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Driving a light source

  • US 8,253,353 B2
  • Filed: 07/14/2008
  • Issued: 08/28/2012
  • Est. Priority Date: 07/16/2007
  • Status: Active Grant
First Claim
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1. Method for driving a light source, wherein the light source is alternately switched ON and OFF in an ON/OFF pattern, wherein the duty cycle of the ON/OFF pattern is varied to vary the average light intensity of the light source, and wherein the shape of the ON/OFF pattern is varied to transmit data, comprising the steps of:

  • defining a duty cycle ratio Δ

    in the range from 0 to 1, Δ

    being unequal to 0.5;

    defining a time base divided into time cells having a duration Tc;

    wherein each time cell is subdivided into two cell segments;

    wherein, in at least one time cell, the first cell segment has a duration Δ

    ·

    Tc, the second cell segment has a duration (1−

    Δ



    Tc, and the light source is switched ON in the first cell segment and switched OFF in the second cell segment for coding a bit having a first value; and

    wherein, in at least one other time cell, the first cell segment has a duration (1−

    Δ



    Tc, the second cell segment has a duration Δ

    ·

    Tc, and the light source is switched OFF in the first cell segment and switched ON in the second cell segment for coding a bit having a second value different from the first value.

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