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Galvo XY Scanning Speed

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yuansheng sun

Galvo XY Scanning Speed

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Dear Listers,

I am trying to figure out the confocal microscope scanning speed that can
be achieved based on the specs of a Galvo XY scanner. What specs of a
Galvo XY scanner (e.g. small angle step response, the travelling angle)
should I look for determining the scanning speed? It seems the Galvo
mirror size would affect the speed a lot. Any help would be greatly
appreciated. Thanks in advance.

Best regards,
Sheng

Craig Brideau

Re: Galvo XY Scanning Speed

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It depends on the resonant frequency of the galvo modified by the
weight/size of the mirror on the end of it, tweaked by how wide an angle
you need it to scan. Basically you have to give the scan angle and mirror
size you need to the manufacturer and they can come back to you with the
resulting maximum speed. Or just look up pre-built galvos with mirrors
attached and find one that suits your application.

Craig

On Tue, Feb 12, 2013 at 1:39 PM, yuansheng sun <[hidden email]>wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> Dear Listers,
>
> I am trying to figure out the confocal microscope scanning speed that can
> be achieved based on the specs of a Galvo XY scanner. What specs of a
> Galvo XY scanner (e.g. small angle step response, the travelling angle)
> should I look for determining the scanning speed? It seems the Galvo
> mirror size would affect the speed a lot. Any help would be greatly
> appreciated. Thanks in advance.
>
> Best regards,
> Sheng
>

John Oreopoulos

Re: Galvo XY Scanning Speed

In reply to this post by yuansheng sun

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Dear Sheng,

There's a little bit of information on this topic in chapter 9 of the 3rd edition of Jim Pawley's Hanbook of Biological Confocal Microscopy:

The Intermediate Optical System of Laser-Scanning Confocal Microscopes
Ernst H.K. Stelzer

Some considerations about the required size of the mirrors and their relation to the scan speed are mentioned. Maybe this will help you.

Cheers,

John Oreopoulos
Staff Scientist
Spectral Applied Research
Richmond Hill, Ontario
Canada
www.spectral.ca

On 2013-02-12, at 3:39 PM, yuansheng sun wrote:

George McNamara

Re: Galvo XY Scanning Speed

In reply to this post by yuansheng sun

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Leica SP5 resonant scanner: 8,000 lines per second
Leica SP8 resonant scanner: 12,500 lines per second (you should look up
exact value at leica)

Ignoring turnaround time and flyback ...

For SP5, 8,000 lines/sec is 125 microeconds per line.
If I choose 1000 pixels per line, this is a dwell time of approximately
125 nanoseconds per pixel.
You would need to know the PMT performance and zoom to know how this
translates to real performance (XY resolution).

For commercial confocals (at least those designed in the past 10 years),
I expect the manufacturer has figured out the right size for the mirror.

On the SP5's I manage, Jonathan Boyd of leica applications (USA) showed
me that SP5 resonant scanner mode produced a brighter signal per pixel
total dwell time than standard scan mode. That is 8000 lines/sec * 100
sum (RS mode) was brighter than (now standard mode) 800 lines/sec * 10
sum was brighter than 80 lines/second. Explanation was almost certainly
that slow scan drives the fluorophores into the triplet state, where
they stay (or reach equilibrium) as long as the laser is on the spot.
This should vary with O2, other triplet quenchers, fluorophore, laser
power.

George

On 2/12/2013 3:39 PM, yuansheng sun wrote:

Guy Cox-2

Re: Galvo XY Scanning Speed

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You don't need to be driving your fluorochrome into a triplet state to see this effect - you just have to be saturating the S1 state - ie exciting a significant proportion of the fluorochromes within the spot, so that a further photon stands a lower chance of hitting an unexcited molecule. It's still a really bad thing to do. You should always check that halving the laser power halves the signal - if not you are killing your specimen.

I'll bet that if the laser power had been set so that there was no saturation at the slow scan speed, and kept the same for the fast scan, you would not have seen this effect. However, 'brightness' is really a meaningless measure here, because the resonant scan has to be adjusted for the non-constant dwell time across the sample so you are always seeing an adjusted level. Signal / noise ratio is the only meaningful criterion.

Guy

-----Original Message-----
From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of George McNamara
Sent: Thursday, 14 February 2013 12:22 PM
To: [hidden email]
Subject: Re: Galvo XY Scanning Speed

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Leica SP5 resonant scanner: 8,000 lines per second
Leica SP8 resonant scanner: 12,500 lines per second (you should look up
exact value at leica)

Ignoring turnaround time and flyback ...

For SP5, 8,000 lines/sec is 125 microeconds per line.
If I choose 1000 pixels per line, this is a dwell time of approximately
125 nanoseconds per pixel.
You would need to know the PMT performance and zoom to know how this
translates to real performance (XY resolution).

For commercial confocals (at least those designed in the past 10 years),
I expect the manufacturer has figured out the right size for the mirror.

On the SP5's I manage, Jonathan Boyd of leica applications (USA) showed
me that SP5 resonant scanner mode produced a brighter signal per pixel
total dwell time than standard scan mode. That is 8000 lines/sec * 100
sum (RS mode) was brighter than (now standard mode) 800 lines/sec * 10
sum was brighter than 80 lines/second. Explanation was almost certainly
that slow scan drives the fluorophores into the triplet state, where
they stay (or reach equilibrium) as long as the laser is on the spot.
This should vary with O2, other triplet quenchers, fluorophore, laser
power.

George

On 2/12/2013 3:39 PM, yuansheng sun wrote: