US20160328854A1

US20160328854A1 - Distance sensor

Info

Publication number: US20160328854A1
Application number: US15/149,429
Authority: US
Inventors: Akiteru Kimura
Original assignee: Magik Eye Inc
Current assignee: Magik Eye Inc
Priority date: 2015-05-10
Filing date: 2016-05-09
Publication date: 2016-11-10
Also published as: US10228243B2; HK1252962A1; EP3295119A1; WO2016182982A1; KR20180005659A; KR20180006377A; TW201706563A; JP2020148784A; TWI687652B; JP2018514783A; WO2016182985A1; HK1253380A1; CN107850420A; EP3295119A4; US20160327385A1; CN107896506A; EP3295118A1; JP6761817B2; TW201706564A; JP2018514780A

Abstract

In one embodiment, a distance sensor includes a projection light source, a first light guiding means positioned to guide light emitted by the projection light source, a diffractive optical element positioned to split the light guided by the first light guiding means into a plurality of projection beams traveling in different directions, and an image capturing device positioned to capture an image of a field of view, including a projection pattern created by an incidence of the plurality of projection beams on an object in the field of view.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/159,286, filed May 10, 2015, which is herein incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally computer vision systems and relates more particularly to sensors for measuring the distance between a vehicle and an object or point in space.
Unmanned vehicles, such as robotic vehicles and drones, typically rely on computer vision systems for obstacle detection and navigation in the surrounding environment. These computer vision systems, in turn, typically rely on various sensors that acquire visual data from the surrounding environment, which the computer vision systems process in order to gather information about the surrounding environment. For instance, data acquired via one or more imaging sensors may be used to determine the distance from the vehicle to a particular object or point in the surrounding environment.

SUMMARY

In one embodiment, a distance sensor includes a projection light source, a first light guiding means positioned to guide light emitted by the projection light source, a diffractive optical element positioned to split the light guided by the first light guiding means into a plurality of projection beams traveling in different directions, and an image capturing device positioned to capture an image of a field of view, including a projection pattern created by an incidence of the plurality of projection beams on an object in the field of view.
In another embodiment, a distance sensor includes a plurality of projection light sources, a first plurality of optical fibers, wherein a first end of each optical fiber of the first plurality of optical fibers is coupled to one projection light source of the plurality of projection light sources, a plurality of diffractive optical elements, wherein each diffractive optical element of the plurality of diffractive optical elements is coupled to a second end of one optical fiber of the first plurality of optical fibers, a plurality of illumination light sources, comprising light sources that are different from the plurality of projection light sources, a second plurality of optical fibers, wherein a first end of each optical fiber of the second plurality of optical fibers is coupled to one illumination light source of the plurality of illumination light sources, a plurality of illumination optics, wherein each illumination optic of the plurality of illumination optics is coupled to a second end of one optical fiber of the second plurality of optical fibers, and an image capturing device, wherein the plurality of diffractive optical elements and the plurality of illumination optics are arranged in a ring around a central optical axis of the image capturing device.
In another embodiment, a distance sensor comprises a plurality of vertical cavity surface emitting lasers arranged on a circuit board, a plurality of gradient-index lenses, wherein each gradient-index lens of the plurality of gradient-index lenses is positioned to collimate a beam of light produced by one vertical cavity surface emitting laser of the plurality of vertical cavity surface emitting lasers, a plurality of diffractive optical elements, wherein each diffractive optical element of the plurality of diffractive optical elements is positioned to split a beam collimated by one gradient-index lens of the plurality of gradient-index lenses into a plurality of beams traveling in different directions, and a plurality of Powell lenses, wherein each Powell lens of the plurality of Powell lenses is positioned to generate a projection pattern from a plurality of beams generated by one diffractive optical element of the plurality of diffractive optical elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present disclosure can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1A illustrates a cross-sectional view of a first embodiment of a distance sensor of the present disclosure;

FIG. 1B illustrates a top view of the distance sensor of FIG. 1A;

FIG. 2 illustrates an example field of view of the distance sensor of FIGS. 1A and 1B;

FIG. 3A illustrates a cross-sectional view of a second embodiment of a distance sensor of the present disclosure;

FIG. 3B illustrates a top view of the distance sensor of FIG. 3A;

FIG. 4 illustrates a flowchart of a method for calculating the distance from a sensor to an object or point in space;

FIG. 5 illustrates a triangulation technique by which the distance from a sensor to an object or point may be calculated;

FIG. 6A illustrates a cross-sectional view of a third embodiment of a distance sensor of the present disclosure;

FIG. 6B illustrates a top view of the distance sensor of FIG. 6A;

FIG. 7 illustrates a first example projection pattern that may be generated by the distance sensor of FIG. 6;

FIG. 8 illustrates a first example projection pattern that may be generated by the distance sensor of FIG. 6;

FIG. 9 depicts a portion of a fourth embodiment of a distance sensor of the present disclosure; and

FIG. 10 depicts a high-level block diagram of a general-purpose computer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION

