A high-resolution x-ray coded aperture imaging apparatus and method

Abstract

The application discloses a kind of high-resolution x ray coded aperture imaging device and imaging method, belong to short wavelength imaging technical field.The high-resolution x ray coded aperture imaging device of the present application is based on circular aperture transform, the aperture size of the electrically controlled circular aperture diaphragm is changed continuously to obtain the light flux promotion multiple intensity point spread function image and corresponding blurred intensity image, the high-resolution x ray coded aperture imaging method of the present application is on the basis of wiener filtering reconstruction method, using iterative deconvolution method is iteratively reconstructed in frequency domain to the recorded multiple intensity point spread function image and corresponding multiple blurred image, to obtain the high-resolution reconstructed sample image, not only can improve the light flux of x ray coded aperture imaging device, and compared with single image reconstruction mode, can greatly improve imaging resolution.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of high-resolution x ray coded aperture imaging device and imaging method, belong to short wavelength imaging field. BACKGROUND

[0002] When imaging object with x ray as light source, since x ray is easily absorbed by object in the process of propagation, therefore ordinary lens-based imaging method is not applicable to x ray imaging.Coded aperture imaging does not need to use lens, but through a specially designed coding board to encode light beam, since it has higher light transmittance and signal-to-noise ratio, since 1960s, coded aperture imaging has been widely used in short wavelength (x ray, beta ray, etc.) imaging, medical and astronomy and other fields.

[0003] Pinhole imaging as the simplest one of coded aperture imaging method, since its imaging structure is simple, and has higher resolution, so far still be used in x ray imaging field.The resolution of pinhole imaging is determined by its aperture, the smaller the pinhole aperture, the higher the corresponding imaging resolution, but the corresponding light flux is also less, so the exposure time required for imaging is longer.Although there are methods to propose using multi-aperture array imaging to improve light flux, but the corresponding imaging effect is also affected by multi-aperture array modulation.The influence of pinhole aperture on imaging resolution and light flux in coded aperture imaging restricts its application in x ray coded aperture imaging field. SUMMARY

[0004] In order to effectively reduce the influence of pinhole aperture on imaging resolution and light flux in x ray coded aperture imaging, the present application provides a kind of high-resolution x ray coded aperture imaging device and imaging method, the technical solution is as follows:

[0005] The first object of the present application is to provide an x ray coded aperture imaging device, comprising: x ray source 1, along the direction of x ray emitted by the x ray source 1 in turn placing holder 2, electrically controlled circular aperture diaphragm 3 and x ray imaging detector 4;

[0006] The holder 2 is used for placing micro-hole and sample to be measured;The aperture size of the electrically controlled circular aperture diaphragm 3 is adjusted by software control, and is used as coded aperture, and the x ray imaging detector 4 is used to record the light spot after the x ray passes through the micro-hole or the sample to be measured, the electrically controlled circular aperture diaphragm 3.

[0007] Optionally, when acquiring system point spread function, the micro-hole is fixed on the holder 2, the electrically controlled circular aperture diaphragm 3 is controlled by computer to continuously change the size of its circular aperture radius, and the x ray imaging detector 4 records a group of corresponding light spots when the circular aperture radius of the electrically controlled circular aperture diaphragm 3 changes at equal intervals.

[0008] Optionally, the device fixes the sample to be tested on the holder 2 when imaging the sample to be tested, the electrically controlled circular aperture diaphragm 3 is controlled by computer to continuously change the size of the circular aperture radius, and the x-ray imaging detector 4 records a group of corresponding light spots when the circular aperture radius of the electrically controlled circular aperture diaphragm 3 changes at equal intervals.

[0009] Optionally, the size of the micropore is not greater than 100 microns.

[0010] Optionally, the range of the aperture diameter of the electrically controlled circular aperture diaphragm 3 is 0.5mm-5mm.

[0011] Optionally, the resolution of the x-ray imaging detector 4 is at least 256x256.

[0012] The second object of the present application is to provide an x-ray coded aperture imaging method, which is realized based on the above-mentioned x-ray coded aperture imaging device and comprises the following steps.

[0013] Step one: fixing the micropore on the holder 2, turning on the x-ray source 1 so that the x-rays pass through the micropore and the electrically controlled circular aperture diaphragm 3, and the circular aperture radius of the electrically controlled circular aperture diaphragm 3 is R0;

[0014] When the circular aperture radius of the electrically controlled circular aperture diaphragm 3 changes at equal intervals as (R0+ΔR*n), the x-ray imaging detector 4 records the corresponding intensity point spread function image, which is marked as h(x,y;n) (n=1,2,3…), wherein n is the number of changes of the radius of the electrically controlled circular aperture diaphragm, and ΔR is a distance constant.

