Methods for measuring work surface illuminance in adaptive solid state lighting networks

The inherent control flexibility implied by solid-state lighting - united with the rich details offered by sensor networks - prompts us to rethink lighting control. In this research, we propose several techniques for measuring work surface illuminance and ambient light using a sensor network. The primary goal of this research is to measure work surface illuminance without distraction to the user. We discuss these techniques, including the lessons learned from our prior research. We present a new method for measuring the illuminance contribution of an arbitrary luminaire at the work surface by decomposing the modulated light into its fundamental and harmonic components.Massachusetts Institute of Technology. Media Laborator

ST-RAP: A Spatio-Temporal Framework for Real Estate Appraisal

In this paper, we introduce ST-RAP, a novel Spatio-Temporal framework for Real estate APpraisal. ST-RAP employs a hierarchical architecture with a heterogeneous graph neural network to encapsulate temporal dynamics and spatial relationships simultaneously. Through comprehensive experiments on a large-scale real estate dataset, ST-RAP outperforms previous methods, demonstrating the significant benefits of integrating spatial and temporal aspects in real estate appraisal. Our code and dataset are available at https://github.com/dojeon-ai/STRAP.Comment: Accepted to CIKM'2

On the Importance of Feature Decorrelation for Unsupervised Representation Learning in Reinforcement Learning

Recently, unsupervised representation learning (URL) has improved the sample efficiency of Reinforcement Learning (RL) by pretraining a model from a large unlabeled dataset. The underlying principle of these methods is to learn temporally predictive representations by predicting future states in the latent space. However, an important challenge of this approach is the representational collapse, where the subspace of the latent representations collapses into a low-dimensional manifold. To address this issue, we propose a novel URL framework that causally predicts future states while increasing the dimension of the latent manifold by decorrelating the features in the latent space. Through extensive empirical studies, we demonstrate that our framework effectively learns predictive representations without collapse, which significantly improves the sample efficiency of state-of-the-art URL methods on the Atari 100k benchmark. The code is available at https://github.com/dojeon-ai/SimTPR.Comment: Accepted to ICML 202

Wideband Electrically Pumped 1050-nm MEMS-Tunable VCSEL for Ophthalmic Imaging

In this paper, we present a 1050-nm electrically pumped microelectromechanically tunable vertical cavity surface-emitting laser (MEMS-VCSEL) with a record dynamic tuning bandwidth of 63.8 nm, suitable for swept-source optical coherence tomography (SS-OCT) imaging. These devices provide reduced cost and complexity relative to previously demonstrated optically pumped devices by obviating the need for a pump laser and associated hardware. We demonstrate ophthalmic SS-OCT imaging with the electrically-pumped MEMS-VCSEL at a 400 kHz axial scan rate for wide-field imaging of the in vivo human retina over a 12 mm × 12 mm field and for OCT angiography of the macula over 6 mm × 6 mm and 3 mm × 3 mm fields to show retinal vasculature and capillary structure near the fovea. These results demonstrate the feasibility of electrically pumped MEMS-VCSELs in ophthalmic instrumentation, the largest clinical application of OCT. In addition, we estimate that the 3 dB coherence length in air is 225 ± 51 m, far greater than required for ophthalmic SS-OCT and suggestive of other distance ranging applications.National Eye InstituteNational Institutes of Health (U.S.) (Grant R01-EY011289-28)National Institutes of Health (U.S.) (Grant R44-EY022864-02)National Institutes of Health (U.S.) (Grant R44-EY022864-03)National Institutes of Health (U.S.) (Grant R01-CA075289-17)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)United States. Air Force Office of Scientific Research (FA9550-12-1-0499

Radio frequency test methods for balanced receivers for swept source optical coherence tomography

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 47-48).Optical coherence tomography (OCT) has risen as a clinical standard of diagnosis and management of ocular diseases since its development in 1991 by the MIT group and the collaborators. Since current cutting-edge OCT technology based on frequency-swept lasers has achieved scanning rate over 1,000,000 axial scans per second, the imaging speed is limited by the detection and analog-to-digital conversion stages. In order to match the rapid advancement of OCT imaging speed, a variety of balanced photoreceivers have been developed. A low-cost setup for systematic performance evaluation of the receivers in radio frequency (RF) range up to 2GHz is presented. The test procedure, including measurements of gain, bandwidth, and harmonic distortion, is automated by National Instruments Virtual Instrument Software Architecture (NI-VISA) programming using USB and GPIB interface. Since the test equipment has parasitic response, quasi-calibration using a fast biased detector is necessary. Detailed description of the equipment and the test protocol is included as well as the performance comparison of the available receiver products and prototypes.by ByungKun Lee.M.Eng

