WO2024184840A1

WO2024184840A1 - Mitigating a point spread function in an optical scanning system

Info

Publication number: WO2024184840A1
Application number: PCT/IB2024/052200
Authority: WO
Inventors: Yuval YIFAT; Shai Ben-Yaish; Boaz Nemet; David Elooz; Amy ENTIN; Neriya FELMUS
Original assignee: Innoviz Technologies Ltd
Current assignee: Innoviz Technologies Ltd
Priority date: 2023-03-07
Filing date: 2024-03-07
Publication date: 2024-09-12
Anticipated expiration: 2025-09-07

Abstract

A system (20) includes an illumination unit (22) configured to emit light, a detector (26) comprising an array of detection elements (40), one or more optical elements (28) configured to direct the light toward a field of view (36) and to direct respective reflections (38) of portions of the light from one or more objects in the field of view, along an optical pathway, toward different respective ones of the detection elements, and one or more point-spread-function-mitigating components (60) disposed along the optical pathway and configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements. Other embodiments are also described.

Description

MITIGATING A POINT SPREAD FUNCTION IN AN OPTICAL SCANNING SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to US Provisional Application 63/488,790, entitled “Lidar embedded blooming reduction system and method,” filed March 7, 2023, whose disclosure is incorporated herein by reference, and US Provisional Application 63/619,334, entitled “Mitigating a point spread function in an optical scanning system,” filed January 10, 2024, whose disclosure is incorporated herein by reference.

FIELD OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention relate generally to optical scanning systems, such as light detection and ranging systems, and specifically to optics for such systems.

BACKGROUND

With the advent of driver-assist systems and autonomous vehicles, vehicles need systems capable of reliably sensing and interpreting their surroundings, including identifying obstacles, hazards, objects, and other physical parameters that might impact navigation of the vehicle. In many cases, the ability of the system to determine surroundings across different conditions - including, rain, fog, darkness, bright light, and snow - is of particular importance. To this end, various technologies such as radar, light detection and ranging, and camera-based systems have been used.

Light detection and ranging measures distances to objects by illuminating the objects and measuring the time to receive the reflected pulses. A light detection and ranging system may include a light deflector for deflecting light emitted by a light source, such as a laser, into the field of view. The light deflector may pivot around at least one axis so as to deflect light in various directions.

SUMMARY

In some embodiments, a system comprises an illumination unit configured to emit light, a detector comprising an array of detection elements, and one or more optical elements configured to direct the light toward a field of view and to direct respective reflections of portions of the light from one or more objects in the field of view, along an optical pathway, toward different respective ones of the detection elements. The system further comprises one or more point- spread-function- mitigating components disposed along the optical pathway and configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements. For example, the point spread function may cause the reflections to have respective lobes, and the point- spread-function- mitigating components may be configured to mitigate the point spread function by reducing a size of the lobes. In some embodiments, the point-spread-function-mitigating components are configured to mitigate the point spread function by modifying at least one edge portion of at least one of the optical elements. For example, the point-spread-function-mitigating components may comprise a coating that coats the edge portion.

There is therefore provided, in accordance with some embodiments of the present invention, a system including an illumination unit, configured to emit light, a detector including an array of detection elements, and one or more optical elements, configured to direct the light toward a field of view, and to direct respective reflections of portions of the light from one or more objects in the field of view, along an optical pathway, toward different respective ones of the detection elements. The system further includes one or more point-spread-function-mitigating components disposed along the optical pathway and configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements.

In some embodiments, the light includes multiple light beams spatially offset from each other, and the reflections are reflections of the light beams, respectively.

In some embodiments, the illumination unit includes a laser including multiple channels and configured to emit the light beams via the channels, respectively.

In some embodiments, the detection elements include respective silicon photomultiplier detection elements.

In some embodiments, the point spread function causes the reflections to have respective lobes, and the point-spread-function-mitigating components are configured to mitigate the point spread function by reducing a size of the lobes.

In some embodiments, the point- spread-function-mitigating components include a transmissive element having at least one edge portion configured to mitigate the point spread function. In some embodiments, the point-spread-function-mitigating components are configured to mitigate the point spread function by modifying at least one edge portion of at least one of the optical elements.

