The optical radiation leaving the integrating sphere

The primary radiation source can be located either in front of the source's entrance port or inside the integrating sphere. In the latter case, only the optical radiation that entering the sphere is relevant for the sphere's internal radiation distribution. As long as we restrict ourselves to those regions which are thus only illuminated by reflections at other of the inner surface and are shielded from direct irradiation by the primary source, the theory of the ideal integrating sphere leads to two important conclusions. The two important conclusions are shown below:

On the one hand, radiance reflected by a region of the sphere's inner surface shielded from direct illumination is independent from the specific location where the reflection occurs and constant in its directional distribution. Thus, the optical radiation leaving the sphere is characterized by existence distributions and homogenous radiance as the integrating sphere's exit port can be used as an ideal Lambert Ian source. This property becomes extremely important when a sphere is used as a standard calibration source.

On the other hand, irradiance of the sphere's inner surface is proportional to the total radiant power either entering the sphere through its entrance port or emitted by a source inside the sphere. Directional and geometrical distribution of the primary source’s radiation does not influence irradiance levels as long as direct illumination of the respective location is prevented. This property becomes extremely important when an integrating sphere is used as the input optical element of a detector for radiant power.

Integrating sphere is a very omnipotent optical element, which are designed to achieve homogenous distribution of optical radiation by means of multiple Lambert Ian reflections at the integrating sphere's inner surface. And it consists of the power meter, the might meter, the connecting box and the ballast. The power meter is used to check the lamp’s power usage. The light meter shows the light level being measured inside the sphere. The connection box is used to connect the ballast to the lamp inside the integrating sphere. At the final, the ballast can’t be in the sphere because of the interference with the light reading. But it is also important to operate nom incandescent lamps. 

Confirming the accurate lack of wavelength dependence in the responsively of the integrating sphere

Using a spreadsheet, this is an example, the responsively at 5 degree intervals in both azimuth and zenith angles was calculated for this sphere. It is easily seen that if this integrating sphere were used for sunlight measurements, with the baffle facing South, negligible cosine errors would be prospective for all results where the zenith angle was less than 75 degrees. Some points near the baffle are some 2%-3% different for calculated and measured responses. This is probably to be the result of multiple localized reflections, each of which looses light through the entrance port, before total randomization within the sphere is achieved. These localized multiple reflection effects, although calculable, are offer little significant improvement in accuracy and beyond the scope of this simple model. Measurements on this sphere, in 15 degree zenith angle steps, at 90 degree and 0 degree azimuth verify that the calculated values of the response are pinpoint. The measured response was determined at wavelengths of 800nm, 700nm, 600nm, 500nm, 400nm and 300nm for all angles. No differences beyond normal experimental error were seen, confirming the accurate lack of wavelength dependence in the responsively of the integrating sphere.

Integrating sphere can be almost perfect devices when designed properly, that means giving highly accurate cosine response at all wavelengths. The integrating sphere response can be estimated precisely from relative simple formulae on a spreadsheet program, as confirmed by actual measurements. In addition, full 3D characterization is possible by calculation, providing detail to the generally incomplete data and enabling components to be optimized provided by some manufacturers. Utility designs can benefit from this modeling, and providing refinements in critical areas. A basic example, the Young & Schneider design, is commercially available from Optioned Laboratories, Inc and makes use of all of the optimization features.

The simple design ideas were used in integrating spheres of four inch and six inch diameter, modeling, and manufacturing. Since the results are close to ideal, they are best expressed as error relative to ideal cosine response. The sphere design, including exit attachments and mounting flanges for a dome window, had been shown is pictures, but not here. Measurements of the cosine response on both two types of integrating spheres agreed well with predictions, and the results are presented for the 6 inch sphere. 

Effective systems have been built that incorporate integrating spheres with detector in the standard averaging mode

The development of a device for absolute measurement of repentance, transmittance, and absorptions of secular samples and the bonnets of using the integrating sphere for more accurate detection of light are used in the design. The method is demonstrated in the case of mirror characterization and IR windows. The ability to measure both reentrance and transmittance in the same geometry is used to quantify directly the total measurement error for nonabsorbent spectral regions, thus also obtaining reliable uncertainty values for results outside these regions.

On careful study and consideration, it can be observed that use of the integrating sphere significantly enabling the levels of accuracy demonstrated in this paper, reduces several important sources of measurement error. These error sources include detector–interferometer and sample– detector introjections, detector spatial no uniformity, detector nonlinearity, and sample–beam geometry interaction （defection, beam deviation, and focus shift）

The integrating sphere system is not suitable for high-sample-throughput applications. For these applications, such instruments can be calibrated with transfer standard samples that are characterized with the sphere system. In turn, other instrumentation designed for fast relative measurements can be used. This approach allows us to improve the accuracy of measurements which made on all our FTS instrumentation, including those designed for variable incidence-angle characterization and variable sample temperature, not directly feasible with the sphere system.

