Abstract:
A tracking system includes an emitter array configured to emit radiation around a subject to be tracked in at least one dimension wherein each emitter or group of emitters is modulated to permit identification of a source of the radiation. A receiver is configured to receive the radiation from the emitter array, wherein one of the emitter array and the receiver are located on the subject to be tracked. A processor is configured to interpret changes in radiation and correlate the changes to a device position to output a device position control signal.

Description:
This application claims the benefit, under 35 U.S.C. §365 of International Application PCT/US2005/043853, filed Dec. 5, 2005, which was published in accordance with PCT Article 21(2) on Jun. 14, 2007, in English. 
     FIELD OF THE INVENTION 
     The present invention generally relates to systems and methods for developing and transmitting telemetry data and more particularly to a video camera unit and method which tracks a camera subject within a viewing frame of a video camera. 
     BACKGROUND OF THE INVENTION 
     Video cameras are employed for many applications including commercial and personal uses. Commercial applications may include making promotional videos, taping performances or lectures, etc. In a particularly useful commercial application, a speaker may record a lecture or provide an instructional video. In many cases these videos require personnel to record the event. Often the speaker may move about requiring the camera personnel to adjust the camera position or angle to maintain the speaker within the video frame. 
     While camera tracking equipment has been employed, such previous products have included motor driven moving parts that frequently wear out and fail. In many situations, it is not possible or inconvenient to provide a manned camera or “tracking” products to video tape a lecture or presentation. It would be beneficial to provide an automatic tracking system and method that would permit a speaker to move about freely and video tape a presentation without the assistance of camera personnel. 
     SUMMARY OF THE INVENTION 
     A tracking system includes an emitter array configured to emit radiation around a subject to be tracked in at least one dimension wherein the emitter array includes at least one individually modulated to permit identification of a source of the radiation. A receiver is configured to receive the radiation from the emitter array, wherein at least one emitter and the receiver are located on the subject to be tracked. A processor in the receiver is configured to measure relative radiation intensity from at least one emitter, interpret such data, correlate changes in the subject&#39;s position and output a device position control signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages, nature, and various additional features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with accompanying drawings wherein: 
         FIG. 1  is schematic diagram showing an emitter array having a pair of diodes transmitting light about a centerline to a subject to be tracked in an exemplary system; 
         FIG. 2  is a block diagram showing an illustrative transmission unit for tracking a subject; 
         FIG. 3  is a block diagram showing an illustrative receiver unit for tracking a subject; 
         FIG. 4  is a block diagram showing an auto tracking system in accordance with a particularly useful embodiment; 
         FIG. 5  shows traces depicting relative amplitudes for four modulation frequencies when a subject is centered in a camera view; 
         FIG. 6  shows traces depicting relative amplitudes for four modulation frequencies when a subject is off-center in the X direction; and 
         FIG. 7  shows traces depicting relative amplitudes for four modulation frequencies when a subject is off-center in the Y direction. 
     
    
    
     It should be understood that the drawings are for purposes of illustrating the concepts of the invention and are not necessarily the only possible configuration for illustrating the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Aspects of the present invention provide systems and methods for developing and transmitting telemetry data, which depict operation angles of a video camera pan-tilt unit with respect to the camera subject. In particularly useful embodiments, an automatic tracking system is employed that keeps a moving subject, such as, e.g., a classroom instructor, within a viewing frame of a video camera. 
     In illustrative embodiments, a robotic or electronically controlled video understood that the number of emitters  18  may be much greater and may be employed in pairs, triples, quads, etc. and may be employed for a plurality of different axes and positions. 
     The array  16  is driven by electronic circuitry  22  that modulates the optical power of individual array elements  18  or array sections at different, strategically assigned frequencies. In the example shown in  FIG. 1 , an emitter A has optical power modulated at 30 kHz while emitter B has an optical power modulated at 32 kHz. In one embodiment, a subject  24  to be tracked by camera  14  wears a small optical receiver  26  which picks up infrared (IR) or other radiation beams  32 ,  34  and demodulates the signal to retrieve AC modulation signals. Appropriate filtering or waveform analysis is then applied to measure and compare amplitude of the recovered modulation signals. This comparison reveals the angular position of the camera relative to the subject and is used to reposition the pan/tilt unit  12  of the camera  14  to track the subject  24 . 
