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Calculating Profile for COB LED Light Source

This example is available in a professional edition.

This example is valid for the reflector synthesis problem.

In this example the profile for COB LED light source is calculated. The luminous intensity distribution of optical system and requirements for level and uniformity of illuminance distribution are specified.

Input data:

Input parameterValue
Type of the problemReflector synthesis
The system symmetryRotational
Type of light distributionLuminous Intensity Distribution
The light source’s parameters 
Type of SourceDisk
Radius, mm9.5
The reflector’s parameters 
Initial Radius, mm100
Start Angle, deg180
Final Angle, deg268
The parameters of the illuminated area 
Start Angle, deg8
Final Angle, deg60

The use of LEDs has become topical in all areas of lighting due to their reliability, efficiency and ability to manage their settings. LED light fixtures are increasingly found in the installation of street lighting. For example, park lighting. In this case a light fixture performs the role of illumination required for pedestrian orientation in the dark. The luminous intensity distribution can be arbitrary and should provide requirements for the level and uniformity of illuminance.

Fig. 1 Typical light fixture for landscape lighting

In this example the optical system for light fixture of park lighting is calculated. Standard light fixture comprises a pole and a crowning of an optical system disposed in the ceiling of the protective (Fig. 1). The light source is COB module (Chip On Board) in the form of a disk, which radiates into an upper hemisphere (Fig. 2).

The light fixture must simultaneously provide the necessary coverage and fulfill a decorative role. Thus, the lamp should illuminate the space around and create a sufficient level of light on the ground. Therefore, we choose the luminous intensity distribution of optical system, as shown in Fig. 3.

Fig. 2 The luminous intensity distribution of the light sourceFig. 3 The luminous intensity distribution of the optical system: green curve - verifying curve, red curve - specified curveFig. 4 The optical system of calculated reflector

The calculated optical system (Fig. 4) redistributes the luminous flux in given angles, factor of calculated optical system equals 58%. The illuminance produced by an optical system on the illuminated area is estimated from the following considerations. Mounting height of luminaire is 3 meters, the illuminated area at the same time make a circle with a diameter of 5 meters. If the light output of the light source is 6550 lm (for example, NFDLJ130B on fig. 5), the minimum illuminance value is 10 lux, and uniformity is 0.24. These illumination conditions are sufficient for safe movement of pedestrians. The illuminance distribution of optical system is shown on fig. 6.

Fig. 5 The COB LED of NICHIA productFig. 6 The illuminance distribution of optical systemFig. 4 The optical system of calculated reflector


In this example the optical system is calculated, which redistributes the light output in the specified angles. Used light source is a disc, radiating into the upper hemisphere. The luminous intensity distribution of calculated optical system corresponds to a given distribution. The ratio of optical system luminous flux to light source luminous flux is 58%. The calculated optical system creates illuminance distribution, that satisfying the necessary requirements.