Transflective synergetic dual-wavelength digital holographic microscopy device and measurement method

Abstract

The invention discloses a transmission and reflection collaborative dual-wavelength digital holographic microscopy device and a measurement method, the device adopts a digital holographic microscopy method, orthogonal polarization laser emitted by two lasers with different wavelengths respectively enters a reference light transmission system and an object light transmission system, the reference light passes through a polarization multiplexing light path unit, and the object light passes through an object light transmission system; dual-wavelength off-axis holographic spectrum separation is satisfied; when the object light passes through the object to be measured and in the transmission mode, the object light interferes with one path of dual-wavelength reference light, and a transmission hologram is recorded; in a reflection mode, the object light interferes with the other path of dual-wavelength reference light, and a reflection hologram is recorded; light path elements do not need to be switched, transmission and reflection measurement modes are achieved at the same time, transmission and reflection information of the to-be-measured object can be obtained at the same time only through one-time imaging, multiple times of light path operation in the measurement process is avoided, measurement efficiency is improved, and the method is suitable for lossless dynamic monitoring of the object with large transmissivity change and large longitudinal range.

Description

Technical Field

[0001] This invention belongs to the field of optical interferometry, specifically relating to a dual-wavelength digital holographic microscope device and measurement method with transmission and reflection coordination. Background Technology

[0002] Digital holographic microscopy is a high-precision, non-contact, real-time three-dimensional measurement technology. By using a camera to record and digitally reproduce the light field interference image, the amplitude and phase information of the sample under test can be obtained, thereby reflecting the three-dimensional morphology and other characteristics of the sample. It has been widely used in many fields such as microstructure morphology detection, biological cell morphology observation and refractive index distribution of micro optical elements.

[0003] In single-wavelength digital holographic microscopy, when the height difference between adjacent samples contains discontinuous features greater than one wavelength (transmission type) or half a wavelength (reflection type) of the light source, single-wavelength digital holography cannot accurately obtain the three-dimensional information of the sample. Dual-wavelength digital holographic microscopy, by illuminating the sample with two light sources of different wavelengths, obtains interference holograms of different wavelengths, expanding the longitudinal measurement range of the sample to a composite wavelength, which is greater than the single wavelength of either light source. Therefore, dual-wavelength holographic microscopy can measure objects with large longitudinal measurement ranges and high aspect ratios, offering advantages such as large measurement range, high precision, non-contact operation, and real-time measurement.

[0004] Existing dual-wavelength digital holographic microscopes are mostly single-mode transmission or reflection devices. For objects with large variations in transmittance, it is impossible to complete the entire measurement process using a single transmission or reflection mode. Existing single-wavelength digital holographic microscopes that combine transmission and reflection modes also perform transmission or reflection mode measurements on a single device in a time-division manner by switching optical path elements, and cannot dynamically monitor the changes in the object. Summary of the Invention

[0005] To overcome the shortcomings of the aforementioned devices, the main objective of this invention is to provide a dual-wavelength digital holographic microscope device and measurement method that combines transmission and reflection. This invention eliminates the need for switching devices; through coordinated transmission and reflection measurements, it completes real-time measurement of transmission and reflection modes with a single imaging operation, simultaneously acquiring the transmission and reflection information of the object under test. It is suitable for dynamic monitoring of objects with large variations in transmittance and a wide longitudinal range, effectively improving the device's measurement efficiency and range.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A dual-wavelength digital holographic microscopy device with transmission-reflection synergy includes: a first laser 1, a first polarizer 2, a first plane mirror 3, a second laser 4, a second polarizer 5, a first beam splitter 6, an attenuator 7, a beam expander 8, a second plane mirror 9, a first quarter-wave plate 10, a polarizing beam splitter 11, a second quarter-wave plate 12, a third plane mirror 13, an optical isolator 14, a fourth plane mirror 15, a second beam splitter 16, a first lens 17, a first microscope objective 18, a sample to be tested 19, a second microscope objective 20, a second lens 21, a third beam splitter 22, a first camera 23, a fifth plane mirror 24, a first half-wave plate 25, a fourth beam splitter 26, a second half-wave plate 27, a sixth plane mirror 28, a fifth beam splitter 29, and a second camera 30.

[0008] The first laser 1 and the second laser 4 emit red and green light beams, respectively. The red light beam emitted by the first laser 1 is modulated by the first polarizer 2 to output vertically vibrating linearly polarized red light, which is then reflected by the first plane mirror 3 to the first beam splitter 6. The green light beam emitted by the second laser 4 is modulated by the second polarizer 5 to output parallel vibrating linearly polarized green light, which is combined with the vertically vibrating linearly polarized red light beam at the first beam splitter 6 and then split into object light and reference light.

