Patent Publication Number: US-2023157881-A1

Title: Imaging and treating a vitreous floater in an eye

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to ophthalmic surgical systems, and more particularly to imaging and treating a floater within an eye. 
     BACKGROUND 
     Vitreous eye floaters are microscopic collagen fibers that clump together and disturb the vision of the patient. Laser vitreolysis treats this condition by directing a laser beam into the vitreous towards a floater. The laser beam fragments and removes the floater to improve vision. 
     BRIEF SUMMARY 
     In certain embodiments, an ophthalmic laser surgical system for imaging and treating a target in an eye includes an imaging system, a treatment system, and a computer. The imaging system directs imaging beams into the eye to generate images of the target within the eye. The imaging beams include a scanning laser ophthalmoscope (SLO) imaging beam and an optical coherence tomography (OCT) imaging beam. The imaging system includes an SLO device and an OCT device. The SLO device includes a scanning system, a light detector, and an SLO detector. The scanning system scans the SLO imaging beam within the eye. The light detector generates an SLO signal in response to detecting the SLO imaging beam reflected from the eye. The SLO detector generates SLO images from the SLO signal. The OCT device includes the scanning system, the light detector, and an OCT detector. The scanning system scans the OCT imaging beam within the eye. The light detector generates an OCT signal in response to detecting the OCT imaging beam reflected from the eye. The OCT detector generates OCT images from the OCT signal. The treatment system includes a laser device that directs a laser beam towards the target. The computer instructs the imaging system to generate the images and the laser device to direct the laser beam towards the target. 
     Embodiments may include none, one, some, or all of the following features:
         The ophthalmic laser surgical system includes an imaging beam source that generates the imaging beams comprising the SLO imaging beam and the OCT imaging beam.   The computer instructs: the OCT device to scan the OCT imaging beam in a z-direction relative to the z-axis to generate an A-scan within the eye; and the SLO device to scan the SLO imaging beam in an xy-direction relative to the xy-planes to generate two-dimensional (2D) enface images.   The scanning system includes: an xy-scanner that scans an imaging beam in an xy-direction relative to an xy-plane within the eye; and a z-scanner that scans the imaging beam in a z-direction relative to the z-axis within the eye. The xy-scanner may: direct the imaging beams along an imaging beam path towards an xy-location of the target; and direct the laser beam along a laser beam path aligned with the imaging beam path towards the xy-location of the target. The z-scanner may: direct the imaging beams along an imaging beam path towards a z-location of the target; and direct the laser beam along a laser beam path aligned with the imaging beam path towards the z-location of the target. The z-scanner may include a corner cube moving mirror (CCMM) that moves to adjust a path length to create a coherence gate for maximum signal.   The light detector includes: a high-frequency filter that provides the SLO signal; and a low-frequency filter that provides the OCT signal.   The OCT detector includes a fringe counter that counts interference fringes.   The OCT device measures a z-location of the target relative to the z-axis.   The laser device receives z-location of the target from the imaging system and direct the laser beam towards the z-location of the target.   The computer: determines a radiant exposure at a retina of the eye resulting from the laser beam directed to the z-location of the target; and determines whether the radiant exposure is less than a maximum radiant exposure.   The SLO device generates two-dimensional (2D) enface images, each enface image located in a different xy-plane. The computer combines the plurality of 2D enface images to yield three-dimensional (3D) images. The computer may output the 3D images via a display.       

     In certain embodiments, a method for imaging and treating a target in an eye comprises directing, by an imaging system, imaging beams into the eye to generate images of the target within the eye. The imaging beams comprise a scanning laser ophthalmoscope (SLO) imaging beam and an optical coherence tomography (OCT) imaging beam. The eye has an eye axis that defines a z-axis, which in turn defines xy-planes orthogonal to the z-axis. The images of the target are generated by: scanning, by a scanning system of an SLO device of the imaging system, the SLO imaging beam within the eye; generating, by a light detector of the SLO device, an SLO signal in response to detecting the SLO imaging beam reflected from the eye; generating, by an SLO detector of the SLO device, a plurality of SLO images from the SLO signal; scanning, by the scanning system of an OCT device of the imaging system, the OCT imaging beam within the eye; generating, by the light detector of the OCT device, an OCT signal in response to detecting the OCT imaging beam reflected from the eye; and generating, by an OCT detector of the OCT device, a plurality of OCT images from the OCT signal. A laser beam is directed by a laser device of a treatment system towards the target within the eye. The imaging system is instructed by a computer to generate the images, and the laser device is instructed by the computer to direct the laser beam towards the target. 
