Beam-angle lens family for a clustered LED downlight

Challenge

An architectural downlight needed one molded lens for each beam class, about 15, 30, 50, and 70 degrees, on a chip scale package LED. Each lens also had to work in a four-LED cluster. A cluster risked lower efficiency and cross-talk between neighboring lenses, especially on the narrow beam.

Approach

A concept study compared seven lens types. A Fresnel-type lens was taken forward for the narrow and medium beams, and a dome style for the wide and flood beams. Each angle was then refined and checked in a four-LED cluster.

Result

The narrow lens held its beam class at about 90% theoretical efficiency. The 30 degree target came in a few degrees narrow, near 90% efficiency, and was expected to sit closer to the target with scattering. The wider lenses stayed within a few degrees of their targets, also near 90% theoretical efficiency. Spatial uniformity was excellent at every angle.

Key figures

• ~90%

  theoretical efficiency of the narrow beam

• ~30°

  medium beam, a few degrees off target before scattering

• ~50°

  wide beam, within a few degrees of the target

• ~70°

  flood beam, within a few degrees of the target