ASTM E2175-01 (R2021) pdf free download.Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers.
1.1 This practice provides a way of specifying the angular and spatial conditions of measurement and angular selectivity of a method of’ measuring the spectral rcllcctance factors of opaque gonioapparcnl materials, for a small number of sets of geometric conditions.
1.2 Measurements to characterize the appearance of retroreflective materials are of such a special nature that they are treated in other ASTM documents and are not included in the scope of this standard.
4. Significance and Use
4. 1 This practice is for the use of manufacturers and users of instruments to measure the appearance of gonioapparent materials, those writing standard specifications for such instruments, and others who wish to specify precisely the geometric conditions of multiangle spectrophotometry. A prominent example of industrial usage is the routine application of such measurements by material suppliers and automobile manufacturers to measure the colors of metallic paints and plastics.
5. Components of Apparatus
5.1 The apparatus shall consist of one or more illuminators and one or more spectrometric receivers at fixed or adjustable angles with respect to a reference plane, a means of positioning specimens in a reference plane. a means of indicating the area on the specimen to he measured, shielding to avoid stray light, and a means of displaying spectral or colorimetric data and/or communicating such data to a data-recorder or computer. (The terms “light,”“illuminator,”“illumination,” and “illurninance” are used here for simplicity, though the corresponding terms “radiant power.”“irradiator,”“irradiation,” and “irradiance” would be more accurate when the incident flux includes ultraviolet flux, as is necessary if the appearance of a fluorescent material is measured.)
6. Ceometric Types of Apparatus
6.1 The geometric configuration of the instrument may be uniplanar, annular, circumferential, or diffuse. In all cases, the specimen is taken to he a flat surface lying in a plane called the “reference plane,” which is designated the x, y plane. When there is a single directional illuminator, the x direction is the direction of the projection of the axis of the incident beam on the reference plane. If there are several directional illuminators or a single diffuse illuminator, the direction of the x-axis must be selected and specified.ASTM E2175 pdf download.