     Embodiments may include none, one, some, or all of the following features:
         The OCT device is instructed by the computer to scan the OCT imaging beam in a z-direction relative to the z-axis to generate an A-scan within the eye. The SLO device is instructed by the computer to scan the SLO imaging beam in an xy-direction relative to the xy-planes to generate two-dimensional (2D) enface images.   An imaging beam is scanned by an xy-scanner of the scanning system in an xy-direction relative to an xy-plane within the eye. The imaging beam is scanned by a z-scanner of the scanning system in a z-direction relative to the z-axis within the eye.   The imaging beams are directed by the xy-scanner along an imaging beam path towards an xy-location of the target. The laser beam is directed by the xy-scanner along a laser beam path aligned with the imaging beam path towards the xy-location of the target.   The imaging beams are directed by the z-scanner along an imaging beam path towards a z-location of the target. The laser beam is directed by the z-scanner along a laser beam path aligned with the imaging beam path towards the z-location of the target.   The z-scanner comprises a corner cube moving mirror (CCMM) that moves to adjust a path length to create a coherence gate for maximum signal.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of an ophthalmic laser surgical system for imaging and treating a target in an eye, according to certain embodiments; 
         FIG.  2    illustrates examples of SLO 2D enface images that may be generated by the SLO device of  FIG.  1   , according to certain embodiments; 
         FIG.  3    illustrates an example of a corner cube moving mirror CCMM and mirror of the z-scanner of  FIG.  1   , according to certain embodiments; and 
         FIG.  4    illustrates an example of a method for imaging and fragmenting a target in an eye, which may be performed by the system of  FIG.  1   , according to certain embodiments. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Referring now to the description and drawings, example embodiments of the disclosed apparatuses, systems, and methods are shown in detail. The description and drawings are not intended to be exhaustive or otherwise limit the claims to the specific embodiments shown in the drawings and disclosed in the description. Although the drawings represent possible embodiments, the drawings are not necessarily to scale and certain features may be simplified, exaggerated, removed, or partially sectioned to better illustrate the embodiments. 
     Laser vitreolysis uses a laser beam to fragment and remove eye floaters. Known systems for performing laser vitreolysis, however, fail to treat floaters effectively and efficiently. For example, known systems often use illumination that generates significant retinal reflections that degrade imaging of floaters. Moreover, the systems typically use a dual beam technique that cannot provide precise depth measurements. 
     Accordingly, the surgical systems described herein have a scanning laser ophthalmoscope (SLO) device that generates two-dimensional (2D) and three-dimensional (3D) images that provide clearer images of floaters. In addition, the systems include an optical coherence tomography (OCT) device that provides more precise depth measurements of the floaters. Moreover, the treatment and imaging systems of the surgical systems share components that allow for co-registration of treatment and imaging beams, as well as reduce manufacturing costs. 
       FIG.  1    illustrates an example of an ophthalmic laser surgical system  10  for imaging and treating a target in an eye, according to certain embodiments. In the example, the target may be a vitreous floater. The eye has an eye axis (e.g., visual or optical axis), which defines a z-axis. Z-locations and the z-direction are relative to the z-axis. The z-axis defines xy-planes orthogonal to the z-axis. Xy-locations and xy-directions are relative to an xy-plane. 
     As an overview of the illustrated example, system  10  includes an imaging and measuring system  20 , a treatment system  22 , and a computer  23 , coupled as shown. Imaging system  20  includes an SLO device  24  and an OCT device  26 , coupled as shown. SLO device  24  and OCT device  26  share certain components of system  10 , including an imaging laser source  30  (e.g., laser diode LD), a lens  31 , a beamsplitter BS 1   32 , a beamsplitter BS 2   34 , an xy-scanner  36 , a lens  37  (which operates with a z-scanner  38 ), z-scanner  38 , an objective lens  40 , and a detector system  42 . Z-scanner  38  includes a corner cube moving mirror CCMM  44 , a mirror M 1   46 , and lens L 1   37 , coupled as shown. 
