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Thanks to everybody for all the interesting comments about this topic.

Juan Luis

James Pawley escribió:
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hi Juan,
>
> I encourage you to pursue the use of this instrument for looking at 
> transparent inorganic materials!
>
> However, I also echo Mike's caution about the effects of surface angle 
> and add the point that "materials" seldom have a refractive index of 1.
>
> When using the no-coverslip dry objectives common in materials, you 
> have spherical aberration the moment you penetrate into the material 
> and any measurements in z will require at least a 
> "back-of-the-envelope" correction for the actual RI of the material 
> between the near surface and the focus plane. You will get different 
> results with different lenses because of differences in NA (and 
> therefore SA).
>
> You can reduce this all somewhat if you can immerse your "rock" in oil 
> and use an oil objective but be careful that the "rock" doesn't get a 
> chance to touch (i.e., "Scratch!") the front element of the objective.
>
> While the oil will help some, as the "rock" is unlikely to have an RI 
> of exactly 1.515, there will still be some SA and the directional 
> dependence of surface reflections can still be a problem.
>
> On the other hand, you should be able to get good contrast from small 
> inclusions. If these are small with respect to the wavelength of the 
> light, they scatter in all directions rather than reflecting. (hence, 
> "backscattered light" rather than "reflected light")
>
> It turns out that living cells are often full of very small highly 
> refractile objects are can be imaged very well using this signal.
>
> Cheers,
>
> Jim P.
>
>
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>>
>> It's typically done using interferometry. Reflection mode in confocal 
>> can be tricky because the signal depends on the tilt of the surface 
>> (see P.C.Cheng's articles in Confocal Handbook)
>>
>> Mike
>>
>> -----Original Message-----
>> From: Confocal Microscopy List [mailto:[log in to unmask]] 
>> On Behalf Of Juan Luis Ribas
>> Sent: Tuesday, November 06, 2007 1:19 PM
>> To: [log in to unmask]
>> Subject: reflection mode in material science
>>
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>>
>> Dear all,
>> Several groups in our University are moving now to the confocal to
>> perform z profiles of materials. I would like to get more information
>> about the way of doing a correct adquisition in reflection mode to
>> ensure a realistic depth map. I've found that a z profile in the same
>> region with different air objectives give very different measurements,
>> so I'm not sure which is the real value. And is very difficult to obtain
>> some useful information about this technique.
>> I'll be very grateful if someone could recomend me  some link, book or
>> paper about reflection mode and z profile caracterization in materials.
>> All the best
>>
>> Juan Luis
>>
>> -- 
>> Juan Luis Ribas, PhD
>> Servicio de Microscopía
>> Centro de Investigación, Tecnología e Innovación
>> Universidad de Sevilla
>> Av. Reina Mercedes 4b
>> 41012 Sevilla
>>
>> Tfno: 954559983
>
>

-- 
Juan Luis Ribas
Servicio de Microscopía
Centro de Investigación, Tecnología e Innovación
Universidad de Sevilla
Av. Reina Mercedes 4b
41012 Sevilla

Tfno: 954559983