Automatic exposure control for endoscopic imaging
An endoscopic apparatus and method to capture an image of in-vivo tissue with automatic exposure control. For example, the method includes capturing image data on an image sensor and analyzing an indication of brightness of each pixel to determine whether the captured image data is saturated. When the image data is saturated, the method includes reducing the exposure period by a first increment, and repeating the capturing and analyzing steps until the captured image data is not saturated. When the captured image data is not saturated, in some embodiments, the method includes analyzing the indication of brightness of each pixel compared to a threshold indicative of use of a proportion of an available dynamic range of the image sensor, and when it is determined that the threshold has not been reached, increasing the exposure period by a second increment that has a magnitude relative to the first increment.
1. A method for automatic exposure control of an endoscopic apparatus configured to capture an image of in-vivo tissue, comprising:
capturing image data on an image sensor using an exposure period, the image data comprising: an indication of brightness captured by each pixel of the image sensor;
analyzing the indication of brightness of each pixel to determine whether the captured image data is saturated, wherein determining whether the captured image data is saturated comprises:
selecting a brightest proportion of the indication of brightness captured by each pixel of the image sensor; and
determining an average intensity of the selected brightest proportion and comparing the average intensity to a saturation threshold; and
when it is determined that the captured image data is saturated:
reducing the exposure period by a first increment, and repeating the steps of capturing image data and analyzing the indication of brightness of each pixel until it is determined that the captured image data is not saturated;
when it is determined that the captured image data is not saturated:
analyzing the indication of brightness of each pixel to determine whether a threshold indicative of use of a selected proportion of an available dynamic range of the image sensor has been reached; and
when it is determined that the threshold has not been reached, increasing said exposure period by a second increment, wherein the first increment has a magnitude at least three times that of the second increment.
2. A method according to claim 1 , wherein reducing the exposure period by a first increment comprises reducing the exposure period by between 33% and 75%.
3. A method according to claim 1 , wherein increasing the exposure period by a second increment comprises increasing the exposure period by between 1% and 20%.
4. A method according claim 1 , wherein the brightest proportion selection is dependent upon image size.
5. A method according to claim 1 , wherein the brightest proportion selection comprises between 0.05% and 2% of the total number of pixels of the image sensor.
6. A method according to claim 1 , wherein the indication of brightness captured by each pixel of the image sensor comprises a numerical value between zero and a maximum recordable brightness and wherein the saturation threshold comprises the maximum recordable brightness.
7. A method according to claim 1 , wherein analyzing the indication of brightness of each pixel to determine whether the threshold indicative of use of the selected proportion of the available range of the image sensor has been reached comprises:
selecting a brightest proportion of the indication of brightness captured by each pixel of the image sensor; and
determining an average intensity of the selected brightest proportion and comparing the average intensity to a range intensity threshold.
8. A method according to claim 7 , wherein the indication of brightness captured by each pixel of the image sensor comprises a numerical value between zero and a maximum recordable brightness and wherein the range intensity threshold comprises a value approximately 75% of the maximum recordable brightness.
9. A method according to claim 1 , wherein capturing image data on the image sensor using the exposure period occurs at a selected frame capture rate and the exposure period is less than a time period between successive frame captures.
10. A method according to claim 1 , further comprising stabilizing a series of images resulting from the captured image data by adjusting the captured image data such that a selected proportion of the indication of brightness captured by each pixel of the image sensor is allocated a minimum possible indication value and a selected proportion of the indication of brightness captured by each pixel of said image sensor is allocated a maximum possible indication value.
11. A non-transitory computer readable storage media storing instructions thereon that, when executed by a processor, cause a computer system to:
capture image data on an image sensor using an exposure period, the image data comprising: an indication of brightness captured by each pixel of the image sensor;
analyze the indication of brightness of each pixel to determine whether the captured image data is saturated, wherein determining whether the captured image data is saturated comprises:
selecting a brightest proportion of the indication of brightness captured by each pixel of the image sensor; and
determining an average intensity of the selected brightest proportion and comparing the average intensity to a saturation threshold; and
when it is determined that the captured image data is saturated:
reduce the exposure period by a first increment, and repeating the steps of capturing image data and analyzing the indication of brightness of each pixel until it is determined that the captured image data is not saturated;
when it is determined that the captured image data is not saturated:
analyze the indication of brightness of each pixel to determine whether a threshold indicative of use of a selected proportion of an available dynamic range of the image sensor has been reached; and
when it is determined that the threshold has not been reached, increasing said exposure period by a second increment, wherein the first increment has a magnitude at least three times that of the second increment.
12. An endoscopic apparatus configured to capture an image of in-vivo tissue and configured to perform automatic exposure control, the apparatus comprising:
image capture logic to capture image data on an image sensor using an exposure period, the image data comprising an indication of brightness captured by each pixel of said image sensor;
analysis logic to analyze the indication of brightness of each pixel to determine whether the captured image data is saturated, wherein determining whether the captured image data is saturated comprises:
selecting a brightest proportion of the indication of brightness captured by each pixel of the image sensor; and
determining an average intensity of the selected brightest proportion and comparing the average intensity to a saturation threshold; and
adjustment logic that:
when it is determined that the captured image data is saturated, reduces the exposure period by a first increment, and repeats the capturing image data and analyzing the indication of brightness steps until it is determined that the captured image data is not saturated;
when it is determined that the captured image data is not saturated, analyzes the indication of brightness of each pixel to determine whether a threshold indicative of use of a selected proportion of an available dynamic range of the image sensor has been reached; and
when it is determined that said threshold has not been reached, increasing the exposure period by a second increment, wherein said first increment has a magnitude at least three times that of the second increment.