1. Light measurement unit
Reference 1. Terminology
Classification
MKS unit
Meaning
Luminous flux
lm (lumen)
The amount of emitted light that is measured based upon CIE standard luminous efficacy and the maximum luminous
efficacy
2 What is ANSI lumen?
Luminous intensity
cd (candela) = lm/sr
A value that a speed of light, directed in any directions from the light source, is divided by a solid
angle.
Illuminance
lx (lux) = lm/㎡
The amount of light entering per unit area (Light receiving part)
Luminance
cd/㎡ = cd/sr
·
㎡
The amount of emitted light per unit area and per unit solid angle (Light emitting part)
2. What is ANSI lumen?
• PJTR brightness standard unit establishing by ANSI(American National Standards Institute)
• A standard which entire luminous flux of projected light can be measured regardless of a level of uniformity
in order to correct the measurements caused by different measurement locations.
g
p
p
g
( g
g p
)
→ Calculated luminous flux (unit lm) based upon the standard is called ANSI lm.
• Measurement procedure :
① Divide the projected screen into a nine equal size (Below figure)
② Measure a center illuminance at the 9 points and calculate the average (lx = lm / ㎡)
③ Calculate the projected screen size (㎡)
③ Calculate the projected screen size (㎡)
④ the calculated average from ② (lx = lm / ㎡) x projected screen size (㎡) = ANSI lm (lm)
* Projected screen size is not specified, but 40 inch projection is general.
Example) 40 inch (SIZE = 0.495 ㎡) when projecting, an average
lluminance 2,500 lx, .
▶
2,500 ( lx ) x 0.495 (㎡) = 1,237.5 (lm) *
∴ 1,237.5 ANSI lm
Copyright © 2012 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only
1,237.5 ANSI lm
Summary of Contents for PB60G
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