Patent Publication Number: US-2023146673-A1

Title: Dynamic light source status indication for endoscopic systems

Description:
FIELD 
     This disclosure relates to light sources for endoscopic imaging systems and in particular, using an endoscopic light source to indicate a status of the endoscopic imaging system. 
     BACKGROUND 
     The imaging of body surfaces through an endoscope is well known within the medical and veterinarian fields. Typically, this involves inserting an endoscope into a body cavity and directing a high intensity light source output through the endoscope to illuminate body tissue. Light reflected by the body tissue is then guided along an optical path to an image sensor to generate both video and still images of the tissue. One such approach, described in U.S. Pat. No. 5,162,913 to Chatenever et al., provides a technique for an automatic adjustment of the exposure of video images detected with an image sensor. 
     The use of high intensity light sources involves potential hazards to medical personnel and patients. Light sources in the past have included light driver systems which may use metal-halide, halogen, xenon, or other high energy bulbs that generate significant heat both in the light source and along the light guide cable. Many light sources now use LED light driver systems which still generate significant heat. In some instances, a light guide cable is used to convey the high intensity-light source output to an endoscope. The cable may be momentarily disconnected from the endoscope and placed on a sterile drape used to protect the patient. The high intensity light output can be sufficient to ignite the drape and pose a fire hazard. In other instances, the user can inadvertently hold the disconnected light guide cable in such a way as to temporarily blind another person in the room or burn tissue of a patient or the user. In some instances, when the endoscope is removed from (i.e., pulled out of) a patient, there can be a risk of these same hazards. 
     When the light source is used with an endoscopic video camera, which has an automatic exposure system, the light source output intensity may be turned up to an intensity level higher than required for the camera to produce well-exposed images. If the light guide cable becomes disconnected, the automatic exposure system may detect a decrease in brightness and cause the light source to increase intensity further to compensate. This increased light intensity level can burn body tissue and cause serious injury to the patient. 
     In some instances, a light source may enter a standby mode to prevent the above-mentioned potential hazards from materializing. The standby mode may be triggered in response to a detection of a disconnected light guide cable. Alternatively, the standby mode may be selected by the user at the conclusion of a procedure or default to standby mode when powered on. In standby mode, the light source may be set to a reduced output level of lower intensity light output. Depending on ambient lighting conditions, the reduced output level may make it difficult for a user or bystander to determine if the light source is in standby mode, is in operational mode but at a low level of output, or in some circumstances, is turned off. In situations with a high level of ambient lighting, this could be exacerbated. 
     In other situations, the light source may provide non-visible illumination. For example, in some imaging modes, the light source may output excitation light in the infrared or ultraviolet light range. This excitation light may be used to excite a dye present in the body or a specific tissue such as a cancerous mass. In these situations, the user may be unaware that the light source is generating this non-visible light energy and that the light guide could be hot. In still other situations, the light source may provide a spectral range of illumination transgressing a broad spectrum of bandwidths, both visible and non-visible. For example, in hyperspectral and multispectral imaging, a variety of hues and colors of light may be emitted by the light source at varying intensities in order to elicit varying responses from the tissue and detected reflectance by the image sensor. 
     Techniques have been proposed to reduce the risks associated with high intensity light sources with disconnected light guide cables. One approach to solve this problem is described in U.S. Pat. No. 5,850,496 to Bellahsene et al. (hereinafter Bellahsene &#39;496). Bellahsene &#39;496, herein incorporated by reference, describes a light guide cable with two conductors running along its length but not in direct electrical contact with each other. Contacts at one end of the cable attach to circuitry internal to the light source while contacts at the other end of the cable attach to the endoscope. When the light guide cable is connected to the light source and the endoscope, the two conductors are shorted together to complete the circuit. When the light guide cable becomes disconnected from the endoscope, the circuit is broken. The light source may detect the broken circuit and determine the light guide cable is connected. The light source may then be forced into a standby mode in which the intensity of light output is reduced. 
     One approach to solve this problem is described in U.S. Pat. No. 6,511,422 to Chatenever (hereinafter Chatenever &#39;422). Chatenever &#39;422, herein incorporated by reference, describes a method and apparatus where the output from a high intensity light source is controlled so that whenever the output is not directed at tissue (meaning that the endoscope/video camera/light source combination is not currently being used to image body tissue), the light source output intensity is automatically reduced to a safer level. This is done by monitoring the reflected light from tissue and when this reflection indicates that the light source is not directed at tissue, the light intensity is turned down to a safer level. This involves generating a modulation signal and modulating the intensity of the light source output with the modulation signal. 
