Optical system for a fundus camera

Abstract

The application provides an optical system of a fundus camera, which comprises an ocular lens, an aperture diaphragm, an aberration-correcting lens group, a field lens group, a half-transmission half-reflection mirror and an imaging lens group, light of a light source is irradiated to a pupil through the ocular lens, the light goes out from the pupil and sequentially passes through the ocular lens, the aperture diaphragm, the aberration-correcting lens group and the field lens group to reach the half-transmission half-reflection mirror, 50% of the light transmits through the half-transmission half-reflection mirror to the imaging lens group and is imaged on a CCD, and the other 50% of the light is reflected by the half-transmission half-reflection mirror and is used for connection with a wavefront sensor, and the field lens group comprises a deformable mirror.The application realizes synchronous and efficient collection of high-resolution fundus imaging and high-precision wavefront sensing by optimizing the structure of the aberration-correcting lens group, integrating the field lens group and the deformable mirror and adopting the half-transmission half-reflection mirror light splitting design, and the imaging quality, light energy utilization rate and functional integration degree of the system are improved, and the high-performance requirement of the fundus camera in modern ophthalmic diagnosis and treatment is met.

Description

Technical Field

[0001] This invention relates to the field of optical equipment technology, and more particularly to an optical system for a fundus camera. Background Technology

[0002] In the field of ophthalmology, fundus imaging technology is a core tool for assessing the health of ocular structures such as the retina and optic nerve. Traditional fundus camera optical systems typically consist of basic components such as eyepieces, aperture diaphragms, and imaging lens groups. An image is formed by reflecting light through the pupil from the fundus. However, such systems face significant technical bottlenecks in clinical applications: 1. Insufficient aberration compensation: The human eye possesses inherent aberrations such as spherical aberration, coma, and chromatic aberration. Especially under dilated or non-dilated conditions, individual differences in pupil diameter and axial length can significantly degrade image quality. Traditional systems rely on fixed aberration-correcting lens groups for static compensation, failing to adapt to dynamically changing ocular parameters in real time. 2. Lack of adaptive accommodation: Existing technologies mostly employ open-loop control, with wavefront sensors only used for post-processing aberration detection, unable to form a closed-loop feedback with optical components. This prevents the system from achieving real-time adaptive adjustment in the face of rapidly changing ocular conditions (such as accommodative reflex and tear film fluctuations), limiting image clarity and diagnostic accuracy. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide an optical system for a fundus camera that can dynamically compensate for human eye aberrations and errors inherent in the optical system itself.

[0004] To achieve the above objectives, this invention proposes an optical system for a fundus camera, comprising an eyepiece, an aperture stop, an aberration correction lens group, a field lens group, a semi-transparent mirror, and an imaging lens group. Light from the light source is directed to the pupil through the eyepiece. The light exits the pupil and passes sequentially through the eyepiece, aperture stop, aberration correction lens group, and field lens group to the semi-transparent mirror. 50% of the light passes through the semi-transparent mirror and enters the imaging lens group for imaging on a CCD, while the other 50% is reflected by the semi-transparent mirror and used to connect with a wavefront sensor. The field lens group includes a deformable mirror.

[0005] In the above scheme: the aberration correction lens group consists of multiple lenses, which are arranged in order from the closest to the pupil to the furthest away from the pupil as a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, wherein the second lens, the third lens, and the fourth lens are stacked together in sequence.

[0006] In the above scheme: among the lenses of the aberration correction lens group, the second lens has the largest thickness.

[0007] In the above scheme: the field lens group consists of multiple lenses, which are arranged in the following order from the closest to the pupil to the furthest from the pupil: the sixth lens, the first cemented lens, the deformable mirror, the seventh lens, the eighth lens, and the second cemented lens.

[0008] In the above scheme: the semi-transparent and semi-reflective mirror is set at a 45° angle to the optical axis.

[0009] In the above scheme: the imaging lens group consists of multiple lenses, which are the ninth lens, the tenth lens and the eleventh lens in sequence from the closest to the pupil to the furthest from the pupil.