In one embodiment, the present disclosure relates to a distance sensor. Distance sensors may be used in unmanned vehicles in order to help a computer vision system determine the distance from the vehicle to a particular object or point in the surrounding environment. For instance, a distance sensor may project one or more beams of light onto the object or point and then compute the distance according to time of flight (TOF), analysis of the reflected light (e.g., lidar), or other means. Conventional distance sensors of this type tend to be bulky, however, and thus may not be suitable for use in compact vehicles. Moreover, the sensors can be very expensive to manufacture and tend to have a limited field of view. For instance, even using an arrangement of multiple conventional imaging sensors provides a field of view that is less than 360 degrees.
Embodiments of the disclosure provide a compact distance sensor that is economical to manufacture, includes few or no moving parts, and can measure distances in a field of view of up to 360 degrees. In one embodiment, the sensor uses a set of beam splitting means such as an array of optical fibers and diffractive optical elements (DOEs) to generate a plurality of projection points around a wide angle lens. Each of the plurality of projection points emits a plurality of beams into a field of view. From the appearances of the beams, the sensor can measure distances in a 180 degree hemispherical field of view. By mounting two such sensors back-to-back, distances can be measured in a 360 degree field of view. The DOEs make it possible to split a beam generated by a single light source (e.g., laser) into multiple projection beams that are projected onto an object or point in the field of view. However, in other embodiments, beams emitted by multiple light sources are split by the DOEs. The distance from the sensor to the object or point can then be calculated in one cycle of projection and image capture from the multiple projections. A compact sensor capable of measuring distances in fields of view of to 360 degrees can provide meaningful data for applications including unmanned vehicle navigation, endoscopy, and other applications.
FIGS. 1A and 1B illustrate a first embodiment of a distance sensor 100 of the present disclosure. In particular, FIG. 1A illustrates a cross-sectional view of the distance sensor 100, while FIG. 1B illustrates a top view of the distance sensor 100 of FIG. 1A. The distance sensor 100 may be mounted, for example, to an unmanned vehicle, or may be used as part of an endoscope.
As illustrated in FIG. 1A, the distance sensor 100 comprises a plurality of components arranged in a compact configuration. The components include at least one light source 104, a first beam splitting means, hereinafter referred to as a first diffractive optical element 106, a plurality of light guiding means such as optical fibers 102 ₁-102 _n(hereinafter collectively referred to as “optical fibers 102”), an array of second beam splitting means, hereinafter referred to as second diffractive optical elements 108 ₁-108 _n(and hereinafter collectively referred to as “second diffractive optical elements 108”), and an imaging sensor 110 including a wide-angle lens 112.
The components are arranged substantially symmetrically about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor 110. In one embodiment, the light source 104 is positioned at a first end of the central axis A-A′. In one embodiment, the light source 104 is a laser light source that emits a single beam of light along the central axis A-A′. Hereinafter, the single beam emitted by the light source 104 may also be referred to as the “primary beam.” In one embodiment, the light source 104 emits light of a wavelength that is known to be relatively safe to human vision (e.g., infrared). In a further embodiment, the light source 104 may include circuitry to adjust the intensity of its output. In a further embodiment, the light source 104 may emit light in pulses, so as to mitigate the effects of ambient light on image capture.
The first diffractive optical element (DOE) 106 is positioned along the central axis A-A′ in proximity to the light source 104 (e.g., “in front” of the light source 104, relative to the direction in which light emitted by the light source 104 propagates). In particular, the first DOE 106 is positioned to intercept the single beam of light emitted by the light source 104 and to split the single or primary beam into a plurality of secondary beams. The first DOE 106 is any optical component that is capable of splitting the primary beam into a plurality of secondary beams that diverge from the primary beam in different directions. For example, in one embodiment, the first DOE 106 may include a conical mirror, a holographic film, a micro lens, o a line generator (e.g., a Powell lens). In this case, the plurality of secondary beams are arranged in a cone shape. In further embodiments, the primary beam may be split by means other than diffraction.
Each of the optical fibers 102 is coupled at one end to the first DOE 106 and is coupled at the other end to one of the DOEs 108 in the array of second DOEs 108. In this way, each of the optical fibers 102 is positioned to carry at least one of the secondary beams produced by the first DOE 106 to one of the DOEs 108 in the array of second DOEs 108.
The array of second DOEs 108 is positioned along the central axis A-A′ in proximity to the first DOE 106 (e.g., “in front” of the first DOE 106, relative to the direction in which light emitted by the light source 104 propagates). In particular, the array of second DOEs 108 is positioned such that the first DOE 106 is positioned between the light source 104 and the array of second DOEs 108. As more clearly illustrated in FIG. 1B, in one embodiment, the second DOEs 108 are arranged in a ring-shaped array, with the central axis A-A′ passing through the center of the ring and the second DOEs 108 spaced at regular intervals around the ring. For instance, in one embodiment, the second DOEs 108 are spaced approximately thirty degrees apart around the ring. In one embodiment, the array of second DOES 108 is positioned “behind” a principal point of the imaging sensor 110 (i.e., the point where the optical axis A-A′ intersects the image plane), relative to the direction in which light emitted by the light source 104 propagates.