In some embodiments, the modification reduces an area of an aperture of the at least one of the optical elements by less than 25%.

In some embodiments, the modification reduces the area by less than 15%.

In some embodiments, the optical elements include a mirror, and the point-spread- function-mitigating components modify at least one edge portion of the mirror.

In some embodiments, the mirror is a scanning mirror configured to rotate while reflecting the light and the reflections.

In some embodiments, the point-spread-function-mitigating components include a coating that coats the at least one edge portion and is configured to attenuate the reflections.

In some embodiments, the coating is continuous.

In some embodiments, the coating is non-continuous.

In some embodiments, the point-spread-function-mitigating components include a cover that is coupled to the at least one edge portion and is configured to attenuate the reflections.

In some embodiments, by virtue of the modification, an attenuation coefficient of the edge portion increases toward an edge of the at least one of the optical elements.

In some embodiments, by virtue of the modification, a shape of an aperture of the at least one of the optical elements is modified.

In some embodiments, by virtue of the modification, an edge of the aperture is shaped to define one or more teeth.

In some embodiments, a length of each of the teeth is 0.2 - 4 mm.

In some embodiments, the edge of the aperture is shaped in a triangle-wave pattern.

In some embodiments, the edge of the aperture is shaped in a sawtooth pattern.

In some embodiments, an angle between each of the teeth and an edge of the at least one of the optical elements is between 30 and 60 degrees.

In some embodiments, the angle is between 40 and 50 degrees.

In some embodiments, by virtue of the modification, an edge of the aperture is curved. In some embodiments, by virtue of the modification, an edge of the aperture is wavy.

In some embodiments, the point-spread-function-mitigating components modify at least one edge portion of a first one of the optical elements, which has a first aperture, and at least one edge portion of a second one of the optical elements, which receives the reflections from the first one of the optical elements and has a second aperture that is smaller than the first aperture.

In some embodiments, the light is polarized, the first one of the optical elements is a mirror, and the second one of the optical elements is a polarizing beamsplitter configured to: reflect the light toward to the mirror, and transmit the reflections from the mirror.

There is further provided, in accordance with some embodiments of the present invention, a system, including an illumination unit, configured to emit light, a detector including an array of detection elements arranged along one or more axes, and one or more optical elements, configured to direct the light toward a field of view, and to direct respective reflections of portions of the light from one or more objects in the field of view toward different respective ones of the detection elements. The optical elements have respective apertures and are configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements, by virtue of no straight edge of an aperture that receives the reflections being perpendicular to at least one of the axes.

In some embodiments, the point spread function causes the reflections to have respective lobes that, without the mitigation, would be parallel to the at least one of the axes.

There is further provided, in accordance with some embodiments of the present invention, a system, including an illumination unit, configured to emit light, a detector including an array of detection elements, and one or more optical elements, configured to direct the light toward a field of view, and to direct respective reflections of portions of the light from one or more objects in the field of view toward different respective ones of the detection elements. An aperture of at least one of the optical elements has an edge shaped to define one or more teeth.

In some embodiments, a length of each of the teeth is 0.2 - 4 mm.

In some embodiments, the edge of the aperture is shaped in a sawtooth pattern.

In some embodiments, the angle is between 40 and 50 degrees.

The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic illustration of an optical scanning system, in accordance with some embodiments of the present invention;

Fig. 2 is a schematic illustration of a mitigation of a point spread function, in accordance with some embodiments of the present invention;

Fig. 3 is a schematic illustration of a mitigation of a point spread function, in accordance with some embodiments of the present invention; and

Fig. 4A, Fig. 4B, and Fig. 4C are schematic illustrations of a mitigation of a point spread function, in accordance with some embodiments of the present invention. DETAILED DESCRIPTION

OVERVIEW

In some light detection and ranging systems, reflections of multiple light beams, or of multiple portions of a single light beam, are received, simultaneously or in close succession, by different respective detection elements of a photodetector. An advantage of such an arrangement, relative to a single-element detector, is faster scanning times.