     Several infrared beams are emitted from the location of the pan/tilt unit  12 , toward the subject  24 . An array of individual IR beam emitters  18  physically conforms to a precise geometric pattern that represents, e.g., X, Y and/or Z axes. The individual emitters  18  are set at precise angles relative to each other, which define a centerline  30  of propagation between beams  32  and  34 . The individual beams also have a specified amount of divergence e.g., +2 degrees for beam  32  or −2 degrees for beam  34 . In all, the array projects a radiation pattern that expands symmetrically with distance from the source (emitters  18 ). 
     The optical power produced by the IR emitter array  16  is modulated at several frequencies. Each frequency is used to drive a specific part of the array. For example, frequency A may represent −X while frequency B represents +X. In one example, frequencies A and B may be e.g., 30 kHz and 32 kHz, respectively. 
     The subject  24  to be tracked is equipped with an IR receiving device  26 . Receiving devices  26  may include a small clip on device that can be easily worn on a shirt pocket or collar of the subject  24  or may hang from the neck of the subject. Other ways of attaching receiver  26  may also be employed. The position of the pan/tilt unit  12  relative to the subject is discerned by comparing the energy levels of the modulation frequencies. 
     Referring to  FIG. 2 , a transmission unit  100  is illustratively shown for emitting radiation for automatically tracking a subject using telemetry. Unit  100  includes a microprocessor  102  capable of generating waveforms for modulating camera and pan-tilt unit automatically follows the movements of a subject, eliminating the requirement for camera operating personal. As a replacement for tracking systems of robotic cameras, the present system eliminates many problems, including frequent failure of moving mechanical or electromechanical parts. The system described herein eliminates such problems because the system includes few moving parts. It also greatly reduces system complexity and associated manufacturing cost while increasing product quality, durability and manufacturability. In addition, the present system may allow for multiple systems to be operated in relatively close proximity, which is not possible with other camera tracking systems. 
     It is to be understood that the present invention is described in terms of a video recording system; however, the present invention is much broader and may include any system, which is capable of tracking a subject. For example, an audio system where a microphone is directionally altered in accordance with apposition of a subject or a system where the subject is an object or a living subject other than a human. In addition, the present invention is applicable to any recording media including recording data taken or transmitted by telephone, set top boxes, computer, wireless, satellite links, etc. 
     It should be understood that the elements shown in the FIGS. may be implemented in various forms of hardware, software or combinations thereof. Preferably, these elements are implemented in a combination of hardware and software on one or more appropriately programmed general-purpose devices, which may include a processor, memory and input/output interfaces. 
     Referring now in specific detail to the drawings in which like reference numerals identify similar or identical elements throughout the several views, and initially to  FIG. 1 , an illustrative embodiment for an automatic camera tracking system  10  is shown. System  10  includes a motorized pan-tilt unit  12  for a video camera or other device  14 . An array  16  of diodes  18  is mounted on or near the pan-tilt unit  12 . In one embodiment, the diodes  18  include infrared emitting diodes (IREDs). 
     The array  16  is mounted on the electronically controlled pan-tilt unit  12 , which may control positioning for a video camera, movie camera, microphone, camera or another suitable device. The individual emitters  18  in the array  16  each represent opposite directions on a given axis and are mounted at complementary angles to each other. An angular relationship between adjacent emitters associated with opposite directions of one axis is illustratively shown in  FIG. 1 . It is to be signals. Microprocessor  102  outputs the waveforms to power amplifiers  104  to amplify the waveforms so that the waveforms may be employed to modulate emitters in the emitter array  106 . The emitters in array  106  transmit optically modulated signals. It should be noted that the microprocessor  102  generates different waveforms of different frequency or amplitude to be employed by different emitters or portions of the emitter array. Multiplexers or other devices (e.g., switches) may be employed such that microprocessor  102  generates different frequency or amplitude signals that can be distributed to modulate different portions of the array. 
     Microprocessors  102  may also be employed to regulate power to amplifier (or amplifiers)  104 . This may be employed to increase the power levels of the emitted signals depending on, e.g., a distance to a subject or other criteria. Microprocessor  102  may also be employed for other functions as well. For example, in one embodiment, microprocessor may be employed to interpret and compare feedback signals from the subject and control a position of a pan unit or other motorized device. Also, in a preferred embodiment, the emitters include IR emitters. 
