Turbulence-free camera system and related method of image enhancement

• US 20140368715A1
• Filed: 06/17/2014
• Published: 12/18/2014
• Est. Priority Date: 06/17/2013
• Status: Active Grant

• Current Assignee: University of Maryland Baltimore County (University of Maryland)
• Original Assignee: University Or Maryland Baltimore County
• Inventors: Shih, Yanhua, Chen, Hui, Peng, Tao
• Granted Patent: US 9,444,978 B2
• Time in Patent Office: Days
• US Class Current: 348/311
• CPC Class Codes: G01J 2001/428 for sunlight scattered by atmosphere
• CPC Class Codes: G01N 2021/4106 Atmospheric distortion; Turbulence
• CPC Class Codes: G01N 21/41 Refractivity; Phase-affecting properties, e.g. optical path length G01N21/21 takes precedence
• CPC Class Codes: G02B 27/1066 for enhancing image performance, like resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 2207/30181 Earth observation
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/63 by using electronic viewfinders
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/626 Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
• CPC Class Codes: H04N 25/71 Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors

Abstract

A turbulence-free CCD camera system with nonclassical imaging resolution, for applications in long- distance imaging, such as satellite and aircraft-to-ground based distant imaging, utilizing an intensity- fluctuation correlation measurement of thermal light. The proposed camera system has the following advantages over classic imaging technology: (1) it is turbulence-free; (2) its spatial resolution is mainly determined by the angular diameter of the light source. For example, using sun as the light source, this camera may achieve a spatial resolution of 200 micrometer for any object on Earth. 200-micrometer resolution is insignificant for short distance imaging, however, taking a picture of a target at 10-kilometer, a classic camera must have a lens of 90-meter diameter in order to achieve 200-micrometer resolution. Unlike a classic camera, the proposed turbulence-free CCD camera system has adequate spatial resolution zoom a long distance and still distinguish the objects within a small area, even with a small lens.

Claims

1. A camera system, comprising:

a beam splitter receiving thermal light photons from an object or area to be imaged, each such photon passing through the beam splitter to either a CCD camera or a bucket photodetector, wherein the CCD camera passes information to a first Pos-Neg identifier and the bucket photodetector passes information to a second Pos-Neg identifier and each of the first and second Pos-Neg identifiers pass information to a positive-negative fluctuation circuit (PNFC) comprising at least one processor, at least one memory operatively associated with the processor, such memory containing a positive-negative fluctuation protocol algorithm, and wherein the PNFC detects photon coincidence from the intensity fluctuation correlation of the sunlight, and passes the resulting correlation information to an image viewer.

2. The camera system of claim 1 wherein the information passed from the CCD camera and the bucket photodetector to the respective Pos-Neg identifier comprises the registration time of each photodetection event.

3. The camera system of claim 1, wherein the information passed from each Pos-Neg identifier to the PNFC comprises counting numbers classified as positive and negative fluctuations.

4. The camera system of claim 1 wherein the PNFC and associated software records the registration time of each photodetection event from the CCD camera and the bucket photodetector in two independent event timers, which are divided in to sequences of short time windows.

5. The camera system of claim 4, wherein the PNFC and associated software analyzes the photon counting number fluctuations in each time window, calculating the average counting numbers per short time window.

6. The camera system of claim 1 wherein the image produced on the image viewer is a series of images comprising a video sequence.

7. A method of use of the camera system of claim 1, comprising the following processor implemented steps not necessarily in sequential order:

providing a series of frames of a given region of interest;

determining the value of each pixel at each location within each frame to form a pixel value array for each frame;

summing the pixel values in each frame to obtain the frame intensity for each frame;

multiplying the pixels in the pixel value array by the frame intensity to produce a frame intensity multiplied pixel value array;

summing the frame intensity multiplied pixel value arrays together and dividing by the number of frames to obtain an average of the frame intensity multiplied pixel value arrays;

using the pixel value arrays, creating an array of average pixel values;

determining the average frame intensity for the series of frames;

multiplying the array of average pixel values by the average frame intensity for all of the inputted frames; and

subtracting the array of average pixel values multiplied by average frame intensity from the average of the frame intensity multiplied pixel value arrays to provide an array of modified pixel values to form an improved image.

8. The method of claim 7, wherein the camera system is located on a satellite, airplane, helicopter, drone or other aerial vehicle.

9. The method of claim 7, wherein the thermal light photons inputted into the camera system were influenced by the effects of turbulence or adverse weather effects.