A high-resolution rapid imaging corneal confocal microscope system

Abstract

This invention discloses a high-resolution, rapid imaging corneal confocal microscope system. In this system, a laser beam, after passing through a filter and polarization encoder, reaches the first lens via a beam expander and is focused on a slit. The beam then passes through a second lens to a scanning lens, where its propagation direction is altered. It then passes through the scanning lens, is refracted by a beam splitter, and enters the microscope objective via a sleeve lens, where it is focused onto the cornea to be imaged. The scattered light signal generated by the laser illumination returns and passes through the beam splitter into the probe light path. After passing through a polarization selector and a filter, it is exposed by the imaging element using a rolling shutter to form an image. An axially moving stage enables three-dimensional corneal imaging. Using a laser source for line scanning offers advantages such as high resolution, rapid imaging, system simplicity and stability, and strong penetration. The rolling shutter blocks out-of-focus light, allowing for convenient adjustment of the depth of focus to accommodate different corneal structures.

Description

Technical Field

[0001] This invention relates to the fields of optical microscopy and biomedical imaging, and more particularly to a high-resolution, rapid imaging corneal confocal microscope system. Background Technology

[0002] The concept of confocal microscopy was proposed by Marvin Minsky in 1957, initially for observing neural networks in living brain tissue (see *Microscopy Apparatus*, US Patent 3013467A). A confocal microscopy system is a scanning imaging system characterized by placing conjugate pinholes behind the light source and in front of the probe plane to block stray light beams around non-imaging points, thereby significantly improving the system's imaging resolution and enabling the separate imaging of portions of the object at a certain depth.

[0003] Corneal confocal microscopy is a technique that uses a confocal microscope to image the structure of living corneal cells. This aids in the study of physiological and pathological structural changes in corneal diseases at the living cellular level, and assists in disease diagnosis and observation of treatment responses. In 1974, Maurice first applied a confocal system to corneal microscopy and successfully obtained microscopic images of the corneal endothelium (see David Maurice, "A scanning slit optical microscope," Invest. Ophthalmol. Vis. Sci. 13, 1033-1037 (1974)). Following a series of improvements, the confocal system used by Maurice gained wider clinical application.

[0004] Currently, there are two main types of confocal corneal microscopes on the market: The first type is the slit-light confocal microscope. This type of system typically uses a halogen lamp that filters out the infrared and ultraviolet components, and replaces the pinhole with a pair of conjugate slits. The linear beam scans and images in one dimension, featuring a simple structure and fast imaging. However, due to the shallow penetration depth of incoherent light sources, slit-light confocal systems have difficulty imaging cloudy corneas, limiting imaging resolution and image clarity. The second type is the laser spot-scanning corneal confocal microscope. This type of microscope system uses a laser as the light source and employs two scanning devices to achieve two-dimensional scanning. The system structure is more complex than the first type. Furthermore, laser spot-scanning corneal confocal microscope systems have a slower imaging speed, and the image is easily distorted by eye movements. Patients also find it difficult to cooperate due to the long operation time and experience eye discomfort. A common characteristic of both types of confocal microscope systems is that the size of the slits and pinholes used is not easily adjustable, and the depth of focus cannot be adjusted to adapt to the structure of different corneal tissues. Summary of the Invention

[0005] To address the shortcomings of existing confocal corneal microscopy technology, this invention provides a high-resolution, rapid-imaging corneal confocal microscopy system that achieves clear and fast corneal confocal microscopic imaging.

[0006] The objective of this invention is achieved through the following technical solution: a high-resolution, rapid imaging corneal confocal microscopy system, which includes an illumination optical path and a probe optical path;

[0007] The illumination optical path includes a laser source, a filter, a beam expander, a polarization encoder, a first lens, a slit, a second lens, a scanning mirror, a scanning lens, a beam splitter, a sleeve lens, and a microscope objective fixed on a displacement stage.

[0008] The beam from the laser source passes through a filter, then through a beam expander, and is polarized by a polarization encoder before reaching the first lens and being focused on the slit. The beam passing through the slit passes through the second lens and reaches the scanning mirror, where its propagation direction is changed. The beam exiting the scanning mirror passes through the scanning lens, is refracted by a beam splitter, and then passes through a sleeve lens before entering the microscope objective and being focused onto the cornea where imaging is required.

[0009] The detection optical path includes a polarization selector, a filter, and an imaging element. After the cornea receives scattered light signals from laser illumination, these signals return and pass through a beam splitter into the detection optical path. First, the polarization selector selects scattered light with a specific polarization. Then, the filter filters out stray light signals, and finally, the imaging element exposes the light using a rolling shutter to form an image. By controlling the rolling shutter, the number of pixel rows exposed simultaneously is adjusted, changing the exposure of the defocused scattered light and regulating the depth of focus. Axial movement of the displacement stage achieves three-dimensional corneal imaging. Furthermore, the first lens is a cylindrical lens, with the cylindrical surface serving as the beam incident surface. The cylindrical axis is parallel to the slit direction and the scanning mirror rotation axis.

