a NBPS, allowing for the center of mass and the geometric center to be co-located, thereby improving stability. The system 900 can be implemented with a permanent magnet region located in the central region of the polygon 901, allowing rotation to be induced responsive to the electromagnetic drive mechanism 902, which may operate in a manner similar to a brushless DC drive motor. In another embodiment, the polygon 901 can include ferromagnetic materials and operate akin to a variable-reluctance (VR) electric motor. In addition to providing the rotation to the polygon 901 , the drive mechanism 902, using magnetic position sensors provides positional stability. As the polygon 901 is sensed to be rotating off axis, additional magnetic flux can be applied to certain windings to allow centralization of the polygon 901. The polygon 901 may have vertical mirror surfaces or may be canted to provide multiple scanning dimensions.

[00119] Figure 10A is a top view of an internal drive polygon system 1000. A polygonal mirror 1001 is created with a central hole, where an

electromagnetic drive mechanism 1002 is located to provide rotation and positional stability. Figure 10B is a three-dimensional perspective view of the internal drive polygon system 1000 of Figure 10A. A polygonal mirror 1001 is created with a central hole therein, and an electromagnetic drive mechanism 1002 is located in the central hole to thereby provide rotational control and positional stability. The embodiment of the invention illustrated in Figures 10A-10B allows for full optical access to the outer mirror surface, but allows for an internal structure to drive the polygonal mirror 1001 and to stabilize it.

As described with reference to Figure 9A and 9B, the internally driven polygon system 1000 may be formed with vertical sides/faces or canted faces.

Multiple position sensors allow for the rotation to be initiated and controlled, and enable the three-dimensional stability of rotating polygon to be

maintained.

[00120] Figure 11A is a side view of a split polygon rotor 1100, which includes an upper polygon 1101 , a lower polygon 1102, and a shaft 1103 connecting the upper and lower polygons. The orientation of the faces on the upper polygon 1101 and lower polygon 1102 are angularly aligned by virtue of the common shaft 1103. Figure 11 B is a three-dimensional perspective view of the split polygon rotor 1100 of Figure 11A, which includes the upper polygon 1101 , lower polygon 1102, and shaft 1103. The split polygon rotor 1100 has an advantage over prior art such as a single tall mirror, because it can have much reduced weight and can allow for send and receive optical paths that are used in a LiDAR system to be arbitrarily separated spatially, but maintain a common speed and angular orientation. The heights of polygons 1 101 and 1102 may be different to allow for gain on the receive optical path in a LiDAR system by virtue of a larger optical aperture.

[00121] Figure 12A is a three-dimensional view of a neutrally buoyant polygon system 1200. The polygon 1201 is packaged in a controlled fluid environment 1202. Figure 12B is a three-dimensional cross sectional view of the neutrally buoyant polygon system 1200, which includes a polygon 1201 having an internal cavity 1203 that can be filled with a solid, fluid, or gas. In some embodiments of the invention, the polygon 1201 can be formed with a fully dense solid material, or a semi dense solid such as a foam or a polymer containing pockets of gas. The system is designed such that the average density of the polygon system 1200 is the same as the density of the surrounding fluid environment 1202. Since the system 1200 may be operated over a range of temperatures where the density of both the solid and fluid components of the system may vary, and embodiment of the invention allows for the average density of the polygon system 1200 to match the fluid environment 1202 at its mean, within the range, or match the most typical density during operation. As such, the combined polygon 1201 and the fluid environment are at neutral density, and not influenced significantly by external accelerations of the system. In an embodiment of the invention, the fluid environment is a liquid, such as water, glycol, fluorinated liquid compounds such as FC-40 or FC-72, silicone oil, or a mixture of fully miscible liquids. In a further embodiment of the invention, the fluid environment is a gas, such as air, nitrogen, argon, sulfur hexafluoride, tungsten hexafluoride, as examples. Potential advantages of using a gas over a liquid include the reduced hydrodynamic drag and associated reduced electrical power required to drive the system. Additional advantages of using gas options as well as fluids is the increased options available to provide the best characteristics that the system requires, such as low viscosity, low optical absorption, low cost, etc. The external environment 1202 may be packaged near ambient pressure, or, in order to increase its density, it may be packaged at elevated pressure. To achieve a neutrally buoyant condition with its external environment 1202, the cavity 1203 may be filled with a low density solid such as foam, or with a gas including helium, hydrogen, nitrogen, or air. [00122] Figure 13A is a top view of a magnetic NBPS 1300 and Figure 13B is a perspective view of the magnetic NBPS 1300. As shown, a main polygon 1201 is shown with a centrally located magnetic material region 1301. The NBPS 1300 is encompassed in a fluid environment 1202. Figure 13C is a three-dimensional, cross sectional view of the magnetic NBPS 1300. A main polygon 1201 is shown with a cavity 1203 and a magnetic material region 1301 therein, and is surrounded by a fluid environment 1202. In an

