Commonly, there are three
types of goniophotometers with the mirrors: the goniophotometer with
rotating-mirror, the goniophotometer with moving-mirror, the goniophotometer
combining the moving mirror and the fixed mirror.

The. goniophotometer with
rotating-mirror is fixed with a photo-detector. Through the autorotation of the
mirror and the circumferential moving and autorotation in the space of the
luminaire under test, we can detect the luminous intensity of the luminaire
under test in different directions. It is easily to be influenced by the
environmental temperature and the air motion, becauses the luminaire under test
is moving during the detecting process and the luminaire under test is in
different environments with different positions.

The goniophotometer with
moving-mirror is fixed with the photo-detector or rotated with the moving
mirror. With the mirror rotating around the luminaire under test and the
autorotation of the luminaire under test in a fixed space position, the optical
parameters of the luminaire under test in different directions can be detected.
It is not easy to be influenced by the environmental temperature and the air
motion because the luminaire under test has a fixed space position. However,
because the cone and the detected distance is fixed, the detected beam is
changed. In addition, the large luminaire under test needs a larger space. A
relatively big error can be caused by the sensitivity difference of the
detector in different directions of the space for the detector is fixed and
cannot follow the rotation,

The goniophotometer
combines the moving mirror and the fixed mirror, which are fixed on the same
rotating arm for synchronously rotating around the luminaire under test. We can
arrange a fixed mirror outside the detecting table for coordinating the moving
mirror and the photo-detector. With a fixed space position, the luminaire under
test is not easy to be influenced by the environmental temperature and the air
motion. While rotating around the cone, the detected beam is always changing. It
is difficult to arrange a series of diaphragms for eliminating the stray light
between the detector and the light source because the detector and the moving
mirror are moving synchronously.