[0010] In the above scheme, the eyepiece is an aspherical lens, which effectively reduces spherical aberration and improves the initial imaging quality.

[0011] The beneficial effects of this invention are:

[0012] 1. The field lens assembly integrates a deformable mirror, enabling real-time adjustment of the wavefront morphology. This component forms a closed-loop control link with the wavefront sensor: after detecting aberrations, the wavefront sensor drives the deformable mirror to dynamically compensate for aberrations generated by the human eye or the optical system itself, achieving a real-time adaptive function of "measurement and calibration simultaneously." 2. The system uses a semi-transparent, semi-reflective mirror to fold the optical path, integrating the imaging path and the wavefront detection path onto the same optical axis, reducing the complexity of the mechanical structure.

[0013] In summary, this invention optimizes the aberration-correcting lens group structure, integrates the field lens group and the deformable mirror, and adopts a semi-transparent and semi-reflective mirror beam splitting design to achieve simultaneous and efficient acquisition of high-resolution fundus imaging and high-precision wavefront sensing, thereby improving the system's imaging quality, light energy utilization, and functional integration, and meeting the high-performance requirements of modern ophthalmic diagnosis and treatment for fundus cameras. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention.

[0015] Figure 2 This is the system optical path diagram of the present invention.

[0016] Figure 3 This is the MTF transfer function diagram of the present invention. Detailed Implementation

[0017] like Figure 1 As shown in Figure 3, an optical system for a fundus camera mainly consists of an eyepiece 1, an aperture stop 2 (with a ring of light sources at the aperture stop 2), an aberration-correcting lens group 3, a field lens group 4, a semi-transparent mirror 5, and an imaging lens group 6.

[0018] The light from the light source shines into the pupil through the eyepiece 1. The reflected light from the fundus comes out of the pupil and passes through the eyepiece 1, aperture stop 2, aberration correction lens group 3, and field lens group 4 in sequence to reach the semi-transparent mirror 5. 50% of the light passes through the semi-transparent mirror 5 and enters the imaging lens group 6 to form an image on the CCD. The other 50% of the light is reflected by the semi-transparent mirror 5 and used to connect with the wavefront sensor.

[0019] The aperture stop 2 has a light transmission diameter of 9.5 mm.

[0020] The eyepiece 1 uses a double-sided aspherical mirror, with both optical surfaces being 16th-order high-precision aspherical surfaces, which effectively reduces spherical aberration and improves the initial imaging quality.

[0021] The field lens group 4 includes a deformable mirror 41, which can adjust the wavefront shape in real time. Furthermore, the deformable mirror 41 is conjugate to the pupil position, meaning its position is specifically designed for the pupil, resulting in exceptionally good aberration correction. This component (deformable mirror 41) forms a closed-loop control link with the wavefront sensor: after detecting aberrations, the wavefront sensor can drive the deformable mirror to dynamically compensate for aberrations generated by the human eye or the optical system itself, achieving a real-time adaptive function of "measurement and calibration simultaneously".

[0022] Specifically, the aberration correction lens group 3 consists of multiple lenses, which are arranged in order from the closest to the pupil to the furthest away from the pupil: the first lens, the second lens, the third lens, the fourth lens, and the fifth lens. The second lens, the third lens, and the fourth lens are overlapped together in sequence (overlapping together means that the maximum gap between the corresponding two lenses is less than 0.5mm, and there is an overlap between them).

[0023] Among the lenses in the aberration correction lens group 3, the second lens has the largest thickness.

[0024] Specifically, the field lens group 4 consists of multiple lenses, which are arranged from the closest to the pupil to the furthest away from the pupil as follows: the sixth lens, the first cemented lens, the deformable mirror 41, the seventh lens, the eighth lens, and the second cemented lens.

[0025] The semi-transparent and semi-reflective mirror 5 is set at a 45° angle to the optical axis.

[0026] Specifically, the imaging lens group 6 consists of multiple lenses, which are the ninth lens, the tenth lens, and the eleventh lens in sequence from the closest to the pupil to the furthest from the pupil.

