Patent Publication Number: US-2022218189-A1

Title: Controlling integral energy of a laser pulse in a fluorescence imaging system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. patent application Ser. No. 16/797,772, filed Feb. 21, 2020, (now U.S. Pat. No. 11,284,784), and which claims the benefit of U.S. Provisional Patent Application No. 62/864,236, filed Jun. 20, 2019, titled “CONTROLLING INTEGRAL ENERGY OF A LASER PULSE IN A HYPERSPECTRAL AND FLUORESCENCE IMAGING ENVIRONMENT,” which are incorporated herein by reference in their entirety, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference being made with the following exception: In the event that any portion of the above-referenced applications are inconsistent with this application, this application supersedes the above-referenced applications. 
    
    
     TECHNICAL FIELD 
     This disclosure is directed to digital imaging and is particularly directed to fluorescence imaging in a light deficient environment. 
     BACKGROUND 
     Advances in technology have provided advances in imaging capabilities for medical use. An endoscope may be used to look inside a body and examine the interior of an organ or cavity of the body. Endoscopes are used for investigating a patient&#39;s symptoms, confirming a diagnosis, or providing medical treatment. A medical endoscope may be used for viewing a variety of body systems and parts such as the gastrointestinal tract, the respiratory tract, the urinary tract, the abdominal cavity, and so forth. Endoscopes may further be used for surgical procedures such as plastic surgery procedures, procedures performed on joints or bones, procedures performed on the neurological system, procedures performed within the abdominal cavity, and so forth. 
     In some instances of endoscopic imaging, it may be beneficial or necessary to view a space in color. A digital color image includes at least three layers, or “color channels,” that cumulatively form an image with a range of hues. Each of the color channels measures the intensity and chrominance of light for a spectral band. Commonly, a digital color image includes a color channel for red, green, and blue spectral bands of light (this may be referred to as a Red Green Blue or RGB image). Each of the red, green, and blue color channels include brightness information for the red, green, or blue spectral band of light. The brightness information for the separate red, green, and blue layers are combined to create the color image. Because a color image is made up of separate layers, a conventional digital camera image sensor includes a color filter array that permits red, green, and blue visible light wavelengths to hit selected pixel sensors. Each individual pixel sensor element is made sensitive to red, green, or blue wavelengths and will only return image data for that wavelength. The image data from the total array of pixel sensors is combined to generate the RGB image. The at least three distinct types of pixel sensors consume significant physical space such that the complete pixel array cannot fit in the small distal end of an endoscope. 
     Because a traditional image sensor cannot fit in the distal end of an endoscope, the image sensor is traditionally located in a handpiece unit of an endoscope that is held by an endoscope operator and is not placed within the body cavity. In such an endoscope, light is transmitted along the length of the endoscope from the handpiece unit to the distal end of the endoscope. This configuration has significant limitations. Endoscopes with this configuration are delicate and can be easily misaligned or damaged when bumped or impacted during regular use. This can significantly degrade the quality of the images and necessitate that the endoscope be frequently repaired or replaced. 
     The traditional endoscope with the image sensor placed in the handpiece unit is further limited to capturing only color images. However, in some implementations, it may be desirable to capture images with fluorescence image data in addition to color image data. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Certain fluorescent materials “glow” or emit a distinct color that is visible to the human eye when the fluorescent material is subjected to ultraviolet light or other wavelengths of electromagnetic radiation. Certain fluorescent materials will cease to glow nearly immediately when the radiation source stops. 
     Fluorescence occurs when an orbital electron of a molecule, atom, or nanostructure is excited by light or other electromagnetic radiation, and then relaxes to its ground state by emitting a photon from the excited state. The specific frequencies of electromagnetic radiation that excite the orbital electron, or are emitted by the photon during relaxation, are dependent on the atom, molecule, or nanostructure. Fluorescence imaging has numerous practical applications, including mineralogy, gemology, medicine, spectroscopy for chemical sensors, detecting biological processes or signals, and others. Fluorescence can be used in biochemistry and medicine as a non-destructive means for tracking or analyzing biological molecules. Some fluorescent reagents or dyes can be configured to attach to certain types of tissue and thereby draw attention to that type of tissue. 
     However, fluorescence imaging requires specialized emissions of electromagnetic radiation and specialized imaging sensors capable of reading the specific relaxation wavelength for a specific fluorescent reagent. Different reagents or dyes are sensitive to different wavelengths of electromagnetic radiation and emit different wavelengths of electromagnetic radiation when fluoresced. A fluorescent imaging system may be highly specialized and tuned for a certain reagent or dye. Such imaging systems are useful for limited applications and are not capable of fluorescing more than one reagent or structure during a single imaging session. It is very costly to use multiple distinct imaging systems that are each configured for fluorescing a different reagent. Additionally, it may be desirable to administer multiple fluorescent reagents in a single imaging session and view the multiple reagents in a single overlaid image. 
     In light of the foregoing, described herein are systems, methods, and devices for fluorescent imaging in a light deficient environment. Such systems, methods, and devices may provide multiple datasets for identifying critical structures in a body and providing precise and valuable information about the body cavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive implementations of the disclosure are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Advantages of the disclosure will become better understood with regard to the following description and accompanying drawings where: 
         FIG. 1  is a schematic view of a system for digital imaging in a light deficient environment with a paired emitter and pixel array; 
         FIG. 2  is a system for providing illumination to a light deficient environment for endoscopic imaging; 
         FIG. 2A  is a schematic diagram of complementary system hardware; 
         FIGS. 3A to 3D  are illustrations of the operational cycles of a sensor used to construct an exposure frame; 
         FIG. 4A  is a graphical representation of the operation of an embodiment of an electromagnetic emitter; 
         FIG. 4B  is a graphical representation of varying the duration and magnitude of the emitted electromagnetic pulse to provide exposure control; 
         FIG. 5  is a graphical representation of an embodiment of the disclosure combining the operational cycles of a sensor, the electromagnetic emitter, and the emitted electromagnetic pulses of  FIGS. 3A-4B , which demonstrate the imaging system during operation; 
         FIG. 6A  is a schematic diagram of a process for recording a video with full spectrum light over a period of time from t(0) to t(1); 
         FIG. 6B  is a schematic diagram of a process for recording a video by pulsing portioned spectrum light over a period of time from t(0) to t(1); 
         FIGS. 7A-7E  illustrate schematic views of the processes over an interval of time for recording a frame of video for both full spectrum light and partitioned spectrum light; 
         FIG. 8  illustrates an illumination system for use in connection with a pulsed imaging system, wherein the illumination system includes a photo diode for measuring energy emitted by a laser module; 
         FIG. 9  illustrates a laser bundle comprising an electromagnetic sensor in communication with an operational amplifier for measuring energy emitted by a laser unit; 
         FIG. 10  illustrates an embodiment of an emitter comprising a plurality of laser bundles each comprising an electromagnetic sensor for measuring energy emitted by a laser unit; 
         FIG. 11  illustrates an embodiment of a digital imaging system including an endoscopic device; 
         FIG. 12  is a schematic diagram of a pattern reconstruction process for generating an RGB image with fluorescence data overlaid thereon by pulsing partitioned spectrums of light; 
         FIGS. 13A-13C  illustrate a light source having a plurality of emitters; 
         FIG. 14  illustrates a single optical fiber outputting via a diffuser at an output to illuminate a scene in a light deficient environment; 
         FIG. 15  illustrates a portion of the electromagnetic spectrum divided into a plurality of different sub-spectrums which may be emitted by emitters of a light source in accordance with the principles and teachings of the disclosure; 
         FIG. 16  is a schematic diagram illustrating a timing sequence for emission and readout for generating an image frame comprising a plurality of exposure frames resulting from differing partitions of pulsed light; 
         FIG. 17  illustrates an imaging system including a single cut filter for filtering wavelengths of electromagnetic radiation; 
         FIG. 18  illustrates an imaging system comprising a multiple cut filter for filtering wavelengths of electromagnetic radiation; 
         FIGS. 19A and 19B  illustrate a perspective view and a side view, respectively, of an implementation of an imaging sensor having a plurality of pixel arrays for producing a three-dimensional image, wherein the plurality of pixel arrays and the image sensor are built on a plurality of substrates; 
         FIGS. 20A and 20B  illustrate an implementation having a plurality of pixel arrays for producing a three-dimensional image in accordance with the principles and teachings of the disclosure; and 
         FIGS. 21A and 21B  illustrate a perspective view and a side view, respectively, of an implementation of an imaging sensor built on a plurality of substrates, wherein a plurality of pixel columns forming the pixel array are located on the first substrate and a plurality of circuit columns are located on a second substrate and showing an electrical connection and communication between one column of pixels to its associated or corresponding column of circuitry. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are systems, methods, and devices for digital imaging that may be primarily suited to medical applications such as medical endoscopic imaging. An embodiment of the disclosure is an endoscopic system for fluorescence and color imaging in a light deficient environment. Such methods, systems, and computer-based products disclosed herein provide imaging or diagnostic capabilities for use in medical robotics applications, such as the use of robotics for performing imaging procedures, surgical procedures, and the like. 
     An embodiment of the disclosure is an imaging system with a light source for providing pulsed illumination in a light deficient environment. In the embodiment, the total energy emitted by the light source is controlled and held to a specified tolerance. The light source may be in communication with a camera control unit (CCU) such that the CCU controls the power level, enabling/disabling, duration, and power level of the light source. The light source may comprise digital light sources such as lasers and light emitting diodes and may also comprise analog light sources. 
     In an embodiment, during operation of the imaging system, a PID (proportional, integral, and derivative) control algorithm is implemented to ensure the captured scene maintains a desired video exposure level to maximize the dynamic range of the image sensor or to achieve a desired scene response desired by the end user. The PID control algorithm may generally be referred to herein as the automatic shutter control (ASC). In some embodiments, each light pulse is adjusted proportionally based on a calculated error measurement, and the error measurement is calculated by comparing desired exposure levels against measured exposure levels. The measured exposure level may be calculated using the mean pixel value of all pixels or some portion of pixels in the image sensor. The ASC may order adjustments to the light pulse to alter the duration and/or intensity of the light source. This ensures the desired setpoint is achieved in some specified time. The imaging system may be implemented in an endoscopic device wherein an image sensor is disposed in the highly space-constrained region of the distal tip of the endoscope. 
     Conventional endoscopes are designed such that the image sensor is placed at a proximal end of the device within a handpiece unit. This configuration requires that incident light travel the length of the endoscope by way of precisely coupled optical elements. The precise optical elements can easily be misaligned during regular use, and this can lead to image distortion or image loss. Embodiments of the disclosure place an image sensor within the highly space-constrained environment in the distal end of the endoscope itself. This provides greater optical simplicity when compared with implementations known in the art. However, an acceptable solution to this approach is by no means trivial and introduces its own set of engineering challenges. 
     There can be a noticeable loss to image quality when the overall size of an image sensor is minimized such that the image sensor can fit within the distal tip of an endoscope. The area of the pixel array of the image sensor can be reduced by reducing the number of pixels and/or the sensing area of each individual pixel. Each of these modifications impacts the resolution, sensitivity, and dynamic range of the resultant images. Traditional endoscopic imaging systems are geared toward sensing steady broadband illumination and providing color information by virtue of segmented pixel arrays such as the Bayer pattern array. In light of the deficiencies associated with segmented pixel arrays, disclosed herein are alternative systems and methods that use a monochromatic (may be referred to as “color agnostic”) pixel array that does not include individual pixel filters. In the embodiments disclosed herein, the color information is provided by pulsing an emitter with different wavelengths of electromagnetic radiation. The pulsed imaging system disclosed herein can generate color images with fluorescence imaging data overlaid thereon. 
     In an embodiment, the color information is determined by capturing independent exposure frames in response to pulses of different wavelengths of electromagnetic radiation. The alternative pulses may include red, green, and blue wavelengths for generating an RGB image frame consisting of a red exposure frame, a green exposure frame, and a blue exposure frame. In an alternative implementation, the alternative pulses may include luminance (“Y”), red chrominance (“Cr”), and blue chrominance “(Cb”) pulses of light for generating a YCbCr image frame consisting of luminance data, red chrominance data, and blue chrominance data. The color image frame may further include data from a fluorescence exposure frame overlaid on the RGB or YCbCr image frame. The fluorescence pulse may include one or more pulses of electromagnetic radiation for eliciting a spectral response. In an embodiment, the fluorescence emission includes one or more of electromagnetic radiation having a wavelength from about 770 nm to about 790; or from about 795 nm to about 815 nm. Alternating the wavelengths of the pulsed electromagnetic radiation allows the full pixel array to be exploited and avoids the artifacts introduced by Bayer pattern pixel arrays. 
     In some instances, it is desirable to generate endoscopic imaging with multiple data types or multiple images overlaid on one another. For example, it may be desirable to generate a color (RGB or YCbCr) image that further includes fluorescence imaging data overlaid on the color image. An overlaid image of this nature may enable a medical practitioner or computer program to identify critical body structures based on the hyperspectral imaging data. Historically, this would require the use of multiple sensor systems including an image sensor for color imaging and one or more additional image sensors for hyperspectral imaging. In such systems, the multiple image sensors would have multiple types of pixel sensors that are each sensitive to distinct ranges of electromagnetic radiation. In systems known in the art, this includes the three separate types of pixel sensors for generating a color image along with additional pixel sensors for generating the fluorescence image data at different wavelengths of the electromagnetic spectrum. These multiple different pixel sensors consume a prohibitively large physical space and cannot be located at a distal tip of the endoscope. In systems known in the art, the camera or cameras are not placed at the distal tip of the endoscope and are instead placed in an endoscope handpiece or robotic unit. This introduces numerous disadvantages and causes the endoscope to be very delicate. The delicate endoscope may be damaged and image quality may be degraded when the endoscope is bumped or impacted during use. Considering the foregoing, disclosed herein are systems, methods, and devices for endoscopic imaging in a light deficient environment. The systems, methods, and devices disclosed herein provide means for employing multiple imaging techniques in a single imaging session while permitting one or more image sensors to be disposed in a distal tip of the endoscope. 
     Fluorescence Imaging 
     The systems, methods, and devices disclosed herein provide means for generating fluorescence imaging data in a light deficient environment. The fluorescence imaging data may be used to identify certain materials, tissues, components, or processes within a body cavity or other light deficient environment. In certain embodiments, fluorescence imaging is provided to a medical practitioner or computer-implemented program to enable the identification of certain structures or tissues within a body. Such fluorescence imaging data may be overlaid on black-and-white or RGB images to provide additional information and context. 
     Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Certain fluorescent materials may “glow” or emit a distinct color that is visible to the human eye when the fluorescent material is subjected to ultraviolet light or other wavelengths of electromagnetic radiation. Certain fluorescent materials will cease to glow nearly immediately when the radiation source stops. 
     Fluorescence occurs when an orbital electron of a molecule, atom, or nanostructure is excited by light or other electromagnetic radiation, and then relaxes to its ground state by emitting a photon from the excited state. The specific frequencies of electromagnetic radiation that excite the orbital electron, or are emitted by the photon during relaxation, are dependent on the particular atom, molecule, or nanostructure. In most cases, the light emitted by the substance has a longer wavelength, and therefore lower energy, than the radiation that was absorbed by the substance. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons. This two-photon absorption can lead to emission of radiation having a shorter wavelength, and therefore higher energy, than the absorbed radiation. Additionally, the emitted radiation may also be the same wavelength as the absorbed radiation. 
     Fluorescence imaging has numerous practical applications, including mineralogy, gemology, medicine, spectroscopy for chemical sensors, detecting biological processes or signals, and so forth. Fluorescence may particularly be used in biochemistry and medicine as a non-destructive means for tracking or analyzing biological molecules. The biological molecules, including certain tissues or structures, may be tracked by analyzing the fluorescent emission of the biological molecules after being excited by a certain wavelength of electromagnetic radiation. However, relatively few cellular components are naturally fluorescent. In certain implementations, it may be desirable to visualize a certain tissue, structure, chemical process, or biological process that is not intrinsically fluorescent. In such an implementation, the body may be administered a dye or reagent that may include a molecule, protein, or quantum dot having fluorescent properties. The reagent or dye may then fluoresce after being excited by a certain wavelength of electromagnetic radiation. Different reagents or dyes may include different molecules, proteins, and/or quantum dots that will fluoresce at particular wavelengths of electromagnetic radiation. Thus, it may be necessary to excite the reagent or dye with a specialized band of electromagnetic radiation to achieve fluorescence and identify the desired tissue, structure, or process in the body. 
