Re: coining of the term confocal

Posted by Guy Cox on
URL: http://confocal-microscopy-list.275.s1.nabble.com/coining-of-the-term-confocal-tp590068p590070.html

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Colin Sheppard has told me that his group didn't like the term confocal

because it also had another meaning in optics, so they used Type I and

Type II scanning microscopes (Type II was confocal) - but the word

did nevertheless appear in some of their publications. 

 

As to the inventor of the confocal microscope, this was Hiroto Naora,

in Japan in the 1940s.  (But this was not a scanning microscope).  An

interesting aside - some years ago I was having a long email exchange with

Marvin Minsky.  Then I asked him whether he'd known about Naora's

work - which was published in Science and other top journals - and the

correspondence came to an abrupt close.

 

                                                                                              Guy

---

From: Confocal Microscopy List on behalf of George McNamara
Sent: Thu 23/08/2007 10:34 AM
To: [hidden email]
Subject: Re: coining of the term confocal

 

 

 

 

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
Scanning 1988 memoir attached. Does not explicitly state that he used the term in 1957


Searching PubMed for "confocal" turned up an irrelevant 1969 reference (something to do with prolate spheroids) and several early 1980's papers (but is clearly missing stuff in the 1970's). Some of the 1980's papers have full text online. The Valkenburg JA 1985 http://jb.asm.org/cgi/reprint/161/2/478?view=long&pmid=3918013 paper had references to three Brackenhoff 1979 papers, including two in J Microscopy:

Brakenhoff, G. J. 1979. Imaging modes in confocal scanning
light microscopy (CSLM). J. Microsc. 117:233-242.

Brakenhoff, G. J., P. Blom, and P. J. Barends. 1979. Confocal
scanning light microscopy with high aperture lenses. J. Microsc.
117:219-232.

I note the above articles do not mention laser.

Brad Amos (2003) wrote in Biology of the Cell 95: 335-342 (history of his and John White's MRC series of confocal scopes ... available online):

"White decided to investigate the confocal microscope, which had been invented by Minsky in 1955 (see Minsky, 1988). The word ’confocal’ seems to have been first used by Brakenhoff and others in 1979 to mean a microscope in which the illumination is confined to a diffraction-limited spot in the specimen and the detection is similarly confined by placing an aperture in front of the detector in a position optically conjugate to the focussed spot. The result of this arrangement is that the response of the instrument to a fluorescent point object falls off approximately according to an inverse fourth-power rule with distance from the plane of focus. This produces an ’optical sectioning’ effect, in which the glare from out-of-focus regions is almost completely eliminated. Brakenhoff et al. (1979 ) had demonstrated this experimentally with microscope objectives of the highest available numerical aperture, of the type used in cell biology, and also verified the prediction that the resolution (as measured by the full-width at half maximum intensity of the point spread function) is improved relative to the nonconfocal microscope by a factor of the square root of 2 (1.414). (In practical microscopes, it is the optical sectioning effect that is more important than the resolution improvement.) The underlying physics was understood (Wilson and Sheppard, 1984): why, then, had the method not been applied earlier to biological fluorescence?


Egger and Petran published their first reflected light tandem scanning scope in 1967 (Science, online). They do not cite Minsky (not surprising - independent invention). "Light reflected from above or below the plane of the object was largely intercepted by the opaque portions of the disc; thus the reflected light image could not be degraded by scattered light reflecting into the microscope."
Clearly a confocal scope, though the word confocal was not used in the paper.


Minsky published as a US patent only.  M. Minsky (1957) U.S. patent #3013467, Microscopy Apparatus.
US Patent Office link: 

3,013,467 356/432 250/215 348/79 359/389    issued December 19, 1961


best wishes with your search,

George





At 11:53 AM 8/22/2007, you wrote:

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Hello.

Does anyone know who (or when/where) the term "confocal"
was actually coined?  I presume it refers to "conjugate focal
planes".  Possibly this is mentioned in Pawley's book, but I alas
do not have a copy.  I also don't know if it was mentioned in Minsky's
original patent or not; it seems that at this time Minsky referred
to the method as "double-focusing" rather than confocal, but I
do not have a copy of the full patent.

thanks for any information,
Don

Donald M. O'Malley
Dept. Biology
Northeastern University

 

George McNamara, Ph.D.
University of Miami, Miller School of Medicine
Image Core
Miami, FL 33010
[hidden email]
[hidden email]
305-243-8436 office