Title: COMPARISON OF VARIOUS METHODS TO MEASURE LUMINOUS INTENSITY WITH AN IMAGING COLORIMETER
1COMPARISON OF VARIOUS METHODS TO MEASURE LUMINOUS
INTENSITY WITH AN IMAGING COLORIMETER
- Ronald Rykowski
- President and Chief Technology Officer
- Radiant Imaging, Inc.
- www.radiantimaging.com
- rykowski_at_radiantimaging.com
- (425) 844-0152
2Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
3Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
4Background
- Market forces have created an increased need for
luminous intensity measurement, particularly with
LEDs and LED light fixtures. - Research, development and production all have
different measurement requirements - Measurement methods are strictly specified in
some industries, but not so in others - Imaging colorimeters and photometers now provide
alternatives to far-field goniometric systems - Understanding instrument capabilities and
limitations enables us to pick the right tool for
a specific job
5Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
6The Imaging Colorimeter
- Main elements include an imaging lens, a set of
color filters, a CCD detector, and data
acquisition and image processing
hardware/software
7The Imaging Colorimeter
- System acquires an image of the DUT through each
of the color filters. - ND filters used to ensure that each color
measurement uses the full dynamic range of the
sensor.
8The Imaging Colorimeter
- System software automatically applies necessary
calibrations and allows data to be manipulated
in a variety of ways
9The Imaging Colorimeter
- Commercially available imaging colorimeters
typically range from 10 to 16 bit dynamic range,
3 luminance accuracy and color accuracy
(chromaticity coordinates) 0.003
10Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
11Measurement Methods (Extended Source)
- Goniophotometer (reference instrument)
- Imaging Colorimeter
- Two Axis Near Field Goniometer (FPMS-LI)
- Imaging Sphere
12 Measurement Methods (Extended Source)
- Goniophotometer
- Source mounted on a two axis goniometer
- Stationary photometer placed in far field
- Source is rotated in two axes, allowing entire
intensity distribution to be sampled - Luminous intensity distribution created from
point measurements - Alternate configuration
- is moving mirror goniometer
-
13 Measurement Methods (Extended Source)
- Imaging Colorimeter
- Project output from the DUT on to a screen
- Screen must be placed in that sources far field
- Screen must be large enough to capture entire
source output - Imaging colorimeter captures the entire
illuminance pattern in a single quick - measurement
14 Measurement Methods (Extended Source)
- Two Axis Near Field Goniometer (FPMS-LI)
- Source mounted on a two axis goniometer
- Stationary imaging colorimeter placed in near
field views DUT directly - Source is rotated in two axes, allowing
luminance measurements - To be recorded at all angles
- Software produces model of luminance and near
field chromaticity - Raytracing is used to yield illuminance or
far-field - Intensity Data
15 Measurement Methods (Extended Source)
16Measurement Methods (Extended Source)
- FPMS-LI actual measurements
At Inclination 3, Azimuth 90
17 FPMS-LI Ray trace simulation
Plane at surface of source
At imaging colorimeter location
Plane at 3.4 meters
18Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
19Performance Comparison (Extended Source)
- Luminous intensity of a sealed beam automotive
headlamp (Philips Halogen H4701 hi beam) was
measured with - spot goniophotometer
- imaging colorimeter
- FPMS-LI
20 Performance Comparison (Extended Source)
21 Performance Comparison (Extended Source)
- Headlamp luminous intensity
- Spot goniophotometer
22 Performance Comparison (Extended Source)
- Headlamp luminous intensity
- Imaging colorimeter
23 Performance Comparison (Extended Source)
- Headlamp luminous intensity
- FPMS-LI
24 Performance Comparison (Extended Source)
25 Performance Comparison (Extended Source)
At 3.4m from Source
26Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Small Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
27Measurement Methods (Small Source)
- Source Imaging Goniometer (SIG)
- Performs equivalent measurement to FPMS-LI
- Source rotates in one axis and imaging
colorimeter is mounted on a goniometric arm - More convenient configuration for smaller
sources
28 Measurement Methods (Small Source)
- Imaging Sphere
- Optical system consists of coated, diffuse, low
reflectance hemisphere, a curved secondary mirror
and an imaging colorimeter
29 Measurement Methods (Small Source)
- Imaging Sphere
- Source illuminates inside surface of dome, which
acts as a curved screen - Essentially 2p steradians of output is captured
30 Measurement Methods (Small Source)
- Imaging Sphere
- Convex mirror enables the imaging colorimeter to
image the entire inner surface of the hemisphere
in a single exposure.
31 Measurement Methods (Small Source)
- System software automatically applies necessary
calibrations and allows data to be analyzed in a
variety of ways
32 Measurement Methods (Small Source)
- Commercially available imaging sphere has a dome
radius of 225 mm - This limits the systemto measuring
smallsources, such as LEDs,since the dome
surface must be in the far field of the source
33Performance Comparison (Small Source)
- Luminous intensity of two LEDs (Super Bright LEDs
RL5 B2545 and Luxeon LXHL-LW5C) were measured
with - Imaging sphere
- SIG
34 Performance Comparison (Small Source)
35 Performance Comparison (Small Source)
Luminous Intensity Measured with Imaging Sphere
36 Performance Comparison (Small Source)
Imaging Sphere
SIG (goniometric)
37 Performance Comparison (Small Source)
38Performance Comparison (Small Source)
RL5-X LEDs were scanned in the Radiant Imaging
SIG300 for reference purposes. Subsequently, they
were measured with the IS-LI. The 2 measurements
were examined to determine the location of the
peak intensity and the position and size of the
full-width-half-maximum (FWHM) of the light
distribution.
39Measuring Luminous Intensity
- Background
- The Imaging Colorimeter
- Measurement of an Extended Source
- Measurement Methods
- Performance Comparison
- Measurement of a Point Source
- Measurement Methods
- Performance Comparison
- Tradeoffs
40Tradeoffs
- All these instruments are capable of delivering
high quality data for a given measurement
requirement. - How do you choose the best tool for a particular
job?
41Tradeoffs
- Imaging Colorimeter (Intensity projected on
screen) - Advantages
- Speed
- Low cost
- Disadvantages
- Must measure in far field
- May require large screen
- Provides luminous intensity only at measured
distance
42Tradeoffs
- FPMS-LI
- Advantages
- Delivers comprehensive data
- Measures in the near field (compact
configuration) - Results compatible with optical design software
- Disadvantages
- Slow speed
- Moderate cost
43Tradeoffs Imaging Sphere
- Advantages
- Speed
- High resolution
- Insensitive to output variation over time
- Small size
- Can work with ambient light
- Disadvantages
- Can only measure small sources or Condition B
distance
44Tradeoffs
- Spot Goniophotometer
- Advantages
- High color and luminance accuracy
- Disadvantages
- Slow speed
- LED output can vary during measurement,
especially for LEDs - Provides luminous intensity only at measured
distance - Large space required for extended sources
45Tradeoffs