     Fluorescence imaging may provide valuable information in the medical field that may be used for diagnostic purposes and/or may be visualized in real-time during a medical procedure. Specialized reagents or dyes may be administered to a body to fluoresce certain tissues, structures, chemical processes, or biological processes. The fluorescence of the reagent or dye may highlight body structures such as blood vessels, nerves, particular organs, and so forth. Additionally, the fluorescence of the reagent or dye may highlight conditions or diseases such as cancerous cells or cells experiencing a certain biological or chemical process that may be associated with a condition or disease. The fluorescence imaging may be used in real-time by a medical practitioner or computer program for differentiating between, for example, cancerous and non-cancerous cells during a surgical tumor extraction. The fluorescence imaging may further be used as a non-destructive means for tracking and visualizing over time a condition in the body that would otherwise not be visible by the human eye or distinguishable in an RGB image. 
     The systems, methods, and devices for generating fluorescence imaging data may be used in coordination with reagents or dyes. Some reagents or dyes are known to attach to certain types of tissues and fluoresce at specific wavelengths of the electromagnetic spectrum. In an implementation, a reagent or dye is administered to a patient that is configured to fluoresce when activated by certain wavelengths of light. The endoscopic imaging system disclosed herein is used to excite and fluoresce the reagent or dye. The fluorescence of the reagent or dye is captured by the endoscopic imaging system to aid in the identification of tissues or structures in the body cavity. In an implementation, a patient is administered a plurality of reagents or dyes that are each configured to fluoresce at different wavelengths and/or provide an indication of different structures, tissues, chemical reactions, biological processes, and so forth. In such an implementation, the endoscopic imaging system emits each of the applicable wavelengths to fluoresce each of the applicable reagents or dyes. This may negate the need to perform individual imaging procedures for each of the plurality of reagents or dyes. 
     Imaging reagents can enhance imaging capabilities in pharmaceutical, medical, biotechnology, diagnostic, and medical procedure industries. Many imaging techniques such as X-ray, computer tomography (CT), ultrasound, magnetic resonance imaging (MRI), and nuclear medicine, mainly analyze anatomy and morphology and are unable to detect changes at the molecular level. Fluorescent reagents, dyes, and probes, including quantum dot nanoparticles and fluorescent proteins, assist medical imaging technologies by providing additional information about certain tissues, structures, chemical processes, and/or biological processes that are present within the imaging region. Imaging using fluorescent reagents enables cell tracking and/or the tracking of certain molecular biomarkers. Fluorescent reagents may be applied for imaging cancer, infection, inflammation, stem cell biology, and others. Numerous fluorescent reagents and dyes are being developed and applied for visualizing and tracking biological processes in a non-destructive manner. Such fluorescent reagents may be excited by a certain wavelength or band of wavelengths of electromagnetic radiation. Similarly, those fluorescent reagents may emit relaxation energy at a certain wavelength or band of wavelengths when fluorescing, and the emitted relaxation energy may be read by a sensor to determine the location and/or boundaries of the reagent or dye. 
     In an embodiment of the disclosure, an endoscopic imaging system pulses electromagnetic radiation for exciting an electron in a fluorescent reagent or dye. The endoscopic imaging system may pulse multiple different wavelengths of electromagnetic radiation for fluorescing multiple different reagents or dyes during a single imaging session. The endoscope includes an image sensor that is sensitive to the relaxation wavelength(s) of the one or more reagents or dyes. The imaging data generated by the image sensor can be used to identify a location and boundary of the one or more reagents or dyes. The endoscope system may further pulse electromagnetic radiation in red, green, and blue bands of visible light such that the fluorescence imaging can be overlaid on an RGB video stream. 
     Pulsed Imaging 
     Some implementations of the disclosure include aspects of a combined sensor and system design that allows for high definition imaging with reduced pixel counts in a controlled illumination environment. This is accomplished with frame-by-frame pulsing of a single-color wavelength and switching or alternating each frame between a single, different color wavelength using a controlled light source in conjunction with high frame capture rates and a specially designed corresponding monochromatic sensor. Additionally, electromagnetic radiation outside the visible light spectrum may be pulsed to enable the generation of a fluorescence image. The pixels may be color agnostic such that each pixel generates data for each pulse of electromagnetic radiation, including pulses for red, green, and blue visible light wavelengths along with other wavelengths used for fluorescence imaging. 
     A system of the disclosure is an endoscopic imaging system for use in a light deficient environment. The system includes an endoscope comprising an image sensor, wherein the image sensor is configured to sense reflected electromagnetic radiation for generating a plurality of exposure frames that can be combined to generate an RGB image frame with fluorescence data overlaid thereon. The system includes an emitter for emitting pulses of electromagnetic radiation. The system includes a controller (may alternatively be referred to as a “control circuit” in electronic communication with the image sensor and the emitter. The controller controls a duty cycle of the emitter in response to signals corresponding to a duty cycle of the emitter. The image sensor includes bidirectional pads that can send and receive information. The bidirectional pads of the image sensor operate in a frame period divided into three defined states, including a rolling readout state, a service line state, and a configuration state. The system includes an oscillator disposed in the controller and a frequency detector connected to the controller. The frequency detector controls a clock frequency of the image sensor in response to signals from the controller that correspond to the frequency of the oscillator. The system is such that clock signal data is transmitted from the bidirectional pads of the image sensor to the controller during the service line phase and the configuration phase. The system is such that exposure frames are synchronized without the use of an input clock or a data transmission clock. 
     For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed. 
     Before the structure, systems and methods for producing an image in a light deficient environment are disclosed and described, it is to be understood that this disclosure is not limited to the particular structures, configurations, process steps, and materials disclosed herein as such structures, configurations, process steps, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the disclosure will be limited only by the appended claims and equivalents thereof. 
     In describing and claiming the subject matter of the disclosure, the following terminology will be used in accordance with the definitions set out below. 
     It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. 
     As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps. 
     As used herein, the phrase “consisting of” and grammatical equivalents thereof exclude any element or step not specified in the claim. 
     As used herein, the phrase “consisting essentially of” and grammatical equivalents thereof limit the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic or characteristics of the claimed disclosure. 
     As used herein, the term “proximal” shall refer broadly to the concept of a portion nearest an origin. 
     As used herein, the term “distal” shall generally refer to the opposite of proximal, and thus to the concept of a portion farther from an origin, or a furthest portion, depending upon the context. 
     As used herein, color sensors or multi spectrum sensors are those sensors known to have a color filter array (CFA) thereon to filter the incoming electromagnetic radiation into its separate components. In the visual range of the electromagnetic spectrum, such a CFA may be built on a Bayer pattern or modification thereon to separate green, red and blue spectrum components of the light. 
     As used herein, monochromatic sensor refers to an unfiltered imaging sensor. Since the pixels are color agnostic, the effective spatial resolution is appreciably higher than for their color (typically Bayer-pattern filtered) counterparts in conventional single-sensor cameras. Monochromatic sensors may also have higher quantum efficiency because fewer incident photons are wasted between individual pixels. 
     As used herein, an emitter is a device that is capable of generating and emitting electromagnetic pulses. Various embodiments of emitters may be configured to emit pulses and have very specific frequencies or ranges of frequencies from within the entire electromagnetic spectrum. Pulses may comprise wavelengths from the visible and non-visible ranges. An emitter may be cycled on and off to produce a pulse or may produce a pulse with a shutter mechanism. An emitter may have variable power output levels or may be controlled with a secondary device such as an aperture or filter. An emitter may emit broad spectrum or full spectrum electromagnetic radiation that may produce pulses through color filtering or shuttering. An emitter may comprise a plurality of electromagnetic sources that act individually or in concert. 
     It should be noted that as used herein the term “light” is both a particle and a wavelength and is intended to denote electromagnetic radiation that is detectable by a pixel array  122  and may include wavelengths from the visible and non-visible spectrums of electromagnetic radiation. The term “partition” is used herein to mean a pre-determined range of wavelengths of the electromagnetic spectrum that is less than the entire spectrum, or in other words, wavelengths that make up some portion of the electromagnetic spectrum. As used herein, an emitter is a light source that may be controllable as to the portion of the electromagnetic spectrum that is emitted or that may operate as to the physics of its components, the intensity of the emissions, or the duration of the emission, or all the above. An emitter may emit light in any dithered, diffused, or collimated emission and may be controlled digitally or through analog methods or systems. As used herein, an electromagnetic emitter is a source of a burst of electromagnetic energy and includes light sources, such as lasers, LEDs, incandescent light, or any light source that can be digitally controlled. 
     Referring now to the figures,  FIG. 1  illustrates a schematic diagram of a system  100  for sequential pulsed imaging in a light deficient environment. The system  100  can be deployed to generate an RGB image with fluorescence imaging data overlaid on the RGB image. The system  100  includes an emitter  102  and a pixel array  122 . The emitter  102  pulses a partition of electromagnetic radiation in the light deficient environment  112  and the pixel array  122  senses instances of reflected electromagnetic radiation. The emitter  102  and the pixel array  122  work in sequence such that one or more pulses of a partition of electromagnetic radiation results in image data sensed by the pixel array  122 . 
     It should be noted that as used herein the term “light” is both a particle and a wavelength and is intended to denote electromagnetic radiation that is detectable by a pixel array  122  and may include wavelengths from the visible and non-visible spectrums of electromagnetic radiation. The term “partition” is used herein to mean a pre-determined range of wavelengths of the electromagnetic spectrum that is less than the entire spectrum, or in other words, wavelengths that make up some portion of the electromagnetic spectrum. As used herein, an emitter is a light source that may be controllable as to the portion of the electromagnetic spectrum that is emitted or that may operate as to the physics of its components, the intensity of the emissions, or the duration of the emission, or all the above. An emitter may emit light in any dithered, diffused, or collimated emission and may be controlled digitally or through analog methods or systems. As used herein, an electromagnetic emitter is a source of a burst of electromagnetic energy and includes light sources, such as lasers, LEDs, incandescent light, or any light source that can be digitally controlled. 
     A pixel array  122  of an image sensor may be paired with the emitter  102  electronically, such that the emitter  102  and the pixel array  122  are synced during operation for both receiving the emissions and for the adjustments made within the system. The emitter  102  may be tuned to emit electromagnetic radiation in the form of a laser, which may be pulsed to illuminate a light deficient environment  112 . The emitter  102  may pulse at an interval that corresponds to the operation and functionality of the pixel array  122 . The emitter  102  may pulse light in a plurality of electromagnetic partitions such that the pixel array receives electromagnetic energy and produces a dataset that corresponds in time with each specific electromagnetic partition. For example,  FIG. 1  illustrates an implementation wherein the emitter  102  emits four different partitions of electromagnetic radiation, including red  104 , green  106 , blue  108 , and a fluorescence excitation  110  wavelength. The fluorescence excitation  110  wavelength may include a plurality of different partitions of electromagnetic radiation that are selected to fluoresce a plurality of fluorescent reagents that are present within the light deficient environment  112 . The fluorescent excitation  110  wavelength may be selected to fluoresce a particular fluorescent reagent that is present in the light deficient environment  112 . 
     In an alternative embodiment not illustrated in  FIG. 1 , the pulsed emissions of light include a luminance (“Y”) emission, a red chrominance (“Cr”) emission, and a blue chrominance (“Cb”) emission in place of the pulsed red  104 , pulsed green  106 , and pulsed blue  108  emissions. In an embodiment, the controller or the emitter  102  modules the pulses of electromagnetic radiation to provide luminance and/or chrominance information according to color transformation coefficients that convert light energy from red, green, and blue light energy spaces to luminance, red chrominance, and blue chrominance light energy space. The pulsed emissions of light may further include modulated blue chrominance (“□Y+Cb”) pulses and/or modulated red chrominance (“□Y+Cr”) pulses. 
     The light deficient environment  112  includes structures, tissues, and other elements that reflect a combination of red  114 , green  116 , and/or blue  118  light. A structure that is perceived as being red  114  will reflect back pulsed red  104  light. The reflection off the red structure results in sensed red  105  by the pixel array  122  following the pulsed red  104  emission. The data sensed by the pixel array  122  results in a red exposure frame. A structure that is perceived as being green  116  will reflect back pulsed green  106  light. The reflection off the green structure results in sensed green  107  by the pixel array  122  following the pulsed green  106  emission. The data sensed by the pixel array  122  results in a green exposure frame. A structure that is perceived as being blue  118  will reflect back pulsed blue  108  light. The reflection off the blue structure results in sensed blue  109  by the pixel array  122  following the pulsed blue  108  emission. The data sensed by the pixel array  122  results in a blue exposure frame. 
     When a structure is a combination of colors, the structure will reflect back a combination of the pulsed red  104 , pulsed green  106 , and/or pulsed blue  108  emissions. For example, a structure that is perceived as being purple will reflect back light from the pulsed red  104  and pulsed blue  108  emissions. The resulting data sensed by the pixel array  122  will indicate that light was reflected in the same region following the pulsed red  104  and pulsed blue  108  emissions. When the resultant red exposure frame and blue exposure frames are combined to form the RGB image frame, the RGB image frame will indicate that the structure is purple. 
     In an embodiment where the light deficient environment  112  includes a fluorescent reagent or dye or includes one or more fluorescent structures, tissues, or other elements, the pulsing scheme may include the emission of a certain fluorescence excitation wavelength. The certain fluorescence excitation wavelength may be selected to fluoresce a known fluorescent reagent, dye, or other structure. The fluorescent structure will be sensitive to the fluorescence excitation wavelength and will emit a fluorescence relaxation wavelength. The fluorescence relaxation wavelength will be sensed by the pixel array  122  following the emission of the fluorescence excitation wavelength. The data sensed by the pixel array  122  results in a fluorescence exposure frame. The fluorescence exposure frame may be combined with multiple other exposure frames to form an image frame. The data in the fluorescence exposure frame may be overlaid on an RGB image frame that includes data from a red exposure frame, a green exposure frame, and a blue exposure frame. 
     In an embodiment where the light deficient environment  112  includes structures, tissues, or other materials that emit a spectral response to certain partitions of the electromagnetic spectrum, the pulsing scheme may include the emission of a hyperspectral partition of electromagnetic radiation for the purpose of eliciting the spectral response from the structures, tissues, or other materials present in the light deficient environment  112 . The spectral response includes the emission or reflection of certain wavelengths of electromagnetic radiation. The spectral response can be sensed by the pixel array  122  and result in a hyperspectral exposure frame. The hyperspectral exposure frame may be combined with multiple other exposure frames to form an image frame. The data in the hyperspectral exposure frame may be overlaid on an RGB image frame that includes data from a red exposure frame, a green exposure frame, and a blue exposure frame. 
     In an embodiment, the pulsing scheme includes the emission of a laser mapping or tool tracking pattern. The reflected electromagnetic radiation sensed by the pixel array  122  following the emission of the laser mapping or tool tracking pattern results in a laser mapping exposure frame. The data in the laser mapping exposure frame may be provided to a corresponding system to identify, for example, distances between tools present in the light deficient environment  112 , a three-dimensional surface topology of a scene in the light deficient environment  112 , distances, dimensions, or positions of structures or objects within the scene, and so forth. This data may be overlaid on an RGB image frame or otherwise provided to a user of the system. 
