Baffles for three-dimensional sensors having spherical fields of view

In one example, a distance sensor includes a camera to capture images of a field of view, a plurality of light sources arranged around a lens of the camera, wherein each light source of the plurality of light sources is configured to project a plurality of beams of light into the field of view, and wherein the plurality of beams of light creates a pattern of projection artifacts in the field of view that is visible to a detector of the camera, a baffle attached to a first light source of the plurality of light sources, wherein the baffle is positioned to limit a fan angle of a plurality of beams of light that is projected by the first light source, and a processing system to calculate a distance from the distance sensor to an object in the field of view, based on an analysis of the images.

BACKGROUND

U.S. patent applications Ser. Nos. 14/920,246, 15/149,323, and 15/149,429 describe various configurations of distance sensors. Such distance sensors may be useful in a variety of applications, including security, gaming, control of unmanned vehicles, operation of robotic or autonomous appliances (e.g., vacuum cleaners), and other applications.

The distance sensors described in these applications include projection systems (e.g., comprising lasers, diffractive optical elements, and/or other cooperating components) which project beams of light in a wavelength that is substantially invisible to the human eye (e.g., infrared) into a field of view. The beams of light spread out to create a pattern (of dots, dashes, or other artifacts) that can be detected by an appropriate light receiving system (e.g., lens, image capturing device, and/or other components). When the pattern is incident upon an object in the field of view, the distance from the sensor to the object can be calculated based on the appearance of the pattern (e.g., the positional relationships of the dots, dashes, or other artifacts) in one or more images of the field of view, which may be captured by the sensor's light receiving system. The shape and dimensions of the object can also be determined.

For instance, the appearance of the pattern may change with the distance to the object. As an example, if the pattern comprises a pattern of dots, the dots may appear closer to each other when the object is closer to the sensor, and may appear further away from each other when the object is further away from the sensor.

SUMMARY

In one example, a distance sensor includes a camera to capture images of a field of view, a plurality of light sources arranged around a lens of the camera, wherein each light source of the plurality of light sources is configured to project a plurality of beams of light into the field of view, and wherein the plurality of beams of light creates a pattern of projection artifacts in the field of view that is visible to a detector of the camera, a baffle attached to a first light source of the plurality of light sources, wherein the baffle is positioned to limit a fan angle of a plurality of beams of light that is projected by the first light source, and a processing system to calculate a distance from the distance sensor to an object in the field of view, based on an analysis of the images.

In another example, a method performed by a processing system of a distance sensor includes instructing a first pair of light sources of the distance sensor to project a first pattern of light into a field of view, wherein the first pattern of light is created when each light source of the first pair of light sources projects a plurality of beams of light, and wherein at least one light source of the first pair of light sources includes a first baffle to limit a fan angle of the plurality of beams of light, instructing a camera of the distance sensor to acquire a first image of the field of view, wherein the first image includes the first pattern of light, instructing a second pair of light sources of the distance sensor to project a second pattern of light into the field of view, wherein the second pattern of light is created when each light source of the second pair of light sources projects a plurality of beams of light, and wherein at least one light source of the second pair of light sources includes a second baffle to limit a fan angle of the plurality of beams of light, instructing the camera to acquire a second image of the field of view, wherein the second image includes the second pattern of light, and calculating a distance from the distance sensor to an object in the field of view, based on appearances of the first pattern of light and the second pattern of light in the first image and the second image.

In another example, a non-transitory machine-readable storage medium is encoded with instructions executable by a processor. When executed, the instructions cause the processor to perform operations including instructing a first pair of light sources of the distance sensor to project a first pattern of light into a field of view, wherein the first pattern of light is created when each light source of the first pair of light sources projects a plurality of beams of light, and wherein at least one light source of the first pair of light sources includes a first baffle to limit a fan angle of the plurality of beams of light, instructing a camera of the distance sensor to acquire a first image of the field of view, wherein the first image includes the first pattern of light, instructing a second pair of light sources of the distance sensor to project a second pattern of light into the field of view, wherein the second pattern of light is created when each light source of the second pair of light sources projects a plurality of beams of light, and wherein at least one light source of the second pair of light sources includes a second baffle to limit a fan angle of the plurality of beams of light, instructing the camera to acquire a second image of the field of view, wherein the second image includes the second pattern of light, and calculating a distance from the distance sensor to an object in the field of view, based on appearances of the first pattern of light and the second pattern of light in the first image and the second image.

