A Miniature Endoscope with High Fluorescence Collection Efficiency

Abstract

The present invention relates to the technical field of medical diagnostic imaging devices, and particularly relates to a miniature endoscope with a high fluorescence collection rate, which includes a miniature imaging probe. The miniature imaging probe includes an objective lens. The miniature imaging probe is fixedly connected with a photodetector, and a hole matching the objective lens is formed on the photodetector. The photodetector includes a protection element, a filter, a photosensitive unit, and a driving circuit. The output end of the driving circuit is connected to an external amplification circuit and a computer. An anti-reflection optical coating is also plated on the surface of the protection element. This solution collects scattered fluorescence photons that cannot be collected by the objective lens through the photodetector, and improves the fluorescence collection rate of the endoscope without changing the volume of the existing endoscope, solving the problems in the prior art that the addition of an optical path leads to an increase in the volume of the miniature imaging probe and limited fluorescence collection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of medical diagnostic imaging devices, and particularly relates to a miniature endoscope with a high fluorescence collection rate. Background Art

[0002] With the development of science and technology, medical endoscopes have been widely used in the medical field. It is one of the important tools for humans to observe and treat internal organs. During the development of more than 200 years, the structure of the endoscope has undergone four major improvements. From the initial rigid endoscope, semi-flexible endoscope to fiber endoscope, and then to today's electronic endoscope, the image quality has also achieved a qualitative leap time after time. Nowadays, with LED lighting, the endoscope can obtain color photos or color TV images. At the same time, its image is no longer an ordinary image of tissues and organs, but a microscopic image observed under a microscope, and tiny lesions can be clearly distinguished. According to existing clinical experience, the smaller the volume of the miniature imaging probe of the endoscope and the shorter the rigid section, the more the patient's pain can be minimized. Therefore, the endoscope has been developing towards miniaturization.

[0003] In non-linear optical imaging technology, for a multi-photon fluorescence endoscope, the near-infrared laser pulse is focused by an objective lens and then excites a fluorescence signal with isotropic emission in the sample. Biological tissues usually exhibit optical properties of strong absorption and high scattering. For epi-fluorescence detection, the same objective lens is used both for focusing the excitation light and for collecting the fluorescence signal. The intensity of the fluorescence signal collected by the objective lens depends on the numerical aperture of the objective lens and the front aperture of the objective lens. The larger the numerical aperture and the front aperture of the objective lens, the greater the intensity of the fluorescence signal that the objective lens can collect.

[0004] In recent years, many technologies have emerged to improve the collection rate of fluorescence photons by the objective lens. Among them, by arranging 5-8 high-numerical-aperture optical fibers around the objective lens to collect the fluorescence that cannot be collected by the objective lens, a 2-fold enhancement in fluorescence collection efficiency can be obtained for a high-numerical-aperture objective lens, and a 20-fold enhancement in fluorescence collection efficiency can be obtained for a low-numerical-aperture microscope objective lens.

[0005] However, for the above method of using an additional optical path to improve the collection efficiency of fluorescence photons, due to the large discreteness of the scattering angles of fluorescence photons, after entering the additional collection optical path, the fluorescence photons have a complex multiple reflection path and large losses, resulting in limited actual collection efficiency of the additional optical path. At the same time, the addition of the additional optical path causes an increase in the volume of the miniature imaging probe, which does not conform to the development trend of the endoscope. Summary of the Invention

[0006] The present invention aims to provide a microendoscope with a high fluorescence collection rate, which can improve the fluorescence collection rate of the endoscope without changing the volume of the existing endoscope, and solve the problems in the prior art that the addition of an optical path leads to an increase in the volume of the microimaging probe and limited fluorescence collection efficiency.

[0007] The solution is basically as follows: A microendoscope with a high fluorescence collection rate includes a microimaging probe. The microimaging probe includes an objective lens. The microimaging probe is fixedly connected with a photodetector. A hole matching the objective lens is opened on the photodetector. The photodetector includes a filter, a photosensitive unit for photoelectric conversion, and a drive circuit connected in series in sequence. The output end of the drive circuit is connected to an external amplifier circuit and a computer.

[0008] Beneficial effects: Some fluorescent photons enter the microimaging probe from the objective lens through the hole of the photodetector. Some fluorescent photons that do not enter the microimaging probe through the objective lens pass through the filter and generate an electrical signal on the photosensitive unit. The drive circuit provides a high voltage and a drive signal to the photosensitive unit and is connected to an external amplifier circuit and a computer, and can transmit the electrical signal generated by the photosensitive unit to the amplifier circuit and the computer. In the existing microimaging probe, the periphery of the objective lens needs to be surrounded by a housing for fixation. In this solution, the housing surrounding the objective lens is replaced with a photodetector. The photodetector collects the fluorescent photons that the objective lens cannot collect, thereby improving the fluorescence collection rate of the microimaging probe without increasing the volume of the microimaging probe.