[0010] Furthermore, the polarization encoder consists of a linear polarizer, a quarter-wave plate, and a half-wave plate.

[0011] Furthermore, the slit is located on the rear focal plane of the first lens and on the front focal plane of the second lens.

[0012] Furthermore, the scanning mirror enables the linear beam of light on the focal plane of the microscope objective to scan in one dimension inside the cornea; the scanning mirror is optically conjugate with the entrance pupil of the microscope objective.

[0013] Furthermore, the scanning lens is a lens group that corrects aberrations and is able to produce a flat image plane during beam scanning, with the center of the entrance pupil of the scanning lens coinciding with the pivot point of the scanning mirror.

[0014] Furthermore, the beam splitter reflects the illumination light and transmits the scattered light from the cornea, forming a 45° angle with both the illumination and detection light paths.

[0015] Furthermore, the back focal plane of the sleeve lens coincides with the entrance pupil plane of the microscope objective; the sleeve lens and the scanning lens constitute a 4f optical system.

[0016] Furthermore, the back focal plane of the first lens, the back focal plane of the scanning lens, the focal plane of the microscope objective, and the photosensitive surface of the imaging element have a conjugate relationship.

[0017] Furthermore, the microscope objective is fixed on a displacement stage capable of moving along the optical axis.

[0018] Furthermore, the polarization selector consists of a phase delayer and a linear polarizer.

[0019] Furthermore, the imaging device is a CMOS camera with a rolling shutter imaging mode, and the scanning mirror and the rolling shutter move synchronously, so that the corneal defocused scattered light is not exposed and does not participate in image formation.

[0020] Furthermore, the operating wavelengths of the laser source and the filter can be adjusted between 600-840nm.

[0021] Furthermore, the optical path includes polarization encoding and polarization selection devices for polarization-coded imaging.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Line scanning using a laser light source offers advantages such as high resolution, rapid imaging, system simplicity and stability, and strong penetration. Using a rolling shutter instead of a physical pinhole to block out-of-focus light allows for convenient adjustment of depth of focus, adapting to the different structures of the cornea. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a high-resolution rapid imaging corneal confocal microscope system in an embodiment of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] like Figure 1As shown, the present invention provides a high-resolution, rapid imaging corneal confocal microscope system. This embodiment of the corneal confocal microscope system includes: a laser source 1, a filter 2, a beam expander 3, a polarization encoder 4, a first lens 5, a slit 6, a second lens 7, a scanning mirror 8, a scanning lens 9, a beam splitter 10, a sleeve lens 11, a microscope objective 12, a stage 13, a polarization selector 15, a filter 16, and an imaging element 17. All optical elements and the cornea 14 to be imaged are located on the coaxial optical path.

[0027] In this embodiment, the light beam from the laser source 1 passes through the filter 2, then through the beam expander 3 and the polarization encoder 4 to reach the first lens 5, where it is focused onto the slit 6. The light beam passing through the slit 6 passes through the second lens 7 to reach the scanning mirror 8, where its propagation direction is changed. The light beam exiting the scanning mirror 8 passes through the scanning lens 9, is refracted by the beam splitter 10, and then passes through the sleeve lens 11 to enter the microscope objective 12, where it is focused onto the cornea 14 to be imaged. The scattered light from the cornea 14 is collected in reverse by the microscope objective 12, and then passes through the beam splitter 10, the polarization selector 15, and the filter 16 to reach the imaging element 17, forming an image. The axially moving stage 13 achieves three-dimensional corneal imaging. The optical path includes the polarization encoder 4 and the polarization selector 15 for polarization-encoded imaging.

[0028] In this embodiment, light source 1 provides a laser beam for the microscopic system. This embodiment uses a white laser with a wavelength range of 470nm to 2400nm, and its power is controlled within a certain range so that the power of the beam entering the cornea 14 does not exceed 2.5mW, preventing damage to the eye.

[0029] The function of filter 2 is to select the desired light source wavelength and output collimated light. In this example, the filter is an adjustable linewidth output filter system used to select the desired laser wavelength and output a collimated beam. It can output lasers with a linewidth of more than 10 nm in the range of 600 nm to 840 nm. Preferably, the center wavelength of the output laser is 690 nm to obtain a stronger scattered light signal.

