Patent Description:
LIDAR represents a sensing method that may be used to detect surface features of a target, such as various areas on the surface of the Earth. A typical LIDAR system includes a laser, a scanner, and a detector. The laser emits light pulses that are used to measure distances with respect to various areas of a particular target. The scanner moves the light pulses over the surface of the target. The light pulses reflect off the target and are received by the detector. The reflected light pulses received at the detector are used to generate three-dimensional information about the surface shape and area of the target.

A typical LIDAR system includes a single scanner that moves emitted light pulses over an area of interest that includes a target. A time of flight of each reflected light pulse is determined, as well as angles at which the light pulses were scanned. The combination of the time of flight and the scan angles are used to generate a three-dimensional image of the area of interest.

In general, the scanner includes a single beam steering element and optical elements. The LIDAR system receives reflected laser light pulses at the detector before emitting a subsequent laser light pulse. Further, the scanner typically includes a large mirror that is used to scan and reflect the light pulses. However, it is often difficult to achieve a fast scan rate with a scanner having a large mirror. Conversely, if a smaller mirror is used, while the scan rate increases, less return light is collected at a detector, as the smaller mirror may be too small to receive certain light pulses reflected from a target at particular angles. Related prior art can be found in <CIT> and <CIT>.

A need exists for a more efficient scanning system and method. A need exists for a faster scanning system and method that accurately generates images of an object within an area of interest.

With those needs in mind, the present disclosure provides a scanning system that configured to scan an area of interest according to claim <NUM>.

The present disclosure also provides a scanning method that is configured to scan an area of interest according to claim <NUM>, utilizing the aforementioned scanning system.

The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. Further, references to "one embodiment" are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments "comprising" or "having" an element or a plurality of elements having a particular condition may include additional elements not having that condition.

The present disclosure also provides LIDAR scanning systems and methods that may include two separate and distinct scanners which LIDAR scanning system is useful for understanding the claimed invention. One of the scanners may provide a relatively large scan angle at a first scan speed. The other scanner may provide a smaller scan angle at a second scan speed that is faster than the first scan speed. Light pulses from a light source (such as a laser light source) pass through both scanners and are diverted particular speeds and angles. As the light pulses are reflected off a target within an area of interest, the reflected light pulses may impinge upon the first scanner and reflect to a detector.

The present disclosure also provides a duel stage scanning system that combines two scanners to achieve an enhanced scan pattern, while maintaining large return signal collection efficiencies. A duel stage scanning system may include a laser source, a high speed scanner, a low speed scanner, a pick off mirror that includes an aperture to allow the passage of a light signal (for example, a laser beam or pulse) through the high speed scanner, a detector, and a focusing lens that may be used to direct a plurality of beams from a target into the detector.

<FIG> illustrates a schematic diagram of a scanning system <NUM>. The scanning system <NUM> may be used to generate a three-dimensional image of a target <NUM> within an area of interest <NUM>. The target <NUM> may be a natural or manmade structure. For example, the target <NUM> may be a feature of a landscape, such as a plain, a hill, a mountain, a body of water, a natural landmark or formation, or the like. As another example, the target <NUM> may be a manmade object, such as a building, vehicle, road, portion of a railway, monument, and/or the like.

The scanning system <NUM> may include a light source <NUM>, a first scanner <NUM>, a deflection mirror <NUM>, a second scanner <NUM>, a lens <NUM>, and a detector <NUM>. A control unit <NUM> may be operatively coupled to the light source <NUM>, the first scanner <NUM>, the second scanner <NUM>, and the detector <NUM>, such as through wired or wireless connections. The control unit <NUM> may be configured to control operation of the scanning system <NUM>. Optionally, the scanning system <NUM> may not include the separate and distinct control unit <NUM>.

The first scanner <NUM> may be configured to receive a light signal <NUM> emitted or otherwise output by the light source <NUM> and deflect the light signal <NUM> to form an initially-deflected light signal <NUM>. The second scanner <NUM> receives the initially-deflected light signal <NUM> and deflects (for example, steers) the initially-deflected light signal <NUM>, thereby outputting a subsequently-deflected light signal <NUM>, which may be scanned over an area of interest.

