Abstract:
An image capture device includes, in part, N optical transmit antennas forming a first array, N phase modulators each associated with and adapted to control a phase of a different one of the transmit antennas, M optical receive antennas forming a second array, M phase modulators each associated with and adapted to control a phase of a different one of the receive antennas, and a controller adapted to control phases of the first and second plurality of phase modulators to capture an image of an object. The first and second arrays may be one-dimensional arrays positioned substantially orthogonal to one another. Optionally, the first array is a circular array of transmitters, and the second array is a one-dimensional array of receivers positioned in the same plane as that in which the circular array of the transmitters is disposed.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit under 35 USC 119 (e) of U.S. provisional application No. 62/294,176, filed Feb. 11, 2016, entitled “ Hybrid Transmitter Receiver Optical Imaging System”, the content of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    RF and mm-wave phased arrays are widely used in a variety of applications, such as communication, beam steering, astonomy and radar. Optical phased arrays have also been used. However, a need continues to exist for a mobile imaging systemt that uses optical phased arrays. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    An image capturing device, in accordance with one embodiment of the present invention includes, in part, N optical transmit antennas forming a first array wherein N is an integer, N phase modulators each associated with and adapted to control a phase of a different one of the transmit antennas, M optical receive antennas forming a second array wherein M is an integer, M phase modulators each associated with and adapted to control a phase of a different one of the receive antennas, and a controller adapted to control phases of the first and second plurality of phase modulators to capture an image of an object. In one embodiment, the first and second arrays are orthogonal to one another when viewed in Cartesian plane. In another embodiment, the first array is a circular array of transmitters, and the second array is a line array of receivers positioned in the same plane as the plane in which the circular array of transmitters is disposed. 
         [0004]    In one embodiment, the image capture device further includes, in part, an optical splitter adapted to split the received coherent optical signal into N optical signals and deliver the N optical signals to the N phase modulators. In one embodiment, the image capture device further includes, in part, an optical signal combiner adapted to combine M optical signals received from M receive antennas to generate a combined received optical signal. In one embodiment, the image capture device further includes, in part, a detector adapted to detect whether the combined received optical signal represents an image of one or more points of the object. In one embodiment, the detector is adapted to supply its output to the controller. In one embodiment, the coherent optical signal is laser. In one embodiment, the M mixers are disposed between the M transmit antennas and the combiner. In one embodiment, M and N are equal. In one embodiment, the coherent optical signal supplies a reference signal to the M mixers. 
         [0005]    A method of forming an image of an object, in accordance with one embodiment of the present invention, includes, in part, transmitting N optical signals from N transmit antennas positioned along a first array to the object, modulating phases of the N transmit antennas via a first N phase modulators and in accordance with a first control information received from a controller, receiving reflection of the N optical signals off the object via M optical receive antennas forming a second array, and modulating phases of the M optical receive antennas via a second M phase modulators and in accordance with a second control information received from the controller. In one embodiment, the first and second arrays are orthogonal to one another when viewed in Cartesian plane. In another embodiment, the first array is a circular array of transmitters, and the second array is a line array of receivers positioned in the same plane as the plane in which the circular array of transmitters is disposed. 
         [0006]    The method, in accordance with one embodiment, further includes, in part, splitting a coherent optical signal received from an optical source into N optical signals, and delivering the N optical signals to the N phase modulators. The method, in accordance with one embodiment, further includes, in part, combining the M optical signals received from the M receive antennas to generate a combined received optical signal. The method, in accordance with one embodiment, further includes, in part, detecting whether the combined received optical signal represents an image of one or more points of the object. 
         [0007]    The method, in accordance with one embodiment, further includes, in part, supplying to the controller a signal representative of whether the combined received optical signal represents an image of one or more points of the object. The method, in accordance with one embodiment, further includes, in part, converting a frequency of M optical signals received by the M receive antennas. The method, in accordance with one embodiment, further includes, in part, converting the frequency of M optical signals in accordance with a reference signal supplied by the coherent optical signal. In one embodiment, the coherent optical signal is laser. In one embodiment, M is equal to N 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a simplified schematic diagram of an image capture device, in accordance with one exemplary embodiment of the present invention. 
