CAN-EYE is free windows-based image processing software developed by INRA. It is freely available. It processes hemispherical images (fish-eye lens) to calculate not only LAI but other parameters such as average leaf inclination angle, Fraction of Absorbed Photosynthetically Active Radiation, Fraction of Canopy Cover and Bidirectional Gap Fraction.
Method:
The software has image segmentation algorithm that identifies vegetation green vegetation pixels against the background. Multiple photographs should be taken to obtain reliable estimates of LAI.
This software has been used in several research studies and range of canopies to measure LAI and published research can be found here.