Abstract:
The present invention provides a polarizer that is motorized and rotates and is attached to the front of a digital camera. A series of images of a scene is acquired with the polarizer whose orientation is changed in a in a systematic sequence from 0 degrees to 180 degrees. The polarized images are processed to present a final image or set of images that amplify the net polarizations inherent in the light scattered or reflected by the various pixels in the scene. Multiple embodiments are given, including an embodiment implemented on a standard smartphone, one implemented on a miniature camera system mounted on a pair of glasses, and an embodiment on a system utilizing two synchronized camera systems mounted on a pair of eyeglasses.

Description:
This application claims the benefit of the U.S. Provisional Patent Application No. 61/979,292 filed Apr. 14, 2014 by the present inventors. This provisional patent application is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of optical elements that are polarized, and more particularly to a controlled rotating linearly polarized optical element used on a digital camera or Smartphone or any device or means capable of acquiring and, in most cases, processing digital images. The object of the invention is to create enhanced views of scenes that maximize the appearance of the net polarization of light that is reflected or scattered to an observer from the various elements within the scene, or to render the net polarization in the scene amenable to automatic detection of features of interest within the image. 
     2. Description of Related Art 
     As can be seen by reference to the following U.S. Pat. Nos. 8,449,409; 7,713,148; 5,414,476; and JP2004317124A2; JP10148521A2; and WO2009128340A1, the prior art is replete with myriad devices designed to enhance certain characteristics of scenes, making them far more apparent to the user. 
     Normal visible light has a component, referred to as the electric vector that is usually oriented in a random direction that is perpendicular to the path of the light beam. Polarized material allows only that light that has its electric vector oriented parallel to a preferential direction to pass through the material. This is analogous to a rope in a picket fence. Without the fence one can create wave motion in the rope horizontally, vertically or any angle in between, representative of the randomness of the wave states. But, if the rope goes through the fence, all horizontal motion is damped by the presence of the fence while the vertical is not. 
     Light that does not have its electric vector more or less parallel to that direction will be absorbed. Light that passes through such a polarized filter has all its electric vectors aligned in one direction, and is said to be polarized. The fraction of light that is absorbed is proportional to the cosine of the angle between the electric vector of the light and the preferential direction. As in conventional polarized sunglasses, each polarized lens has a preferential direction for light filtering. In conventional fixed-mount polarized sunglasses, the polarized preferential direction is vertical for both eyes. This allows light that has its electric vector oriented vertically to pass through unattenuated, light that has been reflected from horizontal surfaces, e.g., a car hood, or the road surface or the water&#39;s surface tends to have its electric vector oriented horizontally, and is thus preferentially absorbed by the polarized lens. This is the reason that conventional polarized sunglasses are so efficient at reducing reflected glare. 
     Many other situations result in different net polarizations of light reflected from various surfaces. Polarization differences in a scene are indicative of differences in the reflecting or scattering surfaces, differences that are not apparent without somehow enhancing the small differences in polarization, to which the eye is not sensitive. These differences include, for instance, light reflected from a golfing green, with different polarizations indicative of different types of grass, or subtle undulations in the green itself. We shall use golf and golfers as examples throughout this application, though it is understood that the principles are universally applicable. 
     To reiterate, the important point is that humans and the unaided human eye are not sensitive in any way to the net polarization of a scene; having an eye that is sensitive to net polarization would be analogous to the difference between seeing in black and white and seeing in color. 
     While all of the aforementioned prior art constructions are adequate for the basic purpose and function for which they have been specifically designed, they are uniformly deficient with respect to their failure to provide a simple, efficient, and practical optical element that maximizes and displays the polarization differences that are inherent in any particular scene. In its simplest form, our approach posits a motorized rotating optical polarizing element for use on a digital camera or a Smartphone. 
     By “motorized” we mean any remotely or automatically controlled or programmed device that changes the preferential filtering direction of a linearly polarizing optical element. The term “linearly polarizing optical element” applies to both the familiar physical forms of polarizer, e.g., the common plastic Polaroid filters, as well as to electronic devices, e.g., those based on Pockels cells, for instance. By “camera” we mean any device or system that is capable of acquiring an image and storing it digitally. Cameras usually have an optical lens, but the term “camera” can include any image formation device, e.g., a telescope minor. The term “microprocessor” means any computing device having a memory capability and computer code that receives digital image input and can output data generated by the computer code. If a capital letter such as P(i) is used to represent digital image number i in a sequence of digital images, then P(i, m, n) represents the individual pixel of P(i) in row m column n. 