     Referring to  FIG. 3 , a receiver device  200 , which is preferably worn by or attached to a subject to be tracked is shown. Receiver  200  includes a tracking pod  202 , which preferably includes a plurality of photodiodes  204 . Photodiodes  204  receive the emitted light from the emitter array  106  ( FIG. 2 ) and input the received signals to input circuits  206 . Input circuits  206  are responsive to at least one of the intensity, amplitude and frequency of the received radiation. The received signal(s) are summed by a summer  208  and may be processed by signal conditioning circuitry or signal processor  210 , in preparation for data extraction and processing farther downstream, where based on the intensity, amplitude and/or frequency the summed signal is processed to determine a position of the subject. The position of the subject may be determined by using the received signal information in a Fourier transform or other signal processing algorithm to determine or measure a position of the subject. 
     Depending on the system, the signal processing of the receiving may be performed at a separate position or location. In one embodiment, the summed signal information may be transmitted back to the microprocessor  102  ( FIG. 2 ) or other device at the camera location, sent to a computer or other processing device or further processed at the receiver  200 . In one embodiment, the data is sent to a computer or processing device to be spectrum analyzed to determine a position of the subject and to generate position or tracking information to update the position/angle of the camera. In such a case, analog signal conditioning  210  and/or a buffer  212  may be useful in conditioning and buffering the incoming data to be sent to a data acquisition and spectral analysis program  214 . 
     Referring to  FIG. 4 , a system  300  is shown for automatically tracking a subject  320  in accordance with principles of the present disclosure. Array driver  100  includes electronic circuitry for powering and modulating an emitter array  106 . Radiation  302  is received by a photodiode array  204  or other photo sensors. Receiver  200  includes processing electronics to receive and condition signals as output by the photo diodes of IR sensor  204 . The received signal information is sent to a personal computer or other processing device  304 . 
     Computer  304  may include one or more software programs for analyzing the data sent from receiver  200 . Computer  304  may include software and algorithms  306  to support data acquisition, fast Fourier transform (FFT), telemetry data interpretation and system command communications. The interpreted data may include determining a position of a subject based upon the energy level received by receiver  200  of a given frequency modulated optical signal. In this way, a telemetric representation of a position of the subject may be determined for each access to permit adjustment of a camera angle or position. 
     Computer  304  preferably includes a printed wiring board, card or a port  308 , which outputs signals for controlling a servo(s) or other motion devices  310 . These signals include pan/tilt control signals for moving a camera  312 . The port  308  may use an RS-232 protocol although other protocols may be employed. The interpretation of the data may include determining a direction and magnitude of a position change for the camera in order to center the subject. Alternately, the subject need not be centered, but may be positioned in accordance with a predetermined position or coordinates. 
     Servos  310  respond to pan/tilt control signals  314  sent from computer  304  to appropriately move the camera  312  to a new position in accordance with the movements of the subject. It should be understood that the receiver  200  may communicate wirelessly with the computer  304 . In this way, the subject is not limited in movement by wires. In addition, in an alternate embodiment, the transmitter  100  may be worn by the subject and the receiver  200  may be located near the camera  312 . 
     Referring to  FIGS. 5-7 , representations of oscilloscope displays showing relative energy levels of four modulation frequencies as seen by an IR receiver are illustratively show. A bottom trace  402  in each display shows a summed signal as received by receiver  200  ( FIG. 4 ). A top trace  404  in each display shows the relative amplitudes for four modulation frequencies as output from a Fourier Transform. The two leftmost peaks represent opposite directions on the X axis while the rightmost two peaks represent opposite directions on the Y axis. 
     In  FIG. 5 , all modulation frequencies of the top trace are of equal amplitude. This condition is the default or “home” position. The subject is standing or positioned in the center of the camera eye. In  FIG. 6 , the subject is centered on the Y axis, but off center on the left of the X axis. The second peak from the left is higher than the other peaks; therefore an x-axis correction is needed. In  FIG. 7 , the subject is centered on the X axis, but off center on the Y axis. The second peak from the right is higher than the other peaks; therefore a y-axis correction is needed. Depending on the relative positions of the emitters a calculation of how much adjustment is needed for correction is performed and provided as a control signal to move the camera. 
     Having described preferred embodiments for system and method for an automatic tracking camera (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope and spirit of the invention as outlined by the appended claims. Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.