[0009] The reference light passes sequentially through attenuator 7 and beam expander 8, and is then split at polarization beam splitter 11 into a vertically vibrating linearly polarized red beam and a parallelly vibrating linearly polarized green beam. The reflected vertically vibrating linearly polarized red light passes through first quarter-wave plate 10, is reflected by second plane mirror 9, and then passes through first quarter-wave plate 10 again, becoming parallelly vibrating linearly polarized red light. The transmitted parallelly vibrating linearly polarized green light passes through second quarter-wave plate 12, is reflected by third plane mirror 13, and then passes through second quarter-wave plate 12 again, becoming vertically vibrating linearly polarized green light. This green light then combines with the parallelly vibrating linearly polarized red beam at polarization beam splitter 11. After combining, the reference beam contains two linearly polarized red and green beams with orthogonal vibration directions. This reference beam is then split at fourth beam splitter 26 into reference beam one and reference beam two. Reference beam one passes through first half-wave plate 25 to third beam splitter 22, and reference beam two passes through second half-wave plate 27 to fifth beam splitter 29.

[0010] The object beam is reflected by the fourth plane mirror 15 through the optical isolator 14 to the second beam splitter 16 and then transmitted. It passes through the first lens 17 and the first microscope objective 18 in sequence. When it passes through the sample to be tested 19, it is divided into transmitted object beam one and reflected object beam two. Transmitted object beam one passes through the second microscope objective 20 and the second lens 21 in sequence and is reflected by the fifth plane mirror 24 to the third beam splitter 22, where it interferes with the reference beam one and is recorded by the first camera 23 as a transmission hologram. Reflected object beam two passes through the first microscope objective 18 and the first lens 17 in sequence and is reflected by the second beam splitter 16 to the sixth plane mirror 28, and then by the sixth plane mirror 28 to the fifth beam splitter 29, where it interferes with the reference beam two and is recorded by the second camera 30 as a reflection hologram.

[0011] Furthermore, the first polarizer 2 and the second polarizer 5 are used to adjust the polarization directions of the two beams emitted by the first laser 1 and the second laser 4 to be orthogonal; the attenuator 7 is used to adjust the intensity of the object beam and the reference beam to be consistent; the first half-wave plate 25 and the second half-wave plate 27 are used to ensure that interference occurs between the transmitted object beam 1 and the reference beam 1 and between the reflected object beam 2 and the reference beam 2, wherein the fast axis of the half-wave plate is at a 45-degree angle to the vertical direction. When vertically vibrating linearly polarized light passes through, its vibration direction will rotate 90 degrees to become horizontal vibration. When horizontally vibrating linearly polarized light passes through, it will also rotate 90 degrees to become vertical vibration.

[0012] Furthermore, the optical isolator 14 is used for unidirectional light beam passage to prevent the object light from mixing with the reference light; the first lens 17 and the first microscope objective 18 form the first telecentric optical path structure, and the second microscope objective 20 and the second lens 21 form the second telecentric optical path structure to eliminate phase aberration.

[0013] Furthermore, the second plane mirror 9 adjusts the angle between the red light in reference light one and the red light in transmitted object light one, and between the red light in reference light two and the red light in reflected object light two by controlling the mirror tilt angle. The third plane mirror 13 adjusts the angle between the green light in reference light one and the green light in transmitted object light one, and between the green light in reference light two and the green light in reflected object light two by controlling the mirror tilt angle, so as to facilitate spectral separation in the transmitted light path and the reflected light path and realize off-axis dual-wavelength recording optical path.

[0014] Furthermore, the first beam splitter 6, the second beam splitter 16, the third beam splitter 22, the fourth beam splitter 26, and the fifth beam splitter 29 are depolarizing beam splitters, splitting the beam in a 1:1 ratio; the function of the polarizing beam splitter 11 is to separate the incident beam into vertically vibrating linearly polarized red light and parallelly vibrating linearly polarized green light according to its polarization state; the function of the beam expander 8 is to expand the beam.

[0015] A measurement method for a dual-wavelength digital holographic microscope with transmission and reflection modes, comprising a transmission mode and a reflection mode, wherein the method steps are as follows:

[0016] The sample to be tested 19 was installed in a dual-wavelength digital holographic microscope with transmission and reflection coordination;

[0017] Turn on the first laser 1 and the second laser 4, and use the first camera 23 to collect a transmission hologram and the second camera 30 to collect a reflection hologram.

