What is Back Focal Length adjustment

Back Focal Length (BFL) adjustment involves moving the lens plane (Lp) closer to or further from the DMD plane. The closer the lens plane is to the DMD plane, the further and larger the depth of field (DoF) will be. Depth of field is the range of distances within which objects appear in sharp focus.

When adjusting the Back Focal Length

The Back Focal Length (BFL) is factory-set to a nominal position suitable for all supported lenses, so adjustment is typically unnecessary. However, for Ultra Short Throw (UST) lenses with a narrow depth of field, slight BFL adjustments may be needed due to mechanical tolerances.

Required tools

• Allen wrench 5 mm
• Allen wrench 4 mm
• Torque wrench with hex socket of 4 mm
• Torque wrench with hex socket of 5 mm

How to set the Back Focal Length to nominal position

1. Remove the projection lens if installed.

2. Loosen the three Scheimpflug lock nuts a half turn (reference A, B, and C). Use an Allen wrench 5 mm.

   

3. Turn the three Scheimpflug adjustment screws clockwise (reference 1, 2, and 3 image Image 5–7) until resistance is noticed. Use a torque wrench with hex socket of 4 mm and apply a torque of maximum 2 Nm.
4. Turn the three Scheimpflug adjustment screws exactly 2 complete turns counterclockwise for nominal Back Focal Length.
5. Fasten the three Scheimpflug lock nuts. Use a torque wrench with a torque of 6 Nm.