Each second DOE 108 is positioned to receive one of the secondary beams transmitted by one of the optical fibers 102 from the first DOE 106 and to split the secondary beam into a plurality of (e.g., two or more) tertiary beams that are directed away from the second DOE 108 in a radial manner. Thus, each second DOE 108 defines a projection point of the sensor 100 from which a group of projection beams (or tertiary beams) is emitted into the field of view. In one embodiment, each respective plurality of tertiary beams fans out to cover a range of approximately one hundred degrees. The second DOEs 108 are any optical components that are capable of splitting a respective secondary beam into a plurality of tertiary beams that diverge from the secondary beam in different directions. For example, in one embodiment, each second DOE 108 may include a conical mirror, a holographic film, a micro lens, or a line generator (e.g., a Powell lens). In other embodiments, however, the secondary beams are split by a means other than diffraction.
In one embodiment, each plurality of tertiary beams is arranged in a fan or radial pattern, with equal angles between each of the beams. In one embodiment, each of the second DOEs 108 is configured to project tertiary beams that create a different visual pattern on a surface. For example, one second DOE 108 may project a pattern of dots, while another second DOE 108 may project a pattern of lines or x's.
The imaging sensor 110 is positioned along the central axis A′A′, in the middle of the array of second DOEs 108 (e.g., at least partially “in front” of the array of second DOEs 108, relative to the direction in which light emitted by the light source 104 propagates). In one embodiment, the imaging sensor 110 is an image capturing device, such as a still or video camera. As discussed above, the imaging sensor 110 includes a wide-angle lens 112, such as a fisheye lens, that creates a hemispherical field of view. In one embodiment, the imaging sensor 110 includes circuitry for calculating the distance from the distance sensor 100 to an object or point. In another embodiment, the imaging sensor includes a network interface for communicating captured images over a network to a processor, where the processor calculates the distance from the distance sensor 100 to an object or point and then communicates the calculated distance back to the distance sensor 100.
Thus, in one embodiment, the distance sensor 100 uses a single light source (e.g., light source 104) to produce multiple projection points from which sets of projection beams (e.g., comprising patterns of dots or lines) are emitted. The distance from the distance sensor 100 to an object can be calculated from the appearances of the projection beams in the field of view (as discussed in greater detail below). In particular, the use of the first and second DOEs makes it possible to generate a plurality of projection points around the lens, from the single beam of light emitted by the light source. This, plus the use of the optical fibers 102 to transmit light from the first DOE to the second DOEs, allows the distance sensor 100 maintain a relatively compact form factor while measuring distance within a wide field of view. The imaging sensor 110 and the light source 104 can also be mounted in the same plane in order to make the design more compact; however, in one embodiment, the second DOEs 108 ₁-108 _nare positioned behind the principal point of the imaging sensor 110 in order to increase the field of view that can be covered by the projection beams (e.g., such that the depth angle of the field of view is closer to a full 180 degrees, or, in some cases, even greater).
Moreover, since each of the second DOEs 108 projects tertiary beams of a different pattern, the circuitry in the imaging sensor can easily determine which beams in a captured image were created by which of the second DOEs 108. This facilitates the distance calculations, as discussed in greater detail below.
FIG. 2 illustrates an example field of view 200 of the distance sensor 100 of FIGS. 1A and 1B. In FIG. 2, certain components of the distance sensor 100 are also illustrated in an exploded view. As shown, the field of view 200 is substantially hemispherical in shape. Furthermore, the plurality of tertiary light beams produced by the distance sensor 100 projects a pattern of light onto the “virtual” hemisphere. The patterns are represented by the series of concentric circles that are illustrated where each tertiary beam meets the hemisphere. The circles are depicted as gradually decreasing in size as the distance from the distance sensor 100 increases, in order to show how the patterns created by the tertiary beams change visually by object distance.
As shown in FIG. 2, the field of view of the distance sensor 100 covers approximately 180 degrees. In one embodiment, the field of view can be expanded to approximately 360 degrees by mounting two distance sensors back-to-back, e.g., such that their respective light sources emit primary beams in two different directions separated by approximately 180 degrees.
Although the sensor 100 is illustrated as including only a single light source 104 (which reduces the total number of components in the sensor 100), in alternative embodiments, the sensor may include a plurality of light sources. FIGS. 3A and 3B, for example, illustrate a second embodiment of a distance sensor 300 of the present disclosure. In particular, FIG. 3A illustrates a cross-sectional view of the distance sensor 300, while FIG. 3B illustrates a top view of the distance sensor 300 of FIG. 3A. The distance sensor 300 may be mounted, for example, to an unmanned vehicle, or may be used as part of an endoscope.
As illustrated in FIG. 3A, the distance sensor 300 comprises a plurality of components arranged in a compact configuration. The components include a plurality of light sources 304 ₁-304 _m(hereinafter collectively referred to as “light sources 304”), a first beam splitting means, hereinafter referred to as a first diffractive optical element 306, a plurality of light guiding means such as optical fibers 302 ₁-302 _n(hereinafter collectively referred to as “optical fibers 302”), an array of second beam splitting means, hereinafter referred to as second diffractive optical elements 308 ₁-308 _n(and hereinafter collectively referred to as “second diffractive optical elements 308”), and an imaging sensor 310 including a wide-angle lens 312.
