CN110411333A - A new type of laser polarization phase-shift interference tomography measurement device and method - Google Patents

Abstract

The invention relates to a novel laser polarization phase shift interference chromatography measuring device, which comprises a laser, wherein a first polaroid and a polarization spectroscope are sequentially arranged on an output light path of the laser from left to right; a first reflecting mirror is arranged on a transmission light path of the polarizing beam splitter, and a second reflecting mirror is arranged on a reflection light path of the polarizing beam splitter; a beam expanding system, a sample to be detected and a beam contracting system are sequentially arranged on a reflection light path of the second reflecting mirror from left to right; a beam splitter is arranged at the intersection of an emergent light path of the beam reduction system and a reflecting light path of the first reflector, and a quarter-wave plate, a second polarizing film, a focusing lens and a CCD detector are sequentially arranged on a transmission light path of the beam splitter from left to right. The novel laser polarization phase shift interference chromatography measuring device and method are used for measuring the refractive index distribution of a transparent/semitransparent medium or a flow field, and the phase detection precision is higher than that of a traditional optical coherence chromatography light path.

Description

A new type of laser polarization phase-shift interference tomography measurement device and method

technical field

The invention relates to the field of measurement technology, in particular to a novel laser polarization phase-shift interference tomography measurement device and method.

Background technique

Optical coherence tomography is a kind of Optical Computed Tomography (OCT), a three-dimensional tomography technology proposed by Fujimoto's research group in 1991 and gradually developed. Based on the principle of interference, it can obtain tomographic capabilities in the depth direction, and can reconstruct the refractive index distribution of the internal structure of the measured sample through multi-projection angle imaging, and then obtain two-dimensional or three-dimensional images. Optical coherence tomography has the characteristics of non-invasive, non-invasive and high-resolution, and has broad application prospects in medical biological detection, flow field detection and transparent medium detection.

The basic principle of optical coherence tomography technology is to use interference optical paths such as Michelson interference optical path and Mach-Zehnder interference optical path, so that the measurement optical path passes through the measured transparent/translucent medium or flow field from a certain angle direction, and the phase can be modulated The reference optical path interferes, and the phase information of the measured transparent/semi-transparent medium or flow field in the incident direction is obtained through the reduction algorithm, and then the optical path or the measured transparent/semi-transparent medium or flow field is rotated to obtain the phase information in multiple incident directions Phase information data, and finally restore the two-dimensional or three-dimensional refractive index distribution of the measured transparent/translucent medium or flow field according to the algorithm based on the Radon inverse transformation principle.

In order to obtain the phase information of the measured transparent/semi-transparent medium or flow field, it is necessary to change the phase of the reference optical path to obtain multiple interference patterns. There are two common methods, one is angle modulation, such as adding optical compensation to the reference optical path The optical path of the reference optical path is changed by rotating the optical compensation plate, thereby modulating the phase of different reference optical paths; the second is displacement modulation, such as adding a beam splitter and a mirror to the reference optical path, and the linear reciprocating movement of the mirror To change the optical path, so as to obtain different phases of the reference light. However, the former is affected by the thickness of the compensation plate, and its phase modulation range cannot be very large, while the latter makes the optical path structure more complicated and the adjustment difficulty also increases.

In order to achieve better measurement results, the present invention proposes a novel laser polarization phase-shift interference tomography measurement device and method.

Contents of the invention

In order to solve the above technical problems, the present invention provides a new type of laser polarization phase shift interference tomography measurement device and method, which is used to measure the refractive index distribution of transparent/translucent media or flow fields, and the phase detection accuracy is higher than that of traditional Optical coherence tomography optical path.

In order to solve the above-mentioned technical problems, the present invention is realized as follows: a novel laser polarization phase-shift interference tomography measurement device, which includes a laser, the output optical path of the laser is sequentially provided with a first polarizer and a polarizer Beam splitter; the transmission light path of the polarization beam splitter is provided with a first reflector, the reflection light path of the polarization beam splitter is provided with a second reflector; the reflection light path of the second reflector is sequentially provided with a beam expander system, The sample to be tested and the reduced beam system; a beam splitter is set at the intersection of the outgoing light path of the reduced beam system and the reflected light path of the first mirror, and a quarter-wave plate is arranged in turn on the transmission light path of the beam splitter from left to right , Second polarizer, focusing lens, CCD detector.

Further, the beam expander system is composed of a first optical lens and a second optical lens sequentially arranged on the reflection optical path of the second mirror.

Further, the beam reduction system is composed of a third optical lens and a fourth optical lens sequentially arranged on the transmission light path of the sample to be measured.

Further, the beam expansion factor of the beam expansion system is equal to the beam reduction factor of the beam contraction system.

Further, the angle between the direction of the optical axis of the first polarizer and the direction of the paper plane is 45°.

Further, the angle between the direction of the optical axis of the quarter-wave plate and the direction of the paper is 45°.

Further, the position of the optical axis of the second polarizer can be adjusted by rotation.

Further, the sample to be tested can be rotated and adjusted.

Another object of the present invention is also to provide a novel laser polarization phase-shift interference tomography measurement method, which includes the following steps:

Step 1: Turn on the laser so that the laser emits a pair of mutually orthogonal linearly polarized lights, that is, a beam of light contains a P-polarized component parallel to the paper surface and an S-polarized component perpendicular to the paper surface;

Step 2: The light reflected by the polarization beam splitter and transmitted by the sample to be tested is the measurement light, and the light transmitted by the polarization beam splitter and not passed through the sample to be tested is the reference light. The measurement light and the reference light are on the image plane of the CCD detector form an interference pattern;

Step 3: Rotate the second polarizer to modulate the phase difference between the measurement light and the reference light, and use the multi-step phase shift method to restore the phase information of the sample to be measured at the current angular position;

Step 4: Rotate the sample to be tested, and repeat steps 2 and 3 to obtain the phase information of the sample to be tested at different angles, and finally restore the two-dimensional or three-dimensional refractive index distribution of the sample to be tested by an algorithm based on the Radon inverse transform principle .

Compared with prior art, the beneficial effect of the present invention is:

① Different polarization states are used in the measurement optical path and the reference optical path. Since the measurement light passes through the sample to be measured, the uneven distribution of the refractive index will cause the wavefront of the measurement light to be distorted. Add a quarter-wave plate and a The rotatable second polarizer can modulate the phase difference between the measurement light and the reference light, so as to restore the phase information of the sample to be measured. The phase detection accuracy of this method is very high, and the influence of the leakage factor of the polarizer can be eliminated at the same time, and the optical path has good anti-interference ability;

②The beam expansion system is used to expand the diameter of the beam so that the sample to be tested can be covered and irradiated by the beam. At the same time, the beam reduction system is used, and the beam reduction multiple of the beam reduction system is equal to the beam expansion multiple of the beam expander system. The beam reduction system reduces the diameter of the beam passing through the sample to be measured to the size before beam expansion, which is convenient for comparison with the reference optical path;

③ The first polarizer with an angle of 45° between the optical axis direction and the paper surface is set. The setting of the first polarizer makes the output laser light of the laser convert into a linearly polarized light whose polarization direction is 45° between the paper surface, so that the polarization The beam splitter can divide it into two beams of approximately equal light intensity, the reflected S light whose polarization state is perpendicular to the paper surface, and the transmitted P light whose polarization state is parallel to the paper surface;

④ The angle between the direction of the optical axis of the quarter-wave plate and the paper surface is 45°, and the setting of the quarter-wave plate converts the S-polarized light of the measurement optical path and the P-polarized light of the reference optical path into left and right circular polarized light respectively.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is a schematic structural diagram of a novel laser polarization phase-shift interference tomography measurement device according to an embodiment of the present invention.

101. Laser; 102. First polarizer; 103. Polarizing beam splitter; 104. First mirror; 105. Second mirror; 106. First optical lens; 107. Second optical lens; 108. Sample to be tested ; 109, the third optical lens; 110, the fourth optical lens; 111, a beam splitter; 112, a quarter wave plate; 113, a second polarizer; 114, a focusing lens; 115, a CCD detector; 116, an expansion Beam system; 117. Beam reduction system

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific implementation methods and accompanying drawings. Here, the exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.

It should be further explained that all directional indications (such as up, down, left, right, front, back...) in the present invention are only used to explain the relationship between the components in a certain posture (as shown in the corresponding drawings). If the specific posture changes, the directional indication will also change accordingly.

Example 1

With reference to Fig. 1, preferred embodiment 1 of the present invention provides a kind of novel laser polarization phase-shift interference tomography measuring device, and it comprises following parts:

Laser 101: common commercial He-Ne laser, output wavelength is 633nm, beam diameter is about Ф4mm;

The first polarizer 102 and the second polarizer 113: select a general-purpose high-precision commercial polarizer with a polarization extinction ratio greater than 100:1;

The first optical lens 106 , the second optical lens 107 , the third optical lens 109 , and the fourth optical lens 110 are high-precision devices commonly used in the market, and the beam expansion and beam reduction ratios are 10 times after assembly.

Sample 108 to be tested: an irregularly shaped crystal with a size of less than 30×30×30 mm is used. In order to reduce the light deflection caused by the light beam passing through the crystal, the crystal is soaked in glycerin.

Polarizing beam splitter 103, first mirror 104, second mirror 105, beam splitter 111, quarter-wave plate 112, focusing lens 114, CCD detector 115: high-precision devices commonly used in the market

The structural associations of the above components are as follows:

It includes a laser 101, the output optical path of the laser 101 is provided with a first polarizer 102 and a polarization beam splitter 103 in sequence from left to right; the angle between the optical axis direction of the first polarizer 102 and the direction of the paper is 45°; the polarization beam splitter A first reflection mirror 104 is arranged on the transmission light path of the mirror 103, a second reflection mirror 105 is arranged on the reflection light path of the polarizing beam splitter 103; a beam expander system 116 is sequentially arranged on the reflection light path of the second reflection mirror 105 from left to right , the sample to be measured 108 and the beam shrinking system 117 whose angle can be rotated and adjusted; the beam expander system 116 is composed of the first optical lens 106 and the second optical lens 107 which are sequentially arranged on the reflected light path of the second mirror 105; Described beam reduction system 117 is made up of the 3rd optical lens 109 and the 4th optical lens 110 that are arranged in order on the transmitted light path of sample 108 to be measured; 10 times; beam splitter 111 is arranged at the intersection of the outgoing light path of the beam shrinking system 117 and the reflected light path of the first reflector 104, and a quarter-wave plate 112 is sequentially arranged on the transmitted light path of the beam splitter 111 from left to right , the second polarizer 113, the focusing lens 114, the CCD detector 115; the angle between the optical axis direction of the quarter-wave plate 112 and the paper direction is 45°; the optical axis position of the second polarizer 113 can be rotated and adjusted.

Example 2

With reference to Fig. 1, preferred embodiment 2 of the present invention provides a kind of novel laser polarization phase-shift interference tomography measurement method based on the device described in embodiment 1, and it comprises the following steps:

Step 1: Turn on the laser 101, so that the laser 101 emits a pair of mutually orthogonal linearly polarized lights, that is, a beam of light contains a P-polarized component parallel to the paper surface and an S-polarized component perpendicular to the paper surface;

Step 2: The light reflected by the polarizing beam splitter 103 and transmitted through the sample to be measured is the measurement light, the light transmitted through the polarizing beam splitter 103 and not passed through the sample to be measured is the reference light, and the measuring light and the reference light are placed between the CCD detector 115 An interference pattern is formed on the image plane;

Step 3: Rotate the second polarizer 113 to modulate the phase difference between the measurement light and the reference light, and use the multi-step phase shift method to restore the phase information of the sample to be measured 108 at the current angular position;

Step 4: Rotate the sample 108 to be tested, and repeat steps 2 and 3 to obtain the phase information of the sample 108 to be tested at different angles, and finally restore the two-dimensional or three-dimensional refraction of the sample to be tested by an algorithm based on the Radon inverse transform principle rate distribution.

Specifically, a new type of laser polarization phase-shift interference tomography measurement method described in this embodiment is as follows: the beam emitted by the laser 101 has a wavelength of 633 nm and a diameter of about Ф4 mm, and passes through the first 45° angle between the optical axis and the paper surface. After a polarizer 102, it is converted into linearly polarized light whose polarization direction is 45° with the paper surface, and then incident on the polarizing beam splitter 103, which is divided into S light with approximately equal light intensity and a polarization state perpendicular to the paper surface and parallel to the paper surface. Two parts of P light on paper. Wherein, the P light is reflected by the first mirror 104 after being transmitted, and then enters and is reflected by the beam splitter 111 . After the S polarized light is reflected by the second reflector 105, it passes through the beam expander system consisting of the first optical lens 106 and the second optical lens 107 with a beam expansion factor of 10 times. The object focus of the second optical lens 107 coincides, the focal length of the second optical lens 107 is greater than the focal length of the first optical lens 106, the beam diameter becomes Ф40mm after passing through the beam expander system, and then irradiates through the sample to be tested 108 immersed in glycerin, After passing through the beam reduction system composed of the third optical lens 109 and the fourth optical lens 110 with a beam reduction factor of 10 times, the beam diameter is restored to Ф4 mm, and then enters the beam splitter 111 and is transmitted. The P-polarized reference light and the S-polarized measurement light are merged into a beam of light at the beam splitter 111, and are converted into left-handed and right-handed circularly polarized light after passing through a quarter-wave plate 112 with an angle of 45° between the optical axis and the paper surface, and then The second polarizer 113 whose optical axis position can be rotatably adjusted is focused by the focusing lens 114 to form an interference pattern on the image plane of the CCD detector 115 . Rotate the second polarizer 113 so that its optical axis is at five positions of -90°, -45°, 0, +45°, and +90° respectively, and modulate the phase difference between the measuring light and the reference light, thereby obtaining five The interference pattern, and then use the five-step phase shift method to restore the phase information of the crystal sample 108 to be tested at a certain irradiation angle. Further rotate the sample 108 to be tested, and repeat the above steps to measure once every 10° within the range of 0° to 180°, to obtain its phase information at 18 irradiation angles, and finally restore it according to the algorithm based on the Radon inverse transform principle to obtain the The refractive index profile of the sample 108 is obtained simultaneously with a three-dimensional image thereof.

A novel laser polarization phase-shift interference tomography measuring device and method disclosed in the present invention has the following working principles:

The light emitted by the laser 101 passes through the first polarizer 102. The angle between the optical axis of the first polarizer 102 and the paper surface is 45°, and its function is to convert the outgoing laser light into a linear polarization whose polarization direction and the angle between the paper surface are 45° Light. Then the light beam is incident on the polarization beam splitter 103, and the polarization beam splitter 103 divides the light beam into two beams of approximately equal light intensity, the reflected S-polarized light whose polarization state is perpendicular to the paper surface, and the transmitted P-polarized light whose polarization state is parallel to the paper surface. Wherein, the P polarized light is reflected by the first reflector 104 after being transmitted, and then enters the beam splitter 111 and is reflected by it, which is the reference optical path; after being reflected by the second reflector 105, the S polarized light passes sequentially through the first optical path. The beam expander system 116 made up of the lens 106 and the second optical lens 107, the sample to be tested 108, the beam shrinker system 117 made up of the third optical lens 109 and the fourth optical lens 110 are then incident on the beam splitter 111 and transmitted, because When the light passes through the sample 108 to be measured, the uneven distribution of the refractive index will cause the wavefront of the measuring light to be distorted, thereby causing the phase of the light beam to change. This is the measuring optical path. The function of the beam expander system 116 is to expand the diameter of the beam so that the sample 108 to be tested can be completely covered and irradiated by the beam. The beam diameter of the sample 108 is reduced to the size before the beam expansion. The sample to be tested 108 can be rotated so that the measuring beam passes through the sample to be tested 108 at different irradiation angles, so as to provide phase information at different irradiation angles for the measurement of the refractive index distribution of the sample to be tested 108 . The P-polarized reference light and the S-polarized measurement light are merged into a beam of light at the beam splitter 111, then pass through the quarter-wave plate 112 and the second polarizer 113 in turn, and are received by the CCD detector 115 after being focused by the focusing lens 114. An interference pattern of measuring light and reference light is formed on its image plane. The included angle between the optical axis of the quarter-wave plate 112 and the paper is 45°, and its function is to convert the P-polarized reference light and the S-polarized measurement light into left-handed and right-handed circularly polarized light respectively. The second polarizer 113 can rotate around the axis of the optical path, and its function is to change the angular position of the optical axis through rotation, and modulate the phase difference between the measuring light and the reference light, so as to obtain the interference of different phase differences on the image plane of the CCD detector 115 pattern, and then use the principle of multi-step phase shift to restore the phase information of the sample to be measured at a certain irradiation angle. Further rotating the sample 108 to be measured can obtain its phase information under different irradiation angles, and finally the refractive index distribution of the sample to be measured can be obtained through algorithm reduction.

Claims (10)

1. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device comprising laser, which is characterized in that laser it is defeated The first polarizing film and polarization spectroscope have been set gradually from left to right in optical path out；It is provided on the transmitted light path of polarization spectroscope First reflecting mirror is provided with the second reflecting mirror on the reflected light path of polarization spectroscope；From a left side on the reflected light path of second reflecting mirror Beam-expanding system, sample to be tested and shrink beam system are disposed with to the right side；The emitting light path of shrink beam system and the first reflecting mirror it is anti- The intersection for penetrating optical path is provided with spectroscope, be set gradually from left to right on spectroscopical transmitted light path quarter-wave plate, Second polarizing film, condenser lens, ccd detector.

2. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as described in claim 1, which is characterized in that the expansion The first optical lens and the second optical lens on reflected light path of the beam system by being successively set on the second reflecting mirror form；It is described Shrink beam system is made of the third optical lens being successively set on the transmitted light path of sample to be tested and the 4th optical lens.

3. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as claimed in claim 2, which is characterized in that the expansion Beam system expand multiple and the shrink beam multiple of shrink beam system is equal.

4. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as described in claim 1, which is characterized in that first partially The optical axis direction of vibration piece and paper angular separation are 45 °.

5. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as described in claim 1, which is characterized in that four/ The optical axis direction of one wave plate and paper angular separation are 45 °.

6. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as described in claim 1, which is characterized in that second partially The optical axis position of vibration piece is rotatably adjustable.

7. a kind of new pattern laser polarization phase-shifting interference chromatography measuring device as described in claim 1, which is characterized in that test sample Product are rotatably adjustable.

8. another object of the present invention, which also resides in, provides a kind of new pattern laser polarization phase-shifting interference chromatography measurement method comprising following Step:

Step 1: opening laser, and so that laser is issued a pair has mutually orthogonal linearly polarized light, i.e. light beam contains in parallel P-polarization component in paper and the S-polarization component perpendicular to paper；

Step 2: reflecting by polarization spectroscope and the light through sample to be tested transmission is measurement light, transmits by polarization spectroscope And without the light by sample to be tested be reference light, light and reference light are measured in ccd detector as forming interference pattern in plane Sample；

Step 3: the second polarizing film of rotation is modulated the phase difference of measurement light and reference light, also using multistep phase shift method Phase information of the former sample to be tested in current angle position；

Step 4: rotation sample to be tested, and step 2 and step 3 are repeated, obtain phase letter of the sample to be tested under different angle Breath, the final two dimension or three-dimensional refractive index distribution that sample is restored through the algorithm based on Radon inverse transformation principle.

9. a kind of new pattern laser polarization phase-shifting interference chromatography measurement method as claimed in claim 8, it is characterised in that: step 2 The second polarizing film of middle rotation makes its optical axis be respectively at -90 °, -45 °, 0 ° ,+45 ° ,+90 ° of five positions.

10. a kind of new pattern laser polarization phase-shifting interference chromatography measurement method as claimed in claim 8, it is characterised in that: step Sample to be tested is rotated in four, it is primary every 10 ° of repetition step 2 and step 3 measurement within the scope of 0~180 °, it obtains to test sample Phase information of the product under 18 irradiating angles.