Abstract:
Embodiments relate to scanning a plurality of light beams across a corresponding plurality of zones in a field of view and collecting scattered light to enable an image of the field of view to be formed that spans the plurality of zones. According to an embodiment, a scanning endoscope tip may include structures configured to launch the plurality of scanned beams toward respective zones and receive separate light scattered from the respective beams impinging upon the respective zones. According to an embodiment, an image processor is operable to receive detection signals from corresponding light detectors and reconstruct an image of the field of view spanning the plurality of zones.

Description:
BACKGROUND 
       [0001]    In a scanned-beam imaging system such as a scanned beam endoscope, image resolution, and hence image quality, may depend on the number of pixels captured in the time allotted to acquire an image or frame. A scanned-beam system may operate, for example, by directing a narrow beam of light across a field of view in a scan pattern calculated to cover substantially the entire field of view in a frame period. The pattern may comprise a raster pattern (e.g., similar to how a television displays images), a bi-sinusoidal pattern, or some other pattern. 
         [0002]    To increase the resolution, the frame rate may be reduced (or equivalently, the frame period may be increased) or the beam scan speed may be increased while the scan pattern (and optionally, the beam diameter) is adjusted to capture more pixels within the field of view. However, reducing the frame rate may result in decreased temporal resolution and can increase the incidence of image “smearing” artifacts related to the movement during the lengthened frame period. Conversely, increasing the beam scan speed may reduce the amount of time available to receive photons associated with each pixel, and thus may increase pixel noise or brightness uncertainty, may increase electronic noise, may place constraints on light collection area and/or detector size, may require higher power light sources, and/or may otherwise hinder other aspects of scanned beam imager cost, size, or performance, for example. Additionally, increasing the beam scan speed may place additional constraints on the beam scanning mechanism that may be difficult or impossible to meet. 
       OVERVIEW 
       [0003]    According to an embodiment, a scanned-beam endoscope may scan a plurality of beams across two or more regions or zones comprising a field of view. The two or more zones may be substantially non-overlapping, or alternatively may overlap at least somewhat. 
         [0004]    According to an embodiment, the scanned-beam system may include two or more light sources and/or optical fibers configured to launch two or more corresponding beams of light onto a beam scanner from differing angles. The separately launched beams may then be scanned across respective zones of the field of view by the beam scanner. 
         [0005]    According to an embodiment, light from the respective scanned beams scattered from objects in the field of view may be de-scanned by the beam scanner and collected retro-reflectively along the respective beam launch axes. According to another embodiment, light scattered from within the respective zones of the field of view may be collected by vignetted or directional staring collection optics. 
         [0006]    According to another embodiment, a scanned beam system may comprise a light source operable to launch a beam of light, an optical element aligned to receive the beam and configured to divide the beam into a plurality of beams or beamlets, and a scanner configured to scan the beam, the plurality of beams, or the beamlets, whereby a plurality of beams are scanned across respective zones of a field of view. 
         [0007]    By increasing the number of light beams scanned across zones of a field of view and providing light collectors and/or detectors configured to receive scattered light from the respective zones, the rate of pixel collection may be increased without necessarily increasing the scanning rate of the beam scanner or decreasing the frame rate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a block diagram that represents a scanned-beam system according to an embodiment. 
           [0009]      FIG. 2  is a diagram that generally represents a portion of a scanned-beam system according to an embodiment. 
           [0010]      FIG. 3A  is a diagram illustrating a structure for generating a plurality of scanning beams, according to an embodiment. 
           [0011]      FIG. 3B  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0012]      FIG. 3C  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0013]      FIG. 3D  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0014]      FIG. 3E  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0015]      FIG. 3F  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0016]      FIG. 3G  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. 
           [0017]      FIG. 4A  is a diagram illustrating a relationship between scanning zones and detection zones at a first instant in time, according to an embodiment. 
           [0018]      FIG. 4B  is a diagram of the scanning zones and detection zones of  FIG. 4A  at a second instant in time, according to an embodiment. 
           [0019]      FIG. 4C  is a diagram of the scanning zones and detection zones of  FIG. 4A  at a third instant in time, according to an embodiment. 
           [0020]      FIG. 5  is a side view of an illustrative detector that detects light from a specific field of view according to an embodiment. 
           [0021]      FIG. 6  is a diagram that generally represents another illustrative mechanism for detecting light from various fields of view according to an embodiment. 
           [0022]      FIG. 7  is a side view of an illustrative optical element for splitting light into beamlets according to an embodiment. 
           [0023]      FIG. 8  is a side view of another illustrative optical element for splitting light into beamlets according to an embodiment. 
           [0024]      FIG. 9  is a side view of another illustrative optical element for splitting light into beamlets according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  is a block diagram that represents a scanned-beam system according to an embodiment. The system includes a controller  105  operatively coupled to light sources  110 A and  110 B, detectors  115 A and  115 B, and scanners (also referred to as light directing elements)  120 A and  120 B. Among other things, the controller  105  may provide light source drive signals operative to vary the intensity of the light sources  110 A and  110 B as well as signals operative to vary the sensitivity of the detectors  115 A and  115 B. In addition, the controller  105  may provide scanner drive signals operative to control the scanners  120 A and  120 B, and hence cause the light transmitted from the light sources  110 A and  110 B to be scanned across a field of view  125 . In some embodiments, the scanners  120 A and  120 B may oscillate at a known or selectable frequency (which may be the same or different from each other). In an embodiment, the frequency is near or substantially at a resonant frequency of the scanner. 
         [0026]    According to another embodiment, one scanner  120 A may be aligned to receive a plurality of beams of light and the second scanner  120 B may be omitted. 
         [0027]    Scanned light that scatters from the field of view  125  may be detected by the detectors  115 A and  115 B. The detectors  115 A and  115 B may generate signals corresponding to the light scattered from the field of view  125 . The signals may then be sent to the controller  105  and used to generate an image frame that corresponds to substantially all or a portion of the field of view  125 . 
         [0028]    Images may be detected at a specified or selected frame rate. For example, in an embodiment, images are detected and converted into frames at a rate of 30 frames per second. 
         [0029]    The controller  105  may optionally modulate light source drive signals to drive the light sources  110 A and  110 B at a relatively low rate (i.e., relative to a scanning frequency) to emit beams of light corresponding to one or more selected zones of a periodic scan pattern. Accordingly, a sequence of field of view zones may be scanned with the periodic scan pattern. Alternatively, the controller  105  may modulate the light source drive signals at a rate substantially higher than a fast scan frequency of the one or more scanners  120 A,  120 B to selectively illuminate pixels in various zones of the field of view corresponding to the plurality of scanned beams. Thus, embodiments may alternatively provide time-sequenced frame detection of the scanned zones of the field of view, time-sequenced line detection across plural zones, or time-sequenced pixel detection across the plural zones. According to embodiments, time-sequencing of light received from a plurality of zones may allow the use of a one detector  115 A configured to view substantially the entire field of view to receive the time-sequenced image information carried by light scattered from the zones. 
         [0030]    In accordance with aspects of the subject matter described herein, in some embodiments, light (sometimes referred to as a “light beam”) comprises visible light. In other embodiments, light comprises radiation detectable by the detectors  115 A and  115 B and may include one or more of infrared, ultraviolet, and visible. 
         [0031]    Light from the light sources  110 A and  110 B may be transmitted toward the scanners  120 A and  120 B via an optical element such as one or more optical fibers. In an embodiment, a light source (e.g., light source  120 A or  120 B) may generate a plurality of wavelengths (e.g., red, blue, and green) that are combined to form a composite beam that is scanned across a zone  130 A,  130 B of the field of view  125 . In some embodiments, a light source may generate other combinations of wavelengths, for example including red, blue, green, and cyan. This may be used to create a 4-channel system with improved color gamut. In yet other aspects, a light source may generate light in the infrared, ultraviolet, or other electromagnetic frequency which may be combined to form an extended spectrum system. 
         [0032]    In an embodiment, a light source may generate light having various other properties. For example, a light source may generate a light beam composed of two red wavelengths differing from each other by several nanometers. This embodiment may be used to improve discrimination between red objects such as blood cells, for example. 
         [0033]    In other embodiments, light wavelengths having therapeutic properties may be selectively launched, such as to be used for treatment. For example, infrared light may be used to cauterize or oblate, ultraviolet light may be used to enable phototropic drugs, modify skin texture, etc. A combination of narrow wavelength light sources may be used to avoid exposure to unwanted wavelengths, for instance when a phototropic drug is present, but it is desired to activate it only in certain cases. Therapeutic beams may be selectively enabled by a physician or remote export, or alternatively may be automatically enabled based on image properties. Therapeutic beams may be enabled for an entire field of view, for a portion of the field of view including specific, small spots within the field of view. 
         [0034]    In an embodiment, a light beam created from a light source may be passed through an aperture in the center of a scanning mirror, bounced off a reflector, returned to the scanning mirror, and then scanned across a scanning zone. This concentric beam path may be used to reduce the size of an imaging tip for use in inserting into a body cavity or other constricted area. In addition, polarization properties of the beam and relevant hardware may be manipulated to maximize signal strength and minimize stray light that reaches the field of view. 
         [0035]    Although two light sources are shown in  FIG. 1 , the light sources  110 A and  110 B may be combined into one light source. The light from the combined light source may be split into multiple beams and scanned across multiple areas (e.g., areas  130 A and  130 B) as described below. According to some embodiments, the areas  130 A and  130 B may overlap. 
         [0036]    In an embodiment, detectors may comprise non-imaging detectors. That is, the detectors may operate without the use of an aperture or other optical device that forms an image from the received light on a focal plane such as a conjugate image plane. According to an embodiment, a light sensor array such as a CCD array, a CMOS array, or the like, may be coupled such that any one sensor receives light from several spots within a detection zone. Thus, embodiments taught herein may be used to multiply the resolution of a sensor array. 
         [0037]    The detectors  115 A and  115 B may receive light scattered from corresponding detection zones  130 A and  130 B. That is, each detector may be arranged such that it receives and detects light that is scattered from a corresponding detection zone. To limit scattered light reaching a given detector to light from substantially a single detection zone, each light receiver may be configured with a numerical aperture sufficiently large to receive light from the entirety of an assigned zone, but sufficiently small to substantially exclude light from other zones. For embodiments such as a scanning endoscope, the light collectors (not shown) may comprise optical fibers that relay light received at a scanning tip to a remote detector. In other embodiments, the detectors may be placed sufficiently near the field of view to receive light from the field of view substantially directly. To exclude light from unwanted zones, the numerical aperture of the detector fibers may be selected to have relatively narrow collection cones. Additionally or alternatively, other structures such as microlens arrays, light baffles, etc. may be used to create a blind between neighboring zones. 
         [0038]    Based on the location to which a scanner was directing light at or near the time the light reaches its corresponding detector, light detected by a detector may be attributed to a spot in the field of view  125  and assigned to a pixel (e.g., via the controller  105 , a portion thereof, or other circuitry) and may be used together with light detected from other spots to form an image. In an embodiment, the detectors  115 A and  115 B may comprise photodiodes or other light-sensitive elements that are aligned to receive light substantially directly from the FOV. In other embodiments, the detectors  115 A and  115 B may receive light from optical fibers that collect light and transmit it to the detectors  115 A and  115 B, where it is converted into electrical signals for further processing. Such gathering fibers may be arranged circumferentially around the scanners  120 A and  120 B, for example. 
         [0039]    In an embodiment, light may be collected retrocollectively, with scanners being used to gather and de-scan light that received from the field of view. For example, light that scatters from the surface  125  or travels other paths may travel back to the scanners  120 A and  120 B. This light may then be directed to the detectors and used to construct an image. In one embodiment, collection fibers may be arranged across the tip of a device transmitting light from the light sources  110 A and  110 B. The collection fibers may be arranged in interstitial spaces between irrigation channels, working channels, and the like, for example. The tip of the device may be made partially translucent or transparent to increase the area over which light may be gathered. 
