Supplementary Optical Parameters for Solar Simulator Evaluation
Optical Angular Characteristics
Optical angular characteristics are supplementary optical parameters used to describe the direction and spread of light from a solar simulator.
These parameters are not a replacement for the main solar simulator performance items such as spectral match, spatial non-uniformity, temporal instability, and irradiance.
They are used when the incident direction, beam spread, or angular behavior of light is important for a specific application.
Relation to Previous CHA Value
SAN-EI previously used CHA (Collimation Half Angle) as a practical indicator of the directional characteristics of light.
CHA was useful in practical evaluation, but it included several different aspects of light behavior in a single value, such as the direction of light, the spread of light, and variation across the irradiation area.
SAN-EI now separates these elements into clearer optical parameters to improve understanding, reproducibility, and technical communication.
New Angular Parameters
Parameter Meaning Purpose
Chief Ray Angle (CRA) Deviation of the main light direction from the reference axis To evaluate the main incident direction of light
Beam Divergence Spread of the light beam during propagation To evaluate how much the light spreads
Angular Uniformity Variation of incident light direction across the irradiation area To evaluate angular variation within the effective area
Angular Stability Temporal variation of the light direction To evaluate whether the light direction changes over time
Important Note
This update changes the method of expression and evaluation only.
It does not change the actual optical performance of SAN-EI products.
Previously provided CHA data remain valid as reference information.
Supplementary Use Cases
Optical angular characteristics are useful for applications where the incident angle, beam direction, or beam spread may affect the result.
Examples include optical material testing, exposure applications, optical alignment evaluation, and other non-standard solar simulator applications.
For standard photovoltaic solar simulator evaluation, the primary performance items remain spectral match, spatial non-uniformity, temporal instability, and irradiance.