           [0009]      FIG. 2A  shows a one dimensional array of transmit antenna elements transmitting optical signals having the same phase. 
           [0010]      FIG. 2B  shows a one dimensional array of transmit antenna elements transmitting optical signals having different phases. 
           [0011]      FIG. 2C  shows an exemplary sweep angle of the optical signal transmitted by the optical phased array transmitter disposed in the image capture device of  FIG. 1 . 
           [0012]      FIG. 2D  shows exemplary directions along which an optical signal may be transmitted by the optical phased array transmitter disposed in the image capture device of  FIG. 1 . 
           [0013]      FIG. 2E  shows exemplary directions along which an optical signal may be detected by the optical phased array receiver disposed in the image capture device of  FIG. 1 . 
           [0014]      FIG. 2F  shows the points of interceptions of the transmit and detect directions shown in  FIGS. 2D and 2E . 
           [0015]      FIGS. 3A-3E  show various arrangements of phased array transmitters and receivers disposed in an image captured device, in accordance with some embodiments of the present invention. 
           [0016]      FIG. 4  is a simplified schematic diagram of an image capture device, in accordance with one exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    An image capture device, in accordance with one embodiment of the present invention, includes an array of phased array transmit elements (alternatively referred to herein as phased array transmitter) transmitting optical signals to an object whose image is being captured, and an array of phased array receive elements (alternatively referred to herein as phased array transmitter) receiving the optical signals reflected from the object. The phased array transmitter has a far field pattern defined by a 2-dimensional Fourier Transform of the phased array transmit elements. Similarly, the phased array receiver has a far field pattern defined by a 2-dimensional Fourier Transform of the phased array receive elements. Embodiments of the present invention are adapted to capture and form an image of an object when the far field Fourier Transform patterns of the phased array transmitter and phased array receive interest one another at only one point. In one embodiment, the phased array transmit elements form a one dimensional array that is perpendicular to a one dimensional array formed by the phased array receive elements. 
         [0018]      FIG. 1  is a simplified high-level block diagram of an image capture device  100 , in accordance with one exemplary embodiment of the present invention. Image capture device  100  is shown as including, in part, a coherent optical signal source, e.g. a laser,  30 , an optical splitter  16 , optical phased array transmitter  10 , an optical phased array receiver  50 , a detector  58 , and a controller  60 . 
         [0019]    Optical phased array transmitter  10  is shown as including N transmit antennas  12   1 ,  12   2  . . .  12   N , and N phase modulators  14   2  . . .  14   N . Optical signal A generated by coherent optical signal source  30  is received by and split by splitter  16  into N optical signals each delivered to a different one of the optical phase modulators  14   i , where i is an index ranging from 1 to N. Each optical phase modulator  14   i  is adapted to modulate the phase of the optical signal it receives, in accordance with the control signal CtrlTi that the phase modulator receives from controller  60 , and delivers the phase-modulated optical signal to its associated optical transmit antenna element  12   i . By varying (modulating) the relative phases of the optical signals transmitted by antenna elements  12   i , the optical signal generated as a result of the interference of the N transmitted optical signals may be steered or rotated, as described further below. 
         [0020]      FIG. 2A  shows a one dimensional array of 8 transmit antenna elements  12   1 ,  12   2  . . .  12   8 , positioned along the y-axis and transmitting signals having the same phase. Accordingly, the wavefront  15  of the resulting interference signal is substantially parallel to the y-z plane (z is perpendicular to the page).  FIG. 2B  shows the same wavefront  15  when the difference between phases of optical signals transmitted by antenna elements  12   j  and  12   j+1  (j is an index varying from 1 to 7 in this example) is selected to be equal to θ. 