[0009] Furthermore, the photodetector further includes a protection element, and the filter, the photosensitive unit, and the drive circuit are all located within the protection element. The protection unit can protect the filter, the photosensitive unit, and the drive circuit, and prevent the filter, the photosensitive unit, and the drive circuit from being contaminated by directly contacting the detection object.

[0010] Furthermore, the protection element is an insulating protection element that can transmit visible light, and its dielectric strength is greater than 5 MV / mm. This electrically isolates the photodetector from the microimaging probe and the detection object, and prevents the high voltage of the photosensitive unit of the photodetector from causing harm to the microimaging probe and the patient.

[0011] Furthermore, an antireflection optical coating is also plated on the surface of the protection element. This reduces the reflection of fluorescent photons and improves the transmittance of fluorescent photons.

[0012] Furthermore, the photosensitive unit uses a single avalanche diode. The hole in the center of the single avalanche diode can be formed by mechanical drilling or etching. The avalanche diode has better integrity compared to other photosensitive devices.

[0013] Further, the photosensitive unit is one or more of CCD, CMOS, FPA, and PMT. The photosensitive units of the above types are all two-dimensional pixel photoelectric sensors, and the operating voltage is easier to control compared to avalanche diodes.

[0014] Further, a plurality of the photosensitive units are provided and arranged in an annular array. The photosensitive unit can use multiple avalanche diodes or multiple two-dimensional pixel photoelectric sensors. Compared with a single avalanche diode and two-dimensional pixel photoelectric sensor, there is no need to process holes.

[0015] Further, the surface of the protection element of the photodetector opposite to the photosensitive unit is a microlens array. When the photosensitive unit uses a two-dimensional pixel photoelectric sensor, the microlens can focus fluorescence onto each pixel of the photosensitive unit, improving the photosensitive efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the endoscopic micro-imaging probe of the present invention.

[0017] Figure 2 It is a schematic diagram of the structure of the photodetector of the present invention.

[0018] Figure 3 It is a schematic diagram of the photodetector of the first embodiment of the present invention.

[0019] Figure 4 It is a schematic diagram of the photodetector of the second embodiment of the present invention.

[0020] Figure 5 It is a schematic diagram of the photodetector of the third embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following is a further detailed description through specific embodiments:

[0022] The reference numerals in the accompanying drawings of the specification include: objective lens 1, photodetector 2, protection element 2.1, filter 2.2, photosensitive unit 2.3, drive circuit 2.4, detection object 9, hole 11, and micro-imaging probe 5.

[0023] The first embodiment is basically as follows:

[0024] A micro-endoscope with a high fluorescence collection rate, such as Figure 1As shown in the figure, it includes a micro imaging probe 5. The micro imaging probe 5 includes a housing and an objective lens 1. The upper end of the housing is connected to a laser optical fiber for incident excitation light. After the excitation light is transmitted and refracted, it exits from the objective lens and irradiates the detection object 9. A through hole is provided in the housing corresponding to the position of the objective lens 1. A photodetector 2 is fixedly connected in the through hole. A hole matching the objective lens 1 is provided at the center position of the photodetector 2. The lower end of the objective lens 1 passes through the hole on the photodetector 2 and is flush with the lower surface of the photodetector 2. At the same time, the objective lens 1 is fixed to the photodetector 2 through the hole, and the fixing method can adopt interference fit. As Figure 2 , the photodetector 2 includes a protection element 2.1, a filter 2.2, a photosensitive unit 2.3 and a drive circuit 2.4. The output end of the protection element 2.1 is connected to the input end of the filter 2.2. The output end of the filter 2.2 is connected to the input end of the photosensitive unit 2.3. The output end of the photosensitive unit 2.3 is connected to the input end of the drive circuit 2.4. The output end of the drive circuit 2.4 is connected to an external amplifier circuit and a computer.

[0025] The objective lens 1 is used to collect the fluorescence photons scattered by the detection object 9 within the aperture. The photodetector 2 is used to collect the fluorescence photons that cannot be collected by the objective lens 1.

[0026] Among them, the protection element 2.1 is used to isolate the filter 2.2, the photosensitive unit 2.3 and the drive circuit 2.4 from the outside. The material of the protection element 2.1 is an insulating material that can transmit light waves, and its dielectric strength is greater than 5 MV / mm. In this way, the protection element 2.1 can also be used for electrical isolation to prevent the high voltage of the photosensitive unit 2.3 of the photodetector 2 from causing harm to the detection object 9 and the operator. An antireflection optical coating is also plated on the surface of the protection element 2.1 to improve the transmittance of fluorescence photons.

[0027] Among them, the filter 2.2 is used to filter out the back-reflected and back-scattered excitation light. Its material is an insulating material that can transmit visible light wavelengths and has a dielectric strength greater than 5 MV / mm.

[0028] The photosensitive unit 2.3 of the photodetector 2 is used to convert the fluorescence photons passing through the filter 2.2 into electrical signals.

[0029] The drive circuit 2.4 is used to provide high voltage and drive signals to the photosensitive unit 2.3, and is connected to an external amplifier circuit and a computer. At the same time, it transmits the electrical signals generated by the photosensitive unit 2.3 to the amplifier circuit and the computer.

[0030] In this embodiment, as Figure 3As shown in the figure, the photosensitive unit 2.3 of the photodetector uses a single large-area avalanche photodiode (LAAPD). The hole 11 in the central area can be formed by mechanical drilling or etching. The hole 11 in the central area is used to transmit the excitation light of the microscope objective 1 and receive some fluorescent photons. The remaining annular part of the large-area avalanche photodiode is used to receive the fluorescent photons that cannot be received outside the front aperture of the microscope objective 1.

[0031] Since the avalanche photodiode needs to work in the reverse bias mode, with the cathode facing the immersion liquid and biological tissue and the driving voltage up to several hundred to 2000 volts, the protection component 2.1 is made of a light-transmitting insulating material, which can prevent high voltage from causing harm to the sample, microscope, and operator.

[0032] Compared with the prior art, this embodiment improves the fluorescence collection rate without increasing the volume of the endoscope.

[0033] Embodiment 2:

[0034] The difference from Embodiment 1 is that, as Figure 4 shown, the photosensitive unit 2.3 of the photodetector 2 consists of an annular array of multiple ordinary-sized avalanche photodiodes (APDs). The central hole 11 or transparent material is used to transmit the excitation light of the microscope objective 1, and the multiple ordinary-sized avalanche photodiodes are used to receive the fluorescent photons that cannot be received by the microscope objective 1. Compared with Embodiment 1, the avalanche photodiodes in this embodiment are easier to obtain and have lower processing difficulty.

[0035] Embodiment 3:

[0036] The difference from Embodiment 1 is that, as Figure 5 shown, the photosensitive unit 2.3 of the photodetector 2 consists of an annular array of two-dimensional pixel photodetectors, such as CCD (charge-coupled device) devices, CMOS (complementary metal-oxide-semiconductor) devices, FPA (focal plane array) devices, PMT (photomultiplier tube) devices, single-photon counting devices, or hybrid devices based on any of the above multiple photoelectric conversion principles, such as the hybrid photodetector (HPD) of Hamamatsu Corporation. The central hole 11 or transparent material is used to transmit the excitation light of the microscope objective 1, and the annular array of two-dimensional pixel photodetectors is used to receive the fluorescent photons that cannot be received by the microscope objective 1.

[0037] The surface of the protection component 2.1 opposite to the photosensitive unit 2.3 can adopt a microlens array, and the microlenses can focus the fluorescence onto each pixel of the two-dimensional pixel photodetector, improving the photosensitivity efficiency.

[0038] The above are only embodiments of the present invention, and common knowledge such as specific structures and characteristics known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A miniature endoscope with a high fluorescence collection rate, comprising a miniature imaging probe, the miniature imaging probe including an objective lens and a housing, characterized in that: The outer shell is fixedly connected with a photodetector. A hole matching with the objective lens is formed in the photodetector. The photodetector includes a filter, a photosensitive unit for photoelectric conversion, and a drive circuit connected in series in sequence. The output end of the drive circuit is connected with an amplifier circuit and a computer. The photodetector further includes a protection element, and the filter, the photosensitive unit, and the drive circuit are all located within the protection element; The photosensitive unit is one or more of CCD, CMOS, FPA, and PMT, or the photosensitive unit is a single avalanche diode; the surface of the protection element of the photodetector opposite to the photosensitive unit is a microlens array; A plurality of the photosensitive units are provided and are arranged in an annular array.

2. The miniature endoscope with a high fluorescence collection rate according to claim 1, wherein: The protection element is an insulating protection element that can transmit visible light, and the dielectric strength is greater than 5 MV / mm.

3. The miniaturized endoscope with a high fluorescence collection rate according to claim 2, characterized in that: An antireflection optical coating is also plated on the surface of the protection element.

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