[0015] Step two: turning off the x-ray source 1, replacing the micropore with the sample to be tested fixed on the holder 2, and turning on the x-ray source 1 again so that the x-rays pass through the sample to be tested and the electrically controlled circular aperture diaphragm 3, and the circular aperture radius of the electrically controlled circular aperture diaphragm 3 is R0;

[0016] When the circular aperture radius of the electrically controlled circular aperture diaphragm 3 changes at equal intervals as (R0+ΔR*n), the x-ray imaging detector 4 records the corresponding blurred intensity image, which is marked as I(x,y;n) (n=1,2,3…).

[0017] Step three: Fourier transform the intensity point spread function image h(x, y; n) and the blurred intensity image I(x, y; n), H(u, v; n) = F{h(x, y; n)}, I(u, v; n) = F{I(x, y; n)}, where F{} is the Fourier transform operator, H(u, v; n) is the frequency spectrum of the intensity point spread function image h(x, y; n) after Fourier transform, I(u, v; n) is the frequency spectrum of the blurred intensity image I(x, y; n) after Fourier transform;

[0018] Step four: guess a random object frequency spectrum distribution O g (u, v; n), the frequency spectrum of the guessed blurred intensity image is represented as I g (u, v; n) = O g (u, v; n)H(u, v; n); g

[0019] Step five: the difference between the frequency spectrum of the guessed blurred intensity image I g (u, v; n) and the frequency spectrum of the actually recorded blurred intensity image I(u, v; n) is detI(u, v; n) = I g (u, v; n) - I(u, v; n);

[0020] Step six: update the guessed object frequency spectrum distribution, obtaining:

[0021]

[0022] Wherein, * represents the conjugate operator symbol;

[0023] Step seven: assign the updated guessed frequency spectrum value O g (u, v; n) to O g (u, v; n), obtaining the updated object frequency spectrum distribution;

[0024] Step eight: calculate the error of the guessed object frequency spectrum distribution after updating, obtaining

[0025]

[0026] Set an error threshold ε0, when ε < ε0, it is considered that the guessed object frequency spectrum distribution O g (u, v; k) and the true object frequency spectrum O(u, v) are close, and O g (u, v; k) is Fourier inverse transformed to obtain the reconstructed high-resolution object distribution o'(x, y) = F -1 {O g '(u, v; k)}, wherein F -1 ​is the inverse Fourier transform operator, k≤n; otherwise, jump to step four, repeat the calculation process of step four to step seven until all intensity point spread function images and blur intensity images are used to calculate the object spectrum as O' g (u,v;n), and O' g (u,v;n) is inverse Fourier transformed to obtain the reconstructed object distribution o'(x,y) = F -1 {O' g '(u,v;n)}.

[0027] Optionally, the number of times of changing the radius of the electrically controlled circular aperture diaphragm is n≤50.

[0028] The present application has the following beneficial effects:

[0029] (1) The x-ray coded aperture imaging device based on circular aperture transformation disclosed in the present application obtains multiple x-ray imaging pictures by continuously changing the aperture size of the electrically controlled circular aperture diaphragm. When the circular aperture continuously changes, the transmitted x-ray light flux is gradually enhanced, thereby improving the light flux of the x-ray coded aperture imaging device.

[0030] (2) The high-resolution x-ray coded aperture imaging method disclosed in the present application is based on the Wiener filter reconstruction method, and uses an iterative deconvolution method to iteratively reconstruct multiple intensity point spread function images and corresponding multiple blur images recorded when the electrically controlled circular aperture continuously changes in the frequency domain, thereby obtaining a high-quality reconstructed sample image, and the imaging resolution is greatly improved compared with a single reconstruction result. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 is a high-resolution x-ray coded aperture imaging device of the present application;

[0033] Wherein, 1-x-ray source, 2-clamp, 3-electrically controlled circular aperture diaphragm, 4-x-ray imaging detector. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0035] Embodiment one:

[0036] The embodiment provides a high-resolution x-ray coded aperture imaging device, referring to Figure 1 The device comprises an x-ray source 1, a holder 2, an electrically-controlled circular aperture diaphragm 3 and an x-ray imaging detector 4 which are sequentially arranged along the direction of x-rays emitted by the x-ray source 1.