     However, none of these solutions provides any clear indication to the user of the status of the light source. For example, should the light guide cable become disconnected, the light source may remain on and at whatever intensity level was previously set. Alternately, in some circumstances such as those disclosed by Chatenever &#39;422, the light source may be reduced to a “safe” level yet still outputting some amount of light when in standby mode. Although the light source may include a display which may relay to the user that status of the light source, the display may be at some distance from the user or otherwise blocked from view. Thus, the user may not be able to discern the actual status of the light source and depending on lighting in the operating room, may not be able to distinguish a light source that is on, off, in a standby mode, or accidentally disconnected from the endoscope and still on. 
     SUMMARY 
     Accordingly, the endoscopic imaging system of the present disclosure includes features which provide a clear indication to the user of the status of the light source and the light guide cable using the light source illumination. 
     In one example, a light source for an endoscope system includes a receptacle for receiving a first end of a light guide cable, a light engine with at least one LED configured to provide light transmitted from the first end of the light guide cable to a second end of the light guide cable connected to an endoscope, and a light output controller configured to adjust an intensity level of the light engine according to a set intensity level when an imaging mode is selected and a first auxiliary mode when a standby mode is selected. 
     In other features, the first auxiliary mode adjusts the intensity level according to a time-based function routine. The time-based function routine includes a repeating, non-linear duty cycle in which the light output controller adjusts the intensity level to increase and decrease in a manner that mimics breathing. In still other features, the time-based function routine includes a repetition of a series of duty cycle pulses, each pulse having a maximum duty cycle and a minimum duty cycle and including pulse widths varying in accordance with a non-linear duty cycle function, the non-linear duty cycle function including a positively biased sinusoidal function. 
     In yet other features, the light source includes a light source input configured to accept user input to select the standby mode and adjust the set intensity level. 
     In yet other features, the light source includes a connection monitor configured to determine when the second end of the light guide cable is connected to the endoscope or disconnected from the endoscope. In still other features, when the connection monitor detects a disconnected light guide cable, the light output controller selects a second auxiliary mode that adjusts the intensity level according to a blinking routine. The blinking routine includes a repeating duty cycle ranging from a minimum duty cycle to a maximum duty cycle, the minimum duty cycle active for a blink off time and the maximum duty cycle active for a blink on time. 
     In another example, a light source for an endoscope system includes a receptacle for receiving a first end of a light guide cable, a light engine with at least one LED configured to provide light transmitted from the first end of the light guide cable to a second end of the light guide cable connected to an endoscope, and a light output controller configured to adjust an intensity level of the light engine according to a set intensity level when an imaging mode is selected and a first auxiliary mode when the second end of the light guide cable is disconnected. 
     In other features, the light source includes a connection monitor configured to determine when the second end of the light guide cable is connected to the endoscope or disconnected from the endoscope. The first auxiliary mode adjusts the intensity level according to a blinking routine. The blinking routine includes a repeating duty cycle ranging from a minimum duty cycle to a maximum duty cycle, the minimum duty cycle active for a blink off time and the maximum duty cycle active for a blink on time. 
     In yet other features, the light output controller is further configured to adjust the intensity level according to a second auxiliary mode when a standby mode is selected. The second auxiliary mode adjusts the intensity level according to a time-based function routine. The time-based function routine includes a repeating, non-linear duty cycle in which the light output controller adjusts the intensity level to increase and decrease in a manner that mimics breathing. In still other features, the time-based function routine includes a repetition of a series of duty cycle pulses, each pulse having a maximum duty cycle and a minimum duty cycle and including pulse widths varying in accordance with a non-linear duty cycle function, the non-linear duty cycle function including a positively biased sinusoidal function. 
     In yet other features, the light source includes a light source input configured to accept user input to select the standby mode and adjust the set intensity level. 
     In another example, a light source for an endoscope system includes a receptacle for receiving a first end of a light guide cable, a light engine with at least one LED configured to provide light transmitted from the first end of the light guide cable to a second end of the light guide cable connected to an endoscope, a connection monitor configured to determine when the second end of the light guide cable is connected to the endoscope or disconnected from the endoscope, and a light output controller configured to adjust an intensity level of the light engine according to a set intensity level when an imaging mode is selected, a first auxiliary mode when a standby mode is selected, and a second auxiliary mode when the second end of the light guide cable is disconnected. 