     The emitter  102  may be a laser emitter that is capable of emitting pulsed red  104  light for generating sensed red  105  data for identifying red  114  elements within the light deficient environment  112 . The emitter  102  is further capable of emitting pulsed green  106  light for generating sensed green  107  data for identifying green  116  elements within the light deficient environment. The emitter  102  is further capable of emitting pulsed blue  108  light for generating sensed blue  109  data for identifying blue  118  elements within the light deficient environment. The emitter  102  is further capable of emitting pulsed fluorescence excitation  110  wavelength(s) of electromagnetic radiation for identifying a fluorescent reagent  120  within the light deficient environment  112 . The fluorescent reagent  120  is identified by exciting the fluorescent reagent  120  with the pulsed fluorescence excitation  110  light and then sensing (by the pixel array  122 ) the fluorescence relaxation  111  wavelength for that particular fluorescent reagent  120 . The emitter  102  is capable of emitting the pulsed red  104 , pulsed green  106 , pulsed blue  108 , and pulsed fluorescence excitation  110  wavelengths in any desired sequence. 
     The pixel array  122  senses reflected electromagnetic radiation. Each of the sensed red  105 , the sensed green  107 , the sensed blue  109 , and the sensed fluorescence relaxation  111  data can be referred to as an “exposure frame.” Each exposure frame is assigned a specific color or wavelength partition, wherein the assignment is based on the timing of the pulsed color or wavelength partition from the emitter  102 . The exposure frame in combination with the assigned specific color or wavelength partition may be referred to as a dataset. Even though the pixels  122  are not color-dedicated, they can be assigned a color for any given dataset based on a priori information about the emitter. 
     For example, during operation, after pulsed red  104  light is pulsed in the light deficient environment  112 , the pixel array  122  senses reflected electromagnetic radiation. The reflected electromagnetic radiation results in an exposure frame, and the exposure frame is catalogued as sensed red  105  data because it corresponds in time with the pulsed red  104  light. The exposure frame in combination with an indication that it corresponds in time with the pulsed red  104  light is the “dataset.” This is repeated for each partition of electromagnetic radiation emitted by the emitter  102 . The data created by the pixel array  122  includes the sensed red  105  exposure frame identifying red  114  components in the light deficient environment and corresponding in time with the pulsed red  104  light. The data further includes the sensed green  107  exposure frame identifying green  116  components in the light deficient environment and corresponding in time with the pulsed green  106  light. The data further includes the sensed blue  109  exposure frame identifying blue  118  components in the light deficient environment and corresponding in time with the pulsed blue  108  light. The data further includes the sensed fluorescence relaxation  111  exposure frame identifying the fluorescent reagent  120  and corresponding in time with the pulsed fluorescence excitation  110  wavelength(s) of light. 
     In one embodiment, three datasets representing RED, GREEN and BLUE electromagnetic pulses are combined to form a single image frame. Thus, the information in a red exposure frame, a green exposure frame, and a blue exposure frame are combined to form a single RGB image frame. One or more additional datasets representing other wavelength partitions may be overlaid on the single RGB image frame. The one or more additional datasets may represent, for example, fluorescence imaging responsive to the pulsed excitation  110  wavelength between 770 nm and 790 nm and between 795 nm and 815 nm. 
     It will be appreciated that the disclosure is not limited to any particular color combination or any particular electromagnetic partition, and that any color combination or any electromagnetic partition may be used in place of RED, GREEN and BLUE, such as Cyan, Magenta and Yellow; Ultraviolet; infrared; any combination of the foregoing, or any other color combination, including all visible and non-visible wavelengths, without departing from the scope of the disclosure. In the figure, the light deficient environment  112  to be imaged includes red  114 , green  116 , and blue  118  portions, and further includes a fluorescent reagent  120 . As illustrated in the figure, the reflected light from the electromagnetic pulses only contains the data for the portion of the object having the specific color that corresponds to the pulsed color partition. Those separate color (or color interval) datasets can then be used to reconstruct the image by combining the datasets at  126 . The information in each of the multiple exposure frames (i.e., the multiple datasets) may be combined by a controller  124 , a control unit, a camera control unit, the image sensor, an image signal processing pipeline, or some other computing resource that is configurable to process the multiple exposure frames and combine the datasets at  126 . The datasets may be combined to generate the single image frame within the endoscope unit itself or offsite by some other processing resource. 
       FIG. 2  is a system  200  for providing illumination to a light deficient environment, such as for endoscopic imaging. The system  200  may be used in combination with any of the systems, methods, or devices disclosed herein. The system  200  includes an emitter  202 , a controller  204 , a jumper waveguide  206 , a waveguide connector  208 , a lumen waveguide  210 , a lumen  212 , and an image sensor  214  with accompanying optical components (such as a lens). The emitter  202  (may be generically referred to as a “light source”) generates light that travels through the jumper waveguide  206  and the lumen waveguide  210  to illuminate a scene at a distal end of the lumen  212 . The emitter  202  may be used to emit any wavelength of electromagnetic energy including visible wavelengths, infrared, ultraviolet, hyperspectral, fluorescence excitation, laser mapping pulsing schemes, or other wavelengths. The lumen  212  may be inserted into a patient&#39;s body for imaging, such as during a procedure or examination. The light is output as illustrated by dashed lines  216 . A scene illuminated by the light may be captured using the image sensor  214  and displayed for a doctor or some other medical personnel. The controller  204  may provide control signals to the emitter  202  to control when illumination is provided to a scene. In one embodiment, the emitter  202  and controller  204  are located within a camera control unit (CCU) or external console to which an endoscope is connected. If the image sensor  214  includes a CMOS sensor, light may be periodically provided to the scene in a series of illumination pulses between readout periods of the image sensor  214  during what is known as a blanking period. Thus, the light may be pulsed in a controlled manner to avoid overlapping into readout periods of the image pixels in a pixel array of the image sensor  214 . 
     In one embodiment, the lumen waveguide  210  includes one or more optical fibers. The optical fibers may be made of a low-cost material, such as plastic to allow for disposal of the lumen waveguide  210  and/or other portions of an endoscope. In one embodiment, the lumen waveguide  210  is a single glass fiber having a diameter of 500 microns. The jumper waveguide  206  may be permanently attached to the emitter  202 . For example, a jumper waveguide  206  may receive light from an emitter within the emitter  202  and provide that light to the lumen waveguide  210  at the location of the connector  208 . In one embodiment, the jumper waveguide  106  includes one or more glass fibers. The jumper waveguide may include any other type of waveguide for guiding light to the lumen waveguide  210 . The connector  208  may selectively couple the jumper waveguide  206  to the lumen waveguide  210  and allow light within the jumper waveguide  206  to pass to the lumen waveguide  210 . In one embodiment, the lumen waveguide  210  is directly coupled to a light source without any intervening jumper waveguide  206 . 
     The image sensor  214  includes a pixel array. In an embodiment, the image sensor  214  includes two or more pixel arrays for generating a three-dimensional image. The image sensor  214  may constitute two more image sensors that each have an independent pixel array and can operate independent of one another. The pixel array of the image sensor  214  includes active pixels and optical black (“OB”) or optically blind pixels. The active pixels may be clear “color agnostic” pixels that are capable of sensing imaging data for any wavelength of electromagnetic radiation. The optical black pixels are read during a blanking period of the pixel array when the pixel array is “reset” or calibrated. In an embodiment, light is pulsed during the blanking period of the pixel array when the optical black pixels are being read. After the optical black pixels have been read, the active pixels are read during a readout period of the pixel array. The active pixels may be charged by the electromagnetic radiation that is pulsed during the blanking period such that the active pixels are ready to be read by the image sensor during the readout period of the pixel array. 
       FIG. 2A  is a schematic diagram of complementary system hardware such as a special purpose or general-purpose computer. Implementations within the scope of the present disclosure may also include physical and other non-transitory computer readable media for carrying or storing computer executable instructions and/or data structures. Such computer readable media can be any available media that can be accessed by a general purpose or special purpose computer system. Computer readable media that stores computer executable instructions are computer storage media (devices). Computer readable media that carry computer executable instructions are transmission media. Thus, by way of example, and not limitation, implementations of the disclosure can comprise at least two distinctly different kinds of computer readable media: computer storage media (devices) and transmission media. 
     Computer storage media (devices) includes RAM, ROM, EEPROM, CD-ROM, solid state drives (“SSDs”) (e.g., based on RAM), Flash memory, phase-change memory (“PCM”), other types of memory, other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store desired program code means in the form of computer executable instructions or data structures and which can be accessed by a general purpose or special purpose computer. 
     A “network” is defined as one or more data links that enable the transport of electronic data between computer systems and/or modules and/or other electronic devices. In an implementation, a sensor and camera control unit may be networked to communicate with each other, and other components, connected over the network to which they are connected. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a computer, the computer properly views the connection as a transmission medium. Transmissions media can include a network and/or data links, which can be used to carry desired program code means in the form of computer executable instructions or data structures and which can be accessed by a general purpose or special purpose computer. Combinations of the above should also be included within the scope of computer readable media. 
     Further, upon reaching various computer system components, program code means in the form of computer executable instructions or data structures that can be transferred automatically from transmission media to computer storage media (devices) (or vice versa). For example, computer executable instructions or data structures received over a network or data link can be buffered in RAM within a network interface module (e.g., a “NIC”), and then eventually transferred to computer system RAM and/or to less volatile computer storage media (devices) at a computer system. RAM can also include solid state drives (SSDs or PCIx based real time memory tiered storage, such as FusionIO). Thus, it should be understood that computer storage media (devices) can be included in computer system components that also (or even primarily) utilize transmission media. 
     Computer executable instructions comprise, for example, instructions and data which, when executed by one or more processors, cause a general-purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, or even source code. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the described features or acts described above. Rather, the described features and acts are disclosed as example forms of implementing the claims. 
     Those skilled in the art will appreciate that the disclosure may be practiced in network computing environments with many types of computer system configurations, including, personal computers, desktop computers, laptop computers, message processors, control units, camera control units, hand-held devices, hand pieces, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, mobile telephones, PDAs, tablets, pagers, routers, switches, various storage devices, and the like. It should be noted that any of the above-mentioned computing devices may be provided by or located within a brick and mortar location. The disclosure may also be practiced in distributed system environments where local and remote computer systems, which are linked (either by hardwired data links, wireless data links, or by a combination of hardwired and wireless data links) through a network, both perform tasks. In a distributed system environment, program modules may be located in both local and remote memory storage devices. 
     Further, where appropriate, functions described herein can be performed in one or more of: hardware, software, firmware, digital components, or analog components. For example, one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs) can be programmed to carry out one or more of the systems and procedures described herein. Certain terms are used throughout the following description and Claims to refer to particular system components. As one skilled in the art will appreciate, components may be referred to by different names. This document does not intend to distinguish between components that differ in name, but not function. 
       FIG. 2A  is a block diagram illustrating an example computing device  250 . Computing device  250  may be used to perform various procedures, such as those discussed herein. Computing device  250  can function as a server, a client, or any other computing entity. Computing device  250  can perform various monitoring functions as discussed herein, and can execute one or more application programs, such as the application programs described herein. Computing device  250  can be any of a wide variety of computing devices, such as a desktop computer, a notebook computer, a server computer, a handheld computer, camera control unit, tablet computer and the like. 
     Computing device  250  includes one or more processor(s)  252 , one or more memory device(s)  254 , one or more interface(s)  256 , one or more mass storage device(s)  258 , one or more Input/Output (I/O) device(s)  260 , and a display device  280  all of which are coupled to a bus  262 . Processor(s)  252  include one or more processors or controllers that execute instructions stored in memory device(s)  254  and/or mass storage device(s)  258 . Processor(s)  252  may also include various types of computer readable media, such as cache memory. 
     Memory device(s)  254  include various computer readable media, such as volatile memory (e.g., random access memory (RAM)  264 ) and/or nonvolatile memory (e.g., read-only memory (ROM)  266 ). Memory device(s)  254  may also include rewritable ROM, such as Flash memory. 
     Mass storage device(s)  258  include various computer readable media, such as magnetic tapes, magnetic disks, optical disks, solid-state memory (e.g., Flash memory), and so forth. As shown in  FIG. 2 , a particular mass storage device is a hard disk drive  274 . Various drives may also be included in mass storage device(s)  258  to enable reading from and/or writing to the various computer readable media. Mass storage device(s)  258  include removable media  276  and/or non-removable media. 
     I/O device(s)  260  include various devices that allow data and/or other information to be input to or retrieved from computing device  250 . Example I/O device(s)  260  include digital imaging devices, electromagnetic sensors and emitters, cursor control devices, keyboards, keypads, microphones, monitors or other display devices, speakers, printers, network interface cards, modems, lenses, CCDs or other image capture devices, and the like. 
     Display device  280  includes any type of device capable of displaying information to one or more users of computing device  250 . Examples of display device  280  include a monitor, display terminal, video projection device, and the like. 
     Interface(s)  256  include various interfaces that allow computing device  250  to interact with other systems, devices, or computing environments. Example interface(s)  256  may include any number of different network interfaces  270 , such as interfaces to local area networks (LANs), wide area networks (WANs), wireless networks, and the Internet. Other interface(s) include user interface  268  and peripheral device interface  272 . The interface(s)  256  may also include one or more user interface elements  268 . The interface(s)  256  may also include one or more peripheral interfaces such as interfaces for printers, pointing devices (mice, track pad, etc.), keyboards, and the like. 
     Bus  262  allows processor(s)  252 , memory device(s)  254 , interface(s)  256 , mass storage device(s)  258 , and I/O device(s)  260  to communicate with one another, as well as other devices or components coupled to bus  262 . Bus  262  represents one or more of several types of bus structures, such as a system bus, PCI bus, IEEE 1394 bus, USB bus, and so forth. 
     For purposes of illustration, programs and other executable program components are shown herein as discrete blocks, although it is understood that such programs and components may reside at various times in different storage components of computing device  250  and are executed by processor(s)  252 . Alternatively, the systems and procedures described herein can be implemented in hardware, or a combination of hardware, software, and/or firmware. For example, one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs) can be programmed to carry out one or more of the systems and procedures described herein. 
       FIG. 3A  illustrates the operational cycles of a sensor used in rolling readout mode or during the sensor readout  300 . The frame readout period may start at and may be represented by vertical line  310 . The readout period  302  is represented by the diagonal or slanted line. The sensor may be read out on a row by row basis, the top of the downwards slanted edge being the sensor top row  312  and the bottom of the downwards slanted edge being the sensor bottom row  314 . The time between the last row readout and the next readout period may be called the blanking period  316 . It should be noted that some of the sensor pixel rows might be covered with a light shield (e.g., a metal coating or any other substantially black layer of another material type). These covered pixel rows may be referred to as optical black rows  318  and  320 . Optical black rows  318  and  320  may be used as input for correction algorithms. As shown in  FIG. 3A , these optical black rows  318  and  320  may be located on the top of the pixel array or at the bottom of the pixel array or at the top and the bottom of the pixel array. 
       FIG. 3B  illustrates a process of controlling the amount of electromagnetic radiation, e.g., light, that is exposed to a pixel, thereby integrated or accumulated by the pixel. It will be appreciated that photons are elementary particles of electromagnetic radiation. Photons are integrated, absorbed, or accumulated by each pixel and converted into an electrical charge or current. An electronic shutter or rolling shutter (shown by dashed line  322 ) may be used to start the integration time by resetting the pixel. The light will then integrate until the next readout period. The position of the electronic shutter  322  can be moved between two readout periods  302  to control the pixel saturation for a given amount of light. It should be noted that this technique allows for a constant integration time between two different lines but introduces a delay when moving from top to bottom rows. 
       FIG. 3C  illustrates the case where the electronic shutter  322  has been removed. In this configuration, the integration of the incoming light may start during the readout period  302  and may end at the next readout period  302 , which also defines the start of the next integration. 
       FIG. 3D  shows a configuration without an electronic shutter  322 , but with a controlled and pulsed light  330  during the blanking period  316 . This ensures that all rows see the same light issued from the same light pulse  330 . In other words, each row will start its integration in a dark environment, which may be at the optical black back row  320  of read out frame (m) for a maximum light pulse width, and will then receive a light strobe and will end its integration in a dark environment, which may be at the optical black front row  318  of the next succeeding read out frame (m+1) for a maximum light pulse width. In the  FIG. 3D  example, the image generated from the light pulse will be solely available during frame (m+1) readout without any interference with frames (m) and (m+2). It should be noted that the condition to have a light pulse to be read out only in one frame and not interfere with neighboring frames is to have the given light pulse firing during the blanking period  316 . Because the optical black rows  318 ,  320  are insensitive to light, the optical black back rows  320  time of frame (m) and the optical black front rows  318  time of frame (m+1) can be added to the blanking period  316  to determine the maximum range of the firing time of the light pulse  330 . 