The light source <NUM> may be a laser source that is configured to emit or otherwise output the light signal <NUM>, such as one or more laser light pulses, beams, or the like. The first scanner <NUM> may be a high speed scanner that is configured to deflect the light signal <NUM> over a scan angle or angular range in one dimension or one degree of freedom. For example, the first scanner <NUM> may be configured to deflect the light signal <NUM> over a first scan angle or angular range α in one linear direction <NUM> at a first rate to form the initially-deflected light signal <NUM>. The first scanner <NUM> may scan at a high rate or frequency, such as <NUM>-<NUM>. Alternatively, the first scanner <NUM> may scan at a lower rate or frequency than <NUM>, or a higher rate or frequency than <NUM>.

For example, the first scanner <NUM> may be a high speed scanner, such as acousto-optic scanner, an electro-optic scanner, a piezo electric scanner, a high speed mechanical scanner, and/or the like. For example, an acousto-optic scanner may use Bragg scattering to deflect a beam at an angle that is proportional to an acoustic wave. The first scanner <NUM> may be configured to perform high speed, precise, low travel range scans. In general, as the scan rate increases, the scan angle may decrease, and vice versa.

As another example, the first scanner <NUM> may be a high speed scanner, such as an electro-optic scanner. Certain optical quality crystals have an index of refraction that changes depending on a magnitude of an electric field applied thereto. An optical element having a wedge formed of such a crystal may be used as a high speed deflector when a particular voltage is applied.

The deflection mirror <NUM> is disposed between the first scanner <NUM> and the second scanner <NUM>. The deflection mirror <NUM> includes a main reflecting body <NUM> having an aperture <NUM> formed therethrough. The aperture <NUM> is sized and shaped to allow the initially-deflected light signal <NUM> to pass therethrough and impinge upon the second scanner <NUM>. The aperture <NUM> is sized and shaped to accommodate the scan angle α.

The second scanner <NUM> may be a low speed scanner (in relation to the first scanner <NUM>) and include a mirror <NUM> (such as a <NUM>-axis mirror - that is, a mirror that may be actuated with respect to two different axes) operatively coupled to one or more actuators <NUM>. The second scanner <NUM> may scan at a lower rate than the first scanner. For example, the second scanner <NUM> may scan at a rate or frequency of <NUM> - <NUM>. Alternatively, the second scanner <NUM> may scan at a rate or frequency of less than <NUM>, or greater than <NUM>. The second scanner <NUM> scans at a rate that may be one or more orders of magnitude less than the first scanner <NUM>. For example, the first scanner <NUM> may scan at a rate than is <NUM> times the rate at which the second scanner <NUM> scans.

The second scanner <NUM> may provide a large field of view (in comparison to the first scanner <NUM>) that is configured to allow for full target scan areas. The actuator <NUM> is configured to steer the light signal deflected by the first scanner <NUM> (the initially-deflected light signal <NUM>) in two dimensions or two degrees of freedom. The first scanner <NUM> deflects the initially-deflected light signal <NUM> over a scan angle β, thereby outputting a subsequently-deflected light signal <NUM>.

