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Choosing the Light Source

This example is available in a professional edition.

This example is valid for the reflector simulation problem.

In this example the optical system is calculated for various light sources. The goal of reflector simulation is to choose the optical system with the highest efficiency.

Input data:

Input parameterValue
Type of the problemReflector simulation
The system symmetryRotational
Type of light distributionLuminous Intensity Distribution
The parameters of the illuminated area 
Initial angle0
Final angle45
The reflector’s parameters 
Reflectance0,8
Type of presentationPolar coordinates
ProfileSpecial

There are common types of light source for industrial lighting (Fig. 1): arc high pressure mercury lamp with iodides (HQI), arc tubular sodium high-pressure lamp (NAV) and mercury arc lamp (HQL).

Fig. 1 Light sources for industrial lighting: HQI (left), NAV (center), HQL (right)

There are calculation parameters in table below:

Light SourceThe parameters of the light source
Type of SourceTransparentLuminanceGeometry
HQICylinderOff15000Z Displacement, mm0
Radius, mm9.1
Length, mm40.86
NAVCylinderOn15000Z Displacement, mm-10
Radius, mm4.8
Length, mm87.5
HQLEllipsoidOff15000Z Displacement, mm8
1st semiaxis, mm100.74
2nd semiaxis,mm61

The light fixture should have high energy efficiency. The light fixture’s optical system consists of reflector and light source. When reflector’s profile is determined it is needed to choose the most effective light source. That means efficiency of the optical system not only efficiency of the light source.

In this example the optical system consisted of specified reflector’s profile and light source is calculated for each of three various types of light sources (Fig. 1) – reflector simulation. The aim of task is to compare luminous intensity distributions of the optical systems and its factors. The reflector used in calculations (Fig. 2) is also appropriate for industrial lighting. The goal is to calculate optical system with the full radiation angle at 0.5 level of axial luminous intensity from 60 degrees or over (Fig. 3).

Furthermore factor of optical system is needed to account. Factor is calculated as ratio of part of luminous flux emitted in angle 60 degrees to full luminous flux. Its value should be over 65 %.

Fig. 2 The reflectors profileFig. 3 The luminous intensity distribution curve with the full angle of optical system radiation at 0.5 level of axial luminous intensity 60 degrees

The general views of calculated optical systems are shown on Figures 4 – 6.

Fig. 4 The optical system with the HQIFig. 5 The optical system with the NAVFig. 6 The optical system with the HQL

Note. There is luminous surface of real lamp shown on the figures above.

There are results of calculations in the table below:

Light sourceThe full angle of optical system radiation at 0.5 level of axial luminous intensity, degFactor of optical system, %
HQI6628
NAV5617
HQL10869

The luminous intensity distribution curves of calculated optical systems are shown on Figures 7 - 9.

Fig. 7 The luminous intensity distribution curve of optical system with the HQI: yellow curve - direct light curve, red curve - optical system curve, green curve - specified curveFig. 8 The luminous intensity distribution curve of optical system with the NAV: yellow curve - direct light curve, red curve - optical system curve, green curve - specified curveFig. 9 The luminous intensity distribution curve of optical system with the HQL: yellow curve - direct light curve, red curve - optical system curve, green curve - specified curve

Note. Light distributions are normalized to the same value of axial luminous intensity for the ease of comparison.

It is clear from the table and Figures above that proper solving is HQL. When it is used the full angle of optical system radiation at 0.5 level of axial luminous intensity equals 108 degrees and its factor 69 %. Thus about 70 % of full light flux of optical system is emitted in utility angle.

Conclusion

Often there is influence of process requirements or it is needed to replace worked-out lamp and therefore reflector is required to have defined profile curve. As the optical system consists of reflector and light source it is necessary to estimate the influence of selected light source on the efficiency of the existing optical system. The efficiency parameters are determined with field of use for concerned light fixture. In this example three various light sources are used for reflector simulation. The full angle of optical system radiation at 0.5 level of axial luminous intensity and factor of the optical system are estimated. Result of calculation shows that HQL is appropriate.