Lensless digital holographic imaging adaptive digital focal length calculation method

Abstract

The invention discloses a lens-free digital holographic imaging adaptive digital focal length calculation method, and relates to the technical field of digital focal length calculation. The method comprises the steps of 1, photographing environment analysis, 2, digital hologram reconstruction image establishment, 3, hologram reconstruction image information acquisition, 4, accurate reconstruction distance acquisition and 5, digital focal length acquisition, the vibration interference index of a digital imaging light path is analyzed, and then the comprehensive stability of a photographing environment is analyzed. The holographic image with a stable shooting environment is screened, the interference degree of the holographic image of the object is reduced, subsequent calculation of the digital focal length is facilitated, the quality of the holographic image of the object is improved, the influence of interference information on reconstruction distance analysis is reduced, the holographic image is helped to rapidly obtain an accurate reconstruction distance, and the reconstruction efficiency is improved. The digital holographic reproduction process is efficiently realized, and the adaptability, the stability and the controllability of digital holographic imaging automatic focusing are improved.

Description

Technical Field

[0001] The invention relates to the technical field of digital focal length calculation, and in particular to a method for calculating the adaptive digital focal length of lens-free digital holographic imaging. Background Art

[0002] Digital holographic imaging is a new holographic imaging technology that has emerged with the development of computer and CCD technology. It records holograms through CCD and uses digital reproduction methods instead of traditional optical reproduction of light waves to realize the digitization of the entire process of holographic recording, storage and reproduction. In terms of mechanical measurement, morphology and deformation measurement, cell culture observation, microcircuit detection, information encryption, etc., digital holography can give full play to its characteristics and advantages and has broad application prospects. The adaptive digital focal length calculation of holographic imaging can quickly obtain the final focal length of digital holographic imaging, help holographic imaging obtain higher clarity, and help improve the quality of holographic images. Therefore, adaptive digital focal length calculation is extremely important in digital holographic imaging.

[0003] But there are still some problems with the current digital focal length calculation: 1. In the prior art, when a holographic image of an object is acquired by a digital holographic imaging optical path, whether the shooting environment is stable is usually determined based on an analysis of environmental stability, and little attention is paid to the vibration of each optical device during shooting. The vibration of each optical device during shooting reflects the stability of the shooting environment to a certain extent, resulting in an increased degree of interference in the holographic image of the object, which is not conducive to the subsequent calculation of the digital focal length and reduces the quality of the holographic image of the object.

[0004] 2. In the prior art, when analyzing the focus criterion of a holographic image, the focus criterion of the image is usually calculated based on the mean of the image grayscale values. When the holographic image captured by the optical device has a lot of interference, the hologram not only captures the information of the object, but also captures the interference information. In the process of determining the criterion standard, all the interference information will affect the calculation result of the mean, and the mean will have large fluctuations and be unstable, thereby affecting the determination of the focal length. Summary of the invention

[0005] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a lens-free digital holographic imaging adaptive digital focal length calculation method for solving the above-mentioned problems.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a lensless digital holographic imaging adaptive digital focal length calculation method, including: Step 1, photography environment analysis: The staff sets up a digital holographic imaging optical path outdoors, and deploys temperature sensors and ultrasonic sensors outdoors to obtain the temperature and air flow rate corresponding to each monitoring time point in each monitoring time period of the digital holographic imaging optical path, and analyzes the environmental stability evaluation index of the digital holographic imaging optical path in each monitoring time period.

[0007] Step 2, establishment of digital hologram reconstructed image: installing vibration sensors on each optical device belonging to the digital holographic imaging optical path, and using the digital holographic imaging optical path to shoot the target object according to the set shooting interval, obtaining the vibration intensity of each optical device belonging to the digital holographic imaging optical path during each shooting, analyzing the vibration interference index of the digital imaging optical path during each shooting, screening each suitable shooting image of the target object, converting each suitable shooting image of the target object into each holographic image by a computer, and obtaining the digital holographic reconstructed image corresponding to each holographic image of the target object at each reconstruction distance according to the set reconstruction distance interval.