For example, the actuator <NUM> moves the mirror <NUM> over a scan angle or angular range β through a distance <NUM>, as well as a scan angle or angular range γ through a distance <NUM>. The angular range γ may be greater than the angular range α. The angular range β may be large enough to cover a lateral distance <NUM> of the area of interest <NUM>. In at least one embodiment, the angular range γ may be at least twice the angular range α. Accordingly, as the second scanner <NUM> steers the subsequently-deflected light signal <NUM> in a first lateral sweep from left to right, the subsequently-deflected light signal <NUM> a half portion over a center <NUM>, and another half portion under center <NUM>, thereby providing a thicker or wider scan area as the second scanner <NUM> sweeps the subsequently-deflected light signal <NUM> from side-to-side. After the second scanner <NUM> reaches a right end of the distance <NUM> (corresponding to the right end of the lateral distance <NUM>), the second scanner <NUM> steers or otherwise deflects the subsequently-deflected light signal <NUM> downwardly a distance <NUM>. Then, the second scanner <NUM> steers or otherwise deflects the subsequently-deflected light signal <NUM> from right to left over the distance <NUM>. During such movement, a top portion of the subsequently-deflected light signal <NUM> reaches the lower level at which the subsequently-deflected light signal <NUM> was scanned in the previous left to right sweep. In this manner, the first scanner <NUM> may continually deflect the light signal <NUM> at a relatively fast rate over the distance <NUM>, while the second scanner <NUM> slowly steers or otherwise the deflected light signal <NUM> over the distance <NUM>, which may be orthogonal to the distance <NUM>. In at least one embodiment, the first scanner <NUM> may deflect the light signal <NUM> over the distance <NUM> at a rate that is <NUM>, <NUM>, or more times the rate at which the second scanner <NUM> steers or otherwise deflects the subsequently-deflected light signal <NUM> over the distance <NUM>. After the second scanner <NUM> reaches a terminal distance <NUM> or <NUM> (which correspond to terminal sides <NUM> and <NUM>, respectively, of the area of interest <NUM>), the second scanner <NUM> adjusts the subsequently-deflected light signal <NUM> in the orthogonal direction <NUM> to cover a different level or height of the area of interest <NUM>.

In operation, the light source <NUM> emits the light signal <NUM> towards the first scanner <NUM>. For example, the control unit <NUM> may operate the light source <NUM> to emit the light signal <NUM> towards the first scanner <NUM>.

The light signal <NUM> passes through the first scanner <NUM>, which deflects the light signal <NUM> the distance <NUM> over the angular range α to output the initially-deflected light signal <NUM>. As such, the first scanner <NUM> outputs the initially-deflected light signal <NUM> that is wider than the light signal <NUM>.

The initially-deflected light signal <NUM> passes through the aperture <NUM> of the deflection mirror <NUM> and impinges upon the mirror <NUM> of the second scanner <NUM>. Alternatively, the scanning system <NUM> may not include the deflection mirror <NUM>. Instead, the detector <NUM> may be aligned such light signals reflected from the object <NUM> impinge on the mirror <NUM> and are received by the detector <NUM> without the use of the deflection mirror <NUM>.

The second scanner <NUM> steers or otherwise deflects the deflected light signal <NUM> over the distance <NUM>, as noted above, to form the subsequently-deflected light signal <NUM>. The second scanner <NUM> steers the subsequently-deflected light signal <NUM> over a first scan path <NUM> that alternates from left to right, and up and down, as shown in <FIG>. As the subsequently-deflected light signal <NUM> is steered over the first scan path, the first scanner <NUM> continually deflects the light signal <NUM> (thereby forming the initially-deflected signal <NUM>), which forms a second scan path <NUM> superimposed over the first scan path <NUM>. The second scan path <NUM> is formed by the continuous deflection of the deflected light signal <NUM> in a direction that is orthogonal to a direction of the distance <NUM>. For example, as the second scanner <NUM> steers the subsequently-deflected light signal <NUM> in lateral directions (for example, from right to left, and vice versa), the first scanner <NUM> continually deflects the light signal <NUM> in vertical directions (for example, from bottom to top, and vice versa). As such, the first and second light paths <NUM> and <NUM> provide a combined light path that covers an increased area (as compared to using only a single scanner) within the area of interest <NUM> with each lateral sweep. In this manner, the first and second scanners <NUM> and <NUM> are able to efficiently cover the area of interest <NUM> much quicker than a single scanner. At the same time, the first and second mirrors <NUM> and <NUM> are not susceptible to missing reflected light signals (such as a high speed scanner having a small mirror), as the large mirror <NUM> of the second scanner <NUM> receives the reflected signals from the object <NUM>.

The first and second scanners <NUM> and <NUM> cooperate to scan the deflected light signal <NUM> over the area of interest <NUM>. The object <NUM> reflects reflected light signals <NUM> that are reflected back to the mirror <NUM>. The reflected light signals <NUM> reflect off the mirror <NUM> and impinge upon the deflection mirror <NUM>, which then deflects the reflected light signals <NUM> into the detector <NUM>. The lens <NUM> may focus the reflected light signals <NUM> into focused light signals <NUM> that are received by the detector <NUM>. Alternatively, the scanning system <NUM> may not include the lens <NUM>. Instead, the reflected light signals <NUM> may directly impinge upon the detector <NUM> without being focused by a lens.