embodiment of the present invention, the magnetic material region 1301 is integrated with a cavity 1203 and a main polygon 1301 in order to create both a system that is neutrally buoyant with its surrounding fluid environment 1202, but also capable of being driven externally by electromagnetic forces. The magnetic region 1301 may be one or more regions of ferromagnetic material such as iron, steel, or nickel, allowing the system to be rotated and stabilized as a variable reluctance motor. In another embodiment of the invention, the magnetic region 1301 may be a permanent magnet, allowing the system to be rotated and stabilized an operated in a manner similar to a brushless DC motor. The permanent magnet may be uniformly magnetized or magnetized in a number of domains in order to couple to external magnetic actuation. In order to achieve neutral buoyancy, the cavity may be filled with fluid or gas, including helium, hydrogen, nitrogen, argon, or air.

[00123] Figure 14A is a top view, Figure 14B is a side view and Figure 14C is a perspective view of a low drag NBPS 1400. As shown, this NBPS 1400 includes a polygon 1401 with reflective faces, which is encased in an optically transparent solid material 1402 that creates a smooth, continuous outer periphery. The smooth outer periphery created by the transparent solid material 1402 illustrated in the present invention allows the NBPS system 1400 to rotate within a fluid environment while creating much lower fluid drag as it rotates. This has the advantage of reducing the power required to rotate the system, as well as reducing the amount of turbulence and associated wakes and eddies that could cause instability of an otherwise unprotected polygon. In an embodiment of the invention, the transparent solid material 1402 is made of glass. In further embodiments of the invention, the

transparent solid material 1402 is made from polymer materials including acrylic, polycarbonate, or polystyrene. The polygon 1401 may be composed of a variety of materials and compositions as previously disclosed, allowing the combined low drag NBPS 1400 to be in neutral buoyancy or near neutral buoyancy with its surrounding fluid. The cross sectional shape of the smoother outer perimeter may be a semicircle, such as in Figures 14A-14C, or in other shapes, such as rectangles or triangles.

[00124] Figure 15 illustrates a fluid driven NBPS 1500, where a polygon

1501 is packaged in a housing 1502 which is composed of one or more fluid inlets 1503 and one or more fluid outlets 1504. Fluid is pumped into the fluid inlets 1503, resulting in a fluid circulation 1505 that in turn causes the polygon

1502 to rotate. The NBPS 1500 of Figure 15 has the potential advantage over alternative NBPS implementations and traditional rotating polygon scanners, because it does not require the rotating polygon to be composed of a permanent magnet or ferromagnetic material, as is a requirement for electromagnetically driven implementations. In an embodiment of the present invention, the polygon 1501 is a polymer coated with an optically reflective material on its faces or a composite of materials as noted hereinabove. The fluid may be a liquid or a gas composed of materials including water, glycol, fluorinated liquids, air, argon, nitrogen, sulfur hexafluoride or tungsten hexafluoride.

[00125] Figure 16 illustrates an optically driven NBPS 1600, in which a polygon 1501 is encased in a chamber 1601 that contains a fluid 1602 therein. Rotational motion is induced and stability of the system in its desired location is maintained by means of a light source 1603 that illuminates the NBPS 1600 with an optical beam 1604. Rotation and/or stability is induced and maintained by one or more physical phenomena that include radiation pressure and thermal induced flow patterns. Radiation pressure imparts momentum to the NBPS 1600 as photons are absorbed on the surface, transferring momentum from the optical beam 1604. Thermal effects can induce motion as specific surfaces are optically heated, and as the fluid 1602 near the heated surface(s) is warmed, buoyancy driven flow is created on selective regions. This flow can induce net rotation and be used to maintain stability of the rotating NBPS 1600.

[00126] Figure 17A is a top view schematic of a circulation stabilized NBPS 1700. A polygon 1701 is rotated in an enclosure 1702 containing a fluid 1703. The top and side surfaces of the polygon 1701 are grooved and striated 1704 in a manner that influences the flow of the fluid 1703.

[00127] Figure 17B is a side cross sectional view of the circulation stabilized NBPS 1700. The striations 1704 on the rotating polygon 1701 induce additional fluid flow that circulates around the polygon 1701 increasing the velocity of the fluid around the system. As such, the increased flow increases the fluid viscous drag around the perimeter, creating an increase in fluid forces that stabilize and cause the rotating system to self-center, in order to balance fluid forces and minimize total fluid drag. According to this

embodiment, the NBPS 1700 is able to rotate in a more stable manner and can be used to compliment other external stabilization methods such as electromagnetic stabilization.

[00128] Further embodiments of the present invention can include the use of, alone or in combination, the aforementioned drive mechanisms and stability mechanisms, including optical methods, driven fluidic methods, induced fluid circulation and electromagnetic methods.