[0018] Based on the principle of off-axis dual-wavelength digital holography, the acquired dual-wavelength digital transmission hologram or reflection hologram is filtered by spectrum to retain the positive first-order spectrum of red light and green light respectively, and remove the interference of the zero-order and negative first-order spatial spectrum.

[0019] By introducing the same reconstructed light as the reference light, the diffraction process of the light wave is simulated by computer, and the complex amplitude of the light wave field on the image plane is digitally reconstructed according to the principle of angular spectrum. The encapsulation phase information of the sample 19 to be tested is obtained from the complex amplitude of the light wave field.

[0020] The phase difference between the red and green wavelengths is calculated, and the phase jump is compensated to obtain the phase of the equivalent composite wavelength, which is the phase information of the sample 19 to be tested.

[0021] Furthermore, the light intensity of the hologram formed by the superposition of red, green, and green light can be expressed as:

[0022] (1)

[0023] In the formula, Represents the spatial coordinates of the recording plane. and These represent the light intensities of the red hologram and the green hologram, respectively. and These represent the amplitude information of the red and green object beams, respectively. and These represent the phase information of the red and green object beams, respectively. and These represent the amplitude information of the red reference light and the green reference light, respectively. and These represent the phase information of the red reference light and the green reference light, respectively. and For red light carrier frequency information, and For green light carrier frequency information, The DC component of the hologram is represented by the central zero-order spectrum. The modulation term is represented by positive and negative first-order spectra in the spectrum; among them, the positive first-order spectrum is a real image containing the phase information of the sample under test (19), which needs to be retained, while the negative first-order spectrum is its conjugate virtual image, which needs to be removed as interference.

[0024] Furthermore, spectral filtering of a hologram can be expressed as:

[0025]

[0026] In the formula, and These represent the filtered red hologram and the filtered green hologram, respectively. and These represent the Fourier transform and the inverse Fourier transform, respectively. and These represent the red light spectrum bandpass filter and the green light spectrum bandpass filter, respectively.

[0027] Furthermore, by introducing the same reconstructed light as the reference light, the carrier modulation effect of the reference light can be removed, and the red and green light field distributions can be represented as follows:

[0028]

[0029] In the formula, and These represent the red light reproduction light and the green light reproduction light, respectively.

[0030] By simulating the diffraction process of light waves using a computer, the complex amplitude of the light wave field on the image plane can be reconstructed based on the angular spectrum principle as follows:

[0031]

[0032] In the formula, The spatial coordinates of the representation surface are represented by j, where j represents the imaginary number. and These represent the wavelengths of red and green light, respectively. This represents the axial distance of the light field as it propagates along the direction of propagation.

[0033] The phase information of the sample 19 to be measured, obtained from the complex amplitude of the light wave field, can be expressed as:

[0034]

[0035] In the formula, Represents the arctangent function. and These represent the operations of extracting the imaginary part and the real part, respectively.

[0036] Furthermore, by taking the phase difference between the red and green wavelengths and compensating for their phase jumps, the phase of the equivalent composite wavelength is obtained. The equivalent composite wavelength can be expressed as:

[0037]

[0038] The phase of the equivalent composite wavelength, i.e., the phase information of the sample under test (19), can be expressed as:

[0039] .

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] Existing dual-wavelength digital holographic microscopes, having only a single transmission or reflection structure, cannot complete real-time measurements of objects with large refractive index variations using a single transmission or reflection mode. Meanwhile, existing single-wavelength digital holographic microscopes with both transmission and reflection capabilities mostly switch optical elements to adjust the optical path structure to achieve the switching between transmission and reflection modes. This requires multiple operations on a single device to obtain transmission and reflection measurement results separately, resulting in low measurement efficiency and the inability to achieve real-time measurement.

[0042] This invention proposes a dual-wavelength digital holographic microscope device and measurement method with transmission and reflection coordination. A single optical path integrates both transmission and reflection measurement modes without the need to switch optical elements. It can simultaneously complete real-time measurements of both modes in one measurement, and has the advantages of high integration, high measurement efficiency, and large measurement range. It is suitable for dynamic monitoring of objects with large transmittance variations and a large longitudinal range. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a dual-wavelength digital holographic microscope device with transmission and reflection coordination according to the present invention;

[0044] Figure 2 This is a schematic diagram of the optical path of the transmission measurement mode of a dual-wavelength digital holographic microscope device with transmission and reflection coordination according to the present invention;

[0045] Figure 3 This is a schematic diagram of the optical path of the reflection measurement mode of a dual-wavelength digital holographic microscope device with transmission and reflection coordination according to the present invention.

