September 10, 2008 / Vol. 6, No. 9 / CHINESE OPTICS LETTERS 661
Correction of ultraviolet single photon counting
image distortion
Xinghua Zhang (
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, Baosheng Zhao (
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, Zhenhua Miao (
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Wei Li (
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, Xiangping Zhu (
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, Yong’an Liu (
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, and Wei Zou (
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State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and
Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119
2
Graduate University of Chinese Academy of Sciences, Beijing 100049
Received March 14, 2008
Single photon counting imaging technology has been widely used in space environment detection, astronomy
observation, nuclear physics, and ultraweak bioluminescence. However, the distortion of the single photon
counting image will badly affect the measurement results. Therefore, the correction of distortion for single
photon counting image is very significant. Ultraviolet single photon imaging system with wedge and strip
anode is introduced and the influence factor leading to image distortion is analyzed. To correct original
distorted image, three different image correction methods, namely, the physical correction, the global
correction, and the local correction, are applied. In addition, two parameters, i.e., the position index and
the linearity index, are defined to evaluate the performance of the three methods. The results suggest
that the correction methods can improve the quality of the initial image without losing gray information of
each counting light spot. And the local correction can provide the best visual inspections and performance
evaluation among the three methods.
OCIS codes: 030.5260, 110.0110, 100.0100.
doi: 10.3788/COL20080609.0661.
With the development of space environment detection,
biology medicine, and nuclear detection technology, sin-
gle photon counting imaging technology
[1−3]
was applied
widely in astronomical observation, biology fluorescent,
and spectroscopic measurement
[4−6]
. The technology can
provide not only the time information of a photon, but
also the position information. However, the distortion of
the original image badly affects the measurements. To
resolve this problem, some measures are implemented to
enhance the performance of the single photon imaging
system. However, only by system improvement the dis-
tortion still exists at image edge. Therefore it is necessary
to adjust the counting image by means of image process-
ing.
In this letter, ultraviolet single photon imaging sys-
tem with wedge and strip anode is introduced and the
influencing factor leading to image distortion of the sys-
tem is analyzed. In order to correct image distortion,
three different image correction methods are applied. In
addition, to evaluate the effect of the three methods, two
parameters are defined to estimate the position distortion
and linearity distortion of the corrected images.
Figure 1 is the sketch of the ultraviolet single photon
imaging system. It consists of Hg lamp, filters, mask, mi-
crochannel plate (MCP), wedge and strip anode (WSA),
charge sensitive amplifier (CSA), shaping amplifier, data
acquisition card (DAQ), and computer. The mask, MCP,
and WSA are in the vacuum chamber. The principle of
the ultraviolet single photon imaging system can be de-
scribed as follow. Firstly, the ultraviolet is weakened
to single photon stream through some filters, the single
photon stream irradiates the MCP surface and produces
second electrons which are multiplied by MCP. Then, the
electron cloud is collected via WSA. Next, the charge sig-
nal is converted to voltage signal through a CSA, which
is shaped and filtered using shaping amplifier, and the
Fig. 1. Sketch of ultraviolet single photon imaging system.
1671-7694/2008/090661-04
c
2008 Chinese Optics Letters