Patent Description:
Light detectors, such as photodiodes, single photon avalanche diodes (SPADs), or other types of avalanche photodiodes (APDs), can be used to detect light that is imparted on their surfaces (e.g., by outputting an electrical signal, such as a voltage or a current, corresponding to an intensity of the light). Many types of such devices are fabricated out of semiconducting materials, such as silicon. In order to detect light over a substantial geometric area, multiple light detectors can be arranged into arrays connected in parallel. These arrays are sometimes referred to as silicon photomultipliers (SiPMs) or multi-pixel photon counters (MPPCs).

Some of the above arrangements are sensitive to relatively low intensities of light, thereby enhancing their detection qualities. However, this can lead to the above arrangements also being disproportionately susceptible to adverse background effects (e.g., extraneous light from outside sources could affect a measurement by the light detectors). United States patent application publication no. <CIT> presents a remote sensing apparatus and method including optical fibers and detectors. United States patent application publication no. <CIT> presents a high speed optical receiver interface including a housing adapted to receive a distal end of a fiber having a slanted end face. United States patent application publication no. <CIT> presents a LIDAR imaging system. United States patent application publication no. <CIT> presents optical analytical devices and their methods of use. United States patent application publication no. <CIT> presents a method of fabricating a turning mirror for an optical device.

In one embodiment according to the invention, a system includes a lens disposed relative to a scene and configured to focus light from the scene. The system also includes an opaque material that defines an aperture. The system also includes a waveguide having a first side that receives light focused by the lens and transmitted through the aperture. The waveguide guides at least a portion of the received light toward a second side of the waveguide opposite to the first side by total internal reflection or frustrated total internal reflection. The waveguide has a third side extending between the first side and the second side. The system also includes a mirror disposed along a propagation path of the guided light. The mirror reflects the guided light toward the third side of the waveguide. The system also includes an array of light detectors that detects the reflected light propagating out of the third side of the waveguide.

Furthermore, the invention provides a method and a light detection and ranging (LIDAR) device according to claims <NUM> and <NUM>, respectively.

Any example embodiment or feature described herein is not necessarily to be construed as preferred or advantageous over other embodiments or features. The example embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed implementations can be arranged and combined in a wide variety of different configurations. Furthermore, the particular arrangements shown in the figures should not be viewed as limiting. It should be understood that other implementations might include more or less of each element shown in a given figure. In addition, some of the illustrated elements may be combined or omitted. Similarly, an example implementation may include elements that are not illustrated in the figures.

Example implementations may relate to devices, systems, and methods for reducing background light imparted onto an array of light detectors. The light detectors in the array may be sensing light from a scene. For example, the light detectors may be a sensing component of a light detection and ranging (LIDAR) device.

One example system includes a lens. The lens may be used to focus light from a scene. However, the lens may also focus background light not intended to be observed by the system (e.g., sunlight). In order to selectively filter the light (i.e., separate background light from light corresponding to information within the scene), an opaque material (e.g., selectively etched metal, a glass substrate partially covered by a mask, etc.) may be placed behind the lens. The opaque material could be shaped as a slab, a sheet, or various other shapes in a variety of embodiments. Within the opaque material, an aperture may be defined. With this arrangement, a portion of, or the entirety of, the light focused by the lens could be selected for transmission through the aperture.

In the direction of propagation of the light transmitted through the aperture, the system includes a waveguide having a first side (e.g., adjacent to the aperture, etc.) and a second side opposite to the first side. The system also includes an array of light detectors (e.g., SPADs) disposed on or otherwise adjacent to a third side of the waveguide. For example, the third side may extend from the first side to the second side along a guiding direction in which the waveguide guides propagation of light therein toward the second side. Further, the array of light detectors may be positioned adjacent to the third side to detect light that propagates through the third side of the waveguide.

According to the invention, the system includes a mirror along a propagation path of the guided light propagating inside the waveguide. Further, the mirror may be tilted toward the third side of the waveguide. For instance, the second side of the waveguide can be tilted (e.g., slanted) toward the third side, and the mirror may be disposed along the second side (e.g., reflective material coating applied to the second side). Thus, for instance, the mirror may reflect the guided light (or a portion thereof) toward a particular region of the third side adjacent to the array of light detectors, and the reflected light may propagate through the particular region toward the array of light detectors.

Because the light from the aperture is guided along a length of the waveguide, the number of light detectors able to fit into a detection area (e.g., adjacent to the third side) can be larger than could fit in a cross-sectional area of the aperture. This may be due to the light being more tightly focused, and thus have a smaller cross-sectional area, at the aperture than along the particular region of the third side of the waveguide adjacent to the array of light detectors.

Other example implementations are possible as well and are described in greater detail within example embodiments herein.

<FIG> is an illustration of a noise limiting system <NUM> that includes an aperture, according to example embodiments. As shown, system <NUM> includes an array <NUM> of light detectors (exemplified by detectors <NUM> and <NUM>), an aperture <NUM> defined within an opaque material <NUM>, and a lens <NUM>. System <NUM> may measure light <NUM> reflected or scattered by an object <NUM> within a scene. Light <NUM> may also come, at least partially, from background sources. In some examples, system <NUM> may be included in a light detection and ranging (LIDAR) device. For example, the LIDAR device may be used for navigation of an autonomous vehicle. Further, in some embodiments, system <NUM>, or portions thereof, may be contained within an area that is unexposed to exterior light other than through lens <NUM>. This may reduce an amount of ambient light (which may affect measurements) reaching the detectors in array <NUM>.

Array <NUM> includes an arrangement of light detectors, exemplified by detectors <NUM> and <NUM>. In various embodiments, array <NUM> may have different shapes. As shown, array <NUM> has a rectangular shape. However, in other embodiments, array <NUM> may be circular or may have a different shape. The size of array <NUM> may be selected according to an expected cross-sectional area of light <NUM> diverging from aperture <NUM>. For example, the size of array <NUM> may be based on the distance between array <NUM> and aperture <NUM>, dimensions of aperture <NUM>, optical characteristics of lens <NUM>, among other factors. In some embodiments, array <NUM> may be movable. For example, the location of array <NUM> may be adjustable so as to be closer to, or further from, aperture <NUM>. To that end, for instance, array <NUM> could be mounted on an electrical stage capable of translating in one, two, or three dimensions.

Further, in some implementations, array <NUM> may provide one or more outputs to a computing device or logic circuitry. For example, a microprocessor-equipped computing device may receive electrical signals from array <NUM> which indicate an intensity of light <NUM> incident on array <NUM>. The computing device may then use the electrical signals to determine information about object <NUM> (e.g., distance of object <NUM> from aperture <NUM>, etc.). In some embodiments, some or all of the light detectors within array <NUM> may be interconnected with one another in parallel. To that end, for example, array <NUM> may be a SiPM or an MPPC, depending on the particular arrangement and type of the light detectors within array <NUM>. By connecting the light detectors in a parallel circuit configuration, for instance, the outputs from the light detectors can be combined to effectively increase a detection area in which a photon in light <NUM> can be detected (e.g., shaded region of array <NUM> shown in <FIG>).

Light detectors <NUM>, <NUM>, etc., may include various types of light detectors. In one example, detectors <NUM>, <NUM>, etc., include SPADs. SPADs may employ avalanche breakdown within a reverse biased p-n junction (i.e., diode) to increase an output current for a given incident illumination on the SPAD. Further, SPADs may be able to generate multiple electron-hole pairs for a single incident photon. In another example, light detectors <NUM>, <NUM>, etc., may include linear-mode avalanche photodiodes (APDs). In some instances, APDs or SPADs may be biased above an avalanche breakdown voltage. Such a biasing condition may create a positive feedback loop having a loop gain that is greater than one. Further, SPADs biased above the threshold avalanche breakdown voltage may be single photon sensitive. In other examples, light detectors <NUM>, <NUM>, etc., may include photoresistors, charge-coupled devices (CCDs), photovoltaic cells, and/or any other type of light detector.

