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).

<CIT> describes a gate-array pulse capture device that senses, receives, and processes signals derived in response to received laser energy, i.e., signals reflected from a target. The reflected signals are initially in the form of light pulses and are converted into analog electrical signals in the detection module and passed on to the pulse capture device. The pulse capture device determines the time delay between the transmitted and received signals and the intensity of the reflected pulse, and then compares its shape to a predetermined pattern to locate the position and intensity of the peak. This information is then used by an image processor to locate and identify targets.

<CIT> describes a ranging system which comprises: a transmitter for transmitting a series of at least one radiation pulse to an object area based on a command signal; a receiver for receiving returning radiation reflected off an object in the object area and selectively redirecting the returning radiation from each pulse dependent upon the command signal and object characteristics; and at least two radiation detectors arranged to receive the redirected returning radiation from the receiver, each of the radiation detectors being representative of different object data. Object data is determined based on which of the radiation detectors receives the redirected returning radiation.

<CIT> describes a single-side growth reflection-based photodetector includes a waveguide structure <NUM> comprising a "strip-loaded rib" waveguide <NUM> which accepts light <NUM> from an input end-face <NUM> and confines the light to a predetermined spatial optical mode <NUM>. The light <NUM> propagates along the waveguide <NUM> and is internally reflected off an edge <NUM> of a retrograde angled region <NUM>, at one end of the waveguide, to a detector layer <NUM> where the light <NUM> is absorbed, thereby creating electron-hole pairs in the detector layer <NUM>. The absorbed light is detected by a metal-semiconductor-metal (MSM) detector comprising an interdigital electrode structure <NUM> disposed on the outer surface of the detector layer <NUM> which is disposed above a wide non-waveguide mesa layer <NUM>. For <NUM> micron wavelength light, the detector layer <NUM> is made of GaAs. Alternatively, for <NUM>-<NUM> micron light, the detector layer <NUM> is made of InGaAs.

In one example, a system includes a lens disposed relative to a scene and configured to focus light from the scene. The system also includes an aperture defined within an opaque material. 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 the received light toward a second side of the waveguide opposite to the first side. The waveguide has a third side extending between the first side and the second side. The system also includes an array of light detectors that intercepts and detects light propagating out of the third side of the waveguide.

In another example, a method involves focusing, via a lens disposed relative to a scene, light from the scene. The method also involves transmitting the focused light through an aperture defined within an opaque material. The method also involves receiving, at a first side of a waveguide, light transmitted through the aperture. The method also involves guiding, by the waveguide, the received light toward a second side of the waveguide. The method also involves detecting, at an array of light detectors, light propagating out of a third side of the waveguide. The third side extends between the first side and the second side.

In yet another example, a light detection and ranging (LIDAR) device includes a LIDAR transmitter that illuminates a scene. The LIDAR device also includes a LIDAR receiver that receives light scattered by one or more objects within the scene. The LIDAR receiver includes a lens that focuses the scattered light. The LIDAR receiver also includes an aperture defined within an opaque material. The LIDAR receiver also includes a waveguide having a first side that receives light focused by the lens and transmitted through the aperture. The waveguide guides the received light toward a second side of the waveguide opposite to the first side. The waveguide has a third side extending between the first side and the second side. The LIDAR receiver also includes an array of light detectors that intercepts and detects light propagating out of the third side of the waveguide.

In still another example, a system comprises means for focusing, via a lens disposed relative to a scene, light from the scene. The system also comprises means for transmitting the focused light through an aperture defined within an opaque material. The system also comprises means for receiving, at a first side of a waveguide, light transmitted through the aperture. The system also comprises means for guiding, by the waveguide, the received light toward a second side of the waveguide. The system also comprises means for detecting, at an array of light detectors, light propagating out of a third side of the waveguide. The third side extends between the first side and the second side.

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.

The present disclosure relates 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.

The disclosed 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 within the scene). 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. The aperture may select a region of, or the entirety of, the light of the scene focused by the lens for transmission through the aperture.

