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Solid-State Lighting and LEDs

Cree® XLamp® XP-G LED

Solid-State Lighting (SSL) uses semiconductor materials to convert electricity into light. Some associate SSL only with with LEDs. In reality SSL is an umbrella term encompassing different types of technologies including Light-Emitting Diodes (LEDs) and Organic Light-Emitting Diodes (OLEDs). More recently, Light Emitting Capacitors (LEC) and Light-Emitting Polymers (LEP)  […]

Light and Colors – Part 4

The CIE 1931 Chromaticity Diagram

The CIE XYZ color space [1] defines all colors in terms of three imaginary primaries X, Y, and Z based on the human visual system that possess the following properties:

Based on experimental data of human color matching; X, Y, and Z work like additive primaries RGB (every […]

Light and Colors – Part 3

Color perception is a brain process that starts in the eye’s cone receptors. These receptors are found in three varieties that exhibit sensitivity to approximately red, green, and blue colors. The separation between colors is not clean and there is significant overlap between the sensitivities of all three varieties, particularly between the red […]

Light and Colors – Part 2

CIE Photometric Curve

The human eye is an incredibly complex detector of electromagnetic radiation with wavelengths between 380 to 770 nm. The sensitivity of the eye to light varies with wavelength (see the CIE photometric curve for the day vision – V(λ) – the photopic visual response function). Photometry can be considered radiometry […]

Light and Colors – Part 1

There are many books and papers dedicated to the study of light from different perspectives: the artist, the scientist, the designer, the historian or the biologist. There is no point in repeating here what the literature provides in abundance. The goal of this post is to introduce some concepts that will be used later […]

CoOS Real Time Kernel ( – Part 3

Lesson learned: the presence of an RTOS doesn’t mean you will get a better real-time performance for your application! I know, it sounds counterintuitive but this is real. A hard real-time system where the interrupts should be serviced as quickly as they come will have to rely on small and fast interrupt service routines […]