The components are arranged substantially symmetrically about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor 310. In one embodiment, the light sources 304 are positioned at a first end of the central axis A-A′. In one embodiment, the light sources 304 comprise a plurality of laser light sources that each emit a single beam of light along the central axis A-A′. Hereinafter, a single beam emitted by one of the light sources 304 may also be referred to as the “primary beam.” The light sources 304 may include two or more different types of light sources, such as two or more laser light sources that emit light of different wavelengths. In one embodiment, each of the light sources 304 emits light of a wavelength that is known to be relatively safe to human vision (e.g., infrared). In a further embodiment, one or more of the light sources 304 may include circuitry to adjust the intensity of its output. In a further embodiment, one or more of the light sources 304 may emit light in pulses, so as to mitigate the effects of ambient light on image capture.
The first diffractive optical element (DOE) 306 is positioned along the central axis A-A′ in proximity to the light sources 304 (e.g., “in front” of the light sources 304, relative to the direction in which light emitted by the light sources 304 propagates). In particular, the first DOE 306 is positioned to intercept the single beam of light emitted by one of the light sources 304 and to split the single or primary beam into a plurality of secondary beams. The first DOE 306 is any optical component that is capable of splitting the primary beam into a plurality of secondary beams that diverge from the primary beam in different directions. For example, in one embodiment, the first DOE 306 may include a conical mirror, a holographic film, a micro lens, or a line generator (e.g., a Powell lens). In this case, the plurality of secondary beams are arranged in a cone shape. In further embodiments, the primary beam may be split by means other than diffraction.
Each of the optical fibers 302 is coupled at one end to the first DOE 306 and is coupled at the other end to one of the DOEs 308 in the array of second DOEs 308. In this way, each of the optical fibers 302 is positioned to carry at least one of the secondary beams produced by the first DOE 306 to one of the DOEs 308 in the array of second DOEs 308.
The array of second DOEs 308 is positioned along the central axis A-A′ in proximity to the first DOE 306 (e.g., “in front” of the first DOE 306, relative to the direction in which light emitted by the light sources 304 propagates). In particular, the array of second DOEs 308 is positioned such that the first DOE 306 is positioned between the light sources 304 and the array of second DOEs 308. As more clearly illustrated in FIG. 3B, in one embodiment, the second DOEs 308 are arranged in a ring-shaped array, with the central axis A-A′ passing through the center of the ring and the second DOEs 308 spaced at regular intervals around the ring. For instance, in one embodiment, the second DOEs 308 are spaced approximately thirty degrees apart around the ring. In one embodiment, the array of second DOES 308 is positioned “behind” a principal point of the imaging sensor 310 (i.e., the point where the optical axis A-A′ intersects the image plane), relative to the direction in which light emitted by the light sources 304 propagates.
Each second DOE 308 is positioned to receive one of the secondary beams transmitted by one of the optical fibers 302 from the first DOE 306 and to split the secondary beam into a plurality of (e.g., two or more) tertiary beams that are directed away from the second DOE 308 in a radial manner. Thus, each second DOE 308 defines a projection point of the sensor 300 from which a group of projection beams (or tertiary beams) is emitted into the field of view. In one embodiment, each respective plurality of tertiary beams fans out to cover a range of approximately one hundred degrees. The second DOEs 308 are any optical components that are capable of splitting a respective secondary beam into a plurality of tertiary beams that diverge from the secondary beam in different directions. For example, in one embodiment, each second DOE 308 may include a conical mirror, a holographic film, a micro lens, or a line generator (e.g., a Powell lens). In other embodiments, however, the secondary beams are split by a means other than diffraction.
In one embodiment, each plurality of tertiary beams is arranged in a fan or radial pattern, with equal angles between each of the beams. In one embodiment, each of the second DOEs 308 is configured to project tertiary beams that create a different visual pattern on a surface. For example, one second DOE 308 may project a pattern of dots, while another second DOE 308 may project a pattern of lines or x's.
The imaging sensor 310 is positioned along the central axis A′A′, in the middle of the array of second DOEs 308 (e.g., at least partially “in front” of the array of second DOEs 308, relative to the direction in which light emitted by the light sources 304 propagates). In one embodiment, the imaging sensor 310 is an image capturing device, such as a still or video camera. As discussed above, the imaging sensor 310 includes a wide-angle lens 312, such as a fisheye lens, that creates a hemispherical field of view. In one embodiment, the imaging sensor 310 includes circuitry for calculating the distance from the distance sensor 300 to an object or point. In another embodiment, the imaging sensor includes a network interface for communicating captured images over a network to a processor, where the processor calculates the distance from the distance sensor 300 to an object or point and then communicates the calculated distance back to the distance sensor 300.
FIG. 4 illustrates a flowchart of a method 400 for calculating the distance from a sensor to an object or point in space. In one embodiment, the method 400 may be performed by a processor integrated in an imaging sensor (such as the imaging sensor 110 illustrated in FIG. 1A or the imaging sensor 310 illustrated in FIG. 3A) or a general purpose computing device as illustrated in FIG. 10 and discussed below.
The method 400 begins in step 402. In step 404, a light source is activated to generate a primary beam of light. In one embodiment, a single primary beam is generated by a single light source; however, in other embodiments, multiple primary beams are generated by multiple light sources. In one embodiment, the light source or light sources comprise a laser light source.