     In other features the first auxiliary mode includes a time-based function routine having a repetition of a series of duty cycle pulses, each pulse having a first maximum duty cycle and a first minimum duty cycle and including pulse widths varying in accordance with a non-linear duty cycle function, the non-linear duty cycle function including a positively biased sinusoidal function. The second auxiliary mode includes a blinking routine having a repeating duty cycle ranging from a second minimum duty cycle to a second maximum duty cycle, the first minimum duty cycle active for a blink off time and the first maximum duty cycle active for a blink on time. 
     In yet other features, the light source includes a light source input configured to accept user input to select the standby mode and adjust the set intensity level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an exemplary endoscopic imaging system according to the principles of the present disclosure. 
         FIG.  2    is a block diagram of the endoscopic imaging system of  FIG.  1    according to the principles of the present disclosure. 
         FIG.  3    is a schematic view of the endoscopic imaging system of  FIG.  2    according to the principles of the present disclosure. 
         FIG.  4    is a flowchart illustrating exemplary control executed by software and hardware of the endoscopic imaging system according to the principles of the present disclosure. 
         FIGS.  5 A- 5 F  are auxiliary modes for adjusting an intensity level of light provided by the light source according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , an endoscopic imaging system  10  includes an optical endoscope  20 , an imaging device  40 , a light source  60 , a camera control unit (CCU)  80 , a display unit  85 , and a display  100 . The system  10  may include the endoscope  20  and the imaging device  40  (such as a detachable camera head) or alternately, the endoscope  20  and imaging device  40  may be an integral unit such as a video endoscope with an image sensor at the distal end. For ease of discussion, the system  10  as described below includes the endoscope  20  and detachable camera head  40 . Although the components are described as separate, modular units, one skilled in the art would recognize they may be combined into fewer units that may perform similar functions. For example, the light source  60 , CCU  80 , and display unit  85  may be housed together as a single unit for receiving image data from the imaging device  40 , processing the image data, and outputting it to the display  100 . 
     Referring now also to  FIG.  2   , a schematic diagram illustrates additional features of the system  10 . The endoscope  20  includes a junction  21  with a light post  22  for receiving light generated by the light source  60  via a connected light guide cable  50 . The light guide cable  50  includes a bundle of fiber optic filaments through which the light travels. The light guide cable  50  includes a first end  50   a  coupled to the light source  60  and a second end  50   b  coupled to the light post  22 . The light source  60  may include any of a number of adjustable light sources with a light assembly such as a Xenon bulb, a halogen bulb, or preferably, one or more light emitting diodes (LEDs). The light may be directed from the second end  50   b  of the light guide cable  50  via the junction  21  to one or more light guide relays and fiber optic filaments within the endoscope  20 . The light exits the endoscope  20  from a distal end  25  of the endoscope  20 . The light may be dispersed by a distal light lens  26  to illuminate or irradiate the surgical site  12  with any of a variety of light including full visible spectrum light (white light), a narrow band of visible light, invisible light (infrared or ultraviolet), or any blending of light. In some instances, the light may produce a visible color as a component of the light. 
     The endoscope  20  includes additional components for the user to view the surgical site  12 . For example, the distal end  25  may include an objective lens  27  for capturing returned light due to reflection or in other cases, emission from a fluorescing substance of tissue at the surgical site  12 . The returned light forms an optical image that may be passed along the endoscope  20  via a lens relay  24  such as a Hopkins rod lens assembly. The lens relay  24  may then pass the optical image through the junction  21  to an image output lens  23  and ultimately to an eyepiece  29 . The eyepiece  29  may include an additional lens system  32  to focus the optical image for use by the attached imaging device  40 . An image sensor  31  captures the optical image output by the lens system  32  and transmits a raw digital image via electrical connections  41  within the image device  40 . The imaging device  40  processes the raw digital image for eventual post-processing by the connected CCU  80 . The CCU  80  may then pass the processed images in the form of a video signal to one of the additional components such as display unit  84  as shown in  FIG.  1   . 
