CN115024674A - Endoscopic optical coherence tomography probe based on Fresnel lens - Google Patents
Endoscopic optical coherence tomography probe based on Fresnel lens Download PDFInfo
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- CN115024674A CN115024674A CN202210357785.2A CN202210357785A CN115024674A CN 115024674 A CN115024674 A CN 115024674A CN 202210357785 A CN202210357785 A CN 202210357785A CN 115024674 A CN115024674 A CN 115024674A
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- 238000012014 optical coherence tomography Methods 0.000 title claims abstract description 40
- 239000000523 sample Substances 0.000 title claims abstract description 23
- 239000000835 fiber Substances 0.000 claims abstract description 19
- 230000003287 optical effect Effects 0.000 claims description 14
- 239000003292 glue Substances 0.000 claims description 9
- 238000003384 imaging method Methods 0.000 abstract description 13
- 238000000034 method Methods 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000009826 distribution Methods 0.000 abstract description 3
- 230000001276 controlling effect Effects 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 239000013307 optical fiber Substances 0.000 description 6
- 238000013461 design Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000009827 uniform distribution Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
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- 238000005520 cutting process Methods 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00163—Optical arrangements
- A61B1/00188—Optical arrangements with focusing or zooming features
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/06—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements
- A61B1/07—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements using light-conductive means, e.g. optical fibres
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0062—Arrangements for scanning
- A61B5/0066—Optical coherence imaging
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Abstract
The invention provides an endoscopic optical coherence tomography probe based on a Fresnel lens, which consists of a single-mode fiber for guiding light, a self-focusing lens for collimating emergent light of the single-mode fiber, the Fresnel lens for optimizing axial light intensity and regulating and controlling light field distribution and a micro prism for turning a light path; the invention expands the focal depth of the optical coherence tomography system under the condition of keeping the transverse resolution unchanged, optimizes the uniformity of axial light intensity, improves the effective imaging depth of the system, realizes the focusing of light beams by utilizing the Fresnel lens to replace a self-focusing lens, and solves the contradiction between high resolution and large focal depth; compared with other methods, the invention does not need mechanical scanning, allows larger manufacturing error and reduces manufacturing cost.
Description
Technical Field
The invention belongs to the field of Optical Coherence Tomography (OCT), and particularly relates to an endoscopic Optical coherence tomography probe based on a Fresnel lens.
Background
Optical Coherence Tomography (OCT) is a new biomedical imaging method that uses the low Coherence of broadband light sources for high resolution imaging, which has the advantages of high resolution, fast imaging speed, and non-invasive measurement. At present, the longitudinal resolution and the transverse resolution of the OCT can reach 1 μm, the longitudinal resolution mainly depends on the coherence length of a light source, and the transverse resolution mainly depends on the numerical aperture of a focusing lens. The larger the numerical aperture of the focusing lens, the higher the lateral resolution of the OCT system, but the smaller the depth of focus, the limited effective imaging range of the OCT system. Therefore, solving the contradictory relationship between the focal depth and the lateral resolution is crucial to improving the performance of the OCT system.
In order to realize an improved OCT system with a large focal depth and a high resolution, various OCT research groups have proposed various schemes such as digital focusing, dynamic focusing, and quasi-needle (Optical needle) focusing. However, some of the above methods require phase stability, some require mechanical scanning, and some require two optical paths for illumination and detection, respectively. These methods are difficult to apply to miniaturized probes. Micro axicons, micro binary phase plates and micro lens arrays have also been used for extending the focal depth of the probe, but these components and parts are either complicated in processing technology or difficult in optical path adjustment. On the other hand, an endoscopic probe based on multi-fiber combination or step-index fiber technology is also a method for solving the contradiction between large focal depth and high resolution, but these methods have the following disadvantages: 1) the precision of cutting and welding the optical fiber has high requirements; 2) the destructive interference phenomenon in the focal depth area causes the light intensity of the emergent light beam to be distributed unevenly in the axial direction, and the overall imaging effect is adversely affected; 3) the use of multimode fiber adversely affects the overall imaging performance by intermodal dispersion and polarization.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the contradiction relation between the focal depth and the transverse resolution and improve the performance of an OCT system, the invention provides an endoscopic optical coherence tomography probe based on a Fresnel lens.
