CN109373905B - Redundant light path-based device and method for measuring out-of-focus distance of micro-scale transparent body - Google Patents
Redundant light path-based device and method for measuring out-of-focus distance of micro-scale transparent body Download PDFInfo
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Abstract
The invention discloses a device and a method for measuring out-of-focus distance of a micro-scale transparent body based on a redundant light path, and relates to the technical field of testing of the micro-scale transparent body. The invention provides a method for acquiring four phase body images under different defocusing degrees through a redundant light path and calculating an SPEC parameter according to the images to determine the position of a phase body relative to an objective lens of an imaging system in the optical axis direction, so that the real-time measurement of the three-dimensional space position of a transparent phase body is realized. According to the invention, the redundant light path is added in the light path, and the light path is adjusted without adopting mechanical movement of the light path, so that the stability of the system is improved. And a direct calculation mode is adopted, an iterative optimization process is not needed, and the calculation process is simple. The redundant light paths work simultaneously, so that real-time image acquisition and processing can be realized, and the redundant light paths can be used for phase body motion analysis.
Description
Technical Field
The invention relates to the technical field of micro-scale transparent body testing, in particular to a measuring system and a measuring method for obtaining the defocusing distance of a transparent body by measuring four phase pictures through a redundant light path, which are suitable for measuring the position of the measured transparent body with different refractive indexes relative to a background medium in the optical axis direction.
Background
The three-dimensional position information of the object is basic data for determining the motion change rule of the object, plays an important role in the fields of biology, physics, chemistry, mechanical engineering, information and the like, and the measurement of the three-dimensional position of a micro-scale transparent body (represented by cells) is the basis of biological research.
Currently, in order to realize micro-scale transparency measurement, fluorescence targeting detection and phase microscopy imaging methods are generally adopted in academia. For the usual test object, cell, fluorescence targeting detection requires the interaction of the fluorescent powder with the cell, which may affect the life process of the cell, ultimately leading to errors between the measurement and the actual process of cell movement change. The phase microscopic imaging method can achieve acquisition of cell thickness distribution data, has little influence on phase volume characteristics, and has been widely regarded in recent years, but in the aspect of acquisition of phase optical axis position data, the conventional phase microscopic imaging method is complex in operation, and needs to mechanically adjust an imaging system or achieve numerical focusing through numerical calculation (p.langhanenberg, b.kemper, d.dirksen, and g.von bally.autofocusing in digital organic phase coherent microscope on phase objects for live cell imaging. applied Optics,2008,47: D176-D182). The stability of the imaging system is easily affected by the way of acquiring the position of the phase body by adopting mechanical adjustment; and the way of numerical calculation requires a complicated trial and error optimization process. In the process of determining the position of the phase body, one key is to adopt a parameter for reasonably measuring the defocusing degree of the phase body. At present, the relation between the existing parameter for measuring the degree of defocus and the parameters of the imaging system, the imaging background and the imaging object is complex, and the determination relation between the degree of defocus parameter and the degree of defocus is difficult to establish, so that the degree of defocus of the imaging object is difficult to measure through the absolute quantity of the parameters. The prior research results (P.Langehanenberg, B.Kemper, D.Dirksen, and G.von Bally. autofocusing in digital pharmacological phase contrast ratio micro-scope on phase objects for live cell imaging, applied Optics,2008,47: D176-D182) show that the Weighted spectral analysis parameter (SPEC) has more ideal performance (good stability, wide operable range, large contrast and wide adaptive range), and the optimal cooperation is the defocus degree measurement parameter of the phase body. It can also be seen from the data in the literature that the SPEC parameter has good symmetry, and the change with defocus can be approximated to be linear in a small range. These features of the SPEC parameter allow for a fast determination of the object plane of the imaging system and the defocus level of the imaging phase from experimental data.
For this purpose, the invention intends to acquire phase body images under four different defocusing degrees through a redundant optical path and calculate the SPEC parameter according to the images so as to determine the position of the phase body relative to an objective lens of an imaging system in the optical axis direction.