In such systems, it is important that each reflection remain confined to its detection element, as any spillover of light onto a neighboring detection element may adversely impact the accuracy of the system. However, as each reflection follows the optical pathway leading to the detector, one or more optical elements along the pathway may spread the reflection, such that the reflection is more likely to impinge on multiple detection elements. For example, typically, the reflections impinge on the optical elements near the edges of the optical elements. The resulting diffraction effect may introduce patterns of light, such as lobes or rings, that extend the reflections, and these extensions may impinge on neighboring detection elements. Although some algorithmic solutions to mitigate this effect exist, these solutions are not always reliable.

Hence, to address this problem, embodiments of the present invention shape and/or orient the problematic edges of the apertures of the optical elements to reduce the size of any introduced reflection extensions and/or to orient the extensions away from the detector, rather than toward neighboring detection elements. In some embodiments, this is done by cutting an edge of the optical element (e.g., in a triangle-wave or sinusoidal pattern) and/or orienting the optical element such that no edge of an aperture that receives the reflections is perpendicular to the axis along which the detection elements are arranged. In other embodiments, this is done by coating or otherwise covering portions of the optical element to create a modified aperture edge, e.g., such that the aperture edge is shaped in a triangle-wave or sinusoidal pattern.

In addition to light detection and ranging systems, embodiments of the present invention can be applied to other optical scanning systems, such as some medical imaging systems. More generally, embodiments of the present invention can be applied to any system in which the cross- sectional shape of a beam is affected by the aperture of one or more of the optical elements in the system.

SYSTEM DESCRIPTION

Reference is initially made to Fig. 1, which is a schematic illustration of an optical scanning system 20, such as a light detection and ranging system, in accordance with some embodiments of the present invention.

System 20 comprises an illumination unit 22 configured to emit light, such as pulsed, continuous-wave (CW), or quasi-CW light. In some embodiments, illumination unit 22 comprises a laser, such as a solid-state laser, a fiber laser, a semiconductor laser diode (e.g., a vertical-cavity surface-emitting laser, an external cavity diode laser, or an edge-emitting laser), an edge emitting laser with an external cavity, an edge emitting laser with an external amplifier, or a photonic crystal surface emitting laser. In other embodiments, the illumination unit comprises another type of light source, such as a light emitting diode (LED).

In some embodiments, the light is emitted in sets of multiple (e.g., between 4 and 64, such as 16 or 32) light beams 24 that are spatially offset from each other. Typically, light beams 24 are emitted simultaneously or in quick succession, e.g., with less than 2 ps between the emission of successive light beams.

For example, illumination unit 22 may comprise a multichannel laser (or “laser array”) comprising multiple channels and configured to emit light beams 24, in the form of laser beams, via the channels, respectively. In other embodiments, the light includes a single light beam 24, such as a laser beam. In general, each emitted light beam (e.g., laser beam) may have any suitable wavelength, such as 650-1150 nm (e.g., 800-1000 nm, such as 905 nm) or 1300-1600 nm, and any suitable cross-sectional shape, such as a circular or elliptical shape.

System 20 further comprises one or more optical elements 28 and a detector 26, which comprises a one-dimensional or two-dimensional array of detection elements 40 such as silicon photomultiplier, single -photon avalanche diode, or avalanche photodiode elements. In Fig. 1, a one-dimensional array of detection elements 40 is oriented into the page, with an inset portion 43 of the figure showing a frontal view of the detector. In some embodiments, detection elements 40 are separated from each other by separators (or “inactive regions”) 54, which may have equal or unequal sizes. Detector 26 is further described below with reference to Fig. 2.

Optical elements 28 are configured to direct (or “deflect”) the emitted light toward a field of view 36. The optical elements are further configured to direct respective reflections 38 of portions of the light (e.g., respective reflections of light beams 24 or of different portions of a single light beam) from one or more objects in field of view 36, along an optical pathway, toward different respective ones of detection elements 40. Optical elements 28 may comprise, for example, one or more mirrors (e.g., folding mirrors), prisms, beamsplitters, and/or lenses. Each optical element has an aperture, which is the optically-functional portion of the optical element, e.g., the portion of the optical element that reflects or transmits the emitted or reflected light. In some embodiments, optical elements 28 comprise a one-dimensional or two- dimensional scanner, which comprises one or more elements configured to deflect the emitted light in various directions (i.e., to scan the field of view).