     As illustrated in the  FIG. 3A , a sensor may be cycled many times to receive data for each pulsed color or wavelength (e.g., Red, Green, Blue, or other wavelength on the electromagnetic spectrum). Each cycle may be timed. In an embodiment, the cycles may be timed to operate within an interval of 16.67 ms. In another embodiment, the cycles may be timed to operate within an interval of 8.3 ms. It will be appreciated that other timing intervals are contemplated by the disclosure and are intended to fall within the scope of this disclosure. 
       FIG. 4A  graphically illustrates the operation of an embodiment of an electromagnetic emitter. An emitter may be timed to correspond with the cycles of a sensor, such that electromagnetic radiation is emitted within the sensor operation cycle and/or during a portion of the sensor operation cycle.  FIG. 4A  illustrates Pulse 1 at  402 , Pulse 2 at  404 , and Pulse 3 at  406 . In an embodiment, the emitter may pulse during the readout period  302  of the sensor operation cycle. In an embodiment, the emitter may pulse during the blanking period  316  of the sensor operation cycle. In an embodiment, the emitter may pulse for a duration that is during portions of two or more sensor operational cycles. In an embodiment, the emitter may begin a pulse during the blanking period  316 , or during the optical black portion  320  of the readout period  302 , and end the pulse during the readout period  302 , or during the optical black portion  318  of the readout period  302  of the next succeeding cycle. It will be understood that any combination of the above is intended to fall within the scope of this disclosure as long as the pulse of the emitter and the cycle of the sensor correspond. 
       FIG. 4B  graphically represents varying the duration and magnitude of the emitted electromagnetic pulse (e.g., Pulse 1 at  412 , Pulse 2 at  414 , and Pulse 3 at  416 ) to control exposure. An emitter having a fixed output magnitude may be pulsed during any of the cycles noted above in relation to  FIGS. 3D and 4A  for an interval to provide the needed electromagnetic energy to the pixel array. An emitter having a fixed output magnitude may be pulsed at a longer interval of time, thereby providing more electromagnetic energy to the pixels or the emitter may be pulsed at a shorter interval of time, thereby providing less electromagnetic energy. Whether a longer or shorter interval time is needed depends upon the operational conditions. 
     In contrast to adjusting the interval of time the emitter pulses a fixed output magnitude, the magnitude of the emission itself may be increased to provide more electromagnetic energy to the pixels. Similarly, decreasing the magnitude of the pulse provides less electromagnetic energy to the pixels. It should be noted that an embodiment of the system may have the ability to adjust both magnitude and duration concurrently, if desired. Additionally, the sensor may be adjusted to increase its sensitivity and duration as desired for optimal image quality.  FIG. 4B  illustrates varying the magnitude and duration of the pulses. In the illustration, Pulse 1 at  412  has a higher magnitude or intensity than either Pulse 2 at  414  or Pulse 3 at  416 . Additionally, Pulse 1 at  412  has a shorter duration than Pulse 2 at  414  or Pulse 3 at  416 , such that the electromagnetic energy provided by the pulse is illustrated by the area under the pulse shown in the illustration. In the illustration, Pulse 2 at  414  has a relatively low magnitude or intensity and a longer duration when compared to either Pulse 1 at  412  or Pulse 3 at  416 . Finally, in the illustration, Pulse 3 at  416  has an intermediate magnitude or intensity and duration, when compared to Pulse 1 at  412  and Pulse 2 at  414 . 
       FIG. 5  is a graphical representation of an embodiment of the disclosure combining the operational cycles, the electromagnetic emitter, and the emitted electromagnetic pulses of  FIGS. 3A-3D and 4A  to demonstrate the imaging system during operation in accordance with the principles and teachings of the disclosure. As can be seen in the figure, the electromagnetic emitter pulses the emissions primarily during the blanking period  316  of the image sensor such that the pixels will be charged and ready to read during the readout period  302  of the image sensor cycle. The dashed lines in  FIG. 5  represent the pulses of electromagnetic radiation (from  FIG. 4A ). The pulses of electromagnetic radiation are primarily emitted during the blanking period  316  of the image sensor but may overlap with the readout period  302  of the image sensor. 
     An exposure frame includes the data read by the pixel array of the image sensor during a readout period  302 . The exposure frame may be combined with an indication of what type of pulse was emitted by the emitter prior to the readout period  302 . The combination of the exposure frame and the indication of the pulse type may be referred to as a dataset. Multiple exposure frames may be combined to generate a black-and-white or RGB color image. Additionally, hyperspectral, fluorescence, and/or laser mapping imaging data may be overlaid on a black-and-white or RGB image. 
     In an embodiment, an exposure frame is the data sensed by the pixel array during the readout period  302  that occurs subsequent to a blanking period  316 . The emission of electromagnetic radiation is emitted during the blanking period  316 . In an embodiment, a portion of the emission of electromagnetic radiation overlaps the readout period  302 . The blanking period  316  occurs when optical black pixels of the pixel array are being read and the readout period  302  occurs when active pixels of the pixel array are being read. The blanking period  316  may overlap the readout period  302 . 
       FIGS. 6A and 6B  illustrate processes for recording an image frame. Multiple image frames may be strung together to generate a video stream. A single image frame may include data from multiple exposure frames, wherein an exposure frame is the data sensed by a pixel array subsequent to an emission of electromagnetic radiation.  FIG. 6A  illustrates a traditional process that is typically implemented with a color image sensor having a color filter array (CFA) for filtering out certain wavelengths of light per pixel.  FIG. 6B  is a process that is disclosed herein and can be implemented with a monochromatic “color agnostic” image sensor that is receptive to all wavelengths of electromagnetic radiation. 
     The process illustrated in  FIG. 6A  occurs from time t(0) to time t(1). The process begins with a white light emission  602  and sensing white light  604 . The image is processed and displayed at  606  based on the sensing at  604 . 
     The process illustrated in  FIG. 6B  occurs from time t(0) to time t(1). The process begins with an emission of green light  612  and sensing reflected electromagnetic radiation  614  subsequent to the emission of green light  612 . The process continues with an emission of red light  616  and sensing reflected electromagnetic radiation  618  subsequent to the emission of red light  616 . The process continues with an emission of blue light  620  and sensing reflected electromagnetic radiation  622  subsequent to the emission of blue light  620 . The process continues with one or more emissions of a fluorescence excitation wavelengths  624  and sensing reflected electromagnetic energy  626  subsequent to each of the one or more emissions of fluorescence excitation wavelengths of electromagnetic radiation  624 . The image is processed and displayed at  628  based on each of the sensed reflected electromagnetic energy instances  614 ,  618 ,  622 , and  626 . 
     The process illustrated in  FIG. 6B  provides a higher resolution image and provides a means for generating an RGB image that further includes fluorescence imaging data. When partitioned spectrums of light are used, (as in  FIG. 6B ) a sensor can be made sensitive to all wavelengths of electromagnetic energy. In the process illustrated in  FIG. 6B , the monochromatic pixel array is instructed that it is sensing electromagnetic energy from a predetermined partition of the full spectrum of electromagnetic energy in each cycle. Therefore, to form an image the sensor need only be cycled with a plurality of differing partitions from within the full spectrum of light. The final image is assembled based on the multiple cycles. Because the image from each color partition frame cycle has a higher resolution (compared with a CFA pixel array), the resultant image created when the partitioned light frames are combined also has a higher resolution. In other words, because each and every pixel within the array (instead of, at most, every second pixel in a sensor with a CFA) is sensing the magnitudes of energy for a given pulse and a given scene, just fractions of time apart, a higher resolution image is created for each scene. 
     As can be seen graphically in the embodiments illustrated in  FIGS. 6A and 6B  between times t(0) and t(1), the sensor for the partitioned spectrum system in  FIG. 6B  has cycled at least four times for every one of the full spectrum system in  FIG. 6A . In an embodiment, a display device (LCD panel) operates at 50-60 frames per second. In such an embodiment, the partitioned light system in  FIG. 6B  may operate at 200-240 frames per second to maintain the continuity and smoothness of the displayed video. In other embodiments, there may be different capture and display frame rates. Furthermore, the average capture rate could be any multiple of the display rate. 
     In an embodiment, it may be desired that not all partitions be represented equally within the system frame rate. In other words, not all light sources have to be pulsed with the same regularity so as to emphasize and de-emphasize aspects of the recorded scene as desired by the users. It should also be understood that non-visible and visible partitions of the electromagnetic spectrum may be pulsed together within a system with their respective data value being stitched into the video output as desired for display to a user. 
     An embodiment may comprise a pulse cycle pattern as follows: 
     i. Green pulse; 
     ii. Red pulse; 
     iii. Blue pulse; 
     iv. Green pulse; 
     v. Red pulse; 
     vi. Blue pulse; 
     vii. Fluorescence excitation pulse; 
     viii. (Repeat) 
     An embodiment may comprise a pulse cycle pattern as follows: 
     i. Luminance pulse; 
     ii. Red chrominance pulse; 
     iii. Luminance pulse; 
     iv. Blue Chrominance pulse; 
     v. Fluorescence excitation pulse; 
     vi. (Repeat) 
     An embodiment may comprise a pulse cycle pattern as follows: 
     i. Luminance pulse; 
     ii. Red chrominance pulse; 
     iii. Luminance pulse; 
     iv. Blue Chrominance pulse; 
     v. Luminance pulse; 
     vi. Red chrominance pulse; 
     vii. Luminance pulse; 
     viii. Blue Chrominance pulse; 
     ix. Fluorescence excitation pulse; 
     x. (Repeat) 
     As can be seen in the example, a fluorescence excitation partition may be pulsed at a rate differing from the rates of the other partition pulses. This may be done to emphasize a certain aspect of the scene, with the fluorescence imaging data simply being overlaid with the other data in the video output to make the desired emphasis. It should be noted that the addition of a fluorescence partition on top of the RED, GREEN, and BLUE partitions does not necessarily require the serialized system to operate at four times the rate of a full spectrum non-serial system because every partition does not have to be represented equally in the pulse pattern. As seen in the embodiment, the addition of a partition pulse that is represented less in a pulse pattern (fluorescence excitation in the above example), would result in an increase of less than 20% of the cycling speed of the sensor to accommodate the irregular partition sampling. 
     In various embodiments, the pulse cycle pattern may further include any of the following wavelengths in any suitable order. Such wavelengths may be particularly suited for exciting a fluorescent reagent to generate fluorescence imaging data by sensing the relaxation emission of the fluorescent reagent based on a fluorescent reagent relaxation emission: 
     i. 770±20 nm; 
     ii. 770±10 nm; 
     iii. 770±5 nm; 
     iv. 790±20 nm; 
     v. 790±10 nm; 
     vi. 790±5 nm; 
     vii. 795±20 nm; 
     viii. 795±10 nm; 
     ix. 795±5 nm; 
     x. 815±20 nm; 
     xi. 815±10 nm; 
     xii. 815±5 nm; 
     xiii. 770 nm to 790 nm; and/or 
     xiv. 795 nm to 815 nm. 
     The partition cycles may be divided so as to accommodate or approximate various imaging and video standards. In an embodiment, the partition cycles comprise pulses of electromagnetic energy in the Red, Green, and Blue spectrum as follows as illustrated best in FIGS.  7 A- 7 D. The timing relationship between the emission of pulses of electromagnetic radiation by the emitter, and the readout of the pixel array is further illustrated in  FIGS. 7A-7D . 
     In  FIG. 7A , the different light intensities have been achieved by modulating the light pulse width or duration within the working range shown by the vertical grey dashed lines.  FIG. 7A  illustrates the general timing relationships within a four-frame cycle, between pulsed mixtures of three wavelengths and the readout cycle of the pixel array of the image sensor. In an embodiment, there are three monochromatic pulsed light sources under the control of the controller. Periodic sequences of monochromatic red, monochromatic green, and monochromatic blue exposure frames are captured, e.g. with an R-G-B-G pulsing pattern and assembled into an sRGB image frame by the image signal processor chain. 
     In  FIG. 7B , the different light intensities have been achieved by modulating the light power or the power of the electromagnetic emitter, which may be a laser or LED emitter, but keeping the pulse width or duration constant. 
       FIG. 7C  shows the case where both the light power and the light pulse width are being modulated, leading to greater flexibility. The partition cycles may use Cyan Magenta Yellow (CMY), infrared, ultraviolet, hyperspectral, and fluorescence using a non-visible pulse source mixed with visible pulse sources and any other color space required to produce an image or approximate a desired video standard that is currently known or yet to be developed. It should also be understood that a system may be able to switch between the color spaces on the fly to provide the desired image output quality. 
     In an embodiment using color spaces Green-Blue-Green-Red (as seen in  FIG. 7D ) it may be desirous to pulse the luminance components more often than the chrominance components because users are generally more sensitive to light magnitude differences than to light color differences. This principle can be exploited using a monochromatic image sensor as illustrated in  FIG. 7D . In  FIG. 7D , green, which contains the most luminance information, may be pulsed more often or with more intensity in a (G-B-G-R-G-B-G-R . . . ) scheme to obtain the luminance data. Such a configuration would create a video stream that has perceptively more detail, without creating and transmitting unperceivable data. 
     In an embodiment, all three sources of light are pulsed in unison with light energies that are modulated to provide pure luminance information in the same exposure frame. The light energies may be modulated according to color transformation coefficients that convert from RGB color space to YCbCr color space. It should be appreciated that the color transformation may be implemented according to any suitable standard such as the ITU-R BT.709 HD standard, the ITU-R BT.601 standard, the ITU-R BT.2020 standard, or any other suitable standard or formula. The conversion may be performed according to the ITU-R BT.709 HD standard as follows: 
     
       
         
           
             
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     In addition to the modulation of luminance information, a full color image further requires the red chrominance and blue chrominance components. However, the algorithm applied for the luminance component cannot be directly applied for chrominance componence because the algorithm is signed as reflected in the fact that some of the RGB coefficients are negative. In an embodiment, a degree of luminance is added so that all of the final pulse energies are a positive value. As long as the color fusion process in the image signal processor is aware of the composition of the chrominance exposure frames, they can be decoded by subtracting the appropriate amount of luminance from a neighboring frame. The pulse energy proportions are given by: 
     
       
         
           
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     If the λ factor is equal to 0.552, the red and green components are cancelled. In the case, the blue chrominance information can be provided with pure blue light. Similarly, if the δ factor is equal to 0.650, the blue and green components are cancelled, and the red chrominance information can be provided with pure red light. This embodiment is a convenient approximation for digital frame reconstruction. 
     In an embodiment where white balance is performed in the illumination domain, then the modulation is imposed in addition to the white balance modulation. 
     In an embodiment, duplicating the pulse of a weaker partition may be used to produce an output that has been adjusted for the weaker pulse. For example, blue laser light is considered weak relative to the sensitivity of silicon-based pixels and is difficult to produce in comparison to the red or green light, and therefore may be pulsed more often during a frame cycle to compensate for the weakness of the light. These additional pulses may be done serially over time or by using multiple lasers that simultaneously pulse to produce the desired compensation effect. It should be noted that by pulsing during a blanking period (time during which the sensor is not reading out the pixel array), the sensor is insensitive to differences/mismatches between lasers of the same kind and simply accumulates the light for the desired output. In another embodiment, the maximum light pulse range may be different from frame to frame. This is shown in  FIG. 7E , where the light pulses are different from frame to frame. The sensor may be built to be able to program different blanking periods with a repeating pattern of two or three or four or n frames. 