[0008] Step 3: Acquisition of hologram reconstructed image information: Perform Fourier transform on the digitally reconstructed images of each holographic image of the target object at each reconstruction distance, and perform grayscale processing to obtain the grayscale value of each pixel point of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance.

[0009] Step 4, accurate reconstruction distance acquisition: analyze the energy of each high-frequency pixel point of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, calculate the mean energy of the high-frequency pixel points corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, and then calculate the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance.

[0010] Step 5, digital focal length acquisition: According to the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, the appropriate focal lengths of the holographic imaging of the target object are screened, and the final focal length of the holographic imaging of the target object is analyzed.

[0011] Preferably, the environmental stability evaluation index corresponding to each monitoring time period of the digital holographic imaging optical path is analyzed by a specific analysis method: according to the temperature corresponding to each monitoring time point of the digital holographic imaging optical path in each monitoring time period, , air velocity ,in Indicates the number of each monitoring time period, , is any integer greater than 2, Indicates the number of each monitoring time point, , is any integer greater than 2, and the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period is analyzed and air flow stability assessment index .

[0012] Analyze the environmental stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in is the proportion factor of temperature stability, is the proportion factor of air flow stability, , The value range of is 0 to 1.

[0013] Preferably, the temperature stability evaluation index and air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period are analyzed, and the specific analysis method is: analyzing the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in represents the number of monitoring time points, Indicates the set allowable temperature deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The temperature at each monitoring time point; Analysis of the air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in Indicates the set allowable air velocity deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The air velocity at each monitoring time point.

[0014] Preferably, the vibration interference index of the digital imaging optical path in each shooting is analyzed by a specific analysis method: according to the vibration intensity of each optical device belonging to the digital holographic imaging optical path in each shooting ,in Indicates the number of each optical device, , is any integer greater than 2, Indicates the number of each shot. , is any integer greater than 2, and the vibration interference index of the digital imaging optical path in each shot is analyzed ,in represents the number of optical devices, Indicates the number of shots.

[0015] Preferably, the specific screening method for screening the suitable photographic images of the target object is: obtaining the time point of each shooting of the digital holographic imaging light path, comparing the time point of each shooting of the digital holographic imaging light path with each monitoring time period, obtaining the monitoring time period corresponding to each shooting of the digital holographic imaging light path, and then obtaining the environmental stability evaluation index corresponding to each shooting of the digital holographic imaging light path .

[0016] Analyze the comprehensive stability evaluation index of the digital holographic imaging optical path in each shooting ,in represents the influence factor of the vibration disturbance index, represents the influencing factor of environmental stability, , The value range of is from 0 to 1; The comprehensive stability evaluation index corresponding to each shooting of the digital holographic imaging optical path is compared with the set comprehensive stability evaluation index threshold. If the comprehensive stability evaluation index corresponding to a certain shooting of the digital holographic imaging optical path is greater than or equal to the set upper limit of the comprehensive stability evaluation index, then the shooting of the digital holographic imaging optical path is marked as a standard shooting, and the standard shootings belonging to the digital holographic imaging optical path are counted.

[0017] The photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are obtained, and the photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are marked as each suitable photographed image of the target object.

[0018] Preferably, the energy of each high-frequency pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is analyzed, and the specific analysis method is: subtracting the grayscale value of each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance from the grayscale value of the adjacent pixel to obtain the grayscale value deviation between each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel, comparing the grayscale value deviation between each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel with a preset grayscale value deviation threshold; if the grayscale value deviation between a pixel corresponding to the digital reconstructed image of a holographic image of the target object at a certain reconstruction distance and the adjacent pixel is greater than or equal to the preset grayscale value deviation threshold, then marking the pixel corresponding to the digital reconstructed image of the holographic image of the target object at the reconstruction distance as a high-frequency pixel.

[0019] According to the gray value of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance, the energy of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is obtained.

