Modeling the encoding structure and spatial resolution of
photon counting imagers with Vernier anode readout
Hao Yang (杨 颢)
1,
*, Baosheng Zhao (赵宝升)
2
, Qiurong Yan (鄢秋荣)
3
,
and Yong’an Liu (刘永安)
2
1
Shaanxi Key Laboratory of Optical Information Technology, School of Science, Northwestern
Polytechnical University, Xi’an 710072, China
2
State Key Labor atory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics,
Chinese Academy of Sciences, Xi’an 710119, China
3
Department of Electronic Information Engineering, Nanchang University, Nanchang 330031, China
*Corresponding author: yhao@nwpu.edu.cn
Received August 25, 2016; accepted November 8, 2016; posted online November 30, 2016
We present the spatial resolution estimation methods for a photon counting system with a Vernier anode.
A limiting resolution model is provided according to discussions of surface encoding structure and quantized
noise. The limiting resolution of a Vernier anode is revealed to be significantly higher than that of a microchannel
plate. The relationship between the actual spatial resolution and equivalent noise charge of a detector is estab-
lished by noise analysis and photon position reconstruction. The theoretical results are demonstrated to be in
good agreement with the experimental results for a 1.2 mm pitch Vernier anode.
OCIS codes: 110.3010, 030.5260, 040.7480.
doi: 10.3788/COL201614.121102.
Position
[1–4]
and arrival time
[5–8]
recordings of single pho-
tons can be achieved by photon counting detection, which
realizes ultra-weak radiation imaging with high spatial
and time resolutions. Thus, photon counting imagers have
been widely used in many important fields such as space
detection, astrono my, biomedicine, nuclear physics, quan-
tum key distribution (QKD), photon counting micros-
copy, etc.
[8–13]
. The previous work from Lapington et al.
reported a Vernier-based imager with a spatial resolution
of ∼10 μm FWHM result, near to the pore size of micro-
channel plates (MCPs), which reveals that a Vernier
structure determined spatial resolution can exceed the
limit of an MCP pore size by structure optimization
and reado ut noise suppression
[14,15]
. However, the relation-
ship between spatial resolution and the anode encoding
structure with or without readout noise is still unclear.
In other words, the estimation models of the limiting
resolution determined by the encoding structure and
the actual spatial resolution determined by readout noise
are not established.
In this Letter, we provide the estimation methods of the
limiting resolution and the actual spatial resolution.
The influence factors of spatial resolution (including the
limiting and actual resolutions) have been analyzed.
The limiting resolution model is deduced by calculations
of the encoding structure and the charge cloud on a Ver-
nier anode. The inner relationship between the actual spa-
tial resolution and the normalized noise characterized by
the equivalent noise charge (ENC) has been revealed
within a low noise range by noise analysis during the de-
coding process. The influence mechanism of the noise and
anode structure on spatial resolution can be well under-
stood using this model. Additionally, the point spread
function (PSF)
[16,17]
for image super-resolution at low light
illumination may be well characterized by using the
resolution estimation model.
A photon counting imaging system based on a Vernier
anode usually consists of the detector, the readout circuit,
and the data acquisition and decoding subsystem
[1–4]
.
The detector consists of an input window, photocathode,
MCP, Vernier anode, vacuum packaging shell, etc.
Figure
1 shows a typical photon counting imaging system
based on a Vernier anode showing noise sources. The
working principle can refer to Refs. [
3,14,15].
Fig. 1. Sketch of the Vernier anode-based imaging system show-
ing the distribution noise of the charge cloud, electronic noise,
and quantized noise of the data acquisition subsystem.
COL 14(12), 121102(2016) CHINESE OPTICS LETTERS December 10, 2016
1671-7694/2016/121102(5) 121102-1 © 2016 Chinese Optics Letters