[00129] Figure 18 is a top view of a polygon light steering system 1800, which includes a polygonal reflector 1801 having any number of sides, including eight as illustrated, but may range from two to several hundred. The polygonal reflector 1801 is used to redirect multiple light sources

simultaneously to provide for enhanced scanning resolution, field of view or temporal update frequency. For example, the light sources 1802 and 1803 may be incident on two opposing faces of the polygonal reflector 1801 simultaneously, providing for a simultaneous scan of beams in two opposing directions. This provides for a capability to increase the effective field of view of a LiDAR system, such as a sensor that ranges in the forward and reverse directions, the left and right directions, or any combination thereof. In another embodiment, two or more light sources 1804 and 1805 may be incident on the same location of the polygonal reflector 1801 , which also allows for the simultaneous scan of multiple directions that can be applied in a LiDAR ranging application. In another embodiment, multiple light sources 1806 and 1807 are incident on the same facet but different locations of the polygon. Alternatively, multiple light sources 1807 and 1808 are incident on the adjacent faces of the polygon. Other combinations are contemplated and will be generally recognized by those skilled in the art.

[00130] The coincidence of multiple light sources on a single polygon allows for the building up of a larger effecting sensing aperture for a LiDAR ranging system. The method may also be employed to create regions of different resolution with a given static field of view. For example, Figure 19A illustrates an embodiment where a LiDAR system mounted on the front of vehicle 1901 sends out a larger field of scanned light sources comprised of a higher spatial density region 1902 and lower spatial density regions 1903 and 1904. A system with multiple vertical regions of differing spatial sampling density may be advantageous wherein the produced data is higher resolution in field regions where greater resolution is desired, which may correspond to regions more likely to contain objects at long distances, such as directly in front of the vehicle on a highway, and lower resolution in regions further away from the forward central area, such as at angle corresponding to adjacent lanes of that in which the vehicle is currently driving, where objects are likely to be closer. The segmentation of the overall sensor view may beneficially enable higher performance decision making and the carrying out of computations with less redundant data. This view segmentation is similar to that which occurs in human drivers, which employ foveated vision to create overall images comprised of high resolution central views and lower resolution peripheral views.

[00131] View segmentation can be created in multiple dimensions of the overall view using the previously described method. For example, in Figure 19B, the view is horizontally segmented in one region of higher resolution 1905 and two regions of lower resolution, 1906 and 1907. In another embodiment, the view segmentations illustrated in Figures 19A and 19B are combined to create a central two dimensional region of higher resolution and a surrounding peripheral field of lower resolution.

[00132] The previously described methods are not limited to symmetric view segmentation. LiDAR systems for automobiles may have better driving outcomes if the sensor view is segmented in asymmetric ways, which may be beneficial at lower speeds or in environments of higher urban density of non- vehicle agents, such as pedestrians and cyclists. For example, Figure 19C and 19D illustrate view segmentations whereupon corner facing ranging sensors asymmetrically point outward with greater spatial sampling in the forward direction in regions 1908 and 1909.

[00133] When light sources are incident upon multiple and opposing sides of the polygon, the sensor system may be able to simultaneously sense into four quadrants of view, as illustrated in Figure 20A. The arrangement of light sources may be configured to overlap, creating regions 2001 of higher spatial sampling or temporal refresh rate and regions 2002 of lower spatial sampling or temporal refresh rate. Simultaneous sensing into four normal directions provides for increased capability and faster scanning. When the sensors are properly registered, it may provide for dramatically lower computational requirements to combine the data streams into one larger set directly computable against machine learning algorithms. In another embodiment illustrated in Figure 20B, simultaneous sensing into opposing directions may be achieved with no overlap between adjacent views, such that gaps 2003 are present in the sensor view.

[00134] For LiDAR systems configured for long distance operation and on highways, it may be computationally advantageous to have a substantially non-rectangular overall field of view, as objects of interest may never be present in the upper right and upper left regions. In one example embodiment illustrated in Figure 21 , the overall box 2101 bounding sub fields of view 2102, 2103, 2104, 2105, and 2106 contains regions of zero sampling in the upper right and upper left. A highway is schematically represented by dashed lines 2107, whereas the objects of interest in this front facing view are solely contained in the aforementioned sub fields of view. Such an arrangement would be more computationally efficient without a reduction in system performance, which enables a lower overall system cost due to reduced component requirements.

[00135] An illustration of the differential spatial sampling of a segmented view is shown in Figure 22A, where the light sources are projected and imaged upon a plane. Two laser sources are shown, each scanned over the vertical and horizontal dimensions. Each of the two sources has a uniquely sized field of view in two dimensions with substantial overlap. The overlapping region is off center and off middle, such as may be desired in a corner facing headlamp LiDAR system. Figure 22B illustrates an arrangement where two overlapping laser sources are each incident on an identical field of view in one dimension, but different fields of view in the orthogonal direction, creating an overall view that has increased resolution in only one of two angular dimensions.

