Dot matrix auxiliary focusing digital holographic microscope system and holographic reconstruction method

Abstract

The invention relates to a dot matrix auxiliary focusing digital holographic microscope system and a holographic reconstruction method, the system comprises a digital holographic microscopy light path part and a dot matrix auxiliary focusing light path part, the digital holographic microscopy light path part adopts polarization modulated narrow-band laser to irradiate an object sample to be measured to become object light; the reference light which is orthogonal with the polarization reflected by the reference mirror is subjected to interference imaging in the polarization camera, so that different phase shift acquisition of a single image is realized; the dot matrix auxiliary focusing light path part calculates the focus position of the object sample to be measured by using the definition of the image, and the optimal inverse diffraction distance required in the digital holographic reconstruction process can be directly obtained. Compared with the prior art, the method has the advantages that the automatic focusing efficiency of the digital holographic microscope is improved, the digital holographic three-dimensional surface reconstruction speed is greatly increased, and the reconstruction efficiency and real-time performance are improved on the premise that the reconstruction measurement precision is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of optical microscopes, and in particular to a dot matrix auxiliary focusing digital holographic microscope system and a holographic reconstruction method. Background Art

[0002] With the development of micro-nano processing technology, more and more functional devices are developing towards high performance and miniaturization. High-precision microstructure surface topography measurement is of great significance to improving the performance and quality of components. At present, there are many optical measurement technologies used to measure the surface topography of micro-nano structures, including white light interferometer, confocal microscope, digital holographic microscope, etc. Among them, digital holographic microscope has the advantages of simple operation, non-contact and high precision, and is widely used in biological cells, materials, and microelectronics.

[0003] In digital holographic systems, especially those combined with microscopic imaging, the precise diffraction distance cannot be obtained by measurement. Obtaining the diffraction distance through the autofocus algorithm is a common method. Its implementation is based on the difference between the focused image and the defocused image, and a reasonable focusing criterion function is set. However, the autofocus algorithm usually takes a lot of time to calculate. The higher the required accuracy, the more calculation time is required. In addition, the autofocus algorithm of a single image is also more susceptible to noise interference.

[0004] How to achieve high-precision and fast holographic reconstruction based on a microscope has become a technical problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a dot matrix assisted focusing digital holographic microscope system and a holographic reconstruction method in order to overcome the defects of the above-mentioned prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, there is provided a dot matrix assisted focusing digital holographic microscope system, the system comprising a digital holographic microscope optical path portion and a dot matrix assisted focusing optical path portion;

[0008] The structure of the digital holographic microscope optical path part is as follows: the LD digital holographic light source passes through the spatial pinhole collimation filter, the polarizer, the second focusing lens and the first semi-transparent and semi-reflective mirror in sequence, and is divided into an object light arm and a reference light arm when passing through the beam splitter prism, wherein the object light arm is provided with a second microscope objective lens, and the light is reflected by the object sample and returned to the beam splitter prism; wherein the reference light arm is provided with a first filter, a first quarter-wave plate, a third microscope objective lens and a plane reflector, and the light is reflected by the plane reflector and returned to the beam splitter prism for beam combination; the beam after beam combination passes through the first tube lens, the dichroic mirror and the second quarter-wave plate in sequence, and finally enters the polarization camera for interference imaging to obtain a digital holographic image;

[0009] The structure of the dot matrix auxiliary focusing optical path part is: the monochromatic light source passes through the third focusing lens, the focusing template and the second tube lens in sequence, the bright field light source passes through the fourth focusing lens and the second filter, the two light beams are merged through the second semi-transparent and semi-reflective mirror, the merged light beam passes through the beam splitter prism, the second microscope objective lens, the object sample and is reflected back to the beam splitter prism, then passes through the first tube lens and is reflected by the dichroic mirror, and finally is imaged by the color camera to obtain a dot matrix image and a bright field color picture.

[0010] Preferably, the spatial pinhole collimating filter comprises a first microscope objective, a pinhole diaphragm and a first focusing lens, wherein the pinhole diaphragm is located at the intersection of the rear focus of the first microscope objective and the front focus of the first focusing lens.

