A binocular is an optical instrument that enables distant objects to be seen more closely and clearly. It typically consists of two identical telescopes and provides a separate image for each eye. This structure supports the human ability to see in three dimensions with both eyes and enhances depth perception. Binoculars are used especially in areas such as terrestrial observation, military reconnaissance, navigation, astronomy, and orientation. The Turkish term dürbün, is derived from the Persian words “dür” (distant) and “bin” (seeing), was adopted into Turkish with the meaning “distant-seer.” This definition directly refers to the primary function of the instrument.

^{Image of a Binocular Device (Generated by Artificial Intelligence)}

Structure and Working Principle

Binoculars essentially consist of two main optical components: the objective lens (front lens) and the ocular lens (eyepiece). The objective lens collects light from distant objects and forms a real image. The ocular lens magnifies this image and delivers it to the observer. To ensure the image is upright and perceived naturally, binoculars use prism systems. These prisms alter the path of light, both correcting image orientation and helping to reduce the length of the device. Porro prisms and roof (or Dach) prisms are commonly used in binoculars. Porro prisms provide a wider field of view, while roof prisms offer a more compact and lightweight design, enhancing portability.

In terms of technical specifications, binoculars are generally described by two numbers (e.g., 7×50). The first number indicates the magnification power, and the second represents the diameter of the objective lens in millimeters. The magnification power shows how much closer the image appears; the objective diameter determines the amount of light the binoculars can gather. A larger lens diameter allows more light to be collected, producing clearer images, especially in low-light conditions.

Historical Development

The history of binoculars is directly linked to the development of the telescope. The telescope was first developed in the early 17th century by Dutch spectacle maker Hans Lippershey. His idea of aligning two lenses to magnify distant objects laid the foundation for binocular technology. It is said that Lippershey was inspired when a customer in his shop held two lenses up to his eyes to look through them. In 1608, he applied to the government for a thirty-year patent for this invention. However, since similar devices had also been proposed by others, the patent was not granted.

During the same period, the Italian astronomer Galileo Galilei took interest in these optical developments, creating his own model of a binocular and beginning astronomical observations. The first Galilean binocular provided 4× magnification, while later models achieved up to 7× and even 32× magnification. Galileo’s binoculars, designed with short focal lengths, were relatively compact, although this limited the field of view. His dual-lens models were eventually combined to create twin binoculars for use with both eyes. This technology was later adopted for military applications as well.

In the later part of the 17th century, the system of two positive lenses proposed by Johannes Kepler laid the groundwork for more advanced versions of telescopes and, consequently, binoculars. Christoph Scheiner was the first to implement Kepler’s model in 1617. These developments enabled the spread of binocular technology in both scientific and practical domains.

^{Antique Binoculars(AA)}

Military Use

Binoculars have been used in military applications for reconnaissance, target identification, fire direction, and observation. This area of use gained particular importance in the late 19th and early 20th centuries. As part of its modernization efforts, the Ottoman Empire purchased binoculars manufactured in Europe for military use and began employing them in artillery units. French-made Som binoculars, used for heavy artillery, played a significant role in coordinating long-range fire. These binoculars provided a wide field of observation and allowed for precise calculation of observation angles to improve target accuracy.

During the Ottoman period, scissors-type battery binoculars were also commonly used. Thanks to their dual-arm structure, these binoculars offered a wider field of view and were utilized particularly in artillery batteries for target detection and directional alignment. The 1914 model scissors-type battery binoculars provided high optical precision with 10×50 magnification power, though they were initially lacking features such as a reticle grid, which were later added through technological improvements.

^{Military Personnel Using Binoculars (AA)}

Additionally, sighting binoculars mounted on the 1908 model German Maxim machine guns are also noteworthy. The prism systems and yellow-filtered lenses used in these binoculars enabled target identification even in foggy, steamy, or low-light conditions. Featuring various range markings on the aiming dial, these binoculars facilitated accurate shooting.

Use in Cartography

The binocular is one of the essential components of the theodolite, a geodetic measurement instrument. The theodolite is used to measure horizontal and vertical angles as well as distances, and the binocular is used to determine the target direction within these angles. Observation lines within the binocular aid in defining the target alignment. Proper adjustment of the binocular in the theodolite is critical for measurement accuracy. It is also necessary to eliminate parallax error, focus the binocular correctly for the user’s eye, and adjust clarity settings. Therefore, binocular alignment is of critical importance in measurements conducted with a theodolite.

Use in Navigation

In navigation, the binocular is a fundamental observational tool, especially during coastal sailing and pilotage. Sailors use binoculars to observe navigational aids such as lighthouses more clearly and to take bearings for position plotting on nautical charts. The functionality of binoculars in this field depends on their optical properties, such as magnification power and objective diameter. For open-sea navigation, waterproof, prism-equipped, and weather-resistant binoculars with specifications such as 7×50 mm are typically preferred. The prisms used in such binoculars extend the light path while keeping the device compact and ensuring image clarity.

Optical Components and Objective Features

A binocular is essentially an optical device based on lens systems. Objective lenses form images by refracting light, and the clarity of these images depends on the quality of the glass used, the arrangement of the lenses, and optical surface coatings. Objectives are classified according to focal length and field of view. In high-quality binoculars, multi-layer anti-reflective coatings (such as nano coatings) are applied to minimize internal reflections and enhance image brightness. As a result, binoculars can provide clear and high-contrast images even under low-light conditions.

Historical and Functional Perspective

Binoculars are historically derived from the development of the telescope and are multi-purpose, portable optical observation instruments. Through advanced lens and prism systems, they provide high-clarity images under various light and weather conditions, serving both scientific and practical applications. Widely used in disciplines such as military, navigation, cartography, and astronomy, binoculars continue to evolve with technological progress, meeting the observational needs of both professional and amateur users.

Modern Production Binoculars and Domestic Optical Systems in Türkiye

The current level of binocular technology includes not only optical imaging but also multifunctional mission systems supported by electronics. Advanced binoculars are now equipped with features such as laser rangefinders, digital compasses, GPS modules, thermal cameras, and digital data transmission capabilities, enabling target identification and observation under all terrain and climate conditions, both day and night. These systems are particularly used in military operations for reconnaissance, surveillance, and precise target coordinate determination.

As part of efforts to develop domestic optical systems in Türkiye, one of the optical observation devices produced and publicly introduced by TÜBİTAK Defense Industries Research and Development Institute (SAGE) is the Engerek 8 Multi-Function Cooled Portable Thermal Binocular. The system was first exhibited at the International Defense Industry Fair in 2019.

The Engerek 8 is designed for use in determining the distance, direction, and coordinate information of stationary ground targets. The device includes a cooled thermal camera, a daytime observation binocular, and laser rangefinder modules. Through this device, the observer operator can determine the direction, distance, and positional coordinates of a target and transmit this data to a connected command and control center via digital communication systems. In addition to its high optical magnification capability, the device enables night-time observation through thermal imaging.

Engerek 8 offers the user the ability to digitally mark a target and automatically calculate its coordinates. These advanced features demonstrate that modern binoculars function not only as passive observation tools but also as components of tactical decision-support systems.

In this context, the structural transformation that binocular technology has undergone since its historical development from the telescope has, in the 21st century, merged with digital optical systems—evolving beyond mechanical lens systems into multi-component integrated optical-electronic systems. Engerek 8, as a domestic production example, stands out as a current example of this transformation.