Ultrahigh Speed OCT Angiography of Retinal and Choriocapillaris Alterations in Diabetic Patients with and without Retinopathy Using Swept Source Optical Coherence Tomography

Purpose: To investigate the utility of ultrahigh speed, swept source optical coherence tomography angiography in visualizing retinal microvascular and choriocapillaris (CC) changes in diabetic patients. Methods: The study was prospective and cross-sectional. A 1,050 nm wavelength, 400 kHz A-scan rate swept source optical coherence tomography prototype was used to perform volumetric optical coherence tomography angiography of the retinal and CC vasculatures in diabetic patients and normal subjects. Sixty-three eyes from 32 normal subjects, 9 eyes from 7 patients with proliferative diabetic retinopathy, 29 eyes from 16 patients with nonproliferative diabetic retinopathy, and 51 eyes from 28 diabetic patients without retinopathy were imaged. Results: Retinal and CC microvascular abnormalities were observed in all stages of diabetic retinopathy. In nonproliferative diabetic retinopathy and proliferative diabetic retinopathy, optical coherence tomography angiography visualized a variety of vascular abnormalities, including clustered capillaries, dilated capillary segments, tortuous capillaries, regions of capillary dropout, reduced capillary density, abnormal capillary loops, and foveal avascular zone enlargement. In proliferative diabetic retinopathy, retinal neovascularization above the inner limiting membrane was visualized. Regions of CC flow impairment in patients with proliferative diabetic retinopathy and nonproliferative diabetic retinopathy were also observed. In 18 of the 51 of eyes from diabetic patients without retinopathy, retinal mircrovascular abnormalities were observed and CC flow impairment was found in 24 of the 51 diabetic eyes without retinopathy. Conclusion: The ability of optical coherence tomography angiography to visualize retinal and CC microvascular abnormalities suggests it may be a useful tool for understanding pathogenesis, evaluating treatment response, and earlier detection of vascular abnormalities in patients with diabetes.National Institutes of Health (U.S.) (Grants NIH R01-EY011289-28, R44-EY022864-03, R01-CA075289-17)United States. Air Force. Office of Scientific Research (Grants AFOSR FA9550-10-1-0551 and FA9550-12-1-0499

High-Speed, Ultrahigh-Resolution Spectral-Domain OCT with Extended Imaging Range Using Reference Arm Length Matching

Purpose: To develop high-speed, extended-range, ultrahigh-resolution spectraldomain optical coherence tomography (UHR SD-OCT) and demonstrate scan protocols for clinical retinal imaging. Methods: A UHR SD-OCT operating at 840-nm with 150-nm bandwidths was developed. The axial imaging range was extended by dynamically matching reference arm length to the retinal contour during acquisition. Two scan protocols were demonstrated for imaging healthy participants and patients with dry age-related macular degeneration. A high-definition raster protocol with intra–B-scan reference arm length matching (ReALM) was used for high-quality cross-sectional imaging. A cube volume scan using horizontal and vertical rasters with inter–B-scan ReALM and software motion correction was used for en face and cross-sectional imaging. Linear OCT signal display enhanced visualization of outer retinal features. Results: UHR SD-OCT was demonstrated at 128-and 250-kHz A-scan rates with 2.7 μm axial resolution and a 1.2-mm, 6-dB imaging range in the eye. Dynamic ReALM was used to maintain the retina within the 6-dB imaging range over wider fields of view. Outer retinal features, including the rod and cone interdigitation zones, retinal pigment epithelium, and Bruch’s membrane were visualized and alterations observed in agerelated macular degeneration eyes. Conclusions: Technological advances and dynamic ReALM improve the imaging performance and clinical usability of UHR SD-OCT. Translational Relevance: These advances should simplify clinical imaging workflow, reduce imaging session times, and improve yield of high quality images. Improved visualization of photoreceptors, retinal pigment epithelium, and Bruch’s membrane may facilitate diagnosis and monitoring of age-related macular degeneration and other retinal diseases.National Institutes of Health (U.S.) (Grant 5-R01-EY011289-33)United States. Air Force. Office of Scientific Research (Grant FA9550-15-1-0473