[0020] Extract the energy of each high-frequency pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance from the energy of each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance. ,in Indicates the number of each holographic image, , is any integer greater than 2, Indicates the number of each reconstruction distance, , is any integer greater than 2, Indicates the number of each high-frequency pixel point, , is any integer greater than 2.

[0021] Preferably, the automatic focusing criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance is analyzed by a specific analysis method: analyzing the mean energy of the high-frequency pixel points corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance. ,in Indicates the number of high-frequency pixels.

[0022] Calculate the statistical root mean square of the high-frequency energy corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance .

[0023] Analyze the automatic focusing criteria of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance .

[0024] Preferably, the final focal length of the holographic imaging to which the target object belongs is analyzed, and the specific analysis method is: the digital reconstructed images of each holographic image belonging to the target object at each reconstruction distance are arranged in descending order according to the automatic focusing criterion, and the reconstruction distance ranked last in each holographic image belonging to the target object is extracted, and it is marked as the appropriate focal length of each holographic image belonging to the target object.

[0025] The appropriate focal lengths of the holographic images of the target object are marked as the appropriate focal lengths of the holographic imaging of the target object.

[0026] Each suitable focal length of the holographic imaging of the target object is averaged to obtain the average suitable focal length of the holographic imaging of the target object, and each suitable focal length of the holographic imaging of the target object is subtracted from the average suitable focal length to obtain the deviation between each suitable focal length of the holographic imaging of the target object and the average suitable focal length.

[0027] The deviations of each suitable focal length of the target object holographic imaging from the average suitable focal length are compared with the set allowable focal length deviation. If the deviation of a certain suitable focal length of the target object holographic imaging from the average suitable focal length is less than or equal to the set allowable focal length deviation, the suitable focal length of the target object holographic imaging is marked as the preferred focal length, and the preferred focal lengths of the target object holographic imaging are counted.

[0028] The preferred focal lengths of the holographic imaging of the target object are averaged to obtain the average preferred focal length of the holographic imaging of the target object, and the average preferred focal length of the holographic imaging of the target object is marked as the final focal length.

[0029] The beneficial effects of the present invention are as follows: 1. When acquiring a holographic image of an object in a digital holographic imaging optical path, the present invention obtains the vibration intensity of each optical device during shooting, analyzes the vibration interference index of the digital imaging optical path, and then analyzes the comprehensive stability of the shooting environment, selects holographic images with relatively stable shooting environments, reduces the degree of interference of the holographic image of the object, is beneficial to the subsequent calculation of the digital focal length, and improves the quality of the holographic image of the object.

[0030] 2. The present invention calculates the automatic focusing criterion of the digital hologram reconstructed image based on the statistical root mean square of the high-frequency energy of the digital hologram reconstructed image at different digital focal lengths and the mean energy of the high-frequency part of the digital hologram reconstructed image, thereby reducing the influence of interference information on the reconstruction distance analysis, helping the holographic image to quickly obtain an accurate reconstruction distance, efficiently realizing the reproduction process of the digital hologram, and improving the adaptability, stability and controllability of the digital holographic imaging automatic focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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 or the description of the prior art 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 work.

[0032] Figure 1 The present invention is a schematic flow chart of the steps for implementing the method. DETAILED DESCRIPTION

[0033] 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.

[0034] Reference Figure 1As shown, the present invention proposes a lensless digital holographic imaging adaptive digital focal length calculation method, including: step one, photographic environment analysis: staff build a digital holographic imaging optical path outdoors, and deploy temperature sensors and ultrasonic sensors outdoors to obtain the temperature and air flow rate corresponding to each monitoring time point of the digital holographic imaging optical path in each monitoring time period, and analyze the environmental stability evaluation index of the digital holographic imaging optical path in each monitoring time period.

[0035] In a specific embodiment of the present invention, the environmental stability evaluation index corresponding to the digital holographic imaging optical path in each monitoring time period is analyzed by a specific analysis method: according to the temperature corresponding to each monitoring time point in each monitoring time period of the digital holographic imaging optical path, , air velocity ,in Indicates the number of each monitoring time period, , is any integer greater than 2, Indicates the number of each monitoring time point, , is any integer greater than 2, and the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period is analyzed and air flow stability assessment index .

[0036] Analyze the environmental stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in is the proportion factor of temperature stability, is the proportion factor of air flow stability, , The value range of is 0 to 1.

[0037] In another specific embodiment of the present invention, the temperature stability evaluation index and air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period are analyzed, and the specific analysis method is: analyzing the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in represents the number of monitoring time points, Indicates the set allowable temperature deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The temperature at each monitoring time point; Analysis of the air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in Indicates the set allowable air velocity deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The air velocity at each monitoring time point.

[0038] Step 2, establishment of digital hologram reconstructed image: installing vibration sensors on each optical device belonging to the digital holographic imaging optical path, and using the digital holographic imaging optical path to shoot the target object according to the set shooting interval, obtaining the vibration intensity of each optical device belonging to the digital holographic imaging optical path during each shooting, analyzing the vibration interference index of the digital imaging optical path during each shooting, screening each suitable shooting image of the target object, converting each suitable shooting image of the target object into each holographic image by a computer, and obtaining the digital holographic reconstructed image corresponding to each holographic image of the target object at each reconstruction distance according to the set reconstruction distance interval.

[0039] It should be noted that the optical devices include: a helium-neon laser, a lens, a beam splitter, and a reflector.

[0040] In a specific embodiment of the present invention, the vibration interference index of the digital imaging optical path in each shooting is analyzed by a specific analysis method: according to the vibration intensity of each optical device belonging to the digital holographic imaging optical path in each shooting ,in Indicates the number of each optical device, , is any integer greater than 2, Indicates the number of each shot. , is any integer greater than 2, and the vibration interference index of the digital imaging optical path in each shot is analyzed ,in represents the number of optical devices, Indicates the number of shots.

[0041] In another specific embodiment of the present invention, the specific screening method for screening the appropriate photographic images of the target object is: obtaining the time point of each shooting of the digital holographic imaging light path, comparing the time point of each shooting of the digital holographic imaging light path with each monitoring time period, obtaining the monitoring time period corresponding to each shooting of the digital holographic imaging light path, and then obtaining the environmental stability evaluation index corresponding to each shooting of the digital holographic imaging light path .

[0042] Analyze the comprehensive stability evaluation index of the digital holographic imaging optical path in each shooting ,in represents the influence factor of the vibration disturbance index, represents the influencing factor of environmental stability, , The value range of is from 0 to 1; The comprehensive stability evaluation index corresponding to each shooting of the digital holographic imaging optical path is compared with the set comprehensive stability evaluation index threshold. If the comprehensive stability evaluation index corresponding to a certain shooting of the digital holographic imaging optical path is greater than or equal to the set upper limit of the comprehensive stability evaluation index, then the shooting of the digital holographic imaging optical path is marked as a standard shooting, and the standard shootings belonging to the digital holographic imaging optical path are counted.

[0043] The photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are obtained, and the photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are marked as each suitable photographed image of the target object.

[0044] When acquiring a holographic image of an object in a digital holographic imaging optical path, the present invention obtains the vibration intensity of each optical device during shooting, analyzes the vibration interference index of the digital imaging optical path, and further analyzes the comprehensive stability of the shooting environment, selects holographic images with relatively stable shooting environments, reduces the degree of interference of the holographic image of the object, is beneficial to the subsequent calculation of the digital focal length, and improves the quality of the holographic image of the object.

[0045] Step 3: Acquisition of hologram reconstructed image information: Perform Fourier transform on the digitally reconstructed images of each holographic image of the target object at each reconstruction distance, and perform grayscale processing to obtain the grayscale value of each pixel point of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance.

[0046] Step 4, accurate reconstruction distance acquisition: analyze the energy of each high-frequency pixel point of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, calculate the mean energy of the high-frequency pixel points corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, and then calculate the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance.

