CN115100056B - Associated imaging method for quick focusing - Google Patents

Abstract

The invention discloses a rapid focusing associated imaging method. Performing correlation calculation on the total light field intensity of the contained target information obtained by each k sampling barrel detectors and the light source space intensity obtained by the CCD detectors; removing background noise of the correlated imaging result of every k times of sampling by using a denoising algorithm; the centroid and the size of the target object obtained by sampling every k times are determined through zero-order moment, first-order moment and second-order moment, so that the target object is focused; substituting the obtained mass center and the size of the target object into a reference light path in the correlation calculation to obtain a new reference light signal, carrying out correlation calculation again with the object light, and removing n imaging results with poor quality according to priori information; and (3) superposing m-n times of new associated imaging results to obtain an average value of the sizes of the target objects obtained m-n times, and finally obtaining the images of the target objects with motion blur removed. The invention can realize the rapid focusing of the moving object and eliminate the influence of motion blur on the final imaging, and has scientific principle, simple device and easy realization.

Description

A fast focusing correlation imaging method

Technical Field

The invention relates to the technology of two light signal correlation, target positioning and image reconstruction, and in particular to a fast-focus correlation imaging method, which can be applied to the imaging field.

Background Art

Correlation imaging is a correlation measurement based on light field intensity, which has strong non-locality. That is, an object is placed on one optical path, and the image of the object can be presented on another optical path through coincidence measurement. Correlation imaging has become an important research direction in the fields of national defense, military, medicine, etc. because it can break through the Rayleigh diffraction limit and has strong anti-interference ability.

In practical applications, there is usually relative motion between the imaging system and the target, the instability of the imaging platform or the vibration of the detector, which can lead to blurred results of correlation imaging. Therefore, in recent years, more and more studies have begun to focus on the correlation imaging of moving objects.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a fast focusing associative imaging method, which has a simple principle, is easy to implement, has practical application value, can achieve fast focusing on targets in associative imaging, and can eliminate motion blur and restore high-quality imaging results in the case of moving targets and detector jitter. It has a simple structure and low economic cost.

In order to achieve the above object, the present invention provides the following method:

(1) The pseudothermal light output by the laser source is divided into two identical parts by a beam splitter, namely, a first split light and a second split light;

The first split light beam illuminates the target object and is detected by a single-pixel bucket detector without spatial resolution capability to obtain a total intensity of the light field containing target information, namely, object light;

The second split light beam is detected by the CCD detector after free transmission to obtain the spatial intensity of the light source, i.e., the reference light;

(2) Perform a second-order correlation calculation between the total intensity of the light field containing the target information obtained by each k sampling and the spatial intensity of the light source;

(3) using a denoising algorithm to eliminate the background noise in the associated imaging results of the target object obtained every k sampling times;

(4) Determine the center of mass and size of the target object obtained by each k sampling through the zero-order moment, the first-order moment, and the second-order moment to achieve focusing on the target object;

(5) Substitute the obtained target object's centroid and size into the reference light path in the correlation calculation, that is, the reference light only takes the positioning range at the corresponding time interval;

(6) The new reference light obtained by each k-times sampling is recalculated with the object light, and n poor-quality imaging results are removed based on prior information;

(7) The average value of the target object size obtained m-n times is taken as the new correlation imaging results, and then superimposed to obtain the image of the target object with motion blur removed.

In the above technical method, the laser source consists of a laser and rotating frosted glass.

In the above technical method, the target object needs to move within the field of view of the system during the entire sampling process.

In the above technical method, k in each k sampling times is an integer greater than or equal to 1 and less than the total number of sampling times N.

In the above technical method, the denoising algorithm can be a BM3D algorithm or a CLEAN algorithm, which processes the obtained small sampling blurred image to eliminate background noise and determine the location of the target object.

In the above technical method, the zero-order moment obtains the pixel sum of the image, that is, m ₀₀ ; the first-order moment obtains the sum of the x and y coordinates multiplied by the x and y grayscales, that is, m ₁₀ , m ₀₁ ; the centroid is obtained by combining the zero-order moment and the first-order moment, and the formula is:

In the above technical method, the second-order moments m ₂₀ , m ₁₁ , and m ₀₂ are used to calculate the shape direction of the target object, and the formula is:

Where θ is the principal axis direction angle, is the long axis, As the main axis, For the short axis.

In the above technical method, in the m times of correlation imaging results, m=N/k, N is the total number of sampling times, and k is the number of sampling times within the small sample interval.

In the above technical method, the prior information is the type and shape of the known measurement target.

In the above technical method, the total intensity of the light field containing the target information obtained by each k samplings is subjected to a second-order correlation calculation with the spatial intensity of the light source. The correlation calculation formula is as follows:

Wherein, O(x, y) is the correlation imaging result obtained every k samplings, x and y are the two-dimensional image coordinates; Ii(x, y) and _Bi are the i-th reference light and object light signals in the k samplings respectively; <·> is the mean value.