[0027] The first lens is a positive lens with a refractive index less than 1.4 and a thickness less than 3 mm; the second lens is a positive lens with a refractive index greater than 2.0 and a thickness greater than 10 mm; the third lens is a negative lens; the fourth lens is a positive lens; the fifth lens is a positive lens; the sixth lens is a positive lens; the first cemented lens is formed by cementing a negative lens closer to the sixth lens and a positive lens farther from the sixth lens; the seventh lens is a positive lens; the eighth lens is a negative lens; the second cemented lens is formed by cementing a negative and a positive lens closer to the eighth lens and a negative lens farther from the eighth lens; the ninth lens is a positive lens; the tenth lens is a negative lens; the eleventh lens is a positive lens.

[0028] In Figure 3, the curves from top to bottom represent the diffraction limit, the center of the field of view, the lower edge arc, the upper edge arc, the lower edge meridian, and the upper edge meridian. As can be seen from the figure, each imaging curve approaches the diffraction limit, proving that the imaging quality of this optical system is good.

Claims

1. An optical system for a fundus camera, comprising an eyepiece (1), an aperture stop (2), and an aberration correction lens group (3), characterized in that: It also includes a field lens group (4), a semi-transparent mirror (5), and an imaging lens group (6). The light from the light source shines into the pupil through the eyepiece (1). The light comes out from the pupil and passes through the eyepiece (1), the aperture stop (2), the aberration aberration lens group (3), and the field lens group (4) in sequence to reach the semi-transparent mirror (5). 50% of the light passes through the semi-transparent mirror (5) and enters the imaging lens group (6) to be imaged on the CCD. The other 50% of the light is reflected by the semi-transparent mirror (5) and used to connect with the wavefront sensor. The aperture stop (2) has a light transmission diameter of 9.5 mm. The field lens group (4) includes a deformable mirror (41). The deformable mirror (41) is conjugate to the position of the pupil. The aberration correction lens group (3) consists of multiple lenses, arranged sequentially from near the pupil to far from the pupil as a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, wherein the second lens, the third lens, and the fourth lens are stacked together in sequence; the first lens is a positive lens with a refractive index less than 1.4 and a thickness less than 3 mm; the second lens is a positive lens with a refractive index greater than 2.0 and a thickness greater than 10 mm; the third lens is a negative lens; the fourth lens is a positive lens; the fifth lens is a positive lens; the field lens group (4) consists of multiple lenses, arranged sequentially from near the pupil to far from the pupil as a sixth lens, a first cemented lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth ... sixth lens, a third lens, a fifth lens, a sixth lens, a sixth lens, a third lens, a fifth lens, a sixth lens, a sixth lens, a third lens, a fifth lens, a sixth lens, a sixth lens, a seventh lens, a fifth lens, a sixth lens, a sixth lens, a seventh lens, a fifth lens, a sixth lens, a sixth lens, a seventh lens, a fifth lens, a sixth lens, a seventh The imaging lens group (6) consists of a lens, a deformable mirror (41), a seventh lens, an eighth lens, and a second cemented lens; wherein the sixth lens is a positive lens; the first cemented lens is formed by cementing a negative lens close to the sixth lens and a positive lens far from the sixth lens; the seventh lens is a positive lens; the eighth lens is a negative lens; the second cemented lens is formed by cementing a negative positive lens close to the eighth lens and a negative lens far from the eighth lens; the imaging lens group (6) consists of multiple lenses, which are the ninth lens, the tenth lens, and the eleventh lens in sequence from the closest to the pupil to the furthest from the pupil; wherein the ninth lens is a positive lens; the tenth lens is a negative lens; and the eleventh lens is a positive lens.

2. The fundus camera optical system according to claim 1, characterized in that: Among the lenses of the aberration correction lens group (3), the second lens has the largest thickness.

3. The fundus camera optical system according to claim 1, characterized in that: The semi-transparent and semi-reflective mirror (5) is set at a 45° angle to the optical axis.

4. The fundus camera optical system according to claim 1, characterized in that: The eyepiece (1) is a double-sided aspherical mirror, and both of its optical surfaces are 16th-order high-precision aspherical surfaces.

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