AU2020101628A4

AU2020101628A4 - An intracavity-enhanced dual-wavelength common-path phase microscopy imaging measurement system based on an F-P interferometer

Info

Publication number: AU2020101628A4
Application number: AU2020101628A
Authority: AU
Inventors: Sheng Li; Lingzhi MENG; Libo Yuan
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2020-08-03
Filing date: 2020-08-03
Publication date: 2020-09-10
Anticipated expiration: 2028-08-03

Abstract

The present invention provides an intracavity-enhanced dual-wavelength common-path phase microscopy imaging measurement system based on an F-P interferometer. It is characterized by: it comprises a laser light source 1, an optical attenuator 2, a fiber coupler (LFC) 3, a single mode fiber 4, a fiber collimator (FCL) 5, an expander 6, an F-P interferometer 7, an object to be measured 8, a microscopic objective 9, a CCD detecting camera 10 and a computer 11. The present invention can be used for digital holography and refractive index measurements of microscopic objects, and can be widely used for three-dimensional microscopic imaging of refractive index of various microscopic objects. 1/2 DRAWINGS 1-11 1-24-2 5 68 8 9 11 10 FIG. 1 1-2 FIG. 2

Description

1/2 DRAWINGS

1-11

5 1-24-2

68 8

9 11

10

FIG. 1

1-2

FIG. 2

DESCRIPTION TITLE OF INVENTION

An intracavity-enhanced dual-wavelength common-path phase microscopy imaging

measurement system based on an F-P interferometer

TECHNICAL FIELD

[0001] The present invention relates to an intracavity-enhanced dual-wavelength common-path

phase microscopy imaging measurement system based on an F-P interferometer, which can be

used for the three-dimensional microscopic imaging of refractive index inside cells and various

microscopic objects, which belongs to the field of optical imaging technology.

BACKGROUND ART

[0002] Micro-optical imaging, also commonly referred to as Optical Microscopy, or Light

Microscopy, is the technology of reflecting visible light through the sample or from the sample,

passing through one or more lens, to obtain a magnified image of the microscopic sample. The

image obtained can be viewed directly with eyes through an eyepiece, or with a photographic

plate or a digital image detector such as a charge coupled device (CCD) and a complementary

metal oxide semiconductor (CMOS) to record, and a computer to display and analyze process.

[0003] Ordinary optical microscopy using bright-field illumination is often limited in three ways: first, it can only be performed on dark-colored samples (transmissive) or strong-reflective samples (reflective) for imaging; second, the optical diffraction limits restrict the maximum resolution of the technique to be approximately 200 nm; third, out-of-focus information reduces image contrast. Based on the excitation of the fluorescent molecules in the sample (exogenous or endogenous) and the Fluorescence Microscopy emitted by fluorescence, it can overcome the limitations of not being able to image transparent samples, but with limited resolution and out of-focus interference, other measures are still needed to address the problem.

[0004] In the 1930s, the Dutch physicist Zemike first proposed the phase contrast technique. The

principle is that by changing the phase of the direct light (i.e. zero frequency light) by 90 and

attenuating appropriately, so the direct light and the diffraction light can interfere to cause the

distribution of complex amplitudes in the image plane to be approximately proportional to the

phase distribution of the object, converting the "invisible" phase change into a "visible" phase

change. Using this technique, direct observation and imaging of unstained live cell samples can

be easily achieved, but it has the disadvantage of being unsuitable for thick samples and very

small samples.

[0005] Digital holography has been used in recent years for its ability to record and display full

information about the object being recorded and apply to microscopy imaging. A three

wavelength reflective digital holographic microscope is disclosed in patent CN109062018A.

The digital holographic microscope consists of three beams of linearly polarized light sources

with different wavelengths, as well as a spectroscopic prism and lens. It achieves the function of

having better image resolution compared to previous microscopy imaging devices, but its system

uses only the reflected light as the forming interference light and a more accurate image cannot

be obtained.

[0006] Disclosed in patent CN109615651A is a three-dimensional microscopic imaging method

and system based on a light field microscope system, the light field intensity image and its first forward projection matrix, the high-resolution intensity image, and the second forward projection matrix, by a preset algorithm, are reconstructed in three dimensions to generate the results of the three-dimensional reconstruction of the three-dimensional sample. By adding one path of acquisition light, to achieve the enhancement of focal plane reconstruction signal-to-noise ratio (SNR) under the circumstance of having same number of iterations, the reconstruction effect of the light field microscopy image is greatly increased. However, the method and system were reconstructed using a more optimized algorithm, relying on an optical path structure that still has no changes, and the iterations are complex and difficult to implement.