The control unit <NUM> may determine features of the object <NUM> based on the light signals received at the detector <NUM>, as well as the time of flight and scan angles of the light signals emitted from the light source <NUM>. Further, the control unit <NUM> may control operation of the first and second scanners <NUM> and <NUM>. For example, the control unit <NUM> may control the rate and distance at which the first and second scanners <NUM> and <NUM> deflect and/or steer the light signal. In at least one embodiment, the control unit <NUM> may not control operation of the first and second scanners <NUM> and <NUM>. In such an embodiment, the first and scanners <NUM> and <NUM> may automatically operate to deflect and/or steer the light signal based on settings that are pre-set in internal control units.

As described above, the control unit <NUM> may be used to control operation of the scanning system <NUM>. As used herein, the term "control unit," "unit," "central processing unit," "CPU," "computer," or the like may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor including hardware, software, or a combination thereof capable of executing the functions described herein. Such are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of such terms. For example, the control unit <NUM> may be or include one or more processors that are configured to control operation of the scanning system <NUM>.

The control unit <NUM> is configured to execute a set of instructions that are stored in one or more storage elements (such as one or more memories), in order to process data. For example, the control unit <NUM> may include or be coupled to one or more memories. The storage elements may also store data or other information as desired or needed. The storage elements may be in the form of an information source or a physical memory element within a processing machine.

The set of instructions may include various commands that instruct the control unit <NUM> as a processing machine to perform specific operations such as the methods and processes of the various embodiments of the subject matter described herein. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs, a program subset within a larger program or a portion of a program. The software may also include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine.

The diagrams of embodiments herein may illustrate one or more control or processing units, such as the control unit <NUM>. It is to be understood that the processing or control units may represent circuits, circuitry, or portions thereof that may be implemented as hardware with associated instructions (e.g., software stored on a tangible and non-transitory computer readable storage medium, such as a computer hard drive, ROM, RAM, or the like) that perform the operations described herein. The hardware may include state machine circuitry hardwired to perform the functions described herein. Optionally, the hardware may include electronic circuits that include and/or are connected to one or more logic-based devices, such as microprocessors, processors, controllers, or the like. Optionally, the control unit <NUM> may represent processing circuitry such as one or more of a field programmable gate array (FPGA), application specific integrated circuit (ASIC), microprocessor(s), and/or the like. The circuits in various embodiments may be configured to execute one or more algorithms to perform functions described herein. The one or more algorithms may include aspects of embodiments disclosed herein, whether or not expressly identified in a flowchart or a method.

As used herein, the terms "software" and "firmware" are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.

<FIG> illustrates a perspective view of the first and second scan paths <NUM> and <NUM> within the area of interest <NUM>, according to the present disclosure. The first and second scan paths <NUM> and <NUM> combine to form a combined scan path <NUM> that quickly and efficiently covers the area of interest <NUM>. Referring to <FIG>, the second scanner <NUM> steers the subsequently-deflected light signal <NUM> over the first scan path <NUM> that alternates from left to right, and up and down, as shown in <FIG>. For example, the first scan path <NUM> may start at an origin <NUM> at a left terminal side <NUM> and move from left to right to the right terminal side <NUM>. The first scan path <NUM> then moves downwardly the distance <NUM>, and then moves from right to left to the left terminal side <NUM>. The first scan path <NUM> continues such movement, alternating between rightward and leftward movement, until an end <NUM> is reached. The end <NUM> may be determined on a desired size and shape of the area of interest <NUM>. The area of interest <NUM> may be larger or smaller than shown. The first scan path <NUM> may be larger or smaller than shown. For example, the first scan path <NUM> may include more or less than six lateral sweeps.

