The emission profiles of light-emitting diodes have typically be measured by goniophotometry. However this technique
suffers from several drawbacks, including the inability to generate three-dimensional intensity profiles as well as poor
spatial resolution. These limitations are particularly pronounced when the technique is used to compared devices whose
emission patterns have been modified through surface texturing at the micrometer and nanometer scales,. In view of such
limitations, confocal microscopy has been adopted for the study of emission characteristics of LEDs. This enables three-dimensional
emission maps to be collected, from which two-dimensional cross-sectional emission profiles can be
generated. Of course, there are limitations associated with confocal microscopy, including the range of emission angles
that can be measured due to the limited acceptance angle of the objective. As an illustration, the technique has been
adopted to compare the emission profiles of LEDs with different divergence angles using an objective with a numerical
aperture of 0.8. It is found that the results are consistent with those obtained by goniophotometry when the divergence
angle is less that the acceptance angle of the objective.
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