On a backside of the opaque material (e.g., a side of the opaque material opposite another side on which focused light from the lens is projected, etc.), the light selected by the aperture may be transmitted through the aperture. In the direction of propagation of the light transmitted through the aperture, the system may include a waveguide having a first side (e.g., adjacent to the aperture, etc.) and a second side opposite to the first side. The system may also include 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. Thus, the array of light detectors may detect light that propagates through the third side of the waveguide (e.g., evanescent light, and/or light leaking through a cladding layer of the waveguide).

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., 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 third side of the waveguide. In some examples, the system may also include a mirror (e.g., light reflector) disposed along the second side to reflect guided light arriving at the second side back into the waveguide. As a result, for instance, a larger amount of the light guided inside the waveguide may propagate out of the third side and toward the array of light detectors.

In one example implementation, the system can employ frustrated total internal reflection (FTIR) to transmit a portion of the guided light in the waveguide to the array of light detectors. For example, the waveguide can be formed as a glass plate (or other material transparent to wavelength(s) of the guided light). The glass plate (i.e., waveguide) may also include a relatively low index of refraction (e.g., a polymer coating, fluorine-doped glass, etc.) cladding layer disposed on the third side of the waveguide to facilitate FTIR of the guided light. The cladding layer may include gaps (e.g., dents, etc.) to increase the amount of light escaping through the cladding layer at the positions of the gaps. Each gap can be aligned with a corresponding light detector in the array such that light escaping from the gap can be detected by the corresponding light detector. Thus, in this example, the waveguide may be configured as a leaky waveguide in which light leaks out of the third side at positions corresponding to the light detectors. Further, in some instances, separation distances between the gaps in the cladding layer can be gradually reduced as the light propagates toward the second side. As a result, a more uniform light intensity of the leaked light can be achieved.

In another example implementation, the system can employ scattered coupling to transmit light through the third side toward the light detectors in the array. For example, the waveguide can be implemented as a grating coupler that varies the strength of scattered light evanescing through the third side in a predetermined manner. Further, in some instances, the system may also include a mirror disposed along a fourth side of the waveguide (opposite to the third side). By doing so, the waveguide can be further configured as a wavelength filter by tuning the separation distances along the grating structures on the third side.

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. 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> scattered by an object <NUM> within a scene. Light <NUM> may also come, at least partially, from background sources. Thus, 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> and/or aperture <NUM>. This may prevent ambient light from triggering the detectors in array <NUM> thereby affecting measurements.

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>, and may thus be based on the distance between array <NUM> and aperture <NUM>, dimensions of aperture <NUM>, optical characteristics of lens <NUM>, etc. In some embodiments, array <NUM> may be movable. For example, array <NUM> may be actuated 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 an SiPM or an MPPC, depending on the particular arrangement and type of the light detectors within array <NUM>. By connecting the 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 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, APDs or 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), and/or photovoltaic cells, among others.

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 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>. As such, opaque material <NUM> is configured to block certain background light that could adversely affect the accuracy of a measurement performed by array <NUM>. Opaque material <NUM>, and therefore the aperture <NUM>, may be positioned at or near a focal plane of the lens <NUM>. In one example, opaque material <NUM> may block transmission by absorbing light <NUM>. In another example, opaque material <NUM> may block transmission by reflecting light <NUM>. 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 (also referred to as a Mylar® sheet), or a glass overlaid with an opaque mask, among other possibilities.

Aperture <NUM> provides a port within opaque material <NUM> through which light <NUM> is transmitted. Aperture <NUM> may be defined within opaque material <NUM> in a variety of ways. In one example, where opaque material <NUM> includes a metal, the metal may be etched to define aperture <NUM>. In another example, where opaque material <NUM> is a glass substrate overlaid with a mask, the mask may include a gap that defines aperture <NUM> (e.g., via photolithography). In various embodiments, aperture <NUM> may be partially or wholly transparent. 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> (because most glass substrates are not <NUM>% transparent).

Aperture <NUM> (in conjunction with opaque material <NUM>) may be configured to spatially filter light <NUM> from the scene at the focal plane. For example, light <NUM> may be focused onto a focal plane along a surface 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..

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 polarizations 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 lens 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 <NUM> (or a portion thereof). In example embodiments where the LIDAR device is used for navigation on an autonomous vehicle, object <NUM> may comprise pedestrians, other vehicles, obstacles (e.g., trees), or road signs, among others.

