Catalog & Manuals
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
What is the purpose of the auxiliary LED accessory for the 3A-IS integrating sphere?
The auxiliary LED emits at 390nm, while the measured UV LED can emit between 350nm and 400nm. Will this increase the measurement error?
For the most demanding accuracy requirements, a broadband source is used for the auxiliary lamp, and a spectrometer monitors the effect of self-absorption across the spectrum. For UVLEDs, in the limited spectral range of 350nm-400nm, using the auxiliary LED at 390nm is an efficient solution, and the error due to self-absorption is reduced from up to ±20% to up to ±5%.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
How much variation in water temperature or flow rate is allowed in Ophir water cooled sensors?
Ophir water cooled sensors measure the heat flow across the thermopile disc and therefore are quite insensitive to the water temperature or flow rate within the given specified limits. However, sudden changes in the water temperature or water flow rate can cause a disturbance to the reading until the flow rate/temperature stabilizes again. Therefore we specify in our water cooled sensors that the water temperature should not change faster than 1C/min. Likewise, sudden changes in flow rate (e.g. switching another device connected to the same water line on and off) can results in temporary disturbances in the power reading.Close
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.
Choosing the right sensor to measure LEDs or similar sources, whose beams are usually divergent and have a broadened spectrum, can be tricky. The LED Sensor Finder will help you get it right.
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.
Integrating Sphere Fundamentals and 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...
White Paper – 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...
Ophir Power/Energy Meter Calibration Procedure and Traceability/Error Analysis
This document discusses the interpretation and basis for stated measurement accuracy of Ophir Laser Power/Energy meters.
1. General Discussion
2. Combination of Errors and Total Error
3. Analysis of Power and Energy Calibration Errors
4. Detailed Analysis of Power and Energy Calibration Errors
VCSEL Measurement Solutions
Laser Measurements in Materials Processing: How and When They Absolutely, Positively Must Be Made
How do I know what range, or scale, to set my power/energy meter to? And what happens if I go over range?
Each given range represents one level of gain of an internal amplifier. The electronics, as always, have a limited Dynamic Range. If the measured signal is too low, in other words near the bottom of the range, then it may be lost in the noise and the reading will be inaccurate and noisy. If it’s too high – there may be saturation issues. To give an instrument a usefully wide dynamic range, multiple scales or ranges are used. Switching from range to range can be automatic (“Autorange”), or manual. Autoranging simply starts automatically at the least sensitive range and works its way down the ranges, sampling the signal as it goes, till it finds a range at which the signal is properly detected. Note, by the way, that only in POWER mode is Autoranging available. If we are working in Single Shot Energy mode, there is no Autoranging – simply because when we are measuring a single pulse, the instrument has no opportunity to work its way down the ranges as in Power mode. 阅读更多...
White Paper – Low Frequency Power Mode
Types of power / Energy Laser Sensors General Introduction
Power and Single Shot Energy Sensors
Ophir provides two types of power sensors: Photodiode sensors and Thermal sensors. Photodiode sensors are used for low powers from picowatts up to hundreds of milliwatts and as high as 3W. Thermal sensors are for use from fractions of a milliwatt up to thousands of watts.
Thermal sensors can also measure single shot energy at pulse rates not exceeding one pulse every ~5s.
Repetitive Pulse Energy Sensors
For higher pulse rates, Ophir has pyroelectric energy sensors able to measure pulse rates up to tens of KHz. These are described in the energy sensor section, section 1.3.
Measuring Average Power of Pulsed Lasers with Photodiodes
5 Situations Where Laser Performance Measurement is Necessary
- 68 L x 95 W x 46 D (mm)
- 0.2 s
- CE, China RoHS
7Z08227This fiber adapter is used for connecting power and energy sensors to a standard SC-type fiber. Many sensors need an additional mounting bracket to connect to all fiber adapters. More information can be found in the datasheet below.
7Z08226This fiber adapter is used for connecting power and energy sensors to a standard ST-type fiber. Many sensors need an additional mounting bracket to connect to all fiber adapters. More information can be found in the datasheet below.
7Z08229This fiber adapter is used for connecting power and energy sensors to a standard FC-type fiber. Many sensors need an additional mounting bracket to connect to all fiber adapters. More information can be found in the datasheet below.
1G01236AThis fiber adapter is used for connecting power and energy sensors to a standard SMA-type fiber. Many sensors need an additional mounting bracket to connect to all fiber adapters. More information can be found in the datasheet below.
7Z08213A mounting bracket is needed to connect most power and energy sensors to a fiber adapter (SC, ST, FC or SMA). This bracket can be used for integrating sphere models 3A-IS and 3A-IS-IRG.