[00136] In another embodiment illustrated in Figure 23, a polygon mirror based beam steering element 2301 is constructed with an inverted structure, where a polygon volume is removed from a cylindrical disk structure, and the internal faces 2302 are mirrored. Incident light source 2303 is directed at the mirror faces and reflected into the field, represented by spherical section 2304. As the inverted structure is rotated about its central axis, the reflected light beam 2305 scans out to the region 2306 in the optical field. The internal region may be comprised of empty volume or a transparent medium, such as plastics such as polystyrene, acrylic, or polycarbonate. The mirrored surfaces may be vertical or canted, allowing for scanning in one or two angular dimensions. In one embodiment, more than one laser is incident on one or more facets of the inverted polygon, providing for view segmentation or the buildup of a larger system field of view. In another embodiment, the polygon is with empty space in its central axis, and compact laser diodes are arranged in the volume. In another embodiment, the mirrored faces are non-planar with positive optical power to increase angular tolerance of the beam steering system. Components to rotate the scanner are not shown but may be arranged inside or outside of the polygon mirror.

[00137] This inverted polygon structure has several advantageous features, including a uniform cross section to reduce fluid drag when configured as a NBPS. The scanner may also be configured in novel system configuration which contains less overall volume, enabling a smaller, more compact and complete system. j

[00138] For LiDAR ranging applications it may be desirable to have an optical beam steering component that can redirect outgoing or incoming beams to different locations to eliminate overlap between lasers and detectors. In one embodiment illustrated in the side view of Figure 24A, a polygon scanner 2400 has two sets of faces 2401 and 2402 separated by an angle 2403. Figure 24B is a top view of the same scanner 2400 where face 2401 is visible. In this embodiment, a central hollow is present for the drive mechanism.

[00139] Referring now to Figure 25, two faces 2501 and 2502 of a polygon scanner 2500 function to redirect outgoing and incoming light, respectively. Outgoing light 2503 is reflected to beam 2504 on the smaller polygon face 2501. The incoming light 2505 has reflected off a faraway object and has diminished intensity and would benefit from a larger light collection aperture, so the larger face 2502 reflects this incoming light 2505 upward as 2506 towards a detector 2507. The relatively larger area of face 2502 increases the signal at detector 2507, which thereby enables greater ranging distance capability of the overall LiDAR system. In one embodiment, faces 2501 and 2502 are separated by an angle of 90 degrees as shown in Figure 25, but in other embodiments the angle may be different, and in a range between 1 and 135 degrees. In another embodiment, the send or receive faces 2501 and 2502 may be curved to provide positive optical power. In addition, the faces may be different vertical angles for faces adjacent and around the rotation axis of the polygon, thereby providing support for scanning in two angular dimensions.

[00140] In yet another embodiment, the field of view is desirably temporally switched, whereupon the sensed views respond to commands from various sensors to increase data collection in regions of interest. This is similar to the oculomotor systems of the human eye, were high resolution foveal vision can be scanned by the extraocular muscles to shift gaze in response to higher level control signals, and to the lens system of the human eye, where the ciliary muscle can contract to shift focus in response to higher level control signals. A LiDAR vision with switchable gaze and focus allows for higher resolution regions of interest at lower overall data rates compared to systems with higher resolution at all times, which advantageously reduces

computational requirements and overall system cost.

[00141] Temporally switchable gaze and field of view can be accomplished with the two level polygonal mirror structure 2600 illustrated in the side view of Figure 26A. As shown, polygon 2600 is comprised of two mechanically coupled sub-polygons 2601 and 2602, which are configured to rotate together about a common axis. Top and three-dimensional views of the polygon 2600 are illustrated in Figures 26B and 26C, respectively. In the currently depicted embodiment, polygon 2601 has eight sides and polygon 2602 has sixteen sides, but other combinations of polygons with unequal numbers of sides are also contemplated.

[00142] In the current embodiment, a light source 2701 is incident on a one dimensional scanning mirror with at least two possible states. In one state, as illustrated in Figure 27A, a light beam 2701 is reflected from the mirror 2702 onto sub-polygon 2703, which scans out the narrower and high resolution field of view 2705 shown in Figure 27C. In another state, as illustrated in Figure 27B, the planar mirror 2702 has switched to a second bi-stable state to redirect the light beam 2701 onto the eight sided sub-polygon 2704. The lower number of sides of sub-polygon 2704 scans a wider field of view 2706, as shown by Figure 27C. While illustrated in Figures 27A and 27B as vertical mirrors, other embodiments may utilize canted mirrors on the polygon sides.

