Development of compact solid-state illumination sources for endoscopy

(NEAT/DoH funded, George Hanna and Dan Elson in DBST, and Mark Neil in Physics)

Current arc-lamp illumination systems have a number of technical and ergonomic limitations. White light-emitting diodes (LEDs) and laser diodes are energy-efficient solid-state lighting devices which are small, durable and inexpensive. Their use as an alternative to arc-lamp light sources in minimal access surgery has not been explored.

We are studying both LED and laser diode-based endo-illuminators to determine their lighting characteristics for use in minimal access surgery.

System 1

We have developed an LED endo-illuminator using a white LED mounted at the tip of a steel rod, and performed comparisons with arc-lamps on the uniformity, shadow sharpness and overall image intensity. Visual perception of fine details at the peripheral endoscopic field was also assessed by 13 subjects using the different illumination systems. Results show that the Illumination from the LED endo-illuminator was more uniform compared to illumination from an arc-lamp source, especially at close working distances. The shadows were also sharper, and the illumination was more stable with less flickering. Higher median scores on visual perception were also obtained.  

Views of the tip of the LED endo-illuminator and the shadow formation

System 2

The second light source proposed is a violet laser diode, which can be powered by a compact lithium ion battery. The light can be coupled into a single, narrow optical fibre to transfer it to the distal end of the endoscope, where it is converted into red, green and blue components by using a custom-blended phosphor, thereby providing white light.  The flatness of illumination, the sharpness of shadows formed and the ease of use have been measured experimentally, and the overall benefits of the system will be determined qualitatively and quantitatively through laparoscopic practitioners testing the instrument in a simulated task.

For further information, please contact Dan Elson at ds.elson@imperial.ac.uk.