Sales Engineer: Grace Gao
Email: grace@bri-elec.com
WhatsApp: 0086-199 2997 5286
Night vision products are very useful devices that provide clear vision in low light conditions. When choosing a night vision product, it is important to understand some key parameters. The following introduces the four core parameters of night vision products: photocathode sensitivity, signal-to-noise ratio, resolution and FOM value.
1. Photocathode sensitivity (quantum efficiency)
Photocathode sensitivity (quantum efficiency) is one of the most important and basic performance parameters of low-light image intensifiers. It determines the viewing distance and image clarity of low-light imaging systems under low illumination. Defined as the ratio of the photocathode emission current to the radiation flux irradiated by the photocathode, this parameter determines the degree of loss of resolution and modulation transfer function of the image tube in a dark light environment. The higher this parameter, the better the image tube's resolution in a dark light environment. The smaller the loss of resolution and modulation transfer function, the clearer and brighter the image will be in use. Photocathode sensitivity (quantum efficiency) is one of the most important and basic performance parameters of low-light image intensifiers. It determines the viewing distance and image clarity of low-light imaging systems under low illumination.
2. Signal-to-noise ratio
The parameter signal-to-noise ratio (S/N) that describes the noise level of the night vision system has no unit. It is defined as projecting a 0.2mm diameter standard light spot of 2856k fixed brightness (photocathode) at the center of the screen in a dark environment. The surface illumination is generally 1.08^10-4lux) and the ratio between the brightness of the image signal excited by the light spot on the fluorescent screen and the noise-equivalent signal brightness of the image tube in the dark is measured. The reflection in use is that the higher the signal-to-noise ratio, the clearer the image under dark light conditions and the less noise.
3. Resolution
The parameter (Resolution) that describes the resolution of the night vision device. The unit is lp/mm, which means line pairs/mm. The definition of lp/mm is how many pairs of black and white lines can be distinguished per millimeter distance on the screen. It can be roughly convert with pixels, each line pair is equal to two pixels, (number of line pairs per millimeter * 2 * screen radius) ² * π can calculate the equivalent resolution of the image tube. The higher this parameter, the higher the resolution of the night vision device.
4. FOM（Figure of Merit）
The FOM value is a parameter that describes the overall performance of the image intensifier. The calculation method is definition * signal-to-noise ratio and is used to evaluate the overall performance of the night vision device.
In summary, understanding the core parameters of night vision products: photocathode sensitivity, signal-to-noise ratio, resolution and FOM value is very important for selecting and purchasing night vision products. Only equipment with high photocathode sensitivity, high signal-to-noise ratio, high resolution, and high FOM value can achieve clearer and more realistic visual effects and improve nighttime observation and safety capabilities.
Sales Engineer: Grace Gao
Email: grace@bri-elec.com
WhatsApp: 0086-199 2997 5286
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