A compact optical system for measuring the curvature of the human cornea

Abstract

The present invention provides a compact optical system for measuring the corneal curvature of a human eye, so that an illumination module and an imaging module can share part of the lens and realize coaxiality, thereby greatly reducing the volume and weight of the optical measurement system for corneal curvature, and can be applied to the design of a keratometer, thereby obtaining a keratometer with a total length of less than 70 mm and an optical lens group weight of less than 30 g. At the same time, the keratometer designed according to the optical measurement system for corneal curvature provided by the present invention also has the advantages of small volume, low cost, and household use.

Description

Technical Field

[0001] The invention belongs to the technical field of optical equipment, and in particular relates to a compact optical system for measuring the curvature of human cornea. Background Art

[0002] At this stage, myopia has developed into a social problem. The number of myopic people in my country has exceeded 600 million, and the prevention and control of myopia is becoming more and more necessary. The refractive power of the human eye mainly comes from the cornea and lens, of which the refractive power of the cornea is about +43.05D, accounting for 70% of the total refractive power of the human eye. Although it is often believed that the main cause of true myopia is axial growth, it is still very necessary to monitor the corneal curvature. On the one hand, it can monitor the changes in corneal curvature during the growth of adolescents as one of the bases for judging their myopia risk. On the other hand, it can be used for preliminary testing and preparation for work such as corneal planing surgery and orthokeratology lens fitting.

[0003] A keratometer is an optical system that can measure the radius of curvature of the front surface of the human cornea. It consists of an illumination optical path and an imaging optical path. Light from a light source is projected onto the front surface of the human eye through the illumination optical path, and after being reflected by the front surface, it is imaged on a receiver through the imaging optical path. That is, the cornea is illuminated by an illumination light source, and the characteristics of the reflected light are measured to calculate the curvature of the cornea to be measured. Currently, the imaging optical path and the illumination optical path of the corneal curvature on the market are usually separated, and both need to be placed at a certain angle with the cornea to be measured as the center, which results in a large size and weight, and can only be used as a professional instrument. Summary of the invention

[0004] To solve the above problems, the present invention provides a compact optical system for measuring the corneal curvature of a human eye, which enables the illumination module and the imaging module to share some lenses and achieve coaxiality, thereby greatly reducing the volume and weight of the corneal curvature measurement system.

[0005] A compact optical system for measuring the curvature of a human cornea comprises a coaxial illumination module and an imaging module, wherein the illumination module and the imaging module share a focusing lens group, and the illumination module further comprises an annular light source component and a reflection component, and the imaging module further comprises an imaging component;

[0006] The annular light source assembly is used to emit annular light, the focusing lens group is used to focus the energy of the annular light, and the reflecting assembly is used to shape the energy-focused annular light into an annular parallel light source, and the annular parallel light source is incident on the human cornea at a set illumination angle;

[0007] The focusing lens group is also used to focus the reflected light from the human cornea, the imaging component is used to image the reflected light after energy focusing, and the external processing module obtains the curvature of the human cornea based on the image formed by the imaging component.

[0008] Furthermore, the method for the external processing module to obtain the corneal curvature of the human eye according to the image formed by the imaging component is:

[0009]

[0010] Among them, R is the curvature of the human cornea, y 1 is the image height in the formed image, θ is the illumination angle, f is the object focal length, and x is the object distance.

[0011] Furthermore, when the image is clearly imaged in the imaging component, the image is an image circle, and the image height y 1 is the radius of the image circle; when the image is blurred in the imaging component, the image is an image ring, and the image height y 1 is the average radius of the image ring.

[0012] Furthermore, the illumination angle θ, the object focal length f and the object distance x are obtained by calibrating the optical system.