[0011] Preferably, using a quarter wave plate to adjust the polarization state in the optical path includes:

[0012] Rotate the first quarter wave plate to adjust the angle between its fast axis and the polarization direction of the polarizer; when the angle between the fast axis and the polarization direction of the polarizer is 45°, the light beam passes through the first quarter wave plate twice after entering the reference light arm, and the linear polarization of the light beam is orthogonal to the linear polarization of the object light arm;

[0013] The second quarter wave plate is rotated to adjust the direction of its fast axis. When the object light and the reference light whose fast axes are orthogonal to the polarization direction are both at an angle of 45°, the light beams entering the polarization camera become left-handed circularly polarized light and right-handed circularly polarized light respectively. The polarization camera simultaneously records multiple polarization states in different polarization directions, and resolves the three-dimensional data of the object sample through interference imaging and multiple polarization states of the polarization camera.

[0014] Preferably, the polarizer is rotated to adjust the linear polarization direction and intensity of the outgoing light so as to maximize the light intensity of the LD digital holographic light source.

[0015] Preferably, each of the light sources is in a different wavelength band, specifically:

[0016] The LD digital holographic light source is a 650nm laser diode monochromatic light source;

[0017] The bright field light source is a white LED light source, and the monochromatic light source is a green LED light source.

[0018] Preferably, the first filter is a 650nm±10nm bandpass filter, which can only pass light with a wavelength within the range of 650nm±10nm and absorb light in other bands;

[0019] The second filter is a 630nm low-pass filter that absorbs light with a wavelength above 630nm.

[0020] Preferably, the dichroic mirror is a 638nm long-wave pass dichroic mirror, which is placed at an angle of 45° in the light path, transmits light with a wavelength greater than 638nm, and reflects light with a wavelength less than 638nm.

[0021] Preferably, the distance from the first tube lens to the color camera is equal to the distance from the second tube lens to the focusing template.

[0022] According to another aspect of the present invention, a holographic reconstruction measurement method is provided, the method comprising:

[0023] Performing separation phase shift interpolation completion and four-step phase shift operation on the input digital holographic image;

[0024] Calculate the clarity curve of the input dot matrix image to obtain the defocus distance of the dot matrix image, thereby obtaining the optimal inverse diffraction distance;

[0025] Diffraction reconstruction is performed based on the results of the four-step phase shift operation and the best inverse diffraction distance;

[0026] Calculate the wrapped phase, perform phase unwrapping, and output the reconstruction result.

[0027] Preferably, the process of acquiring the optimal inverse diffraction distance is specifically as follows: using improved grayscale variance to calculate the clarity value of the dot matrix image, obtaining the z coordinate of the clarity peak, and calculating the distance from the object sample to the focal plane in the z direction, so as to determine the optimal inverse diffraction distance.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The present invention integrates the dot matrix auxiliary focusing optical path into the parallel phase-shifting digital holographic microscope. The parallel phase-shifting digital holographic microscope system uses polarization-modulated narrow-band laser to irradiate the sample of the object to be measured to become object light, and the reference light with polarization orthogonal to that reflected by the reference mirror interferes and forms an image in the polarization camera, which can realize the different phase shift collection of a single image and ensure the good accuracy of the measurement result; the dot matrix auxiliary focusing system uses the clarity of the image to calculate the focal position of the sample of the object to be measured, and can directly obtain the optimal inverse diffraction distance required in the digital holographic reconstruction process, thereby improving the automatic focusing efficiency of the digital holographic microscope, greatly accelerating the speed of digital holographic three-dimensional surface reconstruction, and improving the efficiency and real-time performance of the reconstruction while ensuring the reconstruction measurement accuracy.

[0030] 2) The best inverse diffraction distance in the present invention is calculated directly based on the clarity curve of the dot pattern without the need for cyclic calculation of diffraction reconstruction, which can speed up the reconstruction of the digital holographic three-dimensional surface.

[0031] 3) The optimal inverse diffraction distance in the present invention is obtained based on the calculation results of a series of images, which is more robust than the diffraction reconstruction of a single image.

[0032] 4) Each light source of the present invention uses a different wavelength, and the light of different wavelengths is multiplexed for optical paths, thereby improving the accuracy and efficiency of optical path measurement.

