Method and time-of-flight camera for providing distance information
The invention relates to a method for providing distance information of a scene with a time-of-flight camera, comprising the steps of emitting a modulated light pulse towards the scene, receiving reflections of the modulated light pulse from the scene, evaluating a time-of-flight information for the received reflections of the modulated light pulse, and deriving distance information from the time-of-flight information for the received reflections, whereby a spread spectrum signal is applied to a base frequency of the modulation of the light pulse, and the time-of-flight information is evaluated under consideration of the a spread spectrum signal applied to the base frequency of the modulation of the light pulse. The invention further relates to a time-of-flight camera for providing distance information from a scene, whereby the time-of-flight camera performs the above method.
1. A timing module for a time-of-flight sensor for use with a light source for emitting a periodic light signal towards a scene, the sensor being for providing distance information from the scene, the timing module comprising:
a modulation unit configured to provide a modulation signal for the light source, wherein the modulation signal has a clock timing with a base frequency spread by a periodic perturbation with a perturbation frequency and period,
the modulation unit further being configured to provide the modulation signal over a set of a plurality of measurement durations in accordance with the clock timing that is spread by the periodic perturbation,
wherein each measurement duration of the set is an integer or half integer multiple of the perturbation period and over the set of measurement durations an average of the base frequency is kept constant.
2. The timing module of claim 1 , wherein the modulation signal taken over one measurement duration of the set has a same spectral content as the modulation signal taken over any other measurement duration of the set.
3. The timing module of claim 1 , wherein the perturbation frequency is within 5% of the base frequency of the modulation signal.
4. The timing module of claim 3 , wherein the perturbation frequency is within an interval +/−5% or +/−1.5% of the base frequency of the modulation signal.
5. The timing module of claim 4 , wherein the perturbation frequency is within +/−0.1% of the base frequency of the modulation signal.
6. The timing module of claim 1 , wherein the periodic perturbation has a sinusoidal, trapezoidal, or saw tooth waveform shape.
7. The timing module of claim 1 , wherein the modulation unit is further configured to supply a discontinuous perturbation modulation.
8. The timing module of claim 1 , further comprising a controller configured to dynamically increase or decrease the perturbation frequency.
9. The timing module of claim 1 , further comprising a controller configured to lower the power of the light pulses and reduce the perturbation frequency.