Effective systems have been built that incorporate integrating spheres with detector in the standard averaging mode. For accurate characterization of secular samples, direct mounting onto the sphere is not an absolute necessary. However, there are at least two important advantages of mounting the sample directly onto the sphere. Both of these relate to the characterization of no ideal samples. The first is that this design can measure samples that are not perfectly secular, but that also exhibit some degree of scatter. The second is that one can better handle the worst samples and allow for the greatest amount of focus shift, distortion, deviation, and beam defection. 

Our Engineer and Our Europe Customer

Refer to: http://www.lisungroup.com/blog/training-and-installation-in-turkey-italy-and-portugal/

November seems a special and exciting month for Lisun Electronics Inc the date of Nov.2, Lisun’s engineer James Peng was on his first flight to Turkey and began his two-week technical support for the customers in Turkey,Italy and Portugal.

The three companies are Genel Elektrik Aydinlatma San. Tic. As in Turkey, Pro Light Srl in Italy and CWJ.Componentes S.A.in Portugal. Both the Turkish and Italian customers have purchased Spectrophotometer Integrating Sphere Test System (LPCE-1) [http://www.lisungroup.com/product-id-198.html] and Rotation Luminaire Goniophotometer (LSG-1800) [http://www.lisungroup.com/product-id-241.html]. The Portuguese customer has purchased Rotation Luminaire Goniophotometer (LSG-1800).

Lisun’s engineer James Peng has received a warm welcome from the customers. The detail and professional technical support for the training and installation of the instruments has impressed the customers a lot. Lisun Electronics Inc has also won a high praise and positive feedback for its great service. The Turkish customer said this technical support from Lisun Electronics Inc is even better than most of the world famous companies.

The following pictures show that our engineer James Peng was doing his technical support for the training and installation of Spectrophotometer & Integrating Sphere Test System (LPCE-1) and Rotation Luminaire Goniophotometer (LSG-1800).

Spectrophotometer & Integrating Sphere Test System (LPCE-1): This system is suitable for photometric and colorimetric measurement, such as Energy-saving lamp, Fluorescent lamp, HID lamp (high voltage sodium lamp and high voltage mercury lamp), CCFL and LED test. The measured data meets the requirements of CIE and IES_LM-79 for the measurement of photometry and colorimetry.

Rotation Luminaire Goniophotometer (LSG-1800): LSG-1800 Goniophotometric system is an automatic goniophotometric measurement system for measuring photometric parameters of luminaires, such as LED road lighting fixture, room lighting fixture and projecting lighting fixture. The measured data meets IES standard format and can be applied for lighting design by lighting design software. The measurement system fully satisfy the requirement of lighting design work. LSG-1800B Goniophotometer system is an update version of LSG-1800. The LSG-1800B has a constant temperature detector, and use luminous intensity standard lamp to calibrate the system. Lisun develop a new software to run LSG-1800B.

The basic principle of operation is that light enters the integrating sphere through the sample port, goes through multiple reflections and is scattered uniformly around the interior of the sphere

Integrating sphere is a general function as a light collector. The collected light can be used as a diffuse illumination source or a measurement source. The measurement principle is based on direct illumination and indirect reflection. The basic principle of operation is that light enters the integrating sphere through the sample port, goes through multiple reflections and is scattered uniformly around the interior of the sphere. In the Avantes line of integrated spheres ,the spheres are mostly used as measurement source. The detection fiber optics are SMA-coupled to the port at the side of the sphere which is viewing illumination on a baffle, independent of the angular properties of the light at the sample port.

The reflection version is used to measure total integrated reflectance of a surface, as well as for color measurement and fluorescence spectroscopy. The inside of the integrating sphere is made out of highly reflective diffuse material; that gives a light diffuse reflection (>96 %) over a wide wavelength range (250-2500 nm).  A special gloss-trap is available for the AvaSphere-50-REFL reflection sphere to exclude specular reflection in the measurement. A light source may be connected to the 8 degree SMA-connector port through a fiber optic bundle to make the integrating sphere an ideal uniform light source. This option needs to be ordered together with the sphere. In case specular reflection needs to be included, a white reflective part can be mounted in the position of the gloss trap. 

The irradiance version of the integrating sphere can be used to measure light sources (Laser, LED, and Halogen Lamps). For the irradiance measurements of LED's a special adapter was developed to be connected to the AvaSphere-50-IRRAD. The reflection sphere has an additional SMA- connector port at 8 degrees, for direct illumination, coupling the light into sphere through a fiber and a COL-UV/VIS collimating lens, connected to a light source. The adapter can hold 3, 5 and 8 mm LED's in the correct and reproducible position inside the sphere. The AvaSphere integrating sphere family can be delivered with an active diameter of 30, 50 or 80 mm and an SMA port at 90 degrees for irradiance and reflection measurements. The AvaSphere-30 has a sample port diameter of 6 mm, the AvaSphere-50 10 mm sample port and  15 mm for the 80 mm diameter sphere. All sample ports are knife-edge, this ensures 180 degree field of view of the sample port.