6 research outputs found
Optimal stopping times for estimating Bernoulli parameters with applications to active imaging
We address the problem of estimating the parameter of a Bernoulli process. This arises in many applications, including photon-efficient active imaging where each illumination period is regarded as a single Bernoulli trial. We introduce a framework within which to minimize the mean-squared error (MSE) subject to an upper bound on the mean number of trials. This optimization has several simple and intuitive properties when the Bernoulli parameter has a beta prior. In addition, by exploiting typical spatial correlation using total variation regularization, we extend the developed framework to a rectangular array of Bernoulli processes representing the pixels in a natural scene. In simulations inspired by realistic active imaging scenarios, we demonstrate a 4.26 dB reduction in MSE due to the adaptive acquisition, as an average over many independent experiments and invariant to a factor of 3.4 variation in trial budget.Accepted manuscrip
Beyond Binomial and Negative Binomial: Adaptation in Bernoulli Parameter Estimation
Estimating the parameter of a Bernoulli process arises in many applications,
including photon-efficient active imaging where each illumination period is
regarded as a single Bernoulli trial. Motivated by acquisition efficiency when
multiple Bernoulli processes are of interest, we formulate the allocation of
trials under a constraint on the mean as an optimal resource allocation
problem. An oracle-aided trial allocation demonstrates that there can be a
significant advantage from varying the allocation for different processes and
inspires a simple trial allocation gain quantity. Motivated by realizing this
gain without an oracle, we present a trellis-based framework for representing
and optimizing stopping rules. Considering the convenient case of Beta priors,
three implementable stopping rules with similar performances are explored, and
the simplest of these is shown to asymptotically achieve the oracle-aided trial
allocation. These approaches are further extended to estimating functions of a
Bernoulli parameter. In simulations inspired by realistic active imaging
scenarios, we demonstrate significant mean-squared error improvements: up to
4.36 dB for the estimation of p and up to 1.80 dB for the estimation of log p.Comment: 13 pages, 16 figure
Can Shadows Reveal Biometric Information?
We study the problem of extracting biometric information of individuals by
looking at shadows of objects cast on diffuse surfaces. We show that the
biometric information leakage from shadows can be sufficient for reliable
identity inference under representative scenarios via a maximum likelihood
analysis. We then develop a learning-based method that demonstrates this
phenomenon in real settings, exploiting the subtle cues in the shadows that are
the source of the leakage without requiring any labeled real data. In
particular, our approach relies on building synthetic scenes composed of 3D
face models obtained from a single photograph of each identity. We transfer
what we learn from the synthetic data to the real data using domain adaptation
in a completely unsupervised way. Our model is able to generalize well to the
real domain and is robust to several variations in the scenes. We report high
classification accuracies in an identity classification task that takes place
in a scene with unknown geometry and occluding objects
Learning-based Methods for Occluder-aided Non-Line-of-Sight Imaging
Imaging scenes that are not in our direct line-of-sight, referred to as non-line-of-sight (NLOS) imaging, has recently gained considerable attention from the computational imaging community. With a diverse set of potential applications in several domains, NLOS imaging is an emerging topic with many unanswered questions despite the progress made in the last decade. In this thesis, we aim to find answers to some of these questions by focusing on a popular NLOS imaging setting, namely occluder-aided imaging, which exploits occluding structure in the scenes to extract information from the hidden scenes. We do this by first focusing on the scene classification problem, where we study the problem of identifying individuals by exploiting shadows cast by occluding objects on a diffuse surface. In particular, we develop a learning-based method that discovers hidden cues in the shadows and relies on building synthetic scenes composed of 3D face models obtained from a single photograph of each identity. We transfer what we learn from the synthetic data to the real data using domain adaptation in a completely unsupervised way and report classification accuracies over 75% for a binary classification task that takes place in a scene with unknown geometry and occluding objects. Next, we focus on the problem of scene estimation, which aims to recover an image of the hidden scene from NLOS measurements. We present a learning-based framework that exploits deep generative models and demonstrate the promise of this framework via simulations.S.M