     In other examples, the system  10  may include a video endoscope in place of the endoscope  20  and separate imaging device  40 . In this example (not shown), the imaging device  40  may be positioned closer to the objective lens  27  to receive the optical image more directly. For example, the image sensor  31  may be small enough to be placed near the distal end  25  of the endoscope  20 . The objective lens  27  may include additional features to focus the optical image directly onto the image sensor  31  making the additional components such as the lens relay  24 , image output lens  23 , and eyepiece  29  unnecessary. In place of the additional components, the video endoscope may include electrical connections to additional components in the handle of the video endoscope which may generate image data for processing by the CCU  80 . The principles of the present disclosure are equally applicable to this example of a video endoscope. 
     Referring now to  FIG.  3   , a schematic diagram of the system  10  illustrates additional features of the imaging device  40 , light source  60 , and CCU  80 . The light source  60  may operate in an imaging mode or an auxiliary light mode. When in the imaging mode, the system  10  may adjust an intensity level of the light source  60  based on input from the user or input from the CCU  80 . The user may adjust the intensity level using a light source input  70  or an input device  42  of the imaging device  40 . The CCU  80  may also adjust the intensity level to improve the quality of the image data provided by the image sensor  31 . When in the standby mode, the intensity level set by the user or CCU  80  may be overridden and adjusted according to an auxiliary mode. The user may select the standby mode or the CCU  80  may select the standby mode as described below. In other situations, the intensity level set by the user or CCU  80  may be overridden and adjusted according to other auxiliary modes as described further below. 
     As shown in the exemplary figure, the imaging device  40  includes the camera head coupled with the endoscope  20 . The camera head includes the image sensor  31  and the input device  42 . The camera head may further include a movement sensor  44 . The image sensor  31  receives optical images from the endoscope  20  and generates image data for image processing by the CCU  80 . The input device  42  may be one or more buttons, control pads, or joysticks for inputting commands to the imaging device  40  such as entering commands for controlling one or more features of the system  10  including the light source  60 . The movement sensor  44  may include an inertia measurement unit (IMU), gyroscope, accelerometer(s), or the like as known in the art for determining movement and orientation of the imaging device  40  and/or the connected endoscope  20 . Data provided by the image sensor  31 , input device  42 , and movement sensor  44  may be used by the CCU  80  to execute various methods for imaging the surgical site  12  and controlling the light source  60  in the imaging mode. 
     The light source  60  includes a light guide receptacle  62 , a light engine or lamp  64 , and a light output controller  66 . The light guide receptacle  62  releasably couples with the first end  50   a  of the light guide cable  50 . The light engine  64  may include one light or a plurality of lights. In the present example, the light engine  64  includes light-emitting diodes (LEDs). The light engine  64  may include any number (n) of LEDs and is shown in the figure as including a first LED  1 , a second LED  2 , and up to a last LED n. In some examples, the LEDs may be color LEDs which include the primary colors of red (R), green (G), and blue (B) light such that first LED  1  produces red light, second LED  2  produces green light, and last LED n produces blue light. The LEDs may be blended by the light output controller  66  to produce various colors of illumination. For example, first LED  1  may provide a range of wavelengths within the full-visible spectrum of light commonly referred to as white light. Second LED  2  may provide a narrower spectrum of light such as, for example, light for various applications known in the art including, but not limited to fluorescent imaging such as for photodynamic diagnosis (PDD), multispectral imaging, hyperspectral imaging, indocyanine green (ICG) imaging, and the like. 
     The light output controller  66  may adjust one or more output levels of the LEDs of the light engine  64  by varying power supplied to each of the LEDs. This may be accomplished by varying a duty cycle or pulse width modulation of the power applied to each of the LEDs. The light is delivered to the light guide cable  50  through the light guide receptacle  62 . The light guide receptacle  62  may further include a light collimator to focus the light from the LEDs into the optical fibers. The light source  60  may also include a connection monitor  68 , the light source input  70 , and a light bus interface  72 . The light source input  70  may include one or more buttons to adjust the intensity level of the LEDs from 0% to 100% intensity. The light source input  70  may include a standby button to command the light source  60  to enter into the standby mode and cause the light output controller  66  to output a standby message to the light bus interface  72 . 