In some embodiments, the scanning elements are configured to move (e.g., rotate) while performing the scanning. For example, Fig. 1 shows a two-dimensional scanner 30, which comprises a vertical scanning mirror 32 and a horizontal scanning mirror 44, such as a scanning polygon. Vertical scanning mirror 32 is configured to rotate, as indicated by a rotation indicator 42, so as to direct light beams 24 toward horizontal scanning mirror 44 at various vertical angles. Horizontal scanning mirror 44, in turn, is configured to rotate, as indicated by a rotation indicator 46, so as to direct light beams 24, through a window 29, toward field of view 36 at various horizontal angles. Alternatively, two-dimensional scanner 30 comprises a single mirror configured to rotate about two perpendicular axes.

Alternatively or additionally, the deflection in multiple directions is achieved by virtue of the spatial offset of light beams 24 from each other, and/or by virtue of the cross-sectional shape of each emitted light beam.

Typically, at least some of the optical elements are used both to direct the emitted light to field of view 36 and to direct the reflected light to the detector, thus providing significant advantages such as reduced complexity, lower cost, and better performance. In other words, at least some of the optical elements are used to direct light both in the transmission and reception direction.

In some such embodiments, light beams 24 are polarized, and optical elements 28 comprise at least one polarizing beamsplitter 33 configured to direct light beams 24 toward a mirror and to transmit reflections 38, which are of mixed polarization, from the mirror. For example, Fig. 1 shows an example embodiment in which the emitted polarized light is directed, by a mirror 34, toward beamsplitter 33, which directs the light toward vertical scanning mirror 32. Each reflection 38 is directed from horizontal scanning mirror 44 to vertical scanning mirror 32, and from vertical scanning mirror 32, through beamsplitter 33, to another mirror 34. The latter mirror directs the reflection through a lens 35, such as a telephoto lens, which focuses the reflection onto detector 26.

Typically, there is a fixed, one-to-one correspondence between detection elements 40 and respective portions of the emitted light, such as respective light beams 24 or respective portions of a single light beam. For example, if illumination unit 22 emits N light beams, detector 26 comprises N detection elements 40 such that, for each of the beams, the reflection of the beam is always received by the same detection element. This correspondence is due to the different respective directions from which the respective reflections of the portions of light arrive at system 20.

Typically, system 20 further comprises a controller 50. In response to reflections 38, detector 26 emits electrical signals, which are received by controller 50. Based on the electrical signals, controller 50 performs time-of-flight calculations so as to determine distances to the objects in field of view 36, and constructs a point cloud based on the distance values.

Typically, system 20 further comprises a power supply 48, which is configured to supply power to other elements of the system such as illumination unit 22, scanner 30, and controller 50.

Notwithstanding the specific configuration shown in Fig. 1, it is noted that the scope of the present invention includes any suitable composition and arrangement of optical elements 28.

MITIGATING THE POINT SPREAD FUNCTION

Reference is now made to Fig. 2, which is a schematic illustration of a mitigation of a point spread function of optical elements 28, in accordance with some embodiments of the present invention.

As described above with reference to Fig. 1, detector 26 comprises multiple detection elements 40, which are arranged along a single axis (for a one-dimensional detector) or two axes (for a two-dimensional detector). In some embodiments, detector 26 is fabricated on a single silicon wafer. In some embodiments, for greater detection precision, each detection element 40 is divided into multiple sub -elements 52.

The left portion of Fig. 2 illustrates a possible effect of a point spread function of optical elements 28. In particular, the left portion of Fig. 2 shows that this point spread function may cause a single reflection 38 to impinge on multiple detection elements 40, notwithstanding separators 54: the detection element corresponding to the portion of light that was reflected, and one or more adjacent detection elements. For example, the point spread function may cause some of the reflections to have lobes 56, which extend over separators 54 and onto the adjacent detection elements. This “blooming” effect, which may be particularly problematic for highly reflective objects (especially at close range), causes inaccuracies in the point cloud, given that phantom detections are registered at the adjacent detection elements.