The technical scheme is as follows: an endoscopic optical coherence tomography probe based on a Fresnel lens comprises a single-mode fiber for guiding light, a self-focusing lens for collimating emergent light of the single-mode fiber, the Fresnel lens for focusing light collimated by the self-focusing lens and a micro prism for turning a light path;
the focal length of the Fresnel lens is determined by the lateral resolution required by the OCT system;
where x denotes the lateral resolution, λ denotes the wavelength, D denotes the spot diameter, and f denotes the focal length of the fresnel lens.
Furthermore, the distance between the emergent end of the single-mode fiber and the end face of the self-focusing lens is 0 mm.
Furthermore, the pitch of the self-focusing lens is 0.25P, and the numerical aperture is larger than 0.13.
Furthermore, the microprisms are isosceles right-angle prisms, and the refractive index is between 1.52 and 1.54.
Further, the aperture of the Fresnel lens is determined by the size of the diffraction spot.
Furthermore, the exit end of the single mode fiber is bonded with one end face of the self-focusing lens through optical glue, one end face of the micro prism is bonded with the other end face of the self-focusing lens through optical glue, and the Fresnel lens is bonded with the other end face of the micro prism through optical glue.
Has the advantages that: the invention has the following advantages:
1. compared with digital focusing, dynamic focusing and quasi-optical needle focusing, the invention does not require phase stability, does not need mechanical scanning and uses the same optical path to realize illumination and detection, thereby being beneficial to the miniaturization design of the probe;
2. compared with the method based on the micro axicon and the micro binary phase plate, the Fresnel lens is suitable for the injection molding process and has the advantages of simple processing, lower cost, simple light path adjustment and the like;
3. compared with a multi-optical fiber method, the method does not need fusion welding of a plurality of optical fibers, can avoid the influence of factors such as chromatic dispersion and polarization of different optical fibers on interference signals, can obtain large working distance, and realizes uniform distribution of axial light intensity.
Description of the drawings:
FIG. 1 is a schematic view of the present invention;
FIG. 2 is a diagram showing the relationship between the focal lengths of Fresnel lenses when light with different wavelengths is incident normally;
FIG. 3 is a diagram illustrating the imaging results of a conventional optical coherence tomography system;
FIG. 4 is a diagram illustrating the imaging result of an optical coherence tomography system based on Fresnel lens.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further explained with reference to the following embodiments.
Fig. 1 shows an endoscopic optical coherence tomography probe based on a fresnel lens, which is an endoscopic probe for solving the contradiction between high resolution and large focal depth, and the main structure of the endoscopic probe comprises: the device comprises a single-mode fiber 1 for guiding light, a self-focusing lens 2 for collimating emergent light of the single-mode fiber, a Fresnel lens 3 for optimizing axial light intensity and adjusting and controlling light field distribution and a micro prism 4 for turning a light path.
The single-mode fiber 1 of the present embodiment mainly guides light, and avoids the influence of factors such as intermodal dispersion of the multimode fiber on interference signals.
The self-focusing lens 2 of the present embodiment produces collimated light whose divergence angle is affected by the pitch of the self-focusing lens 1 and the distance from the exit end of the optical fiber to the end face of the self-focusing lens. The pitch of the self-focusing lens 2 used in this embodiment is 0.25P, and the numerical aperture is larger than 0.13.
The fresnel lens 3 of this embodiment is mainly used to focus light collimated by the self-focusing lens, and regulate and control the axial light intensity, so as to achieve uniform distribution of the light intensity in the axial direction and high resolution and large focal depth, and achieve the resolution required by the OCT system. Wherein, the focal length of the Fresnel lens 3 is determined by the lateral resolution required by the OCT system;
where x denotes the lateral resolution, λ denotes the wavelength, D denotes the spot diameter, and f denotes the focal length of the fresnel lens.