In some implementations, array <NUM> may include more than one type of light detector across the array. For example, array <NUM> can be configured to detect multiple predefined wavelengths of light <NUM>. To that end, for instance, array <NUM> may comprise some SPADs that are sensitive to one range of wavelengths and other SPADs that are sensitive to a different range of wavelengths. In some embodiments, light detectors <NUM> may be sensitive to wavelengths between <NUM> and <NUM> (visible and/or infrared wavelengths). Further, light detectors <NUM> may have various sizes and shapes within a given embodiment or across various embodiments. In some embodiments, light detectors <NUM>, <NUM>, etc., may include SPADs that have package sizes that are <NUM>%,. <NUM>%, or. <NUM>% of the area of array <NUM>.

Opaque material <NUM> may block a portion of light <NUM> from the scene (e.g., background light) that is focused by the lens <NUM> from being transmitted to array <NUM>. For example, opaque material <NUM> may be configured to block certain background light that could adversely affect the accuracy of a measurement performed by array <NUM>. Alternatively or additionally, opaque material <NUM> may block light in the wavelength range detectable by detectors <NUM>, <NUM>, etc. In one example, opaque material <NUM> may block transmission by absorbing a portion of incident light. In another example, opaque material <NUM> may block transmission by reflecting a portion of incident light. A non-exhaustive list of example implementations of opaque material <NUM> includes an etched metal, a polymer substrate, a biaxially-oriented polyethylene terephthalate (BoPET) sheet, or a glass overlaid with an opaque mask, among other possibilities. In some examples, opaque material <NUM>, and therefore aperture <NUM>, may be positioned at or near a focal plane of lens <NUM>.

Aperture <NUM> provides a port within opaque material <NUM> through which light <NUM> may be transmitted. Aperture <NUM> may be defined within opaque material <NUM> in a variety of ways. In one example, opaque material <NUM> (e.g., metal, etc.) may be etched to define aperture <NUM>. In another example, opaque material <NUM> may be configured as a glass substrate overlaid with a mask, and the mask may include a gap that defines aperture <NUM> (e.g., via photolithography, etc.). In various embodiments, aperture <NUM> may be partially or wholly transparent, at least to wavelengths of light that are detectable by light detectors <NUM>, <NUM>, etc. For example, where opaque material <NUM> is a glass substrate overlaid with a mask, aperture <NUM> may be defined as a portion of the glass substrate not covered by the mask, such that aperture <NUM> is not completely hollow but rather made of glass. Thus, for instance, aperture <NUM> may be nearly, but not entirely, transparent to one or more wavelengths of light <NUM> scattered by the object <NUM> (e.g., glass substrates are typically not <NUM>% transparent). Alternatively, in some examples, aperture <NUM> may be formed as a hollow region of opaque material <NUM>.

In some examples, aperture <NUM> (in conjunction with opaque material <NUM>) may be configured to spatially filter light <NUM> from the scene at the focal plane. To that end, for example, light <NUM> may be focused onto a focal plane along a surface of opaque material <NUM>, and aperture <NUM> may allow only a portion of the focused light to be transmitted to array <NUM>. As such, aperture <NUM> may behave as an optical pinhole. In one embodiment, aperture <NUM> may have a cross-sectional area of between. <NUM><NUM> and. <NUM><NUM> (e.g.,. <NUM><NUM>). In other embodiments, aperture <NUM> may have a different cross-sectional area depending on various factors such as optical characteristics of lens <NUM>, distance to array <NUM>, noise rejection characteristics of the light detectors in array <NUM>, etc..

Thus, although the term "aperture" as used above with respect to aperture <NUM> may describe a recess or hole in an opaque material through which light may be transmitted, it is noted that the term "aperture" may include a broad array of optical features. In one example, as used throughout the description and claims, the term "aperture" may additionally encompass transparent or translucent structures defined within an opaque material through which light can be at least partially transmitted. In another example, the term "aperture" may describe a structure that otherwise selectively limits the passage of light (e.g., through reflection or refraction), such as a mirror surrounded by an opaque material. In one example embodiment, mirror arrays surrounded by an opaque material may be arranged to reflect light in a certain direction, thereby defining a reflective portion, which may be referred to as an "aperture".

Although aperture <NUM> is shown to have a rectangular shape, it is noted that aperture <NUM> can have a different shape, such as a round shape, circular shape, elliptical shape, among others. In some examples, aperture <NUM> can alternatively have an irregular shape specifically designed to account for optical aberrations within system <NUM>. For example, a keyhole shaped aperture may assist in accounting for parallax occurring between an emitter (e.g., light source that emits light <NUM>) and a receiver (e.g., lens <NUM> and array <NUM>). The parallax may occur if the emitter and the receiver are not located at the same position, for example. Other irregular aperture shapes are also possible, such as specifically shaped apertures that correspond with particular objects expected to be within a particular scene or irregular apertures that select specific polarizations of light <NUM> (e.g., horizontal or vertical polarizations).

Lens <NUM> may focus light <NUM> from the scene onto the focal plane where aperture <NUM> is positioned. With this arrangement, the light intensity collected from the scene, at lens <NUM>, may be focused to have a reduced cross-sectional area over which light <NUM> is projected (i.e., increasing the spatial power density of light <NUM>). For example, lens <NUM> may include a converging lens, a biconvex lens, and/or a spherical lens, among other examples. Alternatively, lens <NUM> can be implemented as a consecutive set of lenses positioned one after another (e.g., a biconvex lens that focuses light in a first direction and an additional biconvex lens that focuses light in a second direction). Other types of lenses and/or lens arrangements are also possible. In addition, system <NUM> may include other optical elements (e.g., mirrors, etc.) positioned near lens <NUM> to aid in focusing light <NUM> incident on lens <NUM> onto opaque material <NUM>.

Object <NUM> may be any object positioned within a scene surrounding system <NUM>. In implementations where system <NUM> is included in a LIDAR device, object <NUM> may be illuminated by a LIDAR transmitter that emits light (a portion of which may return as light <NUM>). In example embodiments where the LIDAR device is used for navigation on an autonomous vehicle, object <NUM> may be or include pedestrians, other vehicles, obstacles (e.g., trees, debris, etc.), or road signs, among others.

As noted above, light <NUM> may be reflected or scattered by object <NUM>, focused by lens <NUM>, transmitted through aperture <NUM> in opaque material <NUM>, and measured by light detectors in array <NUM>. This sequence may occur (e.g., in a LIDAR device) to determine information about object <NUM>. In some embodiments, light <NUM> measured by array <NUM> may additionally or alternatively include light scattered off multiple objects, transmitted by a transmitter of another LIDAR device, ambient light, sunlight, among other possibilities.

In addition, the wavelength(s) of light <NUM> used to analyze object <NUM> may be selected based on the types of objects expected to be within a scene and their expected distance from lens <NUM>. For example, if an object expected to be within the scene absorbs all incoming light of <NUM> wavelength, a wavelength other than <NUM> may be selected to illuminate object <NUM> and to be analyzed by system <NUM>. The wavelength of light <NUM> (e.g., if transmitted by a transmitter of a LIDAR device) may be associated with a source that generates light <NUM> (or a portion thereof). For example, if the light is generated by a laser diode, light <NUM> may comprise light within a wavelength range that includes <NUM> (or other infrared and/or visible wavelength). Thus, various types of light sources are possible for generating light <NUM> (e.g., an optical fiber amplifier, various types of lasers, a broadband source with a filter, etc.).

<FIG> is another illustration of system <NUM>. As shown, system <NUM> may also include a filter <NUM>. Filter <NUM> may include any optical filter configured to selectively transmit light within a predefined wavelength range. For example, filter <NUM> can be configured to selectively transmit light within a visible wavelength range, an infrared wavelength range, or any other wavelength range of the light signal emitted by emitter <NUM>. For example, optical filter <NUM> may be configured to attenuate light of particular wavelengths or divert light of particular wavelengths away from the array <NUM>. For instance, optical filter <NUM> may attenuate or divert wavelengths of light <NUM> that are outside of the wavelength range emitted by emitter <NUM>. Therefore, optical filter <NUM> may, at least partially, reduce ambient light or background light from adversely affecting measurements by array <NUM>.