As the second scanner <NUM> steers the subsequently-deflected light signal <NUM> over the first scan path <NUM>, the first scanner <NUM> continually and alternately deflects the light signal <NUM> over the distance <NUM> to impart a vertical modulation to the subsequently-deflected light signal. The first scanner <NUM> may deflect the light signal <NUM> in a direction that is orthogonal to the lateral direction of the sweep imparted by the second scanner <NUM>. That is, the first scanner <NUM> may deflect the light signal <NUM> in a direction that is orthogonal to the direction of lateral steering of the second scanner <NUM>. Accordingly, as the second scanner <NUM> steers the subsequently-deflected light signal <NUM> over the first scan path <NUM>, the first scanner <NUM> wiggles, pivots, or otherwise modulates the light signal <NUM> to form the deflected light signal <NUM>, which exhibits the second scan path <NUM> as the second scanner <NUM> moves the subsequently-deflected light signal <NUM> over the first scan path <NUM>. In this manner, the second scanner <NUM>, which may be a low speed scanner, sweeps the subsequently-deflected light signal <NUM> over the first scan path <NUM>, and the second scan path <NUM> provides wide coverage for each lateral sweep (substantially wider than if only the second scanner <NUM> were used).

It is to be understood that the first and second scan paths <NUM> and <NUM> are not separate and distinct light paths. Instead, the first and second scan paths <NUM> and <NUM> represent the movement imparted into the light signal <NUM> by both the first and second scanners <NUM> and <NUM>. That is, the first and second scanners <NUM> and <NUM> cooperate to deflect the light signal <NUM> at different rates and directions to cover the area of interest <NUM> in an efficient manner.

The second scan path <NUM> is formed by the continuous deflection of the initially-deflected light signal <NUM> in a direction that is orthogonal to a direction of the distance <NUM>. For example, as the second scanner <NUM> steers the deflected light signal <NUM> in lateral directions (for example, from right to left, and vice versa), the first scanner <NUM> continually deflects the light signal <NUM> in vertical directions (for example, from bottom to top, and vice versa). In this manner, the first and second scanners <NUM> and <NUM> are able to efficiently cover the area of interest <NUM> much quicker than a single scanner having a large mirror. At the same time, the first and second scanners <NUM> and <NUM> are not susceptible to missing reflected light signals (such as a high speed scanner having a small mirror), as the large mirror <NUM> of the second scanner <NUM> receives the reflected signals from the object <NUM>.

The initially-deflected light signal <NUM>, as output by the first scanner <NUM>, deflects off the mirror <NUM> of the second scanner <NUM>, thereby outputting the subsequently-deflected light signal <NUM>, which provides a much larger outgoing scan range than if just the second scanner <NUM> were used. The deflection range and rate of the first scanner <NUM> may correct for scanning inaccuracies that may otherwise by generated by the second scanner <NUM> (which may be a low speed scanner) due to the relatively large size and inertia of the mirror <NUM>.

<FIG> illustrates a schematic view of the first scanner <NUM>, according to an embodiment of the present disclosure. As noted, the first scanner <NUM> may be a high speed scanner, such as an acousto-optic scanner. The first scanner <NUM> may include a housing <NUM> containing a piezo electric crystal <NUM>. The piezo electric crystal generates acoustic waves <NUM>. As the light signal <NUM> passes through the piezo electric crystal <NUM>, the light signal <NUM> is scattered in relation to the acoustic waves <NUM>. The scatted light signal <NUM> forms the deflected signal <NUM>, which includes a portion <NUM> that scatters in relation to a lower acoustic frequency, and a portion <NUM> scattered in relation to a higher acoustic frequency. The deflected light signal <NUM> scatters off the acoustic waves <NUM> at an angle proportional to the frequencies of the acoustic waves <NUM>.

<FIG> illustrates a schematic view of the first scanner <NUM>, according to the present disclosure. The first scanner <NUM> may be an electro-optic scanner including an electro-optic crystal <NUM> shaped as a wedge. Voltage pads <NUM> may be applied to a top and bottom of the crystal <NUM>. When a voltage is applied to the voltage pads, the refractive index of the crystal <NUM> changes, which thereby refracts the light in a different direction. The deflected light signal <NUM> may include a portion <NUM> that refracts due to a lower applied voltage, and a portion <NUM> that refracts due to a higher applied voltage. The deflected light signal <NUM> refracts at an angle proportional to the applied voltage and the shape of the crystal <NUM>.

