How to choose the optimal IR wavelength for LPR/ANPR cameras?
- 2024/12/18
- Attachments
X-Core provides two standard wavelengths of IR illumination, including 850nm and 740nm. Here's how to choose the optimal IR wavelength.
The main difference between 740nm and 850nm is their different reflectance levels for the same color. 740nm has a lower reflectance level for most colors and therefore may appear darker in images than 850nm. For license plate with dark background and light font, using 740nm can prevent the background from being overexposed and make the license plate number more clearly visible.
Comparison Table:
| 740nm | 850nm | |
| Light Reflectance | Lower | Higher |
| Light Font LPR/ANPR Result | Perfect | No good |
| Dark Font LPR/ANPR Result | Good | Perfect |
| Discomfort Glare | Stronger | Weaker |
| Recommendation | In countries or regions that use light font license plate, such as Tennessee or Alabama in the United States, the 740nm IR wavelength is considered the optimal choice. |
In countries or regions that use dark font license plate, common in most European countries, the 850nm IR wavelength is recommended. |
How to choose:
* Light font license plate:
When dealing with light font license plate with colored background, choosing 850nm IR may reduce contrast and make the license plate number unclear. Choose 740nm IR to minimize background reflectance, enhance font reflectance, maximize contrast, and improve license plate number recognition.
* Dark font license plate:
Choosing 850nm IR for dark font license plate ensures optimal recognition, providing higher contrast and accuracy against bright background. While 740nm can work with dark font, its lower reflectance may reduce contrast and clarity.
Other Considerations:
740nm IR illuminator is effective but more noticeable at night than 850nm. This may be a drawback for discreet surveillance applications. Buyers should consider this before purchasing an LPR/ANPR camera.
*** Please refer to the attachment for application examples.