     This new and improved motorized rotating linearly polarized optical element and its ability to present maximum net polarization, or any function of net polarization, inherent in any scene is a stated object of the present invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides at its most basic form, a polarizing optical device that is motorized and rotates about the optical axis, and is attached to the front of a digital camera. The camera acquires images with the angle of polarization at a series of different values. The images are processed in such a way to detect, show, and enhance maximum polarization differences across the field of view. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       These and other attributes of the invention will become more clear upon a thorough study of the following description of the various modes for carrying out the invention, particularly when reviewed in conjunction with drawings, wherein: 
         FIG. 1  is a functional view of the motorized rotating linearly polarized optical device of the first embodiment. 
         FIG. 2  is view of 60 polarization angles of the digital images acquired in the first embodiment. 
         FIG. 3  is a perspective view of the motorized rotating linearly polarized optical device mounted on a shaft of a pair of eyeglasses of the second embodiment. 
         FIG. 4  illustrates a miniature eyeglass mounted camera system of the second embodiment. 
         FIG. 5  illustrates the third embodiment where the motorized rotating linearly polarized optical device is hosted in a device such as Google Glass™. 
         FIG. 6  Illustrate a fourth embodiment involving motion picture enhancement of the first embodiment. 
         FIG. 7  and  FIG. 8  illustrate a fifth embodiment implementing two synchronized cameras. 
         FIG. 9  illustrates a sixth embodiment implementing an automated weapon system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, polarized images may be acquired at different rotation angles, processed, and combined in one of any of a number of ways, ranging from simple subtraction of images acquired with two or more perpendicular polarizations to a more detailed maximization, or any other image processing function, of the differences in all the images. 
     In the first embodiment, illustrated in  FIG. 1 , the motorized rotating linearly polarized optical device  100  is comprised of a camera  108 , a polarizer,  104  a rotator motor  106 , and a microprocessor  110 . The microprocessor  110  controls the rotator motor  106  which rotates the polarizer  104 . The camera in the first embodiment has a spatial resolution corresponds to a scene pixel resolution of roughly VGA type quality, 640×480 pixels or better. This is simply an example. Finer or coarser resolutions would also obtain. The motorized rotating linearly polarized optical device  100  takes a series of 60 successive positions in order to acquire 60 images P(i), i=1 to 60 of scene  102 .  FIG. 2  illustrates the polarization angle of the 60 images. The number of views may be varied as well. Note that cameras with this VGA or better resolution are currently found in almost all state of the art smartphones. 
     The first embodiment performs the following four steps, data acquisition, image subtraction and processing, image feature maximization, and display. One algorithm is presented as an example: 
     Step 1: Camera  108  acquires 60 digital images P(i) of a scene  102 , illustrated in  FIG. 1  over a rotation of 180 degrees, 3 degrees separating successive polarized angle views. The rotator motor  106  rotates the polarizer  104 , and the resulting successive polarized digital images P(i) are sent to the camera  108 , which are then transmitted to the microprocessor  110 . In the first embodiment, R=640, and S=480. 
     Step 2: Image processing software hosted in the microprocessor  110  interfacing with the camera  108  then calculates 30 difference digital images D(i), i=1, 30, by subtracting images taken 90 rotational degrees apart. Hence digital image D( 1 ) is obtained by subtracted, pixel by pixel P( 1 ) from digital image P( 31 ), resulting in polarized difference digital image D( 1 ). Digital image D( 2 ) is calculated by subtracting P( 2 ) from digital image P( 32 ), resulting in polarized difference digital image D( 2 ), etc. The result is 30 polarized difference digital images: D( 1 ), D( 2 ) . . . , D( 30 ). Each difference digital image D(i) is an array of pixels P(i, n, m)−P(i+30, n, m), n=1, 2, . . . , R, m=1, . . . , S, where P(i, n, m) are the pixels in P(i). In embodiment 1, R=640, S=480 and i=1, 2, . . . N where N=30. It is noted that the common image processing conditioning steps, e.g., normalization, boundary condition matching, are not specifically enumerated here, but are common and employed in standard practice. 