     In  FIG. 7E , four different light pulses are illustrated, and Pulse 1 may repeat for example after Pulse 4 and may have a pattern of four frames with different blanking periods. This technique can be used to place the most powerful partition on the smallest blanking period and therefore allow the weakest partition to have wider pulse on one of the next frames without the need of increasing the readout speed. The reconstructed frame can still have a regular pattern from frame to frame as it is constituted of many pulsed frames. 
       FIG. 8  illustrates a system  800  for controlling integral energy of a laser pulse in an environment for hyperspectral, fluorescence, and/or laser mapping imaging. In traditional systems known in the art, a laser consistently delivers a specified light level. These traditional systems do not have a means to counteract the issues that arise during normal use. Such issues can be caused by warmup requirements, changes in temperature, manufacturing defects, and so forth. These issues can degrade image quality due to flickering light and image artifacting. These issues can be ameliorated by the systems disclosed herein, including the system  800  illustrated in  FIG. 8 . 
     The system  800  illustrated in  FIG. 8  represents one example embodiment, and numerous other embodiments may be implemented without departing from the scope of the disclosure. The system  800  includes a laser module  802 , an optical fiber  804  connected to the laser module  802 , and an electromagnetic sensor such as a photo diode  806  connected to the optical fiber  804 . The laser module  802  may generically be referred to as an “emitter” herein, and the term emitter as used herein may include a plurality of laser modules. The laser modules  802  and the photo diodes  806  are each in communication with a controller  808 . The controller  808  receives light sensing readings from the photo diode  806  and alters the wavelength and/or power emitted by the laser module  802  in response to the real-time light readings received from the photo diode  806 . 
     In the example implementation illustrated in  FIG. 8 , the system  800  includes two separate laser modules  802 , two separate optical fibers  804 , and two separate photo diodes  806 . It should be appreciated that the system  800  may include any number of laser modules  802 , photo diodes  806 , and optical fibers  804  without departing from the scope of the disclosure. 
     In an embodiment, the system  800  is implemented to control the duration and/or intensity of light that is pulsed to illuminate a light deficient environment. The laser controller  808  is in communication with each of the multiple laser modules  802  and is configured to control the duration and/or intensity of light emitted by the laser modules  802 . The photo diodes  806  are configured to measure the duration and/or intensity of light emitted by the laser modules  802  by measuring the light traveling the optical fiber  804 . The laser controller  808  works to limit the output light energy of the laser modules  802  within an accepted tolerance. 
     The laser module  802  may include one or more lasers or other light emitters capable of emitting a wide range of wavelengths of electromagnetic radiation. The wavelengths and power of the emitted electromagnetic radiation may be selected to meet application need. In an embodiment, the laser module  802  comprises a plurality of lasers arranged in a linear array as illustrated in  FIG. 9 , or some other geometric pattern. The laser module  802  may typically include ten or more individual laser diodes to ensure precise light output. 
     The optical fiber  804  may include a single optical fiber or a bunch of optical fibers. The optical fiber  804  is connected directly to the laser module  802  and may be connected directly to the optical output of a laser within the laser module  802 . The optical fiber  804  may range from 0.05 mm to 0.5 mm in some embodiments. 
     The photo diode  806  is an electromagnetic sensor. In alternative embodiments, different types of electromagnetic sensors may be used. The photo diode  806  senses light levels traveling the optical fiber  804  by reading the energy transmission on individual optical fibers  804  or bunches of optical fibers  804 . In an embodiment, the photo diode  806  measures the light level information by sensing the voltage or current traveling the optical fiber  804 , and in such an embodiment, the photo diode  806  may be directly attached to the optical fiber  804 . The photo diode  806  sends the light level information to the controller  808 . In some embodiments, the photo diode  806  converts the raw data into usable light level metrics, and in other embodiment, the controller  808  converts the raw data into usable light level metrics. 
     In an embodiment, the total amount of light in a scene is calculated based on the measurements of one, two, or N photo diodes  806 . The one, two, or N photo diodes  806  can be used with an amplifier to compare light output measurements against a desired reference voltage or current level. This circuit may provide direct feedback to the bias current or voltage of the laser module  802  to ensure the desired output light level is met. 
     In an embodiment, a photo diode  806  or another electromagnetic sensor is placed internally on each laser module  802 . A portion of the electromagnetic radiation emitted by the laser module  802  can be directed at the photo diode  806  or other sensing element capable of transforming light into a voltage or current level to measure the light output. 
     The controller  808  receives light level information from the photo diode  806  in real-time. The controller  808  calculates the amount light being emitted by the laser module  802  based on the energy transmission readings received from the photo diode  806 . These energy transmission readings serve as independent feedback to the controller  808  from the photo diode  806 . The controller  808  can compare this independent feedback with a register or variable value that indicates a predetermined desired light level. The register or variable value may be retrieved from computer memory. 
     In an embodiment, the controller  808  calculates the light level and integrates the light energy in less than 1 ms. The controller  808  implements the automatic exposure control (AEC) system to adjust the wavelength and/or duration of light emitted by the laser module  802  in response to the current light readings received from the photo diode  806 . The AEC may include a PID (proportional, integral, and derivative) control algorithm, and the PID control algorithm may be implemented by the controller  808 . 
     In an embodiment, each pulse of electromagnetic radiation is adjusted proportionally based on an error measurement. The error measurement is calculated by the controller  808  by comparing a desired exposure level against a measured exposure level. The measured exposure level is calculated based on the mean pixel value of all pixels within a pixel array of the image sensor. The ASC may request adjustments be made to the duration and/or intensity of light emitted by the laser modules  802  to ensure the desired exposure level is achieved. 
     The controller  808  ensures that once a light energy level is achieved, the laser module  802  is shut-off or disabled to preserve desired image quality. 
     In an embodiment, the controller  808  is a camera control unit (CCU) or includes a CCU. The controller  808  may include a microcontroller, a field-programmable gate array (FPGA) board, an application-specific integrated circuit (ASIC), hardware, software, image signal processor (ISP), support circuitry, and so forth. The controller  808  controls the enabling and disabling of the laser modules  802 . The controller  808  further controls the power level and light level of the laser modules  802 . The controller  808  receives information from the photo diodes  806  and alters the light energy emitted by the laser modules  802  based on the information received from the photo diodes  806 . 
       FIG. 9  illustrates a system  900  for emitting electromagnetic radiation. The system  900  can be implemented in connection with a digital imaging system for use in a light deficient environment as discussed herein. The system  900  can be deployed to control the output of electromagnetic radiation for illuminating a scene. 
     The system  900  includes a laser bundle  902  comprising a plurality of laser units. The laser bundle  902  may generally be referred to as an “emitter” herein, and the term emitter as used herein may include a plurality of laser bundles. The laser bundle  902  is connected to an optical fiber  904 . The system includes an electromagnetic sensor  906  such as a photo diode or other light sensing element. The electromagnetic sensor  906  senses the output of electromagnetic radiation by at least one laser unit of the laser bundle  902 . The system  900  includes an operational amplifier (OPA)  908  circuit that is electrically connected to the electromagnetic sensor  906 . The operational amplifier  908  may apply feedback, or in an alternative embodiment, a light frequency doubler may apply feedback. 
     The electromagnetic sensor  906  senses the output of at least one laser unit of the laser bundle  902 . Based on the value of this measurement, the overall output of the laser bundle  902  is controlled and adjusted in real-time to ensure proper exposure of a scene. In an embodiment, the light output is controlled to a precision level of 0.01% to 10%. 
       FIG. 10  illustrates an implementation of a system  1000  for laser illumination. The system  1000  includes a plurality of laser bundles for emitting a plurality of wavelengths of electromagnetic energy. The system  1000  can be implemented for generating a color RGB image frame based on separate pulses of red electromagnetic radiation, green electromagnetic radiation, and blue electromagnetic radiation that result in a red exposure frame, a green exposure frame, a blue exposure frame, respectively. The system  1000  can further be implemented for generating a fluorescence exposure frame to be overlaid on the RGB image frame. 
     In the example implementation illustrated in  FIG. 10 , the system  1000  includes a red laser bundle  1010 , a green laser bundle  1012 , a blue laser bundle  1014 , and a fluorescence laser bundle  1016 . The laser bundles illustrated in  FIG. 10  are exemplary only, and the system may include alternative laser bundles for different applications. For example, the system  1000  may include a hyperspectral laser bundle, a fluorescence laser bundle  1016 , and/or a laser mapping laser bundle in addition to the red laser bundle  1010 , the green laser bundle  1012 , and the blue laser bundle  1014 . 
     The fluorescence laser bundle  1016  may include a plurality of distinct laser bundles for emitting different fluorescence excitation wavelengths of electromagnetic radiation for fluorescing different reagents within the scene. The laser bundles  1010 ,  1012 ,  1014 ,  1016  may generally be referred to as an “emitter” herein, and the term “emitter” may include any suitable number of laser bundles as needed. In an embodiment, the fluorescence laser bundle  1016  includes two separate fluorescence laser bundles  1016 , wherein one is configured for emitting electromagnetic radiation having a wavelength from about 770 nm to about 790 nm and one is configured for emitting electromagnetic radiation having a wavelength from about 795 nm to about 815 nm. 
     If the system  1000  includes a hyperspectral laser bundle, the system  1000  may include multiple independent hyperspectral laser bundles for emitting different partitions of the electromagnetic spectrum. For example, the system  1000  may include a first hyperspectral laser bundle for emitting electromagnetic radiation having a wavelength from about 513 nm to about 545 nm. The system  1000  may further include a second hyperspectral laser bundle for emitting electromagnetic radiation having a wavelength from about 565 nm to about 585 nm. The system  1000  may further include a second hyperspectral laser bundle for emitting electromagnetic radiation having a wavelength from about 900 nm to about 1000 nm. 
     If the system  1000  includes a laser mapping laser bundle, the system  1000  may include a plurality of independent laser mapping laser bundles for emitting electromagnetic radiation to measure distances, dimensions, and three-dimensional topographical maps of the scene. The system  1000  may include independent laser mapping systems for performing laser mapping measurements through different means, for example through tool tracking, laser tracking, three-dimensional topographical mapping, and so forth. In an embodiment, the laser mapping laser bundle includes multiple laser bundles attached to, for example, tools within the environment such as surgical tools, along with the endoscopic device itself, and other tools within the environment. These multiple laser mapping laser bundles can work together to track the location of tools in the environment relative to other objects, such as tissues, organs, and other critical structures. 
     The laser bundles  1010 ,  1012 ,  1014 ,  1016  may generally be referred to as an “emitter” herein, and the term “emitter” may include any suitable number of laser bundles as needed. In an embodiment, the emitter includes a red laser bundle, a green laser bundle, a blue laser bundle, a hyperspectral laser bundle, a fluorescence laser bundle, and a specialty laser bundle. The emitter may include any suitable number and combination of laser bundles depending on the application. 
     It should be appreciated that the system  1000  may include any number of laser bundles, and that each of the laser bundles may be configured for emitting different wavelengths of electromagnetic radiation. As discussed herein, the system  1000  may include an “emitter,” and the emitter includes a plurality of laser bundles, such as laser bundles for red, green, and blue wavelengths, along with laser bundles for hyperspectral, fluorescence, and/or laser mapping imaging. In one embodiment, the system  1000  includes laser bundles for emitting red, green, and blue wavelengths of electromagnetic radiation, and further includes laser bundles for emitting hyperspectral wavelengths of electromagnetic radiation, for emitting a fluorescence excitation wavelength for fluorescing a reagent, and for emitting a laser mapping pattern. 
     Each of the laser bundles includes a plurality of laser units for emitting pulses of electromagnetic radiation. The system  1000  includes dedicated electromagnetic sensors  1006  for measuring electromagnetic radiation emitted by each of the laser bundles. As illustrated in  FIG. 10 , the system  1000  includes separate electromagnetic sensors  1006  for each of the red laser bundle  1010 , the green laser bundle  1012 , the blue laser bundle  1014 , and the fluorescence laser bundle  1016 . The electromagnetic sensor  1006  may be connected to one or more laser units of the laser bundle  1010 ,  1012 ,  1014 ,  1016 . The electromagnetic sensor  1006  senses the output of electromagnetic radiation by measuring the current or voltage emitted by the at least one laser unit. 
     Light is transmitted from the laser bundles by way of an optical fiber  1004 . Each of the laser bundles  1010 ,  1012 ,  1014 ,  1016  includes an optical fiber  1004 . The optical fibers  1004  are combined to include a single exiting optical fiber  1018 . 
       FIG. 11  is a schematic diagram illustrating a system  1100  for providing illumination to a light deficient environment, such as for endoscopic imaging. The system  1100  may be used in combination with any of the systems, methods, or devices disclosed herein. The system  1100  includes a light source  1102 , a controller  1104 , a jumper waveguide  1106 , a waveguide connector  1108 , a lumen waveguide  1110 , a lumen  1112 , and an image sensor  1114  with accompanying optical components (such as a lens). The light source  1102  (may be referred to as an “emitter” in some embodiments) generates light that travels through the jumper waveguide  1106  and the lumen waveguide  1110  to illuminate a scene at a distal end of the lumen  1112 . The light source  1100  may be used to emit any wavelength of electromagnetic energy including visible wavelengths, infrared, ultraviolet, or other wavelengths. The lumen  1112  may be inserted into a patient&#39;s body for imaging, such as during a procedure or examination. The light is output as illustrated by dashed lines  1116 . A scene illuminated by the light may be captured using the image sensor  1114  and displayed for a doctor or some other medical personnel. The controller  1104  may provide control signals to the light source  1102  to control when illumination is provided to a scene. In one embodiment, the light source  1102  and controller  1104  are located within a camera control unit (CCU) or external console to which an endoscope is connected. If the image sensor  1114  includes a CMOS sensor, light may be periodically provided to the scene in a series of illumination pulses between readout periods of the image sensor  1114  during what is known as a blanking period. Thus, the light may be pulsed in a controlled manner to avoid overlapping into readout periods of the image pixels in a pixel array of the image sensor  1114 . 
     In one embodiment, the lumen waveguide  1110  includes a one or a plurality of optical fibers. The optical fibers may be made of a low-cost material, such as plastic to allow for disposal of the lumen waveguide  1110  and/or other portions of an endoscope. In one embodiment, a single glass fiber having a diameter of 500 microns may be used. The jumper waveguide  1106  may be permanently attached to the light source  1102 . For example, a jumper waveguide  1106  may receive light from an emitter within the light source  1102  and provide that light to the lumen waveguide  1110  at the location of the connector  1108 . In one embodiment, the jumper waveguide  106  may include one or more glass fibers. The jumper waveguide may include any other type of waveguide for guiding light to the lumen waveguide  1110 . The connector  1108  may selectively couple the jumper waveguide  1106  to the lumen waveguide  1110  and allow light within the jumper waveguide  1106  to pass to the lumen waveguide  1110 . In one embodiment, the lumen waveguide  1110  may be directly coupled to a light source without any intervening jumper waveguide  1106 . 
       FIG. 11  illustrates a digital imaging system  1100  that utilizes minimal pad interconnects to reduce the size of the image sensor for use with an endoscopic device within a light deficient environment. The digital imaging system  1100  illustrated in  FIG. 11  includes an endoscopic device  1102  for use in a light deficient environment. The endoscopic device  1102  includes an endoscope  1104 , an endoscope housing  1106 , a controller  1108 , an electronic communication  1120 , a light source  1110 , a light cable  1126 , a display  1112 , and an imaging device  1114 . The electronic communication  1120  may include an electronic cable or other form of wired or wireless communication. The light cable  1126  may be a fiber optic cable in some embodiments. The imaging device  1114  may be an image sensor such as a CMOS image sensor with a pixel array. 