     As noted above, the connection monitor  68  may determine when the light guide cable  50  is disconnected and connected with the light source  60 . For example, the light guide cable  50  and light source  60  may include mechanical features, optical features, electrical circuitry, and software for detecting whether the second end  50   b  of the light guide cable  50  is connected to the light post  22  of the endoscope  20 . In the present example, the connection monitor  68  may determine whether the light guide cable  50  is connected to the endoscope  20  and output a connected state message to the light bus interface  72  or is disconnected from the endoscope  20  and output a disconnected state message to the light bus interface  72  as described further below. 
     The camera control unit  80  includes an image processing module  82 , a display output module  84 , a usage monitor  88 , and a CCU bus interface  92 . The image processing module  82  may receive image data from the imaging device  40  which may be processed for display on the monitor  100  by the display output module  84  or recorded or processed by another component. In some examples, the display output module  84  may be included with the display unit  85 . The user may use the input device  42  to adjust the intensity level of the light engine  64 . Input device  42  may communicate via the CCU bus interface  92  to the light source  60  over the communication link  99 . The intensity level may be transmitted via the light bus interface  72  to the light output controller  66 . 
     The usage monitor  88  may detect when the system  10  is no longer being used in the imaging mode, select the standby mode for the light source  60 , and override the set light level using an auxiliary mode. For example, the image processing module  82  may provide processed image data and movement sensor  44  may provide movement data to the usage monitor  88 . If the image data indicates little or no change in the imaging of the surgical site  12  or other captured scene and the movement data indicates little or no movement, then the usage monitor  88  may select the standby mode and send the standby message over the CCU bus interface  92  and communication link  99  to the light source  60 . The light source  60  may then adjust the intensity level according to an auxiliary mode. 
     Likewise, the usage monitor  88  may detect when the system  10  has experienced a disconnected light guide cable and override the set light level using another auxiliary mode. For example, the image processing module  82  may provide processed image data and movement sensor  44  may provide movement data to the usage monitor  88 . If the image data indicates a significant change in the brightness of the imaging of the surgical site  12  and the movement data indicates continued movement, then the usage monitor  88  may determine the light guide cable  50  is disconnected and send the disconnected message over the CCU bus interface  92  and communication link  99  to the light source  60 . 
     The image processing module  82  and movement sensor  44  may be used to identify other combinations of imagery and movements that correspond to a disconnected light guide cable. For example, a fade in detected image brightness, due to a low level of detected light by the image sensor  31 , for a period of time greater than a time threshold while the intensity level of the light engine  64  is greater than an intensity threshold may indicate the light guide cable is disconnected. If movement data (acceleration, etc.) from the movement sensor  44  indicates the endoscope  20  and imaging device  40  are still being moved while the light source  60  outputs an intensity level greater than the intensity threshold, but the detected image brightness has decreased, the usage monitor  88  may determine the light guide cable  50  is disconnected and output a disconnected message to the CCU bus interface  92  over the communication link  99  to the light source  60 . The light source  60  may then adjust the intensity level according to another auxiliary mode. 
     Referring now to  FIG.  4   , a flowchart illustrates exemplary steps of a method according to the principles of the present disclosure. At step  200 , the system  10  may begin normal operation in the imaging mode in which the endoscope  20 , imaging device  40 , light source  60 , and CCU  80  are connected and configured to provide imaging of the surgical site  12 . At step  202 , the light source  60  has been powered on and the user or CCU  80  has adjusted the intensity level to a set intensity level. This may be due to actuation by the user of light source input  70  to a value greater than 0% or by another user input such as an on/off switch. As the user performs a procedure at the surgical site  12 , the light source  60  may further adjust the light output level based on the user input or control by the CCU  80  in the imaging mode. 
     At step  204 , software executing on the system  10  determines if standby mode has been selected by the user or the usage monitor  88 . For example, the user may select standby mode by choosing the mode using the light source input  70 , the input device  42 , or another menu of the light source  60 , CCU  80  or other user interface of the system  10 . The user selection of standby mode may be communicated via the standby message over the communication link  99 . Alternately, the usage monitor  88  may evaluate whether the standby mode should be activated based on determinations by the image processing module  82  and movement sensor  44  as described above. In either instance, a bit or other variable provided by the standby message may indicate to the light output controller  66  that standby mode is selected. At step  206 , the light output controller  66  may then override the intensity level previously set at step  202  and select a first auxiliary light mode corresponding to the standby mode. At step  208 , the light output controller  66  adjusts the intensity level according to the first auxiliary light mode to indicate to the user via the second end  50   b  of the light guide cable  50  that the light source  60  is in standby mode. Light may exit the distal end of the endoscope  20  if the light guide cable  50  remains connected. 