         [0021]    As is seen from  FIGS. 2A and 2B , by varying the relative phases of the transmit antenna elements, the direction of the resulting wavefront  15  may be varied.  FIG. 2C  shows the angle μ that the resulting signal  15  generated by antenna elements of  FIG. 2A or 2B  may cover. In other words, by varying the relative phases of the signals transmitted by antenna elements  12   1 ,  12   2  . . .  12   8 , the resulting signal may be steered from direction  120  to  122  covering angel μ.  FIGS. 2C and 2D  are side and front views of the resulting optical signal along exemplary directions  106 ,  104 ,  102 ,  108  and  110  within the angle μ. 
         [0022]    In a similar manner, the direction (angle) of the optical signal generated by phased array transmitter  10  of  FIG. 1  may be varied by varying the relative phases generated by phase modulators  14   i . The optical signal so transmitted is reflected off an object (not shown) whose image is being captured by optical phased array receiver  50  disposed in device  100 . Optical phased array receiver  50  is shown as including M receiving antenna elements  52   1 ,  52   2  . . .  52   M , and M phase modulators  54   2  . . .  54   N . The one dimensional phased array receive antenna elements  52   1 ,  52   2  . . .  52   M  are positioned along the z-axis so as to be substantially perpendicular to the y-axis along which the one dimensional phased array transmit antenna elements  12   1 ,  12   2  . . .  12   M  are disposed. In other words, receive antenna elements  52   1 ,  52   2  . . .  52   M  are positioned in parallel to optical signal lines  106 ,  104 ,  102 ,  108  and  110  shown in  FIG. 2D . 
         [0023]    Because in the exemplary embodiment shown in  FIG. 1 , the receive antenna elements  52   k  (k is an index ranging from 1 to M) are positioned in a direction that is perpendicular to the direction of the transmit antenna elements  12   i  (shown along the z-axis in this example) by changing their relative phases via phase modulators  54   k , the receive antenna elements  52   k  may be configured to detect the optical signal reflected off the object along the direction perpendicular to the direction of the optical signal lines  106 ,  104 ,  102 ,  108 ,  110 , i.e., along the y-axis shown in  FIGS. 2D, 2E and 2F . 
         [0024]      FIG. 2E  shows exemplary directions  206 ,  204 ,  202 ,  208  and  210  along which receive antenna elements  52   k  may be configured to detect an optical signal. In other words, by varying the relative phases of receive antenna elements  52   k , optical phased array receiver  50  may be configured to scan and detect an optical signal along the y-axis as shown in  FIG. 2E . 
         [0025]    Because phased array transmitter  10  is configured to transmit and sweep optical signals along the z-axis and phased array receiver  50  is configured to scan and detect optical signals along the y-axis, as shown in  FIGS. 2D, 2E, and 2F , phased array receiver  50  is enabled to detect an optical signal when the optical signal falls within the scan range of optical phased array receiver  50 . For example, if controller  60 , via phase modulators  14   i , selects the relative phases of transmit antenna elements  12   i  so that the transmitted optical is along direction  106  (see  FIGS. 2D, 2E, and 2F ), phased array receiver  50  may detect this signal at  250  when controller  60 , via phase modulators  54   i , selects the relative phases of receive antenna elements  52   i  to look for the optical signal along direction  206 . Similarly, for example, if controller  60 , via phase modulators  14   i , selects the relative phases of transmit antenna elements  12   i  so that the transmitted optical is along direction  104 , phased array receiver  50  may detect this signal at  252  when controller  60 , via phase modulators  54   i , selects the relative phases of receive antenna elements  52   i  to look for the optical signal along direction  208 . 
         [0026]    Accordingly, an optical signal transmitted by transmitter array  10  is detected by receiver array  50  whenever the transmit direction of transmit array  10  and receive or search direction of receive array  50  intercept one another.  FIG. 2F  shows 25 such interceptions 2 of which are identified using reference numbers  250  and  252 . In other words, to form an image of an object, controller  56  adjusts the phases of phase modulators  12   i  so as to direct the optical signal via the phased array transmitter to a region of the object whose image is being captured. The controller then varies the phases of phase modulators  54   i  and determines the amount of power it receives from the phased array receiver for each such phases. If the received power for any such phases is above a predefined threshold value, an image is identified as being detected, thereby causing the controller to move to the next region of the object. 