     Continuing with the overview, detector system  42  includes a detector  50  (e.g., photodiode PD), a high-frequency (HF) filter  52 , an SLO detector  54 , a low-frequency (LF) filter  56 , an OCT detector  58 , a small aperture such as pinhole  60 , and a lens  62 , coupled as shown. Regarding detector system  42 , SLO device  24  utilizes HF filter  52  and SLO detector  54 , and OCT device  26  utilizes LF filter  56  and OCT detector  58 . Treatment system  22  includes a laser device  70 , which includes a treatment laser source  71  and lenses  72 ,  74 , coupled as shown. Treatment system  22  includes and shares beamsplitter BS 2   34 , xy-scanner  36 , lens  37 , and objective lens  40  with imaging system  20 , coupled as shown. Computer includes logic  80 , a memory  82  (which stores a program  84 ), and interface  86  (which includes a display  88 ), coupled as shown. 
     As an example of operation, laser source  30  generates imaging beams, including SLO and OCT imaging beams. Imaging system  20  directs the imaging beams into the eye to generate images of the target within the eye, which reflects the imaging beams. At the SLO device  24 , a scanning system (comprising xy-system  36  and z-scanner  38 ) scans the focus of the SLO imaging beam within the eye. Light detector  50  generates an SLO signal in response to sensing the SLO imaging beam reflected from the eye. SLO detector  54  generates SLO images  90  ( 90   a ,  90   b ,  90   c ) from the SLO signal. 
     Continuing with the example of operation, at OCT device  26 , the scanning system scans the focus of the OCT imaging beam within the eye. Light detector  50  generates an OCT signal in response to sensing the OCT imaging beam reflected from the eye. OCT detector  58  generates OCT images from the OCT signal. Laser device  70  directs a laser beam along a laser beam path towards the target within the eye. Computer  23  instructs the imaging system to generate the images and the laser device to direct the laser beam along the laser beam path towards the target. 
     Turning to the components, imaging system  20  and treatment system  22  direct light beams towards the interior of the eye. Imaging system  20  generates images of the eye interior, including images of the target (e.g., a floater) within the eye. In imaging system  20 , SLO device  24  generates SLO images, and OCT device  26  generates OCT images. Imaging laser source  30  generates imaging beams, including SLO and OCT imaging beams. Imaging laser source  30  may comprise any suitable laser source that generates laser beams of any suitable wavelength. For example, laser source  30  may generate OCT imaging beams in the near-infrared (NIR) range, such as 750 to 1400 nanometers (nm). In general, the central wavelength of OCT imaging beams is selected to achieve maximal penetration depth into the tissue under examination. For ophthalmic systems, the wavelength is typically approximately 850 nm or approximately 1050 nm to allow light penetration through the retinal pigment epithelium (REP) to enable imaging of the choroid. Laser source  30  may generate SLO imaging beams in the visible to NIR range, such as 380 to 910 nm. Lens  31  collimates the imaging beams. 
     Beamsplitter BS 1   32  splits the imaging beams to yield a sample beam for imaging the eye and a reference beam for the reference arm of OCT device  26 . Generally, the imaging beam is split such that the sample beam has greater intensity than that of the reference beam, e.g., the sample beam intensity is 70% to 90% such as 80% of the intensity of the imaging beam. Beamsplitter BS 1   32  also directs imaging beams reflected from the eye towards detector system  42 . Beamsplitter BS 1   32  may comprise any suitable beamsplitter, e.g., a metallic and/or dielectric thin film applied to an optical substrate, a polarization beamsplitter, or a pellicule that allows partial transmission and/or reflection of the incident beam. 
     Treatment system  22  includes a laser device  70  that directs a treatment laser beam into the eye to fragment the target. Treatment laser source  30  generates treatment beams, and may comprise any suitable laser source that generates laser beams of any suitable wavelength, e.g., 1030 to 1065 nanometers (nm). Lenses  72 ,  74  collimate the treatment beams. Lenses  72  and  74  may be an optical relay that focuses the laser beam at the target while maintaining image focus. 