In some cases, the point spread function introduces lobes 56 by diffraction, which results from the reflections impinging on at least one of the optical elements, such as a mirror (e.g., a scanning mirror) or beamsplitter, near an edge 58 of the aperture of the optical element. In particular, the introduced lobes are perpendicular to edge 58. Hence, if edge 58 is perpendicular to an axis along which detection elements are arranged, the lobes will be parallel to the axis, and hence, there is a greater risk of blooming. For example, the left portion of Fig. 2 assumes that the aperture occupies the entire surface of the optical element, such that the horizontal edges of the optical element, which are perpendicular to the axis of the detector, introduce two vertical lobes, and the vertical edges introduce two horizontal lobes.

Hence, in some embodiments, as shown at the right portion of Fig. 2, optical elements 28 are configured to mitigate the point spread function by virtue of no straight edge of an aperture that receives the reflections being perpendicular to at least one of the axes along which detection elements 40 are arranged. In other words, there is at least one axis that is not perpendicular to any straight edge of an aperture that receives the reflections. The orientation and/or the shape of any optical element on the optical pathway followed by the reflections, and/or the orientation of the detector, may contribute to this lack of perpendicularity.

For example, the right portion of Fig. 2 shows a rectangular optical element oriented such that the acute angle a between edge 58 and the axis of the detector is less than 90 degrees, e.g., between 60 and 80 degrees. Advantageously, this range of angles is enough to rotate the set of lobes that would otherwise be parallel to the axis (the vertical lobes in Fig. 2), such that these lobes no longer extend onto neighboring detection elements, without causing the other set of lobes (the horizontal lobes in Fig. 2) to extend onto the neighboring detection elements, and without overly increasing the space 57 occupied by the optical element.

Alternatively or additionally, edge 58 may be shaped to define one or more teeth, e.g., edge 58 may be triangle-wave-shaped or sawtooth- shaped, such that no straight portion of edge 58 is perpendicular to the axis. As yet another option, edge 58 may be curved (e.g., rounded) or wavy (e.g., sinusoidal). Such edge shapes, which are further described below with reference to Figs. 4A- C, may be attained by cutting a rectangular optical element, or by using an off-the-shelf non- rectangular optical element.

For example, in some embodiments, system 20 comprises one or more circular optical elements, such as one or more circular mirrors (e.g., scanning mirrors). Although diffraction at the edge of a circular aperture typically introduces a ring-shaped extension, this extension is typically smaller than the lobes described above. Hence, this point spread function can be ignored, or can be mitigated (e.g., using any of the techniques described below with reference to the subsequent figures) without losing a significant amount of aperture area.

Notwithstanding the specific example shown in Fig. 2, it is emphasized that the embodiments described with reference to Fig. 2 are also applicable to a two-dimensional detector. For example, while the reflection impinges on a one-dimensional sub-array (e.g., column) of detection elements 40 as shown in Fig. 2, adjacent one-dimensional sub-arrays (e.g., adjacent columns) of detection elements may be deactivated, such that the rotated lobes do not cause a blooming effect at these adjacent sub-arrays.

In view of the above, it may be stated that in some embodiments, regardless of the dimensionality of the detector, no straight edge of an aperture that receives the reflections is perpendicular to any axis along which simultaneously-active detection elements 40 are arranged.

Reference is now made to Fig. 3 and Figs. 4A-C, which are schematic illustrations of a mitigation of a point spread function, in accordance with some embodiments of the present invention.

In some embodiments, system 20 (Fig. 1) comprises one or more point- spread-function- mitigating components 60 disposed along the optical pathway followed by reflections 38. Components 60 are configured to mitigate the point spread function of the optical elements, alternatively or additionally to any mitigation provided as described above with reference to Fig. 2. For example, as illustrated in Fig. 3, components 60 may mitigate the point spread function by mitigating the diffraction effect, thereby reducing the size of lobes 56 (e.g., eliminating the lobes) such that the lobes don’t extend onto the adjacent detection elements. Alternatively or additionally, components 60 may change the orientation of lobes 56, as illustrated in Fig. 2.

In some such embodiments, components 60 are integrated with at least one of the optical elements. For example, referring again to Fig. 1, components 60 may be integrated with window 29, a scanning mirror, such as vertical scanning mirror 32 or horizontal scanning mirror 44, another mirror 34, and/or a beamsplitter, such as polarizing beamsplitter 33. Components 60 mitigate the point spread function by modifying at least one edge portion 62 of the optical element (i.e., at least one portion of the optical element that is adjacent to an edge of the optical element). For example, components 60 may comprise a continuous or non-continuous coating (or “layer”) that coats edge portion 62 and is configured to attenuate the reflections. For example, the coating may comprise an absorptive material, e.g., an absorptive paint, such as an ultra-black coating produced by Acktar Advanced Coatings. Alternatively or additionally, components 60 may comprise a cover that is coupled to edge portion 62 and is configured to attenuate the reflections.