[0033] 5) The present invention can improve the real-time measurement of the digital holographic measurement system in actual industrial scenarios and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the optical path structure of the dot matrix auxiliary focusing digital holographic microscope system of the present invention;

[0035] Figure 2 It is a schematic diagram of the focusing distance measurement principle based on the clarity of the dot matrix image in the present invention;

[0036] Figure 2 (a) for the present invention Figure 2 A partial enlarged schematic diagram of the middle A part;

[0037] Figure 2 (b) for the present invention Figure 2 A partial enlarged schematic diagram of the middle B part;

[0038] Figure 3 A schematic diagram of the process of traditional digital holographic reconstruction;

[0039] Figure 4 It is a schematic diagram of the process of optimizing digital holographic reconstruction in the present invention;

[0040] In the accompanying drawings, B is a focusing template, BS is a beam splitter, C1 is a first semi-transparent and semi-reflective mirror, C2 is a second semi-transparent and semi-reflective mirror, DM is a dichroic mirror, F1 is a first filter, F2 is a second filter, L1 is a first focusing lens, L2 is a second focusing lens, L3 is a third focusing lens, L4 is a fourth focusing lens, M is a plane reflector, O1 is an LD digital holographic light source, O2 is a monochromatic light source, O3 is a bright field light source, OL1 is a first microscope objective lens, OL2 is a second microscope objective lens, OL3 is a third microscope objective lens, P is a polarizer, QWP1 is a first quarter wave plate, QWP2 is a second quarter wave plate, S is an object sample, TL1 is a first tube lens, TL2 is a second tube lens, X1 is a polarization camera, X2 is a color camera, and Z is a pinhole aperture. DETAILED DESCRIPTION

[0041] 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 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 should fall within the scope of protection of the present invention.

[0042] The present invention provides a dot matrix assisted focusing digital holographic microscope system and a holographic reconstruction method, the main purpose of which is to use the dot matrix assisted system to quickly calculate the diffraction distance under the premise of ensuring the good accuracy of the parallel phase shift digital holographic microscope system, thereby improving the efficiency of image processing and the real-time performance of measurement.

[0043] The present embodiment relates to a dot matrix assisted focusing digital holographic microscope system, which includes a digital holographic microscope optical path portion and a dot matrix assisted focusing optical path portion.

[0044] The structure of the optical path of digital holographic microscopy is as follows: the LD digital holographic light source passes through the first microscope objective lens, pinhole aperture, first focusing lens, polarizer, second focusing lens and semi-transparent and semi-reflective mirror in sequence. When passing through the beam splitter prism, it is divided into an object light arm and a reference light arm. The object light arm is provided with the second microscope objective lens, and the light is reflected back to the beam splitter prism by the object sample with high reflectivity; the reference light arm is provided with the first filter, the first quarter-wave plate, the third microscope objective lens and the plane reflector, and the light is reflected back to the beam splitter prism by the plane reflector for beam combination. After beam combination, the light beam passes through the first tube lens, the dichroic mirror and the second quarter-wave plate in sequence, and finally enters the polarization camera for interference imaging.

[0045] The structure of the dot matrix assisted focusing optical path is as follows: the monochromatic light source passes through the third focusing lens, the focusing template and the second tube lens in sequence, the bright field light source passes through the fourth focusing lens and the second filter, the two light beams are combined through a semi-transparent and semi-reflective mirror, and then merged into the main light path through a semi-transparent and semi-reflective mirror, and then the light beams pass through the beam splitter prism, the second microscope objective lens, and the sample is reflected back to the beam splitter prism, the first tube lens and the dichroic mirror, and finally imaged on the color camera to obtain a dot matrix assisted focusing image (referred to as dot matrix image) and a bright field color image.

[0046] Specifically, Figure 1, the LD digital holographic light source O1 emits a narrow-band laser of 650nm, which passes through the filtering system composed of the first microscope objective lens OL1 and the pinhole aperture, and then passes through the first focusing lens L1 to collimate into a parallel light source, and passes through the polarizer P to become linearly polarized light. The parallel linearly polarized light passes through the second focusing lens L2 and the first semi-transparent and semi-reflective mirror C1, and then passes through the beam splitter prism BS to be divided into object light and reference light. The object light passes through the second microscope objective lens OL2 and directly irradiates the surface of the highly reflective sample, and is reflected back to the beam splitter prism BS; the reference light passes through the first filter F1, is reflected by the plane reflector M, passes through the first quarter-wave plate QWP1 twice, and also returns to the beam splitter prism BS, and is combined at the beam splitter prism BS. By adjusting the angle between the first quarter-wave plate QWP1 and the polarizer P, the polarization direction and state of the reflected reference light can be changed, and the appropriate angle can be adjusted and found to make the reflected reference light perpendicular to the linear polarization direction of the object light. The two linearly polarized lights pass through the first imaging tube lens TL1 and then transmit through the dichroic mirror DM, and then pass through the second quarter-wave plate QWP2 in front of the camera to become left-handed circularly polarized light and right-handed circularly polarized light, and finally enter the polarization camera X1 to record the spatially multiplexed digital holographic image.