In optional step 406, the primary beam is split into a plurality of secondary beams using a first beam splitting means (e.g., a diffractive optical element) that is positioned in the path along which the primary beam propagates. The first beam splitting means may be, for example, a conical mirror. Step 406 is performed, for example, when the distance sensor (of which the imaging sensor is a part) includes only a single light source.
In step 408, each beam in the plurality of secondary beams is split into a plurality of projection or tertiary beams using a second beam splitting means (e.g., second diffractive optical element) in an array of beam splitting means. In one embodiment, a plurality of second beam splitting means are positioned in a ring, such that each second beam splitting means is positioned in the path along which one of the secondary beams propagates. In one embodiment, at least some of the second beam splitting means are conical mirrors. In one embodiment, where the distance sensor comprises a plurality of light sources, the method 400 may proceed directly from step 404 to step 408. In this case, each primary beam of a plurality of primary beams (generated using the plurality of light sources) is directly split into a plurality of projection beams by one of the second beam splitting means.
In step 410, at least one image of the object or point is captured. The image includes a pattern that is projected onto the object or point and onto the surrounding space. The pattern is created by each of the projection beams projecting a series of dots, lines, or other shapes onto the object, point, or surrounding space.
In step 412, the distance from the sensor to the object or point is calculated using information from the images captured in step 410. In one embodiment, a triangulation technique is used to calculate the distance. For example, the positional relationships between parts of the patterns projected by the sensor can be used as the basis for the calculation.
The method 400 ends in step 414. Thus, the method 400, in combination with the sensor depicted in FIGS. 1A-1B or in FIG. 3, can measure the distance from the sensor to an object or point in space in a single cycle of image capture and calculation.
FIG. 5, for example, illustrates a triangulation technique by which the distance from the sensor to the object or point may be calculated in step 412. In particular, FIG. 5 illustrates the example imaging sensor 110 of FIG. 1, as well as two of the projection points, which may be defined by two of the second diffractive optical elements 108 ₁and 108 ₂. The projection points are spaced equal distances, x, from the imaging sensor 110, such that there is a distance of s between the two projection points (e.g., x=s/2). Each of the projection points emits a respective projection beam 500 ₁and 500 ₂, which is incident upon the object to create a respective point 502 ₁and 502 ₂(e.g., dot or line) in a pattern. These points 502 ₁and 502 ₂are detected by the imaging sensor 110 and may be used to calculate the distance, D, between the imaging sensor 110 and the object as follows:
D=s/(−tan α₂+tan α₁+tan θ₂+tan θ₁) (EQN. 1)
where α₂is the angle formed between the projection beam 500 ₂and a central axis c₂of the second diffractive optical element 108 ₂, α₁is the angle formed between the projection beam 500 ₁and a central axis c₁of the second diffractive optical element 108 ₁, θ₂is the angle formed between the central optical axis O of the imaging sensor 110 and the angle at which the imaging sensor 110 perceives the point 502 ₂created by the projection beam 500 ₂, and θ₁is the angle formed between the central optical axis O of the imaging sensor 110 and the angle at which the imaging sensor 110 perceives the point 502 ₁created by the projection beam 500 ₁.
EQN. 1 is derived from the following relationships:
D*tan α₁ +D*tan θ ₁ =x (EQN. 2)
D*tan α₂ +D*tan θ ₂ =s−x (EQN. 3)
EQNs. 2 and 3 allow one to calculate the distance from a source of a projection pattern (comprising, e.g., a pattern of dots) to an object onto which the projection pattern is projected. The distance is calculated based on the positional relationship between the points of light (e.g., the dots) that form the projection pattern when the points of light are emitted by different projection points around the source. In this embodiment, the positional relationships between the points of light are known a priori (i.e., not measured as part of the calculation).
As discussed above, one application to which the distance sensor of the present disclosure may be well-suited is endoscopy, due to its compact size and ability to measure distances in fields of view of up to 360 degrees. FIGS. 6A and 6B, for example, illustrate a third embodiment of a distance sensor 600 of the present disclosure. In particular, FIG. 6A illustrates a cross-sectional view of the distance sensor 600, while FIG. 6B illustrates a top view of the distance sensor 600 of FIG. 3A. The distance sensor 600 may be suitable for use as part of an endoscope.
As illustrated in FIG. 6A, the distance sensor 600 comprises a plurality of components arranged in a compact configuration. The components include a plurality of illumination light sources (hereinafter collectively referred to as “illumination light sources 602,” of which one illumination light source 602 ₁is visible in FIG. 6A), a plurality of projection light sources (hereinafter collectively referred to as “projection light sources 604,” of which one projection light source 604 ₁is visible in FIG. 6A), a plurality of light guiding means such as optical fibers (hereinafter collectively referred to as “optical fibers 606,” of which two optical fibers 606 ₁and 6066 are visible in FIG. 6A), a plurality of beam splitting means, hereinafter referred to as a diffractive optical elements (hereinafter collectively referred to as “DOEs 608,” of which one DOE 608 ₁is visible in FIG. 6A), a plurality of collimating lenses, such as gradient-index (GRIN) lenses (hereinafter collectively referred to as “GRIN lenses 616,” of which one GRIN lens 616 ₁is visible in FIG. 6A), a plurality of Powell lenses 614 ₁-614 ₃(hereinafter collectively referred to as “Powell lenses 614”), a plurality of illumination optics assemblies 618 ₁-618 ₃(hereinafter collectively referred to as “illumination optics assemblies 614”), and an imaging sensor 610 including a wide-angle lens 612.