In various embodiments, optical filter <NUM> may be located in various positions relative to array <NUM>. As shown, optical filter <NUM> is located between lens <NUM> and opaque material <NUM>. However, optical filter <NUM> may alternatively be located between lens <NUM> and object <NUM>, between opaque material <NUM> and array <NUM>, combined with array <NUM> (e.g., array <NUM> may have a surface screen that optical filter <NUM>, or each of the light detectors in array <NUM> may individually be covered by a separate optical filter, etc.), combined with aperture <NUM> (e.g., aperture <NUM> may be transparent only to a particular wavelength range, etc.), or combined with lens <NUM> (e.g., surface screen disposed on lens <NUM>, material of lens <NUM> transparent only to a particular wavelength range, etc.), among other possibilities.

Further, as shown in <FIG>, system <NUM> could be used with an emitter <NUM> that emits a light signal to be measured by array <NUM>. Emitter <NUM> may include a laser diode, fiber laser, a light-emitting diode, a laser bar, a nanostack diode bar, a filament, a LIDAR transmitter, or any other light source. As shown, emitter <NUM> may emit light which is scattered by object <NUM> in the scene and ultimately measured (at least a portion thereof) by array <NUM>. In some embodiments, emitter <NUM> may be implemented as a pulsed laser (as opposed to a continuous wave laser), allowing for increased peak power while maintaining an equivalent continuous power output.

The following is a mathematical illustration comparing the amount of background light that is received by lens <NUM> to the amount of signal light that is detected by the array <NUM>. As shown, the distance between object <NUM> and lens <NUM> is 'd', the distance between lens <NUM> and opaque material <NUM> is 'f', and the distance between the opaque material <NUM> and the array <NUM> is 'x'. As noted above, material <NUM> and aperture <NUM> may be positioned at the focal plane of lens <NUM> (i.e., 'f' may be equivalent to the focal length). Further, as shown, emitter <NUM> is located at a distance 'd' from object <NUM>.

For the sake of example, it is assumed that object <NUM> is fully illuminated by sunlight at normal incidence, where the sunlight represents a background light source. Further, it is assumed that all the light that illuminates object <NUM> is scattered according to Lambert's cosine law. In addition, it is assumed that all of the light (both background and signal) that reaches array <NUM> is fully detected by array <NUM>.

The power of the signal, emitted by emitter <NUM>, that reaches aperture <NUM>, and thus array <NUM>, can be calculated using the following: <MAT> where Psignal represents the radiant flux (e.g., in W) of the optical signal emitted by emitter <NUM> that reaches array <NUM>, Ptx represents the power (e.g., in W) transmitted by emitter <NUM>, Γ represents the reflectivity of object <NUM> (e.g., taking into account Lambert's Cosine Law), and Alens represents the cross-sectional area of lens <NUM>.

The background light that reaches lens <NUM> can be calculated as follows: <MAT> where Pbackground represents the radiance (e.g., in <MAT>) of the background light (caused by sunlight scattering off object <NUM>) arriving on lens <NUM> that is within a wavelength band that will be selectively passed by filter <NUM>, Psun represents the irradiance (e.g., in <MAT>) density due to the sun (i.e., the background source), and Tfilter represents the transmission coefficient of filter <NUM> (e.g., a bandpass optical filter). The factor of <MAT> relates to the assumption of Lambertian scattering off of object <NUM> from normal incidence.

Aperture <NUM> reduces the amount of background light permitted to be transmitted to the array <NUM>. To calculate the power of the background light that reaches array <NUM>, after being transmitted through aperture <NUM>, the area of aperture <NUM> is taken into account. The cross-sectional area (Aaperture) of aperture <NUM> can be calculated as follows: <MAT> where Aaperture represents the surface area of aperture <NUM> relative to object <NUM>, and w and h represent the width and height (or length) of aperture <NUM>, respectively. In addition, if lens <NUM> is a circular lens, the cross-sectional area (Alens) of lens <NUM> can be calculated as follows: <MAT> where dlens represents the diameter of the lens.

Thus, the background power transmitted to array <NUM> through aperture <NUM> can be calculated as follows: <MAT> where Pbackground represents background power incident on array <NUM>, and <MAT> represents the acceptance solid angle in steradians. The above formula indicates that Pbackground is the amount of radiance in the background signal after being reduced by lens <NUM> and aperture <NUM>.

Substituting the above determined values in for Pbackground, Aaperture, and Alens the following can be derived: <MAT>.

Additionally, the quantity <MAT> may be referred to as the "F number" of lens <NUM>. Thus, with one more substitution, the following can be deduced as the background power: <MAT>.

Making similar substitutions, the following can be deduced for signal power transmitted from the emitter <NUM> that arrives at the array <NUM>: <MAT>.

Further, a signal to noise ratio (SNR) of system <NUM> may be determined by comparing Psignal with Pbackground As demonstrated, the background power (Pbackground) may be significantly reduced with respect to the signal power due to the inclusion of aperture <NUM>, particularly for apertures having small w and/or small h (numerator of Pbackground formula above). Besides reducing aperture area, increasing the transmitted power (Ptx) by emitter <NUM>, decreasing the transmission coefficient (Tfilter) (i.e., reducing an amount of background light that gets transmitted through the filter), and increasing the reflectivity (Γ) of object <NUM> may be ways of increasing the SNR. Further, it is noted that in implementations where emitter <NUM> emits a pulsed signal, the shot noise of the background, as opposed to the power of the background, may be primarily relevant when computing the SNR. Thus, in some implementations, the SNR can be alternatively computed by comparing the shot noise against the signal power.

As shown in <FIG>, light <NUM> diverges as it propagates away from aperture <NUM>. Due to the divergence, a detection area at array <NUM> (e.g., shown as shaded area illuminated by light <NUM>) may be larger than a cross-sectional area of aperture <NUM>. An increased detection area (e.g., measured in m<NUM>) for a given light power (e.g., measured in W) may lead to a reduced light intensity (e.g., measured in <MAT>) incident on array <NUM>.

The reduction in light intensity may be particularly beneficial in embodiments where array <NUM> includes SPADs or other light detectors having high sensitivities. For example, SPADs derive their sensitivity from a large reverse-bias voltage that produces avalanche breakdown within a semiconductor. This avalanche breakdown can be triggered by the absorption of a single photon, for example. Once a SPAD absorbs a single photon and the avalanche breakdown begins, the SPAD cannot detect additional photons until the SPAD is quenched (e.g., by restoring the reverse-bias voltage). The time until the SPAD is quenched may be referred to as the recovery time. If additional photons are arriving at time intervals approaching the recovery time (e.g., within a factor of ten), the SPAD may begin to saturate, and the measurements by the SPAD may thus become less reliable. By reducing the light power incident on any individual light detector (e.g., SPAD) within array <NUM>, the light detectors (e.g., SPADs) in array <NUM> may remain unsaturated. As a result, the light measurements by each individual SPAD may have an increased accuracy.

<FIG> is a simplified block diagram of a LIDAR device <NUM>, according to example embodiments. In some example embodiments, LIDAR device <NUM> can be mounted to a vehicle and employed to map a surrounding environment (e.g., the scene including object <NUM>, etc.) of the vehicle. As shown, LIDAR device <NUM> includes a laser emitter <NUM> that may be similar to emitter <NUM>, a controller <NUM>, and a noise limiting system <NUM> that may be similar to system <NUM>, a rotating platform <NUM>, and one or more actuators <NUM>. In this example, system <NUM> includes an array <NUM> of light detectors, an opaque material <NUM> with an aperture defined therein (not shown), and a lens <NUM>, which can be similar, respectively, to array <NUM>, opaque material <NUM>, and lens <NUM>. It is noted that LIDAR device <NUM> may alternatively include more or fewer components than those shown. For example, LIDAR device <NUM> may include an optical filter (e.g., filter <NUM>). Thus, system <NUM> can be implemented similarly to system <NUM> and/or any other noise limiting system described herein. Device <NUM> may operate emitter <NUM> to emit light <NUM> toward a scene that includes object <NUM>, which may be similar, respectively, to emitter <NUM>, light <NUM>, and object <NUM>. Device <NUM> may then detect scattered light <NUM> to map or otherwise determine information about object <NUM>.