     In the example illustrated in  FIG. 11 , to facilitate discussion, the endoscopic device  1104 , endoscope housing  1106 , controller  1108 , light source  1110 , display  1112 , and imaging device  1114  are shown individually with respect to one another. However, it should be appreciated and understood that this is not to be interpreted as limiting, and any one or more of these components can be integrated and/or connected in any suitable manner. It will be appreciated that the image sensor senses reflected electromagnetic radiation with the pixel array. The pixel array generates an exposure frame comprising image data in response to a pulse of electromagnetic radiation. A processor  1124  may detect image textures and edges within the image frame and may further enhance textures and edges within the image frame. The processor  1124 , whether in the housing  1106  or at the controller  1108 , may also retrieve from memory properties pertaining to the pixel technology and the applied sensor gain to assess an expectation for the magnitude of noise within an image frame created by the image sensor and using the noise expectation to control the edge enhancement application. A stream of image frames may be created by sequentially combining a plurality of image frames, wherein each image frame comprises data from multiple exposure frames. 
     It will be appreciated that traditional rod-lens endoscopes, used for laparoscopy, arthroscopy, urology, gynecology and ENT (ear-nose-throat) procedures, are expensive to manufacture owing to their complex optical composition. The incident image information is transported in the optical domain all the way along the length of the endoscope. Typically, these conventional endoscopes are optically coupled to a handpiece unit that includes the image sensor. This type of conventional endoscope is delicate and prone to damage during handling, use, and sterilization. The necessary repair and sterilization processes add further expense to each procedure for which they are utilized. 
     The endoscope  1102  may be improved by placing the image sensing device at the distal end of the endoscope. In such an embodiment, the optical transport assembly may be replaced by a simple plastic lens stack. Such an endoscope may be so inexpensive that it may make more financial sense to manufacture them for single use only, to be subsequently disposed of or recycled, because this negates the repair and sterilization processes. 
     However, when the image sensor is located at the distal end of the endoscope  1102 , the image sensor must be very small. The distal end of the endoscope  1102  is space constrained in the x and y dimensions. One method of decreasing the size of the image sensor is to reduce the number of bond pads within the image sensor chip. Each bond pad occupies significant physical space on an image sensor chip. Each bond pad is used to provide power or input/output signals to and from the image sensor chip. Therefore, in striving for minimal area, it is desirable to reduce the number of bond pads. This disclosure describes systems and methods for reducing pad count by combining digital input and output functionality into the same bidirectional pads. During image transmission, these bidirectional pads act as differential outputs. In an embodiment, during a defined portion of each exposure frame, the bidirectional pads switch direction to receive commands. In such an embodiment, the camera control electronics are synchronized such that the commands are issued to the image sensor bidirectional pads at a certain time when the bidirectional pads are configured to receive commands. 
     Further to this, in the context of an endoscope system, the simplicity and manufacturability can be enhanced by customizing the image sensor to receive commands and information from the endoscope handpiece. The information may be incorporated into the output data issued by the image sensor. This reduces the overall conductor count from endoscope to camera system. Such information sources may include user instigated button events or measurements of the angle of rotation of the endoscope with respect to the handpiece. Angular measurements are necessitated by certain embodiments of endoscopes having their image sensors placed at the distal end. 
     CMOS image sensors typically incorporate two different power supplies, necessitating three pads: VDD1, VDD2 &amp; GND. The higher of the two voltages is used predominantly for the purpose of biasing the pixel array. Occasionally, the higher of the two voltages is also used to power the input and output circuits. The lower of the two voltages is typically used to power the peripheral analog circuitry and the digital portion of the image sensor, where applicable. 
     In an embodiment, the pad count is reduced by using only a single external power supply. This may be accomplished by using, for example, internal DC (direct current) to DC converters or regulators to provide for multiple internal supplies. Further, the pad count may be reduced by supplying only a single power level. The second power level may then be derived on-chip. This embodiment may be effective in removing a power circuit, such as a regulator, from the camera system. 
       FIG. 12  is a schematic diagram of a pattern reconstruction process. The example pattern illustrated in  FIG. 12  includes Red, Green, Blue, and Fluorescence Excitation pulses of light that each last a duration of T1. In various embodiments, the pulses of light may be of the same duration or of differing durations. The Red, Green, Blue, and Fluorescence exposure frames are combined to generate an RGB image with fluorescence data overlaid thereon. A single image frame comprising a red exposure frame, a green exposure frame, a blue exposure frame, and a fluorescence exposure frame requires a time period of 4*T1 to be generated. The time durations shown in  FIG. 12  are illustrative only and may vary for different implementations. In other embodiments, different pulsing schemes may be employed. For example, embodiments may be based on the timing of each color component or frame (T1) and the reconstructed frame having a period twice that of the incoming color frame (2×T1). Different frames within the sequence may have different frame periods and the average capture rate could be any multiple of the final frame rate. 
     In an embodiment, the dynamic range of the system is increased by varying the pixel sensitivities of pixels within the pixel array of the image sensor. Some pixels may sense reflected electromagnetic radiation at a first sensitivity level, other pixels may sense reflected electromagnetic radiation at a second sensitivity level, and so forth. The different pixel sensitivities may be combined to increase the dynamic range provided by the pixel configuration of the image sensor. In an embodiment, adjacent pixels are set at different sensitivities such that each cycle includes data produced by pixels that are more and less sensitive with respect to each other. The dynamic range is increased when a plurality of sensitivities are recorded in a single cycle of the pixel array. In an embodiment, wide dynamic range can be achieved by having multiple global TX, each TX firing only on a different set of pixels. For example, in global mode, a global TX1 signal is firing a set  1  of pixels, a global TX2 signal is firing a set  2  of pixel, a global TXn signal is firing a set n of pixels, and so forth. 
       FIGS. 13A-13C  each illustrate a light source  1300  having a plurality of emitters. The emitters include a first emitter  1302 , a second emitter  1304 , and a third emitter  1306 . Additional emitters may be included, as discussed further below. The emitters  1302 ,  1304 , and  1306  may include one or more laser emitters that emit light having different wavelengths. For example, the first emitter  1302  may emit a wavelength that is consistent with a blue laser, the second emitter  1304  may emit a wavelength that is consistent with a green laser, and the third emitter  1306  may emit a wavelength that is consistent with a red laser. For example, the first emitter  1302  may include one or more blue lasers, the second emitter  1304  may include one or more green lasers, and the third emitter  1306  may include one or more red lasers. The emitters  1302 ,  1304 ,  1306  emit laser beams toward a collection region  1308 , which may be the location of a waveguide, lens, or other optical component for collecting and/or providing light to a waveguide, such as the jumper waveguide  206  or lumen waveguide  210  of  FIG. 2 . 
     In an implementation, the emitters  1302 ,  1304 , and  1306  emit hyperspectral wavelengths of electromagnetic radiation. Certain hyperspectral wavelengths may pierce through tissue and enable a medical practitioner to “see through” tissues in the foreground to identify chemical processes, structures, compounds, biological processes, and so forth that are located behind the tissues in the foreground. The hyperspectral wavelengths may be specifically selected to identify a specific disease, tissue condition, biological process, chemical process, type of tissue, and so forth that is known to have a certain spectral response. 
     In an implementation where a patient has been administered a reagent or dye to aid in the identification of certain tissues, structures, chemical reactions, biological processes, and so forth, the emitters  1302 ,  1304 , and  1306  may emit wavelength(s) for fluorescing the reagents or dyes. Such wavelength(s) may be determined based on the reagents or dyes administered to the patient. In such an embodiment, the emitters may need to be highly precise for emitting desired wavelength(s) to fluoresce or activate certain reagents or dyes. 
     In an implementation, the emitters  1302 ,  1304 , and  1306  emit a laser mapping pattern for mapping a topology of a scene and/or for calculating dimensions and distances between objects in the scene. In an embodiment, the endoscopic imaging system is used in conjunction with multiple tools such as scalpels, retractors, forceps, and so forth. In such an embodiment, each of the emitters  1302 ,  1304 , and  1306  may emit a laser mapping pattern such that a laser mapping pattern is projected on to each tool individually. In such an embodiment, the laser mapping data for each of the tools can be analyzed to identify distances between the tools and other objects in the scene. 
     In the embodiment of  FIG. 13B , the emitters  1302 ,  1304 ,  1306  each deliver laser light to the collection region  1308  at different angles. The variation in angle can lead to variations where electromagnetic energy is located in an output waveguide. For example, if the light passes immediately into a fiber bundle (glass or plastic) at the collection region  1308 , the varying angles may cause different amounts of light to enter different fibers. For example, the angle may result in intensity variations across the collection region  1308 . Furthermore, light from the different emitters may not be homogenously mixed so some fibers may receive different amounts of light of different colors. Variation in the color or intensity of light in different fibers can lead to non-optimal illumination of a scene. For example, variations in delivered light or light intensities may result at the scene and captured images. 
     In one embodiment, an intervening optical element may be placed between a fiber bundle and the emitters  1302 ,  1304 ,  1306  to mix the different colors (wavelengths) of light before entry into the fibers or other waveguide. Example intervening optical elements include a diffuser, mixing rod, one or more lenses, or other optical components that mix the light so that a given fiber receive a same amount of each color (wavelength). For example, each fiber in the fiber bundle may have a same color. This mixing may lead to the same color in each fiber but may, in some embodiments, still result in different total brightness delivered to different fibers. In one embodiment, the intervening optical element may also spread out or even out the light over the collection region so that each fiber carries the same total amount of light (e.g., the light may be spread out in a top hat profile). A diffuser or mixing rod may lead to loss of light. 
     Although the collection region  1308  is represented as a physical component in  FIG. 13A , the collection region  1308  may simply be a region where light from the emitters  1302 ,  1304 , and  1306  is delivered. In some cases, the collection region  1308  may include an optical component such as a diffuser, mixing rod, lens, or any other intervening optical component between the emitters  1302 ,  1304 ,  1306  and an output waveguide. 
       FIG. 13C  illustrates an embodiment of a light source  1300  with emitters  1302 ,  1304 ,  1306  that provide light to the collection region  1308  at the same or substantially same angle. The light is provided at an angle substantially perpendicular to the collection region  1308 . The light source  1300  includes a plurality of dichroic mirrors including a first dichroic mirror  1310 , a second dichroic mirror  1312 , and a third dichroic mirror  1314 . The dichroic mirrors  1310 ,  1312 ,  1314  include mirrors that reflect a first wavelength of light but transmit (or are transparent to) a second wavelength of light. For example, the third dichroic mirror  1314  may reflect blue laser light provided by the third emitter, while being transparent to the red and green light provided by the first emitter  1302  and the second emitter  1304 , respectively. The second dichroic mirror  1312  may be transparent to red light from the first emitter  1302 , but reflective to green light from the second emitter  1304 . If other colors or wavelengths are included dichroic mirrors may be selected to reflect light corresponding to at least one emitter and be transparent to other emitters. For example, the third dichroic mirror  1314  reflect the light form the third emitter  1306  but is to emitters “behind” it, such as the first emitter  1302  and the second emitter  1304 . In embodiments where tens or hundreds of emitters are present, each dichroic mirror may be reflective to a corresponding emitter and emitters in front of it while being transparent to emitters behind it. This may allow for tens or hundreds of emitters to emit electromagnetic energy to the collection region  1308  at a substantially same angle. 
     Because the dichroic mirrors allow other wavelengths to transmit or pass through, each of the wavelengths may arrive at the collection region  1308  from a same angle and/or with the same center or focal point. Providing light from the same angle and/or same focal/center point can significantly improve reception and color mixing at the collection region  1308 . For example, a specific fiber may receive the different colors in the same proportions they were transmitted/reflected by the emitters  1302 ,  1304 ,  1306  and mirrors  1310 ,  1312 ,  1314 . Light mixing may be significantly improved at the collection region compared to the embodiment of  FIG. 13B . In one embodiment, any optical components discussed herein may be used at the collection region  1308  to collect light prior to providing it to a fiber or fiber bundle. 
       FIG. 13C  illustrates an embodiment of a light source  1300  with emitters  1302 ,  1304 ,  1306  that also provide light to the collection region  1308  at the same or substantially same angle. However, the light incident on the collection region  1308  is offset from being perpendicular. Angle  1316  indicates the angle offset from perpendicular. In one embodiment, the laser emitters  1302 ,  1304 ,  1306  may have cross sectional intensity profiles that are Gaussian. As discussed previously, improved distribution of light energy between fibers may be accomplished by creating a more flat or top-hat shaped intensity profile. In one embodiment, as the angle  1316  is increased, the intensity across the collection region  1308  approaches a top hat profile. For example, a top-hat profile may be approximated even with a non-flat output beam by increasing the angle  1316  until the profile is sufficiently flat. The top hat profile may also be accomplished using one or more lenses, diffusers, mixing rods, or any other intervening optical component between the emitters  1302 ,  1304 ,  1306  and an output waveguide, fiber, or fiber optic bundle. 
       FIG. 14  is a schematic diagram illustrating a single optical fiber  1402  outputting via a diffuser  1404  at an output. In one embodiment, the optical fiber  1402  has a diameter of 500 microns, a numerical aperture of 0.65, and emits a light cone  1406  of about 70 or 80 degrees without a diffuser  1404 . With the diffuser  1404 , the light cone  1406  may have an angle of about 110 or 120 degrees. The light cone  1406  may be a majority of where all light goes and is evenly distributed. The diffuser  1404  may allow for more even distribution of electromagnetic energy of a scene observed by an image sensor. 
     In one embodiment, the lumen waveguide  210  includes a single plastic or glass optical fiber of about 500 microns. The plastic fiber may be low cost, but the width may allow the fiber to carry a sufficient amount of light to a scene, with coupling, diffusion, or other losses. For example, smaller fibers may not be able to carry as much light or power as a larger fiber. The lumen waveguide  210  may include a single or a plurality of optical fibers. The lumen waveguide  210  may receive light directly from the light source or via a jumper waveguide. A diffuser may be used to broaden the light output  206  for a desired field of view of the image sensor  214  or other optical components. 
     Although three emitters are shown in  FIGS. 13A-13C , emitters numbering from one into the hundreds or more may be used in some embodiments. The emitters may have different wavelengths or spectrums of light that they emit, and which may be used to contiguously cover a desired portion of the electromagnetic spectrum (e.g., the visible spectrum as well as infrared and ultraviolet spectrums). The emitters may be configured to emit visible light such as red light, green light, and blue light, and may further be configured to emit hyperspectral emissions of electromagnetic radiation, fluorescence excitation wavelengths for fluorescing a reagent, and/or laser mapping patterns for calculating parameters and distances between objects in a scene. 
       FIG. 15  illustrates a portion of the electromagnetic spectrum  1500  divided into twenty different sub-spectrums. The number of sub-spectrums is illustrative only. In at least one embodiment, the spectrum  1500  may be divided into hundreds of sub-spectrums, each with a small waveband. The spectrum may extend from the infrared spectrum  1502 , through the visible spectrum  1504 , and into the ultraviolet spectrum  1506 . The sub-spectrums each have a waveband  1508  that covers a portion of the spectrum  1500 . Each waveband may be defined by an upper wavelength and a lower wavelength. 
     Hyperspectral imaging incudes imaging information from across the electromagnetic spectrum  1500 . A hyperspectral pulse of electromagnetic radiation may include a plurality of sub-pulses spanning one or more portions of the electromagnetic spectrum  1500  or the entirety of the electromagnetic spectrum  1500 . A hyperspectral pulse of electromagnetic radiation may include a single partition of wavelengths of electromagnetic radiation. A resulting hyperspectral exposure frame includes information sensed by the pixel array subsequent to a hyperspectral pulse of electromagnetic radiation. Therefore, a hyperspectral exposure frame may include data for any suitable partition of the electromagnetic spectrum  1500  and may include multiple exposure frames for multiple partitions of the electromagnetic spectrum  1500 . In an embodiment, a hyperspectral exposure frame includes multiple hyperspectral exposure frames such that the combined hyperspectral exposure frame comprises data for the entirety of the electromagnetic spectrum  1500 . 
