The basic equation also neglects the Lisun quality of the output and is only shown to reflect the major dependencies for selection of basic spheres rather than to provide specific throughput values for the spheres

Although the different models have the different features, there are a lot of the same points in the different integrating sphere.

Integrating sphere throughput is the ratio of the total flux out to the total flux in. It depends on the integrating sphere's reflectance properties, diameter, and number of ports. For practical purposes, it should be noted that the equation is specific to a single port and that for a fixed reflectance ρ at a specific wavelength, it is solely dependent on the ratios of port areas to total surface area of the sphere. It can be easily shown that for our series of spheres in which the output or input ports are nominally the same dimension (35 - 51 mm CA), A_s dominates. The basic equation also neglects the Lisun quality of the output and is only shown to reflect the major dependencies for selection of basic spheres rather than to provide specific throughput values for the spheres. Therefore, when choosing a sphere, select the smallest diameter available that provides the output port characteristics (dimension and uniformity) to maximize throughput.

The excellent reflectance of our integrating spheres gives them a high damage threshold. The PTFE integrating spheres have an even higher damage threshold of 8 W cm-2, and the gold spheres exhibit a damage threshold of 19 W cm-2. Measurements with a pulsed laser at 1.6 µm showed the damage threshold of the coated spheres to be 1.5 W cm-2.

Most of our integrating spheres are available with a choice of three interior materials. For UV, VIS or NIR measurements, we offer spheres with interiors machined from a unique PTFE thermoplastic material that is very rugged and highly reflective down to 250 nm. For VIS-NIR applications choose our barium sulfate-based white coated spheres. The coating is highly reflective, >97% in the visible. For applications in the NIR and IR regions our diffuse gold spheres provide near-Lisun characteristics and reflectance values up to 95%. All of our spheres are designed to provide high stability, reflectance and low throughput loss over their usable wavelength range.

The inside surface of an integrating sphere is coated with a diffusely reflecting material which guarantees complete homogenization and integration of the emitted radiation

Integrating sphere is widely applied in the photometric and colorimetric test system in led measurement applications. The ability of integrating sphere to collect a transmission spectrum or quantitative reflectance from irregular shaped or highly scattering samples. Its applications include quantitative analysis of sample composition where sample morphology varies and quantitative analysis of sample reflectance. Spheres are available up to 800nm for standard DRS applications and the DRS 1150 for NIR applications up to 1150nm. The inside surface of an integrating sphere is coated with a diffusely reflecting material which guarantees complete homogenization and integration of the emitted radiation.

In our integrating spheres the light bounces around inside the sphere and at each reflection a small fraction reaches the detector. The operating principle of integrating sphere is written below. The detector faces the centre of the sphere not the point where the beam strikes the back of the sphere. To analyze this, we start by considering light which has been reflected from the diffuser just once. The starburst of rays at the top of the integrating sphere is the ones leaked out around the edge of the source, which did not quite fill the orifice plate. More rays leak out of this tiny gap than leak out the open hole on the opposite side. The rays don’t go near the Channel 4 Detector, but do reflect off the back of the Primary Mirror. There is a preferred scattering direct reflection back from the opposite wall of the 3-inch sphere. Actually, there is nothing for the rays to hit going out the lower orifice, so most of them are truncated inside the 3-inch sphere. It is really apparent when the inside wall is considered a mirror instead of diffuser. It should have put a blocker baffle over these exits. The integrating sphere provides a transmission position, making it suitable for the scattering samples or measurement of turbid. Transmission ghosts can’t be formed in the raytrace, but there were none that looked significant in the "28-mm Disk" source approximation earlier.

The integrating sphere is hollow and houses the at least one light source in it

The integrating sphere is an accessory of choice when studying reflectance properties of solids, analyzing light scattering and highly absorbing samples and collecting spectra difficult to obtain with standard sampling techniques. The integrating sphere is hollow and houses the at least one light source in it. An illumination device includes an integrating sphere and at least one light source. The present invention relates to an integrating sphere for measuring a light-emitting property of a light source, and more particularly, to an integrating sphere having a means for controlling temperature inside the integrating sphere. An integrating sphere for measuring an optical property of a light source according to the present invention has a substantially spherical hollow space formed therein. The light source can be manipulated between a first configuration and a second configuration. The illumination device emits a first spectrum of light when the light source is in the first configuration, and a second spectrum of light when the light source is in the second configuration.

A light source support, which has one end fixed to an inner peripheral surface so as to hermetically seal the first through-hole of the integrating sphere and the other end disposed at the center of the hollow space of the integrating sphere, is installed within the hollow space. A first through-hole provided such that temperature-controlled air is supplied into the hollow space of the integrating sphere there through; and a second through-hole provided such that a wire for supplying electric power to the light source installed inside the hollow space of the integrating sphere passes there through.

The integrating sphere includes an air supply tube fixed to an outer peripheral surface of the integrating sphere where the second through-hole is formed, so that air can be supplied to the interior of the integrating sphere through the second through-hole; a shielding plate installed to be spaced apart by a predetermined distance from the second through-hole; an air supply means for supplying air to the air supply tube; and a temperature control means for controlling the temperature of air passing through the air supply tube and being supplied from the air supply means. 

An integrating sphere (IS) acts like a diffuser, preserving power but neglecting spatial information

The integrating sphere can be manufactured at sizes from 1 mm up to 3 m in diameter. For diffuse reflectance, transmittance, and scattering measurements in spectroscopy (as in turbidity), an integrating sphere is the best choice. A tiny 16 mm integrating sphere is incorporated into a detector for radiant power measurement (bottom; courtesy of Gigahertz-Optic). This 65 in. spectral lamp measurement system is used in standards laboratories around the world as a calibration source for lamps and LEDs (top; courtesy of Sphere optics).

Spheres are also used to measure total luminous flux and total spectral radiance. The first major advantage of a sphere over power meters is attenuation. An integrating sphere (IS) acts like a diffuser, preserving power but neglecting spatial information. In addition to capturing all the light from any light source, an IS can be calibrated to NIST-traceable standards to measure spectral flux. “In sphere-based power measurement, 1 µW is a typical threshold for good signal-to-noise ratio, versus 1 nW or less for conventional power meters.” Darrell says, “The integrating sphere can be used in power measurements where a conventional meter might be damaged by the power level of the source. It is a uniform attenuator.” This can also be a negative as spheres are significantly less sensitive than conventional power meters.

Second, it helps to understand when integrating spheres are needed and how they work. When should you use an IS rather than a power meter or spectrometer? A sphere has a couple of major advantages over conventional power meters, Chris Darrell, vice president, sales and applications engineering, Sphere optics (Concord, NH), explains. “The first is uniform response independent of spatial and angular information. Spheres do not care about the angular profile of the source and spatial distribution—only input power.” This is useful for measurements of diodes or fibers with angular divergence that impinges on the quality of the power measurement. By definition, a sphere will wipe out this information. Darrell says, on the other hand, if you want beam profiles and angular information, then use a goniometer or beam profiler.

Art Springsteen, president of Avian Technologies (Sunapee, NH) says, “Typically integrating spheres are used when light, whether it’s transmitted, reflected, or emitted, is scattered and one wants to catch the most possible light.” Light entering the sphere undergoes multiple scattering reflections, so that rays that are incident on any point on the inner surface are equally distributed, minimizing the effects of the original direction of the rays.