The aperture of the fresnel lens 3 is determined by the size of the diffraction spot.
When collimated light with the wavelength of lambda is vertically incident on the Fresnel lens along the optical axis, the focal length of the first order diffracted light of the Fresnel lens is as follows:
wherein λ is d And f d And m is the number of wave bands of the Fresnel lens.
When the wavelength of the light incident on the fresnel lens is not much different from the design wavelength, the above formula can be rewritten as follows:
it can be seen that the focal length of the fresnel lens is inversely proportional to the wavelength of the incident light, which means that the depth of focus of the focused light beam is greatly expanded when the incident light is polychromatic. For example, the design wavelength and focal length of the Fresnel lens are 1310nm and 30mm, the wavelength range of the incident light is 1310 + -50 nm, and the collimated light spot size is 4 mm. When the focusing lens is a common lens, the focal depth of the focusing light beam is 8 λ f 2 /(πD 2 ) 187 μm. When the focusing lens is a fresnel lens, the focal length corresponding to each wavelength satisfies formula (2), and the focal length distribution is as shown in fig. 2 through MATLAB simulation, wherein the abscissa in fig. 2 represents the wavelength, and the ordinate represents the focal length; the focal length range of the incident light is 2.29mm, and the focal depth of the Fresnel lens is 2.29+ 0.187-2.477 mm, which is about 13 times the depth of focus of a normal lens.
The microprism 4 of the present embodiment is an isosceles right-angle prism, and the refractive index is between 1.52 and 1.54, so as to realize total light emission, avoid light energy loss, and turn the light path.
The optical coherence tomography probe based on the Fresnel lens provided by the embodiment optimizes the axial light intensity uniformity of an emergent light beam while solving the contradiction between the focal depth and the resolution, and is manufactured by the following steps:
step 1: bonding the single-mode optical fiber exit port with one end face of the self-focusing lens through optical glue; the distance from the single-mode fiber exit port to the end face of the self-focusing lens is 0mm, and collimation of the fiber exit light beam is achieved.
Step 2: one end face of the microprism and the other end face of the self-focusing lens are bonded together through optical glue, so that the turning of a light path is realized;
and 3, step 3: the other end face of the microprism and the Fresnel lens are bonded together through optical glue, and spatial regulation and control of light are achieved.
The invention expands the focal depth of the optical coherence tomography system under the condition of keeping the transverse resolution unchanged, optimizes the axial light intensity uniformity and prolongs the working distance. The Fresnel lens is used for replacing the self-focusing lens to realize the focusing of the light beam, so that the contradiction between high resolution and large focal depth is solved; compared with other methods, the invention does not need mechanical scanning, allows larger manufacturing error and reduces manufacturing cost.
The implementation case is as follows:
a sixth set of third elements of the 1951USAF resolution plate at different depths was imaged using a conventional optical coherence tomography system and a fresnel lens based optical coherence tomography system. The central wavelength of the light sources of the two systems is 830nm, and the bandwidth is 50 nm. The two systems only have different focusing objective lenses of sample arms, the focusing lens of the sample arm of the traditional optical coherence tomography system is a common objective lens, the focal length is 30mm, the focusing objective lens of the sample arm of the optical coherence tomography system based on the Fresnel lens is a Fresnel lens, the focal length is 30mm, and the design wavelength is 830 nm. The conventional optical coherence tomography system showed imaging results as shown in fig. 3, and since the sixth set of the third element of the 1951USAF resolution plate was not visible at-500 and 500 in fig. 3, but was visible at 400 and-400, the effective imaging range was 800 μm. The imaging result of the optical coherence tomography system based on the fresnel lens is shown in fig. 4, and since the sixth group of the third elements of 1951USAF resolution plate can be seen at 1000 and 1000 in fig. 4, the effective imaging range is 2000 μm, which is 2.5 times that of the conventional optical coherence tomography system. The abscissa in fig. 3 and 4 represents the relative intensity, and the ordinate represents the lateral position.