As noted above, light <NUM> may be 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>. For example, if the light is generated by a diode laser, light <NUM> may comprise light within a wavelength range centered on <NUM> (or other wavelength of the diode laser). 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 divert light of particular wavelengths away from the array <NUM>. For instance, optical filter <NUM> may divert a portion of light <NUM> that is not of the wavelength range emitted by emitter <NUM> away from array <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 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.).

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 fiber laser, a photodiode, 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 a laser emitter comprising an optical fiber amplifier or other amplifying system that increases power output of laser emitter <NUM>. Additionally or alternatively, 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> at the focal plane. 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>. Further, as shown, LIDAR device <NUM> includes a controller <NUM>. Further, as shown, LIDAR device <NUM> includes a noise limiting system <NUM> that may be similar to system <NUM>. For example, as shown, 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 are 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>. 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.

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 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 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>. For example, the aperture may, in some embodiments, be selectable from a number of apertures defined within the opaque material. In such embodiments, a MEMS mirror located between the lens and the opaque material may be adjustable by the computing device to determine to which of the multiple apertures the light is directed. 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 the 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 increasing a detection area in which light detectors can intercept light from the scene, while also reducing background noise and efficiently using space available for accommodating system <NUM>.

<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> 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). 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>.

Waveguide <NUM> can be formed from a glass substrate (e.g., glass plate, etc.) or any other material at least partially transparent to one or more wavelengths of light <NUM>. In some examples, 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 projected onto receiving side 360a (e.g., input end) of waveguide <NUM>. Waveguide <NUM> then 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 another end of waveguide <NUM>. For example, where waveguide <NUM> is a rectangular waveguide as shown, waveguide <NUM> can guide received light <NUM> toward side 360b opposite to side 360a.

As shown, for instance, waveguide <NUM> may extend vertically between sides 360c and 360d. To that end, sides 360c and 360d may correspond to interfaces between a relatively high index of refraction medium (e.g., glass, etc.) of waveguide <NUM> and a relatively lower index of refraction medium (e.g., air, vacuum, etc.) adjacent to sides 360c and 360d. 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 refractions adjacent to side 360c, etc.), then the guided light incident on side 360c (or a portion thereof) may be reflected back into waveguide <NUM>. Similarly, as shown, waveguide <NUM> may extend horizontally between side 360e and another side of waveguide <NUM> (not shown) opposite to side 360e to reduce divergence of the guided light horizontally, for example.

Further, as shown, light portions 302a, 302b, 302c of light <NUM> propagates out of side 360c extending along a guiding direction of waveguide <NUM> (e.g., between sides 360a and 360b). In one example, guided light portions 302a, 302b, 302c may correspond to an evanescent field of light evanescing through side 360c. In this example, evanescent light 302a, 302b, 302c may leak out of waveguide <NUM> for various reasons. For instance, light portions 302a, 302b, 302c may correspond to light arriving at side 360c at an angle greater than the critical angle. As a result, guided light portions 302a, 302b, 302c may thus escape waveguide <NUM> rather than reflect (e.g., via total internal reflection) back into waveguide <NUM>. In another example, waveguide <NUM> may comprise deformations (e.g., dents, etc.) along a surface of side 360c that allow light portions 302a, 302b, 302c to propagate out of waveguide <NUM>, while causing a remaining portion of guided light <NUM> to continue propagating toward side 360b.

Thus, unlike light detector array <NUM>, light detector array <NUM> can be positioned (as shown) along the guiding direction of waveguide <NUM> (e.g., adjacent to side 360c) to intercept and/or detect light portions 302a, 302b, 302c propagating out of side 360c. Through this process, 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, 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, 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>).

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, 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 alternatively or 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 leaking out of waveguide <NUM> over an even greater detection area.

In a seventh embodiment, waveguide <NUM> can alternatively have a cylindrical shape, such as an optical fiber. In this embodiment, the light detectors in array <NUM> can be alternatively arranged to surround an outer surface of the optical fiber to detect light portions 302a, 302b, 302c, etc., evanescing or otherwise leaking out of the cylindrical outer surface of the optical fiber. Thus, in various embodiments, waveguide <NUM> can be implemented as a rigid structure (e.g., slab waveguide) or as a flexible structure (e.g., optical fiber).

