System for optical wireless power supply

Abstract

A system incorporating safety features, for optical power transmission to receivers, comprising an optical resonator having end reflectors and a gain medium, a driver supplying power to the gain medium, and controlling its small signal gain, a beam steering apparatus and a controller to control at least the beam steering apparatus and the driver. The controller responds to a safety risk occurring in the system, by outputting a command to change at least some of the small signal gain of the gain medium, the radiance of the optical beam, the power supplied by the driver, the scan speed or the scan direction and position of the beam steering apparatus, or to register the scan pose which defines the location of said optical-to-electrical power converter. The controller may also ensure a high overall radiance efficiency, and may warn of transmitted power not received by a targeted receiver.

1 . A system for optical wireless power transmission to at least one power receiving apparatus, said system comprising:
 an optical resonator having end reflectors and a gain medium, said gain medium comprising either (i) a semiconductor material, or (ii) a solid host, doped with Neodymium ions and in optical communication with a filter attenuating radiation for at least one frequency having a wave number in the range 8,300 cm −1  to 12,500 cm −1 , and   
       wherein said gain medium:
 (a) is positioned inside said optical resonator, 
 (b) has a first bandgap energy, and 
 (c) is thermally attached to a cooling system, 
 such that said gain medium is configured to amplify light passing through it, and said resonator is configured to emit an optical beam of said light; 
 a driver configured to supply power to said gain medium, and enabling control of the small signal gain of said gain medium; 
 a beam steering apparatus configured to direct said optical beam in at least one of a plurality of directions; 
 an optical-to-electrical power converter located in said at least one power receiving apparatus, and configured to convert said optical beam into electrical power having a voltage, said optical-to-electrical power converter having a second bandgap energy; 
 a detector configured to provide a signal indicative of said optical beam impinging on said optical-to-electrical power converter; and 
 a controller adapted to control at least one of the status of said beam steering apparatus and said driver, said controller receiving a control input signal at least from said detector, 
 
       wherein said controller is configured to respond to an indication of a safety risk occurring in the system, by outputting a command to result in at least one of:
 causing said driver to change the small signal gain of the gain medium; 
 changing the radiance of said optical beam; 
 changing the power supplied by said driver; 
 changing the scan speed of said beam steering apparatus; 
 changing the scan pose of said beam steering apparatus; and 
 recording the scan pose which defines the location of said optical-to-electrical power converter. 
 
     
     
         2 . The system according to  claim 1  wherein said indication of a safety risk occurring in the system is obtained at least from said signal generated by said detector configured to provide a signal indicative of said optical beam impinging on said optical-to-electrical power converter, and from a signal generated by the level received at said resonator of said beam reflected from said at least one power receiving apparatus. 
     
     
         3 . The system according to  claim 1 , further including a power sensor disposed such that it provides a signal indicative of the power carried by said optical beam before impingement on said at least one power receiving apparatus. 
     
     
         4 . The system according to  claim 3  wherein said driver is configured to reduce said small signal gain of said gain medium when said power indication of said power sensor exceeds a threshold. 
     
     
         5 . The system according to  claim 3  wherein said detector also provides a signal indicative of the power received by said at least one power receiving apparatus. 
     
     
         6 . The system according to  claim 5  wherein at least one of said indications of safety comes from a difference between said power indicated by said power sensor and said power indicated by said detector in one of said at least one power receiving apparatus. 
     
     
         7 . The system according to  claim 6  wherein said at least one of said indications of safety arises from said difference exceeding a threshold. 
     
     
         8 . The system according to  claim 1 , further including a beam penetration sensor adapted to sense when an unwanted object enters said optical beam, said entry of said unwanted object constituting an indication of a safety risk. 
     
     
         9 . The system according to  claim 1 , further including an enclosure integrity sensor, wherein a warning issued by said sensor of lack of integrity of said enclosure indicates a safety risk. 
     
     
         10 . The system according to  claim 1  further including a sensing device for sensing a deviant operation of at least one critical subsystem in said system, said deviant operation constituting an indication of a safety risk. 
     
     
         11 . The system according to  claim 1 , wherein said second bandgap energy is smaller than said first bandgap energy. 
     
     
         12 . A system for optical wireless power transmission to at least one power receiving apparatus, said system comprising:
 an optical resonator having end reflectors and a gain medium, said gain medium comprising either (i) a semiconductor material, or (ii) a solid host, doped with Neodymium ions and in optical communication with a filter attenuating radiation for at least one frequency having a wave number in the range 8,300 cm −1  to 12,500 cm −1 , and   
       wherein said gain medium:
 (a) is positioned inside said optical resonator, 
 (b) has a first bandgap energy, and 
 (c) is thermally attached to a cooling system, 
 
       such that said gain medium is configured to amplify light passing through it, and said resonator is configured to emit an optical beam of said light;
 a driver configured to supply power to said gain medium, and enabling control of the small signal gain of said gain medium; 
 a beam steering apparatus configured to direct said optical beam in at least one of a plurality of directions; 
 an optical-to-electrical power converter located in said at least one power receiving apparatus, and configured to convert said optical beam into electrical power having a voltage, said optical-to-electrical power converter having a second bandgap energy; 
 a detector configured to provide a signal indicative of said optical beam impinging on said optical-to-electrical power converter; and 
 a controller adapted to control at least one of the status of said beam steering apparatus and said driver, said controller receiving a control input signal at least from said detector, 
 
       such that said optical beam has a radiance of at least 8 kW/m 2 /Steradian, and when said controller directs said optical beam onto one of said power receiving apparatuses, the overall radiance efficiency of transmission is at least 20%. 
     
     
         13 . The system according to  claim 12 , wherein the overall radiance efficiency of said transmission is at least 30%. 
     
     
         14 . The system according to  claim 12 , wherein said system is configured to maintain the overall radiance efficiency of transmission across a predetermined range of operational temperatures. 
     
     
         15 . The system according to  claim 12 , further including a radiance detector in said at least one power receiving apparatus, providing a signal indicative of the radiance received by said power receiving apparatus. 
     
     
         16 . The system according to  claim 15 , wherein said overall radiance efficiency is maintained because of at least one of (i) constructural parameters of said system, and (ii) the provision of a radiance maintaining feedback system, adapted to use said signal indicative said radiance and to adapt system parameters to maintain it. 
     
     
         17 . The system according to  claim 16 , wherein said system parameters include at least one of a lens position, a lens optical power and said beam power. 
     
     
         18 . The system according to  claim 15  further including a transmission radiance detector disposed to provide a signal indicative of the radiance emitted by said optical wireless power transmission system. 
     
     
         19 . The system according to  claim 18 , wherein an indication of a safety risk is triggered when the difference between the signal from said transmission radiance detector and said signal indicative of the radiance received by said power receiving apparatus exceeds a threshold value. 
     
     
         20 . The system according to  claim 12 , wherein said second bandgap energy is smaller than said first bandgap energy.