[00143] In another embodiment, a one dimensional scanning mirror capable of point to point operation changes the angle of incidence of a light beam on a single polygon mirror. The change in angle of incidence changes the field of view without requiring a two sub-polygon scanner component.

[00144] The angular deviation provided by the first point to point scanner limits the amount of movement in the gaze and field of view that can be controlled over time. In general, only small deviations are required in order to alter the gaze and field of view of the LiDAR system in one or more

dimensions. Unlike a raster scanner or point to point scanner used to collect data points in the field of view, the first stage scanner can move slower in comparison. Unlike the large area scanner, which may move continuously or within time steps of approximately 1 microsecond, the gaze control scanning element may move with time steps of 1-100 seconds in response to control signals indicating changes in road conditions, transitions between urban and highway driving, geolocation coordinates, time, date, acceleration, velocity, or triggers from other automotive sensor systems based on cameras, sonar, or radar.

[00145] In one embodiment, the horizontal and vertical fields of view are temporally switched between two stable states as shown in Figure 28. The times at which these transitions occur correspond to a control input from a computer vision system. In another embodiment, the transition is triggered by a change in velocity above or below a threshold value. Other controlling signals are also possible.

[00146] Figure 29 shows a cross sectional view of a NBPS 2900 with an enclosure formed by upper and lower lids 2901 and optically transparent windows 2902. A rotating, reflective polygon 2903 is surrounded by a fluid 2904. At least one light source 2905 and at least one optical sensor 2907 are shown encased within the enclosure and immersed in the fluid 2904. As shown, a light source 2905 is shown emitting light 2906 that is reflected and directed in space by the reflective polygon 2903. Similarly, an optical detector 2907 is located in the fluid 2904, receiving light 2908 that is directed onto the detector 2907 by means of the reflective polygon 2903.

[00147] The architecture illustrated in Figure 29 can have several

advantages. First, by immersing light sources 2905 and optical detectors 2907 in the fluid, the number of interfaces that incoming light 2908 has to traverse is reduced, which increases the intensity of light sent or received (e.g., by reducing undesirable reflections of absorption due to material interfaces and bulk materials). Second, by immersing these components in the enclosed fluid, the cooling of the components can be enhanced to thereby increase performance and/or lifetime.

[00148] As described in previous embodiments of the present invention, it is desirable to have the ability to shift the gaze of outgoing beams as well as shift the view of a detector as incoming signals are received by rotating polygon mirrors. Figure 30A illustrates an embodiment of the present invention of a movable polygon system 3000. A rotating polygon 3001 rotates about its primary axis 3002, allowing an incident beam of light 3003 to be directed in a field of view as an outgoing directed beam of light 3004. Figure 30B illustrates an embodiment where the rotational axis of the polygon is rotated to a new axis 3005, leading to an adjustment of the direction of the field of view that the outgoing beam 3006 addresses relative to the field of view addressed initially. This effect can be advantageous when used in a LiDAR system in a vehicle, allowing the field of view to be adjusted up when approaching an incline, or adjusted down when approaching a decline. The change in rotational axis can be gradual, based on the surroundings and input signals from the driver or the control system of the vehicle. In another embodiment of the present invention, the changes in the axis can be continuous, as a precession of the axis of rotation over time. For example, Figure 30C illustrates adjustment of the rotational axis from its original axis 3002 where the polygon rotation axis is translated laterally to a new position as axis 3007, in the x and/or y direction 3008, with respect to the primary rotational axis in z. These adjustments lead to lateral shifts in the field of view 3009, a mode of adjustment that is desirable in driving conditions where a shift in gaze from more lateral to more forward looking is needed.

Transitioning from lower speed city driving to higher speed highway driving is one transition where a shift towards a more forward looking field of view is desirable and achieved by embodiments of the invention.

[00149] In some of the embodiments of the invention, the polygon scanner system is applied to scan a laser light source for a LiDAR sensor system. In alternative embodiments, the polygon scanner system is utilized for

unmanned aerial vehicle (UAV) collision avoidance, UAV navigation and localization, security intrusion detection, facial recognition, augmented reality spatial recognition, virtual reality spatial recognition, mixed reality spatial recognition, telecommunications, free space optical data links, in eye projection displays, device projection displays, holiday displays, laser headlamps, projection laser light shows, and industrial part marking.

[00150] In still further embodiments of the invention, an NBPS 3100, as shown by Figured 31 , has a motor immersed in fluid which utilizes electrical current as a source of drive power. Electrical leads 3101 are exposed to the non-fluid region so as to be accessible to other parts of a system, for instance, a scanner body comprised of one or multiple parts 3102 and 3103. The electrical leads must be fed through the boundary between the fluid 3104 and non-fluid regions. In some of these embodiments, the feedthrough can occur through connectors attached directly through a printed circuit board 3105. The circuit board can occupy a region at the interface between the fluid and non- fluid regions.