DETAILED DESCRIPTION

The present disclosure broadly describes baffles for three-dimensional sensors having spherical fields of view. As discussed above, distance sensors such as those described in U.S. patent applications Ser. Nos. 14/920,246, 15/149,323, and 15/149,429 determine the distance to an object (and, potentially, the shape and dimensions of the object) by projecting beams of light that spread out to create a pattern (e.g., of dots, dashes, or other artifacts) in a field of view that includes the object. The beams of light may be projected from one or more laser light sources which emit light of a wavelength that is substantially invisible to the human eye, but which is visible to an appropriate detector (e.g., of the light receiving system). The three-dimensional distance to the object may then be calculated based on the appearance of the pattern to the detector.

FIG. 1illustrates one example of a laser light source100that may be used in a distance sensor such as any of the sensors described above. As illustrated the laser light source may project a plurality of beams1021-102nof light (hereinafter individually referred to as a “beam102” or collectively referred to as “beams102”). When each beam102is incident upon an object, it may create an artifact such as a dot, a dash, or the like on the object. Collectively, the artifacts created by all of the beams102form the above-described pattern from which the distance to the object can be calculated.

As shown inFIG. 1, the beams102may fan out from a single point104on the laser light source100. For instance, the laser light source100may include a diffractive optical element such as a mirror or a holographic film that may split a single beam of light emitted by the laser light source100into the plurality of beams102that fan out as shown (where the single point104may represent the diffractive optical element). In one example, the fan angle θ of the beams102is approximately ninety degrees. That is, the beams102may spread out in a “fan” shape that covers up to approximately ninety degrees in a rectangular (i.e., x,y,z) coordinate system as shown. In some cases, the fan angle θ may be even greater than ninety degrees.

FIG. 1illustrates the fan of the beams102between the x and z axes of the illustrated coordinate axis; however, it will be appreciated that the beams102may also fan out between the y and z axes and between the x and y axes, and that the fans angles between these axes may also be up to approximately ninety degrees. Thus, the total coverage area of the plurality of beams102may be approximately equal to one quarter or quadrant of a hemisphere.

As such, a plurality of laser light sources can cooperate to produce a pattern that covers a hemispherical field of view, allowing the distance sensor to calculate distances within a large range. However, if the beams projected by two or more different laser light sources overlap (e.g., as may happen when any of the fan angles are greater than ninety degrees), this can distort the appearance of the pattern to the detector and make it more difficult for the detector to determine from which laser light source a given artifact of the pattern was projected. This, in turn, may complicate the calculation of the distance and lead to longer calculation times and less accurate calculations.

Examples of the present disclosure provide a baffle to limit the fan angle of a plurality of beams projected by a laser light source of a three-dimensional distance sensor. By limiting the fan angle of the plurality of beams, the baffle makes it less likely that the plurality of beams will overlap with beams projected by other laser light sources of the distance sensor. This, in turn, makes it easier for the distance sensor to determine from which laser light source a given artifact in a projected pattern was projected.

FIG. 2Aillustrates a side view of an example distance sensor200of the present disclosure.FIG. 2Billustrates a top view of the arrangement of components of the distance sensor200illustrated inFIG. 2A. The distance sensor200may generally include a housing202, a camera204, and a plurality of laser light sources2061-206m(hereinafter individually referred to as a “laser light source206” or collectively referred to as “laser light sources206”).

The housing202contains the components of the distance sensor200(i.e., the camera204, the laser light sources206, and other components not visible inFIGS. 2A and 2Bsuch as a processor, a power supply, a communication interface, and the like). Optionally, the housing202may contain components of another system with which the distance sensor200works, such as the components of a robotic vacuum cleaner. The housing202may take other shapes or forms from that shown inFIGS. 2A and 2B.

