ON TARGET (1/5): Structure of an optical System
The objective lens is the optical system’s front lens group facing the object and operates like a converging lens. Its purpose is to display an image which, at the image plane, appears upside down, laterally transposed and reduced, and which is subsequently displayed correctly again by the reversal system.
Good to know: The larger the objective lens diameter, the greater the optical system's luminous intensity. However, this lumious intensity can only be utilised if the correct magnification is chosen.
The focusing lens is an adjustable lens inside the optical system for focusing the image at different distances. In some binoculars, focusing is controlled via adjustable eyepieces. Several optical systems come with a fixed-focus lens, and are usually set in focus at 100 m. In the case of rifle scopes, apart from focusing, the focusing lens also facilitates parallax compensation.
In order to compensate for different visual impairments (dioptres) between the left and right eye, the left side in binoculars is mechanically decoupled from the right side, allowing the right and left image to be focused separately. The dioptre adjustment can be made using the focusing button or the eyepiece. For rifle scopes, the reticle can be focused using the dioptre adjustment on the eyepiece, thereby correcting any visual impairment.
The purpose of the reversal system is to reverse the image by means of prisms in binoculars and telescopes, and lenses in rifle scopes. Prisms are divided into two different systems: the porro system and roof system. In prism systems, the incident light is totally reflected several times. This produces an upright image. Unlike lens systems, prism systems can accommodate a shorter design. The lens reversal system is needed in rifle scopes to control the variable magnifi cation and move the exit pupil around 8-9 cm (3.1-3.5 in) outside (eye distance).
Good to know: Binoculars with a roof prism system allow for a more ergonomic and compact design, compared with the porro prism system.
Reticles can incorporate an illumination system for lighting up different areas of the target.
Systems are adapted to the hunters’ requirements: Day/night switch, with adjustment
for light intensity, automatic on/off, tilt sensor, durability, luminosity, etc.
Laser rangefinders operate according to the principle of travel time measurement and are available in three different systems: Binoculars with an integrated rangefinder, targeting optics with an integrated rangefinder, and pocket rangefinders. Travel time measurement means that short, invisible laser pulses are emitted. If they hit objects they are reflected and the refl cted laser pulses are detected by the rangefinder. The time that elapses between emitting and detecting the pulses is measured. Rangefinder systems are often integrated with angle measurement systems. The angle is measured via the sensors inside and is used along with the distance for ballistic calculations or aiming point adjustments. Class 1 lasers are used in hunting and can be used to take measurements up to 1,500 m (1,640 yds). A stronger laser is needed for measurements over longer distances.
Stay connected to this blog for parts 2 to 5 of ON TARGET - An introduction to high quality hunting optics!
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