Controller <NUM> may be configured to control components of LIDAR device <NUM> and to analyze signals received from components of LIDAR device <NUM> (e.g., array <NUM> of light detectors). To that end, controller <NUM> may include one or more processors (e.g., a microprocessor, etc.) that execute instructions stored in a memory (not shown) of device <NUM> to operate device <NUM>. Additionally or alternatively, controller <NUM> may include digital or analog circuitry wired to perform one or more of the various functions described herein.

Rotating platform <NUM> may be configured to rotate about an axis to adjust a pointing direction of LIDAR <NUM> (e.g., direction of emitted light <NUM> relative to the environment, etc.). To that end, rotating platform <NUM> can be formed from any solid material suitable for supporting one or more components of LIDAR <NUM>. For example, system <NUM> (and/or emitter <NUM>) may be supported (directly or indirectly) by rotating platform <NUM> such that each of these components moves relative to the environment while remaining in a particular relative arrangement in response to rotation of rotating platform <NUM>. In particular, the mounted components could be rotated (simultaneously) about an axis so that LIDAR <NUM> may adjust its pointing direction while scanning the surrounding environment. In this manner, a pointing direction of LIDAR <NUM> can be adjusted horizontally by actuating rotating platform <NUM> to different directions about the axis of rotation. In one example, LIDAR <NUM> can be mounted on a vehicle, and rotating platform <NUM> can be rotated to scan regions of the surrounding environment at various directions from the vehicle.

In order to rotate platform <NUM> in this manner, one or more actuators <NUM> may actuate rotating platform <NUM>. To that end, actuators <NUM> may include motors, pneumatic actuators, hydraulic pistons, and/or piezoelectric actuators, among other possibilities.

With this arrangement, controller <NUM> could operate actuator(s) <NUM> to rotate rotating platform <NUM> in various ways so as to obtain information about the environment. In one example, rotating platform <NUM> could be rotated in either direction about an axis. In another example, rotating platform <NUM> may carry out complete revolutions about the axis such that LIDAR <NUM> scans a <NUM>° field-of-view (FOV) of the environment. In yet another example, rotating platform <NUM> can be rotated within a particular range (e.g., by repeatedly rotating from a first angular position about the axis to a second angular position and back to the first angular position, etc.) to scan a narrower FOV of the environment. Other examples are possible.

Moreover, rotating platform <NUM> could be rotated at various frequencies so as to cause LIDAR <NUM> to scan the environment at various refresh rates. In one embodiment, LIDAR <NUM> may be configured to have a refresh rate of <NUM>. For example, where LIDAR <NUM> is configured to scan a <NUM>° FOV, actuator(s) <NUM> may rotate platform <NUM> for ten complete rotations per second.

<FIG> illustrates a perspective view of LIDAR device <NUM>. As shown, device <NUM> also includes a transmitter lens <NUM> that directs emitted light from emitter <NUM> toward the environment of device <NUM>.

To that end, <FIG> illustrates an example implementation of device <NUM> where emitter <NUM> and system <NUM> each have separate respective optical lenses <NUM> and <NUM>. However, in other embodiments, device <NUM> can be alternatively configured to have a single shared lens for both emitter <NUM> and system <NUM>. By using a shared lens to both direct the emitted light and receive the incident light (e.g., light <NUM>), advantages with respect to size, cost, and/or complexity can be provided. For example, with a shared lens arrangement, device <NUM> can mitigate parallax associated with transmitting light (by emitter <NUM>) from a different viewpoint than a viewpoint from which light <NUM> is received (by system <NUM>).

As shown in <FIG>, light beams emitted by emitter <NUM> propagate from lens <NUM> along a pointing direction of LIDAR <NUM> toward an environment of LIDAR <NUM>, and may then reflect off one or more objects in the environment as light <NUM>. LIDAR <NUM> may then receive reflected light <NUM> (e.g., through lens <NUM>) and provide data pertaining to the one or more objects (e.g., distance between the one or more objects and the LIDAR <NUM>, etc.).

Further, as shown in <FIG>, rotating platform <NUM> mounts system <NUM> and emitter <NUM> in the particular relative arrangement shown. By way of example, if rotating platform <NUM> rotates about axis <NUM>, the pointing directions of system <NUM> and emitter <NUM> may simultaneously change according to the particular relative arrangement shown. Through this process, LIDAR <NUM> can scan different regions of the surrounding environment according to different pointing directions of LIDAR <NUM> about axis <NUM>. Thus, for instance, device <NUM> (and/or another computing system) can determine a three-dimensional map of a <NUM>° (or less) view of the environment of device <NUM> by processing data associated with different pointing directions of LIDAR <NUM> about axis <NUM>.

In some examples, axis <NUM> may be substantially vertical. In these examples, the pointing direction of device <NUM> can be adjusted horizontally by rotating system <NUM> (and emitter <NUM>) about axis <NUM>.

In some examples, system <NUM> (and emitter <NUM>) can be tilted (relative to axis <NUM>) to adjust the vertical extents of the FOV of LIDAR <NUM>. By way of example, LIDAR device <NUM> can be mounted on top of a vehicle. In this example, system <NUM> (and emitter <NUM>) can be tilted (e.g., toward the vehicle) to collect more data points from regions of the environment that are closer to a driving surface on which the vehicle is located than data points from regions of the environment that are above the vehicle. Other mounting positions, tilting configurations, and/or applications of LIDAR device <NUM> are possible as well (e.g., on a different side of the vehicle, on a robotic device, or on any other mounting surface).

It is noted that the shapes, positions, and sizes of the various components of device <NUM> can vary, and are illustrated as shown in <FIG> only for the sake of example.

Returning now to <FIG>, in some implementations, controller <NUM> may use timing information associated with a signal measured by array <NUM> to determine a location (e.g., distance from LIDAR device <NUM>) of object <NUM>. For example, in embodiments where laser emitter <NUM> is a pulsed laser, controller <NUM> can monitor timings of output light pulses and compare those timings with timings of signal pulses measured by array <NUM>. For instance, controller <NUM> can estimate a distance between device <NUM> and object <NUM> based on the speed of light and the time of travel of the light pulse (which can be calculated by comparing the timings). In one implementation, during the rotation of platform <NUM>, emitter <NUM> may emit light pulses (e.g., light <NUM>), and system <NUM> may detect reflections of the emitted light pulses. Device <NUM> (or another computer system that processes data from device <NUM>) can then generate a three-dimensional (3D) representation of the scanned environment based on a comparison of one or more characteristics (e.g., timing, pulse length, light intensity, etc.) of the emitted light pulses and the detected reflections thereof.

In some implementations, controller <NUM> may be configured to account for parallax (e.g., due to laser emitter <NUM> and lens <NUM> not being located at the same location in space). By accounting for the parallax, controller <NUM> can improve accuracy of the comparison between the timing of the output light pulses and the timing of the signal pulses measured by the array <NUM>.

In some implementations, controller <NUM> could modulate light <NUM> emitted by emitter <NUM>. For example, controller <NUM> could change the projection (e.g., pointing) direction of emitter <NUM> (e.g., by actuating a mechanical stage, such as platform <NUM> for instance, that mounts emitter <NUM>). As another example, controller <NUM> could modulate the timing, the power, or the wavelength of light <NUM> emitted by emitter <NUM>. In some implementations, controller <NUM> may also control other operational aspects of device <NUM>, such as adding or removing filters (e.g., filter <NUM>) along a path of propagation of light <NUM>, adjusting relative positions of various components of device <NUM> (e.g., array <NUM>, opaque material <NUM> (and an aperture therein), lens <NUM>, etc.), among other possibilities.

