| 摘要 |
A method is disclosed that includes transmitting from an emitter a pulse of an energy beam. The beam creates a field with a varying gradient, where the gradient has a direction substantially transverse to a propagation direction of the beam. One or more detectors receive a portion of the field. For a respective one of the one or more detectors, a value is determined corresponding to an illumination level of the portion of the field received by the detector, wherein the value of the field is indicative of relative position between the detector and the emitter. A transmitter includes an emitter adapted to transmit an energy beam, the beam creating a field with a varying gradient. The gradient has a direction substantially transverse to a propagation direction of the beam. The transmitter further includes control circuitry adapted to cause the emitter to transmit the energy beam for a first duration.
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