     Beamsplitter BS 2   34  transmits imaging and treatment beams to xy-scanner  36 . Beamsplitter BS 2   34  also directs imaging beams reflected from the eye towards beamsplitter BS 1   32 . Beamsplitter BS 2   34  may comprise any suitable beamsplitter, e.g., a dichroic mirror, a polarization beamsplitter, or a partially reflective metallic or dielectric thin film applied to an optical substrate. A dichroic mirror allows for different wavelength to be combined along the same optical path to couple the imaging and treatment beam paths. From beamsplitter BS 2   34  to the eye, the imaging and treatment beam paths are aligned. 
     A scanning system scans laser beams in the x-, y-, and z-directions within the eye. In the example, the scanning system includes xy-scanner  36  that scans beams in xy-directions and z-scanner  38  that scans in the z-direction. The imaging and treatment beam paths are aligned, so a scanner can direct imaging and treatment beams to the same location. For example, xy-scanner  36  directs imaging and treatment beams along the imaging and treatment beam paths towards the xy-location of the target. As another example, z-scanner  38  directs imaging and treatment beams along the imaging and treatment beam paths towards a z-location of the target. 
     Xy-scanner  36  scans treatment and imaging beams transversely in xy-directions. Examples of scanners include a galvo scanner (e.g., a pair of galvanometrically-actuated scanner mirrors that can be tilted about mutually perpendicular axes), an electro-optical scanner (e.g., an electro-optical crystal scanner) that can electro-optically steer the beam, or an acousto-optical scanner (e.g., an acousto-optical crystal scanner) that can acousto-optically steer the beam. XY-scanner  36  may include an afocal relay lens system that allows for the compensation of patient refractive error. The afocal relay lens system may be used to image the scanner onto the pupil of the eye such that, while the optical beam is traversing the retina, the movement of the beam at the pupil of the eye is minimized to reduce or eliminate vignetting. The afocal relay lens system can be designed such that the scanner is conjugate to the pupil and movement of the lenses in the afocal relay (relative spacing between lenses  37  and  40 ) can accommodate for patient refractive error. 
     Z-scanner  38  includes corner cube moving mirror CCMM  44 , mirror M 1   46 , and lens L 1   37 . CCMM  44  moves relative to beamsplitter BS 1   32  and mirror M 1   46  to adjust an imaging and/or treatment path length to create a coherence gate where the imaging and/or treatment beam paths are phase matched for maximum signal. CCMM  44  is described in more detail with reference to  FIG.  3   . Objective lens  40  focuses treatment and imaging beams within the eye. 
     The eye reflects the imaging beams. Detector system  42  receives imaging beams reflected from the eye and generates SLO and OCT images from the reflected beams. Lens  62  focuses the beams through a small aperture or pinhole  60 , which rejects out-of-focus light from the sources other than the object of interest. Pinhole  60  is optically conjugate to the imaging plane Z 2  in the eye and rejects reflected/backscattered light from any object not located at plane Z 2 . Detector  50  detects the reflected beams and generates a signal in response to the beams. Detector  50  may comprise, e.g., a photodiode. HF filter  52  provides an SLO signal to SLO detector  54 , and LF filter  56  provides the OCT signal to OCT detector  58 . OCT detector  58  may comprise any suitable device that can translate interference signals to an images, e.g., a fringe counter configured to count interference fringes. 
     SLO device  24  generates SLO images of the interior of the eye. In general, SLO device  24  can provide higher field of view (FOV) imaging, which may facilitate detection of moving floaters or other vitreous opacities during treatment. Moreover, SLO images enhance the contrast between a floater (or floater shadow) and the retina, allowing for easier detection of floaters. 
     In certain embodiments, SLO device  24  generates two-dimensional (2D) enface images, where each enface image is located in a different xy-plane. For example, a retinal enface image may be taken at or near the retina. The image may show floater shadows that can be used to assess the visual impact of floaters. As another example, a target 2D image may be taken at or near the target to show the floater. In certain embodiments, computer  23  combines the 2D enface images to yield three-dimensional (3D) images of the target within the eye. In the embodiments, computer  23  may output the images via display  88 . 
     OCT device  26  generates OCT images of the interior of the eye and may be any suitable OCT device, e.g., a time domain OCT (TD-OCT) device. A TD-OCT can scan an entire eye at high speed with micron level precision, so can quickly measure the z-location (i.e., depth) of a floater within a few microns. In certain embodiments, OCT device  26  measures the z-location of the target, and laser device  70  receives the z-location of the target from the imaging system  20  and directs the laser beam towards the z-location of the target. 