In some embodiments, for ease of manufacture, a cover is applied to a stationary optical component, whereas a coating is applied to a moving optical component such as scanning mirror 32. As shown in Fig. 3 and Figs. 4A-C, two or more edge portions 62 of a single optical element may be modified. In general, each modified edge portion 62 may be adjacent to any edge of the optical element. For example, in some embodiments, for the reasons described above with reference to Fig. 2, at least one modified portion of the optical element is adjacent to an edge that is perpendicular to an axis along which the detection elements are arranged. Alternatively or additionally, at least one modified portion is adjacent to a non-perpendicular edge, e.g., to reduce any spreading of the emitted light as the light exits the system. (Typically, this spreading is due to an impingement of the emitted light near an edge of one of the optical elements that lies along the transmission pathway.) For example, all edge portions of the optical element may be modified.

In general, the modified edge portion may have any suitable width WO, such as 0.2-4 mm and/or 0.5%-20% of the parallel dimension of the optical element. (For example, in Fig. 3 and Figs. 4A-C, WO is measured vertically, such that the parallel dimension is the height of the optical element.) In general, a larger WO provides greater mitigation of the point spread function. Nonetheless, typically, WO is small enough such that the area of the aperture of the optical element is not overly reduced. For example, in some embodiments, the modification to the one or more edge portions of the optical element reduces the area of the aperture of the optical element by less than 25%, e.g., less than 15%.

In some embodiments, by virtue of the modification, the attenuation coefficient of the edge portion increases toward the edge of the optical element, as shown in Fig. 3. In other words, the point- spread-function-mitigating component provides a (linear or non-linear) gradient in the attenuation coefficient, which may also be referred to as an apodization of the aperture of the optical element. For example, for embodiments in which the edge portion is coated by a non- continuous coating, the density of the coating may increase toward the edge of the optical element.

In other embodiments, by virtue of the modification, the shape of the aperture of the optical element is modified.

For example, by virtue of the modification, an edge of the aperture may be curved (e.g., rounded), as shown for an edge 64 in Fig. 4A.

Alternatively, the edge of the aperture may be shaped to define one or more teeth 66. For example, Fig. 4A shows an aperture edge shaped to define a single tooth 66, while Fig. 4B shows an aperture edge shaped to define multiple teeth. In some such embodiments, as shown in Fig. 4B, the edge of the aperture is shaped in a sawtooth or triangle-wave pattern. The length L0 of each tooth may be 0.2-4 mm and/or 0.5%-20% of the parallel dimension of the optical element. An advantage of multiple teeth, relative to the gradient shown in Fig. 3, is that less of the aperture area is lost for an equivalent width of the edge portion.

The present inventors have found that teeth 66 are particularly effective at mitigating the point spread function when an angle 0 between each of the teeth and the edge of the optical element (in particular, the edge of the modified edge portion) is 30-60 degrees, e.g., 40-50 degrees, such as 45 degrees. For example, in a triangle-wave pattern, each of the teeth may have two such angles, while in a sawtooth pattern, each of the teeth may have one such angle.

As yet another alternative, as shown in Fig. 4C, the edge of the aperture may be wavy (e.g., sinusoidal). The peak-to-peak amplitude AO of the wave (e.g., the sinusoidal wave) may be 0.2-4 mm (e.g., 0.2-2 mm) and/or 0.5-20% (e.g., 0.5-10%) of the parallel dimension of the optical element.

As described above with reference to Fig. 1, typically, multiple optical elements 28 lie along the optical pathway followed by reflections 38. Thus, even if a first optical element is modified by a point-spread-function-mitigating component, a second optical element, which receives the reflections from the first optical element, may introduce a problematic spread to the reflections. This problem is particularly acute if the aperture of the second optical element is smaller than that of the first optical element.