In some implementations, controller <NUM> could also adjust an aperture (not shown) within material <NUM>. In some embodiments, the aperture may be selectable from a number of apertures defined within the opaque material. In such embodiments, a MEMS mirror could be located between lens <NUM> and opaque material <NUM> and may be adjustable by controller <NUM> to direct the focused light from lens <NUM> to one of the multiple apertures. In some embodiments, the various apertures may have different shapes and sizes. In still other embodiments, the aperture may be defined by an iris (or other type of diaphragm). The iris may be expanded or contracted by controller <NUM>, for example, to control the size or shape of the aperture.

Thus, in some examples, LIDAR device <NUM> can modify a configuration of system <NUM> to obtain additional or different information about object <NUM> and/or the scene. In one example, controller <NUM> may select a larger aperture in response to a determination that background noise received by system from the scene is currently relatively low (e.g., during night-time). The larger aperture, for instance, may allow system <NUM> to detect a portion of light <NUM> that would otherwise be focused by lens <NUM> outside the aperture. In another example, controller <NUM> may select a different aperture position to intercept the portion of light <NUM>. In yet another example, controller <NUM> could adjust the distance (e.g., distance 'x' shown in <FIG>) between an aperture and light detector array <NUM>. By doing so, for instance, the cross-sectional area of a detection region in array <NUM> (i.e., cross-sectional area of light <NUM> at array <NUM>) can be adjusted as well (e.g., shaded region shown in <FIG>).

However, in some scenarios, the extent to which the configuration of system <NUM> can be modified may depend on various factors such as a size of LIDAR device <NUM> or system <NUM>, among other factors. For example, referring back to <FIG>, a size of array <NUM> may depend on an extent of divergence of light <NUM> from a location of aperture <NUM> to a location of array <NUM> (e.g., distance 'x' shown in <FIG>). Thus, for instance, the maximum vertical and horizontal extents of array <NUM> may depend on the physical space available for accommodating system <NUM> within a LIDAR device. Similarly, for instance, an available range of values for distance `x' (shown in <FIG>) between array <NUM> and aperture <NUM> may also be limited by physical limitations of a LIDAR device where system <NUM> is employed.

Accordingly, example implementations are described herein for space-efficient noise limiting systems that increase a detection area in which light detectors can intercept light from the scene and reduce background noise.

<FIG> is an illustration of a noise limiting system <NUM> that includes an aperture and a waveguide, according to example embodiments. <FIG> illustrates a cross-section view of system <NUM>, according to example embodiments. In some implementations, system <NUM> can be used with device <NUM> instead of or in addition to system <NUM>. As shown, system <NUM> may measure light <NUM> reflected or scattered by an object <NUM> within a scene similarly to, respectively, system <NUM>, light <NUM>, and object <NUM>. Further, as shown, system <NUM> includes a light detector array <NUM>, an opaque material <NUM>, an aperture <NUM>, and a lens <NUM> which may be similar, respectively, to array <NUM>, material <NUM>, aperture <NUM>, and lens <NUM>. For the sake of example, aperture <NUM> is shown to have a different shape (elliptical) compared to a shape of aperture <NUM> (rectangular). However, in line with the discussion above, various shapes of aperture <NUM> are possible. As shown, system <NUM> also includes a waveguide <NUM> (e.g., optical waveguide, etc.) arranged to receive light <NUM> (or a portion thereof) transmitted through aperture <NUM> and projected onto (e.g., shaded region) a receiving side 360a of waveguide <NUM>. As shown, system <NUM> also includes a mirror <NUM> disposed on side 360b of waveguide <NUM>.

Waveguide <NUM> can be formed from a glass substrate (e.g., glass plate, etc.), a photoresist material (e.g., SU-<NUM>, etc.), or any other material at least partially transparent to one or more wavelengths of light <NUM>. Further, in some examples, waveguide <NUM> may be formed from a material that has a different index of refraction than materials surrounding waveguide <NUM>. Thus, for example, waveguide <NUM> may guide light propagating therein via internal reflection (e.g., total internal reflection, etc.) at one or more edges, sides, walls, etc., of waveguide <NUM>.

Mirror <NUM> may include any reflective material that has reflectivity characteristics suitable for reflecting (at least partially) wavelengths of light <NUM> guided in waveguide <NUM>. To that end, a non-exhaustive list of example reflective materials includes gold, aluminum, other metal or metal oxide, synthetic polymers, hybrid pigments (e.g., fibrous clays and dyes, etc.), among other examples. As shown, mirror <NUM> is tilted (e.g., relative to an orientation of side 360a and/or a guiding direction of waveguide <NUM>) at an offset angle <NUM> toward side 360c of waveguide <NUM> (i.e., angle between mirror <NUM> and side 360a). In general, mirror <NUM> is positioned along a path of at least a portion of guided light <NUM> propagating inside waveguide <NUM> (from side 360a toward side 360b). In one embodiment, as shown, mirror <NUM> may be disposed on side 360b of waveguide <NUM>. For instance, side 360b can be formed to have the offset or tilting angle <NUM> relative to an orientation of side 360a, and mirror <NUM> can be disposed on side 360b (e.g., via chemical vapor deposition, sputtering, mechanical coupling, or any other deposition process). However, in other embodiments, mirror <NUM> can be alternatively disposed inside waveguide <NUM> (e.g., between sides 360a and 360b). In one embodiment, the offset or tilting angle <NUM> of mirror <NUM> is <NUM>°. However, other offset angles are possible.

As shown, waveguide <NUM> may be proximally positioned and/or in contact with opaque material <NUM> such that light <NUM> transmitted through aperture <NUM> is received by receiving side 360a (e.g., input end) of waveguide <NUM>. According to the invention waveguide (<NUM>) guides at least a portion of received light <NUM>, via total internal reflection or frustrated total internal reflection (FTIR) for instance, inside waveguide <NUM> toward an output end of waveguide <NUM>. For example, in the embodiment shown in <FIG> and <FIG>, waveguide <NUM> can guide received light <NUM> toward side 360b opposite to side 360a.

Further, as best shown in <FIG>, waveguide <NUM> may extend vertically between sides 360c and 360d. Sides 360c and 360d may each extend between sides 360a and 360b (e.g., along a guiding direction of waveguide <NUM>). In some examples, side 360c may correspond to an interface between a relatively high index of refraction medium (e.g., glass, photoresist, epoxy, etc.) of waveguide <NUM> and a relatively lower index of refraction medium (e.g., air, vacuum, optical adhesive, etc.) adjacent to side 360c (and/or one or more other sides of waveguide <NUM>). Thus, for instance, if guided light <NUM> propagates to side 360c at less than the critical angle (e.g., which may be based on a ratio of indexes of refraction of the materials at side 360c, etc.), then the guided light incident on side 360c (or a portion thereof) may be reflected back into waveguide <NUM>. Similarly, as best shown in <FIG>, waveguide <NUM> may extend horizontally between side 360e and another side of waveguide <NUM> (not shown) opposite to side 360e to control divergence of the guided light horizontally, for example.

Mirror <NUM> may reflect at least a portion of guided light <NUM> (guided inside waveguide <NUM>) toward a particular region of side 360c and out of waveguide <NUM>, as indicated by arrows 302a and 302b shown in <FIG>. For example, offset or tilting angle <NUM> of mirror <NUM> can be selected such that reflected light 302a, 302b from mirror <NUM> propagates toward the particular region of side 360c at greater than the critical angle, and reflected light 302a, 302b may thus be (at least partially) transmitted through side 360c rather than reflected (e.g., via total internal reflection etc.) back into waveguide <NUM>. Further, light detector array <NUM> can be positioned adjacent to the particular region of side 360c (through which reflected light 302a, 302b is transmitted) to receive reflected light 302a, 302b.

Thus, unlike light detector array <NUM>, light detector array <NUM> can be aligned (as shown in <FIG> and <FIG>) with the guiding direction of waveguide <NUM> (e.g., adjacent to side 360c) to intercept and detect reflected light 302a, 302b propagating out of side 360c. With this configuration, system <NUM> may provide an increased detection area for intercepting light <NUM> while also efficiently utilizing the space behind opaque material <NUM>.