[0013] Further, the annular light source assembly includes an annular light source device 1 and an annular lens 2, the focusing lens group includes a first lens 3, a second lens 4, a third lens 5, a fourth lens 6 and a fifth lens 7, the reflection assembly includes an annular spherical reflector 8 and a plane glass 9 coated with a reflection ring, and the imaging assembly includes a sixth lens 11, a seventh lens 12 and a receiver 13;

[0014] The annular light source device 1 emits annular light, which is incident on the coaxially placed annular lens 2, the first lens 3, the second lens 4, the third lens 5, the fourth lens 6 and the fifth lens 7 in sequence, and then is shaped into an annular parallel light source through the plane glass 9 and the annular spherical reflector 8 in sequence and is incident on the human cornea;

[0015] The reflected light from the human cornea passes through the coaxially placed fifth lens 7, fourth lens 6, third lens 5, second lens 4, first lens 3, sixth lens 11 and seventh lens 12 in sequence, and then enters the receiver 13 for imaging.

[0016] Further, the focal length range of the lens group composed of the annular lens 2, the first lens 3, the second lens 4, the third lens 5, the fourth lens 6 and the fifth lens 7 is 10 to 25 mm;

[0017] The focal length range of the lens group composed of the first lens 3, the second lens 4, the third lens 5, the fourth lens 6, the fifth lens 7, the sixth lens 11 and the seventh lens 12 is 50-85 mm.

[0018] Furthermore, the lighting angle is selected in the range of 10 to 30 degrees.

[0019] Beneficial effects:

[0020] 1. The present invention provides a compact optical system for measuring the corneal curvature of a human eye, which enables an illumination module and an imaging module to share part of the lens and realize coaxiality, greatly reducing the volume and weight of the optical measurement system for corneal curvature, and can be applied to the design of a keratometer, thereby obtaining a keratometer with a total length of less than 70 mm and an optical lens assembly weight of less than 30 g. At the same time, the keratometer designed according to the optical measurement system for corneal curvature provided by the present invention also has the advantages of small volume, low cost, and household use.

[0021] 2. The present invention provides a compact optical system for measuring the curvature of the human cornea. Based on the unique optical path multiplexing corneal curvature measurement system of the present invention, a mapping relationship between the corresponding image height and the corneal curvature radius is given. According to the mapping relationship provided by the present invention, the curvature radius of the human cornea can be quickly obtained.

[0022] 3. The present invention provides a compact optical system for measuring the curvature of the cornea of ​​the human eye. In the shared coupling optical path, the illumination light source is located near the image source, which has the advantage of being multiplexed with the imaging optical path, so that the illumination light source is shaped by more lenses into parallel light that enters the human eye at a specific angle, while greatly reducing the size of the system in the vertical direction; and, in the illumination optical path, the light emitted by a single light-emitting point in the annular light source is refracted by the lens group, converges with the light emitted by other light-emitting points, intersects on the visual axis, and then further transmits forward and reflects on the flat glass at a position on a different side from the light-emitting point. The design of this cross optical path can further compress the size of the entire optical system in the visual axis direction.

[0023] 4. The present invention provides a compact optical system for measuring the curvature of the human cornea. The annular spherical reflector and the plane glass introduce two reflections into the entire illumination light path, which can focus the light in a smaller volume.

[0024] 5. The present invention provides a compact optical system for measuring the curvature of the human cornea. The lens group in the illumination light path is composed of lenses with different optical focal lengths, with a focal length range of 10 to 25 mm, which can ensure that the light incident on the human cornea has a high degree of parallelism. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a compact optical system for measuring the curvature of the human cornea provided by the present invention;

[0026] Figure 2 A schematic diagram of the structure of the lighting module provided by the present invention;

[0027] Figure 3 A schematic diagram of the structure of the imaging module provided by the present invention;

[0028] 1-annular light source device, 2-annular lens, 3-first lens, 4-second lens, 5-third lens, 6-fourth lens, 7-fifth lens, 8-annular spherical reflector, 9-plane glass, 10-human cornea, 11-sixth lens, 12-seventh lens, 13-receiver. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0030] The present invention provides a compact optical system for measuring the curvature of human cornea, comprising a coaxial lighting module and an imaging module, wherein the lighting module and the imaging module share a focusing lens group, and the lighting module further comprises an annular light source component and a reflection component, and the imaging module further comprises an imaging component;

