Photon Factory Activity Report 2014 #32(2015) B

BL-11A/2014G148

Effect of Contrast Enhancement Prior to Iteration Procedure
on Image Correction for Soft X-ray Projection Microscopy
Graduate School of Advanced Integration Science, Chiba Univ., Chiba-shi, Chiba, 263-8522, Japan
2Tokyo Metropolitan Industrial Technol. Res. Inst., Koto-ku, Tokyo 135-0064, Japan3
School of Engineering, Tokai Univ., Hiratsuka-shi, Kanagawa, 259-1292, Japan

I max − I minmax

Two kinds of noise filtering methods were used to avoid
unwanted noise enhancement due to the contrastenhancement. The first filter performs a filtering for small
noises not exceed 1.06 times of the baseline shown in Fig.1.
An average of gray-scales of the image frame was used asbaseline. The value of 1.06 was set by an earlier study
performed for checking of background noise distribution.
The second filter performs a filtering for big noises
emanated rapidly and individually.
Results of iteration procedure on the projection images
treated previously with contrast enhancement are shown in
Table 1 for a latex particle (10 mmφ) and a chromosome.
The gray-scale change due to contrast enhancement and theeffect of iteration correction is also illustrated in Fig.2. The
contrast enhancement method was effective especially forthe correction of the chromosome images, which are notcorrectable by iteration procedure only. The results
suggested that sharpen and deepen the image contrast madeenough difference for the iteration correction between thecontrast of diffraction fringes and background gray-scaledistributions. In the case of a chromosome image whichshown in Table 1, the diffraction fringe contrast wereenhanced by about 1.7 times as described with blue andgreen curves on the Fig.2. As a result, latex-particle image      



I ' max

65635

I max

I min (baseline)

I 'min  

0

Fig.1 Contrast Enhanced Method.
Table 1 Representative images for contrast enhancement effect(Mag.219) at Beam Line 11A.
Projection

1mm

Correction

1mmContrast
enhancing

1mm

Iterationcorrection

5Pm
5Pm

5Pm

1mm

CorrectionGrayscale

Contrast Enhancement
When applying the linear contrast enhancement method
which is calculated by formula (1), minimum andmaximum values of original gray-scale data in theprojection image are assigned to a new set of values so thatthe full range of available gray-scale values can be utilized.
Cross-sectional line graphs before and after contrast
enhancement on projection image are illustrated in Fig.1.
In this model, diffraction fringe height could be increased
by about 2 times as described with arrows in Fig.1.
I(i, j) − I min(1)I '(i, j) =⋅I'observed in any magnification could be corrected, while
the chromosome image of the highest magnification of<219 is well corrected. The chromosome image of >219
was still remained as the insufficient result.

ChromosomeIntroduction
Projection soft X-ray microscopy has characteristics ofeasy zooming function, simple optical layout and so on.
However the image is blurred by the diffraction of X-rays,leading the spatial resolution to be worse. In this study, theblurred images have been corrected by an iteration
procedure, i.e., Fresnel and inverse Fresnel transformations
repeated. It was not enough to some images showing too
low contrast, especially at high magnification. In thepresent study, we installed a contrast enhancement method
into the blurred observation image to make the diffraction
fringes clearer prior to the iteration procedure only.

Latex (10Pm)

1

Tatsuo SHIINA1*, Jamsranjav ERDENETOGTOKH1, Yasuhito KINJO2, Atsushi ITO3



'G=7334
Projection(Enhanced contrast)Projection(Original)'G=4410









PositionFig.2 Gray-scale distribution on a line of chromosome image.

References[1] T. Shiina et al., PF Activity Report 2013 #31 B 0491(2014)
http://pfwww.kek.jp/acr2013pdf/part_b/pf13b0491.pdf* shiina@faculty.chiba-u.jp