System and method for tissue contact detection and for auto-exposure and illumination control

Abstract

A system determines that a change in luminance of captured frames of a scene in response to a change in illumination brightness of the scene is less than a threshold value and commands, based on the determination that the change in luminance of the captured frames of the scene is less than the threshold value, attenuation of the illumination brightness of the scene.

We claim: 
     
         1 . A system comprising:
 a memory storing instructions; and   a processor communicatively coupled to the memory and configured to execute the instructions to:
 determine that a change in luminance of captured frames of a scene in response to a change in illumination brightness of the scene is less than a threshold value; and 
 command, based on the determination that the change in luminance of the captured frames of the scene is less than the threshold value, attenuation of the illumination brightness of the scene. 
   
     
     
         2 . The system of  claim 1 , wherein the processor is further configured to execute the instructions to:
 command varying of the illumination brightness of the scene in a known pattern; and   terminate the attenuation of the illumination brightness of the scene in response to a detection, by a camera, of the known pattern.   
     
     
         3 . The system of  claim 1 , wherein the processor is further configured to execute the instructions to:
 detect the change in luminance of the captured frames of the scene based on an average brightness of a frame of the scene and an average brightness of a subsequently captured frame of the scene.   
     
     
         4 . The system of  claim 3 , wherein the processor is further configured to execute the instructions to:
 create a brightness histogram for the frame of the scene;   determine the average brightness of the frame of the scene based on the brightness histogram for the frame of the scene;   create a brightness histogram for the subsequently captured frame of the scene; and   determine the average brightness of the subsequently captured frame of the scene based on the brightness histogram for the subsequently captured frame of the scene.   
     
     
         5 . The system of  claim 4 , wherein the processor is further configured to execute the instructions to:
 determine a luminance of the frame of the scene as a ratio of the average brightness of the frame of the scene to an exposure time of a camera that captured the frames of the scene; and   determine a luminance of the subsequently captured frame of the scene as a ratio of the average brightness of the subsequently captured frame of the scene to the exposure time of the camera.   
     
     
         6 . The system of  claim 1 , wherein the processor is further configured to execute the instructions to:
 adjust one or both of a camera exposure time of a camera that captured the frames of the scene and a gain that controls a brightness of a displayed frame of the scene; and   adjust, based on a value of the camera exposure time, the illumination brightness of the scene and the camera exposure time to maintain a target brightness of displayed frames of the scene.   
     
     
         7 . A method comprising:
 determining that a change in luminance of captured frames of a scene in response to a change in illumination brightness of the scene is less than a threshold value; and   commanding, based on the determination that the change in luminance of the captured frames of the scene is less than the threshold value, attenuation of the illumination brightness of the scene.   
     
     
         8 . The method of  claim 7 , further comprising:
 commanding varying of the illumination brightness of the scene in a known pattern; and   terminating the attenuation of the illumination brightness of the scene in response to a detection, by a camera, of the known pattern.   
     
     
         9 . The method of  claim 7 , further comprising:
 detecting the change in luminance of the captured frames of the scene based on an average brightness of a frame of the scene and an average brightness of a subsequently captured frame of the scene.   
     
     
         10 . The method of  claim 9 , further comprising:
 creating a brightness histogram for the frame of the scene;   determining the average brightness of the frame of the scene based on the brightness histogram for the frame of the scene;   creating a brightness histogram for the subsequently captured frame of the scene; and   determining the average brightness of the subsequently captured frame of the scene based on the brightness histogram for the subsequently captured frame of the scene.   
     
     
         11 . The method of  claim 10 , further comprising:
 determining a luminance of the frame of the scene as a ratio of the average brightness of the frame of the scene to an exposure time of a camera that captured the frames of the scene; and   determining a luminance of the subsequently captured frame of the scene as a ratio of the average brightness of the subsequently captured frame of the scene to the exposure time of the camera.   
     
     
         12 . The method of  claim 7 , further comprising:
 adjusting one or both of a camera exposure time of a camera that captured the frames of the scene and a gain that controls a brightness of a displayed frame of the scene; and   adjusting, based on a value of the camera exposure time, the illumination brightness of the scene and the camera exposure time to maintain a target brightness of displayed frames of the scene.   
     
     
         13 . A non-transitory computer-readable medium storing instructions that, when executed, cause a processor of a computer system to:
 determine that a change in luminance of captured frames of a scene in response to a change in illumination brightness of the scene is less than a threshold value; and   command, based on the determination that the change in luminance of the captured frames of the scene is less than the threshold value, attenuation of the illumination brightness of the scene.   
     
     
         14 . The non-transitory computer-readable medium of  claim 13 , wherein the instructions, when executed, further cause the processor of the computer system to:
 command varying of the illumination brightness of the scene in a known pattern; and   terminate the attenuation of the illumination brightness of the scene in response to a detection, by a camera, of the known pattern.   
     
     
         15 . The non-transitory computer-readable medium of  claim 13 , wherein the instructions, when executed, further cause the processor of the computer system to:
 detect the change in luminance of the captured frames of the scene based on an average brightness of a frame of the scene and an average brightness of a subsequently captured frame of the scene.   
     
     
         16 . The non-transitory computer-readable medium of  claim 15 , wherein the instructions, when executed, further cause the processor of the computer system to:
 create a brightness histogram for the frame of the scene;   determine the average brightness of the frame of the scene based on the brightness histogram for the frame of the scene;   create a brightness histogram for the subsequently captured frame of the scene; and   determine the average brightness of the subsequently captured frame of the scene based on the brightness histogram for the subsequently captured frame of the scene.   
     
     
         17 . The non-transitory computer-readable medium of  claim 16 , wherein the instructions, when executed, further cause the processor of the computer system to:
 determine a luminance of the frame of the scene as a ratio of the average brightness of the frame of the scene to an exposure time of a camera that captured the frames of the scene; and   determine a luminance of the subsequently captured frame of the scene as a ratio of the average brightness of the subsequently captured frame of the scene to the exposure time of the camera.   
     
     
         18 . The non-transitory computer-readable medium of  claim 13 , wherein the instructions, when executed, further cause the processor of the computer system to:
 adjust one or both of a camera exposure time of a camera that captured the frames of the scene and a gain that controls a brightness of a displayed frame of the scene; and   adjust, based on a value of the camera exposure time, the illumination brightness of the scene and the camera exposure time to maintain a target brightness of displayed frames of the scene.