[0037] The holder 2 is used for placing a sample to be measured and a micropore, and the size of the micropore is not greater than 100 microns.

[0038] The electrically-controlled circular aperture diaphragm 3 is connected to a computer, and the aperture size of the electrically-controlled circular aperture diaphragm 3 is controlled by software; the electrically-controlled circular aperture diaphragm 3 is used as a coded aperture.

[0039] All the optical elements are kept on the optical axis, the aperture range of the electrically-controlled circular aperture diaphragm 3 is 0.5mm-5mm, the aperture of the circular aperture diaphragm can be adjusted by software on the computer, and the resolution of the x-ray imaging detector 4 is at least 256*256.

[0040] The working process of the device is as follows: the micropore is fixed on the holder 2, the x-ray source 1 is turned on, and x-rays pass through the micropore and the electrically-controlled circular aperture diaphragm 3; when the radii of the circular apertures of the electrically-controlled circular aperture diaphragm 3 are changed at equal intervals, the x-ray imaging detector 4 records corresponding intensity point spread function images; then, the x-ray source 1 is turned off, the micropore is replaced by the sample to be measured and fixed on the holder 2, and the x-ray source 1 is turned on again, so that x-rays pass through the sample to be measured and the electrically-controlled circular aperture diaphragm 3; when the radii of the circular apertures of the electrically-controlled circular aperture diaphragm 3 are changed as before, the x-ray imaging detector 4 records corresponding blurred intensity images. The collected intensity point spread function images and corresponding blurred intensity images can be used to iteratively reconstruct a high-resolution sample image to be measured.

[0041] Embodiment two

[0042] The embodiment provides a high-resolution x-ray coded aperture imaging method, and the method is based on the imaging method of the high-resolution x-ray coded aperture imaging device provided in embodiment one, and the method comprises the following steps.

[0043] 1) the micropore is fixed on the holder 2, the x-ray source 1 is turned on, and x-rays pass through the micropore and the electrically-controlled circular aperture diaphragm 3, the radius of the circular aperture of the electrically-controlled circular aperture diaphragm is R0; when the radii of the circular apertures of the electrically-controlled circular aperture diaphragm 3 are changed at equal intervals as (R0+ΔR*n), the x-ray imaging detector 4 records corresponding intensity point spread function images, which are marked as h(x,y;n) (n=1,2,3…), wherein n is the number of times of changes of the radius of the electrically-controlled circular aperture diaphragm and n≤50, and ΔR is a distance constant.

[0044] 2) Close the x-ray source 1, replace the micro-hole with the sample to be measured fixed on the holder 2, and then open the x-ray source 1 so that the x-rays pass through the sample to be measured and the electrically controlled circular aperture diaphragm 3 with a circular aperture radius of R0. When the circular aperture radius of the electrically controlled circular aperture diaphragm 3 is increased at equal intervals as (R0+ΔR*n), the x-ray imaging detector 4 records the corresponding blurred intensity image, marked as I(x,y;n) (n=1,2,3…);

[0045] 3) Fourier transform the intensity point spread function image h(x,y;n) and the blurred intensity image I(x,y;n), H(u,v;n)=F{h(x,y;n)}, I(u,v;n)=F{I(x,y;n)}, where F{} is the Fourier transform operator, H(u,v;n) is the frequency spectrum of the intensity point spread function image h(x,y;n) after Fourier transform, and I(u,v;n) is the frequency spectrum of the blurred intensity image I(x,y;n) after Fourier transform.

[0046] 4) Guess a random object spectrum distribution O g (u,v;n), then the frequency spectrum I g (u,v;n) of the guessed blurred intensity image can be expressed as I g (u,v;n)=O g (u,v;n)H(u,v;n);

[0047] 5) The difference between the frequency spectrum I g (u,v;n) of the guessed blurred intensity image and the frequency spectrum I(u,v;n) of the actually recorded blurred intensity image is detI(u,v;n)=I g (u,v;n)-I(u,v;n);

[0048] 6) Update the guessed object spectrum distribution to obtain

[0049]

[0050] Wherein, * represents the conjugate operator symbol;

[0051] 7) Assign the updated guessed spectrum value O g (u,v;n) to O g (u,v;n), to obtain the updated object spectrum distribution;

[0052] 8) Calculate the error of the guessed object spectrum distribution after updating to obtain

[0053]

[0054] Set an error threshold ε0, when ε<ε0, it is considered that the guessed object spectrum distribution O'g (u,v;k) and the real object spectrum O(u,v) are close, O g (u,v;k) is inverse Fourier transformed to obtain the reconstructed high-resolution object distribution o'(x,y)=F -1 {O' g '(u,v;k)}, where F -1 {} is an inverse Fourier transform operator, k≤n; otherwise, jump to step four, repeat the calculation process of steps four to seven until all intensity point spread function images and blurred intensity images are used to calculate the object spectrum O g (u,v;n), and inverse Fourier transform O g (u,v;n) to obtain the reconstructed object distribution to be imaged o'(x,y)=F -1 {O' g '(u,v;n)}.

