ADAPTIVE METHOD AND SYSTEM FOR EXTRACTING A BRIGHT IMAGE FROM A THERMAL IMAGE
An image processor computes a raw histogram for an unprocessed raw digital image. The image processor positions a clip point at an intensity level within the raw image histogram. The pixels having an intensity level less than the intensity level of the clip point are blacked-out (reduced in intensity). The remaining illuminated pixels are displayed.
1 . An image processor for setting a clip point at an intensity level below which pixel values from an image are suppressed, the image processor comprising
a raw histogram module for computing a raw histogram of pixels in the image;
a clip point positioning module for positioning a clip point at a pixel intensity level within the raw histogram; and
a suppression module for reducing the intensity levels of the pixel values in the image that are lower than the intensity level of the clip point.
2 . The image processor of claim 1 , wherein
the clip point positioning module positions the clip point at a low intensity level within the raw histogram.
3 . The image processor of claim 1 , wherein
the clip point positioning module positions the clip point at an intensity level within the raw histogram corresponding to a bin having the greatest number of pixels per bin.
4 . The image processor of claim 1 , including
a contrast stretch module which stretches the raw histogram of the image; and
a display space mapping module which maps the stretched histogram and the clip point to a reduced bit level display histogram,
wherein a positional relationship between the raw histogram and clip point is similarly maintained between the display histogram and mapped clip point.
5 . The image processor of claim 4 , wherein
the suppression module produces a clipped image by reducing the intensity level of the pixels in the display histogram that have an intensity level lower than the intensity level of the clip point.
6 . The image processor of claim 5 , including
a display for displaying the illuminated pixels remaining in the clipped image.
7 . The image processor of claim 1 , including
a micro-bolometer sensor for generating the image being processed by the image processor,
wherein the raw histogram is computed from the image produced by the micro-bolometer sensor.
8 . A thermal video camera system, including
a micro-bolometer sensor for producing a raw thermal image;
an image processor for processing the raw thermal image,
wherein the image processor includes:
a raw histogram module for computing a raw histogram of the raw thermal image pixel values,
a clip point positioning module for positioning a clip point at a pixel intensity level within the raw histogram, and
a suppression module for reducing the intensity levels of the pixel values in the thermal image that are lower than the intensity level of the clip point; and
a display device for displaying the processed thermal image.
9 . The thermal video camera system of claim 8 , wherein
the clip point positioning module positions the clip point at a high intensity level within the raw histogram.
10 . The thermal video camera system of claim 8 , wherein
the clip point positioning module positions the clip point at an intensity level within the raw histogram corresponding to a bin having the greatest number of pixels per bin.
11 . The thermal video camera system of claim 8 , including
a display space mapping module that maps the raw data histogram and clip point to a reduced bit level display space.
12 . The thermal video camera system of claim 11 , wherein
the suppression module produces a clipped image by blacking-out the pixels in the display space that have an intensity level lower than the intensity level of the clip point.
13 . The thermal video camera system of claim 12 , wherein
the display displays the illuminated pixels remaining in the clipped image.
14 . The thermal video camera system of claim 13 , including
a manual control module allowing a viewer to manually adjust the clip point position set by the clip point positioning module for changing the number of illuminated pixels being displayed,
wherein the clip point is manually adjusted by the viewer after the clip point positioning module initially positions the clip point in the raw histogram.
15 . The thermal video camera system of claim 14 , including
an automatic temperature compensation module which controls the clip point positioning module to adjust the clip point based on a focal plane temperature or an enclosure temperature.
16 . A method for setting a clip point below which low intensity pixel values from an image are suppressed, the method comprising the steps of:
computing the raw histogram of the image;
positioning a clip point at an intensity level within the raw histogram;
contrast stretching and mapping the raw histogram to a reduced bit level display histogram; and
blacking-out the pixels having intensity lower than the intensity level of the clip point.
17 . The method of claim 16 , wherein
the clip point is positioned at a low intensity level within the raw histogram.
18 . The method of claim 16 , wherein
the clip point is positioned at an intensity level within the raw histogram corresponding to a bin having the greatest number of pixels per bin.
19 . The method of claim 16 , wherein
the illuminated pixels remaining in the clipped image are displayed.
20 . The method of claim 19 , wherein
the number of illuminated pixels in the displayed image are changed by manually adjusting the position of the clip point.
21 . The method of claim 16 , wherein
the clip point is repositioned as the raw histogram changes with changes in scene conditions and operating environments, to continuously maintain a position within the he raw histogram.