RED DOT OPTIC WITH BIG APERTURE FREE
Like other reflector sights, the collimated image of the red dot is truly parallax free only at infinity, with an error circle equal to the diameter of the collimating optics for any target at a finite distance. More complex reticle patterns such as crosshairs or concentric circles can be used but need more complex aberration free optics. Using a "dot" shaped reticle also greatly simplifies the sight since the small diameter image does not require a sophisticated optical reflector to focus it. The LED itself is solid state and consumes very little power, allowing battery powered sights to run for hundreds and even tens of thousands of hours. There is no need for other optical elements to focus light behind a reticle. The LED as a reticle is an innovation that greatly improves the reliability and general usefulness of the sight. The size of the dot generated by the LED is controlled by an aperture hole in front of it made from metal or coated glass. The LED used is usually deep red 670 nanometre wavelength since they are very bright, are high contrast against a green scene, and work well with a dichroic coating since they are near one end of the visible spectrum. The mirror has a partially silvered multilayer dielectric dichroic coating designed to reflect just the red spectrum allowing most other light to pass through it. The typical configuration for a red dot sight is a tilted spherical mirror reflector with a red light-emitting diode (LED) at its off axis focus. Telescopes have a narrow field of view and therefore are often equipped with a secondary "finder scope" such as a red dot sight.ĭiagram of a typical "red dot" sight using a collimating mirror with a light-emitting diode at its focus that creates a virtual "dot" image at infinity On cameras they are used to photograph flying aircraft, birds in flight, and other distant, quickly moving subjects. Aside from firearm applications, they are also used on cameras and telescopes. They are considered to be fast-acquisition and easy-to-use gun sights for civilian target shooting, hunting, or in police and military applications. A standard design uses a red light-emitting diode (LED) at the focus of collimating optics which generates a dot-style illuminated reticle that stays in alignment with the weapon the sight is attached to, regardless of eye position (nearly parallax free). Made in Japan for Tasco, the ProPoint 2 was one of the first red dot sight models to become widely popular.Ī red dot sight is a common classification for a type of non- magnifying reflector (or reflex) sight for firearms, and other devices that require aiming, that gives the user a point of aim in the form of an illuminated red dot. View through Tasco ProPoint red dot sight (model PDP2ST) on a Ruger 10/22.