[0031] The annular light source assembly is used to emit annular light, the focusing lens group is used to focus the energy of the annular light, and the reflecting assembly is used to shape the energy-focused annular light into an annular parallel light source, and the annular parallel light source is incident on the human cornea at a set illumination angle;

[0032] The focusing lens group is also used to focus the reflected light from the human cornea, the imaging component is used to image the reflected light after energy focusing, and the external processing module obtains the curvature of the human cornea based on the image formed by the imaging component.

[0033] It should be noted that the lighting module and the imaging module can have a variety of optical element combinations, such as using lenses of different shapes and types to form a focusing lens group, an annular light source assembly, a reflection assembly or an imaging assembly, or using lenses of the same type but with different surface curvatures to form a focusing lens group, an annular light source assembly, a reflection assembly or an imaging assembly, etc. One implementation is given below, and Table 1 shows the curvature radius of each lens used in the lighting module and the imaging module of the present invention.

[0034] like Figure 1 As shown, the annular light source assembly includes an annular light source device 1 and an annular lens 2, the focusing lens group includes a first lens 3, a second lens 4, a third lens 5, a fourth lens 6 and a fifth lens 7, the reflection assembly includes an annular spherical reflector 8 and a plane glass 9 coated with a reflection ring, and the imaging assembly includes a sixth lens 11, a seventh lens 12 and a receiver 13;

[0035] The annular light source device 1 emits annular light, which is incident on the coaxially placed annular lens 2, the first lens 3, the second lens 4, the third lens 5, the fourth lens 6 and the fifth lens 7 in sequence, and then is shaped into an annular parallel light source through the plane glass 9 and the annular spherical reflector 8 in sequence and is incident on the human cornea;

[0036] The reflected light from the human cornea passes through the coaxially placed fifth lens 7, fourth lens 6, third lens 5, second lens 4, first lens 3, sixth lens 11 and seventh lens 12 in sequence, and then enters the receiver 13 for imaging.

[0037] That is to say, Figure 2 As shown, in the illumination light path, the visible light / infrared light with an annular spot is emitted by the annular light source device 1, and the illumination lens group composed of the annular lens 2, the first lens 3, the second lens 4, the third lens 5, the fourth lens 6 and the fifth lens 7, the annular spherical reflector 8, and the plane glass 9 coated with a reflection ring form parallel light to illuminate the human cornea 10, and the parallel light illumination angle is θ. The selection range of θ is 10-30°, with 18° as the preferred value. Among them, the illumination lens group is composed of lenses with different optical focal lengths, with a focal length range of 10-25mm, and its purpose is to ensure the parallelism of the incoming light; the plane glass 9 and the annular spherical reflector 8 introduce two reflections for the entire illumination light path, which can focus the light in a smaller volume. At the same time, by controlling the illumination lens group to form an intermediate image at the position where the annular reflective film is coated on the surface of the plane glass 9, the utilization rate of light energy can be improved, but the requirements for assembly will be relatively increased. In addition, the plane glass 9 with a ring-shaped reflective film on its surface in the illumination light path can be replaced by a semi-reflective and semi-transparent beam splitter, which can be placed in the position of the plane glass 9 and use its own surface to simultaneously refract and transmit the light. The present invention will not elaborate on this.

[0038] At the same time, if Figure 3 As shown, in the imaging optical path, the imaging lens group composed of the annular lens 2, the first lens 3, the second lens 4, the third lens 5, the fourth lens 6, the fifth lens 7, the sixth lens 11 and the seventh lens 12 needs to focus the reflected light after the parallel light at an angle θ in the illumination optical path irradiates the human cornea 10 on the receiver 13. The focal length range of the imaging lens group is 50 to 85 mm, and the image ring diameter formed on the receiver by the cornea with different curvatures reflecting the same parallel light at an angle θ is different, and at the same time, an image side telecentric optical path is formed, that is, the main light is incident on the receiver 13 at 0°.

