Research

Hyperspectral Imagery

Nonlinear Unmixing · Endmember Variability · Spectral Analysis

Nonlinear spectral unmixing, generalized bilinear model, endmember extraction, spectral variability, robust unmixing.

01

Nonlinear Unmixing Using a Generalized Bilinear Model

The generalized bilinear model (GBM) generalizes both the linear mixing model and recently introduced bilinear models by including second-order interaction terms between endmembers. A hierarchical Bayesian algorithm with Metropolis-within-Gibbs sampling ensures positivity and sum-to-one constraints.

A. Halimi, Y. Altmann, N. Dobigeon and J.-Y. Tourneret, "Nonlinear unmixing of hyperspectral images using a generalized bilinear model," IEEE Trans. Geoscience and Remote Sensing, vol. 49, no. 11, pp. 4153-4162, Nov. 2011.
02

Unsupervised Unmixing Accounting for Endmember Variability

This unsupervised Bayesian algorithm models pixels as linear combinations of random endmembers weighted by abundances, generalizing the normal compositional model. It estimates both mean and covariance matrix for each endmember, quantifying material behavior and variability across the scene.

A. Halimi, N. Dobigeon and J.-Y. Tourneret, "Unsupervised Unmixing of Hyperspectral Images Accounting for Endmember Variability," IEEE Trans. Image Processing, vol. 24, no. 12, pp. 4904-4917, 2015.
03

Unmixing in Presence of Endmember Variability, Nonlinearity, or Mismodelling Effects

Three hyperspectral mixture models with Bayesian algorithms for supervised unmixing. Based on residual component analysis, the general formulation assumes the linear model corrupted by additive terms accounting for nonlinearities, endmember variability, or mismodeling effects.

A. Halimi, P. Honeine and J. Bioucas-Dias, "Hyperspectral Unmixing in Presence of Endmember Variability, Nonlinearity or Mismodelling Effects," IEEE Trans. Image Processing, vol. 25, no. 10, Oct. 2016.
04

Fast Hyperspectral Unmixing

Two novel hyperspectral mixture models and unmixing algorithms. The nonlinearity model generalizes bilinear models by including higher order interaction terms. The alternating direction method of multipliers (ADMM) solves the convex problem with theoretical convergence guarantees.

A. Halimi, J. M. Bioucas-Dias, N. Dobigeon, G. S. Buller and S. McLaughlin, "Fast Hyperspectral Unmixing in Presence of Nonlinearity or Mismodelling Effects," IEEE Trans. Computational Imaging, vol. 3, no. 2, June 2017.
05

Correntropy Maximization via ADMM

Correntropy-based cost functions provide robustness to outliers in hyperspectral unmixing, down-weighting large residual errors compared to standard least-squares cost.

F. Zhu, A. Halimi, P. Honeine, B. Chen, and N. Zheng, "Correntropy Maximization via ADMM — Application to Robust Hyperspectral Unmixing," IEEE Trans. Geoscience and Remote Sensing, vol. 55, no. 9, Sept. 2017.
06

Estimating the Intrinsic Dimension of Hyperspectral Images

The proposed noise-whitened eigen-gap approach achieves near-perfect accuracy across all noise overestimation levels, significantly outperforming existing methods.

A. Halimi, P. Honeine, M. Kharouf, C. Richard and J.-Y. Tourneret, "Estimating the Intrinsic Dimension of Hyperspectral Images Using a Noise Whitened Eigen-Gap Approach," IEEE Trans. Geoscience and Remote Sensing, vol. 54, no. 7, July 2016.
07

DTU-Net for Nonlinear Unmixing

C. Wang, J. Gao, F. Zhu, A. Halimi, C. Richard, "DTU-Net: A Multi-Scale Dilated Transformer Network for Nonlinear Hyperspectral Unmixing," IEEE Trans. Geoscience and Remote Sensing, vol. 64, pp. 1-17, 2026.