Dangers of Stacking Projectors for Passive 3D
By George Walter
Installers will be required to create perfect alignment, account for lens shift and possibly deal with HDMI headaches in passive applications.

At first thought, the idea of utilizing two projectors to generate a 3D image seems like a very logical approach. After all, standard 60Hz projectors can be employed, on screen brightness is doubled and the application automatically benefits from redundancy for 2D applications.

The dual projector 3D design, however, is very complex and creates numerous hazards in terms of installation flexibility and overall experience.

Perfect Alignment Required
First, consider the fact that both images must be perfectly converged on screen. Experienced installers will remember the days of converging CRT projectors and how difficult that could be. Expect the same, without the benefit of electronic convergence controls in each projector (as was the case with CRT projectors of days past).

Unless the installation includes accurate and costly warp engines, the ONLY way to converge two digital projectors is to do so mechanically with the use of lens shift. While a good alignment is possible, the corners are likely to be the most difficult to align between the two projectors.

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