Photometric and Colorimetric Tests

Abstract

The chapter describes the tests that can be performed on lamps and luminaires. The first two sections of the chapter report photometric tests and measurements, starting from the measurement of luminous flux. There are two principal methods for measuring total luminous flux or radiant flux. One incorporates an integrating sphere (Sect. 1), and the other utilizes a goniometer (Sect. 2). Section 1 describes calibration procedures and tricks that are needed to obtain a precise measurement when using an integrating sphere. The correct procedure takes into account the difference between an ideal sphere internally coated by an ideal diffuser and the real setup, with non-perfect surfaces and missing portions of the sphere surface (for creating apertures to put instruments or cables). The luminous flux can be measured also by goniophotometry, i.e. interpolating of a set of measurements performed with a detector that scans the whole spherical space around the luminaire. Goniophotometry (Sect. 2) gives information about the angular dependence of the luminous intensity over the whole solid angle. Thus, the total luminous flux can be obtained from integration. On the other hand, the measurement of both the flux of the bare source and the flux of the source after putting it inside the luminaire allows obtaining the overall efficiency of the real source (light source plus luminaire).