Dear Confocal Microscopists,
On Dec. 7 I wrote a response to a question Barry Burbach had about
possible mis-alignment of his MRC-600. Barry then replied to the
message, and I will respond to his further questions here.
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First of all, yes that was a typo in the first sentence of the third
paragraph: the scanhead should be realigned so the beam is exiting
on-axis.
Secondly, in reference to the question about making any adjustments to
the filter blocks, and if they would all have to be adjusted then.
Yes, if you adjust one of the filter blocks to realign the system, all
of the blocks will have to be realigned to that one block. Rather than
assuming that one of the blocks is a "master", by using the alignment
tool we can align the system with confidence.
Ideally only M1 would ever have to be adjusted, but over time and heavy
use, the pins that hold the angle of the filter blocks can wear down
slightly or lose position, so occassionaly they may have to be
adjusted as well (it is a good idea to teach users to insert and remove
the filter blocks without "scraping" the pins in the filter block
socket).
(I am not sure what rings you are referring to, as I have never before
made any adjustments to mounting rings.) If you remove the cap from
the filter blocks you will have access to the three allen screws which
dictate the angle of the filter block. There is a grub screw which
holds each of the three alignment screws in place. These should not be
loosened to make adjustments to the alignment screws. But, you might
check to make sure they are tightened properly.
(As far as centering the beam on the galvos, I suspect there is a
certain limit to what I can explain accurately on paper. It's not the
type of operation that I would call routine maintenance, but is used in
more extreme circumstances. This is the type of procedure that we
spend time training our service engineers to do properly, and is more
of a hands on training. But, I will attempt to explain in a slightly
more detailed manner what this involves.)
I guess I need to state here that if the scanhead is opened up the
warranty is violated. Since I'm sure you've already done that Barry,
let's get down to business.
If you take the cover off of the black box that protects the galvos,
you can then monitor the position of the beam on the galvos. To do
this properly you must park the beam by using a "Zoom=999". You want
the beam to be centered on the axis of both galvos. This is so that
when beam strikes the galvo at all angles, it is in focus. If the beam
is striking the galvo off axis, it would be traveling a shorter
distance before hitting the galvo when it is at one of it's limits, and
a longer distance when the galvo is at the other limit. If the beam is
centered though, it is always focusing to the same spot on the
galvo, and traveling the same distance. If the beam is not centered,
there are several adjustments that need to be made, depending on where
and why it is off. Three possible adjustments are 1) mirror M1; 2)
the first position filter block; 3) the galvo feedback control card.
Rather than attempting to make corrections with 2) and 3), we typically
can realign the system by correcting 1) mirror M1. Once an adjustment
is made with M1 and one of the filter blocks, they should all be
co-aligned by aligning their three allen screws until the beam is
centered in the turret prism on the microscope without making any
adjustments to M1. For example, if the system is re-aligned using the
reflection block, and you do an experiment using the BHS block and then
have to adjust M1 to center the beam in the turret prism, the alignment
will be off again. So, once you align the system with one block,
adjust all of the blocks to that one block so that the system is always
in alignment.
It is important to state, in case any new users are reading this that
this is in no way a routine adjustment the user is expected to make.
These adjustments are part of a service procedure though, and our
service engineers will be able to take care of it if necessary. It
could also be checked as part of Preventative Maintenance, for those of
you with service contracts.
As far as getting hold of one of these alignment tools that fit on the
eyepiece of the scanhead, I am in the process of having our machine
shop manufacture another batch of them. I will have to discuss with
our service manager how he would like this handled.
For the users general information, I will give the number for technical
support here: 1-800-4BIO-RAD.
If you have any more questions Barry, or if any other users would like
to comment, feel free. I agree that there are probably more users that
would be interested in this information, so why don't we keep all
correspondence public on the confocal user net.
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