Abstract:
A method and apparatus for wireless power beaming consisting of a transmitter assembly ( 20 ), free space ( 40 ), and an optical-to-electric assembly ( 50 ). The transmitter assembly ( 20 ) has eye-safe lasers ( 26 ) that create a beam of light ( 90 ). The beam of light goes through free space ( 40 ) and impinges upon the surface of optical-to-electric assembly ( 50 ). Optical-to-electric assembly ( 50 ) has power conversion photodiode(s) ( 54 ) to convert the energy in the light ( 90 ) into electricity. Power Accounting ( 14 ) accounts for the power in the beam and controls the lasers to turn them off whenever radiation is not accounted for in the system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application claims the benefit of provisional patent application Ser. No. 40/659,357. filed 2005 Mar. 9 by the present inventor. 
     
    
     FEDERALLY SPONSORED RESEARCH  
       [0002]     Not applicable.  
       SEQUENCE LISTING OR PROGRAM  
       [0003]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     This invention relates to providing electrical power to electronic devices without a wire or other connection to a power source. It also relates to providing electronic signals to the device without a wire connection.  
         [0006]     2. Prior Art  
         [0007]     The current state-of-the-art in common home and business electrical and electronic devices is that they receive power from five types of sources.  
         [0008]     1. Many are plugged into a wall outlet. An example would be a lamp with a power cord. In this case, the cord usually requires proximity to a wall outlet. It can get tangled or be tripped on. It may be unsightly. There may be insufficient outlets for all of the devices requiring power.  
         [0009]     2. Some are plugged directly into another device. An example is a stereo speaker plugged into a stereo. In this case the wire must run from the stereo across the room to the speaker. This often involves a costly, difficult installation. To move the speaker later becomes difficult.  
         [0010]     3. Others are operated by rechargeable batteries. Electric shavers, cordless drills, and cell phones fit this mode. This requires a power cord for recharging. In this case, there can be many cords. There may be more cords and chargers than there are convenient outlets, and batteries may run out at inconvenient times during use. This is usually limited to low-power devices.  
         [0011]     4. Others are operated by disposable batteries. Travel alarm clocks and portable radios often operate this way. These devices cannot be very powerful. The batteries must be replaced.  
         [0012]     5. A very few devices are powered by solar cells. The most common are inexpensive pocket calculators. These cannot be very powerful at all. As a result, solar cells are rarely used to power devices.  
         [0013]     Currently no completely cordless solution for power to these kinds of common devices is available.  
         [0014]     One solution to this is beamed power.  
         [0015]     In the early 20 th  century, Nicola Tesla wanted to send power over the air in large amounts, but he did not succeed 1 .    1 http://www.pbs.org/tesla/    
         [0016]     NASA has done experiments to transmit microwave power to a rectenna. The rectenna, or rectifying antenna, outputs DC electricity. 2  Microwaves have four disadvantages and one advantage compared to lasers. The disadvantages are substantial. First, they are intentional emitters under Federal Communications Commission regulations. They require licensing and bandwidth. Second, they can cause signal interference, and because they are regulated spectrum, any unwanted reflection will cause interference. Third, the components to contain them are not as easy to manufacture and work with as optical components. Fourth, they are unsafe around people. They can burn a person. Also, microwave radiation is also linked to cancer. Microwaves have one advantage: that they penetrate rain and fog better than light does.    2 http://www.kurasc.kyoto-u.acjp/plasma-group/spshistory2-e.html    
         [0017]     For more detail on microwave systems, please see the following patents: 
        Remote piloted vehicle powered by beamed radiation U.S. Pat. No. 6,542,253     Microwave-powered aircraft U.S. Pat. No. 5,503,350     Power-beaming system U.S. Pat. No. 5,068,669     Dual Polarization Reception and Conversion System U.S. Pat. No. 4,943,811     Orbiting Solar Power Station U.S. Pat. No. 4,078,447        
 