[0007] Disclosed in patent CN109520988A is a microscopic imaging system, consists of a shock-isolated platform, a removable slide, and an imaging component. It can conduct high accuracy tests on different types of cell samples, but the system is based on the principle of cellular fluorescence to image and cannot be used to image other non-cell-particles and objects, it has a limited applicability.

[0008] Patent CN201710904860.1 discloses an optical coherence tomography imaging system. The imaging system uses a Mach-Zehnder interferometric optical path, which features an optical fiber to simplify the system and reduce costs, but comparing to an F-P cavity optical path structure, it is still quite complex.

[0009] Patent CN201810145657.5 discloses a high-resolution digital holographic diffraction topographic imaging, characterized by a Mach-Zehnder interferometric optical path structure, using a synthetic aperture method to obtain N numbers of synthetic high resolution holograms, thereby obtaining a high-resolution three-dimensional refractive index reproduction of the measured sample. In contrast, the structure is more complex and fundamentally different from the present invention.

[0010] Patent CN201910136421.X discloses a super-resolution digital holographic imaging

system and imaging method, the characteristic of the imaging system is that a piece of

transmissive spatial light modulator is incorporated in front of a conventional Mach-Zehnder

interference optical pat, which can modulate the light source. There is a fundamental difference

compared to the present invention which uses an optical path structure with an F-P cavity.

[0011] In this regard, the dual-wavelength common-path phase microscopy imaging

measurement system based on an F-P interferometer designed by the present invention, the F-P

interferometer has a fine degree of 20 or more, which allows the use of multiple reflections of

light beams in the F-P interferometer, and the interference strips produced after its reflection and

transmission will be multiplied, directly improving the resolution of imaging from the

interference structure part.

[0012] In addition, the dual-wavelength common-path phase microscopy imaging measurement

system based on an F-P interferometer designed by the present invention is capable of using

dual-wavelength to improve the stability and accuracy of phase measurements. The two light

sources emit different wavelengths of light to form a composite hologram. The synthesized

wavelength is then obtained by calculating, to reduce the scattering noise in the numerical

reconstruction and to improve the accuracy and stability. The structure of the invention is simple

and easy to operate and adjust, which is a more optimized microscopic imaging and

measurement system for microscopic objects.

SUMMARY OF INVENTION

[0013] It is an object of the present invention to provide a simple and compact structured, and

easy to operate and adjust dual-wavelength common-path phase microscopy imaging

measurement system based on an F-P interferometer

[0014] The object of the present invention is achieved by the following method:

[0015] A dual-wavelength common-path phase microscopy imaging measurement system

comprises a laser light source 1, an optical attenuator 2, a LFC fiber coupler 3 , a single mode

fiber 4, an FCL fiber collimator 5, an expander 6, an F-P interferometer 7, an object to be

measured 8, a microscopic objective 9, a CCD detecting camera 10 and a computer 11.

[0016] In the system, the laser light source 1 is divided into two light sources of different

wavelengths 1-1 and 1-2, the light X1 emitted from the light source 1-1 passes through the optical

attenuator 2-1, and couple into the single-mode optical fiber 4-1 through the LFC fiber coupler

3-1. The light X1 is transmitted in the optical fiber to the optical fiber collimator 5 for collimation

and the expander 6 for expansion, and then transmitted to the F-P interferometer. The light beam

X1 is reflected multiple times in the F-P cavity, multiply-magnifying the optical path difference

of the particle to be measured placed in the F-P cavity, thus multiply-magnifying its phase

information, the transmitted light carrying information of the particle to be measured particle is

transmitted to the microscopic objective 9 underneath, then passes the microscopic objective to

the detecting camera 10 underneath, and then transmits the signal of the particle to be measured

to the computer 11. Then, the light X2 emitted from the light source 1-2 passes through the optical

attenuator 2-2, and couple into the single-mode optical fiber 4-2 through the LFC fiber coupler

3-2. The light X2 is transmitted in the optical fiber to the optical fiber collimator 5 for collimation

X2 is reflected multiple times in the F-P cavity, multiply-magnifying the optical path difference

of the particle to be measured placed in the F-P cavity, the transmitted light carrying information

of the particle to be measured particle is transmitted to the microscopic objective 9 underneath,

then passes the microscopic objective to the detecting camera 10 underneath, and then transmits

the signal of the particle to be measured to the computer 11. The computer 11 gets the

synthesized wavelength based on the calculation of the two wavelengths, thus reducing the

speckle noise in the numerical reconstruction and improving the accuracy.