     In one embodiment, at least one emitter (such as a laser emitter) is included in a light source (such as the light sources  202 ,  1300 ) for each sub-spectrum to provide complete and contiguous coverage of the whole spectrum  1500 . For example, a light source for providing coverage of the illustrated sub-spectrums may include at least 20 different emitters, at least one for each sub-spectrum. In one embodiment, each emitter covers a spectrum covering 40 nanometers. For example, one emitter may emit light within a waveband from 500 nm to 540 nm while another emitter may emit light within a waveband from 540 nm to 580 nm. In another embodiment, emitters may cover other sizes of wavebands, depending on the types of emitters available or the imaging needs. For example, a plurality of emitters may include a first emitter that covers a waveband from 500 to 540 nm, a second emitter that covers a waveband from 540 nm to 640 nm, and a third emitter that covers a waveband from 640 nm to 650 nm. Each emitter may cover a different slice of the electromagnetic spectrum ranging from far infrared, mid infrared, near infrared, visible light, near ultraviolet and/or extreme ultraviolet. In some cases, a plurality of emitters of the same type or wavelength may be included to provide sufficient output power for imaging. The number of emitters needed for a specific waveband may depend on the sensitivity of a monochrome sensor to the waveband and/or the power output capability of emitters in that waveband. 
     The waveband widths and coverage provided by the emitters may be selected to provide any desired combination of spectrums. For example, contiguous coverage of a spectrum using very small waveband widths (e.g., 10 nm or less) may allow for highly selective hyperspectral and/or fluorescence imaging. The waveband widths may allow for selectively emitting the excitation wavelength(s) for one or more particular fluorescent reagents. Additionally, the waveband widths may allow for selectively emitting certain partitions of hyperspectral electromagnetic radiation for identifying specific structures, chemical processes, tissues, biological processes, and so forth. Because the wavelengths come from emitters which can be selectively activated, extreme flexibility for fluorescing one or more specific fluorescent reagents during an examination can be achieved. Additionally, extreme flexibility for identifying one or more objects or processes by way of hyperspectral imaging can be achieved. Thus, much more fluorescence and/or hyperspectral information may be achieved in less time and within a single examination which would have required multiple examinations, delays because of the administration of dyes or stains, or the like. 
       FIG. 16  is a schematic diagram illustrating a timing diagram  1600  for emission and readout for generating an image. The solid line represents readout (peaks  1602 ) and blanking periods (valleys) for capturing a series of exposure frames  1604 - 1614 . The series of exposure frames  1604 - 1614  may include a repeating series of exposure frames which may be used for generating laser mapping, hyperspectral, and/or fluorescence data that may be overlaid on an RGB video stream. In an embodiment, a single image frame comprises information from multiple exposure frames, wherein one exposure frame includes red image data, another exposure frame includes green image data, and another exposure frame includes blue image data. Additionally, the single image frame may include one or more of hyperspectral image data, fluorescence image data, and laser mapping data. The multiple exposure frames are combined to produce the single image frame. The single image frame is an RGB image with hyperspectral imaging data. The series of exposure frames include a first exposure frame  1604 , a second exposure frame  1606 , a third exposure frame  1608 , a fourth exposure frame  1610 , a fifth exposure frame  1612 , and an Nth exposure frame  1626 . 
     Additionally, the hyperspectral image data, the fluorescence image data, and the laser mapping data can be used in combination to identify critical tissues or structures and further to measure the dimensions of those critical tissues or structures. For example, the hyperspectral image data may be provided to a corresponding system to identify certain critical structures in a body such as a nerve, ureter, blood vessel, cancerous tissue, and so forth. The location and identification of the critical structures may be received from the corresponding system and may further be used to generate topology of the critical structures using the laser mapping data. For example, a corresponding system determines the location of a cancerous tumor based on hyperspectral imaging data. Because the location of the cancerous tumor is known based on the hyperspectral imaging data, the topology and distances of the cancerous tumor may then be calculated based on laser mapping data. This example may also apply when a cancerous tumor or other structure is identified based on fluorescence imaging data. 
     In one embodiment, each exposure frame is generated based on at least one pulse of electromagnetic energy. The pulse of electromagnetic energy is reflected and detected by an image sensor and then read out in a subsequent readout ( 1602 ). Thus, each blanking period and readout results in an exposure frame for a specific spectrum of electromagnetic energy. For example, the first exposure frame  1604  may be generated based on a spectrum of a first one or more pulses  1616 , a second exposure frame  1606  may be generated based on a spectrum of a second one or more pulses  1618 , a third exposure frame  1608  may be generated based on a spectrum of a third one or more pulses  1620 , a fourth exposure frame  1610  may be generated based on a spectrum of a fourth one or more pulses  1622 , a fifth exposure frame  1612  may be generated based on a spectrum of a fifth one or more pulses  2424 , and an Nth exposure frame  1626  may be generated based on a spectrum of an Nth one or more pulses  1626 . 
     The pulses  1616 - 1626  may include energy from a single emitter or from a combination of two or more emitters. For example, the spectrum included in a single readout period or within the plurality of exposure frames  1604 - 1614  may be selected for a desired examination or detection of a specific tissue or condition. According to one embodiment, one or more pulses may include visible spectrum light for generating an RGB or black and white image while one or more additional pulses are emitted to sense a spectral response to a hyperspectral wavelength of electromagnetic radiation. For example, pulse  1616  may include red light, pulse  1618  may include blue light, and pulse  1620  may include green light while the remaining pulses  1622 - 1626  may include wavelengths and spectrums for detecting a specific tissue type, fluorescing a reagent, and/or mapping the topology of the scene. As a further example, pulses for a single readout period include a spectrum generated from multiple different emitters (e.g., different slices of the electromagnetic spectrum) that can be used to detect a specific tissue type. For example, if the combination of wavelengths results in a pixel having a value exceeding or falling below a threshold, that pixel may be classified as corresponding to a specific type of tissue. Each frame may be used to further narrow the type of tissue that is present at that pixel (e.g., and each pixel in the image) to provide a very specific classification of the tissue and/or a state of the tissue (diseased/healthy) based on a spectral response of the tissue and/or whether a fluorescent reagent is present at the tissue. 
     The plurality of frames  1604 - 1614  is shown having varying lengths in readout periods and pulses having different lengths or intensities. The blanking period, pulse length or intensity, or the like may be selected based on the sensitivity of a monochromatic sensor to the specific wavelength, the power output capability of the emitter(s), and/or the carrying capacity of the waveguide. 
     In one embodiment, dual image sensors may be used to obtain three-dimensional images or video feeds. A three-dimensional examination may allow for improved understanding of a three-dimensional structure of the examined region as well as a mapping of the different tissue or material types within the region. 
     In an example implementation, a fluorescent reagent is provided to a patient, and the fluorescent reagent is configured to adhere to cancerous cells. The fluorescent reagent is known to fluoresce when radiated with a specific partition of electromagnetic radiation. The relaxation wavelength of the fluorescent reagent is also known. In the example implementation, the patient is imaged with an endoscopic imaging system as discussed herein. The endoscopic imaging system pulses partitions of red, green, and blue wavelengths of light to generate an RGB video stream of the interior of the patient&#39;s body. Additionally, the endoscopic imaging system pulses the excitation wavelength of electromagnetic radiation for the fluorescent reagent that was administered to the patient. In the example, the patient has cancerous cells and the fluorescent reagent has adhered to the cancerous cells. When the endoscopic imaging system pulses the excitation wavelength for the fluorescent reagent, the fluorescent reagent will fluoresce and emit a relaxation wavelength. If the cancerous cells are present in the scene being imaged by the endoscopic imaging system, then the fluorescent reagent will also be present in the scene and will emit its relaxation wavelength after fluorescing due to the emission of the excitation wavelength. The endoscopic imaging system senses the relaxation wavelength of the fluorescent reagent and thereby senses the presence of the fluorescent reagent in the scene. Because the fluorescent reagent is known to adhere to cancerous cells, the presence of the fluorescent reagent further indicates the presence of cancerous cells within the scene. The endoscopic imaging system thereby identifies the location of cancerous cells within the scene. The endoscopic imaging system may further emit a laser mapping pulsing scheme for generating a topology of the scene and calculating dimensions for objects within the scene. The location of the cancerous cells (as identified by the fluorescence imaging data) may be combined with the topology and dimensions information calculated based on the laser mapping data. Therefore, the precise location, size, dimensions, and topology of the cancerous cells may be identified. This information may be provided to a medical practitioner to aid in excising the cancerous cells. Additionally, this information may be provided to a robotic surgical system to enable the surgical system to excise the cancerous cells. 
     In a further example implementation, a patient is imaged with an endoscopic imaging system to identify quantitative diagnostic information about the patient&#39;s tissue pathology. In the example, the patient is suspected or known to suffer from a disease that can be tracked with hyperspectral imaging to observe the progression of the disease in the patient&#39;s tissue. The endoscopic imaging system pulses partitions of red, green, and blue wavelengths of light to generate an RGB video stream of the interior of the patient&#39;s body. Additionally, the endoscopic imaging system pulses one or more hyperspectral wavelengths of light that permit the system to “see through” some tissues and generate imaging of the tissue that is affected by the disease. The endoscopic imaging system senses the reflected hyperspectral electromagnetic radiation to generate hyperspectral imaging data of the diseased tissue, and thereby identifies the location of the diseased tissue within the patient&#39;s body. The endoscopic imaging system may further emit a laser mapping pulsing scheme for generating a topology of the scene and calculating dimensions of objects within the scene. The location of the diseased tissue (as identified by the hyperspectral imaging data) may be combined with the topology and dimensions information that is calculated with the laser mapping data. Therefore, the precise location, size, dimensions, and topology of the diseased tissue can be identified. This information may be provided to a medical practitioner to aid in excising, imaging, or studying the diseased tissue. Additionally, this information may be provided to a robotic surgical system to enable the surgical system to excise the diseased tissue. 
       FIG. 17  is a schematic diagram of an imaging system  1700  having a single cut filter. The system  1700  includes an endoscope  1706  or other suitable imaging device having a light source  1708  for use in a light deficient environment. The endoscope  1706  includes an image sensor  1704  and a filter  1702  for filtering out unwanted wavelengths of light or other electromagnetic radiation before reaching the image sensor  1704 . The light source  1708  transmits light that may illuminate the surface  1712  in a light deficient environment such as a body cavity. The light  1710  is reflected off the surface  1712  and passes through the filter  1702  before hitting the image sensor  1704 . 
     The filter  1702  may be used in an implementation where a fluorescent reagent or dye has been administered. In such an embodiment, the light source  1708  emits the excitation wavelength for fluorescing the fluorescent reagent or dye. Commonly, the relaxation wavelength emitted by the fluorescent reagent or dye will be of a different wavelength than the excitation wavelength. The filter  1702  may be selected to filter out the excitation wavelength and permit only the relaxation wavelength to pass through the filter and be sensed by the image sensor  1704 . 
     In one embodiment, the filter  1702  is configured to filter out an excitation wavelength of electromagnetic radiation that causes a reagent or dye to fluoresce such that only the expected relaxation wavelength of the fluoresced reagent or dye is permitted to pass through the filter  1702  and reach the image sensor  1704 . In an embodiment, the filter  1702  filters out at least a fluorescent reagent excitation wavelength between 770 nm and 790 nm. In an embodiment, the filter  1702  filters out at least a fluorescent reagent excitation wavelength between 795 nm and 815 nm. In an embodiment, the filter  1702  filters out at least a fluorescent reagent excitation wavelength between 770 nm and 790 nm and between 795 nm and 815 nm. In these embodiments, the filter  1702  filters out the excitation wavelength of the reagent and permits only the relaxation wavelength of the fluoresced reagent to be read by the image sensor  1704 . The image sensor  1704  may be a wavelength-agnostic image sensor and the filter  1702  may be configured to permit the image sensor  1704  to only receive the relaxation wavelength of the fluoresced reagent and not receive the emitted excitation wavelength for the reagent. The data determined by the image sensor  1704  may then indicate a presence of a critical body structure, tissue, biological process, or chemical process as determined by a location of the reagent or dye. 
     The filter  1702  may further be used in an implementation where a fluorescent reagent or dye has not been administered. The filter  1702  may be selected to permit wavelengths corresponding to a desired spectral response to pass through and be read by the image sensor  1704 . The image sensor  1704  may be a monochromatic image sensor such that pixels of the captured image that exceed a threshold or fall below a threshold may be characterized as corresponding to a certain spectral response or fluorescence emission. The spectral response or fluorescence emission, as determined by the pixels captured by the image sensor  1704 , may indicate the presence of a certain body tissue or structure, a certain condition, a certain chemical process, and so forth. 
       FIG. 18  is a schematic diagram of an imaging system  1800  having multiple cut filters. The system  1800  includes an endoscope  1806  or other suitable imaging device having a light source  1808  for use in a light deficient environment. The endoscope  1806  includes an image sensor  1804  and two filters  1802   a ,  1802   b . It should be appreciated that in alternative embodiments, the system  1800  may include any number of filters, and the number of filters and the type of filters may be selected for a certain purpose e.g., for gathering imaging information of a particular body tissue, body condition, chemical process, and so forth. The filters  1802   a ,  1802   b  are configured for preventing unwanted wavelengths of light or other electromagnetic radiation from being sensed by the image sensor  1804 . The filters  1802   a ,  1802   b  may be configured to filter out unwanted wavelengths from white light or other electromagnetic radiation that may be emitted by the light source  1808 . 
     Further to the disclosure with respect to  FIG. 17 , the filters  1802   a ,  1802   b  may be used in an implementation where a fluorescent reagent or dye has been administered. The filters  1802   a ,  1802   b  may be configured for blocking an emitted excitation wavelength for the reagent or dye and permitting the image sensor  1804  to only read the relaxation wavelength of the reagent or dye. Further, the filters  1802   a ,  1802   b  may be used in an implementation where a fluorescent reagent or dye has not been administered. In such an implementation, the filters  1802   a ,  1802   b  may be selected to permit wavelengths corresponding to a desired spectral response to pass through and be read by the image sensor  1804 . 
     The multiple filters  1802   a ,  1802   b  may each be configured for filtering out a different range of wavelengths of the electromagnetic spectrum. For example, one filter may be configured for filtering out wavelengths longer than a desired wavelength range and the additional filter may be configured for filtering out wavelengths shorter than the desired wavelength range. The combination of the two or more filters may result in only a certain wavelength or band of wavelengths being read by the image sensor  1804 . 
     In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 513 nm and 545 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 565 nm and 585 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 900 nm and 1000 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 417 nm and 475 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 520 nm and 545 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 617 nm and 645 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 760 nm and 795 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 795 nm and 815 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 370 nm and 420 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are customized such that electromagnetic radiation between 600 nm and 670 nm contacts the image sensor  1804 . In an embodiment, the filters  1802   a ,  1802   b  are configured for permitting only a certain fluorescence relaxation emission to pass through the filters  1802   a ,  1802   b  and contact the image sensor  1804 . In an embodiment, a first filter blocks electromagnetic radiation having a wavelength from about 770 nm to about 790 nm, and a second filter blocks electromagnetic radiation having a wavelength from about 795 nm to about 815 nm. 
     In an embodiment, the system  1800  includes multiple image sensors  1804  and may particularly include two image sensors for use in generating a three-dimensional image. The image sensor(s)  1804  may be color/wavelength agnostic and configured for reading any wavelength of electromagnetic radiation that is reflected off the surface  1812 . In an embodiment, the image sensors  1804  are each color dependent or wavelength dependent and configured for reading electromagnetic radiation of a particular wavelength that is reflected off the surface  1812  and back to the image sensors  1804 . Alternatively, the image sensor  1804  may include a single image sensor with a plurality of different pixel sensors configured for reading different wavelengths or colors of light, such as a Bayer filter color filter array. Alternatively, the image sensor  1804  may include one or more color agnostic image sensors that may be configured for reading different wavelengths of electromagnetic radiation according to a pulsing schedule such as those illustrated in  FIGS. 5-7E , for example. 
       FIGS. 19A and 19B  illustrate a perspective view and a side view, respectively, of an implementation of an imaging sensor  1900  having a plurality of pixel arrays for producing a three-dimensional image. The three-dimensional image sensor may be built on a plurality of substrates and may comprise the plurality of pixel arrays and other associated circuitry, wherein a plurality of pixel columns  1904   a  forming the first pixel array and a plurality of pixel columns  1904   b  forming a second pixel array are located on respective substrates  1902   a  and  1902   b , respectively, and a plurality of circuit columns  1908   a  and  1908   b  are located on a separate substrate  1906 . Also illustrated are the electrical connections and communications between columns of pixels to associated or corresponding column of circuitry. 