[0046] In the figure, 1-first laser; 2-first polarizer; 3-first plane mirror; 4-second laser; 5-second polarizer; 6-first beam splitter; 7-attenuator; 8-beam expander; 9-second plane mirror; 10-first quarter-wave plate; 11-polarizing beam splitter; 12-second quarter-wave plate; 13-third plane mirror; 14-optical isolator; 15-fourth plane mirror; 16-second beam splitter; 17-first lens; 18-first microscope objective; 19-sample under test; 20-second microscope objective; 21-second lens; 22-third beam splitter; 23-first camera; 24-fifth plane mirror; 25-first half-wave plate; 26-fourth beam splitter; 27-second half-wave plate; 28-sixth plane mirror; 29-fifth beam splitter; 30-second camera. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] A dual-wavelength digital holographic microscopy device with transmission-reflection synergy includes: a first laser 1, a first polarizer 2, a first plane mirror 3, a second laser 4, a second polarizer 5, a first beam splitter 6, an attenuator 7, a beam expander 8, a second plane mirror 9, a first quarter-wave plate 10, a polarizing beam splitter 11, a second quarter-wave plate 12, a third plane mirror 13, an optical isolator 14, a fourth plane mirror 15, a second beam splitter 16, a first lens 17, a first microscope objective 18, a sample to be tested 19, a second microscope objective 20, a second lens 21, a third beam splitter 22, a first camera 23, a fifth plane mirror 24, a first half-wave plate 25, a fourth beam splitter 26, a second half-wave plate 27, a sixth plane mirror 28, a fifth beam splitter 29, and a second camera 30.

[0049] The first laser 1 and the second laser 4 emit red and green light beams, respectively. The red light beam emitted by the first laser 1 is modulated by the first polarizer 2 to output vertically vibrating linearly polarized red light, which is then reflected by the first plane mirror 3 to the first beam splitter 6. The green light beam emitted by the second laser 4 is modulated by the second polarizer 5 to output parallel vibrating linearly polarized green light, which is combined with the vertically vibrating linearly polarized red light beam at the first beam splitter 6 and then split into object light and reference light.

[0050] The reference light passes sequentially through attenuator 7 and beam expander 8, and is then split at polarization beam splitter 11 into a vertically vibrating linearly polarized red beam and a parallelly vibrating linearly polarized green beam. The reflected vertically vibrating linearly polarized red light passes through first quarter-wave plate 10, is reflected by second plane mirror 9, and then passes through first quarter-wave plate 10 again, becoming parallelly vibrating linearly polarized red light. The transmitted parallelly vibrating linearly polarized green light passes through second quarter-wave plate 12, is reflected by third plane mirror 13, and then passes through second quarter-wave plate 12 again, becoming vertically vibrating linearly polarized green light. This green light then combines with the parallelly vibrating linearly polarized red beam at polarization beam splitter 11. After combining, the reference beam contains two linearly polarized red and green beams with orthogonal vibration directions. This reference beam is then split at fourth beam splitter 26 into reference beam one and reference beam two. Reference beam one passes through first half-wave plate 25 to third beam splitter 22, and reference beam two passes through second half-wave plate 27 to fifth beam splitter 29.

[0051] The object beam is reflected by the fourth plane mirror 15 through the optical isolator 14 to the second beam splitter 16 and then transmitted. It passes through the first lens 17 and the first microscope objective 18 in sequence. When it passes through the sample to be tested 19, it is divided into transmitted object beam one and reflected object beam two. Transmitted object beam one passes through the second microscope objective 20 and the second lens 21 in sequence and is reflected by the fifth plane mirror 24 to the third beam splitter 22, where it interferes with the reference beam one and is recorded by the first camera 23 as a transmission hologram. Reflected object beam two passes through the first microscope objective 18 and the first lens 17 in sequence and is reflected by the second beam splitter 16 to the sixth plane mirror 28, and then by the sixth plane mirror 28 to the fifth beam splitter 29, where it interferes with the reference beam two and is recorded by the second camera 30 as a reflection hologram.

[0052] The first polarizer 2 and the second polarizer 5 are used to adjust the polarization directions of the two beams emitted by the first laser 1 and the second laser 4 to be orthogonal; the attenuator 7 is used to adjust the intensity of the object beam and the reference beam to be consistent; the first half-wave plate 25 and the second half-wave plate 27 are used to ensure that interference occurs between the transmitted object beam 1 and the reference beam 1 and between the reflected object beam 2 and the reference beam 2. The fast axis of the half-wave plate is at a 45-degree angle to the vertical direction. When vertically vibrating linearly polarized light passes through, its vibration direction will rotate 90 degrees to become horizontal vibration. When horizontally vibrating linearly polarized light passes through, it will also rotate 90 degrees to become vertical vibration.