In line with the discussion above, for example, waveguide <NUM> can be configured as a waveguide diffuser that diffuses light <NUM> (or a portion thereof) transmitted through aperture <NUM> into 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 waveguide <NUM> coupled to a mirror <NUM>, according to example embodiments. Waveguide <NUM> may be similar to waveguide <NUM>. Thus, for example, waveguide <NUM> can be used in system <NUM> instead of or in addition to waveguide <NUM>. To that end, light <NUM>, light portions 402a, 402b, 402c, and sides 460a, 460b, 460c, 460d may be similar, respectively, to light <NUM>, light portions 302a, 302b, 302c, and sides 360a, 360b, 360c, 360d.

Mirror <NUM> may comprise any reflective material that reflects light propagating out of side 460b back into waveguide <NUM>. As a result, for instance, light that did not diffuse through side 460c can be returned back into waveguide <NUM> to further increase the likelihood of diffusion toward light detectors (not shown) adjacent to side 460c.

As shown, waveguide <NUM> includes a core region <NUM> that is partially surrounded by a cladding layer <NUM>. Core region <NUM> may comprise a relatively high index of refraction material, such as a glass substrate for instance, that is transparent to at least some wavelengths of light <NUM>. Cladding layer <NUM> may comprise a relatively low index of refraction material, such as polymer coated or fluorine doped glass substrates for instance. In some examples, waveguide <NUM> can be formed from a glass substrate that includes doped regions corresponding to cladding layer <NUM>. Thus, regions of the glass substrate that are not doped may correspond to core <NUM>.

As shown, cladding layer <NUM> is disposed on side 460d but not on side 460c. With this arrangement, for instance, diffusing light portions 402a, 402b, 402c may be more likely to exit waveguide <NUM> through side 460c relative to side 460d. For example, the presence of cladding layer <NUM> may cause the critical angle for light incident on an interface between core <NUM> and cladding <NUM> to be greater than a corresponding critical angle at side 460c. As a result, a greater extent of guided light inside waveguide <NUM> may diffuse out of side 460c toward light detectors (not shown), such as the light detectors in array <NUM> of system <NUM> for example.

In some examples, cladding layer <NUM> can extend along other sides of waveguide <NUM> in addition to or instead of side 460d. Referring back to <FIG> and <FIG> for example, a cladding layer may be configured to surround waveguide <NUM> along sides 360e and a side of waveguide <NUM> opposite to side 360e (not shown). With this arrangement, for instance, diffusion of light portions 402a, 402b, 402c through side 460c can be further improved relative to other sides that are surrounded by cladding <NUM>.

To enhance diffusion of light portions 402a, 402b, 402c through side 460c, in some implementations, a texture of a surface of side 460c can additionally or alternatively have a greater roughness than other sides (e.g., side 460d) of waveguide <NUM>. Thus, for example, waveguide <NUM> can be implemented as a rough waveguide having a pseudorandom rough surface 460c. Alternatively or additionally, in some examples, the surface of side 460c can have scattering features (e.g., dents, indentations, etc.) positioned in predefined locations that overlap with light detectors (not shown). In these examples, the scattering features may increase the likelihood of diffusion of light portions 402a, 402b, 402c, at particular locations where corresponding light detectors are positioned.

In some implementations, it may be desirable to include a cladding layer at side 460c as well. For example, as a length of waveguide <NUM> between sides 460a and 460b increases, more of guided light <NUM> may exit from a region of side 460c closer to side 460a than a region of side 460c closer to side 460b.

Accordingly, <FIG> illustrates a cross-section view of a waveguide <NUM> that includes a cladding layer <NUM> having a plurality of deformations <NUM>, <NUM>, <NUM>, according to example embodiments. Waveguide <NUM> may be similar to waveguide <NUM>. Thus, for example, waveguide <NUM> can be used in system <NUM> instead of or in addition to waveguide <NUM>. To that end, diverging light <NUM>, light portions 502a, 502b, 502c, and sides 560a, 560b, 560c, 560d may be similar, respectively, to diverging light <NUM>, light portions 302a, 302b, 302c, and sides 360a, 360b, 360c, 360d. Further, waveguide <NUM> includes a core <NUM> and a cladding layer <NUM> that may be similar, respectively, to core <NUM> and cladding layer <NUM>.

