1.7 HD calculation of multi-projector stacks

Sometimes two or more projectors are stacked (projecting on the same surface). In this case, because of the overlap of the images, possibly a system Hazard Distance needs to be applied instead of a single projector hazard distance.

Only projectors stacked along one axis (horizontal or vertical) should be considered. Physical stacking of projectors in two dimensions (for example 2x2), can be reduced to separate “N”x1 systems.

The information needed is:

• The Hazard Distance (HD) of a single projector with the given lens.
• The distance (h) between two adjacent projector lens centers in the stack.

Note: For 3 or more projectors, in case the distances between adjacent lenses are not equal, take the shortest distance.

HD calculation:

• For stacking two-projectors:

  • If the single projector hazard distance HD ≥ 9*h, then the system hazard distance to implement is 1.15*HD.
  • If the single projector hazard distance HD < 9*h, then keep the original HD and risk zone per projector.

• For stacking “N” projectors along the same axis, “N” being 3 or more:

  • If the single projector hazard distance HD ≥ 12*h, then the system hazard distance to implement is (“N”/2 + 0.15) * HD.
  • If the single projector hazard distance 9*h ≤ HD < 12*h, then the system hazard distance to implement is 1.15*HD.
  • If the single projector hazard distance HD < 9*h, then keep the original HD and risk zone per projector.