[0053] The optical isolator 14 is used for unidirectional light beam passage to prevent the object light from mixing with the reference light; the first lens 17 and the first microscope objective 18 form the first telecentric optical path structure, and the second microscope objective 20 and the second lens 21 form the second telecentric optical path structure to eliminate phase aberration.

[0054] The second plane mirror 9 adjusts the angle between the red light in reference light one and the red light in transmitted object light one, and between the red light in reference light two and the red light in reflected object light two by controlling the mirror tilt angle. The third plane mirror 13 adjusts the angle between the green light in reference light one and the green light in transmitted object light one, and between the green light in reference light two and the green light in reflected object light two by controlling the mirror tilt angle, so as to facilitate spectral separation in the transmitted light path and the reflected light path and realize off-axis dual-wavelength recording optical path.

[0055] The first beam splitter 6, the second beam splitter 16, the third beam splitter 22, the fourth beam splitter 26, and the fifth beam splitter 29 are depolarizing beam splitters, splitting the beam in a 1:1 ratio; the function of the polarizing beam splitter 11 is to separate the incident beam into vertically vibrating linearly polarized red light and parallelly vibrating linearly polarized green light according to its polarization state; the function of the beam expander 8 is to expand the beam.

[0056] A measurement method for a dual-wavelength digital holographic microscope with transmission and reflection modes, comprising a transmission mode and a reflection mode, wherein the method steps are as follows:

[0057] Step 1: Install the sample to be tested 19 into the dual-wavelength digital holographic microscope with transmission and reflection synergy.

[0058] Step 2: Turn on the first laser 1 and the second laser 4, and use the first camera 23 to acquire a transmission hologram and the second camera 30 to acquire a reflection hologram.

[0059] Step 3: Based on the principle of off-axis dual-wavelength digital holography, the acquired dual-wavelength digital transmission hologram or reflection hologram is processed by spectral filtering to retain the positive first-order spectra of red and green light, while removing interference from the zeroth and negative first-order spatial spectra. The specific steps are as follows:

[0060] The light intensity of a hologram with superimposed red and green light can be expressed as:

[0061]

[0062] In the formula, Represents the spatial coordinates of the recording plane. and These represent the light intensities of the red hologram and the green hologram, respectively. and These represent the amplitude information of the red and green object beams, respectively. and These represent the phase information of the red and green object beams, respectively. and These represent the amplitude information of the red reference light and the green reference light, respectively. and These represent the phase information of the red reference light and the green reference light, respectively. and For red light carrier frequency information, and For green light carrier frequency information, The DC component of the hologram is represented by the central zero-order spectrum. The modulation term is represented by positive and negative first-order spectra in the spectrum; among them, the positive first-order spectrum is a real image containing the phase information of the sample under test (19), which needs to be retained, while the negative first-order spectrum is its conjugate virtual image, which needs to be removed as interference.

[0063] Spectral filtering of a hologram can be expressed as:

[0064]

[0065] In the formula, and These represent the filtered red hologram and the filtered green hologram, respectively. and These represent the Fourier transform and the inverse Fourier transform, respectively. and These represent the red light spectrum bandpass filter and the green light spectrum bandpass filter, respectively.

[0066] Step 4: Introduce the same reconstructed light as the reference light, simulate the diffraction process of the light wave using a computer, and digitally reconstruct the complex amplitude of the light wave field on the image plane based on the angular spectrum principle. Obtain the encapsulation phase information of the sample 19 from the complex amplitude of the light wave field. The specific procedure is as follows:

[0067] By introducing the same reconstructed light as the reference light, the carrier modulation effect of the reference light can be removed, and the light field distributions of red and green light can be represented as follows:

[0068]

[0069] In the formula, and These represent the red light reproduction light and the green light reproduction light, respectively.

[0070] By simulating the diffraction process of light waves using a computer, the complex amplitude of the light wave field on the image plane can be reconstructed based on the angular spectrum principle as follows:

[0071]

[0072] In the formula, The spatial coordinates of the representation surface are represented by j, where j represents the imaginary number. and These represent the wavelengths of red and green light, respectively. This represents the axial distance of the light field as it propagates along the direction of propagation.

[0073] The phase information of the sample 19 to be measured, obtained from the complex amplitude of the light wave field, can be expressed as:

[0074]

[0075] In the formula, Represents the arctangent function. and These represent the operations of extracting the imaginary part and the real part, respectively.

[0076] Step 5: Calculate the difference between the phases of the red and green wavelengths and compensate for their phase jumps to obtain the phase of the equivalent composite wavelength, which is the phase information of the sample 19 to be tested.

