SBAA615 December   2023 OPT4003-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Light Source Detection
  6. 3Light Source Ratios
  7. 4Design and Calibration Considerations
    1. 4.1 Cover Materials
    2. 4.2 Cover Glass Application Example
  8. 5Near Infrared Components of Common Light Sources
    1. 5.1 Incandescent
    2. 5.2 Halogen
    3. 5.3 Light Emitting Diode
    4. 5.4 Fluorescent
    5. 5.5 Sunlight
  9. 6Summary
  10. 7References

4.2 Cover Glass Application Example

To illustrate the effect of cover glass on the calculated visible/ NIR ratios, a 3000K LED bulb was used to illuminate the OPT4003-Q1. The initial measurements were taken without a window or cover glass to attenuate light transmission.

The sensor output was recorded, and then the testing was repeated with a 0.1% transmission cover glass placed on top of the sensor. The measurements for both cases were compared and used to calculate the CH0 / CH1 ratio across samples. Table 4-2 shows the observed change in ratio.

Table 4-1 OPT4003-Q1 Visible / NIR Attenuation, 3000K LED Bulb
Average ALS ResponseAverage NIR ResponseALS / NIR
No Cover Glass6577341 codes21715 codes303
Cover Glass9361 codes113 codes83

The dark cover glass prevents a portion of visible light from reaching the sensor and results in signal attenuation. Depending on the characteristics of the chosen cover glass, the attenuation of visible and near infrared light can vary. Therefore, it is important to consider how the cover glass affects both the visible and near infrared channels before setting light source detection thresholds.