         [0040]    The controller  105  may comprise one or more application-specific integrated circuits (ASICs), discrete components, embedded controllers, general or special purpose processors, combinations of the above, and the like. In some embodiments, the functions of the controller  105  may be performed by various components. For example, the controller may include hardware components that interface with the light sources  110 A and  110 B and the detectors  115 A and  115 B, hardware components (e.g., such as a processor or ASIC) that performs calculations based on received signal, and software components (e.g., software, firmware, circuit structures, and the like) encoding instructions that a processor or the like executes to perform calculations. These components may be included on a single device or distributed across more than one device without departing from the spirit or scope of the subject matter described herein. 
         [0041]    In an embodiment, at least part of the scanned-beam system is part of a camera, video recorder, document scanner, endoscope, laparoscope, boroscope, machine vision camera, other image capturing device, or the like. In an embodiment, the scanned-beam system may comprise a microelectromechanical (MEMS) scanner that operates in a progressive or bi-sinusoidal scan pattern. In other embodiments, the scanned-beam system may comprise a scanner having electrical, mechanical, optical, fluid, other components, a combination thereof, or the like that is capable of directing light in a pattern. According to an embodiment, the scanner may be operable to move an optical fiber in a pattern with a beam of light being directed toward a spot or spots according to the angle or position made by the fiber tip as it is vibrated. 
         [0042]      FIG. 2  is a diagram that generally represents a portion of a scanned-beam system according to an embodiment. The system includes a single scanner  220  that scans a plurality of light beams  240 A-C across areas  230 A-C, respectively. According to embodiments, the light beams  240 A-C may comprise beamlets. The detectors  215 A- 215 C are aligned and structured to detect light scattered from areas  230 A-C, respectively. The detectors  215 A- 215 C may be placed in other orientations than that shown as long as they are aligned to detect light substantially from their corresponding detection zones. For example, the detectors  215 A- 215 C may be placed around the scanner  220 . 
         [0043]    The scanner  220  scans the light beams  240 A-C in unison such that the light beams  240 A-C scan over their respective areas  230 A- 230 C. The scan amplitudes  245 A-C may be selected such that the areas overlap to provide sufficient coverage of the field of view  225 . 
         [0044]    As indicated above, a plurality of scanned beams may alternatively be produced using one scanner.  FIG. 3A  is a diagram illustrating a structure  301  for generating a plurality of scanning beams from one scanner, according to an embodiment. Two light sources  110   a  and  110   b  are operable to produce respective beams of light  302   a ,  302   b . A scanner  120  is aligned to receive the beams  302   a ,  302   b  and scan the beams as corresponding scanned beams  304   a ,  304   b  across respective scanning zones  130   a ,  130   b.    
         [0045]    For a scanner  120  having 1:1 angular reproduction, the converging angle made between emitted beams  302   a  and  302   b  is preserved as a diverging angle between scanning beams  304   a ,  304   b . The light sources and the scanner may be constructed according to a range of embodiments such as lasers with a reflective, refractive, or diffractive scanner, scanned fibers moved by a common actuator mechanism, etc. In some embodiments, the light sources are multi-wavelength laser, collimator, and beam-combiner assemblies, beams  302   a ,  302   b  are composite beams including red, green, and blue wavelength components, and the scanner is a biaxial MEMS scanner. 
         [0046]      FIG. 3B  is a diagram illustrating a structure  305  for generating a plurality of scanning beams, according to another embodiment. A light source  110  produces a beam of light  302  and projects it to be incident upon a scanner  120 . The scanner  120  is aligned to receive the beam of light and configured to scan the beam of light as a scanned beam  306  across an optical element  308 . The optical element  308  is configured to split the incident scanned beam into a plurality of scanned output beams  304   a ,  304   b , and direct the scanned output beams toward respective scanning zones  130   a ,  130   b  in a field of view. 
         [0047]    As is described elsewhere herein, the optical element  308 , which may alternatively be referred to as a beam multiplier or a beam multiplying optical element, may be constructed according to various embodiments. For example the optical element  308  may include one or more diffraction gratings, one or more microlens arrays, lenses, mirrors, diffusers, etc. according to the preferences of the system designer. The operation of microlens arrays in particular is described more fully below. 