[0017] The invention also has the following technical features.

[0018] The F-P interferometer of the optical path system is used as an interference device, it allows the light beam to produce self-interference in the optical path through multiple reflections of light in the F-P cavity, which can significantly increase the width of the interference strip due to its high number of reflections, and achieves the purpose of increasing the spatial resolution.

[0019] The adjustable F-P interferometer described herein has a fixed cavity length and the heights of the two flat plates of the cavity are parallel, producing a more desirable interference strip.

[0020] The microscopic objective 9 described herein uses an apochromatic microscope objective, which has excellent correction and an extremely high numerical aperture, thus providing maximum resolution, color purity, contrast, and image straightness in observation and microphotography.

[0021] The single-mode fiber can transmit the two light sources of different wavelengths to a fiber collimator, avoiding complexity of optical paths and instability of various reflection and transmission devices, and achieving the goal of simplifying the optical path.

[0022] The present invention records two interferograms separately in a computer based on optical information recorded from two beams of light with different wavelengths, and derives a

synthesized wavelength based on A 21 2 . The synthesized wavelength is significantly

shorter than the wavelengths of the two waves, thereby reducing phase scattering noise and improving accuracy stability in the two-wavelength numerical reconstruction.

[0023] In the F-P cavity, the beam is reflected and transmitted multiple times, the phase is

enhanced, and the final complex amplitude of the beam passing through the F-P cavity is.

Ur u~= = Ao4 1- R_-R

[0024] 1- Re' (1)

[0025] Where UT is the complex amplitude of the transmitted light, A, is the complex

amplitude of the incident light in the F-P cavity, R is the surface reflectance on the inside of the

two parallel planar glass plates in the F-P cavity, and 6 is the phase distribution of the cells to

be measured.

[0026] When multiple light beams are interfering in the F-P cavity, the phase distribution

obtained by digital holography for F-P cavity multi-beam interference is.

2rc 5(X ,y - - l d c#>

[0027] (2)

[0028] Where n is the refractive index of the cavity medium, d is the thickness of the F-P cavity,

and I is the synthesized wavelength of the light source.

[0029] Along the direction of propagation of the beam, the accumulation of the refractive index

at each point through the interior of the object to be measured is the phase distribution obtained

from a digital hologram, and when the difference in refractive indexes within the object to be

measured and with the ambient medium surrounding the object to be measured is small, and the

optical path difference is the accumulation of the refractive index in the direction of the beam path, the phase distribution is related to the refractive index distribution of the object to be measured as follows:

2/c 5(x,y)= -- 2.[n(x,y,z)-no]dz

[0030] (3)

[0031]Where n(x,y,z) is the refractive index distribution within the cell to be tested 2, the z

axis is the direction of light beam propagation, and no is the refractive index of the ambient

medium surrounding the cell to be tested 2.

[0032] The corresponding synthesized wavelength is:

1 2

[0033] " +2 (4)

[0034] A more accurate strip was obtained by reducing the scattering noise through the holographic superposition effect of the synthesized wavelength.

[0035] A comparison between the phase distribution map obtained and the phase distribution map generally obtained by M-Z interference is shown in FIG. 4. Compared to the conventional M-Z method, a more pronounced rate of change image can be obtained, indicating that the sharpness of the interference strips will be significantly enhanced, and the particle hologram image thus reconstructed by the computer will have a higher resolution than the conventional method and will be more suitable for fine measurements.

[0036] The device of the present invention, due to its small number of optical components, it is convenient for at a later stage to add various tunable devices onto the F-P interferometer, to effectively control the parallelism of the F-P interferometer and increase the reflectivity of the F P interferometer, there is a large room for modifications. In addition, if the synthesized wavelength is obtained using a method in which the number of wavelengths is greater than two, only the corresponding number of wavelengths is increased, which is the same method to the present invention's synthesized wavelength microscopy imaging method, and should also be within the scope of protection of the present invention.

[0037] The method of the present invention can significantly improve the resolution of the reproduced image.

BRIEF DESCRIPTION OF DRAWINGS

[0038] FIG. 1 is an embodiment of an intracavity-enhanced dual-wavelength common-path phase microscopy imaging measurement system based on an F-P interferometer, it is characterized by: it comprises a laser light source 1, an optical attenuator 2, a LFC fiber coupler 3 , a single mode fiber 4, an FCL fiber collimator 5, an expander 6, an F-P interferometer 7, an object to be measured 8, a microscopic objective 9, a CCD detecting camera 10 and a computer 11.