[0030] The laser source 1 and the filter 2 can be replaced by a monochromatic laser source with a wavelength in the visible and near-infrared range. Preferably, the laser wavelength is between 680 nm and 800 nm.

[0031] The beam expander 3 is used to change the diameter of the collimated beam output by the filter 2. Preferably, the changed diameter is greater than the length of the slit 6. In this embodiment, the length of the slit 6 is 3 mm, and the preferred output beam diameter is 8 mm.

[0032] The polarization encoder 4 is used to polarize the light beam. In a preferred embodiment, the polarization encoder 4 consists of a linear polarizer, a quarter-wave plate, and a half-wave plate.

[0033] The light beam passing through the polarization encoder 4 is focused by the first lens 5. The first lens 5 is a cylindrical lens, with its cylindrical axis parallel to the direction of the slit 6 and the rotation axis of the scanning mirror 8. Its function is to shape the incident collimated light beam into a linear spot at the focal point. In a preferred embodiment, the first lens 5 is a plano-convex cylindrical lens with a focal length of 25mm, and the cylindrical surface is the incident surface of the light beam.

[0034] The slit 6 can be approximated as a rectangular aperture with its long side much longer than its wide side. The direction of the long side coincides with the cylindrical axis of the first lens 5 and is placed at the focal point of the first lens 5. The function of the slit 6 is to form a linear light source with good spatial coherence. In a preferred embodiment, the long side of the slit is 3 mm long and the wide side is 5 μm long.

[0035] The light beam passing through slit 6 is incident on scanning mirror 8 after passing through second lens 7. Preferably, the centers of slit 6 and scanning mirror 8 are located at two focal planes of second lens 7, and the light beam forms a linear focal spot at scanning mirror 8.

[0036] The scanning mirror 8 functions to change the deflection angle of the light beam at the entrance pupil of the microscope objective 12, so that the linear light beam on the focal plane of the microscope objective 12 can perform a one-dimensional scan inside the cornea 14. In a preferred embodiment, the scanning mirror 8 is a galvanometer mirror, and its rotation axis is parallel to the direction of the slit 6.

[0037] The light beam emitted from the scanning lens 8 passes through the scanning lens 9, is reflected by the beam splitter 10, passes through the sleeve lens 11, and enters the entrance pupil of the microscope objective 12, where it is focused inside the cornea 14.

[0038] The scanning lens 9 is a special lens group that corrects field curvature. Its function is to produce a flat image plane when the direction of the emitted beam from the scanning mirror 8 changes. The entrance pupil surface of the scanning lens 9 coincides with the center of the scanning mirror 8, and its rear focal surface coincides with the front focal surface of the sleeve lens 11. The line light source at the slit 6 forms a conjugate image on the focal plane of the scanning lens 9.

[0039] Preferably, the back focal plane of the sleeve lens 11 coincides with the entrance pupil plane of the microscope objective 12, so that the center of the scanning mirror 8 and the entrance pupil plane of the microscope objective 12 have a conjugate relationship.

[0040] Preferably, in order to fill the entrance pupil of the microscope objective 12 with the light beam, the ratio of the effective focal length of the sleeve lens 11 to the effective focal length of the scanning lens 9 is equal to the ratio of the entrance pupil size of the microscope objective 12 to the spot size of the scanning mirror 8, so that the light beam fills the entrance pupil of the microscope objective 12. The sleeve lens 11 and the scanning lens 9 constitute a 4f optical system.

[0041] The microscope objective 12 is used to focus the light beam inside the cornea 14 for illumination and to collect the scattered light from the cornea 14 in the opposite direction. Preferably, a plan achromatic immersion microscope objective with a numerical aperture greater than 1.05, a working distance greater than 1 mm, and water as the immersion solution is selected to ensure imaging resolution and avoid direct contact with the corneal surface.

[0042] The stage 13 has one-dimensional movement capability, and its function is to drive the microscope objective 12 to move back and forth along the axis, so that the image plane is located at different depths of the cornea 14, thereby realizing three-dimensional imaging of the cornea. In a preferred embodiment, the axial movement range of the stage 13 is 800 μm, and the minimum movement step is 5 nm.

[0043] Backscattered light from inside the cornea 14 is collected in reverse by the microscope objective 12, and enters the imaging element 17 after passing through the sleeve lens 11, beam splitter 10, polarization selector 15, and filter 16. The beam splitter 10 connects the illumination and probe light paths, reflects the illumination light, and projects the scattered light from the cornea 14, forming a 45° angle with both light paths, with a preferred splitting ratio of 8:92 (R / T). The polarization selector 15, composed of a phase retarder and a linear polarizer, selects scattered light with a specific polarization state for transmission. The filter 16 filters out stray light signals that do not belong to the probe spectrum, allowing the scattered light signal to pass through.