It is noted that the sizes, positions, orientations, and shapes of the various components and features shown in <FIG> and <FIG> are not necessarily to scale, but are illustrated as shown for convenience in description. Further, in some embodiments, system <NUM> may include fewer or more components than those shown. Further, in some embodiments, one or more of the components shown can be combined, or divided into separate components.

In a first embodiment, light detector array <NUM> can be alternatively disposed (e.g., molded, etc.) on side 360c.

In a second embodiment, a distance between waveguide <NUM> and aperture <NUM> can vary. In one example, as shown in <FIG> and <FIG>, waveguide <NUM> can be disposed along (e.g., in contact with, etc.) opaque material <NUM>. Thus, for instance, side 360a (i.e., input end of waveguide <NUM>) can be substantially coplanar with or proximal to aperture <NUM>. With this arrangement for instance, waveguide <NUM> can receive and guide light <NUM> prior to divergence of light <NUM> transmitted through aperture <NUM>. However, in other examples, waveguide <NUM> can be alternatively positioned at a distance (e.g., gap) from opaque material <NUM> (and aperture <NUM>). For instance, an optical adhesive can be used to couple opaque material <NUM> with waveguide <NUM>.

In a third embodiment, the arrangement of aperture <NUM> (and/or side 360a of waveguide <NUM>) relative to lens <NUM> can vary. In one example, aperture <NUM> (and/or an input end of waveguide <NUM>) can be disposed along the focal plane of lens <NUM>. In another example, aperture <NUM> (and/or an input end of waveguide <NUM>) can be disposed parallel to the focal plane of lens <NUM> but at a different distance to lens <NUM> than the distance between the focal plane and lens <NUM>. Thus, in this example, optical characteristics (e.g., focus configuration, etc.) of system <NUM> can be adjusted depending on an application of system <NUM>. As such, in some instances, focused light <NUM> may continue converging (after transmission through aperture <NUM>) inside waveguide <NUM> before beginning to diverge toward side 360b. In some instances, system <NUM> may also include an actuator that moves lens <NUM>, opaque material <NUM>, and/or waveguide <NUM> to achieve a particular optical configuration while scanning the scene. In yet another example, aperture <NUM> (and/or side 360a of waveguide <NUM>) can be arranged at an offset orientation relative to the focal plane of lens <NUM>. For instance, system <NUM> can rotate (e.g., via an actuator) opaque material <NUM> (and/or array <NUM>) to adjust the entry angle of light <NUM> into waveguide <NUM>. By doing so, a controller (e.g., controller <NUM>) can further control optical characteristics of system <NUM> depending on various factors such as lens characteristics of lens <NUM>, environment of system <NUM> (e.g., to reduce noise / interference arriving from a particular region of the scanned scene, etc.), among other factors.

In a fourth embodiment not according to claims <NUM>-<NUM>, material <NUM> can be omitted and side 360a can be alternatively positioned along or parallel to the focal plane of lens <NUM>. In this embodiment, side 360a may thus correspond to an aperture.

In a fifth embodiment, the light detectors in array <NUM> can be alternatively implemented as separate physical structures coupled (e.g., disposed on or molded to, etc.) to waveguide <NUM>.

In a sixth embodiment, light detector array <NUM> can be implemented to additionally overlap other sides of waveguide <NUM> (e.g., side 360e, side 360d, etc.). Thus, in this embodiment, the light detectors in array <NUM> can detect light propagating out of waveguide <NUM> over a greater detection area.

In a seventh embodiment, waveguide <NUM> can alternatively have a cylindrical shape, such as an optical fiber, or any other shape. In this embodiment, the light detectors in array <NUM> can be alternatively arranged to surround (at least partially) an outer surface of the optical fiber to receive reflected light 302a, 302b propagating out of the cylindrical outer surface of the optical fiber. Thus, in some examples, waveguide <NUM> can be implemented as a rigid structure (e.g., slab waveguide) or as a flexible structure (e.g., optical fiber). For example, waveguide <NUM> can be alternatively configured as a waveguide diffuser that diffuses light <NUM> (or a portion thereof) transmitted through aperture <NUM> toward a detection area that can have various shapes or positions, as opposed to a flat surface (e.g., shaded region shown in <FIG>) orthogonal to a direction of propagation of diverging light <NUM>.

<FIG> illustrates a partial top view of a noise limiting system <NUM> that includes multiple waveguides <NUM>, <NUM>, <NUM>, <NUM>, according to example embodiments. It is noted that some of the components of system <NUM>, such as light detectors, etc., are omitted from the illustration of <FIG> for convenience in description. For purposes of illustration, <FIG> shows an x-y-z axis, in which the z-axis is pointing out of the page.

System <NUM> may be similar to any of systems <NUM>, <NUM>, and/or <NUM>, and can be used instead of or in addition to system <NUM> of device <NUM>. As shown, system <NUM> includes an opaque material <NUM> and a lens <NUM> that may be similar, respectively, to opaque material <NUM> and lens <NUM>. Further, as shown, system <NUM> includes multiple waveguides <NUM>, <NUM>, <NUM>, <NUM>, each of which may be similar to waveguide <NUM>.

Lens <NUM> may focus light <NUM> from a scene onto opaque material <NUM>, similarly to lens <NUM>, light <NUM>, and opaque material <NUM> of system <NUM>, for example. However, unlike system <NUM>, opaque material <NUM> may define multiple apertures <NUM>, <NUM>, <NUM>, <NUM> that are respectively aligned with (e.g., adjacent to) waveguides <NUM>, <NUM>, <NUM>, <NUM>. Thus, with this arrangement, system <NUM> may be configured to simultaneously capture light portions from multiple regions of focused light <NUM> projected by lens <NUM> on opaque material <NUM> at the respective positions of apertures <NUM>, <NUM>, <NUM>, <NUM>. Each light portion can be guided by a respective one of waveguides <NUM>, <NUM>, <NUM>, <NUM> onto a respective array of light detectors having a larger cross-sectional detection area than a cross-sectional area of a corresponding aperture. Through this process, for instance, system <NUM> can capture a 1D image of the scanned scene by defining multiple receive channels in a horizontal arrangement (e.g., in the x-y plane) along the focal plane of lens <NUM>.

Further, as shown, each waveguide of waveguides <NUM>, <NUM>, <NUM>, <NUM> may have a different length between a respective input end adjacent to opaque material <NUM> and a respective opposite output end (e.g., similar to side 360b, etc.) of the respective waveguide. With this arrangement for instance, system <NUM> may allow efficient use of space where respective arrays of light detectors can be placed for each of waveguides <NUM>, <NUM>, <NUM>, <NUM>.

Although <FIG> shows four waveguides <NUM>, <NUM>, <NUM>, <NUM>, system <NUM> may alternatively include fewer or more waveguides (and therefore a different number of receive channels). In one embodiment, system <NUM> may include <NUM> waveguides horizontally arranged (e.g., in the x-y plane) adjacent opaque material <NUM>. Other waveguide arrangements are possible as well. Additionally, it is noted that the various sizes, shapes, and positions (e.g., distance between adjacent waveguides, etc.) shown for the various components of system <NUM> is not necessarily to scale but is illustrated as shown only for convenience in description.

<FIG> illustrates a cross-section view of system <NUM> of <FIG>. In the cross-section view illustrated in <FIG> the y-axis extends through the page. It is noted that some of the components of system <NUM>, such as lens <NUM> for instance, are omitted from the illustration of <FIG> for convenience in description.

As shown, system <NUM> also includes an array of light detectors <NUM>, a mirror <NUM> (also shown in <FIG>), a first substrate <NUM>, a second substrate <NUM>, a third substrate <NUM>, a first optical adhesive <NUM>, a second optical adhesive <NUM>, an optical filter <NUM>, one or more optical shields <NUM>, a support structure <NUM>, and an optical element <NUM>. Further, as shown, opaque material <NUM> (e.g., black carbon, etc.) defines aperture <NUM> adjacent to a first side of waveguide <NUM>, similarly to, respectively, the arrangement of opaque material <NUM> and waveguide <NUM>.

