Consulting services for the generation, control, and application of light

Activity Highlights

  • Improving the accuracy of Pulse Oximetry

    Pulse oximeters provide a convenient, noninvasive measurement of blood oxygen saturation and have become essential tools for both critical medical care and health monitoring. Numerous studies over the past 20 years, however, have revealed inaccuracies and biased reading for people with dark skin pigmentation. Namreiba is working with the Icahn School of Medicine at Mount Sinai on a NIH grant to
    improve pulse oximetry through a better understanding of the spectral changes of light propagation through biological tissue.

    Learn more at NIH's rePORTER.

  • Circadian Standard Observer

    Good lighting design involves providing for the biological health needs of occupants as well as their visual needs and expectations while limiting energy use and environmental impacts. With the recent publication of “Standard observer watts: Evaluating the efficiency of circadian-effective luminaires using a standard observer methodology” designers now have a simple way of evaluating the effectiveness of luminaires for delivering circadian-effective light at the eye.

Light for technology.

Light for people.

Agriculture:

Plant Growth- Light powers the growth of plants and the type of light shapes how they grow. Whether plants put energy into being tall vs bushy, or growing fruit vs foliage is influenced by the spectrum of the light they receive. Spectrum can also influence the nutritive value of food crops. I have extensive knowledge and experience working with light source spectra and the technologies that generate light (LED, discharge, fluorescent, solar) as well as familiarity with plant science and metrics regarding light.

Pest Control- Over the last 5 years I have been heavily involved with research and demonstrations on the use of UV for pest control for commercial crops. Most of my work concerned the control of powdery mildew in strawberry and grape by application of UV-C at night. Dosing calculations, equipment design/specification and safety are key strengths.

Illumination:

Light enables vision. Good lighting makes clear what we want to see and does so efficiently, comfortably and appeals to our artistic aesthetic that enriches life. I am not an artist, but I work with artists to bring their visions and inspirations to light.

Experienced in all aspects of illumination engineering including point calculations, radiative flux transfer (zonal cavity method), luminance and glare, efficiency metrics, electrical drive and control gear.

UV Disinfection:

A resurgence of UV applications have emerged over the last few years for water, surface and air disinfection. UV LED technology is facilitating many new applications. While traditional germicidal radiation (250 nm – 280 nm) accounts for most applications, far UV-C (e.g., 222 nm) and UV-A (~365 nm) are emerging approaches that can be used when people are present.

I have experience in the evaluation of UV systems for disinfection of water and air, both upper room and in-duct systems and most recently surface disinfection in hospitals. In 2020 I coauthored an online publication evaluating the effectiveness of commercial UV disinfection products

Color:

Color is the human interpretation of the physical spectrum. Working with color starts with understanding the physics of a spectral power distribution and then adding layers of eye physiology and cognitive perception as captured by color models.

Capabilities include color matching, mixing, color tuning (cool to warm), color rendering and all types of color metrics including CIE standards, IES TM30, circadian and melanopic sensitivity, mesopic and scotopic vision.

Dimming:

LEDs are the first light sources that are truly dimmable without suffering efficacy losses, color shifts and life issues. Still, different methods, control gear compatibility and perceptual effects can make quality dimming difficult.

Smooth, full range, artifact-free dimming and color tuning requires knowledge in electrical driver circuits, LED characteristics and human perception. I have over 25 years of experience in these areas.

Imaging & Measurement:

Machine vision depends on proper illumination. The directionality, spectrum and amount of incident light greatly affect image features and resolution. Different imaging modalities including UV, IR, color, fluorescence and polarization can make the invisible visible.

Light is also ideal for many remote sensing and non-invasive medical instruments. I have experience with PIR occupancy sensors, pulse oximeters, pyrometers, and many types of photosensors and optical feedback systems.

Flicker:

Other than perhaps cozy candle or firelight, light source flicker is at best annoying and at worst can cause heath and safety problems. Related stroboscopic effects arise when flicker and motion are involved, often at higher frequencies.

Nearly all electric light sources have some amount of flicker which is the unavoidable result of efficient and cost-effective driver technology (pulse-width-modulation and switching drivers). With an understanding human temporal response perception and signal processing, flicker can be eliminated, and stroboscopic effects minimized.

Health & Circadian Rhythms:

Electric light is not just for vision anymore. With people spending most of their time indoors, the non-visual benefits of light on health need to be provided by the built environment. Whether this is by the inclusion of daylight or solely by electric lighting the requirements are much different that that needed for vision.

I have been on the forefront of studying the human circadian system’s response to light for 20 years while a scientist at the Lighting Research Center. I have in-depth knowledge of the metrics for circadian effectiveness (CS, CLA, EML, α-optic) and how the timing of light exposure effects response.

The benefit of UV-B for vitamin D synthesis as well as the potentially harmful effects of too much UV or even blue light exposure, either from natural or electric sources, is another aspect of lighting and health. I have experience calculating permissible exposure limits and working with safety standards such as CIE/IEC 62471.

Agriculture • UV Disinfection • Imaging and Measurement

Illumination • Color • Dimming • Flicker • Health & Circadian Rhythms