     In certain embodiments, OCT device  26  sends a reference signal to the reference arm and a sample signal to the eye and detects the reflected signals. The reference path length is adjusted by moving CCMM  44 . As the reference path length is adjusted, detector  50  detects alternating bright and dark signals, i.e., optical fringes, to generate an A-scan (z-direction scan). The optical fringes are analyzed to measure the z-locations of, e.g., the target (e.g., the floater), laser beam focus, and/or anatomical feature of the eye (e.g., lens and/or retina). 
     Computer  23  controls the operation of system  10 , e.g., may control the operation of imaging system  20  and/or treatment system  22 . In certain embodiments, computer  23  instructs OCT device  26  to scan an OCT imaging beam in a z-direction to generate an OCT A-scan, and instructs SLO device  24  to scan an SLO imaging beam in an xy-direction to generate two-dimensional (2D) enface images. The OCT and SLO imaging beams may scanned simultaneously. In certain embodiments, computer  23  performs image procession on an image to evaluate the visual impact of a floater. For example, the size of a floater&#39;s shadow indicates the size of the floater. As another example, the contrast of a floater&#39;s shadow relative to the retina indicates the density and/or thickness of the floater. 
     In certain embodiments, computer  23  determines a radiant exposure at the retina resulting from a laser beam directed to the z-location of the target, and determines whether the radiant exposure is greater or less than a maximum acceptable radiant exposure. In the embodiments, computer  23  calculates the radiant exposure H e  by determining a laser spot size of the laser beam on the retina and calculating the radiant exposure H e  according to the target-to-retina distance ΔZ and the laser spot size on the retina. For example, the laser spot diameter Φ may be calculated according to Φ=2*ΔZ*tan α, where α represents the known half angle of the cone of the laser beam. The radiant exposure H e  may be calculated according to H e =4*E/Φ 2 *π=4*E/(2*ΔZ*tan α) 2 π, where E is the energy of the laser pulse. If the radiant exposure is greater than a maximum acceptable radiant exposure, computer  23  may notify the user, adjust the energy of the laser beam, and/or prevent the laser from firing to avoid overexposing the retina. 
       FIG.  2    illustrates examples of SLO 2D enface images  90  ( 90   a ,  90   b ,  90   c ) that may be generated by SLO device  24  of  FIG.  1   , according to certain embodiments. Different 2D enface images  90  image xy-planes at different z-locations. For example, image S 1   90   a  images the xy-plane at z 1 , image S 2   90   b  images the xy-plane at z 2 , and image S 3   90   c  images the xy-plane at z 3 . 
     In certain embodiments, computer  23  generates a 3D image from the 2D images. Computer  23  aligns the 2D images in order according to their z-locations and then generates the 3D image from the aligned 2D images. For example, computer  23  corrects each image  90   a ,  90   b ,  90   c  for eye movement during the z-scan to yield a corrected 3D data set by laterally matching and shifting each image with respect to the previous image within the z-scan. Computer  23  may perform further processing and analysis of the corrected 3D data set. For example, computer  23  may calculate a topography and/or a reflectance image from the 3D data set. As another example, computer  23  may analyze the z-profile for each xy-pixel to detect floater in the corresponding 2D image. 
       FIG.  3    illustrates an example of corner cube moving mirror CCMM  44  and mirror M 1   46  of z-scanner  38  of  FIG.  1   , according to certain embodiments. CCMM  44  is used to adjust the path length to create a coherence gate where paths are phase matched for maximum signal. CCMM  44  moves relative to beamsplitter BS 1   32  and mirror M 1   46  to match the optical path length of the OCT/SLO imaging path and laser beam path in the z-direction. For example, CCMM  44  moves to change the length of the reference arm of OCT device  26 , the focus of the SLO imaging beam, and/or the focus of the laser beam. CCMM  44  allows for greater alignment tolerance, as CCMM  44  does not have to be perfectly aligned to direct beams back to beamsplitter BS 1   32 . 
