What is better, 850nm or 940nm?

Comparison of 850nm and 940nm Infrared Wavelengths

In the context of infrared applications, particularly surveillance, night vision, and photography, the choice between 850nm and 940nm wavelengths depends on several factors. Here's a detailed explanation comparing both wavelengths.

Visibility at 850nm

The 850nm wavelength is slightly visible to the human eye as a faint red glow when looking directly at the source. This can be an advantage or disadvantage depending on the application. In surveillance, it may alert an intruder, while in photography, it allows for better camera sensor response due to higher sensitivity in the near-infrared range.

Visibility at 940nm

The 940nm wavelength is considered virtually invisible to the human eye, which makes it more suitable for covert operations where undetectable surveillance is crucial. However, the trade-off is that camera sensors are less sensitive at this wavelength, requiring more powerful emitters for equivalent illumination levels.

Effectiveness of Illumination

850nm: Devices that use 850nm IR LEDs are typically more efficient and have longer illumination ranges due to better camera sensor compatibility and a stronger intensity of light.

940nm: Devices with 940nm IR LEDs generally have shorter illumination ranges because they need more power to provide the same level of brightness visible to cameras as 850nm LEDs.

Application-Specific Choices

  • Surveillance: If the priority is to remain undetected, 940nm is preferable. However, for general surveillance where camera performance and range are prioritized, 850nm is better.
  • Scientific and Wildlife Research: For applications that require not disturbing the subject, such as wildlife research at night, 940nm is advantageous.
  • Consumer Electronics: In devices like TV remotes, 850nm is commonly used because it is cost-effective and aligns well with the sensitivity of silicon photodiodes.

Cost Implications

Generally, 850nm IR LEDs are less expensive compared to 940nm LEDs. This is due to the widespread use of 850nm components in various applications and devices, leading to economies of scale that reduce costs.

Conclusion

Whether 850nm or 940nm is better depends on the specific requirements of the application in question. Each wavelength has its advantages and drawbacks, and the choice should be guided by considerations of visibility, camera sensor compatibility, illumination range, covert needs, and cost.

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