Diffraction-limited or Diffraction-unlimited?

[Xiang Hao]

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Dear all:
   I have a very fundamental question. As a foreigner from non-English
country, recently, I'm absolutely confused with the definitions of
diffraction-limited and diffraction-unlimited.
   For example, it is well known that a focal spot by an objective has a
lateral size of 200 nm and an axial size of 600 nm. If I can obtain a focal
spot with a size of 100 nm, it is apparent that it has broken the
diffractive limit. Therefore, should I call it a diffraction-limited focal
spot, or a diffraction-unlimited one? Actually, some papers I have ever
read use the former word, but on the other hand, there are some other
persons who tend to use the latter one. So, which one is correct?
    Thank you very much!

--
------
Hao, Xiang
Ph.D Candidate,
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University
[phone]

[Guy Cox-2]

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Diffraction-unlimited refers to techniques, such as STED, STORM and PALM, where there is no absolute theoretical limit to the resolution attainable.  Other super-resolution techniques, such as 4-pi and linear structured illumination, give improved resolution, below the Rayleigh limit, but are still diffraction limited in that there is a defined limit to the resolution improvement available.  

Of course even diffraction-unlimited techniques are ultimately limited by signal to noise ratios.

                                       Guy

Optical Imaging Techniques in Cell Biology
by Guy Cox   2nd edition, 2012 CRC Press
     http://www.guycox.com/optical.htm
______________________________________________
Associate Professor Guy Cox, MA, DPhil(Oxon)
Aust. Centre for Microscopy & Microanalysis, F09,
University of Sydney, NSW 2006
______________________________________________
Phone [phone]     Fax [phone]
Mobile [phone]
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      http://www.guycox.net
 


-----Original Message-----
From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Hao,Xiang
Sent: Thursday, 15 November 2012 4:03 PM
To: [hidden email]
Subject: Diffraction-limited or Diffraction-unlimited?

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To join, leave or search the confocal microscopy listserv, go to:
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Dear all:
   I have a very fundamental question. As a foreigner from non-English
country, recently, I'm absolutely confused with the definitions of
diffraction-limited and diffraction-unlimited.
   For example, it is well known that a focal spot by an objective has a
lateral size of 200 nm and an axial size of 600 nm. If I can obtain a focal
spot with a size of 100 nm, it is apparent that it has broken the
diffractive limit. Therefore, should I call it a diffraction-limited focal
spot, or a diffraction-unlimited one? Actually, some papers I have ever
read use the former word, but on the other hand, there are some other
persons who tend to use the latter one. So, which one is correct?
    Thank you very much!

--
------
Hao, Xiang
Ph.D Candidate,
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University
[phone]

[Mark Cannell-2]

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Unfortunately, English is sometimes badly used and the introduction of the term "diffraction-unlimited" is an example. Whoever invented this term did not realise/know that the hyphen makes the term "diffraction-limited" effectively one word. This new word should then be modified as per the usual english usage which require the modifier in front. I think that what is/was meant is "sub-diffraction-limited"  but better english would be to use negation as in "the spot size is not diffraction-limited"
IMHO.

You do not have to use incorrect constructions just because some else does.

Cheers Mark

On 15/11/2012, at 5:02 AM, "Hao,Xiang" <[hidden email]> wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> Dear all:
>   I have a very fundamental question. As a foreigner from non-English
> country, recently, I'm absolutely confused with the definitions of
> diffraction-limited and diffraction-unlimited.
>   For example, it is well known that a focal spot by an objective has a
> lateral size of 200 nm and an axial size of 600 nm. If I can obtain a focal
> spot with a size of 100 nm, it is apparent that it has broken the
> diffractive limit. Therefore, should I call it a diffraction-limited focal
> spot, or a diffraction-unlimited one? Actually, some papers I have ever
> read use the former word, but on the other hand, there are some other
> persons who tend to use the latter one. So, which one is correct?
>    Thank you very much!
>
> --
> ------
> Hao, Xiang
> Ph.D Candidate,
> State Key Laboratory of Modern Optical Instrumentation, Zhejiang University
> [phone]

Mark  B. Cannell Ph.D. FRSNZ
Professor of Cardiac Cell Biology
School of Physiology&  Pharmacology
Medical Sciences Building
University of Bristol
Bristol
BS8 1TD UK

[hidden email]