The Endoscope – Design and Technology

An endoscope is a device that especially in medicine serves to facilitate the technical work in the diagnosis of diseases. The endoscope offers the possibility of examining organs and body regions with outstanding results that cannot even be compared to conventional radiographies. For this reason we cannot imagine today's medicine without endoscopes.  
An endoscope is a hose-like device with a light source, that allows examining hollow spaces and cavities or illuminate and view areas that are difficult to access. The traditional part in this technology has for a long time been the light that had to be transmitted into and through the examination device in order to illuminate the area to be examined. Today there are many different endoscope models allowing the best possible diagnostics thanks to their optimized lighting and imaging results.
Whether it is the gastro-intestinal tract, the trachea, the esophagus or the throat, nose or pharynx or other difficult-to-access human organs (or that of animals) – in many examinations the endoscope is an absolute must.
In today's medicine endoscopes are often fitted with a camera and a cable connection to a monitor providing high-resolution images of the examined areas, even video images are not a problem any more and represent an important instrument when treating a patient. Unfortunately such devices are cost-intensive and are not found in every practitioner's or specialist's practice.

The endoscope provides new insights

For the patient the endoscope is a completely new way of experiencing an examination at the general practitioner's or medical specialist's office. The recorded images transmitted to the high-definition monitor and the accompanying explanations of the doctor in charge are easy to understand for the patient, i.e. the patient can get a real idea of the problem and understand the diagnosis more easily.
Endoscopes therefore are an outstanding technical application for the examination and treatment of acute and chronical diseases, both for the doctor and for the patient. Nowadays it is much easier treating diseased joints, because thanks to the use of endoscopes even otherwise inaccessible areas can be examined and illuminated. Joints surrounded by tendons, ligaments, cartilage etc. and connected to blood vessels as well as tumors can be treated more easily by using endoscopic techniques.
The rigid or flexible variants of the endoscope are not only used in medicine. Today they are also used in industrial production, research, archeology and other areas.
Basically the endoscope is a kind of high-tech torch for the most versatile uses. The laws of physics, however, dictate its size: that the bigger the diameter the better the image and therefore the result. As today - especially in medicine – biocompatible materials are used, no patient should refuse an examination with an endoscope if its use is indicated.

Image formation in a rigid rod lense endoscope
Image formation in a rigid rod lense endoscope

Design of a rod lens endoscope

Rigid endoscopes consist of a long cladding tube (endoscope sheath) within which  the optical components such as prisms and lenses are aligned to form a lens system. The sheath also contains a separate channel made of glass fibers for transmitting light. There may be more channels, e.g. for suction and irrigation fluid and/or instruments. Rigid rod lens endoscopes have optical systems that comprise three main assemblies:

  • Objective lens
  • Transmission system (or reversal system)
  • Eyepiece

Objective lens

The objective lens is required to reproduce the image inside the endoscope.  It is located in the distal tip of the endoscope. The objective lens can be composed of up to 9 individual lenses. All angled directions of view such as 5°, 12°, 30°, 50° 70°, etc. require a prism with the corresponding angle as the first component of the objective lens. Endoscopes with an angle of view of  0° do not need a prism.
The objective lens and the subsequent single lenses give the endoscope its optimum properties for the intended clinical use. The specific requirements placed on the endoscope depend on the following:

  • Will it be used under water or in air?
  • What image angle is required?
  • What working distance is required?
  • What depth of field is necessary?
  • Ist a distortion-free image wanted?
  • etc.

Rod lenses and reversal system

The  reversal system consists of a series of rod lenses. They serve to transmit the image within the endscope. In Richard Wolf rod lens systems so-called long rod lenses made of glass are used. They provide a clearly higher light transmission efficiency compared to conventional lenses where the area filled with air between the lenses is relatively lage.
As a result, Richard Wolf endoscopes meet the highes requirements in medical diagnostics and therapy. Their realistic image with supreme light transmission and excellent image brightness is kown around the globe.

The eyepiece

The ocular lens or eyepiece serves to magnify the virtual image thus allowing image focus adjustment. The object distance can be changed depending on the application.

Image formation in a flexible endoscope with glas fibre bundle
Image formation in a flexible endoscope with glas fibre bundle

Design of a flexible endoscope

Flexible endoscopes consist of an elongate plastic-coated endosope sheath contaning optical components such as the objective lens and the image guide as well as the light-transmitting glass fibers.
Flexible endoscopes are also equipped with additional separate channels for suction and irrigation fluid supply and/or for instrument passage. The light is usually supplied to the endoscope tip via light-transmitting glass fibers. Flexible endoscopes with image guide technology comprise three different assemblies that form the optical system.

  • Objective lens (see description above)
  • Image guide, a precisely arranged glass fiber bundle for transmitting the image
  • Ocular lens  (see description above)

The  objective lens projects the object onto a thin bundle of precisely arranged glass fibers. Our high-resolution semiflexible image guide for human medicine is only 1.2 mm in diameter but has 50.000 precisely arranged single fibers.
The individual fibers have typical diameters between 4 µm and 14 µm. Between  3,000 and 50,000 fibers are used depending on the diameter and field of use.
This so-called image guide transmits the virtually image of the objective lens optically to the ocular lens (eyepiece) of the flexible endoscope, where it is magnified and becomes visible for the viewer.

Image formation in a CCD endoscope with integreated video sensor
Image formation in a CCD endoscope with integreated video sensor

Design of a chip-on-the-tip endoscope

The chip-on-the-tip or chip-on-the-stick endoscope is a releatively new technology in human medicine, where the endoscope tip itself contains a camera sensor. The image generated in the objective lens is guided onto to the video chip
The latter converts the optical signals into electrical signals and transmits them to the camera controller. The resolution can be up to 2 Megapixel depending on the chip technology used.
Richard Wolf offers video chip technology under the "Eyemax" product family. Rigid and flexible endoscopes with intergrated chip on the tip are offered for the following disciplines:

  • Urology
  • Bronchoscopy
  • Laparoscopy