[0055] Some steps in the embodiments of the present application can be implemented by software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0056] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An X-ray coded aperture imaging device, characterized in that, The device includes: an X-ray source (1), a clamp (2) placed sequentially along the X-ray direction emitted by the X-ray source (1), an electrically controlled circular aperture (3), and an X-ray imaging detector (4); The holder (2) is used to place the micropore and the sample to be tested; the aperture size of the electrically controlled circular aperture (3) is controlled and adjusted by software and is used as the coded aperture; the X-ray imaging detector (4) is used to record the light spot after the X-ray passes through the micropore or the sample to be tested and the electrically controlled circular aperture (3); The imaging process of the device includes: Step 1: Fix the microhole on the holder (2), turn on the X-ray source (1) so that the X-ray passes through the microhole and the electrically controlled circular aperture (3), the radius of the circular aperture of the electrically controlled circular aperture (3) is R0; When the radius of the circular aperture of the electrically controlled circular aperture (3) increases at equal intervals of (R0 + ΔR * n), the x-ray imaging detector (4) records the corresponding intensity point spread function image, labeled as h(x, y; n) (n = 1, 2, 3...), where n is the number of times the radius of the electrically controlled circular aperture changes, and ΔR is a distance constant; Step 2: Turn off the X-ray source (1), replace the micro-hole with the sample to be tested and fix it on the holder (2), turn the X-ray source (1) back on, so that the X-rays pass through the sample to be tested and the electrically controlled circular aperture (3), the circular aperture radius of the electrically controlled circular aperture (3) is R0; When the radius of the circular aperture of the electrically controlled circular aperture (3) increases at equal intervals of (R0+ΔR*n), the X-ray imaging detector (4) records the corresponding blurred intensity image, labeled as I(x,y;n) (n=1,2,3…); Step 3: Perform Fourier transforms on the intensity point spread function image h(x,y;n) and the blurred intensity image I(x,y;n), where H(u,v;n) = F{h(x,y;n)} and I(u,v;n) = F{I(x,y;n)}, where F{} is the Fourier transform operator, H(u,v;n) is the spectrum of the intensity point spread function image h(x,y;n) after Fourier transform, and I(u,v;n) is the spectrum of the blurred intensity image I(x,y;n) after Fourier transform. Step 4: Guess the spectral distribution O of a random object g (u,v;n), then the spectrum I of the guessed blurred intensity image. g (u,v;n) is represented as I g (u,v;n)=O g (u,v;n)H(u,v;n); Step 5: The spectrum I of the guessed blur intensity image g The difference between (u,v;n) and the spectrum I(u,v;n) of the actual recorded blurred intensity image is detI(u,v;n) = I g (u,v;n)-I(u,v;n); Step Six: Update the guessed object spectral distribution to obtain: Where * represents the conjugate operator; Step 7: Update the guessed spectrum value O' g (u, v; n) are assigned to O g (u,v;n), to obtain the updated object spectrum distribution; Step 8: Calculate the error of the guessed object spectral distribution in the updated value, and obtain... Set an error threshold ε0, and consider the guessed object spectral distribution O' to be true when ε < ε0. g (u,v;k) is close to the real object spectrum O(u,v), and for O' g The reconstructed high-resolution object distribution o'(x,y) = F can be obtained by performing an inverse Fourier transform on (u,v;k). -1 {O' g '(u,v;k)}, where F -1 {} represents the inverse Fourier transform operator, k≤n; otherwise, jump to step four and repeat the calculation process from step four to step seven until all intensity point spread function images and blur intensity images have been used to calculate the object spectrum as O'. g (u,v;n), for O' g Performing an inverse Fourier transform on (u,v;n) yields the reconstructed object distribution o'(x,y)=F -1 {O' g '(u,v;n)}.