     Step 3: For each difference digital image, D(i), i=1,2, . . . 30, the scalar Q(i), i=1 to 30 is calculated as the sum of the squares of the individual elements D(i, m, n) in each difference digital image D(i), i.e:
 
 Q ( i )= D ( i ,1,1)**2 +D ( i ,1,2)**2 + . . . +D ( i,R,S )**2.
 
     Step 4: The microprocessor  110  computes the maximum difference digital image D(I) where I has the largest value Q(i), i=1, . . . 30 and transmit the resulting digital image D(I) to the display  112 . This completes the process. 
     If this process is done on a putting green, the maximum difference image D(I) of the putting green is therefore presented to the golfer. This image makes clear differences in vegetation, cut of green, etc. If this process is accomplished on a military scene, camouflaged equipment, e.g., vehicles and artillery pieces, as well as the camouflaged fabric on uniforms, may well present an image of net polarization that differs substantially from the background. 
     Alternate embodiments are consistent with the inventive concept presented herein. As shown in  FIG. 1 , a function f(D(i,j,k))  109 . In embodiment 1 f( ) is the sum of squares function Q(i) shown above. In other embodiments, function f may be any function of the array of difference pixels D(i, j,k,), i=1 through N, j=1 through R, k=1 through S. Many functions f are well known in the field of digital image processing. Furthermore, more generally, the integers N, R and S may be any positive integers, each at least 2 although it is unlikely that N will be less than 30 and R and S will be less than those of a VGA scenario. Typically the function f is chosen based on the objective of the device, e.g., viewing a camouflaged target, or looking at a putting green. The function f for a particular application is often determined by extensive testing of many potential candidate functions. 
       FIGS. 3 and 4  illustrate a second embodiment. The miniature eyeglass mounted camera system  114  of the second embodiment is a miniaturized unit that is mounted on one of the temple pieces of a pair of eyeglasses  116 . In this embodiment, the miniature eyeglass mounted camera system  114  has a processing component  111   a  and a display component  111   b . An example of a miniature eyeglass mounted camera system  114  is Google Glass™. A polarizer,  104  and a rotator motor  106  are installed on the front of the processing component  111   a . The processing component  111   a  has customized code (not shown in  FIG. 4 ) that controls the rotator motor  106 . The polarizer  104  transfers successive digital images P(i), i=1, . . . 60 to customized code in the processing component  111   a . The processing component  111   a  computes the maximum difference digital image D(I) and sends it to the display component  111   b  where the resulting image can be viewed by the user. 
       FIGS. 3 and 5  illustrate a third embodiment. In the third embodiment, the polarizer,  104  and a rotator motor  106  are mounted in front of a customized camera  122  that has a camera component  118  and a microprocessor component  120 . The microprocessor component  120  controls the rotator motor  106  which rotates the polarizer  104 . The camera component  118  send the successive digital images P(i), i=1, . . . 60 to the customized code located in the microprocessor component  120 . The microprocessor component  120  computes the maximum difference digital image D(I) where I has the largest value Q(i), i=1, 30 and transmits the resulting digital image D(I) to the display  112 . This completes the process. 
     Alternate embodiments of embodiments one through three are consistent with the embodiments presented herein. The number of pixels can be greater or less then the VGA example above. The microprocessor  110  and display  112  may or not be part of the motorized rotating linearly polarized optical device. The number of difference digital images D(i) can be greater than or less than 30. The algorithm may be different from the sample shown here. 
     The fourth embodiment: the motion picture embodiment. Sequence of digital images D(I, 1 ), D(I, 2 ), . . . are displayed, where the second index refers to the particular sequence in which that image set was acquired. Referring to  FIG. 6 , this embodiment is an enhancement of the first embodiment. Instead of transmitting a single maximum difference digital image, D(I), representing the single digital image obtained from 60 polarized digital images P(i), i=1 to 60, successive difference digital images D(I, 1 ), D(I, 2 ) D(I, 3 ) are processed by the motorized rotating linearly polarized optical device  100  and are transmitted and displayed on display  112 , thereby displaying a motion picture of difference digital images D(I), 1=1,2, . . . .  FIG. 6  illustrate processing three of the digital images D(I). 
     Alternate embodiments of the fourth embodiment displays the sequence of digital images D(I, 1 ), D(I, 2 ) . . . on different camera systems, for example the second or the third embodiment. 