         [0048]      FIG. 3C  is a diagram illustrating a structure  309  for generating a plurality of scanning beams, according to another embodiment. A light source  110  produces a beam of light  302  that impinges onto a scanner  120 . The scanner is configured with a beam multiplier such that the incident beam of light is split into plural output beams of light  304   a ,  304   b . The beam multiplier or other portions of the scanner  120  are operated to scan output beams  304   a ,  304   b  across respective scanning zones  130   a ,  130   b  of a field of view. For example, the scanner may include a diffraction grating or a microlens array over a mirror or integral with a mirror. 
         [0049]      FIG. 3D  is a diagram illustrating a structure  311  for generating a plurality of scanning beams, according to another embodiment. A light source  110  is configured to produce a beam of light  312  that is made incident upon an optical element  314 . The optical element  314  splits the input beam  312  into plural beams  302   a ,  302   b . Beams  302   a ,  302   b  are projected at a converging propagation angle toward the scanner  120 , which scans the beams as corresponding output scanned beams  304   a ,  304   b  toward respective scanning zones  130   a ,  130   b  of a field of view. 
         [0050]    A diverging angle may be maintained between output scanned beams  304   a ,  304   b  corresponding to the converging angle between the input beams  302   a ,  302   b . Alternatively (and also for at least many other embodiments described herein), the output scanned beams  304   a ,  304   b  may be parallel or converging, or be produced at a diverging angle differing from the angle of convergence of the input beams  302   a ,  302   b . Thus, the structure  120  indicated “scanner” may include an optical assembly (not shown) to condition, reflect, refract, collimate, or otherwise affect the input beams (here  302   a ,  302   b ) or output beams  304   a ,  304   b  prior to propagation toward the scanning zones. 
         [0051]      FIG. 3E  is a diagram illustrating a structure  315  for generating a plurality of scanning beams, according to another embodiment. A light source  110  projects a beam of light  302  toward a scanner  120 . The scanner  120  may include an optical element configured to cooperate with another optical element  318  to produce a plurality of scanning beams  304   a ,  304   b  that are propagated toward respective zones  130   a ,  130   b  of a field of view. The optical element of the scanner  120  is configured to provide scanned intermediate beamlets  316  to the optical element  318 , which in turn converts the intermediate beamlets  316  into scanned output beams  304   a ,  304   b.    
         [0052]    For example, the scanner optical element and the optical element  318  may operate cooperatively in a manner akin to that described in conjunction with  FIG. 7 ,  8 , or  9 . That is, a microlens array  705  may be incorporated with the scanner  120  to produce beamlets  316  focused at a distance substantially corresponding to the distance to the optical element  318 . The optical element  318  may include a second microlens array  710  configured to receive the beamlets and output corresponding scanned output beams  304   a ,  304   b.    
         [0053]      FIG. 3F  is a diagram illustrating a structure  319  for generating a plurality of scanning beams, according to another embodiment. A light source  110  is configured to illuminate an optical element  320  with a beam of light  312 . The optical element  320  is configured to convert the input beam into intermediate beamlets  316 . The input beamlets are received by the scanner  120 , which includes another optical element configured to convert the intermediate beamlets  316  into output beams  314   a ,  314   b . As with other embodiments described herein, output beams  314   a ,  314   b  are scanned across respective zones  130   a ,  130   b  of a field of view. 
         [0054]      FIG. 3G  is a diagram illustrating a structure for generating a plurality of scanning beams, according to another embodiment. A light source  110  outputs a beam of light  312  that impinges upon a first optical element  320 . The first optical element  320  is configured to split incident light into a plurality of intermediate beamlets  316   a  and direct the intermediate beamlets toward a scanner  120 . The scanner  120  may have a mirror surface and be operable to scan the intermediate beamlets  316   b  across a second optical element  318  configured to convert the scanned intermediate beamlets  316   b  into a plurality of scanned beams  304   a ,  304   b  and direct the scanned beams toward corresponding scanning zones  130   a ,  130   b  of a field of view. The first and second optical elements may include microlens arrays with lenslets having a focal length, and the first and second optical elements may, for example, be separated from one another by an optical propagation distance substantially equal to the focal length. Other optical elements such as fixed mirrors, prisms, telecentric lenses, etc. may cooperate to converge the first intermediate beamlets  316   a  onto the scanner surface and subsequently collimate the scanned intermediate beamlets  316   b  for receipt by the second optical element  318 . 