Hence, some embodiments provide multiple point-spread-function-mitigating components, which modify at least one edge portion of both the first optical element and the second optical element. For example, both a mirror (e.g., vertical scanning mirror 32) and beamsplitter 33 may be modified by point-spread-function-mitigating components 60.

In some embodiments, components 60 include at least one standalone point-spread- function-mitigating component, which is positioned along the optical pathway but is not integrated with any of the optical elements. This standalone component comprises a transmissive element having at least one edge portion configured to mitigate the point spread function, e.g., as described above with reference to Fig. 3 or any of Figs. 4A-C. For example, even if an optical element preceding the standalone component on the optical pathway introduces lobes, the standalone point- spread-function-mitigating component may function as an aperture stop that at least partly removes (i.e., “masks out”) the lobes. An advantage of such embodiments is that the optical elements need not be modified.

For example, Fig. 1 shows a standalone point-spread-function-mitigating component 60s positioned immediately before lens 35 on the optical pathway and configured to reduce the size of, and/or rotate, any lobes introduced by any of the optical elements preceding component 60s on the optical pathway. As described above with reference to Fig. 2, any of the aperture-edge shapes shown in Figs. 4A-C may be attained by virtue of the shape of the optical element, such that component 60 is not required. Thus, for example, the scope of the present invention includes any aperture having an edge shaped to define one or more teeth as shown in Figs. 4A-B, whether such an edge is attained by virtue of a point-spread-function-mitigating component or by virtue of the edge of the optical element being shaped in this manner.

As yet another option, the standard coating for an optical element (i.e., the coating that gives the optical element its optical properties) may be applied non-uniformly to the substrate of the optical element, such that component 60 is not required. For example, a mirror may be manufactured by applying a reflective coating (e.g., a gold coating) to a substrate such that the density of the coating decreases toward the edge of the mirror, and hence, the reflectivity of the mirror decreases toward the edge, as shown in Fig. 3.

Although the present description relates mostly to mitigating a point spread function along the reception pathway (i.e., the optical pathway followed by the reflected light that is received from the field of view), it is also possible to have some spreading of the emitted light along the transmission pathway, as noted above with reference to Fig. 3 and Figs. 4A-C. Hence, some embodiments of the present invention provide one or more point-spread-function-mitigating components along the transmission pathway, even if these point-spread-function-mitigating components do not also lie along the reception pathway. For example, referring again to Fig. 1, one or more edge portions of the mirror 34 that directs light beams 24 to beamsplitter 33 may be modified as described above with reference to Fig. 3 and Figs. 4A-C.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

1. A system, comprising: an illumination unit, configured to emit light; a detector comprising an array of detection elements; one or more optical elements, configured to: direct the light toward a field of view, and direct respective reflections of portions of the light from one or more objects in the field of view, along an optical pathway, toward different respective ones of the detection elements; and one or more point-spread-function-mitigating components disposed along the optical pathway and configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements.

2. The system according to claim 1, wherein the light includes multiple light beams spatially offset from each other, and wherein the reflections are reflections of the light beams, respectively.

3. The system according to claim 2, wherein the illumination unit comprises a laser comprising multiple channels and configured to emit the light beams via the channels, respectively.

4. The system according to claim 1, wherein the detection elements comprise respective silicon photomultiplier detection elements.

5. The system according to claim 1, wherein the point spread function causes the reflections to have respective lobes, and wherein the point-spread-function-mitigating components are configured to mitigate the point spread function by reducing a size of the lobes.

6. The system according to claim 1, wherein the point-spread-function-mitigating components comprise a transmissive element having at least one edge portion configured to mitigate the point spread function.

7. The system according to any one of claims 1-6, wherein the point- spread-function- mitigating components are configured to mitigate the point spread function by modifying at least one edge portion of at least one of the optical elements.

8. The system according to claim 7, wherein the modification reduces an area of an aperture of the at least one of the optical elements by less than 25%.

9. The system according to claim 8, wherein the modification reduces the area by less than

10. The system according to claim 7, wherein the optical elements comprise a mirror, and wherein the point- spread-function-mitigating components modify at least one edge portion of the mirror.

11. The system according to claim 10, wherein the mirror is a scanning mirror configured to rotate while reflecting the light and the reflections.