The camera204may comprise any type of camera that is capable of capturing an image in a field of view. For instance, the camera may comprise a red, green, blue (RGB) camera. In one example, the camera may also include a lens208and a detector (not shown) that is capable of detecting light of a wavelength that is substantially invisible to the human eye (e.g., an infrared detector). In one example, the lens208may comprise a fisheye lens. In another example, however, the lens208may comprise a mirror optical system.

In one example, the plurality of laser light sources206is arranged around the camera204(e.g., in a circle), so that the camera204is positioned in the center of the laser light sources206, equidistant from each laser light source206. This arrangement is illustrated clearly inFIG. 2B. In one example, the distance sensor200includes at least four laser light sources206which are positioned at regular distances around the camera204(e.g., every ninety degrees). Assuming that the beams projected by each laser light source206have fan angles of ninety degrees, using four laser light sources206would allow the distance sensor200to project a pattern of light that covers a hemispherical field of view.

Each laser light source206may include a light emitting diode (LED) or other light source that is capable of emitting light in a wavelength that is substantially invisible to the human eye (e.g., infrared), but that is visible to a detector of the camera204. Each laser light source206may also include a diffractive optical element that splits a beam emitted by the LED into a plurality of beams as shown inFIG. 1.

For instance, taking a first laser light source2061as an example (where each laser light source206functions in a manner similar to the first laser light source2061), the laser light source2061may project a first plurality of beams2101-210n(hereinafter individually referred to as a “beam210” or collectively referred to as “beams210”) that fan out from a center point or beam210. As discussed above, the beams210may fan out in multiple directions (e.g., between each pair of axes illustrated inFIG. 1). For instance, the beams210may fan out in the vertical direction (e.g., between the laser light source2061and the optical axis A-A′ of the camera204, or between the x and z axes or y and z axes ofFIG. 1) and in the horizontal direction (e.g., around the optical axis A-A′ of the camera204, or between the x and y axes ofFIG. 1).

For the sake of simplicity, three beams210of the first plurality of beams210forming a vertical fan out are illustrated inFIG. 2A: a first beam2101that represents a first outer boundary of the fan, a second beam2102that represents a center beam or center of the fan, and a third beam210nthat represents a second outer boundary of the fan.

The “vertical” fan angle θv(i.e., the fan angle between the laser light source2061and the optical axis A-A′ of the camera204, or between the x and z axes or y and z axes ofFIG. 1)) is defined between the outer boundaries of the fan, i.e., between the first beam2101and the third beam210n. In one example, when the front nodal point of the camera lens208and the projection point of the laser light source2061(i.e., the point from which the plurality of beams210fans out) are at an even height (i.e., the height difference is zero or nearly zero), the vertical fan angle θvmay be up to approximately ninety degrees.

Similarly, three beams210of the first plurality of beams210forming a horizontal fan out are illustrated inFIG. 2B: a fourth beam210n-1that represents a first outer boundary of the fan, a fifth beam210n-2that represents a center beam or center of the fan, and a sixth beam210n-3that represents a second outer boundary of the fan.

The “horizontal” fan angle θh(i.e., the fan angle around the optical axis A-A′ of the camera204, or between the x and y axes ofFIG. 1) is defined between the outer boundaries of the fan, i.e., between the fourth beam210n-1and the sixth beam210n-3, and in one example is up to approximately ninety degrees. Moreover, there is an area of clearance c between the surface of the housing202and the first beam2101. Within this area of clearance c, the first plurality of beams210does not produce a projection artifact.

In one example, one or more of the laser light sources206may include a baffle to limit the fan angle in one or more directions.FIG. 3, for example, illustrates a side view of one example of a baffle300that may be used to limit the fan angle associated with a laser light source2061ofFIG. 1.