         [0055]    According to an embodiment, the relationship between scanned zones and detection zones may be other than 1:1. For example, a beam may be scanned across a scanning zone that traverses detection zones corresponding to a plurality of detectors.  FIGS. 4A-4C  are simplified depictions of such an illustrative arrangement. 
         [0056]    In  FIG. 4A , a one-dimensional field of view  401  is comprised of four detection zones  402 ,  404 ,  406 , and  408 . Two instantaneous beam locations  410  and  412  are shown on the field of view, with beam location  410  lying within detection zone  402  and beam location  412  lying within detection zone  406  and at the very edge of detection zone  404 . With the scanning beams in the positions shown, a detector corresponding to detection zone  402  may be selected to detect light scattered from the beam spot  410 , and a detector corresponding to detection zone  406  may be selected to detect light scattered from the beam spot  412 . 
         [0057]      FIG. 4B  corresponds to a later instant in time when the scanned beams have partially traversed their respective scanning zones of the field of view  401 , with beam spot  410  now lying within an overlap between detection zones where scattered light is detected by detectors corresponding to detection zones  402  and  404 . Similarly, beam spot  412  has traversed the field of view  401  to a position within both detection zones  406  and  408 . In the positions illustrated by  FIG. 4B , light scattered from spot  410  may be received and detected by either a detector corresponding to detection zone  402  or by a detector corresponding to detection zone  404 . The controller may select a detector channel based, for example, on measured signal strength or other criteria. According to an embodiment, detector values for spots corresponding to such overlaps between detection zones may be averaged or otherwise combined, for example to improve signal-to-noise. 
         [0058]    In some embodiments, detector sensitivity may not be equal across the entirety of a detection zone, but may rather decrease somewhat at the edges of the detection zone. In such a case, the controller may apply an equalization algorithm to adjust pixel values to compensate for such systematic variations in detector gain. 
         [0059]    Proceeding to  FIG. 4C , corresponding to a still later instant in time, spot  410  lies within detection zone  404  and spot  412  lies within detection zone  408 . At such an instant light from spots  410  and  412  are respectively detected by detectors corresponding to detection zones  404  and  408 . 
         [0060]      FIG. 5  is a side view of an illustrative detector that detects light from a zone in a field of view, according to an embodiment. The detector  505  may be oriented toward the area of interest and may receive light within the light cone defined by lines  510  and  511 . Note that the detector  505  may detect light scattered toward the detector within the area defined by lines  510  and  511  (which may extend to a field of view). The lines  510  and  511  are illustrated to show the detectable zone of the detector  505  and are not actually part of the detector  505 . 
         [0061]    Baffles  515  may also be provided to limit the numerical aperture of the detector  505  to the area of interest. The arrangement of baffles  515  is illustrative, and it will be recognized that more, fewer, or different shaped baffles may be used depending on the geometry of the detector  505  and the intended field of view. The detector  505  may be coupled to a light conducting element (not shown) such as an optical fiber at an end  520  so as to transmit detected light to a remote detection unit capable of creating electrical signals corresponding to the detected light. 
         [0062]    It will be recognized that the field of view of a detector may be constructed via a plurality of other mechanisms without departing from the spirit or scope of the subject matter described herein. 
         [0063]      FIG. 6  is a diagram that generally represents another illustrative mechanism for detecting light from various zones according to an embodiment. A light collection assembly  605  includes a lens  620  arranged to focus light scattered from zones  630 ,  631 , and  632  onto fiber ends  612 ,  611 , and  610 , respectively. The lens  620  may be selected to have a focal length such that light scattered from the field of view  640  forms as a conjugate image within the collection assembly  605 . Detectors or fiber ends  610 - 612  leading to detectors may be placed in the conjugate image plane. A detector may be sampled at a frequency corresponding to a scanning light spot size and its scanning speed across the field of view  640 . In an embodiment, this sampling frequency is 50 MHz. To obtain the same resolution image and frame rate as a single beam scanned-beam system, the sampling frequency may be reduced in proportion to the number of zones. 