12. The system according to claim 7, wherein the point-spread-function-mitigating components comprise a coating that coats the at least one edge portion and is configured to attenuate the reflections.

13. The system according to claim 12, wherein the coating is continuous.

14. The system according to claim 12, wherein the coating is non-continuous.

15. The system according to claim 7, wherein the point-spread-function-mitigating components comprise a cover that is coupled to the at least one edge portion and is configured to attenuate the reflections.

16. The system according to claim 7, wherein, by virtue of the modification, an attenuation coefficient of the edge portion increases toward an edge of the at least one of the optical elements.

17. The system according to claim 7, wherein, by virtue of the modification, a shape of an aperture of the at least one of the optical elements is modified.

18. The system according to claim 17, wherein, by virtue of the modification, an edge of the aperture is shaped to define one or more teeth.

19. The system according to claim 18, wherein a length of each of the teeth is 0.2 - 4 mm.

20. The system according to claim 18, wherein the edge of the aperture is shaped in a trianglewave pattern.

21. The system according to claim 18, wherein the edge of the aperture is shaped in a sawtooth pattern.

22. The system according to claim 18, wherein an angle between each of the teeth and an edge of the at least one of the optical elements is between 30 and 60 degrees.

23. The system according to claim 22, wherein the angle is between 40 and 50 degrees.

24. The system according to claim 17, wherein, by virtue of the modification, an edge of the aperture is curved.

25. The system according to claim 17, wherein, by virtue of the modification, an edge of the aperture is wavy.

26. The system according to claim 7, wherein the point-spread-function-mitigating components modify at least one edge portion of a first one of the optical elements, which has a first aperture, and at least one edge portion of a second one of the optical elements, which receives the reflections from the first one of the optical elements and has a second aperture that is smaller than the first aperture.

27. The system according to claim 26, wherein the light is polarized, wherein the first one of the optical elements is a mirror, and wherein the second one of the optical elements is a polarizing beamsplitter configured to: reflect the light toward to the mirror, and transmit the reflections from the mirror.

28. A system, comprising: an illumination unit, configured to emit light; a detector comprising an array of detection elements arranged along one or more axes; and one or more optical elements, configured to: direct the light toward a field of view, and direct respective reflections of portions of the light from one or more objects in the field of view toward different respective ones of the detection elements, the optical elements having respective apertures and being configured to mitigate a point spread function of the optical elements, which without the mitigation would cause at least one of the reflections to impinge on multiple ones of the detection elements, by virtue of no straight edge of an aperture that receives the reflections being perpendicular to at least one of the axes.

29. The system according to claim 28, wherein the light includes multiple light beams spatially offset from each other, and wherein the reflections are reflections of the light beams, respectively.

30. The system according to claim 29, wherein the illumination unit comprises a laser comprising multiple channels and configured to emit the light beams via the channels, respectively.

31. The system according to claim 28, wherein the detection elements comprise respective silicon photomultiplier detection elements.

32. The system according to any one of claims 28-31 , wherein the point spread function causes the reflections to have respective lobes that, without the mitigation, would be parallel to the at least one of the axes.

33. A system, comprising: an illumination unit, configured to emit light; a detector comprising an array of detection elements; and one or more optical elements, configured to: direct the light toward a field of view, and direct respective reflections of portions of the light from one or more objects in the field of view toward different respective ones of the detection elements, an aperture of at least one of the optical elements having an edge shaped to define one or more teeth.

34. The system according to claim 33, wherein the light includes multiple light beams spatially offset from each other, and wherein the reflections are reflections of the light beams, respectively.

35. The system according to claim 34, wherein the illumination unit comprises a laser comprising multiple channels and configured to emit the light beams via the channels, respectively.

36. The system according to claim 33, wherein the detection elements comprise respective silicon photomultiplier detection elements.

37. The system according to claim 33, wherein a length of each of the teeth is 0.2 - 4 mm.

38. The system according to claim 33, wherein the edge of the aperture is shaped in a trianglewave pattern.

39. The system according to claim 33, wherein the edge of the aperture is shaped in a sawtooth pattern.

40. The system according to any one of claims 33-39, wherein an angle between each of the teeth and an edge of the at least one of the optical elements is between 30 and 60 degrees.

41. The system according to claim 40, wherein the angle is between 40 and 50 degrees.