[0047] The structure of the dot matrix assisted focusing optical path is as follows: the light emitted by the monochromatic light source O2 is first converged by the third focusing lens L3 to increase the energy concentration, and then passes through the focusing template B to become a monochromatic dot matrix focusing light source array, and then passes through the second tube lens TL2 and merges with the bright field light source O3 at the second semi-transparent and semi-reflective mirror C2. The bright field light source O3 is emitted by a white LED, passes through the fourth focusing lens L4, and then merges with the monochromatic dot matrix focusing light source through the second filter F2. The two converged light sources are divided into two beams after passing through the beam splitter prism BS, of which the transmitted light is absorbed by the first filter F1, and the reflected light is irradiated on the object sample after passing through the second microscope objective lens OL2, and reflected back to the imaging tube lens TL1. Then the light beam is reflected by the dichroic mirror DM and enters the color camera X2 for imaging, and a dot matrix assisted focusing image and a bright field color picture are obtained.

[0048] LD digital holographic light source O1 is a 650nm laser diode monochromatic light source, and its coherence length can reach 85μm.

[0049] The first microscope objective lens OL2, the pinhole aperture Z and the first focusing lens L1 form a spatial pinhole collimating filter. The diameter of the pinhole aperture Z is 20 μm, and its position is strictly located at the rear focus of the first microscope objective lens OL1 and the front focus of the first focusing lens L1.

[0050] The polarizer P is rotated to adjust the linear polarization direction and intensity of the outgoing light. By adjusting the linear polarization direction of the polarizer P, the light intensity of the LD digital holographic light source O1 is maximized.

[0051] The first filter F1 is a 650nm±10nm bandpass filter that can only pass light within the wavelength range of 650nm±10nm and absorb light in other bands. This filter can pass the light emitted by the LD digital holographic light source O1 and allow it to enter the reference light arm. It absorbs the light emitted by the bright field light source O3 and the monochromatic light source O2 to prevent the reference light arm from interfering with the imaging of the object sample in the color camera X2.

[0052] The first quarter wave plate QWP1 of the reference light arm can be rotated to adjust the angle between its fast axis and the polarization direction of the polarizer. The angle of the first quarter wave plate QWP1 is adjusted so that the angle between its fast axis and the linear polarization is 45°. At this time, after the light beam enters the reference light arm, it passes through the first quarter wave plate QWP1 twice, and the linear polarization of the light beam is orthogonal to the linear polarization of the object light arm.

[0053] The specification of the dichroic mirror DM is a 638nm long-wave dichroic mirror, which is placed at an angle of 45° in the optical path. It transmits light with a wavelength greater than 638nm and reflects light with a wavelength less than 638nm. This dichroic mirror DM can transmit the light emitted by the LD digital holographic light source O1 and allow it to enter the polarization camera X1; it can reflect the light emitted by the bright field light source O3 and the monochromatic light source O2 and allow it to enter the color camera X2.

[0054] The second quarter wave plate QWP2 can be rotated to adjust the direction of its fast axis. The angle of the second quarter wave plate QWP2 is adjusted so that the object light and the reference light whose fast axis is orthogonal to the polarization direction are both at an angle of 45°. At this time, the light beams entering the polarization camera X1 become left-handed circularly polarized light and right-handed circularly polarized light respectively. The polarization camera X1 can simultaneously record four polarization states of different polarization directions, and analyze the three-dimensional data of the object sample through interference imaging and the four polarization states of the polarization camera.

[0055] The distance between the first tube lens TL1 and the color camera X2 is equal to the distance between the second tube lens TL2 and the focus template B. At this time, the focus template B is conjugate with the CMOS of the color camera X2. Therefore, when the object sample is focused and clearly imaged on the color camera X2, the dot pattern can also be clearly imaged at the same time.

[0056] The bright field light source O3 is a white LED light source, and the monochromatic light source O2 is a green LED light source.

[0057] The second filter F2 is a 630nm low-pass filter that can absorb light with a wavelength above 630nm. This filter can ensure that the output light of the bright field light source O3 is less than 630nm, preventing it from entering the reference light arm.

