基于环孔法的辐射成像系统低频模糊效应研究

王东明; 尤文豪; 杨高照; 张成俊; 贾清刚; 黄展常; 陈进川; 叶繁; 章法强; 游海波

doi:10.11884/HPLPB202537.250211

基于环孔法的辐射成像系统低频模糊效应研究

doi: 10.11884/HPLPB202537.250211

1.
中国工程物理研究院核物理与化学研究所，中子科学与技术全国重点实验室，四川绵阳 621999
2.
北京应用物理与计算数学研究所，北京 100088

基金项目: 国家自然科学基金项目(52072183、12175206)；中子科学与技术全国重点实验室基金项目（NST20240205）

详细信息

作者简介:
王东明，xjtuwdm@foxmail.com

通讯作者:
尤文豪，1985971446@qq.com。

中图分类号: TL816.3
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- 文章访问数: 24
- HTML全文浏览量: 10
- PDF下载量: 3
- 被引次数: 0
出版历程
- 收稿日期: 2025-07-14
- 修回日期: 2025-09-01
- 录用日期: 2025-09-01
- 网络出版日期: 2025-09-10

Experimental study on long-range blur of radiation imaging system by ring-aperture method

1.
National Key Laboratory of Neutron Science and Technology, Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621999, China
2.
Institute of Applied Physics and Computational Mathematics, Beijing 100088, China

摘要

摘要: 辐射成像技术作为一种重要的诊断手段，被广泛应用于惯性约束聚变、闪光照相等各类科学装置上。实践中发现，成像系统点扩散函数通常存在预期之外的低频成分，导致图像出现低频模糊退化、图像灰度分布与射线注量分布之间呈现复杂的非线性关系，进而干扰源区强度分布或客体密度分布等关键物理量的诊断分析。由于点扩散函数低频成分强度极低，实验测量难度较大，其具体来源及份额目前尚未明确。针对这一难题，提出了基于环孔法的点扩散函数低频成分测量方法，首次获得了辐射成像系统点扩散函数低频成分的直接测量结果，将测量下限扩展至点扩散函数峰下10⁻⁶量级。同时，发现了闪烁屏表面状态对低频成分存在显著影响；将闪烁屏的非成像面涂覆黑色吸光材料后，可大幅降低闪烁屏导致的低频模糊。
- 辐射成像 /
- 图像退化 /
- 低频模糊 /
- 点扩散函数 /
- 闪烁屏
Abstract: Background
The radiation imaging technology, as an important diagnostic, has been widely used in scientific devices such as inertial confinement fusion and flash photography. It has been found that unexpected low-frequency components usually exit in the point spread function (PSF) of radiation imaging system, leading to the so-called low-frequency blur or long-range blur. Because of long-range blur, the image grayscale varies nonlinearly with the ray flux, which in turn interferes with the analysis of the object density or the source intensity. An experimental measurement of the low-frequency components is challenging because of the extremely low intensity. The specific sources of low-frequency components are not very clear currently.
Purpose
This study aims to address these challenges by proposing a new experimental method for the low-frequency components. The goal is to ensure the reliability of the measurement data on low-frequency components and to identify the main sources of low-frequency components.
Methods
A series of experiments were conducted on different components of the imaging system. A collimator called ring-aperture is used to modulate the x-ray or optical photons into a circular pattern, which led to a significant increase in the signal strength from low-frequency components by orders of magnitude.
Results
A direct measurement result of the low-frequency components was obtained for the first time, and the measurement lower limit was extended to 10⁻⁶ orders below the peak of PSF. Experiments shown that the surface state of scintillators can have a significant impact on low-frequency components. By blackening the non-light-emitting surface, the low-frequency components caused by scintillator can be reduced by 22%～62%.
Conclusions
The ring- aperture method provides a reliable experimental approach for measuring low-frequency components of PSF. The research results indicate that optical photon transport is an important factor leading to long-range blur. By surface treatment of scintillators, such as blackening and polishing, long-range blur can be effectively suppressed.
- radiation imaging /
- image degradation /
- long-range blur /
- PSF /
- scintillator

HTML全文

图 1 环孔法测量过程原理图

Figure 1. Experimental setup

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图 2 环孔准直器实物图

Figure 2. The ring-aperture

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图 3 不同实验条件下的环孔图像

Figure 3. Images of the ring-aperture

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图 4 不同实验条件下的刃边图像

Figure 4. Images of the knife-edge

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图 5 PSF低频成分强度分布

Figure 5. The low-frequency component of PSF

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图 6 不同实验条件下的ESF和PSF

Figure 6. The ESF and PSF

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图 7 闪烁屏中能量沉积分布的模拟结果

Figure 7. Simulations of energy deposition in scintillators

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图 8 Geant4模拟模型（仅展示了到达像面的光子径迹）