         [0023]     NASA has used lasers to power a small model airplane as part of its studies of beaming power from space to earth and of keeping planes aloft for long periods of time. 3  To do this, the experimenters put a 1 kW laser on a swivel and manually tracked a model airplane on a tether. They used non-eye-safe lasers in a manner that would not be safe or effective in a commercial application. These methods had no way to account for where the optical energy went, or if it was within FDA permitted limits.    3 http://www.nasa.gov/centers/dryden/news/FactSheets/FS-087-DFRC.html    
         [0024]     For more detail on laser or optical systems, please see the following patents:  
         [0025]     Optically powered remote microdevices employing fiber optics U.S. Pat. No. 5,402,586 shows that devices can be powered at a distance by lasers. This system, however, requires that the device be connected to the laser by an optical fiber. Similar systems are sold by JDS-Uniphase, Inc.  
         [0026]     Wireless power supply method U.S. Pat. No. 6,635,818 uses a visible light to drive a small micromachine. It does not provide sufficient power to drive a large load, like an audio speaker. It is not at an eye-safe wavelength. It does not have a system to assure that the human exposure remains within regulatory limits. It does not show a means of delivering the optical power beam to the photovoltaic cell.  
         [0027]     Methods and apparatus for beaming power US Patent Application 20020056763 shows a system for beaming light to an airplane or other object. Basically it is a laser on a gimble, as demonstrated by NASA. It is not suitable for use in a home or business because it lacks precautions to allow a human not wearing eye-safety goggles nearby, and because it has no means to avoid being blocked generally. Line of sight is often not available in a home or business.  
         [0028]     There is little prior art for use of a laser to power remote objects in the home or business because of safety issues, efficiency issues, and the difficulty of guaranteeing line-of-sight.  
       OBJECTS AND ADVANTAGES  
       [0029]     The objects of this invention are: 
        a) to safely provide power without cords or cables to common devices that usually have to be plugged-in;     b) to remove the inconvenience of battery charging and battery charging stations;     c) to reduce the congestion of wall outlets;     d) to provide signal along with power by the same channel wherever convenient.        
 
         [0034]     Advantages of this invention are that it is convenient compared to attaching devices to walls with wires. It is more aesthetic—no rats-nested wires. It also enables entirely new applications. Examples might be lights made from balloons, with no attachment to any surface or clothes with built-in heating and cooling systems.  
       SUMMARY  
       [0035]     This invention consists of an apparatus and a method to transfer power without the use of wires, in a way that is safe for use in a location with people who are not taking precautions, such as an average household or office.  
         [0036]     To transfer the power a transmitter assembly containing a laser(s) is plugged into an electrical socket. It uses its camera to search for an optical-to-electrical converter. When it finds a possible optical-to-electrical-converter, the transmitter assembly attempts to handshake with the optical-to-electrical-converter. In the preferred embodiment, the handshake consists of light pulses from the Transmitter and light pulses from a small photodiode of the receiver. When the handshake succeeds, the transmitter assembly and the optical-to-electrical-converter go through a Power Accounting algorithm. This algorithm assures that the Transmitter is safe to illuminate the optical-to-electrical-converter. If the result of the power accounting is positive, the Lasers are turned on. Then the Power Accounting algorithm executes continuously. When it no longer is positive, it turns off the lasers.  
         [0037]     The apparatus for this method is as follows:  
         [0038]     A transmitter assembly containing: 
        1. A high-efficiency, eye-safe, light source to transmit power. In the preferred embodiments, the source is an eye-safe laser(s).     2. Lens(es) for focusing and pointing the lasers. In the preferred embodiment, the outgoing light is nearly collimated, and the beam intensity is 1 mW/sq. mm-10 mW/sq.mm. The beam profile should be substantially uniform.     3. A mechanism for pointing the lasers. In one embodiment, this mechanism is powered and controlled from the CPU. It may be a powered pan-and tilt system. In an alternative embodiment, this mechanism is just a fixed pointing system. When a fixed pointing system is used, a visible indicator laser is used to facilitate pointing.     4. The transmitter part of the safety subsystem consisting of: 
            a. a CMOS camera, such as a VGA camera from Kodak,     b. an illumination light source that points along the same path as the camera     c. a photodiode that is sensitive at the same wavelength as the optical-to-electrical converter&#39;s transmitter diode     d. a monitor photodiode that is sensitive at the same wavelength as the power lasers and optics to image a fraction of the outgoing light onto the photodiode     e. a CPU that controls the power lasers.     d. software that accounts for the power in the beam    
            Free space in between the transmitter assembly and the receiver box. It may or may not contain mirrors to redirect the light.        
 
