Integration spheres are hollow optical spheres used for measuring the diffuse reflectance or transmittance of objects within a specific spectral range. Integration spheres are spherical optical detectors, with an internal surface coated with a diffusely reflective coating. Integration spheres are also configured with ports for gathering measurements with peripheral devices. The interior of an integration sphere is configured with a series of light baffles or barriers to screen the sphere’s detectors from the direct light emitted by test objects. Integration spheres vary in size from very small to very large, depending on the application, and can range from less than 3 millimeters to 3 meters in diameter.
Integration spheres are used to analyze color measurement and reflectance of a variety of substances, including materials used in painting or powder coating applications. Integration spheres are also used to analyze the total luminous flux of a light bulb or lamp or a light-emitting diode (LED), or to measure the power of a laser beam. Some integration spheres are designed to test reflectivity while others are designed to measure irradiance. An integration sphere can test materials in the visible spectrum, ultraviolet (UV) or near infrared (NIR) spectrums. Integrating spheres are frequently used for optical detection in photonics applications to characterize the optical properties of many substances, including solids, liquids, and powders. The most common use of an integrating sphere is to test reflectance and transmittance of specular or diffuse materials, such as thin films, turbid or diffuse liquids, and glass used in architecture or engineering applications.
Integration spheres used for laser power measurement typically have more ports to provide a wider variety of testing parameters. Using an integration sphere as an optical detector for laser power measurement, operators can either place the source in the sphere or capture the light from an external beam, diode, or bundle of optical fibers. The sphere can measure a variety of incident angles from the beam as well as measure the beam’s radiant power and spectral characterization.