Figure 8. The Geant4 simulation setup

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图 9 不同闪烁屏对应的PSF模拟结果

Figure 9. Simulations of PSF

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表 1 不同PSF测量方法的定性比较

Table 1. Comparison of different PSF measurement methods

method	formula	prior information	data processing methods	applications	experimental conditions
knife-edge method	$ \displaystyle\int_{ - \infty }^{ + \infty } {{H_{PSF}}(x,y)} dy = \dfrac{d}{{dx}}{H_{ESF}}(x) $	PSF should be circularly and symmetrically distributed	solving ill posed inverse problems and is sensitive to measurement errors	usually used for high-frequency component measurement	low source strength requirements, good radiation shielding, high dynamic range recording unit
point source method	$ {H_{PSF}}(x,y) $	——	no need to solve ill posed problems	usually used for high-frequency component measurement	high source strength, good radiation shielding, high dynamic range recording unit
ring-aperture method	$ {H_{PSF}}(R) = \dfrac{1}{{2\pi }}\displaystyle\int_0^{2\pi } {{H_{PSF}}(R,\theta )} d\theta $	PSF should be circularly and symmetrically distributed	no need to solve ill posed problems	suitable for low-frequency component measurement, but not for high-frequency component measurement	the requirements for source strength, radiation shielding, and dynamic range of recording units are relatively low

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表 2 主要部组件

Table 2. Main components

components	model	identifier	specifications	function
scintillator	plastic scintillator EJ262	EJ262-1	ϕ124 mm×5 mm，front and back surfaces are polished with roughness R_a=0.2 μm, the side surface is ground	image conversion
	plastic scintillator EJ262	EJ262-2	ϕ124 mm×5 mm，front and back surfaces are polished with roughness R_a=0.2 μm, the side surface is ground, black paint is applied to non-optical surfaces
	inorganic scintillator LYSO: Ce	LYSO-1	ϕ124 mm×5 mm，front and back surfaces are polished with roughness R_a=20 nm
	inorganic scintillator LYSO: Ce	LYSO-2	ϕ124 mm×5 mm，front and back surfaces are polished with roughness R_a=20 nm, black paint is applied to non-optical surfaces
imaging module	Integrated optical imaging module	——	field of view: ϕ120 mm image size: ϕ22 mm spatial resolution: 5 lp/mm	optical imaging and light shielding
camera	Scientific ICCD camera	——	pixels：2 048×2 048 data range：16 bit dynamic range：10 000 spatial resolution：28.5 lp/mm	image selection, enhancement and recording

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表 3 实验配置

Table 3. experimental configuration

source	component to be tested	collimator	purpose
pulsed X-ray generator	Scintillator + lens + camera	ring-aperture 1#、2#、3#	measure the low-frequency components of PSF excited by X rays
		tungsten sharp edge	measure PSF excited by X rays
		tungsten plate	Measure the radiation background in the X-ray field
		——	Measure the flat-field image
pulsed uniform visible light source	lens + camera	ring mask 1#、2#、3#	measure the low-frequency components of the PSF of lens and camera
pulsed uniform visible light source	lens + camera	——	measure the flat-field image

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表 4 PSF在不同距离r处的实测值

Table 4. Measured values of PSF at different distances

source	component to be tested	H_PSF(r), normalized by total intensity
source	component to be tested	r=10.0 mm	r=20.0 mm	r=30.0 mm
pulsed X-ray generator	EJ262-1+lens+camera	7.02E-7 (1±9%)	1.30E-7 (1±16%)	7.72E-8 (1±19%)
	EJ262-2 (blackening)+lens+camera	4.02E-7 (1±21%)	5.46E-8 (1±36%)	2.90E-8 (1±22%)
	LYSO-1+ lens+camera	3.57E-7 (1±8%)	5.79E-8 (1±16%)	3.00E-8 (1±20%)
	LYSO-2 (blackening)+ lens+camera	2.76E-7 (1±9%)	3.90E-8 (1±15%)	1.77E-8 (1±25%)
pulsed uniform visible light source	lens+camera	1.33E-7 (1±9%)	6.87E-9 (1±23%)	4.94E-9 (1±14%)
Note: the confidence factor for uncertainty is k=1.

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表 5 模拟计算条件

Table 5. Simulation conditions

number	research subject	front surface	back surface	side surcafe	Geant4 physics list related to optical photons
1	the influence of specular reflection	polished	polished	polished	scintillation boundary absorption
2	the influence of diffuse reflection	ground	ground	ground
3	the influence of lateral dispersion	ground	ground	ground+ black paint
4	the influence of diffuse reflection occurring on the side	ground+ black paint	ground	ground+ black paint
5	the influence of internal scattering	polished	polished	ground+ black paint	scintillation boundary absorption a custom scattering process
5	the influence of internal scattering	polished+ black paint	polished	ground+ black paint

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