In the above technical solution, the new reference light obtained by sampling every k times is re-calculated with the object light, and the formula for the correlation calculation is as follows:

Among them, Δx and Δy are the centroids of the target object obtained after every k samplings.

In the above technical method, the m-n times of new correlation imaging results are superimposed with the average value of the target object size obtained m-n times to obtain the image of the target object with motion blur removed.

Wherein, O'(x, y) is the image obtained by using this method to eliminate motion blur; N is the total number of sampling times; ε represents noise; _Tk represents the measurement time, that is, t(k-1)N/m+1-t(k)N/m.

In the above technical method, the fast in the fast focus depends on the sampling frequency of the system, and the formula is as follows:

Where v is the target motion speed or system jitter speed, 1/t _se is the bucket detector sampling frequency, k is the number of samples in each small sampling interval, l is the distance between the lighting system and the object, and r is the angular resolution of the system.

Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

1. The present invention can quickly focus on targets with unknown moving speed and direction in correlation imaging, and can observe the object's motion trajectory and the image of the moving target after correlation calculation in real time on the computer;

2. In the imaging stage of the present invention, the reference light only takes the focused range at the corresponding time interval, thereby reducing the amount of calculation and greatly shortening the time required for correlation imaging;

3. The present invention can achieve high-quality reconstruction of the target after correlation imaging with fewer sampling times, eliminating the influence of motion blur caused by relative motion between the system and the target on the correlation imaging;

4. The device of the present invention has a simple structure, is easy to adjust, and has a low manufacturing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a schematic diagram of a fast-focusing correlation imaging method and device provided by an embodiment of the present invention, in which 1-laser source, 2-beam splitter, 3-CCD detector, 4-target object, 5-single-pixel barrel detector without spatial resolution capability, and 6-computer;

FIG. 2 is a flow chart of a fast focusing solution for a moving object based on associated imaging provided by an embodiment of the present invention.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The purpose of the present invention is to provide a fast focusing solution for moving objects based on associated imaging, which can achieve fast focusing and imaging of moving targets in the fields of national defense and military, and has a simple implementation structure and low manufacturing cost.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

The present invention proposes a fast-focusing correlation imaging method, which can achieve fast focusing on a target, locate the target position within each small sampling interval and observe the target information. The method proposed by the present invention can eliminate motion blur caused by relative motion between an imaging system and a target, jitter of an imaging platform, etc. with fewer sampling times, and reconstruct an image of a moving target with better quality by post-processing the data obtained by correlation calculation.

As shown in FIG1 , a schematic diagram of a rapid focusing correlation imaging method and device includes:

Laser source 1, used for outputting pseudothermal light, composed of a laser and frosted glass;

A beam splitter 2 is used to evenly split the incident light into two outgoing lights of equal intensity and the same state as the incident light;

CCD detector 3, used to receive and record the spatial intensity of the light source;

The target object 4 needs to move within the field of view of the system during the entire sampling process;

The single-pixel bucket detector 5 without spatial resolution capability is used to receive and record the total intensity of the light field containing target information.

The computer 6 inputs the signals received by each detector for processing and quickly focuses on the target and reconstructs the image of the target object with motion blur eliminated through the method proposed by the present invention.

As shown in FIG2 , an embodiment of the present invention provides a flowchart of a fast-focusing associated imaging method, including:

S1: Correlation calculation is performed on the light intensity data obtained under small sample intervals.

The small sample interval is to perform an association calculation once every k samplings, where k is an integer greater than or equal to 1 and less than the total number of sampling times N; the light intensity data is the total intensity of the light field containing the target information obtained by the bucket detector and the spatial intensity of the light source obtained by the CCD detector; optionally, the formula for the association calculation is as follows:

Wherein, O(x, y) is the correlation imaging result obtained every k samplings, x and y are the two-dimensional image coordinates; Ii(x, y) and _Bi are the i-th reference light and object light signals in the k samplings respectively; <·> is the mean value.

S2: Use denoising algorithm to eliminate background noise.

The denoising algorithm may be a BM3D algorithm or a CLEAN algorithm, which processes the obtained small sampling blurred image to eliminate background noise and determine the location of the target object.

S3: Determine the center of mass and size of the target object to achieve focusing on the target object.

The center of mass and size of the target object are determined by the zero-order moment, the first-order moment and the second-order moment. The zero-order moment obtains the pixel sum of the image, that is, m ₀₀ ; the first-order moment obtains the sum of the x and y coordinates multiplied by the x and y grayscales, that is, m ₁₀ , m ₀₁ ; the center of mass is obtained by combining the zero-order moment and the first-order moment, and the formula is:

The second-order moments m ₂₀ , m ₁₁ , and m ₀₂ are used to calculate the shape direction of the target object. The formula is:

Where θ is the principal axis direction angle, is the long axis, As the main axis, For the short axis.