     If standby mode is not selected at step  204 , the system  10  evaluates the status of the light guide cable  50  and light source  60  at step  210 . For example, the connection monitor  68  may evaluate whether the light guide cable  50  remains connected to the light post  22  by checking the light guide receptacle  62  for a completed circuit as noted above. Alternately, the usage monitor  88  may evaluate whether the light guide cable  50  remains connected to the light post  22  based on data provided by the image processing module  82  and movement sensor  44 . If the light guide cable  50  become disconnected from the light post  22 , the connection monitor  68  or usage monitor  88  outputs the disconnected message via a bit or other variable in the software which indicates to the light output controller  66  that the light guide cable  50  is disconnected. At step  212 , the light output controller  66  may then override the intensity level set by the user previously at step  202  and select a second auxiliary light mode to indicate to the user via the second end  50   b  of the light guide cable  50  that the light guide cable  50  is disconnected from the light post  22 . 
     If standby mode is not selected and no disconnected light guide cable is detected, the method proceeds to step  216  where the procedure may continue in imaging mode. The light source  60  may be maintained at the intensity level set by the user or the CCU  80  in step  218 . The method ends at step  220  when the imaging mode is no longer active and the system  10  is powered off. 
     Referring now to  FIGS.  5 A- 5 F , six exemplary auxiliary modes are depicted using several graphs showing % duty cycle of the light engine  64  vs. time. Various combinations of the auxiliary modes may be used to indicate to the user the status of the light source  60  and light guide cable  50 . 
     As shown in  FIG.  5 A , one exemplary auxiliary mode may include a blinking routine. Here, six pulses labeled P 1 -P 6  are provided in a 2000 millisecond timeframe. Each pulse P 1 -P 6  may be the same color of light. The light engine  64  may drive a single LED or a plurality of LEDs to produce full spectrum visible light (white light) or a color of light such as red, green, or blue light. If a plurality of LEDs is provided including red, green, and blue LEDs, the single color of light may be any blended color. The light output controller  66  may drive the LED(s) from a minimum duty cycle Dc(min) such as 0% duty cycle to a maximum duty cycle Dc(max) such as a 20% duty cycle (and up to 100% duty cycle) and hold for a predetermined blink on time Tb(on) such as 50 milliseconds. The light output controller  66  may then decrease from the Dc(max) to the Dc(min) and hold for a predetermined blink off time Tb(off) such as 250 milliseconds. 
     Alternately, as shown in  FIG.  5 B , each pulse P may be a different color of light provided by a different combination of color LEDs. For example, P 1  may be red, P 2  may be green, and P 3  may be blue. The colors may repeat in a sequence and P 4  may be red, P 5  may be green, and P 6  may be blue. Dc(max) may be 50% duty cycle. Likewise, each pulse P may include a different minimum duty cycle Dc(min) and/or a different maximum duty cycle Dc(max) as shown in  FIG.  5 C . Though Tb(on) and Tb(off) are shown as the same values for all examples in  FIGS.  5 A- 5 C , the blink on time Tb(on) and blink off time Tb(off) may vary between pulses as well. Thus, any combination of pulses P may be provided and may be customized to produce different pulse colors, durations, and intensity levels. Each combination of pulses may be used to indicate to the user a different status of the system  10 , such as for example, a disconnected light guide cable. 
     As shown in  FIG.  5 D , another exemplary auxiliary mode may include a time-based function routine which may provide a continuous or near-continuous output of light according to a predetermined function. For example, the light engine  64  may vary the duty cycle Dc according to a time-based function to produce an effect similar to a cadence of typical human breathing. The time-based function routine may include a linear duty cycle function having a positive slope increasing from Dc(min) to Dc(max) followed by a negative slope decreasing from Dc(max) to Dc(min). The time-based function routine may include a non-linear duty cycle function including a positively biased sinusoidal function having a period A during which the duty cycle increases to the maximum duty cycle Dc(max) and decreases to the minimum duty cycle Dc(min). Similar to the blinking routine, the light engine  64  may drive a single LED or a plurality of LEDs to produce full spectrum visible light (white light) or a single color of light such as red, green, or blue light. If a plurality of LEDs is provided including red, green, and blue LEDs, the single color of light may be any blended color. 