[0077] The equivalent composite wavelength can be expressed as:

[0078]

[0079] The phase of the equivalent composite wavelength, i.e., the phase information of the sample under test (19), can be expressed as:

[0080] .

[0081] Example 1

[0082] When the sample to be tested is transparent, a hologram is acquired in the optical path of the transmission mode, such as... Figure 2 As shown.

[0083] The working process of this embodiment is as follows: the first laser 1 and the second laser 4 emit red light beams and green light beams respectively. The red light beam emitted by the first laser 1 is modulated by the first polarizer 2 to output vertically vibrating linearly polarized red light, which is then reflected by the first plane mirror 3 to the first beam splitter 6. The green light beam emitted by the second laser 4 is modulated by the second polarizer 5 to output parallel vibrating linearly polarized green light, which is then combined with the vertically vibrating linearly polarized red light beam at the first beam splitter 6 and then split into object light and reference light.

[0084] The reference light passes sequentially through attenuator 7 and beam expander 8, and is then split at polarizing beam splitter 11 into a vertically vibrating linearly polarized red beam and a parallelly vibrating linearly polarized green beam. The reflected vertically vibrating linearly polarized red light passes through first quarter-wave plate 10, is reflected by second plane mirror 9, and then passes through first quarter-wave plate 10 again, becoming parallelly vibrating linearly polarized red light. The transmitted parallelly vibrating linearly polarized green light passes through second quarter-wave plate 12, is reflected by third plane mirror 13, and then passes through second quarter-wave plate 12 again, becoming vertically vibrating linearly polarized green light. This green light and the parallelly vibrating linearly polarized red beam are then combined at polarizing beam splitter 11. After the beam is combined, the reference beam contains two beams of red and green light with orthogonal vibration directions. This beam is reflected by fourth beam splitter 26, passes through first half-wave plate 25, and reaches third beam splitter 22.

[0085] The object beam is reflected by the fourth plane mirror 15 through the optical isolator 14 to the second beam splitter 16 and then transmitted through the first lens 17 and the first microscope objective 18. After being transmitted through the sample to be tested 19, it is reflected by the fifth plane mirror 24 through the second microscope objective 20 and the second lens 21 and then to the third beam splitter 22, where it interferes with the reference beam and is recorded by the first camera 23 as a transmission hologram.

[0086] Example 2

[0087] When the sample to be tested is non-transparent, a hologram is acquired in the optical path of the reflection mode, such as... Figure 3 As shown.

[0088] The working process of this embodiment is as follows: the first laser 1 and the second laser 4 emit red light beams and green light beams respectively. The red light beam emitted by the first laser 1 is modulated by the first polarizer 2 to output vertically vibrating linearly polarized red light, which is then reflected by the first plane mirror 3 to the first beam splitter 6. The green light beam emitted by the second laser 4 is modulated by the second polarizer 5 to output parallel vibrating linearly polarized green light, which is then combined with the vertically vibrating linearly polarized red light beam at the first beam splitter 6 and then split into object light and reference light.

[0089] The reference light passes sequentially through attenuator 7 and beam expander 8, and is then split at polarizing beam splitter 11 into a vertically vibrating linearly polarized red beam and a parallelly vibrating linearly polarized green beam. The reflected vertically vibrating linearly polarized red light passes through first quarter-wave plate 10, is reflected by second plane mirror 9, and then passes through first quarter-wave plate 10 again, becoming parallelly vibrating linearly polarized red light. The transmitted parallelly vibrating linearly polarized green light passes through second quarter-wave plate 12, is reflected by third plane mirror 13, and then passes through second quarter-wave plate 12 again, becoming vertically vibrating linearly polarized green light. This green light then combines with the parallelly vibrating linearly polarized red beam at polarizing beam splitter 11. After combining, the reference beam contains two beams of red and green light with orthogonal vibration directions. This reference beam passes through second half-wave plate 27 and reaches fifth beam splitter 29.