[0039] Table 1

[0040] Lens serial number Front surface curvature radius range (mm) Rear surface curvature radius range (mm) 2 20～25 50～75 3 10～25 5～16 4 10～35 10～35 5 10～35 55～60 6 12～24 12～24 7 28～32 28～34 8 45～85 11 8～16 3～6 12 8～16 4～9

[0041] The following describes in detail how the external processing module obtains the corneal curvature of the human eye based on the image formed by the imaging component after the imaging module obtains the image of the ring light source.

[0042] It should be noted that the outgoing light after the parallel light is reflected by the cornea can be regarded as emitted by an equivalent point light source behind the cornea, and the distance between this point and the front surface of the cornea is equal to the corneal curvature radius R. Assuming that corneas with different curvatures can be clearly presented to the receiver, for the imaging lens group, since different corneas can be clearly imaged on the receiver and the distance between the receiver and the imaging lens group is fixed, according to Newton's formula:

[0043] xxx 1 =f×f 1

[0044] Among them, x and x 1 Denote object distance and image distance, f and f respectively. 1 Respectively represent the object focal length and the image focal length. In the present invention, f=f 1 The distance from the equivalent object surface to the lens group is equal for different corneal curvatures. According to the magnification formula, it can be known that the image height and the equivalent object height are proportional under the same lens group. In the present invention, the angle of the illumination light incident on the cornea is θ, and the selection range of θ is 10 to 30°. Then the equivalent object height can be obtained by y=f 3 ×tan(θ) is obtained, where f 3 represents the focal length of the equivalent lens group of the cornea to be measured, and |f 3 |=|R|. At the same time, it can be known that the equivalent height is proportional to the radius of corneal curvature. Based on the above conclusions, it can be concluded that the image height is proportional to the radius of corneal curvature. The image height y 1 The relationship with the corneal curvature radius R is as follows:

[0045]

[0046] It should be noted that the illumination angle θ, the object focal length f, and the object distance x are obtained by calibrating the optical system in advance, that is, Figure 1 After the compact optical system for measuring the curvature of the human cornea is shown, the illumination angle θ, the object focal length f and the object distance x can be determined and kept constant in the subsequent measurement process of the radius of curvature of the human cornea; at the same time, if the radius of curvature of the human cornea 10 to be measured changes, the entire system is compensated by changing the distance between the human cornea 10 to be measured and the flat glass 9 to ensure that the system can clearly image the receiver 13, wherein the receiver 13 can be CCD or CMOS.

[0047] At the same time, since the present invention adopts an annular light source, the final image on the receiver is an annular image. When the image is a clear image in the imaging component, the image is an image circle, and the image height y 1is the radius of the image circle; when the system cannot guarantee a clear image, that is, the image is blurred in the imaging component, the image is an image ring. Since the system is a telecentric optical path, the image height can also be obtained by measuring the average radius of the image ring. The image height y is 1 is the average radius of the image ring.

[0048] In the present invention, as an example, the same device is used to perform measurement simulation calculations on human corneas with different curvature radii, and the curvature radius of the measured human cornea and the simulated diameter of the imaging ring are obtained as shown in Table 2:

[0049] Table 2

[0050] The radius of curvature of the cornea being measured Image ring simulation diameter 11mm 6.12mm 10mm 5.64mm 9mm 5.13mm 8mm 4.64mm 7mm 4.12mm 6mm 6.62mm 5mm 3.11mm

[0051] In summary, the present invention provides a novel optical path multiplexing structure, which allows the lighting module and the imaging module to share some lenses and achieve coaxialization. In the shared coupling optical path, the lighting light source is located near the image source. Its advantage is that it can be multiplexed with the imaging optical path, so that the lighting light source is shaped by more lenses into parallel light that enters the human eye at a specific angle, while greatly reducing the size of the system in the vertical direction. In addition, in the lighting optical path, the light emitted by a single light-emitting point in the annular light source is refracted by the lens group, and then converges with the light emitted by other light-emitting points, intersects on the visual axis, and then further transmits forward, and is reflected at a position on the flat glass 9 that reaches a different side from the light-emitting point. This cross-optical path design can further compress the size of the entire optical system in the visual axis direction.

