- Ø154 (mm)
- ±40 deg
Integrating spheres are used when you have divergent light sources. How do they work?
Integrating Sphere Theory
Integrating spheres are used when we have divergent light sources. As shown in the illustration, an integrating sphere has its inner surface coated with a surface that highly reflects (typically 99%) in a scattering, nonspecular way. Thus when a divergent beam hits the walls of the integrating sphere, the light is reflected and scattered many times until the light hitting any place on the walls of the sphere has the same intensity.
A detector placed in the sphere thus gets the same intensity as anywhere else and the power the detector detects is thus proportional to the total incident power independent of the beam divergence. (The detector is so arranged that it only sees scattered light and not the incident beam). An ideal integrating sphere has a surface with reflective properties are Lambertian. This means that light incident on the surface is scattered uniformly in all directions in the 2pi steradians solid angle above the surface. The surface used by Ophir closely approximates a Lambertian surface.
The 3A-IS series has two 50mm integrating spheres in series with a photodiode detector. The two series spheres scramble up the light very well thus giving output very independent of incident beam divergence angle. The two spheres in series also insure that the light hitting the detector is greatly reduced in intensity thus allowing use up to 3 Watts even though photodiodes saturate at about 1mW. There are two models, the 3A-IS with a silicon photodiode for 400 – 1100nm and the 3A-ISIRG with an InGaAs detector for 800 – 1700nm
Are there any special problems with the calibration stability of integrating sphere sensors?
The Ophir integrating sphere sensors, models 3A-IS and 3A-IS-IRG have a white diffuse reflecting coating on the inside of the integrating sphere. The sensitivity of the sensor is quite sensitive to the reflectivity of the coating. If the coating absorption goes up 1%, it can cause a 5% change in reading. Therefore, care must be taken not to soil or damage the white coating of the sensors. Also it may be a good idea to send the sensors for recalibration yearly.Close
When using the fiber optic adaptor, how do we handle power loss due to the fiber relative to calibration?
All Ophir power meters, including photodiode power meters, have an air gap between the fiber tip and the sensor. Therefore they measure the power emitted by the fiber into the air and do not take into account any reflection losses there are in the fiber. Therefore, if in actual use, the fiber will be coupled with no loss to another element, then the losses should be added to the reading. These losses are usually about 4%. Thus if the reading on the Ophir meter is say 100mW, then in lossless use, the real power will be 104mW.Close
Do I need to recalibrate my instrument? How often must it be recalibrated?
Among the Integrating Sphere accessories offered, there are “Port Plugs” (white), and “Port Covers” (black). What’s the difference?
An unused port should be closed, to prevent unwanted light from entering the sphere. Closing it with a diffuse white port plug, however, adds the surface area of that plug to the (diffuse white) effective area of the sphere that is doing the “integrating”. For a calibrated integrating sphere sensor, this change in the behavior of the sphere changes its calibration, and results in incorrect readings. In such applications, a black “Port Cover” should be used.Close
Measuring the emitted power of an LED can be tricky; it is different in some important ways from measuring the power of a laser beam. This video shows you how to use the Ophir 3A-IS Integrating Sphere Sensor, along with the Auxiliary LED accessory, to easily make accurate measurements in LED applications.
When a power/energy meter is in "Calibrate" mode, various "Factors" are displayed to the user. This video explains the meaning of each of these factors.
When you measure a beam coming out of a fiber, there are some parameters that have a different meaning than they do when referring to "regular" beam measurements. This video clarifies some issues you'll need to keep in mind.
Integrating Sphere Fundamentals an Applications
Measuring Power of Divergent Beams with Integrating Sphere Sensors
An integrating sphere is used to measure a divergent light source. As shown in the illustration, an integrating sphere has its inner surface coated with a surface that highly reflects (typically 99%) in a scattering, nonspecular way. Thus when a divergent beam hits the walls of the integrating sphere, the light is reflected and scattered many times until the light hitting any place on the walls of the sphere has the same intensity. 阅读更多...
Measuring LED Power and Irradiance with Calibrated Photodiodes
In many industries LEDs are replacing traditional broadband light sources such as mercury, deuterium, Xenon, and quartz-halogen lamps. Systems and applications transitioning to LEDs are reengineered in terms of optics, electronics, heat management and more. Similarly, the equipment used by professionals to measure the output of these sources needs to be fitted for measuring LEDs. 阅读更多...
- Ø154 (mm)
- ±40 deg
See specification sheet for details on which accessories are supplied with sphere.
White reflectance material Ø63.5mm plug
White reflectance material Ø25.4mm plug
Matt black coated Ø63.5mm cover
Matt black coated Ø25.4mm cover
Attaches to the 2.5” port and turns it into a 1” port
Attaches to the 1” port for FC fiber input/output
Attaches to the 1” port and has a female SM1 thread
Attaches to the 1” port for SMA fiber input/output
Attaches to the 1” port and has a female C-mount thread
Attaches to the 1” port. Has a male C-mount thread and 11mm aperture