The components are arranged substantially symmetrically about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor 610. In one embodiment, the illumination light sources 602 and the projection light sources 604 are positioned at a first end of the central axis A-A′. In one embodiment, the illumination light sources 602 comprise a plurality of light emitting diodes (LEDs) that each emit illumination in a direction substantially parallel to the central axis A-A′.
In one embodiment, the projection light sources 604 comprise a plurality of laser light sources, such as vertical cavity surface emitting lasers (VCSELs), that each emit a single beam of light in a direction substantially parallel to the central axis A-A′. Hereinafter, a single beam emitted by one of the projection light sources 604 may also be referred to as the “primary beam.” In one embodiment, each of the projection light sources 604 emits light of a wavelength that is known to be relatively safe to human vision (e.g., infrared). In a further embodiment, the projection light sources 604 may include circuitry to adjust the intensity of their output. In a further embodiment, one or more of the projection light sources 604 may emit light in pulses, so as to mitigate the effects of ambient light on image capture.
The illumination light sources 602 are connected to the illumination optics assemblies 618 via a first subset of the optical fibers 606. The illumination optics assemblies 618 may include lenses, diffractive elements, or other components that help to direct illumination generated by the illumination light sources 602 in the appropriate directions. In one embodiment, the illumination optics assemblies 618 are positioned along the central axis A-A′ in proximity to the illumination light sources 602 (e.g., “in front” of the illumination light sources 602, relative to the direction in which light emitted by illumination light sources 602 propagates). As more clearly illustrated in FIG. 6B, in one embodiment, the illumination optics assemblies 618 are arranged in a ring-shaped array, with the central axis A-A′ passing through the center of the ring and the illumination optics assemblies 618 spaced at regular intervals around the ring, e.g., alternating with the Powell lenses 614. For instance, in one embodiment, the second DOEs 308 are spaced approximately 120 degrees apart around the ring. In one embodiment, the illumination optics assemblies 618 are positioned “behind” a principal point of the imaging sensor 610 (i.e., the point where the optical axis A-A′ intersects the image plane), relative to the direction in which light emitted by the illumination light sources 602 propagates.
The projection light sources 604 are connected to the GRIN lenses 616 via a second subset of the optical fibers 606. In one embodiment, GRIN lenses 616 are positioned along the central axis A-A′ in proximity to the projection light sources 604 (e.g., “in front” of the projection light sources 604, relative to the direction in which light emitted by the projection light sources 604 propagates). Each GRIN lens 616 is coupled to one of the DOEs 608, which is in turn coupled to one of the Powell lenses 614. Together, each set of GRIN lens 616, DOE 608, and Powell lens 614 receives, via an optical fiber 606, a single beam of light emitted by one of the projection light sources 604 and splits the single or primary beam into a plurality of secondary beams. The DOEs 608 may be any optical components that are capable of splitting a primary beam into a plurality of secondary beams that diverge from the primary beam in different directions. For example, in one embodiment, the DOEs 608 may include a conical mirror, a holographic film, a micro lens, or a line generator. In further embodiments, the primary beam may be split by means other than diffraction.
As illustrated in FIG. 6B, the sensor 600 may include three sets each of: (1) illumination light source 602, optical fiber 606, and illumination optics 618 (hereinafter an “illumination assembly”); and (2) projection light source 604, optical fiber 606, GRIN lens 616, DOE 608, and Powell lens 614 (hereinafter a “projection assembly”). The illumination assemblies and projection assemblies may be arranged in an alternating fashion around the central axis A-A′, such that each illumination assembly is spaced from the next illumination assembly by approximately 120 degrees, and each projection assembly is spaced from the next projection assembly by approximately 120 degrees. In further embodiments, however, different numbers of illumination assemblies and projection assemblies may be used. In addition, the spacing between illumination assemblies and projection assemblies may be varied.
The imaging sensor 610 is positioned along the central axis A′A′, in the middle of the ring of illumination assemblies and projection assemblies (e.g., at least partially “in front” of the illumination assemblies and projection assemblies, relative to the direction in which light emitted by the illumination assemblies and projection assemblies propagates). In one embodiment, the imaging sensor 610 is an image capturing device, such as a still or video camera. As discussed above, the imaging sensor 610 includes a wide-angle lens 612, such as a fisheye lens, that creates a hemispherical field of view. In one embodiment, the imaging sensor 610 includes circuitry for calculating the distance from the distance sensor 600 to an object or point. In another embodiment, the imaging sensor includes a network interface for communicating captured images over a network to a processor, where the processor calculates the distance from the distance sensor 600 to an object or point and then communicates the calculated distance back to the distance sensor 300.
As discussed above, the distance sensor 600 may be especially well-suited for endoscopy applications, due to its ability to emit both illuminating radiation and a projection pattern. FIG. 7 illustrates a first example projection pattern that may be generated by the distance sensor 600 of FIG. 6. As illustrated, the projection pattern comprises a plurality of groups of parallel lines (e.g., where each projection assembly of the distance sensor 600 projects one group of parallel lines. The planes of the groups of parallel lines may intersect near the central axis A-A′.
FIG. 8 illustrates a second example projection pattern that may be generated by the distance sensor 600 of FIG. 6. As illustrated, the projection pattern comprises a plurality of groups of parallel lines (e.g., where each projection assembly of the distance sensor 600 projects one group of parallel lines. The planes of the groups of parallel lines may intersect to form a triangular shape whose center is located near the central axis A-A′.
