September 4, 2013 / Unknown Fast mapping

Close Menu
 


September 4, 2013 / Unknown Fast mapping

Unknown Fast mapping

Time of analysis is an important factor for investigations and a determining factor for fast processes .
What is the fast and ultra-fast Raman imaging? Everything has to be compared and the terminology doesn't matter.

Minimal time of acquisition of Raman spectrum for each pixel of an image is basically limited by CCD detector operation speed (about: 760 µs – 1 ms) and makes in practice about 5 ms. In Confotec NR500 system we apply two modes for Raman imaging. Alongside with CCD detection mode we apply the mode in which PMT is a receiver and the scanning is realized with galvanic mirrors at a fixed sample. We call this mode Fast mapping, rather modestly, considering that the time of acquisition of each pixel of the image is only 3 µs!
And the minimal time of 1001 pixels x 1001 pixels Raman image acquisition is
only 3 s!

Some capabilities of Fast mapping mode have been shown at its application to the investigation of Granite Gneiss India sample (the sample has been supplied by Brno University of Technology). Fast mapping mode allows imaging both at relatively strong signals and maximal signals which are several orders weaker,
if compared with the Raman signal from silicon. Two dry objectives have been applied for the measurements: 100х and 20х.

As an example the confocal (1AU) megapixel (1002001 pixels) images of Granite Gneiss India sample with total measurement time of 3 seconds are shown in Fig.1. The images in Fig. 1 have been obtained with the objective 100х by scanning of maximum sample size e for the given objective (150 μm х 150 μm) at scanning step of 150 nm.

 
 

Fig. 1 Parameters of images

  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 150 μm х 150 μm
  • Number of pixels: 1002001
  • Scanning step: 150 nm
  • Time per 1 pixel: 3 µs
  • Registration time: 3 s
  • Objective: 100х dry
 

Figure 1

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig1a fast mapping unknown

a – sample surface image in the reflected laser light on the wavelength of 488 nm

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig1b fast mapping unknown
b – Raman image of anatase (titanium dioxide) distribution

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig1c fast mapping unknown

c – summarized image of anatase distribution relative to the image of the sample surface in the reflected light
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig1d3D fast mapping unknown 1001
d – summarized axonometric image

 

 

It is possible to choose only an informative part of the obtained image and realize the scanning of the appropriate part of the object with the same number of pixels. As a result, a more detailed image with higher spatial resolution will be obtained. In Fig. 2a the examples of such megapixel (1002001 pixels) images scanned with the step of 43 nm are given. The informative part of the object can be scanned also in a high sensitivity mode. Thus the image with higher ratio signal/noise will be obtained. Examples of such Fast mapping application for imaging are shown in Fig. 2b.  
   Figure 2  
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2 part2 fast mapping unknown v2

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2 part1 fast mapping unknown v2

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2 part3 fast mapping unknown v2
Figure 2a

Figure 2b

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2a fast mapping unknown

anatase
distribution
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2a fast mapping unknown 251

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2b fast mapping unknown

laser
image
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2b fast mapping unknown 251
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2c fast mapping unknown
summed image of anatase distribution relative to the image of sample surface in the reflected light
SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2c fast mapping unknown 251
 SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2d3D fast mapping unknown1001
summed axonometric image
 SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig2d3D fast mapping unknown 251
  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 43 μm х 43 μm
  • Number of pixels: 1002001
  • Scanning step: 43 nm
  • Time per 1 pixel: 3 mcs
  • Registration time: 3seconds
  • Objective: 100х dry

Parameters

  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 43 μm х 43 μm
  • Number of pixels: 63001
  • Scanning step: 172 nm
  • Time per 1 pixel: 43 mcs
  • Registration time: 3 seconds
  • Objective: 100х dry
     


Anatase spectrum in one of the points of the image (100х objective) is given in Fig.3. The Raman line used for imaging is schematically marked with a rectangle.

Figure 3

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig3 fast mapping unknown

Anatase spectrum in one of the points of image 1 (100x objective)

   
     


Photoluminescence from the studied material or from sample impurities is a problem interfering with the detection of Raman images. In Confotec NR500 Raman confocal microscope a specially developed system of removing the photoluminescence is applied for the imaging in Fast mapping mode. Its application is successful regardless of photoluminescence appearance- in the form of separate bright spots distorting Raman image, in the form of photoluminescence background in the whole image or in the case of both photoluminescence appearance simultaneously . In Fig. 4a the anatase distribution obtained with the 20x objective in Fast mapping mode with distortions induced by the photoluminescence in the form of separate bright spots is shown. Separate photoluminescence spots are marked with circles for visual demonstration. In Fig. 4b a real anatase distribution is shown after the photoluminescence distortions have been removed. The image of the same sample area but in CCD detection mode (Mapping mode) after use of Baseline Correction function for the photoluminescence removing is shown for comparison in Fig. 4c. Both images have no distortions induced by the photoluminescence. Anatase spectrum in one of the points of sample (20x objective) is shown in Fig. 4d.