[0047] In a specific embodiment of the present invention, the energy of each high-frequency pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is analyzed, and the specific analysis method is: subtract the grayscale value of each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance from the grayscale value of the adjacent pixel to obtain the grayscale value deviation between each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel, compare the grayscale value deviation between each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel with a preset grayscale value deviation threshold, if the grayscale value deviation between a pixel corresponding to the digital reconstructed image of a holographic image of the target object at a certain reconstruction distance and the adjacent pixel is greater than or equal to the preset grayscale value deviation threshold, then the pixel corresponding to the digital reconstructed image of the holographic image of the target object at the reconstruction distance is marked as a high-frequency pixel.

[0048] According to the gray value of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance, the energy of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is obtained.

[0049] It should be noted that the energy of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is obtained by a specific method as follows: the energy corresponding to each grayscale value interval is extracted from a web database, and the grayscale value of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is compared with each grayscale value interval to obtain the grayscale value interval corresponding to each pixel point of the digital reconstructed image of each holographic image of the target object at each reconstruction distance, and then the energy of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance is obtained.

[0050] Extract the energy of each high-frequency pixel corresponding to each digitally reconstructed image of each holographic image of the target object at each reconstruction distance from the energy of each pixel corresponding to each digitally reconstructed image of each holographic image of the target object at each reconstruction distance. ,in Indicates the number of each holographic image, , is any integer greater than 2, Indicates the number of each reconstruction distance, , is any integer greater than 2, Indicates the number of each high-frequency pixel point, , is any integer greater than 2.

[0051] Step 5, digital focal length acquisition: According to the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, the appropriate focal lengths of the holographic imaging of the target object are screened, and the final focal length of the holographic imaging of the target object is analyzed.

[0052] In a specific embodiment of the present invention, the automatic focusing criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance is analyzed by a specific analysis method: analyzing the mean energy of the high-frequency pixel points corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance. ,in Indicates the number of high-frequency pixels.

[0053] Calculate the statistical root mean square of the high-frequency energy corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance .

[0054] Analyze the automatic focusing criteria of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance .

[0055] In another specific embodiment of the present invention, the final focal length of the holographic imaging to which the target object belongs is analyzed, and its specific analysis method is: the digital reconstructed images of each holographic image belonging to the target object at each reconstruction distance are arranged in descending order according to the automatic focusing criterion, and the reconstruction distance ranked last in each holographic image belonging to the target object is extracted, and it is marked as the appropriate focal length of each holographic image belonging to the target object.

[0056] The appropriate focal lengths of the holographic images of the target object are marked as the appropriate focal lengths of the holographic imaging of the target object.

[0057] Each suitable focal length of the holographic imaging of the target object is averaged to obtain the average suitable focal length of the holographic imaging of the target object, and each suitable focal length of the holographic imaging of the target object is subtracted from the average suitable focal length to obtain the deviation between each suitable focal length of the holographic imaging of the target object and the average suitable focal length.

[0058] The deviations of each suitable focal length of the target object holographic imaging from the average suitable focal length are compared with the set allowable focal length deviation. If the deviation of a certain suitable focal length of the target object holographic imaging from the average suitable focal length is less than or equal to the set allowable focal length deviation, the suitable focal length of the target object holographic imaging is marked as the preferred focal length, and the preferred focal lengths of the target object holographic imaging are counted.

[0059] The preferred focal lengths of the holographic imaging of the target object are averaged to obtain the average preferred focal length of the holographic imaging of the target object, and the average preferred focal length of the holographic imaging of the target object is marked as the final focal length.

[0060] The present invention calculates the automatic focusing criterion of the digital hologram reconstructed image based on the statistical root mean square of the high-frequency energy of the digital hologram reconstructed image at different digital focal lengths and the mean energy of the high-frequency part of the digital hologram reconstructed image, thereby reducing the influence of interference information on the reconstruction distance analysis, helping the hologram image to quickly obtain an accurate reconstruction distance, efficiently realizing the reproduction process of the digital hologram, and improving the adaptability, stability and controllability of the digital holographic imaging automatic focusing.