Disclosure of Invention
The invention aims to provide a method for acquiring images of a phase body under four different defocusing degrees through a redundant optical path and calculating a SPEC parameter according to the images to determine the position of the phase body relative to an objective lens of an imaging system in the optical axis direction, so that the real-time measurement of the three-dimensional space position of the transparent phase body is realized.
The invention is realized according to the following technical scheme:
the device for measuring the out-of-focus distance of the micro-scale transparent body based on the redundant light path comprises: three redundant imaging optical paths for acquiring phase body diffraction patterns with different defocusing degrees are added in a Mach-Zehnder (Mach-Zehnder) optical path imaging system.
In the above-mentioned device, the imaging system used is a Mach-Zehnder optical path imaging system, the basic optical path thereof is composed of a light source, a spectroscope, an object optical arm optical path and a reference arm optical path, a beam combiner, a spectroscope, a first imaging optical path and a CCD1 (charge coupled device), the light source is selected from a laser with coherence, the object optical arm optical path is composed of a spectroscope, a reflector, a sample cell, an objective lens and a beam combiner for generating an object beam carrying optical phase information of a sample, and the reference arm optical path is composed of a spectroscope, a reflector and a beam combiner for generating a reference beam which is interfered with the object beam to present a specific diffraction pattern.
In the device, partial light beams of the basic light path are divided into three additional redundant light paths by the spectroscope outside the basic light path, the first redundant light path is composed of the spectroscope, the second imaging light path and the CCD2, the second redundant light path is composed of the spectroscope, the third imaging light path and the CCD3, and the third redundant light path is composed of the spectroscope, the reflector, the fourth imaging light path and the CCD 4.
In the device, the phase body diffraction patterns with different defocusing degrees are obtained through three redundant imaging optical paths and a basic imaging optical path of a traditional Mach-Zehnder optical path imaging system by adjusting the optical path difference between an objective lens and a CCD in different imaging optical paths, wherein the optical path difference between a middle objective lens and the CCD in a first imaging optical path is v1The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v2The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v3The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v4And 150mm<v1<v2<v3<v4<600mm。
In the above device, the object plane of the imaging system is determined by the focal length f of the objective lens and the optical path difference v between the CCD and the objective lens, and the optical path difference u between the object plane of the imaging system and the objective lens satisfies 1/f as 1/u + 1/v.
A redundant light path-based method for measuring the out-of-focus distance of a micro-scale transparent body comprises the following steps: acquiring four phase body diffraction patterns with different defocusing conditions through three redundant imaging optical paths and a basic imaging optical path of a traditional Mach-Zehnder optical path imaging system; processing the diffraction patterns by a certain phase recovery method to obtain corresponding phase patterns; calculating SPEC (weight spectrum analysis parameter) parameters of the four phase maps by fourier transform; the distance of the phase body relative to the objective lens can be calculated by substituting the SPEC parameter and the thickness information of the phase plate which are obtained by calculation into a calculation formula of the patent.
In the method, before obtaining the diffraction pattern, the sample cell is moved to make the range of the sample cell within the imaging range of the four imaging optical paths of the imaging system.
In the method, the range of the sample cell is within the imaging range of the four imaging optical paths of the imaging system, the object plane corresponding to the first imaging optical path is higher than the upper wall surface of the sample cell, and the object plane corresponding to the fourth imaging optical path is lower than the lower wall surface of the sample cell.
In the above method, obtaining the diffraction patterns of the phase bodies is achieved by the CCD1, the CCD2, the CCD3 and the CCD4, respectively.
In the above method, the position of the object plane defined by each optical path relative to the object plane defined by the first imaging optical path is recorded as z1＝0，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)，z4＝1/(1/f-1/v4)-1/(1/f-1/v1)。
In the above method, the phase map can be obtained by performing a differential phase recovery method on the obtained diffraction map (refer to basic bhanduri and Gabriel popecum.deviation method for phase acquisition in off-axis quantitative phase imaging. optics LETTERS 2012,37: 1868-1870.).