[0039] FIG. 2 is an example of an embodiment of the F-P cavity of a dual-wavelength common path phase microscopy imaging measurement system based on an F-P interferometer.

[0040] FIG. 3 shows the interference strips obtained by synthesizing wavelengths in a dual wavelength common-path phase microscopy imaging measurement system based on an F-P interferometer.

[0041] FIG. 4 is a comparison diagram of the intensity variations obtained by a dual-wavelength

common-path phase microscopy imaging measurement system based on an F-P interferometer

and a general M-Z interferometer.

DESCRIPTION OF EMBODIMENTS

[0042] The invention is further described below in relation to specific embodiments. However,

this should not be used to limit the scope of protection of the present invention.

[0043] Referring to FIG. 1, FIG. 1 is a dual-wavelength common-path phase microscopy

imaging measurement system based on an F-P interferometer, it is characterized by: it comprises

a laser light source 1, an optical attenuator 2, a LFC fiber coupler 3 , a single mode fiber 4, an

FCL fiber collimator 5, an expander 6, an F-P interferometer 7, an object to be measured 8, a

microscopic objective 9, a CCD detecting camera 10 and a computer 11. The location

relationships of the above components are as follows:

[0044] Refer to the light source 1-1, along the direction of the optical axis of the output light of

the laser light source 1-1, in order there are the attenuator 2-1 and the LFCfiber coupler 3-1.

Connect the single-mode optical fiber 4-1 to the LFC fiber coupler 3-1 and the FCL optical fiber

collimator 5, and then along the direction of the optical axis after the beam is emitted from the

collimator is the expander 6 and the F-P interferometer 7 where the object to be measured 8 is in.

Then, refer to the light source 1-2, along the direction of the optical axis of the output light of the

laser light source 1-2, in order there are the attenuator 2-2 and the LFC fiber coupler 3-2.

Connect the single-mode optical fiber 4-2 to the LFC fiber coupler 3-2 and the FCL optical fiber collimator 5, and then along the direction of the optical axis after the beam is emitted from the collimator is the expander 6 and the F-P interferometer 7. The MO micro-objective lens and the CCD detecting camera 10 are below the F-P interferometer, and then the detecting camera is connected to the computer 11 on the side.

[0045] A method of achieving dual-wavelength three-dimensional phase imaging enhancement of an object to be measured using the present invention, refer to FIG. 2, the method comprises the following steps:

[0046] The operation of placing the object to be measured 8 in the F-P interferometer 7 is divided into two parts, the first of which is: Adjust the position of each device in the optical path so that the output coherent light from the laser light source 1-1 is attenuated by the attenuator 2 1, and couple into the single-mode fiber 4-1 at the LFC fiber coupler 3-1, the light is transmitted through the single-mode fiber, and then collimated at the fiber collimator 5. Then expanded by the expander 6 into the F-P interferometer, at this time adjust the position of the F-P interferometer, so that the beam in the F-P cavity, where the object to be measured is in, is reflected multiple times. Adjust the microscopic objective 9, so that the transmitted light from the interferometer can completely enter the microscopic objective 9, slowly move the detecting camera 10 so that it is at the back focal plane of the light passing through the microscopic objective 9.

[0047] Then proceed to the second part: Adjust the position of each device in the optical path so that the output coherent light from the laser light source 1-2 of another wavelength is attenuated by the attenuator 2-2, and couple into the single-mode fiber 4-2 at the LFC fiber coupler 3-2, the light is transmitted through the single-mode fiber, and then also collimated at the fiber collimator 5. Then expanded by the expander 6 into the F-P interferometer, at this time adjust the position of the F-P interferometer, so that the beam in the F-P cavity, where the object to be measured is in, is reflected multiple times. Adjust the microscopic objective 9, so that the transmitted light from the interferometer can completely enter the microscopic objective 9, slowly move the detecting camera 10 so that it is at the back focal plane of the light passing through the microscopic objective 9. Then use A = to obtain the synthesized wavelength, calculating with the above formula to obtain the desired composite recording map, reducing the phase parcel required for reconstruction.

[0048] The working embodiment of the F-P cavity of a dual-wavelength common-path phase

microscopy imaging measurement system based on an F-P interferometer is as follows:

[0049] Refer first to FIG. 3, which shows the working steps of the F-P cavity in a dual

wavelength common-path phase microscopy imaging measurement system based on an F-P

interferometer. After light enters the F-P cavity at an angle, it is reflected several times in the

cavity, and each time the reflection passes through the object to be measured. Every time the

reflective light passes the object to be measured, the optical path difference will be multiply

amplified, and finally the light is transmitted out of the F-P cavity, passes the MO microscopic

objective, then converge to the CCD detecting camera and an amplified interference strip is

obtained.

