Gain

Gain, also called brightness gain or luminance gain, is the measurement of the increase in brightness between the input and the output of an image intensifier tube.

Specification

There are two different units used to specify gain, imperial and metric.

Imperial

Gain specified in imperial units uses the units of foot-Lamberts by foot-candle (${\textstyle \mathrm {fL} /\mathrm {fc} }$).

Measurement

To measure gain in accordance to the MX-10160/AVS-6 specification, the photocathode is exposed to ${\textstyle 2*10^{-6}\mathrm {fc} }$ of input light. A photometer is then used to measure the luminance (brightness) of the phosphor screen (in ${\textstyle \mathrm {fL} }$). The resulting value is divided by ${\textstyle 2*10^{-6}}$ to obtain the gain in ${\textstyle \mathrm {fL} /\mathrm {fc} }$.

To further test auto brightness control, the same procedure is usually repeated with ${\textstyle 2*10^{-4}\mathrm {fc} }$.

Manufacturers

The following manufacturers are known to use imperial units when specifying gain:

• Elbit Systems of America
• L3Harris

Metric

Gain specified in metric units uses the units of candela per square-meter per lux (${\textstyle \mathrm {cd} /\mathrm {m} ^{2}/\mathrm {lx} }$).

Manufacturers

The following manufacturers are known to use metric units when specifying gain:

• Photonis Technologies SAS

Conversion

To convert between metric and imperial units, use the following formula:

$$\mathrm {G} _{\mathrm {fL} /\mathrm {fc} }=\mathrm {G} _{\mathrm {cd} /\mathrm {m} ^{2}/\mathrm {lx} }*\pi$$

So, a gain of 10,000 ${\textstyle \mathrm {cd} /\mathrm {m} ^{2}/\mathrm {lx} }$ is equivalent to roughly 31,416 ${\textstyle \mathrm {fL} /\mathrm {fc} }$.