         [0050]     An optical-to-electrical converter box containing: 
        1. One or more photodiodes. The best photodiodes depend on the nature of the load. For example, for the most efficient high-power conversion, Indium Phosphide diodes such as those from JDS-Uniphase are best. In one embodiment, these are used with lens(es) for focus-down. An example might be a TV. In another embodiment, such as for a cell phone, thin film photodiodes might be used with no focus down.     2. Optics to focus down onto the photodiodes. One embodiment has optics to focus-down the light. Another does not     3. The optical-to-electrical converter part of the safety subsystem consisting of: 
            a. a light source. In the preferred embodiment, the light source is an 8500 nm VCSEL.     b. Indicium. In the preferred embodiment, the indicium are made from retroreflective film, such as that from 3M.     c. a circuit to monitor the current and voltage at the photodiodes.     d. a CPU that controls the power lasers.     e. software that accounts for the power in the beam   
               
 
     
    
     DRAWINGS  
     Figures  
       [0059]      FIG. 1  shows a flow chart of the method of operation.  
         [0060]      FIG. 2  shows a schematic diagram of preferred embodiment 1-A system.  
         [0061]      FIG. 3  shows a schematic diagram of preferred embodiment 1-B system.  
         [0062]      FIG. 4  shows the indicium on the front surface of the optical-to-electrical converter. 
     
    
       [0063]    
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                   
               
               
                 DRAWINGS - REFERENCE NUMBERS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 Search 
                 12 
                 Power Accounting 
               
               
                 14 
                 Turn On Laser(s) 
               
               
                 20 
                 transmitter assembly 
                 22 
                 CPU 
               
               
                 24 
                 camera 
                 26 
                 laser(s) 
               
               
                 28 
                 monitor photodiode(s) 
                 30 
                 illumination diode 
               
               
                 32 
                 signal photodiode 
                 34 
                 lens(es) 
               
               
                 36 
                 pointing mechanism 
                 38 
                 alignment laser 
               
               
                 40 
                 free space 
                 42 
                 mirror 
               
               
                 44 
                 pan and tilt mechanism 
               
               
                 50 
                 optical-to-electrical converter 
                 52 
                 CPU 
               
               
                 54 
                 power conversion photodiode(s) 
                 56 
                 indicium 
               
               
                 58 
                 optics 
                 60 
                 IR-LED 
               
               
                 62 
                 current and voltage circuit 
                 64 
                 optical diffusion layer 
               