As shown, unlike waveguide <NUM>, cladding layer <NUM> extends over side 560c from which light portions 502a, 502b, 502c diffuse out of waveguide <NUM>. Various configurations are possible for deformations <NUM>, <NUM>, <NUM>. In one example, deformations <NUM>, <NUM>, <NUM> may correspond to removed, thinned, and/or otherwise distorted portions of cladding layer <NUM>. To that end, deformations <NUM>, <NUM>, <NUM> may be formed using various techniques such as mechanical friction (e.g., sandpaper, etc.), machining, etching, etc. In another example, deformations <NUM>, <NUM>, <NUM> may correspond to materials having a same or higher index of refraction as core <NUM>. For example, deformations <NUM>, <NUM>, <NUM> may include a same polymer as core region <NUM> or another polymer having a similar (or higher) index of refraction. In yet another example, the deformations <NUM>, <NUM>, <NUM> may correspond to regions of cladding layer <NUM> having a smaller thickness than other areas of the cladding layer <NUM>.

Regardless of the implementation, light portions 502a, 502b, 502c may exit waveguide <NUM> via, respectively, deformations <NUM>, <NUM>, <NUM> due to the higher index of refraction in these regions. In turn, for example, light detectors (not shown) can be aligned with deformations <NUM>, <NUM>, <NUM> to detect diffusing light portions 502a, 502b, 502c. For instance, each light detector can be disposed in contact with or proximate to a deformation. Further, for example, the presence of cladding layer <NUM> between deformations <NUM>, <NUM>, <NUM> may cause more of the guided light inside waveguide <NUM> to continue propagating toward side 560b.

In an alternative implementation, although not shown, deformations <NUM>, <NUM>, <NUM> can be alternatively implemented as regions of cladding layer <NUM> that have a smaller thickness compared to other regions that are not aligned with a light detector. In yet another alternative implementation, although not shown, the thickness of core <NUM> can be alternatively reduced in regions that overlap respective light detectors. Regardless of the implementation, frustrated total internal reflection (FTIR) may occur at the locations of deformations <NUM>, <NUM>, <NUM> due to the index of refraction distortions at these locations.

As a result of the deformations and the cladding layer in waveguide <NUM>, guided light <NUM> can diffuse over a relatively larger surface area of side 560c compared to a surface area of side 460c of waveguide <NUM> from which guided light <NUM> diffuses.

<FIG> illustrates a waveguide <NUM> that includes a cladding layer <NUM> having a plurality of variably spaced deformations, exemplified by deformations <NUM>, <NUM>, <NUM>, according to example embodiments. Waveguide <NUM> may be similar to waveguide <NUM>. Thus, for example, waveguide <NUM> can be used in system <NUM> instead of or in addition to waveguide <NUM>. To that end, diverging light <NUM>, light portions 602a, 602b, 602c, sides 660a, 660b, 660c, 660d, core <NUM>, cladding <NUM>, and deformations <NUM>, <NUM>, <NUM> may be similar, respectively, to diverging light <NUM>, light portions 502a, 502b, 502c, sides 560a, 560b, 560c, 560d, core <NUM>, and cladding <NUM>.

However, unlike deformations <NUM>, <NUM>, <NUM> of waveguide <NUM>, deformations <NUM>, <NUM>, <NUM> may be variably spaced along cladding layer <NUM>. By doing so, for instance, waveguide <NUM> can enhance uniformity of light portions 602a, 602b, 602c propagating out of deformations <NUM>, <NUM>, <NUM>, and/or increase a region of side 660c (e.g., lengthwise between sides 660a and 660b) through which the guided light continues to diffuse out of waveguide <NUM>.