         [0064]    The optical elements for producing plural beams may include one or more beamlet-producing optical elements such as a diffraction grating, a microlens array (MLA), a dual microlens array (DMLA), etc. An optical element may be embodied as a reflective element, or may be embodied as a transmissive element. Some embodiments are illustrated in  FIGS. 7-9 . 
         [0065]      FIG. 7  is a simplified side view of an illustrative optical element for producing a plurality of beams from an input beam according to an embodiment. A dual-microlens array (DMLA)  700  includes first and second microlens arrays (MLAs)  705  and  710 , which are made from a transparent optical material such as plastic or glass and which include a number of lenslets  715  and  720 , respectively. The lenslets of MLA  705  lie on a plane  725  and have a focal length f. Likewise, the lenslets of MLA  710  lie on a plane  730 , and have the same focal length f. The MLAs  705  and  710  are positioned such that the planes of the lenslet arrays  725  and  730  are separated by the distance f, equal to the focal lengths. In some embodiments, gap between the MLAs is filled with air. Lenslets  715  and  720  have a width D, which is the pitch of the MLAs  705  and  710 , and each lenslet  715  is aligned with a corresponding lenslet  720 . 
         [0066]    Before striking the DLMA  700 , incident light may pass through a collimating lens (not shown) such as a telecentric lens. In another embodiment, the DLMA  700  may be formed as shown in  FIG. 8  and a collimating lens may be omitted. 
         [0067]      FIG. 8  is a side view of a curved DMLA according to an embodiment. The DMLA  800  includes curved MLAs  805  and  810 , which respectively include lenslets  815  and  820 . Corresponding pairs of lenslets  815  and  820  are aligned such that incident light rays follow radial paths  825 . The MLAs  805  and  810  each have the same focal length f in the radial dimension, and the lenslet arrays lie on respective curved planes  830  and  835 , which are spaced apart by f in the radial dimension. 
         [0068]    Returning to  FIG. 7 , in the far field, the beams  735 ,  740 , and  745  may interfere to create a plurality of beamlets. In an embodiment, the size of the beamlet aperture may depend on the wavelength of the beam  750  that strikes the MLA  705 . These beamlets are scanned across respective areas as the received beam  750  is scanned across the DLMA  700 . 
         [0069]    In another embodiment, the optical element shown in  FIGS. 7 and 8  may comprise one or more diffraction gratings replacing one or both of the MLAs. Such a diffraction grating may be formed, for example, via reactive ion etching in quartz. 
         [0070]      FIG. 9  is a side view of a reflective DMLA according to another embodiment. Like the DMLA  700  of  FIG. 7 , the DMLA  900  includes the MLA  705 . Instead of including another MLA (e.g., MLA  710 ), however, the DMLA  900  includes a mirror  905 . The mirror  905  includes a reflecting surface  910  that is located f/2 from the plane of the lenslets. 
         [0071]    While scanned-beam systems having a small number of zones have been described, it will be recognized that the principles described herein may be extended tens, hundreds, thousands, or more zones. The scanned light may be split into beamlets along multiple dimensions to form a 1×2, 2×2, 2×3, 3×3, or other dimensional matrix (e.g., contiguous set of zones) as desired. This may involve passing the light through multiple optical elements, for example. 
         [0072]    Light beams suitable for scanning inside a living organism (such as a human being) may have the intensity selected such that they are non-damaging or acceptably damaging to the tissue of the living organism. 
         [0073]    The foregoing detailed description has set forth some embodiments via the use of block diagrams, flow diagrams, or examples. Insofar as such block diagrams, flow diagrams, or examples are associated with one or more actions, functions, or operations, it will be understood by those within the art that each action, function, or operation or set of actions, functions, or operations associated with such block diagrams, flowcharts, or examples may be implemented, individually or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. 
         [0074]    As can be seen from the foregoing detailed description, a range of alternative embodiments may embody the spirit and scope of the subject matter presented herein. While some embodiments have been described in detail, others may be omitted for the sake of clarity. Accordingly, the scope of the invention shall not be limited by the illustrative embodiments, but rather shall extend to the broadest valid interpretation of the claims appended hereto.