Publications de Adam James Scholefield

Lippmann Photography: A Signal Processing Perspective

Martin Vetterli, Gilles Baechler, Arnaud Latty, Adam James Scholefield, Michalina Wanda Pacholska

Lippmann (or interferential) photography is the first and only analog photography method that can capture the full color spectrum of a scene in a single take. This technique, invented more than a hundred years ago, records the colors by creating interferen ...

2022

Three-Dimensional Cubic Barcodes

Martin Vetterli, Golnooshsadat Elhami, Adam James Scholefield

We consider three-dimensional cubic barcodes, consisting of smaller cubes, each built from one of two possible materials and carry one bit of information. To retrieve the information stored in the barcode, we measure a 2-D projection of the barcode using a ...

2022

Asynchrony Increases Efficiency: Time Encoding of Videos and Low-Rank Signals

Martin Vetterli, Adam James Scholefield, Karen Adam

In event-based sensing, many sensors independently and asynchronously emit events when there is a change in their input. Event-based sensing can present significant improvements in power efficiency when compared to traditional sampling, because (1) the out ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Blind as a Bat: Audible Echolocation on Small Robots

Martin Vetterli, Mihailo Kolundzija, Frederike Dümbgen, Adrien Guillaume Olivier Hoffet, Adam James Scholefield

For safe and efficient operation, mobile robots need to perceive their environment, and in particular, perform tasks such as obstacle detection, localization, and mapping. Although robots are often equipped with microphones and speakers, the audio modality ...

2022

Shedding light on 19th century spectra by analyzing Lippmann photography

Martin Vetterli, Gilles Baechler, Arnaud Latty, Adam James Scholefield, Michalina Wanda Pacholska

2021

How Asynchronous Events Encode Video

Martin Vetterli, Adam James Scholefield, Karen Adam

As event-based sensing gains in popularity, theoretical understanding is needed to harness this technology’s potential. Instead of recording video by capturing frames, event-based cameras have sensors that emit events when their inputs change, thus encodin ...

IEEE2021

Sampling and Reconstruction of Bandlimited Signals with Multi-Channel Time Encoding

Martin Vetterli, Adam James Scholefield, Karen Adam

Sampling is classically performed by recording the amplitude of the input at given time instants; however, sampling and reconstructing a signal using multiple devices in parallel becomes a more difficult problem to solve when the devices have an unknown sh ...

2020

Shape From Bandwidth: Central Projection Case

Martin Vetterli, Golnooshsadat Elhami, Adam James Scholefield

Consider an unknown surface painted with a band-limited texture. We show that only the knowledge of the bandwidth of the texture is enough to estimate the shape of the surface from a single image taken by a camera. We model the problem as a central project ...

IEEE2020

Encoding And Decoding Mixed Bandlimited Signals Using Spiking Integrate-And-Fire Neurons

Martin Vetterli, Adam James Scholefield, Karen Adam

Conventional sampling focuses on encoding and decoding bandlimited signals by recording signal amplitudes at known time points. Alternately, sampling can be approached using biologically-inspired schemes. Among these are integrate-and-fire time encoding ma ...

IEEE2020

Realizability of planar point embeddings from angle measurements

Frederike Dümbgen, Adam James Scholefield, Majed El Helou

Localization of a set of nodes is an important and a thoroughly researched problem in robotics and sensor networks. This paper is concerned with the theory of localization from inner-angle measurements. We focus on the challenging case where no anchor loca ...

IEEE2020

Relax and Recover: Guaranteed Range-Only Continuous Localization

Frederike Dümbgen, Adam James Scholefield, Michalina Wanda Pacholska

Range-only localization has applications as diverse as underwater navigation, drone tracking and indoor localization. While the theoretical foundations of lateration---range-only localization for static points---are well understood, there is a lack of unde ...

2020

Multi-channel Time Encoding for Improved Reconstruction of Bandlimited Signals

Martin Vetterli, Adam James Scholefield, Karen Adam

Traditional sampling involves encoding a signal through (time, value)-pairs. In contrast, time encoding machines (TEMs) characterize a signal by recording time points which depend on the integral of the signal over time. We study multi-channel TEMs where c ...

2019

Multi-spectral image priniting method

Martin Vetterli, Yves Bellouard, Gilles Baechler, Arnaud Latty, Adam James Scholefield, Michalina Wanda Pacholska

The present disclosure concerns a multi-spectral image printing method. The method includes the steps of: - providing a multi-spectral image; - providing a material; - determining changes in a refractive index value of the material permitting to reproduce ...

2019

Bound and Conquer: Improving Triangulation by Enforcing Consistency

Martin Vetterli, Alireza Ghasemi, Adam James Scholefield

We study the accuracy of triangulation in multi-camera systems with respect to the number of cameras. We show that, under certain conditions, the optimal achievable reconstruction error decays quadratically as more cameras are added to the system. Furtherm ...

2019

Multi-Modal Probabilistic Indoor Localization on a Smartphone

Serge Ayer, Mihailo Kolundzija, Johan Leuenberger, Frederike Dümbgen, Emmanuel Girardin, Cynthia Oeschger, Adam James Scholefield

IEEE2019

Embedded Polarizing Filters to Separate Diffuse and Specular Reflection

Gilles Baechler, Laurent Valentin Jospin, Adam James Scholefield

Polarizing filters provide a powerful way to separate diffuse and specular reflection; however, traditional methods rely on several captures and require proper alignment of the filters. Recently, camera manufacturers have proposed to embed polarizing micro ...

SPRINGER INTERNATIONAL PUBLISHING AG2019

Combining Range and Direction for Improved Localization

Martin Vetterli, Robin Scheibler, Gilles Baechler, Frederike Dümbgen, Golnooshsadat Elhami, Miranda Krekovic, Adam James Scholefield

Self-localization of nodes in a sensor network is typically achieved using either range or direction measurements; in this paper, we show that a constructive combination of both improves the estimation. We propose two localization algorithms that make use ...

2018

Sampling at unknown locations: Uniqueness and reconstruction under constraints

Martin Vetterli, Golnooshsadat Elhami, Benjamin Bejar Haro, Adam James Scholefield, Michalina Wanda Pacholska

Traditional sampling results assume that the sample locations are known. Motivated by simultaneous localization and mapping (SLAM) and structure from motion (SfM), we investigate sampling at unknown locations. Without further constraints, the problem is of ...

2018

Point and sensor estimation from images

Martin Vetterli, Alireza Ghasemi, Adam James Scholefield

System comprising at least one sensor configured to take a set of images from different viewpoints of a scene; a processor configured to identifying a point source represented in the images of a set of images; computing for each image of the set of images ...

2017

Sampling and Exact Reconstruction of Pulses with Variable Width

Martin Vetterli, Loïc Arnaud Baboulaz, Gilles Baechler, Adam James Scholefield

Recent sampling results enable the reconstruction of signals composed of streams of fixed-shaped pulses. These results have found applications in topics as varied as channel estimation, biomedical imaging and radio astronomy. However, in many real signals, ...

Institute of Electrical and Electronics Engineers2017