[0090] The object beam is reflected by the fourth plane mirror 15 through the optical isolator 14 to the second beam splitter 16 and then transmitted. It passes through the first lens 17 and the first microscope objective 18 in sequence. After being reflected by the sample to be tested 19, it passes through the first microscope objective 18 and the first lens 17 in sequence and is reflected by the second beam splitter 16 to the sixth plane mirror 28. It is then reflected by the sixth plane mirror 28 to the fifth beam splitter 29, where it interferes with the reference beam and is recorded as a reflection hologram by the second camera 30.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dual-wavelength digital holographic microscope with transmission and reflection synergy, characterized in that, include: First laser (1), first polarizer (2), first plane mirror (3), second laser (4), second polarizer (5), first beam splitter (6), attenuator (7), beam expander (8), second plane mirror (9), first quarter-wave plate (10), polarizing beam splitter (11), second quarter-wave plate (12), third plane mirror (13), optical isolator (14), fourth plane mirror (15), second beam splitter (16), first lens (17), first microscope objective (18), sample to be tested (19), second microscope objective (20), second lens (21), third beam splitter (22), first camera (23), fifth plane mirror (24), first half-wave plate (25), fourth beam splitter (26), second half-wave plate (27), sixth plane mirror (28), fifth beam splitter (29), second camera (30); The first laser (1) and the second laser (4) emit red and green light beams respectively. The red light beam emitted by the first laser (1) is modulated by the first polarizer (2) to output vertically vibrating linearly polarized red light, which is then reflected by the first plane mirror (3) to the first beam splitter (6). The green light beam emitted by the second laser (4) is modulated by the second polarizer (5) to output parallel vibrating linearly polarized green light, which is combined with the vertically vibrating linearly polarized red light beam at the first beam splitter (6) and then split into object light and reference light. The reference light passes sequentially through an attenuator (7) and a beam expander (8), and is then split at the polarizing beam splitter (11) into a vertically vibrating linearly polarized red beam and a parallel-vibrating linearly polarized green beam. The reflected vertically vibrating linearly polarized red light passes through a first quarter-wave plate (10), is reflected by a second plane mirror (9), and then passes through the first quarter-wave plate (10) again, becoming parallel-vibrating linearly polarized red light. The transmitted parallel-vibrating linearly polarized green light passes through a second quarter-wave plate (12) and is reflected by a third plane mirror (13). After passing through the second quarter-wave plate (12), it becomes vertically vibrating linearly polarized green light, which is combined with the parallel vibrating linearly polarized red light beam at the polarizing beam splitter (11). After the beam is combined, the reference beam contains two linearly polarized red light and linearly polarized green light with orthogonal vibration directions. The reference beam is split into reference beam one and reference beam two at the fourth beam splitter (26). Reference beam one passes through the first half-wave plate (25) to reach the third beam splitter (22), and reference beam two passes through the second half-wave plate (27) to reach the fifth beam splitter (29). The object light is reflected by the fourth plane mirror (15) through the optical isolator (14) to the second beam splitter (16) and then transmitted. It passes through the first lens (17) and the first microscope objective (18) in sequence. When it passes through the sample to be tested (19), it is divided into transmitted object light one and reflected object light two. Transmitted object light one passes through the second microscope objective (20) and the second lens (21) in sequence and is reflected by the fifth plane mirror (24) to the third beam splitter (22), where it interferes with the reference light one and is recorded by the first camera (23) as a transmission hologram. Reflected object light two passes through the first microscope objective (18) and the first lens (17) in sequence and is reflected by the second beam splitter (16) to the sixth plane mirror (28), and then by the sixth plane mirror (28) to the fifth beam splitter (29), where it interferes with the reference light two and is recorded by the second camera (30) as a reflection hologram.

2. The dual-wavelength digital holographic microscope device with transmission-reflection synergy according to claim 1, characterized in that, The first polarizer (2) and the second polarizer (5) are used to adjust the polarization directions of the two beams emitted by the first laser (1) and the second laser (4) to be orthogonal; the attenuator (7) is used to adjust the intensity of the object beam and the reference beam to be consistent; the first half-wave plate (25) and the second half-wave plate (27) are used to ensure that interference occurs between the transmitted object beam and the reference beam and between the reflected object beam and the reference beam. The fast axis of the half-wave plate is at a 45-degree angle to the vertical direction. When vertically vibrating linearly polarized light passes through, its vibration direction will rotate 90 degrees to become horizontal vibration. When horizontally vibrating linearly polarized light passes through, it will also rotate 90 degrees to become vertical vibration.

3. The dual-wavelength digital holographic microscope device with transmission-reflection synergy according to claim 1, characterized in that, The optical isolator (14) is used for unidirectional light beam passage to prevent the object light from mixing with the reference light; the first lens (17) and the first microscope objective (18) form the first telecentric optical path structure, and the second microscope objective (20) and the second lens (21) form the second telecentric optical path structure to eliminate phase aberration.

4. The dual-wavelength digital holographic microscope device with transmission-reflection synergy according to claim 1, characterized in that, The second plane mirror (9) adjusts the angle between the red light in reference light one and the red light in transmitted object light one, and between the red light in reference light two and the red light in reflected object light two by controlling the tilt angle of the mirror. The third plane mirror (13) adjusts the angle between the green light in reference light one and the green light in transmitted object light one, and between the green light in reference light two and the green light in reflected object light two by controlling the tilt angle of the mirror, so as to facilitate the spectral separation in the transmitted light path and the reflected light path and realize the off-axis dual-wavelength recording light path.