Array <NUM> and mirror <NUM> may be similar, respectively, to array <NUM> and mirror <NUM>. For example, mirror <NUM> may reflect light guided inside waveguide <NUM> out of waveguide <NUM> toward array <NUM>. For instance, as shown, mirror <NUM> could be disposed on a tilted side of waveguide <NUM> (opposite to the side adjacent to opaque material <NUM>) to reflect the guided light toward array <NUM>.

Substrates <NUM>, <NUM>, <NUM> can be formed from any transparent solid material configured to allow propagation of light (e.g., wavelengths of light transmitted through aperture <NUM>, guided by waveguide <NUM>, and/or reflected by mirror <NUM> toward array <NUM>) through the respective substrates. For example, substrates <NUM>, <NUM>, <NUM> may include glass substrates.

Optical adhesives <NUM>, <NUM> may be formed from any type of material that cures from a liquid form into a solid form to attach one or more components of system <NUM> to one another. Example optical adhesives may include photopolymers or other polymers that can transform from a clear, colorless, liquid form into a solid form (e.g., in response to exposure to ultraviolet light or other energy source).

As shown, adhesive <NUM> may be disposed between substrates <NUM> and <NUM> and surrounding one or more sides of waveguide <NUM> to couple substrate <NUM> with substrate <NUM>. With this arrangement, for instance, multiple waveguides along the x-y plane (e.g., waveguides <NUM>, <NUM>, <NUM>, <NUM>, etc.) can be supported in a particular arrangement (e.g., horizontally in the x-y plane) relative to one another. Further, as shown, adhesive <NUM> may be disposed between opaque material <NUM> and the waveguides sandwiched between substrates <NUM> and <NUM>.

In an example scenario, the waveguide arrangement between substrates <NUM>, <NUM> can be assembled as a "chip" that is then be diced near an edge of substrates <NUM>, <NUM> without cutting through any of the "sandwiched" waveguides between the two substrates. For instance, a portion of adhesive <NUM> may still surround the side of waveguide <NUM> adjacent to opaque material <NUM> after the dicing. Next, in this example, the second adhesive <NUM> can be used to attach opaque material <NUM> to the waveguide sandwich arrangement. Further, for instance, adhesive <NUM> can be formed from a similar material as <NUM> (e.g., same index of refraction, etc.). As a result, light propagating through the aperture may continue propagating toward waveguide <NUM> in a substantially uniform optical medium (e.g., adhesives <NUM>, <NUM>) to reduce or prevent reflection or refraction of the light prior to reaching waveguide <NUM>. To that end, as shown, adhesive <NUM> may extend through the aperture defined by opaque material <NUM> to couple (e.g., attach) substrate <NUM> to substrates <NUM> and <NUM>.

Alternatively, in some embodiments, system <NUM> can include the sandwiched waveguide arrangement without the gap between the edge of substrates <NUM>, <NUM> and the waveguides. For example, the waveguide sandwich arrangement can be formed by dicing substrates <NUM>, <NUM> and the waveguides. In this example, the waveguides can be formed from a material having a sufficient hardness to mitigate damage due to the dicing. Further, in this example, the diced sides of the waveguides can optionally be polished after the dicing to improve a smoothness of the diced sides.

Optical filter <NUM> may include any light filter configured to attenuate light propagating toward waveguide <NUM>. For example, where system <NUM> is employed in a LIDAR device, filter <NUM> may be configured to attenuate wavelengths of light outside a wavelength range of light emitted by a transmitter of the LIDAR device. By doing so, for instance, filter <NUM> may reduce an amount of ambient or background light reaching array <NUM>, thereby improving the accuracy of measurements obtained using array <NUM>. As shown, filter <NUM> may be disposed on a side of substrate <NUM> (opposite to the side adjacent to opaque material <NUM>).

In another embodiment, filter <NUM> can be alternatively disposed on the side adjacent to opaque material <NUM> or at any other location along a propagation path of the light prior to arrival of the light at array <NUM>. In yet another embodiment, substrate <NUM> can be formed from a material that has light filtering characteristics of filter <NUM>. Thus, in this embodiment, filter <NUM> can be omitted from system <NUM> (i.e., the functions of filter <NUM> can be performed by substrate <NUM>). In still another embodiment, filter <NUM> can be implemented as multiple (e.g., smaller) filters that are each disposed between substrate <NUM> and a respective one of the arrays of light detectors. For instance, a first filter can be used to attenuate light propagating toward array <NUM>, and a second separate filter can be used to attenuate light propagating toward another array of light detectors (not shown), etc..

In some examples, substrate <NUM> (and filter <NUM>) may extend through the page in the illustration of <FIG> (e.g., along the y-axis) to similarly attenuate light propagating toward waveguides <NUM>, <NUM>, and <NUM>.

Optical or light shield(s) <NUM> may comprise one or more light absorbing materials (e.g., black carbon, black chrome, black plastic, etc.) arranged around array <NUM> to reduce or prevent light (other than light reflected by mirror <NUM>) from reaching array <NUM>. Referring back to <FIG> for example, one or more arrays of light detectors similar to array <NUM> can be disposed near one another on support structure <NUM>. Data from each array, for instance, may correspond to a receive channel of system <NUM>. Thus, in this example, light shield(s) <NUM> can prevent cross-talk between the respective receive channels by shielding each array from light intended for receipt by another nearby array. Additionally or alternatively, light shield(s) <NUM> may help reduce light from other sources (e.g., ambient light, etc.) from reaching array <NUM>. Further, with this arrangement for instance, multiple arrays of light detectors can be densely packed next to one another to achieve efficient utilization of space in system <NUM>.

For example, support structure <NUM> may include a printed circuit board (PCB) that mounts groups of light detectors (including array <NUM>), where each group is separated by optical shields such as optical shield(s) <NUM>. Alternatively or additionally, structure <NUM> may include any other solid material having material characteristics suitable for supporting array <NUM> and/or one or more other arrays of light detectors.

In some implementations, system <NUM> includes an optical element <NUM> disposed between mirror <NUM> and array <NUM>. Optical element <NUM> may include any optical element or combination of optical elements that modify optical characteristics of the light reflected by mirror <NUM> toward array <NUM>. In one example, optical element <NUM> includes a mixing rod or homogenizer configured to distribute the energy density of the reflected light prior to reaching array <NUM>. This can be useful when the light reflected by mirror <NUM> has a non-uniform energy distribution. Further, in some instances, the light detectors in array <NUM> may include single photon detectors (e.g., avalanche photodiodes, etc.) that are associated with a "quenching" time period after detection of a photon. Distributing the energy of the light using optical element <NUM> may reduce the likelihood of a second photon reaching the same light detector during the "quenching" time period because the second photon may be directed toward a different light detector in array <NUM>. In some examples, optical element <NUM> may alternatively or additionally include other types of optical elements, such as lenses, filters, etc..

<FIG> illustrates another cross section view of system <NUM>. In the cross section view of <FIG>, the surface of support structure <NUM> that mounts array <NUM> is parallel to the page (e.g., x-y plane of the x-y-z axis shown). As shown, support structure <NUM> mounts multiple arrays of light detectors <NUM>, <NUM>, <NUM>, <NUM>. To that end, arrays <NUM>, <NUM>, and <NUM> may include a plurality of light detectors similarly to any of arrays <NUM>, <NUM>, etc. For instance, each of arrays <NUM>, <NUM>, <NUM> may include a plurality of APDs (or SPADs) that are connected in parallel to one another (e.g., SiPM, MPCC, etc.). Additionally, arrays <NUM>, <NUM>, <NUM> may be aligned, respectively, with reflected light propagating out of waveguides <NUM>, <NUM>, <NUM> (shown in <FIG>), similarly to the alignment of array <NUM> with waveguide <NUM>.