In one example, the baffle300may comprise a metal, plastic, glass, or ceramic component that may be removably attached to the laser light source2061. As illustrated, the baffle300generally comprises a body302and a flange304. The body302may attach to and rest substantially flush against the exterior surface of the laser light source2061. The flange304may extend from the body302at an angle, so that when the baffle300is attached to the laser light source2061, the flange304extends over a portion of the face of the laser light source2061from which the first plurality of beams210projects. As shown inFIG. 3, this placement of the baffle300, and specifically of the flange304, may decrease the fan angle θ of the first plurality of beams210.

In one example, the baffle300may reduce the fan angle θ to sixty degrees or less. This may leave a space in the field of view, defined by an angle α between the outer boundary of the fan (e.g., third beam210n) and a zero degree line that is parallel to the camera's optical axis, where there is no pattern coverage. That is, within the space defined by the angle α, no projection artifacts may be created when the laser light source2061projects the plurality of beams210. However, the first plurality of beams210will not overlap with a second plurality of beams that is simultaneously projected from a second laser light source206of the distance sensor.

The baffle300is shown as extending around a portion of the laser light source's perimeter. This may reduce the fan angle θ in some directions, but not others. For instance, the baffle300may be positioned to reduce the vertical fan angle θv, but not the horizontal fan angle θh. As an example, the placement of the baffle may result in a horizontal fan angle θhof ninety degrees and a vertical fan angle θvof sixty degrees. However, it will be appreciated that in other examples, the baffle300may extend all the way around the laser light source's perimeter. This may further reduce the fan angle θ in all directions.

Although the baffle300creates areas in the pattern where there is no coverage (i.e., no projection artifacts in the field of view), it remains possible for the distance sensor to perform a trigonometric distance calculation with little to no loss of accuracy. This is in part because the baseline length, L (illustrated inFIG. 2B), for triangulation remains constant with respect to the projection angles of the laser light sources206). In this case, the baseline length L may define the distance between any two projection points of the distance sensor200. This also allows the distance sensor200to accurately calculate distance even when the fan outs of two separate pluralities of beams may overlap in the horizontal direction (e.g., around the camera's optical axis, or in a direction perpendicular to the camera's optical axis).

FIG. 4is a flow diagram illustrating one example of a method400for distance measurement using a distance sensor with a baffle attached to at least one light source, e.g., as illustrated inFIGS. 2-3. The method400may be performed, for example, by a processor, such as the processor of a distance sensor or the processor702illustrated inFIG. 7. For the sake of example, the method400is described as being performed by a processing system.

The method400may begin in step402. In step404, the processing system may send a first signal to a first pair of laser light sources of a distance sensor, instructing the first pair of laser light sources to project a first pattern of light into a field of view. In one example, the distance sensor includes four laser light sources, and the first pair of laser light sources comprises two laser light sources that are positioned on opposite sides of the lens of the distance sensor's camera (i.e., the laser light sources in the first pair of laser light sources are non-adjacent). For instance, using the distance sensor200ofFIGS. 2A-2Bas an example, the first pair of laser light sources might comprise laser light sources2061and2063.

As discussed above, the first pattern of light may comprise a plurality of projection artifacts that is projected into the field of view. The projection artifacts may be created by respective beams of light that are incident on objects in the distance sensor's field of view, where each laser light source of the first pair of laser light sources projects a plurality of beams that fan out from a central projection point or beam. The wavelength of the light that forms the beams (and, therefore, the projection artifacts) may be substantially invisible to the human eye, but visible to a detector of the distance sensor's camera (e.g., infrared).

Furthermore, in one example, at least one laser light source in the first pair of laser light sources includes an attached baffle to constrain a boundary of the portion of the first pattern of light that is created by the at least one laser light source. The baffle may constrain the boundary by limiting a fan angle of the beams of light that are emitted by the at least one laser light source. For instance, the baffle may resemble the baffle300illustrated inFIG. 3. Limiting the fan angle may prevent the respective beams of light emitted by the two laser light sources in the first pair of laser light sources from overlapping.