[00151] In further embodiments of the invention, an NBPS 3200 as shown by Figure 32 may include a mirror 3201 immersed in a fluid 3202 with a refractive index greater than 1.3, which results in refraction that occurs between the transition from air into the fluid and between the transition from fluid into air. This also results in a beneficial expansion of the scanned field of view compared to a polygon scanner operated without fluid immersion. This expansion can occur in multiple angular dimensions. The increase in scanned field of view is dependent on the refractive index, with the scanned field of view advantageously increasing as the refractive index increases. Nonetheless, if the field of view is not desirably increased, than the number of polygon facets may be increased to thereby increase the scan refresh rate for a regular polygon configuration and/or increase the vertical resolution or field of view for an irregular polygon configuration.

[00152] As highlighted hereinabove, an NBPS is desirably operable over a wide temperature range, for example, from -40 °C to 120 °C. As the NBPS is stored or operated over a temperature range, the physical constituents of the NBPS may expand at different rates. Most materials exhibit a positive coefficient of thermal expansion (CTE), and in general a CTE is material specific. Typically, and in the absence of a media phase change, fluids have a higher CTE than solids. For this typical case, at elevated temperatures, the fluids contained within a solid may expand at a greater rate than the solid or solids which contain it. Should there be no compressible media within a solid container, an increased pressure differential will typically be created between the inside and outside of the solid, which would need to be counteracted by seals or the solid itself. For certain configurations, this increased pressure may not be supported by the container, causing failure to seals or container walls.

[00153] In other embodiments, as shown by Figure 33, an NBPS 3300 may contain solid constituents 3301 that exhibit a negative CTE, and solid constituents 3302 and fluid constituents 3303 that exhibit a positive CTE. In this configuration, the pressure that might otherwise be created by the expanded volume of the fluid 3303 is reduced by the solid which provides additional volume into which the fluid can expand. This configuration would therefore reduce the likelihood of seal or container wall 3304 failure. There are a number of materials which exhibit negative CTE, which could be included in the NBPS. [00154] In another embodiment, the NBPS 3400 of Figure 34 is configured with a container 3401 that contains a region of the container 3402 constructed from an elastic solid material with a low Young’s modulus. At an elevated temperature, the elastic container region deforms to accommodate the increased volume of the expanded fluid 3403. The low Young’s modulus material is configured to expand such that the tensile stress it experiences is below its fracture limit. In this embodiment, the solid container increases in volume with its outer envelope increasing highest near the wall region 3402 constructed of material with low Young’s modulus. Numerous materials with a low Young’s modulus could be utilized for the container wall.

[00155] In another embodiment, an NBPS 3500 of Figure 35 is configured with a container 3501 that contains a region 3502 of the container constructed from an elastic material with corrugations, ridges, or grooves. At elevated temperatures, the elastic material within the region 3502 deforms to

accommodate the increased volume of the expanded fluid contained inside. The corrugations, ridges, or grooves locally deform to reduce the overall stress in the container region. In this embodiment, the solid container increases in volume with its outer envelope increasing highest near the wall region constructed from an elastic material with corrugations, ridges, or grooves. Numerous materials with numerous specific shapes corrugations, ridges, or grooves could be utilized for the container wall.

[00156] In a further embodiment, an NBPS 3600 of Figure 36 is configured to contain a pocket of gas 3601 contained within a solid elastic sub-container

3602 within an overall solid container 3603. At elevated temperature, the elastic sub-container region deforms to accommodate the increased volume of the expanded fluid 3604. In this instance, the compressible gas is reduced in volume to accommodate the increased volume of fluid, and the sub- container is also compressed. In this embodiment, the NBPS solid container

3603 does not need to change in total volume during operation at elevated temperatures. Numerous materials could be utilized for the sub-container wall, including polymers or rubber. The shape of the sub-container could also be customized to fit within the NBPS and may be shaped in simple geometric shapes, such as hollow spheres or tubes, or other more unique shapes to conformally fit within the internal cavity. [00157] In another embodiment, an NBPS 3700 of Figure 37 is configured to contain a pocket of gas 3701 that is surrounded directly with fluid 3702 any which may circulate in part or whole throughout the fluid body within an overall solid container 3703. At elevated temperature, the compressible gas is reduced in volume to accommodate the increased volume of fluid. The gas is desirably not circulated during NBPS operation, as gas pockets or bubbles which circulate may intersect the path of incident or scanned light, affecting scattering, transmission amplitude, phase, and wavefront distortion. Such circulation could occur to NBPS orientation during operation or shipping, or due to external accelerations.