Further, as shown, light shield(s) <NUM> (e.g., black carbon, etc.) is arranged as a honeycomb structure, where each cell of the honeycomb structure shields a respective array of light detectors of arrays <NUM>, <NUM>, <NUM>, <NUM>. However, other arrangements of light shield(s) <NUM> are possible as well (e.g., rectangular cells, other shapes of cells, etc.). Thus, in some examples, this arrangement of system <NUM> may allow space-efficient placement of multiple arrays of light detectors (e.g., along a sign that are each aligned with a respective waveguide in system <NUM>, while shielding light propagating toward each respective array from reaching an adjacent array.

Although not shown in <FIG>, system <NUM> may include additional waveguides that are each aligned with a different cell in the honeycomb-shaped light shield(s) <NUM>. In one example, system <NUM> may include more than four waveguides that are disposed on substrate <NUM> (shown in <FIG>) similarly to waveguide <NUM> (e.g., an array of waveguides arranged horizontally in the x-y plane).

In another example, system <NUM> may include additional waveguides mounted along a different horizontal plane (e.g., disposed on substrate <NUM>) and also aligned with respective light detector arrays (not shown) in the honeycomb-shaped light shield(s) <NUM>. In this example, opaque material <NUM> may include additional apertures aligned with these additional waveguides. With this arrangement, system <NUM> can image additional regions of the focal plane of lens <NUM> to provide a two-dimensional (2D) scanned image of the scene associated with focused light <NUM>. Alternatively or additionally, the entire assembly of system <NUM> can be rotated or moved to generate the 2D scanned image of the scene.

Thus, within examples, system <NUM> can be configured to detect light propagating through adjacent apertures (i.e., corresponding to portions of focused light <NUM>) simultaneously over relatively larger detection areas (e.g., arrays <NUM>, <NUM>, <NUM>, <NUM>), while preventing overlap between the light from the respective adjacent apertures. By way of example, opaque material <NUM> may comprise a grid of apertures along the focal plane of lens <NUM>, and each aperture in the grid may detect light from a particular portion of the FOV of lens <NUM>. In one embodiment, opaque material <NUM> may comprise four rows of <NUM> apertures, where each row is along the y-axis shown in <FIG> and is separated by an offset (e.g., along z-axis) from an adjacent row of apertures. In this embodiment, system <NUM> may provide <NUM> * <NUM> = <NUM> receive channels. Other embodiments are possible as well.

Thus, system <NUM> may allow for multi-pixel imaging of the scene indicated by light <NUM> transmitted through apertures in opaque material <NUM>, while also reducing background noise since only a small respective portion of the light (and its associated background noise) are transmitted through each respective waveguide. For example, combined outputs from light detectors in array <NUM> may correspond to a first pixel that indicates light transmitted through a first aperture, combined outputs from light detectors in array <NUM> may correspond to a second pixel that indicates light transmitted through a second aperture, combined outputs from light detectors in array <NUM> may correspond to a third pixel that indicates light transmitted through a third aperture, and combined outputs from light detectors in array <NUM> may correspond to a fourth pixel that indicates light transmitted through a fourth aperture. As such, for example, controller <NUM> of device <NUM> can compute a one-dimensional (1D) image (e.g., horizontally in the y-z plane) of the scene by combining the four (adjacent) pixels.

Although waveguides <NUM>, <NUM>, <NUM>, <NUM> are shown in <FIG> to be in a horizontal (e.g., along x-y plane) arrangement, in some examples, system <NUM> may include waveguides in a different arrangement. In a first example, the receiving sides of the waveguides can alternatively or additionally be arranged vertically (e.g., along y-z plane) to obtain a vertical 1D image of the scene. In a second example, the receiving sides of the waveguides can alternatively be arranged both horizontally and vertically (e.g., as a two-dimensional grid) adjacent to opaque material <NUM>. For instance, system <NUM> may include additional waveguides that are arranged horizontally (e.g., disposed on substrate <NUM> of <FIG>, etc.). In this instance, system <NUM> may similarly assemble multiple horizontal pixels based on apertures along the y-z plane (but at a different z-height (vertical location) than the apertures of waveguides <NUM>, <NUM>, <NUM>, <NUM>). Thus, in this example, controller <NUM> can combine outputs from the waveguides to generate a two-dimensional (2D) image of the scene (e.g., system <NUM> can combine horizontal pixels from multiple vertical positions on the z-axis to generate the 2D image of the scene).

In some examples, the respective apertures defined by opaque material <NUM> may have different sizes relative to one another. By way of example, a first aperture adjacent to waveguide <NUM> may have a greater size than a second aperture adjacent to waveguide <NUM>. In this example, due to the difference between the cross-sectional areas of respective portions of light <NUM> incident on respective waveguides <NUM> and <NUM>, light detected at array <NUM> may represent a larger angular field-of-view (FOV) of the scanned scene relative to an angular FOV indicated by light incident on array <NUM>.

Alternatively or additionally, in some examples, waveguides <NUM>, <NUM>, <NUM>, <NUM> may have different widths compared to one another. In these examples, the difference between the cross-sectional areas of the respective waveguides may similarly result in different respective angular FOVs of the scanned scene detected via the respective waveguides.

<FIG> is a flowchart of a method <NUM>, according to example embodiments. Method <NUM> presents an embodiment of a method that could be used with any of systems <NUM>, <NUM>, <NUM>, and/or device <NUM>, for example. Method <NUM> may include one or more operations, functions, or actions as illustrated by one or more of blocks <NUM>-<NUM>. Although the blocks are illustrated in a sequential order, these blocks may in some instances be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation.

In addition, for method <NUM> and other processes and methods disclosed herein, the flowchart shows functionality and operation of one possible implementation of present embodiments. In this regard, each block may represent a module, a segment, a portion of a manufacturing or operation process, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer readable medium, for example, such as a storage device including a disk or hard drive. The computer readable medium may include a non-transitory computer readable medium, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a computer readable storage medium, for example, or a tangible storage device. In addition, for method <NUM> and other processes and methods disclosed herein, each block in <FIG> may represent circuitry that is wired to perform the specific logical functions in the process.

At block <NUM>, method <NUM> involves focusing, by a lens (e.g., lens <NUM>) disposed relative to a scene, light from the scene. In some examples, the light from the scene may be reflected or scattered by an object (e.g., object <NUM>) within the scene. In some examples, a computing device (e.g., controller <NUM>) may actuate or otherwise adjust a characteristic of the lens (e.g., focal plane, focal length, etc.). At block <NUM>, method <NUM> involves transmitting the focused light through an aperture (e.g., aperture <NUM>) defined within an opaque material (e.g., opaque material <NUM>). At block <NUM>, method <NUM> involves receiving, at a first side (e.g., side 360a) of a waveguide, at least a portion of the light transmitted through the aperture. At block <NUM>, method <NUM> involves guiding, by the waveguide, the received light toward a second side of the waveguide (e.g., side 360b). At block <NUM>, method <NUM> involves reflecting, via a mirror, the guided light toward a third side of the waveguide (e.g., side 360c) extending between the first side and the second side. At block <NUM>, method <NUM> involves detecting, at the array of light detectors, the reflected light (e.g., 302a, 302b) propagating out of the third side of the waveguide.

Claim 1:
A system (<NUM>; <NUM>; <NUM>; <NUM>) comprising:
a lens (<NUM>; <NUM>; <NUM>; <NUM>) disposed relative to a scene, wherein the lens focuses light (<NUM>; <NUM>; <NUM>; <NUM>) from the scene;
an opaque material that defines an aperture;
a waveguide having a first side that receives light focused by the lens and transmitted through the aperture, wherein the waveguide guides at least a portion of the received light toward a second side of the waveguide opposite to the first side by total internal reflection or frustrated total internal reflection, and wherein the waveguide has a third side extending between the first side and the second side;
characterized by a mirror disposed along a path of the guided light, wherein the mirror reflects the guided light toward the third side of the waveguide; and
an array of light detectors that detects the reflected light propagating out of the third side of the waveguide.