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig4d fast mapping unknown

d - Anatase spectrum in one of the image pixels (20x objective)

 


Figure 4
Demonstration of removing interfering photoluminescence
in the form of separate spots

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig4a fast mapping unknown251

а- Fast mapping image distorted by the photoluminescence. Some photoluminescence spots are marked with circles for visual demonstration.

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig4b fast mapping unknown251

b- real anatase distribution without photoluminescence traces(251 pixel x 251 pixel)

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig4c fast mapping unknown101

c- image of the same sample area obtained in CCD detection mode after use of Baseline correction function for the photoluminescence subtraction

     


Another example of photoluminescence subtraction that totally distorts Raman image and appear both in the form of separate bright spots and in the form of the photoluminescence background in the whole image is shown in Fig. 5.

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig5d fast mapping unknown

d - quartz spectrum in one of the image pixels (20x objective lens)

 


Figure 5
Example of photoluminescence subtraction that totally distorts image

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig5a fast mapping unknown101

a - initial image scanned with Fast mapping mode (101 pixel x 101 pixel ) with 20x objective lens

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig5b fast mapping unknown101

b - Fast mapping image (101 pixel x 101 pixel) of real quartz distribution with no photoluminescence impact

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig5c fast mapping unknown101

c - image of the same sample area scanned with resolution of 21 pixel x 21 pixel obtained with the CCD detection mode after subtraction of photoluminescence

     


Fig. 6-8 shows the examples of Fast mapping mode application for investigation of Granite Gneiss India with 20x objective.

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig6c fast mapping unknown

с - spectrum measured in one of image pixels with Raman lines used for analysis

 

Image parameters in Fig.6

  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 194 μm х 194 μm
  • Number of pixels: 10201
  • Scanning step: 1.94 nm
  • Time per 1 pixel: 4.4 mcs
  • Registration time: 45 s
  • Objective: 20х dry
 


Figure 6

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig6a fast mapping unknown101

a - image obtained at Raman shift ~240 sm-1

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig6b fast mapping unknown101

b - image of the same sample area at Raman shift ~1353 sm-1

     


SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig7b fast mapping unknown

b - spectrum in one of the image pixels with the marked Raman line used for analysis

 

Image parameters in Fig.7

  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 194 μm х 194 μm
  • Number of pixels: 63001
  • Scanning step: 0.776 μm
  • Time per 1 pixel: 0.7 ms
  • Registration time: 45 s
  • Objective: 20х dry

 

 


Figure 7

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig7a fast mapping unknown

a - image of quartz distribution

     


SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig8c fast mapping unknown

c - spectrum in one of image pixels

 

Parameters of the image in Fig.8

  • System: Confotec NR500
  • Mode: Fast mapping
  • Sample: Granite Gneiss India
  • Scanning field: 194 μm х 194 μm
  • Number of pixels: 63001
  • Scanning step: 0.776 μm
  • Time per 1 pixel: 48 µs
  • Registration time: 3 s
  • Objective: 20х dry

 

 


Figure 8

 SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig8a fast mapping unknown

a - image of anatase distribution

 

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. fig8b fast mapping unknown

b - summed image of anatase distribution in relation to the image of the sample surface in the reflected laser light

     


Advantages of Fast mapping mode application
:

 

 

  • High speed of confocal Raman image scanning – up to 3 µs pixel.
  • High spatial resolution. Minimal scanning step – less than 21.5 nm.
    Possibility of selection of resolution depending on size of the investigated area: 
    101 pixel x 101 pixel
    251 pixel х 251 pixel
    501 pixel х 501 pixel
    1001 pixel х 1001 pixel
  • High sensitivity. A special mode for increasing the signal/noise ratio at measurement of weak Raman signals.
  • Combination of high speed, high sensitivity and high resolution allows the fast acquisition of reliable data on distribution of the chemical compound over a sample. When such high-speed and sensitive mode as our Fast mapping is not available the following technique is used for acquisition of chemical compound distribution over a sample: at first a large sample area is measured with a low resolution, and then the informative areas are scanned with higher resolution. However at low resolution a specific compound in a sample may not be found at all, especially if this chemical compound has a form of separate inclusions in a sample.
  • Raman images acquisition with photoluminescence subtraction .
  • Channel Reflection Fast Mapping for acquisition of the same high-speed images with high spatial resolution of the same investigated sample areas but in the reflected laser light. Besides the auxiliary information about a sample obtained in the reflected laser light this channel quickly finds the focused areas of the relief surface of a sample.

author:
Alexander Gvozdev
Leading research engineer