Light to Image: What is image fibre technology and how does it work?

Fused-silica image fibre is one of several technologies used in medical endoscopes. It enables doctors and surgeons to see inside the human body via natural orifices, or through small incisions. Engineers also use fibre scopes to inspect engines without dismantling them.

Optical imaging fibre is a fascinating technology that transmits light through flexible, hair-thin cores to deliver clear, real-time images from otherwise inaccessible places. Whether it’s guiding surgeons during delicate medical procedures, or inspecting deep within machinery, optical fibre image transmission plays a vital role in enabling visibility.

At the heart of optical image fibre technology, the principle of total internal reflection enables multiple wavelengths of light to travel efficiently through thousands of cores, this principle is crucial to the function of imaging fibres. Image fibres are essentially a fused bundle of optical fibres arranged in a fixed, parallel structure that preserves the spatial relationship of light signals from one end of a fibre to the other. By maintaining image integrity as light travels through each core, image fibres play a vital role in optical imaging systems, enabling high-resolution visualisation in a variety of medical and industrial applications.

What is image fibre?

Image fibre, also known as a fused-silica coherent image fibre bundle, is an optical waveguide specifically designed to transmit colour images rather than data. Unlike internet fibres, image fibres collect light and keep its spatial arrangement. This allows true-to-life colour images to be reconstructed at the eyepiece other end.

Key applications:

• Medical endoscopes: Flexible and semi-rigid endoscopes help doctors see inside the body for diagnosis and minimally invasive procedures like kidney stone removal and tumour treatment.
• Security: Passive fibre optic imaging systems can be deployed for covert surveillance or monitoring in restricted areas. Their discreet size and ability to transmit clear images, makes them suitable for law enforcement and military applications.
• Industrial inspection: They are also used for monitoring non-destructive testing, quality control, remote visual inspection of machinery, pipelines, and other critical components. They can be used to detect cracks, corrosion, and other defects in hard-to-reach places.

Total internal reflection

Total internal reflection is a principle that allows light to travel through optical fibres with minimal loss, even when the fibres bend or twist. It’s the reason why light transmission in fibres is so efficient and reliable.

An optical fibre is made up of two distinct layers that work together to guide light. The core, which has a higher refractive index and is typically made of glass or plastic, and the cladding, which surrounds the core and has a lower refractive index. When light enters the fibre at a specific angle, it strikes the boundary between these two layers. If the angle of incidence is greater than the critical angle, the light is not transmitted into the cladding but instead reflects into the core. This process, known as total internal reflection, continues along the entire length of the fibre, allowing light to travel through it by repeatedly bouncing within the core, even over long distances or around curves.

How fibre bundles transmit an image

A coherent fibre bundle contains thousands of fibres arranged in a fixed pattern. Each core works like a pixel, carrying one point of light from end to end. Together, the cores recreate colour images with fine detail.

 There are three key characteristics of an image fibre:

1. Fixed Arrangement – The fibres are aligned in the same order at both ends of the bundle. This means the spatial relationship between each point of light is preserved, allowing the transmitted image to retain its original structure.
2. Resolution – The image resolution depends on two factors:
   1. Number of cores (pixels): More cores result in greater image detail.
   1. Diameter of each fibre: Smaller diameter fibres have greater flexibility, smaller cores allow for finer resolution.
3. Flexibility – fused-silica image fibres are relatively flexible, allowing them to bend and twist without disrupting the image. This makes them ideal for navigating through narrow, curved, or complex environments, such as inside the human body or deep within mechanical systems.
   

Fujikura image fibres

Our image fibres are ultra-thin silica bundles with thousands of fused glass cores inside a common cladding structure. They deliver bright, high-contrast colour images over distances of 10 metres or more with minimal loss. They are highly flexible, which makes them ideal for navigating complex and narrow pathways, whether within the human body during endoscopic procedures or inside machinery during industrial inspections. In environments where heat is a concern, our polyimide coated fibres offer heat resistance up to 300°C, ensuring reliable performance under thermal stress. For medical use, our fibres are also biocompatible and suitable for use in medical equipment.

In a world driven by visuals, it’s easy to forget the technology that makes them possible. For decades fibre optic imaging has transformed how we access hard-to-reach spaces, enabling life-saving medical diagnoses, precision engineering inspections, and enhanced security operations.

Image fibres bring clarity where it matters most. Their ability to transmit high-resolution images through ultra-thin flexible, heat-resistant, and biocompatible optical fibre makes them indispensable across several important market sectors.