# Virtual Laboratory for the Full-Field Goniophotometer of Luminaires
## 3 System Design Process
### Measurement of Spatial Light Intensity Distribution  
The simulation of spatial light intensity distribution measurements focuses on simulating the measurement options of a distribution photometer, allowing the user to understand the basic principles of near field, intermediate field, and far field measurements.  
In the transient test session, the light is switched on and off to simulate the light emitted from the luminaire by the point source of the light source assembly.  
\begin{table}
\begin{tabular}{c c c} \hline
**Region** & **Location** & **Rotation** \\ \hline Virtual experimenter & (19.5, 1.5, 50.0) & (\(-\)90, 0, 0) \\ Table for lamps & (0, 1.3, \(-\)0.1) & (\(-\)180, 0, 0) \\ Bench scales & (0, 0.1, 0) & (\(-\)90, 0, 0) \\ Full-field Goniophotometer & (\(-\)0.1, 1.1, 0.7) & (\(-\)180, 0, 90) \\ \hline \end{tabular}
\end{table}
Table 1: Information on the location of the luminaire.  
Figure 4: Diagram the location of the light fittings: (**a**) At the Virtual experimenter, (**b**) On the luminaire stand, (**c**) On the bench scale, (**d**) On Full-field Goniophotometer.  
By clicking on the measurement when the lamp is switched on, the swivel arm of the distribution photometer carrying the rotatable reflector, near-field, and far-field detectors starts to rotate around the \(\gamma\)-axis, allowing the light intensity of the luminaire to be measured at different angles in different planes. The luminaire is rotated around the C-axis in order to switch between different measurement planes, and then, the measurement of the light intensity of the luminaire is completed by the measurement mode that has been selected.  
The measurement selection module simulates near-field measurements, intermediate field measurements, and far-field measurements by means of a material switching technique. In the virtual experiment, the rotatable reflector and fixed reflector of the distribution photometer are covered with black cloth by default, so they are represented by black material. When manipulating the virtual experimenter to the distribution photometer, the user clicks on the measurement selection button to bring up the near-field measurement, middle-field measurement, far-field measurement, reselect, and close buttons. When clicking on the near-field measurement, no material switch is made as the near-field detector receives the light source directly. When clicking on the middle-field measurement button, the material switch is made for the rotatable reflector to achieve the effect of the black cloth being uncovered as the light source passes through the rotatable reflector to the middle-field detector. When clicking on the far-field measurement button, the light emitted by the luminaire in all directions is reflected by the rotatable reflector through the diaphragm to the fixed reflector, which is then reflected by the fixed reflector through the diaphragm and incident on the far-field detector, so the material is switched for the rotatable reflector and fixed reflector. The user clicks on reselect to switch the material to the initial one, and the measurement selection module is shown in Figure 5.  
Figure 5: Diagram of the various experimental modules. (**a**) Near-field Measurement models; (**b**) intermediate-field Measurement models; (**c**) far-field Measurement models.