FIG. 5A, for instance, illustrates a top view a first plurality of beams500emitted by a first laser light source of a distance sensor and a second plurality of beams502emitted by a second laser light source of the distance sensor, where the fan angles of the first and second pluralities of beams are not limited by a baffle.FIG. 5Billustrates a side view of the first plurality of beams500and the second plurality of beams502illustrated inFIG. 5A. The pair of laser light sources projecting the first plurality of beams500and the second plurality of beams502are positioned on opposite sides of a camera lens506(i.e., are not adjacent).

As shown inFIGS. 5A and 5B, when a baffle is not used on at least one of the laser light sources, the first plurality of beams500and the second plurality of beams502may overlap, creating a region504in which it may be difficult for the distance sensor to discern the origins (emitting laser light sources) of the projection artifacts that are visible. This may occur when the vertical fan angle θvof one or both of the first and second pluralities of beams500and502is greater than ninety degrees.

By contrast,FIG. 6Aillustrates a top view a first plurality of beams600emitted by a first laser light source of a distance sensor and a second plurality of beams602emitted by a second laser light source of the distance sensor, where the fan angles of the first and second pluralities of beams are limited by a baffle.FIG. 6Billustrates a side view of the first plurality of beams600and the second plurality of beams602illustrated inFIG. 6A. The pair of laser light sources projecting the first plurality of beams600and the second plurality of beams602are positioned on opposite sides of a camera lens606(i.e., are not adjacent).

As shown inFIGS. 6A and 6B, when a baffle is used on at least one of the laser light sources, the first plurality of beams600and the second plurality of beams602will not overlap. This may create a region604in which no projection artifacts are visible (e.g., there is no pattern coverage). However, the loss of pattern coverage in this small area should not substantially affect the accuracy of any distance calculations. As illustrated, the vertical fan angle θvof one or both of the first and second pluralities of beams600and602is no more than ninety degrees.

Referring back toFIG. 4, once the first pair of laser light sources projects the first pattern of light into the field of view, the method proceeds to step406. In step406, the processing system may send a second signal to the camera of the distance sensor instructing the camera to capture a first image of the field of view, including the first pattern of light projected by the first pair of laser light sources.

In step408, the processing system may send a third signal to a second pair of laser light sources of the distance sensor to project a second pattern of light into a field of view. In the example in which the distance sensor includes four laser light sources, the second pair of laser light sources may comprise two laser light sources that are positioned on opposite sides of the lens of the distance sensor's camera (i.e., the laser light sources in the second pair of laser light sources are non-adjacent). For instance, using the distance sensor200of FIGS.2A-2B as an example, if the first pair of laser light sources referenced above comprise laser light sources2061and2063, then the second pair of laser light sources might comprise laser light sources2062and206n.

As discussed above, the second pattern of light, like the first pattern of light, may comprise a plurality of projection artifacts that is projected into the field of view. The projection artifacts may be created by respective beams of light that are incident on objects in the distance sensor's field of view, where each laser light source of the second pair of laser light sources projects a plurality of beams that fan out from a central projection point or beam. The wavelength of the light that forms the beams (and, therefore, the projection artifacts) may be substantially invisible to the human eye, but visible to a detector of the distance sensor's camera (e.g., infrared).

Furthermore, in one example, at least one laser light source in the second pair of laser light sources includes an attached baffle to constrain a boundary of the portion of the second pattern of light that is created by the at least one laser light source. The baffle may constrain the boundary by limiting a fan angle of the beams of light that are emitted by the at least one laser light source. For instance, the baffle may resemble the baffle300illustrated inFIG. 3. Limiting the fan angle may prevent the respective beams of light emitted by the two laser light sources in the second pair of laser light sources from overlapping, as discussed above.

In one example, the processing system does not send the third signal to the second pair of laser light sources until after the camera has captured the first image. This ensures that the first pair of laser light sources and the second pair of laser light sources do not project the first and second patterns of light simultaneously. In other words, the first pair of laser light sources and the second pair of laser light sources project their respective patterns of light in sequence, on after the other. Thus, at any time, only half of the hemispherical field of view may be covered by a projection pattern. Put another way, the first pattern of light covers (up to) a first half of the distance sensor's hemispherical field of view, while the second pattern of light covers (up to) a different, second half of the field of view. This further avoids the potential for beam overlap.

