Hand held optical time stamping device for video streams synchronization

Ref-Nr:

CHRONOFLASH device delivering a flash.

Technology abstract

Chronoflash is an optical time-stamping device which delivers a luminous flash at predefined times provided by its internal GPS/GALILEO receiver. The synchronization of video streams can be done without cables and the cameras themselves can be of any type.
Established by a CNES engineer, the startup Platineo is looking to cooperate with companies from the audiovisual industry interested by this synchronization method for providing 3D videos.

Technology Description

Chronoflash is a hand held optical time stamping device developed by CNES (the French Space Agency) in order to correlate photometric data registered during total solar eclipses. The scientific objective, in the frame of the French (with contributions from Belgium, Switzerland and ESA) PICARD space mission was to measure the diameter of the Sun and determine its possible variation with time.
This optical synchronization method can obviously be applied to video streams synchronization, opening the way to the production of 3D video sequences.
 
In its current version, Chronoflash is programmed from a PC and is connected by USB.
 
Chronoflash uses GPS or Galileo time, the universal reference, to trigger a lighting signal emitted by 3 LEDs. This signal is then used to synchronize several shooting sequences from different standpoints. This allows reconstituting dynamic scenes in 3 dimensions.
Several flash parameters can be set :

  • Starting time of the sequence
  • Flash emission cycle
  • Intensity and color
  • Shape of the pulse

The precision of the timing is ~5 microsecond. In theory, this allows the use of this method up to a frequency of 100,000 frames/s.
 
Chronoflash can be used in two ways :

  • Synchronization of several instruments located on the same site. The Chronoflash needs to be placed sequentially in the field of view of the optical instruments. The times at which the flashes are seen are different, but each corresponds to a precise known time (5 microseconds).
  • If the optical instruments are far apart, one Chronoflash per recording site is required. Since the trigger is based on absolute GPS time, different sites can be operated in an independent manner.

 
From the luminous flash which is visible on the video stream, it is easy to resynchronize the various video streams and from then, the image processing methods that are commonly used to produce dynamic 3D models from otherwise synchronized cameras can be used as well.
Chronoflash is then proposed as a way to synchronize video streams when connecting a set of cameras is not feasible, due to their distance, a difficult environment (public, terrain, airborne video recording) or operational constraints (time for set up and wrap up, logistics, limitation in professional expertise).
 
Several applications have been identified :

  • 3D modelling of natural events (lava flow, landslides, avalanches, flash floods, river / ocean interactions, aerology)
  • 3D modelling of structure or terrain behaviour when exposed to some events (mining with explosives, wind effect on large structures, wave effects on man-made structures...) 
  • Sports: training, competition, refereeing
  • Audiovisual events, performances and shows

Innovations & Advantages

Compared to other technologies, Chronoflash is particularly adapted to outdoor use, as it does not require any particular infrastructure (no cables required to link the cameras) nor logistics.
It is also adapted to the use of several cameras that can be of any type or manufacturer.3D dynamic scenes, up to several 1000x frames per second can be produced thanks to a synchronization precision of ~5 microseconds.
 
The technology doesn’t require any modification of the embedded hardware.
It is also very easy to use, since the only thing to do is to switch on the device and point it toward a camera before or after the video recording of the scene of interest.
 
The technology can be used anywhere (ground, air, sea and even underwater with a buoyant type) at a very low cost (~300€ per device).

Further Information

Current and Potential Domains of Application

The current domain of application is for timing some natural events (solar eclipses, stellar occultation from asteroids).
Several applications have been identified :

  • 3D Modelling of natural events (lava flow, landslides, avalanches, flash floods, river / ocean interactions, aerology)
  • 3D Modelling of structure or terrain behaviour when exposed to some events (mining with explosives, wind effect on large structures...) 
  • Sports: training, competition
  • Audiovisual events, performances and shows