FIG. 9 depicts a portion of a fourth embodiment of a distance sensor of the present disclosure. In particular, FIG. 9 illustrates an optical unit 900 of a distance sensor, which may be used to project a pattern for detection by an imaging sensor (not shown). A plurality of similarly configured optical units may be arranged on a common circuit board to project a plurality of projection patterns into a field of view.
As illustrated in FIG. 9, the optical unit 900 comprises a plurality of components arranged in a compact configuration. The components include a circuit board 902, a light source 904, a light guiding means such as a collimator lens 906, a beam splitting means, hereinafter referred to as a diffractive optical element (DOE) 908, and a line generator 910.
The components are arranged substantially symmetrically on the circuit board 902, about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor of the distance sensor. The light source 904 may be positioned directly on the circuit board 902, and in one embodiment, the light source 904 is positioned at a first end of the central axis A-A′. In one embodiment, the light source 904 is a laser light source, such as a VCSEL, that emits a single beam of light along the central axis A-A′. Hereinafter, the single beam emitted by the light source 904 may also be referred to as the “primary beam.” In one embodiment, the light source 904 emits light of a wavelength that is known to be relatively safe to human vision (e.g., infrared). In a further embodiment, the light source 904 may include circuitry to adjust the intensity of its output. In a further embodiment, the light source 904 may emit light in pulses, so as to mitigate the effects of ambient light on image capture.
The collimator lens 906 is positioned along the central axis A-A′ in proximity to the light source 904 (e.g., “in front” of the light source 904, relative to the direction in which light emitted by the light source 904 propagates). In particular, the collimator lens 906 is positioned to intercept the single beam of light emitted by the light source 904 and to focus the single or primary beam onto the DOE 908.
The DOE 908 is positioned along the central axis A-A′ in proximity to the light source 904 (e.g., “in front” of the light source 904, relative to the direction in which light emitted by the light source 904 propagates). In particular, the DOE 908 is positioned to intercept the single beam of light focused by the collimator lens 906 and to split the single or primary beam into a plurality of secondary beams. The DOE 908 is any optical component that is capable of splitting the primary beam into a plurality of secondary beams that diverge from the primary beam in different directions. For example, in one embodiment, the DOE 908 may include a conical mirror, a holographic film, or a micro lens. In this case, the plurality of secondary beams are arranged in a cone shape. In further embodiments, the primary beam may be split by means other than diffraction.
The line generator 910 is positioned along the central axis A-A′ in proximity to the light source 904 (e.g., “in front” of the light source 904, relative to the direction in which light emitted by the light source 904 propagates). In particular, the line generator 910 is positioned to intercept the plurality of secondary beams produced by the DOE 908 and to further split the secondary beams into a plurality of tertiary beams. In one embodiment, the line generator 910 is a Powell lens.
Because the optical unit 900 can be fabricated without optical fibers, it can be fabricated on a very small scale for use in compact distance sensors.
FIG. 10 depicts a high-level block diagram of a general-purpose computer suitable for use in performing the functions described herein. As depicted in FIG. 10, the system 1000 comprises one or more hardware processor elements 1002 (e.g., a central processing unit (CPU), a microprocessor, or a multi-core processor), a memory 1004, e.g., random access memory (RAM) and/or read only memory (ROM), a module 1005 for calculating distance, and various input/output devices 1006 (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 lens and optics, an output port, an input port and a user input device (such as a keyboard, a keypad, a mouse, a microphone and the like)). Although only one processor element is shown, it should be noted that the general-purpose computer may employ a plurality of processor elements. Furthermore, although only one general-purpose computer is 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 steps of the above method(s) or the entire method(s) are implemented across multiple or parallel general-purpose computers, then the general-purpose computer of this figure is intended to represent each of those multiple general-purpose computers. Furthermore, one or more hardware processors can be utilized in supporting a virtualized or shared computing environment. The virtualized computing environment may support one or more virtual machines representing computers, servers, or other computing devices. In such virtualized virtual machines, hardware components such as hardware processors and computer-readable storage devices may be virtualized or logically represented.
It should be noted that the present disclosure can be implemented in software and/or in a combination of software 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 steps, functions and/or operations of the above disclosed methods. In one embodiment, instructions and data for the present module or process 1005 for calculating distance (e.g., a software program comprising computer-executable instructions) can be loaded into memory 1004 and executed by hardware processor element 1002 to implement the steps, functions or operations as discussed above in connection with the example method 400. 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 computer readable or software instructions relating to the above described method(s) can be perceived as a programmed processor or a specialized processor. As such, the present module 1005 for calculating distance (including associated data structures) 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 a computing device such as a computer or an application server.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