In an example scenario, light portion 602c propagating out of deformation <NUM> may have a lower amount, intensity, brightness, etc., than light portion 602a propagating out of deformation <NUM>. Such discrepancy may be caused by various factors. For example, an amount of light 602a propagating out of deformation <NUM> may be greater due to deformation <NUM> being closer to side 660a. As guided light <NUM> propagates toward side 660b, for instance, less of the guided light may remain for diffusion through deformation <NUM> due to diffusion of portions of guided light <NUM> via successive deformations in waveguide <NUM>. Accordingly, in some examples, deformations <NUM>, <NUM>, <NUM>, etc., can be variably spaced to provide a more uniform intensity of diffused light portions 602a, 602b, 602c. For example, as shown in <FIG>, a distance between deformations <NUM> and <NUM> may be smaller than a distance between deformations <NUM> and <NUM>. The diffused light portions 602a, 602b, 602c could be intercepted by light detectors (not shown), such as the light detectors in array <NUM>.

Additionally, in some examples, the distance between adjacent deformations may be based on a given distance from the adjacent deformations to side 660a. For example, the distance between adjacent deformations in waveguide <NUM> could be gradually reduced depending on how far the deformations are from side 660a.

Alternatively or additionally, the distances between adjacent deformations in waveguide <NUM> can be selected according to an expected wavelength of light <NUM>. For example, where light <NUM> comprises light pulses emitted by a LIDAR laser emitter (e.g., emitter <NUM>), the spacing between deformations <NUM>, <NUM>, <NUM>, etc., can be selected such that waveguide <NUM> is configured as a grating coupler that selects particular wavelengths for diffusion via the deformations toward respective light detectors. To facilitate this, in some implementations, the thickness of cladding <NUM> can also be predefined to enhance constructive interference of the light having the selected wavelength(s). Additionally, although not shown, a mirror (similar to mirror <NUM>) can be arranged adjacent to side 660d to reflect evanescing light escaping through cladding <NUM> back into waveguide <NUM>, thereby further improving constructive interference.

Referring back to <FIG>, in some scenarios, it may be desirable to obtain additional information from multiple apertures (or a large aperture) simultaneously with the information obtained using the current aperture configuration, while still achieving a target SNR. By way of example, a light pulse emitted by emitter <NUM> could be scattered off several objects at different distances to LIDAR device <NUM>, and a portion of the scattered light may thus be focused, via lens <NUM>, onto a region of opaque material <NUM> outside the current aperture. Therefore, referring back to <FIG> for instance, it may be desirable to detect light focused onto a region adjacent to aperture <NUM> while simultaneously detecting light focused onto aperture <NUM>. However, if an additional aperture is positioned adjacent to aperture <NUM> (or the size of aperture <NUM> is increased), the diverging light from the additional aperture may overlap with diverging light <NUM> prior to arrival at array <NUM>, thereby reducing the SNR of the detected signal.

<FIG> is an illustration of a noise limiting system <NUM> that includes an aperture and multiple waveguides, according to example embodiments. System <NUM> may be similar to system <NUM>, for example. To that end, a lens <NUM> may focus light <NUM> into an aperture <NUM> defined within opaque material <NUM> similarly to, respectively, lens <NUM>, light <NUM>, aperture <NUM>, and opaque material <NUM>. Thus, light <NUM> may be transmitted through aperture <NUM>. Further, system <NUM> includes light detector arrays <NUM>, <NUM>, and <NUM> that are each similar to array <NUM>. For example, array <NUM> may include a plurality of light detectors (not shown) that are connected in parallel to one another (e.g., parallel circuit configuration) to provide a combined output indicative of light portion 702a incident on array <NUM>. Similarly, for example, array <NUM> may include another plurality of connected light detectors that intercept light portion 702b, and array <NUM> may include yet another plurality of connected light detectors that intercept light 702c.

Unlike system <NUM> however, as shown, system <NUM> includes multiple waveguides <NUM>, <NUM>, <NUM> arranged behind opaque material <NUM> to receive the respective portions of diverging light <NUM>. Thus, for example, waveguide <NUM> may receive a first portion of light <NUM> at side 760a and guide the received portion toward an opposite side 760b of waveguide <NUM>. Some of the guided light can be diffused through side 760c (extending between sides 760a and 760b along a guiding direction of waveguide <NUM>) as light 702a that can then be intercepted and detected by light detectors in array <NUM>. Similarly, for example, waveguide <NUM> can receive a second portion of light <NUM> at side 762a and guide the second portion toward an opposite side 762b of waveguide <NUM>. Some of the guided light can thus be diffused through side 762c as light 702b that can be intercepted and detected by light detectors in array <NUM>. Similarly, for example, waveguide <NUM> can receive a third portion of light <NUM> at side 764a and guide the third portion toward an opposite side 764b of waveguide <NUM>. Some of the guided light can thus be diffused through side 764c as light 702c that can be intercepted and detected by light detectors in array <NUM>.