       FIG.  4    illustrates an example of a method for imaging and fragmenting a target in an eye, which may be performed by system  10  of  FIG.  1   , according to certain embodiments. The method starts at step  110 , where an imaging laser source generates an imaging beam. A scanning system scans the imaging beam within the eye at step  112 . For example, the scanning system includes an xy-scanner that scans beams in the xy-direction and a z-scanner that scans beams in the z-direction. A computer may instruct an OCT device to scan an OCT imaging beam in the z-direction to generate an A-scan and instruct an SLO device to scan an SLO imaging beam in the xy-direction to generate two-dimensional (2D) enface images. The OCT and SLO imaging beams may scanned simultaneously. 
     The eye reflects the imaging beam. A detector system detects the reflected imaging beam at step  114 . The detector system provides an OCT signal to an OCT detector at step  120 . For example, a LF filter provides the OCT signal to the OCT detector. The OCT device generates OCT images of target at step  122 . The OCT device determines the z-location of target at step  124 . The detector system provides an SLO signal to an SLO detector at step  130 . For example, a HF filter provides an SLO signal to the SLO detector. The SLO device generates 2D SLO enface images of target at step  132 . Each enface image may be located in a different xy-plane. The computer generates 3D images of the target at step  134  from the 2D images. The computer may combine aligned 2D enface images to yield a 3D SLO image of the target. 
     The computer calculates at step  140  the radiant exposure at the retina resulting from a laser beam directed to the z-location of the target. In certain embodiments, the computer calculates the radiant exposure H e  by determining a laser spot size of the laser beam on the retina, and calculating the radiant exposure H e  according to the target z-location and the laser spot size. In the embodiments, the computer may determine whether the radiant exposure is greater or less than a maximum radiant exposure. If the radiant exposure is greater than the maximum acceptable radiant exposure, the computer may notify the user, adjust the laser energy, and/or prevent the laser from firing. A treatment system directs the laser beam towards the target at step  142  to fragment and remove the target. The laser device may receive the xy- and z-locations of the target from the imaging system and direct the laser beam towards the xy- and z-locations. The method then ends. 
     A component (such as the control computer) of the systems and apparatuses disclosed herein may include an interface, logic, and/or memory, any of which may include computer hardware and/or software. An interface can receive input to the component and/or send output from the component, and is typically used to exchange information between, e.g., software, hardware, peripheral devices, users, and combinations of these. A user interface is a type of interface that a user can utilize to communicate with (e.g., send input to and/or receive output from) a computer. Examples of user interfaces include a display, Graphical User Interface (GUI), touchscreen, keyboard, mouse, gesture sensor, microphone, and speakers. 
     Logic can perform operations of the component. Logic may include one or more electronic devices that process data, e.g., execute instructions to generate output from input. Examples of such an electronic device include a computer, processor, microprocessor (e.g., a Central Processing Unit (CPU)), and computer chip. Logic may include computer software that encodes instructions capable of being executed by an electronic device to perform operations. Examples of computer software include a computer program, application, and operating system. 
     A memory can store information and may comprise tangible, computer-readable, and/or computer-executable storage medium. Examples of memory include computer memory (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (e.g., a hard disk), removable storage media (e.g., a Compact Disk (CD) or Digital Video or Versatile Disk (DVD)), database, network storage (e.g., a server), and/or other computer-readable media. Particular embodiments may be directed to memory encoded with computer software. 
     Although this disclosure has been described in terms of certain embodiments, modifications (such as changes, substitutions, additions, omissions, and/or other modifications) of the embodiments will be apparent to those skilled in the art. Accordingly, modifications may be made to the embodiments without departing from the scope of the invention. For example, modifications may be made to the systems and apparatuses disclosed herein. The components of the systems and apparatuses may be integrated or separated, or the operations of the systems and apparatuses may be performed by more, fewer, or other components, as apparent to those skilled in the art. As another example, modifications may be made to the methods disclosed herein. The methods may include more, fewer, or other steps, and the steps may be performed in any suitable order, as apparent to those skilled in the art. 
     To aid the Patent Office and readers in interpreting the claims, Applicants note that they do not intend any of the claims or claim elements to invoke 35 U.S.C. § 112(f), unless the words “means for” or “step for” are explicitly used in the particular claim. Use of any other term (e.g., “mechanism,” “module,” “device,” “unit,” “component,” “element,” “member,” “apparatus,” “machine,” “system,” “processor,” or “controller”) within a claim is understood by the applicants to refer to structures known to those skilled in the relevant art and is not intended to invoke 35 U.S.C. § 112(f).