[00158] In another embodiment, an NBPS 3800 of Figure 38 is configured with a container 3801 containing the two regions: one region 3802 which includes gas and optionally fluid 3802 and another region 3803 which contains fluid, separated by a physical barrier 3804 that includes one or more one-way valves or check valves 3805, including diaphragm check valves. These valves are designed to allow errant gas bubbles from the lower region 3803 to flow to the upper region 3802. In the event that the structure is tilted or turned upside down, the valves will close, limiting the transit of gas regions into the volume near the polygon mirrors. Valve actuation may occur via buoyancy or due to pressure differentials associated with fluid flow.

[00159] In particular, one or more of the check valves 3805 can function to provide a means for thermal expansion of the fluid to compress a gas pocket. Two volumes 3802 and 3803 are separated by one or more check valves. A first region 3803 is fluid and a second region 3802 is a comprised of a fluid and a gas pocket. At elevated temperature, the first region 3803 will build up a higher pressure than the second region 3802, which will actuate the check valve to allow flow to minimize the pressure differential until the check valve 3805 closes again. A similar process can occur during temperature reduction for a check valve configured to operate in the reverse direction. The check valves may only open a small amount during non-equilibrium conditions of pressure differences. Under normal operation, the check values remain closed and thus limit flow between the two regions, and limiting gas pockets to transit into the first region, which could be configured to contain the polygon reflector. [00160] In the NBPS 3900 of Figure 39, a cavity 3901 is provided, which surrounds a polygon mirror 3902. The cavity 3901 is substantially asymmetric to thereby preferentially eject entrained gas pockets. In a fluid cavity arrangement that is substantially rotationally symmetric, the chances of entrainment occurring are high due to the fluid velocity flow distribution. By way of example, a circular impeller spinning in a circular tank will create a fluid flow field that is rotationally uniform, but a circular impeller placed non- symmetrically in a rectangular tank results in a fluid flow field that is

substantially asymmetric, which can cause flow nulls and eddies that will eject both low density media (vapor bubbles) and high density media (particulate solids) out of the rotational field. As will be understood by those skilled in the art, these types of media can collect in the higher vapor pocket and lower particulate collection pocket. In an NBPS with a fluid cavity arrangement that is substantially rotationally asymmetric, entrainment probability is substantially reduced.

[00161] In a further embodiment of the invention, the NBPS 4000 of Figure 40 is configured to include an integral fluid inlet 4001 within the fluid body 4007 contained with one or more parts of a solid container 4008, 4009, and 4010. Pumping action created by the rotating optic 4002 can be used to keep bubbles of gas out of the optical path of the NBPS 4000. As in the case of an impeller in a centrifugal pump, a rotating mirror 4002 used in the present invention creates a pressure gradient between the low velocity flow near the rotational axis (high pressure) 4003 and the perimeter 4004 where there is high speed liquid flow (low pressure). By creating a fluid inlet 4001 near the high pressure central axis that continually draws bubble free liquid into the rotating chamber, and a complimentary fluid outlet 4005 at the lower pressure perimeter, gas bubbles can be effectively expelled from the optically sensitive region of the scanner, and ejected to the opposite end of the fluid outlet 4006 maintained elsewhere, whereupon the presence of gas bubbles can mitigate the effects of pressure changes within the system.

[00162] In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

THAT WHICH IS CLAIMED IS:

1. A light-based detection and ranging (LiDAR) system, comprising: an optical beam steering device including primary and secondary reflectors therein, which are collectively configured to support reflection of incoming light from at least one reflective surface on the primary reflector to at least one reflective surface on the secondary reflector as the primary reflector moves relative to the secondary reflector.

2. The LiDAR system of Claim 1 , wherein the primary and secondary reflectors are configured as first and second polygonal reflectors, respectively.

3. The LiDAR system of Claim 2, wherein the primary and secondary polygonal reflectors are collectively configured to support the sweeping of reflected light from a first reflective surface on the primary polygonal reflector to a first reflective surface on the secondary polygonal reflector as the first polygonal reflector rotates relative to the second polygonal reflector.

4. The LiDAR system of Claim 3, wherein the primary and secondary polygonal reflectors are configured to rotate about respective first and second axes, which are orthogonal to each other.

5. The LiDAR system of Claim 1 , wherein said optical beam steering device further comprises an optically transparent container having the primary and secondary reflectors therein, which are at least partially surrounded within the optically transparent container by an optically transparent fluid.

6. The LiDAR system of Claim 5, wherein the primary and secondary reflectors are surrounded on all sides thereof by the optically transparent fluid; and wherein the primary and secondary reflectors and the optically

transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

7. An optical beam steering device, comprising:

a multi-lobed polygonal reflector; and

a drive mechanism surrounding at least a portion of said multi-lobed polygonal reflector.

8. The device of Claim 7, wherein said multi-lobed polygonal reflector comprises first and second polygonal reflectors and a magnet extending therebetween.