Thus, with this arrangement, system <NUM> can allow detection of light propagating through smaller adjacent apertures (i.e., corresponding to portions of aperture <NUM>) simultaneously over relatively larger detection areas, while preventing overlap between the light from the respective adjacent apertures. To facilitate this, as shown, each pair of adjacent waveguides may extend away from one another along the respective guiding directions of receiving waveguides. For example, as shown, waveguide <NUM> extends away from waveguide <NUM> and waveguide <NUM> extends away from waveguide <NUM>.

Although input ends 760a, 762a, 764a of waveguides <NUM>, <NUM>, <NUM> are shown to have a similar size, in some examples, input ends 760a, 762a, 764a may have different sizes relative to one another. By way of example, input end 762a of waveguide <NUM> may have a greater size than input end 760a of 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 702b 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 702a and incident on light detector <NUM>.

In some examples, to prevent cross-talk between the waveguides, each waveguide may be configured to begin diffusing light onto a respective light detector array at a location where adjacent waveguides are sufficiently separated. For example, waveguide <NUM> may comprise cladding (e.g., cladding <NUM>), and the cladding may not include any deformations until waveguide <NUM> bends away (e.g., based on a curvature of curved side 760c) from waveguide <NUM> to provide a sufficient separation distance to reduce or prevent leakage of guided light between waveguides <NUM> and <NUM>.

In some examples, system <NUM> may also include absorber layer(s) (e.g., carbon black, black chrome, etc.) positioned (not shown) between the various waveguides to further prevent potential cross-talk between the adjacent waveguides. For example, an absorber layer may absorb evanescing light or other light propagating between the adjacent waveguides (e.g., cladding modes of light propagating inside a waveguide cladding).

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

However, it is noted that system <NUM> can alternatively include more or fewer waveguides to generate a 1D image with more or fewer pixels. Further, although waveguides <NUM>, <NUM>, <NUM> are shown in a lengthwise (e.g., vertical) arrangement relative to aperture <NUM>, in some examples, system <NUM> may include waveguides in a different arrangement. In one example, the receiving sides (e.g., 760a, 762a, 764a) of the waveguides can alternatively be arranged horizontally (e.g., along a direction perpendicular to the page) to obtain a horizontal 1D image of the scene. In another example, the receiving sides of the waveguides can alternatively be arranged both horizontally and vertically (e.g., as a two-dimensional grid) adjacent to aperture <NUM>. Thus, in this example, controller <NUM> can combine outputs from the waveguides to generate a two-dimensional (2D) image of the scene.

<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>, device <NUM>, and/or waveguides <NUM>, <NUM>, and <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 nonvolatile 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 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 detecting light propagating out of a third side (e.g., side 360c, etc.) extending between the first side and the second side.

Claim 1:
A system comprising:
a lens (<NUM>, <NUM>) disposed relative to a scene and configured to focus light from the scene;
an aperture (<NUM>, <NUM>) defined within an opaque material (<NUM>, <NUM>), wherein the opaque material is configured to block a portion of the light focused by the lens, and wherein the aperture is configured to transmit therethrough another portion of the light focused by the lens;
a waveguide (<NUM>) having a first side (360a) that receives the portion of the light transmitted through the aperture, wherein the waveguide guides the received light, by total internal reflection or frustrated total internal reflection, toward a second side (360b) of the waveguide opposite to the first side, and wherein the waveguide has a third side (360c) extending along a guiding direction of the waveguide between the first side and the second side; and
an array (<NUM>, <NUM>) of light detectors (<NUM>, <NUM>) that detects a portion of the received light that evanesces or otherwise leaks out of the third side of the waveguide as the received light is guided by total internal reflection or frustrated total internal reflection along the guiding direction of the waveguide.