[0044] The imaging element 17 is a CMOS camera, and its photosensitive surface forms a conjugate relationship with the focal plane (sample plane) of the microscope objective 12, the back focal plane of the first lens 5, and the back focal plane of the scanning lens 9. When the light beam is incident on the photosensitive surface of the imaging element 17, the imaging element 17 uses a rolling shutter to control the exposure. The rolling shutter is a working mode of a CMOS camera used for sequential exposure and data processing of the pixel elements on the sensor array. In a preferred embodiment, the sensor array of the imaging element 17 and the scanning mirror 8 are controlled by software to ensure that the rows being exposed form a conjugate relationship with the linear light beam focused on the focal plane of the objective, thus preventing out-of-focus, scattered light from being exposed.

[0045] The number of lines being exposed simultaneously by the imaging element 17 can be adjusted to regulate the exposure of scattered light rays from out of focus, thereby changing the depth of focus. Generally, the width of the pixels being exposed simultaneously is roughly equivalent to the width of the linear beam on the photosensitive surface of the imaging element 17. To adapt to complex corneal structures and improve image quality, when imaging corneal tissue with large feature structures and weak scattering ability, the number of lines being exposed simultaneously should be increased to improve the depth of focus; when imaging corneal tissue with small feature structures and strong scattering ability, the number of lines being exposed simultaneously should be decreased.

[0046] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A high-resolution, rapid imaging corneal confocal microscope system, characterized in that, The system includes an illumination optical path and a detection optical path; The illumination optical path includes a laser source, a filter, a beam expander, a polarization encoder, a first lens, a slit, a second lens, a scanning mirror, a scanning lens, a beam splitter, a sleeve lens, and a microscope objective fixed on a displacement stage. The laser beam emitted by the laser source passes sequentially through a filter, a beam expander, and a polarization encoder before reaching the first lens and being focused onto the slit. The beam passing through the slit then passes through the second lens and reaches the scanning mirror, where its propagation direction is changed. The beam exiting the scanning mirror passes through the scanning lens, is refracted by a beam splitter, and then passes through a sleeve lens before entering the microscope objective, where it is focused onto the cornea to be imaged. The slit is located on the rear focal plane of the first lens and on the front focal plane of the second lens. The detection optical path includes a polarization selector, a filter, and an imaging element; the imaging element is a CMOS camera with a rolling shutter imaging mode, and the scanning mirror and the rolling shutter move synchronously, so that the corneal defocused scattered light is not exposed and does not participate in image formation; After the cornea is illuminated by laser, the scattered light signal returns and enters the detection optical path through the beam splitter. The polarization selector selects a specific polarization state, and the stray light signal is filtered out by the filter. Finally, the imaging element exposes the image through a rolling shutter to form an image. By controlling the rolling shutter, the number of pixels exposed at the same time can be adjusted to change the exposure of the defocused scattered light and adjust the depth of focus. When imaging corneal tissue with large feature structures and weak scattering ability, the number of lines exposed at the same time should be increased to improve the depth of focus; When imaging corneal tissue with small feature structures and strong scattering ability, the number of rows exposed at the same time should be reduced; the displacement stage should be moved axially to achieve three-dimensional corneal imaging.

2. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The first lens is a cylindrical lens, with the cylindrical surface serving as the incident surface for the light beam. The cylindrical axis is parallel to the slit direction and the rotation axis of the scanning mirror.

3. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The scanning mirror enables a linear beam of light on the focal plane of the microscope objective to scan the cornea in a one-dimensional direction; the scanning mirror is optically conjugate with the entrance pupil of the microscope objective.

4. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The scanning lens is a lens group that corrects aberrations and can produce a flat image plane during beam scanning. The center of the entrance pupil of the scanning lens coincides with the pivot point of the scanning mirror.

5. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The beam splitter reflects the illumination light and transmits the scattered light from the cornea, forming a 45° angle with both the illumination and detection light paths.

6. The high-resolution rapid imaging corneal confocal microscope system according to claim 4, characterized in that, The back focal plane of the sleeve lens coincides with the entrance pupil plane of the microscope objective; the sleeve lens and the scanning lens constitute a 4f optical system.

7. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The rear focal plane of the first lens, the rear focal plane of the scanning lens, the focal plane of the microscope objective, and the photosensitive surface of the imaging element have a conjugate relationship.

8. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The microscope objective is fixed on a displacement stage capable of moving along the optical axis.

9. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The operating wavelength of the laser source and filter can be adjusted between 600-840nm.

10. The high-resolution rapid imaging corneal confocal microscope system according to claim 1, characterized in that, The optical path includes polarization encoding and polarization selection devices for polarization-coded imaging.

Images