In the above method, the calculation of the SPEC parameter of the phase map is performed according to the following formula,
f () is Fourier transform and is realized by adopting fast Fourier transform, the image is firstly subjected to discrete processing before the fast Fourier transform, the size of discrete units is delta x delta y, g (x, y) is a phase diagram, mu and v are frequency spectrum spaces, and the frequency spectrum cut-off frequency is muth＝1/Δx，νth＝1/Δy。
In the above method, the calculated SPEC parameter is calculated for acquiring 4 phase maps using 4 imaging optical paths, and is respectively recorded as SPEC1，SPEC2，SPEC3，SPEC4。
In the method, the calculation of the distance between the phase body and the objective lens is obtained by calculating the relative position of the image plane of the first imaging optical path and substituting the relative position of the image plane of the imaging system into a distance calculation formula between the phase body and the objective lens.
In the above method, the relative position of the image plane of the first imaging optical path is realized according to the following formula, namely | (SPEC)2-SPEC1)/(z2-z1)|，|(SPEC3-SPEC2)/(z3-z2) I and I (SPEC)4-SPEC3)/(z4-z3) Of the three parameters, | (SPEC)2-SPEC1)/(z2-z1) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)4-SPEC3)/(z4-z3) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4>SPEC1The relative position of the image plane of the imaging system is
In the other cases, the number of times,the relative position of the image plane of the imaging system is
In the method, the calculation formula of the distance between the phase body and the objective lens is 1/(1/f-1/v)1)+z。
In the above method, the maximum test range in the optical axis direction is 1/(1/f-1/v)4)-1/(1/f-1/v1)。
The invention has the following technical advantages:
by adding the redundant light path in the light path, the light path can be adjusted without adopting the mechanical movement of the light path, and the stability of the system is improved.
And a direct calculation mode is adopted, an iterative optimization process is not needed, and the calculation process is simple.
The redundant light paths work simultaneously, so that real-time image acquisition and processing can be realized, and the redundant light paths can be used for phase body motion analysis.
Drawings
FIG. 1 imaging system optical path;
FIG. 2 is a schematic phase diagram;
FIG. 3 is a schematic diagram of the change of SPEC parameter with relative optical path length;
fig. 4 test case 1;
fig. 5 test case 2;
fig. 6 test case 3;
fig. 7 test case 4;
the system comprises a laser 1, a spectroscope 2, a reflector 3, an object light arm light path 4, a sample cell 5, an objective 6, a beam combining mirror 7, a spectroscope 8, a first imaging light path 9, a CCD1 10, a CCD2, a second imaging light path 12, a CCD3, a third imaging light path 14, a CCD4 and a reflector 16, a third imaging light path 17, a spectroscope 18, a spectroscope 19, a reference arm light path 20 and a reflector 21.
Detailed Description
The details of the implementation and operation of the specific process proposed by the present invention are described below in conjunction with fig. 1-7.
The optical path schematic diagram of the imaging system is shown in fig. 1, and the imaging system in the drawing should include a laser 1, a beam splitter 2, an object light arm optical path 4, a reflector 3, a sample cell 5, an objective 6, a reference arm optical path 21, a reflector 20, a beam combiner 7, a beam splitter 8, a first imaging optical path 9, a CCD 110, a beam splitter 19, a second imaging optical path 12, a CCD 211, a beam splitter 18, a third imaging optical path 14, a CCD 313, a beam splitter 16, a fourth imaging optical path 17, and a CCD 415. The laser emitted from the laser 1 is split, and then part of the laser carries sample thickness information through the object light arm light path 4 and is imaged through the objective lens 6, and part of the laser passes through the reference arm light path 21 and is combined with the light beam passing through the object light arm light path 4 at the beam combining mirror 7 to generate interference fringes, and the split light beam split by the beam splitter 8 forms a diffraction pattern on the CCD 110 of the image plane of the first imaging light path, part of the split light beam passes through the beam splitter 19 and forms a diffraction pattern on the CCD 211 of the image plane of the second imaging light path, part of the light beam split by the beam splitter 19 passes through the beam splitter 18 and forms a diffraction pattern on the CCD 313 of the image plane of the third imaging light path, and part of the light beam split by the beam splitter 18 forms a diffraction pattern on the CCD 415 of the image plane of the fourth imaging light path, and the diffraction patterns are recorded by the CCDs and transmitted to a computer for subsequent processing.
Before a sample is tested, the sample cell is moved, the range of the sample cell is in the imaging range of four imaging optical paths of an imaging system, namely, an object plane corresponding to a first imaging optical path is higher than the upper wall surface of the sample cell, an object plane corresponding to a fourth imaging optical path is lower than the lower wall surface of the sample cell, the upper wall surface and the lower wall surface of the sample cell are set with mark points for imaging to be examined, in the first imaging optical path, the sample cell is moved, so that the mark points on the upper wall surface are clearly imaged on the CCD1, in the fourth imaging optical path, the sample cell is moved downwards, so that the mark points on the lower wall surface are clearly imaged on the CCD4, and then the position of the sample cell is kept unchanged in the whole testing process.
In the test, the diffraction pattern of the sample is acquired by the CCD1 in the first imaging optical path, and the phase diagram of the acquired diffraction pattern is acquired by performing a differential phase recovery method, which is denoted as phase diagram 1, as shown in fig. 2. And respectively acquiring a phase diagram 2, a phase diagram 3 and a phase diagram 4 through a second imaging optical path, a third imaging optical path and a fourth imaging optical path in the same way. And determine each for several conditionsThe position z of the object plane defined by the beam path relative to the object plane defined by the first imaging beam path1＝0，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)，z4＝1/(1/f-1/v4)-1/(1/f-1/v1)。
The SPEC parameters were calculated by MATLAB using the following equations for the acquired phase maps 1, 2,3 and 4:
f () is Fourier transform and is realized by adopting fast Fourier transform, the image is firstly subjected to discrete processing before the fast Fourier transform, the size of discrete units is delta x delta y, g (x, y) is a phase diagram, mu and v are frequency spectrum spaces, and the frequency spectrum cut-off frequency is muth＝1/(2Δx)，νth＝1/(2Δy)。
Calculating absolute value of slope of straight line formed by adjacent test points (SPEC)2-SPEC1)/(z2-z1)|，|(SPEC3-SPEC2)/(z3-z2) I and I (SPEC)4-SPEC3)/(z4-z3) L. The magnitudes of the three absolute values are compared to determine the formula for calculating the relative position of the image plane of the imaging system. When | (SPEC)2-SPEC1)/(z2-z1) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)4-SPEC3)/(z4-z3) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4>SPEC1The relative position of the image plane of the imaging system is
In other cases, the imaging system has an image plane with a relative position of
Calculating the distance of the phase body relative to the objective lens according to the calculated relative position of the image plane of the imaging system, wherein the calculation formula is 1/(1/f-1/v)1)+z。
The following describes embodiments of different calculation formulas, taking the typical SPEC parameter variation with relative optical path (fig. 4) as an example. Wherein 1/(1/f-1/v)1) The value is 10mm, and the parameters are obtained by substituting the parameters of the experimental system into the above calculation formula during implementation.
Example 1(| (SPEC)2-SPEC1)/(z2-z1) The case of | Max, FIG. 5)
Calculating the obtained parameters according to the phase diagram: SPEC1＝1810，z1＝0；SPEC2＝1580，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)＝145μm；SPEC3＝1795，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)＝292μm；SPEC4＝1985，z4＝1/(1/f-1/v4)-1/(1/f-1/v1) 442 μm. Calculated absolute value of slope of straight line formed by adjacent measurement points: [ PROFILE OF SPEC ]2-SPEC1)/(z2-z1)|＝1.586，|(SPEC3-SPEC2)/(z3-z2) 1.463 and | (SPEC)4-SPEC3)/(z4-z3) 1.267. Judged is | (SPEC)2-SPEC1)/(z2-z1) Maximum, the formula used for determining the relative position of the image plane of the imaging system is
And calculating z as 150.73 μm according to the formula. Then according to the formula (1/f-1/v)1) + z the calculated phase volume is 10.15073mm from the objective lens.
Example 2(| (SPEC)4-SPEC3)/(z4-z3) The case of | Max, FIG. 6)
Calculating the obtained parameters according to the phase diagram: SPEC1＝1960，z1＝0；SPEC2＝1770，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)＝157μm；SPEC3＝1500，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)＝301μm；SPEC4＝1860，z4＝1/(1/f-1/v4)-1/(1/f-1/v1) 451 μm. Calculated absolute value of slope of straight line formed by adjacent measurement points: [ PROFILE OF SPEC ]2-SPEC1)/(z2-z1)|＝1.210，|(SPEC3-SPEC2)/(z3-z2) 1.875 and | (SPEC)4-SPEC3)/(z4-z3) 2.4. Judged is | (SPEC)4-SPEC3)/(z4-z3) Maximum, the formula used for determining the relative position of the image plane of the imaging system is
And calculating z as 285.25 μm according to the formula. Then according to the formula (1/f-1/v)1) + z the calculated phase volume is 10.28525mm from the objective lens.
Example 3(| (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4>SPEC1In the case of FIG. 7)
Calculating the obtained parameters according to the phase diagram: SPEC1＝1770，z1＝0；SPEC2＝1500，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)＝144μm；SPEC3＝1860，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)＝294μm；SPEC4＝2010，z4＝1/(1/f-1/v4)-1/(1/f-1/v1) 450 μm. Calculated absolute value of slope of straight line formed by adjacent measurement points: [ PROFILE OF SPEC ]2-SPEC1)/(z2-z1)|＝1.875，|(SPEC3-SPEC2)/(z3-z2) 2.4 and | (SPEC)4-SPEC3)/(z4-z3)|＝0.962. Judged is | (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4>SPEC1The formula used for determining the image plane relative position calculation of the imaging system is
And calculating z as 128.25 μm according to the formula. Then according to the formula (1/f-1/v)1) + z the calculated phase volume is 10.12825mm from the objective lens.
Example 4(| (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4<SPEC1Condition (2)
Calculating the obtained parameters according to the phase diagram: SPEC1＝2010，z1＝0；SPEC2＝1840，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)＝160μm；SPEC3＝1630，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)＝306.2μm；SPEC4＝1760，z4＝1/(1/f-1/v4)-1/(1/f-1/v1) 457 μm. Calculated absolute value of slope of straight line formed by adjacent measurement points: [ PROFILE OF SPEC ]2-SPEC1)/(z2-z1)|＝1.063，|(SPEC3-SPEC2)/(z3-z2) 1.436 and SPEC4-SPEC3)/(z4-z3) And | ═ 0.862. Judged is | (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4<SPEC1The formula used for determining the image plane relative position calculation of the imaging system is
And calculating z as 336.35 μm according to the formula. Then according to the formula (1/f-1/v)1) + z the calculated phase volume is 10.33635mm from the objective lens.
Claims (7)
1. Redundant light path-based device for measuring out-of-focus distance of micro-scale transparent body is characterized in that: three redundant imaging optical paths for acquiring phase body diffraction patterns with different defocusing degrees are added in the Mach-Zehnder optical path imaging system;
outside the basic light path, part of light beams of the basic light path are divided into three added redundant light paths through a spectroscope, wherein the first redundant light path is composed of the spectroscope, a second imaging light path and a CCD2, the second redundant light path is composed of the spectroscope, a third imaging light path and a CCD3, and the third redundant light path is composed of the spectroscope, a reflector, a fourth imaging light path and a CCD 4;
the phase body diffraction patterns with different defocusing degrees are obtained through three redundant imaging optical paths and a basic imaging optical path of a traditional Mach-Zehnder optical path imaging system by adjusting the optical path difference between an objective lens and a CCD in different imaging optical paths, wherein the optical path difference between the objective lens and the CCD in the first imaging optical path is v1The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v2The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v3The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v4And 150mm<v1<v2<v3<v4<600mm。
2. The defocus distance measuring apparatus of a micro-scale transparent body based on a redundant optical path as claimed in claim 1, wherein the imaging system used is a Mach-Zehnder optical path imaging system, the basic optical path of which is composed of a light source, a beam splitter, an object arm optical path and a reference arm optical path, a beam combiner, a beam splitter, a first imaging optical path, and a CCD1 (charge coupled device), the light source is selected from a laser having coherence, the object arm optical path is composed of a beam splitter, a mirror, a sample cell, an objective lens, and a beam combiner to generate an object beam carrying optical phase information of the sample, and the reference arm optical path is composed of a beam splitter, a mirror, and a beam combiner to generate a reference beam which interferes with the object beam to present a specific diffraction pattern.