         [0027]    Referring to  FIG. 1 , combiner  56  is adapted to combine the M received optical signals and deliver the combined signal to controller  60  via signal detector  58 . In addition to controlling the phases of phase modulators  14   i  and  54   j , controller  60  may be further configured to store the positions of the detected signals, thereby to from a 3-dimensional image of the object. In some embodiments the number of transmit antenna elements in phased array transmitter, i.e. i, is equal to the number of receive antenna elements, i.e., j. Controller  60  may be configured to perform signal processing operations to capture and form a 3D image of an object. Such signal processing operations mat be similar to those used in pulsed LIDAR for depth measurement. 
         [0028]    As described above, a device in accordance with embodiments of the present invention is adapted to capture and form an image of an object when the far field Fourier Transform patterns of the device&#39;s phased array transmitter and the device&#39;s phased array receive interest one another at only one point.  FIG. 3A-3F  shows a multitude of exemplary arrangements of the transmit and receive elements respectively of the phased array transmitter and receiver, in accordance with embodiments of the present invention. 
         [0029]    In  FIG. 3A , the transmit antennas of the phased array are positioned along direction  305 , and the receive antennas of the phased array are positioned along direction  310  which is perpendicular to direction  305 . In  FIG. 3B , the transmit antennas of the phased array are positioned along direction  305 , and the receive antennas of the phased array are positioned along direction  310  which is perpendicular to direction  305 . In  FIG. 3C , the transmit antennas of the phased array are positioned along direction  305 , and the receive antennas of the phased array are positioned along direction  310 . The angel between directions  305  and  310  may have any value other than zero 
         [0030]    The array of transmit and receive elements of an image capture device, in accordance with embodiments of the present invention, may be two or three dimensional arrays.  FIG. 3D  shows a two-dimensional array of transmit antennas  352  and receive antennas  354  of an image capture device, in accordance with another embodiments of the present invention. Transmit antennas  352  are shown as being positioned along the periphery of rectangular region  350 . Receive antennas  358  are shown as being positioned along the periphery of rectangular region  355 . The two rectangular regions  350  and  355  are substantially in the same plane. 
         [0031]      FIG. 3E  shows the arrangement of arrays of transmit and receive antennas of an image capture device, in accordance with yet another embodiment of the present invention. The transmit antennas  390  are assumed to be positioned along the circumference(s) of one or more concentric circles  370 ,  372  and  374 . The receive antennas may be positioned along line  380  poisoned in the same plane as that in which the concentric circles are positioned. It is understood that in  FIGS. 3A-3E  other elements of an image capture device, such as phase modulators (see, for example,  FIGS. 1 and 4 ) are not shown. It is also understood that the one dimensional arrays shown in  FIGS. 3A-3C  and the two-dimensional arrays shown in  FIGS. 3D and 3E  may have any number of transmit and receive antennas. 
         [0032]      FIG. 4  is a simplified schematic diagram of an image capture device  300 , in accordance with another exemplary embodiment of the present invention. Image capture device  300  is similar to image capture device  100  except that image capture device  300  also includes M mixers  70   j  each associated with a different one of the receive antenna elements  52   i . For example, mixer  70   1  converts the frequency of the signal received by antenna element  52   1  and delivers the frequency converted signal to combiner  56 . Similarly, mixer  70   M  converts the frequency of the signal received by antenna element  52 M and delivers the frequency converted signal to combiner  56 . Mixer  70   j  are adapted to simplify the measurement process by shaping and reducing the noise in the system. Accordingly device  300  has a relatively higher sensitivity and accuracy. Image capture device  300  may be used with, for example, with pulsed LIDAR or other techniques that use linear frequency modulation. 
         [0033]    The above embodiments of the present invention are illustrative and not limitative. Embodiments of the present invention are not limited by the number of transmit or receive antennas, the wavelength of the optical source, the type of frequency conversion, the type of optical signal splitter, combiner, and the like. Embodiments of the present invention are not limited by the type of substrate, semiconductor or otherwise, in which various optical and electrical components of the image capture device are formed. Other additions, subtractions or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims.