Systems and methods for spatially controlled scene illumination

Abstract

A scene illumination system is provided that produces spatially uniform or controlled brightness levels for machine vision applications. The system includes a camera, multiple light sources that preferentially illuminate different regions within the camera's field-of-view, and a processing unit coupled to the camera and light sources. Focal regions of the light sources within the camera's field-of-view are sampled to determine average regional brightness and compared to target brightness levels. The processing unit controls the light sources to increase or decrease illumination levels to converge toward the target brightness levels within the field-of-view. This modulation of the light sources may be repeated with successive video images until target brightness levels are achieved. Once achieved, the iterative feedback control may be locked-in for some applications, while for others, the iterative process may continue periodically or continuously to account for different scenes or changes in lighting conditions.

1 . A system for monitoring an eye of a person, comprising:
 a device configured to be worn on a person's head;   a camera mounted on the device and positioned for viewing a first eye of the person wearing the device;   a plurality of light sources on the device that preferentially illuminate respective focal regions of the person's face around the first eye and within the camera's field-of-view; and   a controller coupled to the camera and the light sources, the controller configured for sampling brightness in the respective focal regions of the light sources using the camera and modulating the light sources based at least in part on the sampled brightness to provide desired brightness levels within the respective focal regions.   
     
     
         2 - 3 . (canceled) 
     
     
         4 . The system of  claim 1 , wherein the controller is configured for sampling brightness from multiple pixels of the camera that correspond to a first focal region within the camera's field-of-view that is illuminated by a first light source, the controller combining the sampled brightness to determine an average brightness provided by the first light source, the controller modulating the first light source to provide a desired brightness level within the first focal region. 
     
     
         5 . The system of  claim 4 , wherein the controller is configured for amplitude modulation of at least one of the current and the voltage to the first light source to provide the desired brightness level. 
     
     
         6 . The system of  claim 4 , wherein the controller is configured for pulse-width modulation of at least one of the current and the voltage to the first light source to provide the desired brightness level. 
     
     
         7 . The system of  claim 1 , wherein the controller is configured for activating the light sources only during periods when the camera is activated to acquire images of the first eye. 
     
     
         8 - 11 . (canceled) 
     
     
         12 . A feedback controlled system for producing spatially controlled illumination comprising:
 a camera that measures scene brightness in two or more spatial regions of a field-of-view;   light sources that preferentially illuminate corresponding regions within the camera's field-of-view; and   a processor that computes average brightness within each region of the camera's field-of-view and modulates corresponding light sources to one or more target brightness levels to provide desired brightness levels within the field-of-view.   
     
     
         13 . The system of  claim 12 , wherein the camera and the light sources are mounted on a device configured to be worn on a person's head, the camera positioned on the device for viewing a first eye of the person wearing the device, the light sources located on the device for preferentially illuminating respective focal regions of the person's face around the first eye and within the camera's field-of-view. 
     
     
         14 . (canceled) 
     
     
         15 . The system of  claim 12 , wherein the processor is configured for sampling brightness from multiple pixels of the camera that correspond to a first focal region within the camera's field-of-view that is illuminated by a first light source, the processor combining the sampled brightness to determine an average brightness provided by the first light source, the processor modulating the first light source to provide a desired brightness level within the first focal region. 
     
     
         16 - 19 . (canceled) 
     
     
         20 . The system of  claim 12 , wherein the processor is coupled to the light sources for deactivating the light sources when the camera is inactive. 
     
     
         21 . The system of  claim 12 , wherein the desired brightness levels of the light sources are substantially uniform. 
     
     
         22 . The system of  claim 12 , wherein the desired brightness levels of the light sources are variable based at least in part on the location of the respective focal regions within the field-of-view. 
     
     
         23 - 26 . (canceled) 
     
     
         27 . The system of  claim 12 , wherein the camera is mounted to a dashboard of a vehicle such that the camera is oriented towards the face of an operator of the vehicle. 
     
     
         28 . The system of  claim 27 , wherein the light sources are mounted to the vehicle such that the light sources are oriented towards the face of the operator for preferentially illuminating respective focal regions of the operator's face within the camera's field-of-view. 
     
     
         29 . The system of  claim 12 , wherein the camera is mounted to a structure adjacent an assembly line or conveyor belt for obtaining images of objects being directed along the assembly line or conveyor belt. 
     
     
         30 . The system of  claim 12 , wherein the camera is mounted to a structure adjacent a plurality of storage areas for obtaining images of objects located in the storage areas. 
     
     
         31 . The system of  claim 30 , wherein the light sources are mounted adjacent the storage areas to preferentially illuminate respective focal regions of the storage areas within the camera's field-of-view. 
     
     
         32 . The system of  claim 31 , wherein the processor is coupled to the light sources to modulate the light sources based on average brightness within each of the focal regions to provide a substantially uniform brightness level within the field-of-view. 
     
     
         33 . The system of  claim 31 , wherein the processor is coupled to the light sources to modulate the light sources based on average brightness within each of the focal regions to provide a variable brightness level within the field-of-view. 
     
     
         34 . The system of  claim 33 , wherein the processor is coupled to the light sources to modulate the light sources to provide a greater brightness level for focal regions that are further from the camera than other focal regions. 
     
     
         35 . A method for controlling illumination of a first eye of a person,
 comprising:   positioning a camera towards a person's face such that a first eye of the person lies within a field-of-view of the camera;   illuminating at least a portion of the person's face with a plurality of light sources that preferentially illuminate respective focal regions of the person's face around the first eye and within the camera's field-of-view;   sampling brightness in the respective focal regions of the light sources using the camera; and   modulating the light sources based at least in part on the sampled brightness to provide desired brightness levels within the respective focal regions.   
     
     
         36 - 70 . (canceled)