3. The device for measuring defocus distance of a micro-scale transparent body based on a redundant light path of claim 1, wherein the object plane of the imaging system is determined by the focal length f of the objective lens and the optical path difference v between the CCD and the objective lens, and the optical path difference u between the object plane of the imaging system and the objective lens satisfies 1/f-1/u + 1/v.
4. The method for measuring the out-of-focus distance of the micro-scale transparent body based on the redundant light path is characterized by comprising the following steps: the method comprises the following steps: acquiring four phase body diffraction patterns with different defocusing conditions through three redundant imaging optical paths and a basic imaging optical path of a traditional Mach-Zehnder optical path imaging system; processing the diffraction patterns by a certain phase recovery method to obtain corresponding phase patterns; calculating SPEC weight spectrum analysis parameters of the four phase diagrams through Fourier transform; substituting the SPEC parameter and the thickness information of the phase plate obtained by calculation into a calculation formula of the patent to calculate the distance of the phase body relative to the objective lens;
let z denote the position of the object plane defined by each optical path relative to the object plane defined by the first imaging optical path1＝0，z2＝1/(1/f-1/v2)-1/(1/f-1/v1)，z3＝1/(1/f-1/v3)-1/(1/f-1/v1)，z4＝1/(1/f-1/v4)-1/(1/f-1/v1)；
Acquiring a phase diagram can be realized by carrying out a differential phase recovery method on the acquired diffraction diagram;
calculating the SPEC parameter of the phase map is done according to the following formula,
f () is Fourier transform and is realized by adopting fast Fourier transform, the image is firstly subjected to discrete processing before the fast Fourier transform, the size of discrete units is delta x delta y, g (x, y) is a phase diagram, mu and v are frequency spectrum spaces, and the frequency spectrum cut-off frequency is muth＝1/Δx，νth＝1/Δy；
The calculated SPEC parameter is calculated for acquiring 4 phase maps using 4 imaging light paths, and is respectively marked as SPEC1，SPEC2，SPEC3，SPEC4；
Calculating the distance between the phase body and the objective lens by calculating the relative position of an image plane of the first imaging optical path and substituting the relative position of the image plane of the imaging system into a distance calculation formula of the phase body and the objective lens;
the relative position of the image plane of the first imaging beam path is realized according to the following formula, namely | (SPEC)2-SPEC1)/(z2-z1)|，|(SPEC3-SPEC2)/(z3-z2) I and I (SPEC)4-SPEC3)/(z4-z3) Of the three parameters, | (SPEC)2-SPEC1)/(z2-z1) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)4-SPEC3)/(z4-z3) When | is maximum, the relative position of the image plane of the imaging system is
When | (SPEC)3-SPEC2)/(z3-z2) Maximum and SPEC4>SPEC1The relative position of the image plane of the imaging system is
In other cases, the imaging system has an image plane with a relative position of
The calculation formula of the distance between the phase body and the objective lens is 1/(1/f-1/v)1)+z；
The maximum test range in the optical axis direction is 1/(1/f-1/v)4)-1/(1/f-1/v1)；
Wherein the optical path difference between the middle objective lens of the first imaging optical path and the CCD is v1The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v2The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v3The optical path difference between the middle objective lens of the first imaging optical path and the CCD is v4。
5. The method for measuring the defocus distance of the micro-scale transparent body based on the redundant light path as claimed in claim 4, wherein: before obtaining the diffraction pattern, the sample cell is moved to make the range of the sample cell be in the imaging range of the four imaging light paths of the imaging system.
6. The method for measuring the defocus distance of the micro-scale transparent body based on the redundant light path as claimed in claim 4, wherein: the range of the sample cell is within the imaging range of the four imaging optical paths of the imaging system, namely, the object plane corresponding to the first imaging optical path is higher than the upper wall surface of the sample cell, and the object plane corresponding to the fourth imaging optical path is lower than the lower wall surface of the sample cell.
7. The method for measuring the defocus distance of the micro-scale transparent body based on the redundant light path as claimed in claim 4, wherein: the acquisition of the diffraction patterns of the phase bodies is realized by CCD1, CCD2, CCD3 and CCD4, respectively.
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