[0050] The present invention is a dual-wavelength common-path phase microscopy imaging

measurement system based on an F-P interferometer, which uses an F-P interferometer with a

fixed cavity length to repeatedly reflect and enhance the coherent light, which carries the phase

information of the object to be measured. Meanwhile the dual-wavelength beams measure the

object to be measured sequentially, producing the interferograms obtained by two light sources

with different wavelengths, and then calculates the arc tangent of the two reconstructed images

as well as the amplitude of the product, in the meantime obtain the reconstructed image

according to the synthesized wavelength.

[0051] Preferably, the single-mode fiber used in this example is Corning's corning SMF-28 single-mode fiber, which has good transmission efficiency.

[0052] Preferably, the object to be measured in this embodiment is a polystyrene sphere. A good uniform strip can be obtained.

[0053] Preferably, the two light sources used in this embodiment have wavelengths of 632.8 nm and 532 nm, respectively. These two beams of light yield better holograms when sheared transversely to form a composite hologram.

[0054] Preferably, the F-P cavity has a free spectral range of FSR > 100 GHz, a fineness of F > ,and aloss of<3 dB.

[0055] The foregoing embodiments are merely better embodiments for the purpose of fully illustrating the invention, and the scope of protection of the invention is not limited to them. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the scope of protection of the present invention. The scope of protection of the present invention is governed by the claims.

Claims

1. An intracavity-enhanced dual-wavelength common-path phase microscopy imaging

measurement system based on an F-P interferometer. It comprises a laser light source 1, an

optical attenuator 2, a fiber coupler (LFC) 3 , a single mode fiber 4, a fiber collimator (FCL) 5,

an expander 6, an F-P interferometer 7, an object to be measured 8, a microscopic objective 9, a

CCD detecting camera 10 and a computer 11. In the system, the laser light source 1 is divided

into two light sources of different wavelengths 1-1 and 1-2, the light emitted from the light

source 1-1 (the wavelength is Xi) passes through the optical attenuator 2-1, and couple into the

single-mode optical fiber 4-1 through the LFC fiber coupler 3-1. The light X1 is transmitted in the

optical fiber to the optical fiber collimator 5 for collimation and the expander 6 for expansion,

and then transmitted to the F-P interferometer. The beam with the wavelength ofX1 is reflected

multiple times in the F-P cavity, multiply-magnifying the optical path difference of the particle to

be measured placed in the F-P cavity, thus multiply-magnifying its phase information, the

transmitted light carrying information of the particle to be measured particle is transmitted to the

microscopic objective 9 underneath, then passes the microscopic objective to the detecting

camera 10 underneath, and then transmits the signal of the particle to be measured to the

computer 11. Then, the light X2 emitted from the light source 1-2 passes through the optical

3-2. The light with a wavelength of X2 is transmitted in the optical fiber to the optical fiber

collimator 5 for collimation and the expander 6 for expansion, and then transmitted to the F-P

interferometer. The beam with the wavelength of X2 is reflected multiple times in the F-P cavity,

multiply-magnifying the optical path difference of the particle to be measured placed in the F-P

cavity, the transmitted light carrying information of the particle to be measured particle is

to the computer 11. The computer 11 gets the synthesized wavelength based on the calculation of

the two wavelengths, thus reducing the speckle noise in the numerical reconstruction and

improving the accuracy.

2. As claimed by claim 1, a microscopy imaging measurement system, it is characterized by:

The F-P interferometer in the optical path system used acts as the device to produce multiplied

optical path difference, through the multiple reflections of light in the F-P cavity, each time it

passes the particles to be measured the optical path difference can be multiply-increased, thereby

significantly increasing the width of the interference strip, to achieve the purpose of improving

the resolution.

3. As claimed by claim 1, a microscopy imaging measurement system, it is characterized by:

the system uses two light sources of different wavelengths to obtain two interference strip

distributions with different wavelengths. Then obtains a synthesized wavelengths through the

two different wavelengths, the synthesized wavelength is significantly shorter than the two

wavelengths, then a compound hologram is obtained.

4. As claimed by claim 1, a microscopy imaging measurement system, it is characterized by:

the number of wavelengths used is greater than or equal to 2.

5. As claimed by claim 1, a microscopy imaging measurement system, it is characterized by:

the F-P interferometer, the cavity length remains unchanged, the object to be measured is placed

in the cavity, through multiple reflections to obtain multiply-amplified interference strips.