[0061] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined in this specification, they shall all fall within the protection scope of the present invention.

Claims

1. A method for calculating adaptive digital focal length of lensless digital holographic imaging, characterized in that: include: Step 1: Photographic environment analysis: Staff will build a digital holographic imaging optical path outdoors, and deploy temperature sensors and ultrasonic sensors outdoors to obtain the temperature and air velocity corresponding to each monitoring time point of the digital holographic imaging optical path in each monitoring period, and analyze the environmental stability assessment index of the digital holographic imaging optical path in each monitoring period; Step 2, establishing a digital hologram reconstructed image: installing a vibration sensor on each optical device belonging to the digital holographic imaging optical path, shooting the target object by the digital holographic imaging optical path according to the set shooting interval, obtaining the vibration intensity of each optical device belonging to the digital holographic imaging optical path in each shooting, analyzing the vibration interference index of the digital imaging optical path in each shooting, screening each suitable shooting image of the target object, converting each suitable shooting image of the target object into each holographic image by a computer, and obtaining the digital holographic reconstructed image corresponding to each holographic image of the target object at each reconstruction distance according to the set reconstruction distance interval; Step 3: Acquisition of hologram reconstructed image information: Perform Fourier transformation on the digitally reconstructed images of each holographic image of the target object at each reconstruction distance, and perform grayscale processing to obtain the grayscale value of each pixel point of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance; Step 4: Acquire accurate reconstruction distance: Analyze the energy of each high-frequency pixel point of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, calculate the mean energy of the high-frequency pixel points corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, and then calculate the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance; Step 5, digital focal length acquisition: According to the digital focus criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance, the appropriate focal lengths of the holographic imaging of the target object are screened, and the final focal length of the holographic imaging of the target object is analyzed.

2. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific analysis method of analyzing the environmental stability evaluation index corresponding to the digital holographic imaging optical path in each monitoring time period is as follows: According to the temperature corresponding to each monitoring time point in each monitoring time period according to the digital holographic imaging optical path , air velocity ,in Indicates the number of each monitoring time period, , is any integer greater than 2, Indicates the number of each monitoring time point, , is any integer greater than 2, and the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period is analyzed and air flow stability assessment index ; Analyze the environmental stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in is the proportion factor of temperature stability, is the proportion factor of air flow stability, , The value range of is 0 to 1.

3. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 2, characterized in that: The specific analysis method of analyzing the temperature stability evaluation index and the air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period is as follows: Analysis of the temperature stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in represents the number of monitoring time points, Indicates the set allowable temperature deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The temperature at each monitoring time point; Analysis of the air flow stability evaluation index of the digital holographic imaging optical path in each monitoring time period ,in Indicates the set allowable air velocity deviation, Indicates the optical path of digital holographic imaging The monitoring time period belongs to The air velocity at each monitoring time point.

4. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific analysis method of analyzing the vibration interference index of the digital imaging optical path in each shooting is as follows: According to the vibration intensity of each optical device in the digital holographic imaging optical path during each shooting ,in Indicates the number of each optical device, , is any integer greater than 2, Indicates the number of each shot. , is any integer greater than 2, and the vibration interference index of the digital imaging optical path in each shot is analyzed ,in represents the number of optical devices, Indicates the number of shots.

5. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific screening method for screening the suitable photographed images of the target object is as follows: Obtain the time point of each shooting of the digital holographic imaging optical path, compare the time point of each shooting of the digital holographic imaging optical path with each monitoring time period, obtain the monitoring time period corresponding to each shooting of the digital holographic imaging optical path, and then obtain the environmental stability evaluation index corresponding to each shooting of the digital holographic imaging optical path ; Analyze the comprehensive stability evaluation index of the digital holographic imaging optical path in each shooting ,in represents the influence factor of the vibration disturbance index, represents the influencing factor of environmental stability, , The value range of is from 0 to 1; Compare the comprehensive stability evaluation index corresponding to each shooting of the digital holographic imaging optical path with the set comprehensive stability evaluation index threshold; if the comprehensive stability evaluation index corresponding to a certain shooting of the digital holographic imaging optical path is greater than or equal to the set upper limit of the comprehensive stability evaluation index, then mark the shooting of the digital holographic imaging optical path as a standard shooting, and count the standard shootings of the digital holographic imaging optical path; The photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are obtained, and the photographed images corresponding to each standard shooting belonging to the digital holographic imaging optical path are marked as each suitable photographed image of the target object.

6. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific analysis method of analyzing the energy of each high-frequency pixel point corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance is as follows: Subtract the grayscale value of each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance from the grayscale value of the adjacent pixel point to obtain the grayscale value deviation between each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel point, compare the grayscale value deviation between each pixel point corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance and the adjacent pixel point with a preset grayscale value deviation threshold, if the grayscale value deviation between a pixel point corresponding to the digital reconstructed image of a holographic image of the target object at a certain reconstruction distance and the adjacent pixel point is greater than or equal to the preset grayscale value deviation threshold, then mark the pixel point corresponding to the digital reconstructed image of the holographic image of the target object at the reconstruction distance as a high-frequency pixel point; According to the gray value of each pixel point of the digitally reconstructed image corresponding to each holographic image of the target object at each reconstruction distance, the energy of each pixel point of the digitally reconstructed image corresponding to each holographic image of the target object at each reconstruction distance is obtained; Extract the energy of each high-frequency pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance from the energy of each pixel corresponding to the digital reconstructed image of each holographic image of the target object at each reconstruction distance. ,in Indicates the number of each holographic image, , is any integer greater than 2, Indicates the number of each reconstruction distance, , is any integer greater than 2, Indicates the number of each high-frequency pixel point, , is any integer greater than 2.

7. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific analysis method of the automatic focusing criterion of the digitally reconstructed image of each holographic image of the target object at each reconstruction distance is as follows: Analyze the mean energy of high-frequency pixels corresponding to the digitally reconstructed images of each holographic image of the target object at each reconstruction distance ,in Indicates the number of high-frequency pixels; Calculate the statistical root mean square of the high-frequency energy corresponding to the digitally reconstructed image of each holographic image of the target object at each reconstruction distance ; Analyze the automatic focusing criteria of the digitally reconstructed images of each holographic image of the target object at each reconstruction distance .

8. The method for calculating the adaptive digital focal length of lensless digital holographic imaging according to claim 1, characterized in that: The specific analysis method of the final focal length of the holographic imaging of the target object is as follows: Arrange the digitally reconstructed images of the holographic images of the target object at each reconstruction distance in descending order according to the auto-focus criterion, extract the reconstruction distance ranked last in the holographic images of the target object, and mark it as the appropriate focal length of the holographic images of the target object; Marking the appropriate focal lengths of the holographic images of the target object as the appropriate focal lengths of the holographic imaging of the target object; Performing mean processing on each suitable focal length of the holographic imaging of the target object to obtain an average suitable focal length of the holographic imaging of the target object, and subtracting each suitable focal length of the holographic imaging of the target object from the average suitable focal length to obtain a deviation between each suitable focal length of the holographic imaging of the target object and the average suitable focal length; Compare the deviations of each suitable focal length of the target object holographic imaging from the average suitable focal length with the set allowable focal length deviation; if the deviation of a certain suitable focal length of the target object holographic imaging from the average suitable focal length is less than or equal to the set allowable focal length deviation, then mark the suitable focal length of the target object holographic imaging as the preferred focal length, and count the preferred focal lengths of the target object holographic imaging; The preferred focal lengths of the holographic imaging of the target object are averaged to obtain the average preferred focal length of the holographic imaging of the target object, and the average preferred focal length of the holographic imaging of the target object is marked as the final focal length.

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