So, in Physics, we have been learning about optics, and last lesson we began to look at optical fibres…optical fibres are used for quite a variety of things, but the one I found most interesting was their use in medicine, as they are used in endoscopes. As you may (but probably won’t) know, during my week of work experience at the hospital, I got to spend the morning in endoscopy, so I thought I’d write a bit about how endoscopes work. If you want to read more about my week of work experience, click here.
Just to warn you, this post is going to be quite physicsy, so if that’s not what you find interesting, you might not want to read this 😉
So, basically, we got onto the topic of Total Internal Reflection, which occurs when the incident substance has a larger refractive index than the other substance involved, and also when the critical angle is less than the angle of incidence. At the critical angle, the angle of refraction is 90′, as the light ray goes along the boundary, like the boundary is a plane mirror.
Endoscopes use optical fibres, and are used to see inside the body. In optical fibres, a light ray is passed down the fibre. Every time the light ray hits the boundary, it is “totally internally reflected”, even if the fibre is bent. Whenever the light ray meets the boundary, the angle of incidence is larger than the critical angle, which is what causes it to be totally internally reflected along the wire.
So, in a medical endoscope, there are two bundles of fibre. The endoscope is then put into the body through an orifice of some type, usually the mouth, nose or colon. Then, light is sent through one of the fibre bundles. There is a lens on the end of the other fibre which is used to form an image of the inside of the body on the end of the fibre bundle. The light forming this image travels along the fibres to the other end of the fibres, where the image can be seen. The fibre bundles must be in a coherent position (the fibres at each end are in the same relative position).
That’s all I really have to say..I know this is quite boring…and quite short…but I hope you found it interesting 🙂 I found it interesting, as it’s always useful to link the stuff I am learning about in lessons to medicine, so I hope it’s just as useful to all of you 😀
Thanks for reading,