In step410, the processing system may send a fourth signal to the camera of the distance sensor instructing the camera to capture a second image of the field of view, including the second pattern of light projected by the second pair of laser light sources.

In step412, the processing system may calculate the distance from the distance sensor to an object in the camera's field of view, using the first and second images captured in steps406and410. In particular, the distance is calculated based on the appearances of the first pattern of light and the second pattern of light in the first image and the second image, respectively.

The method400may end in step414.

It should be noted that although not explicitly specified, some of the blocks, functions, or operations of the method400described above may include storing, displaying and/or outputting for a particular application. In other words, any data, records, fields, and/or intermediate results discussed in the method400can be stored, displayed, and/or outputted to another device depending on the particular application. Furthermore, blocks, functions, or operations inFIG. 4that recite a determining operation, or involve a decision, do not imply that both branches of the determining operation are practiced. In other words, one of the branches of the determining operation may not be performed, depending on the results of the determining operation.

FIG. 7depicts a high-level block diagram of an example electronic device700for calculating the distance from a sensor to an object. As such, the electronic device700may be implemented as a processor of an electronic device or system, such as a distance sensor.

As depicted inFIG. 7, the electronic device700comprises a hardware processor element702, e.g., a central processing unit (CPU), a microprocessor, or a multi-core processor, a memory704, e.g., random access memory (RAM) and/or read only memory (ROM), a module705for calculating the distance from a sensor to an object, and various input/output devices706, e.g., storage devices, including but not limited to, a tape drive, a floppy drive, a hard disk drive or a compact disk drive, a receiver, a transmitter, a display, an output port, an input port, and a user input device, such as a keyboard, a keypad, a mouse, a microphone, a camera, a laser light source, an LED light source, and the like.

Although one processor element is shown, it should be noted that the electronic device700may employ a plurality of processor elements. Furthermore, although one electronic device700is shown in the figure, if the method(s) as discussed above is implemented in a distributed or parallel manner for a particular illustrative example, i.e., the blocks of the above method(s) or the entire method(s) are implemented across multiple or parallel electronic devices, then the electronic device700of this figure is intended to represent each of those multiple electronic devices.

It should be noted that the present disclosure can be implemented by machine readable instructions and/or in a combination of machine readable instructions and hardware, e.g., using application specific integrated circuits (ASIC), a programmable logic array (PLA), including a field-programmable gate array (FPGA), or a state machine deployed on a hardware device, a general purpose computer or any other hardware equivalents, e.g., computer readable instructions pertaining to the method(s) discussed above can be used to configure a hardware processor to perform the blocks, functions and/or operations of the above disclosed method(s).

In one example, instructions and data for the present module or process705for calculating the distance from a sensor to an object, e.g., machine readable instructions can be loaded into memory704and executed by hardware processor element702to implement the blocks, functions or operations as discussed above in connection with the method400. Furthermore, when a hardware processor executes instructions to perform “operations”, this could include the hardware processor performing the operations directly and/or facilitating, directing, or cooperating with another hardware device or component, e.g., a co-processor and the like, to perform the operations.

The processor executing the machine readable instructions relating to the above described method(s) can be perceived as a programmed processor or a specialized processor. As such, the present module705for calculating the distance from a sensor to an object of the present disclosure can be stored on a tangible or physical (broadly non-transitory) computer-readable storage device or medium, e.g., volatile memory, non-volatile memory, ROM memory, RAM memory, magnetic or optical drive, device or diskette and the like. More specifically, the computer-readable storage device may comprise any physical devices that provide the ability to store information such as data and/or instructions to be accessed by a processor or an electronic device such as a computer or a controller of a safety sensor system.

It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, or variations therein may be subsequently made which are also intended to be encompassed by the following claims.