S4: The reference light only intercepts the acquired target range and re-correlates with the object light.

The reference light is intercepted by the obtained target range and re-associated with the object light. The formula for calculation is as follows:

Among them, Δx and Δy are the centroids of the target object obtained after every k samplings.

S5: Remove poor quality correlation imaging results based on prior information.

The prior information is the type and shape of the known measurement target.

S6: Using the average value of the target object size obtained, multiple correlation imaging results are superimposed to obtain an image of the target.

The multiple correlation imaging results are superimposed to obtain the image of the target, and the formula is as follows:

Wherein, O'(x, y) is the image obtained by using this method to eliminate motion blur; N is the total number of sampling times; ε represents noise; _Tk represents the measurement time, that is, t(k-1)N/m+1-t(k)N/m.

The fast in the fast focus depends on the sampling frequency of the system, and the formula is as follows:

Among them, v is the detection target movement speed or system jitter speed, 1/t _se is the bucket detector sampling frequency, k is the number of samples in each small sampling interval, l is the distance between the lighting system and the object, and r is the angular resolution of the system.

Obviously, when the system sampling frequency is faster and the number of samples in the small sample interval in the method is smaller, the tolerable object target movement speed or detector jitter speed is higher, and the speed of focusing on the target is also faster.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of the present invention. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims (6)

1. The related imaging method of quick focusing includes laser source, beam splitter, CCD detector, target object, single pixel barrel detector without space resolution, computer, and features that the method includes:

(1) The pseudo-heat light output by the laser source is divided into two identical parts, namely a first beam splitting light and a second beam splitting light by a beam splitter; the first beam splitting light irradiates a target object to be detected by a single-pixel barrel detector without spatial resolution capability, so that the total intensity of a light field containing target information, namely object light, is obtained; the second split light is detected by a CCD detector after being freely transmitted, so that the space intensity of a light source, namely reference light, is obtained;

(2) Performing second-order correlation calculation on the total light field intensity of the target information obtained by sampling every k times and the light source space intensity, wherein the formula of the correlation calculation is as follows: Wherein O (x, y) is an associated imaging result obtained by sampling every k times, x, y are two-dimensional image coordinates, I _i (x, y) and B _i are respectively an ith reference light and an object light signal in the k times of sampling, and [ DEG ] is a mean value;

(3) Removing background noise of a target object associated imaging result obtained by sampling every k times by using a denoising algorithm;

(4) The centroid and the size of the target object obtained by sampling every k times are determined through zero-order moment, first-order moment and second-order moment, so that the target object is focused, and the pixel sum of an image, namely m ₀₀, is obtained through zero-order moment; the sum of x and y coordinates multiplied by x and y gray scales is obtained by the first moment, namely the m ₁₀、m_01, centroid is obtained by combining the zero moment and the first moment, and the formula is as follows: the second moment is m ₂₀、m₁₁、m₀₂ and is used for calculating the shape direction of the target object, and the formula is as follows: wherein θ is the principal axis direction angle, Is the long axis of the tube,Is used as a main shaft, and is provided with a plurality of grooves,Is a short axis;

(5) Substituting the obtained mass center and the size of the target object into a reference light path in the correlation calculation, namely, only taking a positioning range of the reference light at a corresponding time interval;

(6) And carrying out correlation calculation on the new reference light and the object light obtained by sampling every k times, wherein the formula of the correlation calculation is as follows: the delta x and delta y are the mass centers of the target object obtained by sampling every k times, and n imaging results with poor quality are removed according to prior information;

(7) And taking the average value of the sizes of the target objects obtained in m-n times by m-n times of new associated imaging results, and superposing to obtain the image of the target object with motion blur removed, wherein the formula is as follows: Wherein O' (x, y) is an image of a target for eliminating motion blur obtained by the method, N is the total sampling times, epsilon represents noise, and T _k represents measurement time, namely T (k-1) N/(m+1) to T (k) N/m.

2. A method of fast focusing associative imaging according to claim 1, wherein the target object is moved within the field of view of the system throughout the sampling process.

3. A method of fast focusing associative imaging according to claim 1, wherein k is an integer greater than or equal to 1 and less than the total number of samples N per k samples.

4. The method for correlated imaging of claim 1, wherein the denoising algorithm can be BM3D algorithm or CLEAN algorithm, and the method is used for processing the obtained small-sample blurred image, eliminating background noise and determining the position of the target object.

5. The method of claim 1, wherein m = N/k in the m correlated imaging results, where N is the total number of samples and k is the number of samples in a small sample interval.

6. A method of correlated imaging for fast focusing according to claim 1, wherein the fast in-focus is dependent on the sampling frequency of the system, as follows:

Where v is the detected target motion speed or system jitter speed, 1/t _se is the bucket detector sampling frequency, k is the number of samples in each small sampling interval, l is the distance between the illumination system and the object, and θ _r is the angular resolution of the system.