Solar Simulator - Spatial Non-Uniformity
In order to quantify the spatial non-uniformity of a solar simulator we must map the irradiance of the simulator beam over the test area. By dividing the test area into a grid of measurement positions we can apply the following equation from the standards to calculate the non-uniformity in percentage terms:
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The number of measurement positions to use depends upon a combination the size of the test area and which standard you are using. Outlines for each of the three standards are given below.

ASTM

  • "Divide the defined test area into at least 36 equally sized (by area) test positions. Using the uniformity device, determine the irradiance in each of the test positions."
  • "The uniformity device shall be no larger than the area of the individual test positions."
  • "The uniformity device shall be at least large enough that the area of the device times the number of test positions is greater than 25 % of the total defined test area."

IEC

  • "Divide the designated test area into at least 64 equally sized (by area) test positions (blocks). The maximum uniformity detector size shall be the minimum of a) the designated test area divided by 64, or b) 400 cm². The area covered by the detector measurements should be 100 % of the designated test area. The measurement positions should be distributed uniformly over the designated test area."
  • "Example: Large-area solar simulator A designated test area of 240 cm x 160 cm gives a maximum area of uniformity detector size of 600 cm² if divided by 64. As this value is greater than 400 cm² the maximum uniformity detector size is 400 cm² leading to 76 test positions."

JIS

  • "The light receiving area of light receiver to be used for measurement shall be a circle with a diameter not exceeding 2cm or a square with a side not exceeding 2cm and 4% or under of the effective irradiated plane by the solar simulator. Carry out the measurement with a detector capable of receiving at least the light with incident angle +/-15% without any trouble."
  • There are 17 measurement positions which are specified via diagrams for circular and square beams. Please see the JIS standard.

An Excel spreadsheet for conducting uniformity maps can be downloaded here here