     The fifth embodiment: the two camera embodiment. The fifth embodiment, shown in  FIGS. 7 and 8 , involves the use of two miniature eyeglass mounted camera systems  114   a  and  114   b  (see  FIG. 7 ) with coordinated rotating polarizers This embodiment, based on the third embodiment, requires a relatively careful alignment of the two miniature eyeglass mounted camera systems  114   a  and  114   b . In this embodiment both digital images are taken simultaneously, for example P( 1 ) and P( 31 ) are taken simultaneously, P( 2 ) and P( 32 ) are take simultaneously, etc. The major advantage is that the pairs of perpendicularly polarized digital images are acquired at the same time. Compare this to the first and second embodiments, where the perpendicularly polarized digital images are obtained 30 frames apart, so significant movement between digital images either in the scene itself, or by motion or orientation change of the camera can spoil the technique if there is no compensation for these digital image differences. This fifth embodiment avoids this problem. 
     Referring to the fifth embodiment (see  FIG. 8 ) the microprocessor component  120  of the first customized camera system  114   a  transmits synchronization signal  124  and the difference digital image D(i) to the second customized camera system  114   b . The second customized camera system  114   b  computes the maximum difference digital image D(I) and transmits the image signal  126  D(I) to the display  112 . 
       FIG. 9  illustrates a sixth embodiment of the current invention. Only the changes between this embodiment and the first embodiment are discussed herein in detail. The main differences between the first embodiment and the sixth embodiment is that the sixth embodiment does not have a display  112  and does not have a human in the loop. The microprocessor  110  of the first embodiment is replaced by a customized automatic image recognition system  128 . The customized automatic image recognition system  128  is designed to identify specific targets such as a camouflaged person  132  hiding among foliage  140 . The customized automatic image recognition system  128  when a camouflaged person  132  is identified, it communicates the camouflage person coordinates 134 of the camouflaged person  132  to an automated targeting system  136  which targets the camouflage person coordinates 134 and fires a missile  138  at the camouflaged person  132 . 
     Alternate embodiments of the sixth embodiment may be implemented. A human with a display may be included to make a decision whether to fire the missile. Instead of targeting a camouflaged person  132 , it could target an animal. Instead of firing a missile  138 , it could take a picture of the animal. 
     The present invention is advantageous for use in sport-oriented activities, where accentuating subtle changes in scene provides major change in awareness. For example, in golf, even the most subtle undulations in the green and changes in vegetation become readily observable. In sailing, differences in water surface due to current or wind(e.g., “cat&#39;s paw” swirl of water) become much more apparent. Further, for hunting animals whose color schemes blend into the background, the animal as seen in polarized light will appear to stand out. In skiing, ice shows up very clearly, as do moguls and holes. In driving, black ice would show up very clearly on otherwise clear roadways. For use when piloting an airplane, the appearance of changes in the sky scene, e.g., an approaching plane, or in observation of the ground, e.g., change in elevation in vegetation (which could characterize the condition of a grass strip runway) or an otherwise uniform background, e.g., the desert, can lead to material improvements in safety. 
     Combining results from maximally polarized imagery and images derived from other types of remote sensing, e.g., FLIR thermal imaging for moisture detection, can yield maps or images of very specific content. For example, on the golf course, the data from both could produce a map showing moisture, vegetation type, and undulation of the surface. Such imaging data fusion could be as simple as putting the two images on a common reference frame by applying simple arithmetic operations, e.g., dividing the pixels of one by the other, or more complex operation, e.g., mapping 2 or 3 standard deviations in local background from each image separately into a single resulting image that would highlight regions where both maps indicated deviations. The algorithm is a function of the particular characteristic under investigation. Thus, simple spectral filters, e.g., a notch filter that allows only a narrow spectral band to pass through without absorption, will present a different polarization digital image than will a notch filter placed over a different spectral region. Low-pass and high-pass spectral filters will similarly present different net correlation digital images with the polarization data, and so can yield better information on other physical conditions, particularly moisture. In another golf example of the advantages of combining data, the processed output of the polarized digital images in combination with the digital image output of range-finding cameras, can be input to an algorithm to choose a best path for a golfer to aim his shot on the green. 
     Although only an exemplary embodiment of the invention has been described in detail above, those skilled in the art will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. 
     Having thereby described the subject matter of the present invention, it should be apparent that many substitutions, modifications, and variations of the invention are possible in light of the above teachings. It is therefore to be understood that the invention as taught and described herein is only to be limited to the extent of the breadth and scope of the appended claims.