[0058] Focus template B is a circular hole array with a diameter of 7 μm, and a film is coated around the circular holes to prevent light from passing through.

[0059] The present invention utilizes light sources of different wavelength bands to perform different optical processes, so as to maximize the reuse of optical paths and compress the structural volume. The specific wavelength division method is as follows:

[0060] LD digital holographic light source O1 is a 650nm narrow-band laser. After being split by the beam splitter (BS), it can transmit through the first filter F1 (650nm±10nm bandpass filter) to obtain the light of the reference light arm, and then pass through the 638nm long-wave pass dichroic mirror (DM) to enter the polarization camera X1.

[0061] The bright field light source O3 is a white LED light source. After passing through the second filter F2 (630nm low-pass filter), the light emitted is only light with a wavelength less than 630nm. After being split by the beam splitter prism BS, the light on the reference light arm is absorbed by the first filter F1, so it will not return to the imaging of the plane reflector M and interfere with the imaging of the object sample. After passing through the 638nm long-wave pass dichroic mirror DM, it can be reflected into the color camera X2.

[0062] The monochromatic light source O2 is a green LED light source with a wavelength range of about 530nm. After being split by the beam splitter BS, the light on the reference light arm will be absorbed by the first filter F1 and can be reflected into the color camera X2 after passing through the 638nm long-wave pass dichroic mirror DM.

[0063] This embodiment also relates to a holographic reconstruction method based on a dot matrix assisted focusing digital holographic microscope system, comprising the following process:

[0064] Performing separation phase shift interpolation completion and four-step phase shift operation on the input digital holographic image;

[0065] Calculate the sharpness curve of the input dot matrix image to obtain the defocus distance of the dot matrix image, thereby obtaining the optimal inverse diffraction distance;

[0066] Diffraction reconstruction is performed based on the results of the four-step phase shift operation and the best inverse diffraction distance;

[0067] Calculate the wrapped phase, perform phase unwrapping, and output the reconstruction result.

[0068] The dot matrix auxiliary focusing method of the present invention is to measure the focusing distance based on the clarity of the dot matrix image, so as to determine the diffraction distance of the digital holographic reconstruction. Figure 2 The specific implementation method is as follows:

[0069] By observing the state of the dot pattern in the color camera, the focal plane of the sample of the object under test can be found more quickly and accurately. When the sample is on the focal plane of the microscope, the dot pattern on the color camera is clear and obvious dark boundaries can be seen between the dots; when the sample deviates from the focal plane of the microscope, the dot pattern is blurred. Based on the above characteristics, the present invention uses improved grayscale variance to calculate the clarity value of the dot image, which is used to solve the z coordinate of the clarity peak, and can calculate the distance from the current sample to the focal plane in the z direction, so as to determine the inverse diffraction distance.

[0070] The collected dot matrix image is blurred first, then clear, and then blurred again before and after the focus. Calculating the clarity operator of the image can obtain the distance value of the focus position of the dot matrix pattern. Figure 2(a) and 2(b) Schematic diagrams of clear and blurred dot matrix images respectively.

[0071] In the polarization phase shift digital holographic reconstruction calculation, the inverse diffraction distance is related to the focal distance of the object sample. Therefore, Figure 3 The traditional digital holographic reconstruction process can be optimized as follows Figure 4 reconstruction process.

[0072] Compared with the traditional digital holographic reconstruction process, the optimized calculation of the best inverse diffraction distance is directly calculated based on the dot pattern clarity curve, without the need for cyclic calculation of diffraction reconstruction, which can speed up the reconstruction of digital holographic three-dimensional surfaces. In addition, the best inverse diffraction distance calculated with dot matrix assistance is calculated based on the calculation results of a series of pictures, which is more robust than the diffraction reconstruction of a single image.