5. The dual-wavelength digital holographic microscope device with transmission-reflection synergy according to claim 1, characterized in that, The first beam splitter (6), the second beam splitter (16), the third beam splitter (22), the fourth beam splitter (26), and the fifth beam splitter (29) are depolarizing beam splitters, which split the beam in a 1:1 ratio; the function of the polarizing beam splitter (11) is to separate the incident beam into vertically vibrating linearly polarized red light and parallelly vibrating linearly polarized green light according to its polarization state; the function of the beam expander (8) is to expand the beam.

6. A measurement method for a dual-wavelength digital holographic microscope with transmission-reflection synergy as described in any one of claims 1-5, characterized in that, Including transmission mode and reflection mode, the method steps are as follows: The sample to be tested was loaded into a dual-wavelength digital holographic microscope with a transmission-reflection synergy (19). Turn on the first laser (1) and the second laser (4), and collect the transmission hologram through the first camera (23) and the reflection hologram through the second camera (30); Based on the principle of off-axis dual-wavelength digital holography, the acquired dual-wavelength digital transmission hologram or reflection hologram is filtered by spectrum to retain the positive first-order spectrum of red light and green light respectively, and remove the interference of the zero-order and negative first-order spatial spectrum. The same reconstructed light as the reference light is introduced, and the diffraction process of the light wave is simulated by computer. The complex amplitude of the light wave field on the image plane is digitally reconstructed according to the principle of angular spectrum. The encapsulation phase information of the sample to be tested (19) is obtained from the complex amplitude of the light wave field. The phase difference between the red and green wavelengths is calculated and the phase jump is compensated to obtain the phase of the equivalent composite wavelength, which is the phase information of the sample (19) to be tested.

7. The measurement method of a dual-wavelength digital holographic microscope with transmission-reflection synergy according to claim 6, characterized in that, The light intensity of a hologram with superimposed red and green light can be expressed as: （1）； In the formula, Represents the spatial coordinates of the recording plane. and These represent the light intensities of the red hologram and the green hologram, respectively. and These represent the amplitude information of the red and green object beams, respectively. and These represent the phase information of the red and green object beams, respectively. and These represent the amplitude information of the red reference light and the green reference light, respectively. and These represent the phase information of the red reference light and the green reference light, respectively. and For red light carrier frequency information, and For green light carrier frequency information, The DC component of the hologram is represented by the central zero-order spectrum. The modulation term is represented by positive and negative first-order spectra in the spectrum; among them, the positive first-order spectrum is a real image containing the phase information of the sample under test (19), which needs to be retained, while the negative first-order spectrum is its conjugate virtual image, which needs to be removed as interference.

8. The measurement method of a dual-wavelength digital holographic microscope with transmission-reflection synergy according to claim 6, characterized in that, Spectral filtering of a hologram can be expressed as: （2）； （3）； In the formula, and These represent the filtered red hologram and the filtered green hologram, respectively. and These represent the Fourier transform and the inverse Fourier transform, respectively. and These represent the red light spectrum bandpass filter and the green light spectrum bandpass filter, respectively.

9. The measurement method of a dual-wavelength digital holographic microscope with transmission-reflection synergy according to claim 6, characterized in that, By introducing the same reconstructed light as the reference light, the carrier modulation effect of the reference light can be removed, and the light field distributions of red and green light can be represented as follows: （4）； （5）； In the formula, and These represent the red light reproduction light and the green light reproduction light, respectively. By simulating the diffraction process of light waves using a computer, the complex amplitude of the light wave field on the image plane can be reconstructed based on the angular spectrum principle as follows: （6）； （7）； In the formula, The spatial coordinates of the reconstructed surface are represented by j, where j represents the imaginary number. and These represent the wavelengths of red and green light, respectively. This represents the axial distance of the light field as it propagates along the direction of propagation. The phase information of the sample (19) to be measured, obtained from the complex amplitude of the light wave field, can be expressed as: （8）； （9）； In the formula, Represents the arctangent function. and These represent the operations of extracting the imaginary part and the real part, respectively.

10. The measurement method of a dual-wavelength digital holographic microscope with transmission-reflection synergy according to claim 6, characterized in that, By taking the phase difference between the red and green wavelengths and compensating for their phase transitions, the phase of the equivalent composite wavelength is obtained. The equivalent composite wavelength can be expressed as: （10）； The phase of the equivalent composite wavelength, i.e., the phase information of the sample under test (19), can be expressed as: （11）。

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