Re: Microscope adapter for digicam
- From: pentagrid@xxxxxxxxx
- Date: Tue, 13 Dec 2005 23:21:13 +0000
On Tue, 13 Dec 2005 09:06:03 -0600, "Mike Henry"
<MichaelHenry@xxxxxxx> wrote:
>
>"Larry Fishel" <ldfishel@xxxxxxxxx> wrote in message
>news:1134365700.738170.71530@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> For reference, I've had pretty good luck just holding a digital camera
>> with the lens against the eyepiece of my microscope...
>
>I tried that and got decent results at the expense of some vignetting.
>Maybe that's the best that can be expected without spending considerable
>money.
>
Unless you're prepared to make major
modifications to the microscope mechanics you can't get at the
design focal plane of the microscope objective so you're forced
to use the eyepiece or a relay lens to bring the final focal
plane outside the tube length.
The normal working range of eyepiece focusing
produces an apparent image distance of between infinity and about
10". If the infinity end of this range chosen, the light leaving
the eyepiece can be brought to a focus by a digital camera which
has preferably had any autofocus option disabled and fixed at
infinity.
While this can produce an excellent focussed image
there may be severe vignetting. This is because the light leaving
the eypiece emerges as a cone of rays. This is produced by the
eyepiece lenses forming a real image of the objective aperture.
This is the exit pupil. In visual use, to make use of the full
field, the observer automatically positions his eye so that this
exit pupil is located within his eye.
In the camera case the axial position of the
camera must be adjusted so that this exit pupil is located in the
optical centre of the camera lens. It's a bit fiddly to do this
so it helps to first experimentally locate the exit pupil.
Focus the microscope on to a very bright object. Then in a
darkened room move a piece of ground glass or tracing paper near
the eyepiece eye lens. At the right distance a small bright disc
will appear. This is the exit pupil. Now organise the mechanics
so that this pupil location is coincident with the optical centre
of the camera lens.
The best choice for this is one of the small security
cameras which use physically small lenses. The pupil location is
pretty close to the eye lens and if the camera lens is a
relatively long multiple element assembly such as a zoom lens it
may be impossible to reach the optimum position and vignetting
will remain.
Jim
If the digital camera auto focus is disabled and left set at
infinity microscope; focusing the microscope for best final image
will permit both the microscope and the camera to work within
their normal
.
- References:
- Microscope adapter for digicam
- From: Mike Henry
- Re: Microscope adapter for digicam
- From: Larry Fishel
- Re: Microscope adapter for digicam
- From: Mike Henry
- Microscope adapter for digicam
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