               
                 66 
                 cross hair 
                 68 
                 perimeter 
               
               
                 90 
                 light 
                 92 
                 obstruction 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION  
       [0064]      FIG. 1  Method of Operation Flow Chart  
         [0065]     Search  10 . In embodiment 1A, the Camera  24  takes images. The images are parsed by the CPU  22 , which is looking for the indicium  56  of the optical-to-electric converter  50 . In Embodiment 1A, the load is stationary, like a lamp or television. In this embodiment, the user aims the laser(s) at the load and fixes it in place. In this embodiment, a low-power visible alignment laser is used for installation. In Embodiment 1B, the load may be anywhere in the room or may move during use, like a cell phone, laptop computer, or vacuum cleaner. In this embodiment, the Camera  24  scans the room to search for the load. Whether searching involves scanning the Camera  24  or continuously processing the same image, the search algorithm is similar.  
         [0066]     To make this easier, the surface of the optical-to-electrical converter  50  has visible indicium  56  that are unlikely to exist on anything else. In the preferred embodiments, the indicium  56  is a box with a cross-hair. The indicium  56  is made from a retroreflective film to make it extremely visible when the transmitter assembly turns on its illumination diode  30 , which operates at a wavelength that the camera is sensitive to. In the preferred embodiments, the camera is a CMOS camera, and a near IR illumination diode is used.  
         [0067]     The last part of the search is the recognition handshake. The following steps are observed. In the preferred embodiments, when the CPU  22  believes the Camera  24  has seen an optical-to-electrical converter, it supplies a series of pulses of power to the Laser(s)  26 . The optical-to-electrical converter  50  receives the power. The pulses are usually &lt;10 milliseconds duration.  
         [0068]     In the preferred embodiments, the optical-to-electrical  50  converter signals on back channel. In the preferred embodiments, the CPU  52  it then blinks a light such as an IR-LED  60 . The signal is a train of optical pulses at &gt;1 MHz. The signal photodiode  32  receives these signals. In the preferred embodiments, the optical-to-electrical converter signals its identity, its power requirement, safety information, its dimensions, and other information useful for operation.  
         [0069]     In another embodiment the back channel is a radio-frequency transmitter, such as 802.11, and the signal photodiode  32  is replaced by a radio receiver. In this way there is a 2-way communication path. This path can be used to send any data, not just safety data. For example, music might be transmitted to audio speakers by modulating the lasers. This can be a digital or analog modulation.  
         [0070]     Power Accounting  12 . If the Search  10  is successful, the Camera  24  takes a series of images of the optical-to-electrical converter  50 . CPU  22  then examines the beampath. CPU  22  examines the images of the beampath for shadows or bright areas, which suggest an interruption; CPU  22  examines the images of surface of the optical-to-electrical converter for scattering and retro-reflection. CPU  22  pulses Laser(s)  26 . Optical-to-electrical converter  50  receives the pulses. Current and voltage circuit  62  provides data to CPU  52  on how much power was received by power conversion photodiode(s)  54 , including amount of light and uniformity. CPU  22  has data from its own monitor photodiode(s)  28  on the power beamed from laser(s)  26 .  
         [0071]     The safety algorithm on CPU  22  makes a safety assessment. The safety assessment determines whether or not the system is complying with FDA or other regulations.  
         [0072]     Turn On Laser(s)  14 . In the preferred embodiments, the laser(s)  26  are on watchdog timers. They turn off automatically if the CPU  22  does not turn them on frequently. The CPU  22  can also turn them off. Power Accounting  12  runs continuously, turning on the lasers as long as it succeeds. When it fails, it returns to Search  10 .  
         [0073]      FIG. 2  Embodiment 1A  
         [0074]     A preferred embodiment of the present invention is illustrated in  FIG. 1A . This is for a system that might be used in a person&#39;s living room to illuminate a light attached to the ceiling. The load is assumed to require 20 Watts.  
         [0075]     The preferred embodiment consists generally of transmitter assembly  20 , free space  40 , and optical to electrical converter  50 .  
         [0076]     Transmitter assembly  20  converts electricity to light. In the preferred embodiments, it uses an eye-safe diode laser(s)  26 . These operate at &gt;1500 nm wavelength. Such lasers are made by nLight Photonics, Inc, Princeton Lightwave, Covega, and other sources. Light  90  from the laser(s)  26  goes immediately into lens(es)  34  for focusing and pointing the lasers. In the preferred embodiment, the outgoing light  90  is nearly collimated, and the beam intensity is 1 mW/sq. mm-10 mW/sq.mm. The beam profile is substantially uniform.  
         [0077]     The Transmitter assembly  20  must aim the light. To aim the light the pointing mechanism  36  is used. In Embodiment 1A this is just a simple mechanical pan-and-tilt operated by knobs that can be turned to aim it and then locked in place. A visible indicator laser  38  is used to facilitate pointing. Its beam is collimated and is parallel to the light  90 .  