[0052] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may certainly make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A compact optical system for measuring the curvature of the human cornea, characterized in that: It includes a coaxial lighting module and an imaging module, wherein the lighting module and the imaging module share a focusing lens group, and the lighting module also includes a ring light source component and a reflection component, and the imaging module also includes an imaging component; The annular light source assembly is used to emit annular light, the focusing lens group is used to focus the energy of the annular light, the reflecting assembly is used to shape the energy-focused annular light into an annular parallel light source, and to make the annular parallel light source incident on the cornea of ​​a human eye at a set illumination angle; the reflecting assembly comprises an annular spherical reflector (8) and a plane glass (9) coated with a reflecting ring, the plane glass coated with a reflecting ring is used to reflect the energy-focused annular light toward the annular spherical reflector, the annular spherical reflector is located between the focusing lens group and the plane glass coated with a reflecting ring, and is used to reflect the annular light toward the human eye in the form of parallel light; The focusing lens group is also used to focus the reflected light from the human cornea, the imaging component is used to image the reflected light after energy focusing, and the external processing module obtains the curvature of the human cornea based on the image formed by the imaging component.

2. A compact optical system for measuring corneal curvature of a human eye according to claim 1, characterized in that: The method for the external processing module to obtain the corneal curvature of the human eye according to the image formed by the imaging component is: Among them, R is the curvature of the human cornea, y1 is the image height in the image, θ is the illumination angle, f is the object focal length, and x is the object distance.

3. A compact optical system for measuring corneal curvature of a human eye as claimed in claim 2, characterized in that: When the image is a clear image in the imaging component, the image is an image circle, and the image height y1 is the radius of the image circle; when the image is a blurred image in the imaging component, the image is an image ring, and the image height y1 is the average radius of the image ring.

4. A compact optical system for measuring the curvature of the human cornea according to claim 2, characterized in that: The illumination angle θ, object focal length f and object distance x are obtained by calibrating the optical system.

5. A compact optical system for measuring the curvature of the human cornea according to any one of claims 1 to 4, characterized in that: The annular light source assembly comprises an annular light source device (1) and an annular lens (2); the focusing lens group comprises a first lens (3), a second lens (4), a third lens (5), a fourth lens (6) and a fifth lens (7); and the imaging assembly comprises a sixth lens (11), a seventh lens (12) and a receiver (13); The annular light source device (1) emits annular light, which is incident on a coaxially placed annular lens (2), a first lens (3), a second lens (4), a third lens (5), a fourth lens (6) and a fifth lens (7) in sequence, and then is shaped into an annular parallel light source through a plane glass (9) and an annular spherical reflector (8) and is incident on the cornea of ​​a human eye; The reflected light from the human cornea passes through the coaxially arranged fifth lens (7), fourth lens (6), third lens (5), second lens (4), first lens (3), sixth lens (11) and seventh lens (12) in sequence, and then enters the receiver (13) for imaging.

6. A compact optical system for measuring the curvature of the human cornea according to claim 5, characterized in that: The focal length range of the lens group composed of the annular lens (2), the first lens (3), the second lens (4), the third lens (5), the fourth lens (6) and the fifth lens (7) is 10 to 25 mm; The focal length range of the lens group composed of the first lens (3), the second lens (4), the third lens (5), the fourth lens (6), the fifth lens (7), the sixth lens (11) and the seventh lens (12) is 50 to 85 mm.

7. A compact optical system for measuring the curvature of the human cornea according to any one of claims 1 to 4, characterized in that: The lighting angle is selected in the range of 10 to 30 degrees.

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