Patent Application
20090154886
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.
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.
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.
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.
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.
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.
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.
According to another embodiment, one scanner 120A may be aligned to receive a plurality of beams of light and the second scanner 120B may be omitted.
Scanned light that scatters from the field of view 125 may be detected by the detectors 115A and 115B. The detectors 115A and 115B 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.
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.
The controller 105 may optionally modulate light source drive signals to drive the light sources 110A and 110B 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 120A, 120B 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 115A configured to view substantially the entire field of view to receive the time-sequenced image information carried by light scattered from the zones.
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 115A and 115B and may include one or more of infrared, ultraviolet, and visible.
Light from the light sources 110A and 110B may be transmitted toward the scanners 120A and 120B via an optical element such as one or more optical fibers. In an embodiment, a light source (e.g., light source 120A or 120B) 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 130A, 130B 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.
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.
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.
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.
Although two light sources are shown in
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.
The detectors 115A and 115B may receive light scattered from corresponding detection zones 130A and 130B. 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.
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 115A and 115B may comprise photodiodes or other light-sensitive elements that are aligned to receive light substantially directly from the FOV. In other embodiments, the detectors 115A and 115B may receive light from optical fibers that collect light and transmit it to the detectors 115A and 115B, where it is converted into electrical signals for further processing. Such gathering fibers may be arranged circumferentially around the scanners 120A and 120B, for example.
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 120A and 120B. 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 110A and 110B. 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.
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 110A and 110B and the detectors 115A and 115B, 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.
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.
The scanner 220 scans the light beams 240A-C in unison such that the light beams 240A-C scan over their respective areas 230A-230C. The scan amplitudes 245A-C may be selected such that the areas overlap to provide sufficient coverage of the field of view 225.
As indicated above, a plurality of scanned beams may alternatively be produced using one scanner.
For a scanner 120 having 1:1 angular reproduction, the converging angle made between emitted beams 302a and 302b is preserved as a diverging angle between scanning beams 304a, 304b. 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 302a, 302b are composite beams including red, green, and blue wavelength components, and the scanner is a biaxial MEMS scanner.
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.
A diverging angle may be maintained between output scanned beams 304a, 304b corresponding to the converging angle between the input beams 302a, 302b. Alternatively (and also for at least many other embodiments described herein), the output scanned beams 304a, 304b may be parallel or converging, or be produced at a diverging angle differing from the angle of convergence of the input beams 302a, 302b. 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 302a, 302b) or output beams 304a, 304b prior to propagation toward the scanning zones.
For example, the scanner optical element and the optical element 318 may operate cooperatively in a manner akin to that described in conjunction with
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.
In
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.
Proceeding to
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.
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.
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
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
Returning to
In another embodiment, the optical element shown in
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.
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.
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.
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.
