Emitter

Emitter is a light source that, in red dot sights and other tactical accessories, generates the aiming point (dot, reticle) or another active optical element. Most commonly, this is a LED or a laser diode, whose light is projected through optics into the shooter’s field of view so that it appears as a point “at infinity.” An emitter is therefore an active light source that enables the function of red dot sights and other tactical accessories. Its type, design, and placement have a major impact on reliability, dot visibility, and usability in demanding conditions. The difference between an open and a closed emitter is today one of the most important parameters when choosing modern optics.

Comparison of open and closed emitters in red dot sights

The role of the emitter in red dot sights

The emitter is the heart of every red dot sight. It determines:

dot brightness and visibility,
the shape and sharpness of the aiming point,
power consumption,
reliability in various lighting conditions.

Without an emitter, a red dot sight would not be able to actively display an aiming point.

Basic types of emitters in red dot sights

LED emitter (most common)
The most widely used solution. An LED diode emits light that is reflected on a specially coated lens. It offers long service life, low power consumption, and high reliability. Used in the majority of both open and closed red dot sights.
Laser emitter
Uses a laser diode instead of an LED. It provides a very sharp and precise dot, but requires more power and more complex output control. It is typically used in specialized or combined systems.

Open vs. closed emitter

Open emitter
The emitter is exposed to the environment. Advantages include lower weight, smaller size, and lower cost. The downside is sensitivity to mud, rain, snow, or dust, which can block the light source.
Closed emitter
The emitter is housed in a sealed tube. Even if the front lens becomes dirty, the dot remains visible. This solution is preferred for military and duty red dot sights.

Emitter color (aiming dot)

Red emitter – the most common; good visibility in various conditions and lower power consumption.
Green emitter – more visible in bright sunlight; higher power consumption.
IR emitter – designed for use with night vision (NVG); invisible to the naked eye.

Emitters in other tactical accessories

Emitters are not used only in red dot sights, but also in:

Laser designators (visible and IR lasers),
Tactical flashlights (high-output LED emitters),
IR illuminators for night vision,
Tracer units for illuminating BBs.