Wireless laser system for power transmission utilizing a gain medium between retroreflectors

• US 9,653,949 B2
• Filed: 04/11/2016
• Issued: 05/16/2017
• Est. Priority Date: 01/03/2008
• Status: Active Grant

• Current Assignee: Wi-Charge Ltd.
• Original Assignee: Wi-Charge Ltd.
• Inventors: Alpert, Ortal, Paschotta, Rudiger
• Primary Examiner(s): Sohn, Seung C
• Application Number:
  US15/095,373
• Publication Number:
  US 20160329754A1
• Time in Patent Office: 400 Days
• Field of Search: 250216, 250221, 2502141
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0604 in the form of a plate or disc
• CPC Class Codes: H01S 3/0805 by apertures, e.g. pin-holes or knife-edges
• CPC Class Codes: H01S 3/08059 Constructional details of the reflector, e.g. shape mirrors in general G02B5/08; mountings for mirrors G02B7/18
• CPC Class Codes: H01S 3/08072 Thermal lensing or thermally induced birefringence; Compensation thereof
• CPC Class Codes: H01S 3/083 Ring lasers fibre ring lasers H01S3/06791
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/1307 Stabilisation of the phase
• CPC Class Codes: H01S 5/041 Optical pumping
• CPC Class Codes: H01S 5/10 Construction or shape of the optical resonator , e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region H01S5/20 takes precedence
• CPC Class Codes: H01S 5/14 External cavity lasers H01S5/18 takes precedence; mode locking H01S5/065
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H02J 50/30 using light, e.g. lasers
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems
• CPC Class Codes: H04B 10/807 Optical power feeding, i.e. transmitting power using an optical signal
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control

Abstract

An optical power beam transmission systems, with a directional light transmitter and receiver. The transmitter contains an amplifying laser medium, and this together with a retroreflector in the receiver, forms a laser resonator. When lasing sets in, the receiver can extract optical power through an output coupler and convert it to electrical power. The gain medium may be a disc having a thickness substantially smaller than its lateral dimensions. The laser resonator is operated as a stable resonator to ensure safe operation. This is achieved by use of an adaptive optical element, for reducing the diameter of the energy beam impinging on the gain medium, thereby increasing the overlap between the energy beam and the gain medium. As the transmitter-receiver distance is changed, such as by movement of the receiver, the adaptive optical element focal length changes to ensure that the cavity remains within its stability zone.

Claims

1. A method for assuring safe operation of a system for transmitting power from a laser transmitter into a region, for reception of said power by receivers, and conversion to electrical power, the transmitted power being controlled by the gain of the gain medium of said laser, said method comprising:

transmitting a search signal from said transmitter into said region for reception of said power by said receivers;

searching for a confirmation signal from at least one receiver that it is entitled to receive power;

commencing transmission of laser power at a reduced level from said transmitter to said at least one receiver;

validating that the path between said transmitter and receiver is clear of any foreign object;

checking that no safety-related disabling signals are received by said transmitter;

increasing the gain of the gain medium of said laser, to increase said transmitted power towards its intended level;

continuously verifying for the presence of safety indicators; and

reducing the laser gain to generate a safer power level if at least one of said safety indicators indicates a danger,

wherein at least one of said safety indicators is an enabling signal generated by said receiver when lasing is detected by said receiver.

2. A method according to claim 1, wherein said validating of said path between said transmitter and receiver includes a procedure for detecting a transparent or partially transparent window in said path.

3. A method according to claim 1, wherein said safety-related disabling signals include warning signals about at least one of:

power fluctuations;

loss of control signal;

transmitted status from the receiver;

a stop signal from the receiver; and

the presence of a transparent or partially transparent window.

4. A method according to claim 1, wherein said foreign object is a portion of a human body.

5. A method according to claim 1, wherein said confirmation signal is optically retroreflected from said receiver.

6. A method according to claim 1, wherein said confirmation signal contains receiver identification information.

7. A method according to claim 1, wherein at least one of said safety indicators is the correlation of the transmitted power loss between said transmitter and said at least one receiver.

8. A method according to claim 1, wherein said region for reception is limited in both angle and range.

9. A method according to claim 1, wherein said step of validating that the path between said transmitter and receiver is clear of any foreign object is performed by monitoring the shape of the beam of power transmitted, by use of a beam imaging device.