Abstract
Chip-On-Board Light-Emitting Diodes (COB LED) are increasingly more common. Their development in recent years has directly contributed to increasing the power of LED sources, whilst simultaneously increasing the luminous flux from the entire COB. Consequently, it has led to new developments in some applications. Information regarding the size of the light source luminous surface and luminance distribution on its surface is critical for a designer whilst designing optical systems. The purpose of this conducted research was to establish to what extent luminance distribution is even on the examined COB LEDs. In order to verify luminance distributions on an LED surface, direct measurements with a matrix luminance measuring device were made. As a result of the research, it has been observed that luminance distribution is not even, and in many cases luminance maximum does not fall in the geometric center of the luminous surface, which was initially expected. So, it has been concluded that while designing optical systems for COB LEDs, irregular luminance distribution on their surface needs to be considered.
Highlights
The producers of light-emitting diodes (LEDs) aim to create sources of light that will have as many diverse applications as possible
The increasingly bigger power of the produced Chip-On-Board Light-Emitting Diodes (COB LED), and as a result their bigger luminous flux, makes it possible for these light sources to be put to various uses
Circular COB was selected for the tests and only during the research it appeared that the micro-chips were not always arranged in a circle, and in a hexagon (COB5) or a square (COB1)
Summary
The producers of light-emitting diodes (LEDs) aim to create sources of light that will have as many diverse applications as possible. Despite high luminous efficacy, LEDs continue to have both low unit power and luminous flux This fact has caused considerable limitations in terms of application where higher values of luminous flux were required (e.g. road lighting, stage lighting, floodlighting). LED matrixes are in particular frequently used in the construction of road lighting luminaires [3,4,5,6] To deal with this problem, single LEDs have been put together into matrices with over 100 single LED chips each. Such a solution, resulted in a considerable decrease of the luminaire size and caused difficulty of heat dissipation emitted by the LEDs, as considerable heat flows of as much as 300 W/cm or more occur on the matrix level [7]
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