     The plurality of pixel arrays may sense information simultaneously and the information from the plurality of pixel arrays may be combined to generate a three-dimensional image. In an embodiment, an endoscopic imaging system includes two or more pixel arrays that can be deployed to generate three-dimensional imaging. The endoscopic imaging system may include an emitter for emitting pulses of electromagnetic radiation during a blanking period of the pixel arrays. The pixel arrays may be synced such that the optical black pixels are read (i.e., the blanking period occurs) at the same time for the two or more pixel arrays. The emitter may emit pulses of electromagnetic radiation for charging each of the two or more pixel arrays. The two or more pixel arrays may read their respective charged pixels at the same time such that the readout periods for the two or more pixel arrays occur at the same time or at approximately the same time. In an embodiment, the endoscopic imaging system includes multiple emitters that are each individual synced with one or more pixel arrays of a plurality of pixel arrays. Information from a plurality of pixel arrays may be combined to generate three-dimensional image frames and video streams. 
       FIGS. 20A and 20B  illustrate a perspective view and a side view, respectively, of an implementation of a monolithic sensor  2000  having a plurality of pixel arrays for producing a three-dimensional image in accordance with the teachings and principles of the disclosure. Such an implementation may be desirable for three-dimensional image capture, wherein the two-pixel arrays  2002  and  2004  may be offset during use. In another implementation, a first pixel array  2002  and a second pixel array  2004  may be dedicated to receiving a predetermined range of wave lengths of electromagnetic radiation, wherein the first pixel array is dedicated to a different range of wavelength electromagnetic radiation than the second pixel array. 
       FIGS. 21A and 21B  illustrate a perspective view and a side view, respectively, of an implementation of an imaging sensor  2100  built on a plurality of substrates. As illustrated, a plurality of pixel columns  2104  forming the pixel array are located on the first substrate  2102  and a plurality of circuit columns  2108  are located on a second substrate  2106 . Also illustrated in the figure are the electrical connection and communication between one column of pixels to its associated or corresponding column of circuitry. In one implementation, an image sensor, which might otherwise be manufactured with its pixel array and supporting circuitry on a single, monolithic substrate/chip, may have the pixel array separated from all or a majority of the supporting circuitry. The disclosure may use at least two substrates/chips, which will be stacked together using three-dimensional stacking technology. The first  2102  of the two substrates/chips may be processed using an image CMOS process. The first substrate/chip  2102  may be comprised either of a pixel array exclusively or a pixel array surrounded by limited circuitry. The second or subsequent substrate/chip  2106  may be processed using any process and does not have to be from an image CMOS process. The second substrate/chip  1306  may be, but is not limited to, a highly dense digital process to integrate a variety and number of functions in a very limited space or area on the substrate/chip, or a mixed-mode or analog process to integrate for example precise analog functions, or a RF process to implement wireless capability, or MEMS (Micro-Electro-Mechanical Systems) to integrate MEMS devices. The image CMOS substrate/chip  2102  may be stacked with the second or subsequent substrate/chip  2106  using any three-dimensional technique. The second substrate/chip  2106  may support most, or a majority, of the circuitry that would have otherwise been implemented in the first image CMOS chip  2102  (if implemented on a monolithic substrate/chip) as peripheral circuits and therefore have increased the overall system area while keeping the pixel array size constant and optimized to the fullest extent possible. The electrical connection between the two substrates/chips may be done through interconnects, which may be wire bonds, bump and/or TSV (Through Silicon Via). 
     It will be appreciated that the teachings and principles of the disclosure may be used in a reusable device platform, a limited use device platform, a re-posable use device platform, or a single use/disposable device platform without departing from the scope of the disclosure. It will be appreciated that in a re-usable device platform an end-user is responsible for cleaning and sterilization of the device. In a limited use device platform, the device can be used for some specified amount of times before becoming inoperable. Typical new device is delivered sterile with additional uses requiring the end-user to clean and sterilize before additional uses. In a re-posable use device platform, a third-party may reprocess the device (e.g., cleans, packages and sterilizes) a single-use device for additional uses at a lower cost than a new unit. In a single use/disposable device platform a device is provided sterile to the operating room and used only once before being disposed of. 
     Examples 
     The following examples pertain to preferred features of further embodiments: 
     Example 1 is a system. The system includes an emitter for emitting pulses of electromagnetic radiation and an image sensor comprising a pixel array for sensing reflected electromagnetic radiation. The system includes an electromagnetic sensor for sensing energy emitted by the emitter. The system includes a controller in electronic communication with the emitter, the electromagnetic sensor, and the image sensor, wherein the controller is configured to synchronize timing of the emitter and the image sensor to generate a plurality of exposure frames. The system is such that at least a portion of the pulses of electromagnetic radiation emitted by the emitter comprises one or more of: electromagnetic radiation having a wavelength from about 770 nm to about 790 nm or electromagnetic radiation having a wavelength from about 795 nm to about 815 nm. 
     Example 2 is a system as in Example 1, wherein the emitter comprises a laser bundle and the laser bundle comprises a plurality of discrete laser units each capable of emitting electromagnetic radiation. 
     Example 3 is a system as in any of Examples 1-2, wherein the electromagnetic sensor is embedded within the emitter, and wherein the electromagnetic sensor senses the energy emitted by the emitter by sensing energy emitted by at least one, but less than all, of the plurality of discrete laser units within the laser bundle. 
     Example 4 is a system as in any of Examples 1-3, wherein: the electromagnetic sensor provides a value for the energy emitted by the emitter to the controller; and the controller controls a duty cycle of the emitter based on a predetermined, known output and the value for the energy emitted by the emitter such that the emitter illuminates a scene with a desired exposure for images captured by the image sensor. 
     Example 5 is a system as in any of Examples 1-4, wherein: the emitter comprises a plurality of laser bundles and each of the plurality of laser bundles comprises a plurality of laser units; the system comprises a dedicated electromagnetic sensor for each of the plurality of laser bundles such that energy emitted by each of the plurality of laser bundles is sensed by a different dedicated electromagnetic sensor; and the dedicated electromagnetic sensor is configured to sense energy emitted by at least one, but fewer than all, of the plurality of laser units for its assigned laser bundle. 
     Example 6 is a system as in any of Examples 1-5, wherein the controller comprises one or more processors configurable for executing instructions stored in non-transitory computer readable storage media, the instructions comprising: receiving from the electromagnetic sensor a value for the energy emitted by the emitter; comparing the value for the energy emitted by the emitter with a desired light output for the emitter; determining whether the value for the energy emitted by the emitter is within an accepted tolerance with respect to the desired light output for the emitter; and in response to the value for the energy emitted by the emitter not being within the accepted tolerance, adjusting a duration of at least one of the pulses of electromagnetic radiation. 
     Example 7 is a system as in any of Examples 1-6, wherein the emitter comprises a plurality of laser bundles and each of the plurality of laser bundles comprises a plurality of laser units, wherein the plurality of laser bundles comprises: a red laser bundle for emitting a red wavelength of electromagnetic radiation; a green laser bundle for emitting a green wavelength of electromagnetic radiation; a blue laser bundle for emitting a blue wavelength of electromagnetic radiation; and a fluorescence bundle for emitting a fluorescence excitation wavelength of electromagnetic radiation for fluorescing a reagent. 
     Example 8 is a system as in any of Examples 1-7, wherein the fluorescence bundle for emitting the fluorescence excitation wavelength of electromagnetic radiation comprises one or more of: a first fluorescence bundle for emitting the electromagnetic radiation having the wavelength from about 770 nm to about 790 nm; or a second fluorescence bundle for emitting the electromagnetic radiation having the wavelength from about 795 nm to about 815 nm. 
     Example 9 is a system as in any of Examples 1-8, wherein the pixel array of the image sensor senses reflected electromagnetic radiation to generate the plurality of exposure frames during a readout period of the pixel array, wherein the readout period is a duration of time when active pixels in the pixel array are read. 
     Example 10 is a system as in any of Examples 1-9, wherein at least a portion of the pulses of electromagnetic radiation emitted by the emitter is a fluorescence excitation wavelength for fluorescing a reagent, wherein the fluorescence excitation wavelength comprises one or more of: the electromagnetic radiation having the wavelength from about 770 nm to about 790 nm; or the electromagnetic radiation having the wavelength from about 795 nm to about 815 nm. 
     Example 11 is a system as in any of Examples 1-10, wherein the emitter is configured to emit, during a pulse duration, a plurality of sub-pulses of electromagnetic radiation having a sub-duration shorter than the pulse duration. 
     Example 12 is a system as in any of Examples 1-11, wherein one or more of the pulses of electromagnetic radiation emitted by the emitter comprises electromagnetic radiation emitted at two or more wavelengths simultaneously as a single pulse or a single sub-pulse. 
     Example 13 is a system as in any of Examples 1-12, wherein at least a portion of the pulses of electromagnetic radiation emitted by the emitter is a fluorescence excitation emission that results in a fluorescence exposure frame created by the image sensor, and wherein the controller is configured to provide the fluorescence exposure frame to a corresponding system that determines a location of a critical tissue structure within a scene based on the fluorescence exposure frame. 
     Example 14 is a system as in any of Examples 1-13, wherein the fluorescence excitation emission comprises each of: the electromagnetic radiation having the wavelength from about 770 nm to about 790 nm; and the electromagnetic radiation having the wavelength from about 795 nm to about 815 nm. 
     Example 15 is a system as in any of Examples 1-14, wherein the controller is further configured to: receive the location of the critical tissue structure from the corresponding system; generate an overlay frame comprising the location of the critical tissue structure; and combine the overlay frame with a color image frame depicting the scene to indicate the location of the critical tissue structure within the scene. 
     Example 16 is a system as in any of Examples 1-15, wherein the critical structure comprises one or more of a nerve, a ureter, a blood vessel, an artery, a blood flow, or a tumor. 
     Example 17 is a system as in any of Examples 1-16, wherein the controller is configured to synchronize timing of the pulses of electromagnetic radiation during a blanking period of the image sensor, wherein the blanking period corresponds to a time between a readout of a last row of active pixels in the pixel array and a beginning of a next subsequent readout of active pixels in the pixel array. 
     Example 18 is a system as in any of Examples 1-17, wherein two or more pulses of electromagnetic radiation emitted by the emitter result in two or more instances of reflected electromagnetic radiation that are sensed by the pixel array to generate two or more exposure frames that are combined to form an image frame. 
     Example 19 is a system as in any of Examples 1-18, wherein the image sensor comprises a first image sensor and a second image sensor such that the image sensor can generate a three-dimensional image. 
     Example 20 is a system as in any of Examples 1-19, wherein the emitter is configured to emit a sequence of pulses of electromagnetic radiation repeatedly sufficient for generating a video stream comprising a plurality of image frames, wherein each image frame in the video stream comprises data from a plurality of exposure frames, and wherein each of the exposure frames corresponds to a pulse of electromagnetic radiation. 
     Example 21 is a system as in any of Examples 1-20, wherein the pulses of electromagnetic radiation are emitted in a pattern of varying wavelengths of electromagnetic radiation, and wherein the emitter repeats the pattern of varying wavelengths of electromagnetic radiation. 
     Example 22 is a system as in any of Examples 1-21, wherein at least a portion of the pulses of electromagnetic radiation comprise a red wavelength, a green wavelength, a blue wavelength, and a fluorescence excitation wavelength such that reflected electromagnetic radiation sensed by the pixel array corresponding to each of the red wavelength, the green wavelength, the blue wavelength, and the fluorescence excitation wavelength can be processed to generate a Red-Green-Blue (RGB) image frame comprising an overlay of fluorescence imaging data, wherein the fluorescence excitation wavelength of electromagnetic radiation comprises: the electromagnetic radiation having the wavelength from about 770 nm to about 790 nm; or the electromagnetic radiation having the wavelength from about 795 nm to about 815 nm. 
     Example 23 is a system as in any of Examples 1-22, wherein at least a portion of the pulses of electromagnetic radiation comprise a luminance emission, a red chrominance emission, a blue chrominance emission, and a fluorescence excitation emission such that reflected electromagnetic radiation sensed by the pixel array corresponding to each of the luminance emission, the red chrominance emission, the blue chrominance emission, and the fluorescence excitation emission can be processed to generate a YCbCr image frame comprising an overlay of fluorescence imaging data, wherein the fluorescence excitation emission of electromagnetic radiation comprises: the electromagnetic radiation having the wavelength from about 770 nm to about 790 nm; or the electromagnetic radiation having the wavelength from about 795 nm to about 815 nm. 
     Example 24 is a system as in any of Examples 1-23, further comprising an operational amplifier circuit in electronic communication with the electromagnetic sensor. 
     Example 25 is a system as in any of Examples 1-24, wherein the image sensor is configured to generate a plurality of exposure frames, wherein each of the plurality of exposure frames corresponds to a pulse of electromagnetic radiation emitted by the emitter. 
     Example 26 is a system as in any of Examples 1-25, wherein the emitter comprises a laser bundle and the system further comprises an optical fiber connected to the laser bundle, wherein the electromagnetic sensor is connected to the optical fiber. 
     Example 27 is a system as in any of Examples 1-25, wherein the electromagnetic sensor is a photo diode. 
     Example 28 is a system as in any of Examples 1-27, wherein the emitter comprises a plurality of laser bundles for emitting a plurality of different wavelengths of electromagnetic radiation, and the system comprises a plurality of electromagnetic sensors for sensing each of the plurality of laser bundles independently. 
     Example 29 is a system as in any of Examples 1-28, wherein the emitter comprises a laser bundle and the electromagnetic sensor is disposed in an optical fiber connected to the laser bundle. 
     Example 30 is a system as in any of Examples 1-29, further comprising an operational amplifier circuit, wherein the electromagnetic sensor is in electronic communication with the operational amplifier circuit. 
     Example 31 is a system as in any of Examples 1-30, wherein the controller comprises one or more processors configurable for executing instructions stored in non-transitory computer readable storage media, the instructions comprising: determining a mean pixel value for pixels in the pixel array based on an exposure level of the image sensor; calculating a measured exposure level for the image sensor based on the mean pixel value; calculating an error measurement based on the measured exposure level and a desired exposure level; determining whether the error measurement is within a tolerance threshold; and in response to the error measurement not being within the tolerance threshold, adjusting wavelength and/or duration of at least one pulse of the pulses of electromagnetic radiation to bring the error measurement within the tolerance threshold. 
     Example 32 is a system as in any of Examples 1-31, further comprising a filter that filters electromagnetic radiation having a wavelength from about 770 nm to about 790 nm. 
     Example 33 is a system as in any of Examples 1-32, further comprising a filter that filters electromagnetic radiation having a wavelength from about 795 nm to about 815 nm. 
     It will be appreciated that various features disclosed herein provide significant advantages and advancements in the art. The following claims are exemplary of some of those features. 
     In the foregoing Detailed Description of the Disclosure, various features of the disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. 
     It is to be understood that any features of the above-described arrangements, examples, and embodiments may be combined in a single embodiment comprising a combination of features taken from any of the disclosed arrangements, examples, and embodiments. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the disclosure and the appended claims are intended to cover such modifications and arrangements. 
     Thus, while the disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein. 
     Further, where appropriate, functions described herein can be performed in one or more of: hardware, software, firmware, digital components, or analog components. For example, one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs) can be programmed to carry out one or more of the systems and procedures described herein. Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, components may be referred to by different names. This document does not intend to distinguish between components that differ in name, but not function. 
     The foregoing description has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. Further, it should be noted that any or all the aforementioned alternate implementations may be used in any combination desired to form additional hybrid implementations of the disclosure. 
     Further, although specific implementations of the disclosure have been described and illustrated, the disclosure is not to be limited to the specific forms or arrangements of parts so described and illustrated. The scope of the disclosure is to be defined by the claims appended hereto, any future claims submitted here and in different applications, and their equivalents.