Claims (6)
1. An endoscopic optical coherence tomography probe based on Fresnel lens is characterized in that: the device comprises a single-mode fiber for guiding light, a self-focusing lens for collimating emergent light of the single-mode fiber, a Fresnel lens for focusing the light collimated by the self-focusing lens and a micro prism for turning a light path;
the focal length of the Fresnel lens is determined by the lateral resolution required by the OCT system;
where x denotes the lateral resolution, λ denotes the wavelength, D denotes the spot diameter, and f denotes the focal length of the fresnel lens.
2. A fresnel lens-based endoscopic optical coherence tomography probe according to claim 1, wherein: the distance between the emergent end of the single-mode fiber and the end face of the self-focusing lens is 0 mm.
3. A fresnel lens-based endoscopic optical coherence tomography probe according to claim 1, wherein: the pitch of the self-focusing lens is 0.25P, and the numerical aperture is larger than 0.13.
4. A fresnel lens-based endoscopic optical coherence tomography probe according to claim 1, wherein: the microprism is an isosceles right-angle prism, and the refractive index is between 1.52 and 1.54.
5. A fresnel lens-based endoscopic optical coherence tomography probe according to claim 1, wherein: the aperture of the Fresnel lens is determined by the size of the diffraction light spot.
6. A fresnel lens-based endoscopic optical coherence tomography probe according to claim 1, wherein: the exit end of the single mode fiber is bonded with one end face of the self-focusing lens through optical glue, one end face of the micro prism is bonded with the other end face of the self-focusing lens through optical glue, and the Fresnel lens is bonded with the other end face of the micro prism through optical glue.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210357785.2A CN115024674A (en) | 2022-04-07 | 2022-04-07 | Endoscopic optical coherence tomography probe based on Fresnel lens |
| PCT/CN2022/088757 WO2023193316A1 (en) | 2022-04-07 | 2022-04-24 | Endoscopic optical coherence tomography detector based on fresnel lens |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210357785.2A CN115024674A (en) | 2022-04-07 | 2022-04-07 | Endoscopic optical coherence tomography probe based on Fresnel lens |
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| CN115024674A true CN115024674A (en) | 2022-09-09 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118986241A (en) * | 2024-08-15 | 2024-11-22 | 上海交通大学 | Endoscopic optical coherence tomography probe design method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN119717250B (en) * | 2025-02-21 | 2025-07-22 | 大连理工大学 | An electrically adjustable focal length OCT scanning probe |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010240151A (en) * | 2009-04-06 | 2010-10-28 | Sumitomo Electric Ind Ltd | OCT device for dental diagnosis |
| CN102499648B (en) * | 2011-11-16 | 2013-11-06 | 清华大学 | Spectral-domain optical coherence tomography imaging system based on Fresnel spectrometer |
| CN104958061B (en) * | 2015-07-28 | 2016-09-14 | 北京信息科技大学 | Fundus OCT imaging method and system for binocular stereo vision three-dimensional imaging |
| JP6765928B2 (en) * | 2016-10-11 | 2020-10-07 | 株式会社日立製作所 | Optical scanning equipment, TOF type analyzer, and optical interference tomography equipment |
| CN107233069A (en) * | 2017-07-11 | 2017-10-10 | 中国科学院上海光学精密机械研究所 | Increase the optical coherence tomography system of focal depth range |
| EP3608625B1 (en) * | 2018-08-07 | 2023-10-25 | Hexagon Technology Center GmbH | Oct measuring system |
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- 2022-04-07 CN CN202210357785.2A patent/CN115024674A/en not_active Withdrawn
- 2022-04-24 WO PCT/CN2022/088757 patent/WO2023193316A1/en not_active Ceased
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118986241A (en) * | 2024-08-15 | 2024-11-22 | 上海交通大学 | Endoscopic optical coherence tomography probe design method |
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Application publication date: 20220909 |