Eyepieces

01:00:13.15 something that is often taken for granted
01:00:15.13 in the microscope, and that is the eyepieces
01:00:17.10 of the microscope.
01:00:18.08 Oftentimes, we're not even actually using eyepieces,
01:00:21.03 nowadays. Looking directly at the image
01:00:24.10 on the camera, or other imaging device,
01:00:26.28 rather than in the eyepiece.
01:00:29.09 However, eyepieces are fairly important
01:00:31.28 and when you're looking
01:00:32.27 for the specimen of interest,
01:00:35.09 you should know how to properly
01:00:36.15 adjust the eyepieces
01:00:37.15 and know what they do.
01:00:38.19 So the eyepieces don't actually
01:00:41.08 contribute to the resolution
01:00:42.29 of the optical system.
01:00:43.27 They magnify the image
01:00:45.22 and relay it to the retina in your eye.
01:00:48.12 And they do determine
01:00:50.27 the field of view of the microscope
01:00:52.22 to your eye.
01:00:54.04 They're also the place
01:00:56.23 where if you had a reticle
01:00:58.01 or a mask, something that you wanted to
01:01:00.08 put a scale, for example, in,
01:01:02.03 would be located in the eyepiece.
01:01:04.26 One point I want to make
01:01:06.12 about eyepieces is that most eyepieces
01:01:08.14 nowadays are termed what they call
01:01:10.10 "high eye point eyepieces."
01:01:12.16 And what that means is
01:01:13.24 they're designed for people
01:01:15.07 with or without eyeglasses.
01:01:17.05 So you don't have to take your eyeglasses off
01:01:20.09 when you're looking in the eyepiece
01:01:22.03 of the microscope.
01:01:23.01 They're designed for that.
01:01:25.08 Useful magnification of the microscope
01:01:28.08 and system based on the NA
01:01:30.06 is about 500 to 1000 times.
01:01:32.12 So there are conjugate planes
01:01:36.06 within the eyepiece itself.
01:01:37.22 But the important thing that you want
01:01:39.22 to get from an eyepiece
01:01:40.19 is that you have a field plane,
01:01:42.16 here in the middle,
01:01:43.07 and there's actually a shelf there
01:01:45.13 that normally you can access
01:01:46.29 with a little ring that would put
01:01:49.14 a reticle, or an eyepiece reticle.
01:01:51.11 So you'd unscrew that ring
01:01:52.14 drop in your reticle,
01:01:53.23 and screw it back down tight.
01:01:55.15 The eyepiece actually produces
01:01:58.06 a virtual image, which is 250mm
01:02:02.05 away from the eye.
01:02:04.24 Or appears 250mm away.
01:02:06.27 That is sort of defined as 1X
01:02:10.09 to the human eye.
01:02:12.09 And was based actually
01:02:13.16 on the comfortable reading distance
01:02:16.06 of the human eye.
01:02:16.28 And the light from there,
01:02:19.19 you can see, goes through the eyepiece
01:02:21.12 and actually uses the lens in the eye
01:02:25.01 to reflect the image focused back on the retina.
01:02:28.25 So that's just a short tip on the eyepieces.

This Talk

Speaker: Steve Ross

Audience:

Researcher

Recorded: March 2012

Talk Overview

In this talk about eyepieces, Stephen Ross gives a short description of what is in an eyepiece and how it works.

Speaker Bio

Steve Ross

Stephen Ross is the General Manager of Product and Marketing at Nikon Instruments. He is also very involved in teaching microscopy at the Marine Biological Laboratory in Woods Hole and at the Bangalore Microscopy Course at the National Centre for Biological Sciences. Continue Reading

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