2. The X-ray coded aperture imaging device according to claim 1, characterized in that, When the device acquires the system point spread function, it fixes the micro-hole on the holder (2). The electronically controlled circular aperture (3) is continuously changed in size by computer control. The X-ray imaging detector (4) records a set of corresponding light spots when the circular aperture radius of the electronically controlled circular aperture (3) increases at equal intervals.

3. The X-ray coded aperture imaging device according to claim 1, characterized in that, When imaging the sample to be tested, the device fixes the sample to be tested on the holder (2). The electronically controlled circular aperture (3) is continuously changed in size by computer control. The X-ray imaging detector (4) records a set of corresponding light spots when the circular aperture radius of the electronically controlled circular aperture (3) increases at equal intervals.

4. The X-ray coded aperture imaging device according to claim 1, characterized in that, The size of the micropore is no greater than 100 micrometers.

5. The X-ray coded aperture imaging device according to claim 1, characterized in that, The aperture diameter of the electrically controlled circular aperture stop (3) varies from 0.5 mm to 5 mm.

6. The X-ray coded aperture imaging device according to claim 1, characterized in that, The resolution of the x-ray imaging detector (4) is at least 256×256.

7. An X-ray coded aperture imaging method, characterized in that, The method is implemented based on the X-ray coded aperture imaging device according to any one of claims 1-6, and includes: Step 1: Fix the microhole on the holder (2), turn on the X-ray source (1) so that the X-ray passes through the microhole and the electrically controlled circular aperture (3), the radius of the circular aperture of the electrically controlled circular aperture (3) is R0; When the radius of the circular aperture of the electrically controlled circular aperture (3) increases at equal intervals of (R0 + ΔR * n), the x-ray imaging detector (4) records the corresponding intensity point spread function image, labeled as h(x, y; n) (n = 1, 2, 3...), where n is the number of times the radius of the electrically controlled circular aperture changes, and ΔR is a distance constant; Step 2: Turn off the X-ray source (1), replace the micro-hole with the sample to be tested and fix it on the holder (2), turn the X-ray source (1) back on, so that the X-rays pass through the sample to be tested and the electrically controlled circular aperture (3), the circular aperture radius of the electrically controlled circular aperture (3) is R0; When the radius of the circular aperture of the electrically controlled circular aperture (3) increases at equal intervals of (R0+ΔR*n), the X-ray imaging detector (4) records the corresponding blurred intensity image, labeled as I(x,y;n) (n=1,2,3…); Step 3: Perform Fourier transforms on the intensity point spread function image h(x,y;n) and the blurred intensity image I(x,y;n), where H(u,v;n) = F{h(x,y;n)} and I(u,v;n) = F{I(x,y;n)}, where F{} is the Fourier transform operator, H(u,v;n) is the spectrum of the intensity point spread function image h(x,y;n) after Fourier transform, and I(u,v;n) is the spectrum of the blurred intensity image I(x,y;n) after Fourier transform. Step 4: Guess the spectral distribution O of a random object g (u,v;n), then the spectrum I of the guessed blurred intensity image. g (u,v;n) is represented as I g (u,v;n)=O g (u,v;n)H(u,v;n); Step 5: The spectrum I of the guessed blur intensity image g The difference between (u,v;n) and the spectrum I(u,v;n) of the actual recorded blurred intensity image is detI(u,v;n) = I g (u,v;n)-I(u,v;n); Step Six: Update the guessed object spectral distribution to obtain: Where * represents the conjugate operator; Step 7: Update the guessed spectrum value O' g (u, v; n) are assigned to O g (u,v;n), to obtain the updated object spectrum distribution; Step 8: Calculate the error of the guessed object spectral distribution in the updated value, and obtain... Set an error threshold ε0, and consider the guessed object spectral distribution O' to be true when ε < ε0. g (u,v;k) is close to the real object spectrum O(u,v), and for O' g The reconstructed high-resolution object distribution o'(x,y) = F can be obtained by performing an inverse Fourier transform on (u,v;k). -1 {O' g '(u,v;k)}, where F -1 {} represents the inverse Fourier transform operator, k≤n; otherwise, jump to step four and repeat the calculation process from step four to step seven until all intensity point spread function images and blur intensity images have been used to calculate the object spectrum as O'. g (u,v;n), for O' g Performing an inverse Fourier transform on (u,v;n) yields the reconstructed object distribution o'(x,y)=F -1 {O' g '(u,v;n)}.

8. The X-ray coded aperture imaging method according to claim 7, characterized in that, The number of times the radius of the electrically controlled circular aperture changes is n≤50.

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