NetNotes
There are two issues, it seems: pixel depth and look-up table. I was a little confused by your statement of low contrast images, for HDR is usually used for high contrast images, where some places are saturated and/or some are lost in the black. That issue beside, with an 8-bit detector signal, one could take two images - at lower and higher gain - and then map the two onto a single 16 or 32 bit image. Then the gray levels need to be compressed into a non-linear scale that allows the wide range to show in a human-detectable fashion. A method used in astronomy is the wavelet-log representation, for example, where the pixel values are converted to a log scale. This allows many orders of magnitude of signal to be represented in a nice way visually. See Starck and Bobin, Astronomical Data Analysis , 2009, Equation (2). Of course, you must start with a high bit-depth image. I wrote an ImageJ macro that does such a wavelet transform, and my meager testing found it to be good for bringing out faint details in 32-bit STEM images. Low contrast images don’t look good, for they get compressed into too few gray levels. I would be glad to send it to you offline, as the listserver doesn’t digest attachments. Larry Scipioni
les@zsgenetics.com Thu Jun 18
We did this for TEM some time ago and finally got round to publishing a little letter on it last year: see Microscopy and Microanalysis 20 1601-4 (2014), DOI: 10.1017/S1431927614012975. Also at
https://www.researchgate.net/publication/266246078_High_ dynamic_range_electron_imaging_the_new_standard . You should be able to find the Digital Micrograph script there too, under supple- mentary resources. It doesn’t help with low contrast samples, but it does help with very high contrast data (e.g. diffraction patterns). For low contrast samples it would be better to use a phase plate ($$$) or a through-focal series to produce an exit wave reconstruction (or in-line holography, however you want to label it). Richard Beanland
contact@integrityscientific.com Thu Jun 18
Thank you all for the suggestions. I confused myself and misspoke when I said low contrast images. Usually when you have an image with very bright or very dark areas in it, you’ll need to take a very low contrast image to make all of the data visible. I just think this is an interesting technique for data as well as artistic reasons that should be able to be applied to EM. Just haven’t found an easy way of making it happen yet. Eric Miller
eric-miller@northwestern.edu Thu Jun 18
TEM: pressurized air vs. nitrogen gas
Yet again a new chapter in the life of a biologist responsible for a FEI Tecnai G20! Our TEM is connected to a N 2 cylinder to deliver the pressure necessary for the valves to work. Now we got a new air compressor with all the necessary filters to avoid having water in the lines so I want to use it to feed the TEM valves with pressurized air. In the water/air rack, we have 2 manometers. The first one limits the pressure to 5 bar, the lines are labeled CCD camera, blow off (whatever it is) and probably the cushioning of the microscope (it is labeled “S34”). The second one is connected to the first one and limits the pressure to 0.3 bar, it is used for the TEM Valves. I am concerned with the use of pressurized air in state of N 2 because the second manometer has a label “N 2 gas”. So my questions: Can I safely connect pressurized air in place of N 2 ? - Is there any reason why I would absolutely need a N 2 line? (e.g., for flushing during the procedure of SF 6 filling, we bring a cylinder next to the microscope). Stephane Nizets nizets2@
yahoo.com Tue May 19
You can use pressurized air as your main air supply. The N 2 line is for back filling as in a filament exchange, column vent or camera vent. Bringing in a gas cylinder when needed works well. John Schreiber
js51@princeton.edu Tue May 19
54 SEM: proximity of sputter coater to SEM
I’m in the process of reorganizing my lab and I currently have my sputter coater and JEOL JCM-6000 Benchtop SEM placed 115 cm apart. My concern is that if the column is open to the atmosphere and the sputter coater is run that the column may get contaminated. Is this a legitimate concern? Lisa Stafford
lstafford@sono-tek.com Wed May 6
With all due respect I think you have your priorities wrong! A sputter coater, like any other piece of equipment using a rotary pump, can be a contamination device due to the pump fluid vapor which is brought out of the pump with the gas. This contamination will pollute the laboratory air, fall on surfaces and on people. But even these problems should not worry you as much as your staff breathing this contaminated air! Please make sure you use the best possible filter on the pump, and change it regularly; to wait until you smell the contamination, in my mind, too late! Alternatively, vent the pump to the outside world. Have in mind that the way to clean out some of the contamination within any rotary pump fluid is to run a high level of air/gas through it. As the sputter coater rotary pump starts to operate it ejects a high level of gas which will contain pump fluid. Even under its actual operating conditions you are purging gas into the system that is also passing through the pump fluid. Add to this that the sputter coater is usually the first instrument to put the specimens under vacuum, thus it has all the vapors from the specimen to cope with. This combination of vapors and chemical reactions within the pump fluid, result in the smell you sense if the filter fitted to the pump is unable to cope. I do hope that this helps you and the many others who should be aware of rotary pump vapors? Steve Chapman
protrain@emcourses.com Thu May 7
STEM: polymer blends
What is the best imaging mode\setup to image polymer blends samples? Actually, I am trying to image a sample that contains PTB7:PC71BM with DIO. Basically what I am looking for is to generate some contrast between these three materials. The first one is a sulfur-rich while the second rich with carbon. DIO is Iodine rich. We tried to use HAADF and dark field imaging in STEM with low convergence angle probe in the objective off mode. Unfortunately, it was not successful. We are not keen to attempt anything with EFTEM, as the doses required to get good signal to noise are rather high and likely to fry the sample. Additionally, finding small amounts of I using EFTEM will be very hard (slow rising edge at a fairly high energy of 619 eV gives very weak signal and therefore requires a huge dose to see it, which probably destroys the sample). Ala’ Afeef
alaa.afeef@
gmail.com Wed May 13 If all you want is contrast then plasmonic imaging in EELS will be much, much lower dose than core loss EELS. Here’s an example of plasmonic EELS imaging of block copolymers which will give you some idea of what can be done this way.
http://www.sciencedirect. com/science/article/pii/S0304399110003256# Zack Gainsforth zackg@
berkeley.edu Wed May 13
STEM-EDS: software quantification
I’ve been trying to decipher the quantification options for our STEM-EDS analysis program. The program is called “Analysis Station” and its sub-program is “MappingProgram.” It gives me three options: * ZAF * Ratio * NET Int. I have figured out what ZAF is, but I’m not sure about the other two. Does anyone know if these routines automati- cally deconvolve overlapping peaks (judging by the appearance of my maps they do…)? Moreover, does anyone happen to have a manual
www.microscopy-today.com • 2015 September
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