     Alternately, the time-based function routine may produce a different color of light at different times during period A. For example, during a first portion A 1  of period A, the color of the LED may be a first color; during a second portion A 2  of period A, the color of the LED may be a second color; and during a third portion A 3  of period A, the color of the LED may be a third color. The LED may transition from the first color to the second color to the third color continuously through a color spectrum. Thus, multiple colors may be used in the first period. If red, green, and blue LEDs are present, the various combinations of LEDs may be driven to produce different colors at different times each period A. For example, a red LED may be driven according to the duty cycle Dc from times T=0 to T=500, a green LED may be driven according to the duty cycle Dc from times T=500 to T=1000, and the blue LED may be driven according to the duty cycle from times T=1000-2000. The red, green, and blue LEDs may be independently controlled to produce a continuously changing color scheme throughout the first period, cycling from the first color at time T=0 to the second color at time T=1000 and back to the first color at T=2000. 
     In  FIG.  5 E , three sequential periods A, B, and C illustrate another example of the time-based function. In a first period A, the color of the LED may be red. In a second period B, the color of the LED may be green. In a third period C, the color of the LED may be blue. Likewise, each period A, B, and C may include a different minimum duty cycle Dc(min) and/or a different maximum duty cycle Dc(max) as shown in  FIG.  5 F . Thus, any combination of periods may be provided and may be customized to produce different colors, durations, and intensities of light according to a time-based function. Each combination may be used to indicate to the user a different status of the imaging system  10 , such as for example, that the system  10  is in standby mode. 
     Specific values for the duty cycle and time and specific colors are provide for exemplary purposes only. Dc(max), Dc(min), Tb(on) and Tb(off) and selected colors may be any combination of values which would be perceptible to alert the user that the auxiliary mode is adjusting the light source  60  and imaging mode is no longer active. 
     Referring back to  FIG.  4   , when the standby mode has been selected at step  204 , the light output controller  66  may adjust the intensity level according to one of the auxiliary modes such as, for example, the auxiliary mode shown in  FIG.  5 D . Thus, when in standby mode, the light output controller  66  drives the LEDs to output light according to the time-based function routine and the second end  50   b  of the light guide cable  50  will output light that appears to mimic “breathing.” This is an improvement over the prior art which simply reduces the intensity level of the light to nothing or a “safe” low level. From afar, the “breathing” cadence of the light emitted from the light guide cable  50  or endoscope  20  readily identifies to the user that the light source  60  is still on but is in standby mode. 
     When the light guide cable  50  disconnection is detected at step  210 , the light output controller  66  may adjust the intensity level according to another one of the auxiliary modes such as, for example, the mode shown in  FIG.  5 A . Thus, when the disconnect occurs, the light output controller  66  drives the LEDs to output light according to the blinking routine. Thus, the second end  50   b  of the light guide cable  50  will output light at a reduced duty cycle of 20% and blink repeatedly. This is an improvement over the prior art which simply reduces the intensity level of the light to nothing or a “safe” low level. From afar, the blinking of the light emitted from the disconnected second end  50   b  readily identifies to the user that the light source  60  is still on and the light guide cable  50  is disconnected. 
     The principles of the present disclosure may be applied to other endoscopic imaging systems  10  and the light guide cable  50  may be used to visually communicate to the user additional statuses related to the functioning of the imaging device  40 , the light source  60 , the CCU  80 , or another component connected, for example, over the communication link  99 . This visual indication provided by the light source  60 , whether the light guide cable  50  or from the endoscope  20 , may be more readily discernable by the user when the light source  60 , CCU  80 , or display  100  are located far away or obstructed from the user&#39;s view. For example, the light output control module  66  may receive messages over the communication link  99  from any of a number of other connected components. The messages may indicate one or more statuses of the other connected components. In response to receiving the messages, the light output controller  66  may activate additional auxiliary light modes disclosed in  FIGS.  5 A- 5 F  or various other combinations not disclosed herein but ascertainable by a person of ordinary skill. 
     Example embodiments of the methods and systems of the present invention have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only, and are not limiting. Other embodiments are possible and are covered by the invention. Such embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 
     While the invention has been described in connection with various embodiments, it will be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention, and including such departures from the present disclosure as, within the known and customary practice within the art to which the invention pertains.