The Study Of Near-field Goniophotometry

In recent years,with the rapid development of LED and other new light source manufacturing technology,people no longer only pursued higher lighting efficiency,but also put forward higher requirements on the quality of lighting.In order to obtain high-quality lighting,we need to design the spatial light distribution by using computer simulation combining with the environmental structure.Therefore,we need to get the raydata of light source,which is the result from the rawdata measured by a goniophotometer.At present,the far-field goniophotometer is widely used in lighting field,which takes tested lamp as a point source,but actually,light source usually have a certain emitting area,and lighting environment does not meet the far-field photometric conditions.Therefore,in recent years,the imaging photometry based on CCD camera has been applied to the near-field situation.However,in the near-field photometric system,the deviation of mechanical axis in spatial position,the tilt of imaging luminance meter and so on will cause excessive errors to the final synthetic images and optical model;the uneven response of CCD imaging device,the distortion of the images,etc.will affect the uncertainty of spatial photometry.To solve the problem,the paper proposes a scheme based on four auxiliary lamps for positioning,then uses the auxiliary lamps to calculate the transformation matrix to calibrate the position of tested lamp.We construct a simple near-field photometric system for experiments and the result shows that the new scheme can significantly reduce the spacial position error of imgaes.