4.11.3.1. Lens stereoscopes

Lens stereoscope is also called as pocket stereoscope, as it can be kept in pocket owing to its small size. Being light-weight, it is easy to transport in the field, if required. It consists of two plano-convex lenses with magnifying capability, which are mounted on a metallic frame.

A lens stereoscope, often referred to as a pocket stereoscope, is a compact optical device designed for viewing stereo images. Its lightweight and portable nature make it suitable for field use. The device comprises two plano-convex lenses that serve to magnify images. These lenses are mounted on a metal frame that holds them in place, ensuring stability when viewing the images.

Imagine using a pair of binoculars while bird watching. Just like binoculars allow you to see distant birds clearly, a lens stereoscope magnifies stereo pairs of photographs to create a three-dimensional view, helping you see details that would be difficult to discern with the naked eye.

The distance between these two lenses is adjustable as per the comfort of users’ eyes. The eye base average distance is approximately 65 mm for a human-being. The height of pocket stereoscope is normally 10 cm, but its legs can be folded when not in use.

One of the practical features of lens stereoscopes is the adjustable distance between the two lenses. This adjustability accommodates different users’ eye distances, which averages around 65 mm. The typical height of a pocket stereoscope is about 10 cm, and it is designed with foldable legs for easy storage and portability.

Think of wearing glasses. Just like glasses can be adjusted to fit comfortably on different face shapes, a lens stereoscope allows users to customize the distance between lenses for optimal viewing, ensuring a clear, comfortable three-dimensional picture.

Distance between legs of the stereoscope and the focal length of lenses are normally so designed that the stereo-model can be created.

The design of a lens stereoscope includes specific arrangements for the distance between its legs and the focal length of its lenses. These elements work together to create a three-dimensional model from stereo images. When correctly aligned, they facilitate the visual perception of depth, enabling the viewer to judge distances more accurately.

Think about how car headlights are positioned. Just as the angle and distance between car headlights help illuminate the road ahead effectively, the arrangement of the legs and focal lengths in a lens stereoscope ensures that images are viewed from the right perspective, allowing the viewer to understand the spatial relationship between objects.

Lens stereoscopes are handy, economical and light-weight, and thus convenient for studying the small format aerial photographs. They have disadvantages, such as limited magnification (2x–4x), and limited field of view to view the larger size photos in 3D at one single glance.

Lens stereoscopes present several advantages such as portability, affordability, and lightweight construction, making them practical tools for analyzing small-format aerial photographs. However, they also have some limitations, including a magnification range of only 2x to 4x, which may not be sufficient for all applications, and a restricted field of view when attempting to view larger photographs in three-dimensional form.

Consider a magnifying glass. While it can help you read tiny print on a map, it can sometimes make it hard to get a full view of the entire map at once. Similarly, lens stereoscopes are excellent for detailed examination but might require another type of tool when needing to view a larger area comprehensively.

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