[0073] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A dot matrix assisted focusing digital holographic microscope system, characterized in that: The system includes a digital holographic microscopic optical path part and a dot matrix auxiliary focusing optical path part; The structure of the digital holographic microscope optical path is as follows: the LD digital holographic light source (O1) passes through a spatial pinhole collimating filter, a polarizing plate (P), a second focusing lens (L2) and a first semi-transparent and semi-reflective mirror (C1) in sequence, and is divided into an object light arm and a reference light arm when passing through a beam splitter prism (BS), wherein the object light arm is provided with a second microscope objective lens (OL2), and the light is reflected by an object sample (S) and returns to the beam splitter prism (BS); The reference light arm is provided with a first filter (F1), a first quarter wave plate (QWP1), a third microscope objective lens (OL3) and a plane reflector (M). The light is reflected by the plane reflector (M) back to the beam splitter prism (BS) for beam combining. After beam combining, the light beam passes through the first tube lens (TL1), the dichroic mirror (DM) and the second quarter wave plate (QWP2) in sequence, and finally enters the polarization camera (X1) for interference imaging to obtain a digital holographic image. The structure of the dot matrix auxiliary focusing optical path part is as follows: a monochromatic light source (O2) passes through a third focusing lens (L3), a focusing template (B) and a second tube lens (TL2) in sequence; a bright field light source (O3) passes through a fourth focusing lens (L4) and a second filter (F2); the two light beams are combined through a second semi-transparent and semi-reflective mirror (C2); the combined light beams are successively passed through a beam splitter prism (BS), a second microscope objective lens (OL2) and an object sample (S) and reflected back to the beam splitter prism (BS); then, the light beams are passed through a first tube lens (TL1) and reflected by a dichroic mirror (DM); finally, the light beams are imaged in a color camera (X2) to obtain a dot matrix image and a bright field color image.

2. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: The spatial pinhole collimating filter comprises a first microscope objective lens (OL1), a pinhole diaphragm (Z) and a first focusing lens (L1), wherein the pinhole diaphragm (Z) is located at the intersection of the rear focus of the first microscope objective lens (OL1) and the front focus of the first focusing lens (L1).

3. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: Use quarter wave plates to adjust the polarization state in the optical path, including: Rotate the first quarter wave plate (QWP1) to adjust the angle between its fast axis and the polarization direction of the polarizer; when the angle between the fast axis and the polarization direction of the polarizer is 45°, the light beam passes through the first quarter wave plate (QWP1) twice after entering the reference light arm, and the linear polarization of the light beam is orthogonal to the linear polarization of the object light arm; The second quarter wave plate (QWP2) is rotated to adjust the direction of its fast axis. When the angles between the object light and the reference light, whose fast axes are orthogonal to the polarization directions, are both 45°, the light beams enter the polarization camera (X1) and become left-handed circularly polarized light and right-handed circularly polarized light respectively. The polarization camera (X1) simultaneously records multiple polarization states in different polarization directions, and three-dimensional data of the object sample (S) is analyzed through interference imaging and the multiple polarization states of the polarization camera.

4. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: The polarizing plate (P) is rotated to adjust the linear polarization direction and intensity of the outgoing light, so that the light intensity of the LD digital holographic light source (O1) is maximized.

5. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: Each of the light sources is in a different wavelength band, specifically: The LD digital holographic light source (O1) is a 650nm laser diode monochromatic light source; The bright field light source (O3) is a white LED light source, and the monochromatic light source (O2) is a green LED light source.

6. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: The first filter (F1) is a 650nm±10nm bandpass filter, which can only pass light with a wavelength within the range of 650nm±10nm and absorb light in other bands; The second filter (F2) is a 630nm low-pass filter that absorbs light with a wavelength above 630nm.

7. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: The dichroic mirror (DM) is a 638nm long-wave pass dichroic mirror, which is placed at an angle of 45° in the light path, transmits light with a wavelength greater than 638nm, and reflects light with a wavelength less than 638nm.

8. The dot matrix assisted focusing digital holographic microscope system according to claim 1, characterized in that: The distance from the first tube lens (TL1) to the color camera (X2) is equal to the distance from the second tube lens (TL2) to the focusing template (B).

9. A holographic reconstruction method using the dot matrix assisted focusing digital holographic microscope system according to any one of claims 1 to 8, characterized in that: The method includes: Performing separation phase shift interpolation completion and four-step phase shift operation on the input digital holographic image; Calculate the clarity curve of the input dot matrix image to obtain the defocus distance of the dot matrix image, thereby obtaining the optimal inverse diffraction distance; Diffraction reconstruction is performed based on the results of the four-step phase shift operation and the best inverse diffraction distance; Calculate the wrapped phase, perform phase unwrapping, and output the reconstruction result.

10. The holographic reconstruction method according to claim 9, characterized in that: The process of obtaining the optimal inverse diffraction distance is specifically as follows: using improved grayscale variance to calculate the clarity value of the dot matrix image, obtaining the z coordinate of the clarity peak, and calculating the distance from the object sample (S) to the focal plane in the z direction to determine the optimal inverse diffraction distance.

Images