OL 454 Integrating Sphere Calibration Standard0 pages

Bulletin 137 / Rev. 4-99
OL Series 454
Integrating Sphere Calibration Source
General
The OL Series 454 Integrating Sphere Source is
designed for calibrating telephotometers or
microphotometers. It is a stable, large area, highly
diffuse sphere source consisting of an OL 454
Series Optics Head and a separate OL 53 Constant
Current Source. Calibration options include
luminance, color temperature and spectral radiance.
The separate Optics Head and Current Source
enables remote location of either unit which
facilitates alignment or positioning of the source with
respect to the device to be calibrated. The Optics
Head is designed such that it can be configured with
integrating spheres having diameters of 4, 6, 8, 12
and 18 inches with exit (radiating) ports of 1, 1, 2,
3, and 6 inches respectively.
Source Module/Optics Head
The Source Module/Optics Head uses a 150-W
tungsten-halogen reflectorized lamp with a
micrometer-controlled variable aperture between the
lamp and the integrating sphere.
The source is calibrated for luminance or radiance
with the variable aperture completely open. The
variable aperture can be used to attenuate the
output of the sphere source over a range of six
decades. The sphere has a highly reflecting,
diffusely reflecting PTFE based coating. The in-line
sphere port geometry, with an intermediate spider
baffle in the middle of the sphere, provides for
exceptional uniformity in the near normal luminance
over the entire radiating port of the sphere. A
shutter is located between the lamp and the
entrance port of the sphere. A filter holder, mounted
at the exit port, accommodates optional spectral
shaping filters for simulation of various sources such
as Illuminants A, B, C, D65, etc.
Controller
The OL 53 is a highly regulated constant current DC
power supply that optimizes source stability and
accuracy. The lamp current is displayed on a 4
digit ammeter and can be adjusted via a 10 turn
control pot from 0 to 6.5000 amperes. The
uncertainty in the current setting is ± 0.05%. In
order to enhance the stability and life of the lamp, a
current ramp up/ramp down circuit is employed
which prevents thermal shock to the lamp. An
elapsed time meter is provided with a maximum
range of 9999.99 hours to accurately monitor the
calibration life of the source. In addition, an
automatic shut down circuit is employed which turns
off the unit in case of excessive current due to
system malfunction or accidental setting of too high
a lamp current by the user.