         [0078]     In addition, as described above, camera  24 , illumination diode  30 , signal photodiode  32 , and alignment laser  38 , all are mounted substantially coaxially with light  90 . Their field of view is substantially similar to and slightly larger than that of Laser(s)  26 . In Embodiment 1A at 20 meters their field of view should be approximately 4× that of Laser(s)  26 . In the preferred embodiments the camera  24  is a CMOS VGA camera, such as those made by Kodak, with a single plastic lens; the illumination diode is a near-IR VCSEL, such as the 850 nm VCSELs made by Truelight; the signal photodiode is a silicon photodiode; and the red laser is a collimated red VCSEL. CPU  22  can be any standard CPU sufficient to handle the data from the camera and the diodes. An ARM7-based microprocessor at &gt;50 MHz is preferred.  
         [0079]     Monitor photodiode(s)  28  is a germanium photodiode. It is mounted close to laser(s)  26  such that it receives the back-reflection from lens(es)  34 .  
         [0080]     In Embodiment 1A, Light  90  does not point in the direction of Optical-to-electrical converter  50 . Obstruction  92  is in the path. Instead mirror  42  is in the path. In Embodiment 1A mirror  42  is just a small (75 mm×75 mm) mirror affixed to a pan and tilt mechanism  44  similar to pointing mechanism  36 . Embodiment 1A, during installation, while alignment laser  38  is on, mechanism  44  is used to steer Light  90  and is then locked in place.  
         [0081]     In Embodiment 1A, Optical-to-electrical converter  50  has indicium  56  on its front surface. The indicium  56  is a rectangular crosshair that surrounds the photodiodes. See  FIG. 4 . It is made of retroreflective material, such as that sold by 3M.  
         [0082]     In Embodiment 1A optics  58  are the front surface. They focus light through diffusion layer  44 , described in Safe Power Beaming System U.S. No. 40/678,577, and onto power conversion photodiode(s)  54 . The power conversion photodiode(s)  54  is a GaSb photodiode(s) as provided by EdTek, Incorporated. The optics  58  is a Fresnel lens. All optics in this system should be coated for 1400 nm light. Focus-down should exceed 10-1. When more than one diode is used, the parallel-series arrangement of the diodes determines the output voltage and current.  
         [0083]     In Embodiment 1A for safe operation as described above, a current and voltage circuit  62  monitors the power being received. A cpu  52  operates it and communicates with transmitter assembly  20  by modulating an IR-LED  64 . The cpu can be an 8-bit CPU, such as those made by Microchip. IR-LED  64  is a 780 nm LED.  
         [0084]      FIG. 3  Embodiment 1B  
         [0085]     A preferred embodiment of the present invention is illustrated in  FIG. 1B . This is for a system that might be used in a café or office to charge cell phones, laptops, etc. The load of a cell phone is 3-5 W and of a laptop 30-50 W. The elements are the same.  
         [0086]     The elements of Embodiment 1B are the same as those for Embodiment 1A except as described here.  
         [0087]     Transmit assembly  20  is assumed to be on the ceiling pointing downward for this embodiment. Obstruction  92  does not exist, so mirror  42  is not used. In embodiment 1B, the loads, the cell phones, place different requirements on the system.  
         [0088]     Cell phones move, and may be anywhere. Pointing mechanism  36  is powered and controlled from the CPU  22 . It may be a powered pan-and tilt system, as is commonly seen on security cameras. In an alternate embodiment, pointing mechanism  36  may be fixed, and an actuated mirror may be used to alter the beampath and allow the camera to scan.  
         [0089]     Because the application requires thin, cheap electronics, power conversion photodiode(s)  54  in this embodiment are thin film diodes, not bulk diodes. Optics  52  are not used, and the optical system has no focus-down. So optical diffusion layer  64  is the front surface.  
         [0090]      FIG. 4  Indicium  
         [0091]     The indicium on the front surface of the optical-to-electrical converter is shown. Indicium  52  has cross hair  66  and perimeter  68 . In the preferred embodiments, perimeter  68  is rectangular, but it may also be square. In preferred embodiment 1A it surrounds optics  58 . In preferred embodiment 1B, it surrounds The cross-hair  66  should be approximately 1 mm wide. The perimeter  68  may be wider.  
       CONCLUSION, RAMIFICATIONS, AND SCOPE  
       [0092]     Accordingly, the reader will see that wireless power beaming is desireable in the same way that cellular telephones and other wireless networked devices are desireable. They allow people to move around while keeping their devices with them. They remove an impediment or inconveniece, the cord or the need to find a jack or outlet.  
         [0093]     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some presently preferred embodiment of this invention. For example, the sequence of steps in the method may be slightly altered. The positions of some of the elements may be shifted. Efficient light sources at very short eye-safe wavelengths may become available. Different loads require different combinations of elements for maximum usability and minimum cost.  
         [0094]     The scope of this invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.