<FIG> illustrate examples of high speed scanners. Various other types of high speed scanners may be used. For example, the first scanner <NUM> may be or include a piezo electric scanner, a high speed mechanical scanner, or the like.

<FIG> illustrates a flow chart of a method of scanning an area of interest, according to the present disclosure. The control unit <NUM> may operate the scanning system <NUM> according to the method described and shown with respect to <FIG>.

The method begins at <NUM>, in which light signals are emitted towards a first scanner. For example, a laser source may emit pulsed lasers into and through the first scanner, which may be a high speed scanner.

At <NUM>, the first scanner is used to deflect the light signal at a first rate, thereby outputting an initially-deflected light signal. The first scanner may deflect the light signal in relation to a first linear dimension (for example, parallel to an X or Y axis).

At <NUM>, a second scanner, such as a low speed scanner, is used to deflect the initially-deflected light signal (as first deflected by the first scanner) at a second rate, which differs from the first rate. The second scanner may deflect the initially-deflected light signal in relation to two dimensions (for example, in a first direction that is parallel to a Y or Z axis, and also in a second direction that is parallel to an X axis). A subsequently-deflected light signal is output by the second scanner.

At <NUM>, an area of interest is scanned with the subsequently-deflected light signal that has been deflected by both the first and second scanners. The first and second scanners cooperate to move the subsequently-deflected light signal over the area of interest through a path that is a combination of a first scan path (defined by the motion of the light signal as imparted by the first scanner) and a second path (defined by the motion of the light signal as imparted by the second scanner). It is to be understood that the terms "first" and "second," are merely used to designate distinct paths. A first path is not necessarily correlated with a first scanner, nor is a second path necessarily correlated with a second scanner. Instead, the first scanner may move the light signal in relation to a second scan path, while the second scanner may move the light signal in relation to a first scan path, or vice versa.

At <NUM>, light signals reflected from an object within an area of interest are received by a detector. The light signals may be focused into the detector through one or more lenses. At <NUM>, an image is formed based on the received light signal.

As described above, the present disclosure provides efficient scanning systems and methods, such as may be used with LIDAR. The present disclosure provides faster scanning systems and methods that accurately generate images of an object within an area of interest.

While various spatial and directional terms, such as top, bottom, lower, mid, lateral, horizontal, vertical, front and the like may be used to describe embodiments of the present disclosure, it is understood that such terms are merely used with respect to the orientations shown in the drawings. The orientations may be inverted, rotated, or otherwise changed, such that an upper portion is a lower portion, and vice versa, horizontal becomes vertical, and the like.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the disclosure without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the disclosure, the embodiments are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein. " Moreover, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

Claim 1:
A scanning system (<NUM>) configured to scan an area of interest (<NUM>), wherein the scanning system (<NUM>) comprises:
- a first scanner (<NUM>) configured to deflect a light signal (<NUM>), wherein the light signal (<NUM>) that is deflected by the first scanner (<NUM>) is output as an initially-deflected light signal (<NUM>); and
- a second scanner (<NUM>) configured to receive the initially-deflected light signal (<NUM>) and deflect the initially-deflected light signal (<NUM>), wherein the initially-deflected signal (<NUM>) that is deflected by the second scanner (<NUM>) is output as a subsequently-deflected light signal (<NUM>);
- a deflection mirror (<NUM>) disposed between the first and second scanners (<NUM>, <NUM>), wherein the deflection mirror (<NUM>) comprises an aperture (<NUM>) through which the initially-deflected light signal passes (<NUM>);
wherein the second scanner (<NUM>) comprises a mirror (<NUM>) configured to be actuated with respect to two different axes, wherein the first scanner (<NUM>) is configured to deflect the light signal (<NUM>) at a first scan angle (α), and
wherein the second scanner (<NUM>) is configured to deflect the initially-deflected light signal (<NUM>) at a second scan angle (γ) that differs from the first scan angle (α), and
wherein the aperture is sized and shaped to accommodate the scan angle (α).