Goniophotometer is mainly used for measuring photometric characteristics of luminaries and light source; that is luminaries laser photometric and colorimetric value distribution in different spatial directions.
Goniophotometer should be placed to do test in dark room. Many customers concern the size of goniophotometer.
According to Energy Star IESNA-LM-79 Clause 10, For measurement of luminous intensity distribution, a sufficient photometric distance should be used –generally, more than five times of the largest dimension of the test SSL product having broad angular distributions. A longer distance may be needed for narrow beam sources.
According to CIE 121-1996 The Photometry and Goniophotometry of Luminaries, about test distance(for measurements based on the photometric distance law): The photometric test distance is the distance from the photometric centre of the luminaries to the surface of the photometer head.
Measurements of intensity should be made at a distance such that the inverse square law applies within practical limits. In general the test distance should not be less than 15 times the maximum dimension of the light emitting area of the luminaire. However, for luminaries with an approximately cosine distribution in planes passing through the long axis of the luminaire, the minimum test distance can be determined as 15 times the dimension of the light emitting area normal to the lamp axis or 5 times the dimension of the light emitting area parallel to the lamp axis. The minimum test distance to be used should be greater of these two distances.
It should be noted that in certain cases, e.g. luminaries with a very narrow beam, even a test distance ratio of fifteen may not be sufficient.
For example, Lisun LSG-1800B High Precision Rotation Luminaire Goniophotometer, we recommend the Dimension of Dark Room for Goniometric Rotating Console and Photometric Light Patch should be W3.5m*H2.5m*L8m. Operator Room for controlling cabinet, computer and printer Dimension should be no less than W3.0m*L3m.