9. The device of Claim 8, wherein said drive mechanism is an electro-magnetic drive mechanism that surrounds the magnet.

10. The device of Claim 9, wherein said drive mechanism comprises a ring-shaped electro-magnet.

11. The device of Claim 7, further comprising an optically

transparent container having said multi-lobed polygonal reflector and said drive mechanism therein, which are surrounded within the optically

transparent container by an optically transparent fluid.

12. The device of Claim 11 , wherein said multi-lobed polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

13. An optical beam steering device, comprising:

a polygonal reflector; and

an electro-magnetic drive mechanism extending at least partially through said polygonal-reflector.

14. The device of Claim 13, wherein said polygonal reflector has an annular-shaped opening extending therethrough; and wherein said electro- magnetic drive mechanism is aligned to a geometric center of the annularshaped opening.

15. The device of Claim 13, further comprising an optically transparent container having said polygonal reflector therein, which is surrounded within the optically transparent container by an optically transparent fluid.

16. The device of Claim 15, wherein said polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

17. An optical beam steering device, comprising:

a polygonal reflector having a magnet extending at least partially therethrough.

18. The device of Claim 17, wherein said polygonal reflector has a cavity therein; and wherein the magnet extends at least partially through said cavity.

19. The device of Claim 18, further comprising an optically transparent container having said polygonal reflector therein, which is at least partially surrounded within the optically transparent container by an optically transparent fluid.

20. The device of Claim 19, wherein said polygonal reflector is surrounded on all sides thereof by the optically transparent fluid; and wherein said polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

21. The device of Claim 18, wherein said polygonal reflector is encased within an optically transparent solid material.

22. An optical beam steering device, comprising:

an optically transparent container having a polygonal reflector therein, which is surrounded on all sides thereof by an optically transparent fluid.

23. The device of Claim 22, wherein the polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within said optically transparent container.

24. The device of Claim 23, wherein the optically transparent container includes a fluid inlet port and a fluid outlet port, which are selectively enabled to support rotation of said polygonal reflector within the optically transparent fluid.

25. The device of Claim 23, further comprising a plurality of light sources configured to optically drive rotation of said polygonal reflector within the optically transparent container when enabled to direct light towards said polygonal reflector.

26. The device of Claim 23, wherein said polygonal reflector is configured to be self-centering within the optically transparent container when rotating within the optically transparent fluid.

27. The device of Claim 26, wherein said polygonal reflector is annular shaped with a centrally-located opening therein through which the optically transparent fluid can pass.

28. An optical beam steering device, comprising:

an annular-shaped reflector having a polygonal-shaped inner surface therein that faces a center of said annular-shaped reflector.

29. The device of Claim 28, further comprising an optically transparent container having said annular-shaped reflector therein, which is surrounded within the optically transparent container by an optically transparent fluid.

30. The device of Claim 29, wherein said annular-shaped reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

31. An optical beam steering device, comprising:

a multi-lobed polygonal reflector including a first polygonal reflector having a first number of sides mounted to a second polygonal reflector having a second number of sides unequal to the first number of sides.

32. The device of Claim 31 , wherein the first and second polygonal reflectors are disc-shaped having planar top and bottom surfaces; and wherein a bottom planar surface of the first polygonal reflector is in contact with a top planar surface of the second polygonal reflector.

33. The device of Claim 32, further comprising an optically transparent container having said multi-lobed polygonal reflector therein, which is surrounded within the optically transparent container by an optically transparent fluid.

34. The device of Claim 33, wherein said multi-lobed polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the optically transparent container.

35. A light-based detection and ranging (LiDAR) system, comprising: a sealed container having at least one transparent window in a sidewall thereof, said sealed container comprising a polygonal reflector at a location adjacent a first of the at least one transparent window, and an optically transparent fluid having a refractive index greater than 1.3, which surrounds the polygonal reflector and extends between the polygonal reflector and the first of the at least one transparent window.

36. The LiDAR system of Claim 35, wherein the polygonal reflector and the optically transparent fluid are collectively configured to be neutrally buoyant relative to each other within the sealed container.

37. The LiDAR system of Claim 36, wherein the optically transparent fluid has a pocket of gas therein, which is sufficiently large to buffer changes in pressure within the optically transparent fluid over an operating temperature range of the LiDAR system.

38. The LiDAR system of Claim 36, wherein the optically transparent fluid has an elastic subcontainer therein, which is at least partially filled with a pocket of gas.

39. The LiDAR system of Claim 36, wherein said sealed container has an elastic subcontainer therein, which is at least partially submersed within the optically transparent fluid and at least partially filled with a pocket of gas.

40. The LiDAR system of Claim 35, wherein said sealed container further comprises an asymmetric cavity within the optically transparent fluid; and wherein the polygonal reflector is disposed within the asymmetric cavity.