What is claimed is:

1. An apparatus, comprising:

a projection light source;

a first light guiding means positioned to guide light emitted by the projection light source;

a diffractive optical element positioned to split the light guided by the first light guiding means into a plurality of projection beams traveling in different directions; and

an image capturing device positioned to capture an image of a field of view, including a projection pattern created by an incidence of the plurality of projection beams on an object in the field of view.

2. The apparatus of claim 1, wherein the projection light source comprises a single laser light source.

3. The apparatus of claim 1, wherein the projection light source comprises a plurality of laser light sources.

4. The apparatus of claim 3, wherein the plurality of laser light sources comprises at least two different types of laser light sources.

5. The apparatus of claim 1, wherein the first light guiding means comprises a plurality of optical fibers.

6. The apparatus of claim 5, wherein the diffractive optical element comprises a plurality of diffractive optical elements, and wherein each optical fiber of the plurality of optical fibers is coupled to one diffractive optical element of the plurality of diffractive optical elements.

7. The apparatus of claim 6, further comprising:

an additional diffractive optical element, separate from the plurality of diffractive optical elements, coupling the projection light source to the plurality of optical fibers.

8. The apparatus of claim 6, wherein the plurality of diffractive optical elements is arranged in a ring around a central optical axis of the image capturing device.

9. The apparatus of claim 1, further comprising:

an illumination light source, comprising a light source different from the projection light source;

a second light guiding means positioned to guide light emitted by the projection light source;

an illumination optic positioned to direct the light from the second light guiding means into the field of view.

10. The apparatus of claim 9, wherein the illumination optic comprises a plurality of illumination optics, the diffractive optical element comprises a plurality of diffractive optical elements, and the plurality of illumination optics and the plurality of diffractive optical elements are arranged in an alternating pattern in a ring configuration around a central optical axis of the image capturing device.

11. The apparatus of claim 9, further comprising:

a collimating lens positioned between the first light guiding means and the diffractive optical element; and

a line generator, wherein the line generator is positioned such that the diffractive optical element is situated between the collimating lens and the line generator.

12. The apparatus of claim 11, wherein the line generator is a Powell lens.

13. The apparatus of claim 11, wherein the collimating lens is a gradient-index lens.

14. The apparatus of claim 1, wherein the projection light source comprises a plurality of vertical cavity surface emitting lasers arranged on a circuit board.

15. The apparatus of claim 14, wherein the light guiding means comprises a collimating lens positioned between the projection light source and the diffractive optical element.

16. The apparatus of claim 15, wherein the collimating lens is a gradient-index lens.

17. The apparatus of claim 15, further comprising:

18. The apparatus of claim 17, wherein the line generator is a Powell lens.

19. An apparatus, comprising:

a plurality of projection light sources;

a first plurality of optical fibers, wherein a first end of each optical fiber of the first plurality of optical fibers is coupled to one projection light source of the plurality of projection light sources;

a plurality of diffractive optical elements, wherein each diffractive optical element of the plurality of diffractive optical elements is coupled to a second end of one optical fiber of the first plurality of optical fibers;

a plurality of illumination light sources, comprising light sources that are different from the plurality of projection light sources;

a second plurality of optical fibers, wherein a first end of each optical fiber of the second plurality of optical fibers is coupled to one illumination light source of the plurality of illumination light sources;

a plurality of illumination optics, wherein each illumination optic of the plurality of illumination optics is coupled to a second end of one optical fiber of the second plurality of optical fibers; and

an image capturing device, wherein the plurality of diffractive optical elements and the plurality of illumination optics are arranged in a ring around a central optical axis of the image capturing device.

20. An apparatus, comprising:

a plurality of vertical cavity surface emitting lasers arranged on a circuit board;

a plurality of gradient-index lenses, wherein each gradient-index lens of the plurality of gradient-index lenses is positioned to collimate a beam of light produced by one vertical cavity surface emitting laser of the plurality of vertical cavity surface emitting lasers;

a plurality of diffractive optical elements, wherein each diffractive optical element of the plurality of diffractive optical elements is positioned to split a beam collimated by one gradient-index lens of the plurality of gradient-index lenses into a plurality of beams traveling in different directions; and

a plurality of Powell lenses, wherein each Powell lens of the plurality of Powell lenses is positioned to generate a projection pattern from a plurality of beams generated by one diffractive optical element of the plurality of diffractive optical elements.